Friday, November 06, 2009

Insulin’s Role in the Aging Body :: Scienceline

Insulin’s Role in the Aging Body - Scienceline

Insulin, a hormone well known for its role in diabetes, may also lie at the root of another common but serious medical condition: age-related muscle loss, known as sarcopenia.

In fact, sarcopenia is in part due to muscle tissue not responding properly to insulin, according to a new study in the journal Diabetologia.

The researchers found that an increased dose of insulin restored the muscle-building processes that tend to deteriorate with old age. Unfortunately, insulin cannot be used as a treatment for sarcopenia due to its toxic effects in high concentrations. Still, the new results help clarify its role in muscle growth and could serve as a basis for future treatments. Sarcopenia affects 24 percent of adults between 45 and 70 years old, and half of people over 80.

“The new finding serves as a proof of concept,” said Elena Volpi, a researcher at the University of Texas Medical Branch at Galveston. “It confirms our belief that the age-related decline in muscle growth is a true case of insulin resistance, which is an important piece to the larger puzzle of treating sarcopenia.”

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In type 2 diabetes, insulin resistance — a condition in which normal amounts of insulin fail to produce a typical insulin response in the body — prevents the body from storing sugar molecules in cells, eventually leading to high blood sugar. Test subjects in the Texas study, however, had normal blood sugar levels. This suggests the insulin resistance seen in elderly people is not a matter of sugar control.

Instead, the researchers believe insulin resistance seen in old age results from changes in blood flow. In addition to helping store sugar, insulin acts as a signal for the dilation of blood vessels to increase blood flow and deliver nutrients to muscle tissue. When capillaries fail to respond to these signals, blood flow slows down and muscle growth decreases.

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