DPP4 and obesity due to melanocortin 4 receptor deficiency: In addition to being an incretin hormone, GIP signaling and GIPR have been shown to play a role in diet-induced obesity,98 adipokine secretion,99 lipoprotein lipase activity, and TG accumulation.100 Degradation of significant amounts of GIP by DPP4 occurs within in the gut by both endothelial and immune cell populations.30