Improved meal-related insulin processing contributes to the enhancement of B-Cell function by the DPP-4 inhibitor vildagliptin in patients with type 2 diabetes

The aim of this study was to evaluate the contribution of insulin processing to the improved meal-related B-cell function previously shown with the DPP-4 inhibitor vildagliptin. Fifty-five patients with type 2 diabetes (56.5 +/- 1.5 years; BMI=29.6 +/- 0.5kg/m(2); FPG = 9.9 +/- 0.2 mmol/l; HbA1c=7.7 +/- 0.1 %) were studied: 29 pateients were treated with vildagliptin and 26 patients with placebo, both added to an ongoing metformin regimen (1.5-3.0g/day). A standardized breakfast was given at baseline and after 52 weeks of treatment, and proinsulin related to insulin secretion was measured with C-peptide in the fasting and postprandial (over 4h post-meal) states to evaluate B-cell function. The between-treatment difference (vildaglip-tin-placebo) in mean change from baseline in fasting proinsulin to C-peptide ratio (fastP/C) was -0.007 +/- 0.009 (p=0.052). Following the standard breakfast, 52 weeks of treatment with vildagliptin significantly decreased the dynamic proinsulin to C-peptide ratio (dynP/C) relative to placebo by 0.010 +/- 0.008 (p = 0.037). Importantly, when the P/C was expressed in relation to the glucose stimulus (i.e., the fasting glucose and glucose AUC(0-240min), respectively), the P/C relative to glucose was significantly reduced with vildagliptin vs. placebo, both in the fasting state (p = 0.023) and postprandially (p = 0.004). In conclusion, a more efficient B-cell insulin processing provides further evidence that vildagliptin treatment ameliorates abnormal B-cell function in patients with type 2 diabetes.