Equine laminitis: induced by 48 h hyperinsulinaemia in Standardbred horses.
BACKGROUND
Hyperinsulinaemia is known to induce laminitis experimentally in healthy ponies with no history of the condition. Horses are more insulin sensitive than ponies and whether prolonged hyperinsulinaemia and euglycaemia would have a similar laminitogenic effect requires study.


OBJECTIVE
To determine if laminitis results when the prolonged euglycaemic hyperinsulinaemic clamp technique (p-EHC) is applied to clinically normal Standardbred horses, and to monitor hoof wall temperature seeking an association between vascular activity and laminitis development.


METHODS
Eight young, clinically normal Standardbred horses were assigned into 4 pairs and within each pair, one was assigned randomly to either treatment (n = 4) or control (n = 4) groups. Treated horses received continuous infusions of insulin and glucose until clinical signs of laminitis developed, at which point the horses were subjected to euthanasia. Control horses received an equivalent volume of a balanced electrolyte infusion for the same period. Hoof wall surface temperature (HWST) was monitored continuously throughout the experimental period.


RESULTS
All horses in the treatment group were calculated to have normal insulin sensitivity. All treated horses, and none in the control group, developed laminitis (P = 0.01). Pronounced digital pulses were a feature of the treatment group, while insignificant digital pulses occurred in control horses. HWST was higher and less variable in treated horses once hyperinsulinaemia was established.


CONCLUSIONS
Healthy Standardbred horses subjected to prolonged hyperinsulinaemia develop laminitis within 48 h, demonstrating that laminitis in horses can be triggered by insulin.


CONCLUSIONS
Insulin resistance and the associated hyperinsulinaemia place horses and ponies at risk of developing laminitis. This study demonstrates a need for prompt management of the persistent hyperinsulinaemia seen in some endocrinopathies.
Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Brisbane, Queensland 4072, Australia.
M A
MA
de Laat
C M
CM
McGowan
M N
MN
Sillence
C C
CC
Pollitt
D000818:Animals; D005260:Female; D005534:Foot Diseases / Q000139:chemically induced / Q000209:etiology / Q000662:veterinary*; D006724:Hoof and Claw / Q000187:drug effects* / Q000473:pathology; D006736:Horses; D006946:Hyperinsulinism / Q000139:chemically induced / Q000150:complications / Q000662:veterinary*; D007249:Inflammation / Q000662:veterinary; D007328:Insulin / Q000009:adverse effects*; D008297:Male
D007328:Insulin