Istanbul University Cerrahpasa Medical School, Department of Internal Medicine, Division of Endocrinology Diabetes and Metabolism, Istanbul, Turkey. tdamci@superonline.com
OBJECTIVE: Orlistat leads to improved glycemic control in obese type 2 diabetic patients, which is attributed to decreased insulin resistance associated with weight loss. Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) are gut hormones that are secreted in response to food intake, and they both stimulate insulin secretion. Orlistat decreases fat absorption and increases intestinal fat content, which may lead to increased secretion of these peptides. In this pilot study, we tested the hypothesis that increased levels of these intestinal hormones may be involved in the improvement of postprandial hyperglycemia observed previously with orlistat in type 2 diabetic patients. RESEARCH DESIGN AND METHODS: A total of 29 type 2 diabetic patients, who were not taking insulin or alpha-glucosidase inhibitors, were enrolled in the study. On a crossover and single-blind design, after an overnight fasting, the patients received 120-mg orlistat or placebo capsules, followed by a standard 600-kcal mixed meal that contained 38% fat. At baseline and 60 min after the meal, blood samples were obtained for the measurement of GLP-1, GIP, insulin, C-peptide, triglycerides, free fatty acids, and glucose. RESULTS: All measured parameters increased significantly in response to the mixed meal compared with baseline, both with orlistat or placebo. When compared with the placebo, the orlistat administration resulted in a significantly enhanced postprandial increase in GLP-1 and C-peptide levels and attenuated the postprandial rise in glucose and triglycerides. CONCLUSIONS: The results of this study suggest that apart from decreasing insulin resistance as a result of weight loss, orlistat may increase postprandial GLP-1 levels, thereby enhancing the insulin secretory response to the meal and blunting the postprandial rise in glucose in type 2 diabetic patients. Increased GLP-1 levels, which lead to decreased food intake, may also contribute to the weight loss that is associated with the use of this drug.