A marathon run increases the susceptibility of LDL to oxidation in vitro and modifies plasma antioxidants

Physical activity increases the production of oxygen free radicals, which m ay consume antioxidants and oxidize low-density lipoprotein (LDL). To deter mine whether this occurs during strenuous aerobic exercise, we studied 11 w ell-trained runners who participated in the Helsinki City Marathon. Blood s amples were collected before, immediately after, and 4 days after the race to determine its effect on circulating antioxidants and LDL oxidizability i n vitro. LDL oxidizability was increased as determined from a reduction in the lag time for formation of conjugated dienes both immediately after (180 +/- 7 vs. 152 +/- 4 min, P < 0.001) and 4 days after (155 +/- 7 min, P < 0 .001) the race. No significant changes in lipid-soluble antioxidants in LDL or in the peak LDL particle size were observed after the race. Total perox yl radical trapping antioxidant capacity of plasma (TRAP) and uric acid con centrations were increased after the race, but, except for TRAP, these chan ges disappeared within 4 days. Plasma thiol concentrations were reduced aft er the race. No significant changes were observed in plasma ascorbic acid, a-tocopherol, p-carotene, and retinol concentrations after the marathon rac e. We conclude that strenuous aerobic exercise increases the susceptibility of LDL to oxidation in vitro for up to 4 days. Although the increase in th e concentration of plasma TRAP reflects an increase of plasma antioxidant c apacity, it seems insufficient to prevent the increased susceptibility of L DL to oxidation in vitro, which was still observed 4 days after the race.