CD38 and obesity due to melanocortin 4 receptor deficiency: A CD38-deficient mouse model has higher metabolic rate and showed protection against diet-induced obesity through increasing NAD-dependent activation of sirtuin (SIRT) proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), which is involved in the regulation of mitochondrial biogenesis and energy homeostasis (Barbosa et al., 2007).