Effects of an intravenous endotoxin challenge on glucose and insulin dynamics in horses.

This study evaluates how the injection of endotoxins affects glucose and insulin dynamics in horses, revealing a decrease in insulin sensitivity and an increased insulin response following treatment. Long-term, these disturbances may contribute to conditions like laminitis in horses.

Research Methodology

• The study was conducted over a period of two weeks, involving 16 healthy adult mares in a randomized crossover experiment.
• Each horse had an intravenous (IV) injection every week, which was either a bacterial endotoxin known as lipopolysaccharide (LPS) from the Escherichia coli O55:B5 strain or a control treatment of sterile saline solution.
• During the procedure, glucose tolerance tests were performed 24 hours before and 24 and 48 hours after the injections to track glucose and insulin dynamics.

Key Findings

• Out of 16 horses, 13 exhibited a clinical response to the LPS injection, identifiable by symptoms such as mild discomfort or colic and a decrease in white blood cells, or leukopenia.
• Prior to the treatment, the average insulin sensitivity was established as 2.9 x 10⁴ L x min(1) x mU(1). This value significantly decreased to 0.9 x 10⁴ L x min(1) x mU(1) 24 hours after the treatment—a 69% reduction—and further to 1.5 x 10⁴ L x min(1) x mU(1) 48 hours following treatment.
• Simultaneously, there was a significant increase in the acute response of insulin to glucose following LPS treatment, seeing an 80% increase at 24 hours and a 45% increase at 48 hours after treatment.

Implications

• The results indicate that insulin sensitivity in horses was significantly reduced for 24 hours after an IV injection of LPS.
• This decrease in insulin sensitivity triggered a compensatory pancreatic response in the horses, causing greater insulin production in response to glucose.
• These disturbances in both glucose and insulin dynamics could be a contributing factor to the development of laminitic conditions in horses. Laminitis is a serious disease that affects the horse’s feet, causing inflammation and severe pain.
• This study has therefore provided valuable insight into the physiological responses to endotoxins in horses, and potential consequences of these reactions.