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Han KH, Arlian BM, Lin CW, Jin HY, Kang GH, Lee S, Lee PCW, Lerner RA. Agonist Antibody Converts Stem Cells into Migrating Brown Adipocyte-Like Cells in Heart. Cells 2020; 9:cells9010256. [PMID: 31968623 PMCID: PMC7017361 DOI: 10.3390/cells9010256] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 01/16/2020] [Accepted: 01/20/2020] [Indexed: 12/17/2022] Open
Abstract
We present data showing that Iodotyrosine Deiodinase (IYD) is a dual-function enzyme acting as a catalyst in metabolism and a receptor for cooperative stem cell differentiation. IYD is present both in thyroid cells where it is critical for scavenging iodine from halogenated by-products of thyroid hormone production and on hematopoietic stem cells. To close the cooperative loop, the mono- and di-Iodotyrosine (MIT and DIT) substrates of IYD in the thyroid are also agonists for IYD now acting as a receptor on bone marrow stem cells. While studying intracellular combinatorial antibody libraries, we discovered an agonist antibody, H3 Ab, of which the target is the enzyme IYD. When agonized by H3 Ab, IYD expressed on stem cells induces differentiation of the cells into brown adipocyte-like cells, which selectively migrate to mouse heart tissue. H3 Ab also binds to IYD expressed on human myocardium. Thus, one has a single enzyme acting in different ways on different cells for the cooperative purpose of enhancing thermogenesis or of regenerating damaged heart tissue.
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Affiliation(s)
- Kyung Ho Han
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA; (K.H.H.); (C.-W.L.)
- Department of Biomedical Sciences, University of Ulsan College of Medicine, ASAN Medical Center, Seoul 05505, Korea
| | - Britni M. Arlian
- Departments of Molecular Medicine, Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA;
| | - Chih-Wei Lin
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA; (K.H.H.); (C.-W.L.)
| | - Hyun Yong Jin
- Department of Urology, University of California, San Francisco, CA 94158, USA;
| | - Geun-Hyung Kang
- Division of Cardiology, Asan Medical Center Heart Institute, University of Ulsan College of Medicine, Seoul 05505, Korea; (G.-H.K.); (S.L.)
| | - Sahmin Lee
- Division of Cardiology, Asan Medical Center Heart Institute, University of Ulsan College of Medicine, Seoul 05505, Korea; (G.-H.K.); (S.L.)
| | - Peter Chang-Whan Lee
- Department of Biomedical Sciences, University of Ulsan College of Medicine, ASAN Medical Center, Seoul 05505, Korea
- Correspondence: (P.C.-W.L.); (R.A.L.); Tel.: +82-2-3010-2799 (P.C.-W.L.); +1-858-784-8265 (R.A.L.)
| | - Richard A. Lerner
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA; (K.H.H.); (C.-W.L.)
- Correspondence: (P.C.-W.L.); (R.A.L.); Tel.: +82-2-3010-2799 (P.C.-W.L.); +1-858-784-8265 (R.A.L.)
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Abstract
The combination of next generation sequencing (NGS) and automated liquid handling platforms has led to a revolution in single-cell genomic studies. However, many molecules that are critical to understanding the functional roles of cells in a complex tissue or organs, are not directly encoded in the genome, and therefore cannot be profiled with NGS. Lipids, for example, play a critical role in many metabolic processes but cannot be detected by sequencing. Recent developments in quantitative imaging, particularly coherent Raman scattering (CRS) techniques, have produced a suite of tools for studying lipid content in single cells. This article reviews CRS imaging and computational image processing techniques for non-destructive profiling of dynamic changes in lipid composition and spatial distribution at the single-cell level. As quantitative CRS imaging progresses synergistically with microfluidic and microscopic platforms for single-cell genomic analysis, we anticipate that these techniques will bring researchers closer towards combined lipidomic and genomic analysis.
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Affiliation(s)
- Anushka Gupta
- UC Berkeley-UC San Francisco Graduate Program in Bioengineering, University of California, Berkeley Graduate Division, Berkeley, California, USA.
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Larson CJ. Translational Pharmacology and Physiology of Brown Adipose Tissue in Human Disease and Treatment. Handb Exp Pharmacol 2019; 251:381-424. [PMID: 30689089 DOI: 10.1007/164_2018_184] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Human brown adipose tissue (BAT) is experimentally modeled to better understand the biology of this important metabolic tissue, and also to enable the potential discovery and development of novel therapeutics for obesity and sequelae resulting from the persistent positive energy balance. This chapter focuses on translation into humans of findings and hypotheses generated in nonhuman models of BAT pharmacology. Given the demonstrated challenges of sustainably reducing caloric intake in modern humans, potential solutions to obesity likely lie in increasing energy expenditure. The energy-transforming activities of a single cell in any given tissue can be conceptualized as a flow of chemical energy from energy-rich substrate molecules into energy-expending, endergonic biological work processes through oxidative degradation of organic molecules ingested as nutrients. Despite the relatively tight coupling between metabolic reactions and products, some expended energy is incidentally lost as heat, and in this manner a significant fraction of the energy originally captured from the environment nonproductively transforms into heat rather than into biological work. In human and other mammalian cells, some processes are even completely uncoupled, and therefore purely energy consuming. These molecular and cellular actions sum up at the physiological level to adaptive thermogenesis, the endogenous physiology in which energy is nonproductively released as heat through uncoupling of mitochondria in brown fat and potentially skeletal muscle. Adaptive thermogenesis in mammals occurs in three forms, mostly in skeletal muscle and brown fat: shivering thermogenesis in skeletal muscle, non-shivering thermogenesis in brown fat, and diet-induced thermogenesis in brown fat. At the cellular level, the greatest energy transformations in humans and other eukaryotes occur in the mitochondria, where creating energetic inefficiency by uncoupling the conversion of energy-rich substrate molecules into ATP usable by all three major forms of biological work occurs by two primary means. Basal uncoupling occurs as a passive, general, nonspecific leak down the proton concentration gradient across the membrane in all mitochondria in the human body, a gradient driving a key step in ATP synthesis. Inducible uncoupling, which is the active conduction of protons across gradients through processes catalyzed by proteins, occurs only in select cell types including BAT. Experiments in rodents revealed UCP1 as the primary mammalian molecule accounting for the regulated, inducible uncoupling of BAT, and responsive to both cold and pharmacological stimulation. Cold stimulation of BAT has convincingly translated into humans, and older clinical observations with nonselective 2,4-DNP validate that human BAT's participation in pharmacologically mediated, though nonselective, mitochondrial membrane decoupling can provide increased energy expenditure and corresponding body weight loss. In recent times, however, neither beta-adrenergic antagonism nor unselective sympathomimetic agonism by ephedrine and sibutramine provide convincing evidence that more BAT-selective mechanisms can impact energy balance and subsequently body weight. Although BAT activity correlates with leanness, hypothesis-driven selective β3-adrenergic agonism to activate BAT in humans has only provided robust proof of pharmacologic activation of β-adrenergic receptor signaling, limited proof of the mechanism of increased adaptive thermogenesis, and no convincing evidence that body weight loss through negative energy balance upon BAT activation can be accomplished outside of rodents. None of the five demonstrably β3 selective molecules with sufficient clinical experience to merit review provided significant weight loss in clinical trials (BRL 26830A, TAK 677, L-796568, CL 316,243, and BRL 35135). Broader conclusions regarding the human BAT therapeutic hypothesis are limited by the absence of data from most studies demonstrating specific activation of BAT thermogenesis in most studies. Additionally, more limited data sets with older or less selective β3 agonists also did not provide strong evidence of body weight effects. Encouragingly, β3-adrenergic agonists, catechins, capsinoids, and nutritional extracts, even without robust negative energy balance outcomes, all demonstrated increased total energy expenditure that in some cases could be associated with concomitant activation of BAT, though the absence of body weight loss indicates that in no cases did the magnitude of negative energy balance reach sufficient levels. Glucocorticoid receptor agonists, PPARg agonists, and thyroid hormone receptor agonists all possess defined molecular and cellular pharmacology that preclinical models predicted to be efficacious for negative energy balance and body weight loss, yet their effects on human BAT thermogenesis upon translation were inconsistent with predictions and disappointing. A few new mechanisms are nearing the stage of clinical trials and may yet provide a more quantitatively robust translation from preclinical to human experience with BAT. In conclusion, translation into humans has been demonstrated with BAT molecular pharmacology and cell biology, as well as with physiological response to cold. However, despite pharmacologically mediated, statistically significant elevation in total energy expenditure, translation into biologically meaningful negative energy balance was not achieved, as indicated by the absence of measurable loss of body weight over the duration of a clinical study.
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Affiliation(s)
- Christopher J Larson
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
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4
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Fuller-Jackson JP, Henry BA. Adipose and skeletal muscle thermogenesis: studies from large animals. J Endocrinol 2018; 237:R99-R115. [PMID: 29703782 DOI: 10.1530/joe-18-0090] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 04/05/2018] [Indexed: 12/30/2022]
Abstract
The balance between energy intake and energy expenditure establishes and preserves a 'set-point' body weight. The latter is comprised of three major components including metabolic rate, physical activity and thermogenesis. Thermogenesis is defined as the cellular dissipation of energy via heat production. This process has been extensively characterised in brown adipose tissue (BAT), wherein uncoupling protein 1 (UCP1) creates a proton leak across the inner mitochondrial membrane, diverting protons away from ATP synthesis and resulting in heat dissipation. In beige adipocytes and skeletal muscle, thermogenesis can occur independent of UCP1. Beige adipocytes have been shown to produce heat via UCP1 as well as via both futile creatine and calcium cycling pathways. On the other hand, the UCP1 homologue UCP3 is abundant in skeletal muscle and post-prandial thermogenesis has been associated with UCP3 and the futile calcium cycling. This review will focus on the differential contributions of adipose tissue and skeletal muscle in determining total thermogenic output and energy expenditure in large mammals. Sheep and pigs do not have a circumscribed brown fat depot but rather possess white fat depots that contain brown and beige adipocytes interspersed amongst white adipose tissue. This is representative of humans, where brown, beige and white adipocytes have been identified in the neck and supraclavicular regions. This review will describe the mechanisms of thermogenesis in pigs and sheep and the relative roles of skeletal muscle and adipose tissue thermogenesis in controlling body weight in larger mammals.
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Affiliation(s)
| | - Belinda A Henry
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Department of Physiology, Monash University, Clayton, Victoria, Australia
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Abstract
Brown fat is emerging as an interesting and promising target for therapeutic intervention in obesity and metabolic disease. Activation of brown fat in humans is associated with marked improvement in metabolic parameters such as levels of free fatty acids and insulin sensitivity. Skeletal muscle is another important organ for thermogenesis, with the capacity to induce energy-consuming futile cycles. In this Review, we focus on how these two major thermogenic organs - brown fat and muscle - act and cooperate to maintain normal body temperature. Moreover, in the light of disease-relevant mechanisms, we explore the molecular pathways that regulate thermogenesis in brown fat and muscle. Brown adipocytes possess a unique cellular mechanism to convert chemical energy into heat: uncoupling protein 1 (UCP1), which can short-circuit the mitochondrial proton gradient. However, recent research demonstrates the existence of several other energy-expending 'futile' cycles in both adipocytes and muscle, such as creatine and calcium cycling. These mechanisms can complement or even substitute for UCP1-mediated thermogenesis. Moreover, they expand our view of cold-induced thermogenesis from a special feature of brown adipocytes to a more general physiological principle. Finally, we discuss how thermogenic mechanisms can be exploited to expend energy and hence offer new therapeutic opportunities.
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Affiliation(s)
- Matthias J Betz
- Department of Endocrinology, Diabetes and Metabolism, University Hospital Basel, Petersgraben 4, CH-4031 Basel, Switzerland
| | - Sven Enerbäck
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Medicinaregatan 9A, SE-405 30 Gothenburg, Sweden
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Chu DT, Tao Y, Son LH, Le DH. Cell source, differentiation, functional stimulation, and potential application of human thermogenic adipocytes in vitro. J Physiol Biochem 2017; 73:315-321. [PMID: 28612196 DOI: 10.1007/s13105-017-0567-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 05/29/2017] [Indexed: 12/14/2022]
Abstract
Recent investigations have showed that the functional thermogenic adipocytes are present in both infants and adult humans. Accumulating evidence suggests that the coexistence of classical and inducible brown (brite) adipocytes in humans at adulthood and these adipocytes function to generate heat from energy resulting in reducing body fat and improving glucose metabolism. Human thermogenic adipocytes can be differentiated in vitro from stem cells, cell lines, or adipose stromal vascular fraction. Pre-activated human brite adipocytes in vitro can maintain their thermogenic function in normal or obese immunodeficient mice; therefore, they improve glucose homeostasis and reduce fat mass in obese animals. These key findings have opened a new door to use in vitro thermogenic adipocytes as a cell therapy to prevent obesity and related disorders. Thus, this paper intends to highlight our knowledge in aspects of in vitro human brite/brown adipocytes for the further studies.
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Affiliation(s)
- Dinh-Toi Chu
- Institute for Research and Development, Duy Tan University, 03 Quang Trung, Da Nang, Vietnam. .,Faculty of Biology, Hanoi National University of Education, Hanoi, Vietnam.
| | - Yang Tao
- College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Vietnam
| | - Le Hoang Son
- VNU University of Science, Vietnam National University, Hanoi, Vietnam
| | - Duc-Hau Le
- VINMEC Research Institute of Stem Cell and Gene Technology, Hanoi, Vietnam
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7
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Mukaida S, Evans BA, Bengtsson T, Hutchinson DS, Sato M. Adrenoceptors promote glucose uptake into adipocytes and muscle by an insulin-independent signaling pathway involving mechanistic target of rapamycin complex 2. Pharmacol Res 2016; 116:87-92. [PMID: 28025104 DOI: 10.1016/j.phrs.2016.12.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 11/12/2016] [Accepted: 12/13/2016] [Indexed: 12/15/2022]
Abstract
Uptake of glucose into skeletal muscle and adipose tissue plays a vital role in metabolism and energy balance. Insulin released from β-islet cells of the pancreas promotes glucose uptake in these target tissues by stimulating translocation of GLUT4 transporters to the cell surface. This process is complex, involving signaling proteins including the mechanistic (or mammalian) target of rapamycin (mTOR) and Akt that intersect with multiple pathways controlling cell survival, growth and proliferation. mTOR exists in two forms, mTOR complex 1 (mTORC1), and mTOR complex 2 (mTORC2). mTORC1 has been intensively studied, acting as a key regulator of protein and lipid synthesis that integrates cellular nutrient availability and energy balance. Studies on mTORC2 have focused largely on its capacity to activate Akt by phosphorylation at Ser473, however recent findings demonstrate a novel role for mTORC2 in cellular glucose uptake. For example, agonists acting at β2-adrenoceptors (ARs) in skeletal muscle or β3-ARs in brown adipose tissue increase glucose uptake in vitro and in vivo via mechanisms dependent on mTORC2 but not Akt. In this review, we will focus on the signaling pathways downstream of β-ARs that promote glucose uptake in skeletal muscle and brown adipocytes, and will highlight how the insulin and adrenergic pathways converge and interact in these cells. The identification of insulin-independent mechanisms that promote glucose uptake should facilitate novel treatment strategies for metabolic disease.
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Affiliation(s)
- Saori Mukaida
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Bronwyn A Evans
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Tore Bengtsson
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-10691 Stockholm, Sweden
| | - Dana S Hutchinson
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Masaaki Sato
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
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8
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Chu DT, Tao Y. Human thermogenic adipocytes: a reflection on types of adipocyte, developmental origin, and potential application. J Physiol Biochem 2016; 73:1-4. [PMID: 27826900 DOI: 10.1007/s13105-016-0536-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 10/24/2016] [Indexed: 01/07/2023]
Abstract
Obesity is a leading health problem facing the modern world; however, no effective therapy for this health issue has yet been developed. A promising research direction to identify novel therapies to prevent obesity has emerged from discoveries on development and function of brown/brite adipocytes in mammals. Importantly, there is evidence for the presence and function of active thermogenic brown adipocytes in both infants and adult humans. Several new investigations have shown that thermogenic adipocytes are beneficial to maintain glucose homeostasis, insulin sensitivity, and a healthy body fat content. Such thermogenic adipocytes have been considered as targets to develop a therapy for preventing obesity. This short review seeks to highlight recent findings on the development and function of brown/brite adipocytes in humans and to discuss potential treatments based on these adipocytes to reduce obesity and its related disorders.
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Affiliation(s)
- Dinh-Toi Chu
- Institute for Research and Development, Duy Tan University, K7/25 Quang Trung, Danang, Vietnam. .,Faculty of Biology, Hanoi National University of Education, Hanoi, Vietnam. .,Centre for Molecular Medicine Norway, Nordic European Molecular Biology Laboratory Partnership, University of Oslo and Oslo University Hospital, Oslo, Norway.
| | - Yang Tao
- College of Food Science and Technology, Nanjing Agricultural University, Nanjing, 210095, China
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9
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Thoonen R, Hindle AG, Scherrer-Crosbie M. Brown adipose tissue: The heat is on the heart. Am J Physiol Heart Circ Physiol 2016; 310:H1592-605. [PMID: 27084389 DOI: 10.1152/ajpheart.00698.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 04/13/2016] [Indexed: 12/17/2022]
Abstract
The study of brown adipose tissue (BAT) has gained significant scientific interest since the discovery of functional BAT in adult humans. The thermogenic properties of BAT are well recognized; however, data generated in the last decade in both rodents and humans reveal therapeutic potential for BAT against metabolic disorders and obesity. Here we review the current literature in light of a potential role for BAT in beneficially mediating cardiovascular health. We focus mainly on BAT's actions in obesity, vascular tone, and glucose and lipid metabolism. Furthermore, we discuss the recently discovered endocrine factors that have a potential beneficial role in cardiovascular health. These BAT-secreted factors may have a favorable effect against cardiovascular risk either through their metabolic role or by directly affecting the heart.
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Affiliation(s)
- Robrecht Thoonen
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, Massachusetts
| | - Allyson G Hindle
- Department of Anesthesia and Critical Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts; and
| | - Marielle Scherrer-Crosbie
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, Massachusetts; Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Boston, Massachusetts
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Ernande L, Stanford KI, Thoonen R, Zhang H, Clerte M, Hirshman MF, Goodyear LJ, Bloch KD, Buys ES, Scherrer-Crosbie M. Relationship of brown adipose tissue perfusion and function: a study through β2-adrenoreceptor stimulation. J Appl Physiol (1985) 2016; 120:825-32. [PMID: 26823340 DOI: 10.1152/japplphysiol.00634.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 01/27/2016] [Indexed: 12/16/2022] Open
Abstract
Brown adipose tissue (BAT) activation increases glucose and lipid consumption; as such, it is been considered as a potential therapy to decrease obesity. BAT is highly vascularized and its activation is associated with a necessary increase in blood flow. However, whether increasing BAT blood flow per se increases BAT activity is unknown. To examine this hypothesis, we investigated whether an isolated increase in BAT blood flow obtained by β2-adrenoreceptor (β2-AR) stimulation with salbutamol increased BAT activity. BAT blood flow was estimated in vivo in mice using contrast-enhanced ultrasound. The absence of direct effect of salbutamol on the function of isolated brown adipocytes was assessed by measuring oxygen consumption. The effect of salbutamol on BAT activity was investigated by measuring BAT glucose uptake in vivo. BAT blood flow increased by 2.3 ± 0.6-fold during β2-AR stimulation using salbutamol infusion in mice (P= 0.003). β2-AR gene expression was detectable in BAT but was extremely low in isolated brown adipocytes. Oxygen consumption of isolated brown adipocytes did not change with salbutamol exposure, confirming the absence of a direct effect of β2-AR agonist on brown adipocytes. Finally, β2-AR stimulation by salbutamol increased BAT glucose uptake in vivo (991 ± 358 vs. 135 ± 49 ng glucose/mg tissue/45 min in salbutamol vs. saline injected mice, respectively,P= 0.046). In conclusion, an increase in BAT blood flow without direct stimulation of the brown adipocytes is associated with increased BAT metabolic activity. Increasing BAT blood flow might represent a new therapeutic target in obesity.
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Affiliation(s)
- Laura Ernande
- Cardiac Ultrasound Laboratory and Cardiovascular Research Center, Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; DHU Ageing-Thorax-Vessel-Blood, Hôpital Henri Mondor, Assistance Publique-Hôpitaux de Paris, Créteil, France
| | - Kristin I Stanford
- Research Division, Joslin Diabetes Center, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Robrecht Thoonen
- Cardiac Ultrasound Laboratory and Cardiovascular Research Center, Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Haihua Zhang
- Cardiac Ultrasound Laboratory and Cardiovascular Research Center, Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Maëva Clerte
- Cardiac Ultrasound Laboratory and Cardiovascular Research Center, Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Michael F Hirshman
- Research Division, Joslin Diabetes Center, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Laurie J Goodyear
- Research Division, Joslin Diabetes Center, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; and
| | - Kenneth D Bloch
- Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Emmanuel S Buys
- Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Marielle Scherrer-Crosbie
- Cardiac Ultrasound Laboratory and Cardiovascular Research Center, Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts;
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Flynn A, Li Q, Panagia M, Abdelbaky A, MacNabb M, Samir A, Cypess AM, Weyman AE, Tawakol A, Scherrer-Crosbie M. Contrast-Enhanced Ultrasound: A Novel Noninvasive, Nonionizing Method for the Detection of Brown Adipose Tissue in Humans. J Am Soc Echocardiogr 2015; 28:1247-54. [PMID: 26255029 PMCID: PMC4593741 DOI: 10.1016/j.echo.2015.06.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Indexed: 12/21/2022]
Abstract
BACKGROUND Brown adipose tissue (BAT) consumes glucose when it is activated by cold exposure, allowing its detection in humans by (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) with computed tomography (CT). The investigators recently described a novel noninvasive and nonionizing imaging method to assess BAT in mice using contrast-enhanced ultrasound (CEUS). Here, they report the application of this method in healthy humans. METHODS Thirteen healthy volunteers were recruited. CEUS was performed before and after cold exposure in all subjects using a continuous intravenous infusion of perflutren gas-filled lipid microbubbles and triggered imaging of the supraclavicular space. The first five subjects received microbubbles at a lower infusion rate than the subsequent eight subjects and were analyzed as a separate group. Blood flow was estimated as the product of the plateau (A) and the slope (β) of microbubble replenishment curves. All underwent (18)F-FDG PET/CT after cold exposure. RESULTS An increase in the acoustic signal was noted in the supraclavicular adipose tissue area with increasing triggering intervals in all subjects, demonstrating the presence of blood flow. The area imaged by CEUS colocalized with BAT, as detected by ¹⁸F-FDG PET/CT. In a cohort of eight subjects with an optimized CEUS protocol, CEUS-derived BAT blood flow increased with cold exposure compared with basal BAT blood flow in warm conditions (median Aβ = 3.3 AU/s [interquartile range, 0.5-5.7 AU/s] vs 1.25 AU/s [interquartile range, 0.5-2.6 AU/s]; P = .02). Of these eight subjects, five had greater than twofold increases in blood flow after cold exposure; these responders had higher BAT activity measured by (18)F-FDG PET/CT (median maximal standardized uptake value, 2.25 [interquartile range, 1.53-4.57] vs 0.51 [interquartile range, 0.47-0.73]; P = .02). CONCLUSIONS The present study demonstrates the feasibility of using CEUS as a noninvasive, nonionizing imaging modality in estimating BAT blood flow in young, healthy humans. CEUS may be a useful and scalable tool in the assessment of BAT and BAT-targeted therapies.
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Affiliation(s)
- Aidan Flynn
- Cardiac Ultrasound Laboratory, Division of Cardiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Qian Li
- Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Marcello Panagia
- Cardiac Ultrasound Laboratory, Division of Cardiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Amr Abdelbaky
- Department of Nuclear Cardiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Megan MacNabb
- Department of Nuclear Cardiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Anthony Samir
- Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Aaron M Cypess
- Section of Integrative Physiology and Metabolism, Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts; Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Arthur E Weyman
- Cardiac Ultrasound Laboratory, Division of Cardiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Ahmed Tawakol
- Department of Nuclear Cardiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Marielle Scherrer-Crosbie
- Cardiac Ultrasound Laboratory, Division of Cardiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
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12
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Betz MJ, Enerbäck S. Human Brown Adipose Tissue: What We Have Learned So Far. Diabetes 2015; 64:2352-60. [PMID: 26050667 DOI: 10.2337/db15-0146] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 03/26/2015] [Indexed: 11/13/2022]
Abstract
Brown adipose tissue (BAT) is a unique tissue that is able to convert chemical energy directly into heat when activated by the sympathetic nervous system. While initially believed to be of relevance only in human newborns and infants, research during recent years provided unequivocal evidence of active BAT in human adults. Moreover, it has become clear that BAT plays an important role in insulin sensitivity in rodents and humans. This has opened the possibility for exciting new therapies for obesity and diabetes. This review summarizes the current state of research with a special focus on recent advances regarding BAT and insulin resistance in human adults. Additionally, we provide an outlook on possible future therapeutic uses of BAT in the treatment of obesity and diabetes.
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Affiliation(s)
- Matthias J Betz
- Department of Endocrinology, Diabetes & Metabolism, University Hospital Basel, Basel, Switzerland
| | - Sven Enerbäck
- Department of Medical and Clinical Genetics, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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13
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Abstract
Evidence from rodents established an important role of brown adipose tissue (BAT) in energy expenditure. Moreover, to sustain thermogenesis, BAT has been shown to be a powerful sink for draining and oxidation of glucose and triglycerides from blood. The potential of BAT activity in protection against obesity and metabolic syndrome is recognized. Recently, an unexpected presence and activity of BAT has been found in adult humans. Here we review the most recent research in this field and, specifically, how new findings apply to humans. Moreover, we seek to clarify the underlying biological processes occurring beyond the burst of new nomenclature in the field. The cell type responsible for thermogenesis, the brown adipocyte, arises from complex developmental processes. In addition to 'classical' brown adipocytes, present in developmentally programmed BAT depots, there are brown adipocytes, named 'brite' (from 'brown-in-white') or 'beige', which appear in response to thermogenic stimuli in white fat due to the so-called 'browning' process. Beige/brite cells appear to be important components of BAT depots in adult humans. In addition to the known control of BAT activity by the sympathetic nervous system, metabolic and hormonal signals originating in muscle or liver (e.g. irisin, FGF21) are recognized as activators of BAT and beige/brite adipocytes.
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Affiliation(s)
- Rubén Cereijo
- Departament de Bioquímica i Biologia Molecular, Institute of Biomedicine (IBUB), University of Barcelona, and CIBER Fisiopatología de la Obesidad y Nutrición , Barcelona, Catalonia , Spain
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14
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Devlin MJ. The “Skinny” on brown fat, obesity, and bone. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2014; 156 Suppl 59:98-115. [DOI: 10.1002/ajpa.22661] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Maureen J. Devlin
- Department of Anthropology; University of Michigan; Ann Arbor MI 48104
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15
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Zhang Z, Cypess AM, Miao Q, Ye H, Liew CW, Zhang Q, Xue R, Zhang S, Zuo C, Xu Z, Tang Q, Hu R, Guan Y, Li Y. The prevalence and predictors of active brown adipose tissue in Chinese adults. Eur J Endocrinol 2014; 170:359-66. [PMID: 24288355 PMCID: PMC4127998 DOI: 10.1530/eje-13-0712] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVE Previous studies have shown that active brown adipose tissue (BAT) is present in adults and may play important roles in the regulation of energy homeostasis. However, nearly every study has been carried out in patients undergoing scanning for cancer surveillance (CS), whose metabolism and BAT activity may not reflect those of healthy individuals. The objective of this study was to investigate the prevalence and predictors of active BAT in Chinese adults, particularly in healthy individuals. DESIGN A total of 31,088 consecutive subjects aged ≥18 years who had undergone positron emission tomography/computed tomography (PET/CT) scanning of BAT were evaluated in this study. METHODS We measured BAT activity via (18)F-fluorodeoxyglucose PET/CT in subjects who had undergone scanning for either a routine medical checkup (MC) or CS in Shanghai. Then, we investigated the predictors of active BAT, particularly in healthy individuals. RESULTS In both groups, the prevalence of BAT was higher in women than in men. Using a multivariate logistic analysis, we found age, sex, BMI, and high thyroid glucose uptake to be significant predictors of BAT activity in the MC group. Similarly, we found age, sex, and BMI to be significant predictors of BAT activity, but not thyroid high glucose uptake, in the CS group. CONCLUSIONS In Chinese adults, BAT activity inversely correlates with BMI and thyroid high glucose uptake, which reinforces the central role of brown fat in adult metabolism and provides clues to a potential means for treating the metabolic syndrome.
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Affiliation(s)
- Zhaoyun Zhang
- The Division of Endocrinology and Metabolism, the Department of Internal Medicine
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16
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Lidell ME, Betz MJ, Enerbäck S. Two types of brown adipose tissue in humans. Adipocyte 2014; 3:63-6. [PMID: 24575372 DOI: 10.4161/adip.26896] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 10/21/2013] [Indexed: 01/23/2023] Open
Abstract
During the last years the existence of metabolically active brown adipose tissue in adult humans has been widely accepted by the research community. Its unique ability to dissipate chemical energy stored in triglycerides as heat makes it an attractive target for new drugs against obesity and its related diseases. Hence the tissue is now subject to intense research, the hypothesis being that an expansion and/or activation of the tissue is associated with a healthy metabolic phenotype. Animal studies provide evidence for the existence of at least two types of brown adipocytes. Apart from the classical brown adipocyte that is found primarily in the interscapular region where it constitutes a thermogenic organ, a second type of brown adipocyte, the so-called beige adipocyte, can appear within white adipose tissue depots. The fact that the two cell types develop from different precursors suggests that they might be recruited and stimulated by different cues and therefore represent two distinct targets for therapeutic intervention. The aim of this commentary is to discuss recent work addressing the question whether also humans possess two types of brown adipocytes and to highlight some issues when looking for molecular markers for such cells.
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17
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A novel SP1/SP3 dependent intronic enhancer governing transcription of the UCP3 gene in brown adipocytes. PLoS One 2013; 8:e83426. [PMID: 24391766 PMCID: PMC3877035 DOI: 10.1371/journal.pone.0083426] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 11/05/2013] [Indexed: 11/19/2022] Open
Abstract
Uncoupling protein (UCP) 3 is a mitochondrial inner membrane protein implicated in lipid handling and metabolism of reactive oxygen species. Its transcription is mainly regulated by peroxisome proliferator-activated receptors (PPAR), a family of nuclear hormone receptors. Employing bandshift assays, RNA interference and reporter gene assays we examine an intronic region in the UCP3 gene harboring a cis-element essential for expression in brown adipocytes. We demonstrate binding of SP1 and SP3 to this element which is adjacent to a direct repeat 1 element mediating activation of UCP3 expression by PPARγ agonists. Transactivation mediated by these elements is interdependent and indispensable for UCP3 expression. Systematic deletion uncovered a third binding element, a putative NF1 site, in close proximity to the SP1/3 and PPARγ binding elements. Data mining demonstrated binding of MyoD and Myogenin to this third element in C2C12 cells, and, furthermore, revealed recruitment of p300. Taken together, this intronic region is the main enhancer driving UCP3 expression with SP1/3 and PPARγ as the core factors required for expression.
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18
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Abstract
Brown adipose tissue (BAT) plays a key role in energy homeostasis and thermogenesis in animals, conferring protection against diet-induced obesity and hypothermia through the action of uncoupling protein 1 (UCP1). Recent metabolic imaging studies using positron emission tomography computerized tomography (PET-CT) scanning have serendipitously revealed significant depots of BAT in the cervical-supraclavicular regions, demonstrating persistence of BAT beyond infancy. Subsequent cold-stimulated PET-CT studies and direct histological examination of adipose tissues have demonstrated that BAT is highly prevalent in adult humans. BAT activity correlates positively with increment of energy expenditure during cold exposure and negatively with age, body mass index, and fasting glycemia, suggesting regulatory links between BAT, cold-induced thermogenesis, and energy metabolism. Human BAT tissue biopsies express UCP1 and harbor inducible precursors that differentiate into UCP1-expressing adipocytes in vitro. These recent discoveries represent a metabolic renaissance for human adipose biology, overturning previous belief that BAT had no relevance in adult humans. They also have implications for the understanding of the pathogenesis and treatment of obesity and its metabolic sequelae.
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Affiliation(s)
- Paul Lee
- School of Medicine, University of Queensland, Brisbane, Queensland 4107, Australia.
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19
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Affiliation(s)
- Charmaine S Tam
- Human Physiology, Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA
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20
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Khanna A, Branca RT. Detecting brown adipose tissue activity with BOLD MRI in mice. Magn Reson Med 2012; 68:1285-90. [PMID: 22231619 DOI: 10.1002/mrm.24118] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 11/04/2011] [Accepted: 11/28/2011] [Indexed: 12/22/2022]
Abstract
The recent discovery of active brown adipose tissue (BAT) in adult humans and the correlation found between the activity of this tissue and resting metabolic rate strongly suggest that this tissue may be implicated in the development of obesity in humans, as it is in rodents. Despite the possible physiological role of this tissue in the onset of human obesity, few noninvasive imaging techniques to detect BAT activity in humans exist. The scope of this work is to investigate the possibility of detecting BAT activity using blood-oxygen-level-dependent MRI. Our results show that the strong increase in oxygen consumption and consequent increase in blood deoxyhemoglobin levels following BAT activation lead to a well-localized signal drop in BAT. This strongly suggests the possibility to use blood-oxygen-level-dependent MRI for the noninvasive detection of BAT activity.
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Affiliation(s)
- Arjun Khanna
- Chemistry Department, French Family Science Center, Duke University, Durham, North Carolina 27708-0346, USA
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21
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Klingenspor M, Herzig S, Pfeifer A. Brown fat develops a brite future. Obes Facts 2012; 5:890-6. [PMID: 23296106 DOI: 10.1159/000346337] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 12/10/2012] [Indexed: 01/02/2023] Open
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22
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Cypess AM, Zhang H, Schulz TJ, Huang TL, Espinoza DO, Kristiansen K, Unterman TG, Tseng YH. Insulin/IGF-I regulation of necdin and brown adipocyte differentiation via CREB- and FoxO1-associated pathways. Endocrinology 2011; 152:3680-9. [PMID: 21862615 PMCID: PMC3176640 DOI: 10.1210/en.2011-1229] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Brown adipose tissue plays an important role in obesity, insulin resistance, and diabetes. We have previously shown that the transition from brown preadipocytes to mature adipocytes is mediated in part by insulin receptor substrate (IRS)-1 and the cell cycle regulator protein necdin. In this study, we used pharmacological inhibitors and adenoviral dominant negative constructs to demonstrate that this transition involves IRS-1 activation of Ras and ERK1/2, resulting in phosphorylation of cAMP response element-binding protein (CREB) and suppression of necdin expression. This signaling did not include an elevation of intracellular calcium. A constitutively active form of CREB expressed in IRS-1 knockout cells decreased necdin promoter activity, necdin mRNA, and necdin protein levels, leading to a partial restoration of differentiation. By contrast, forkhead box protein (Fox)O1, which is regulated by the phosphoinositide 3 kinase-Akt pathway, increased necdin promoter activity. Based on reporter gene assays using truncations of the necdin promoter and chromatin immunoprecipitation studies, we demonstrated that CREB and FoxO1 are recruited to the necdin promoter, likely interacting with specific consensus sequences in the proximal region. Based on these results, we propose that insulin/IGF-I act through IRS-1 phosphorylation to stimulate differentiation of brown preadipocytes via two complementary pathways: 1) the Ras-ERK1/2 pathway to activate CREB and 2) the phosphoinositide 3 kinase-Akt pathway to deactivate FoxO1. These two pathways combine to decrease necdin levels and permit the clonal expansion and coordinated gene expression necessary to complete brown adipocyte differentiation.
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Affiliation(s)
- Aaron M Cypess
- Research Division, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215, USA.
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23
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Berryman DE, List EO, Sackmann-Sala L, Lubbers E, Munn R, Kopchick JJ. Growth hormone and adipose tissue: beyond the adipocyte. Growth Horm IGF Res 2011; 21:113-123. [PMID: 21470887 PMCID: PMC3112270 DOI: 10.1016/j.ghir.2011.03.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 03/03/2011] [Indexed: 01/04/2023]
Abstract
The last two decades have seen resurgence in research focused on adipose tissue. In part, the enhanced interest stems from an alarming increase in obesity rates worldwide. However, an understanding that this once simple tissue is significantly more intricate and interactive than previously realized has fostered additional attention. While few would argue that growth hormone (GH) radically alters fat mass, newer findings revealing the complexity of adipose tissue requires that GH's influence on this tissue be reexamined. Therefore, the objective of this review is to describe the more recent understanding of adipose tissue and to summarize our current knowledge of how GH may influence and contribute to these newer complexities of this tissue with special focus on the available data from mice with altered GH action.
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Affiliation(s)
- Darlene E Berryman
- School of Applied Health Sciences and Wellness College of Health Sciences and Human Performance, Ohio University, Athens, OH 45701, United States.
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24
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van Marken Lichtenbelt WD, Schrauwen P. Implications of nonshivering thermogenesis for energy balance regulation in humans. Am J Physiol Regul Integr Comp Physiol 2011; 301:R285-96. [PMID: 21490370 DOI: 10.1152/ajpregu.00652.2010] [Citation(s) in RCA: 191] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The incidence of the metabolic syndrome has reached epidemic levels in the Western world. With respect to the energy balance, most attention has been given to reducing energy (food) intake. Increasing energy expenditure is an important alternative strategy. Facultative thermogenesis, which is the increase in energy expenditure in response to cold or diet, may be an effective way to affect the energy balance. The recent identification of functional brown adipose tissue (BAT) in adult humans promoted a renewed interest in nonshivering thermogenesis (NST). The purpose of this review is to highlight the recent insight in NST, general aspects of its regulation, the major tissues involved, and its metabolic consequences. Sustainable NST in adult humans amounts to 15% of the average daily energy expenditure. Calculations based on the limited available literature show that BAT thermogenesis can amount to 5% of the basal metabolic rate. It is likely that at least a substantial part of NST can be attributed to BAT, but it is possible that other tissues contribute to NST. Several studies on mitochondrial uncoupling indicate that skeletal muscle is another potential contributor to facultative thermogenesis in humans. The general and synergistic role of the sympathetic nervous system and the thyroid axis in relation to NST is discussed. Finally, perspectives on BAT and skeletal muscle NST are given.
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Affiliation(s)
- Wouter D van Marken Lichtenbelt
- Department of Human Biology, School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands.
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25
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Abstract
PURPOSE OF REVIEW Children and adults have two major types of adipocytes, which represent the predominant cells in white adipose tissue, which is involved in energy storage, and brown adipose tissue (BAT), which is responsible for thermogenesis and energy expenditure. This review discusses BAT physiology and evaluates the recent discoveries regarding its development, identification, and function. RECENT FINDINGS Last year, multiple independent research teams using combined PET and computed tomography imaging, immunohistochemistry, and gene and protein expression have proven conclusively that adult humans have functional BAT. In parallel, basic studies defined BAT origins, its transcriptional regulation, and the role of hormones in BAT growth and activation. These methods have begun to be applied to children to understand pediatric BAT anatomy and physiology. SUMMARY Adult humans have functional BAT, which plays a role in energy balance. BAT is more prevalent in children, suggesting an even greater physiological role than that seen in adults. Future studies will identify safe ways to quantify BAT mass and activity and which interventions might be used to increase BAT mass, thermogenesis, or both to treat obesity.
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26
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Abstract
Obesity develops when energy intake exceeds energy expenditure. Although most current obesity therapies are focused on reducing calorific intake, recent data suggest that increasing cellular energy expenditure (bioenergetics) may be an attractive alternative approach. This is especially true for adaptive thermogenesis - the physiological process whereby energy is dissipated in mitochondria of brown fat and skeletal muscle in the form of heat in response to external stimuli. There have been significant recent advances in identifying the factors that control the development and function of these tissues, and in techniques to measure brown fat in human adults. In this article, we integrate these developments in relation to the classical understandings of cellular bioenergetics to explore the potential for developing novel anti-obesity therapies that target cellular energy expenditure.
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Affiliation(s)
- Yu-Hua Tseng
- Joslin Diabetes Center, Harvard Medical School, One Joslin Place, Boston, Massachusetts 02215, USA.
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27
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Abstract
The BAT organ is unique in that it has evolved to safely dissipate large amounts of chemical energy--a quality that might be harnessed to help humans deal with a dangerously hypercaloric environment and still remain in good health.
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Affiliation(s)
- Sven Enerbäck
- Department of Medical and Clinical Genetics, Institute of Biomedicine, University of Gothenburg, Medicinaregatan 9A, P.O. Box 440, SE 40530 Göteborg, Sweden.
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28
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Abstract
PURPOSE OF REVIEW Human fat consists of white and brown adipose tissue (WAT and BAT). Though most fat is energy-storing WAT, the thermogenic capacity of even small amounts of BAT makes it an attractive therapeutic target for inducing weight loss through energy expenditure. This review evaluates the recent discoveries regarding the identification of functional BAT in adult humans and its potential as a therapy for obesity and diabetes. RECENT FINDINGS Over the past year, several independent research teams used a combination of positron-emission tomography and computed tomography (PET/CT) imaging, immunohistochemistry, and gene and protein expression assays to prove conclusively that adult humans have functional BAT. This has occurred against a backdrop of basic studies defining the origins of BAT, new components of its transcriptional regulation, and the role of hormones in stimulation of BAT growth and differentiation. SUMMARY Adult humans have functional BAT, a new target for antiobesity and antidiabetes therapies focusing on increasing energy expenditure. Future studies will refine the methodologies used to measure BAT mass and activity, expand our knowledge of critical-control points in BAT regulation, and focus on testing pharmacological agents that increase BAT thermogenesis and help achieve long-lasting weight loss and an improved metabolic profile.
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Affiliation(s)
- Aaron M Cypess
- Joslin Diabetes Center, Harvard Medical School, One Joslin Place, Boston, Massachusetts, 02215, USA
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29
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Affiliation(s)
- Patrick Seale
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts
- Corresponding author: Patrick Seale, , or Mitchell A. Lazar,
| | - Mitchell A. Lazar
- Division of Endocrinology, Diabetes & Metabolism, Department of Medicine, University of Pennsylvania, and the Institute for Diabetes, Obesity & Metabolism, Philadelphia, Pennsylvania
- Corresponding author: Patrick Seale, , or Mitchell A. Lazar,
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30
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Wijers SLJ, Saris WHM, van Marken Lichtenbelt WD. Recent advances in adaptive thermogenesis: potential implications for the treatment of obesity. Obes Rev 2009; 10:218-26. [PMID: 19021870 DOI: 10.1111/j.1467-789x.2008.00538.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Large inter-individual differences in cold-induced (non-shivering) and diet-induced adaptive thermogenesis exist in animals and humans. These differences in energy expenditure can have a large impact on long-term energy balance and thus body weight (when other factors remain stable). Therefore, the level of adaptive thermogenesis might relate to the susceptibility to obesity; efforts to increase adaptive thermogenesis might be used to treat obesity. In small mammals, the main process involved is mitochondrial uncoupling in brown adipose tissue (BAT), which is regulated by the sympathetic nervous system. For a long time, it was assumed that mitochondrial uncoupling is not a major physiological contributor to adaptive thermogenesis in adult humans. However, several studies conducted in recent years suggest that mitochondrial uncoupling in BAT and skeletal muscle tissue in adult humans can be physiologically significant. Other mechanisms besides mitochondrial uncoupling that might be involved are futile calcium cycling, protein turnover and substrate cycling. In conjunction with recent advances on signal transduction studies, this knowledge makes manipulation of adaptive thermogenesis a more realistic option and thus a pharmacologically interesting target to treat obesity.
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Affiliation(s)
- S L J Wijers
- Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands.
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31
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Stefanidis A, Verty ANA, Allen AM, Owens NC, Cowley MA, Oldfield BJ. The role of thermogenesis in antipsychotic drug-induced weight gain. Obesity (Silver Spring) 2009; 17:16-24. [PMID: 19107124 DOI: 10.1038/oby.2008.468] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The administration of antipsychotic drugs to human patients or experimental animals leads to significant weight gain, which is widely presumed to be driven by hyperphagia; however, the contribution from energy expenditure remains unclear. These studies aim to examine the contribution of shifts in energy expenditure, particularly those involving centrally mediated changes in thermogenesis, to the body weight gain associated with the administration of olanzapine to female Sprague Dawley rats. Olanzapine (6 mg/kg/day orally) caused a transient increase in food intake but a maintained increase in body weight. When pair-fed rats were treated with olanzapine, body weight continued to rise compared to vehicle-treated rats, consistent with a reduction in energy expenditure. Brown adipose tissue (BAT) temperature, measured using biotelemetry devices, decreased immediately after the onset of olanzapine treatment and remained depressed, as did physical activity. UCP1 expression in interscapular BAT was reduced following chronic olanzapine treatment. An acute injection of olanzapine was preceded by an injection of a retrograde tracer into the spinal cord to evaluate the nature of the olanzapine-activated neural pathway. Levels of Fos protein in a number of spinally projecting neurons within discrete hypothalamic and brainstem sites were elevated in olanzapine-treated rats. Some of these neurons in the perifornical region of the lateral hypothalamus (LHA) were also Orexin A positive. These data collectively show a significant impact of thermogenesis (and physical activity) on the weight gain associated with olanzapine treatment. The anatomical studies provide an insight into the central neuroanatomical substrate that may subserve the altered thermogenic responses brought about by olanzapine.
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Affiliation(s)
- Aneta Stefanidis
- Department of Physiology, Monash University, Clayton, Victoria, Australia
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32
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Increased uncoupling protein 1 mRNA expression in mice brown adipose tissue after burn injury. J Burn Care Res 2008; 29:358-62. [PMID: 18354294 DOI: 10.1097/bcr.0b013e318166739c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Brown adipose tissue (BAT) contains numerous mitochondria and is characterized by the presence of uncoupling protein 1 (UCP1). UCP1 is the main mediator of thermogenesis that plays an important role in the modulation of energy balance. The authors hypothesize that alterations in the expression of UCP1 might be involved in the major metabolic disorders occurring during burn trauma. The present study is designed to explore the potential role of the UCP1 in metabolic disorders after burn injury. The authors have used the real-time reverse transcription-polymerase chain reaction to quantify UCP1 mRNA expression in the mice BAT and white adipose tissue (WAT). UCP1 mRNA expression was up-regulated in BAT, especially at 24 hours after burn. UCP1 mRNA expression was detectable and also up-regulated by burn injury in WAT. The authors provide evidence that one of the mechanisms mediating hypermetabolism and increased energy expenditure in burn injury is a pronounced increase in thermogenic capacity, as illustrated by robust gene expression of UCP1 in BAT and WAT.
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33
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Nedergaard J, Bengtsson T, Cannon B. Unexpected evidence for active brown adipose tissue in adult humans. Am J Physiol Endocrinol Metab 2007; 293:E444-52. [PMID: 17473055 DOI: 10.1152/ajpendo.00691.2006] [Citation(s) in RCA: 1279] [Impact Index Per Article: 75.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The contention that brown adipose tissue is absent in adult man has meant that processes attributed to active brown adipose tissue in experimental animals (mainly rodents), i.e., classical nonshivering thermogenesis, adaptive adrenergic thermogenesis, diet-induced thermogenesis, and antiobesity, should be either absent or attributed to alternative (unknown) mechanisms in man. However, serendipidously, as a consequence of the use of fluorodeoxyglucose positron emission tomography (FDG PET) to trace tumor metastasis, observations that may change that notion have recently been made. These tomography scans have visualized symmetrical areas of increased tracer uptake in the upper parts of the human body; these areas of uptake correspond to brown adipose tissue. We examine here the published observations from a viewpoint of human physiology. The human depots are somewhat differently located from those in rodents, the main depots being found in the supraclavicular and the neck regions with some additional paravertebral, mediastinal, para-aortic, and suprarenal localizations (but no interscapular). Brown adipose tissue activity in man is acutely cold induced and is stimulated via the sympathetic nervous system. The prevalence of active brown adipose tissue in normal adult man can be only indirectly estimated, but it would seem that the prevalence of active brown adipose tissue in the population may be at least in the range of some tens of percent. We conclude that a substantial fraction of adult humans possess active brown adipose tissue that thus has the potential to be of metabolic significance for normal human physiology as well as to become pharmaceutically activated in efforts to combat obesity.
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Affiliation(s)
- Jan Nedergaard
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91 Stockholm, Sweden.
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34
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Affiliation(s)
- A Prentice
- Public Health Nutrition Unit, London School of Hygiene and Tropical Medicine, London, UK.
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35
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Golozoubova V, Cannon B, Nedergaard J. UCP1 is essential for adaptive adrenergic nonshivering thermogenesis. Am J Physiol Endocrinol Metab 2006; 291:E350-7. [PMID: 16595854 DOI: 10.1152/ajpendo.00387.2005] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Participation of brown adipose tissue [through the action of the uncoupling protein-1 (UCP1)] in adaptive adrenergic nonshivering thermogenesis is recognized, but the existence of a response to adrenergic stimulation in UCP1-ablated mice implies that a mechanism for an alternative adaptive adrenergic thermogenesis may exist. Here, we have used UCP1-ablated mice to examine the existence of an alternative adaptive adrenergic nonshivering thermogenesis, examined as the oxygen consumption response to systemically injected norepinephrine into anesthetized or conscious mice acclimated to different temperatures. We confirm that UCP1-dependent adrenergic nonshivering thermogenesis is adaptive, but we demonstrate that the adrenergic UCP1-independent thermogenesis is not recruitable by cold acclimation. Thus, at least in the mouse, no other proteins or enzymatic pathways exist that can participate in or with time take over the UCP1 mediation of adaptive adrenergic nonshivering thermogenesis, even in the total absence of UCP1. UCP1 is thus the only protein capable of mediating cold acclimation-recruited adaptive adrenergic nonshivering thermogenesis.
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Affiliation(s)
- Valeria Golozoubova
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91, Stockholm, Sweden
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36
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Avram AS, Avram MM, James WD. Subcutaneous fat in normal and diseased states: 2. Anatomy and physiology of white and brown adipose tissue. J Am Acad Dermatol 2006; 53:671-83. [PMID: 16198791 DOI: 10.1016/j.jaad.2005.05.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Revised: 02/09/2005] [Accepted: 05/03/2005] [Indexed: 11/16/2022]
Abstract
White and brown adipose tissues, both present to some degree in all mammals, represent counter actors in energy metabolism. One of the primary functions of white adipocytes is to store excess energy as lipid, which is then mobilized to other tissues in response to metabolic needs that arise in times of food shortage. White adipocyte physiology can be grouped into 3 main categories with potentially overlapping mechanisms: lipid metabolism, glucose metabolism, and endocrine functions. Brown adipocytes, on the other hand, use accumulated lipid from food primarily as a source for chemical energy that can then be released from the cell in the form of heat. Recently, new discoveries about the significance of brown fat have sparked interest in this organ as a potential tool in the fight against obesity in adult humans. A basic overview of the anatomy and physiology of adipose tissue, with particular emphasis on the differences between white and brown fat, is presented.
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37
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Abstract
The function of brown adipose tissue is to transfer energy from food into heat; physiologically, both the heat produced and the resulting decrease in metabolic efficiency can be of significance. Both the acute activity of the tissue, i.e., the heat production, and the recruitment process in the tissue (that results in a higher thermogenic capacity) are under the control of norepinephrine released from sympathetic nerves. In thermoregulatory thermogenesis, brown adipose tissue is essential for classical nonshivering thermogenesis (this phenomenon does not exist in the absence of functional brown adipose tissue), as well as for the cold acclimation-recruited norepinephrine-induced thermogenesis. Heat production from brown adipose tissue is activated whenever the organism is in need of extra heat, e.g., postnatally, during entry into a febrile state, and during arousal from hibernation, and the rate of thermogenesis is centrally controlled via a pathway initiated in the hypothalamus. Feeding as such also results in activation of brown adipose tissue; a series of diets, apparently all characterized by being low in protein, result in a leptin-dependent recruitment of the tissue; this metaboloregulatory thermogenesis is also under hypothalamic control. When the tissue is active, high amounts of lipids and glucose are combusted in the tissue. The development of brown adipose tissue with its characteristic protein, uncoupling protein-1 (UCP1), was probably determinative for the evolutionary success of mammals, as its thermogenesis enhances neonatal survival and allows for active life even in cold surroundings.
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Affiliation(s)
- Barbara Cannon
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, Stockholm, Sweden
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38
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Abstract
Bw gain is controlled by energy intake on one hand and expenditure on the other. The components of energy expenditure are basal metabolism, exercise induced thermogenesis and adaptive thermogenesis. In this short review we shall discuss the main determinants of adaptive thermogenesis.
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Affiliation(s)
- A P Russell
- Department of Medical Biochemistry, University Medical Center, Geneva, Switzerland
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Steegmann AT, Cerny FJ, Holliday TW. Neandertal cold adaptation: physiological and energetic factors. Am J Hum Biol 2002; 14:566-83. [PMID: 12203812 DOI: 10.1002/ajhb.10070] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
European Neandertals employed a complex set of physiological cold defenses, homologous to those seen in contemporary humans and nonhuman primates. While Neandertal morphological patterns, such as foreshortened extremities and low relative surface-area, may have explained some of the variance in cold resistance, it is suggested the adaptive package was strongly dependent on a rich array of physiological defenses. A summary of the environmental cold conditions in which the Neandertals lived is presented, and a comparative ethnographic model from Tierra del Fuego is used. Muscle and subcutaneous fat are excellent "passive" insulators. Neandertals were quite muscular, but it is unlikely that they could maintain enough superficial body fat to offer much cold protection. A major, high-energy metabolic adaptation facilitated by modest amounts of highly thermogenic brown adipose tissue (BAT) is proposed. In addition, Neandertals would have been protected by general mammalian cold defenses based on systemic vasoconstriction and intensified by acclimatization, aerobic fitness, and localized cold--induced vasodilation. However, these defenses are energetically expensive. Based on contemporary data from circumpolar peoples, it is estimated that Neandertals required 3,360 to 4,480 kcal per day to support strenuous winter foraging and cold resistance costs. Several specific genetic cold adaptations are also proposed--heat shock protein (actually, stress shock protein), an ACP*1 locus somatic growth factor, and a specialized calcium metabolism not as yet understood.
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Affiliation(s)
- A Theodore Steegmann
- Department of Anthropology, 380 MFAC, SUNY Buffalo, Buffalo, New York 14261, USA.
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40
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Abstract
The hypothesis that the novel uncoupling protein UCP3 is thermogenic and/or thermoregulatory is discussed. In vitro, ex vivo, and in vivo models are presented. The beta(3)-adrenoceptors are crucial for the appearance of UCP1-expressing cells in the white adipose tissue. These cells might differ from classical brown adipocytes. Besides its well-known effect on brown adipose tissue UCP1, leptin might stimulate indirectly muscle UCP3 expression.
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Del Mar Gonzalez-Barroso M, Ricquier D, Cassard-Doulcier AM. The human uncoupling protein-1 gene (UCP1): present status and perspectives in obesity research. Obes Rev 2000; 1:61-72. [PMID: 12119988 DOI: 10.1046/j.1467-789x.2000.00009.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Energy expenditure through brown adipose tissue thermogenesis contributes either to maintenance of body temperature in a cold environment or to wasted food energy, i.e. cold-induced or diet-induced thermogenesis. Both mechanisms are due to a specific and unique protein: the uncoupling protein-1. Uncoupling protein-1 is exclusively expressed in mitochondria of brown adipocytes where it uncouples respiration from ATP synthesis, dissipating the proton gradient as heat. In humans, although uncoupling protein-1 can be detected, the inability to quantify brown adipose tissue makes it difficult to argue for a role for uncoupling protein-1 in thermogenesis and energy expenditure. This review summarizes data supporting the existence of brown adipocytes and the role of UCP1 in energy dissipation in adult humans. Understanding the mechanisms which regulate transcription and expression of the human UCP1 gene will facilitate the identification of molecules able to increase the levels of this protein in order to modulate energy expenditure in adult humans.
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Affiliation(s)
- M Del Mar Gonzalez-Barroso
- Centre de Recherches sur l'Endocrinologie Moléculaire et le Développement, CNRS, 9 rue Jules Hetzel, 92190 Meudon, France
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Pedersen SB, Borglum JD, Kristensen K, Norrelund H, Otto J, Jorgensen L, Richelsen B. Regulation of uncoupling protein (UCP) 2 and 3 in adipose and muscle tissue by fasting and growth hormone treatment in obese humans. Int J Obes (Lond) 2000; 24:968-75. [PMID: 10951534 DOI: 10.1038/sj.ijo.0801265] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE To investigate whether the expression of uncoupling proteins (UCP2 and UCP3) was affected by a very low calorie diet (VLCD) and growth hormone (GH) treatment for 4 weeks. DESIGN A randomized, placebo-controlled intervention study of VLCD with or without concomitant GH-treatment. SUBJECTS Seventeen obese women (body mass index, BMI=42.1+/-1.4 kg/m2 (range 31.8-54.5 kg/m2)) treated with VLCD for 4 weeks and randomized to concomitant placebo treatment (n=9) or GH treatment (n=8). MEASUREMENTS Fat mass and lean body mass were measured by dual-energy X-ray absorptiometry. Energy expenditure (EE) was measured by indirect calorimetry. UCP2 and UCP3 mRNA were measured in adipose tissue and skeletal muscle biopsies before VLCD and after VLCD+/-GH-treatment by reverse transcription polymerase chain reaction (RT-PCR). RESULTS VLCD treatment resulted in a mean weight loss of 5.23 kg+/-0.8 (P<0.01), a 4.1% decrease in EE (P<0.05) and a 24% decrease in UCP3 mRNA in adipose tissue (P<0.03), whereas adipose tissue UCP2 mRNA and skeletal muscle UCP2 and UCP3 mRNA levels were unchanged. GH-treatment had no effects on EE, changes in body weight or UCP mRNA level. In multiple regression analysis the change in EE caused by VLCD was significantly correlated with changes in adipose tissue UCP2 mRNA (r=0.66, P<0.02) and a tendency towards a significant association with the change in adipose tissue UCP3 mRNA (r=0.45, P=0.09), but not with change in body weight, skeletal muscle UCP2 or UCP3 mRNA levels. CONCLUSION VLCD for 4 weeks decreased UCP3 mRNA expression in human adipose tissue, whereas GH-treatment had no effect on UCP expression. Multiple regression analysis demonstrated that changes in adipose tissue UCP2 and probably UCP3 mRNA were correlated with the change in EE. These findings indicate that UCPs in adipose tissue in very obese individuals might play a role for the reduction in EE observed during energy restriction.
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Affiliation(s)
- S B Pedersen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus Amtssygehus, DK-8000 Aarhus C, Denmark.
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43
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Affiliation(s)
- A G Hoppin
- Massachusetts General Hospital Weight Center, Massachusetts General Hospital, Boston 02114-2696, USA
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Daly TJ, Williams LA, Buffenstein R. Catecholaminergic innervation of interscapular brown adipose tissue in the naked mole-rat (Heterocephalus glaber). J Anat 1997; 190 ( Pt 3):321-6. [PMID: 9147219 PMCID: PMC1467613 DOI: 10.1046/j.1469-7580.1997.19030321.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The thermogenic potential of the interscapular brown fat pad in the naked mole-rat Heterocephalus glaber, that exhibits poikilothermic thermal responses to changing temperatures is reported. Histological and ultrastructural study of the brown fat pad showed that it consists of layers of skeletal muscle interposed between the layers of brown adipose tissue with both unilocular and multilocular adipocytes. Large numbers of mitochondria were present between and around the lipid droplets of these cells. Glyoxylic acid condensation, used to demonstrate catecholaminergic nerves, was evident in low concentrations in the connective tissue between the brown adipocytes. A 3-dimensional computer-aided reconstruction of the fat pad showed the extent and ramification of nerves and blood vessels between the adipocytes. These findings show that although the naked mole-rat is regarded as an endothermic poikilotherm, it possesses anatomical features usually found in homeothermic mammals, which are essential for thermogenesis.
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Affiliation(s)
- T J Daly
- Department of Anatomical Sciences, University of the Witwatersrand, Johannesburg, South Africa
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45
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Jung R. Wherefore art thou brown fat? Clin Endocrinol (Oxf) 1994; 41:149-50. [PMID: 7923818 DOI: 10.1111/j.1365-2265.1994.tb02522.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- R Jung
- Ninewells Hospital and Medical School, Dundee
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46
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Abstract
The antihyperglycaemic agent metformin (dimethylbiguanide) increases metabolic energy expenditure. The possibility that this might involve increased fuel utilization by brown adipose tissue (BAT) was studied. Basal and noradrenaline-stimulated (10(-6) mol/L) oxygen consumption by isolated brown adipocytes from normal and streptozotocin diabetic mice was unaffected by incubation with metformin (10(-4) mol/L) for 30 min. Basal and insulin-stimulated (10(-8) and 10(-6) mol/L) aerobic and anaerobic glucose metabolism was also unaffected during 2 hr incubations of BAT with metformin (10(-4) mol/L). Treatment of normal mice with metformin (250 mg/kg/day) for 7 days did not significantly alter the amount or cytochrome oxidase activity of BAT, and a preliminary semi-quantitative estimation of mitochondrial uncoupling protein showed no apparent change. The results suggest that metformin does not increase energy expenditure of brown adipose tissue.
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Affiliation(s)
- A C Keates
- Department of Pharmaceutical Sciences, Aston University, Birmingham, U.K
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47
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Abstract
Facultative (adaptive) thermogenesis is primarily controlled by the sympathetic nervous system (SNS). The participation of thyroid hormones in adaptive thermogenesis has been considered minor or, at most, permissive. The finding of type II-thyroxine (T(4)) 5'-deiodinase in brown adipose tissue (BAT) has opened a way to uncover a more important role for thyroid hormone in adaptive thermogenesis. This enzyme is activated by the. SNS and insulin. When activated, it generates high BAT concentrations of triiodothyronine (T(3)) from plasma T(4). T(3), intrinsically 10 times more active than T(4), has been shown essential for the expression of the key protein in BAT thermogenesis, uncoupling protein (UCP). The multihormonal control of BAT type-II 5'-deiodinase and the marked influence of T(3) on UCP and BAT thermogenesis suggest that the local control of T(3) generation may be an important source of variability in the potential of mammals to maintain temperature and dissipate energy.
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Affiliation(s)
- J Enrique Silva
- J. Enrique is at the Director of the Endocrine Division, Department of Medicine, Sir Mortimer B. Davis Jewish General Hospital, Canada; Professor of Medicine at McGill University, Montreal, Quebec H3T 1E2, Canada
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48
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Affiliation(s)
- R T Jung
- Department of Medicine, Ninewells Hospital and Medical School, Dundee
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49
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Klaus S, Casteilla L, Bouillaud F, Ricquier D. The uncoupling protein UCP: a membraneous mitochondrial ion carrier exclusively expressed in brown adipose tissue. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1991; 23:791-801. [PMID: 1773883 DOI: 10.1016/0020-711x(91)90062-r] [Citation(s) in RCA: 230] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- S Klaus
- Centre de Recherche sur la Nutrition-CNRS, Meudon-Bellevue, France
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50
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Affiliation(s)
- N G Norgan
- Department of Human Sciences, Loughborough University
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