Effect of Dietary Oxidized Stigmasterol on the Antioxidant System in Mice

Dietary phytosterols exhibit beneficial functions, such as hypocholesterolemic action; however, oxidized phytosterols may exhibit various harmful effects that include cytotoxicity and inflammation. The effects of dietary oxidized phytosterols, especially individual oxidized phytosterols, on the antioxidant system in vivo are currently unknown. Stigmasterol is a major phytosterol, and its oxidation products have been shown to be cytotoxic as they induce reactive oxygen species (ROS) generation. Therefore, we examined the toxic effects of dietary oxidized stigmasterol on the antioxidant system in mice. Mice were fed a standard diet (C group) or that plus 0.25% oxidized stigmasterol (OS group) for 14 days. Oxidized stigmasterol levels in the liver were higher in the OS group than in the C group. Dietary oxidized stigmasterol increased the levels of thiobarbituric acid-reactive substances in the liver. However, plasma alanine transaminase and aspartate transaminase activities did not differ between the two groups. The plasma ferric ion-reducing antioxidant power value and liver glutathione (GSH) levels were significantly higher in the OS group than in the C group. The enzyme activities of catalase, GSH reductase, and GSH-S-transferase in the liver cytosol were higher in the OS group than in the C group, despite the lack of change observed in their gene expression. Therefore, dietary oxidized stigmasterol may disturb the antioxidant system; however, its effects may be temporary due to the rapid action of antioxidant enzymes or GSH in response to the generation of ROS.