Glucagon-like peptide-1 (GLP-1)-based agents (including GLP-1 analogues and dipeptidyl peptidase 4 inhibitors) have been recently approved as new therapeutic options for patients with type 2 diabetes, based upon the evidence that GLP-1 can stimulate glucose-dependent insulin secretion from pancreatic β cells. Here, GCG is linked to type 2 diabetes mellitus.