Many insects in temperate regions overwinter in diapause, during which they are cold hardy. In these insects, one of the metabolic adaptations to the unfavorable environmental conditions is the synthesis of cryoprotectants/anhydroprotectants. The aim of this study was to investigate the connection between the antioxidative system and synthesis of cryoprotectants (mainly glycerol) in diapausing larvae of the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae). At two periods during diapause (November and February), in three groups of insects (kept under field conditions; -12°C for two weeks; 8°C for two weeks), the activity of key enzymes of the antioxidative system and oxidative part of the hexose monophosphate shunt were measured: superoxide dismutase, catalase, non selenium glutathione peroxidase, glutathione S-transferase, glutathione reductase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, as well that of the antioxidative components: total glutathione and ascorbate, and dehydroascorbate reductase. There was a higher activity of antioxidative enzymes at the beginning of the diapause period (November) compared to late diapause (February), while glutathione and ascorbate were higher in February. Similarly, there was a lower activity of the hexose monophosphate shunt enzymes in February. Exposure of larvae to -12°C resulted in an elevation of hexose monophosphate shunt enzyme activity, especially in November. This was accompanied by a significant increase in glycerol content in February. Changes in ascorbate levels and dehydroascorbate reductase activity in both experimental groups (-12°C and 8°C) suggest a connection between the antioxidative system, metabolism during diapause and cold hardiness. Our results support the notion that antioxidative defense in larvae of Ostrinia nubilalis is closely connected with metabolic changes characteristic of diapause, mechanisms of cold hardiness involved in diapause and the maintenance of a stable redox state.
The intracellular levels of antioxidant and free radical scavenging enzymes are gradually altered during the aging process. An age-dependent increase of oxidative stress occurring throughout the lifetime is hypothesized to be the major cause of aging. The current study examined the effects of L-malate on oxidative stress and antioxidative defenses in the liver and heart of aged rats. Sprague-Dawley male rats were randomly divided into four groups, each group consisting of 6 animals. Group Ia and Group IIa were young and aged control rats. Group Ib and Group IIb were young and aged rats treated with L-malate (210 mg/kg body weight per day). L-malate was orally administrated via intragastric canula for 30 days, then the rats were sacrificed and the liver and heart were removed to determine the oxidant production, lipid peroxidation and antioxidative defenses of young and aged rats. Dietary L-malate reduced the accumulation of reactive oxygen species (ROS) and significantly decreased the level of lipid peroxidation in the liver and heart of the aged rats. Accordingly, L-malate was found to enhance the antioxidative defense system with an increased activity of antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) and increased glutathione (GSH) levels in the liver of aged rats, a phenomenon not observed in the heart of aged rats. Our data indicate that oxidative stress was reversed and the antioxidative defense system was strengthened by dietary supplementation with L-malate., J.-L. Wu, Q.-P. Wu, X.-F. Yang, M.-K. Wei, J.-M. Zhang, Q. Huang, X.-Y. Zhou., and Obsahuje bibliografii a bibliografické odkazy