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Rojo D, Hael CE, Soria A, de Souza FSJ, Low MJ, Franchini LF, Rubinstein M. A mammalian tripartite enhancer cluster controls hypothalamic Pomc expression, food intake, and body weight. Proc Natl Acad Sci U S A 2024; 121:e2322692121. [PMID: 38652744 PMCID: PMC11067048 DOI: 10.1073/pnas.2322692121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 03/12/2024] [Indexed: 04/25/2024] Open
Abstract
Food intake and energy balance are tightly regulated by a group of hypothalamic arcuate neurons expressing the proopiomelanocortin (POMC) gene. In mammals, arcuate-specific POMC expression is driven by two cis-acting transcriptional enhancers known as nPE1 and nPE2. Because mutant mice lacking these two enhancers still showed hypothalamic Pomc mRNA, we searched for additional elements contributing to arcuate Pomc expression. By combining molecular evolution with reporter gene expression in transgenic zebrafish and mice, here, we identified a mammalian arcuate-specific Pomc enhancer that we named nPE3, carrying several binding sites also present in nPE1 and nPE2 for transcription factors known to activate neuronal Pomc expression, such as ISL1, NKX2.1, and ERα. We found that nPE3 originated in the lineage leading to placental mammals and remained under purifying selection in all mammalian orders, although it was lost in Simiiformes (monkeys, apes, and humans) following a unique segmental deletion event. Interestingly, ablation of nPE3 from the mouse genome led to a drastic reduction (>70%) in hypothalamic Pomc mRNA during development and only moderate (<33%) in adult mice. Comparison between double (nPE1 and nPE2) and triple (nPE1, nPE2, and nPE3) enhancer mutants revealed the relative contribution of nPE3 to hypothalamic Pomc expression and its importance in the control of food intake and adiposity in male and female mice. Altogether, these results demonstrate that nPE3 integrates a tripartite cluster of partially redundant enhancers that originated upon a triple convergent evolutionary process in mammals and that is critical for hypothalamic Pomc expression and body weight homeostasis.
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Affiliation(s)
- Daniela Rojo
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires1428, Argentina
| | - Clara E. Hael
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires1428, Argentina
| | - Agustina Soria
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires1428, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires1428, Argentina
| | - Flávio S. J. de Souza
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires1428, Argentina
- Instituto de Fisiología, Biología Molecular y Neurociencias, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires1428, Argentina
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI48105
| | - Lucía F. Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires1428, Argentina
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires1428, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires1428, Argentina
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI48105
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Eliason NL, Martin L, Low MJ, Sharpe AL. Melanocortin receptor agonist melanotan-II microinjected in the nucleus accumbens decreases appetitive and consumptive responding for food. Neuropeptides 2022; 96:102289. [PMID: 36155088 PMCID: PMC10152796 DOI: 10.1016/j.npep.2022.102289] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 08/20/2022] [Accepted: 09/13/2022] [Indexed: 01/23/2023]
Abstract
RATIONALE Obesity is a major health problem worldwide. An understanding of the factors that drive feeding behaviors is key to the development of pharmaceuticals to decrease appetite and consumption. Proopiomelanocortin (POMC), the melanocortin peptide precursor, is essential in the regulation of body weight and ingestive behaviors. Deletion of POMC or impairment of melanocortin signaling in the brain results in hyperphagic obesity. Neurons in the hypothalamic arcuate nucleus produce POMC and project to many areas including the nucleus accumbens (NAcc), which is well established in the rewarding and reinforcing effects of both food and drugs of abuse. OBJECTIVE These studies sought to determine the role of melanocortins in the NAcc on consumption of and motivation to obtain access to standard rodent chow. METHODS Male, C57BL/6J mice were microinjected bilaterally into the NAcc (100 nl/side) with the melanocortin receptor 3/4 agonist melanotan-II (MT-II; 0.1, 0.3, and 1 nmol), and ingestive behaviors were examined in both home cage and operant food self-administration experiments. In addition, the ability of MT-II in the NAcc to produce aversive properties or affect metabolic rate were tested. RESULTS MT-II injected into the NAcc significantly decreased consumption in both home cage and operant paradigms, and furthermore decreased appetitive responding to gain access to food. There was no development of conditioned taste avoidance or change in metabolic parameters following anorexic doses of MT-II. CONCLUSIONS MT-II in the NAcc decreased both the motivation to eat and the amount of food consumed without inducing an aversive state or affecting metabolic rate, suggesting a role for melanocortin signaling in the NAcc that is selective for appetite and satiety without affecting metabolism or producing an aversive state.
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Affiliation(s)
- Nicole L Eliason
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States of America
| | - Lynne Martin
- Department of Pharmaceutical Sciences, Feik College of Pharmacy, University of the Incarnate Word, San Antonio, TX, United States of America
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Amanda L Sharpe
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States of America; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States of America.
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Shakya M, Martin NK, Arunagiri A, Martin MG, Arvan P, Low MJ, Lindberg I. The G209R mutant mouse as a model for human PCSK1 polyendocrinopathy. Endocrinology 2022; 163:6542675. [PMID: 35245347 PMCID: PMC9044177 DOI: 10.1210/endocr/bqac024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Indexed: 11/19/2022]
Abstract
PCSK1 encodes an enzyme required for prohormone maturation into bioactive peptides. A striking number of SNPs and rare mutations in PCSK1 are associated with a range of clinical phenotypes. Infants bearing two copies of a catalytically inactivating mutation, such as G209R, exhibit life-threatening chronic diarrhea and subsequently develop systemic endocrinopathies. Using CRISPR/Cas9 technology, we have engineered a mouse model bearing a G209R missense mutation in exon 6 of the murine Pcsk1 locus. Most pups homozygous for the G209R mutation succumbed by day 2, and surviving pups were severely dwarfed. In homozygous (but not heterozygous) pups, blood glucose levels were significantly lower, accompanied by elevated plasma insulin-like immunoreactivity and accumulation of large quantities of unprocessed proinsulin in the pancreas. Peptide hormone processing was also aberrant in G209R mouse pituitary, with mature ACTH levels markedly reduced in homozygotes, accompanied by a significant accumulation of POMC. We also observed a significant reduction in PC1/3 protein in the brains of G209R homozygous mice by Western blotting, while PC2 levels remained unaffected. Most likely due to the continued presence of PC2, pituitary and brain levels of α-MSH were not impaired. Analysis of intestinal cell types indicated a modest reduction of enteroendocrine cells in G209R homozygotes. We suggest that the G209R Pcsk1 mouse model recapitulates many of the dramatic neonatal deficiencies of human patients with this homozygous mutation.
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Affiliation(s)
- Manita Shakya
- Department of Anatomy & Neurobiology, University of Maryland School of
Medicine, Baltimore, MD, USA
| | - Surbhi
- Department Molecular & Integrative Physiology, University of
Michigan, Ann Arbor, MI, USA
| | - Nicolle K Martin
- Department of Pediatrics, Division of Gastroenterology and Nutrition, Mattel
Children’s Hospital and the David Geffen School of Medicine, University of California Los
Angeles, Los Angeles, CA, USA
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of
Michigan, Ann Arbor, MI, USA
| | - Martin G Martin
- Department of Pediatrics, Division of Gastroenterology and Nutrition, Mattel
Children’s Hospital and the David Geffen School of Medicine, University of California Los
Angeles, Los Angeles, CA, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of
Michigan, Ann Arbor, MI, USA
| | - Malcolm J Low
- Department Molecular & Integrative Physiology, University of
Michigan, Ann Arbor, MI, USA
| | - Iris Lindberg
- Department of Anatomy & Neurobiology, University of Maryland School of
Medicine, Baltimore, MD, USA
- Correspondence: Iris Lindberg, PhD, Department of Anatomy and Neurobiology, University of Maryland
School of Medicine, 20 Penn St, HSF2, S218, Baltimore, MD 21201, USA.
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Yu H, Rubinstein M, Low MJ. Developmental single-cell transcriptomics of hypothalamic POMC neurons reveal the genetic trajectories of multiple neuropeptidergic phenotypes. eLife 2022; 11:e72883. [PMID: 35044906 PMCID: PMC8806186 DOI: 10.7554/elife.72883] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Accepted: 01/18/2022] [Indexed: 11/21/2022] Open
Abstract
Proopiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus are essential to regulate food intake and energy balance. However, the ontogenetic transcriptional programs that specify the identity and functioning of these neurons are poorly understood. Here, we use single-cell RNA-sequencing (scRNA-seq) to define the transcriptomes characterizing Pomc-expressing cells in the developing hypothalamus and translating ribosome affinity purification with RNA-sequencing (TRAP-seq) to analyze the subsequent translatomes of mature POMC neurons. Our data showed that Pomc-expressing neurons give rise to multiple developmental pathways expressing different levels of Pomc and unique combinations of transcription factors. The predominant cluster, featured by high levels of Pomc and Prdm12 transcripts, represents the canonical arcuate POMC neurons. Additional cell clusters expressing medium or low levels of Pomc mature into different neuronal phenotypes featured by distinct sets of transcription factors, neuropeptides, processing enzymes, cell surface, and nuclear receptors. We conclude that the genetic programs specifying the identity and differentiation of arcuate POMC neurons are diverse and generate a heterogeneous repertoire of neuronal phenotypes early in development that continue to mature postnatally.
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Affiliation(s)
- Hui Yu
- Department of Molecular and Integrative Physiology, University of Michigan Medical SchoolAnn ArborUnited States
| | - Marcelo Rubinstein
- Department of Molecular and Integrative Physiology, University of Michigan Medical SchoolAnn ArborUnited States
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y TécnicasBuenos AiresArgentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos AiresBuenos AiresArgentina
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical SchoolAnn ArborUnited States
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Surbhi, Wittmann G, Low MJ, Lechan RM. Adult-born proopiomelanocortin neurons derived from Rax-expressing precursors mitigate the metabolic effects of congenital hypothalamic proopiomelanocortin deficiency. Mol Metab 2021; 53:101312. [PMID: 34329773 PMCID: PMC8383116 DOI: 10.1016/j.molmet.2021.101312] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 07/12/2021] [Accepted: 07/25/2021] [Indexed: 12/19/2022] Open
Abstract
OBJECTIVE Proopiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus are essential regulators of energy balance. Selective loss of POMC production in these cells results in extreme obesity and metabolic comorbidities. Neurogenesis occurs in the adult hypothalamus, but it remains uncertain whether functional POMC neurons emerge in physiologically significant numbers during adulthood. Here, we tested whether Rax-expressing precursors generate POMC neurons in adult mice and rescue the metabolic phenotype caused by congenital hypothalamic POMC deficiency. METHODS Initially, we identified hypothalamic Rax-expressing cell types using wild-type and Rax-CreERT2:Ai34D mice. Then we generated compound Rax-CreERT2:ArcPomcloxTB/loxTB mice in which endogenous hypothalamic Pomc expression is silenced, but can be restored by tamoxifen administration selectively in neurons derived from Rax+ progenitors. The number of POMC neurons generated by Rax+ progenitors in adult mice and their axonal projections was determined. The metabolic effects of these neurons were assessed by measuring food intake, bodyweight, and body composition, along with glucose and insulin levels. RESULTS We found that Rax is expressed by tanycytes and a previously unrecognized cell type in the hypothalamic parenchyma of adult mice. Rax+ progenitors generated ~10% of the normal adult hypothalamic POMC neuron population within two weeks of tamoxifen treatment. The same rate and steady state of POMC neurogenesis persisted from young adult to aged mice. These new POMC neurons established terminal projections to brain regions that were involved in energy homeostasis. Mice with Rax+ progenitor-derived POMC neurons had reduced body fat mass, improved glucose tolerance, increased insulin sensitivity, and decreased bodyweight in proportion to the number of new POMC neurons. CONCLUSIONS These data demonstrate that Rax+ progenitors generate POMC neurons in sufficient numbers during adulthood to mitigate the metabolic abnormalities of hypothalamic POMC-deficient mice. The findings suggest that adult hypothalamic neurogenesis is a robust phenomenon in mice that can significantly impact energy homeostasis.
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Affiliation(s)
- Surbhi
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, 2800 Plymouth Rd, Ann Arbor, MI, 48109, USA.
| | - Gábor Wittmann
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tufts Medical Center, 800 Washington St, Boston, MA, 02111, USA.
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, 2800 Plymouth Rd, Ann Arbor, MI, 48109, USA.
| | - Ronald M Lechan
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tufts Medical Center, 800 Washington St, Boston, MA, 02111, USA.
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Abstract
Pro-opiomelanocortin (POMC) neurons form an integral part of the central melanocortin system regulating food intake and energy expenditure. Genetic and pharmacological studies have revealed that defects in POMC synthesis, processing, and receptor signaling lead to obesity. It is well established that POMC is extensively processed by a series of enzymes, including prohormone convertases PC1/3 and PC2, and that genetic insufficiency of both PC1/3 and POMC is strongly associated with obesity risk. However, whether PC1/3-mediated POMC processing is absolutely tied to body weight regulation is not known. To investigate this question, we generated a Pomc-CreER T2; Pcsk1 lox/lox mouse model in which Pcsk1 is specifically and temporally knocked out in POMC-expressing cells of adult mice by injecting tamoxifen at eight weeks of age. We then measured the impact of Pcsk1 deletion on POMC cleavage to ACTH and α-MSH, and on body weight. In whole pituitary, POMC cleavage was significantly impacted by the loss of Pcsk1, while hypothalamic POMC-derived peptide levels remained similar in all genotypes. However, intact POMC levels were greatly elevated in Pomc-CreER T2; Pcsk1 lox/lox mice. Males expressed two-fold greater levels of pituitary PC1/3 protein than females, consistent with their increased POMC cleavage. Past studies show that mice with germline removal of PC1/3 do not develop obesity, while mice expressing mutant PC1/3 forms do develop obesity. We conclude that obesity pathways are not disrupted by PC1/3 loss solely in POMC-expressing cells, further disfavoring the idea that alterations in POMC processing underlie obesity in PCSK1 deficiency.
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Affiliation(s)
- Manita Shakya
- Department of Anatomy and Neurobiology, University of
Maryland-Baltimore, Baltimore, MD 21201,
USA
| | - Surbhi
- Department of Molecular & Integrative Physiology,
University of Michigan, Ann Arbor, MI
481091, USA
| | - Anne White
- Division of Diabetes, Endocrinology and Gastroenterology,
University of Manchester, Manchester, M13
9PT, United Kingdom
| | - C Bruce Verchere
- Departments of Pathology & Laboratory Medicine and
Surgery, University of British Columbia, British
Columbia, V5Z 4H4, Canada
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology,
University of Michigan, Ann Arbor, MI
481091, USA
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of
Maryland-Baltimore, Baltimore, MD 21201,
USA
- Correspondence: Iris Lindberg, PhD,
Department of Anatomy and Neurobiology, 20 Penn St., HSF2, S267, University of
Maryland-Baltimore, Baltimore, MD 21201, USA. E-mail:
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Na ES, Lam DD, Yokosawa E, Adams JM, Olson DP, Low MJ. Decreased sensitivity to the anorectic effects of leptin in mice that lack a Pomc-specific neural enhancer. PLoS One 2021; 15:e0244793. [PMID: 33382813 PMCID: PMC7775064 DOI: 10.1371/journal.pone.0244793] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 11/24/2020] [Indexed: 11/18/2022] Open
Abstract
Enhancer redundancy has been postulated to provide a buffer for gene expression against genetic and environmental perturbations. While work in Drosophila has identified functionally overlapping enhancers, work in mammalian models has been limited. Recently, we have identified two partially redundant enhancers, nPE1 and nPE2, that drive proopiomelanocortin gene expression in the hypothalamus. Here we demonstrate that deletion of nPE1 produces mild obesity while knockout of nPE2 has no discernible metabolic phenotypes. Additionally, we show that acute leptin administration has significant effects on nPE1 knockout mice, with food intake and body weight change significantly impacted by peripheral leptin treatment. nPE1 knockout mice became less responsive to leptin treatment over time as percent body weight change increased over 2 week exposure to peripheral leptin. Both Pomc and Agrp mRNA were not differentially affected by chronic leptin treatment however we did see a decrease in Pomc and Agrp mRNA in both nPE1 and nPE2 knockout calorie restricted mice as compared to calorie restricted PBS-treated WT mice. Collectively, these data suggest dynamic regulation of Pomc by nPE1 such that mice with nPE1 knockout become less responsive to the anorectic effects of leptin treatment over time. Our results also support our earlier findings in which nPE2 may only be critical in adult mice that lack nPE1, indicating that these neural enhancers work synergistically to influence metabolism.
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Affiliation(s)
- Elisa S. Na
- Department of Psychology & Philosophy Texas Woman’s University, Denton, Texas, United States of America
- * E-mail: (ESN); (DDL)
| | - Daniel D. Lam
- Institute of Neurogenomics, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
- Chair of Neurogenetics, Neurological Clinic and Polyclinic, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, Germany
- * E-mail: (ESN); (DDL)
| | - Eva Yokosawa
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Jessica M. Adams
- Division of Endocrinology, Department of Pediatrics, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - David P. Olson
- Division of Endocrinology, Department of Pediatrics, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Malcolm J. Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
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Yu H, Thompson Z, Kiran S, Jones GL, Mundada L, Rubinstein M, Low MJ. Expression of a hypomorphic Pomc allele alters leptin dynamics during late pregnancy. J Endocrinol 2020; 245:115-127. [PMID: 32027603 DOI: 10.1530/joe-19-0576] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 02/06/2020] [Indexed: 12/11/2022]
Abstract
Proopiomelanocortin (POMC) neurons in the hypothalamic arcuate nucleus (ARC) are essential for normal energy homeostasis. Maximal ARC Pomc transcription is dependent on neuronal Pomc enhancer 1 (nPE1), located 12 kb upstream from the promoter. Selective deletion of nPE1 in mice decreases ARC Pomc expression by 70%, sufficient to induce mild obesity. Because nPE1 is located exclusively in the genomes of placental mammals, we questioned whether its hypomorphic mutation would also alter placental Pomc expression and the metabolic adaptations associated with pregnancy and lactation. We assessed placental development, pup growth, circulating leptin and expression of Pomc, Agrp and alternatively spliced leptin receptor (LepR) isoforms in the ARC and placenta of Pomc∆1/∆1 and Pomc+/+ dams. Despite indistinguishable body weights, lean mass, food intake, placental histology and Pomc expression and overall pregnancy outcomes between the genotypes, Pomc ∆1/∆1 females had increased pre-pregnancy fat mass that paradoxically decreased to control levels by parturition. However, Pomc∆1/∆1 dams had exaggerated increases in circulating leptin, up to twice of that of the typically elevated levels in Pomc+/+ mice at the end of pregnancy, despite their equivalent fat mass. Pomc∆1/∆1dams also had increased placental expression of soluble leptin receptor (LepRe), although the protein levels of LEPRE in circulation were the same as Pomc+/+ controls. Together, these data suggest that the hypomorphic Pomc∆1/∆1 allele is responsible for the perinatal super hyperleptinemia of Pomc∆1/∆1 dams, possibly due to upregulated leptin secretion from individual adipocytes.
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Affiliation(s)
- Hui Yu
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Zoe Thompson
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Sylee Kiran
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,School of Literature, Science, and Arts, University of Michigan, Ann Arbor, Michigan, USA
| | - Graham L Jones
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
| | - Lakshmi Mundada
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | -
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Marcelo Rubinstein
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Instituto de Investigaciones en Ingeniería Genética y Biología Molecular Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Exactas y Naturales, Universidad de Buenos, Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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Gahlot S, Wittmann G, Lechan RM, Low MJ. OR16-03 Metabolic Effects Of Hypothalamic Pomc Neurons Generated Postnatally From Tanycytes On A Pomc Null Genetic Background. J Endocr Soc 2020. [PMCID: PMC7208480 DOI: 10.1210/jendso/bvaa046.142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Hypothalamic proopiomelanocortin (POMC) neurons are an integral part of the central melanocortin system and regulate feeding and energy balance in vertebrates. Tanycytes are radial glial-like cells lining the third ventricle that contain a subpopulation of adult stem cells, which can differentiate under specific circumstances into glia and neurons, including POMC neurons. However, the capacity of these stem cell-derived neurons to fully mature and integrate into existing neural circuits of physiological relevance is unknown. This study systematically tested whether Pomc mRNA-positive cells newly generated from tanycyte precursors can differentiate into melanocortin-secreting POMC neurons, integrate into the normal anatomical projection pathways of these cells and rescue the obesity phenotype caused by the loss of Pomc expression in ArcPomcfneo/fneo mice. We generated an inducible compound genetic mouse model by crossing RaxCreERT2 with the Cre-dependent ArcPomcfneo/fneo and LSL-syp-tdTomato alleles. Rax is expressed exclusively in postnatal tanycytes, thereby limiting tamoxifen-induced recombination of the two floxed alleles by CreERT2 to tanycytes. As expected, tamoxifen treatment of the mice at age 4–5 wk recapitulated endogenous Rax expression 16 wk later as observed by red fluorescent tdTomato expression in all tanycytes. In addition, Cre recombinase-mediated deletion of the floxed-neomycin cassette from the neuronal enhancer region of the ArcPomcfneo alleles relieved their constitutive transcriptional silencing. Consequently, tamoxifen treatment consistently generated a significant number of newly generated POMC neurons from tanycytes (~10% of the POMC neurons in a WT mouse), identified by Pomc FISH and POMC/α-MSH immunofluorescence in the soma and established terminal projections to hypothalamic nuclei including the PVH and DMH involved in energy homeostasis. A subpopulation of these neurons also expressed the synaptophysin-tDTomato reporter. We performed serial body weight, food intake, body composition, oral GTT and insulin measurements with the RaxCreERT2/+, ArcPomcfneo/fneo mice and found no significant differences in any of these metabolic variables compared to untreated obese ArcPomcfneo/fneo mice. These data are consistent with previous studies from our lab suggesting that Pomc expression has to be at least ~30% of normal to mitigate the obesity phenotype in Pomc-null mice. In conclusion, we demonstrated that tanycytes are capable of generating mature Pomc-expressing neurons in the hypothalamus of adult mice. However, we propose that determining the underlying mechanisms involved in the generation of hypothalamic POMC neurons from tanycytes and interventions to increase their number, might lead to a novel approach to treat obesity. Nothing to Disclose: SG, GW, RML, MJL
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Affiliation(s)
- Surbhi Gahlot
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Gabor Wittmann
- Division of Endocrinology, Tufts Medical Center, Boston, MA, USA
| | - Ronald M Lechan
- Division of Endocrinology, Tufts Medical Center, Boston, MA, USA
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
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Thompson Z, Shah BP, Low MJ. SAT-299 Chronic Treatment Of Juvenile Hypothalamic Pomc-deficient Mice With RM-493 Prevents The Development Of Obesity. J Endocr Soc 2020. [PMCID: PMC7208318 DOI: 10.1210/jendso/bvaa046.330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Arc-Pomc knockout mice have a disruption of the two neural enhancers for the Pomc (proopiomelanocortin) gene, resulting in selective loss of Pomc gene expression in the arcuate nucleus of the hypothalamus. This gene targeting strategy leaves pituitary Pomc expression unaffected. These mice are hyperphagic starting at weaning, and develop progressive obesity, infertility and insulin resistance over their lifetime. RM-493 (setmelanotide) is a melanocortin-4 receptor agonist that has shown promise in treating humans with Pomc null mutations. In this preclinical study, we investigated the effects of chronic RM-493 treatment using subcutaneously implanted osmotic minipumps in two groups of male mice: Arc-Pomc knockout mice, fed regular chow throughout the study period, and their wildtype counterparts, fed a 45% high-fat diet. Each of these groups of mice was randomized into three treatment cohorts at weaning: one that was given RM-493 throughout the entire study period (4–24 weeks of age, “RM-493” group), one that was given RM-493 only for the first 4 weeks of the study (4–8 weeks of age, “switch” group) and then switched to vehicle, and one cohort that received vehicle for the entire study (“vehicle” group). We serially measured body weight, food intake, body composition, glucose tolerance, insulin tolerance, and several measures of metabolism using the Comprehensive Lab Animal Monitoring System, including oxygen consumption, energy expenditure, ambulatory activity and lipid and glucose oxidation. Among other results, at the end of the study (24 weeks of age), Arc-Pomc knockout mice in the RM-493 group weighed significantly less than either the switch or vehicle groups (p<0.05). Arc-Pomc knockout mice on RM-493 also had higher energy expenditure when compared to the switch and vehicle groups (p<0.05). In addition, RM-493 improved the glucose-insulin index for Arc-Pomc knockout mice (p<0.05). According to our preliminary results, wildtype mice on high-fat diet, treated chronically with RM-493, did not differ in any of these measurements from their switch and vehicle groups. We conclude that the obesity syndrome caused by a loss of hypothalamic Pomc expression was completely blocked by RM-493 treatment started before the onset of obesity, with no apparent desensitization to the drug’s action over 20 weeks. However, the beneficial effects of a single month’s treatment were steadily reversed within one month after switching to vehicle treatment. In contrast to the dramatic effects of RM-493 in the genetic obesity syndrome, at this time, there does not appear to be any phenotypic changes in wild-type mice with RM-493 administration on the development of obesity or secondary metabolic disruptions in response to high-fat diet consumption.
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Affiliation(s)
- Zoe Thompson
- University of Michigan Medical School, Ann Arbor, MI, USA
| | | | - Malcolm J Low
- University of Michigan Medical School, Ann Arbor, MI, USA
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Hael CE, Rojo D, Orquera DP, Low MJ, Rubinstein M. The transcriptional regulator PRDM12 is critical for Pomc expression in the mouse hypothalamus and controlling food intake, adiposity, and body weight. Mol Metab 2020; 34:43-53. [PMID: 32180559 PMCID: PMC7011018 DOI: 10.1016/j.molmet.2020.01.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 01/04/2020] [Accepted: 01/07/2020] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVE Regulation of food intake and energy balance depends on a group of hypothalamic neurons that release anorexigenic melanocortins encoded by the Pomc gene. Although the physiological importance of central melanocortins is well appreciated, the genetic program that defines the functional identity of melanocortin neurons and assures high levels of hypothalamic Pomc expression is only beginning to be understood. This study assessed whether the transcriptional regulator PRDM12, identified as a highly expressed gene in adult mouse POMC neurons, plays an important role in the identity and function of melanocortin neurons. METHODS We first determined the cellular distribution of PRDM12 in the developing hypothalamus. Then we studied mutant mice with constitutively inactivated Prdm12 to evaluate possible changes in hypothalamic Pomc expression. In addition, we characterized conditional mutant mice specifically lacking Prdm12 in ISL1-positive or POMC neurons during development. Finally, we measured food intake, body weight progression up to 16 weeks of age, adiposity, and glucose tolerance in adult mice lacking Prdm12 selectively from POMC neurons. RESULTS PRDM12 co-expressed with POMC in mouse hypothalamic neurons from early development to adulthood. Mice lacking Prdm12 displayed greatly reduced Pomc expression in the developing hypothalamus. Selective ablation of Prdm12 from ISL1 neurons prevented hypothalamic Pomc expression. The conditional ablation of Prdm12 limited to POMC neurons greatly reduced Pomc expression in the developing hypothalamus and in adult mice led to increased food intake, adiposity, and obesity. CONCLUSIONS Altogether, our results demonstrate that PRDM12 plays an essential role in the early establishment of hypothalamic melanocortin neuron identity and the maintenance of high expression levels of Pomc. Its absence in adult mice greatly impairs Pomc expression and leads to increased food intake, adiposity, and obesity.
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Affiliation(s)
- Clara E Hael
- Institute of Investigations in Genetic Engineering and Molecular Biology, National Council of Scientific and Technological Research, 1428 Buenos Aires, Argentina
| | - Daniela Rojo
- Institute of Investigations in Genetic Engineering and Molecular Biology, National Council of Scientific and Technological Research, 1428 Buenos Aires, Argentina
| | - Daniela P Orquera
- Institute of Investigations in Genetic Engineering and Molecular Biology, National Council of Scientific and Technological Research, 1428 Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48105, USA.
| | - Marcelo Rubinstein
- Institute of Investigations in Genetic Engineering and Molecular Biology, National Council of Scientific and Technological Research, 1428 Buenos Aires, Argentina; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48105, USA; Department of Physiology, Molecular and Cellular Biology, School of Exact and Natural Sciences, University of Buenos Aires, 1428 Buenos Aires, Argentina.
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Yu H, Chhabra KH, Thompson Z, Jones GL, Kiran S, Shangguan G, Low MJ. Hypothalamic POMC deficiency increases circulating adiponectin despite obesity. Mol Metab 2020; 35:100957. [PMID: 32244188 PMCID: PMC7082555 DOI: 10.1016/j.molmet.2020.01.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/22/2020] [Accepted: 01/31/2020] [Indexed: 02/06/2023] Open
Abstract
Objective The steep rise in the prevalence of obesity and its related metabolic syndrome have become a major worldwide health concerns. Melanocortin peptides from hypothalamic arcuate nucleus (Arc) POMC neurons induce satiety to limit food intake. Consequently, Arc Pomc-deficient mice (ArcPomc−/−) exhibit hyperphagia and obesity. Previous studies demonstrated that the circulating levels of adiponectin, a protein abundantly produced and secreted by fat cells, negatively correlate with obesity in both rodents and humans. However, we found that ArcPomc−/− mice have increased circulating adiponectin levels despite obesity. Therefore, we investigated the physiological function and underlying mechanisms of hypothalamic POMC in regulating systemic adiponectin levels. Methods Circulating adiponectin was measured in obese ArcPomc−/− mice at ages 4–52 weeks. To determine whether increased adiponectin was a direct result of ArcPomc deficiency or a secondary effect of obesity, we examined plasma adiponectin levels in calorie-restricted mice with or without a history of obesity and in ArcPomc−/− mice before and after genetic restoration of Pomc expression in the hypothalamus. To delineate the mechanisms causing increased adiponectin in ArcPomc−/− mice, we determined sympathetic outflow to adipose tissue by assessing epinephrine, norepinephrine, and tyrosine hydroxylase protein levels and measured the circulating adiponectin in the mice after acute norepinephrine or propranolol treatments. In addition, adiponectin mRNA and protein levels were measured in discrete adipose tissue depots to ascertain which fat depots contributed the most to the high level of adiponectin in the ArcPomc−/− mice. Finally, we generated compound Adiopoq−/−:ArcPomc−/− mice and compared their growth, body composition, and glucose homeostasis to the individual knockout mouse strains and their wild-type controls. Results Obese ArcPomc−/− female mice had unexpectedly increased plasma adiponectin compared to wild-type siblings at all ages greater than 8 weeks. Despite chronic calorie restriction to achieve normal body weights, higher adiponectin levels persisted in the ArcPomc−/− female mice. Genetic restoration of Pomc expression in the Arc or acute treatment of the ArcPomc−/− female mice with melanotan II reduced adiponectin levels to control littermate values. The ArcPomc−/− mice had defective thermogenesis and decreased epinephrine, norepinephrine, and tyrosine hydroxylase protein levels in their fat pads, indicating reduced sympathetic outflow to adipose tissue. Injections of norepinephrine into the ArcPomc−/− female mice reduced circulating adiponectin levels, whereas injections of propranolol significantly increased adiponectin levels. Despite the beneficial effects of adiponectin on metabolism, the deletion of adiponectin alleles in the ArcPomc−/− mice did not exacerbate their metabolic abnormalities. Conclusion In summary, to the best of our knowledge, this study provides the first evidence that despite obesity, the ArcPomc−/− mouse model has high circulating adiponectin levels, which demonstrated that increased fat mass is not necessarily correlated with hypoadiponectinemia. Our investigation also found a previously unknown physiological pathway connecting POMC neurons via the sympathetic nervous system to circulating adiponectin, thereby shedding light on the biological regulation of adiponectin. Obese female hypothalamic-specific Pomc-deficient mice have unexpectedly elevated circulating adiponectin. Restoration of Pomc expression in the hypothalamus reduces plasma adiponectin. Low sympathetic output to subcutaneous fat depots in the Pomc-deficient mice contributes to high adiponectin levels. Deletion of adiponectin in hypothalamic-specific Pomc-deficient mice does not alter their metabolic phenotype.
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Affiliation(s)
- Hui Yu
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
| | - Kavaljit H Chhabra
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48105, USA; Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Zoe Thompson
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Graham L Jones
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Sylee Kiran
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48105, USA; School of Literature, Science, and Arts, University of Michigan, Ann Arbor, MI, USA
| | - Gary Shangguan
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48105, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
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Jarvela TS, Shakya M, Bachor T, White A, Low MJ, Lindberg I. Reduced Stability and pH-Dependent Activity of a Common Obesity-Linked PCSK1 Polymorphism, N221D. Endocrinology 2019; 160:2630-2645. [PMID: 31504391 PMCID: PMC6892424 DOI: 10.1210/en.2019-00418] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/26/2019] [Indexed: 02/06/2023]
Abstract
Common mutations in the human prohormone convertase (PC)1/3 gene (PCKSI) are linked to increased risk of obesity. Previous work has shown that the rs6232 single-nucleotide polymorphism (N221D) results in slightly decreased activity, although whether this decrease underlies obesity risk is not clear. We observed significantly decreased activity of the N221D PC1/3 enzyme at the pH of the trans-Golgi network; at this pH, the mutant enzyme was less stable than wild-type enzyme. Recombinant N221D PC1/3 also showed enhanced susceptibility to heat stress. Enhanced susceptibility to tunicamycin-induced endoplasmic reticulum stress was observed in AtT-20/PC2 cell clones in which murine PC1/3 was replaced by human N221D PC1/3, as compared with wild-type human PC1/3. However, N221D PC1/3-expressing AtT-20/PC2 clones processed proopiomelanocortin to α-MSH similarly to wild-type PC1/3. We also generated a CRISPR-edited mouse line expressing the N221D mutation in the PCKSI gene. When homozygous N221D mice were fed either a standard or a high-fat diet, we found no increase in body weight compared with their wild-type sibling controls. Sexual dimorphism was observed in pituitary ACTH for both genotypes, with females exhibiting lower levels of pituitary ACTH. In contrast, hypothalamic α-MSH content for both genotypes was higher in females compared with males. Hypothalamic corticotropin-like intermediate peptide content was higher in wild-type females compared with wild-type, but not N221D, males. Taken together, these data suggest that the increased obesity risk linked to the N221D allele in humans may be due in part to PC1/3-induced loss of resilience to stressors rather than strictly to decreased enzymatic activity on peptide precursors.
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Affiliation(s)
- Timothy S Jarvela
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Surbhi
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Manita Shakya
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Tomas Bachor
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Anne White
- Division of Diabetes, Endocrinology and Gastroenterology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
- Correspondence: Iris Lindberg, PhD, Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn Street, Room S267, Baltimore, Maryland 21210. E-mail:
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Zhou Y, Liang Y, Low MJ, Kreek MJ. Nuclear transcriptional changes in hypothalamus of Pomc enhancer knockout mice after excessive alcohol drinking. Genes Brain Behav 2019; 18:e12600. [PMID: 31339663 DOI: 10.1111/gbb.12600] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 07/13/2019] [Accepted: 07/19/2019] [Indexed: 12/13/2022]
Abstract
Persistent alterations of proopiomelanocortin (Pomc) and mu-opioid receptor (Oprm1) activity and stress responses after alcohol are critically involved in vulnerability to alcohol dependency. Gene transcriptional regulation altered by alcohol may play important roles. Mice with genome-wide deletion of neuronal Pomc enhancer1 (nPE1-/- ), had hypothalamic-specific partial reductions of beta-endorphin and displayed lower alcohol consumption, compared to wildtype littermates (nPE1+/+ ). We used RNA-Seq to measure steady-state nuclear mRNA transcripts of opioid and stress genes in hypothalamus of nPE1+/+ and nPE1-/- mice after 1-day acute withdrawal from chronic excessive alcohol drinking or after water. nPE1-/- had lower basal Pomc and Pdyn (prodynorphin) levels compared to nPE1+/+ , coupled with increased basal Oprm1 and Oprk1 (kappa-opioid receptor) levels, and low alcohol drinking increased Pomc and Pdyn to the basal levels of nPE1+/+ in the water group, without significant effects on Oprm1 and Oprk1. In nPE1+/+ , excessive alcohol intake increased Pomc and Oprm1, with no effect on Pdyn or Oprk1. For stress genes, nPE1-/- had lowered basal Oxt (oxytocin) and Avp (arginine vasopressin) that were restored by low alcohol intake to basal levels of nPE1+/+ . In nPE1+/+ , excessive alcohol intake decreased Oxt and Avpi1 (AVP-induced protein1). Functionally examining the effect of pharmacological blockade of mu-opioid receptor, we found that naltrexone reduced excessive alcohol intake in nPE1+/+ , but not nPE1-/- . Our results provide evidence relevant to the transcriptional profiling of the critical genes in mouse hypothalamus: enhanced opioid and reduced stress gene transcripts after acute withdrawal from excessive alcohol may contribute to altered reward and stress responses.
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Affiliation(s)
- Yan Zhou
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, New York
| | - Yupu Liang
- Research Bioinformatics, CCTS, The Rockefeller University, New York, New York
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Mary J Kreek
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, New York
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Zestos AG, Carpenter C, Kim Y, Low MJ, Kennedy RT, Gnegy ME. Ruboxistaurin Reduces Cocaine-Stimulated Increases in Extracellular Dopamine by Modifying Dopamine-Autoreceptor Activity. ACS Chem Neurosci 2019; 10:1960-1969. [PMID: 30384585 DOI: 10.1021/acschemneuro.8b00259] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Cocaine is a highly abused drug, and cocaine addiction affects millions of individuals worldwide. Cocaine blocks normal uptake function at the dopamine transporter (DAT), thus increasing extracellular dopamine. Currently, no chemical therapies are available to treat cocaine abuse. Previous works showed that the selective inhibitors of protein kinase Cβ (PKCβ), enzastaurin and ruboxistaurin, attenuate dopamine overflow and locomotion stimulated by another psychostimulant drug, amphetamine. We now test if ruboxistaurin similarly affects cocaine action. Perfusion of 1 μM ruboxistaurin directly into the core of the nucleus accumbens via retrodialysis reduced cocaine-stimulated increases in dopamine overflow, measured using microdialysis sampling, with simultaneous reductions in locomotor behavior. Because cocaine activity is highly regulated by dopamine autoreceptors, we examined whether ruboxistaurin was acting at the level of the D2 autoreceptor. Perfusion of 5 μM raclopride, a selective D2-like receptor antagonist, before addition of ruboxistaurin, abrogated the effect of ruboxistaurin on cocaine-stimulated dopamine overflow and hyperlocomotion. Further, ruboxistaurin was inactive against cocaine-stimulated locomotor activity in mice with a genetic deletion in D2 receptors as compared to wild-type mice. In contrast, blockade or deletion of dopamine D2 receptors did not abolish the attenuating effect of ruboxistaurin on amphetamine-stimulated activities. Therefore, the inhibition of PKCβ reduces dopamine overflow and locomotor activity stimulated by both cocaine and amphetamine, but the mechanism of action differs for each stimulant. These data suggest that inhibition of PKCβ would serve as a target to reduce the abuse of either amphetamine or cocaine.
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Affiliation(s)
- Alexander G. Zestos
- Department of Chemistry and Center for Behavioral Neuroscience, American University, Washington, D.C. 20016, United States
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Jones GL, Wittmann G, Yokosawa EB, Yu H, Mercer AJ, Lechan RM, Low MJ. Selective Restoration of Pomc Expression in Glutamatergic POMC Neurons: Evidence for a Dynamic Hypothalamic Neurotransmitter Network. eNeuro 2019; 6:ENEURO.0400-18.2019. [PMID: 30957016 PMCID: PMC6449166 DOI: 10.1523/eneuro.0400-18.2019] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 02/15/2019] [Accepted: 02/17/2019] [Indexed: 01/19/2023] Open
Abstract
Hypothalamic POMC deficiency leads to obesity and metabolic deficiencies, largely due to the loss of melanocortin peptides. However, POMC neurons in the arcuate nucleus (ARC) are comprised of glutamatergic and GABAergic subpopulations. The developmental program, relative proportion and function of these two subpopulations are unresolved. To test whether glutamatergic POMC neurons serve a distinct role in maintaining energy homeostasis, we activated Pomc expression Cre- dependently in Vglut2-expressing neurons of mice with conditionally silenced Pomc alleles. The Vglut2-Pomc restored mice had normal ARC Pomc mRNA levels, POMC immunoreactivity, as well as body weight and body composition at age 12 weeks. Unexpectedly, the cumulative total of Vglut2+ glutamatergic- and Gad67+ GABAergic-Pomc neurons detected by in situ hybridization (ISH) exceeded 100% in both Vglut2- Pomc restored and control mice, indicating that a subpopulation of Pomc neurons must express both neuronal markers. Consistent with this hypothesis, triple ISH of C57BL/6J hypothalami revealed that 35% of ARC Pomc neurons were selectively Gad67+, 21% were selectively Vglut2+, and 38% expressed both Gad67 and Vglut2. The single Gad67+ and Vglut2+Pomc neurons were most prevalent in the rostral ARC, while the Vglut2/Gad67+ dual-phenotype cells predominated in the caudal ARC. A lineage trace using Ai9-tdTomato reporter mice to label fluorescently all Vglut2-expressing neurons showed equal numbers of tdTomato+ and tdTomato- POMC immunoreactive neurons. Together, these data suggest that POMC neurons exhibit developmental plasticity in their expression of glutamatergic and GABAergic markers, enabling re-establishment of normal energy homeostasis in the Vglut2-Pomc restored mice.
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Affiliation(s)
- Graham L. Jones
- Neuroscience Graduate Program
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Gábor Wittmann
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tufts Medical Center, Boston, MA 02111
| | - Eva B. Yokosawa
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Hui Yu
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Aaron J. Mercer
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Ronald M. Lechan
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tufts Medical Center, Boston, MA 02111
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105
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Tooke BP, Yu H, Adams JM, Jones GL, Sutton-Kennedy T, Mundada L, Qi NR, Low MJ, Chhabra KH. Hypothalamic POMC or MC4R deficiency impairs counterregulatory responses to hypoglycemia in mice. Mol Metab 2018; 20:194-204. [PMID: 30503832 PMCID: PMC6358536 DOI: 10.1016/j.molmet.2018.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/09/2018] [Accepted: 11/14/2018] [Indexed: 11/15/2022] Open
Abstract
Objective Life-threatening hypoglycemia is a major limiting factor in the management of diabetes. While it is known that counterregulatory responses to hypoglycemia are impaired in diabetes, molecular mechanisms underlying the reduced responses remain unclear. Given the established roles of the hypothalamic proopiomelanocortin (POMC)/melanocortin 4 receptor (MC4R) circuit in regulating sympathetic nervous system (SNS) activity and the SNS in stimulating counterregulatory responses to hypoglycemia, we hypothesized that hypothalamic POMC as well as MC4R, a receptor for POMC derived melanocyte stimulating hormones, is required for normal hypoglycemia counterregulation. Methods To test the hypothesis, we induced hypoglycemia or glucopenia in separate cohorts of mice deficient in either POMC or MC4R in the arcuate nucleus (ARC) or the paraventricular nucleus of the hypothalamus (PVH), respectively, and measured their circulating counterregulatory hormones. In addition, we performed a hyperinsulinemic-hypoglycemic clamp study to further validate the function of MC4R in hypoglycemia counterregulation. We also measured Pomc and Mc4r mRNA levels in the ARC and PVH, respectively, in the streptozotocin-induced type 1 diabetes mouse model and non-obese diabetic (NOD) mice to delineate molecular mechanisms by which diabetes deteriorates the defense systems against hypoglycemia. Finally, we treated diabetic mice with the MC4R agonist MTII, administered stereotaxically into the PVH, to determine its potential for restoring the counterregulatory response to hypoglycemia in diabetes. Results Stimulation of epinephrine and glucagon release in response to hypoglycemia or glucopenia was diminished in both POMC- and MC4R-deficient mice, relative to their littermate controls. Similarly, the counterregulatory response was impaired in association with decreased hypothalamic Pomc and Mc4r expression in the diabetic mice, a phenotype that was not reversed by insulin treatment which normalized glycemia. In contrast, infusion of an MC4R agonist in the PVH restored the counterregulatory response in diabetic mice. Conclusion In conclusion, hypothalamic Pomc as well as Mc4r, both of which are reduced in type 1 diabetic mice, are required for normal counterregulatory responses to hypoglycemia. Therefore, enhancing MC4R function may improve hypoglycemia counterregulation in diabetes. Hypothalamic POMC as well as MC4R is necessary to counteract hypoglycemia. Type 1 diabetic mice exhibit a reduced Pomc and Mc4r expression in the hypothalamus. Insulin treatment does not restore Pomc and Mc4r expression in diabetic mice. MC4R agonist improves hypoglycemia counterregulation in diabetic mice.
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Affiliation(s)
- Benjamin P Tooke
- Case Western Reserve University, Cleveland, OH, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Hui Yu
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jessica M Adams
- Department of Pediatrics, University of Michigan, Ann Arbor, MI, USA
| | - Graham L Jones
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Talisha Sutton-Kennedy
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Lakshmi Mundada
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Nathan R Qi
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA.
| | - Kavaljit H Chhabra
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
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Jiman AA, Chhabra KH, Lewis AG, Cederna PS, Seeley RJ, Low MJ, Bruns TM. Electrical stimulation of renal nerves for modulating urine glucose excretion in rats. Bioelectron Med 2018; 4:7. [PMID: 32232083 PMCID: PMC7098252 DOI: 10.1186/s42234-018-0008-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 05/17/2018] [Indexed: 12/12/2022] Open
Abstract
Background The role of the kidney in glucose homeostasis has gained global interest. Kidneys are innervated by renal nerves, and renal denervation animal models have shown improved glucose regulation. We hypothesized that stimulation of renal nerves at kilohertz frequencies, which can block propagation of action potentials, would increase urine glucose excretion. Conversely, we hypothesized that low frequency stimulation, which has been shown to increase renal nerve activity, would decrease urine glucose excretion. Methods We performed non-survival experiments on male rats under thiobutabarbital anesthesia. A cuff electrode was placed around the left renal artery, encircling the renal nerves. Ureters were cannulated bilaterally to obtain urine samples from each kidney independently for comparison. Renal nerves were stimulated at kilohertz frequencies (1–50 kHz) or low frequencies (2–5 Hz), with intravenous administration of a glucose bolus shortly into the 25–40-min stimulation period. Urine samples were collected at 5–10-min intervals, and colorimetric assays were used to quantify glucose excretion and concentration between stimulated and non-stimulated kidneys. A Kruskal-Wallis test was performed across all stimulation frequencies (α = 0.05), followed by a post-hoc Wilcoxon rank sum test with Bonferroni correction (α = 0.005). Results For kilohertz frequency trials, the stimulated kidney yielded a higher average total urine glucose excretion at 33 kHz (+ 24.5%; n = 9) than 1 kHz (− 5.9%; n = 6) and 50 kHz (+ 2.3%; n = 14). In low frequency stimulation trials, 5 Hz stimulation led to a lower average total urine glucose excretion (− 40.4%; n = 6) than 2 Hz (− 27.2%; n = 5). The average total urine glucose excretion between 33 kHz and 5 Hz was statistically significant (p < 0.005). Similar outcomes were observed for urine flow rate, which may suggest an associated response. No trends or statistical significance were observed for urine glucose concentrations. Conclusion To our knowledge, this is the first study to investigate electrical stimulation of renal nerves to modulate urine glucose excretion. Our experimental results show that stimulation of renal nerves may modulate urine glucose excretion, however, this response may be associated with urine flow rate. Future work is needed to examine the underlying mechanisms and identify approaches for enhancing regulation of glucose excretion.
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Affiliation(s)
- Ahmad A Jiman
- 1Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA.,2Biointerfaces Institute, University of Michigan, Ann Arbor, MI USA
| | - Kavaljit H Chhabra
- 3Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI USA
| | - Alfor G Lewis
- 4Department of Surgery, University of Michigan, Ann Arbor, MI USA
| | - Paul S Cederna
- 1Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA.,5Department of Surgery, Plastic Surgery Section, Michigan Medicine, Ann Arbor, MI USA
| | - Randy J Seeley
- 4Department of Surgery, University of Michigan, Ann Arbor, MI USA
| | - Malcolm J Low
- 3Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI USA
| | - Tim M Bruns
- 1Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA.,2Biointerfaces Institute, University of Michigan, Ann Arbor, MI USA
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19
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Kim GH, Shi G, Somlo DR, Haataja L, Song S, Long Q, Nillni EA, Low MJ, Arvan P, Myers MG, Qi L. Hypothalamic ER-associated degradation regulates POMC maturation, feeding, and age-associated obesity. J Clin Invest 2018; 128:1125-1140. [PMID: 29457782 PMCID: PMC5824855 DOI: 10.1172/jci96420] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 11/14/2017] [Indexed: 12/18/2022] Open
Abstract
Pro-opiomelanocortin (POMC) neurons function as key regulators of metabolism and physiology by releasing prohormone-derived neuropeptides with distinct biological activities. However, our understanding of early events in prohormone maturation in the ER remains incomplete. Highlighting the significance of this gap in knowledge, a single POMC cysteine-to-phenylalanine mutation at position 28 (POMC-C28F) is defective for ER processing and causes early onset obesity in a dominant-negative manner in humans through an unclear mechanism. Here, we report a pathologically important role of Sel1L-Hrd1, the protein complex of ER-associated degradation (ERAD), within POMC neurons. Mice with POMC neuron–specific Sel1L deficiency developed age-associated obesity due, at least in part, to the ER retention of POMC that led to hyperphagia. The Sel1L-Hrd1 complex targets a fraction of nascent POMC molecules for ubiquitination and proteasomal degradation, preventing accumulation of misfolded and aggregated POMC, thereby ensuring that another fraction of POMC can undergo normal posttranslational processing and trafficking for secretion. Moreover, we found that the disease-associated POMC-C28F mutant evades ERAD and becomes aggregated due to the presence of a highly reactive unpaired cysteine thiol at position 50. Thus, this study not only identifies ERAD as an important mechanism regulating POMC maturation within the ER, but also provides insights into the pathogenesis of monogenic obesity associated with defective prohormone folding.
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Affiliation(s)
- Geun Hyang Kim
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Guojun Shi
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Diane Rm Somlo
- Division of Nutritional Sciences, Cornell University, Ithaca, New York, USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Soobin Song
- Division of Nutritional Sciences, Cornell University, Ithaca, New York, USA
| | - Qiaoming Long
- Cam-Su Genomic Resource Center, Soochow University, Suzhou, Jiangsu, China
| | - Eduardo A Nillni
- The Warren Alpert Medical School, Department of Medicine, Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA
| | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Peter Arvan
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Martin G Myers
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
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20
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Steyn FJ, Ngo ST, Chen VP, Bailey-Downs LC, Xie TY, Ghadami M, Brimijoin S, Freeman WM, Rubinstein M, Low MJ, Stout MB. 17α-estradiol acts through hypothalamic pro-opiomelanocortin expressing neurons to reduce feeding behavior. Aging Cell 2018; 17. [PMID: 29168299 PMCID: PMC5770854 DOI: 10.1111/acel.12703] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2017] [Indexed: 11/28/2022] Open
Abstract
Weight loss is an effective intervention for diminishing disease burden in obese older adults. Pharmacological interventions that reduce food intake and thereby promote weight loss may offer effective strategies to reduce age‐related disease. We previously reported that 17α‐estradiol (17α‐E2) administration elicits beneficial effects on metabolism and inflammation in old male mice. These observations were associated with reduced calorie intake. Here, we demonstrate that 17α‐E2 acts through pro‐opiomelanocortin (Pomc) expression in the arcuate nucleus (ARC) to reduce food intake and body mass in mouse models of obesity. These results confirm that 17α‐E2 modulates appetite through selective interactions within hypothalamic anorexigenic pathways. Interestingly, some peripheral markers of metabolic homeostasis were also improved in animals with near complete loss of ARC Pomc transcription. This suggests that 17α‐E2 might have central and peripheral actions that can beneficially affect metabolism cooperatively or independently.
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Affiliation(s)
- Frederik J. Steyn
- University of Queensland Centre for Clinical Research; Faculty of Medicine Brisbane Qld Australia
- Department of Neurology; Royal Brisbane & Women's Hospital; Brisbane Qld Australia
- Wesley Medical Research; Auchenflower Qld Australia
| | - Shyuan T. Ngo
- University of Queensland Centre for Clinical Research; Faculty of Medicine Brisbane Qld Australia
- Department of Neurology; Royal Brisbane & Women's Hospital; Brisbane Qld Australia
- Wesley Medical Research; Auchenflower Qld Australia
- Australian Institute for Bioengineering and Nanotechnology; University of Queensland; Brisbane Qld Australia
- Queensland Brain Institute; University of Queensland; Brisbane Qld Australia
| | - Vicky Ping Chen
- Robert and Arlene Kogod Center on Aging; Mayo Clinic; Rochester MN USA
| | - Lora C. Bailey-Downs
- Department of Nutritional Sciences; University of Oklahoma Health Sciences Center; Oklahoma City OK USA
| | - Teresa Y. Xie
- School of Biomedical Sciences; The University of Queensland; Brisbane Qld Australia
| | - Martin Ghadami
- School of Biomedical Sciences; The University of Queensland; Brisbane Qld Australia
| | - Stephen Brimijoin
- Robert and Arlene Kogod Center on Aging; Mayo Clinic; Rochester MN USA
| | - Willard M. Freeman
- Department of Physiology; University of Oklahoma Health Sciences Center; Oklahoma City OK USA
- Reynolds Oklahoma Center on Aging; University of Oklahoma Health Sciences Center; Oklahoma City OK USA
- Harold Hamm Diabetes Center; University of Oklahoma Health Sciences Center; Oklahoma City OK USA
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Consejo Nacional de Investigaciones Científicas y Técnicas; Buenos Aires Argentina
- Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires Argentina
- Department of Molecular and Integrative Physiology; University of Michigan Medical School; Ann Arbor MI USA
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology; University of Michigan Medical School; Ann Arbor MI USA
| | - Michael B. Stout
- Department of Nutritional Sciences; University of Oklahoma Health Sciences Center; Oklahoma City OK USA
- Reynolds Oklahoma Center on Aging; University of Oklahoma Health Sciences Center; Oklahoma City OK USA
- Harold Hamm Diabetes Center; University of Oklahoma Health Sciences Center; Oklahoma City OK USA
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21
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Sundaresan S, Meininger CA, Kang AJ, Photenhauer AL, Hayes MM, Sahoo N, Grembecka J, Cierpicki T, Ding L, Giordano TJ, Else T, Madrigal DJ, Low MJ, Campbell F, Baker AM, Xu H, Wright NA, Merchant JL. Gastrin Induces Nuclear Export and Proteasome Degradation of Menin in Enteric Glial Cells. Gastroenterology 2017; 153:1555-1567.e15. [PMID: 28859856 PMCID: PMC5705278 DOI: 10.1053/j.gastro.2017.08.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 07/31/2017] [Accepted: 08/13/2017] [Indexed: 12/21/2022]
Abstract
BACKGROUND & AIMS The multiple endocrine neoplasia, type 1 (MEN1) locus encodes the nuclear protein and tumor suppressor menin. MEN1 mutations frequently cause neuroendocrine tumors such as gastrinomas, characterized by their predominant duodenal location and local metastasis at time of diagnosis. Diffuse gastrin cell hyperplasia precedes the appearance of MEN1 gastrinomas, which develop within submucosal Brunner's glands. We investigated how menin regulates expression of the gastrin gene and induces generation of submucosal gastrin-expressing cell hyperplasia. METHODS Primary enteric glial cultures were generated from the VillinCre:Men1FL/FL:Sst-/- mice or C57BL/6 mice (controls), with or without inhibition of gastric acid by omeprazole. Primary enteric glial cells from C57BL/6 mice were incubated with gastrin and separated into nuclear and cytoplasmic fractions. Cells were incubated with forskolin and H89 to activate or inhibit protein kinase A (a family of enzymes whose activity depends on cellular levels of cyclic AMP). Gastrin was measured in blood, tissue, and cell cultures using an ELISA. Immunoprecipitation with menin or ubiquitin was used to demonstrate post-translational modification of menin. Primary glial cells were incubated with leptomycin b and MG132 to block nuclear export and proteasome activity, respectively. We obtained human duodenal, lymph node, and pancreatic gastrinoma samples, collected from patients who underwent surgery from 1996 through 2007 in the United States or the United Kingdom. RESULTS Enteric glial cells that stained positive for glial fibrillary acidic protein (GFAP+) expressed gastrin de novo through a mechanism that required PKA. Gastrin-induced nuclear export of menin via cholecystokinin B receptor (CCKBR)-mediated activation of PKA. Once exported from the nucleus, menin was ubiquitinated and degraded by the proteasome. GFAP and other markers of enteric glial cells (eg, p75 and S100B), colocalized with gastrin in human duodenal gastrinomas. CONCLUSIONS MEN1-associated gastrinomas, which develop in the submucosa, might arise from enteric glial cells through hormone-dependent PKA signaling. This pathway disrupts nuclear menin function, leading to hypergastrinemia and associated sequelae.
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Affiliation(s)
- Sinju Sundaresan
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Cameron A Meininger
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Anthony J Kang
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Amanda L Photenhauer
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Michael M Hayes
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Nirakar Sahoo
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Jolanta Grembecka
- Department of Pathology, University of Michigan, Ann Arbor, Michigan
| | - Tomasz Cierpicki
- Department of Pathology, University of Michigan, Ann Arbor, Michigan
| | - Lin Ding
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan
| | - Thomas J Giordano
- Department of Pathology, University of Michigan, Ann Arbor, Michigan
| | - Tobias Else
- Division of Metabolism Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan
| | - David J Madrigal
- Endocrine Oncology Program, University of Michigan, Ann Arbor, Michigan
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Fiona Campbell
- Department of Pathology, Royal Liverpool University Hospital, Liverpool, United Kingdom
| | - Ann-Marie Baker
- Center for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Nicholas A Wright
- Center for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Juanita L Merchant
- Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan.
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22
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Zhou Y, Rubinstein M, Low MJ, Kreek MJ. V1b Receptor Antagonist SSR149415 and Naltrexone Synergistically Decrease Excessive Alcohol Drinking in Male and Female Mice. Alcohol Clin Exp Res 2017; 42:195-205. [PMID: 29105118 DOI: 10.1111/acer.13544] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 10/26/2017] [Indexed: 11/30/2022]
Abstract
BACKGROUND A recent clinical trial found that pharmacological blockade of V1b receptors reduces alcohol relapse in alcohol-dependent patients. SSR149415 is a selective V1b receptor antagonist that has potential for development as an alcohol dependency treatment. In this study, we investigated whether SSR149415 alone or in combination with the mu-opioid receptor (MOP-r) antagonist naltrexone (NTN) would alter excessive alcohol drinking in mice. METHODS Both sexes of C57BL/6J (B6) mice were subjected to a chronic intermittent access (IA) drinking paradigm (2-bottle choice, 24-hour access every other day) for 3 weeks. Sucrose and saccharin drinking were used as controls for alcohol-specific drug effects. Neuronal proopiomelanocortin (POMC) enhancer (nPE) knockout mice with hypothalamic-specific loss of POMC (including beta-endorphin, the main endogenous ligand of MOP-r) were used as a genetic control for the effects of NTN. RESULTS Acute administration of SSR149415 (1 to 30 mg/kg) reduced alcohol intake and preference in a dose-dependent manner in both male and female B6 mice after IA. To investigate potential synergistic effects between NTN and SSR149415, we tested 6 different combination doses of SSR149415 and NTN, and found that a combination of SSR149415 (3 mg/kg) and NTN (1 mg/kg) reduced alcohol intake profoundly at doses lower than the individual effective doses in both sexes of B6 mice. We confirmed the effect of SSR149415 on reducing alcohol intake in nPE-/- male mice, consistent with independent mechanisms by which SSR149415 and NTN decrease alcohol drinking. CONCLUSIONS The combination of V1b antagonist SSR149415 with NTN at individual subthreshold doses shows potential in alcoholism treatment, possibly with less adverse effects.
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Affiliation(s)
- Yan Zhou
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, New York
| | | | - Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Mary Jeanne Kreek
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, New York
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23
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Rubinstein M, Low MJ. Molecular and functional genetics of the proopiomelanocortin gene, food intake regulation and obesity. FEBS Lett 2017; 591:2593-2606. [PMID: 28771698 PMCID: PMC9975356 DOI: 10.1002/1873-3468.12776] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/31/2017] [Accepted: 07/31/2017] [Indexed: 12/20/2022]
Abstract
A specter is haunting the world, the specter of obesity. During the last decade, this pandemia has skyrocketed threatening children, adolescents and lower income families worldwide. Although driven by an increase in the consumption of ultraprocessed edibles of poor nutritional value, the obesogenic changes in contemporary human lifestyle affect people differently, revealing that some individuals are more prone to develop increased adiposity. During the last years, we performed a variety of genetic, evolutionary, biochemical and behavioral experiments that allowed us to understand how a group of neurons present in the arcuate nucleus of the hypothalamus regulate the expression of the proopiomelanocortin (Pomc) gene and induce satiety. We disentangled the neuronal transcriptional code of Pomc by identifying the cis-acting regulatory elements and primary transcription factors controlling hypothalamic Pomc expression and determined their functional importance in the regulation of food intake and adiposity. Altogether, our studies reviewed here shed light on the power and limitations of the mammalian central satiety pathways and may contribute to the development of individual and collective strategies to reduce the debilitating effects of the self-induced obesity pandemia.
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Affiliation(s)
- Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina,Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina,Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA,Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
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24
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Burke LK, Ogunnowo-Bada E, Georgescu T, Cristiano C, de Morentin PBM, Valencia Torres L, D'Agostino G, Riches C, Heeley N, Ruan Y, Rubinstein M, Low MJ, Myers MG, Rochford JJ, Evans ML, Heisler LK. Lorcaserin improves glycemic control via a melanocortin neurocircuit. Mol Metab 2017; 6:1092-1102. [PMID: 29031711 PMCID: PMC5641625 DOI: 10.1016/j.molmet.2017.07.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 07/05/2017] [Accepted: 07/10/2017] [Indexed: 02/07/2023] Open
Abstract
Objective The increasing prevalence of type 2 diabetes (T2D) and associated morbidity and mortality emphasizes the need for a more complete understanding of the mechanisms mediating glucose homeostasis to accelerate the identification of new medications. Recent reports indicate that the obesity medication lorcaserin, a 5-hydroxytryptamine (5-HT, serotonin) 2C receptor (5-HT2CR) agonist, improves glycemic control in association with weight loss in obese patients with T2D. Here we evaluate whether lorcaserin has an effect on glycemia without body weight loss and how this effect is achieved. Methods Murine models of common and genetic T2D were utilized to probe the direct effect of lorcaserin on glycemic control. Results Lorcaserin dose-dependently improves glycemic control in mouse models of T2D in the absence of reductions in food intake or body weight. Examining the mechanism of this effect, we reveal a necessary and sufficient neurochemical mediator of lorcaserin's glucoregulatory effects, brain pro-opiomelanocortin (POMC) peptides. To clarify further lorcaserin's therapeutic brain circuit, we examined the receptor target of POMC peptides. We demonstrate that lorcaserin requires functional melanocortin4 receptors on cholinergic preganglionic neurons (MC4RChAT) to exert its effects on glucose homeostasis. In contrast, MC4RChAT signaling did not impact lorcaserin's effects on feeding, indicating a divergence in the neurocircuitry underpinning lorcaserin's therapeutic glycemic and anorectic effects. Hyperinsulinemic-euglycemic clamp studies reveal that lorcaserin reduces hepatic glucose production, increases glucose disposal and improves insulin sensitivity. Conclusions These data suggest that lorcaserin's action within the brain represents a mechanistically novel treatment for T2D: findings of significance to a prevalent global disease. Obesity medication lorcaserin directly improves glycemic control without altering energy balance or body weight. Unlike current frontline type 2 diabetes medications, lorcaserin acts within the brain to improve glycemic control. Brain Pro-opiomelanocortin (POMC) peptides are a neurochemical mediator of lorcaserin's glucoregulatory effects. Lorcaserin increases insulin sensitivity, reduces hepatic glucose production and increases glucose disposal.
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Affiliation(s)
- Luke K Burke
- Department of Pharmacology, University of Cambridge, Cambridge, UK; Department of Medicine and Wellcome Trust/MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Emmanuel Ogunnowo-Bada
- Department of Medicine and Wellcome Trust/MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | | | | | | | - Lourdes Valencia Torres
- Department of Pharmacology, University of Cambridge, Cambridge, UK; The Rowett Institute, University of Aberdeen, Aberdeen, UK
| | - Giuseppe D'Agostino
- Department of Pharmacology, University of Cambridge, Cambridge, UK; The Rowett Institute, University of Aberdeen, Aberdeen, UK
| | - Christine Riches
- Department of Medicine and Wellcome Trust/MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Nicholas Heeley
- Department of Medicine and Wellcome Trust/MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Yue Ruan
- Department of Medicine and Wellcome Trust/MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Martin G Myers
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | | | - Mark L Evans
- Department of Medicine and Wellcome Trust/MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK.
| | - Lora K Heisler
- Department of Pharmacology, University of Cambridge, Cambridge, UK; The Rowett Institute, University of Aberdeen, Aberdeen, UK.
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25
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Chhabra KH, Morgan DA, Tooke BP, Adams JM, Rahmouni K, Low MJ. Reduced renal sympathetic nerve activity contributes to elevated glycosuria and improved glucose tolerance in hypothalamus-specific Pomc knockout mice. Mol Metab 2017; 6:1274-1285. [PMID: 29031726 PMCID: PMC5641634 DOI: 10.1016/j.molmet.2017.07.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 07/02/2017] [Accepted: 07/10/2017] [Indexed: 11/11/2022] Open
Abstract
Objective Hypothalamic arcuate nucleus-specific pro-opiomelanocortin deficient (ArcPomc−/−) mice exhibit improved glucose tolerance despite massive obesity and insulin resistance. We demonstrated previously that their improved glucose tolerance is due to elevated glycosuria. However, the underlying mechanisms that link glucose reabsorption in the kidney with ArcPomc remain unclear. Given the function of the hypothalamic melanocortin system in controlling sympathetic outflow, we hypothesized that reduced renal sympathetic nerve activity (RSNA) in ArcPomc−/− mice could explain their elevated glycosuria and consequent enhanced glucose tolerance. Methods We measured RSNA by multifiber recording directly from the nerves innervating the kidneys in ArcPomc−/− mice. To further validate the function of RSNA in glucose reabsorption, we denervated the kidneys of WT and diabetic db/db mice before measuring their glucose tolerance and urine glucose levels. Moreover, we performed western blot and immunohistochemistry to determine kidney GLUT2 and SGLT2 levels in either ArcPomc−/− mice or the renal-denervated mice. Results Consistent with our hypothesis, we found that basal RSNA was decreased in ArcPomc−/− mice relative to their wild type (WT) littermates. Remarkably, both WT and db/db mice exhibited elevated glycosuria and improved glucose tolerance after renal denervation. The elevated glycosuria in obese ArcPomc−/−, WT and db/db mice was due to reduced renal GLUT2 levels in the proximal tubules. Overall, we show that renal-denervated WT and diabetic mice recapitulate the phenotype of improved glucose tolerance and elevated glycosuria associated with reduced renal GLUT2 levels observed in obese ArcPomc−/− mice. Conclusion Hence, we conclude that ArcPomc is essential in maintaining basal RSNA and that elevated glycosuria is a possible mechanism to explain improved glucose tolerance after renal denervation in drug resistant hypertensive patients. Hypothalamic POMC is essential in maintaining basal renal sympathetic nerve activity. Renal denervation improves glucose tolerance in wild-type and db/db mice by elevating their glycosuria. Decreased renal GLUT2 is responsible for elevated glycosuria in mice with suppressed renal sympathetic nerve activity.
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Affiliation(s)
- Kavaljit H Chhabra
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Donald A Morgan
- Department of Pharmacology, University of Iowa, Iowa City, IA, USA
| | - Benjamin P Tooke
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Case Western Reserve University, Cleveland, OH, USA
| | - Jessica M Adams
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Kamal Rahmouni
- Department of Pharmacology, University of Iowa, Iowa City, IA, USA
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA.
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Zhou Y, Rubinstein M, Low MJ, Kreek MJ. Hypothalamic-specific proopiomelanocortin deficiency reduces alcohol drinking in male and female mice. Genes Brain Behav 2017; 16:449-461. [PMID: 27870313 DOI: 10.1111/gbb.12362] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 11/07/2016] [Accepted: 11/16/2016] [Indexed: 01/21/2023]
Abstract
Opioid receptor antagonist naltrexone reduces alcohol consumption and relapse in both humans and rodents. This study investigated whether hypothalamic proopiomelanocortin (POMC) neurons (producing beta-endorphin and melanocortins) play a role in alcohol drinking behaviors. Both male and female mice with targeted deletion of two neuronal Pomc enhancers nPE1 and nPE2 (nPE-/-), resulting in hypothalamic-specific POMC deficiency, were studied in short-access (4-h/day) drinking-in-the-dark (DID, alcohol in one bottle, intermittent access (IA, 24-h cycles of alcohol access every other day, alcohol vs. water in a two-bottle choice) and alcohol deprivation effect (ADE) models. Wild-type nPE+/+ exposed to 1-week DID rapidly established stable alcohol drinking behavior with more intake in females, whereas nPE-/- mice of both sexes had less intake and less preference. Although nPE-/- showed less saccharin intake and preference than nPE+/+, there was no genotype difference in sucrose intake or preference in the DID paradigm. After 3-week IA, nPE+/+ gradually escalated to high alcohol intake and preference, with more intake in females, whereas nPE-/- showed less escalation. Pharmacological blockade of mu-opioid receptors with naltrexone reduced intake in nPE+/+ in a dose-dependent manner, but had blunted effects in nPE-/- of both sexes. When alcohol was presented again after 1-week abstinence from IA, nPE+/+ of both sexes displayed significant increases in alcohol intake (ADE or relapse-like drinking), with more pronounced ADE in females, whereas nPE-/- did not show ADE in either sex. Our results suggest that neuronal POMC is involved in modulation of alcohol 'binge' drinking, escalation and 'relapse', probably via hypothalamic-mediated mechanisms, with sex differences.
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Affiliation(s)
- Y Zhou
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
| | - M Rubinstein
- INGEBI/CONICET, University of Buenos Aires, Buenos Aires, Argentina
| | - M J Low
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - M J Kreek
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
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Affiliation(s)
- Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, 6116 Brehm Tower, 1000 Wall Street, Ann Arbor, Michigan 48105, USA
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Chhabra KH, Adams JM, Jones GL, Yamashita M, Schlapschy M, Skerra A, Rubinstein M, Low MJ. Reprogramming the body weight set point by a reciprocal interaction of hypothalamic leptin sensitivity and Pomc gene expression reverts extreme obesity. Mol Metab 2016; 5:869-881. [PMID: 27689000 PMCID: PMC5034612 DOI: 10.1016/j.molmet.2016.07.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 07/29/2016] [Indexed: 12/26/2022] Open
Abstract
Objective A major challenge for obesity treatment is the maintenance of reduced body weight. Diet-induced obese mice are resistant to achieving normoweight once the obesogenic conditions are reversed, in part because lowered circulating leptin leads to a reduction in metabolic rate and a rebound of hyperphagia that defend the previously elevated body weight set point. Because hypothalamic POMC is a central leptin target, we investigated whether changes in circulating leptin modify Pomc expression to maintain normal energy balance in genetically predisposed obese mice. Methods Mice with reversible Pomc silencing in the arcuate nucleus (ArcPomc−/−) become morbidly obese eating low-fat chow. We measured body composition, food intake, plasma leptin, and leptin sensitivity in ArcPomc−/− mice weight-matched to littermate controls by calorie restriction, either from weaning or after developing obesity. Pomc was reactivated by tamoxifen-dependent Cre recombinase transgenes. Long acting PASylated leptin was administered to weight-reduced ArcPomc−/− mice to mimic the super-elevated leptin levels of obese mice. Results ArcPomc−/− mice had increased adiposity and leptin levels shortly after weaning. Despite chronic calorie restriction to achieve normoweight, ArcPomc−/− mice remained moderately hyperleptinemic and resistant to exogenous leptin's effects to reduce weight and food intake. However, subsequent Pomc reactivation in weight-matched ArcPomc−/− mice normalized plasma leptin, leptin sensitivity, adiposity, and food intake. In contrast, extreme hyperleptinemia induced by PASylated leptin blocked the full restoration of hypothalamic Pomc expression in calorie restricted ArcPomc−/− mice, which consequently regained 30% of their lost body weight and attained a metabolic steady state similar to that of tamoxifen treated obese ArcPomc−/− mice. Conclusions Pomc reactivation in previously obese, calorie-restricted ArcPomc−/− mice normalized energy homeostasis, suggesting that their body weight set point was restored to control levels. In contrast, massively obese and hyperleptinemic ArcPomc−/− mice or those weight-matched and treated with PASylated leptin to maintain extreme hyperleptinemia prior to Pomc reactivation converged to an intermediate set point relative to lean control and obese ArcPomc−/− mice. We conclude that restoration of hypothalamic leptin sensitivity and Pomc expression is necessary for obese ArcPomc−/− mice to achieve and sustain normal metabolic homeostasis; whereas deficits in either parameter set a maladaptive allostatic balance that defends increased adiposity and body weight. Hypothalamic POMC-deficiency increases adiposity and induces leptin resistance. PASylated leptin blocks the normalization of Pomc expression, weight and adiposity. Interactions of leptin sensitivity and Pomc expression dictate body weight set point.
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Affiliation(s)
- Kavaljit H Chhabra
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jessica M Adams
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Graham L Jones
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Miho Yamashita
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Martin Schlapschy
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85354 Freising (Weihenstephan), Germany
| | - Arne Skerra
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85354 Freising (Weihenstephan), Germany
| | - Marcelo Rubinstein
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina; Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA.
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Omary MB, Cohen DE, El-Omar EM, Jalan R, Low MJ, Nathanson MH, Peek RM, Turner JR. Not All Mice Are the Same: Standardization of Animal Research Data Presentation. Cell Mol Gastroenterol Hepatol 2016; 2:391-393. [PMID: 28174724 PMCID: PMC5042602 DOI: 10.1016/j.jcmgh.2016.04.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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Omary MB, Cohen DE, El-Omar EM, Jalan R, Low MJ, Nathanson MH, Peek RM, Turner JR. Not All Mice Are the Same: Standardization of Animal Research Data Presentation. Gastroenterology 2016; 150:1503-1504. [PMID: 27063865 DOI: 10.1053/j.gastro.2016.03.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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Omary MB, Cohen DE, El-Omar EM, Jalan R, Low MJ, Nathanson MH, Peek RM, Turner JR. Not all mice are the same: Standardization of animal research data presentation. Hepatology 2016; 63:1752-4. [PMID: 27205897 DOI: 10.1002/hep.28608] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 04/20/2016] [Indexed: 12/07/2022]
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Orquera DP, Nasif S, Low MJ, Rubinstein M, de Souza FSJ. Essential function of the transcription factor Rax in the early patterning of the mammalian hypothalamus. Dev Biol 2016; 416:212-224. [PMID: 27212025 DOI: 10.1016/j.ydbio.2016.05.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 05/08/2016] [Accepted: 05/16/2016] [Indexed: 12/31/2022]
Abstract
The hypothalamus is a region of the anterior forebrain that controls basic aspects of vertebrate physiology, but the genes involved in its development are still poorly understood. Here, we investigate the function of the homeobox gene Rax/Rx in early hypothalamic development using a conditional targeted inactivation strategy in the mouse. We found that lack of Rax expression prior to embryonic day 8.5 (E8.5) caused a general underdevelopment of the hypothalamic neuroepithelium, while inactivation at later timepoints had little effect. The early absence of Rax impaired neurogenesis and prevented the expression of molecular markers of the dorsomedial hypothalamus, including neuropeptides Proopiomelanocortin and Somatostatin. Interestingly, the expression domains of genes expressed in the ventromedial hypothalamus and infundibulum invaded dorsal hypothalamic territory, showing that Rax is needed for the proper dorsoventral patterning of the developing medial hypothalamus. The phenotypes caused by the early loss of Rax are similar to those of eliminating the expression of the morphogen Sonic hedgehog (Shh) specifically from the hypothalamus. Consistent with this similarity in phenotypes, we observed that Shh and Rax are coexpressed in the rostral forebrain at late head fold stages and that loss of Rax caused a downregulation of Shh expression in the dorsomedial portion of the hypothalamus.
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Affiliation(s)
- Daniela P Orquera
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina
| | - Sofia Nasif
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48105, United States
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48105, United States; Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina.
| | - Flávio S J de Souza
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina; Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina.
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Chhabra KH, Adams JM, Fagel B, Lam DD, Qi N, Rubinstein M, Low MJ. Hypothalamic POMC Deficiency Improves Glucose Tolerance Despite Insulin Resistance by Increasing Glycosuria. Diabetes 2016; 65:660-72. [PMID: 26467632 PMCID: PMC4764146 DOI: 10.2337/db15-0804] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/07/2015] [Indexed: 12/18/2022]
Abstract
Hypothalamic proopiomelanocortin (POMC) is essential for the physiological regulation of energy balance; however, its role in glucose homeostasis remains less clear. We show that hypothalamic arcuate nucleus (Arc)POMC-deficient mice, which develop severe obesity and insulin resistance, unexpectedly exhibit improved glucose tolerance and remain protected from hyperglycemia. To explain these paradoxical phenotypes, we hypothesized that an insulin-independent pathway is responsible for the enhanced glucose tolerance. Indeed, the mutant mice demonstrated increased glucose effectiveness and exaggerated glycosuria relative to wild-type littermate controls at comparable blood glucose concentrations. Central administration of the melanocortin receptor agonist melanotan II in mutant mice reversed alterations in glucose tolerance and glycosuria, whereas, conversely, administration of the antagonist Agouti-related peptide (Agrp) to wild-type mice enhanced glucose tolerance. The glycosuria of ArcPOMC-deficient mice was due to decreased levels of renal GLUT 2 (rGLUT2) but not sodium-glucose cotransporter 2 and was associated with reduced renal catecholamine content. Epinephrine treatment abolished the genotype differences in glucose tolerance and rGLUT2 levels, suggesting that reduced renal sympathetic nervous system (SNS) activity is the underlying mechanism for the observed glycosuria and improved glucose tolerance in ArcPOMC-deficient mice. Therefore, the ArcPOMC-SNS-rGLUT2 axis is potentially an insulin-independent therapeutic target to control diabetes.
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Affiliation(s)
- Kavaljit H Chhabra
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
| | - Jessica M Adams
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI
| | - Brian Fagel
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
| | - Daniel D Lam
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
| | - Nathan Qi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Marcelo Rubinstein
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, and Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
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Burke LK, Doslikova B, D'Agostino G, Greenwald-Yarnell M, Georgescu T, Chianese R, Martinez de Morentin PB, Ogunnowo-Bada E, Cansell C, Valencia-Torres L, Garfield AS, Apergis-Schoute J, Lam DD, Speakman JR, Rubinstein M, Low MJ, Rochford JJ, Myers MG, Evans ML, Heisler LK. Sex difference in physical activity, energy expenditure and obesity driven by a subpopulation of hypothalamic POMC neurons. Mol Metab 2016; 5:245-252. [PMID: 26977396 PMCID: PMC4770275 DOI: 10.1016/j.molmet.2016.01.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Revised: 01/12/2016] [Accepted: 01/14/2016] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE Obesity is one of the primary healthcare challenges of the 21st century. Signals relaying information regarding energy needs are integrated within the brain to influence body weight. Central among these integration nodes are the brain pro-opiomelanocortin (POMC) peptides, perturbations of which disrupt energy balance and promote severe obesity. However, POMC neurons are neurochemically diverse and the crucial source of POMC peptides that regulate energy homeostasis and body weight remains to be fully clarified. METHODS Given that a 5-hydroxytryptamine 2c receptor (5-HT2CR) agonist is a current obesity medication and 5-HT2CR agonist's effects on appetite are primarily mediated via POMC neurons, we hypothesized that a critical source of POMC regulating food intake and body weight is specifically synthesized in cells containing 5-HT2CRs. To exclusively manipulate Pomc synthesis only within 5-HT2CR containing cells, we generated a novel 5-HT 2C R (CRE) mouse line and intercrossed it with Cre recombinase-dependent and hypothalamic specific reactivatable Pomc (NEO) mice to restrict Pomc synthesis to the subset of hypothalamic cells containing 5-HT2CRs. This provided a means to clarify the specific contribution of a defined subgroup of POMC peptides in energy balance and body weight. RESULTS Here we transform genetically programed obese and hyperinsulinemic male mice lacking hypothalamic Pomc with increased appetite, reduced physical activity and compromised brown adipose tissue (BAT) into lean, healthy mice via targeted restoration of Pomc function only within 5-HT2CR expressing cells. Remarkably, the same metabolic transformation does not occur in females, who despite corrected feeding behavior and normalized insulin levels remain physically inactive, have lower energy expenditure, compromised BAT and develop obesity. CONCLUSIONS These data provide support for the functional heterogeneity of hypothalamic POMC neurons, revealing that Pomc expression within 5-HT2CR expressing neurons is sufficient to regulate energy intake and insulin sensitivity in male and female mice. However, an unexpected sex difference in the function of this subset of POMC neurons was identified with regard to energy expenditure. We reveal that a large sex difference in physical activity, energy expenditure and the development of obesity is driven by this subpopulation, which constitutes approximately 40% of all POMC neurons in the hypothalamic arcuate nucleus. This may have broad implications for strategies utilized to combat obesity, which at present largely ignore the sex of the obese individual.
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Affiliation(s)
- Luke K Burke
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK; Department of Medicine and Institute of Metabolic Science, University of Cambridge, Wellcome Trust/Medical Research Council, Cambridge, UK; Department of Pharmacology, University of Cambridge, Cambridge, UK
| | | | - Giuseppe D'Agostino
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK; Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Megan Greenwald-Yarnell
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Teodora Georgescu
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - Raffaella Chianese
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | | | - Emmanuel Ogunnowo-Bada
- Department of Medicine and Institute of Metabolic Science, University of Cambridge, Wellcome Trust/Medical Research Council, Cambridge, UK
| | - Celine Cansell
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - Lourdes Valencia-Torres
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK; Department of Pharmacology, University of Cambridge, Cambridge, UK
| | | | | | - Daniel D Lam
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - John R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK; State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428, Buenos Aires, Argentina
| | - Malcolm J Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Justin J Rochford
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - Martin G Myers
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Mark L Evans
- Department of Medicine and Institute of Metabolic Science, University of Cambridge, Wellcome Trust/Medical Research Council, Cambridge, UK.
| | - Lora K Heisler
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK.
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Deng Q, Riquelme D, Trinh L, Low MJ, Tomić M, Stojilkovic S, Aguilera G. Rapid Glucocorticoid Feedback Inhibition of ACTH Secretion Involves Ligand-Dependent Membrane Association of Glucocorticoid Receptors. Endocrinology 2015; 156:3215-27. [PMID: 26121342 PMCID: PMC4541620 DOI: 10.1210/en.2015-1265] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The hypothesis that rapid glucocorticoid inhibition of pituitary ACTH secretion mediates a feedforward/feedback mechanism responsible for the hourly glucocorticoid pulsatility was tested in cultured pituitary cells. Perifusion with 30 pM CRH caused sustained the elevation of ACTH secretion. Superimposed corticosterone pulses inhibited CRH-stimulated ACTH release, depending on prior glucocorticoid clearance. When CRH perifusion started after 2 hours of glucocorticoid-free medium, corticosterone levels in the stress range (1 μM) caused a delayed (25 min) and prolonged inhibition of CRH-stimulated ACTH secretion, up to 60 minutes after corticosterone withdrawal. In contrast, after 6 hours of glucocorticoid-free medium, basal corticosterone levels inhibited CRH-stimulated ACTH within 5 minutes, after rapid recovery 5 minutes after corticosterone withdrawal. The latter effect was insensitive to actinomycin D but was prevented by the glucocorticoid receptor antagonist, RU486, suggesting nongenomic effects of the classical glucocorticoid receptor. In hypothalamic-derived 4B cells, 10 nM corticosterone increased immunoreactive glucocorticoid receptor content in membrane fractions, with association and clearance rates paralleling the effects on ACTH secretion from corticotrophs. Corticosterone did not affect CRH-stimulated calcium influx, but in AtT-20 cells, it had biphasic effects on CRH-stimulated Src phosphorylation, with early inhibition and late stimulation, suggesting a role for Src phosphorylation on the rapid glucocorticoid feedback. The data suggest that the nongenomic/membrane effects of classical GR mediate rapid and reversible glucocorticoid feedback inhibition at the pituitary corticotrophs downstream of calcium influx. The sensitivity and kinetics of these effects is consistent with the hypothesis that pituitary glucocorticoid feedback is part of the mechanism for adrenocortical ultradian pulse generation.
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Affiliation(s)
- Qiong Deng
- Sections on Endocrine Physiology (Q.D., D.R., L.T., G.A.) and Cellular Signaling (M.T., S.S.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; College of Animal Sciences (Q.D.), Jilin University, Chang Chun 130021, China; and Department of Molecular and Integrative Physiology (M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Denise Riquelme
- Sections on Endocrine Physiology (Q.D., D.R., L.T., G.A.) and Cellular Signaling (M.T., S.S.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; College of Animal Sciences (Q.D.), Jilin University, Chang Chun 130021, China; and Department of Molecular and Integrative Physiology (M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Loc Trinh
- Sections on Endocrine Physiology (Q.D., D.R., L.T., G.A.) and Cellular Signaling (M.T., S.S.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; College of Animal Sciences (Q.D.), Jilin University, Chang Chun 130021, China; and Department of Molecular and Integrative Physiology (M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Malcolm J Low
- Sections on Endocrine Physiology (Q.D., D.R., L.T., G.A.) and Cellular Signaling (M.T., S.S.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; College of Animal Sciences (Q.D.), Jilin University, Chang Chun 130021, China; and Department of Molecular and Integrative Physiology (M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Melanija Tomić
- Sections on Endocrine Physiology (Q.D., D.R., L.T., G.A.) and Cellular Signaling (M.T., S.S.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; College of Animal Sciences (Q.D.), Jilin University, Chang Chun 130021, China; and Department of Molecular and Integrative Physiology (M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Stanko Stojilkovic
- Sections on Endocrine Physiology (Q.D., D.R., L.T., G.A.) and Cellular Signaling (M.T., S.S.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; College of Animal Sciences (Q.D.), Jilin University, Chang Chun 130021, China; and Department of Molecular and Integrative Physiology (M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Greti Aguilera
- Sections on Endocrine Physiology (Q.D., D.R., L.T., G.A.) and Cellular Signaling (M.T., S.S.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892; College of Animal Sciences (Q.D.), Jilin University, Chang Chun 130021, China; and Department of Molecular and Integrative Physiology (M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan 48109
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Lam DD, Attard CA, Mercer AJ, Myers MG, Rubinstein M, Low MJ. Conditional expression of Pomc in the Lepr-positive subpopulation of POMC neurons is sufficient for normal energy homeostasis and metabolism. Endocrinology 2015; 156:1292-302. [PMID: 25594696 PMCID: PMC4399319 DOI: 10.1210/en.2014-1373] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Peptides derived from the proopiomelanocortin (POMC) precursor are critical for the normal regulation of many physiological parameters, and POMC deficiency results in severe obesity and metabolic dysfunction. Conversely, augmentation of central nervous system melanocortin function is a promising therapeutic avenue for obesity and diabetes but is confounded by detrimental cardiovascular effects including hypertension. Because the hypothalamic population of POMC-expressing neurons is neurochemically and neuroanatomically heterogeneous, there is interest in the possible dissociation of functionally distinct POMC neuron subpopulations. We used a Cre recombinase-dependent and hypothalamus-specific reactivatable PomcNEO allele to restrict Pomc expression to hypothalamic neurons expressing leptin receptor (Lepr) in mice. In contrast to mice with total hypothalamic Pomc deficiency, which are severely obese, mice with Lepr-restricted Pomc expression displayed fully normal body weight, food consumption, glucose homeostasis, and locomotor activity. Thus, Lepr+ POMC neurons, which constitute approximately two-thirds of the total POMC neuron population, are sufficient for normal regulation of these parameters. This functional dissociation approach represents a promising avenue for isolating therapeutically relevant POMC neuron subpopulations.
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Affiliation(s)
- Daniel D Lam
- Department of Molecular and Integrative Physiology (D.D.L., C.A.A., A.J.M., M.R., M.J.L.), and Department of Internal Medicine (M.G.M.), Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105; and Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (M.R.), Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
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Adams JM, Otero-Corchon V, Hammond GL, Veldhuis JD, Qi N, Low MJ. Somatostatin is essential for the sexual dimorphism of GH secretion, corticosteroid-binding globulin production, and corticosterone levels in mice. Endocrinology 2015; 156:1052-65. [PMID: 25551181 PMCID: PMC4330306 DOI: 10.1210/en.2014-1429] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Distinct male and female patterns of pituitary GH secretion produce sexually differentiated hepatic gene expression profiles, thereby influencing steroid and xenobiotic metabolism. We used a fully automated system to obtain serial nocturnal blood samples every 15 minutes from cannulated wild-type (WT) and somatostatin knockout (Sst-KO) mice to determine the role of SST, the principal inhibitor of GH release, in the generation of sexually dimorphic GH pulsatility. WT males had lower mean and median GH values, less random GH secretory bursts, and longer trough periods between GH pulses than WT females. Each of these parameters was feminized in male Sst-KO mice, whereas female Sst-KO mice had higher GH levels than all other groups, but GH pulsatility was unaffected. We next performed hepatic mRNA profiling with high-density microarrays. Male Sst-KO mice exhibited a globally feminized pattern of GH-dependent mRNA levels, but female Sst-KO mice were largely unaffected. Among the differentially expressed female-predominant genes was Serpina6, which encodes corticosteroid-binding globulin (CBG). Increased CBG was associated with elevated diurnal peak plasma corticosterone in unstressed WT females and both sexes of Sst-KO mice compared with WT males. Sst-KO mice also had exaggerated ACTH and corticosterone responses to acute restraint stress. However, consistent with their lack of phenotypic signs of excess glucocorticoids, cerebrospinal fluid concentrations of free corticosterone in Sst-KO mice were not elevated. In summary, SST is necessary for the prolonged interpulse troughs that define masculinized pituitary GH secretion. SST also contributes to sexual dimorphism of the hypothalamic-pituitary-adrenal axis via GH-dependent regulation of hepatic CBG production.
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Affiliation(s)
- Jessica M Adams
- Neuroscience Graduate Program (J.M.A.), University of Michigan, Ann Arbor, Michigan, 48109; Department of Molecular and Integrative Physiology (J.M.A., V.O.-C., M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan, 48109; Department of Cellular and Physiological Sciences (G.L.H.), University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3; Department of Internal Medicine (J.D.V.), Endocrine Research Unit, Mayo Clinic College of Medicine, Rochester, Minnesota, 55905; and Department of Internal Medicine (N.Q., M.J.L.), Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, 48109
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Lam DD, de Souza FSJ, Nasif S, Yamashita M, López-Leal R, Otero-Corchon V, Meece K, Sampath H, Mercer AJ, Wardlaw SL, Rubinstein M, Low MJ. Partially redundant enhancers cooperatively maintain Mammalian pomc expression above a critical functional threshold. PLoS Genet 2015; 11:e1004935. [PMID: 25671638 PMCID: PMC4335486 DOI: 10.1371/journal.pgen.1004935] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 12/02/2014] [Indexed: 11/29/2022] Open
Abstract
Cell-specific expression of many genes is conveyed by multiple enhancers, with each individual enhancer controlling a particular expression domain. In contrast, multiple enhancers drive similar expression patterns of some genes involved in embryonic development, suggesting regulatory redundancy. Work in Drosophila has indicated that functionally overlapping enhancers canalize development by buffering gene expression against environmental and genetic disturbances. However, little is known about regulatory redundancy in vertebrates and in genes mainly expressed during adulthood. Here we study nPE1 and nPE2, two phylogenetically conserved mammalian enhancers that drive expression of the proopiomelanocortin gene (Pomc) to the same set of hypothalamic neurons. The simultaneous deletion of both enhancers abolished Pomc expression at all ages and induced a profound metabolic dysfunction including early-onset extreme obesity. Targeted inactivation of either nPE1 or nPE2 led to very low levels of Pomc expression during early embryonic development indicating that both enhancers function synergistically. In adult mice, however, Pomc expression is controlled additively by both enhancers, with nPE1 being responsible for ∼80% and nPE2 for ∼20% of Pomc transcription. Consequently, nPE1 knockout mice exhibit mild obesity whereas nPE2-deficient mice maintain a normal body weight. These results suggest that nPE2-driven Pomc expression is compensated by nPE1 at later stages of development, essentially rescuing the earlier phenotype of nPE2 deficiency. Together, these results reveal that cooperative interactions between the enhancers confer robustness of Pomc expression against gene regulatory disturbances and preclude deleterious metabolic phenotypes caused by Pomc deficiency in adulthood. Thus, our study demonstrates that enhancer redundancy can be used by genes that control adult physiology in mammals and underlines the potential significance of regulatory sequence mutations in common diseases. The stability of animal form and function in the face of genetic and environmental variation relies on consistent gene expression. Multiple enhancers, each specifying a unique regulatory domain, control the precise spatiotemporal expression of many genes. However, in some genes apparently redundant enhancers regulate expression in overlapping cell-specific patterns. Although this arrangement has been shown to be important for developmental robustness in invertebrates, the role of apparently redundant enhancers in vertebrate species and in genes functioning in adulthood is poorly understood. Here, we show that expression of the mammalian Pomc gene is controlled in a tissue-specific manner by two such apparently redundant enhancers. We used targeted deletion of the individual enhancers to delineate their respective contributions to Pomc expression in the brain. Since Pomc expression from its intact locus exceeds the sum of the individual enhancer contributions to Pomc mRNA levels in embryonic mice, we infer a synergistic action between the enhancers during development. In contrast, the interaction between the enhancers is additive in adult mice. Deletion of both enhancers simultaneously almost completely abolished Pomc expression and the mutant mice displayed extreme obesity and metabolic dysfunction, while deletion of the individual enhancers had a modest or no phenotypic effect. Together, our results demonstrate that the two enhancers cooperatively maintain Pomc expression above a critical functional threshold.
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Affiliation(s)
- Daniel D. Lam
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Flavio S. J. de Souza
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Sofia Nasif
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Miho Yamashita
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | | | - Veronica Otero-Corchon
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Kana Meece
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Harini Sampath
- Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Aaron J. Mercer
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Sharon L. Wardlaw
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Marcelo Rubinstein
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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Burke LK, Doslikova B, D'Agostino G, Garfield AS, Farooq G, Burdakov D, Low MJ, Rubinstein M, Evans ML, Billups B, Heisler LK. 5-HT obesity medication efficacy via POMC activation is maintained during aging. Endocrinology 2014; 155:3732-8. [PMID: 25051442 PMCID: PMC4164923 DOI: 10.1210/en.2014-1223] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The phenomenon commonly described as the middle-age spread is the result of elevated adiposity accumulation throughout adulthood until late middle-age. It is a clinical imperative to gain a greater understanding of the underpinnings of age-dependent obesity and, in turn, how these mechanisms may impact the efficacy of obesity treatments. In particular, both obesity and aging are associated with rewiring of a principal brain pathway modulating energy homeostasis, promoting reduced activity of satiety pro-opiomelanocortin (POMC) neurons within the arcuate nucleus of the hypothalamus (ARC). Using a selective ARC-deficient POMC mouse line, here we report that former obesity medications augmenting endogenous 5-hydroxytryptamine (5-HT) activity d-fenfluramine and sibutramine require ARC POMC neurons to elicit therapeutic appetite-suppressive effects. We next investigated whether age-related diminished ARC POMC activity therefore impacts the potency of 5-HT obesity pharmacotherapies, lorcaserin, d-fenfluramine, and sibutramine and report that all compounds reduced food intake to a comparable extent in both chow-fed young lean (3-5 months old) and middle-aged obese (12-14 months old) male and female mice. We provide a mechanism through which 5-HT anorectic potency is maintained with age, via preserved 5-HT-POMC appetitive anatomical machinery. Specifically, the abundance and signaling of the primary 5-HT receptor influencing appetite via POMC activation, the 5-HT2CR, is not perturbed with age. These data reveal that although 5-HT obesity medications require ARC POMC neurons to achieve appetitive effects, the anorectic efficacy is maintained with aging, findings of clinical significance to the global aging obese population.
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Affiliation(s)
- Luke K Burke
- Department of Pharmacology (L.K.B., B.D., G.D., A.S.G., G.F., D.B., B.B., L.K.H.) and Wellcome Trust/Medical Research Council Institute of Metabolic Science (M.L.E.), University of Cambridge, Cambridge, CB2 0QQ, United Kingdom; Rowett Institute of Nutrition and Health (G.D., L.K.H.), University of Aberdeen, Aberdeen, AB21 9SB, United Kingdom; Department of Molecular and Integrative Physiology (M.J.L., M.R.), University of Michigan Medical School, Ann Arbor, Michigan 48105; and Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (M.R.), Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina
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Hu J, Jiang L, Low MJ, Rui L. Glucose rapidly induces different forms of excitatory synaptic plasticity in hypothalamic POMC neurons. PLoS One 2014; 9:e105080. [PMID: 25127258 PMCID: PMC4134273 DOI: 10.1371/journal.pone.0105080] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 07/17/2014] [Indexed: 12/21/2022] Open
Abstract
Hypothalamic POMC neurons are required for glucose and energy homeostasis. POMC neurons have a wide synaptic connection with neurons both within and outside the hypothalamus, and their activity is controlled by a balance between excitatory and inhibitory synaptic inputs. Brain glucose-sensing plays an essential role in the maintenance of normal body weight and metabolism; however, the effect of glucose on synaptic transmission in POMC neurons is largely unknown. Here we identified three types of POMC neurons (EPSC(+), EPSC(-), and EPSC(+/-)) based on their glucose-regulated spontaneous excitatory postsynaptic currents (sEPSCs), using whole-cell patch-clamp recordings. Lowering extracellular glucose decreased the frequency of sEPSCs in EPSC(+) neurons, but increased it in EPSC(-) neurons. Unlike EPSC(+) and EPSC(-) neurons, EPSC(+/-) neurons displayed a bi-phasic sEPSC response to glucoprivation. In the first phase of glucoprivation, both the frequency and the amplitude of sEPSCs decreased, whereas in the second phase, they increased progressively to the levels above the baseline values. Accordingly, lowering glucose exerted a bi-phasic effect on spontaneous action potentials in EPSC(+/-) neurons. Glucoprivation decreased firing rates in the first phase, but increased them in the second phase. These data indicate that glucose induces distinct excitatory synaptic plasticity in different subpopulations of POMC neurons. This synaptic remodeling is likely to regulate the sensitivity of the melanocortin system to neuronal and hormonal signals.
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Affiliation(s)
- Jun Hu
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- Department of Orthopedics, The First Affiliated Hospital of Nanjing Medical University, Nanjing, P. R. China
| | - Lin Jiang
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Malcolm J. Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Liangyou Rui
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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Mercer AJ, Stuart RC, Attard CA, Otero-Corchon V, Nillni EA, Low MJ. Temporal changes in nutritional state affect hypothalamic POMC peptide levels independently of leptin in adult male mice. Am J Physiol Endocrinol Metab 2014; 306:E904-15. [PMID: 24518677 PMCID: PMC3989737 DOI: 10.1152/ajpendo.00540.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Hypothalamic proopiomelanocortin (POMC) neurons constitute a critical anorexigenic node in the central nervous system (CNS) for maintaining energy balance. These neurons directly affect energy expenditure and feeding behavior by releasing bioactive neuropeptides but are also subject to signals directly related to nutritional state such as the adipokine leptin. To further investigate the interaction of diet and leptin on hypothalamic POMC peptide levels, we exposed 8- to 10-wk-old male POMC-Discosoma red fluorescent protein (DsRed) transgenic reporter mice to either 24-48 h (acute) or 2 wk (chronic) food restriction, high-fat diet (HFD), or leptin treatment. Using semiquantitative immunofluorescence and radioimmunoassays, we discovered that acute fasting and chronic food restriction decreased the levels of adrenocorticotropic hormone (ACTH), α-melanocyte-stimulating hormone (α-MSH), and β-endorphin in the hypothalamus, together with decreased DsRed fluorescence, compared with control ad libitum-fed mice. Furthermore, acute but not chronic HFD or leptin administration selectively increased α-MSH levels in POMC fibers and increased DsRed fluorescence in POMC cell bodies. HFD and leptin treatments comparably increased circulating leptin levels at both time points, suggesting that transcription of Pomc and synthesis of POMC peptide products are not modified in direct relation to the concentration of plasma leptin. Our findings indicate that negative energy balance persistently downregulated POMC peptide levels, and this phenomenon may be partially explained by decreased leptin levels, since these changes were blocked in fasted mice treated with leptin. In contrast, sustained elevation of plasma leptin by HFD or hormone supplementation did not significantly alter POMC peptide levels, indicating that enhanced leptin signaling does not chronically increase Pomc transcription and peptide synthesis.
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Affiliation(s)
- Aaron J Mercer
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
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Hermanussen M, Meitinger T, Veldhuis JD, Low MJ, Pfäffle R, Staub K, Panczak R, Groth D, Brabec M, von Salisch M, Loh CPA, Tassenaar V, Scheffler C, Mumm R, Godina E, Lehmann A, Tutkuviene J, Gervickaite S, Nierop AFM, Holmgren A, Assmann C, van Buuren S, Koziel S, Zadzińska E, Varela-Silva I, Vignerová J, Salama E, El-Shabrawi M, Huiji A, Satake T, Bogin B. Adolescent growth: genes, hormones and the peer group. Proceedings of the 20th Aschauer Soiree, held at Glücksburg castle, Germany, 15th to 17th November 2013. Pediatr Endocrinol Rev 2014; 11:341-353. [PMID: 24716402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The association between poverty, malnutrition, illness and poor socioeconomic conditions on the one side, and poor growth and short adult stature on the other side, is well recognized. Yet, the simple assumption by implication that poor growth and short stature result from poor living conditions, should be questioned. Recent evidence on the impact of the social network on adolescent growth and adult height further challenges the traditional concept of growth being a mirror of health. Twenty-nine scientists met at Glücksburg castle, Northern Germany, November 15th - 17th 2013, to discuss genetic, endocrine, mathematical and psychological aspects and related issues, of child and adolescent growth and final height.
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Domené S, Bumaschny VF, de Souza FSJ, Franchini LF, Nasif S, Low MJ, Rubinstein M. Enhancer turnover and conserved regulatory function in vertebrate evolution. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130027. [PMID: 24218639 DOI: 10.1098/rstb.2013.0027] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mutations in regulatory regions including enhancers are an important source of variation and innovation during evolution. Enhancers can evolve by changes in the sequence, arrangement and repertoire of transcription factor binding sites, but whole enhancers can also be lost or gained in certain lineages in a process of turnover. The proopiomelanocortin gene (Pomc), which encodes a prohormone, is expressed in the pituitary and hypothalamus of all jawed vertebrates. We have previously described that hypothalamic Pomc expression in mammals is controlled by two enhancers-nPE1 and nPE2-that are derived from transposable elements and that presumably replaced the ancestral neuronal Pomc regulatory regions. Here, we show that nPE1 and nPE2, even though they are mammalian novelties with no homologous counterpart in other vertebrates, nevertheless can drive gene expression specifically to POMC neurons in the hypothalamus of larval and adult transgenic zebrafish. This indicates that when neuronal Pomc enhancers originated de novo during early mammalian evolution, the newly created cis- and trans-codes were similar to the ancestral ones. We also identify the neuronal regulatory region of zebrafish pomca and confirm that it is not homologous to the mammalian enhancers. Our work sheds light on the process of gene regulatory evolution by showing how a locus can undergo enhancer turnover and nevertheless maintain the ancestral transcriptional output.
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Affiliation(s)
- Sabina Domené
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, , C1428ADN Buenos Aires, Argentina
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Abstract
Central proopiomelanocortin (POMC) neurons form a potent anorexigenic network, but our understanding of the integration of this hypothalamic circuit throughout the central nervous system (CNS) remains incomplete. POMC neurons extend projections along the rostrocaudal axis of the brain, and can signal with both POMC-derived peptides and fast amino acid neurotransmitters. Although recent experimental advances in circuit-level manipulation have been applied to POMC neurons, many pivotal questions still remain: how and where do POMC neurons integrate metabolic information? Under what conditions do POMC neurons release bioactive molecules throughout the CNS? Are GABA and glutamate or neuropeptides released from POMC neurons more crucial for modulating feeding and metabolism? Resolving the exact stoichiometry of signals evoked from POMC neurons under different metabolic conditions therefore remains an ongoing endeavor. In this review, we analyze the anatomical atlas of this network juxtaposed to the physiological signaling of POMC neurons both in vitro and in vivo. We also consider novel genetic tools to further characterize the function of the POMC circuit in vivo. Our goal is to synthesize a global view of the POMC network, and to highlight gaps that require further research to expand our knowledge on how these neurons modulate energy balance.
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Affiliation(s)
- Aaron J Mercer
- Department of Molecular and Integrative Physiology, University of Michigan Ann Arbor, MI, USA
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Affiliation(s)
- Malcolm J Low
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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Bumaschny VF, Yamashita M, Casas-Cordero R, Otero-Corchón V, de Souza FSJ, Rubinstein M, Low MJ. Obesity-programmed mice are rescued by early genetic intervention. J Clin Invest 2012; 122:4203-12. [PMID: 23093774 DOI: 10.1172/jci62543] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 08/20/2012] [Indexed: 11/17/2022] Open
Abstract
Obesity is a chronic metabolic disorder affecting half a billion people worldwide. Major difficulties in managing obesity are the cessation of continued weight loss in patients after an initial period of responsiveness and rebound to pretreatment weight. It is conceivable that chronic weight gain unrelated to physiological needs induces an allostatic regulatory state that defends a supranormal adipose mass despite its maladaptive consequences. To challenge this hypothesis, we generated a reversible genetic mouse model of early-onset hyperphagia and severe obesity by selectively blocking the expression of the proopiomelanocortin gene (Pomc) in hypothalamic neurons. Eutopic reactivation of central POMC transmission at different stages of overweight progression normalized or greatly reduced food intake in these obesity-programmed mice. Hypothalamic Pomc rescue also attenuated comorbidities such as hyperglycemia, hyperinsulinemia, and hepatic steatosis and normalized locomotor activity. However, effectiveness of treatment to normalize body weight and adiposity declined progressively as the level of obesity at the time of Pomc induction increased. Thus, our study using a novel reversible monogenic obesity model reveals the critical importance of early intervention for the prevention of subsequent allostatic overload that auto-perpetuates obesity.
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Affiliation(s)
- Viviana F Bumaschny
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
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Reilly PT, Teo WL, Low MJ, Amoyo-Brion AA, Dominguez-Brauer C, Elia AJ, Berger T, Greicius G, Pettersson S, Mak TW. Lipocalin 2 performs contrasting, location-dependent roles in APCmin tumor initiation and progression. Oncogene 2012; 32:1233-9. [PMID: 22614012 PMCID: PMC3594828 DOI: 10.1038/onc.2012.159] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Evidence that lipocalin 2 (LCN2) is oncogenic has grown in recent years and comes from both animal models and expression analysis from a variety of human cancers. In the intestine, LCN2 is overexpressed in colitis patients and its overexpression is a negative prognostic indicator in colorectal cancer. Functionally, LCN2 has a number of different activities that may contribute to its oncogenic potential, including increasing matrix metalloproteinase activity, control of iron availability and stimulating inflammation. In this report, we examined APCmin intestinal tumorigenesis in an LCN2-deficient background. We found that the loss of LCN2 increased tumor multiplicity specifically in the duodenum, suggesting a potential tumor-suppressive activity. Concurrently, however, LCN2 increased the average small intestinal tumor size particularly in the distal small intestine. We found that this increase was correlated to tumor iron(II) content, suggesting that an iron-scavenging role is important for LCN2 oncogenic activity in the intestine.
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Affiliation(s)
- P T Reilly
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, Singapore, Singapore
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Franchini LF, de Souza FS, Low MJ, Rubinstein M. Positive selection of co-opted mobile genetic elements in a mammalian gene: If you can't beat them, join them. Mob Genet Elements 2012; 2:106-109. [PMID: 22934245 PMCID: PMC3429518 DOI: 10.4161/mge.20267] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The proopiomelanocortin (Pomc) gene encodes a prepropeptide with essential functions in the response to stress and energy balance, which is expressed in the pituitary and hypothalamus of vertebrate animals. Neuronal expression of Pomc is controlled by two distal enhancers named nPE1 and nPE2. Using transgenic mice, we observed that both enhancers drive identical expression patterns in the mammalian hypothalamus, starting at embryonic day 10.5, when endogenous Pomc expression commences. This overlapping enhancer activity is maintained throughout hypothalamic development and into adulthood. We also found that nPE1 and nPE2 were exapted as neuronal enhancers into the POMC locus after the sequential insertion of two unrelated retroposons. Thus, nPE1 and nPE2 are functional analogs and represent an authentic first example of convergent molecular evolution of cell-specific transcriptional enhancers. In this Commentary we discuss the following questions that remain unanswered: (1) how does transcriptional control of POMC operate in hypothalamic neurons of non-mammalian vertebrates? (2) What evolutionary forces are maintaining two discrete neuronal POMC enhancers under purifying selection for the last ~100 million years in all placental mammals? (3) What is the contribution of MaLRs to genome evolution?
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Affiliation(s)
- Lucia F. Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Consejo Nacional de Investigaciones Científicas y Técnicas; Buenos Aires, Argentina
| | - Flavio S.J. de Souza
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires, Argentina
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology; University of Michigan; Ann Arbor, MI USA
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires, Argentina
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Franchini LF, López-Leal R, Nasif S, Beati P, Gelman DM, Low MJ, de Souza FJS, Rubinstein M. Convergent evolution of two mammalian neuronal enhancers by sequential exaptation of unrelated retroposons. Proc Natl Acad Sci U S A 2011; 108:15270-5. [PMID: 21876128 PMCID: PMC3174587 DOI: 10.1073/pnas.1104997108] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The proopiomelanocortin gene (POMC) is expressed in a group of neurons present in the arcuate nucleus of the hypothalamus. Neuron-specific POMC expression in mammals is conveyed by two distal enhancers, named nPE1 and nPE2. Previous transgenic mouse studies showed that nPE1 and nPE2 independently drive reporter gene expression to POMC neurons. Here, we investigated the evolutionary mechanisms that shaped not one but two neuron-specific POMC enhancers and tested whether nPE1 and nPE2 drive identical or complementary spatiotemporal expression patterns. Sequence comparison among representative genomes of most vertebrate classes and mammalian orders showed that nPE1 is a placental novelty. Using in silico paleogenomics we found that nPE1 originated from the exaptation of a mammalian-apparent LTR retrotransposon sometime between the metatherian/eutherian split (147 Mya) and the placental mammal radiation (≈ 90 Mya). Thus, the evolutionary origin of nPE1 differs, in kind and time, from that previously demonstrated for nPE2, which was exapted from a CORE-short interspersed nucleotide element (SINE) retroposon before the origin of prototherians, 166 Mya. Transgenic mice expressing the fluorescent markers tomato and EGFP driven by nPE1 or nPE2, respectively, demonstrated coexpression of both reporter genes along the entire arcuate nucleus. The onset of reporter gene expression guided by nPE1 and nPE2 was also identical and coincidental with the onset of Pomc expression in the presumptive mouse diencephalon. Thus, the independent exaptation of two unrelated retroposons into functional analogs regulating neuronal POMC expression constitutes an authentic example of convergent molecular evolution of cell-specific enhancers.
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Affiliation(s)
- Lucía F. Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Rodrigo López-Leal
- Centro de Estudios Científicos and Universidad Austral de Chile, Valdivia 5110466, Chile
| | - Sofía Nasif
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Paula Beati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Diego M. Gelman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
| | - Malcolm J. Low
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48105; and
| | - Flávio J. S. de Souza
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, C1428ADN Buenos Aires, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
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Abstract
Hypothalamic pro-opiomelanocortin (POMC) neurons are the major source of anorectic melanocortin peptides in the brain. A recent study (Mineur et al., 2011) demonstrates that nicotine directly stimulates arcuate POMC neurons through nicotinic acetylcholinergic α3β4 receptors, suggesting a new mechanism to understand the inverse relationship between tobacco smoking and body weight.
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Affiliation(s)
- Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas and Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Malcolm J. Low
- Department of Molecular & Integrative Physiology, Department of Internal Medicine, and Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, MI
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