ACE2 and obesity due to melanocortin 4 receptor deficiency: Considering that 5-HT has localized effects on adipose tissues, specifically on the lipogenesis of WAT [30], as well as the fact that the decrease in peripheral 5-HT confers protection from HFD-induced obesity [29,30], and that ACE2-/y mice have less 5-HT [28] due to the defective intestinal absorption of the 5-HT precursor amino acid, tryptophan [23], it is plausible to consider that their protection against HFD-induced obesity is mediated by decreased levels of 5-HT.