Glutathione and astaxanthin: Both enhance antioxidant capacity and regulate lipid metabolism in Pacific white shrimp (Litopenaeus vannamei) fed with high-lipid diets

Glutathione (GSH) and astaxanthin (AX) have the function of helping lipid metabolism and antioxidant capacity; which one is better? The feeding experiment of an 8 weeks was conducted to investigate the advantages of these two working on <i>Litopenaeus vannamei</i> fed with high-lipid diets. Four diets were formulated: basal diet (CON, 9 % lipid content); high-lipid diet (HL, 11 % lipid content); and supplementation with 6.7 g/kg Glutathione-rich yeast hydrolysate (GSH, 5 %) and 0.3 g/kg Carophyll^Ⓡ Pink (AX, 10 %) based on the HL diet, recorded as HLG and HLA, respectively. The results demonstrated a clear distinction between these two supplements. Compared to the HL group, shrimp in the HLG and HLA groups exhibited a consistent pattern of improvement that significantly reduced hepatic triglyceride levels, markedly downregulated expression of the fatty acid synthase (<i>fas</i>) gene, and enhanced activities of the key antioxidant enzymes catalase and glutathione peroxidase. Compared to the HLA group, the HLG group exhibited upregulation of triacylglycerol lipase (<i>tgl</i>) and glucose-6-phosphatedehydrogenase (<i>g6pdh</i>) gene expression and lower TG content. Shrimp fed HLG diet exhibited superior overall performance, maintaining growth at levels equivalent to the control (CON) group. Specifically, the HLG group showed significantly greater thickness of intestinal muscular layer, and height and width for intestinal villus compared to both the HL and HLA groups (<i>P</i> < 0.05). In summary, while both additives mitigated hepatic lipid accumulation and oxidative stress, GSH delivered stronger benefits for growth performance through regulating antioxidant capacity and intestinal health when shrimp fed high-lipid diet.