The present study demonstrated that GIP and GLP-1 in T2DM without DPP-4 inhibitor were lower than those of NGT, although previous reports indicated that plasma GIP and GLP-1 levels in subjects with T2DM are increased, comparable, or decreased compared to those in NGT subjects based on ELISA assays (13, 14). Here, DPP4 is linked to type 2 diabetes mellitus.