Effects of moderate exercise on hepatic amino acid and fatty acid composition, liver transcriptome, and intestinal microbiota in channel catfish (Ictalurus punctatus)

Previous research on swimming exercise in fish has focused on muscle building and quality of flesh. However, the effects of hepatic amino acid and fatty acid composition, liver gene expression profile, and intestinal microbiota are poorly understood. In this study, channel catfish (Ictalurus punctatus) were subjected to a 4-week swimming exercise, and liver transcriptome and intestinal microbiota analyses were performed to broaden our understanding of fish under exercise. When compared to non-exercised channel catfish (N-EXF), exercised channel catfish (EXF) had improved arachidonic acid (C20:4n6; ARA), docosahexaenoic acid (C22:6n3; DHA), aspartic acid (Asp) and glycine (Gly). The liver transcriptome analysis revealed 2912 differentially expressed genes and numerous enriched signaling pathways including those involved in nutrient synthesis, such as biosynthesis of unsaturated fatty acids and amino acids; glucose metabolism, such as glycolysis/gluconeogenesis, insulin signaling, and AMPK signaling pathways; and oxygen transport, such as HIF-1, PI3K-Akt, and MAPK signaling pathways. In addition, bacterial 16S rRNA gene sequencing data revealed that long-term exercise increased bacterial diversity and richness, and changed the intestinal microbial composition in channel catfish. In summary, this study provides insights into hepatic metabolic pathways, candidate genes, and intestinal microbiota underlying the long-term exercised channel catfish.