Transcriptomic and Metabolomic Insights into the Hepatic Response to Dietary Carvacrol in Pengze Crucian Carp (Carassius auratus var. Pengze)

Abstract

Background/Objectives: Carvacrol, a major active component of oregano oil and common feed additive, has been widely studied for its effects on fish growth, immunity, and intestinal health. But its transcriptional/metabolic impacts on fish liver remain unclear. This study investigated these effects in Pengze crucian carp (Carassius auratus var. Pengze). Methods: Fish were fed a basal diet (control) or basal diet supplemented with 10% microencapsulated carvacrol (600 mg/kg) for 56 days; liver samples were analyzed via transcriptomics and metabolomics. Results: Transcriptomic analysis revealed 482 differentially expressed genes (DEGs) in the liver of Pengze crucian carp following carvacrol supplementation, with 158 upregulated and 324 downregulated genes. Functional annotation highlighted enrichment in translation, signal transduction, amino acid metabolism, and posttranslational modification pathways. GO analysis further identified key processes, including carboxylic acid transport, tRNA aminoacylation, and mitochondrial nucleoid function, while KEGG pathways were implicated in amino acid biosynthesis, lipid metabolism (e.g., alpha-linolenic acid), and insulin signaling. Metabolomic profiling identified 679 significantly altered metabolites, including 113 upregulated and 566 downregulated ones. Among these, upregulated compounds like L-asparaginyl-L-lysine (Log₂FC = 4.36) and 2′-Deoxyadenosine-5′-diphosphate (Log₂FC = 4.31) are linked to nucleotide metabolism, and downregulated peptides (e.g., Ala-Phe-Tyr-Arg) suggesting modulated protein turnover. Joint omics analysis revealed convergent pathways in glycerophospholipid metabolism, aminoacyl-tRNA biosynthesis, and autophagy. Notably, the chaperone gene dnaja3b was correlated strongly with neuroactive metabolites (e.g., normetanephrine), potentially implicating carvacrol in stress response regulation. Conclusions: Our findings demonstrate that carvacrol modulates liver gene expression and metabolic profiles, primarily influencing amino acid and lipid metabolism pathways, autophagy, and stress responses. The observed correlations between dnaja3b and specific metabolites offer mechanistic insights into the action of carvacrol in fish liver.