Adipose Tissue Remodeling as Homeostatic Inflammation

Figure 3

Regulation of macrophage polarity in adipose tissue. Recent evidence has also pointed to the heterogeneity of adipose tissue macrophages, that is, M1 or classically activated (pro-inflammatory) macrophages and M2 or alternatively activated (anti-inflammatory) macrophages. Under lean condition, adipocytes secrete factors that promote M2 activation of macrophages, such as interleukin-4 (IL) and interleukin-13 (IL-13). M2 macrophages secrete anti-inflammatory mediators. On the other hand, adipocytes secrete pro-inflammatory FFAs, chemokines, and cytokines under obese condition. Activated M1 macrophages produce large amounts of pro-inflammatory cytokines, thereby accelerating inflammatory responses in adipose tissue through paracrine interaction between adipocytes and macrophages.