EXCEED THE SPACE PROVIDED. Short-term variations in serum leptin in response to changes in nutritional status are likely to be critical to leptin's ability to modulate appetite and metabolism in advance of alterations in body fat. Although the abundance of leptin mRNA is important in the long-term regulation of leptin, post-transcriptional mechanisms appear to account for short term changes in leptin secretion. Little is known, however, about the cellular regulation of leptin. We will use newly-developed methods for pulse-labelling leptin with 35S-methionine to analyze relative rates of leptin synthesis, turnover and secretion as a function of hormonal and nutritional state. Our preliminary studies indicate that insulin can stimulate the release of leptin without affecting leptin mRNA levels. Two mechanisms appear to be involved: a potentiation of the rate of leptin secretion, and an increase in relative rates of leptin biosynthesis, i.e.a translational effect. To enable detailed studies of the mechanisms regulating the post-transcriptional regulation of leptin, we will turn to a rat adipocyte model.
Specific Aim 1 will assess the effects of insulin on leptin biosynthesis, turnover and secretion using pulse-chase analysis. The role of the long 3'-UTR of leptin mRNA in the insulin regulation of translation will be.determined using transient transfections of reporter constructs. Glucocorticoids also increase leptin synthesis over the short term and its effects are additive with insulin; thus, we will investigate the mechanisms involved.
Specific Aim 2 will address the hypothesis that short-term decrease in leptin with fasting are mediated by the ability of the catecholamines to decrease leptin release without affecting leptin synthesis. Experiments will also address the hypothesis that the balance between insulin and adrenergic agonists regulate leptin synthesis, turnover, and secretion via opposing effects of cyclic AMP.
Specific Aim 3 will use pulse-chase studies to investigate the mechanisms underlying the increased basal and blunted nutritional responses of leptin in spontaneously obese rats. Focused studies of human adipocytes will follow-up on findings in the rat model. This work may lead to new insights into the nutritional regulation of leptin. PERFORMANCE SITE ========================================Section End===========================================

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK052398-07
Application #
6843804
Study Section
Nutrition Study Section (NTN)
Program Officer
Haft, Carol R
Project Start
1997-09-06
Project End
2007-02-28
Budget Start
2005-03-01
Budget End
2006-02-28
Support Year
7
Fiscal Year
2005
Total Cost
$259,960
Indirect Cost
Name
University of Maryland Baltimore
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Lee, M-J; Fried, S K (2014) The glucocorticoid receptor, not the mineralocorticoid receptor, plays the dominant role in adipogenesis and adipokine production in human adipocytes. Int J Obes (Lond) 38:1228-33
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
Lee, Mi-Jeong; Fried, Susan K (2014) Optimal protocol for the differentiation and metabolic analysis of human adipose stromal cells. Methods Enzymol 538:49-65
Lee, Mi-Jeong; Wu, Yuanyuan; Fried, Susan K (2013) Adipose tissue heterogeneity: implication of depot differences in adipose tissue for obesity complications. Mol Aspects Med 34:1-11
Carswell, Kirstin A; Lee, Mi-Jeong; Fried, Susan K (2012) Culture of isolated human adipocytes and isolated adipose tissue. Methods Mol Biol 806:203-14
Lee, Mi-Jeong; Fried, Susan K (2012) Glucocorticoids antagonize tumor necrosis factor-?-stimulated lipolysis and resistance to the antilipolytic effect of insulin in human adipocytes. Am J Physiol Endocrinol Metab 303:E1126-33
Nimitphong, Hataikarn; Holick, Michael F; Fried, Susan K et al. (2012) 25-hydroxyvitamin D? and 1,25-dihydroxyvitamin D? promote the differentiation of human subcutaneous preadipocytes. PLoS One 7:e52171
Lee, Mi-Jeong; Wu, Yuanyuan; Fried, Susan K (2012) A modified protocol to maximize differentiation of human preadipocytes and improve metabolic phenotypes. Obesity (Silver Spring) 20:2334-40
Lee, Eun Kyung; Lee, Mi Jeong; Abdelmohsen, Kotb et al. (2011) miR-130 suppresses adipogenesis by inhibiting peroxisome proliferator-activated receptor gamma expression. Mol Cell Biol 31:626-38
Lee, Mi-Jeong; Gong, Da-Wei; Burkey, Bryan F et al. (2011) Pathways regulated by glucocorticoids in omental and subcutaneous human adipose tissues: a microarray study. Am J Physiol Endocrinol Metab 300:E571-80

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