Skeletal muscle IL-15/IL-15Rα and myofibrillar protein synthesis after resistance exercise.

TL;DR: In conclusion, IL‐15/IL‐15Rα signaling pathway is activated in skeletal muscle in response to a session of resistance exercise.

Abstract: In vitro and in vivo studies described the myokine IL-15 and its receptor IL-15Rα as anabolic/anti-atrophy agents, however, the protein expression of IL-15Rα has not been measured in human skeletal muscle and data regarding IL-15 expression remain inconclusive. The purpose of the study was to determine serum and skeletal muscle IL-15 and IL-15Rα responses to resistance exercise session and to analyze their association with myofibrillar protein synthesis (MPS). Fourteen participants performed a bilateral leg resistance exercise composed of four sets of leg press and four sets of knee extension at 75% 1RM to task failure. Muscle biopsies were obtained at rest, 0, 4 and 24 hours post-exercise and blood samples at rest, mid-exercise, 0, 0.3, 1, 2, 4 and 24 hours post-exercise. Serum IL-15 was increased by ~5.3-fold immediately post-exercise, while serum IL-15Rα decreased ~75% over 1 hour post-exercise (P<.001). Skeletal muscle IL-15Rα mRNA and protein expression were increased at 4 hours post-exercise by ~2-fold (P<.001) and ~1.3-fold above rest (P=.020), respectively. At 24 hours post-exercise, IL-15 (P=.003) and IL-15Rα mRNAs increased by ~2-fold (P=.002). Myofibrillar fractional synthetic rate between 0-4 hours was associated with IL-15Rα mRNA at rest (r=.662, P=.019), 4 hours (r=.612, P=.029), and 24 hours post-exercise (r=.627, P=.029). Finally, the muscle IL-15Rα protein up-regulation was related to Leg press 1RM (r=.688, P=.003) and total weight lifted (r=.628, P=.009). In conclusion, IL-15/IL-15Rα signaling pathway is activated in skeletal muscle in response to a session of resistance exercise.

Summary

Take down policy

• IL-15Rα has not been determined in human skeletal muscle.
• Therefore, despite the 67 fact that in vitro studies indicate a role for skeletal muscle IL-15 in anabolism, studies in 68 humans are inconclusive.
• Of 119 the 16 participants included in the original study, 14 were analysed in the present investigation 120 due to insufficient muscle tissue in the two subjects excluded.

Experimental protocol 123

• A detailed description of the experimental protocol and analytical methods can be found 124 elsewhere (McKendry et al., 2016) .
• Thereafter, one-repetition maximum (1RM) strength during leg press and 127 knee extension was assessed (Cybex VR-3, MA, USA).
• The following morning at 7.00 h, participants returned to the 142 laboratory after a 10-12h overnight fast and a cannula was inserted into a forearm vein to obtain 143 a blood sample followed by the fourth and last biopsy, which was obtained from the vastus 144 lateralis of the contralateral leg.
• The participants received three standardised meals for consumption the evening prior to 147 the experimental trial, as well as the afternoon and evening after the experimental trial.

Serum IL-15 and IL-15Rα 154

• After collection, all blood samples were centrifuged for 15 minutes at 1000 g, aliquoted and 155 stored at -80 ºC.
• Two high-sensitivity enzyme-linked immunosorbent assay kits were 156 used to determine the serum concentration of IL-15 and IL-15Rα in duplicates.

Both antibodies were diluted into BSA-blocking buffer containing 4% bovine serum albumin in 175

• Antibody specific labelling was revealed by 176 incubation with an HRP-conjugated goat anti-rabbit (IL-15) or anti-mouse (IL-15Rα) antibodies 177 (1:5000), both diluted in 5% blotto blocking buffer and visualised with ECL Western blotting 178 detection system using a ChemiDoc XRS (Bio-Rad, Copenhagen, Denmark).
• Imaging and band 179 quantification were performed using the Quantity One 1-D Analysis software (Bio-Rad, 180 Copenhagen, Denmark).
• Test samples were run together with a control sample from a subject 181 who did not take part in the study.
• The control sample was loaded in three different lanes and 182 used as an internal control for inter-gel variability.

RNA Isolation and quantitative real-time reverse transcription polymerase chain reaction 187 (qRT-PCR). 188

• Approximately 15-20 mg of skeletal muscle tissue was used for the RNA isolation.
• The RNA 189 was extracted by guanine-phenol-chloroform isothiocyanate procedures using TRIzol 190 (AUC) was determined using trapezoid method and compared between groups using a paired 242 Student's t-test.
• Since no significant differences were observed between the 1-and 5-min 243 recovery, both groups were combined for further analyses.
• To determine time effects of the intervention on serum, protein and mRNA levels of IL-245 15 and IL-15Rα, ANOVA for repeated measures was performed.
• Tukey HSD correction was 246 used as post-hoc test when significant differences were detected.

Skeletal muscle IL-15/IL-15Rα expression and myofibrillar protein synthesis. 306

• This lack of 328 differences could be interpreted as evidence to refute the association between skeletal muscle 329 IL-15/IL-15Rα and MPS.
• Nevertheless, the effect sizes and statistical outputs (P<0.10) indicate 330 that a potential difference between groups may actually exist.
• In agreement, the authors have observed a positive association between serum concentration of 395 IL-15 and IL-15 protein levels in skeletal muscle, suggesting that muscle may be an important 396 source of IL-15 in the basal state.
• In the present study, the authors observed that basal IL-15 protein 397 levels in skeletal muscle were associated with serum concentration immediately post-exercise, 398 also suggesting that the size of the intramuscular pool could determine the magnitude of the 399 increase in serum IL-15 elicited by resistance exercise.

Full text

University of Birmingham
Skeletal muscle IL-15/IL-15R and myofibrillar protein
synthesis after resistance exercise
Pérez López, Alberto; McKendry, James; Martin-Rincon, Marcos ; Morales-Alamo, David;
Pérez-Köhler, Bárbara ; Valadés, David; Buján, Julia ; Calbet, Jose; Breen, Leigh
DOI:
10.1111/sms.12901
License:
None: All rights reserved
Document Version
Peer reviewed version
Citation for published version (Harvard):
Pérez López, A, McKendry, J, Martin-Rincon, M, Morales-Alamo, D, Pérez-Köhler, B, Valadés, D, Buján, J,
Calbet, J & Breen, L 2017, 'Skeletal muscle IL-15/IL-15R and myofibrillar protein synthesis after resistance
exercise', Scandinavian Journal of Medicine and Science in Sports. https://doi.org/10.1111/sms.12901
Link to publication on Research at Birmingham portal
Publisher Rights Statement:
Checked for eligibility: 27/04/2017
"This is the peer reviewed version of the following article: Pérez-López A, McKendry J, Martin-Rincon M, et al. Skeletal muscle IL-15/IL-15R
and myofibrillar protein synthesis after resistance exercise. Scand J Med Sci Sports. 2017, which has been published in final form at
https://doi.org/10.1111/sms.12901. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions
for Self-Archiving."
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Download date: 09. Aug. 2022

PROOF
Skeletal muscle IL
-
15
/IL
-
15Rα and myofibrillar protein
synthesis after resistance exercise
Journal:
Scandinavian Journal of Medicine and Science in Sports
Manuscript ID
SJMSS-O-694-16.R2
Manuscript Type:
Original Article
Date Submitted by the Author:
27-Mar-2017
Complete List of Authors:
Pérez-López, Alberto; University of Alcalá, Medicine and Medical
Specialties. Faculty of Medicine and Health Sciences. Biomedical Research
Networking Centre on Bioengineering, Biomaterials and Nanomedicine
(CIBER-BBN); University of Alcalá, Biomedical Sciences. Faculty of
Medicine and Health Sciences; University of Birmingham, School of Sport,
Exercise and Rehabilitation Sciences; University of Las Palmas de Gran
Canaria, Department of Physical Education. Faculty of Physical Education
McKendry, James; University of Birmingham, School of Sport, Exercise and
Rehabilitation Sciences; University of Birmingham, MRC-ARUK Centre for
Musculoskeletal Ageing Research
Martin-Rincon, Marcos; University of Las Palmas de Gran Canaria,
Department of Physical Education. Faculty of Physical Education; University
of Las Palmas de Gran Canaria, Research Institute of Biomedical and
Health Sciences (IUIBS)
Morales-Alamo, David; University of Las Palmas de Gran Canaria,
Department of Physical Education. Faculty of Physical Education; University
of Las Palmas de Gran Canaria, Research Institute of Biomedical and
Health Sciences (IUIBS)
Pérez-Köhler, Bárbara; University of Alcalá, Department of Medicine and
Medical Specialities. Faculty of Medicine and Health Sciences. Biomedical
Research Networking Centre on Bioengineering, Biomaterials and
Nanomedicine (CIBER-BBN)
Valadés, David; University of Alcalá, Department of Biomedical Sciences.
Faculty of Medicine and Health Sciences.
Buján, Julia; University of Alcalá, Department of Medicine and Medical
Specialities. Faculty of Medicine and Health Sciences. Biomedical Research
Networking Centre on Bioengineering, Biomaterials and Nanomedicine
(CIBER-BBN)
Calbet, Jose; University of Las Palmas de Gran Canaria, Department of
Physical Education. Faculty of Physical Education; University of Las Palmas
de Gran Canaria, Research Institute of Biomedical and Health Sciences
(IUIBS)
Breen, Leigh; University of Birmingham, School of Sport, Exercise and
Rehabilitation Sciences; University of Birmingham, MRC-ARUK Centre for
Musculoskeletal Ageing Research
Keywords:
Myokines, IL-15/IL-15Rα axis, strength training, muscle protein
synthesis/breakdown
Scandinavian Journal of Medicine & Science in Sports - PROOF
Scandinavian Journal of Medicine & Science in Sports - PROOF

PROOF
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PROOF
1
Skeletal muscle IL-15/IL-15Rα and myofibrillar protein synthesis after resistance 1
exercise 2
3
Alberto Pérez-López
1,2,3,4
, James McKendry
3,5
, Marcos Martin-Rincon
4,6
, David Morales-4
Alamo
4,6
, Bárbara Pérez-Köhler
1
, David Valadés
2
, Julia Buján
1
, Jose A. L. Calbet
4,6
and 5
Leigh Breen
3,5
.6
7
1
Department of Medicine and Medical Specialities. Faculty of Medicine and Health Sciences. 8
University of Alcalá, Madrid, Spain. Biomedical Research Networking Centre on 9
Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain. 10
2
Department of Biomedical Sciences. Faculty of Medicine and Health Sciences. University of 11
Alcalá, Madrid, Spain. 12
3
School of Sport, Exercise and Rehabilitation Sciences. University of Birmingham, 13
Birmingham, UK. 14
4
Department of Physical Education. Faculty of Physical Education. University of Las Palmas 15
de Gran Canaria, Las Palmas de Gran Canaria, Spain. 16
5
MRC-ARUK Centre for Musculoskeletal Ageing Research. University of Birmingham, 17
Birmingham, UK. 18
6
Research Institute of Biomedical and Health Sciences (IUIBS). Las Palmas de Gran Canaria, 19
Spain. 20
21
Address for correspondence: 22
Alberto Pérez-López 23
Department of Medicine and Medical Specialties. 24
Faculty of Medicine and Health Sciences, University of Alcalá. 25
Ctra. Madrid-Barcelona km 33,600 26
28871 Alcalá de Henares, Madrid (Spain) 27
E-mail: Alberto_perez-lopez@hotmail.com
28
Phone: (+34) 636 710 130 29
30
Running head: IL-15/IL-15Rα in Resistance Exercise
31
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ABSTRACT 32
In vitro and in vivo studies described the myokine IL-15 and its receptor IL-15Rα as 33
anabolic/anti-atrophy agents, however the protein expression of IL-15Rα has not been measured 34
in human skeletal muscle and data regarding IL-15 expression remain inconclusive. The 35
purpose of the study was to determine serum and skeletal muscle IL-15 and IL-15Rα responses 36
to resistance exercise session and to analyse their association with myofibrillar protein synthesis 37
(MPS). Fourteen participants performed a bilateral leg resistance exercise composed of 4 sets of 38
leg press and 4 sets of knee extension at 75% 1RM to task failure. Muscle biopsies were 39
obtained at rest, 0, 4 and 24h post-exercise and blood samples at rest, mid-exercise, 0, 0.3, 1, 2, 40
4 and 24h post-exercise. Serum IL-15 was increased by ~5.3-fold immediately post-exercise, 41
while serum IL-15Rα decreased ~75% over 1h post-exercise (P<0.001). Skeletal muscle IL-42
15Rα mRNA and protein expression were increased at 4h post-exercise by ~2-fold (P<0.001) 43
and ~1.3-fold above rest (P=0.020), respectively. At 24h post-exercise IL-15 (P=0.003) and IL-44
15Rα mRNAs increased by ~2-fold (P=0.002). Myofibrillar fractional synthetic rate between 0-45
4h was associated with IL-15Rα mRNA at rest (r=0.662, P=0.019), 4h (r=0.612, P=0.029) and 46
24h post-exercise (r=0.627, P=0.029). Finally, the muscle IL-15Rα protein up-regulation was 47
related to Leg press 1RM (r=0.688, P=0.003) and total weight lifted (r=0.628, P=0.009). In 48
conclusion, IL-15/IL-15Rα signalling pathway is activated in skeletal muscle in response to a 49
session of resistance exercise. 50
Keywords: Myokines, IL-15/IL-15Rα axis, strength training, muscle protein 51
synthesis/breakdown. 52
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Q1. What are the contributions in this paper?

`` This is the peer reviewed version of the following article: Pérez-López A, McKendry J, Martin-Rincon M, et al. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ``