ENTPD1 and obesity due to melanocortin 4 receptor deficiency: Adenosine and inosine are the purine metabolites that are generated, when CD39 degrades extracellular adenosine triphosphate (ATP) [41], which can enhance the thermogenic capacity of adipose tissue by increasing intracellular cyclic adenosine monophosphate (cAMP) levels [42] or indirectly reduce obesity by modulating the host immunity [43].