NAMPT and obesity due to melanocortin 4 receptor deficiency: Hepatic miR-34a is the only miR that related to both the expression of hepatic SIRT1 and the severity of NAFLD so far31, 32.In addition, it has been shown that the elevated miR-34a in obesity reduces NAD+ levels and SIRT1 activity by directly targeting nicotinamide phosphoribosyltransferase (NAMPT), one of the rate-limiting enzyme for NAD biosynthesis33.