Effects of secondary plant metabolites on expression and activation of the insulin-like growth factor system in skeletal muscle

The insulin-like growth factor (IGF) system represents the most important endocrine system for controlling muscle accretion. Substantial evidence has been provided to demonstrate the importance of exercise and amino acid supply for its activation in skeletal muscle. However, expression and activity of the IGF system in muscle are also controlled by secondary plant metabolites (SPMs). SPMs are abundantly present in plants and, therefore, in plant-based nutrition. SPMs are formulated, sometimes at high doses, in food supplements designed to support immune functions or increase muscle accretion. In the present manuscript, recent evidence on the effects of SPMs on the expression and activation of the IGF system in skeletal muscle is collected and discussed. In fact, SPMs exert positive effects on muscle mass and accretion not only during growth and development in a wide spectrum of vertebrate species but also have great potential to protect muscle mass during stress, illness, and aging.