The effects of centrally applied ghrelin on appetite and metabolic parameters during aging

Abstract

The main purpose of this study was to evaluate specifically, ingestive behavior and bloodborne indicators of metabolic status, after daily intracerebroventricular (ICV) ghrelin injections, in rats of different ages. Four age ranges were tested: peripubertal (similar to 38 days), young (similar to 2 months), adult (similar to 7 months) and middle-aged (similar to 11 months). Multiple variables were measured, including body weight (BW), food and water intake (F, WI), and terminal blood levels of triglycerides (Tg), cholesterol (Chol), free fatty acids (FFA) and glucose (Glu). Five daily ICV injections of ghrelin or saline were administered (n = 8/group, 0.15 nmol of ghrelin in 5 mu L) to rats of different ages. After 5 days of treatment, ICV ghrelin resulted in an increased (p LT 0.05) absolute and relative BW, FI, WI and in elevated blood levels of Chol, Tg, and FFA as well, while blood Glu levels were decreased (p LT 0.05) within each of the four age-matched groups. Differences (p LT 0.05) in ghrelin effects over the ages included the following: relative FI was higher in 2 younger groups vs 2 older ones. Relative WI was higher in 2 younger groups vs 2 older ones. Tg, Chol and FFA in the oldest rats, both control and treated, were higher than corresponding values at the other 3 ages. The youngest age group had the lowest Glu after ghrelin.