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Murphy J, Dera A, Morais JA, Tsoukas MA, Khor N, Sazonova T, Almeida LG, Cooke AB, Daskalopoulou SS, Tam BT, Santosa S. Age of obesity onset affects subcutaneous adipose tissue cellularity differently in the abdominal and femoral region. Obesity (Silver Spring) 2024; 32:1508-1517. [PMID: 39045668 DOI: 10.1002/oby.24059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 04/18/2024] [Accepted: 04/19/2024] [Indexed: 07/25/2024]
Abstract
OBJECTIVE We aimed to examine the effect of age of obesity onset, sex, and their interaction on abdominal and femoral subcutaneous adipose tissue (SAT) morphology (degree of adipocyte hyperplasia or hypertrophy). METHODS In this cross-sectional study, we isolated adipocytes via collagenase digestion from abdominal and femoral SAT biopsies taken from male and female adults with childhood-onset obesity (CO; n = 8 males, n = 16 females) or adult-onset obesity (AO; n = 8 males, n = 13 females). Regional body composition was measured with dual-energy x-ray absorptiometry and a single-slice abdominal computed tomography scan. Mean adipocyte size was measured in abdominal and femoral SAT and was used to quantify morphology in android and gynoid subcutaneous fat, respectively. RESULTS Abdominal SAT morphology was more hyperplastic in females with CO than females with AO (p = 0.004) but did not differ between males with CO and males with AO (p = 0.996). Conversely, femoral SAT morphology was more hypertrophic in males and females with CO than those with AO. CONCLUSIONS Age of obesity onset appears to affect SAT morphology differently in the abdominal and femoral regions of male and female adults. Our findings challenge the notion that SAT is uniformly hyperplastic in CO and hypertrophic in AO.
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Affiliation(s)
- Jessica Murphy
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada
- Centre de recherche - Axe maladies chroniques, Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Ile de-Montréal, Hôpital du Sacré-Coeur de Montréal, Montréal, Québec, Canada
| | - Abdulrahman Dera
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada
- Centre de recherche - Axe maladies chroniques, Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Ile de-Montréal, Hôpital du Sacré-Coeur de Montréal, Montréal, Québec, Canada
| | - José A Morais
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Division of Geriatric Medicine, Department of Medicine, McGill University, McGill University Health Centre (MUHC) - Montréal General Hospital, Montréal, Québec, Canada
| | - Michael A Tsoukas
- Division of Endocrinology and Metabolism, Department of Medicine, McGill University, Royal Victoria Hospital, MUHC Glen Site, Montréal, Québec, Canada
| | - Natalie Khor
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada
| | - Taisiia Sazonova
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada
| | - Lucas Guimarães Almeida
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada
- Centre de recherche - Axe maladies chroniques, Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Ile de-Montréal, Hôpital du Sacré-Coeur de Montréal, Montréal, Québec, Canada
| | - Alexandra B Cooke
- Division of Experimental Medicine, Department of Medicine, McGill University, MUHC Glen Site, Montréal, Québec, Canada
| | - Stella S Daskalopoulou
- Division of Experimental Medicine, Department of Medicine, McGill University, MUHC Glen Site, Montréal, Québec, Canada
- Cardiovascular Health Across the Lifespan (CHAL) Program, Research Institute of the McGill University Health Centre (MUHC), Montréal, Québec, Canada
- Division of Internal Medicine, Department of Medicine, McGill University, Royal Victoria Hospital, MUHC Glen Site, Montréal, Québec, Canada
| | - Bjorn T Tam
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada
- Department of Sport, Physical Education, and Health, Faculty of Social Sciences, Hong Kong Baptist University, Kowloon Tong, China
| | - Sylvia Santosa
- Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montréal, Québec, Canada
- Metabolism, Obesity, and Nutrition Laboratory, School of Health, Concordia University, Montréal, Québec, Canada
- Centre de recherche - Axe maladies chroniques, Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Ile de-Montréal, Hôpital du Sacré-Coeur de Montréal, Montréal, Québec, Canada
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Han SM, Nahmgoong H, Yim KM, Kim JB. How obesity affects adipocyte turnover. Trends Endocrinol Metab 2024:S1043-2760(24)00185-1. [PMID: 39095230 DOI: 10.1016/j.tem.2024.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 07/08/2024] [Accepted: 07/09/2024] [Indexed: 08/04/2024]
Abstract
Cellular turnover is fundamental for tissue homeostasis and integrity. Adipocyte turnover, accounting for 4% of the total cellular mass turnover in humans, is essential for adipose tissue homeostasis during metabolic stress. In obesity, an altered adipose tissue microenvironment promotes adipocyte death. To clear dead adipocytes, macrophages are recruited and form a distinctive structure known as crown-like structure; subsequently, new adipocytes are generated from adipose stem and progenitor cells in the adipogenic niche to replace dead adipocytes. Accumulating evidence indicates that adipocyte death, clearance, and adipogenesis are sophisticatedly orchestrated during adipocyte turnover. In this Review, we summarize our current understandings of each step in adipocyte turnover, discussing its key players and regulatory mechanisms.
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Affiliation(s)
- Sang Mun Han
- National Leader Research Initiatives Center for Adipocyte Structure and Function, Institute of Molecular Biology and Genetics, School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Hahn Nahmgoong
- National Leader Research Initiatives Center for Adipocyte Structure and Function, Institute of Molecular Biology and Genetics, School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Kyung Min Yim
- National Leader Research Initiatives Center for Adipocyte Structure and Function, Institute of Molecular Biology and Genetics, School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Jae Bum Kim
- National Leader Research Initiatives Center for Adipocyte Structure and Function, Institute of Molecular Biology and Genetics, School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea.
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3
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Stojchevski R, Chandrasekaran P, Hadzi-Petrushev N, Mladenov M, Avtanski D. Adipose Tissue Dysfunction Related to Climate Change and Air Pollution: Understanding the Metabolic Consequences. Int J Mol Sci 2024; 25:7849. [PMID: 39063092 PMCID: PMC11277516 DOI: 10.3390/ijms25147849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 07/12/2024] [Accepted: 07/16/2024] [Indexed: 07/28/2024] Open
Abstract
Obesity, a global pandemic, poses a major threat to healthcare systems worldwide. Adipose tissue, the energy-storing organ during excessive energy intake, functions as a thermoregulator, interacting with other tissues to regulate systemic metabolism. Specifically, brown adipose tissue (BAT) is positively associated with an increased resistance to obesity, due to its thermogenic function in the presence of uncoupled protein 1 (UCP1). Recently, studies on climate change and the influence of environmental pollutants on energy homeostasis and obesity have drawn increasing attention. The reciprocal relationship between increasing adiposity and increasing temperatures results in reduced adaptive thermogenesis, decreased physical activity, and increased carbon footprint production. In addition, the impact of climate change makes obese individuals more prone to developing type 2 diabetes mellitus (T2DM). An impaired response to heat stress, compromised vasodilation, and sweating increase the risk of diabetes-related comorbidities. This comprehensive review provides information about the effects of climate change on obesity and adipose tissue, the risk of T2DM development, and insights into the environmental pollutants causing adipose tissue dysfunction and obesity. The effects of altered dietary patterns on adiposity and adaptation strategies to mitigate the detrimental effects of climate change are also discussed.
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Affiliation(s)
- Radoslav Stojchevski
- Friedman Diabetes Institute, Lenox Hill Hospital, Northwell Health, New York, NY 10003, USA;
- Feinstein Institutes for Medical Research, Manhasset, NY 11030, USA
- Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY 11549, USA
| | | | - Nikola Hadzi-Petrushev
- Faculty of Natural Sciences and Mathematics, Institute of Biology, Ss. Cyril and Methodius University, 1000 Skopje, North Macedonia; (N.H.-P.); (M.M.)
| | - Mitko Mladenov
- Faculty of Natural Sciences and Mathematics, Institute of Biology, Ss. Cyril and Methodius University, 1000 Skopje, North Macedonia; (N.H.-P.); (M.M.)
| | - Dimiter Avtanski
- Friedman Diabetes Institute, Lenox Hill Hospital, Northwell Health, New York, NY 10003, USA;
- Feinstein Institutes for Medical Research, Manhasset, NY 11030, USA
- Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY 11549, USA
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4
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Palacios-Marin I, Serra D, Jimenez-Chillarón J, Herrero L, Todorčević M. Adipose Tissue Dynamics: Cellular and Lipid Turnover in Health and Disease. Nutrients 2023; 15:3968. [PMID: 37764752 PMCID: PMC10535304 DOI: 10.3390/nu15183968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Revised: 08/30/2023] [Accepted: 09/10/2023] [Indexed: 09/29/2023] Open
Abstract
The alarming increase in obesity and its related metabolic health complications, such as type 2 diabetes, has evolved into a global pandemic. Obesity is mainly characterized by excessive accumulation of adipose tissue, primarily due to an imbalance between energy intake and expenditure. Prolonged positive energy balance leads to the expansion of existing adipocytes (hypertrophy) and/or an increase in preadipocyte and adipocyte number (hyperplasia) to accommodate excess energy intake. However, obesity is not solely defined by increases in adipocyte size and number. The turnover of adipose tissue cells also plays a crucial role in the development and progression of obesity. Cell turnover encompasses the processes of cell proliferation, differentiation, and apoptosis, which collectively regulate the overall cell population within adipose tissue. Lipid turnover represents another critical factor that influences how adipose tissue stores and releases energy. Our understanding of adipose tissue lipid turnover in humans remains limited due to the slow rate of turnover and methodological constraints. Nonetheless, disturbances in lipid metabolism are strongly associated with altered adipose tissue lipid turnover. In obesity, there is a decreased rate of triglyceride removal (lipolysis followed by oxidation), leading to the accumulation of triglycerides over time. This review provides a comprehensive summary of findings from both in vitro and in vivo methods used to study the turnover of adipose cells and lipids in metabolic health and disease. Understanding the mechanisms underlying cellular and lipid turnover in obesity is essential for developing strategies to mitigate the adverse effects of excess adiposity.
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Affiliation(s)
- Ivonne Palacios-Marin
- Endocrinology Department, Institut de Recerca Sant Joan de Déu, Esplugues, E-08950 Barcelona, Spain
- Department of Biochemistry and Physiology, School of Pharmacy and Food Sciences, Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, E-08028 Barcelona, Spain
| | - Dolors Serra
- Department of Biochemistry and Physiology, School of Pharmacy and Food Sciences, Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, E-08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, E-28029 Madrid, Spain
| | - Josep Jimenez-Chillarón
- Endocrinology Department, Institut de Recerca Sant Joan de Déu, Esplugues, E-08950 Barcelona, Spain
- Department of Physiological Sciences, School of Medicine, University of Barcelona, E-08907 L’Hospitalet, Spain
| | - Laura Herrero
- Department of Biochemistry and Physiology, School of Pharmacy and Food Sciences, Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, E-08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, E-28029 Madrid, Spain
| | - Marijana Todorčević
- Department of Biochemistry and Physiology, School of Pharmacy and Food Sciences, Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, E-08028 Barcelona, Spain
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Abstract
In this review, we provide a brief synopsis of the connections between adipose tissue and metabolic health and highlight some recent developments in understanding and exploiting adipocyte biology. Adipose tissue plays critical roles in the regulation of systemic glucose and lipid metabolism and secretes bioactive molecules possessing endocrine, paracrine, and autocrine functions. Dysfunctional adipose tissue has a detrimental impact on metabolic health and is intimately involved in key aspects of metabolic diseases such as insulin resistance, lipid overload, inflammation, and organelle stress. Differences in the distribution of fat depots and adipose characteristics relate to divergent degrees of metabolic dysfunction found in metabolically healthy and unhealthy obese individuals. Thermogenic adipocytes increase energy expenditure via mitochondrial uncoupling or adenosine triphosphate-consuming futile substrate cycles, while functioning as a metabolic sink and participating in crosstalk with other metabolic organs. Manipulation of adipose tissue provides a wealth of opportunities to intervene and combat the progression of associated metabolic diseases. We discuss current treatment modalities for obesity including incretin hormone analogs and touch upon emerging strategies with therapeutic potential including exosome-based therapy, pharmacological activation of brown and beige adipocyte thermogenesis, and administration or inhibition of adipocyte-derived factors.
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Affiliation(s)
- Sung-Min An
- Division of Endocrinology, Department of Internal Medicine, University of California Davis School of Medicine, Davis, CA, USA
| | - Seung-Hee Cho
- Division of Endocrinology, Department of Internal Medicine, University of California Davis School of Medicine, Davis, CA, USA
| | - John C. Yoon
- Division of Endocrinology, Department of Internal Medicine, University of California Davis School of Medicine, Davis, CA, USA
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Kibodeaux D, Savoie J, Ravussin E, Fitch M, Hellerstein MK, White U. Measuring In Vivo Adipose Tissue Kinetics in Humans Using the Deuterium (2H)-Labeling Approach. J Vis Exp 2023:10.3791/64883. [PMID: 37590512 PMCID: PMC10521058 DOI: 10.3791/64883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/19/2023] Open
Abstract
White adipose tissue is a highly plastic organ that is necessary to maintain whole-body energy homeostasis. The adipose tissue mass and changes in the fat mass or distribution are regulated by changes in the synthesis and breakdown (i.e., turnover) of adipose cells and triacylglycerols. Evidence suggests that the manner and magnitude of subcutaneous adipose tissue expansion (i.e., hypertrophy vs. hyperplasia) and turnover can influence metabolic health, as adipogenesis has been implicated in the pathogenesis of obesity and related diseases. Despite the potential role of adipose turnover in human health, there is a lack of knowledge about the in vivo kinetics of adipose cells. This is due, in part, to the slow turnover rate of the cells in adipose tissue and the practical complexity of directly labeling their metabolic precursors in vivo. Herein, we describe methods to measure in vivo adipose kinetics and turnover rates in humans through the consumption of deuterium (2H)-labeled water. The incorporation of 2H into the deoxyribonucleotide moieties of DNA in pre-adipocytes and adipocytes provides an accurate measure of cell formation and death (adipose turnover). Overall, this is an innovative approach to measuring in vivo adipose kinetics and represents a substantive departure from other in vitro assessments.
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Affiliation(s)
- Dereck Kibodeaux
- Pennington Biomedical Research Center, Louisiana State University System
| | - Jonathan Savoie
- Pennington Biomedical Research Center, Louisiana State University System
| | - Eric Ravussin
- Pennington Biomedical Research Center, Louisiana State University System
| | | | | | - Ursula White
- Pennington Biomedical Research Center, Louisiana State University System;
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7
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White U. Adipose tissue expansion in obesity, health, and disease. Front Cell Dev Biol 2023; 11:1188844. [PMID: 37181756 PMCID: PMC10169629 DOI: 10.3389/fcell.2023.1188844] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 04/14/2023] [Indexed: 05/16/2023] Open
Abstract
White adipose tissue (WAT) expands under physiological conditions via an increase in adipocyte size (hypertrophy) and/or number (hyperplasia; adipogenesis), and the ability of WAT to expand to accommodate energy demands is a significant determinant of metabolic health status. Obesity is associated with impaired WAT expansion and remodeling, which results in the deposition of lipids to other non-adipose organs, leading to metabolic derangements. Although increased hyperplasia has been implicated as a cornerstone in promoting healthy WAT expansion, recent developments suggest that the role of adipogenesis as a contributing factor in the transition from impaired subcutaneous WAT expansion to impaired metabolic health remains up for debate. This mini-review will summarize recent developments and highlight emerging concepts on the features of WAT expansion and turnover, and the significance in obesity, health, and disease.
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Affiliation(s)
- Ursula White
- Clinical Science Division, LSU Pennington Biomedical Research Center, Baton Rouge, LA, United States
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8
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Microscopic image-based classification of adipocyte differentiation by machine learning. Histochem Cell Biol 2022; 159:313-327. [PMID: 36504003 DOI: 10.1007/s00418-022-02168-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/17/2022] [Indexed: 12/14/2022]
Abstract
Adipocyte differentiation is a sequential process involving increased expression of peroxisome proliferator-activated receptor gamma (PPARγ), adipocyte-specific gene expression, and accumulation of lipid droplets in the cytoplasm. Expression of the transcription factors involved is usually detected using canonical biochemical or biomolecular procedures such as Western blotting or qPCR of pooled cell lysates. While this provides a useful average index for adipogenesis for some populations, the precise stage of adipogenesis cannot be distinguished at the single-cell level, because the heterogenous nature of differentiation among cells limits the utility of averaged data. We have created a classifier to sort cells, and used it to determine the stage of adipocyte differentiation at the single-cell level. We used a machine learning method with microscopic images of cell stained for PPARγ and lipid droplets as input data. Our results show that the classifier can successfully determine the precise stage of differentiation. Stage classification and subsequent model fitting using the sequential reaction model revealed the action of pioglitazone and rosiglitazone to be promotion of transition from the stage of increased PPARγ expression to the next stage. This indicates that these drugs are PPARγ agonists, and that our classifier and model can accurately estimate drug action points and would be suitable for evaluating the stage/state of individual cells during differentiation or disease progression. The incorporation of both biochemical and morphological information derived from immunofluorescence image of cells and so overcomes limitations of current models.
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White U, Beyl RA, Ravussin E. A higher proportion of small adipocytes is associated with increased visceral and ectopic lipid accumulation during weight gain in response to overfeeding in men. Int J Obes (Lond) 2022; 46:1560-1563. [PMID: 35599261 PMCID: PMC9348546 DOI: 10.1038/s41366-022-01150-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 05/05/2022] [Accepted: 05/10/2022] [Indexed: 02/03/2023]
Abstract
BACKGROUND Adipose tissue (AT) expansion occurs by hypertrophy (increase in size) and hyperplasia (increase in number) of adipocytes. The AT expandability hypothesis postulates that impaired subcutaneous AT expansion leads to ectopic fat accretion, contributing to impaired metabolic health. The role of adipogenesis as a contributing factor is debatable. SUBJECTS/METHODS In the present analysis, we assess changes in adipocyte size distribution in relation to changes in ectopic fat accretion in response to 8-weeks of overfeeding in 22 men (28 ± 5.4 years; BMI 25.5 ± 2.3 kg/m2) who were fed 40% over their baseline energy requirements. RESULTS Participants gained 6.7 ± 2.1 kg. The percentage of small adipocytes (p = 0.03) and the peak diameter of large adipocytes (p = 0.01) increased after overfeeding. At baseline, the percentage of small adipocytes was positively correlated with % body fat (p = 0.03), SAT mass (p = 0.01), VAT mass (p = 0.02), VAT:TAT (p = 0.05), and IHL (p = 0.09; trend). The relative (percent) change in small adipocytes was positively associated with the increase in whole-body fat (p = 0.001), VAT mass (p = 0.0003), VAT:TAT (p = 0.01), and IHL (p = 0.007) in response to overfeeding. CONCLUSIONS These findings, surprisingly, indicate that during substantial weight gain, an increase in small adipocytes (suggesting hyperplastic expansion) is associated with impaired (not improved) metabolic health outcomes, specifically visceral and ectopic fat accumulation. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov Identifier- NCT01672632.
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Affiliation(s)
- Ursula White
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA.
| | - Robbie A Beyl
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA
| | - Eric Ravussin
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA
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Exercise reduced the formation of new adipocytes in the adipose tissue of mice in vivo. PLoS One 2021; 16:e0244804. [PMID: 33471817 PMCID: PMC7817033 DOI: 10.1371/journal.pone.0244804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 12/16/2020] [Indexed: 12/20/2022] Open
Abstract
Exercise has beneficial effects on metabolism and health. Although the skeletal muscle has been a primary focus, exercise also mediates robust adaptations in white adipose tissue. To determine if exercise affects in vivo adipocyte formation, fifty-two, sixteen-week-old C57BL/6J mice were allowed access to unlocked running wheels [Exercise (EX) group; n = 13 males, n = 13 females] or to locked wheels [Sedentary (SED) group; n = 13 males, n = 13 females] for 4-weeks. In vivo adipocyte formation was assessed by the incorporation of deuterium (2H) into the DNA of newly formed adipocytes in the inguinal and gonadal adipose depots. A two-way ANOVA revealed that exercise significantly decreased new adipocyte formation in the adipose tissue of mice in the EX group relative to the SED group (activity effect; P = 0.02). This reduction was observed in male and female mice (activity effect; P = 0.03). Independent analysis of the depots showed a significant reduction in adipocyte formation in the inguinal (P = 0.05) but not in the gonadal (P = 0.18) of the EX group. We report for the first time that exercise significantly reduced in vivo adipocyte formation in the adipose tissue of EX mice using a physiologic metabolic 2H2O-labeling protocol.
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White U, Fitch MD, Beyl RA, Hellerstein MK, Ravussin E. Adipose depot-specific effects of 16 weeks of pioglitazone on in vivo adipogenesis in women with obesity: a randomised controlled trial. Diabetologia 2021; 64:159-167. [PMID: 33001232 PMCID: PMC7718382 DOI: 10.1007/s00125-020-05281-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 08/14/2020] [Indexed: 12/22/2022]
Abstract
AIMS/HYPOTHESIS In vitro and rodent studies suggest that pioglitazone, a thiazolidinedione, can promote adipogenesis in adipose tissue (AT); however, there is a lack of in vivo studies in humans to support these findings. The objectives of this randomised, placebo-controlled, parallel-arm trial were to test if pioglitazone stimulates in vivo adipogenesis in the subcutaneous adipose tissue depots and if these measures were related to metabolic health outcomes in women with obesity. METHODS Forty-one healthy women with obesity (20 black; 21 white; 29 ± 6 years; BMI 32.0 ± 1.7 kg/m2; 44.0 ± 3.6% body fat) were randomised to consume 30 mg/day of pioglitazone (n = 21) or placebo (n = 20) for 16 weeks. SAS v9.4 was used to generate the block randomisation code sequence (stored in password-protected files) with a 1:1 allocation ratio. The participants and study staff involved in assessing and analysing data outcomes were blinded to the group assignments. The trial was conducted at Pennington Biomedical Research Center and ended in 2016. At baseline and post-intervention, subcutaneous abdominal (scABD) and femoral (scFEM) AT biopsies were collected, and in vivo cellular kinetics (primary endpoint of the trial) were assessed by an 8 week labelling protocol of deuterium (2H) into the DNA of adipose cells. Body composition was measured by dual-energy x-ray absorptiometry (DXA), scABD and visceral AT (VAT) by MRI, ectopic fat by 1H-MRS, and insulin sensitivity by an OGTT. RESULTS After the 16 week intervention, there was a significant decrease in visceral fat (VAT:total abdominal AT [as a %]; p = 0.002) and an increase in the Matsuda index (i.e. improved insulin sensitivity; p = 0.04) in the pioglitazone group relative to the placebo group. A significant increase in the formation of new adipocytes was observed in the scFEM (Δ = 3.3 ± 1.6%; p = 0.04) but not the scABD depot (Δ = 2.0 ± 2.1%; p = 0.32) in the pioglitazone group relative to the placebo group. No serious adverse events were reported. CONCLUSIONS/INTERPRETATION Pioglitazone may elicit distinct differences in in vivo adipogenesis in subcutaneous adipose depots in women with obesity, with increased rates in the protective scFEM. Trial registration ClinicalTrials.gov NCT01748994 Funding This study was funded by R01DK090607, P30DK072476, and R03DK112006 from the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health. U54 GM104940 from the National Institute of General Medical Sciences of the National Institutes of Health. The Robert C. and Veronica Atkins Foundation. Graphical abstract.
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Affiliation(s)
- Ursula White
- Physiology of Human Adipose Tissue, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA.
| | - Mark D Fitch
- Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA, USA
| | - Robbie A Beyl
- Biostatistics, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA
| | - Marc K Hellerstein
- Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA, USA
| | - Eric Ravussin
- Human Translational Physiology, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA
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Abstract
Adipose, or fat, tissue (AT) was once considered an inert tissue that primarily existed to store lipids, and was not historically recognized as an important organ in the regulation and maintenance of health. With the rise of obesity and more rigorous research, AT is now recognized as a highly complex metabolic organ involved in a host of important physiological functions, including glucose homeostasis and a multitude of endocrine capabilities. AT dysfunction has been implicated in several disease states, most notably obesity, metabolic syndrome and type 2 diabetes. The study of AT has provided useful insight in developing strategies to combat these highly prevalent metabolic diseases. This review highlights the major functions of adipose tissue and the consequences that can occur when disruption of these functions leads to systemic metabolic dysfunction.
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Affiliation(s)
- Innocence Harvey
- Adipocyte Biology Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA
| | - Anik Boudreau
- Adipocyte Biology Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA
| | - Jacqueline M Stephens
- Adipocyte Biology Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA.,Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
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Smith GI, Mittendorfer B, Klein S. Metabolically healthy obesity: facts and fantasies. J Clin Invest 2020; 129:3978-3989. [PMID: 31524630 DOI: 10.1172/jci129186] [Citation(s) in RCA: 326] [Impact Index Per Article: 81.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Although obesity is typically associated with metabolic dysfunction and cardiometabolic diseases, some people with obesity are protected from many of the adverse metabolic effects of excess body fat and are considered "metabolically healthy." However, there is no universally accepted definition of metabolically healthy obesity (MHO). Most studies define MHO as having either 0, 1, or 2 metabolic syndrome components, whereas many others define MHO using the homeostasis model assessment of insulin resistance (HOMA-IR). Therefore, numerous people reported as having MHO are not metabolically healthy, but simply have fewer metabolic abnormalities than those with metabolically unhealthy obesity (MUO). Nonetheless, a small subset of people with obesity have a normal HOMA-IR and no metabolic syndrome components. The mechanism(s) responsible for the divergent effects of obesity on metabolic health is not clear, but studies conducted in rodent models suggest that differences in adipose tissue biology in response to weight gain can cause or prevent systemic metabolic dysfunction. In this article, we review the definition, stability over time, and clinical outcomes of MHO, and discuss the potential factors that could explain differences in metabolic health in people with MHO and MUO - specifically, modifiable lifestyle factors and adipose tissue biology. Better understanding of the factors that distinguish people with MHO and MUO can produce new insights into mechanism(s) responsible for obesity-related metabolic dysfunction and disease.
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14
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Aitken-Buck HM, Moharram M, Babakr AA, Reijers R, Van Hout I, Fomison-Nurse IC, Sugunesegran R, Bhagwat K, Davis PJ, Bunton RW, Williams MJA, Stiles MK, Jones PP, Coffey S, Lamberts RR. Relationship between epicardial adipose tissue thickness and epicardial adipocyte size with increasing body mass index. Adipocyte 2019; 8:412-420. [PMID: 31829077 PMCID: PMC6948959 DOI: 10.1080/21623945.2019.1701387] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Macroscopic deposition of epicardial adipose tissue (EAT) has been strongly associated with numerous indices of obesity and cardiovascular disease risk. In contrast, the morphology of EAT adipocytes has rarely been investigated. We aimed to determine whether obesity-driven adipocyte hypertrophy, which is characteristic of other visceral fat depots, is found within EAT adipocytes. EAT samples were collected from cardiac surgery patients (n = 49), stained with haematoxylin & eosin, and analysed for mean adipocyte size and non-adipocyte area. EAT thickness was measured using echocardiography. A significant positive relationship was found between EAT thickness and body mass index (BMI). When stratified into standardized BMI categories, EAT thickness was 58.7% greater (p = 0.003) in patients from the obese (7.3 ± 1.8 mm) compared to normal (4.6 ± 0.9 mm) category. BMI as a continuous variable significantly correlated with EAT thickness (r = 0.56, p < 0.0001). Conversely, no correlation was observed between adipocyte size and either BMI or EAT thickness. No difference in the non-adipocyte area was found between BMI groups. Our results suggest that the increased macroscopic EAT deposition associated with obesity is not caused by adipocyte hypertrophy. Rather, alternative remodelling via adipocyte proliferation might be responsible for the observed EAT expansion.
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Affiliation(s)
- Hamish M. Aitken-Buck
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Mohammed Moharram
- Department of Medicine, HeartOtago, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Aram A Babakr
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Robin Reijers
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Isabelle Van Hout
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Ingrid C. Fomison-Nurse
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Ramanen Sugunesegran
- Department of Cardiothoracic Surgery, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Krishna Bhagwat
- Department of Cardiothoracic Surgery, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Phillip J Davis
- Department of Cardiothoracic Surgery, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Richard W. Bunton
- Department of Cardiothoracic Surgery, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Michael J. A. Williams
- Department of Medicine, HeartOtago, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Martin K. Stiles
- Department of Cardiology, Waikato District Health Board, Hamilton, New Zealand
- Waikato Clinical School, University of Auckland, Hamilton, New Zealand
| | - Peter P. Jones
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Sean Coffey
- Department of Medicine, HeartOtago, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Regis R. Lamberts
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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15
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Lumish HS, O'Reilly M, Reilly MP. Sex Differences in Genomic Drivers of Adipose Distribution and Related Cardiometabolic Disorders: Opportunities for Precision Medicine. Arterioscler Thromb Vasc Biol 2019; 40:45-60. [PMID: 31747800 DOI: 10.1161/atvbaha.119.313154] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
This review focuses on the human genetics, epidemiology, and molecular pathophysiology of sex differences in central obesity, adipose distribution, and related cardiometabolic disorders. Distribution of fat is important for cardiometabolic health, with peripheral fat depots having a protective effect and central visceral fat depots conferring a detrimental effect on health. There are important sex differences in fat distribution that are masked when studying body mass index as a measure of obesity. From epidemiological, murine, and in vitro studies, several mechanisms have been proposed to explain the sex differences in adipose distribution, including sex hormonal effects, cell-intrinsic properties, and the microenvironment in fat depots. More recently, human genetics have revealed hundreds of loci for central obesity providing disruptive opportunities for mechanistic discoveries and clinical translation. A striking feature is that over one-third of these loci have reproducible but poorly understood sexual dimorphic associations with central obesity, most having stronger effects in women. Understanding the genetic and molecular mechanisms of adipose distribution and its sexual dimorphism in humans provides a unique opportunity to promote the use of precision medicine for early identification of at-risk individuals, and the development of novel therapeutic strategies for central obesity and related cardiometabolic disorders.
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Affiliation(s)
- Heidi S Lumish
- From the Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, New York, NY (H.S.L., M.O., M.P.R.)
| | - Marcella O'Reilly
- From the Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, New York, NY (H.S.L., M.O., M.P.R.)
| | - Muredach P Reilly
- From the Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, New York, NY (H.S.L., M.O., M.P.R.).,Irving Institute for Clinical and Translational Research, Columbia University, New York, NY (M.P.R.)
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16
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Nouws J, Fitch M, Mata M, Santoro N, Galuppo B, Kursawe R, Narayan D, Vash-Margita A, Pierpont B, Shulman GI, Hellerstein M, Caprio S. Altered In Vivo Lipid Fluxes and Cell Dynamics in Subcutaneous Adipose Tissues Are Associated With the Unfavorable Pattern of Fat Distribution in Obese Adolescent Girls. Diabetes 2019; 68:1168-1177. [PMID: 30936147 PMCID: PMC6610014 DOI: 10.2337/db18-1162] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 03/24/2019] [Indexed: 12/20/2022]
Abstract
Patterns of abdominal fat distribution (for example, a high vs. low visceral adipose tissue [VAT]/[VAT + subcutaneous adipose tissue (SAT)] ratio), independent of obesity, during adolescence carry a high risk for insulin resistance and type 2 diabetes. Longitudinal follow-up of a cohort of obese adolescents has recently revealed that a high ratio (high VAT/[VAT + SAT]) is a major determinant of fatty liver and metabolic impairment over time, with these effects being more pronounced in girls than in boys. To unravel the underlying metabolic alterations associated with the unfavorable VAT/(VAT + SAT) phenotype, we used the 2H2O labeling method to measure the turnover of adipose lipids and cells in the subcutaneous abdominal and gluteal/femoral adipose tissue (SAT) of weight-stable obese adolescent girls with a similar level of obesity but discordant VAT/(VAT + SAT) ratios. Girls with the unfavorable (high VAT/[VAT + SAT]) phenotype exhibited higher in vivo rates of triglyceride (TG) turnover (representing both lipolysis and synthesis at steady state), without significant differences in de novo lipogenesis in both abdominal and gluteal depots, compared with obese girls with the favorable phenotype. Moreover, mature adipocytes had higher turnover, with no difference in stromal vascular cell proliferation in both depots in the metabolically unfavorable phenotype. The higher TG turnover rates were significantly correlated with higher intrahepatic fat stores. These findings are contrary to the hypothesis that impaired capacity to deposit TGs or proliferation of new mature adipocytes are potential mechanisms for ectopic fat distribution in this setting. In summary, these results suggest that increased turnover of TGs (lipolysis) and of mature adipocytes in both abdominal and gluteal SAT may contribute to metabolic impairment and the development of fatty liver, even at this very early stage of disease.
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Affiliation(s)
- Jessica Nouws
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Mark Fitch
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA
| | - Mariana Mata
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Nicola Santoro
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Brittany Galuppo
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Romy Kursawe
- Diabetes and Obesity, The Jackson Laboratory, Farmington, CT
| | - Deepak Narayan
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Yale University School of Medicine, New Haven, CT
| | - Alla Vash-Margita
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, New Haven, CT
| | - Bridget Pierpont
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Gerald I Shulman
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT
| | - Marc Hellerstein
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA
| | - Sonia Caprio
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
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Stephens J, Ravussin E, White U. The Expression of Adipose Tissue-Derived Cardiotrophin-1 in Humans with Obesity. BIOLOGY 2019; 8:biology8020024. [PMID: 31013924 PMCID: PMC6627495 DOI: 10.3390/biology8020024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 04/01/2019] [Accepted: 04/09/2019] [Indexed: 01/23/2023]
Abstract
Cardiotrophin-1 (CT-1) is a gp130 cytokine that was previously characterized for its effects on cardiomyocytes and identified as a marker of heart failure. More recent studies reported elevated circulating levels of CT-1 in humans with obesity and metabolic syndrome (MetS). However, a subsequent rodent study implicated CT-1 as a potential therapeutic target for obesity and MetS. Adipose tissue (AT) is broadly acknowledged as an endocrine organ and is a substantial source of CT-1. However, no study has examined the expression of adipose-derived CT-1 in humans. We present the first analysis of CT-1 mRNA expression in subcutaneous AT and its association with clinical variables in 22 women with obesity and 15 men who were 40% overfed for 8-weeks. We observed that CT-1 expression was higher in the subcutaneous abdominal (scABD) than the femoral (scFEM) depot. Importantly, we reveal that scFEM but not scABD, CT-1 expression was negatively associated with visceral adiposity and intrahepatic lipid, while positively correlated with insulin sensitivity in obese women. Also, men with higher CT-1 levels at baseline had less of a decline in insulin sensitivity in response to overfeeding. Our data provide new knowledge on the regulation of adipose-derived CT-1 in obesity and during weight gain in response to overfeeding in humans and suggest that CT-1 may play a protective role in obesity and related disorders.
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Affiliation(s)
| | - Eric Ravussin
- Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA.
| | - Ursula White
- Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA.
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18
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White U, Ravussin E. Dynamics of adipose tissue turnover in human metabolic health and disease. Diabetologia 2019; 62:17-23. [PMID: 30267179 PMCID: PMC6476187 DOI: 10.1007/s00125-018-4732-x] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 07/25/2018] [Indexed: 12/17/2022]
Abstract
White adipose tissue is a highly plastic organ and is an important regulator of whole-body metabolism and energy balance. The magnitude of adipose tissue mass is determined by dynamic changes in the synthesis and breakdown (i.e. turnover) of adipocytes and triacylglycerols (TGs). Obesity is a disorder characterised by excessive adiposity and is a risk factor for diseases, including the metabolic syndrome and type 2 diabetes. Adipose tissue expansion is necessary to accommodate chronic excess energy intake and is characterised by enlargement of existing adipocytes (hypertrophy) and by increase in pre-adipocyte and adipocyte numbers (hyperplasia). Evidence suggests that the manner of subcutaneous adipose expansion can influence metabolic health, as impaired adipogenesis, namely restricted hyperplasia, may lead to ectopic lipid deposition in the liver and skeletal muscle, contributing to the pathogenesis of obesity-related disorders. Despite the plausible role of adipose turnover in human health and pathology, little is known about the in vivo kinetics of adipose tissue components (both adipose cells and TGs). This is due, in part, to the slow turnover rate of adipose tissue and the complexity of directly labelling pathway precursors. This review provides a brief summary of findings derived from in vitro techniques, as well as an overview of two in vivo methods that are being implemented to assess the turnover of adipose cells and TGs. Finally, the role of adipose tissue turnover in metabolic health and disease is discussed.
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Affiliation(s)
- Ursula White
- Physiology of Human Adipose Tissue Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, 70808, USA.
| | - Eric Ravussin
- Human Translational Physiology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA
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19
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White UA, Fitch MD, Beyl RA, Hellerstein MK, Ravussin E. Racial differences in in vivo adipose lipid kinetics in humans. J Lipid Res 2018; 59:1738-1744. [PMID: 29910190 DOI: 10.1194/jlr.p082628] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 05/16/2018] [Indexed: 11/20/2022] Open
Abstract
The storage of lipids in the form of triglycerides (TGs) and the de novo synthesis (lipogenesis) of fatty acids from nonlipid precursors [de novo lipogenesis (DNL)] are important functions of adipose tissue (AT) that influence whole-body metabolism. Yet, few studies have reported in vivo estimates of adipose lipid kinetics in humans. Fifty-two women with obesity (27 African-American and 25 Caucasian; 29.7 ± 5.5 years; BMI 32.2 ± 2.8 kg/m2; 44.3 ± 4.0% body fat) were enrolled in the study. In vivo synthesis (or replacement) of TGs (fTG) as well as the synthesis of the fatty acid, palmitate [a measure of adipose DNL (fDNL)], were assessed using an 8 week incorporation of deuterium into lipids (glycerol and palmitate moieties of TGs) in subcutaneous abdominal (scABD) and subcutaneous femoral (scFEM) AT. We report, for the first time, significant race differences in both TG synthesis and absolute DNL, with Caucasians having higher fTG and fDNL as compared with African-Americans. The DNL contribution to newly synthesized TG (corrected fDNL) was not different between races. Interestingly, our findings also show that the scFEM adipose depot had higher TG replacement rates relative to the scABD. Finally, the replacement rate of TG (fTG) was negatively correlated with changes in body weight over the 8 week labeling period. Our results provide the first evidence that in vivo TG replacement (synthesis and breakdown) rates differ by ethnicity. In addition, TG turnover varies by depot location in humans, implying an increased capacity for TG storage and higher lipolytic activity in the scFEM AT.
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Affiliation(s)
- Ursula A White
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA
| | - Mark D Fitch
- University of California at Berkeley, Berkeley, CA
| | - Robbie A Beyl
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA
| | | | - Eric Ravussin
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA.
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20
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Cellular Mechanisms Driving Sex Differences in Adipose Tissue Biology and Body Shape in Humans and Mouse Models. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1043:29-51. [PMID: 29224089 DOI: 10.1007/978-3-319-70178-3_3] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sex differences in adipose tissue distribution and the metabolic, endocrine, and immune functions of different anatomical fat depots have been described, but they are incompletely documented in the literature. It is becoming increasingly clear that adipose depots serve distinct functions in males and females and have specific physiological roles. However, the mechanisms that regulate the size and function of specific adipose tissues in men and women remain poorly understood. New insights from mouse models have advanced our understanding of depot differences in adipose growth and remodeling via the proliferation and differentiation of adipose progenitors that can expand adipocyte number in the tissue or simply replace dysfunctional older and larger adipocytes. A limited ability of a depot to expand or remodel can lead to excessive adipocyte hypertrophy, which is often correlated with metabolic dysfunction. However, the relationship of adipocyte size and function varies by depot and sex. For example, femoral adipose tissues of premenopausal women appear to have a greater capacity for adipose expansion via hyperplasia and hypertrophy; although larger, these gluteal-femoral adipocytes remain insulin sensitive. The microenvironment of specific depots, including the composition of the extracellular matrix and cellular composition, as well as cell-autonomous genetic differences, influences sex- and depot-dependent metabolic and growth properties. Although there are some species differences, studies of the molecular and physiological determinants of sex differences in adipocyte growth and function in humans and rodents are both needed for understanding sex differences in health and disease.
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