The study of a mouse model of diet-induced obesity found that exposure to PM2.5 induces the infiltration of macrophages into visceral fat, thus triggering the release of inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α), which accelerate the accumulation of visceral fat [31]. The gene discussed is IL6; the disease is obesity due to melanocortin 4 receptor deficiency.