Abstract
Repeated bouts of episodic myofibrillar contraction associated with exercise training are potent stimuli for physiological adaptation. However, the time course of adaptation and the continuity between alterations in mRNA expression and protein content are not well described in human skeletal muscle. Eight healthy, sedentary males cycled for 60 min at 80% of peak oxygen consumption (VO2peak) each day for fourteen consecutive days, resulting in an increase in VO2peak of 17.5±3.8%. Skeletal muscle biopsies were taken at baseline, and on the morning following (+16 h after exercise) the first, third, seventh, tenth and fourteenth training sessions. Markers of mitochondrial adaptation (Cyt c and COXIV expression, and citrate synthase activity) were increased within the first week of training, but the mtDNA/nDNA ratio was unchanged by two weeks of training. Accumulation of PGC-1α and ERRα protein during training suggests a regulatory role for these factors in adaptations of mitochondrial and metabolic gene expression. A subset of genes were transiently increased after one training session, but returned to baseline levels thereafter, which is supportive of the concept of transcriptional capacity being particularly sensitive to the onset of a new level of contractile activity. Thus, gene-specific temporal patterns of induction of mRNA expression and protein content are described. Our results illustrate the phenomenology of skeletal muscle plasticity and support the notion that transcript level adjustments, coupled to accumulation of encoded protein, underlie the modulation of skeletal muscle metabolism and phenotype by regular exercise.
Highlights
The phenomenon of skeletal muscle plasticity is illustrated by the remodeling of muscle’s structure and functional make-up, as seen in muscular force, endurance and contractile velocity, as a result of alterations in functional demand [1,2]
We have recently reported that extensive remodeling of the human skeletal muscle mitochondrial proteome is achieved by short-term aerobic exercise training [25]
Exercise training resulted in 17.863.5% increase in VO2peak compared to pre-training values (P = 0.002, Figure 3A), with individual improvements ranging from 1.3% to 36.6% (Figure 3B)
Summary
The phenomenon of skeletal muscle plasticity is illustrated by the remodeling of muscle’s structure and functional make-up, as seen in muscular force, endurance and contractile velocity, as a result of alterations in functional demand [1,2] These adaptations in skeletal muscle to exercise training are widely-hypothesized to result from the gradual alteration of protein content consequent to repeated, but transient, alterations in transcript abundance induced by individual, acute bouts of exercise [3,4]. Transcript induction is transient, but generally several-fold above resting values, peaking 3–12 h after cessation of exercise, and returning to basal levels within 24 hours [5,9]. Molecular events underlying training adaptations in this time frame occur at the level of the mitochondrion [15], and metabolic [13], intracellular signaling [18], and transcriptional [5] responses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
