Glucagon-like peptide-1 receptor agonists (GLP-1 RAs), a kind of secreted peptide that release from neuroendocrine intestinal L-cells, are recently recommended by American Diabetes Association/European Association for the Study of Diabetes (ADA/EASD) as a second-line treatment when first-line treatment (mainly metformin monotherapy) fails to achieve well controlled glucose. The gene discussed is GCG; the disease is diabetes mellitus.