FGF21 and obesity due to melanocortin 4 receptor deficiency: TAX also mitigates obesity development by increasing the mRNA levels of uncoupling protein-1 and fibroblast growth factor 21 (FGF21) in brown adipose tissue and high body temperatures in our in vivo and in vitro study [9] and activating the phosphatidylinositol 3-kinase/protein kinase B signaling pathway in rats [10].