Effect of dietary quercetin on brain quercetin levels and the expression of antioxidant and Alzheimer's disease relevant genes in mice

The aim of the present feeding trial was to investigate the effect of the dietary flavonol quercetin on brain quercetin concentration and the expression of antioxidant and Alzheimer's disease relevant genes in mouse brain. Laboratory mice were fed control and quercetin-enriched diets (2 mg/g diet) for 6 weeks. Dietary quercetin supplementation significantly increased the levels of quercetin and its methylated metabolite isorhamnetin in plasma and brain. However, quercetin and isorhamnetin levels in the brain were manifold lower as compared to the plasma. Both mRNA and activity levels of alpha- and beta-secretase in cortex remained unchanged by the dietary quercetin supplementation. Furthermore dietary quercetin did not affect brain mRNA levels of neprilysin, heme oxygenase-1 and gamma-glutamylcysteine synthetase. Taken together, a short term dietary treatment with quercetin increased quercetin and isorhamnetin levels in the brain but had no effect on mRNA levels of antioxidant and Alzheimer's disease relevant genes in mouse brain.