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. 2022 Aug;107(8):919-932.
doi: 10.1113/EP090446. Epub 2022 Jul 7.

Protein signalling in response to ex vivo dynamic contractions is independent of training status in rat skeletal muscle

Jesper Emil Jakobsgaard  1 , Frank Vincenzo de Paoli  2 , Kristian Vissing  1
Affiliations

Protein signalling in response to ex vivo dynamic contractions is independent of training status in rat skeletal muscle

Jesper Emil Jakobsgaard et al. Exp Physiol. 2022 Aug.

Abstract

New findings: What is the central question of this study? Are myofibre protein signalling responses to ex vivo dynamic contractions altered by accustomization to voluntary endurance training in rats? What is the main finding and its importance? In response to ex vivo dynamic muscle contractions, canonical myofibre protein signalling pertaining to metabolic transcriptional regulation, as well as translation initiation and elongation, was not influenced by prior accustomization to voluntary endurance training in rats. Accordingly, intrinsic myofibre protein signalling responses to standardized contractile activity may be independent of prior exercise training in rat skeletal muscle.

Abstract: Skeletal muscle training status may influence myofibre regulatory protein signalling in response to contractile activity. The current study employed a purpose-designed ex vivo dynamic contractile protocol to evaluate the effect of exercise-accustomization on canonical myofibre protein signalling for metabolic gene expression and for translation initiation and elongation. To this end, rats completed 8 weeks of in vivo voluntary running training versus no running control intervention, whereupon an ex vivo endurance-type dynamic contraction stimulus was conducted in isolated soleus muscle preparations from both intervention groups. Protein signalling response by phosphorylation was evaluated by immunoblotting at 0 and 3 h following ex vivo stimulation. Phosphorylation of AMP-activated protein kinase α-isoforms and its downstream target, acetyl-CoA carboxylase, as well as phosphorylation of eukaryotic elongation factor 2 (eEF2) was increased immediately following the dynamic contraction protocol (at 0 h). Signalling for translation initiation and elongation was evident at 3 h after dynamic contractile activity, as evidenced by increased phosphorylation of p70 S6 kinase and eukaryotic translation initiation factor 4E-binding protein 1, as well as a decrease in phosphorylation of eEF2 back to resting control levels. However, prior exercise training did not alter phosphorylation responses of the investigated signalling proteins. Accordingly, protein signalling responses to standardized endurance-type contractions may be independent of training status in rat muscle during ex vivo conditions. The present findings add to our current understanding of molecular regulatory events responsible for skeletal muscle plasticity.

Keywords: ex vivo contractions; protein signalling; training status.

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Figures

FIGURE 1
FIGURE 1
Weekly running distance performed by rats allocated to voluntary running training group. Bars represent means ± SD, n = 8
FIGURE 2
FIGURE 2
Force development and changes in maximal tetanic force and glycogen content in response to electrostimulation‐evoked dynamic muscle contraction cycles. (a, b) Force development during the 40‐min main stimulation protocol, relative to initial 30 s and maximal tetanic force (P o), respectively, with filled and open circles representing means ±SD for every 5 min in muscle preparations from sedentary (n = 18) and runners (n = 16), respectively. (c, d) Summed force–time integral for the 40‐min main stimulation protocol (c), and the same normalized to P o (d) (n = 18 and 16 in sedentary and runners, respectively). P‐values are derived from an unpaired Student's t‐test. (e) Relative changes in P o from pre‐ to post‐stimulation (n = 9 and 8 in sedentary and runners, respectively). *P < 0.0001 vs. pre within group. #P < 0.0001 vs. post in sedentary. (f) Total muscle glycogen content in control and stimulated muscle strip preparations from sedentary (n = 9 for each condition) and runners (n = 8 for each condition), *P < 0.0001 and 0.002 vs. control condition within group in sedentary and runners, respectively, and #P = 0.002 and 0.006 vs. control or stimulation condition in sedentary, respectively. Bars are means ± SD; dashed lines represent individual paired data
FIGURE 3
FIGURE 3
Representative blots of all target proteins for both time points and conditions in soleus muscle preparations from sedentary and runners. The displayed blots within each group are obtained from soleus muscle preparations originating from the same rat. 4E‐BP1, eukaryotic translation initiation factor 4E‐binding protein 1; ACC, acetyl‐CoA carboxylase; AMPKα, 5′‐AMP‐activated protein kinase subunit α‐1/2; CREB, cAMP‐response element‐binding protein; eEF2, eukaryotic elongation factor 2; p53, tumour suppressor protein p53; p70 S6K, p70 S6 kinase
FIGURE 4
FIGURE 4
5′‐AMP‐activated protein kinase (AMPK)‐related protein signalling. Protein expression of phosphorylated AMPKα, ACC, tumour suppressor p53, and cAMP‐response element‐binding protein (CREB) signalling in soleus muscle preparations of sedentary (a, d, g, j) and runners (b, e, h, k), measured immediately (0 h) or 3 h after 40 min of dynamic muscle contractions (Stimulation) or time‐matched, non‐stimulated control condition (Control). Comparisons between sedentary and runners for stimulated data relative to control are displayed in (c, f, i, l). Interaction and main effects derived from linear mixed‐effects analysis are displayed to the right of each panel. *Difference vs. control within time point as evaluated by pairwise comparisons. #Difference in stimulated–control contrasts between time points as evaluated by linear comparison analysis. Bars represent means ± SD. n = 9 and 8 for each condition and time point in sedentary and running trained group, respectively
FIGURE 5
FIGURE 5
Protein signalling related to the mechanistic target of rapamycin complex 1 (mTORC1) substrates of eukaryotic initiation factor 4E‐binding protein (4E‐BP1) and p70 S6 kinase (p70 S6K), as well as eukaryotic elongation factor 2 (eEF2). Protein expression of phosphorylated 4E‐BP1, p70 S6K and eEF2 in soleus muscle preparations of controls (a, d, g) and runners (b, e, h), measured immediately (0 h) or 3 h after 40 min of dynamic muscle contractions (Stimulated) or time‐matched, non‐stimulated control condition (Control). Bars represent means and lines paired control‐stimulation muscle split preparations pairs in (a, b, d, e, g, h). Comparisons between sedentary and runners for stimulated data relative to control are displayed in (c, f, i). Interaction and main effects derived from linear mixed‐effects analysis are displayed to the right of each panel. *Difference vs. control within time point as evaluated by pairwise comparisons. #Difference in stimulated–control contrasts between time points as evaluated by linear comparison analysis. Bars represent means ± SD. n = 9 and 8 for each condition and time point in sedentary and running trained group, respectively, except for n = 7 in p70 S6K in running trained at 3 h time point due exclusion of one outlier pair
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References

    1. Atherton, P. J. , Babraj, J. , Smith, K. , Singh, J. , Rennie, M. J. , & Wackerhage, H. (2005). Selective activation of AMPK‐PGC‐1α or PKB‐TSC2‐mTOR signaling can explain specific adaptive responses to endurance or resistance training‐like electrical muscle stimulation. FASEB Journal, 19(7), 1–23. 10.1096/fj.04-2179fje - DOI - PubMed
    1. Bahreinipour, M. A. , Joukar, S. , Hovanloo, F. , Najafipour, H. , Naderi, V. , Rajiamirhasani, A. , & Esmaeili‐Mahani, S. (2018). Mild aerobic training with blood flow restriction increases the hypertrophy index and MuSK in both slow and fast muscles of old rats: Role of PGC‐1α. Life Sciences, 202, 103–109. 10.1016/j.lfs.2018.03.051 - DOI - PubMed
    1. Bartlett, J. D. , Close, G. L. , Drust, B. , & Morton, J. P. (2014). The emerging role of p53 in exercise metabolism. Sports Medicine, 44(3), 303–309. 10.1007/s40279-013-0127-9 - DOI - PubMed
    1. Beleza, J. , Albuquerque, J. , Santos‐Alves, E. , Fonseca, P. , Santocildes, G. , Stevanovic, J. , Rocha‐Rodrigues, S. , Rizo‐Roca, D. , Ascensao, A. , Torrella, J. R. , & Magalhaes, J. (2019). Self‐paced free‐running wheel mimics high‐intensity interval training impact on rats' functional, physiological, biochemical, and morphological features. Frontiers in Physiology, 10, 593. 10.3389/fphys.2019.00593 - DOI - PMC - PubMed
    1. Benziane, B. , Burton, T. J. , Scanlan, B. , Galuska, D. , Canny, B. J. , Chibalin, A. V. , Zierath, J. R. , & Stepto, N. K. (2008). Divergent cell signaling after short‐term intensified endurance training in human skeletal muscle. American Journal of Physiology. Endocrinology and Metabolism, 295(6), E1427–E1438. 10.1152/ajpendo.90428.2008 - DOI - PubMed

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