Dietary taurine stimulates the hepatic biosynthesis of both bile acid and cholesterol in the marine teleost, tiger puffer (Takifugu rubripes)

Taurine plays important roles in the metabolism of bile acid, cholesterol and lipid. However, little relevant information has been available in fish where taurine has been identified as a conditionally essential nutrient. The present study aimed to investigate the effects of dietary taurine on the metabolism of bile acid, cholesterol, and lipid in tiger puffer, which is both an important aquaculture species and a good research model having a unique lipid storage pattern. An 8-week feeding trial was conducted in a flow-through seawater system. Three experimental diets differed only in taurine level, i.e., 1.7, 8.2, and 14.0 mg kg-1. Taurine supplementation increased the total bile acid content in liver, but decreased the content in serum. Taurine supplementation also increased the contents of total cholesterol (TC) and HDL-C in both liver and serum. The hepatic bile acid profile mainly includes taurocholic acid (94.48%), taurochenodeoxycholic acid (4.17%), and taurodeoxycholic acid (1.35%), and the contents of all these conjugated bile acids were increased by dietary taurine. The hepatic lipidomics analysis showed that taurine tended to decrease the abundance of individual phospholipids, and increase those of some individual triglycerides and ceramides. The hepatic mRNA expression study showed that taurine stimulated the biosynthesis of both bile acid and cholesterol, possibly via regulation of FXR and HDL metabolism. Taurine also stimulated the hepatic expression of lipogenic genes. In conclusion, dietary taurine stimulated the hepatic biosynthesis of both bile acid and cholesterol, and tended to regulate the lipid metabolism in multiple ways.