Combination of mangiferin and dipeptidyl peptidase-4 inhibitor sitagliptin improves impaired glucose tolerance in streptozotocin-diabetic rats.

In this study, we combined the dipeptidyl peptidase-4 inhibitor sitagliptin with the antidiabetic drug mangiferin to examine the effects on active glucagon-like peptide-1 (GLP-1) and glucose tolerance in streptozotocin-diabetic rats. Active GLP-1 levels were measured by an ELISA kit. Insulin levels were measured by an RIA kit. Islet morphology was determined by double immunolabeling. Sitagliptin (1 mg/kg) or mangiferin (20 mg/kg) single treatment improved glucose tolerance during an oral glucose tolerance test. In addition, the combination therapy improved glucose tolerance with an increase in plasma insulin level and active GLP-1 levels. Islets from combination-treated diabetic rats had markedly increased β-cell/islet area ratio compared with islets from the diabetic or single-treatment rats. In conclusion, these results indicate that the combination therapy is useful as a therapeutic agent for impaired glucose tolerance and type 2 diabetes.