Other rare but certainly important causes such as the disruption with incretin biology resulting from decreased synthesis of glucagon-like peptide-1 (GLP-1) or incretin resistance along with adipokine dysregulation, glucagonomas, inflammation, increased renal glucose reabsorption, and abnormalities in gut microbiota may also play a role in the development of T2DM [13]. Here, GCG is linked to type 2 diabetes mellitus.