Effects of Bacillus subtilis on hepatic lipid metabolism and oxidative shess response in grass carp(Ctenopharyngodon idellus)fed a high-fat diet

Bacillus subtilis is widely used in aquaculture as a probiotic.However,few studies have been conducted to examine the effect of B.subtilis on liver lipid metabolism.A total of 135 healthy grass carp(50.24±1.38 g)were randomly divided into three groups:control(Con),high-fat diet(HF),and high-fat diet+B.subtilis(HF4-B.subtilis),and fed for 8 weeks.The results showed that compared with the HF group,the weight gain rate(WGR)significantly increased(Pc0.05)and the hepatic lipid content,serum low-density lipoprotein cholesterol(LDL-C),and aspartate aminotransferase(AST)decreased in the group supplemented with B.subtilis(P<0.05).Moreover,the hepatic mRNA expression of fatty acid synthase(FAS)was significantly down-regulated and the carnitine palmitoyl transferases(CPTlala)were up-regulated in the HF+B.subtilis group compared to the HF group(P<0.05),respectively.Additionally,in the HF+B.subtilis group,glutathione(GSH)significantly increased(Pv 0.()5),while hydrogen peroxide(H2O2)and malondialdehyde(MDA)contents significantly decreased compared to the HF group(P v0.05).B.subtilis may reduce the hepatic lipid content by inhibiting its synthesis and promoting p-oxidation of fatty acids.B.subtilis may also alleviate dyslipidaemia and prevent oxidative damage in the liver caused by the high-fat diet of grass carp.Hence,dietary supplementation with B.subtilis shows promise as a therapeutic or preventive tool against fatty liver disease.