Endothelial lipase: regulation and biological function.

Endothelial lipase is synthetized almost exclusively in endothelial cells and then fixed on the luminal surface of the endothelium by means of heparan sulphate proteoglycans. The enzyme is expressed in the endothelium of nearly all tissues and the degree of expression is higher in richly vascularized tissues than in the less vascularized ones. The endothelial lipase expression in tissues is upregulated by shear and cyclic stress, angiotensin II and hypertension. The plasma enzyme level is elevated by pro-inflammatory cytokines, in metabolic syndrome and obesity. Prolonged exercise reduces the plasma enzyme level in the rat. The activity of the enzyme is inhibited by: sphingomyelin, angiopoietin-like protein 3 and 4, and insulin. Endothelial lipase reduces the plasma high density lipoprotein concentration and changes its properties. The enzyme is considered to be the main regulator of the plasma high density lipoprotein concentration. The plasma endothelial lipase concentration is elevated in coronary atherosclerosis and it is inversely correlated with the plasma high density lipoprotein level. The enzyme is considered to exert mostly pro-atherogenic effects. Its action as triglyceride lipase is important in hypertriglyceridemia.