| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
FJ
EXPRESS SUMMARY ARTICLE The Full-length version of this article is also available, published online February 16, 2005 as doi:10.1096/fj.04-2179fje. |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
or PKB-TSC2-mTOR signaling can explain specific adaptive responses to endurance or resistance training-like electrical muscle stimulation
,
,1
* School of Life Sciences, University of Dundee;
Department of Biological Sciences, University of Central Lancashire; and
Clinical Physiology Laboratory, University of Nottingham, UK
1 Correspondence: Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK. E-mail jsingh3{at}uclan.ac.uk
SPECIFIC AIMS
Endurance training induces a partial fast-to-slow muscle phenotype transformation and mitochondrial biogenesis, but it usually induces no growth. In contrast, resistance training stimulates muscle growth but has little effect on phenotype. We used 3 h of low-frequency stimulation (LFS) of isolated rat skeletal muscle to mimic endurance training and sixty 3 s bursts of high-frequency stimulation (HFS) to mimic resistance training. The specific aims were to identify signaling events that are activated by either LFS or HFS and that can explain the specific muscle adaptations to such stimulation patterns.
PRINCIPAL FINDINGS
LFS and HFS had specific effects on adaptation markers and on the activation of numerous signal transduction proteins.
1. LFS, but not HFS, increases AMPK Thr172 phosphorylation and induces PGC-1
and UCP-3
AMP kinase (AMPK) Thr172 phosphorylation and peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) increased significantly to 2.02 ± 0.11 and 1.30 ± 0.04 of control directly after LFS, respectively (all signaling data relative to control; n=8; ANOVA, P<0.05; mean±SE). In contrast, AMPK Thr172 was 1.01 ± 0.03 and PGC-1 significantly decreased to 0.82 ± 0.03 directly after HFS, showing that only LFS can activate AMPK-PGC-1 signaling. We measured the expression of uncoupling protein-3 (UCP3) as a marker because has been reported to acutely increase after endurance training and to be AMPK dependent. In line with our hypothesis, UCP3 mRNA increased significantly 11.70 ± 0.96 times 3 h after LFS but it remained at 1.25 ± 0.12 of control 3 h after HFS, confirming that only LFS induced this marker. A study in which PGC-1 was overexpressed in mice suggests that the increase in PGC-1 can explain many of the specific adaptations to chronic LFS and endurance training.
2. HFS, but not LFS, activates PKB-TSC2-mTOR-dependent translation initiation, elongation and protein synthesis
A specific adaptation to resistance training is a prolonged increase in protein synthesis resulting in skeletal muscle hypertrophy. Myofibrillar protein synthesis increased significantly from a control value of 0.23 ± 0.01%·h–1 by 5-fold to 1.24 ± 0.09%·h–1 3 h after HFS and to 0.33 ± 0.02%·h–1 3 h after LFS, which was not significant. The large increase in protein synthesis induced by HFS can be explained by a selective activation of the protein kinase B-tuberin mammalian target of rapamycin (PKB-TSC2-mTOR)-signaling cascade and of downstream regulators of translation initiation and elongation. PKB Ser473 phosphorylation significantly increased to 5.22 ± 1.38 directly after HFS but was unchanged after LFS. Phosphorylation of the PKB-sensitive TSC2 Thr1462 and mTOR Ser2448 sites significantly increased directly after HFS but not LFS and was not significantly changed 3 h later. Glycogen synthase kinase-3ß (GSK-3ß) Ser9 phosphorylation was significantly increased to 1.58 ± 0.05 directly after LFS and 3.08 ± 0.12 after HFS. Phosphorylation of translational regulators downstream of PKB, mTOR, and GSK-3ß suggested that they were all significantly activated directly after HFS and 3 h after HFS, with the exception of eIF4E binding protein 1 (4E-BP1). The prolonged activation of most translational regulators can explain that protein synthesis was increased 3 h after HFS. For example, p70 ribosomal S6 kinase (p70 S6k) Thr389 phosphorylation increased significantly to 6.85 ± 0.94 and 9.76 ± 0.60 of control directly and 3 h after HFS, respectively. The activation of the PKB-TSC2-mTOR-signaling cascade and the prolonged activation of multiple downstream regulators of translation initiation and elongation can explain the increase in protein synthesis that is a specific adaptation to HFS and resistance training.
3. LFS inhibits translation initiation and elongation
LFS reduced TSC2 Thr1462 phosphorylation significantly to 0.24 ± 0.02 directly and to 0.55 ± 0.06 3 h after. AMPK has recently been reported to directly phosphorylate TSC2 at the Thr1227 and Ser1345 sites, which are close to the PKB-phosphorylated Thr1462 site. Therefore, interference between the AMPK- and PKB-phosphorylated sites could potentially explain the decreased phosphorylation of Thr1462 after LFS. mTOR Ser2448 is directly phosphorylated by PKB but not TSC2, which can explain why this site is not affected when TSC2 Thr1462 is dephosphorylated after LFS. Downstream regulators of translation initiation and elongation were all significantly inhibited directly and 3 h after LFS. An example is p70 S6k Thr389 phosphorylation, which was 0.22 ± 0.03 directly and 0.17 ± 0.03 of control 3 h after LFS. However, protein synthesis was not significantly changed 3 h after LFS. This was likely due to the need of amino acid supplementation in order to be able to measure muscle protein synthesis compared with the "fasted" muscles used to measure the phosphorylation state of signaling analysis. Amino acids can activate mTOR via a phosphoinositide 3-kinase-phosphoinositide-dependent protein kinase-1 (PI3K-PDK1)-PKB-independent signaling pathway that can explain why protein synthesis was restored to control levels 3 h after LFS.
Finally, none of the mitogen-activated protein kinase pathway (ERK1/2, p38, or JNK) investigated was specifically activated by either LFS or HFS.
CONCLUSIONS AND SIGNIFCANCE
The major result of our study is that electrical muscle stimulation mimicking endurance or resistance training can switch signaling to either a catabolic AMPK-PGC-1 or anabolic PKB-TSC2-mTOR-dominated state. We term this behavior the AMPK-PKB switch (Fig. 1
). We hypothesize that the selective activation of AMPK and increased expression of PGC-1 is a major response to the prolonged catabolism associated with LFS or endurance training. Previous results suggest that the increased expression of PGC-1 can at least partially explain increases in mitochondrial biogenesis and a progression toward a slower muscle phenotype. In a fasted muscle, LFS activation of AMPK suppresses TSC2-dependent, energy-consuming translation. This could possibly explain why endurance training does not usually stimulate muscle growth. We hypothesize that HFS and resistance training induce an anabolic signaling state without the need for systemic effectors or feeding. The observed effects of HFS on the PKB-TSC2-mTOR signaling cascade can potentially explain the observed increase in protein synthesis 3 h after HFS because fibers expressing a constitutively active PKB construct hypertrophy. The novelty of our study is the demonstration that LFS and HFS can selectively activate either AMPK-PGC-1 or PKB-TSC2-mTOR-signaling, respectively. We hypothesize that these two signaling states can at least partially explain specific adaptations to electrical muscle stimulation, endurance, and resistance training. This does not exclude that AMPK and PKB can both be activated by some forms of contractile activity such as combinations of resistance and endurance training or specific stimulation protocols. Future work needs to integrate myostatin-Smad2/3, calcineurin-NFAT-c1, and CamK IV signaling into a larger model because these pathways are all activated by contractile activity and regulate fiber phenotype, mitochondrial biogenesis, or muscle growth.
|
FOOTNOTES
To read the full text of this article, go to http://www.fasebj.org/cgi/doi/10.1096/fj.04-2179fje;
This article has been cited by other articles:
|
|
 |
|
  M. A. Rhodes, M. S. Carraway, C. A. Piantadosi, C. M. Reynolds, A. D. Cherry, T. E. Wester, M. J. Natoli, E. W. Massey, R. E. Moon, and H. B. Suliman Carbon monoxide, skeletal muscle oxidative stress, and mitochondrial biogenesis in humans Am J Physiol Heart Circ Physiol, July 1, 2009; 297(1): H392 - H399. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. Kumar, P. Atherton, K. Smith, and M. J. Rennie Human muscle protein synthesis and breakdown during and after exercise J Appl Physiol, June 1, 2009; 106(6): 2026 - 2039. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. K. LeBrasseur, T. M. Schelhorn, B. L. Bernardo, P. G. Cosgrove, P. M. Loria, and T. A. Brown Myostatin Inhibition Enhances the Effects of Exercise on Performance and Metabolic Outcomes in Aged Mice J Gerontol A Biol Sci Med Sci, May 29, 2009; (2009) glp068v1. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. J. Rose and E. A. Richter Regulatory mechanisms of skeletal muscle protein turnover during exercise J Appl Physiol, May 1, 2009; 106(5): 1702 - 1711. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D.M. Thomson, J.D. Brown, N. Fillmore, S.K. Ellsworth, D. L. Jacobs, W.W. Winder, C.A. Fick, and S.E. Gordon AMP-activated protein kinase response to contractions and treatment with the AMPK activator AICAR in young adult and old skeletal muscle J. Physiol., May 1, 2009; 587(9): 2077 - 2086. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Miyazaki and K. A. Esser Cellular mechanisms regulating protein synthesis and skeletal muscle hypertrophy in animals J Appl Physiol, April 1, 2009; 106(4): 1367 - 1373. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. G. Coffey, H. Pilegaard, A. P. Garnham, B. J. O'Brien, and J. A. Hawley Consecutive bouts of diverse contractile activity alter acute responses in human skeletal muscle J Appl Physiol, April 1, 2009; 106(4): 1187 - 1197. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. J. Rose, T. J. Alsted, T. E. Jensen, J. B. Kobbero, S. J. Maarbjerg, J. Jensen, and E. A. Richter A Ca2+-calmodulin-eEF2K-eEF2 signalling cascade, but not AMPK, contributes to the suppression of skeletal muscle protein synthesis during contractions J. Physiol., April 1, 2009; 587(7): 1547 - 1563. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Gibala, S. L. McGee, A. P. Garnham, K. F. Howlett, R. J. Snow, and M. Hargreaves Brief intense interval exercise activates AMPK and p38 MAPK signaling and increases the expression of PGC-1{alpha} in human skeletal muscle J Appl Physiol, March 1, 2009; 106(3): 929 - 934. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. J. Rose, B. Bisiani, B. Vistisen, B. Kiens, and E. A. Richter Skeletal muscle eEF2 and 4EBP1 phosphorylation during endurance exercise is dependent on intensity and muscle fiber type Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2009; 296(2): R326 - R333. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. R Moore, M. J Robinson, J. L Fry, J. E Tang, E. I Glover, S. B Wilkinson, T. Prior, M. A Tarnopolsky, and S. M Phillips Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men Am. J. Clinical Nutrition, January 1, 2009; 89(1): 161 - 168. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. B. Wilkinson, S. M. Phillips, P. J. Atherton, R. Patel, K. E. Yarasheski, M. A. Tarnopolsky, and M. J. Rennie Differential effects of resistance and endurance exercise in the fed state on signalling molecule phosphorylation and protein synthesis in human muscle J. Physiol., August 1, 2008; 586(15): 3701 - 3717. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Murase, S. Haramizu, N. Ota, and T. Hase Tea catechin ingestion combined with habitual exercise suppresses the aging-associated decline in physical performance in senescence-accelerated mice Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2008; 295(1): R281 - R289. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. Ljubicic and D. A. Hood Kinase-specific responsiveness to incremental contractile activity in skeletal muscle with low and high mitochondrial content Am J Physiol Endocrinol Metab, July 1, 2008; 295(1): E195 - E204. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Thomson, C. A. Fick, and S. E. Gordon AMPK activation attenuates S6K1, 4E-BP1, and eEF2 signaling responses to high-frequency electrically stimulated skeletal muscle contractions J Appl Physiol, March 1, 2008; 104(3): 625 - 632. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Vissing, S. L. McGee, C. Roepstorff, P. Schjerling, M. Hargreaves, and B. Kiens Effect of sex differences on human MEF2 regulation during endurance exercise Am J Physiol Endocrinol Metab, February 1, 2008; 294(2): E408 - E415. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. C. Dreyer, M. J. Drummond, B. Pennings, S. Fujita, E. L. Glynn, D. L. Chinkes, S. Dhanani, E. Volpi, and B. B. Rasmussen Leucine-enriched essential amino acid and carbohydrate ingestion following resistance exercise enhances mTOR signaling and protein synthesis in human muscle Am J Physiol Endocrinol Metab, February 1, 2008; 294(2): E392 - E400. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Hakimi, J. Yang, G. Casadesus, D. Massillon, F. Tolentino-Silva, C. K. Nye, M. E. Cabrera, D. R. Hagen, C. B. Utter, Y. Baghdy, et al. Overexpression of the Cytosolic Form of Phosphoenolpyruvate Carboxykinase (GTP) in Skeletal Muscle Repatterns Energy Metabolism in the Mouse J. Biol. Chem., November 9, 2007; 282(45): 32844 - 32855. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Koopman, B. Pennings, A. H. G. Zorenc, and L. J. C. van Loon Protein Ingestion Further Augments S6K1 Phosphorylation in Skeletal Muscle Following Resistance Type Exercise in Males J. Nutr., August 1, 2007; 137(8): 1880 - 1886. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. A. Frost and C. H. Lang Protein kinase B/Akt: a nexus of growth factor and cytokine signaling in determining muscle mass J Appl Physiol, July 1, 2007; 103(1): 378 - 387. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Q. Hong-Brown, C. R. Brown, D. S. Huber, and C. H. Lang Alcohol Regulates Eukaryotic Elongation Factor 2 Phosphorylation via an AMP-activated Protein Kinase-dependent Mechanism in C2C12 Skeletal Myocytes J. Biol. Chem., February 9, 2007; 282(6): 3702 - 3712. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Freyssenet Energy sensing and regulation of gene expression in skeletal muscle J Appl Physiol, February 1, 2007; 102(2): 529 - 540. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Sacheck, J.-P. K. Hyatt, A. Raffaello, R. T. Jagoe, R. R. Roy, V. R. Edgerton, S. H. Lecker, and A. L. Goldberg Rapid disuse and denervation atrophy involve transcriptional changes similar to those of muscle wasting during systemic diseases FASEB J, January 1, 2007; 21(1): 140 - 155. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Eliasson, T. Elfegoun, J. Nilsson, R. Kohnke, B. Ekblom, and E. Blomstrand Maximal lengthening contractions increase p70 S6 kinase phosphorylation in human skeletal muscle in the absence of nutritional supply Am J Physiol Endocrinol Metab, December 1, 2006; 291(6): E1197 - E1205. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Raney and L. P. Turcotte Regulation of contraction-induced FA uptake and oxidation by AMPK and ERK1/2 is intensity dependent in rodent muscle Am J Physiol Endocrinol Metab, December 1, 2006; 291(6): E1220 - E1227. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. W. Dolinsky and J. R. B. Dyck Role of AMP-activated protein kinase in healthy and diseased hearts Am J Physiol Heart Circ Physiol, December 1, 2006; 291(6): H2557 - H2569. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Leger, R. Cartoni, M. Praz, S. Lamon, O. Deriaz, A. Crettenand, C. Gobelet, P. Rohmer, M. Konzelmann, F. Luthi, et al. Akt signalling through GSK-3{beta}, mTOR and Foxo1 is involved in human skeletal muscle hypertrophy and atrophy J. Physiol., November 1, 2006; 576(3): 923 - 933. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Sakamoto, D. E. Arnolds, N. Fujii, H. F. Kramer, M. F. Hirshman, and L. J. Goodyear Role of Akt2 in contraction-stimulated cell signaling and glucose uptake in skeletal muscle Am J Physiol Endocrinol Metab, November 1, 2006; 291(5): E1031 - E1037. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.-T. Hwang, Y. M. Kim, Y.-J. Surh, H. W. Baik, S.-K. Lee, J. Ha, and O. J. Park Selenium Regulates Cyclooxygenase-2 and Extracellular Signal-Regulated Kinase Signaling Pathways by Activating AMP-Activated Protein Kinase in Colon Cancer Cells. Cancer Res., October 15, 2006; 66(20): 10057 - 10063. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. C. Dreyer, S. Fujita, J. G. Cadenas, D. L. Chinkes, E. Volpi, and B. B. Rasmussen Resistance exercise increases AMPK activity and reduces 4E-BP1 phosphorylation and protein synthesis in human skeletal muscle J. Physiol., October 15, 2006; 576(2): 613 - 624. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Gibala, J. P. Little, M. van Essen, G. P. Wilkin, K. A. Burgomaster, A. Safdar, S. Raha, and M. A. Tarnopolsky Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance J. Physiol., September 15, 2006; 575(3): 901 - 911. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. M. Reznick and G. I. Shulman The role of AMP-activated protein kinase in mitochondrial biogenesis J. Physiol., July 1, 2006; 574(1): 33 - 39. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. A. Hood, I. Irrcher, V. Ljubicic, and A.-M. Joseph Coordination of metabolic plasticity in skeletal muscle J. Exp. Biol., June 15, 2006; 209(12): 2265 - 2275. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Williamson, N. Kubica, S. R. Kimball, and L. S. Jefferson Exercise-induced alterations in extracellular signal-regulated kinase 1/2 and mammalian target of rapamycin (mTOR) signalling to regulatory mechanisms of mRNA translation in mouse muscle J. Physiol., June 1, 2006; 573(2): 497 - 510. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Atherton and M. J. Rennie Protein synthesis a low priority for exercising muscle J. Physiol., June 1, 2006; 573(2): 288 - 289. [Full Text] [PDF]
|
|
|
|
|
|
R. Koopman, A. H. G. Zorenc, R. J. J. Gransier, D. Cameron-Smith, and L. J. C. van Loon Increase in S6K1 phosphorylation in human skeletal muscle following resistance exercise occurs mainly in type II muscle fibers Am J Physiol Endocrinol Metab, June 1, 2006; 290(6): E1245 - E1252. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. J. Cuthbertson, J. Babraj, K. Smith, E. Wilkes, M. J. Fedele, K. Esser, and M. Rennie Anabolic signaling and protein synthesis in human skeletal muscle after dynamic shortening or lengthening exercise Am J Physiol Endocrinol Metab, April 1, 2006; 290(4): E731 - E738. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Funai, J. D. Parkington, S. Carambula, and R. A. Fielding Age-associated decrease in contraction-induced activation of downstream targets of Akt/mTor signaling in skeletal muscle Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2006; 290(4): R1080 - R1086. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. G. Hardie and K. Sakamoto AMPK: A Key Sensor of Fuel and Energy Status in Skeletal Muscle Physiology, February 1, 2006; 21(1): 48 - 60. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. E. Norton and D. K. Layman Leucine Regulates Translation Initiation of Protein Synthesis in Skeletal Muscle after Exercise J. Nutr., February 1, 2006; 136(2): 533S - 537S. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Blomstrand, J. Eliasson, H. K. R. Karlsson, and R. Kohnke Branched-Chain Amino Acids Activate Key Enzymes in Protein Synthesis after Physical Exercise J. Nutr., January 1, 2006; 136(1): 269S - 273S. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. J. Rose, C. Broholm, K. Kiillerich, S. G. Finn, C. G. Proud, M. H. Rider, E. A. Richter, and B. Kiens Exercise rapidly increases eukaryotic elongation factor 2 phosphorylation in skeletal muscle of men J. Physiol., November 15, 2005; 569(1): 223 - 228. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Hurst, E. B. Taylor, T. D. Cline, L. J. Greenwood, C. L. Compton, J. D. Lamb, and W. W. Winder AMP-activated protein kinase kinase activity and phosphorylation of AMP-activated protein kinase in contracting muscle of sedentary and endurance-trained rats Am J Physiol Endocrinol Metab, October 1, 2005; 289(4): E710 - E715. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. F Miller, J. L Olesen, M. Hansen, S. Dossing, R. M Crameri, R. J Welling, H. Langberg, A. Flyvbjerg, M. Kjaer, J. A Babraj, et al. Coordinated collagen and muscle protein synthesis in human patella tendon and quadriceps muscle after exercise J. Physiol., September 15, 2005; 567(3): 1021 - 1033. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. J Rennie Body maintenance and repair: how food and exercise keep the musculoskeletal system in good shape Exp Physiol, July 1, 2005; 90(4): 427 - 436. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
