Vascular Dysfunction in Horses with Endocrinopathic Laminitis.
Authors: Morgan Ruth A, Keen John A, Walker Brian R, Hadoke Patrick W F
Journal: PloS one
Summary
# Vascular Dysfunction in Horses with Endocrinopathic Laminitis Endocrinopathic laminitis represents a vascular crisis within the hoof, yet its underlying mechanisms remain incompletely understood despite clear associations with equine metabolic syndrome and Cushing's disease. Morgan and colleagues investigated whether impaired blood vessel function—specifically endothelial dysfunction—contributes to laminitis development by examining tissue samples from the hooves and facial skin of six laminitic horses and six healthy controls using wire myography to assess responses to vasoconstrictors (phenylephrine and serotonin) and the vasodilator acetylcholine. The results were striking: acetylcholine-induced relaxation was dramatically suppressed across all intact vessels from affected horses, with laminar artery relaxation reduced from 323.5% to just 90.8% (P = 0.01) and laminar vein relaxation falling from 129.4% to 71.2% (P = 0.005), whilst contractile responses to vasoconstrictors were paradoxically increased in laminitic laminar veins. Critically, these vascular abnormalities appeared systemically—also evident in facial skin arteries—suggesting the dysfunction stems from the underlying endocrinopathy rather than local hoof pathology. For practitioners, this work provides mechanistic insight into why metabolic control remains paramount in laminitis prevention and management; addressing insulin dysregulation and Cushing's disease may directly restore vascular function essential to maintaining laminar blood supply.
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Practical Takeaways
- •Endocrinopathic laminitis involves systemic vascular dysfunction affecting the hoof's blood supply; managing the underlying metabolic syndrome and Cushing's disease is critical for addressing root cause
- •The impaired vasodilation response suggests compromised microvascular perfusion in the laminae, which may explain the severity and recurrent nature of laminitis in metabolically affected horses
- •Screening for equine metabolic syndrome and Cushing's disease in laminitis cases is essential, as vascular dysfunction appears to be a key pathophysiologic mechanism
Key Findings
- •Acetylcholine-induced relaxation was dramatically reduced in laminar arteries (90.8% vs 323.5% in controls, P=0.01), laminar veins (71.2% vs 129.4%, P=0.005), and facial skin arteries (91.4% vs 182.0%, P=0.01) in horses with endocrinopathic laminitis
- •Contractile responses to phenylephrine and 5-HT were significantly increased in intact laminar veins from horses with EL compared to healthy controls
- •Vascular dysfunction in laminar vessels extends systemically to facial skin arteries, indicating the dysfunction is associated with underlying endocrinopathy rather than localized hoof changes