Predisposition to LDL oxidation during copper-catalyzed oxidative modification and its relation to α-tocopherol content in humans

The predisposition to LDL oxidation during copper-catalyzed oxidative modification and its relationship with LDL α-tocopherol concentration was studied in 41 control subjects. The results show that the predisposition of LDL to oxidation expressed as duration of the inhibition period and rate of the propagation period varied greatly in the controls, but did not correlate with the values of LDL α-tocopherol. On the contrary the experiments with α-tocopherol incorporated in LDL demonstrate that even small increases of incorporated α-tocopherol, under circumstances where other variables were probably largely unaffected, increased proportionally the length of the inhibition period and reduced the rate of the propagation period. The values of LDL α-tocopherol achieved after the enrichment turned out to be positively correlated with the duration of the inhibition period and negatively with the rate of the propagation period. Finally the results of this study also show that there was a variability in the LDL α-tocopherol decay of different subjects under the same oxidative stress. In our conditions however, the time in which α-tocopherol contributed to the LDL protection was much shorter than the mean length of the inhibition period. The results demonstrate that the variability in the predisposition to LDL oxidation during copper-catalyzed oxidative modification is not determined only by the concentration of α-tocopherol in LDL and that therefore its value as a sole indicator of antioxidant status is probably inadequate.