reducing horse insulin concentrations

High circulating insulin concentrations can cause horses to develop laminitis, so any tool to reduce insulin concentrations could be valuable for reducing the risk of this painful hoof disease developing in certain horses. Researchers recently evaluated one potential option with encouraging results.

Research in humans has shown that a compound called resveratrol can improve insulin sensitivity. When combined with the amino acid leucine, it takes even less resveratrol to improve insulin sensitivity in rats. So Jane Manfredi, DVM, MS, PHD, Dipl. ACVS-LA, ACVSMR, and her team from Michigan State University (MSU) recently tested whether a supplement containing that combination could improve metabolic function in horses with equine metabolic syndrome (EMS, an endocrine disorder that can negatively affect insulin levels and lead to laminitis) and/or insulin dysregulation (ID, abnormal blood insulin levels).

Manfredi, assistant professor of pathobiology and diagnostic investigation at the MSU College of Veterinary Medicine, in East Lansing, presented the results at the 2018 American Association of Equine Practitioners Convention, held Dec. 1-5 in San Francisco, California.

The researchers supplemented 15 Morgan and Arabian horses previously diagnosed with EMS and/or ID for six weeks with a high- or low-dose mix of synergistic polyphenol (resveratrol, which horse owners might be familiar with from positive results in osteoarthritis studies, and quercetin) and a blend of amino acids including leucine. On Day 0 (before supplementation began), they collected bloodwork and conducted an OST. The test involves administering a bolus of Karo corn syrup orally after an overnight fast, which stimulates insulin production in the horse. The veterinarian compares blood glucose and insulin concentrations in samples taken before syrup administration and then 60 and, in this study, 75 minutes later. After 43 days of supplementation, they repeated the bloodwork and OST.

The team also evaluated the supplement’s effect on high-molecular-weight (HMW) adiponectin, a hormone found in fat tissue, because researchers found that horses with high levels of this hormone are more sensitive to insulin. Researchers have shown that adiponectin concentrations are lower in ponies that develop laminitis than in those that don’t, so raising HMW adiponectin levels could potentially decrease laminitis risk.

The researchers said the supplement was very palatable—horses had no problem consuming it. They found no significant differences between the low- and high-dose groups after supplementation—all horses had significantly higher HMW adiponectin concentrations and lower insulin concentrations 60 and 75 minutes after glucose administration.

Researchers know that equine insulin sensitivity decreases with age, which results in greater insulin level increases after an OST. Manfredi had insulin data on the same group of study horses from a 2013 research project, so she compared those figures to those from the current study. As expected, horses’ mean baseline and 60-minute-post-OST insulin levels before supplementation in the current study were higher than they had been in 2013. However, she said, the average baseline insulin and 60-minute-post-OST results after six weeks of supplementation had decreased so much that they were not significantly different from what they’d been in 2013—a finding of particular interest, she said.

These findings led the team to conclude that feeding the supplemental mix of synergistic polyphenols and amino acids (marketed in the U.S. as InsulinWise, Manfredi said) could help improve metabolic function in some horses with EMS and ID.