In this episode of the Disease Du Jour podcast, Erica Macon, MS, PAS, PhD, joined us to discuss equine metabolic syndrome and insulin dysregulation. She talked about diagnostic tools, feeding recommendations, pharmaceutical treatments, ongoing research, and more.
About EMS and ID
Macon described equine metabolic syndrome (EMS) as “a collection of symptoms and characteristics that indicate that a horse has a higher likelihood or risk of developing hyperinsulinemia-associated laminitis,” or laminitis caused by high insulin in the blood. She continued to explain that insulin dysregulation (ID) is a collective term for both hyperinsulinemia, either at rest or after the horse eats, and tissue insulin resistance.
Horses with ID and EMS are often obese, and they might have regional fat deposits on the neck, around the tail, and behind the withers. Bloodwork might reveal high triglycerides. However, “a horse does not have to have metabolic syndrome to have insulin dysregulation,” Macon said. “We see a lot more horses nowadays that are actually lean.” These cases are harder for owners to detect.
Macon said certain breeds are more at risk for developing metabolic disease, including Morgans, Haflingers, warmbloods, and gaited breeds. Horses can develop metabolic disease at any age, though it most commonly develops in their teen years. Senior horses with ID often have concurrent pituitary pars intermedia dysfunction (PPID). “Those guys are more apt to develop insulin dysregulation if they have already developed Cushing’s disease,” Macon said.
Diagnostic Techniques
Macon said diagnostic testing is still a relatively new area of research in the field of equine nutritional endocrinology, and it’s changing every year. The most common procedure for diagnosing ID is to draw blood and analyze resting insulin. However, Macon said season can impact test results.
“I always recommend to have horses diagnosed for insulin dysregulation either in the late fall, winter, or in the spring because ideally that’s when their resting insulins would be at their highest,” she said.
Macon also explained that not all insulin-dysregulated horses have high insulin in the blood. Therefore, she likes to use the oral sugar test (OST) to more accurately detect metabolic horses.
“For horses that have severe insulin dysregulation, they oftentimes will have resting hyperinsulinemia as well as post-meal hyperinsulinemia, and you can easily identify those,” she said. “But for the ones that don’t have resting hyperinsulinemia, you have to do an oral sugar test on those animals to figure out that they actually do have insulin dysregulation.”
Dietary Recommendations for Horses With EMS and ID
Feeding strategies for ID horses involve limiting the horse’s overall nonstructural carbohydrate (NSC) intake across all feedstuffs. “Equine nutritionists take this matter very seriously, because the research has shown that insulin responses following meals with high NSC increase the likelihood of that horse developing laminitis,” Macon said.
She recommends feeding metabolic horses a ration balancer. If they need extra calories, she recommends finding a low-NSC commercial feed with higher fat and fiber. Horses’ daily rations should be split into at least two meals.
Macon discussed her research on NSC thresholds for metabolic horses, gave more dietary recommendations, and talked about the role of exercise in the podcast episode.
Pharmaceutical Treatment
Macon said many veterinarians are seeing great results from SGLT2 inhibitors in horses with high insulin and clinical signs of laminitis. This drug works by removing glucose from the blood to lower insulin levels.
“Insulin helps shuttle glucose into respective tissues, so if there’s no glucose circulating in the blood, insulin isn’t going to be released as much,” she explained. “I think that they’re our best tool right now in terms of pharmaceuticals to help a currently laminitic horse.”
Ongoing Research
At the end of the episode, Macon took a few minutes to explain some of her ongoing equine endocrinology research. She’s currently working on releasing a national survey to quantify endocrine disease in the United States. “We know those numbers in Australia and Europe, but we don’t have a good idea of what those numbers are here in the U.S.,” she said.
This summer, she is also working on a project that will analyze the impact of dopamine on insulin dysregulation.
Other areas of ongoing research focus on improving feeding recommendations for metabolic horses, the circadian clock’s impact on metabolic parameters, and the role of exercise in modulating insulin sensitivity. Macon discussed these projects in more detail in the episode.
About Dr. Erica Macon
Erica Macon, MS, PAS, PhD, is an Assistant Professor of Equine Science in the Department of Animal Science at Texas A&M University, where she teaches graduate equine nutrition, as well as equine health and disease for undergraduate students. She also serves as the faculty advisor for the Horsemen’s Association at Texas A&M University.
Macon is an agricultural enthusiast and grew up showing livestock in 4-H. She received her bachelor’s in animal science from the University of Florida, where she worked on determining ammonia output volumes from horses fed different concentrations of protein. For her master’s and PhD, she focused on equine nutritional endocrinology, more specifically equine metabolic syndrome or insulin dysregulation. Her dissertation serves as the foundation for nutritional recommendations for horses with insulin dysregulation associated with metabolic syndrome. Parts of her dissertation have been cited as the most clinically relevant articles by the Equine Veterinary Education Journal. Upon completion of her PhD, Macon completed about 1.5 years of postdoctoral training in endocrinology at the University of Kentucky’s College of Medicine.
At Texas A&M University, Macon investigates what leads to impaired insulin signaling in the endocrine diseased equid. Her primary focus is the development of improved diagnostics and therapies that have the potential to elucidate the mechanisms behind hyperinsulinemia-associated laminitis.
Related Reading
- How to Feed Horses Prone to Endocrinopathic Laminitis
- Managing EMS and ID Horses
- Equine Endocrinopathies: Is it ID, PPID, or Both?
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