The Physiology of Incretin Hormones and the Basis for DPP-4 Inhibitors

With the rising prevalence of diabetes, new therapies that provide glucose control are needed. Although many medications are available, tight glucose control is still a challenge. In this article, the physiology of glucose homeostasis is explored with respect to type 2 diabetes. The incretin effect is explained in detail, and the incretin hormones, glucose-dependent insulinotrophic polypeptide and glucagon-like peptide 1, are investigated as well as their contribution to type 2 diabetes therapy. Studies involving dipeptidyl-peptidase 4 (DPP-4) inhibitors are summarized as to their effects on glucose homeostasis. Specifically, vildagliptin (Galvus; Novartis International AG, Basel, Switzerland) and sitagliptin (Januvia; Merck & Co, Inc, Whitehouse Station, NJ) are described. The use and efficacy of the currently available incretin mimetic, exenatide (Byetta; Amylin Pharmaceuticals, Inc and Eli Lilly and Company, San Diego, Calif, and Indianapolis, Ind), are briefly discussed. Throughout this article, the rationale for the use of DPP-4 inhibitors is presented.