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Posted 01.05.05

Inactivity Leads To Rapid Decline in Insulin Efficiency, Researchers Find

MU Researcher Find Links to Pre-Diabetes, Heart Disease, Obesity and Hypertension

COLUMBIA, Mo. - In as little as two days of physical inactivity, a body's efficient use of insulin may decrease, according to two University of Missouri-Columbia researchers in a study published recently in the Journal of the Physiological Society.

In a study involving rats, Frank Booth, professor of biomedical science and director of the MU Health Activity Center, and David Kump, a doctoral student in the Department of Medical Pharmacology and Physiology, found that insulin sensitivity decreases the longer the rats stay inactive. This decreased insulin efficiency may be a precursor to diabetes and other related diseases.

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"The less efficient your insulin is, the greater risk you have of diabetes, heart disease, obesity and hyptertension," Kump said. "Insulin works by taking glucose, or blood sugar, out of the blood stream and into the muscle to be used for energy. Our research found that when the rats stopped running for two days, the amount of sugar taken into the muscle in response to insulin was reduced by about one-third."

Typically, when insulin binds with a muscle cell, it starts a chain of events to transfer glucose from the blood into the muscle. The process starts when insulin binds to receptors on the muscle wall to open a path for the glucose. At the same time, proteins inside the muscle are activated to accept the glucose and begin the process of turning the glucose into energy. In a person who has been active, this process is typically very efficient, but for someone who has not been active, not only are there fewer receptors on the muscle wall to bind to the insulin, but there is less activity inside the muscle, making the transferring of the glucose to the muscle difficult.

"Everyone is looking at the benefits of exercise, but we are looking at the consequences of stopping that exercise," Kump said. "People already know that exercise is good for them. This shows that within a very short time frame of inactivity, the insulin does not work as well and might have negative effects."

To simulate the sudden drop in activity, researchers allowed the rats to run on exercise wheels for three weeks and then locked the wheels for a period of up to two days. Past studies have indicated increases in human blood sugar and insulin as early as five days, but these findings show that changes could be occurring even earlier in the muscle, Booth said. The American Heart Association and the National Institutes of Health funded the study.



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