The use of dietary supplements to enhance the benefit of exercise training is a common practice. The liver is the organ where all substances are metabolized, and certain supplements have been associated with liver injury. Vitamin A (VA), a liposoluble vitamin stored in the liver, is commonly used as an antioxidant supplement. Here, we evaluated the effect of chronic VA supplementation on oxidative damage and stress parameters in trained rats. Animals were divided into the following groups:

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... tary (SE), sedentary/VA (SE+VA), exercise training (ET), and exercise training/VA (ET+VA). During 8 weeks, animals were subjected to swimming (0, 2, 4, 6% body weight) 5 days/week and a VA daily intake of 450 retinol equivalents/day. Parameters were evaluated by enzymatic activity analysis, ELISA, and western blotting. VA caused liver lipid peroxidation and protein damage in exercised rats and inhibited the increase in HSP70 expression acquired with exercise alone. ET group showed higher levels of antioxidant enzyme activity, and VA inhibited this adaptation. Expression of the proinflammatory cytokines, interleukin (IL)-1β and tumor necrosis factor-α, was reduced in the ET+VA group, while the anti-inflammatory cytokine, IL-10, was increased. Western blotting showed that both exercised groups had lower levels of the receptor for advanced glycation end products (RAGE), suggesting that VA did not affect this receptor. Our study demonstrated that, although VA caused oxidative damage, a controlled administration might exert anti-inflammatory effects. Further studies with higher VA doses and longer ET interventions would elucidate more the effects of the supplementation and exercise on liver parameters. Page 4 of 34 https://mc06.manuscriptcentral.com/apnm-pubs Applied Physiology, Nutrition, and Metabolism lipoperoxidation in the lungs (Gasparotto et al. 2015) and skeletal muscle (Petiz et al. 2017). Due to the role of the liver in the regulation of energetic homeostasis during exercise and also in the metabolism of VA, this study is intended to improve the understanding of the mechanisms by which VA supplementation presented potentially harmful effects when combined with ET.