Apple peel makes mice mighty

Jun 07, 2011

For Popeye, spinach was the key to extra muscle. For the mice in a new University of Iowa study, it was apples, or more precisely a waxy substance called ursolic acid that's found in apple peel.

The UI study, published in the June 8 issue of the journal , showed that ursolic acid reduced (also known as muscle wasting) and promoted in mice. It also reduced fat, , cholesterol and triglycerides in the animals. The findings suggest that the compound may be useful for treating muscle wasting and possibly such as diabetes.

"Muscle atrophy causes big problems. It's also very common -- it affects most people at some point in their lives, during illness or aging. But, there's no medicine for it," said Christopher Adams, M.D., Ph.D., UI endocrinologist and senior author of the study. "We studied muscle 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.

"The old saying goes that 'an apple a day keeps the doctor away.' So, we tested ursolic acid in mice, and found that it increased the size and strength of their muscles," Adams added. "It did this by helping two hormones that build muscle: insulin-like growth factor-1 (IGF1) and insulin. Because ursolic acid increased muscle, it reduced muscle atrophy. Surprisingly, it had some other beneficial effects in mice: for example, it reduced body fat, and lowered and cholesterol."

Adams and colleagues homed in on ursolic acid by using connectivity maps, a relatively new technique that compares gene expression patterns in cells under different conditions. The team determined which genes are turned on or off in human muscle during atrophy and compared that pattern with in cultured cell lines treated with a library of different compounds. They discovered that one of those compounds -- ursolic acid -- causes a pattern of gene expression that is the opposite of the pattern caused by atrophy. This suggested that ursolic acid might reverse atrophy.

In follow-up experiments, the researchers proved that mice fed ursolic acid were indeed protected from muscle atrophy caused by both fasting and nerve damage. Furthermore, healthy mice fed ursolic acid developed larger, stronger muscles than mice that did not receive the compound.

The study suggests that ursolic acid's ability to both inhibit muscle wasting and promote muscle growth stems from its ability to influence IGF1. This hormone, and its close cousin insulin, both bind to receptors on muscle cells setting off a cascade of cellular pathways that either enhance muscle growth or block atrophy. Ursolic acid appears to increase the activity of the receptors for IGF1 and insulin, amplifying the beneficial effects of these hormones in muscle.

Interestingly, although ursolic acid increased muscle weight in mice, it did not increase total body weight, and further investigation showed that mice fed ursolic acid had less body fat than mice that were not fed the compound.

Adams and his colleagues now hope to move the research toward human trials.

Explore further: Brand new technology detects probiotic organisms in food

Related Stories

Muscle atrophy through thick but not thin

Jun 08, 2009

During desperate times, such as fasting, or muscle wasting that afflicts cancer or AIDS patients, the body cannibalizes itself, atrophying and breaking down skeletal muscle proteins to liberate amino acids. In a new study ...

To keep muscles strong, the 'garbage' has to go

Dec 01, 2009

In order to maintain muscle strength with age, cells must rid themselves of the garbage that accumulates in them over time, just as it does in any household, according to a new study in the December issue of Cell Metabolism. In the ...

'Mighty mice' made mightier

Aug 29, 2007

The Johns Hopkins scientist who first showed that the absence of the protein myostatin leads to oversized muscles in mice and men has now found a second protein, follistatin, whose overproduction in mice lacking ...

Recommended for you

Fighting bacteria—with viruses

43 minutes ago

Research published today in PLOS Pathogens reveals how viruses called bacteriophages destroy the bacterium Clostridium difficile (C. diff), which is becoming a serious problem in hospitals and healthcare institutes, due to its re ...

Atomic structure of key muscle component revealed

1 hour ago

Actin is the most abundant protein in the body, and when you look more closely at its fundamental role in life, it's easy to see why. It is the basis of most movement in the body, and all cells and components ...

Brand new technology detects probiotic organisms in food

Jul 23, 2014

In the food industr, ity is very important to ensure the quality and safety of products consumed by the population to improve their properties and reduce foodborne illness. Therefore, a team of Mexican researchers ...

Protein evolution follows a modular principle

Jul 23, 2014

Proteins impart shape and stability to cells, drive metabolic processes and transmit signals. To perform these manifold tasks, they fold into complex three-dimensional shapes. Scientists at the Max Planck ...

Report on viruses looks beyond disease

Jul 22, 2014

In contrast to their negative reputation as disease causing agents, some viruses can perform crucial biological and evolutionary functions that help to shape the world we live in today, according to a new report by the American ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

dirk_bruere
not rated yet Jun 07, 2011
Attention all athletes!
http://en.wikiped...lic_acid
jamesrm
not rated yet Jun 07, 2011
Look like the perfect, treatment for Steve Jobs, everytime apple makes a thinner product it seems to cost him a couple of kilos as well.

Rgds
James