Adipose tissue macrophages in aging-associated adipose tissue function

Fig. 1. Macrophages in young, obese and old adipose tissue. In young adipose tissue, most of ATMs are M2 cells. Their functions are not only anti-inflammatory, but also efferocytosis, lipid buffering, angiogenesis, regulation of iron flux. They can help maintain homeostasis of adipose tissue (AT). In obesity, a large number of macrophages in the blood are collected into adipose tissue. The number of ATMs increased from 5 to 50% of the total number of adipose tissue cells and transformed from M2 to M1 cells. Many M1 ATMs surround the necrotic adipocytes to form crown-like structures (CLS), a hallmark of low-grade inflammation and insulin resistance. In aging adipose tissue, the total ATM content is unchanged, but the ratio of M1/M2 ATMs is increasing. Aging alters the balance of adipose tissue macrophages toward the pro-inflammatory M1 phenotype

Fig. 2. Effect of aging on adipose tissue macrophages