Although numerous oral antidiabetic drugs are available, including sulfonylureas, meglitinides, metformin, thiazolidinediones, glucagon-like peptide-1 (GLP-1) agonists, and dipeptidyl peptidase-4 (DPP-4) inhibitors, maintaining long-term optimal blood glucose control has been difficult in most patients with T2D, even those administered with antidiabetics plus insulin (1–3). This evidence concerns the gene GCG and type 2 diabetes mellitus.