Two novel classes of glucose-lowering agents for the treatment of T2D have been introduced in the market in the last years: glucagon-like peptide-1 receptor (GLP-1R) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors or incretin enhancers (Tahrani et al., 2011). This evidence concerns the gene GCG and type 2 diabetes mellitus.