GCG and type 2 diabetes mellitus: Following the recognition that GLP‐1 serves as an incretin, various incretin or GLP‐1‐based drugs including GLP‐1 receptor (GLP‐1R) agonists (GLP‐1RAs) and dipeptidyl peptidase‐4 inhibitors (DPP‐4i) have been developed for treating type 2 diabetes (T2D).