EFFECT OF AGE ON INSULIN MEDIATED REGULATION OF GHRELIN

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ghrelin, a peptide which is mainly derived from the stomach, is present in plasma in an active (acylated) and inactive (des-acylated) form. The major active form of ghrelin contains 28 amino acids with a unique post-translational modification: the hydroxyl group of ser3 is esterified by octanoic acid. The n-octanoyl group is essential for the GH (growth hormone) releasing activity. Plasma ghrelin plays a role in energy homeostasis, food intake, and possibly in GH release and obesity. To date, it is unclear how circulating ghrelin levels are regulated and whether there are age-specific differences in the regulation of ghrelin. Insulin sensitivity decreases with age. This is partially a result of the age-dependent increase in abdominal visceral fat. The studies proposed will investigate whether there are differences between young and older adults regarding the acute insulin mediated decrease in circulating ghrelin (bioactive, inactive form) levels. Using assays developed in our laboratory, both bioactive and inactive ghrelin will be measured.