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Abstract. Moderate caloric restriction prolongs lifespan. Changes in oxidative stress and hormesis may be involved in this process. The aim of this study is to examine the effects of different levels of chronic caloric restriction (CR) and acute fasting on stress response and oxidative stress parameters in rat liver and plasma. Forty-two rats were divided into groups: control group, calorie-restricted groups with intake of 80-90%, 60-70%, 40-50%, 20-30% of daily caloric needs and acute fasting group. To determine alanine aminotransferase (ALT), aspartate aminotransferase (AST) and superoxide dismutase (SOD) activity, concentration of corticosterone, nitrites and nitrates (NO x ), malondialdehyde (MDA) and glutathione (GSH), liver samples and blood were collected. Increase in plasma corticosterone concentration and AST and ALT activity was found in severe CR. Ingestion 40-50% daily caloric needs or less increased liver MDA and NO x concentration and decreased SOD activity. Ingestion 60-70% daily caloric needs increased Mn-SOD activity, GSH and NO x . In acute fasting group and group taking 20-30% daily caloric needs, GSH was significantly lower than in control group. Severe CR and acute fasting increase oxidative damage and decrease antioxidative capacity of hepatocytes. Moderate CR increases antioxidative capacity of hepatocytes due to increase in Mn-SOD activity and GSH concentration, which might have a role in anti-aging and hormetic mechanism of CR.

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Insulin resistance, oxidative stress, and proinflammatory cytokines play a key role in pathogenesis of nonalcoholic fatty liver disease (NAFLD). The aim of our study was to investigate the dynamics of oxidative/nitrosative stress in methionine–choline-deficient (MCD) diet -induced NAFLD in mice. Male C57BL/6 mice were divided into following groups: group 1: control group on standard diet; group 2: MCD diet for 2, 4, and 6 weeks (MCD2, MCD4, and MCD6, respectively). After treatment, liver and blood samples were taken for histopathology, alanine- and aspartate aminotransferase, acute phase reactants, and oxidative/nitrosative stress parameters. Liver malondialdehyde level was higher in all MCD-fed groups versus control group ( p < 0.01), while nitrites + nitrates level showed a progressive increase. The activity of total superoxide dismutase and its isoenzymes was significantly lower in all MCD-fed groups ( p < 0.01). Although catalase activity was significantly lower in MCD-fed animals at all intervals ( p < 0.01), the lowest activity of this enzyme was evident in MCD4 group. Liver content of glutathione was lower in MCD4 ( p < 0.05) and MCD6 group ( p < 0.01) versus control.Ferritin and C-reactive protein serum concentration were significantly higher only in MCD6 group. Our study suggests that MCD diet induces a progressive rise in nitrosative stress in the liver. Additionally, the most prominent decrease in liver antioxidative capacity is in the fourth week, which implies that application of antioxidants would be most suitable in this period, in order to prevent nonalcoholic steatohepatitis but not the initial NAFLD phase.