Insulinotropic actions of nateglinide in type 2 diabetic patients and effects on dipeptidyl peptidase-IV activity and glucose-dependent insulinotropic polypeptide degradation

BackgroundNateglinide restores early-phase insulin secretion to feeding and reduces postprandial hyperglycaemia in type 2 diabetes. This study evaluated the effects of nateglinide on dipeptidyl peptidase-IV (DPP-IV) activity and glucose-dependent insulinotropic polypeptide (GIP) degradation.Research design and methodsBlood samples were collected from type 2 diabetic subjects (n=10, fasting glucose 9.36±1.2 mmol/l) following administration of oral nateglinide (120 mg) 10 min prior to a 75 g oral glucose load in a randomised crossover design.ResultsPlasma glucose reached 18.2±1.7 and 16.7±1.7 mmol/l at 90 min in control and placebo groups (PPPPPin vitro. Comparison of in vitro inhibition of DPP-IV by nateglinide and vildagliptin revealed IC50 values of 17.1 and 2.1 μM respectively.ConclusionsAlthough considerably less potent than specified DPP-IV inhibitors, the possibility that some of the beneficial actions of nateglinide are indirectly mediated through DPP-IV inhibition and increased bioavailability of GIP and other incretins merits consideration.