title: Divergent cell signaling after short-term intensified endurance training in human skeletal muscle.
abstract: Endurance training represents one extreme in the continuum of skeletal muscle plasticity. The molecular signals elicited in response to acute and chronic exercise and the integration of multiple intracellular pathways are incompletely understood. We determined the effect of 10 days of intensified cycle training on signal transduction in nine inactive males in response to a 1-h acute bout of cycling at the same absolute workload (164 +/- 9 W). Muscle biopsies were taken at rest and immediately and 3 h after the acute exercise. The metabolic signaling pathways, including AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR), demonstrated divergent regulation by exercise after training. AMPK phosphorylation increased in response to exercise ( approximately 16-fold; P < 0.05), which was abrogated posttraining (P < 0.01). In contrast, mTOR phosphorylation increased in response to exercise ( approximately 2-fold; P < 0.01), which was augmented posttraining (P < 0.01) in the presence of increased mTOR expression (P < 0.05). Exercise elicited divergent effects on mitogen-activated protein kinase (MAPK) pathways after training, with exercise-induced extracellular signal-regulated kinase (ERK) 1/2 phosphorylation being abolished (P < 0.01) and p38 MAPK maintained. Finally, calmodulin kinase II (CaMKII) exercise-induced phosphorylation and activity were maintained (P < 0.01), despite increased expression ( approximately 2-fold; P < 0.05). In conclusion, 10 days of intensified endurance training attenuated AMPK, ERK1/2, and mTOR, but not CaMKII and p38 MAPK signaling, highlighting molecular pathways important for rapid functional adaptations and maintenance in response to intensified endurance exercise and training.
authors.affiliation: Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden.
authors.forename: Boubacar
authors.initials: B
authors.lastname: Benziane
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Burton
authors.forename: Brendan
authors.initials: B
authors.lastname: Scanlan
authors.forename: Dana
authors.initials: D
authors.lastname: Galuska
authors.forename: Benedict J
authors.initials: BJ
authors.lastname: Canny
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Chibalin
authors.forename: Juleen R
authors.initials: JR
authors.lastname: Zierath
authors.forename: Nigel K
authors.initials: NK
authors.lastname: Stepto
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D053858:Metabolic Networks and Pathways / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases; D013997:Time Factors; D055815:Young Adult
chemical_list: D011494:Protein Kinases; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases