High density lipoprotein subfractions: isolation, composition, and their duplicitous role in oxidation.
The plasma HDLs represent a major class of cholesterol-transporting lipoprotein that can be divided into two distinct subfractions, HDL(2) and HDL(3), by ultracentrifugation. Existing methods for the subfractionation of HDL requires lengthy ultracentrifugations, making them unappealing for large-scale studies. We describe a method that subfractionates HDL from plasma in only 6 h, representing a substantial decrease in total isolation time. The subfractions so isolated were assessed for a variety of lipid and protein components, in addition to their susceptibility to oxidation, both alone and in combination with VLDL and LDL. We report for the first time a prooxidant role for HDL during VLDL oxidation, in which HDL donates preformed hydroperoxides to VLDL in a cholesteryl ester transfer protein (CETP)-dependent process. Examination of the participation of HDL in LDL oxidation has reinforced its classic role as a potent antioxidant. Furthermore, we have also implicated the second major HDL-associated enzyme, LCAT, in these processes, whereby it acts as a potent prooxidant during VLDL oxidation but as an antioxidant during LDL oxidation. Thus, we have identified a potentially duplicitous role for HDL in the pathogenesis of atherosclerosis, attributable to both CETP and LCAT.
McPherson
Peter A C
PA
Centre for Clinical and Population Sciences, Nutrition and Metabolism Group, Queen's University, Belfast, United Kingdom.
Young
Ian S
IS
McKibben
Bronac
B
McEneny
Jane
J
D000975:Antioxidants / Q000032:analysis; D002784:Cholesterol / Q000097:blood; D006801:Humans; D015227:Lipid Peroxidation; D008075:Lipoproteins, HDL / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D008077:Lipoproteins, LDL / Q000097:blood / Q000302:isolation & purification; D008079:Lipoproteins, VLDL / Q000097:blood / Q000302:isolation & purification; D010084:Oxidation-Reduction; D010743:Phospholipids / Q000097:blood; D012016:Reference Values; D014280:Triglycerides / Q000097:blood
D000975:Antioxidants; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D010743:Phospholipids; D014280:Triglycerides; D002784:Cholesterol