Dietary lipid source alters quercetin effects on antioxidant enzyme/phase I and II gene expression in rat colon

Abstract

We have demonstrated changes in antioxidant enzyme activities and glutathione metabolism in colonocytes from rats consuming diets containing 0.45% quercetin combined with corn oil or fish oil. The goal of this study was to query whether these changes were regulated at the transcriptional level. Therefore, real‐time PCR was used to assess the relative expression of 15 genes involved in maintaining cellular antioxidant levels and xenobiotic metabolism. Fish oil alone enhanced the level of catalase, and did not affect the expression of any other genes tested. Quercetin decreased the expression of six genes (SOD2, GPx2, GPx4, GLR2, Ephx2, Cyp1a1) and elevated the expression of Ephx1. When the interaction between quercetin and dietary lipid was analyzed, it was noted that quercetin and fish oil tended to lower the expression levels of seven genes, when compared with the fish oil rats not consuming quercetin. However, when quercetin was combined with corn oil, there was a tendency for mixed responses with four genes enhanced and two suppressed. These data suggest that the ability of quercetin to suppress expression of genes involved in regulating cellular antioxidant status and xenobiotic activation/ detoxification is amplified by its combination with fish oil. Funding USDA/CSREES 2005‐34402‐16401, 2007‐118409, and NIEHS P30‐ES09106.