Abstract: Circulating miRNAs (ci-miRNAs) are endogenous, non-coding RNAs emerging as potential diagnostic biomarkers. Equine miRNAs have been previously identified including subsets of tissue-specific miRNAs. In order to investigate ci-miRNAs as diagnostic tools, normal patterns of expression for different scenarios including responses to exercise need to be identified. Human studies have demonstrated that many ci-miRNAs are up-regulated following exercise with changes in expression patterns in skeletal muscle. However, technical challenges such as haemolysis impact on accurate plasma ci-miRNA quantification, with haemolysis often occurring naturally in horses following moderate-to-intense exercise. The objectives of this study were to identify plasma ci-miRNA profiles and skeletal muscle miRNAs before and after exercise in Thoroughbreds (Tb), and to evaluate for the presence and effect of haemolysis on plasma ci-miRNA determination. Resting and post-exercise plasma ci-miRNA profiles and haemolysis were evaluated in twenty 3 year-old Tbs in sprint training. Resting and post-exercise skeletal muscle miRNA abundance was evaluated in a second cohort of eleven 2 year-old Tbs just entering sprint training. Haemolysis was further quantified in resting blood samples from twelve Tbs in sprint training. A human plasma panel containing 179 miRNAs was used for profiling, with haemolysis assessed spectrophotometrically. Data was analysed using a paired Student's t-test and Pearson's rank correlation. Results: Plasma ci-miRNA data for 13/20 horses and all skeletal muscle miRNA data passed quality control. From plasma, 52/179 miRNAs were detected at both time-points. Haemolysis levels were greater than the threshold for accurate quantification of ci-miRNAs in 18/25 resting and all post-exercise plasma samples. Positive correlations (P < 0.05) between haemolysis and miRNA abundance were detected for all but 4 miRNAs, so exercise-induced changes in plasma ci-miRNA expression could not be quantified. In skeletal muscle samples, 97/179 miRNAs were detected with 5 miRNAs (miR-21-5p, let-7d-3p, let-7d-5p, miR-30b-5p, miR-30e-5p) differentially expressed (DE, P < 0.05) between time-points. Conclusions: The degree of haemolysis needs to be determined prior to quantifying plasma ci-miRNA expression from horses in high-intensity exercise training. Identification of DE miRNAs in skeletal muscle indicates modification of miRNA expression may contribute to adaptive training responses in Tbs. Using a human plasma panel likely limited detection of equine-specific miRNAs.
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The research evaluates how a certain type of RNA in horses, called microRNA, change in response to exercise in racehorses. The study focused both on microRNAs found in the bloodstream and those inside muscle tissue. The results suggest that the degree of red blood cell destruction, known as haemolysis, needs to be considered when studying blood-based microRNA in horses, as it can affect the accuracy of such studies. This knowledge can help in the future development of diagnostic tools.
About MicroRNA and its Significance
MicroRNAs (miRNAs) are small, non-coding RNA molecules that have crucial roles in the regulation of gene expression.
In this study, the researchers were interested in circulating miRNAs (ci-miRNAs) found in the bloodstream and tissue-specific miRNAs in skeletal muscle.
ci-miRNAs are gaining attention as potential diagnostic biomarkers in many diseases due to their stability and detectability in plasma and other body fluids.
The Research Methodology
Three separate groups of Thoroughbred horses in sprint training were studied with different aims: to identify the normal profiles of plasma ci-miRNAs and skeletal muscle miRNAs, investigate the changes these molecules undergo after exercise, and assess the impact of haemolysis on ci-miRNA determination.
Haemolysis, the breakage of red blood cells, is a process that often naturally occurs in Thoroughbred horses after moderate to intense exercise and can potentially influence the measurement of ci-miRNAs in blood plasma.
A panel derived from human plasma, containing 179 miRNAs, was used to profile the ci-miRNAs in horse blood samples.
Haemolysis was monitored using a method called spectrophotometry, and the results were analyzed with statistical methods.
Key Findings
The study found that 52 out of 179 miRNAs being investigated were detectable in the plasma samples, while 97 were detectable in the skeletal muscle samples.
The degree of haemolysis was greater than the threshold required for accurate miRNA quantification in a majority of the plasma samples. This result suggests the importance of determining haemolysis prior to quantifying plasma ci-miRNAs in horses, especially those undergoing high-intensity exercise.
Five miRNAs were differentially expressed (meaning their expression was significantly different before and after exercise) in skeletal muscle samples.
The results imply that changes in miRNA expression may contribute to the way horses’ bodies adapt to training.
Limitations and Future Directions
The study used a panel designed for human plasma to detect miRNAs in horse samples, which likely limited the detection of horse-specific miRNAs.
Future research should take into consideration horse-specific miRNA detection and also continue to explore the role of miRNAs in training adaptation.
Cite This Article
APA
McGivney BA, Griffin ME, Gough KF, McGivney CL, Browne JA, Hill EW, Katz LM.
(2017).
Evaluation of microRNA expression in plasma and skeletal muscle of thoroughbred racehorses in training.
BMC Vet Res, 13(1), 347.
https://doi.org/10.1186/s12917-017-1277-z
UCD School of Agriculture and Food Science, Section of Animal & Crop Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
Griffin, M E
UCD School of Veterinary Medicine, Section of Veterinary Biomedical Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
Gough, K F
UCD School of Agriculture and Food Science, Section of Animal & Crop Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
McGivney, C L
UCD School of Agriculture and Food Science, Section of Animal & Crop Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
Browne, J A
UCD School of Agriculture and Food Science, Section of Animal & Crop Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
Hill, E W
UCD School of Agriculture and Food Science, Section of Animal & Crop Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
Katz, L M
UCD School of Veterinary Medicine, Section of Veterinary Biomedical Sciences, University College Dublin, Belfield, Dublin 4, Ireland. lisa.katz@ucd.ie.
MeSH Terms
Animals
Female
Hemolysis / physiology
Horses / blood
Horses / metabolism
Male
MicroRNAs / blood
MicroRNAs / metabolism
Muscle, Skeletal / metabolism
Physical Conditioning, Animal / physiology
Rest / physiology
Grant Funding
11/PI/1166 / Science Foundation Ireland
Conflict of Interest Statement
ETHICS APPROVAL: University College Dublin Animal Research Ethics Committee approval, a Department of Health License (B100/3525) and explicit owner/trainer informed consent were obtained for the use of the horses and procedures in this study. CONSENT FOR PUBLICATION: Not applicable. COMPETING INTERESTS: None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper. E.W.H. is a shareholder in Plusvital Ltd., an equine nutrition and genetic testing company. Plusvital Ltd. has been granted a license for commercial use of data contained within patent applications: United States Provisional Serial Number 61/136553 and Irish patent application number 2008/0735, Patent Cooperation Treaty filing: A method for predicting athletic performance potential, September 7, 2009. E.W.H. and L.M.K. are named on the applications. The patent contents are not related to this manuscript. Plusvital Ltd. had no part in the research in the manuscript. PUBLISHER’S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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