Fatty Acid Triheptanoin Comes Up Short for Horses with PSSM

Unlike the positive results obtained in humans with storage diseases, the short chain fatty acid triheptanoin does not appear to be a good fat supplement for horses with polysaccharide storage myopathy (PSSM), reported Stephanie Valberg, DVM, PhD, professor of large animal medicine and director of the University of Minnesota's Equine Center.

PSSM is a form of exertional rhabdomyolysis (ER, tying-up) that is common in Quarter Horses. Affected horses have very high levels of glycogen--a storage form of glucose--in the muscle fibers. (Read more.)

"Feeding a low-starch, fat-supplemented diet that includes corn oil or a high-fat, low-starch (HFLS) commercially prepared feed can decreased the number of episodes of ER in horses with PSSM," relayed Valberg. "To date, the amount and type of fat that is best utilized by horses with PSSM remains unclear."

Triheptanoin is a short, 7-carbon fat that has been used in human medicine to treat such disease as type II glycogen storage disease (such as Pompe's disease).

Valberg and colleagues hypothesized that supplementing triheptanoin in the diet of horses with PSSM might attenuate ER during submaximal exercise.

They tested this theory on eight Quarter Horses diagnosed with PSSM (six mares, one stallion, one gelding, 2-14 years of age).

Four separate isocaloric diets were evaluated in the study: grain, triheptanoin, corn oil, and a HFLS diet (as a negative control). Horses were fed each diet for three weeks. Effect of diet was assessed using a treadmill and blood and muscle specimens were collected before and after exercise.

Some of the key findings were:

  • Exercise intolerance was more common in PSSM horses fed triheptanoin compared to corn oil;
  • Higher creatine kinase (a muscle enzyme) levels were measured in horses fed triheptanoin; and
  • Higher insulin and lower nonesterified fatty acid concentrations blood levels were also measured in horses supplemented with triheptanoin.

"To our surprise, triheptanoin had detrimental effects on PSSM. This fat seems to decrease the availability of nonesterified fatty acids and increase the simulation of glycogen synthesis by insulin," summarized Valberg.

Based on this study, long-chain fatty acids (like those in vegetable oils and the HFLS feed) appear to be the best choice for horses with PSSM.

The study, "Effect of dietary fats with odd or even numbers of carbon atoms on metabolic response and muscle damage with exercise in Quarter Horse-type horses with type 1 polysaccharide storage myopathy," was published in the March 2010 edition of the American Journal of Veterinary Research. The abstract is available for free 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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