title: Age-dependent modulation of central ghrelin effects on food intake and lipid metabolism in rats.
abstract: Ghrelin is an endogenous peptide potentially useful in therapy of anorexia and other age-related metabolic disturbances. We evaluated the influence of age on the orexigenic and lipid metabolism-altering effects of ghrelin. Peripubertal, young, adult and middle-aged rats (1, 2, 7 and 12 months old, respectively) were treated with 5 daily intracerebroventricular injections of ghrelin (0.15 nmol) or saline (control). The food intake was measured daily before treatment, while white adipose tissue and serum/plasma samples for detection of lipid metabolites/hormones were collected at the end of the experiment. The values of cumulative food intake and body weight gain declined, while the white adipose tissue deposits and blood concentrations of triglycerides, cholesterol and free fatty acids all increased with age. Ghrelin significantly increased all parameters, but the stimulatory effects on body weight gain and food intake were more pronounced in peripubertal/young rats, while the increase in white adipose mass, triglyceride and low-density lipoprotein cholesterol levels was more noticeable in adult/middle-aged animals. The decrease in sensitivity to ghrelin-mediated stimulation of food intake in older animals could not be explained by alterations in ghrelin's ability to reduce anorexigenic hormones insulin and leptin. However, the higher responsiveness of aged rats to ghrelin-mediated increase in lipid metabolites was accompanied by an increase in adrenocorticotropic hormone and corticosterone levels. These results indicate that aging, while reducing sensitivity to ghrelin-mediated increase in body weight gain and food intake, might enhance the responsiveness to the stimulatory effects of ghrelin on lipid metabolites and hypothalamic-pituitary-adrenal axis activity.
authors.affiliation: Institute of Medical Physiology, School of Medicine, University of Belgrade, Visegradska 26/II, 11000 Belgrade, Serbia. dejance@med.bg.ac.rs
authors.forename: Dejan M
authors.initials: DM
authors.lastname: Nesic
authors.forename: Darko M
authors.initials: DM
authors.lastname: Stevanovic
authors.forename: Sanja D
authors.initials: SD
authors.lastname: Stankovic
authors.forename: Verica L
authors.initials: VL
authors.lastname: Milosevic
authors.forename: Vladimir
authors.initials: V
authors.lastname: Trajkovic
authors.forename: Vesna P
authors.initials: VP
authors.lastname: Starcevic
authors.forename: Walter B
authors.initials: WB
authors.lastname: Severs
mesh_terms: D052436:Adipose Tissue, White / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000375:Aging / Q000502:physiology*; D000818:Animals; D001835:Body Weight / Q000187:drug effects*; D003345:Corticosterone / Q000097:blood; D004435:Eating / Q000187:drug effects*; D054439:Ghrelin / Q000494:pharmacology*; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D050356:Lipid Metabolism / Q000187:drug effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D054439:Ghrelin; D007328:Insulin; D020738:Leptin; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone