Effect of taurine levels on liver lipid metabolism: an in vivo study in the rat.

Previous studies using guinea pigs and cats have shown that liver lipid composition is affected by intrahepatic taurine levels. The purpose of the present study was to determine whether this sulfonated amino acid could also affect lipid metabolism in the rat, an animal capable of synthesizing substantial amounts of taurine and used extensively in studies on lipid metabolism. Wide variations in the hepatic taurine content were induced by administering either 1% taurine or 1% guanidinoethane sulfonate in the drinking water for 2 weeks. These treatments increased and decreased taurine liver content, respectively, but did not affect either food or water intakes, or growth rates. The plasma concentrations of the major lipid classes in treated animals did not show any significant alteration in comparison to control animals, except for nonesterified fatty acid levels that were significantly lowered by guanidinoethane sulfonate administration. Taurine supplementation did cause a significant decrease in total hepatic lipid content that was attributable to the reduction of free and esterified cholesterol, triglyceride, and phosphatidylethanolamine hepatic concentrations. This same treatment slightly increased both bile flow and secretion of taurine-conjugated primary bile salts. In particular, the proportion of tauro-beta-muricholate significantly increased, whereas that of taurodeoxycholate greatly decreased. The administration of guanidinoethane sulfonate reduced both the bile flow and the secretion of taurine-conjugated bile salts and caused a significant alteration in the ratio between glycine- and taurine-conjugated bile salts. This did not occur after the treatment with taurine. Interestingly, we observed an inverse correlation between hepatic taurine levels and the proportion of either cholesteryl ester in hepatic lipids or taurochenodeoxycholate in biliary bile salts. These facts suggest that taurine hepatic levels influence mostly hepatic steroid metabolism, but they also affect the metabolism of other lipid classes.