Temporal effects of perfluorononanoic acid (PFNA) exposure on metabolic disorders and gut-liver axis injury in large yellow croaker (Larimichthys crocea).

To investigate the toxic effects of PFNA on aquatic organisms, this study used large yellow croaker (L. crocea) as a model and examined the impacts of 1000 ng/L PFNA exposure for 3, 7, and 14 days on the hepatic and intestinal systems. Histopathological examination, transcriptomic profiling, and 16S rRNA gene sequencing were employed to evaluate tissue damage, gene expression changes, and gut microbial alterations. The results revealed that PFNA exposure induced progressive histopathological changes in the liver, including nuclear enlargement and vacuolization, with increasing severity over time. In the intestine, PFNA caused structural damage to villi, characterized initially by vacuolization and subsequently by erosion, swelling, and dissolution as exposure duration increased. Transcriptomic analysis of liver showed early activation of the peroxisome proliferator-activated receptor (PPAR) signaling pathway, followed by the predominant enrichment of the phosphatidylinositol-3-kinase/protein kinase B (PI3K-Akt) pathway at later stages. These findings suggest a "two-phase" mechanism by which PFNA disrupted lipid and carbohydrate metabolism. Gut microbiota analysis showed that PFNA exposure significantly reduced α-diversity, increased the abundance of Proteobacteria, enriched opportunistic pathogens such as Vibrio spp., and altered functional profiles related to amino acid and carbohydrate metabolism. Correlation analysis identified significant associations between specific gut microbial taxa (e.g., Deferribacterota, Dependentiae) and the expression levels of key hepatic metabolic genes (lpl, foxo3), suggesting a potential mediating role of the gut-liver axis in PFNA-induced hepatotoxicity. From the perspective of aquaculture, this study provided a view of metabolic disruption and host-microbe interaction caused by PFNA. It contributes critical scientific evidence for assessing the ecological risks of per- and polyfluoroalkyl substances (PFAS) in aquatic environments.