Dipeptidyl Peptidase-4 Inhibitor (Vildagliptin) Improves Glycemic Control After Meal Tolerance Test by Suppressing Glucagon Release

AIM: We aimed to evaluate changes in insulin and glucagon secretion, as well as glucose levels, with a meal tolerance test (MTT) before and after 6 months of treatment with vildagliptin in a clinical setting. MATERIALS AND METHODS: Participants were 15 patients with uncontrolled type 2 diabetes mellitus (glycated hemoglobin [HbA(1c)] over 6.9 % for more than 3 months). MTTs were conducted before and 6 months after addition of vildagliptin (50 mg twice daily [bid]). Blood samples were collected immediately before, and 1 and 2 h after the test meal for measurement of blood glucose concentration, immune-reactive insulin (IRI), and glucagon. HbA(1c) was measured at 6 months. RESULTS: Mean age of participants was 55.5 ± 2.8 years, and ten (66.7 %) were male. Mean HbA(1c) significantly improved from 7.6 to 6.8 % at 6 months after addition of vildagliptin. Blood glucose at 1 and 2 h after the test meal was significantly reduced after addition of vildagliptin, while the reduction in glucagon showed borderline significance and IRI showed no difference. In a comparison of blood glucose-related parameters between subgroups based on median glucose change in area under the curve during MTT (ΔAUC(0–2h)), glucagon ΔAUC(0–2h) was significantly lower in the group with more improved glucose levels (ΔAUC(0–2h) ≥65 mg/dL), but that of IRI did not differ. CONCLUSION: Suppression of glucagon release by vildagliptin may improve glycemic control without increasing insulin levels in patients with type 2 diabetes.