Pro-oxidative effect of α-tocopherol in the oxidation of LDL isolated from co-antioxidant-depleted non-diabetic hemodialysis patients

The association between the antioxidants in LDL and the oxidizability of LDL assessed by the oxidation lag time during copper ion-catalyzed oxidation was investigated in 69 non-diabetic hemodialysis patients and 23 healthy volunteers. The concentrations of co-antioxidants, including ubiquinol-10, lycopene and β-carotene, in LDL were significantly lower in the hemodialysis patients than in the healthy volunteers, while there was no difference in the α-tocopherol concentration between the groups. The lag time showed a significantly positive correlation with the α-tocopherol level (r = 0.62, P< 0.01) in the healthy subjects, but a significantly negative correlation (r = −0.38, P< 0.05) in the hemodialysis patients. Furthermore, in vitro incubation of LDL with α-tocopherol prolonged the lag time in the healthy subjects, but shortened it in the hemodialysis patients. These results suggested that the α-tocopherol might exert the pro-oxidative effect in co-antioxidant-depleted LDL that was isolated from the hemodialysis patients. Despite such co-antioxidant depletion and the pro-oxidative effect of α-tocopherol, the lag time in the hemodialysis patients was not statistically different from that in the healthy volunteers. This might have been because the polyunsaturated fatty acids concentration, another determinant of the lag time, in LDL was less in the hemodialysis patients than in the healthy controls.