Vasorelaxation responses to insulin in laminar vessel rings from healthy, lean horses.
Authors: Wooldridge A A, Waguespack R W, Schwartz D D, Venugopal C S, Eades S C, Beadle R E
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Hyperinsulaemia is well-established as a trigger for laminitis in horses, yet the precise vascular mechanisms remain unclear. Wooldridge and colleagues examined how insulin affects blood vessel relaxation in isolated laminar tissue, using rings of arteries and veins from healthy horses exposed to varying insulin concentrations and pre-treatment protocols, alongside pharmacological inhibition of mitogen-activated protein kinase (MAPK) signalling. Laminar arteries demonstrated dose-dependent relaxation to insulin, but this response became significantly blunted when arteries were pre-incubated with insulin—a finding suggesting that chronic hyperinsulaemia impairs the vasodilatory capacity of these critical vessels. Laminar veins showed minimal relaxation to insulin regardless of treatment conditions, indicating a compartment-specific vascular dysfunction, whilst MAPK inhibition actually enhanced arterial relaxation, pointing to MAPK as a key mediator of vascular dysfunction in hyperinsulinaemia. For equine practitioners, these results suggest that insulin-induced endothelial dysfunction in laminar arteries may compromise nutrient and oxygen delivery to the hoof, providing a mechanistic link between metabolic syndrome and laminitis; further, the established in vitro model offers a valuable platform for testing potential therapeutic interventions before clinical application.
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Practical Takeaways
- •Understanding differential vascular responses between laminar arteries and veins to insulin may help explain the vascular component of hyperinsulinemia-induced laminitis in clinical cases
- •This in vitro model provides a potential tool for testing new therapeutic interventions targeting insulin-related vascular dysfunction in laminitis-prone horses
- •Hyperinsulinemic horses may have compromised laminar vascular regulation that could contribute to laminitis development, supporting the importance of insulin management in at-risk individuals
Key Findings
- •Laminar veins showed minimal relaxation response to insulin regardless of preincubation conditions, while arteries demonstrated insulin-induced relaxation that was blunted after insulin preincubation
- •MAPK inhibitor PD-98059 increased arterial relaxation response to insulin, indicating MAPK plays a role in maintaining basal tone in laminar arteries
- •In vitro insulin incubation successfully induced vascular dysfunction in laminar arteries, demonstrating a model for studying hyperinsulinemia-related laminitis mechanisms