Integrated transcriptomics and metabolomics analysis of the intestine of cobia (Rachycentron canadum) under hypoxia stress

In intensive aquaculture systems , dissolved oxygen (DO) is the most critical and limiting factor for the development and health of aquatic organisms. Hypoxia is a common phenomenon in aquaculture. Its effects on fish’s growth and immune system have been widely reported, but the molecular mechanisms of hypoxic stress on damage to the fish gut are not fully understood. Additionally, studies on the effects of hypoxic stress on the intestinal metabolism of cobia ( Rachycentron canadum ) are still limited. Therefore, this study used cobia to explore the effects of hypoxic stress on intestinal metabolism. In this study, the combination of high-throughput RNA sequencing (RNA-Seq) and non-targeted liquid chromatography-mass spectrometry (LC-MS) based metabolomics analyses were used to investigate changes in key genes and metabolites in the intestinal tract of juvenile cobia after 28 days of hypoxic stress (DO: 3.15 ± 0.21 mg/L). Transcriptomics analysis revealed the significant enrichment of 62 metabolic pathways, including glutathione metabolism, fat digestion and absorption, bile secretion, glycerolipid metabolism, tricarboxylic acid cycle, glycolysis/gluconeogenesis, and other pathways. Metabolomics analysis revealed that most of the significantly differential metabolites were related to the metabolism of amino acids and lipids. The combined transcriptomics and metabolomics analyses showed that the sustained hypoxic stress could cause some degree of oxidative damage to the gut of cobia, thereby interfering with its digestive absorption and physiological and metabolic processes, such as abnormalities in antioxidant and detoxification functions, disturbances in the metabolisms of amino acids, lipids, and carbohydrates, and reduction of ion transport capacity. These findings might help understand the molecular mechanisms of the intestinal tract under hypoxic stress in cobia, thereby reducing the damage caused by hypoxic stress to farmed fish. • Hypoxia stress leads to antioxidant and detoxification dysfunction of cobia intestinal tract. • Hypoxia stress leads to the disorder of intestinal amino acid metabolism and lipid metabolism of cobia. • Cobia adapts to low oxygen conditions by producing energy through intestinal glycolysis. • Hypoxic stress resulted in decreased ion transport capacity of cobia. • These findings might help in understanding the molecular mechanisms of intestinal tract under hypoxic stress in cobia and fish in genera.