Effects of Dietary Alpha-Lipoic Acid on Growth Performance, Serum Biochemical Indexes, Liver Antioxidant Capacity and Transcriptome of Juvenile Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂)

SIMPLE SUMMARY: As global demand for animal protein increases, the entire animal production system is gradually moving towards intensification. The aquaculture industry is growing rapidly, but it is vulnerable to disease and environmental stress, resulting in aquaculture losses. Antioxidant supplementation in diets can improve the resistance of fish to environmental stress, which is an important measure to reduce the loss of the aquaculture industry. Alpha-lipoic acid (α-LA) is considered to be a “general antioxidant” or “ideal antioxidant” which has a strong antioxidant capacity. In this study, juvenile hybrid groupers were fed a diet supplemented with α-LA for 56 days. The results indicated that the addition of 0.4 and 0.6 g/kg α-LA to the diet inhibited the growth performance of juvenile hybrid groupers. Furthermore, 1.2 g/kg α-LA could reduce the blood lipid level, improve hepatocyte damage, and increase the antioxidant enzyme activity of the liver. In addition, transcriptome results indicated that dietary α-LA significantly affected the pathway related to immune function (the JAK/STAT signaling pathway, prolactin signaling pathway, and antigen processing and presentation) and glucose homeostasis (glycolysis/gluconeogenesis). ABSTRACT: We aimed to investigate the effects of dietary alpha-lipoic acid (α-LA) on the growth performance, serum biochemical indexes, liver morphology, antioxidant capacity, and transcriptome of juvenile hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂). Four experimental diets supplemented with 0 (SL0), 0.4 (L1), 0.6 (L2), and 1.2 (L3) g/kg α-LA were formulated and fed to three replicates of juvenile hybrid grouper (24.06 ± 0.15 g) for 56 d. The results indicated that dietary 0.4 and 0.6 g/kg α-LA significantly decreased the weight gain rate in juvenile hybrid groupers. Compared with SL0, the content of total protein in the serum of L1, L2, and L3 increased significantly, and alanine aminotransferase decreased significantly. The content of albumin in the serum of L3 increased significantly, and triglyceride, total cholesterol, and aspartate aminotransferase decreased significantly. In addition, the hepatocyte morphology in L1, L2, and L3 all showed varying degrees of improvement, and the activities of glutathione peroxidase and superoxide dismutase in the liver of L2 and L3 were significantly increased. A total of 42 differentially expressed genes were screened in the transcriptome data. KEGG showed that a total of 12 pathways were significantly enriched, including the pathway related to immune function and glucose homeostasis. The expression of genes (ifnk, prl4a1, prl3b1, and ctsl) related to immune were significantly up-regulated, and the expressions of gapdh and eno1 genes related to glucose homeostasis were significantly down-regulated and up-regulated, respectively. In summary, dietary supplementation of 0.4 and 0.6 g/kg α-LA inhibited the growth performance of juvenile hybrid groupers. A total of 1.2 g/kg α-LA could reduce the blood lipid level, improve hepatocyte damage, and increase the hepatic antioxidant enzyme activity. Dietary α-LA significantly affected the pathway related to immune function and glucose homeostasis.