Incretin pathway and diabetes mellitus

Incretins are a group of gastrointestinal hormones that cause an increase in the amount of insulin released from the beta cells after eating, even before blood glucose levels become elevated. The two main incretins are glucagon-like peptide-1 (GLP-1) and Gastric inhibitory peptide(GIP). Both GLP-1 and GIP are rapidly inactivated by the enzyme dipeptidyl peptidase-4 (DPP-4). DPP-4 inhibitors improve glucose control by increasing incretin levels in type 2 diabetes. They are less likely to produce hypoglycemia. DPP-4 inhibitors target the beta cells through the incretin pathway. Sitaglipgtin is an FDA approved DPP-4 inhibitor. Sitagliptin and metformin are complementary to each other. Metformin also has a direct action on the incretin pathway.