Effects of different modes of exercise on skeletal muscle mass and function and IGF-1 signaling during early aging in mice

Skeletal muscle mass and function tend to decline with increasing age. Insulin-like growth factor 1 (IGF-1) plays a key role in promoting skeletal muscle growth. Exercise improves skeletal muscle mass and function via activating the IGF-1 signaling. The aim of this study was to investigate whether different types of exercise could promote muscle hypertrophy, exercise and metabolic capacities, and activate IGF-1 signaling in early aging mice. 12-month-old male C57/BL6 mice were randomly divided into five groups: control group (CON), aerobic exercise group (AE), resistance exercise group (RE), whole-body vibration group (WBV) and electrical stimulation group (ES). Muscle weight, myofiber size, levels of IGF-1 signaling, oxidative stress, protein synthesis and degradation, and apoptosis in gastrocnemius muscle were detected. C2C12 cells were used to explore the mechanism. In this study, we confirmed that four modes of exercise increased skeletal muscle mass, exercise capacity, indicators of metabolism and protein synthesis, and inhibited oxidative stress and apoptosis via activating the IGF-1 pathway. The most effective intervention was RE. We found that WBV promoted muscle hypertrophy better than AE. Furthermore, in vitro experiment, the importance of IGF-1 / IGF-1R-PI3K / Akt signaling for maintaining skeletal muscle mass was further confirmed. AE, RE, WBV and ES increase skeletal muscle mass, exercise capacities, protein synthesis and metabolic enzyme activities, inhibit protein degradation and apoptosis in mice undergoing early aging via activating IGF-1 signaling. Among them, WBV has been shown to be significantly effective and has a similar effect of conventional exercise in promoting muscle hypertrophy.