Continuous intravenous infusion of glucose induces endogenous hyperinsulinaemia and lamellar histopathology in Standardbred horses.

This study investigates the role of glucose in the development of endocrinopathic laminitis in horses. The researchers determined that a continuous intravenous infusion of glucose can cause an endogenous insulin response in the horse’s body and lead to clinical and histopathological symptoms of laminitis.

Study Objective and Methodology

• The aim of this study was to assess the body’s natural insulin response to an amount of glucose equivalent to that used in a euglycaemic, hyperinsulinaemic clamp procedure over a period of 48 hours in insulin-sensitive Standardbred racehorses.
• The study also explored whether the infusion of glucose without the addition of exogenous insulin would result in the development of laminitis – a condition that affects the horse’s lamellae, leading to severe pain and potential lameness.
• The researchers infused a 50% dextrose solution intravenously into the treated horses at a rate of 0.68 mL/kg/h for 48 hours. The control group of horses received a balanced electrolyte solution.
• At the end of the experiment, the researchers examined the lamellar histology of all horses involved in the study.

Results and Findings

• The treated horses displayed insulin sensitivity, developing hyperglycaemia (high blood sugar levels) and hyperinsulinaemia (an excessive amount of insulin).
• Unlike the control horses, those in the treatment group developed glycosuria – an excessive amount of glucose in the urine – indicating that their bodies were not processing the sugar appropriately.
• While none of the horses displayed overt signs of lameness following treatment, all treated horses showed signs of histopathological laminitis in one foot at least.
• On comparing with previous studies, the researchers inferred that laminitis could be caused by insulin alone or in combination with glucose, but it is unlikely to occur as a result of a glucose overload alone.

Conclusions and Implications

• The study concludes that the potential threshold for insulin toxicity that could lead to laminitis in horses may be at or below a serum concentration of around 200 μIU/mL.
• The findings suggest the need for further research to confirm the effects of glucose and insulin levels on the development of laminitis.
• The results have significant implications for the understanding of endocrinopathic laminitis and could help inform feeding and care practices for racehorses and other equines that may be at risk.