Laminitis is a painful condition of the equine foot which can result in permanent lameness or euthanasia affecting 1.5-34% of horses.

It occurs as a single acute episode or, more commonly, as repeated bouts (recurrent laminitis). The disease most frequently arises in association with pasture consumption, although gastrointestinal disease, endotoxaemia and endocrine disorders are also risk factors. However the exact pathogenesis of the disease remains to be determined.

White pony grazing in a field
A 10 year old laminitis prone pony with a metabolic phenotype which includes hyperinsulinaemia and obesity. (Photo credit: Nicola Menzies-Gow)

Animals at greatest risk of pasture-associated laminitis have a metabolic phenotype which includes high circulating concentrations of the hormone insulin (hyperinsulinaemia) and/or abnormal responses to insulin (insulin dysregulation), altered circulating concentrations of fat (dyslipidaemia) and of hormones produced by fat (adipokines), and obesity (in some but not all individuals) similar to that in seen human metabolic syndrome (HMS).

Consequently, the same pathologic mechanisms that underlie the cardiovascular diseases associated with HMS, including changes in insulin signalling, adipokines and endothelial (cells which line every blood vessel) function could contribute to equine laminitis. Thus, our research currently focusses on endothelial function in normal and recurrently laminitic ponies; and on whether metabolic alterations occur prior to disease occurrence and if management practices influence laminitis development in animals with no previous laminitis.

flow meter attached to a pony's leg
Measuring flow mediated vasodilation in a pony using Doppler ultrasonography (Photo credit: Liz Finding)

Concentrating on endothelial function includes trying to adapt some of the non-invasive techniques used in people to assess endothelial function. These techniques include those which utilise Doppler ultrasound to assess blood flow within specific vessels after temporary occlusion and measurement of concentrations of certain hormones and metabolites within the blood which reflect endothelial function. Additionally a novel method for isolating endothelial cells from the blood and growing them in the laboratory is being validated to allow the function of endothelial cells from specific individuals to be assessed.

Our research focusing on metabolic alterations prior to disease onset and the influence of management practices involves a prospective study using ponies with no previous laminitis. Animals are evaluated every 6 months for up to 4 years including assessment of obesity, insulin dysregulation and measurement of circulating concentrations of lipids and adipokines. At the end of the four-year period, a predictive algorithm for laminitis predisposition based on a number of risk factors and test results will be developed. In addition, the management regimens will be assessed in order to determine their influence on laminitis development.

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