Acute high-temperature stress induces fatty liver accompanied by ferroptosis, inflammation and gut bacteria imbalance in largemouth bass (Micropterus salmoides)

With the development of global warming, extreme high-temperature weather events have frequently occurred. Elevated water temperature can promote lipid deposition in the liver of fish and then cause fish death, ultimately leading to considerable economic losses in fish aquaculture. However, the effects of acute high-temperature stress on lipid metabolism in largemouth bass and the underlying regulatory mechanisms remain unknown. The present study hypothesized that acute high-temperature stress induces fatty liver syndrome in largemouth bass ( Micropterus salmoides ), accompanied with intestinal barrier damage, gut microbial dysbiosis, and hepatic ferroptosis and inflammatory responses. In this study, histological analysis, gene expression analysis, and biochemical index detection combined with omics technologies were employed to investigate the prominent alterations in gut and liver induced by acute high-temperature stress. Our results demonstrated that acute high-temperature stress might induce lipid deposition by promoting fatty acid synthesis. In addition, acute high-temperature stress regulated intercellular lipid homeostasis by affecting the contents of lipid classes in fish. Moreover, hepatocyte ferroptosis and inflammation in largemouth bass were observed alongside fatty liver induced by high temperature. After acute high-temperature stress, the intestine exhibited histological abnormalities, and the expression of tight-junction protein-related genes were significantly downregulated. The results based on 16S rDNA amplicon sequencing analysis showed that the abundance and composition of intestinal bacteria were altered. Specifically, differentially abundant bacterial genera exhibited significant correlation with host metabolism, such as lipid metabolism. The present study demonstrated that acute high-temperature stress induced fatty liver syndrome in largemouth bass ( Micropterus salmoides ), accompanied with intestinal barrier damage, gut microbial dysbiosis, and hepatic ferroptosis and inflammatory responses. Our study preliminarily explored the pathogenic mechanism of fatty liver in largemouth bass under acute high heat stress, laying a foundation for further studies on the pathogenesis of fatty liver in fish.