DPP4 and Insulin resistance: While some of the effects of DPP-4—and, arguably, most, if not all of the pharmacological effects of DPP-4 inhibitors (38)—on glucose homeostasis are mediated primarily by modulating the activity of the incretin hormones, it has also been proposed that DPP-4 may influence metabolic control via mechanisms which do not necessarily involve its catalytic activity, with several studies noting a positive correlation between DPP-4 and insulin resistance (79, 81, 88).