YKL-40, a new inflammatory marker with relation to insulin resistance and with a role in endothelial dysfunction and atherosclerosis.

Substantial evidence supports a role of chronic subclinical inflammation and activation of the innate immune system in the pathogenesis of insulin resistance and endothelial dysfunction and the development of type 2 diabetes (T2D) and atherosclerosis. Several proinflammatory cytokines, acute phase-reactants and cell adhesion molecules play a pivotal role in this chronic subclinical inflammation but a comprehensive understanding of the interrelations of these molecules is still needed. YKL-40 is a new inflammatory marker with relation to acute and chronic inflammation as well as cancer. It is secreted in vitro from a variety of human cells, including vascular smooth muscle cells (VSMCs), activated macrophages and macrophages during late stages of differentiation and is found in vivo in subpopulations of macrophages in tissues with inflammation and extracellular tissue remodelling, such as macrophages in atherosclerotic plaques. YKL-40 promotes chemotaxis, cell attachment and migration of VSMCs and the formation of branching tubules suggesting that YKL-40 plays a role in angiogenesis. Latest studies reveal that YKL-40 is elevated in patients with T2D and is related to insulin resistance. This article reviews the studies of YKL-40 with focus on a possible role of YKL-40 in insulin resistance, endothelial dysfunction and atherosclerosis.