Abstract
This study investigated the epigenetic mechanisms through which graded levels of dietary methionine (Met) regulates growth, muscle quality, and health in juvenile Megalobrama amblycephala fed an all-plant-protein diet. Dietary Met supplementation improved growth performance in a dose-dependent manner and enhanced muscle nutritional quality, particularly protein content and amino acid composition. Optimal Met intake also strengthened hepatic antioxidant defenses, stabilized mitochondrial function, and modulated plasma metabolite profiles, including metabolites associated with antioxidant, anti-inflammatory, and antimicrobial activity. Epigenetic analysis revealed that dietary Met influenced hepatic N(6)-methyladenosine (m(6)A) RNA methylation and the expression of genes involved in autophagy and apoptosis, suggesting that these molecular pathways contribute to the observed physiological benefits. Collectively, these findings indicate that appropriate dietary Met of 10.1 g/kg not only supports growth and nutrient utilization but also promotes metabolic and cellular homeostasis through epigenetic regulation. This work provides novel insights into the nutritional and molecular strategies for improving the health and performance of juvenile M. amblycephala under plant-based feeding regimes, with potential implications for sustainable aquaculture practices.