Effect of training and vitamin E administration on rat liver oxidative metabolism.

We studied vitamin E effects on metabolic changes and oxidative damage elicited by swim training in rat liver. Training reduced mitochondrial aerobic capacity but increased liver content of mitochondrial proteins, so that tissue aerobic capacity was not different in trained and sedentary animals. Vitamin E supplementation prevented the training-induced mitochondrial changes. Training and vitamin E effects were consistent with the changes in tissue content of factors involved in mitochondrial biogenesis (peroxisomal proliferator-activated receptor-γ coactivator and nuclear respiratory factors 1 and 2). Tissue and mitochondrial oxidative damage was reduced by training decreasing the rate of mitochondrial reactive oxygen species (ROS) production and enhancing glutathione levels and glutathione peroxidase and glutathione reductase activities. The effects of vitamin E were different when it was administered to sedentary or trained rats. In the former, vitamin E reduced liver preparations oxidative damage decreasing ROS production rate and increasing GSH content without any effect on antioxidant enzyme activities. In the latter, vitamin E did not modify ROS production and oxidative damage but decreased antioxidant levels. This decrease was likely responsible for the enhanced susceptibility to in vitro oxidative attack of the hepatic tissue from trained rats following vitamin E supplementation. These results indicate that vitamin E integration, which can be healthy for animals subjected to acute exercise, is not advisable during training because it prevents or reduces the favourable effects of the physical activity. They also support the idea that the stimulus for training-induced adaptive responses can derive from the increased ROS production that accompanies the single sessions of the training program.