Oxidative status of human low density lipoprotein isolated by anion-exchange high-performance liquid chromatography—Assessment by total hydroxyoctadecadienoic acid, 7-hydroxycholesterol, and 8-iso-prostaglandin F2α

This study aims to measure the oxidative status of LDL from human plasma (n = 26) as assessed by biomarkers for lipid peroxidation, total hydroxyoctadecadienoic acid (tHODE), 7α- and 7β-hydroxycholesterol (t7-OHCh), and 8-iso-prostaglandin F2α (t8-iso-PGF2α) after subfractionation of LDL with an anion-exchange HPLC (AE-HPLC). LDL was separated and quantified by AE-HPLC as LDL-1, LDL-2, and LDL-3 in the order of the anionic charge of the LDL particles. The concentrations of tHODE, t7-OHCh, and t8-iso-PGF2α in both plasma and LDL subfractions were assessed after reduction and saponification. In this method, the free and ester forms of hydroperoxides, ketones, and hydroxides of linoleic acid and cholesterol are measured as tHODE and t7-OHCh, respectively. It was found that tHODE significantly correlated with the proportion of LDL-2 and LDL-3 as well as with the concentration of malondialdehyde-modified LDL in plasma. Further, by the analyses of LDL subfractions, the concentrations of tHODE, t8-iso-PGF2α, and t7-OHCh in LDL-3 were found to be significantly higher than those in LDL-1 and LDL-2. These results clearly indicate that the extent of oxidation increases in the order of LDL-1 < LDL-2 ≪ LDL-3 and that the oxidative status of LDL in plasma can be quantitatively evaluated by using AE-HPLC and biomarkers, tHODE, t7-OHCh, and t8-iso-PGF2α.