Effects of Quercetin and Catechin on Hepatic Glutathione-S Transferase (GST), NAD(P)H Quinone Oxidoreductase 1 (NQO1), and Antioxidant Enzyme Activity Levels in Rats

Abstract

Cell culture data indicate that quercetin and catechin may affect the activity of phase II and antioxidant enzymes. However, little is known about the impact of dietary flavonoids in vivo. Therefore, the present study aimed to investigate the in vivo effects of the flavonoids quercetin and catechin on mRNA and activity levels of phase II enzymes glutathione-S transferase (GST) and NAD(P)H quinone oxidoreductase-1 (NQO1) in rat liver. Furthermore, the activity of the hepatic antioxidant enzymes catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) was determined. Feeding male Wistar rats (3 × 6 animals) over 3 wk with semisynthetic diets enriched with quercetin and catechin (2 g/kg diet) did not affect liver enzyme activity of CAT, GPx, and SOD as well lipid peroxidation and glutathione levels. Dietary quercetin significantly decreased activity of hepatic GST (24%), whereas dietary catechin significantly decreased NQO1 activity (26%) compared to controls. Changes in GST and NQO1 activity were partly reflected on mRNA levels. Current data indicate that dietary flavonoids have little effects on liver oxidant/antioxidant status but do significantly affect the phase II enzymes GST and NQO1 in rat liver. This in turn may affect the ability of the organism to detoxify endogenous and exogenous xenobiotics.

ACKNOWLEDGMENTS

This project was financially supported by a grant of the German Ministry of Education and Science (BMBF 0313856A) entitled “Functional Foods for Vascular Health—from Neutraceuticals to Personalized Diets.”

Abbreviations: GST, glutathione S-transferase; NQO1, NAD(P)H quinone oxidoreductase 1; CAT, catalase, GPx, glutathione peroxidase; SOD, superoxide dismutase.

Notes

^a Abbreviations are as follows: qRT-PCR, quantitated reverse transcription polymerase chain reaction; AT, annealing temperature; F, forward primer; R, reverse primer; GST, glutathione S-transferase; a, class alpha; p, class pi; m, class mu; NQO1, NAD(P)H quinone oxidoreductase 1; Gclc, glutamate-cysteine ligase, catalytic subunit; Gclm, glutamate cysteine ligase, modifier subunit; Actb, beta-actin.

^a Abbreviations are as follows: TBA-RS, thiobarbituric acid reactive substances with and without ferrous provocation; mRNA, messenger RNA; γ-GCS, γ-glutamylcysteine synthetase; Gclc, glutamate-cysteine ligase, catalytic subunit; Gclm, glutamate cysteine ligase, modifier subunit; GPx, glutathione peroxidase; SOD, superoxide dismutase; CAT, catalase; GSH, glutathione (red). No significant differences between groups.

^a Abbreviations are as follows: GST, glutathione S-transferase; NQO1, nicotinamide adenine dinucleotide phosphate quinone oxidoreductase 1.

^b Indicates significant differences (P < 0.05) as compared to control animals (Dunnett).

^a Abbreviations are as follows: mRNA, messenger RNA; Gst, glutathione S-transferase; Nqo1, nicotinamide adenine dinucleotide phosphate quinone oxidoreductase 1.

^b Indicates significant differences (P < 0.05) as compared to control animals (Dunnett).