Regulatory Effects of Bile Acids on Growth Performance and Hepatic Metabolism in Largemouth Bass

Objective This study aimed to investigate the regulatory effects of bile acids on growth performance and hepatic metabolism in largemouth bass (Micropterus salmoides).

Methods Three isonitrogenous and isolipidic experimental diets were formulated by supplementing the basal diet with bile acids at inclusion levels of 0, 150, and 300 mg/kg, respectively. Largemouth bass with an initial body weight of (16.21 ± 0.07) g were fed these diets for 8 weeks. At the end of the feeding trial, fish growth performance was determined. Serum biochemical parameters, hepatic lipid metabolism and antioxidant indices were analyzed, and the serum bile acid profile was characterized. Liver transcriptome sequencing was further performed to decipher the underlying regulatory mechanisms.

Results Compared with the control group, dietary supplementation of grass carp-derived bile acids at 150 mg/kg significantly increased the weight gain rate, reduced hepatic lipid content, serum total cholesterol (TC) and aspartate aminotransferase (AST) levels. Meanwhile, the expression of hepatic antioxidant-related genes (cat, gpx) and GPX enzyme activity were upregulated. In addition, grass carp-derived bile acid intervention markedly altered the serum bile acid profile of largemouth bass. The 150 mg/kg grass carp bile acid treatment increased the relative proportions of serum ursodeoxycholic acid (UDCA) and taurohyocholic acid (THCA). Hepatic transcriptomic analysis revealed that 150 mg/kg dietary grass carp bile acids significantly activated growth-promoting and stress-adaptive signaling pathways (e.g., MAPK, Ras, TGF‑β), while generally suppressing basal catabolic pathways including the PPAR signaling pathway and fatty acid metabolism.

Conclusion Grass carp-derived bile acids can reshape the host serum bile acid profile by elevating the proportions of UDCA and THCA in circulating bile acids, thereby systematically reprogramming hepatic gene expression patterns to achieve integrated benefits including growth promotion, hepatic lipid reduction and enhanced antioxidant capacity. Such effects exhibit evident species specificity. This work provides new insights and theoretical foundations for the precise regulation of fish growth and health via bile acid manipulation.

As important metabolic signaling molecules, bile acids are not only involved in lipid digestion and absorption, but also mediate diverse physiological processes including energy metabolism, inflammatory response and oxidative stress via receptors such as FXR and TGR5, playing pivotal roles in the regulation of fish growth. Nevertheless, bile acids do not act as a uniform “single additive”; their biological effects are jointly shaped by multiple factors, including bile acid composition, dietary inclusion level, host species, and nutritional background of basal diets. Results of the present study demonstrated that dietary supplementation of bile acids at 150 mg/kg significantly increased the weight gain rate of largemouth bass without affecting feed intake, indicating that the growth-promoting effect of grass carp-derived bile acids is closely associated with improved digestibility and utilization of nutrients, especially lipids, as well as enhanced internal energy utilization, rather than elevated feed consumption. Similar findings have been reported in other fish species such as common carp, large yellow croaker and rainbow trout (Oncorhynchus mykiss). Those studies suggested that bile acids could indirectly promote growth by improving lipid digestion and utilization and alleviating hepatic metabolic burden.

Sun H, Li Y S H, Chen H J, et al. Mechanism of grass carp-derived bile acids reshaping hepatic metabolism in largemouth bass via regulation of bile acid profile[J]. Journal of Fisheries of China, 2026, 50(8): 180-196.