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Heat shock proteins in exercised human skeletal muscle
Örebro University, School of Health Sciences.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Exercise is considered as an important stressor accompanied by concerted molecular and cellular changes leading to adaptations at the level of skeletal muscle size and function. An important protein family produced by cells in response to stressful conditions is the heat shock proteins (HSPs). It is suggested that the different HSPs play specific roles in acute and longterm responses to exercise-induced stress. The overall aim of this thesis was to explore the expression of four different HSPs (αB-crystallin, HSP27, HSP60 and HSP70) in human skeletal muscle exposed to exercise, with a special emphasis on the role played by HSP27 in the hypertrophy of human skeletal muscle.

One of the major findings was the fibre type-specific expression of HSPs in resting human skeletal muscle, including the preferential expression of HSP27 in fast type II muscle fibres. Another finding was the occurrence of training background-related differences in the expression of HSPs. Also, a cytoplasmic relocation of HSP27, occurring specifically in type II muscle fibres, was shown in response to a single bout of resistance exercise. Interestingly, there were no corresponding changes in response to an endurance exercise bout, suggesting that HSP27 may be specifically involved in the adaptations to resistance exercise. In order to test this hypothesis, an in-vitro exercise model based on the electrical pulse stimulation (EPS) of muscle cells was developed. The EPS protocol, including an 8 h restitution period, induced a significant hypertrophy of muscle cells together with molecular changes similar to those previously described in response to exercise in humans. The role of HSP27 in the hypertrophy of human muscle cells was examined through the downregulation of HSP27. Based on data from morphological and microarray analyses, findings indicate that HSP27 is not mandatory for the hypertrophy of human muscle cells. Overall, the present thesis clarified the expression of different HSPs in human skeletal muscle and provided an in-vitro-based approach for the elucidation of the exact role played by HSPs in the adaptations of human skeletal muscle to exercise.

Place, publisher, year, edition, pages
Örebro: Örebro University , 2018. , p. 56
Series
Örebro Studies in Sport Sciences, ISSN 1654-7535 ; 28
Keywords [en]
Endurance training, Resistance training, Muscle Fibre Type, Electrical Pulse Stimulation, Muscle Hypertrophy
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:oru:diva-68028ISBN: 978-91-7529-260-1 (print)OAI: oai:DiVA.org:oru-68028DiVA, id: diva2:1234179
Public defence
2018-10-17, Örebro universitet, Gymnastik- och idrottshuset, Hörsal G, Fakultetsgatan 1, Örebro, 09:00 (English)
Opponent
Supervisors
Available from: 2018-07-23 Created: 2018-07-23 Last updated: 2018-09-25Bibliographically approved
List of papers
1. The expression of heat shock protein in human skeletal muscle: effects of muscle fibre phenotype and training background
Open this publication in new window or tab >>The expression of heat shock protein in human skeletal muscle: effects of muscle fibre phenotype and training background
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2013 (English)In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 209, no 1, p. 26-33Article in journal (Refereed) Published
Abstract [en]

Aim: Exercise-induced adaptations of skeletal muscle are related to training mode and can be muscle fibre type specific. This study aimed to investigate heat shock protein expression in type I and type II muscle fibres in resting skeletal muscle of subjects with different training backgrounds.

Methods: Three groups of subjects were included: healthy active not engaged in any training programme (ACT, n = 12), resistance trained (RES, n = 6) and endurance trained (END, n = 8). Biopsies were obtained from vastus lateralis, and immunohistochemistry was performed using monoclonal antibodies against myosin heavy chain I and IIA, αB-crystallin, HSP27, HSP60 and HSP70.

Results: In ACT and RES, but not in END, a fibre type–specific expression with higher staining intensity in type I than type II fibres was seen for αB-crystallin. The opposite (II > I) was found for HSP27 in subjects from ACT (6 of 12 subjects) and RES (3 of 6), whereas all subjects from END displayed uniform staining. HSP60 showed no fibre-specific expression. HSP70 displayed a fibre-specific expression pattern (I > II) in ACT (4 of 12), but not in END or RES.

Conclusion: This study shows that the level of expression of the different HSPs in human skeletal muscle is influenced by muscle fibre phenotype. The fibre type–specific expression of HSP70 is influenced by resistance and endurance training, whereas those of αB-crystallin and HSP27 is influenced only by endurance training, suggesting the existence of a training-modality-specific action on the adaptive processes including heat shock proteins in human skeletal muscle.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2013
Keywords
Adaptation, endurance, heat shock protein, immunohistochemistry, resistance
National Category
Sport and Fitness Sciences
Research subject
Sports Physiology/Medicine
Identifiers
urn:nbn:se:oru:diva-30127 (URN)10.1111/apha.12124 (DOI)000322950400006 ()23710799 (PubMedID)2-s2.0-84881557932 (Scopus ID)
Note

Funding agency:

Nordea Foundation

Available from: 2013-08-06 Created: 2013-08-06 Last updated: 2018-11-19Bibliographically approved
2. Immunohistochemical changes in the expression of HSP27 in exercised human vastus lateralis muscle
Open this publication in new window or tab >>Immunohistochemical changes in the expression of HSP27 in exercised human vastus lateralis muscle
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2008 (English)In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 194, no 3, p. 215-222Article in journal (Refereed) Published
Abstract [en]

Aim: The role of HSP27 in the adaptive process of skeletal muscle to exercise, especially in humans, is not well understood. The objective of this study was to investigate immunohistochemical changes in HSP27 expression in human vastus lateralis muscle following resistance and endurance exercises.

Methods: Two different exercise protocols were used: (1) one-leg ergometer cycling (EC, n = 6) consisting of two 30-min bouts at 40% and 75% of peak oxygen uptake, respectively, and (2) leg extension resistance exercise (RE, n = 9) including 10 sets of eight repetitions at a load corresponding to 70% of one maximal repetition (1RM). Immunohistochemistry using specific monoclonal antibodies was used to determine the location of HSP27 protein in muscle biopsies from human vastus lateralis.

Results: Our results show that RE, but not EC, induced a significant appearance of scattered accumulations of HSP27 protein in muscle fibres from five of nine subjects. The number of fibres with accumulation of HSP27 in RE ranged from 0% to 32% with a mean of 6.3% of the total number of fibres.

Conclusion: We conclude that this rapid HSP27 protein relocation after RE is an important player in the cellular remodelling of human muscle fibres in response to exercise involving high-force contractions, but not in response to endurance exercises.

Place, publisher, year, edition, pages
Blackwell Publishing, 2008
Keywords
adaptation, endurance and resistance exercise, fibre type, heat shock protein, stress response
National Category
Physiology
Research subject
Physiology
Identifiers
urn:nbn:se:oru:diva-4751 (URN)10.1111/j.1748-1716.2008.01875.x (DOI)000259863100005 ()18489727 (PubMedID)2-s2.0-53549112177 (Scopus ID)
Funder
Swedish National Centre for Research in Sports
Available from: 2008-11-24 Created: 2008-11-24 Last updated: 2018-09-24Bibliographically approved
3. Electrical pulse stimulation: an in vitro exercise model for the induction of human skeletal muscle cell hypertrophy. A proof-of-concept study
Open this publication in new window or tab >>Electrical pulse stimulation: an in vitro exercise model for the induction of human skeletal muscle cell hypertrophy. A proof-of-concept study
2017 (English)In: Experimental Physiology, ISSN 0958-0670, E-ISSN 1469-445X, Vol. 102, no 11, p. 1405-1413Article in journal (Refereed) Published
Abstract [en]

New Findings:

  • What is the central question of this study?

Is electrical pulse stimulation (EPS) an in vitro exercise model able to elicit the hypertrophy of human muscle cells?

  • What is the main finding and its importance?

The addition of a restitution period of 8h after EPS induces the enlargement of human muscle cells, a major physiological end-point to resistance exercise. This is supported by downregulationof myostatin, a negative regulator of muscle mass, and increased phosphorylated mTOR and 4E-BP1, key factors in the growth cascade. This proof-of-concept study provides a model of physiologically mediated muscle growth, which will be the basis for future studies aiming to depict molecular events governing the hypertrophy of human muscle cells.

Electrical pulse stimulation (EPS) of muscle cells has previouslybeenused as an in vitro exercise model. The present study aimedto establish an EPS protocol promoting the hypertrophy ofhuman muscle cells, which represents a major physiological end-point to resistance exercise in humans. We hypothesized that adding a resting period after EPS would be crucial for the occurrence of the morphological change. Myoblasts obtained from human muscle biopsies (n=5) were differentiated into multinucleated myotubes and exposed to 8h of EPS consisting of 2ms pulses at 12V, with a frequency of 1Hz. Myotube size was assessed using immunohistochemistry immediately, 4 and 8h after completed EPS. Gene expression and phosphorylation status of selected markers of hypertrophy were assessed using RT-PCR and Western blotting, respectively. Release of the myokine interleukin-6 in culture medium was measured using enzyme-linked immunosorbent assay. We demonstrated a significant increase (31 +/- 14%; P=0.03) in the size of myotubes when EPS was followed by an 8h resting period, but not immediately or 4h after completion of EPS. The response was supported by downregulation (P=0.04) of the gene expression of myostatin, a negative regulator of muscle mass, and an increase in phosphorylated mTOR (P=0.03) and 4E-BP1 (P=0.01), which are important factors in the cellular growth signalling cascade. The present work demonstrates that EPS is an in vitro exercise model promoting the hypertrophy of human muscle cells, recapitulating a major physiological end-point to resistance exercise in human skeletal muscle.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
Cell growth, muscle contraction, myotube morphology
National Category
Physiology
Identifiers
urn:nbn:se:oru:diva-61685 (URN)10.1113/EP086581 (DOI)000414175100010 ()28861930 (PubMedID)2-s2.0-85032974682 (Scopus ID)
Available from: 2017-11-14 Created: 2017-11-14 Last updated: 2018-09-24Bibliographically approved
4. HSP27 is not mandatory for the hypertrophy of human skeletal muscle cells
Open this publication in new window or tab >>HSP27 is not mandatory for the hypertrophy of human skeletal muscle cells
(English)Manuscript (preprint) (Other academic)
National Category
Physiology
Identifiers
urn:nbn:se:oru:diva-69017 (URN)
Available from: 2018-09-24 Created: 2018-09-24 Last updated: 2018-09-24Bibliographically approved

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