Effects of saline-alkaline stress on metabolomics profiles, biochemical parameters, and liver histopathology in large yellow croaker (Larimichthys crocea).

China has several saline-alkaline bodies. Studies on the adaptation of fish in saline-alkaline conditions are important for the efficient utilization of such areas. In this study, we employed a comprehensive approach combining histopathological analysis, biochemical markers, and metabolomic profiling to examine the impact of saline-alkaline stress on the liver of the large yellow croaker (Larimichthys crocea). It was found that the survival rate of L. crocea in the saline-alkaline treated group (EX) was significantly higher than that of the control group (CK). Saline-alkaline stress could not influence the structure of the liver of L. crocea, and not change the levels of superoxide dismutase (SOD), catalase (CAT), alkaline phosphatase (ALP), acid phosphatase (ACP). In addition, we identified 5953 metabolites, and 312 differentially expressed metabolites (DEMs) showed significant differential expression between the CK and EX groups. In the positive ion mode, 216 DEMs were identified, including 120 up-regulated and 96 down-regulated DEMs, and in the negative ion mode, 178 DEMs were identified, including 131 up-regulated and 47 down-regulated DEMs. Pathway enrichment analysis revealed significant involvement in 58 metabolic pathways, primarily linked to energy metabolism. These included the metabolism of amino acid, carbohydrate, and lipid pathways, including cysteine and methionine metabolism, biosynthesis of valine, leucine, isoleucine, and ascorbate; aldarate metabolism; galactose metabolism; glycerophospholipid metabolism; and the biosynthesis of unsaturated fatty acids. Metabolomics revealed that increased synthesis of compounds, such as succinic acid, arachidonic acid, and L-gulonic acid in the liver of L.crocea, is associated with adaptation to saline-alkaline aquaculture conditions. The findings of this study indicated that the fish mitigate reactive oxygen species induced by hyperosmotic environments and improve cellular membrane fluidity and intercellular signal transduction through the metabolism of unsaturated fatty acids and carbohydrates, facilitating adaptation to saline-alkaline conditions.