Plasma glucagon-like peptide-1 (GLP-1) responses to duodenal fat and glucose infusions in lean and obese men

It has been suggested that obesity is associated with a reduced glucagon-like peptide-1 (GLP-1) response to oral carbohydrate, but not fat. The latter may, however, be attributable to changes in gastric emptying. We have assessed plasma GLP-1 levels in response to these infusions in lean and obese subjects. Seven healthy lean (body mass index (BMI), 19.1-24.6 kg/m(2)) and seven obese (BMI, 31.3-40.8 kg/m(2)) young men received an intraduodenal infusion of glucose and fat for 120 min (2.86 kcal/min) on two separate days. Blood samples for plasma GLP-1 were obtained at baseline and every 20 min during the infusion. Plasma GLP-1 increased during infusion of glucose and fat (P = 0.001), but there were no differences between lean and obese subjects, nor the two nutrients. We conclude that GLP-1 secretion in response to duodenal infusion of glucose and fat is not altered in obese subjects.