Clinically, T1DM is mainly treated with insulin replacement therapy.405,406 T2DM is the predominent cause of diabetes, with an incidence rate as high as 90–95%.407 Primary drug therapy includes insulin secretion inhibitors, biguanides, insulin sensitizers, alpha-glucosidase inhibitors, incretin mimetics, glucagon-like peptide-1 (GLP-1) and sodium-glucose co-transporter-2 (SGLT2) inhibitors.382 For patients who fail to achieve treatment goals with first-line oral antidiabetic drugs, combination therapy is often recommended. This evidence concerns the gene GCG and type 1 diabetes mellitus.