Inflammation and macrophage modulation in adipose tissues

Summary The adipose tissue is an active endocrine organ that harbours not only mature and developing adipocytes but also a wide array of immune cells, including macrophages, a key immune cell in determining metabolic functionality. With adipose tissue expansion, M 1 pro‐inflammatory macrophage infiltration increases, activates other immune cells, and affects lipid trafficking and metabolism, in part via inhibiting mitochondrial function and increasing reactive oxygen species ( ROS ). The pro‐inflammatory cytokines produced and released interfere with insulin signalling, while inhibiting M 1 macrophage activation improves systemic insulin sensitivity. In healthy adipose tissue, M 2 alternative macrophages predominate and associate with enhanced lipid handling and mitochondrial function, anti‐inflammatory cytokine production, and inhibition of ROS . The sequence of events leading to macrophage infiltration and activation in adipose tissue remains incompletely understood but lipid handling of both macrophages and adipocytes appears to play a major role.