Sedentary lifestyle induces oxidative stress and atrophy in rat skeletal muscle.

Abundant evidence indicates that skeletal muscle plays a key role in regulating metabolic homeostasis. Therefore, maintaining healthy skeletal muscles is essential to good health. While prolonged muscle inactivity is known to cause oxidative stress and muscle loss, it remains unclear whether a shift from an active to a sedentary lifestyle induces similar effects. This study tested the hypothesis that transitioning to a sedentary lifestyle rapidly leads to oxidative stress and muscle loss in the load-bearing soleus muscle. Adult Wistar rats were randomly divided into control (CON; n = 8) and sedentary (SED; n = 8) groups. During a 7-day experimental period, CON rats were housed in standard cages allowing free movement, while SED rats were confined to smaller cages promoting sedentary behaviour. Soleus muscles were analysed for antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX)), as well as two oxidative stress biomarkers (advanced protein oxidation products (AOPPs) and 4-hydroxynonenal (4-HNE)). Sedentary behaviour caused a 17.2% reduction in the soleus-to-body weight ratio (P < 0.001). Moreover, the activities of SOD, CAT and GPX were significantly lower in the soleus muscle of SED animals (P < 0.05), while AOPPs and 4-HNE levels were higher (P < 0.001 and P < 0.05) compared to CON animals. These findings provide the first evidence that transitioning from an active to a sedentary lifestyle leads to the rapid onset of oxidative stress and atrophy in the soleus muscle. Importantly, the results suggest that impaired antioxidant defences contribute to sedentary behaviour-induced oxidative stress in load-bearing muscles.