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Resistance exercise-induced S6K1 kinase activity is not inhibited in human skeletal muscle despite prior activation of AMPK by high-intensity interval cycling
journal contribution
posted on 2015-03-01, 00:00 authored by William Apró, Marcus Moberg, Lee HamiltonLee Hamilton, Björn Ekblom, Gerrit van Hall, Hans-Christer Holmberg, Eva BlomstrandCombining endurance and strength training in the same session has been reported to reduce the anabolic response to the latter form of exercise. The underlying mechanism, based primarily on results from rodent muscle, is proposed to involve AMPK-dependent inhibition of mTORC1 signaling. This hypothesis was tested in eight trained male subjects who in randomized order performed either resistance exercise only (R) or interval cycling followed by resistance exercise (ER). Biopsies taken from the vastus lateralis before and after endurance exercise and repeatedly after resistance exercise were assessed for glycogen content, kinase activity, protein phosphorylation, and gene expression. Mixed muscle fractional synthetic rate was measured at rest and during 3 h of recovery using the stable isotope technique. In ER, AMPK activity was elevated immediately after both endurance and resistance exercise (∼90%, P < 0.05) but was unchanged in R. Thr(389) phosphorylation of S6K1 was increased severalfold immediately after exercise (P < 0.05) in both trials and increased further throughout recovery. After 90 and 180 min recovery, S6K1 activity was elevated (∼55 and ∼110%, respectively, P < 0.05) and eukaryotic elongation factor 2 phosphorylation was reduced (∼55%, P < 0.05) with no difference between trials. In contrast, markers for protein catabolism were differently influenced by the two modes of exercise; ER induced a significant increase in gene and protein expression of MuRF1 (P < 0.05), which was not observed following R exercise only. In conclusion, cycling-induced elevation in AMPK activity does not inhibit mTOR complex 1 signaling after subsequent resistance exercise but may instead interfere with the hypertrophic response by influencing key components in protein breakdown.
History
Journal
American journal of physiology: endocrinology and metabolismVolume
308Issue
6Pagination
E470 - E481Publisher
American Physiological SocietyLocation
Bethesda, Md.Publisher DOI
eISSN
1522-1555Language
engPublication classification
C1 Refereed article in a scholarly journalCopyright notice
2015, the American Physiological SocietyUsage metrics
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AMPKconcurrent exerciseS6K1mTORC1AMP-Activated Protein KinasesBicyclingEnzyme ActivationGlycogenMuscle, SkeletalProtein BindingResistance TrainingRibosomal Protein S6 Kinases, 70-kDaUp-RegulationScience & TechnologyLife Sciences & BiomedicineEndocrinology & MetabolismPhysiologyMYOFIBRILLAR PROTEIN-SYNTHESISMESSENGER-RNAUBIQUITIN LIGASESAEROBIC EXERCISEMOLECULAR RESPONSESADAPTIVE RESPONSESMAMMALIAN TARGETMTORPHOSPHORYLATIONENDURANCE
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