GCG and diabetes mellitus: Among genetic variants, the diabetes-associated variants in TCF7L2 (rs7903146) and WFS1 (rs10010131) have been shown to affect the response to exogenous GLP-1, while variants in KCNQ1 (rs151290, rs2237892, and rs2237895) have been reported to alter endogenous GLP-1 secretion [6–8].