Effects of Porphyra yezoensis polysaccharide on antioxidant and liver health of spotted sea bass, Lateolabrax maculatus

This study investigated the effects of Porphyra yezoensis polysaccharide (PP) on the antioxidant and liver health of spotted sea bass (Lateolabrax maculatus). A total of 360 spotted sea bass (10.53 ± 0.02 g) were divided into 6 groups on average, and the diets of these groups were supplemented with 0, 3, 6, 9, 12, and 15 g/kg PP (control group: K, PP1, PP2, PP3, PP4, and PP5), respectively. The experiment lasted for 52 days. The results showed that, compared with the control group, the serum glutathione (GSH) content was significantly increased and the malondialdehyde (MDA) content was significantly decreased in the PP1 group. The serum catalase (CAT) activity was significantly increased in the PP1, PP2, PP3, and PP4 groups. Additionally, the superoxide dismutase (SOD) activity was significantly increased in the PP2 and PP3 groups. In terms of liver antioxidant indexes, GSH and MDA content were not significantly different among all groups. CAT activity in the PP2 and PP3 groups was significantly higher than that in the control group, and SOD activity in the PP4 groups was significantly higher than that in the control group. The activity of amylase (AMS) and trypsin (TRS) was significantly increased in the PP1, PP2, PP3, and PP4 groups compared to the control group. Additionally, the activity of lipase (LPS) was significantly increased in the PP5 group compared to the control group. Liver injury indexes showed that serum GOT and GPT activities in the PP3 group were significantly lower than those in the control group. There was no significant difference in T-CHO and TG between the experimental group and the control group. Histological analysis showed that dietary PP improved liver cell morphology and reduced fat vacuoles. Liver transcriptome analysis of the control group and the PP4 group showed that the main change pathways were arachidonic acid metabolism, purine metabolism, and fatty acid degradation. In addition, PP regulates fibroblast growth factor 19 (FGF19), solute carrier family 3,expression of member 2 (SLC3A2), angiopoietin-like 8 (ANGPTL8), thrombospondin 1 (THBS1), tyrosinase (TYR), and kelch-like protein 19 (KEAP1) genes, making adjustments to liver health and function. In summary, PP increased the antioxidant capacity and improved the liver health of spotted sea bass.