DPP4 and obesity due to melanocortin 4 receptor deficiency: A recent study demonstrated that obesity triggers a Ca2+−Ca2+-calmodulin-dependent protein kinase II (CaMKII)−activating transcription factor 4 (ATF4) pathway in hepatocytes, leading to induction of DPP4 expression and secretion of soluble DPP4 (Figure 1A), which acts cooperatively with plasma factor Xa to promote inflammation and insulin resistance [20].