title: Time course of GLUT4 and AMPK protein expression in human skeletal muscle during one month of physical training.
abstract: Endurance training elicits profound adaptations of skeletal muscle, including increased expression of several proteins. The 5'-AMP activated protein kinase (AMPK) may be one of these, considering the fact that acute exercise increases AMPK activity. Eight young (26 +/- 1 year) lean, healthy males endurance trained one leg (while the other leg remained resting) on an ergometer bicycle for 30 min/day for four weeks (workload corresponding to approximately 70% of maximal oxygen uptake). Muscle biopsies were obtained approximately 18 h after the previous training session. On day eight GLUT4 protein expression was 36% higher in trained (T) compared with untrained (UT) (P < 0.05), but no further increase was seen at day 14 and 30 despite continuously increasing absolute workloads. Expression of AMPKalpha2 and actin did not change with training. In contrast, expression of AMPKalpha1 was 27% higher in T vs. UT muscle (P < 0.05) (measured only on day 30).
  
  
  CONCLUSIONS
  GLUT4 protein expression increases substantially after seven days of endurance training with no further increase with prolonged training at progressively increasing workloads. AMPKalpha1 and alpha2 behave differently in their expression in response to endurance training. AMPKalpha1 protein content is increased after one month of training, while no change in AMPKalpha2 and actin expression was detected over the time course of the training period.
authors.affiliation: Copenhagen Muscle Research Center, Department of Medical Physiology, The Panum Institute, University of Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Langfort
authors.forename: M
authors.initials: M
authors.lastname: Viese
authors.forename: T
authors.initials: T
authors.lastname: Ploug
authors.forename: F
authors.initials: F
authors.lastname: Dela
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001706:Biopsy; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000032:analysis; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007866:Leg / Q000033:anatomy & histology; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010806:Physical Education and Training / Q000379:methods*; D011494:Protein Kinases / Q000096:biosynthesis*; D012146:Rest / Q000502:physiology; D013995:Time
chemical_list: D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human; D006003:Glycogen; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases