The research team was surprised to find one of the biomarkers, RNA, which is important for coding DNA and for protein synthesis, is more quickly damaged by aging than the more frequently studied DNA. RNA damage, therefore, could be an excellent early signal to indicate the onset of aging, researchers say.
"Because it is more sensitive to oxidative stress, RNA can be useful as an early marker of oxidative damage and even aging," said Arnold Y. Seo, a doctoral student in UF's Institute on Aging.
Seo authored the report along with Tim Hofer, Ph.D., an Institute on Aging research associate.
"To avoid disease, we can increase our defense and look for aging biomarkers and then test interventions," Hofer said. "It is better to protect what is there to improve the quality of life than to have to resort to invasive procedures."
In the study, which followed the rats over their lifespan, one group of animals ate as much food as they wanted and did not exercise, another group of animals exercised lightly and were fed slightly less than they would have eaten if allowed to have their fill. Liver samples from these groups were compared with samples taken from young rats.
The old sedentary rats that ate until they were full had increased levels of harmful oxidizing and inflammatory molecules in the liver that were associated with cell damage caused by aging. Meanwhile, aging rats that exercised and consumed a calorie-restricted diet, had the reverse outcome - they showed a decrease in these molecules in the liver.
Leeuwenburgh said the study results support the theory that cell death and aging-related organ damage are caused by unstable molecules known as free radicals and by cellular oxidation and inflammation.
"In a calorie-restricted environment, you reduce the inflammatory response and prevent cell death," Leeuwenburgh said.