EMND and Glucose Metabolism

EMND, or equine lower motor neuron disease, is a degenerative disorder resulting from oxidative damage to specific spinal cord nerve cells. Early on, it causes a sudden onset of trembling, shifting weight between the hind limbs, muscle twitching, abnormally increased sweating, and more time lying down. Once EMND becomes chronic, affected horses develop weight loss, altered gaits, fatigue, and general poor performance. About 50% of affected horses have lowered blood glucose curves after being given glucose uptake and tolerance tests.

Johannes van der Kolk, DVM, PhD, and fellow researchers from Utrecht University in the Netherlands examined three EMND horses to determine whether increased glucose metabolism was responsible for the lowered blood glucose curves.

Three Dutch Warmbloods with EMND were used for the study. Two horses with unrelated diseases were used as "diseased controls" to rule out the possibility that abnormal glucose uptake and tolerance was simply due to a disease state and not specifically to EMND. Also, data from five horses' glucose tolerance tests in a previous study were used as healthy control data.

Results indicated that EMND horses had a significantly higher rate of glucose metabolism (3.7 times higher on average) compared to healthy controls. And one of the EMND horses was 5.6 times more sensitive to exogenous insulin than control horses.

It was concluded that EMND horses did not have a problem with insulin secretion and glucose uptake into cells, but rather with glucose metabolism. The increased glucose metabolic rate might be related to increased activity of a specialized structure in muscle cells called a glucose transporter (GLUT-4). It's responsible for uptake of glucose from the blood into skeletal muscle. Clinically, it seems that muscles in EMND horses have to work harder to fulfill basic requirements, and they have increased requirements for glucose.

These data also help explain why EMND horses can have low plasma vitamin E concentrations. Increased glucose metabolism requires increased oxygen consumption, which generates more free radicals. Free radicals cause oxidative damage to tissues, especially motor neurons; vitamin E helps prevent this damage and thus is used up.

With this information, the authors concluded that supportive treatments could be developed for horses with EMND, including glucose and vitamin E supplements.

Van der Kolk, J.H.; Rijnen, K.E.P.M.; Rey, F.; et al. American Journal of Veterinary Research, 66(2): 271-276, 2005.

About the Author

Susan Piscopo, DVM, PhD

Susan Piscopo, DVM, PhD, is a free-lance writer in the biomedical sciences. She practiced veterinary medicine in North Carolina before accepting a fellowship to pursue a PhD in physiology at North Carolina State University. She lives in northern New Jersey with her husband and two sons.

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