Extent of copper LDL oxidation depends on oxidation time and copper/LDL ratio: chemical characterization

The aim of our study was to determine, as a function of [Cu(2+)]/[LDL] ratios (0.5 and 0.05) and of oxidation phases, the extent of LDL oxidation by assessing the lipid and apo B oxidation products. The main results showed that: (i) kinetics of conjugated diene formation presented four phases for Cu(2+)/LDL ratio of 0.5 and two phases for [Cu(2+)]/[LDL] ratio of 0.05; (ii) oxidation product formation (cholesteryl ester and phosphatidylcholine hydroperoxides, apo B carbonyl groups) occurred early in the presence of endogenous antioxidants, under both copper oxidation conditions; (iii) apo B carbonylated fragments appeared when antioxidants were totally consumed at [Cu(2+)]/[LDL] ratio of 0.5; and (iv) antioxidant concentrations were stable, oxysterol formation was negligible, and no carbonylated fragment was detected at [Cu(2+)]/[LDL] ratio of 0.05. Depending on the copper/LDL ratio, oxidized LDL differ greatly in the nature of lipid peroxidation product and the degree of apo B fragmentation.