VIP and diabetes mellitus: There have been major advances in DPP-4-based therapeutics for treatment of diabetes, especially in creating stabilized GLP-1 analogs and DPP-4 inhibitors such as sitagliptin (Januvia).7–10 Beyond GLP-1, DPP-4 cleaves a diverse repertoire of bioactive peptides, such as vasoactive intestinal peptide (VIP), substance P, pancreatic polypeptide (PP), peptide YY (PYY), and neuropeptide Y (NPY).