Ascorbic acid inhibits the increase in low-density lipoprotein (LDL) susceptibility to oxidation and the proportion of electronegative LDL induced by intense aerobic exercise

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Abstract
We have previously reported the finding of an acute increment in the susceptibility of low-density lipoprotein (LDL) to oxidation and in the proportion of electronegative LDL [LDL(−)] after intense exercise. We have now studied the effect of oral supplementation with 1 g ascorbic acid, immediately before a 4-h athletic race, on the susceptibility of LDL to oxidation, the proportion of LDL(−), and the α-tocopherol and lipid peroxides content in LDL, in order to inhibit such deleterious changes, and to confirm the oxidative nature of modifications of LDL induced by exercise. We studied seven highly trained runners who received a supplement of 1 g ascorbic acid and a control group of seven who did not receive the supplement. The susceptibility of LDL to oxidation was assessed by measurement of conjugated dienes after CuSO4-induced oxidation, the proportion of LDL(−) was determined by anion exchange chromatography, α-tocopherol was quantified by reverse-phase high performance liquid chromatography, and lipid peroxides were measured by the thiobarbituric acid-reactive substances (TBARS) method. After exercise, in the control group there was an increase in both the susceptibility of LDL to oxidation (change in lag phase from 51.4 ± 4.7 min to 47.0 ± 4.6 min, P P We conclude that 1 g ascorbic acid inhibits the increase in LDL susceptibility to oxidation after exercise, preventing this acute pro-atherogenic effect. In addition, the observation that LDL(−) enhancement is prevented by ascorbic acid supports the hypothesis that at least some of the circulating LDL(−) originates from oxidative processes. Coronary Artery Dis 9:249–255

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