Effects of caloric restriction on oxidative stress parameters.

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 (NOx), 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 NOx concentration and decreased SOD activity. Ingestion 60-70% daily caloric needs increased Mn-SOD activity, GSH and NOx. 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.