Effects of dietary bile acid on lipid deposition, lipid metabolism enzyme activities and related gene expression to juvenile Schizothorax prenanti

This experiment was conducted to investigate the effects of dietary bile acid levels on growth, lipid deposition, lipid metabolism enzyme activities and related gene expression of juvenile Schizothorax prenanti. A total of 360 juvenile S. prenanti with an average body weight of (12.74±0.14) g were randomly divided into 4 groups with 3 replicates per group and 30 fish per replicate.The diets with different bile acid supplemental levels (0, 75, 150 and 300 mg/kg) were fed to juvenile S. prenanti for 70 days. The results showed that: with bile acid supplemental level raising, the weight gain rate(WGR) had a trend of increasing first and decreasing later(P<0.05). The WGR was the highest (226.63%) when the bile acid supplemental level was 150 mg/kg. At the same time, the activities of intestinal lipase (LPS), hepatopancreas hepatic lipase (HL), lipoprotein lipase (LPL) and total lipase (TL) were all increased at first and then leveled off (P < 0.05), conversely, the activities of fatty acid synthase (FAS) were decreased at first and then leveled off (P < 0.05) with dietary bile acid levels raising. Meanwhile, with dietary bile acid levels raising, the liver LPL mRNA expression of S. prenanti increased first and then tended to stabilization (P<0.05), FAS mRNA expression decreased first and then tended to level off (P<0.05). The lipid content of liver, muscle and whole fish were all trended to level off with dietary bile acid levels raising (P < 0.05). As well as the survival rate and lipid deposition rate were not significantly different of S. prenanti (P > 0.05). Collectively, the results of above indicate that the suitable dietary bile acid levels can upregulate LPL mRNA expression and downregulate FAS mRNA expression of S. prenanti, enhance the activities of fat metabolism enzymes, promote the digestion and utilization of feed fat, reduce lipid deposition and protect liver health effectively.