FGF21 and obesity due to melanocortin 4 receptor deficiency: Moreover, in the animal experiments, the beneficial effects of MHW intake on MetS with type 2 diabetes mellitus in a mouse model of diet-induced obesity (DIO) or db/db mice genetically deficient in leptin receptor are reportedly induced by the upregulation of hepatocyte secretion of fibroblast growth factor-21 (FGF-21) [7,21] and enhanced expenditure of fatty acids and glucose [22].