Researchers Examine Link Between Obesity, Laminitis, and EMS

Researchers Examine Link Between Obesity, Laminitis, and EMS

The study examined whether inflammation was involved in the development of chronic laminitis that sometimes occurs in obese horses with equine metabolic syndrome.

Photo: Christy M. West

From grain overload and colic to metritis (inflammation of the lining of the uterus) and limb injuries, laminitis has many causes. Could the inflammatory side effects of insulin resistance and equine metabolic syndrome be one of them? A team of researchers from Virginia Tech recently examined that scenario.

"Previous studies have shown that the link between these seemingly unrelated causes of laminitis has to do with inflammatory events somewhere in the body, other than the feet," relayed Jessica Suagee, PhD, a postdoctoral research associate in the Department of Animal and Poultry Sciences at Virginia Polytechnic Institute and State University in Blacksburg, Va.

With this knowledge in hand, Suagee and colleagues set out to determine whether inflammation was involved in the development of chronic laminitis that sometimes occurs in obese horses with equine metabolic syndrome (EMS).

"We know that hyperinsulinemia (insulin resistance) in other species has an inflammatory aspect, and it is possible that it is the high circulating insulin levels in horses with EMS that drives an increase in inflammation in obese EMS horses," explained Suagee.

To test their hypothesis that high insulin levels cause increased production of proinflammatory mediators called cytokines, Suagee et al. administered insulin to 10 obese mares for six hours before measuring blood cells, fat, and muscle tissues to determine if there was an increase in various inflammatory mediators or the genes encoding these molecules.

Key findings of the study were:

  • The insulin significantly increased blood levels of the proinflammatory cytokines tumor necrosis factor alpha and interleukin-6; and
  • The insulin did not increase the expression of the genes that encode these mediators.

Suagee noted, "These findings indicate that an abrupt increase in insulin levels in obese horses does alter the concentration of cytokines in the bloodstream, but whether this increase in proinflammatory mediators has a direct role in initiating laminitis remains to be established."

The association between obesity, high insulin levels, and laminitis is an important area of research considering the number of obese, insulin-resistant, and EMS affected horses currently residing in the U.S. combined with the fact that laminitis causes severe pain, loss of use, and in many cases necessitates euthanasia. Researchers are still working diligently to better understand laminitis and EMS and to find treatments for both.

The study, "Effects of acute hyperinsulinemia on inflammatory proteins in horses," will be published in August in Veterinary Immunology and Immunopathology. The abstract is available on PubMed.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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