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Apple peel in the diet helps mice build muscle

Kathleen Blanchard's picture
Ursolic acid in apple peel

A waxy substance in apple peel, called ursolic acid, might help humans suffering from muscle wasting that can accompany disease, illness and aging. In a new study, researchers found apple peel in the diet reduced muscle atrophy in mice, promoted muscle growth and fat loss and even lowered blood sugar, cholesterol and triglyceride levels.

Compound in apple peel helps muscle building hormones

The researchers were looking for a chemical that could stop muscle atrophy that Christopher Adams, M.D., Ph.D., University of Iowa endocrinologist and senior author of the study says is very common, but lacks treatment.

"We studied muscle gene activity in people with atrophy and used that information to find chemicals that might block atrophy. One of those chemicals was especially interesting. It's called ursolic acid and it's particularly concentrated in apple peels.

When the scientists tested ursolic acid in mice, they found it increased muscle size and strength, in addition to reducing body fat, cholesterol and triglyceride levels.

Adams explained, the apple peel compound works to build muscle and protect from muscle atrophy in the mice "by helping two hormones that build muscle: insulin-like growth factor-1 (IGF1) and insulin."

Apple peel given to the mice and added to the daily diet corrected abnormal gene signaling that leads to muscle atrophy. The mice were fasting to simulate what happens to humans during prolonged illness that leads to muscle weakness and longer hospitalization times from debilitation.

Natural compound in apples changes gene expression to promote muscle building

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The research team isolated 63 genes that change in a fasting state in mice and in humans, and another 29 that change expression in the presence of spinal cord injury and during fasting.

Dr. Adams said ursolic acid is an “interesting compound”. An apple a day changed gene expression in the mice to promote strong muscles, opposing the pattern that causes muscle wasting.

"We know if you eat a balanced diet like mom told us to eat you get this material," Adams said. "People who eat junk food don't get this."

It’s not clear if the same results will be found in humans, but if so, the compound could be developed to protect patients with chronic illness from debilitation that comes from muscle atrophy during prolonged illness, immobility and inability to eat.

Ursolic acid, a natural compound found in apple peel, boosts the effect of the muscle building hormone IGF1 without increasing body weight and fat. The researchers hope to study the compound in human trials to see if daily intake of apple peel is enough to provide the same muscle building benefits to humans found in the mouse studies.

Cell Metabolism
"mRNA Expression Signatures of Human Skeletal Muscle Atrophy
Identify a Natural Compound that Increases Muscle Mass"
Steven D. Kunkel, Manish Suneja, Scott M. Ebert, Kale S. Bongers, Daniel K. Fox, Sharon E. Malmberg, Fariborz Alipour, Richard K. Shields, Christopher M. Adams

Image credit: Morguefile