Relative Workload Determines Exercise-Induced Increases in PGC-1α mRNA

NORDSBORG, N. B., C. LUNDBY, L. LEICK, and H. PILEGAARD. Relative Workload Determines Exercise-Induced Increases in PGC-1 alpha mRNA. Med. Sci. Sports Exerc., Vol. 42, No. 8, pp. 1477 -1484, 2010. Introduction: The hypothesis that brief intermittent exercise-induced increases in human skeletal muscle metabolic mRNA is dependent on relative workload was investigated. Methods: Trained (n = 10) and untrained (n = 8) subjects performed exhaustive intermittent cycling exercise (4 x 4 min at 85% of (V)over dotO(2peak), interspersed by 3 min). Trained subjects also performed the intermittent exercise at the same absolute workload as the untrained subjects, corresponding to 70% of (V)over dotO(2peak) (n = 6). Results: Exercise at 85% of (V)over dotO(2peak) elevated (P < 0.001) venous plasma lactate to 10.1 +/- 0.4 and 10.8 +/- 0.5 mM in the trained and untrained subjects, respectively. Peroxisome proliferator-activated receptor F coactivator 1 alpha (PGC-1 alpha) mRNA expression was increased (P < 0.001) approximately four-to fivefold for several hours after exercise in both groups. After exercise at 70% of (V)over dotO(2peak) venous plasma lactate was less (P < 0.001) elevated (3.1 +/- 0.7 mM) and PGC-1 alpha mRNA content was less (P < 0.05) increased (approximately threefold) than after exercise at 85% of (V)over dotO(2peak). Likewise, pyruvate dehydrogenase kinase 4 and hexokinase II mRNA expressions were increased (P < 0.05) only after exercise performed at 85% of (V)over dotO(2peak) in the trained subjects. Hypoxia-inducible factor 2 alpha mRNA only increased (P < 0.05) 3 h into recovery in trained subjects, with no difference between the 70% and 85% of (V)over dotO(2peak) trial. No change in hypoxia-inducible factor 1 alpha, phosphofructokinase, citrate synthase, or lactate dehydrogenase, heart and muscle isoforms, mRNA expressions was detected after any of the exercise trials. Conclusions: The relative intensity of brief intermittent exercise is of major importance for the exerciseinduced increase of several mRNA, including PGC-1 alpha.