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Temporal and intra-horse consistency of circulating myostatin concentrations in Thoroughbred racehorses.
Abstract: In Thoroughbred horses, a highly prevalent short interspersed nuclear element (SINE) mutation in the myostatin gene (MSTN) promoter influences circulating myostatin concentration and is associated with muscle morphology, fracture risk and optimal race distance. Our prior data reveal that within horses there is substantial variation in serum myostatin concentration, particularly in MSTN heterozygotes and wild type horses but it was unclear whether such variation relates to within-horse differences or to environmental or temporal effects. Here we report the intra-horse consistency of circulating myostatin, and investigated the hypothesis that it is affected by season. 49 racing Thoroughbreds under identical management were genotyped for the MSTN promoter SINE insertion and myostatin concentrations were measured in plasma with a validated enzyme-linked immunosorbent assay, from blood samples collected repeatedly over a year. As expected, genotype was significantly associated with circulating myostatin, with homozygotes having the lowest concentration, followed by heterozygous and then wild-type horses. Intra-horse plasma myostatin had low to moderate variability throughout the year, within genotyped groups (coefficient of variation: 17 to 23%): aside from a direct mutation effect, horses tended to be low, moderate, or higher myostatin expressers. Neither season, sex, nor age significantly influenced plasma myostatin concentration. Further work is necessary to determine whether an individual's plasma myostatin concentration is associated with any performance advantages, muscle characteristics or fracture risk within SINE genotyped groups.
© 2025. The Author(s).
Publication Date: 2025-11-05 PubMed ID: 41193553PubMed Central: PMC12589566DOI: 10.1038/s41598-025-22472-7Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Overview
- This study investigated the consistency of circulating myostatin protein levels within individual Thoroughbred racehorses over time and examined whether factors like season, sex, or age influence these levels.
- The researchers also explored how genetic differences in the myostatin gene promoter affect circulating myostatin concentrations.
Background
- Myostatin is a protein that regulates muscle growth, with variations in its levels linked to muscle characteristics and injury risks in horses.
- A specific genetic mutation—a short interspersed nuclear element (SINE) insertion in the promoter region of the myostatin gene (MSTN)—is common in Thoroughbred racehorses and known to affect circulating myostatin concentrations.
- This SINE mutation correlates with traits relevant to racing such as muscle morphology, fracture risk, and optimal race distance.
- Previous observations showed considerable variation in serum myostatin levels within horses, especially among those with heterozygous or wild-type MSTN genotypes, but it was unclear whether this variability was due to individual differences or external factors like environment or time.
Objectives
- To determine the consistency of circulating myostatin levels within individual horses over a one-year period.
- To analyze whether circulating myostatin concentrations are influenced by season, sex, or age.
- To confirm if MSTN genotypes predict plasma myostatin concentrations in a group of standardized management Thoroughbred racehorses.
Methods
- Sample Population: 49 Thoroughbred racehorses managed identically were included.
- Genotyping: Horses were genotyped for the MSTN promoter SINE insertion mutation, categorizing them into homozygous mutant, heterozygous, or wild-type groups.
- Data Collection: Blood samples were collected repeatedly over a year to measure plasma myostatin concentrations.
- Myostatin Measurement: A validated enzyme-linked immunosorbent assay (ELISA) was used to quantify circulating myostatin levels.
- Analysis: Within-horse variability in myostatin concentration over time was computed using the coefficient of variation (CV). The effects of genotype, season, sex, and age on myostatin levels were statistically evaluated.
Key Findings
- Genotype Effects:
- Horses homozygous for the SINE mutation had the lowest plasma myostatin concentrations.
- Heterozygous horses showed intermediate levels.
- Wild-type horses (no mutation) exhibited the highest myostatin concentrations.
- Intra-Horse Variability:
- Within individual horses, myostatin levels showed low to moderate variability over the year (CV ranged from 17% to 23%) within genotype groups.
- This suggests a relatively consistent baseline myostatin expression per horse, with some horses naturally expressing lower or higher levels.
- Influence of External Factors:
- Season did not significantly affect circulating myostatin levels.
- Sex and age were also not significant modulators of plasma myostatin concentrations.
Implications
- The findings reinforce that the MSTN promoter mutation is a major genetic control element of circulating myostatin levels in Thoroughbreds.
- The individual consistency in myostatin expression implies stable regulation within horses regardless of seasonal or demographic factors.
- These consistent individual myostatin levels might influence muscle characteristics and injury risks but require further investigation.
- Understanding myostatin profiles more thoroughly could potentially assist in tailoring training or management plans according to genetic and physiological muscle growth predispositions.
Recommended Future Research
- Explore whether an individual horse’s stable myostatin concentration correlates with performance outcomes such as race success or muscle condition.
- Investigate relationships between circulating myostatin and fracture risk within genotypic groups to assess potential predictive or preventative strategies.
- Expand sample size and include different management settings to validate the current findings more broadly.
Cite This Article
APA
Hanousek K, O'Hara V, Riddell DO, Piercy RJ.
(2025).
Temporal and intra-horse consistency of circulating myostatin concentrations in Thoroughbred racehorses.
Sci Rep, 15(1), 38708.
https://doi.org/10.1038/s41598-025-22472-7 Publication
Researcher Affiliations
- Comparative Neuromuscular Diseases Laboratory, Royal Veterinary College, London, UK.
- Comparative Neuromuscular Diseases Laboratory, Royal Veterinary College, London, UK.
- Comparative Neuromuscular Diseases Laboratory, Royal Veterinary College, London, UK.
- Comparative Neuromuscular Diseases Laboratory, Royal Veterinary College, London, UK. rpiercy@rvc.ac.uk.
MeSH Terms
- Animals
- Myostatin / blood
- Myostatin / genetics
- Horses / genetics
- Horses / blood
- Female
- Male
- Genotype
- Short Interspersed Nucleotide Elements
- Promoter Regions, Genetic
- Seasons
Grant Funding
- 6044 / Horserace Betting Levy Board
Conflict of Interest Statement
Declarations. Competing interests: The authors declare no competing interests.
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