title: Molecular adaptations in human skeletal muscle to endurance training under simulated hypoxic conditions.
abstract: This study was performed to explore changes in gene expression as a consequence of exercise training at two levels of intensity under normoxic and normobaric hypoxic conditions (corresponding to an altitude of 3,850 m). Four groups of human subjects trained five times a week for a total of 6 wk on a bicycle ergometer. Muscle biopsies were taken, and performance tests were carried out before and after the training period. Similar increases in maximal O(2) uptake (8.3-13.1%) and maximal power output (11.4-20.8%) were found in all groups. RT-PCR revealed elevated mRNA concentrations of the alpha-subunit of hypoxia-inducible factor 1 (HIF-1) after both high- (+82.4%) and low (+78.4%)-intensity training under hypoxic conditions. The mRNA of HIF-1alpha(736), a splice variant of HIF-1alpha newly detected in human skeletal muscle, was shown to be changed in a similar pattern as HIF-1alpha. Increased mRNA contents of myoglobin (+72.2%) and vascular endothelial growth factor (+52.4%) were evoked only after high-intensity training in hypoxia. Augmented mRNA levels of oxidative enzymes, phosphofructokinase, and heat shock protein 70 were found after high-intensity training under both hypoxic and normoxic conditions. Our findings suggest that HIF-1 is specifically involved in the regulation of muscle adaptations after hypoxia training. Fine-tuning of the training response is recognized at the molecular level, and with less sensitivity also at the structural level, but not at global functional responses like maximal O(2) uptake or maximal power output.
authors.affiliation: Institute of Anatomy, University of Bern, 3012 Bern, Switzerland. vogt@ana.unibe.ch
authors.forename: M
authors.initials: M
authors.lastname: Vogt
authors.forename: A
authors.initials: A
authors.lastname: Puntschart
authors.forename: J
authors.initials: J
authors.lastname: Geiser
authors.forename: C
authors.initials: C
authors.lastname: Zuleger
authors.forename: R
authors.initials: R
authors.lastname: Billeter
authors.forename: H
authors.initials: H
authors.lastname: Hoppeler
mesh_terms: D042964:Acyl-CoA Dehydrogenase; D000222:Adaptation, Physiological; D000328:Adult; D002196:Capillaries / Q000473:pathology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004798:Enzymes / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000235:genetics; D006019:Glycolysis; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008297:Male; D008931:Mitochondria, Muscle / Q000648:ultrastructure; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology*; D009687:Nuclear Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010732:Phosphofructokinase-1 / Q000378:metabolism; D010806:Physical Education and Training; D010807:Physical Endurance; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D004798:Enzymes; C497442:HIF1A protein, human; D018840:HSP70 Heat-Shock Proteins; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D044943:Fatty Acid Desaturases; D042964:Acyl-CoA Dehydrogenase; D010732:Phosphofructokinase-1