Relative workload determines exercise-induced increases in PGC-1alpha mRNA.
BACKGROUND
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 VO(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 VO(2peak) (n = 6).


RESULTS
Exercise at 85% of V(O2peak) 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 gamma coactivator 1alpha (PGC-1alpha) mRNA expression was increased (P < 0.001) approximately four- to fivefold for several hours after exercise in both groups. After exercise at 70% of VO(2peak), venous plasma lactate was less (P < 0.001) elevated (3.1 +/- 0.7 mM) and PGC-1alpha mRNA content was less (P < 0.05) increased (approximately threefold) than after exercise at 85% of VO(2peak). Likewise, pyruvate dehydrogenase kinase 4 and hexokinase II mRNA expressions were increased (P < 0.05) only after exercise performed at 85% of VO(2peak) in the trained subjects. Hypoxia-inducible factor 2alpha mRNA only increased (P < 0.05) 3 h into recovery in trained subjects, with no difference between the 70% and 85% of VO(2peak) trial. No change in hypoxia-inducible factor 1alpha, 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 exercise-induced increase of several mRNA, including PGC-1alpha.
Copenhagen Muscle Research Centre, University of Copenhagen, Denmark. nnordsborg@ifi.ku.dk
Nikolai Baastrup
NB
Nordsborg
Carsten
C
Lundby
Lotte
L
Leick
Henriette
H
Pilegaard
D000222:Adaptation, Physiological; D000328:Adult; D051792:Basic Helix-Loop-Helix Proteins / Q000032:analysis; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006593:Hexokinase / Q000032:analysis; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000502:physiology*; D010101:Oxygen Consumption; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011494:Protein Kinases / Q000032:analysis; D012333:RNA, Messenger / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D055815:Young Adult; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D006360:Heat-Shock Proteins; D006593:Hexokinase; D019344:Lactic Acid; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011494:Protein Kinases; D012333:RNA, Messenger; D014157:Transcription Factors; D000099162:Endothelial PAS Domain-Containing Protein 1; C486497:PPARGC1A protein, human; C403287:pyruvate dehydrogenase kinase 4