The long-term objective of this proposal is to understand how the brain senses levels of peripheral energy stores and integrates these signals to maintain energy balance. Studies will focus on the central melanocortin system in rodent models and on the mechanisms by which it can sense and integrate a variety of nutrient, hormonal and neuronal signals to regulate food intake, energy expenditure and nutrient metabolism. This system consists of proopiomelanocortin (POMC) and the POMC-derived MSH peptides together with agouti related protein (AGRP) which is a potent antagonist of the MSH peptides at specific melanocortin receptors (MC3/4-R). a-MSH inhibits feeding and stimulates energy expenditure while AGRP exerts opposite effects.
Aim 1 will use recently generated transgenic mice that overexpress a-MSH and g- MSH (Tg-MSH) to study the role of the melanocortin system in modulating responses to energy excess on a high fat diet and to characterize underlying mechanisms with a focus on energy expenditure, fuel oxidation, sympathetic activity and hepatic steatosis. Tg-MSH mice demonstrate reduced body weight, adiposity and hepatic fat accumulation (without changes in food intake) and improved glucose metabolism, particularly in the setting of diet-induced obesity. The role of AGRP will be similarly studied in Aim 2 using a genetic model of Agrp deletion and a novel, potent, small molecule AGRP antagonist.
Aims 3 &4 will focus on the regulation of POMC and AGRP peptide processing in the hypothalamus in vivo and in vitro with respect to energy balance. This is an important consideration because POMC is processed to a number of peptides with different and even opposing biological activities. The ability of these peptide products to interact and regulate energy balance will be studied in parallel using icv injection protocols. AGRP is also processed by PC1 to a biologically active C-terminal fragment but little is known about the regulation of processing or about the N-terminal peptides that are produced that may also affect energy balance. AGRP processing will be characterized using novel assays and the effects of these processed peptides on energy balance will then be studied. This proposal is highly relevant to human energy balance as mutations in POMC, POMC processing enzymes and in the MC4-R have all been associated with human obesity and there are many parallels with rodent models of melanocortin deficiency.

Public Health Relevance

The increasing prevalence of obesity and diabetes makes it imperative to understand the mechanisms by which the brain regulates energy balance in order to design more effective prevention and treatment options. This proposal will use rodent models to study the brain melanocortin system which plays a key role in regulating energy balance. This system consists of proopiomelanocortin (POMC) and the POMC-derived MSH peptides together with agouti related protein (AGRP) which is a potent antagonist of the MSH peptides at specific melanocortin receptors (MC3/4-R). ?-MSH inhibits feeding and stimulates energy expenditure while AGRP exerts opposite effects. This proposal is highly relevant to human energy balance as mutations in POMC, POMC processing enzymes and in the MC4-R have all been associated with human obesity and there are many parallels with rodent models of melanocortin deficiency.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK080003-05
Application #
8231464
Study Section
Integrative Physiology of Obesity and Diabetes Study Section (IPOD)
Program Officer
Hyde, James F
Project Start
2008-01-01
Project End
2013-12-31
Budget Start
2012-01-01
Budget End
2013-12-31
Support Year
5
Fiscal Year
2012
Total Cost
$335,316
Indirect Cost
$127,045
Name
Columbia University (N.Y.)
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
621889815
City
New York
State
NY
Country
United States
Zip Code
10032
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Dutia, Roxanne; Kim, Andrea J; Modes, Matthew et al. (2013) Effects of AgRP inhibition on energy balance and metabolism in rodent models. PLoS One 8:e65317
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Ren, Hongxia; Plum-Morschel, Leona; Gutierrez-Juarez, Roger et al. (2013) Blunted refeeding response and increased locomotor activity in mice lacking FoxO1 in synapsin-Cre-expressing neurons. Diabetes 62:3373-83
Ren, Hongxia; Orozco, Ian J; Su, Ya et al. (2012) FoxO1 target Gpr17 activates AgRP neurons to regulate food intake. Cell 149:1314-26
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Dutia, Roxanne; Meece, Kana; Dighe, Shveta et al. (2012) β-Endorphin antagonizes the effects of α-MSH on food intake and body weight. Endocrinology 153:4246-55
Wardlaw, Sharon L (2011) Hypothalamic proopiomelanocortin processing and the regulation of energy balance. Eur J Pharmacol 660:213-9
Xiao, Ennian; Kim, Andrea J; Dutia, Roxanne et al. (2010) Effects of estradiol on cerebrospinal fluid levels of agouti-related protein in ovariectomized rhesus monkeys. Endocrinology 151:1002-9

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