Impact of repeated bouts of eccentric exercise on myogenic gene expression.
Evidence indicates that repeated-bouts of eccentric exercise (EE) do not exacerbate the extent of muscle damage indices, as compared to a single-bout. We hypothesized that molecular adaptations, under repeated-bouts of EE, would include suppression of muscle repair inhibitory factors such as myostatin and up-regulation of muscle repair positive regulatory factors such as myogenic regulatory factors (MRFs). Fifteen males were recruited for this study. The exercise group (n=9) successfully completed six sets of 15 reps of maximum voluntary eccentric contractions, for six consecutive days, using a dynamometer (Multicont-II). Blood and muscle biopsy samples were obtained from each subject 1 week prior to exercise, 2 days post the first training session, and 24 h after the last training session. Gene expression levels were determined using real-time RT-PCR. Blood samples were analyzed for creatine kinase (CK) and lactate-dehydrogenase (LDH) activity. Repeated-bouts of EE induced a large down-regulation of myostatin mRNA (-73%) which persisted throughout the study. The responses of MRFs were mild. At day 3 only myogenin increased significantly (1.9 fold) while MyoD decreased by 45%. Surprisingly, at day 7, despite the presence of muscle damage indices, all MRFs returned to the pre-exercise levels. The results of the present study showed that repeated-bouts of EE, for six consecutive days, dramatically decreased Myostatin mRNA expression but impaired the expression patterns of MRFs such that, with the exception of myogenin that showed a moderate non-sustained increase, MyoD and MYf5 response was minimal.
Costa
Andreas
A
Department of Biomechanics, Faculty of Physical Education and Sport Sciences, Semmelweis University, Budapest, Hungary.
Dalloul
Hicham
H
Hegyesi
Hargita
H
Apor
Peter
P
Csende
Zsolt
Z
Racz
Levente
L
Vaczi
Mark
M
Tihanyi
Jozsef
J
D000328:Adult; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D003402:Creatine Kinase / Q000378:metabolism; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D015444:Exercise / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology*; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology; D017570:MyoD Protein / Q000096:biosynthesis / Q000235:genetics; D051787:Myogenic Regulatory Factor 5 / Q000096:biosynthesis / Q000235:genetics; D018006:Myogenic Regulatory Factors / Q000096:biosynthesis* / Q000235:genetics*; D055435:Myostatin; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*; D015854:Up-Regulation / Q000502:physiology; D054462:p21-Activated Kinases / Q000096:biosynthesis / Q000235:genetics
D018076:DNA, Complementary; D019394:Ki-67 Antigen; C525911:MSTN protein, human; C497417:MYF5 protein, human; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D018006:Myogenic Regulatory Factors; D055435:Myostatin; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D007770:L-Lactate Dehydrogenase; D054462:p21-Activated Kinases; D003402:Creatine Kinase