Effects of silk fibroin on myoblasts differentiation in C2C12 cells

Sarcopenia is characterized by the progressive loss of skeletal muscle mass and function, largely associated with impaired myogenic differentiation and protein synthesis. This study investigated the effects of silk fibroin derived from Bombyx mori cocoons on myogenic differentiation and myotube formation in C2C12 myoblasts and explored the underlying molecular mechanisms associated with the mTOR signaling pathway. Silk fibroin was primarily composed of glycine, alanine, and serine of free amino acids and contained branched-chain amino acids, including valine, leucine, and isoleucine. Silk fibroin treatment enhanced myotube formation and significantly increased myotube diameter, reaching 12.47 μm at 50 µg/mL compared with 9.90 μm in the control group. Furthermore, treatment with 50 µg/mL silk fibroin markedly upregulated the mRNA expression of Mtor , Rptor , and Irs2 , whereas Rictor , Prkaa1 , and Prkaa2 expression remained unchanged. At the protein level, silk fibroin significantly increased the p-mTOR/mTOR ratio and elevated myogenin expression. Therefore, silk fibroin promoted myogenic differentiation and myotube maturation in C2C12 cells through activation of mTOR signaling, particularly the mTORC1-associated pathway. These findings suggest that silk fibroin may have potential as a functional ingredient or biomaterial for improving skeletal muscle health.