Gene-metabolite correlations underpin the hepatic fibrosis and metabolic disruption induced by methyltestosterone in juvenile Chinese longsnout catfish (Leiocassis longirostris).

Methyltestosterone (MT), a synthetic androgen frequently employed in aquaculture to induce sex reversal and boost growth rates, has yet to be extensively examined for its enduring effects on the health of fish. This study systematically evaluated the toxic effects of MT on the liver of Chinese longsnout catfish (Leiocassis longirostris) using an integrated approach of histopathology, transcriptomics, and metabolomics. The fish were subjected to three doses of MT (100 ng, 200 ng, and 300 ng) over 30 days, followed by pathological examinations of liver tissue. The study unveiled a novel discovery that MT induced perivascular fibrosis and abnormal protein accumulation in the liver, which bore a striking resemblance to effects seen in humans. Transcriptomic analysis pinpointed differentially expressed genes (DEGs) that were predominantly enriched in metabolic pathways, including those related to PPAR signaling, nitrogen metabolism, and cholesterol metabolism. Metabolomic analysis further revealed significant disruptions in the metabolic profiles of MT-treated fish, particularly in fatty acid and amino acid metabolism pathways. Key differential metabolites, such as oleic acid, phosphocholine, and various lipids and amino acids, were identified through VIP value screening. Correlation analysis showed MT induced liver fibrosis via upregulating fibrosis-related COL6A6 and disease related genes (F2R, ESR1, PGR). MT also induced lipid anabolism upregulation and amino acid metabolism suppression, linking MT to NAFLD-like obesity in fish. This study offers comprehensive insights into MT's hepatic toxicity, guiding safe aquaculture practices.