Effects of Alpha- Tocopherol on the Velocity of Low Density Lipoprotein Oxidation by Cupric Ions

We studied the effect of different concentrations of alpha-tocopherol on in vitro cupric ions induced oxidation of low density lipoproteins (LDL). Human native LDL (50 µg protein/ml) oxidation was induced by 10 µmol/L of CuSO4. Conjugated dienes were measured spectrophotometrically for up to 440 minutes. The length of the lag phase (Tlag), maximum velocity of the reaction (Vmax) and the maximum amount of generated dienes were obtained from kinetic data. Alpha-tocopherol increased Tlag and decreased Vmax with a dependence upon concentration (0-100 µmol/L). There was no difference between the Dmax obtained with cupric ions alone or in the presence of the various concentrations of alpha-tocopherol. The results suggest that alpha-tocopherol may decrease free radicals presence in LDL and thus decrease velocity of LDL oxidation by cupric ions. This mechanism may be a reason for alpha-tocopherol effect in ameliorating atherosclerosis.