Multi-omics analysis reveals the glycolipid metabolism response mechanism in the liver of genetically improved farmed Tilapia (GIFT, Oreochromis niloticus) under hypoxia stress

Dissolved oxygen (DO) in the water is a vital abiotic factor in aquatic animal farming. A hypoxic environment affects the growth, metabolism, and immune system of fish. Glycolipid metabolism is a vital energy pathway under acute hypoxic stress, and it plays a significant role in the adaptation of fish to stressful environments. In this study, we used multi-omics integrative analyses to explore the mechanisms of hypoxia adaptation in Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus). The 96 h median lethal hypoxia (96 h-LH50) for GIFT was determined by linear interpolation. We established control (DO: 5.00 mg/L) groups (CG) and hypoxic stress (96 h-LH50: 0.55 mg/L) groups (HG) and extracted liver tissues for high-throughput transcriptome and metabolome sequencing. A total of 581 differentially expressed (DE) genes and 93 DE metabolites were detected between the CG and the HG. Combined analyses of the transcriptome and metabolome revealed that glycolysis/gluconeogenesis and the insulin signaling pathway were down-regulated, the pentose phosphate pathway was activated, and the biosynthesis of unsaturated fatty acids and fatty acid metabolism were up-regulated in GIFT under hypoxia stress. The results show that lipid metabolism became the primary pathway in GIFT under acute hypoxia stress. Our findings reveal the changes in metabolites and gene expression that occur under hypoxia stress, and shed light on the regulatory pathways that function under such conditions. Ultimately, this information will be useful to devise strategies to decrease the damage caused by hypoxia stress in farmed fish.