Effect of dietary α-lipoic acid on the mRNA expression of genes involved in drug metabolism and antioxidation system in rat liver

In the present study, the mRNA levels of hepatic proteins involved in the drug metabolism of rats fed a-lipoic acid were evaluated by DNA microarray and real-time PCR analyses. Experimental diets containing 0, 0.1, 0.25 and 0.5% (w/w) alpha-lipoic acid were fed to four groups of rats consisting of seven animals each for 21 d. DNA microarray analysis revealed that the diet containing 0.5% alpha-lipoic acid significantly (P<0.05) increased the mRNA levels of various phase I drug-metabolising enzymes up to 15-fold and phase II enzymes up to 52-fold in an isoenzyme-specific manner. alpha-Lipoic acid also up-regulated the mRNA levels of some members of the ATP-binding cassette transporter superfamily, presumed to be involved in the exportation of xenobiotics, up to 6.6-fold. In addition, we observed that alpha-lipoic acid increased the mRNA levels of many proteins involved in antioxidation, such as members of the thiol redox system (up to 5.5-fold), metallothioneins (up to 12-fold) and haeme oxygenase 1 (1.5-fold). These results were confirmed using real-time PCR analysis, and alpha-lipoic acid dose dependently increased the mRNA levels of various proteins involved in drug metabolism and antioxidation. Consistent with these observations, alpha-lipoic acid dose dependently increased the hepatic concentration of glutathione and the activities of glutathione reductase and glutathione transferase measured using 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates, but decreased the hepatic and serum concentrations of malondialdehyde. In conclusion, the present study unequivocally demonstrated that alpha-lipoic acid increases the mRNA expression of proteins involved in drug metabolism and antioxidation in the liver.