DPP4 and obesity due to melanocortin 4 receptor deficiency: Soluble DPP4 has also been suggested to be a novel regulator, and elevated levels are indicative of several disorders in addition to diabetes, such as obesity, cardiovascular disease, and nonalcoholic fatty liver disease (dos Santos et al., 2013; Baumeier et al., 2017; Nargis and Chakrabarti, 2018).