In vitro and in vivo studies of homocysteine in equine tissues: implications for the pathophysiology of laminitis.
Authors: Berhane Y, Bailey S R, Harris P A, Griffiths M J, Elliott J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Homocysteine and Equine Endothelial Function Homocysteine (HCy) is recognised in human medicine as a vascular risk factor linked to endothelial dysfunction and ischaemic disease, prompting Berhane and colleagues to investigate whether elevated plasma HCy might similarly compromise equine digital vascular health and predispose to laminitis. Using both in vitro cell culture work and intact tissue perfusion studies, the researchers exposed equine digital vein endothelial cells and isolated perfused digits to various HCy concentrations whilst measuring nitric oxide (NO) production and vasodilatory responses. HCy at concentrations of 10 and 100 micromol/l inhibited endothelial function in the isolated digit model, with higher concentrations (>100 micromol/l) suppressing NO production by cultured cells; however, resting plasma HCy levels in both normal and laminitis-susceptible ponies measured only 13–14.7 micromol/l, showing no seasonal variation or disease-related elevation. Whilst the in vitro findings demonstrate that physiologically achievable HCy concentrations can impair the endothelial mechanisms critical for digit perfusion regulation, the absence of elevated baseline plasma HCy in clinically affected animals suggests this may not be a primary driver of laminitis risk—though practitioners should remain mindful that management practices elevating HCy (such as B-vitamin deficiency) could theoretically compromise vascular resilience in susceptible individuals.
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Practical Takeaways
- •Management practices that elevate plasma homocysteine should be avoided in laminitis-susceptible ponies, as homocysteine can impair the digital vascular endothelium at physiologically relevant concentrations
- •While this study did not establish plasma homocysteine as a laminitis risk factor, the in vitro evidence supports monitoring dietary and management factors known to increase homocysteine levels
- •Consider homocysteine metabolism when evaluating nutritional protocols for laminitis-prone horses, particularly regarding B-vitamin status (B6, B12, folate)
Key Findings
- •Homocysteine at 10-100 micromol/l inhibited equine vascular endothelial cell function in vitro
- •Homocysteine concentrations above 100 micromol/l reduced nitric oxide production by cultured equine digital vein endothelial cells
- •Plasma total homocysteine concentrations in normal and laminitis-predisposed ponies ranged 13-14.7 micromol/l with no seasonal or disease status effect
- •No significant association was found between elevated plasma homocysteine and risk of laminitis despite in vitro evidence of endothelial dysfunction