Abstract
There are two major muscle fiber types: type 1 fibers (slow-twitch oxidative) and type 2 fibers (fast-twitch glycolytic) . Muscle fiber type is a critical physiological property that affects sports performance as well as metabolic ability. First, we developed an electrophoresis protocol that allows clear separation of the myosin heavy chain (MyHC) isoforms, which are common molecular markers of muscle fiber type. Then we examined the effects of nutritional treatment on muscle fiber type in rats. Food deprivation for 48 h did not alter the MyHC composition of skeletal muscles. Exposure to cold (4℃) for 4 weeks increased slow-type MyHC1 in the soleus muscle. Intake of fish oil for 4 weeks induced significantly lower levels of fast-type MyHC2B and higher levels of the intermediate-type MyHC2X composition in the extensor digitorum longus (EDL) muscle in comparison with soybean oil intake. These results clearly indicate that muscle fiber type can be modified by nutritional components.
