Insulin is a hormone involved in the regulation of glucose (sugar) levels in the blood and tissues of the body. In response to feeding, insulin is secreted by the pancreas into the blood stream. Insulin in the blood stream directs the glucose (sugar) absorbed from the food into the body’s tissues including liver, fat and muscle. Insulin resistance occurs when insulin no longer has a normal effect on the tissues. In the insulin resistant horse, the pancreas releases insulin into the blood stream, and the insulin arrives at the tissues and binds the cells, however the glucose enters the tissue cells at a much lower rate than normal. This lower rate of glucose uptake into tissues results in higher levels of blood glucose.
Horses and ponies compensate for insulin resistance by secreting even more insulin into the bloodstream in order to keep the blood glucose concentration within the normal range. Therefore, horses and ponies with EMS have a higher concentration of insulin within the blood, which can be measured to determine if insulin resistance is present.
*This project was supported by Agriculture and Food Research Initiative competitive grant no. 2009-55205-05254 from the USDA National Institute of Food and Agriculture Animal Genome Program.