This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Overweight is the most common chronic disorder of the adolescent years and is associated with components of the metabolic syndrome. Regional fat distribution predicts insulin resistance and lipid levels. Hormonal determinants of hunger and regional fat distribution and the relationship with the metabolic syndrome have not been systemmatically examined in the adolescent population. In the proposed study, we plan to test the following hypotheses:
Specific Aim 1 : Overweight adolescents will have higher cortisol and lower ghrelin and GH levels compared to normal weight controls. These hormonal alterations will predict regional fat distribution, insulin resistance, and cardiovascular risk.1A: Overweight adolescent girls will have lower ghrelin and GH levels compared with normal weight adolescent controls. We will compare ghrelin and growth hormone secretory dynamics by frequent sampling in overweight subjects vs. normal weight controls. 1B: High cortisol and low ghrelin and GH levels will be associated with visceral fat accumulation and truncal adiposity, and overweight adolescent girls with greater truncal adiposity will be more insulin resistant and have higher lipid and cardiovascular risk marker levels than those without central fat accumulation. We will determine the relationship between ghrelin, GH, and cortisol status, regional fat distribution, insulin resistance, lipid levels, and other cardiovascular risk markers.
Specific Aim 2 : Carbohydrates will decrease postprandial ghrelin levels while fats and proteins will increase ghrelin levels. The extent of alteration in ghrelin levels will predict the degree of hunger and amount of intake at a subsequent meal in both overweight and normal weight subjects. Overweight subjects will have lower ghrelin responses compared to normal weight controls.2A: Carbohydrate ingestion will increase postprandial satiety and decrease ghrelin levels, hunger, and amount of intake at a subsequent meal. Fat and protein ingestion will decrease postprandial satiety and increase ghrelin levels, hunger, and amount of intake at a subsequent meal in both overweight and normal weight adolescent females. We will characterize the ghrelin response after different types of meals in the adolescent age group and determine the impact of the various macronutrients on ghrelin, hunger, satiety, and subsequent food intake. 2B: Overweight adolescent girls will have lower ghrelin levels prior to and after meals and will have a lesser magnitude of change in ghrelin compared to normal weight adolescent girls. We will compare ghrelin responses to a food challenge in overweight and normal weight subjects.
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