Skeletal Muscle Fiber Type Composition and Citrate Synthase Activity in Fit and Unfit Warmbloods and Quarter Horses.
Abstract: Selective breeding and discipline specific training has led to equine breeds adept at various athletic disciplines. Breed-specific skeletal muscle adaptations have been studied in many breeds but not Warmbloods (WB). We evaluated gluteal muscle contractile muscle fiber types and citrate synthase activity (CS), a marker for mitochondrial volume density, in WB trained for dressage (second level-Grand Prix) contrasted with Quarter Horses (QH). Gluteus medius muscle biopsies from 14 unfit/18 fit dressage-trained WB and 20 unfit/16 fit reining/working cow QH were analyzed fluorometrically and fiber types determined by ATPase activity. Comparisons were made by one-way ANOVA. Unfit and fit WB had significantly higher % type 1 and lower % type 2X fibers than QH. Unfit WB had significantly higher CS than unfit QH but CS did not differ between fit WB and fit QH. CS was only significantly higher in fit versus unfit QH, not fit versus unfit WB. In conclusion, WB gluteal muscle has an inherently high % type 1/low % type 2X fibers and high mitochondrial content whether unfit or trained for dressage, contrasting QH with an inherently low % type 1/high % type 2X and low mitochondrial content, that was enhanced in fit QH. Similar CS activity in fit WB versus QH despite a two-fold difference in % type 2X fibers indicates that mitochondrial volume density cannot accurately be predicted from contractile fiber type composition.
Copyright © 2022. Published by Elsevier Inc.
Publication Date: 2022-09-10 PubMed ID: 36096315DOI: 10.1016/j.jevs.2022.104123Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article investigates the skeletal muscle adaptations in Warmbloods (WB) in comparison to Quarter Horses (QH), with a particular focus on the muscle fiber types and citrate synthase (CS) activity. The purpose of the study is to understand how selective breeding and discipline-specific training has affected muscle composition in these breeds.
Objective and Methodology
- The researchers aimed to analyze skeletal muscle fiber composition and CS activity (a marker for mitochondrial volume density) in both fit and unfit Warmbloods and Quarter Horses.
- This analysis involved taking gluteus medius muscle biopsies from fit and unfit horses in both breeds. These samples were then analyzed via ATPase activity to determine the types of muscle fibers present.
- The researchers compared the data collected from both these breeds using one-way ANOVA.
Findings
- The study found significant differences in the muscle fiber profile between the breeds. Both fit and unfit WBs had a significantly higher proportion of type 1 fibers and lower proportion of type 2X fibers compared to QHs.
- The CS activity differed between the breeds and reflected fitness level to some extent. Unfit WBs demonstrated significantly higher CS activity than unfit QHs. However, there was no significant difference in CS activity between the fit WBs and fit QHs.
- CS activity was notably higher in fit QHs compared to unfit ones. This increase was not found between the fit and unfit WBs, suggesting that fitness training has different impacts on mitochondrial dynamics across breeds.
Conclusions
- The research concluded that WBs inherently have a high percentage of type 1 (slow-twitch) fibers and low percentage of type 2X (fast-twitch) fibers regardless of their fitness level. They also have high mitochondrial content; this contrasts with QHs that are inherently low in type 1 fibers, high in type 2X fibers, and that have low mitochondrial content.
- The research also suggested that the mitochondrial volume density (as indicated by citrate synthase activity) can’t accurately be predicted from the contractile fiber type composition alone. This was concluded based on the similar CS activity observed in fit WBs and QHs, even though there was a significant difference in type 2X fibers between the breeds.
Cite This Article
APA
Valberg SJ, Iglewski H, Henry ML, Schultz AE, McKenzie EC.
(2022).
Skeletal Muscle Fiber Type Composition and Citrate Synthase Activity in Fit and Unfit Warmbloods and Quarter Horses.
J Equine Vet Sci, 118, 104123.
https://doi.org/10.1016/j.jevs.2022.104123 Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing MI. Electronic address: valbergs@msu.edu.
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing MI.
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing MI.
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing MI.
- Department of Clinical Sciences, Carlson College of Veterinary Medicine, Oregon State University 227 Magruder Hall, OR.
MeSH Terms
- Female
- Cattle
- Horses
- Animals
- Citrate (si)-Synthase / metabolism
- Muscle Fibers, Skeletal / metabolism
- Muscle, Skeletal / metabolism
- Buttocks
- Mitochondria
Conflict of Interest Statement
Declaration of Competing Interest None
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