Effects of Camellia japonica Roots Extract on Myoblast Differentiation and Muscle Atrophy in Association with Mitochondrial Function

Skeletal muscle atrophy is caused by various diseases and conditions including aging, cancer, and cancer treatments. Chemotherapy-induced muscle atrophy leads to decrease quality of life and increase morbidity and mortality. Recent evidence suggests oxidative stress is a cause and/or consequence of mitochondrial dysfunction, which is strongly associated with muscle atrophy. Given Camellia japonica roots extract (CJT) has antioxidant property, we investigated whether CJT would ameliorate myoblast differentiation and chemotherapy-induced muscle atrophy in vitro and in vivo to provide evidence for candidates to prevent and treat muscle atrophy. C2C12 myoblasts were differentiated in the presence of CJT (0.1, 1, 10, and 100 ng/mL) and cells were collected to perform myosin heavy chain (MHC) immunostaining and qRT-PCR for the measurement of markers related with myogenesis and mitochondrial function. Wild type AB * zebrafish (Danio rerio) embryos were treated with FOLFIRI (5-FU, LV, and CPT-11) and CJT, and immunostained to detect slow and fast types of muscle. The Tg(Xla.Eef1a1: mlsEGFP) zebrafish line expressing mitochondria-targeted green fluorescent protein (mito-GFP) was used to monitor mitochondrial morphology. CJT increased the formation of MHC-positive multinucleated myotubes (≥5 nuclei) in a dose-dependent manner, while it decreased the number of mononuclear myotubes. CJT significantly enhanced the expression of myogenic differentiation markers including Myod (early stage), Myog (mid stage), and MHC isoforms (late stage) including Myh 1, Myh 2, Myh 4, and Myh7. Mitochondrial biogenesis markers such as SDHA (Complex Ⅱ) and COX1 (Complex IV) were significantly increased at 100 ng/mL of CJT than control. CJT tended to increase the expression of MFN2 and NRF1 involved in mitochondrial fusion and biogenesis, respectively. In addition, CJT alleviated FOLFIRI-induced muscle atrophy both in slow and fast muscle fibers in zebrafish embryos. Similarly, CJT improved FOLFIRI-induced mitochondrial dysfunction in a dose-dependent manner. Our data indicates that CJT promotes myogenesis and alleviates muscle atrophy in association with mitochondrial function, suggesting CJT has potential as a nutritional supplement for the prevention and treatment of muscle atrophy. NRF (2020R1C1C1007553 to S-EK)