HIF3A and obesity due to melanocortin 4 receptor deficiency: The aims of this study are: (1) identifying the association between the HIF3A rs3826795 polymorphism and plasma ALT; (2) determining whether obesity could interact with rs3826795 on plasma ALT; and (3) investigating whether the effect of rs3826795 on ALT is mediated by HIF3A DNA methylation.