Roles of Chemokines and Chemokine Receptors in Obesity-Associated Insulin Resistance and Nonalcoholic Fatty Liver Disease

Abundant evidence has demonstrated that obesity is a state of low-grade chronic inflammation that triggers the release of lipids, aberrant adipokines, pro-inflammatory cytokines, and several chemokines from adipose tissue. This low-grade inflammation underlies the development of insulin resistance and associated metabolic comorbidities such as type 2 diabetes mellitus (T2DM) and nonalcoholic fatty liver disease (NAFLD). During this development, adipose tissue macrophages accumulate through chemokine (C-C motif) receptor 2 and the ligand for this receptor, monocyte chemoattractant protein-1 (MCP-1), is considered to be pivotal for the development of insulin resistance. To date, the chemokine system is known to be comprised of approximately 40 chemokines and 20 chemokine receptors that belong to the seven-transmembrane G protein-coupled receptor family and, as a result, chemokines appear to exhibit a high degree of functional redundancy. Over the past two decades, the physiological and pathological properties of many of these chemokines and their receptors have been elucidated. The present review highlights chemokines and chemokine receptors as key contributing factors that link obesity to insulin resistance, T2DM, and NAFLD.