Vildagliptin Added to Metformin on β-Cell Function After a Euglycemic Hyperinsulinemic and Hyperglycemic Clamp in Type 2 Diabetes Patients

Background: This study evaluated the effect of vildagliptin + metformin on glycemic control and beta-cell function in type 2 diabetes patients. Subjects and Methods: One hundred seventy-one type 2 diabetes patients, naive to antidiabetes therapy and with poor glycemic control, were instructed to take metformin for 8+/-2 months up to a mean dosage of 2,500+/-500 mg/day; then they were randomly assigned to add vildaglipin 50 mg twice a day or placebo for 12 months. We evaluated at 3, 6, 9, and 12 months: body mass index, glycemic control, fasting plasma insulin, homeostasis model assessment insulin resistance index (HOMA-IR), homeostasis model assessment beta-cell function index (HOMA-beta), fasting plasma proinsulin, proinsulin/fasting plasma insulin ratio, C-peptide, glucagon, adiponectin, and high-sensitivity C-reactive protein. Before and at 12 months after the addition of vildagliptin, patients underwent a combined euglycemic hyperinsulinemic and hyperglycemic clamp, with subsequent arginine stimulation, to assess insulin sensitivity and insulin secretion. Results: After 12 months of treatment, vildagliptin + metformin gave a better decrease of body weight, glycemic control, HOMA-IR, and glucagon and a better increase of HOMA-beta compared with placebo + metformin. Regarding the measures of beta-cell function, treatment-induced changes in M-value, first- and second-phase C-peptide response to glucose, and C-peptide response to arginine were significantly higher in the vildagliptin+metformin group compared with the placebo + metformin group. Conclusion: The addition of vildagliptin to metformin gave a better improvement of glycemic control, insulin resistance, and beta-cell function compared with metformin alone.