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一项研究发现，在锻炼之后服用抗氧化维生素可能减少这种锻炼的有益效应。 Michael Ristow及其同事提出，锻炼通过产生活性氧组分——或称为“自由基”——从而帮助增加人体对胰岛素的敏感性。而氧自由基恰好是抗氧化剂所针对的物质。活性氧被认为能损伤细胞和加速衰老过程，但是人体也利用这种物质防止锻炼后的细胞损伤。 这组科学家比较了每天服用维生素C和E补充剂的进行锻炼的男性和不服用维生素的男性的胰岛素敏感性和活性氧的数量。这组科学家报告说，服用了抗氧化补充剂的男性的活性氧水平没有变化，而没有服用抗氧化剂的男性的氧自由基形成增加。在经过了4周的训练后，只有未服用抗氧化补充剂的那组男性的胰岛素敏感性水平恢复了。这组作者证明了活性氧很可能通过增加胰岛素敏感性从而对人体产生有益作用，而且这种效应被服用抗氧化维生素阻断。 推荐原始出处： PNAS May 11, 2009, doi: 10.1073/pnas.0903485106 Antioxidants prevent health-promoting effects of physical exercise in humans Michael Ristowa,b,1,2, Kim Zarsea,2, Andreas Oberbachc,2, Nora Kl?tingc, Marc Birringera, Michael Kiehntopfd, Michael Stumvollc, C. Ronald Kahne and Matthias Blüherc,2 Exercise promotes longevity and ameliorates type 2 diabetes mellitus and insulin resistance. However, exercise also increases mitochondrial formation of presumably harmful reactive oxygen species (ROS). Antioxidants are widely used as supplements but whether they affect the health-promoting effects of exercise is unknown. We evaluated the effects of a combination of vitamin C (1000 mg/day) and vitamin E (400 IU/day) on insulin sensitivity as measured by glucose infusion rates (GIR) during a hyperinsulinemic, euglycemic clamp in previously untrained (n = 19) and pretrained (n = 20) healthy young men. Before and after a 4 week intervention of physical exercise, GIR was determined, and muscle biopsies for gene expression analyses as well as plasma samples were obtained to compare changes over baseline and potential influences of vitamins on exercise effects. Exercise increased parameters of insulin sensitivity (GIR and plasma adiponectin) only in the absence of antioxidants in both previously untrained (P < 0.001) and pretrained (P < 0.001) individuals. This was paralleled by increased expression of ROS-sensitive transcriptional regulators of insulin sensitivity and ROS defense capacity, peroxisome-proliferator-activated receptor gamma (PPARγ), and PPARγ coactivators PGC1α and PGC1β only in the absence of antioxidants (P < 0.001 for all). Molecular mediators of endogenous ROS defense (superoxide dismutases 1 and 2; glutathione peroxidase) were also induced by exercise, and this effect too was blocked by antioxidant supplementation. Consistent with the concept of mitohormesis, exercise-induced oxidative stress ameliorates insulin resistance and causes an adaptive response promoting endogenous antioxidant defense capacity. Supplementation with antioxidants may preclude these health-promoting effects of exercise in humans. (责任编辑：Doctor001) |
