Transcriptional events in human skeletal muscle at the outset of concentric resistance exercise training

We sought to ascertain the time-course of transcriptional events that occur in human skeletal muscle at the outset of resistance exercise (RE) training in RE nave individuals, and determine if the magnitude of any response was associated with exercise induced muscle damage. Sixteen RE nave males were recruited, 8 underwent 2 sessions of 5x30 maximum, isokinetic knee extensions (180.s-1) separated by 48 hrs. Muscle biopsies of the vastus lateralis were taken at baseline and 24 hrs after each exercise bout. Eight individuals acted as non-exercise controls with biopsies obtained at the same time intervals. Transcriptional changes were assessed by microarray, and binding of HSP27 and B-crystallin to insoluble proteins by immunohistochemistry as a measure of muscle damage. In control subjects, no probesets were significantly altered (FDR<0.05) and HSP27 and B-crystallin binding remained unchanged throughout the study. In exercised subjects, significant inter-subject variability following the initial bout of RE was observed in the muscle transcriptome, with greatest changes occurring when HSP27 and B-crystallin binding was elevated. Following the second bout of RE, the transcriptome response was more consistent among subjects revealing a cohort of probesets associated with immune activation, the suppression of oxidative metabolism and protein ubiquitination as differentially regulated. The results reveal that the initial transcriptional response to RE is highly variable in RE nave volunteers, is associated with muscle damage, and unlikely to reflect longer-term adaptations to RE training. These results highlight the importance of considering multiple time-points when determining the transcriptional response to RE and associated physiological adaptation.

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Murton AJ, Billeter R, Stephens FB, Des Etages SG, Graber F, Hill RJ, Marimuthu K, Greenhaff PL