In our study, DPP-4 protein expression and enzymatic activity were significantly higher in OB+/DM+ compared with OB+/DM− subjects, consistent with previous reports describing increased DPP-4 expression and activity in obesity and T2DM (Barchetta et al., 2019; Sell et al., 2013). This evidence concerns the gene DPP4 and obesity due to melanocortin 4 receptor deficiency.