CD38 and obesity due to melanocortin 4 receptor deficiency: CD38, as a multifunctional enzyme, is responsible for degradation of intracellular NAD+ and the generation of the second messengers such as cyclic ADP-ribose in mammalian cells, in which CD38 has been implicated in the regulation of physiological functions such as maintaining intracellular NAD+ homeostasis and modulating intracellular Ca2+ signals, and in the occurrence of numerous diseases such as cardiovascular diseases, aging, obesity, diabetes and inflammation at the pathological conditions 7, 8.