Training state and fasting-induced PDH regulation in human skeletal muscle

The aim of the present study was to examine the influence of training state on fasting-inducedskeletal muscle pyruvate dehydrogenase (PDH) regulation, including PDH phosphorylation. Trained and untrained subjects, matched for skeletal muscle CS activity and OXPHOS protein, fasted for 36h after receiving a standardized meal. Respiratory exchange ratio (RER) was measured and blood as well as vastus lateralis muscle biopsies were obtained 2, 12, 24, and 36h after the meal. RER decreased with fasting only in untrained individuals, while PDHa activity decreased from 12h after the meal in untrained, but only tended to decrease at 36h in trained. PDH-E1, PDP1 protein, PDH phosphorylation, and PDH acetylation in skeletal muscle was higher in trained than untrained subjects, but did not change with fasting, while PDK4 protein was higher at 36h than at 2h after the meal in both groups. In conclusion, the present results suggest that endurance exercise training modifies the fasting-induced regulation of PDHa activity in skeletal muscle and the substrate switch towards fat oxidation. PDH phosphorylation could not explain the fasting-induced regulation of PDHa activity suggesting other post translational modifications.