Because IL-6, COX2/PGE2, and M2a macrophage activation have been proven to protect against obesity27,44,45, our results indicate that the Klf9 transgene in macrophages promotes obesity by inhibiting M2a macrophage polarization and IL-6 and PGE2 secretion. This evidence concerns the gene IL6 and obesity due to melanocortin 4 receptor deficiency.