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Researchers have identified more than 3000 genes in the Thoroughbred with a role in equine skeletal muscle’s remarkable ability to adapt to physical exercise and long-term training.
University College Dublin researchers set out in their study to explore equine skeletal muscle adaptations to exercise and training in Thoroughbreds at a genetic level.
“Equine athletes have a genetic heritage that has been influenced by millions of years of evolution as grazing animals on prairie and steppe,” Kenneth Bryan and his colleagues wrote in the journal BMC Genomics.
“More recently, centuries of intense selective breeding in the Thoroughbred horse has led to the refinement of multiple physiological adaptations for athletic performance, resulting in an ideal model of a natural athlete for the investigation of exercise and adaptive training responses.”
Equine skeletal muscle, they said, showed a remarkable ability to adapt to physical exercise and long-term training. However, the gene-based and molecular changes underlying these adaptive responses had yet to be fully explored.
Cyclic muscle contraction during repeated exercise over time − training or conditioning − is known to induce physiological adaptation in skeletal muscle.
“In equine athletes, training generally leads to an increase in muscle mass and aerobic capacity but the specific response, in terms of muscle fibre type and metabolic adaptation, depends mainly on the type of training regime (e.g. endurance or sprint type exercise), nutrition and an individual’s specific genetic potential.”
In their study, which used 51 young Thoroughbreds, the researchers explored changes in the transcriptome – that’s the the sum total of all the messenger RNA molecules expressed from the genes of an organism – of the skeletal muscle of untrained horses in response to a single bout of high-intensity sprint exercise, and following a six-month training regime.
“We hypothesised that regular bouts of high-intensity exercise training would prime the transcriptome of Thoroughbred skeletal muscle for the demands of the next exercise bout.”
The researchers found that an extensive set of genes, 3241 in all, were significantly differentially regulated − that is, their production of specific gene products were significantly altered − in response to a single bout of high-intensity exercise in the untrained group. Following multiple bouts of high-intensity exercise training over a six-month period, 3405 genes were found to be similarly affected.
About one-third of these genes – 1025 – and several biological processes related to energy metabolism were common to both the exercise and training responses.
The study team said they had generated, for the first time, a comprehensive set of genes that were differentially expressed (respond to signals or triggers) in Thoroughbred skeletal muscle in response to both exercise and training.
The data, they said, indicated that consecutive bouts of high-intensity exercise resulted in a priming of the skeletal muscle transcriptome for the demands of the next exercise session.
The authors noted that, given the training period for the young Thoroughbreds was six months, it was possible that some of the changes in gene expression attributed to training may be age-related.
The study team comprised Bryan, Beatrice McGivney, Gabriella Farries, Paul McGettigan, Charlotte McGivney, Katie Gough, David MacHugh, Lisa Katz and Emmeline Hill.
Equine skeletal muscle adaptations to exercise and training: evidence of differential regulation of autophagosomal and mitochondrial components
Kenneth Bryan, Beatrice A. McGivney, Gabriella Farries, Paul A. McGettigan, Charlotte L. McGivney, Katie F. Gough, David E. MacHugh, Lisa M. Katz and Emmeline W. Hill.
BMC Genomics 2017 18:595 https://doi.org/10.1186/s12864-017-4007-9