Considering the role of macrophages in the propagation of inflammatory signals in adipose tissue, we hypothesized that deletion of Postn in hematopoietic-derived cells, which include macrophages, could reduce obesity-related increases in macrophage infiltration and inflammation and subsequently prevent in vivo ectopic lipid accumulation and insulin resistance. The gene discussed is POSTN; the disease is obesity due to melanocortin 4 receptor deficiency.