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Boosting insulin restores aging muscles

Kathleen Blanchard's picture

New research shows that finding a way to boost insulin levels could restore muscles in the elderly. Insulin is needed to regulate blood sugar levels. It is also an important hormone that helps nutrients reach muscles. Insulin acts like a signal for muscle growth. Boosting insulin levels could restore muscles in the elderly.

Researchers from University of Texas Medical Branch found they could make 14 elders participating in a study stronger by raising insulin levels above the normal range.

According to Dr. Elena Volpi, senior author of the paper discussing the study results, “When you give insulin intravenously and increase the blood insulin levels to the same amount produced after a meal, you see that in young people it stimulates protein synthesis and muscle growth, while in older people it really doesn't. But when we gave seniors double the insulin they would normally produce after eating, their muscles were stimulated like those of young people."

The researchers injected insulin into the main artery of the thigh in elders. They then measured how the thigh muscles responded to two different insulin levels by monitoring molecules that signal muscle growth, using muscle biopsy, blood flow calculations, and protein synthesis. They consistently found that higher insulin levels - double the amount produced by a typical meal - helped aging muscles grow.

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Insulin resistance that leads to inability to build muscle as we age is different from insulin resistance that leads to diabetes. Dr Volpi explains, "While we had called this 'insulin resistance' in the past, we didn't really have evidence that you can get an elderly person's muscle to grow if you give it a lot more insulin, which is what we needed to truly say this is insulin resistance. So what we have identified is a novel kind of insulin resistance that's not related to sugar control."

The team of researchers say endothelial dysfunction that comes with aging is the reason we use muscle mass, that cannot be rebuilt. Changes in the lining of the blood vessels (endothelium) limits blood flow and nutrients, depriving muscles of oxygen.

“Having a capillary dilation induced by insulin is important, because it exposes more muscle to the nutrients and hormones and everything flows better and gets stored away better. But in even healthy older people, this dilation response doesn't work, because they have this endothelial dysfunction," explains Dr. Volpi. Giving the body an insulin boost seems to reverse the whole process that prevents muscle building as we age.

Dr. Volpi refers to a paper published two years ago in Diabetes that showed one bout of aerobic exercise could help restore muscle growth in the elderly. The researchers are in the process of testing drugs that could boost insulin levels by dilating blood vessels during insulin exposure. The previous findings and the current study results are encouraging that aging muscles can indeed be restored to a more youthful state.

Source: UTMB Newsroom