GCG and prediabetes syndrome: Our results demonstrated that the response to DPP-IV inhibitor in prediabetes and T2D is influenced by the baseline endogenous GLP-1 levels as evidenced by the greater reduction in the HbA1c, FPG, AUCGlucose0-2h, as well as the glucose excursion seen in the high GLP-1 compared to the low GLP-1 groups in both the prediabetes and T2D populations.