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 [HbA1c] 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. HbA1c was measured at 6 months. RESULTS Mean age of participants was 55.5 ± 2.8 years, and ten (66.7%) were male. Mean HbA1c 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 (ΔAUC0-2h), glucagon ΔAUC0-2h was significantly lower in the group with more improved glucose levels (ΔAUC0-2h ≥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.