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Plasma lipoproteins play a crucial role in transport and receptor-mediated metabolism of lipids. Low-density lipoprotein (LDL) is the main carrier of cholesterol to peripheral tissues, whereas excess of tissue cholesterol is returned to liver by the high-density lipoprotein (HDL)–mediated reverse cholesterol transport. In parallel with their transport functions, high LDL cholesterol associates with elevated risk of cardiovascular diseases, while high HDL cholesterol protects from the disease (1). Oxidized LDL is a general term for LDL particles with oxidatively modified structural components. As a result from free radical attack, both lipid and protein parts of LDL can be oxidized in the vascular wall. Besides the oxidative reactions taking place in vascular wall, oxidized lipids in LDL can also be derived from oxidized dietary lipids (2,3). Oxidized LDL is known to associate with the development of atherosclerosis, and it is therefore widely studied as a potential risk factor of cardiovascular diseases (4). Atherogenicity of oxidized LDL has been explained by lack of recognition of oxidation-modified LDL structures by the LDL receptors, preventing the normal metabolism of LDL particles and leading eventually to development of atherosclerotic plaques (4). Of the lipid material contained in LDL, various lipid oxidation products are known as the ultimate atherogenic species (5). Acting as a transporter of these injurious molecules is another mechanism by which LDL can increase the risk of atherosclerosis (3,6).

References 1.	Barter P, Gotto AM, LaRosa JE, Maroni J, Szarek M, Grundy SM, et al. HDL cholesterol, very low levels ofLDL cholesterol, and cardiovascular events. N Engl J Med 2007;357:1301–1310. 2.	Staprans I, Rapp JH, Pan XM, Feingold KR. Oxidized lipids in the diet are incorporated by the liver into very low density lipoprotein in rats. J Lipid Res 1996;37:420–430. 3.	Ahotupa M. Oxidized lipoprotein lipids and atherosclerosis. Free Radical Res, 51:4, 439-447. 4.	Stocker R, Keaney JF Jr. Role of oxidative modifications in atherosclerosis. Physiol Rev 2004;84:1381–1478. 5.	Birukov KG. Oxidized lipids: the two faces of vascular inflammation. Curr Atheroscler Rep. 2006;8:223 – 31. 6.	Shao B, Heinecke JW. HDL, lipid peroxidation, and atherosclerosis. J Lipid Res 2009;50:716–722.