Purpose: Skeletal muscle, accounting for approximately 40% of the total body mass, plays a critical role in movement, postural support, and metabolic homeostasis. Muscle mass is determined by the balance between protein synthesis and degradation, which is closely regulated by the mitochondrial function. Mitochondrial dysfunctions contribute to muscle loss by promoting oxidative stress and cellular damage. This study examined the effects of masutakeside I, a lignan glycoside derived from Styrax japonicus, on the mitochondrial function and muscle differentiation in C2C12 myoblasts. Methods: C2C12 myoblasts differentiated into myotubes in the presence of masutakeside I (0–10 ng/mL). Myogenic differentiation was assessed by myosin heavy chain (MHC) immunofluorescence, and multinucleated myotubes and relative diameters were quantified.The mitochondrial function was evaluated by measuring the mitochondrial reactive oxygen species (ROS), mitochondrial mass, and mitochondrial membrane potential using MitoSOX, MitoTracker Green, and JC-1 staining, respectively. Gene expression related to muscle differentiation, protein degradation, and the mitochondrial life cycle was analyzed using quantitative reverse transcription polymerase chain reaction. Results: Masutakeside I significantly increased the number of multinucleated (≥ 5 nuclei) MHC-positive myotubes and relative myotube diameter compared to the control. In addition, masutakeside I upregulated the myogenic markers, including phosphoinositide 3-kinase and MHC isoforms (Myh2, Myh4, and Myh7), while significantly downregulating protein degradation–related genes, including mothers against decapentaplegic homolog 2/3, forkhead box protein O1, atrogin-1, and muscle RING finger-1. Masutakeside I modulated the mRNA expression of the mitochondrial function and mitophagy-related markers, suggesting its potential involvement in mitochondrial quality control. Consistent with these effects, the mitochondrial ROS levels decreased, whereas mitochondrial mass and membrane potential increased. Conclusion These findings suggest that masutakeside I modulates the markers related to myogenic differentiation, muscle protein degradation, and mitochondrial function.

Purpose: The balance between synthesis and degradation of proteins plays a critical role in the maintenance of skeletal muscle mass. Mitochondrial dysfunction has been closely associated with skeletal muscle atrophy caused by aging, cancer, and chemotherapy.Polygalacin D is a saponin derivative isolated from Platycodon grandiflorum (Jacq.) A. DC. This study aimed to investigate the effects of polygalacin D on myoblast differentiation and muscle atrophy in association with mitochondrial function in in vitro and in zebrafish models in vivo. Methods: C2C12 myoblasts were cultured in differentiation media containing different concentrations of polygalacin D, followed by the immunostaining of the myotubes with myosin heavy chain (MHC). The mRNA expression of markers related to myogenesis, muscle atrophy, and mitochondrial function was determined by real-time quantitative reverse transcription polymerase chain reaction. Wild type AB* zebrafish (Danio rerio) embryos were treated with 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) with or without polygalacin D, and immunostained to detect slow and fast types of muscle fibers. The Tg(Xla.Eef1a1:mito-EGFP) zebrafish expressing mitochondria-targeted green fluorescent protein was used to monitor mitochondrial morphology. Results: The exposure of C2C12 myotubes to 0.1 ng/mL of polygalacin D increased the formation of MHC-positive multinucleated myotubes (≥ 8 nuclei) compared with the control.Polygalacin D significantly increased the expression of MHC isoforms (Myh1, Myh2, Myh4, and Myh7) involved in myoblast differentiation while it decreased the expression of atrophic markers including muscle RING-finger protein-1 (MuRF1), mothers against decapentaplegic homolog (Smad)2, and Smad3. In addition, polygalacin D promoted peroxisome proliferatoractivated receptor-gamma coactivator (Pgc1α) expression and reduced the level of mitochondrial fission regulators such as dynamin-1-like protein (Drp1) and mitochondrial fission 1 (Fis1). In a zebrafish model of FOLFIRI-induced muscle atrophy, polygalacin D improved not only mitochondrial dysfunction but also slow and fast muscle fiber atrophy. Conclusion These results demonstrated that polygalacin D promotes myogenesis and alleviates chemotherapy-induced muscle atrophy by improving mitochondrial function.Thus, polygalacin D could be useful as nutrition support to prevent and ameliorate muscle wasting and weakness.

Eight distinct bacteria were isolated form diseased mycelia of the edible mushroom, Pleurotus eryngii. 16S rDNA sequence analysis showed that the isolates belonged to a variety of bacterial genera including Bacillus (LBS5), Enterobacter (LBS1), Sphingomonas (LBS8 and LBS10), Staphylococcus (LBS3, LBS4 and LBS9) and Moraxella (LBS6). Among them, 4 bacterial isolates including LBS1, LBS4, LBS5, and LBS9 evidenced growth inhibitory activity on the mushroom mycelia. The inhibitory activity on the growth of the mushroom fruiting bodies was evaluated by the treatment of the bacterial culture broth or the heat-treated cell-free supernatant of the broth. The treatment of the culture broths or the cell-free supernatants of LBS4 or LBS9 completely inhibited the formation of the fruiting body, thereby suggesting that the inhibitory agent is a heat-stable compound. In the case of LBS5, only the bacterial cell-containing culture broth was capable of inhibiting the formation of the fruiting body, whereas the cell-free supernatant did not, which suggests that an inhibitory agent generated by LBS5 is a protein or a heat-labile chemical compound, potentially a fungal cell wall-degrading enzyme. The culture broth of LBS1 was not inhibitory. However, its cell-free supernatant was capable of inhibiting the formation of fruiting bodies. This indicates that LBS1 may produce an inhibitory heat-stable chemical compound which is readily degraded by its own secreted enzyme.
Agaricales ; Bacillus ; Bacteria ; DNA, Ribosomal ; Enterobacter ; Fruit ; Moraxella ; Ostreidae ; Pleurotus ; Sequence Analysis ; Sphingomonas ; Staphylococcus