A potential role for lamellar insulin-like growth factor-1 receptor in the pathogenesis of hyperinsulinaemic laminitis.

This study investigates how sustained high concentrations of insulin could cause laminitis, a painful condition affecting the hooves of horses, potentially through the activation of insulin-like growth factor-1 receptors (IGF-1R) in the hoof. Researchers found that the expression of IGF-1R and insulin receptor genes was reduced during experiments, and that serum IGF-1 concentrations remained unchanged, suggesting that these receptors could be down-regulated by insulin. The findings suggest that insulin-induced activation of IGF-1R could contribute to the damaging proliferation of cells in the hoof, providing a potential area for treatment research.

Understanding the Problem

• This study focuses on laminitis in horses, a painful and severe health condition that affects the hooves. The process leading to this disease isn’t fully understood; however, prolonged high concentrations of insulin in the bloodstream have been identified as a possible cause.
• During laminitis, cell proliferation has been observed in the horse’s hoof (lamellae) – a possible link to insulin and receptor activity.
• Insulin-like growth factor (IGF-1) is pivotal for cell proliferation, and under high insulin concentrations, might get its receptors (IGF-1R) activated. This speculation formed the basis of this research study.

The Experiment

• The researchers aimed to test if IGF-1 receptors got activated during insulin-induced laminitis by studying the gene expression for IGF-1R and the insulin receptor in horses’ lamellar tissue under controlled conditions.
• Expression was measured during the mid-developmental and acute phases of induced laminitis via a euglycaemic, hyperinsulinaemic clamp.
• they also aimed to test whether a potential increase in circulating IGF-1 could account for the down-regulation observed in receptor gene expression.
• To do this, the serum IGF-1 was measured post-treatment in horses that were given a prolonged EHC alongside controls.

Findings and Implications

• The results showed that the gene expression for both IGF-1R and insulin receptors decreased considerably during the experiment. In addition, there was no measurable increase in serum IGF-1 concentrations.
• This suggested that both types of receptors might be down-regulated by insulin.
• Further, this study implicates insulin’s activation of IGF-1R in mediating the abnormal cell proliferation in the lamellae, which may lead to laminitis.
• This insight could help guide future research into the disease’s pathogenesis and possible treatments targeting this receptor.