Effect of single-dose DPP-4 inhibitor sitagliptin on beta-cell function and incretin hormone secretion after meal ingestion in healthy volunteers and drug-naïve, well-controlled type 2 diabetes subjects

To explore the effects of a single dose of the DPP-4 inhibitor sitagliptin on glucose-standardized insulin secretion and beta-cell glucose sensitivity after meal ingestion, 12 healthy and 12 drug-naïve, well-controlled type 2 diabetes (T2D) subjects (mean HbA1c 43mmol/mol, 6.2%) received sitagliptin (100mg) or placebo before a meal (525kcal). beta-cell function was measured as the insulin secretory rate at a standardized glucose concentration and the beta-cell glucose sensitivity (the slope between glucose and insulin secretory rate). Incretin levels were also monitored. Sitagliptin increased standardized insulin secretion, in both healthy and T2D subjects, compared to placebo, but without increasing ?-cell glucose sensitivity. Sitagliptin also increased active glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) and reduced total (reflecting the secretion) GIP, but not total GLP-1 levels. We conclude that a single dose of DPP-4 inhibition induces dissociated effects on different aspects of ?-cell function and incretin hormones after meal ingestion in both healthy and well-controlled T2D subjects.