Dietary geniposide supplementation could enhance hepatic lipid metabolism, immunity, antioxidant capacity, and ammonia stress resistance in turbot (Scophthalmus maximus)

This study aimed to evaluate the effects of dietary geniposide supplementation on growth performance, lipid metabolism, health status, and ammonia stress resistance in turbot (<i>Scophthalmus maximus</i>). Four hundred fifty fish were randomly allocated into 5 treatments with triplicate tanks (30 fish per tank). They were hand-fed to apparent satiety for 56 d with a basal diet (GP0) or diets containing 100, 200, 400, and 800 mg/kg geniposide (termed as GP100, GP200, GP400, GP800, respectively). After the conclusion of the feeding trial, the fish were exposed to ammonia stress for 96 h. The results showed that the growth performance were not affected by geniposide (<i>P</i> > 0.05). Dietary supplementation with geniposide decreased crude lipid in viscera without liver, subcutaneous adipose tissue (SAT), and the liver, as well as triglyceride concentrations in plasma, the liver and SAT (<i>P</i> < 0.05). Dietary supplementation with 400 and 800 mg/kg geniposide significantly down-regulated lipogenesis-related gene expression, as well as fatty acid uptake-related gene expression, while significantly up-regulated triglyceride secretion-related gene expression in the liver compared with the control group (<i>P</i> < 0.05). The GP800 group exhibited a significant reduction in plasma malondialdehyde contents compared with the control group, while both the GP200 and GP800 groups showed a significant increase in plasma complement C3 activities (<i>P</i> < 0.05). Furthermore, there was a notable enhancement in plasma lysozyme and total superoxide dismutase levels in the geniposide supplemented groups compared to the control group (<i>P</i> < 0.05). Additionally, a significant decrease in the mRNA level of pro-inflammatory cytokine and a remarkable increase in the mRNA expression of anti-inflammatory cytokines were discovered in geniposide supplemented groups relative to the control group (<i>P</i> < 0.05). Cumulative survival rates after ammonia stress in the GP400 and GP800 groups were statistically higher than that in the control group (<i>P</i> < 0.05). In conclusion, dietary geniposide supplementation could reduce lipid deposition in turbot by regulating lipid metabolism and transportation, and remarkably enhance immunity, antioxidant ability, and resistance to ammonia stress in turbot. Based on the quadratic regression analyses, the optimal concentrations of geniposide were estimated to be 545.21 to 668.41 mg/kg feed.