GCG and type 2 diabetes mellitus: Peptide drugs such as glucagon-like peptide 1 (GLP-1) have shown promise for the treatment of type-II diabetes, but they are degraded by dipeptidyl peptidase (DPPIV) in the body and lose their biological activity, with a half-life of about 2 min, requiring frequent administration to maintain therapeutic effects, which seriously affects patient compliance [92].