The Effects of Moderate, Strenuous, and Overtraining on Oxidative Stress Markers and DNA Repair in Rat Liver

Abstract

Physical exercise above a certain load has been suggested as being a cause of oxidative stress. We have tested whether training with moderate (MT), strenuous (ST), or over (OT) load can cause alterations in the activities of antioxidant enzymes, lipid peroxidation, protein oxidation, DNA damage, or activity of 8-oxoG-DNA glycosylase (OGG1) in rat liver. The levels of corticosterone decreased in all exercising groups but the differences were not significant. Adrenocorticotrophin hormone (ACTH) levels decreased, not significantly, in MT and OT compared to C. Activity levels of antioxidant enzymes did not change significantly in the liver. The levels of reactive carbonyl derivative (RCD) content decreased in the liver of exercising animals, and the differences reached significance between control and moderately trained groups. The changes in the levels of lipid peroxidation (LIPOX) were not significant, but were lower in the exercised groups. The 8-hydroxydeoxyguanosine (8-OHdG) levels increased in the OT group, and the activity of OGG1 measured from crude cell extracts tended to increase in MT and ST. The findings of this study imply that overtraining induces oxidative damage to nuclear DNA, but not to liver lipids and proteins.

Comparação do treinamento físico de quatro e oito semanas sobre atividade da cadeia transportadora de elétrons e marcadores de estresse oxidativo em fígado de camundongos

“…Células hepáticas precisam de energia para realizar diversas funções. A alta taxa metabólica do fígado (200kcal/kg/tecido/dia) está diretamente associada a um alto fluxo de elétrons na cadeia respiratória mitocondrial (4) . Entretanto, parte desses elétrons é desviado, produzindo ERO adicionais.…”

“…Especificadamente no fígado, diversos autores demonstram que esse órgão sofre aumento de estresse oxidativo após o exercício físico (1,4) . Por outro lado, outros estudos têm reportado que o treinamento regular tem sido eficaz, na diminuição do estresse oxidativo provocado por diversas doenças (5,6) .…”

“…A alta taxa metabólica do fígado (200kcal/kg/tecido/dia) está diretamente associada a um alto fluxo de elétrons na cadeia respiratória mitocondrial (4) . Entretanto, parte desses elétrons é desviado, produzindo ERO adicionais.Especificadamente no fígado, diversos autores demonstram que esse órgão sofre aumento de estresse oxidativo após o exercício físico (1,4) . Por outro lado, outros estudos têm reportado que o treinamento regular tem sido eficaz, na diminuição do estresse oxidativo provocado por diversas doenças (5,6) .…”

Physical exercise on serum electrolytes and acid base balance in Mangalarga Marchador horses submitted to cavalcade of 4, 8 and 20km

“…These changes occur as the organism attempts to adapt and supply the increased metabolic demand triggered by physical effort (PICCIONE et al, 2007) and are under most circumstances considered beneficial to the animal. However, physical exertion, when overly exhaustive or without proper training, can induce severe organic alterations, especially when the different tissues, organs or systems are not sufficiently adapted to support the different types of overload required of them without causing large changes in homeostasis (OGONOVSZKY et al, 2005 Lack of physical conditioning can be responsible for high serum concentrations of haptoglobin observed in horses after long-distance competitions (CYWINSKA et al, 2010). The persistence of the sharp increase in the enzymatic activity of CK and LDH has also been associated with lack of proper physical preparation of horses submitted to endurance competitions.…”

“…These changes occur as the organism attempts to adapt and supply the increased metabolic demand triggered by physical effort (PICCIONE et al, 2007) and are under most circumstances considered beneficial to the animal. However, physical exertion, when overly exhaustive or without proper training, can induce severe organic alterations, especially when the different tissues, organs or systems are not sufficiently adapted to support the different types of overload required of them without causing large changes in homeostasis (OGONOVSZKY et al, 2005 …”