Modulation of branched-chain 2-oxo acid dehydrogenase complex activity in rat skeletal muscle by endurance training

Effects of endurance training and high-fat diet intake on the branched-chain 2-oxo acid dehydrogenase complex in skeletal muscle were examined in rats. The basal activities of the enzyme complex (approximately 4% in active form of the total enzyme) in the muscle of rats under the fed conditions were not different between trained and untrained rats. The basal activity in the muscle was elevated by 24 h starvation in both groups of rats, but the level of the elevation was significantly greater in the trained rats than in the untrained rats. On the other hand, high-fat diet intake did not alter the basal activity of the enzyme complex in the muscle or the profile of activation of the enzyme complex by muscle contractions elicited by the electrical stimulation, suggesting that the fat content in the diet does not affect the enzyme activity in the muscle. Neither training nor diet affected the total enzyme activity or the amount of enzyme protein. Activation by leucine administration of the enzyme complex in the muscle was greater in the trained rats than in the untrained rats, suggesting that the activity state of the enzyme complex is more responsive to regulation by the 2-oxo acid derived from leucine in the muscles of endurance-trained rats.