Photo of zebrafish (Danio rerio) by Azul (Own work) [Copyrighted free use], via Wikimedia Commons
We all know that aerobic exercise is good for us because it helps improve muscle function and our ability to move well. For fish, aerobic exercise helps animals escape predators, catch prey as well as improve reproduction success. When we exercise, our muscles adapt by altering the metabolism of energy, the way calcium is handled as well as the type of contractile proteins present in the muscle. Together these changes alter how muscles contract. Histone deacetylases (HDAC) are known to change gene expression rather quickly. For this reason, researchers wanted to know if HDAC were responsible for causing short term changes in muscles of exercising zebrafish (Danio rerio). Their findings were published last month in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. Fish that were able to sustain swimming exercise had higher aerobic metabolism and calcium handling as well as more slow contractile muscle fibers than fish that were better at sprinting. For fish that were were good at sprinting exercise, four weeks of aerobic exercise training (not surprisingly) improved their ability to perform endurance exercise. The switch to becoming more tolerant of endurance exercise (i.e resistant to fatigue) happened in two ways: their muscles made more ATP, while the muscle demand for ATP was reduced. If you recall, ATP is important because it is needed for muscles to relax in between contractions.
The researchers also found that inhibiting certain HDACs in the muscle could be a way to help animals (and perhaps people) adapt to sustained exercise by increasing the presence of slow muscle fiber types. In addition, they predict that increased expression of slow muscle fiber types may be beneficial to the treatment of diseases that affect muscles such as muscular dystrophy.