Type 2 diabetes mellitus can be treated with monotherapy or various therapeutic combinations including metformin, sulfonylureas, thiazolidinediones, dipeptidyl peptidase-4 inhibitors (DDP-4), glucagon like peptide-1 (GLP-1) agonists, sodium-glucose co-transporter-2 (SGLT-2) inhibitors, or insulin. Here, GCG is linked to diabetes mellitus.