Isoliquiritigenin, an Extract from Licorice, Attenuates Dexamethasone-Induced Muscle Atrophy via Akt/mTOR Pathway

Muscle atrophy is a pathological condition characterized by the excessive degradation of muscle proteins, leading to impaired physical performance. Isoliquiritigenin (ISL) is a promising extract known for its medical effects; however, its impact on muscle atrophy remains unclear. We investigated the effects of ISL on muscle atrophy both in vitro and in vivo. The results showed that 5-µM ISL exhibited no significant cytotoxicity on C2C12 cells, as reflected by cell count kit-8 and 5-ethynyl-2'-deoxyuridine (EdU) tests. ISL increased the diameter of myotubes and downregulated forkhead box O proteins, muscle-specific RING finger protein 1 (MuRF-1), and Atrogin-1 induced by Dexamethasone (Dex). ISL could also enhance the phosphorylation of Akt, the mammalian target of rapamycin (mTOR), eIF4E-binding protein 1, and p70 S6 kinase in C2C12 myotubes. In animal experiments, ISL increased the muscle mass, improved the cross-sectional area of muscles, and inhibited the expression of MuRF-1 and Atrogin-1 in muscle tissues. For physical performance, ISL enhanced grip strength and running endurance. ISL ameliorated Dex-induced muscle atrophy both in vitro and in vivo, associated with increased diameter of myotubes and decreased Atrogin-1 and MuRF-1 expression via the Akt/mTOR signaling pathway. This suggested that ISL could be used as a natural drug for muscle atrophy.