On the other side, when it comes to the effect of GLP1-RAs, the authors followed the markers of reduced β-cell function (such as longer DM duration [or proxies such as insulin treatment], diminished fasting C-peptide, lower urine C-peptide-to-creatinine ratio, positive antibodies to glutamic acid decarboxylase or islet autoantibodies type 2), which were associated with lesser glycemic response to GLP1-RA in many observational studies. This evidence concerns the gene GCG and diabetes mellitus.