We therefore assessed DPP4 gene expressions, protein levels and enzymatic activities in the VAT and SAT depots from obese patients undergoing abdominal surgery with (n = 20) or without T2DM (n = 23) with comparable BMI (38 ± 11 vs. 42 ± 10, p = 0.224) and leptin levels (36147.75 ± 33624.77 pg/ml vs. 24707.27 ± 29473.27 pg/ml, p = 0.297). Here, LEP is linked to type 2 diabetes mellitus.