Two natural compounds—one in apple peel and one in green tomatoes—may fight the effects of aging on muscles.
Elderly mice fed the compounds saw a 10 percent increase in muscle mass and 30 percent increase in strength.
“Many of us know from our own experiences that muscle weakness and atrophy are big problems as we become older,” said Christopher Adams, professor of internal medicine in the University of Iowa Carver College of Medicine and senior study author. “These problems have a major impact on our quality of life and health.”
Previously, Adams and his team had identified ursolic acid, which is found in apple peel, and tomatidine, which comes from green tomatoes, as small molecules that can prevent acute muscle wasting caused by starvation and inactivity. Those studies set the stage for testing whether ursolic acid and tomatidine might be effective in blocking the largest cause of muscle weakness and atrophy: aging.
In their latest study, Adams’s team found that ursolic acid and tomatidine dramatically reduce age-related muscle weakness and atrophy in mice. Elderly mice with age-related muscle weakness and atrophy were fed diets lacking or containing either 0.27 percent ursolic acid, or 0.05 percent tomatidine for two months.
The scientists found that both compounds increased muscle mass by 10 percent, and more importantly, increased muscle quality, or strength, by 30 percent. The sizes of these effects suggest the compounds largely restored muscle mass and strength to young adult levels.
They report the results in the Journal of Biological Chemistry.
“Based on these results, ursolic acid and tomatidine appear to have a lot of potential as tools for dealing with muscle weakness and atrophy during aging,” Adams said. “We also thought we might be able to use ursolic acid and tomatidine as tools to find a root cause of muscle weakness and atrophy during aging.”
Adams’s team investigated the molecular effects of ursolic acid and tomatidine in aged skeletal muscle. They found that both compounds turn off a group of genes that are turned on by the transcription factor ATF4. This led them to engineer and study a new strain of mice that lack ATF4 in skeletal muscle. Like old muscles that were treated with ursolic acid and tomatidine, old muscles lacking ATF4 were resistant to the effects of aging.
“By reducing ATF4 activity, ursolic acid and tomatidine allow skeletal muscle to recover from effects of aging,” said Adams.
The study was conducted in collaboration with Emmyon, Inc., a biotechnology company founded by Adams and based at the University of Iowa. A grant to Emmyon from the National Institute on Aging, as well as grants from the Department of Veterans Affairs and the Fraternal Order of Eagles Diabetes Research Center at the University of Iowa, funded the study.