TREM2 and obesity due to melanocortin 4 receptor deficiency: It has been reported that the loss of TREM2 affects the functions of macrophages in the central nervous system (CNS) and in macrophages in adipose and hepatic tissues during obesity, hinting that the AD-associated TREM2 variants might act in multiple macrophage populations within and outside of the CNS, at baseline or in conditions of lipid overload and metabolic stress [74, 75].