One session of exercise regulates cathepsin B activity in the livers of trained and untrained rats

Physical exercise causes adaptive changes, mainly in muscles, but it also influences other organs, including liver. Most changes are beneficial; however, strenuous exercise is a strong stressor, and it can result in splanchnic hypoperfusion with subsequent disturbances in liver homeostasis and energy. Cathepsin B is a protease linked to protein turnover and extracellular matrix degradation. It is also involved in autophagy and the activation of proinflammatory and profibrotic pathways. This study investigated the influences of one session of exercise and endurance training on the mRNA, protein level, and activity of cathepsin B in rat liver. Healthy rats were randomly divided into two groups (n = 30, each); one group was untrained and the other received 6-weeks of endurance training with an increasing load. For each group, rats were sacrificed before (controls, n = 10), immediately after (n = 10), and 3 h after (n = 10) an acute bout of intense exercise. Liver gene expression was evaluated with quantitative real-time PCR. Liver protein content was measured with ELISA. Liver enzyme activity was measured fluorometrically. One session of exercise or training did not influence cathepsin B gene expression or protein concentration at any investigated time point. In untrained rats, cathepsin B activity decreased 3 hours after (P = 0.027) one session of exercise. In trained rats, cathepsin B activity increased immediately (P = 0.005) after one session of exercise. Training did not influence baseline cathepsin B activity. In conclusion, one session of exercise differentially influenced cathepsin B activity in the liver, depending on training status.