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The study aimed to investigate the impact of astaxanthin on the hepatic health in juvenile Anguilla rostrata under histamine stress. Four hundred juvenile fish with an initial weight of (25.01 ± 0.17) g were randomly divided into four groups (with four replicates per group and 25 fish per replicate): CK group, H group, H+AST4 group, and H+AST8 group. The juvenile fish were fed a basal feed, high histamine feed, and high histamine feed supplemented with 4 or 8 mg/kg of astaxanthin, respectively. The experiment lasted for 70 days. The results showed that compared to the CK group, the H group exhibited elevated serum AST and ALT activities (P<0.05). The hepatic SOD, CAT, GSH-Px activities, GSH concentration, and T-AOC decreased (P<0.05), while the MDA concentration increased in the H group (P<0.05). In the H+AST4 group and H+AST8 group, the serum AST and ALT activities were significantly lower than those in the H group (P<0.05), and the hepatic SOD, CAT, GSH-Px activities, GSH concentration, and T-AOC were higher than those in the H group (P<0.05), while the MDA concentration was lower than those in the H group (P<0.05). Compared to the CK group, the H group exhibited blurred cell boundaries, incomplete hepatic lobule structure, and numerous hepatocytes with nuclear displacement and vacuolar degeneration. The H+AST4 group and H+AST8 group showed clear cell boundaries, polygonal shapes, large and round nuclei centrally located, with no significant changes compared to the CK group. The study indicates that adding 4 mg/kg of astaxanthin to the feed under histamine stress can reduce serum aminotransferase activity and hepatic MDA concentrations, enhance hepatic antioxidant capacity, and improve hepatic structure, benefiting hepatic health. Adding 8 mg/kg of astaxanthin does not further improve the above indicators in juvenile Anguilla rostrata. [ABSTRACT FROM AUTHOR]

The current study was aimed to examine the effect of grape seed proanthocyanidin extract (GSPE) on regulating lipid metabolism of American eels. A total of six cement tanks of fish were randomly divided into a control group fed with a commercial diet and a GSPE group fed with a commercial diet supplemented 400 mg/kg GSPE. There were three replicates in each group. Results suggested that GSPE could decrease the levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol, and increase the high-density lipoprotein cholesterol level in serum. GSPE might regulate lipid metabolism through upregulating linoleic acid metabolism and arachidonic acid metabolism along with downregulating metabolisms of phenylalanine, tyrosine, and tryptophan biosynthesis and valine, leucine, and isoleucine biosynthesis. [ABSTRACT FROM AUTHOR]