Kazumi Masuda

Aim Endurance exercise training is known to increase mitochondrial respiration in skeletal muscle. However, the molecular mechanisms behind this are not fully understood. Myoglobin (Mb) is a member of the globin family, which is highly expressed in skeletal and cardiac muscles. We recently found that Mb localizes inside mitochondria in skeletal muscle and interacts with cytochrome c oxidase subunit IV (COXIV), a subunit of mitochondrial complex IV, which regulates respiration by augmenting complex IV activity. In the present study, we investigated the effect of endurance training on Mb‐COXIV interaction within mitochondria in rat skeletal muscle. Methods Eight‐week‐old male Wistar rats were subjected to 6‐week treadmill running training. Forty‐eight hours after the last training session, the plantaris muscle was removed under anesthesia and used for biochemical analysis. Results The endurance training increased mitochondrial content in the skeletal muscle. It also augmented complex IV‐dependent oxygen consumption and complex IV activity in isolated mitochondria from skeletal muscle. Furthermore, endurance training increased Mb expression at the whole muscle level. Importantly, mitochondrial Mb content and Mb‐COXIV binding were increased by endurance training. Conclusion These findings suggest that an increase in mitochondrial Mb and the concomitant enhancement of Mb interaction with COXIV may contribute to the endurance training‐induced upregulation of mitochondrial respiration by augmenting complex IV activity.