Further Possible Mechanisms of Dipeptidyl Peptidase-4 Inhibitors to Decrease Blood Glucose in Subjects with Type 2 Diabetes

Recently, dipeptidyl peptidase-4 (DPP-4) inhibitors have been launched into clinical use for type 2 diabetes in Japan. Shortly after its use, several cases have been reported, in which the co-administration of DPP-4 inhibitors with sulfonylureas caused severe hyperglycemia in Japan. Additionally, the efficacy to improve glycemic control was greater than expected. Taken together, it is suggested that DPP-4 inhibitors may have other action mechanisms than to stimulate insulin secretion in glucose-dependent manner. I present here several possible mechanisms of DPP-4 inhibitors to reduce blood glucose in type 2 diabetes; first, to inhibit glucagon secretion, second, to stimulate glucose-dependent insulinotropic peptide (GIP) secretion, which may regain its action to stimulate insulin secretion when hyperglycemia has been improved, third, to recover the response to sulfonylureas by restoring pancreatic ATP levels, fourth, to stimulate glucagon-like peptide 1 (GLP-1) secretion directly from the intestine, and finally to inhibit the action of DPP-4 as an adipokine.