Effects of branched-chain amino acids on starvation-induced macroautophagy and chaperone-mediated autophagy in common carp (Cyprinus carpio)

Most fish experience starvation stress during overwintering, typically resulting in excessive protein degradation and muscle atrophy. Branched-chain amino acids (BCAAs), are important substrates for protein synthesis and play active roles in promoting muscle growth. Although BCAAs have received widespread attention for their role in autophagy regulation, their ability to alleviate starvation-induced damage via macroautophagy and chaperone-mediated autophagy (CMA) pathways remains unclear. In this study, common carp were starved for 7 or 14 days, then administered BCAAs alone via gavage at 1.25 g/kg for 14 days. Starvation induced muscle atrophy and autophagy-related structural changes in carp muscle. Supplementation with BCAAs helped restore normal tissue morphology. Macroautophagy-related ( atg4b , atg12 , and lc3 ) and CMA-related ( hsp70 and lamp2a ) gene expression was upregulated under starvation conditions. These genes were downregulated after supplementation with BCAAs, whereas p62 and gfap showed the opposite trend. At the protein level, LC3-II, lysosome-associated membrane protein 2A (LAMP2A), and heat shock protein 70 (HSP70) were upregulated after starvation and downregulated after supplementation with BCAAs, but P62 showed the opposite trend. In addition, branched-chain amino acid transaminase (BCAT) and branched-chain ketoacid dehydrogenase (BCKDH) enzyme activity assays revealed that supplementation with BCAAs significantly increased amino acid metabolism. Overall, supplementation with BCAAs reduced macroautophagy and CMA levels in carp muscle tissues during starvation stress, and enhanced metabolic utilization of BCAAs. This study provides valuable insights for developing nutritional strategies to reduce starvation-induced muscle atrophy. These findings may help improve fish health and flesh quality during overwintering or feed restriction in aquaculture. • Starvation induces macroautophagy and the CMA pathway, with a temporal sequence and mutual interference. • BCAAs regulate autophagy and apoptosis in starved carp muscle, showing better efficacy than individual amino acids. • BCAAs may affect autophagy and muscle protein synthesis by activating the mTOR pathway and modulating key factors. • Supplementation with BCAAs during starvation enhances amino acid synthesis and suppresses catabolism in skeletal muscle.