Effect of small intestinal nutrient infusion on appetite, gastrointestinalhormone release, and gastric myoelectrical activity in young and older men

OBJECTIVE: The mechanisms responsible for the reduction in appetite and slo wing of gastric emptying in older persons are poorly understood. The aim of this study was to evaluate the effects of aging on small intestinal regula tion of appetite, GI hormone release, and gastric myoelectrical activity. METHODS: Thirteen older (65-84 yr) and 13 young (18-32 yr) healthy men rece ived isovolumetric, intraduodenal (ID) infusions of saline (control), lipid , and glucose for 120 min, on separate days. The energy content of the lipi d and glucose infusions was identical at 2.86 kcal/min. Immediately after t he ID infusions, each subject was offered a buffet meal, and ad libitum foo d intake was quantified. Blood glucose and plasma insulin, glucagon-like pe ptide 1, and glucose-dependent insulinotropic peptide were measured. Gastri c myoelectrical activity was measured by surface electrogastrography (EGG). RESULTS: ID lipid suppressed food intake in both the young and older men (p < 0.05), whereas ID glucose suppressed food intake only in the older men ( p < 0.05). The blood glucose (p < 0.01) and insulin (p < 0.05) responses to ID glucose were greater in older than young men. However, there were no di fferences in glucagon-like peptide 1 or glucose-dependent insulinotropic pe ptide responses to any of the infusions. There was a greater increase in th e EGG power ratio both during and after ID glucose infusion in the young (p < 0.05) than the older men, and an attenuation of EGG frequency by nutrien t infusions in older, but not young, men. CONCLUSIONS: Our findings indicate that aging is associated with nutrient-s pecific changes in appetite, hormonal, and gastric myoelectrical (EGG) resp onses to ID nutrients. An enhanced satiating effect of small intestinal car bohydrates may potentially contribute to the anorexia of aging. (Am J Gastr oenterol 2001;96.997-1007. (C) 2001 by Am. Coll. of Gastroenterology).