DPP-4 inhibitors were developed largely to prevent the degradation of the incretin hormones glucagon-like peptide-1 (GLP-1) and gastric inhibitory peptide (GIP) that are secreted by enteroendocrine cells in response to postprandial hyperglycemia and account for as much as 70% of postprandial insulin secretion (the incretin effect) [11]. The gene discussed is GCG; the disease is Hyperglycemia.