Effects of Corn oligopeptide on Dexamethasone-induced muscle atrophy in Sprague-Dawley rats

Abstract Corn oligopeptide (COP) derived from corn gluten meal (CGM) was proved to possess plenty of biological properties. However, there is no scientific evidence to support that COP can ameliorate muscle atrophy. To find a new therapeutic nutritional substrate of muscle atrophy, we investigated the anti-myopathy effects of COP in DEX-inducted rat muscle atrophy model and tried to explore the underlying mechanisms. Co-administration of COP (2.0g/kg.bw) with DEX for 5 weeks reversed DEX-induced reduction in gastrocnemius (Gas) and plantaris (Pla) muscles weight, grip strength, exercise tolerance and myofiber cross sectional area (CSA) of soleus (Sol), up-regulated the protein levels of Phospho-Akt and mTOR that are closely relate to protein synthesis, and down-regulated the expression of FoxO3a, NF-κBp65, Atrogin-1, MuRF-1, LC3 and ULK1 that are the key components of Ubiquitin–proteasome system and Autophagy that activate proteolysis. In addition, according to muscles weight, grip strength, exercise tolerance changing over experiment time, we found the three indexes were all improved at 3rd week. Therefore, we conclude that the optimal duration for COP to improve DEX-induced muscle atrophy might be 3 weeks, and mechanistically, COP activates protein synthesis through Akt/mTOR pathway, while inhibits proteolysis by inactivating the expression of Ubiquitin proteasome system (UPS) and Autophagy.