Prior exercise and postprandial incretin responses in lean and obese individuals

PURPOSE: The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) help regulate postprandial triacylglycerol (TAG) and insulin concentrations, but the effects of acute aerobic exercise on GLP-1 or GIP responses are unclear. The purpose of this study was to determine whether reductions in postprandial TAG and insulin with exercise are associated with GLP-1 and GIP responses. METHODS: Thirteen normal-weight (NW) and 13 obese (Ob) individuals participated in two, 4-d trials in random order including an exercise (EX) and a no exercise (NoEX) trial. Diet was controlled during both trials. The EX trial consisted of 1 h of treadmill walking (55%-60% of V̇O2peak) during the evening of day 3 of the trial, 12 h before a 4-h mixed meal test on day 4, during which frequent blood samples were collected to assess postprandial lipemia, glycemia, insulin, C-peptide, GIP, and GLP-1 responses. Insulin secretion was estimated using the insulinogenic index, and insulin clearance was estimated using the ratio of insulin to C-peptide. RESULTS: Postprandial TAG were 29% lower after EX in Ob individuals (P < 0.05) but were not significantly altered in NW individuals (P > 0.05). The drop in postprandial HDL cholesterol was attenuated with EX in Ob individuals (P < 0.05). Insulin responses were 14% lower after EX in Ob individuals (P < 0.05), and this was associated with reduced insulin secretion (P < 0.05), with no change in insulin clearance (P > 0.05). Glucose, C-peptide, GIP, and GLP-1 were not different between trials. CONCLUSION: A 1-h bout of moderate-intensity aerobic exercise the night before a mixed meal attenuates TAG and insulin responses in Ob but not NW individuals, an effect not associated with altered GLP-1 or GIP responses.