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Plasma Homocysteine Concentrations in Horses with Left-Sided Valvular Heart Disease.
Abstract: In human medicine, homocysteine, a sulfur-containing amino acid, is used as a biomarker reflecting endothelial dysfunction, inflammation, thrombogenesis, oxidative stress and cardiovascular disease. An automated enzyme-cycling assay for homocysteine, established for humans, has been validated and reference ranges have been created for horses. In this study the homocysteine assay was further evaluated by assessing short-term stability (whole blood and plasma samples stored at 4 °C and room temperature for 24 h), long-term stability (two years), the effect of different anticoagulants (lithium heparin, sodium citrate, EDTA, no additives) and repeated freeze-thaw cycles (five times). Further, associations between plasma homocysteine concentrations ([HCY]) and echocardiographic variables of left heart size, left heart function, and left-sided valve regurgitation were investigated. Homocysteine concentrations remained stable in whole blood at room temperature for at least four hours, or longer when plasma is separated and kept at 4 °C. Samples could be collected in serum blood tubes, lithium heparin (LH), or EDTA without affecting homocysteine concentrations ([HCY]). Plasma [HCY] in frozen samples increased slightly with storage time (years), though up to five freeze-thaw cycles did not affect [HCY]. In a cohort of 169 horses with left-sided valvular regurgitation, plasma creatinine concentrations and age were positively associated with higher [HCY], but no association between [HCY] and changes in cardiac size, function or severity of valvular regurgitation could be established. Homocysteine is not associated with left-sided valvular heart disease in horses and is not a useful biomarker for structural or functional cardiac changes.
Publication Date: 2026-07-26 PubMed ID: 42588945DOI: 10.3390/ani16152307Google 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 evaluated the stability and measurement of plasma homocysteine in horses, and investigated whether homocysteine levels are related to left-sided valvular heart disease in horses.
- The research found that while homocysteine measurement is reliable under various conditions, plasma homocysteine levels do not correlate with heart disease severity in horses, indicating it is not a useful biomarker for this condition in equine patients.
Background and Purpose
- Homocysteine is a sulfur-containing amino acid used in human medicine as a biomarker for:
- Endothelial dysfunction
- Inflammation
- Thrombogenesis (formation of blood clots)
- Oxidative stress
- Cardiovascular disease
- Similar assays to measure homocysteine have been validated for use in horses, with established reference ranges.
- The purpose of this study was:
- To further evaluate the stability and reliability of the homocysteine assay under various pre-analytical conditions in horses.
- To examine any associations between plasma homocysteine levels and echocardiographic indicators of left heart size, function, and valve regurgitation in horses with left-sided valvular heart disease.
Methods: Assay Validation and Stability Testing
- Short-term stability was tested by storing whole blood and plasma samples at 4 °C and room temperature for 24 hours.
- Long-term stability was examined over a two-year period of frozen sample storage.
- Effects of different anticoagulants on homocysteine levels were assessed:
- Lithium heparin (LH)
- Sodium citrate
- EDTA
- No additives (serum tubes)
- Impact of repeated freeze-thaw cycles (up to five times) on homocysteine concentration was evaluated.
Findings: Assay Stability and Reliability
- Homocysteine concentrations remained stable in whole blood samples kept at room temperature for at least four hours.
- Plasma samples that were separated and stored at 4 °C maintained stability for longer periods.
- Samples collected with serum blood tubes, lithium heparin, or EDTA anticoagulants did not show differences in homocysteine concentration, indicating assay flexibility regarding sample type.
- Frozen samples showed a slight increase in homocysteine concentration over years but the extent was small.
- Up to five freeze-thaw cycles did not significantly alter homocysteine measurements, demonstrating robustness during repeated handling.
Clinical Associations with Left-Sided Valvular Heart Disease
- The study analyzed 169 horses diagnosed with left-sided valvular regurgitation, evaluating associations between plasma homocysteine levels and:
- Left heart size (echocardiographic measure)
- Left heart function
- Severity of valvular regurgitation
- Results showed that higher plasma homocysteine concentrations were positively associated with:
- Increased plasma creatinine levels (indicating kidney function)
- Older age of the horse
- There was no significant relationship between homocysteine levels and:
- Changes in cardiac size
- Cardiac functional measures
- Severity of valve regurgitation
Conclusions and Implications
- The homocysteine assay is reliable and stable for equine plasma under various sample handling and storage conditions.
- Despite its utility in human cardiovascular disease, plasma homocysteine is not associated with structural or functional cardiac changes in horses suffering from left-sided valvular heart disease.
- Therefore, homocysteine concentrations are not a useful biomarker for diagnosing or monitoring left-sided valvular heart disease in horses.
- Elevated homocysteine levels correlate with age and kidney function in horses, which may be factors to consider in interpreting results.
Cite This Article
APA
Egli P, Williams Louie E, Stirn M, van Loon G, Decloedt A, Schwarzwald CC, Mitchell KJ.
(2026).
Plasma Homocysteine Concentrations in Horses with Left-Sided Valvular Heart Disease.
Animals (Basel), 16(15), 2307.
https://doi.org/10.3390/ani16152307 Publication
Researcher Affiliations
- Equine Department, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
- Clinical Laboratory, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
- Equine Cardioteam Ghent, Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium.
- Equine Cardioteam Ghent, Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium.
- Equine Department, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
- Equine Department, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Grant Funding
- Stiftung Pro Pferd, University of Zurich
Citations
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