A recent study suggests compounds found in apples and green tomatoes could help fight muscle aging.

Scientists determined the protein ATF4 is a transcription factor that can alter gene expression and cause a reduction in muscle protein synthesis and strength, but two natural compounds could reduce the activity of this muscle-wasting protein, the University of Iowa reported.

"Many of us know from our own experiences that muscle weakness and atrophy are big problems as we become older," said Christopher Adams, UI professor of internal medicine and senior study author. "These problems have a major impact on our quality of life and health."

In past studies, the researchers had identified that ursolic acid, which is found in apples, and tomatidine from green tomatoes, could prevent acute muscle wasting caused by a sedentary lifestyle or malnutrition. These new findings suggest the compounds can also reduce age-related muscle weakness and atrophy in mice.

In the study, mice suffering from age-related muscle weakness and atrophy were put on diets consisting of either 0.27 percent ursolic acid, or 0.05 percent tomatidine for a period of two months. Both compounds proved to increase muscle mass by 10 percent and muscle quality by an impressive 30 percent.

"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 says. "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."

The researchers discovered both natural compounds work by turning off a group of genes that are turned on by the transcription factor ATF4.

"By reducing ATF4 activity, ursolic acid and tomatidine allow skeletal muscle to recover from effects of aging," Adams concluded.

The findings were published in a recent edition of the Journal of Biological Chemistry.