In a recent pioneering study, Davidsohn et al. [132] showed in mice that a single delivery of three longevity associated genes, including fibroblast growth factor 21 (FGF21), αKlotho, and a soluble form of mouse transforming growth factor-β receptor 2 (sTGFβR2) using adeno-associated viruses can mitigate four age-related diseases: obesity, type 2 diabetes, heart failure, and renal failure. This evidence concerns the gene FGF21 and obesity due to melanocortin 4 receptor deficiency.