Quinine inhibits myogenic differentiation by disrupting AKT signaling pathway.

Sarcopenia is a disease characterized by decreased muscle fibers and mass. Although it mainly affects the older adults, it can also occur in various age groups as a secondary effect of medications used for treating certain diseases, such as cancer and diabetes. With population aging, sarcopenia has drawn significant attention owing to its increasing prevalence. However, its pathogenesis remains unclear, and no specific treatment is available. Natural products containing bioactive compounds have long been used as therapeutic agents and are crucial sources for drug development. However, the use of drugs derived from natural extracts is limited because of their ambiguous mechanisms of action and potential side effects. Therefore, a systematic analysis of the potential effects of using natural products is required. In this study, we investigated the effects of the antimalarial drug quinine on myogenic differentiation. Our findings revealed that quinine significantly inhibited the expression of marker genes and proteins associated with myogenic differentiation and markedly impaired muscle regeneration following injury. Furthermore, this reduction occurred when quinine selectively decreased the AKT signaling activity. Quinine reduced muscle protein and gene expression by modulating AKT signaling and inhibiting myogenic differentiation and muscle regeneration. Therefore, quinine may cause sarcopenia, and this risk should be considered when using quinine for treatment.