BCAA combined resistance exercise alleviate disuse muscle atrophy via the upregulation of LAT1-4F2HC complex

Background: Immobilization leads to the reduction of mechanical load on skeletal muscle, further resulting in muscle atrophy, also known as disuse muscle atrophy. Recent studies have demonstrated the effect of disuse muscle atrophy on protein turnover through the regulation of amino acid transporters. OBJECTIVE: The purpose of the study is to examine the effect of BCAA injection and resistance training on amino acids transporters in disuse muscle atrophy rats. Hypothesis: BCAA injection combined with resistance training can upregulate amino acid transporters, improve muscle protein synthesize and alleviate disuse muscle atrophy. Methods: 31 male Sprague–Dawley rats aged 8 weeks were used in this study. All rats received a left hindlimb immobilization for 4 weeks after a one-week acclimatization. After the immobilization procedure, body composition of rats was measured by DEXA. All rats were randomly divided into four groups: control placebo (CP, n=8), exercise placebo (EP, n=8), BCAA control (CB, n=8), and BCAA exercise (EB, n=7) and received oral gavage of BCAAs or resistance training for the following 4 weeks. The weight of gastrocnemius muscles was measured and were used to measure the expression of amino acids transporters and muscle synthesis proteins. Results: (1) For gastrocnemius muscle mass, no statistical difference was not observed between four groups (p>0.05). (2) The expression of LAT1 and 4F2HC were significantly increased in EB group compared to CP group (p< 0.05). No statistical difference was observed in CB and EP groups compared to CP group (p>0.05). However, the expression of SNAT2 shows no statistical difference between four groups. (3) For the expression of mTOR signaling pathway, the expression of mTOR was significantly increased in EB group compared to CP (p< 0.01) and EP group (p< 0.05). the expression of S6K1 significantly increased in EB group compared to CP (p< 0.05) and CB group (p< 0.05). (4) membrane localization of LAT1 was significantly increased in EB group compared to CP group (p< 0.05). Conclusion: BCAA combined resistance exercise upregulates the expression of amnio acids transporter LAT1 and 4F2HC, as well as the expression of mTOR and S6K1, suggesting that BCAA combined resistance exercise alleviated disuse muscle atrophy through the increasing of muscle protein synthesis. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.