Muscles become weaker with age, but a new study may have found how to restore an elderly person’s strength to that of a young adult. Researchers from the University of Iowa have found a compound in tomatoes and apples can turn off a protein responsible for aging muscles. The study, published in the Journal of Biological Chemistry, could lead to a new line of supplements and drugs for treating muscle weakness.
"Many of us know from our own experiences that muscle weakness and atrophy are big problems as we become older," said the study’s co-author Dr. Christopher Adams, a professor of internal medicine at U-Iowa, in a press release. "These problems have a major impact on our quality of life and health." As humans inevitably age and their muscle mass declines, they can experience weakness and loss of stamina. This ultimately interferes with their ability to be physically active, which only further weakens muscles.
Fruits, however, could prevent this from happening. Adams and his colleagues discovered that the ursolic acid in apple peels and tomatidine compounds in the skin of green tomatoes prevented muscle atrophy — the loss of muscle mass due to the natural aging process —  by turning off the problematic protein ATF4. This protein reportedly "changes the formation of genes typically seen in the muscle wastage of older individuals." And researchers believe turning it off may stop the cyclical process of age-related muscle atrophy altogether.
The research team made this discovery as they were examining how the fruit compounds affected elderly mice experiencing atrophy. For two months, mice ate a diet containing or not containing ursolic acid or tomatidine. When researchers later measured muscle mass, they found mice eating both compounds were able to increase muscle mass by 10 percent and muscle strength by 30 percent, the equivalent to that of a young adult mouse. Essentially, mice lacking ATF4 were resistant to the effects of aging.
Acording to WebMD, muscles continue to grow larger and stronger from the time of birth up until around age 30; people can lose as much as 3 to 5 percent of their muscle mass every 10 years after their 30th birthday. After the age of 75, atrophy tends to accelerate.
Researchers plan to eventually continue their investigation in human clinical trials, which could potentially lead to a new line of muscle strengthening supplements and drugs.
Source: Adams CM, Ebert SM, Dyle MC, et al. Identification and Small Molecule Inhibition of an ATF4-dependent Pathway to Age-related Skeletal Muscle Weakness and Atrophy. Journal of Biological Chemistry. 2015.