Ferulic acid improved lipid metabolism of blunt snout bream, Megalobrama amblycephala juveniles via the intestinal microbiota and metabolites

Fish is an important source of protein for human, and lipid homeostasis is essential for fish health. As a green plant extract, ferulic acid (FA) plays a crucial role in modulating lipid metabolism. This study investigate the effects of dietary FA supplementation on lipid metabolic homeostasis, intestinal microbiota, and metabolites in plasma and intestinal contents of Megalobrama amblycephala juveniles. M. amblycephala (average weight: 9.75 ± 0.04 g) juveniles were fed with three feeds containing 0 (Control), 100 (FA100), and 200 (FA200) mg/kg FA with equivalent nitrogen and energy levels for 8 weeks. The results indicate that FA supplementation significantly reduce the content of plasma lipids and liver lipids, and markedly increase total bile acid content in liver. It is possible that FA regulates liver fatty acid metabolism and cholesterol-bile acid metabolism by up-regulating genes such as carnitine palmitoyl transferase 1 A, cholesterol 7α-hydroxylase, and down-regulating genes such as sterol regulatory element-binding protein. The diversity of the intestinal microbiota is significantly enhanced, while the abundance of harmful bacteria exhibits a marked reduction in FA100 group. Further, metabolites are altered in FA100 group. Epoxy eicosatrienoic acid is a co-upregulated metabolite in both intestinal contents and plasma, and was significantly correlated with multiple indicators related to lipid metabolism. In summary, supplementing FA to feed decrease liver and plasma lipid accumulation and maintained lipid metabolic homeostasis. This may be due to the changed intestinal microbiota of M. amblycephala, as well as enrichment of intestinal and plasma metabolites.