Chemokine Systems Link Obesity to Insulin Resistance

Obesity is a state of chronic low-grade systemic inflammation. This chronic inflammation is deeply involved in insulin resistance, which is the underlying condition of type 2 diabetes and metabolic syndrome. A significant advance in our understanding of obesity-associated inflammation and insulin resistance has been recognition of the critical role of adipose tissue macrophages (ATMs). Chemokines are small proteins that direct the trafficking of immune cells to sites of inflammation. In addition, chemokines activate the production and secretion of inflammatory cytokines through specific G protein-coupled receptors. ATM accumulation through C-C motif chemokine receptor 2 and its ligand monocyte chemoattractant protein-1 is considered pivotal in the development of insulin resistance. However, chemokine systems appear to exhibit a high degree of functional redundancy. Currently, more than 50 chemokines and 18 chemokine receptors exhibiting various physiological and pathological properties have been discovered. Therefore, additional, unidentified chemokine/chemokine receptor pathways that may play significant roles in ATM recruitment and insulin sensitivity remain to be fully identified. This review focuses on some of the latest findings on chemokine systems linking obesity to inflammation and subsequent development of insulin resistance.