Aspects on lipoprotein lipase and atherosclerosis

Lipoprotein lipase (LPL) hydrolyses blood lipids at the vascular endothelium. This action makes fatty acids available for tissue metabolic requirements. LPL is anchored to the endothelium by electrostatic forces and may act as a bridge connecting lipoproteins to cell surfaces. Clusters of positively charged amino acid residues in LPL interact with anionic groups on oligosaccharides covering the cell surfaces. Heparin competes with cell surface oligosaccharides for binding to LPL. Interaction of LPL with soluble and cell surface- ound oligosaccharides influences the activity and catabolism of the enzyme. LPL has a dual role in the development of atherosclerosis. Hydrolysis of lipoproteins by LPL contributes to clearance of lipids from plasma, resulting in an anti-atherogenic lipid profile. On the other hand, trough its bridging function, LPL contributes to lipoprotein retention at the endothelium and in the connective tissue of the artery wall. Furthermore LPL may stimulate uptake of lipoproteins in cells, converting them to foam cells. In this way LPL is considered to be proatherogenic. We have investigated the effects caused by a synthetic heparin analogue, RG-13577, developed for treatment of tumors by anti-angiogenesis theraphy (Paper I) and by heparin (Paper II) on the turnover and biological role of LPL. The variation of LPL activity in kidney among animal species was studied in Paper III. Localization of LPL in healthy and atherosclerotic human arteries in relation to two other heparin-binding proteins (extracellular superoxide dismutase and apolipoprotein B) was studied in Paper IV.