ROS/RNS-related adaptations of skeletal muscles to aerobic exercise

Cellular metabolic processes produce Reactive Oxygen and Nitrogen Species (ROS/RNS) in small amounts in the course of normal activities. In skeletal muscle ROS/RNS production is greatly enhanced by contractile activity (1). Aerobic exercise training is known to induce a number of relevant adaptations in skeletal muscle, including fiber-type and metabolic shift of fast-twitch/glycolytic fibers towards a more fatigue-resistant and oxidative phenotype (2,3). On the other hand, excess ROS/RNS production is potentially damaging (4). Aim of the present work was to evaluate which adaptations are induced by moderate aerobic training in two opposite types of muscle cells: Tibialis Anterior (fast-twitch/glycolytic) and Soleus (slow-twitch/oxidative), with special attention to ROS/RNS-induced or -regulated pathways. Moreover, we intended to examine whether moderate exercise training caused ROS/RNS-related damages and/or activated defensive responses. Experimentation was carried out on 12 young male Sprague-Dowley rats which were gradually trained to run on a treadmill 1hr/day, 3 times/week, 14 weeks and reached ~60% VO2max at the end of training. Unexpectedly, training-induced ROS/RNS signaling promoted cell proliferation in both types of muscle cells; the small consequent redox unbalance activated, rather than inhibited, calcium-handling molecules and channels. Moderate exercise training was not damaging, probably because anti-oxidant and cytoprotective mechanisms were induced, however some oxidative stress markers appeared. Relevant results are summarized in the diagram below. References: 1. McArdle A et al. Am. J Physiol Cell Physiol 2001; 280: C621-C627. 2. Flück M, Hoppeler H.. Rev Physiol Biochem Pharmacol 2003; 146: 159-216. 3. Marini M, Veicsteinas A. European Journal Translational Myology - Myology Reviews 2010; 20: 113-128. 4. Sahlin K et al. J Appl Physiol 2010; 108: 780-787.