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Coria-Caballero V, Jaramillo-Narvaez MDLL, Leon-Verdin MG, Martinez F, Lazo-de-la-Vega-Monroy ML, Barbosa-Sabanero G. Desacylghrelin modulates GHS-R1 receptor expression and cell differentiation in placental BeWo cells. Mol Cell Endocrinol 2023; 577:112035. [PMID: 37506870 DOI: 10.1016/j.mce.2023.112035] [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] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 07/25/2023] [Accepted: 07/26/2023] [Indexed: 07/30/2023]
Abstract
BACKGROUND and purpose: Ghrelin is the endogenous ligand of the growth hormone secretagogue receptor (GHS-R1). Ghrelin, and GHS-R1, may have a role in placental growth and function, and its unacylated form desacylghrelin (DAG) could be involved in fetal growth. Nevertheless, the effects of DAG on placental function, and the receptor involved in its actions, remain to be determined. We aimed to investigate the effect of DAG in placental BeWo cells viability, proliferation, differentiation, and GSH-R1 expression. METHODS BeWo cells, a human trophoblast cell line, was cultured with 3 nM DAG during 12, 24, 48, and 72 h. Cell viability, proliferation, differentiation (assessed by human Chorionic Gonadotropin quantification), and GSH-R1 expression were analyzed. To evaluate the mechanism of DAG effect on GSH-R1, 30 nM receptor antagonist ([D-Lys3]-GHRP-6) was added alone or in combination with 3 nM DAG during 12 h and 24 h. RESULTS DAG has no effect on cell proliferation or viability, but it has an inhibitory effect on cell differentiation. DAG had a stimulatory effect on GSH-R1 expression at 12 and 24 h (p = 0.029 and p = 0.025, respectively). On the contrary, culture with 48 h DAG inhibits GSH-R1 expression compared to the control (p = 0.005), while GSH-R1 antagonist inhibited the effect of DAG on GSH-R1 expression. DAG also reduces intracellular (p = 0.020) and secreted (p = 0.011) hCG concentration in BeWo cells. CONCLUSION DAG increases GHS-R1 expression, potentially mediated through GHS-R1 itself. DAG may also inhibit placental BeWo cell differentiation, suggesting a possible role of DAG in placental and fetal physiology.
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Affiliation(s)
- Vanessa Coria-Caballero
- Medical Sciences Department, Health Sciences Division, University of Guanajuato, Leon Campus, Mexico
| | | | - Ma Guadalupe Leon-Verdin
- Department of Engineering Physics, Division of Sciences and Engineering, University of Guanajuato, Leon Campus, Mexico
| | - Federico Martinez
- Biochemistry Department, Medicine Faculty, UNAM, Mexico City, Mexico
| | | | - Gloria Barbosa-Sabanero
- Medical Sciences Department, Health Sciences Division, University of Guanajuato, Leon Campus, Mexico.
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Tian J, Du E, Jia K, Wang T, Guo L, Zigman JM, Du H. Elevated Ghrelin Promotes Hippocampal Ghrelin Receptor Defects in Humanized Amyloid-β Knockin Mice During Aging. J Alzheimers Dis 2023; 96:1579-1592. [PMID: 38007666 PMCID: PMC10841720 DOI: 10.3233/jad-231002] [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] [Indexed: 11/27/2023]
Abstract
BACKGROUND Emerging evidence has revealed that dysregulation of the hormone ghrelin and its receptor, growth hormone secretagogue receptor (GHSR), contributes to the pathogenesis of Alzheimer's disease (AD). Specifically, defective GHSR function and resultant hippocampal ghrelin resistance are linked to hippocampal synaptic injury in AD paradigms. Also, AD patients exhibit elevated ghrelin activation. However, the detailed molecular mechanisms of hippocampal GHSR dysfunction and the relevance of ghrelin elevation to hippocampal ghrelin resistance in AD-relevant pathological settings are not fully understood. OBJECTIVE In the current study, we employed a recently established mouse line of AD risk [humanized amyloid beta knockin (hAβ KI mice), also referred to as a mouse model of late-onset AD in previous literature] to further define the role of ghrelin system dysregulation in the development of AD. METHODS We employed multidisciplinary techniques to determine the change of plasma ghrelin and the functional status of GHSR in hAβ KI mice as well as primary neuron cultures. RESULTS We observed concurrent plasma ghrelin elevation and hippocampal GHSR desensitization with disease progression. Further examination excluded the possibility that ghrelin elevation is a compensatory change in response to GHSR dysfunction. In contrast, further in vitro and in vivo results show that agonist-mediated overstimulation potentiates GHSR desensitization through enhanced GHSR internalization. CONCLUSIONS These findings suggest that circulating ghrelin elevation is a pathological event underlying hippocampal GHSR dysfunction, culminating in hippocampal ghrelin resistance and resultant synaptic injury in late-onset AD-related settings.
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Affiliation(s)
- Jing Tian
- Department of Pharmacology and Toxicology, The University of Kansas, Lawrence, KS, USA
| | - Eric Du
- Department of Pharmacology and Toxicology, The University of Kansas, Lawrence, KS, USA
- Blue Valley West High School, Overland Park, KS, USA
| | - Kun Jia
- Department of Pharmacology and Toxicology, The University of Kansas, Lawrence, KS, USA
| | - Tienju Wang
- Department of Pharmacology and Toxicology, The University of Kansas, Lawrence, KS, USA
| | - Lan Guo
- Department of Pharmacology and Toxicology, The University of Kansas, Lawrence, KS, USA
| | - Jeffrey M. Zigman
- Department of Internal Medicine, Center for Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Heng Du
- Department of Pharmacology and Toxicology, The University of Kansas, Lawrence, KS, USA
- Alzheimer’s disease Research Center (ADRC), Department of Neurology, The University of Kansas Medical Center, Kansas City, KS, USA
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Yu M, Zhu QQ, Niu ML, Li N, Ren BQ, Yu TB, Zhou ZS, Guo JD, Zhou Y. Ghrelin infusion into the basolateral amygdala suppresses CTA memory formation in rats via the PI3K/Akt/mTOR and PLC/PKC signaling pathways. Acta Pharmacol Sin 2022; 43:2242-2252. [PMID: 35169271 PMCID: PMC9433413 DOI: 10.1038/s41401-022-00859-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 01/03/2022] [Indexed: 12/11/2022] Open
Abstract
Ghrelin is a circulating orexigenic hormone that promotes feeding behavior and regulates metabolism in humans and rodents. We previously reported that local infusion of ghrelin into the basolateral amygdala (BLA) blocked memory acquisition for conditioned taste aversion (CTA) by activating growth hormone secretagogue receptor 1a. In this study, we further explored the underlying mechanism and signaling pathways mediating ghrelin modulation of CTA memory in rats. Pharmacological agents targeting distinct signaling pathways were infused into the BLA during conditioning. We showed that preadministration of the PI3K inhibitor LY294002 abolished the repressive effect of ghrelin on CTA memory. Moreover, LY294002 pretreatment prevented ghrelin from inhibiting Arc and zif268 mRNA expression in the BLA triggered by CTA memory retrieval. Preadministration of rapamycin eliminated the repressive effect of ghrelin, while Gsk3 inhibitors failed to mimic ghrelin's effect. In addition, PLC and PKC inhibitors microinfused in the BLA blocked ghrelin's repression of CTA acquisition. These results demonstrate that ghrelin signaling in the BLA shapes CTA memory via the PI3K/Akt/mTOR and PLC/PKC pathways. We conducted in vivo multichannel recordings from mouse BLA neurons and found that microinjection of ghrelin (20 µM) suppressed intrinsic excitability. By means of whole-cell recordings from rat brain slices, we showed that bath application of ghrelin (200 nM) had no effect on basal synaptic transmission or synaptic plasticity of BLA pyramidal neurons. Together, this study reveals the mechanism underlying ghrelin-induced interference with CTA memory acquisition in rats, i.e., suppression of intrinsic excitability of BLA principal neurons via the PI3K/Akt/mTOR and PLC/PKC pathways.
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Affiliation(s)
- Ming Yu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, 266071, China
| | - Qian-Qian Zhu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, 266071, China
| | - Ming-Lu Niu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, 266071, China
| | - Nan Li
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, 266071, China
| | - Bai-Qing Ren
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, 266071, China
| | - Teng-Bo Yu
- Department of Sports Medicine, Affiliated Hospital of Qingdao University, Qingdao, 266000, China.
| | - Zhi-Shang Zhou
- Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, 266071, China
| | - Ji-Dong Guo
- Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Yu Zhou
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, 266071, China.
- Department of rehabilitation medicine, Affiliated Hospital of Qingdao University, Qingdao, 266000, China.
- Institute of Brain Sciences and Related Disorders, Qingdao University, Qingdao, 266071, China.
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Ringuet MT, Furness JB, Furness SGB. G protein-coupled receptor interactions and modification of signalling involving the ghrelin receptor, GHSR1a. J Neuroendocrinol 2022; 34:e13077. [PMID: 34931385 DOI: 10.1111/jne.13077] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 12/05/2021] [Indexed: 12/28/2022]
Abstract
The growth hormone secretagogue receptor 1a (GHSR1a) is intriguing because of its potential as a therapeutic target and its diverse molecular interactions. Initial studies of the receptor focused on the potential therapeutic ability for growth hormone (GH) release to reduce wasting in aging individuals, as well as food intake regulation for treatment of cachexia. Known roles of GHSR1a now extend to regulation of neurogenesis, learning and memory, gastrointestinal motility, glucose/lipid metabolism, the cardiovascular system, neuronal protection, motivational salience, and hedonic feeding. Ghrelin, the endogenous agonist of GHSR1a, is primarily located in the stomach and is absent from the central nervous system (CNS), including the spinal cord. However, ghrelin in the circulation does have access to a small number of CNS sites, including the arcuate nucleus, which is important in feeding control. At some sites, such as at somatotrophs, GHSR1a has high constitutive activity. Typically, ghrelin-dependent and constitutive GHSR1a activation occurs via Gαq/11 pathways. In vitro and in vivo data suggest that GHSR1a heterodimerises with multiple G protein-coupled receptors (GPCRs), including dopamine D1 and D2, serotonin 2C, orexin, oxytocin and melanocortin 3 receptors (MCR3), as well as the MCR3 accessory protein, MRAP2, providing possible mechanisms for its many physiological effects. In all cases, the receptor interaction changes downstream signalling and the responses to receptor agonists. This review discusses the signalling mechanisms of GHSR1a alone and in combination with other GPCRs, and explores the physiological consequences of GHSR1a coupling with other GPCRs.
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Affiliation(s)
- Mitchell Ty Ringuet
- Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
| | - John Barton Furness
- Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
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5
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Lu Z, Cui D, Liu JYH, Jiang B, Ngan MP, Sakata I, Takemi S, Sakai T, Lin G, Chan SW, Rudd JA. The Actions of Centrally Administered Nesfatin-1 on Emesis, Feeding, and Locomotor Activity in Suncus murinus (House Musk Shrew). Front Pharmacol 2022; 13:858522. [PMID: 35462894 PMCID: PMC9019301 DOI: 10.3389/fphar.2022.858522] [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] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 03/15/2022] [Indexed: 11/13/2022] Open
Abstract
Nesfatin-1 is an anorectic peptide expressed in both peripheral tissues and brain areas involved in the regulation of feeding, emotion and emesis. The aim of the present study is to characterize the distribution of NUCB2/nesfatin-1 in Suncus murinus and to investigate the actions of nesfatin-1 to affect gastrointestinal contractility, emesis, food and water intake, and locomotor activity. The deduced amino acid sequence of S. murinus nesfatin-1 using in silico cloning showed high homology with humans and rodents. NUCB2 mRNA was detected throughout the entire brain and in the gastrointestinal tract, including the stomach and gut. Western blot analysis and immunohistochemistry confirmed the expression of nesfatin-1 protein in these regions. The NUCB2 mRNA levels in the hypothalamus, hippocampus and brainstem were significantly decreased, whereas that in the striatum were increased after 24 h starvation compared to ad libitum-fed animals (p < 0.05). In in vitro studies, nesfatin-1 (0.3–1,000 pM) failed to contract or relax the isolated gastric antrum and intestinal segments. In conscious, freely moving animals, intracerebroventricular administration of nesfatin-1 (1–50 pmol) induced emesis (p < 0.05) and suppressed 6-h cumulative food intake (p < 0.05), without affecting the latency to feeding. Nesfatin-1 (25 pmol, i.c.v.) decreased 24-h cumulative food and water intake by 28.3 and 35.4%, respectively (p < 0.01). No significant differences in locomotor activity were observed. In conclusion, NUCB2/nesfatin-1 might be a potent regulator of feeding and emesis in S. murinus. Further studies are required to elucidate the mechanism of actions of this peptide as a mediator linking the brainstem NUCB2/nesfatin-1 to forebrain system.
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Affiliation(s)
- Zengbing Lu
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
- School of Health Sciences, Caritas Institute of Higher Education, Hong Kong, Hong Kong SAR, China
| | - Dexuan Cui
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Julia Yuen Hang Liu
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Bin Jiang
- School of Health Sciences, Caritas Institute of Higher Education, Hong Kong, Hong Kong SAR, China
| | - Man Piu Ngan
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Ichiro Sakata
- Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Shota Takemi
- Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Takafumi Sakai
- Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Ge Lin
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Sze Wa Chan
- School of Health Sciences, Caritas Institute of Higher Education, Hong Kong, Hong Kong SAR, China
- *Correspondence: Sze Wa Chan,
| | - John A. Rudd
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
- The Laboratory Animal Services Centre, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
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6
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Du A, Li N, Li Z, Shen R, Li N, Zhou Y. GHS-R1a activity suppresses synaptic function of primary cultured hippocampal neurons. Biochem Biophys Res Commun 2022; 602:91-7. [DOI: 10.1016/j.bbrc.2022.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 03/01/2022] [Indexed: 11/18/2022]
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Li N, Xiao K, Mi X, Li N, Guo L, Wang X, Sun Y, Li GD, Zhou Y. Ghrelin signaling in dCA1 suppresses neuronal excitability and impairs memory acquisition via PI3K/Akt/GSK-3β cascades. Neuropharmacology 2022; 203:108871. [PMID: 34742928 DOI: 10.1016/j.neuropharm.2021.108871] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 11/01/2021] [Accepted: 11/01/2021] [Indexed: 12/22/2022]
Abstract
Ghrelin is a circulating peptide hormone that promotes feeding and regulates metabolism in humans and rodents. The action of ghrelin is mediated by the growth hormone secretagogue receptor type 1a (GHSR-1a) that is widely distributed in the brain, including the hippocampus. Studies have demonstrated the critical role of hippocampal ghrelin/GHS-R1a signaling in synaptic physiology and memory. However, those findings are controversial, and the mechanism underlying ghrelin modulation of learning and memory is uncertain. Here, we report that micro-infusion of ghrelin in the CA1 region of the dorsal hippocampus during training specifically impairs memory acquisition. The activation of GHS-R1a and the subsequent PI3K/Akt/GSK3β signaling cascades are involved in this process. Moreover, we report that bath application of ghrelin suppresses the intrinsic excitability of dCA1 pyramidal neurons through activating GHS-R1a, and PI3K inhibitor LY294002 blocks ghrelin's effect. However, LY294002 fails to rescue ghrelin-induced LTP impairment. Our findings support an adverse effect of ghrelin-dependent activation of GHS-R1a on memory acquisition, and suggest that PI3K/Akt/GSK3β signaling-dependent repression of neuronal intrinsic excitability is an important novel mechanism underlying memory inhibition of ghrelin in the hippocampus.
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Affiliation(s)
- Nan Li
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China
| | - Kewei Xiao
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China
| | - Xue Mi
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China
| | - Na Li
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China
| | - Li Guo
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China
| | - Xiaorong Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China
| | - Yuxiang Sun
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, United States
| | - Guo-Dong Li
- Department of Surgery, Valley Presbyterian Hospital, Van Nuys, CA, 91405, United States
| | - Yu Zhou
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, Shandong, 266071, China; Institute of Brain Sciences and Related Disorders, Qingdao University, Qingdao, Shandong, 266071, China; Department of Rehabilitation Medicine, Affiliated Hospital of Qingdao University, Qingdao, Shangdong, 266000, China.
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Kornyushin O, Sonin D, Polozov A, Masley V, Bulavinova N, Chervyak M, Istomina M, Mukhametdinova D, Neimark A, Cheburkin Y, Toropova Y, Derkach K, Shpakov A, Galagudza M, Shlyakhto E. Effect of sleeve gastrectomy, Roux-en-Y gastric bypass, and ileal transposition on myocardial ischaemia-reperfusion injury in non-obese non-diabetic rats. Sci Rep 2021; 11:23888. [PMID: 34903800 DOI: 10.1038/s41598-021-03283-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 11/30/2021] [Indexed: 11/12/2022] Open
Abstract
Bariatric surgery (BS) improves outcomes in patients with myocardial infarction (MI). Here we tested the hypothesis that BS-mediated reduction in fatal MI could be attributed to its infarct-limiting effect. Wistar rats were randomized into five groups: control (CON), sham (SHAM), Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and ileotransposition (IT). Ten weeks later, animals were subjected to 30-min myocardial ischemia plus 120-min reperfusion. Infarct size (IS) and no-reflow area were determined histochemically. Fasting plasma levels of glucagon-like peptide-1 (GLP-1), leptin, ghrelin, and insulin were measured using ELISA. Compared with SHAM, RYGB and SG reduced IS by 22% (p = 0.011) and 10% (p = 0.027), and no-reflow by 38% (p = 0.01) and 32% (p = 0.004), respectively. IT failed to reduce IS and no-reflow. GLP-1 level was increased in the SG and RYGB groups compared with CON. In both the SG and RYGB, leptin level was decreased compared with CON and SHAM. In the SG group, ghrelin level was lower than that in the CON and SHAM. Insulin levels were not different between groups. In conclusion, RYGB and SG increased myocardial tolerance to ischemia-reperfusion injury of non-obese, non-diabetic rats, and their infarct-limiting effect is associated with decreased leptin and ghrelin levels and increased GLP-1 level.
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Ginter G, Ceranowicz P, Warzecha Z. Protective and Healing Effects of Ghrelin and Risk of Cancer in the Digestive System. Int J Mol Sci 2021; 22:10571. [PMID: 34638910 DOI: 10.3390/ijms221910571] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 09/24/2021] [Accepted: 09/27/2021] [Indexed: 01/19/2023] Open
Abstract
Ghrelin is an endogenous ligand for the ghrelin receptor, previously known as the growth hormone secretagogue receptor. This hormone is mainly produced by endocrine cells present in the gastric mucosa. The ghrelin-producing cells are also present in other organs of the body, mainly in the digestive system, but in much smaller amount. Ghrelin exhibits a broad spectrum of physiological effects, such as stimulation of growth hormone secretion, gastric secretion, gastrointestinal motility, and food intake, as well as regulation of glucose homeostasis and bone formation, and inhibition of inflammatory processes. This review summarizes the recent findings concerning animal and human data showing protective and therapeutic effects of ghrelin in the gut, and also presents the role of growth hormone and insulin-like growth factor-1 in these effects. In addition, the current data on the possible influence of ghrelin on the carcinogenesis, its importance in predicting the risk of developing gastrointestinal malignances, as well as the potential usefulness of ghrelin in the treatment of cancer, have been presented.
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Yamada C. Relationship between Orexigenic Peptide Ghrelin Signal, Gender Difference and Disease. Int J Mol Sci 2021; 22:ijms22073763. [PMID: 33916403 PMCID: PMC8038632 DOI: 10.3390/ijms22073763] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 03/29/2021] [Accepted: 03/30/2021] [Indexed: 12/11/2022] Open
Abstract
Growth hormone secretagogue receptor 1a (GHS-R1a), which is one of the G protein-coupled receptors (GPCRs), is involved in various physiological actions such as energy consumption, growth hormone secretion promoting action, and cardiovascular protective action. The ligand was searched for as an orphan receptor for a while, but the ligand was found to be acylated ghrelin (ghrelin) discovered by Kangawa and Kojima et al. in 1999. Recently, it has also been reported that dysregulation of GHS-R1a mediates reduced feeding in various diseases. On the other hand, since the physiological effects of ghrelin have been studied exclusively in male mice, few studies have been conducted on gender differences in ghrelin reactivity. In this review, we describe (1) the characteristics of GHS-R1a, (2) the role of ghrelin in hypophagia due to stress or anticancer drugs, and (3) the gender differences in the physiological effects of GHS-R1a and the influence of stress on it.
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Affiliation(s)
- Chihiro Yamada
- Tsumura Kampo Research Laboratories, Tsumura & Co., Ibaraki 300-1192, Japan
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Stone LA, Harmatz ES, Goosens KA. Ghrelin as a Stress Hormone: Implications for Psychiatric Illness. Biol Psychiatry 2020; 88:531-540. [PMID: 32912426 DOI: 10.1016/j.biopsych.2020.05.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [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: 09/12/2019] [Revised: 05/11/2020] [Accepted: 05/11/2020] [Indexed: 12/28/2022]
Abstract
The stress response is an adaptive means of maintaining physiological homeostasis in the face of changing environmental conditions. However, protracted recruitment of stress systems can precipitate wear and tear on the body and may lead to many forms of disease. The mechanisms underlying the connection between chronic stress and disease are not fully understood and are likely multifactorial. In this review, we evaluate the possibility that the hormone ghrelin may contribute to the pathophysiology that follows chronic stress. Since ghrelin was discovered as a pro-hunger hormone, many additional roles for it have been identified, including in learning, memory, reward, and stress. We describe the beneficial effects that ghrelin exerts in healthy mammals and discuss that prolonged exposure to ghrelin has been linked to maladaptive responses and behaviors in the realm of psychiatric disease. In addition, we consider whether chronic stress-associated altered ghrelin signaling may enhance susceptibility to posttraumatic stress disorder and comorbid conditions such as major depressive disorder and alcohol use disorder. Finally, we explore the possibility that ghrelin-based therapeutics could eventually form the basis of a treatment strategy for illnesses that are linked to chronic stress and potentially also ghrelin dysregulation, and we identify critical avenues for future research in this regard.
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Affiliation(s)
| | | | - Ki A Goosens
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York.
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Christie S, O'Rielly R, Li H, Wittert GA, Page AJ. High fat diet induced obesity alters endocannabinoid and ghrelin mediated regulation of components of the endocannabinoid system in nodose ganglia. Peptides 2020; 131:170371. [PMID: 32659299 DOI: 10.1016/j.peptides.2020.170371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 05/31/2020] [Accepted: 07/09/2020] [Indexed: 12/18/2022]
Abstract
BACKGROUND Ghrelin and anandamide (AEA) can regulate the sensitivity of gastric vagal afferents to stretch, an effect mediated via the transient receptor potential vanilloid 1 (TPRV1) channel. High fat diet (HFD)-induced obesity alters the modulatory effects of ghrelin and AEA on gastric vagal afferent sensitivity. This may be a result of altered gastric levels of these hormones and subsequent changes in the expression of their receptors. Therefore, the current study aimed to determine the effects of ghrelin and AEA on vagal afferent cell body mRNA content of cannabinoid 1 receptor (CB1), ghrelin receptor (GHSR), TRPV1, and the enzyme responsible for the breakdown of AEA, fatty acid amide hydrolase (FAAH). METHODS Mice were fed a standard laboratory diet (SLD) or HFD for 12wks. Nodose ganglia were removed and cultured for 14 h in the absence or presence of ghrelin or methAEA (mAEA; stable analogue of AEA). Relative mRNA content of CB1, GHSR, TRPV1, and FAAH were measured. RESULTS In nodose cells from SLD-mice, mAEA increased TRPV1 and FAAH mRNA content, and decreased CB1 and GHSR mRNA content. Ghrelin decreased TRPV1, CB1, and GHSR mRNA content. In nodose cells from HFD-mice, mAEA had no effect on TRPV1 mRNA content, and increased CB1, GHSR, and FAAH mRNA content. Ghrelin decreased TRPV1 mRNA content and increased CB1 and GHSR mRNA content. CONCLUSIONS AEA and ghrelin modulate receptors and breakdown enzymes involved in the mAEA-vagal afferent satiety signalling pathways. This was disrupted in HFD-mice, which may contribute to the altered vagal afferent signalling in obesity.
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Affiliation(s)
- Stewart Christie
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia
| | - Rebecca O'Rielly
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia
| | - Hui Li
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia; Nutrition, Diabetes & Gut Health, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA 5000, Australia
| | - Gary A Wittert
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia; Nutrition, Diabetes & Gut Health, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA 5000, Australia
| | - Amanda J Page
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia; Nutrition, Diabetes & Gut Health, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA 5000, Australia.
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13
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Affiliation(s)
- Dennis J. Worm
- Faculty of Life Sciences, Institute of BiochemistryLeipzig University Leipzig Germany
| | - Sylvia Els‐Heindl
- Faculty of Life Sciences, Institute of BiochemistryLeipzig University Leipzig Germany
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14
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James J, Mair S, Doll W, Sandefer E, Wurtman D, Maurer A, Deane AM, Harris MS. The effects of ulimorelin, a ghrelin agonist, on liquid gastric emptying and colonic transit in humans. Neurogastroenterol Motil 2020; 32:e13784. [PMID: 32017341 DOI: 10.1111/nmo.13784] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [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: 07/20/2019] [Revised: 10/26/2019] [Accepted: 12/02/2019] [Indexed: 02/08/2023]
Abstract
BACKGROUND Ulimorelin, a small molecule ghrelin agonist and prokinetic agent, was effective in animal models of gastroparesis and delayed transit. However, employing once daily administration, it failed in clinical trials of postoperative ileus (POI), a condition in which colonic motility recovers last. The aim of this study was to evaluate drug dosing and regional differences in drug activity between stomach and colon. METHODS Gastric emptying was assessed by scintigraphy in healthy adults at single doses of 600-1200 µg kg-1 and multiple doses of 80-600 µg kg-1 Q8H for 7 days. Colonic motility was assessed by 7-region scintigraphic analysis at a dose of 600 µg kg-1 for 2 days. The primary endpoints were percent change in time to 50% (∆t50 ) liquid gastric emptying on Days 1, 4, and 6 and the geometric mean center of colonic transit at 24 hours (GC24 ). Plasma concentrations of free and total ulimorelin were measured for pharmacokinetic and exposure-response modeling. KEY RESULTS Ulimorelin 150-600 µg kg-1 every 8 hours resulted in statistically significant improvements (∆t50 = 23% to 46% (P < .05)) in gastric emptying from baseline that were sustained through Day 6. However, no effects on GC24 were observed. Pharmacokinetic analyses suggested that the free concentrations of ulimorelin achieved in POI trials and dosing frequency may have been inadequate. CONCLUSIONS AND INFERENCES Ulimorelin is a potent gastric prokinetic but lacks evidence of activity in the human colon, pointing to the stomach as the predominant site of action of ghrelin in humans; ClinicalTrials.gov NCT02993055.
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Affiliation(s)
- Joyce James
- Lyric Pharmaceuticals, Inc., South San Francisco, CA, USA
| | | | | | | | - David Wurtman
- Lyric Pharmaceuticals, Inc., South San Francisco, CA, USA
| | - Alan Maurer
- Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Adam M Deane
- Intensive Care Unit, Royal Melbourne Hospital, University of Melbourne, Melbourne, Vic., Australia
| | - M Scott Harris
- Lyric Pharmaceuticals, Inc., South San Francisco, CA, USA
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15
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Billert M, Kołodziejski PA, Strowski MZ, Nowak KW, Skrzypski M. Phoenixin-14 stimulates proliferation and insulin secretion in insulin producing INS-1E cells. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2019; 1866:118533. [DOI: 10.1016/j.bbamcr.2019.118533] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 08/13/2019] [Accepted: 08/14/2019] [Indexed: 12/25/2022]
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16
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Torres-Fuentes C, Golubeva AV, Zhdanov AV, Wallace S, Arboleya S, Papkovsky DB, El Aidy S, Ross P, Roy BL, Stanton C, Dinan TG, Cryan JF, Schellekens H. Short-chain fatty acids and microbiota metabolites attenuate ghrelin receptor signaling. FASEB J 2019; 33:13546-13559. [DOI: 10.1096/fj.201901433r] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Cristina Torres-Fuentes
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | - Anna V. Golubeva
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | | | - Shauna Wallace
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | - Silvia Arboleya
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
- Teagasc Food Research Centre, Cork, Ireland
| | | | - Sahar El Aidy
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | - Paul Ross
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | | | - Catherine Stanton
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
- Teagasc Food Research Centre, Cork, Ireland
| | - Timothy G. Dinan
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
- Department of Psychiatry and Neurobehavioral Science, University College Cork, Cork, Ireland
| | - John F. Cryan
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Harriet Schellekens
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
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17
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Barrile F, M'Kadmi C, De Francesco PN, Cabral A, García Romero G, Mustafá ER, Cantel S, Damian M, Mary S, Denoyelle S, Banères JL, Marie J, Raingo J, Fehrentz JA, Perelló M. Development of a novel fluorescent ligand of growth hormone secretagogue receptor based on the N-Terminal Leap2 region. Mol Cell Endocrinol 2019; 498:110573. [PMID: 31499133 DOI: 10.1016/j.mce.2019.110573] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 08/27/2019] [Accepted: 09/03/2019] [Indexed: 01/13/2023]
Abstract
Liver-expressed antimicrobial peptide 2 (LEAP2) was recently recognized as an endogenous ligand for the growth hormone secretagogue receptor (GHSR), which also is a receptor for the hormone ghrelin. LEAP2 blocks ghrelin-induced activation of GHSR and inhibits GHSR constitutive activity. Since fluorescence-based imaging and pharmacological analyses to investigate the biology of GHSR require reliable probes, we developed a novel fluorescent GHSR ligand based on the N-terminal LEAP2 sequence, hereafter named F-LEAP2. In vitro, F-LEAP2 displayed binding affinity and inverse agonism to GHSR similar to LEAP2. In a heterologous expression system, F-LEAP2 labeling was specifically observed in the surface of GHSR-expressing cells, in contrast to fluorescent ghrelin labeling that was mainly observed inside the GHSR-expressing cells. In mice, centrally-injected F-LEAP2 reduced ghrelin-induced food intake, in a similar fashion to LEAP2, and specifically labeled cells in GHSR-expressing brain areas. Thus, F-LEAP2 represents a valuable tool to study the biology of GHSR in vitro and in vivo.
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Affiliation(s)
- Franco Barrile
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata], 1900, La Plata, Buenos Aires, Argentina
| | - Céline M'Kadmi
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France
| | - Pablo N De Francesco
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata], 1900, La Plata, Buenos Aires, Argentina
| | - Agustina Cabral
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata], 1900, La Plata, Buenos Aires, Argentina
| | - Guadalupe García Romero
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata], 1900, La Plata, Buenos Aires, Argentina
| | - Emilio R Mustafá
- Laboratory of Electrophysiology of the Multidisciplinary Institute of Cell Biology [IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata], 1900, La Plata, Buenos Aires, Argentina
| | - Sonia Cantel
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France
| | - Marjorie Damian
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France
| | - Sophie Mary
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France
| | - Séverine Denoyelle
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France
| | - Jean-Louis Banères
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France
| | - Jacky Marie
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France
| | - Jesica Raingo
- Laboratory of Electrophysiology of the Multidisciplinary Institute of Cell Biology [IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata], 1900, La Plata, Buenos Aires, Argentina
| | - Jean-Alain Fehrentz
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Faculté de Pharmacie, 34093, Montpellier, France.
| | - Mario Perelló
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata], 1900, La Plata, Buenos Aires, Argentina.
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18
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Abstract
PURPOSE OF REVIEW There is compelling evidence in the clinical population that long-term weight loss secondary to bariatric surgery is mitigated by the reemergence of maladaptive feeding behaviors and in some cases new onset substance abuse. RECENT FINDINGS A review of the current literature suggests that physical restructuring of the GI tract during WLS alters secretion of feeding peptides and nutrient-sensing mechanisms that directly target the brain's endogenous reward system, the mesolimbic dopamine system. Post-surgical changes in GI physiology augment activation of the mesolimbic system. In some patients, this process may contribute to a reduced appetite for palatable food whereas in others it may support maladaptive motivated behavior for food and chemical drugs. It is concluded that future studies are required to detail the timing and duration of surgical-induced changes in GI-mesolimbic communication to more fully understand this phenomenon.
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Affiliation(s)
- Julianna N Brutman
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, 1815 Ferdinand's Lane, Pullman, WA, 99164, USA
| | - Sunil Sirohi
- Laboratory of Endocrine and Neuropsychiatric Disorders, Division of Basic Pharmaceutical Sciences, College of Pharmacy, Xavier University of Louisiana, New Orleans, LA, USA
| | - Jon F Davis
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, 1815 Ferdinand's Lane, Pullman, WA, 99164, USA.
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19
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Buckinx A, Van Den Herrewegen Y, Pierre A, Cottone E, Ben Haj Salah K, Fehrentz JA, Kooijman R, De Bundel D, Smolders I. Differential Effects of a Full and Biased Ghrelin Receptor Agonist in a Mouse Kindling Model. Int J Mol Sci 2019; 20:ijms20102480. [PMID: 31137460 PMCID: PMC6567032 DOI: 10.3390/ijms20102480] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/15/2019] [Accepted: 05/15/2019] [Indexed: 12/23/2022] Open
Abstract
The ghrelin system has received substantial recognition as a potential target for novel anti-seizure drugs. Ghrelin receptor (ghrelin-R) signaling is complex, involving Gαq/11, Gαi/o, Gα12/13, and β-arrestin pathways. In this study, we aimed to deepen our understanding regarding signaling pathways downstream the ghrelin-R responsible for mediating anticonvulsive effects in a kindling model. Mice were administered the proconvulsive dopamine 1 receptor-agonist, SKF81297, to gradually induce a kindled state. Prior to every SKF81297 injection, mice were treated with a ghrelin-R full agonist (JMV-1843), a Gαq and Gα12 biased ligand unable to recruit β-arrestin (YIL781), a ghrelin-R antagonist (JMV-2959), or saline. Mice treated with JMV-1843 had fewer and less severe seizures compared to saline-treated controls, while mice treated with YIL781 experienced longer and more severe seizures. JMV-2959 treatment did not lead to differences in seizure severity and number. Altogether, these results indicate that the Gαq or Gα12 signaling pathways are not responsible for mediating JMV-1843′s anticonvulsive effects and suggest a possible involvement of β-arrestin signaling in the anticonvulsive effects mediated by ghrelin-R modulation.
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Affiliation(s)
- An Buckinx
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Yana Van Den Herrewegen
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Anouk Pierre
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Eleonora Cottone
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Khoubaib Ben Haj Salah
- Max Mousseron Institute of Biomolecules UMR524, CNRS, University of Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier, 34090 Montpellier, France.
| | - Jean-Alain Fehrentz
- Max Mousseron Institute of Biomolecules UMR524, CNRS, University of Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier, 34090 Montpellier, France.
| | - Ron Kooijman
- Research Group Experimental Pharmacology, Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium.
| | - Dimitri De Bundel
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Ilse Smolders
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
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20
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Lunder M, Vodnik M, Kubale V, Grgurevič N, Majdič G, Štrukelj B. Peptide mimetic of N-terminal ghrelin enhances ghrelin-induced growth hormone secretion and c-Fos expression in mice. J Neuroendocrinol 2018; 30:e12656. [PMID: 30394584 DOI: 10.1111/jne.12656] [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] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 10/12/2018] [Accepted: 10/31/2018] [Indexed: 11/30/2022]
Abstract
Orexigenic peptide ghrelin and its receptor have been extensively investigated as potential therapeutic targets, primarily because of their role in feeding initiation and growth hormone (GH) release. However, no specific ghrelin targeting anti-obesity or cachexia therapeutics are available for clinical use thus far and further efforts in this direction are warranted. The present study aimed to find new peptide drug leads modulating ghrelin signal transduction. By targeting neutralising antibodies against ghrelin with phage display libraries, we aimed to identify peptides binding to the cognate receptor. Four synthetic peptides were selected and tested using calcium screening assays. The most effective competitive antagonist FSFLPPE was further tested in vivo. Administration of the peptide produced no significant effect on either food intake or GH release. Surprisingly, when co-administered with ghrelin, the peptide significantly enhanced GH secretion and c-Fos expression. The evidence obtained in the present study indicates that FSFLPPE might act as an ago-allosteric modulator.
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Affiliation(s)
- Mojca Lunder
- Chair of Pharmaceutical Biology, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Miha Vodnik
- Chair of Pharmaceutical Biology, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Valentina Kubale
- Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Neža Grgurevič
- Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Gregor Majdič
- Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Borut Štrukelj
- Chair of Pharmaceutical Biology, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
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21
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Ramirez VT, van Oeffelen WEPA, Torres-Fuentes C, Chruścicka B, Druelle C, Golubeva AV, van de Wouw M, Dinan TG, Cryan JF, Schellekens H. Differential functional selectivity and downstream signaling bias of ghrelin receptor antagonists and inverse agonists. FASEB J 2018; 33:518-531. [PMID: 30020830 DOI: 10.1096/fj.201800655r] [Citation(s) in RCA: 18] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The ghrelin receptor [growth hormone secretagogue receptor (GHSR)-1a] represents a promising pharmacologic target for the treatment of metabolic disorders, including obesity and cachexia, via central appetite modulation. The GHSR-1a has a complex pharmacology, highlighted by G-protein-dependent and -independent downstream signaling pathways and high basal constitutive activity. The functional selectivity and signaling bias of many GHSR-1a-specific ligands has not been fully characterized. In this study, we investigated the pharmacologic properties of ghrelin, MK-0677, L692,585, and [d-Lys3]-growth hormone-releasing peptide-6 (Dlys), JMV2959, and [d-Arg(1),d-Phe(5),d-Trp(7, 9),Leu(11)]-substance P (SP-analog). We investigated their effect on basal GHSR-1a constitutive signaling, ligand-directed downstream GHSR-1a signaling, functional selectivity, and signaling bias. Dlys behaved as a partial antagonist with a strong bias toward GHSR-1a-β-arrestin signaling, whereas JMV2959 acted as a full unbiased GHSR-1a antagonist. Moreover, the SP-analog behaved as an inverse agonist increasing G-protein-dependent signaling, but only at high concentrations, whereas, at low concentrations, the SP-analog attenuated β-arrestin-dependent signaling. Considering the limited success in the clinical development of GHSR-1a-targeted drugs so far, these findings provide a novel insight into the pharmacologic characteristics of GHSR-1a ligands and their signaling bias, which has important implications in the design of novel, more selective GHSR-1a ligands with predictable functional outcome and selectivity for preclinical and clinical drug development.-Ramirez, V. T., van Oeffelen, W. E. P. A., Torres-Fuentes, C., Chruścicka, B., Druelle, C., Golubeva, A. V., van de Wouw, M., Dinan, T. G., Cryan, J. F., Schellekens, H. Differential functional selectivity and downstream signaling bias of ghrelin receptor antagonists and inverse agonists.
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Affiliation(s)
- Valerie T Ramirez
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | | | - Cristina Torres-Fuentes
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | - Barbara Chruścicka
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | - Clementine Druelle
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | - Anna V Golubeva
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland
| | - Marcel van de Wouw
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland.,Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Timothy G Dinan
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland.,Department of Psychiatry, University College Cork, Cork, Ireland; and
| | - John F Cryan
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland.,Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.,Food for Health Ireland, University College Cork, Cork, Ireland
| | - Harriët Schellekens
- Alimentary Pharmabiotic Centre (APC) Microbiome Ireland, University College Cork, Cork, Ireland.,Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.,Food for Health Ireland, University College Cork, Cork, Ireland
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22
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Li N, Song G, Wang Y, Zhu Q, Han F, Zhang C, Zhou Y. Blocking constitutive activity of GHSR1a in the lateral amygdala facilitates acquisition of conditioned taste aversion. Neuropeptides 2018; 68:22-27. [PMID: 29254662 DOI: 10.1016/j.npep.2017.12.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 11/05/2017] [Accepted: 12/05/2017] [Indexed: 11/28/2022]
Abstract
Ghrelin is a circulating peptide hormone promoting feeding and regulating energy metabolism in human and rodents. Ghrelin functions by binding to its receptor, the growth hormone secretagogue receptor 1a (GHSR1a), which are widely distributed throughout the brain including the amygdala, a brain region important for regulating valenced behavior, such as aversion. Interestingly, GHSR1a was once characterized by highly constitutive, ligand-independent activity. However, the physiological importance of such ligand-independent signaling on aversive memory processing has not been tested yet. Here, we applied [D-Arg1, D-Phe5, D-Trp7,9, Leu11]-Substance P (D-SP), a full inverse agonist for GHSR1a, into the lateral amygdala (LA) and investigated the effect of blocking GHSR1a constitutive activity on conditioned taste aversion (CTA) in rats. We found that intra-LA infusion of a single low dose of D-SP (8ng/0.5μl/side) facilitates CTA acquisition. Moreover, pre-administration of a high dose of D-SP into the LA abolishes the suppressive effect of exogenous ghrelin on CTA acquisition. In contrast, pre-administration of the same dose of D-SP does not affect the suppression of substance P, a potent neurokinin-1 (NK1) receptor ligand, on CTA. Therefore, our data indicated that the spontaneous or basal activity of GHSR1a signaling in the LA might interfere with CTA memory formation. D-SP decreases the constitutive activity of GHSR1a and thus facilitates CTA. Altogether, our present findings along with previous results support the idea that ghrelin/GHSR1a signaling in the LA circuit blocks conditioned taste aversion.
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Affiliation(s)
- Nan Li
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Ge Song
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Yaohui Wang
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Qianqian Zhu
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Fubing Han
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Chonghui Zhang
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Yu Zhou
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China.
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23
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Huang XF, Weston-Green K, Yu Y. Decreased 5-HT2cR and GHSR1a interaction in antipsychotic drug-induced obesity. Obes Rev 2018; 19:396-405. [PMID: 29119689 DOI: 10.1111/obr.12638] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [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: 07/19/2017] [Revised: 09/20/2017] [Accepted: 10/01/2017] [Indexed: 12/19/2022]
Abstract
Second generation antipsychotics (SGAs), notably atypical antipsychotics including olanzapine, clozapine and risperidone, can cause weight gain and obesity side effects. Antagonism of serotonin 2c receptors (5-HT2cR) and activation of ghrelin receptor type 1a (GHSR1a) signalling have been identified as a main cause of SGA induced obesity. Here we review the pivotal regulatory role of the 5-HT2cR in ghrelin-mediated appetite signalling. The 5-HT2cR dimerizes with GHSR1a to inhibit orexigenic signalling, while 5-HT2cR antagonism reduces dimerization and increases GHSR1a-induced food intake. Dimerization is specific to the unedited 5-HT2cR isoform. 5-HT2cR antagonism by SGAs may disrupt the normal inhibitory tone on the GHSR1a, increasing orexigenic signalling. The 5-HT2cR and its interaction with the GHSR1a could serve as the basis for discovering novel approaches to preventing and treating SGA-induced obesity.
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Affiliation(s)
- X-F Huang
- School of Medicine, University of Wollongong and Illawarra Health and Medical Research Institute, NSW, Australia.,Jiangsu Key Laboratory for Immunity and Metabolism, Xuzhou Medical University, Jiangsu, China.,Centre for Medical and Molecular Biosciences, Faculty of Science, Medicine and Health, University of Wollongong, NSW, Australia
| | - K Weston-Green
- School of Medicine, University of Wollongong and Illawarra Health and Medical Research Institute, NSW, Australia.,Centre for Medical and Molecular Biosciences, Faculty of Science, Medicine and Health, University of Wollongong, NSW, Australia
| | - Y Yu
- School of Medicine, University of Wollongong and Illawarra Health and Medical Research Institute, NSW, Australia.,Jiangsu Key Laboratory for Immunity and Metabolism, Xuzhou Medical University, Jiangsu, China
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24
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Cleverdon ER, McGovern-Gooch KR, Hougland JL. The octanoylated energy regulating hormone ghrelin: An expanded view of ghrelin's biological interactions and avenues for controlling ghrelin signaling. Mol Membr Biol 2017; 33:111-124. [PMID: 29143554 DOI: 10.1080/09687688.2017.1388930] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [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: 12/26/2022]
Abstract
Ghrelin is a small peptide hormone that requires a unique post-translational modification, serine octanoylation, to bind and activate the GHS-R1a receptor. Initially demonstrated to stimulate hunger and appetite, ghrelin-dependent signaling is implicated in a variety of neurological and physiological processes influencing diseases such as diabetes, obesity, and Prader-Willi syndrome. In addition to its cognate receptor, recent studies have revealed ghrelin interacts with a range of binding partners within the bloodstream. Defining the scope of ghrelin's interactions within the body, understanding how these interactions work in concert to modulate ghrelin signaling, and developing molecular tools for controlling ghrelin signaling are essential for exploiting ghrelin for therapeutic effect. In this review, we discuss recent findings regarding the biological effects of ghrelin signaling, outline binding partners that control ghrelin trafficking and stability in circulation, and summarize the current landscape of inhibitors targeting ghrelin octanoylation.
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Affiliation(s)
| | | | - James L Hougland
- a Department of Chemistry , Syracuse University , Syracuse , NY , USA
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25
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Harmatz ES, Stone L, Lim SH, Lee G, McGrath A, Gisabella B, Peng X, Kosoy E, Yao J, Liu E, Machado NJ, Weiner VS, Slocum W, Cunha RA, Goosens KA. Central Ghrelin Resistance Permits the Overconsolidation of Fear Memory. Biol Psychiatry 2017; 81:1003-1013. [PMID: 28010876 PMCID: PMC5447505 DOI: 10.1016/j.biopsych.2016.11.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [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: 07/18/2016] [Revised: 10/25/2016] [Accepted: 11/10/2016] [Indexed: 02/07/2023]
Abstract
BACKGROUND There are many contradictory findings about the role of the hormone ghrelin in aversive processing, with studies suggesting that ghrelin signaling can both inhibit and enhance aversion. Here, we characterize and reconcile the paradoxical role of ghrelin in the acquisition of fearful memories. METHODS We used enzyme-linked immunosorbent assay to measure endogenous acyl-ghrelin and corticosterone at time points surrounding auditory fear learning. We used pharmacological (systemic and intra-amygdala) manipulations of ghrelin signaling and examined several aversive and appetitive behaviors. We also used biotin-labeled ghrelin to visualize ghrelin binding sites in coronal brain sections of amygdala. All work was performed in rats. RESULTS In unstressed rodents, endogenous peripheral acyl-ghrelin robustly inhibits fear memory consolidation through actions in the amygdala and accounts for virtually all interindividual variability in long-term fear memory strength. Higher levels of endogenous ghrelin after fear learning were associated with weaker long-term fear memories, and pharmacological agonism of the ghrelin receptor during the memory consolidation period reduced fear memory strength. These fear-inhibitory effects cannot be explained by changes in appetitive behavior. In contrast, we show that chronic stress, which increases both circulating endogenous acyl-ghrelin and fear memory formation, promotes profound loss of ghrelin binding sites in the amygdala and behavioral insensitivity to ghrelin receptor agonism. CONCLUSIONS These studies provide a new link between stress, a novel type of metabolic resistance, and vulnerability to excessive fear memory formation and reveal that ghrelin can regulate negative emotionality in unstressed animals without altering appetite.
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Affiliation(s)
- Elia S Harmatz
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Lauren Stone
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Seh Hong Lim
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge; Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts
| | - Graham Lee
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Anna McGrath
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Barbara Gisabella
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Xiaoyu Peng
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Eliza Kosoy
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Junmei Yao
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Elizabeth Liu
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Nuno J Machado
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge; Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal; Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Veronica S Weiner
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Warren Slocum
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge
| | - Rodrigo A Cunha
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal; Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Ki A Goosens
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge.
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26
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Bake T, Hellgren KT, Dickson SL. Acute ghrelin changes food preference from a high-fat diet to chow during binge-like eating in rodents. J Neuroendocrinol 2017; 29:10.1111/jne.12463. [PMID: 28219000 PMCID: PMC5434925 DOI: 10.1111/jne.12463] [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] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 01/25/2017] [Accepted: 02/16/2017] [Indexed: 01/20/2023]
Abstract
Ghrelin, an orexigenic hormone released from the empty stomach, provides a gut-brain signal that promotes many appetitive behaviours, including anticipatory and goal-directed behaviours for palatable treats high in sugar and/or fat. In the present study, we aimed to determine whether ghrelin is able to influence and/or may even have a role in binge-like eating behaviour in rodents. Accordingly, we used a palatable scheduled feeding (PSF) paradigm in which ad lib. chow-fed rodents are trained to 'binge' on a high-fat diet (HFD) offered each day for a limited period of 2 hours. After 2 weeks of habituation to this paradigm, on the test day and immediately prior to the 2-hour PSF, rats were administered ghrelin or vehicle solution by the i.c.v. route. Remarkably and unexpectedly, during the palatable scheduled feed, when rats normally only binge on the HFD, those injected with i.c.v. ghrelin started to eat more chow and chow intake remained above baseline for the rest of the 24-hour day. We identify the ventral tegmental area (VTA) (a key brain area involved in food reward) as a substrate involved because these effects could be reproduced, in part, by intra-VTA delivery of ghrelin. Fasting, which increases endogenous ghrelin, immediately prior to a palatable schedule feed also increased chow intake during/after the schedule feed but, in contrast to ghrelin injection, did not reduce HFD intake. Chronic continuous central ghrelin infusion over several weeks enhanced binge-like behaviour in palatable schedule fed rats. Over a 4-week period, GHS-R1A-KO mice were able to adapt and maintain large meals of HFD in a manner similar to wild-type mice, suggesting that ghrelin signalling may not have a critical role in the acquisition or maintenance in this kind of feeding behaviour. In conclusion, ghrelin appears to act as a modulating factor for binge-like eating behaviour by shifting food preference towards a more nutritious choice (from HFD to chow), with these effects being somewhat divergent from fasting.
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Affiliation(s)
- T. Bake
- Department of Physiology/EndocrineInstitute of Neuroscience and PhysiologyThe Sahlgrenska Academy at the University of GothenburgGothenburgSweden
| | - K. T. Hellgren
- Department of Physiology/EndocrineInstitute of Neuroscience and PhysiologyThe Sahlgrenska Academy at the University of GothenburgGothenburgSweden
| | - S. L. Dickson
- Department of Physiology/EndocrineInstitute of Neuroscience and PhysiologyThe Sahlgrenska Academy at the University of GothenburgGothenburgSweden
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27
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Labarthe A, Tolle V. [Ghrelin: a gastric hormone at the crossroad between growth and appetite regulation]. Biol Aujourdhui 2017; 210:237-257. [PMID: 28327282 DOI: 10.1051/jbio/2016027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Indexed: 06/06/2023]
Abstract
Ghrelin is a 28 amino acid peptide hormone synthesized within the gastrointestinal tract. Initially identified as the endogenous ligand of the GHS-R1a (Growth Hormone Secretagogue Receptor 1a), ghrelin is a powerful stimulator of growth hormone (GH) secretion. At the crossroad between nutrition, growth and long-term energy metabolism, ghrelin also plays a unique role as the first identified gastric hormone increasing appetite and adiposity. However, the role of the ghrelin/GHS-R system in the physiology of growth, feeding behaviour and energy homeostasis needs to be better understood. Utilization of pharmacological tools and complementary animal models with deficiency in preproghrelin, ghrelin-O-acyl-transferase (GOAT - the enzyme that acylates ghrelin -) or GHS-R in situations of chronic undernutrition or high fat diet gives a more precise overview of the role of ghrelin in the pathophysiology of eating and metabolic disorders.
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28
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Cabral A, López Soto EJ, Epelbaum J, Perelló M. Is Ghrelin Synthesized in the Central Nervous System? Int J Mol Sci 2017; 18:E638. [PMID: 28294994 DOI: 10.3390/ijms18030638] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/09/2017] [Accepted: 03/10/2017] [Indexed: 02/06/2023] Open
Abstract
Ghrelin is an octanoylated peptide that acts via its specific receptor, the growth hormone secretagogue receptor type 1a (GHSR-1a), and regulates a vast variety of physiological functions. It is well established that ghrelin is predominantly synthesized by a distinct population of endocrine cells located within the gastric oxyntic mucosa. In addition, some studies have reported that ghrelin could also be synthesized in some brain regions, such as the hypothalamus. However, evidences of neuronal production of ghrelin have been inconsistent and, as a consequence, it is still as a matter of debate if ghrelin can be centrally produced. Here, we provide a comprehensive review and discussion of the data supporting, or not, the notion that the mammalian central nervous system can synthetize ghrelin. We conclude that no irrefutable and reproducible evidence exists supporting the notion that ghrelin is synthetized, at physiologically relevant levels, in the central nervous system of adult mammals.
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29
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Howick K, Griffin BT, Cryan JF, Schellekens H. From Belly to Brain: Targeting the Ghrelin Receptor in Appetite and Food Intake Regulation. Int J Mol Sci 2017; 18:E273. [PMID: 28134808 DOI: 10.3390/ijms18020273] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 01/19/2017] [Indexed: 12/20/2022] Open
Abstract
Ghrelin is the only known peripherally-derived orexigenic hormone, increasing appetite and subsequent food intake. The ghrelinergic system has therefore received considerable attention as a therapeutic target to reduce appetite in obesity as well as to stimulate food intake in conditions of anorexia, malnutrition and cachexia. As the therapeutic potential of targeting this hormone becomes clearer, it is apparent that its pleiotropic actions span both the central nervous system and peripheral organs. Despite a wealth of research, a therapeutic compound specifically targeting the ghrelin system for appetite modulation remains elusive although some promising effects on metabolic function are emerging. This is due to many factors, ranging from the complexity of the ghrelin receptor (Growth Hormone Secretagogue Receptor, GHSR-1a) internalisation and heterodimerization, to biased ligand interactions and compensatory neuroendocrine outputs. Not least is the ubiquitous expression of the GHSR-1a, which makes it impossible to modulate centrally-mediated appetite regulation without encroaching on the various peripheral functions attributable to ghrelin. It is becoming clear that ghrelin’s central signalling is critical for its effects on appetite, body weight regulation and incentive salience of food. Improving the ability of ghrelin ligands to penetrate the blood brain barrier would enhance central delivery to GHSR-1a expressing brain regions, particularly within the mesolimbic reward circuitry.
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30
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Pastor-Cavada E, Pardo LM, Kandil D, Torres-Fuentes C, Clarke SL, Shaban H, McGlacken GP, Schellekens H. A Novel Non-Peptidic Agonist of the Ghrelin Receptor with Orexigenic Activity In vivo. Sci Rep 2016; 6:36456. [PMID: 27819353 PMCID: PMC5098229 DOI: 10.1038/srep36456] [Citation(s) in RCA: 10] [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] [Received: 06/13/2016] [Accepted: 10/17/2016] [Indexed: 01/13/2023] Open
Abstract
Loss of appetite in the medically ill and ageing populations is a major health problem and a significant symptom in cachexia syndromes, which is the loss of muscle and fat mass. Ghrelin is a gut-derived hormone which can stimulate appetite. Herein we describe a novel, simple, non-peptidic, 2-pyridone which acts as a selective agonist for the ghrelin receptor (GHS-R1a). The small 2-pyridone demonstrated clear agonistic activity in both transfected human cells and mouse hypothalamic cells with endogenous GHS-R1a receptor expression. In vivo tests with the hit compound showed significant increased food intake following peripheral administration, which highlights the potent orexigenic effect of this novel GHS-R1a receptor ligand.
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Affiliation(s)
- Elena Pastor-Cavada
- Alimentary Pharmabiotic Centre (APC) Microbiome Institute, University College Cork, Cork, Ireland
| | - Leticia M Pardo
- Department of Chemistry and the Analytical and Biological Chemistry Research Facility (ABCRF), University College Cork, Cork, Ireland
| | - Dalia Kandil
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Cristina Torres-Fuentes
- Alimentary Pharmabiotic Centre (APC) Microbiome Institute, University College Cork, Cork, Ireland
| | - Sarah L Clarke
- Department of Chemistry and the Analytical and Biological Chemistry Research Facility (ABCRF), University College Cork, Cork, Ireland
| | - Hamdy Shaban
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Gerard P McGlacken
- Department of Chemistry and the Analytical and Biological Chemistry Research Facility (ABCRF), University College Cork, Cork, Ireland
| | - Harriet Schellekens
- Alimentary Pharmabiotic Centre (APC) Microbiome Institute, University College Cork, Cork, Ireland.,Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
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31
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Denney WS, Sonnenberg GE, Carvajal-Gonzalez S, Tuthill T, Jackson VM. Pharmacokinetics and pharmacodynamics of PF-05190457: The first oral ghrelin receptor inverse agonist to be profiled in healthy subjects. Br J Clin Pharmacol 2016; 83:326-338. [PMID: 27621150 DOI: 10.1111/bcp.13127] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [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: 02/09/2016] [Revised: 08/25/2016] [Accepted: 09/08/2016] [Indexed: 02/06/2023] Open
Abstract
AIM To evaluate safety, tolerability and pharmacokinetics of oral PF-05190457, an oral ghrelin receptor inverse agonist, in healthy adults. METHODS Single (SAD) and multiple ascending dose (MAD) studies were randomised, placebo-controlled, double-blind studies. Thirty-five healthy men (age 38.2 ± 10.4 years; body mass index 24.8 ± 3.1 kg m-2 [mean ± standard deviation]) received ≥1 dose (2, 10, 40 [divided], 50, 100, 150, and 300 [single or divided] mg) of PF-05190457 and/or placebo in the SAD. In the MAD study, 35 healthy men (age 39.7 ± 10.1 years; body mass index 25.9 ± 3.3 kg m-2 ) received ≥1 dose (2, 10, 40 and 100 mg twice daily) of PF-05190457 and/or placebo daily for 2 weeks. RESULTS PF-05190457 absorption was rapid with a Tmax of 0.5-3 hours and a half-life between 8.2-9.8 hours. PF-05190457 dose-dependently blocked ghrelin (1 pmol kg-1 min-1 )-induced growth hormone (GH) release with (mean [90% confidence interval]) 77% [63-85%] inhibition at 100 mg. PF-05190457 (150 mg) delayed gastric emptying lag time by 30% [7-58%] and half emptying time by 20% [7-35%] with a corresponding decrease in postprandial glucose by 9 mg dL-1 . The most frequent adverse event reported by 30 subjects at doses ≥50 mg was somnolence. PF-05190457 plasma concentrations also increased heart rate up to 13.4 [4.8-58.2] beats min-1 and, similar to the effect on glucose and ghrelin-induced GH, was lost within 2 weeks. CONCLUSIONS PF-05190457 is a well-tolerated first-in-class ghrelin receptor inverse agonist with acceptable pharmacokinetics for oral daily dosing. Blocking ghrelin receptors inhibits ghrelin-induced GH, and increases heart rate, effects that underwent tachyphylaxis with chronic dosing. PF-051940457 has the potential to treat centrally-acting disorders such as insomnia.
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Affiliation(s)
- William S Denney
- Biotherapeutics Clinical Pharmacology, Pfizer Worldwide Research and Development, Cambridge, Massachusetts, 02139, USA
| | - Gabriele E Sonnenberg
- Cardiovascular, Metabolic, and Endocrine Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts, 02139, USA
| | - Santos Carvajal-Gonzalez
- Cardiovascular, Metabolic, and Endocrine Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts, 02139, USA
| | - Theresa Tuthill
- Cardiovascular, Metabolic, and Endocrine Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts, 02139, USA
| | - V Margaret Jackson
- Cardiovascular, Metabolic, and Endocrine Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts, 02139, USA
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32
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Abstract
The gut-derived hormone ghrelin regulates growth hormone release, appetite, metabolism, and immune function through its receptor, the growth hormone secretagogue receptor 1a (GHSR1a). In this issue of Science Signaling, Chebani et al decode GHSR1a signaling by using transgenic rats with a mutation in GHSR1a that prevents its interaction with β-arrestin. These mutant rats are more responsive to endogenous ghrelin, resulting in increased fat deposition and insulin resistance without affecting food intake.
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Affiliation(s)
- Roy G Smith
- Department of Metabolism and Aging, Scripps Research Institute-Florida, 130 Scripps Way, #3B3, Jupiter, FL 33458, USA.
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33
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Bouzo-Lorenzo M, Santo-Zas I, Lodeiro M, Nogueiras R, Casanueva FF, Castro M, Pazos Y, Tobin AB, Butcher AJ, Camiña JP. Distinct phosphorylation sites on the ghrelin receptor, GHSR1a, establish a code that determines the functions of ß-arrestins. Sci Rep 2016; 6:22495. [PMID: 26935831 DOI: 10.1038/srep22495] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 02/15/2016] [Indexed: 01/14/2023] Open
Abstract
The growth hormone secretagogue receptor, GHSR1a, mediates the biological activities
of ghrelin, which includes the secretion of growth hormone, as well as the
stimulation of appetite, food intake and maintenance of energy homeostasis. Mapping
phosphorylation sites on GHSR1a and knowledge of how these sites control specific
functional consequences unlocks new strategies for the development of therapeutic
agents targeting individual functions. Herein, we have identified the
phosphorylation of different sets of sites within GHSR1a which engender distinct
functionality of ß-arrestins. More specifically, the
Ser362, Ser363 and Thr366 residues
at the carboxyl-terminal tail were primarily responsible for ß-arrestin
1 and 2 binding, internalization and ß-arrestin-mediated proliferation
and adipogenesis. The Thr350 and Ser349 are not
necessary for ß-arrestin recruitment, but are involved in the
stabilization of the GHSR1a-ß-arrestin complex in a manner that
determines the ultimate cellular consequences of ß-arrestin signaling.
We further demonstrated that the mitogenic and adipogenic effect of ghrelin were
mainly dependent on the ß-arrestin bound to the phosphorylated GHSR1a.
In contrast, the ghrelin function on GH secretion was entirely mediated by G protein
signaling. Our data is consistent with the hypothesis that the phosphorylation
pattern on the C terminus of GHSR1a determines the signaling and physiological
output.
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34
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Naitou K, Mamerto TP, Pustovit RV, Callaghan B, Rivera LR, Chan AJ, Ringuet MT, Pietra C, Furness JB. Site and mechanism of the colokinetic action of the ghrelin receptor agonist, HM01. Neurogastroenterol Motil 2015; 27:1764-71. [PMID: 26416336 DOI: 10.1111/nmo.12688] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [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: 07/02/2015] [Accepted: 08/23/2015] [Indexed: 02/06/2023]
Abstract
BACKGROUND It has been recently demonstrated that the ghrelin receptor agonist, HM01, caused defecation in rats that were treated to provide a model for the constipation of Parkinson's disease. HM01 significantly increased fecal output and increased Fos activity in neurons of the hypothalamus and hindbrain, but not in the spinal defecation center. Other ghrelin agonists act on the defecation center. METHODS Receptor pharmacology was examined in ghrelin receptor (GHSR1a) transfected cells. Anesthetized rats were used to investigate sites and mechanisms of action. KEY RESULTS HM01 activated rat GHSR1a at nanomolar concentrations and was antagonized by the GHSR1a antagonist, YIL781. HM01, intravenous, was potent to activate propulsive colorectal contractions. This was prevented by pelvic nerve section and by intravenous YIL781, but not by spinal cord section rostral to the defecation centers. Direct intrathecal application of HM01 to the defecation center at spinal level L6-S1 initiated propulsive contractions of the colorectum. CONCLUSIONS & INFERENCES HM01 stimulates GHSR1a receptors on neurons in the lumbosacral defecation centers to cause propulsive contractions and emptying of the colorectum. It has greater potency when given systemically, compared with other GHSR1a agonists.
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Affiliation(s)
- K Naitou
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia.,Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - T P Mamerto
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - R V Pustovit
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - B Callaghan
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - L R Rivera
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - A J Chan
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - M T Ringuet
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - C Pietra
- Helsinn Research and Preclinical Department, Lugano, Switzerland
| | - J B Furness
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia.,Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
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35
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Muniz BG, Isokawa M. Ghrelin receptor activity amplifies hippocampal N-methyl-d-aspartate receptor-mediated postsynaptic currents and increases phosphorylation of the GluN1 subunit at Ser896 and Ser897. Eur J Neurosci 2015; 42:3045-53. [PMID: 26490687 DOI: 10.1111/ejn.13107] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [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: 06/09/2015] [Revised: 10/13/2015] [Accepted: 10/15/2015] [Indexed: 12/31/2022]
Abstract
Although ghrelin and its cognate receptor growth hormone secretagogue receptor (GHSR1a) are highly localized in the hypothalamic nuclei for the regulation of metabolic states and feeding, GHSR1a is also highly localized in the hippocampus, suggesting its involvement in extra-hypothalamic functions. Indeed, exogenous application of ghrelin has been reported to improve hippocampal learning and memory. However, the underlying mechanism of ghrelin regulation of hippocampal functions is poorly understood. Here, we report ghrelin-promoted phosphorylation of GluN1 and amplified N-methyl-d-aspartate receptor (NMDAR)-mediated excitatory postsynaptic currents in the CA1 pyramidal cells of the hippocampus in slice preparations. The ghrelin-induced responses were sensitive to a GHSR1a antagonist and inverse agonist, and were absent in GHSR1a homozygous knock-out mice. These results indicated that activation of GHSR1a was critical in the ghrelin-induced enhancement of the NMDAR function. Interestingly, heterozygous mouse hippocampi were also insensitive to ghrelin treatment, suggesting that a slight reduction in the availability of GHSR1a may be sufficient to negate the effect of ghrelin on GluN1 phosphorylation and NMDAR channel activities. In addition, NMDAR-mediated spike currents, which are of dendritic origin, were blocked by the GHSR1a antagonist, suggesting the presence of GHSR1a on the pyramidal cell dendrites in physical proximity to NMDAR. Together with our findings on the localization of GHSR1a in the CA1 region of the hippocampus, which was shown by fluorescent ghrelin binding, immunoreactivity, and enhanced green fluorescent protein reporter gene expression, we conclude that the activation of GHSR1a favours rapid modulation of the NMDAR-mediated glutamatergic synaptic transmission by phosphorylating GluN1 in the hippocampus.
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Affiliation(s)
- Brandon G Muniz
- Department of Health and Biomedical Sciences, The University of Texas Rio Grande Valley, One West University Boulevard, Brownsville, TX, 78520, USA
| | - Masako Isokawa
- Department of Health and Biomedical Sciences, The University of Texas Rio Grande Valley, One West University Boulevard, Brownsville, TX, 78520, USA
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Ferro P, Gutiérrez-Gallego R, Bosch J, Farré M, Segura J. Fit-for-Purpose Radio Receptor Assay for the Determination of Growth Hormone Secretagogues in Urine. ACTA ACUST UNITED AC 2015; 20:1268-76. [DOI: 10.1177/1087057115594590] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 06/14/2015] [Indexed: 12/27/2022]
Abstract
The everlasting pharmacological development is continuously producing new substances with potential doping abuse. Among these, secretagogues are very prone to misuse by athletes for their properties to release growth hormone (GH) and some limitations in the actual analytical methods to detect them. In this paper, an in-depth study on the key variables of the radio receptor method previously developed by our group is performed and a fit-for-purpose protocol is established. Thus, this sensitive and robust screening method is proposed as an intelligent and preventive antidoping method to detect new growth hormone secretagogues (GHSs) in exceptional suspicious urine samples obtained from athletes and will support the current detection methods based on liquid chromatography–mass spectrometry (LC-MS).
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Affiliation(s)
- P. Ferro
- Bioanalysis Research Group, Neuroscience Research Program, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain
| | - R. Gutiérrez-Gallego
- Department of Experimental and Health Sciences, Pompeu Fabra University, Barcelona Biomedical Research Park, Barcelona, Spain
- Anapharm Biotech, Barcelona, Spain
| | - J. Bosch
- Bioanalysis Research Group, Neuroscience Research Program, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain
| | - M. Farré
- Human Pharmacology and Neurosciences Research Group, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain
- Department of Pharmacology, Therapeutics and Toxicology, Universitat Autònoma de Barcelona–UAB, Cerdanyola del Vallés (Bellaterra), Spain
| | - J. Segura
- Bioanalysis Research Group, Neuroscience Research Program, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain
- Department of Experimental and Health Sciences, Pompeu Fabra University, Barcelona Biomedical Research Park, Barcelona, Spain
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Karasawa H, Pietra C, Giuliano C, Garcia-Rubio S, Xu X, Yakabi S, Taché Y, Wang L. New ghrelin agonist, HM01 alleviates constipation and L-dopa-delayed gastric emptying in 6-hydroxydopamine rat model of Parkinson's disease. Neurogastroenterol Motil 2014; 26:1771-82. [PMID: 25327342 PMCID: PMC4457321 DOI: 10.1111/nmo.12459] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [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: 08/07/2014] [Accepted: 09/18/2014] [Indexed: 12/31/2022]
Abstract
BACKGROUND Constipation and L-dopa-induced gastric dysmotility are common gastrointestinal (GI) symptoms in Parkinson's disease (PD). We investigated the novel ghrelin agonist, HM01 influence on GI motor dysfunctions in 6-hydroxydopamine (6-OHDA) rats. METHODS HM01 pharmacological profiles were determined in vitro and in vivo in rats. We assessed changes in fecal output and water content, and gastric emptying (GE) in 6-OHDA rats treated with orogastric (og) HM01 and L-dopa/carbidopa (LD/CD, 20/2 mg/kg). Fos immunoreactivity (ir) cells in specific brain and lumbosacral spinal cord were quantified. KEY RESULTS HM01 displayed a high binding affinity to ghrelin receptor (Ki: 1.42 ± 0.36 nM), 4.3 ± 1.0 h half-life and high brain/plasma ratio. 6-OHDA rats had reduced daily fecal output (22%) and water intake (23%) compared to controls. HM01 (3 and 10 mg/kg) similarly reversed the decreased 4-h fecal weight and water content in 6-OHDA rats. Basal GE was not modified in 6-OHDA rats, however, LD/CD (once or daily for 8 days) delayed GE in 6-OHDA and control rats that was prevented by HM01 (3 mg/kg acute or daily before LD/CD). HM01 increased Fos-ir cell number in the area postrema, arcuate nucleus, nucleus tractus solitarius, and lumbosacral intermediolateral column of 6-OHDA rats where 6-OHDA had a lowering effect compared to controls. CONCLUSIONS & INFERENCES 6-OHDA rats display constipation- and adipsia-like features of PD and L-dopa-inhibited GE. The new orally active ghrelin agonist, HM01 crosses the blood-brain barrier and alleviates these alterations suggesting a potential benefit for PD with GI disorders.
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Affiliation(s)
- H Karasawa
- Department of Medicine, CURE/Digestive Diseases Center, Digestive Diseases Division, University of California at Los Angeles, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA
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Arslan G, Ayyildiz M, Agar E. The interaction between ghrelin and cannabinoid systems in penicillin-induced epileptiform activity in rats. Neuropeptides 2014; 48:345-52. [PMID: 25256087 DOI: 10.1016/j.npep.2014.09.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 09/04/2014] [Accepted: 09/08/2014] [Indexed: 02/03/2023]
Abstract
The majority of experimental and clinical studies show that ghrelin and cannabinoids are potent inhibitors of epileptic activity in various models of epilepsy. A number of studies have attempted to understand the connection between ghrelin and cannabinoid signalling in the regulation of food intake. Since no data show a functional interaction between ghrelin and cannabinoids in epilepsy, we examined the relationship between these systems via penicillin-induced epileptiform activity in rats. Doses of the CB1 receptor agonist arachidonyl-2-chloroethylamide (ACEA) (2.5 and 7.5 µg), the CB1 receptor antagonist N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3 carboxamide (AM-251) (0.25 and 0.5 µg) and ghrelin (0.5 and 1 µg) were administered intracerebroventricularly (i.c.v.) 30 minutes after the intracortical (i.c.) application of penicillin. In the interaction groups, the animals received either an effective dose of ACEA (7.5 µg, i.c.v.) or a non-effective dose of ACEA (2.5 µg, i.c.v.) or effective doses of AM-251 (0.25, 0.5 µg, i.c.v.) 10 minutes after ghrelin application. A 1 µg dose of ghrelin suppressed penicillin-induced epileptiform activity. The administration of a 0.25 µg dose of AM-251 increased the frequency of penicillin-induced epileptiform activity by producing status epilepticus-like activity. A 7.5 µg dose of ACEA decreased the frequency of epileptiform activity, whereas a non-effective dose of ACEA (2.5 µg) did not change it. Effective doses of AM-251 (0.25, 0.5 µg) reversed the ghrelin's anticonvulsant activity. The application of non-effective doses of ACEA (2.5 µg) together with ghrelin (0.5 µg) within 10 minutes caused anticonvulsant activity, which was reversed by the administration of AM-251 (0.25 µg). The electrophysiological evidence from this study suggests a possible interaction between ghrelin and cannabinoid CB1 receptors in the experimental model of epilepsy.
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Affiliation(s)
- Gokhan Arslan
- Department of Physiology, Faculty of Medicine, University of Ondokuz Mayis, Samsun, Turkey
| | - Mustafa Ayyildiz
- Department of Physiology, Faculty of Medicine, University of Ondokuz Mayis, Samsun, Turkey
| | - Erdal Agar
- Department of Physiology, Faculty of Medicine, University of Ondokuz Mayis, Samsun, Turkey.
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Meyer RM, Burgos-Robles A, Liu E, Correia SS, Goosens KA. A ghrelin-growth hormone axis drives stress-induced vulnerability to enhanced fear. Mol Psychiatry 2014; 19:1284-94. [PMID: 24126924 PMCID: PMC3988273 DOI: 10.1038/mp.2013.135] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [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: 02/13/2013] [Revised: 08/20/2013] [Accepted: 09/09/2013] [Indexed: 01/05/2023]
Abstract
Hormones in the hypothalamus-pituitary-adrenal (HPA) axis mediate many of the bodily responses to stressors, yet there is no clear relationship between the levels of these hormones and stress-associated mental illnesses such as posttraumatic stress disorder (PTSD). Therefore, other hormones are likely to be involved in this effect of stress. Here we used a rodent model of PTSD in which rats repeatedly exposed to a stressor display heightened fear learning following auditory Pavlovian fear conditioning. Our results show that stress-related increases in circulating ghrelin, a peptide hormone, are necessary and sufficient for stress-associated vulnerability to exacerbated fear learning and these actions of ghrelin occur in the amygdala. Importantly, these actions are also independent of the classic HPA stress axis. Repeated systemic administration of a ghrelin receptor agonist enhanced fear memory but did not increase either corticotropin-releasing factor (CRF) or corticosterone. Repeated intraamygdala infusion of a ghrelin receptor agonist produced a similar enhancement of fear memory. Ghrelin receptor antagonism during repeated stress abolished stress-related enhancement of fear memory without blunting stress-induced corticosterone release. We also examined links between ghrelin and growth hormone (GH), a major downstream effector of the ghrelin receptor. GH protein was upregulated in the amygdala following chronic stress, and its release from amygdala neurons was enhanced by ghrelin receptor stimulation. Virus-mediated overexpression of GH in the amygdala was also sufficient to increase fear. Finally, virus-mediated overexpression of a GH receptor antagonist was sufficient to block the fear-enhancing effects of repeated ghrelin receptor stimulation. Thus, ghrelin requires GH in the amygdala to exert fear-enhancing effects. These results suggest that ghrelin mediates a novel branch of the stress response and highlight a previously unrecognized role for ghrelin and growth hormone in maladaptive changes following prolonged stress.
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Affiliation(s)
- Retsina M. Meyer
- McGovern Institute for Brain Research and the Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 43 Vassar St, Cambridge, MA 02139, USA
| | - Anthony Burgos-Robles
- McGovern Institute for Brain Research and the Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 43 Vassar St, Cambridge, MA 02139, USA
| | - Elizabeth Liu
- McGovern Institute for Brain Research and the Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 43 Vassar St, Cambridge, MA 02139, USA
| | - Susana S. Correia
- McGovern Institute for Brain Research and the Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 43 Vassar St, Cambridge, MA 02139, USA
| | - Ki A. Goosens
- McGovern Institute for Brain Research and the Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 43 Vassar St, Cambridge, MA 02139, USA
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Abstract
The G protein-coupled ghrelin receptor GHSR1a is a potential pharmacological target for treating obesity and addiction because of the critical role ghrelin plays in energy homeostasis and dopamine-dependent reward. GHSR1a enhances growth hormone release, appetite, and dopamine signaling through G(q/11), G(i/o), and G(12/13) as well as β-arrestin-based scaffolds. However, the contribution of individual G protein and β-arrestin pathways to the diverse physiological responses mediated by ghrelin remains unknown. To characterize whether a signaling bias occurs for GHSR1a, we investigated ghrelin signaling in a number of cell-based assays, including Ca(2+) mobilization, serum response factor response element, stress fiber formation, ERK1/2 phosphorylation, and β-arrestin translocation, utilizing intracellular second loop and C-tail mutants of GHSR1a. We observed that GHSR1a and β-arrestin rapidly form metastable plasma membrane complexes following exposure to an agonist, but replacement of the GHSR1a C-tail by the tail of the vasopressin 2 receptor greatly stabilizes them, producing complexes observable on the plasma membrane and also in endocytic vesicles. Mutations of the contiguous conserved amino acids Pro-148 and Leu-149 in the GHSR1a intracellular second loop generate receptors with a strong bias to G protein and β-arrestin, respectively, supporting a role for conformation-dependent signaling bias in the wild-type receptor. Our results demonstrate more balance in GHSR1a-mediated ERK signaling from G proteins and β-arrestin but uncover an important role for β-arrestin in RhoA activation and stress fiber formation. These findings suggest an avenue for modulating drug abuse-associated changes in synaptic plasticity via GHSR1a and indicate the development of GHSR1a-biased ligands as a promising strategy for selectively targeting downstream signaling events.
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Affiliation(s)
| | | | | | - Yushi Bai
- From the Departments of Cell Biology
| | | | - Marc G Caron
- From the Departments of Cell Biology, Neurobiology, and Medicine, Duke University, Medical Center, Durham, North Carolina 27710
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Torres-Fuentes C, Theeuwes WF, McMullen MK, McMullen AK, Dinan TG, Cryan JF, Schellekens H. Devil's Claw to suppress appetite--ghrelin receptor modulation potential of a Harpagophytum procumbens root extract. PLoS One 2014; 9:e103118. [PMID: 25068823 PMCID: PMC4113378 DOI: 10.1371/journal.pone.0103118] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 06/25/2014] [Indexed: 11/29/2022] Open
Abstract
Ghrelin is a stomach-derived peptide that has been identified as the only circulating hunger hormone that exerts a potent orexigenic effect via activation of its receptor, the growth hormone secretagogue receptor (GHS-R1a). Hence, the ghrelinergic system represents a promising target to treat obesity and obesity-related diseases. In this study we analysed the GHS-R1a receptor activating potential of Harpagophytum procumbens, popularly known as Devil's Claw, and its effect on food intake in vivo. H. procumbens is an important traditional medicinal plant from Southern Africa with potent anti-inflammatory and analgesic effects. This plant has been also used as an appetite modulator but most evidences are anecdotal and to our knowledge, no clear scientific studies relating to appetite modulation have been done to this date. The ghrelin receptor activation potential of an extract derived from the dried tuberous roots of H. procumbens was analysed by calcium mobilization and receptor internalization assays in human embryonic kidney cells (Hek) stably expressing the GHS-R1a receptor. Food intake was investigated in male C57BL/6 mice following intraperitoneal administration of H. procumbens root extract in ad libitum and food restricted conditions. Exposure to H. procumbens extract demonstrated a significant increased cellular calcium influx but did not induce subsequent GHS-R1a receptor internalization, which is a characteristic for full receptor activation. A significant anorexigenic effect was observed in male C57BL/6 mice following peripheral administration of H. procumbens extract. We conclude that H. procumbens root extract is a potential novel source for potent anti-obesity bioactives. These results reinforce the promising potential of natural bioactives to be developed into functional foods with weight-loss and weight maintenance benefits.
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Affiliation(s)
| | - Wessel F. Theeuwes
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Michael K. McMullen
- Life Force Research, Ljungskile, Sweden
- School of Biosciences, University of Westminster, London, United Kingdom
| | | | - Timothy G. Dinan
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- Dept of Psychiatry, University College Cork, Cork, Ireland
| | - John F. Cryan
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Harriët Schellekens
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
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Yin Y, Li Y, Zhang W. The growth hormone secretagogue receptor: its intracellular signaling and regulation. Int J Mol Sci. 2014;15:4837-4855. [PMID: 24651458 PMCID: PMC3975427 DOI: 10.3390/ijms15034837] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/06/2014] [Accepted: 03/11/2014] [Indexed: 01/29/2023] Open
Abstract
The growth hormone secretagogue receptor (GHSR), also known as the ghrelin receptor, is involved in mediating a wide variety of biological effects of ghrelin, including: stimulation of growth hormone release, increase of food intake and body weight, modulation of glucose and lipid metabolism, regulation of gastrointestinal motility and secretion, protection of neuronal and cardiovascular cells, and regulation of immune function. Dependent on the tissues and cells, activation of GHSR may trigger a diversity of signaling mechanisms and subsequent distinct physiological responses. Distinct regulation of GHSR occurs at levels of transcription, receptor interaction and internalization. Here we review the current understanding on the intracellular signaling pathways of GHSR and its modulation. An overview of the molecular structure of GHSR is presented first, followed by the discussion on its signaling mechanisms. Finally, potential mechanisms regulating GHSR are reviewed.
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Pustovit RV, Callaghan B, Kosari S, Rivera LR, Thomas H, Brock JA, Furness JB. The mechanism of enhanced defecation caused by the ghrelin receptor agonist, ulimorelin. Neurogastroenterol Motil 2014; 26:264-71. [PMID: 24304447 DOI: 10.1111/nmo.12259] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [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: 09/23/2013] [Accepted: 10/11/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND Discovery of adequate pharmacological treatments for constipation has proven elusive. Increased numbers of bowel movements were reported as a side-effect of ulimorelin treatment of gastroparesis, but there has been no investigation of the site of action. METHODS Anesthetized rats were used to investigate sites and mechanisms of action of ulimorelin. KEY RESULTS Intravenous ulimorelin (1-5 mg/kg) caused a substantial and prolonged (~1 h) increase in colorectal propulsive activity and expulsion of colonic contents. This was prevented by cutting the nerves emerging from the lumbosacral cord, by the nicotinic receptor antagonist hexamethonium and by antagonists of the ghrelin receptor. The effect of intravenous ulimorelin was mimicked by direct application of ulimorelin (5 μg) to the lumbosacral spinal cord. CONCLUSIONS & INFERENCES Ulimorelin is a potent prokinetic that causes propulsive contractions of the colorectum by activating ghrelin receptors of the lumbosacral defecation centers. Its effects are long-lasting, in contrast with other colokinetics that target ghrelin receptors.
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Affiliation(s)
- R V Pustovit
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
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Dong J, Xu H, Xu H, Wang PF, Cai GJ, Song HF, Wang CC, Dong ZT, Ju YJ, Jiang ZY. Nesfatin-1 stimulates fatty-acid oxidation by activating AMP-activated protein kinase in STZ-induced type 2 diabetic mice. PLoS One 2013; 8:e83397. [PMID: 24391760 PMCID: PMC3877039 DOI: 10.1371/journal.pone.0083397] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Accepted: 11/05/2013] [Indexed: 11/19/2022] Open
Abstract
Nesfatin-1 is an anorexigenic peptide involved in energy homeostasis. Recently, nesfatin-1 was reported to decrease blood glucose level and improve insulin sensitivity in high-fat diet-fed rats. However, little information is known about the influence of nesfatin-1 on lipid metabolism either in physiological or diabetic condition. This study undertook whether nesfatin-1 was involved in the pathophysiology in Streptozotocin-induced type 2 diabetic mice (T2DM), which was induced by a combination of high-calorie diet and two low-doses Streptozotocin. We observed that plasma nesfatin-1 was significantly increased while expression of nesfatin-1 neurons were decreased in hypothalamus in diabetes group compared to only high-calorie diet control group; intravenous injection of nesfatin-1 decreased 0–1h, 0–2h, 0–3h cumulative food intake in T2DM, but 0–24h total food intake had no difference between groups. Body weight and plasma FFA were normalized after nesfatin-1(10 µg/Kg) administration for 6 days. These results suggested that nesfatin-1 improved lipid disorder in T2DM. It was found that blood glucose and insulin resistance coefficient decreased with treatment of nesfatin-1 (both in 1 µg/Kg and 10 µg/Kg doses) in diabetes mice. For further understanding the role of nesfatin-1 on lipid metabolism, we detected p-AMPK and p-ACC of skeletal muscle in T2DM using western blotting. The expression of p-AMPK and p-ACC increased when nesfatin-1 was given with doses 1 µg/Kg but not in doses 10 µg/Kg. Taken together, nesfatin-1 participated in the development of T2DM and stimulated free fatty acid utilization via AMPK-ACC pathway in skeletal muscle in T2DM.
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MESH Headings
- AMP-Activated Protein Kinases/metabolism
- Acetyl-CoA Carboxylase/metabolism
- Animals
- Blood Glucose/metabolism
- Calcium-Binding Proteins/administration & dosage
- Calcium-Binding Proteins/blood
- Calcium-Binding Proteins/metabolism
- DNA-Binding Proteins/administration & dosage
- DNA-Binding Proteins/blood
- DNA-Binding Proteins/metabolism
- Diabetes Mellitus, Experimental/blood
- Diabetes Mellitus, Experimental/etiology
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/etiology
- Diabetes Mellitus, Type 2/metabolism
- Diet, High-Fat/adverse effects
- Enzyme Activation
- Fatty Acids, Nonesterified/blood
- Fatty Acids, Nonesterified/metabolism
- Gastric Mucosa/metabolism
- Hypothalamus/metabolism
- Insulin/blood
- Insulin Resistance
- Male
- Mice
- Muscle, Skeletal/metabolism
- Nerve Tissue Proteins/administration & dosage
- Nerve Tissue Proteins/blood
- Nerve Tissue Proteins/metabolism
- Nucleobindins
- Oxidation-Reduction
- Phosphorylation
- Streptozocin/toxicity
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Affiliation(s)
- Jing Dong
- Physiology Department of Medical College, Qingdao University, Qingdao, China
- Special Medicine Department of Medical College, Qingdao University, Qingdao, China
- * E-mail: (JD); (Z-YJ)
| | - Huan Xu
- Class 2, Grade 2009, Medical College, Qingdao University, Qingdao, China
| | - Huan Xu
- Grade 2009, Medical College, Qingdao University, Qingdao, China
| | - Peng-fei Wang
- Grade 2008, Medical College, Qingdao University, Qingdao, China
| | - Gui-ju Cai
- Grade 2008, Medical College, Qingdao University, Qingdao, China
| | - Hai-feng Song
- Grade 2009, Medical College, Qingdao University, Qingdao, China
| | - Chang-chen Wang
- Grade 2009, Medical College, Qingdao University, Qingdao, China
| | - Zhao-tong Dong
- Grade 2010, Medical College, Qingdao University, Qingdao, China
| | - Yan-jiao Ju
- Grade 2010, Medical College, Qingdao University, Qingdao, China
| | - Zheng-yao Jiang
- Physiology Department of Medical College, Qingdao University, Qingdao, China
- * E-mail: (JD); (Z-YJ)
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Avau B, Carbone F, Tack J, Depoortere I. Ghrelin signaling in the gut, its physiological properties, and therapeutic potential. Neurogastroenterol Motil 2013; 25:720-32. [PMID: 23910374 DOI: 10.1111/nmo.12193] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [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: 05/08/2013] [Accepted: 06/26/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND Ghrelin, an orexigenic hormone secreted from the stomach, was soon after its discovery hypothesized to be a prokinetic agent, due to its homology to motilin. Studies in animals and humans, using ghrelin and ghrelin receptor agonists, confirmed this hypothesis, suggesting a therapeutic potential for the ghrelin receptor in the treatment of gastrointestinal motility disorders. Precilinical studies demonstrated that ghrelin can act directly on ghrelin receptors on the enteric nervous system, but the predominant route of action under physiological circumstances is signaling via the vagus nerve in the upper gastrointestinal tract and the pelvic nerves in the colon. Different pharmaceutical companies have designed stable ghrelin mimetics that revealed promising results in trials for the treatment of diabetic gastroparesis and post-operative ileus. Nevertheless, no drug was able to reach the market so far, facing problems proving superiority over placebo treatment in larger trials. PURPOSE This review aims to summarize the road that led to the current knowledge concerning the prokinetic properties of ghrelin with a focus on the therapeutic potential of ghrelin receptor agonists in the treatment of hypomotility disorders. In addition, we outline some of the problems that could be at the basis of the negative outcome of the trials with ghrelin agonists and question whether the right target groups were selected. It is clear that a new approach is needed to develop marketable drugs with this class of gastroprokinetic agents.
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Affiliation(s)
- B Avau
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
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Abstract
Ingestion of food affects the secretion of hormones from specialized endocrine cells scattered within the intestinal mucosa. Upon release, these hormones mostly decrease food intake by signaling information to the brain. Although enteroendocrine cells in the small intestine were thought to represent the predominant gut-brain regulators of food intake, recent advances also established a major role for gastric hormones in these regulatory pathways. First and foremost, the gastric endocrine X/A-like cell was in the focus of many studies due to the production of ghrelin, which is until now the only known orexigenic hormone that is peripherally produced and centrally acting. Although X/A-cells were initially thought to only release one hormone that stimulates food intake, this view has changed with the identification of additional peptide products also derived from this cell, namely desacyl ghrelin, obestatin, and nesfatin-1. Desacyl ghrelin may play a counter-regulatory role to the food intake stimulatory effect of ghrelin. The same property was suggested for obestatin; however, this hypothesis could not be confirmed in numerous subsequent studies. Moreover, the description of the stomach as the major source of the novel anorexigenic hormone nesfatin-1 derived from the NUCB2 gene further corroborated the assumption that the gastric X/A-like cell products are not only stimulant but also inhibitors of feeding, thereby acting as so far unique dual regulator of food intake located in a logistically important place where the gastrointestinal tract has initial contact with food.
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Affiliation(s)
- Andreas Stengel
- Charité Center for Internal Medicine and Dermatology, Division Psychosomatic Medicine, Obesity Center Berlin, Charité Universitätsmedizin Berlin, Campus Mitte, Charitéplatz 1, 10117 Berlin, Germany.
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Santos-Zas I, Lodeiro M, Gurriarán-Rodríguez U, Bouzo-Lorenzo M, Mosteiro CS, Casanueva FF, Casabiell X, Pazos Y, Camiña JP. β-Arrestin signal complex plays a critical role in adipose differentiation. Int J Biochem Cell Biol 2013; 45:1281-92. [PMID: 23557604 DOI: 10.1016/j.biocel.2013.03.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 02/14/2013] [Accepted: 03/04/2013] [Indexed: 11/21/2022]
Abstract
β-Arrestins were identified as scaffold-proteins that have the capacity to desensitize G protein-coupled receptors. However, it has been found that β-arrestins activate signaling pathways independent of G protein activation. The diversity of these signaling pathways has also been recognized for receptor tyrosine kinase. The aim of the present study was to validate the β-arrestin-dependent signaling mechanism(s) responsible for regulation of adipogenesis. Two signal models were selected, ghrelin and insulin, based on its β-arrestin-associated Akt activity. Herein, we found that β-arrestin 1 and 2 were essential molecules for adipocyte differentiation. More specifically, the role of these scaffolding proteins was demonstrated by depletion of β-arrestin 1 and 2 during ghrelin-induced adipogenesis in 3T3-L1 cells, which decreased the adipocyte differentiation and the expression levels of master regulators of early, the CCAAT/enhancer-binding protein β (C/EBPβ) and the CCAAT/enhancer-binding protein δ (C/EBPδ), and terminal, the peroxisome proliferator-activated receptor (PPARγ) and the CCAAT/enhancer-binding protein α (C/EBPα), adipogenesis. Accordingly ghrelin-induced Akt activity and its downstream targets, the mammalian target of rapamycin complex 1 (mTORC1) and the ribosomal protein S6 kinase beta-1 (S6K1), were inhibited by β-arrestin 1 and 2 siRNAs. By contrast, assays performed during insulin-activated adipogenesis showed an intensifying effect on the adipocyte differentiation as well as on the expression of C/EBPβ, C/EBPδ, PPARγ and C/EBPα. The increase in insulin-induced adipogenesis by β-arrestin knock-down was concomitant to a decrease in the insulin receptor susbtrate-1 (IRS-1) serine phosphorylation, proving the loss of the negative feedback loop on IRS-1/phosphoinositide 3-kinase (PI3K)/Akt. Therefore, β-arrestins control the extent and intensity of the lipogenic and adipogenic factors associated to Akt signaling, although the mechanistic and functional principles that underlie the connection between signaling and β-arrestins are specifically associated to each receptor type.
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Schaeffer M, Langlet F, Lafont C, Molino F, Hodson DJ, Roux T, Lamarque L, Verdié P, Bourrier E, Dehouck B, Banères JL, Martinez J, Méry PF, Marie J, Trinquet E, Fehrentz JA, Prévot V, Mollard P. Rapid sensing of circulating ghrelin by hypothalamic appetite-modifying neurons. Proc Natl Acad Sci U S A 2013; 110:1512-7. [PMID: 23297228 DOI: 10.1073/pnas.1212137110] [Citation(s) in RCA: 209] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
To maintain homeostasis, hypothalamic neurons in the arcuate nucleus must dynamically sense and integrate a multitude of peripheral signals. Blood-borne molecules must therefore be able to circumvent the tightly sealed vasculature of the blood-brain barrier to rapidly access their target neurons. However, how information encoded by circulating appetite-modifying hormones is conveyed to central hypothalamic neurons remains largely unexplored. Using in vivo multiphoton microscopy together with fluorescently labeled ligands, we demonstrate that circulating ghrelin, a versatile regulator of energy expenditure and feeding behavior, rapidly binds neurons in the vicinity of fenestrated capillaries, and that the number of labeled cell bodies varies with feeding status. Thus, by virtue of its vascular connections, the hypothalamus is able to directly sense peripheral signals, modifying energy status accordingly.
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Abstract
The ghrelin receptor, also known as growth hormone secretagogue receptor (GHS-R), was identified in porcine and rat anterior pituitary membranes, where the synthetic secretagogue MK-0677 causes amplified pulsatile growth hormone (GH) release. In addition to its function in the stimulation of GH secretion, ghrelin, the natural ligand of ghrelin receptor is now recognized as a peptide hormone with fundamental influence on energy homeostasis. Despite the potential existence of multiple subtypes of ghrelin receptor, the effects of ghrelin on energy metabolism, obesity, and diabetes are mediated by its classical receptor GHS-R1a, whose activation requires the n-octanoylation of ghrelin. Here we review the current understanding of the role of the ghrelin receptor in the regulation of energy homeostasis. An overview of the ghrelin receptor is presented first, followed by the discussion on its effects on food intake, glucose homeostasis, and lipid metabolism. Finally, potential strategies for treating obesity and diabetes via manipulation of the ghrelin/ghrelin receptor axis are explored.
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Affiliation(s)
- Ziru Li
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University, Beijing, China
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