Central obesity, especially visceral obesity, is associated with higher risk for metabolic disease such as Type 2 diabetes. Glucocorticoids (GCs) are powerful regulators of adipose tissue function that modulate fat storage and release, regulate the production of adipokines, and suppress inflammation. GCs promote the preferential accumulation of visceral (e.g. Omental (Om)) adipose tissue, and also increase abdominal subcutaneous (Abdsc) adipose tissue. To elucidate mechanisms by which GCs regulate fat distribution and function of human adipose tissues, we tested its long-term effects using an organ culture system. The results indicated that GCs regulate ~30% of all genes, and that the dose-dependent and magnitude of the response was highly depot dependent. In addition to genes that regulate metabolic pathways, GCs caused clear changes in the expression of genes in the transforming growth factor beta (TGF) pathway. The TGF superfamily includes many secreted factors, including TGFb1 and 3, activin A (INHBA) that are known to regulate adipogenesis. This pathway was of interest because the ability to recruit new adipocytes from adipose stem cells (ASCs) within the tissues prevents excessive hypertrophy of existing adipocytes, and thereby preserves the normal metabolic and endocrine functions of the adipose tissues that are essential for metabolic health. Paradoxically, compared to Abdsc ASCs, Om ASCs differentiate poorly. New preliminary data show that expression of anti-adipogenic factors including INHBA is higher in Om. GCs shifted the balance to favor adipogenesis, but Om was less sensitive to these effects. Consistent with this model, net TGF pathway signaling (indicated by the activation of SMAD2) was increased in Om ASCs, in proportional to differentiation degree under standard conditions, and conditioned media from Om adipose tissue or ASC inhibited differentiation of Abdsc ASCs. The goal of this proposal is elucidate the molecular and cellular mechanisms that regulate depot-dependent adipose tissue growth and metabolism. We will address three Specific Aims: 1) To determine the importance of TGF pathway in mediating depot differences in adipogenesis, 2) To test the hypothesis that GC-TGF crosstalk modulates depot-dependent gene expression, adipogenesis and adipocyte function, and 3) To elucidate mechanisms by which mild, chronic hypercortisolemia modulates human adipose tissue function in vivo. Collectively, this work may lead to the identification of therapeutic targets downstream o GR to treat or prevent abdominal obesity and its metabolic consequences.

Public Health Relevance

Obesity increases risk for many chronic diseases, including type 2 diabetes, and thus is a major public health problem. People who store more fat inside the abdomen are at greater risk for obesity-related diseases. This proposal will lead to a deeper understanding of how fat distribution is controlled.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Haft, Carol R
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Boston Medical Center
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Karastergiou, Kalypso; Fried, Susan K (2017) Cellular Mechanisms Driving Sex Differences in Adipose Tissue Biology and Body Shape in Humans and Mouse Models. Adv Exp Med Biol 1043:29-51
Wu, Yuanyuan; Lee, Mi-Jeong; Ido, Yasuo et al. (2017) High-fat diet-induced obesity regulates MMP3 to modulate depot- and sex-dependent adipose expansion in C57BL/6J mice. Am J Physiol Endocrinol Metab 312:E58-E71
Fried, Susan K (2017) Adipocyte size redux. Obesity (Silver Spring) 25:15
Karastergiou, Kalypso; Bredella, Miriam A; Lee, Mi-Jeong et al. (2016) Growth hormone receptor expression in human gluteal versus abdominal subcutaneous adipose tissue: Association with body shape. Obesity (Silver Spring) 24:1090-1096
Pickering, R Taylor; Lee, Mi-Jeong; Karastergiou, Kalypso et al. (2016) Depot Dependent Effects of Dexamethasone on Gene Expression in Human Omental and Abdominal Subcutaneous Adipose Tissues from Obese Women. PLoS One 11:e0167337
Lee, Mi-Jeong; Yang, Rong-Ze; Karastergiou, Kalypso et al. (2016) Low expression of the GILZ may contribute to adipose inflammation and altered adipokine production in human obesity. J Lipid Res 57:1256-63
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Fried, Susan K; Lee, Mi-Jeong; Karastergiou, Kalypso (2015) Shaping fat distribution: New insights into the molecular determinants of depot- and sex-dependent adipose biology. Obesity (Silver Spring) 23:1345-52
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Lee, Mi-Jeong; Pramyothin, Pornpoj; Karastergiou, Kalypso et al. (2014) Deconstructing the roles of glucocorticoids in adipose tissue biology and the development of central obesity. Biochim Biophys Acta 1842:473-81

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