Endurance training increases mitochondrial myoglobin and enhances its interaction with complex IV in rat plantaris muscle.

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.