SIRT1 and obesity due to melanocortin 4 receptor deficiency: Oil Red O staining showed that resveratrol resulted in decrease in lipid accumulation compared to the control, but nicotinamide increased lipogenesis (Fig. 5A) and the accumulations were quantitatively summarized in Figure 5B. Taken together, our data further demonstrated that anti‐obesity of CD38 deficiency was involved in inhibitions of adipogenesis and lipogenesis probably by activating Sirt1‐mediated PPARγ inhibition.