Horses with insulin dysregulation (ID) and hyperinsulinemia are at a greater risk of developing other metabolic problems, such as equine metabolic syndrome, and laminitis secondary to these conditions. Researchers are still working to understand the mechanisms of these diseases, but they believe insulin thresholds for the onset of laminitis likely vary between individual horses based on body mass and preexisting damage to the lamellar tissues that suspend the coffin bone within the hoof. “Insulin dysregulation appears to be mostly related to excessive insulin secretion,” said Melody de Laat, PhD, BVSc, associate professor of biology and environmental science at Queensland University of Technology, in Australia, during her presentation at the 2023 American College of Veterinary Internal Medicine Forum, held June 15-17, in Philadelphia, Pennsylvania.

A horse might develop insulin dysregulation due to insulin resistance (a condition where the body is unable to convert glucose into energy), decreased insulin clearance, or increased glucose intake and uptake from diets high in nonstructural carbohydrates (NSCs), she added. How much glucose a horse absorbs into the bloodstream likely depends on his individual glucose uptake capacity.

“Both EMS and PPID are risk factors for laminitis, and while these diseases can occur together or separately, EMS might precede PPID,” said de Laat. “A recent (study) of animals with hyperinsulinemia-associated laminitis showed that when EMS and PPID occur together, the basal (resting) insulin concentration is higher than in horses with either EMS or PPID.”

Medical Management Options for Insulin Dysregulation in Horses

Key factors that owners can adjust for their metabolic horse are diet and exercise, but new medications such as sodium-glucose co-transporter 2 inhibitors (SGLTi2) might support these management efforts. Physicians are using these drugs to treat Type 2 diabetes in people, and equine practitioners can use them to inhibit glucose resorption in horses’ kidneys, leading to lower insulin levels, said de Laat. However, until researchers conduct further work on these drugs, veterinarians using the drug off-label need to do so with caution, she added, as the drug carries some known side effects.

Scientists have tested drugs that target the gut peptide glucagon-like peptide-1 (GLP-1 agonists) and saw overall decreased insulin levels in horses treated with both GLP-1 agonists and antagonists, said de Laat. GLP-1 agonists likely slow gastric motility and decrease glucose absorption, she said, while antagonists block additional insulin release, which might be a preferable treatment option for animals with more severe metabolic disease. Researchers do not yet know why one drug might be more effective than another, but blocking insulin release is a more direct response to the cause of the problem, which is excessive release of insulin, said de Laat.

Take-Home Message

Horse owners should work closely with their veterinarians to create a management and treatment plan for horses with ID that is best for the individual animals’ needs. Because insulin thresholds for the onset of laminitis can vary between horses, de Laat says an individualized approach is necessary for the horse’s success.