Author(s): VAN DOORSLAER DE TE RYEN, S., WARNIER, G., ANTOINE, N., BOYER, E., KIENLEN-CAMPARD, P., COPINE, S., FRANCAUX, M., DELDICQUE, L., Institution: UNIVERSITÉ CATHOLIQUE DE LOUVAIN, Country: BELGIUM, Abstract-ID: 277

INTRODUCTION:
Satellite cells participate to myogenesis and contribute to skeletal muscle regeneration and hypertrophy. Amongst other stimuli, satellite cells can be activated by exercise and hypoxia. However, the cumulative effect of those conditions on myogenesis is not well understood yet, certainly in human. Furthermore, whether satellite cells activation and myogenesis differs between environmental hypoxia and blood flow restriction is not known.
The purpose of this study was to analyse satellite cell and myogenic markers in response to an acute eccentric resistance exercise in normoxia, normobaric environmental hypoxia and with blood flow restriction (local hypoxia).
METHODS:
Thirty-eight healthy young men were allocated to one of the three experimental conditions: normoxia (n=13), normobaric environmental hypoxia (n=12) and blood flow restriction (n=13). They all performed 5 series of 15 repetitions at 60°/s for the knee extension and 30°/s for the knee flexion on an isokinetic dynamometer. Vastus lateralis muscle biopsies and blood samples were taken before, 1 h, 24 h and 72 h after exercise. In addition, human skeletal muscle myotubes were stimulated with electrical pulse stimulation at 21%, 5% and 1% O2 and directly harvested.
RESULTS:
Pax7 and myogenic regulatory factor expression were upregulated after exercise to a greater extent in the normoxic group than in the hypoxic group and almost blunted in the blood flow restriction group. Additionally, compared to pre-exercise, circulating creatine kinase levels increased at 72 h post-exercise by about 5-fold in normoxia and by about 20-fold in normobaric environmental hypoxia but did not change with blood flow restriction. Despite differential regulation of myogenic regulatory factor expression and circulating creatine kinase levels, none of the regulators of myogenesis investigated such as immediate early genes, inflammatory markers and the mitogen-activated protein kinase pathway was differently regulated between the groups. In vitro experiments showed no changes in myogenic regulatory factors between conditions.
CONCLUSION:
Contrary to our hypothesis, satellite cell activation and myogenesis were not potentiated by the combination of eccentric resistance exercise and hypoxic conditions. Satellite cell and myogenic markers were expressed in a lesser extent when exercising with blood flow restriction than in environmental hypoxia.