Since 1935, medical research has shown a clear connection between calorie restriction and longer life expectancy, but no study since then has been able to establish exactly why. That is, until now.
A study published earlier this month by researchers at the Lewis Katz School of Medicine at Temple University indicates that calorie restriction slows the speed at which proteins and chemical compounds attach to our DNA and activate certain genes. Slowing the rate of these “epigenome changes” has been associated with greater longevity.
The researchers’ findings center around chemical modifications at the genetic level called DNA methylation. In basic terms, this process is used to control when a gene expresses itself. Senior investigator Dr. Jean-Pierre Issa says these findings explain why certain animals tend to live longer than others.
"Our study shows that epigenetic drift, which is characterized by gains and losses in DNA methylation in the genome over time, occurs more rapidly in mice than in monkeys and more rapidly in monkeys than in humans," he said, noting that more rapid movement is associated with shorter lifespans.
Extending lifespan at the genetic level
Issa explains that DNA methylation patterns “drift steadily throughout life, with methylation increasing in some areas of the genome, and decreasing in others.”
Until now, epigenetic drift was generally associated with age, but researchers had no way of proving that it affected overall lifespan. However, when Issa and his team analyzed methylation patterns in mice and monkeys, they found distinct differences between the epigenetic drift in older subjects and younger subjects.
Building on these findings, Issa and his team set out to see if epigenetic drift could be altered to increase test subjects’ lifespan. They found that one of the strongest factors for slowing epigenetic drift (and subsequently increasing lifespan) was restricting the calories that subjects consumed.
Great impact on future health studies
While the findings only support a theory that researchers have longed suspected, Issa says his team’s conclusions could greatly impact future health research.
"The impacts of calorie restriction on lifespan have been known for decades, but thanks to modern quantitative techniques, we are able to show for the first time a striking slowing down of epigenetic drift as lifespan increases," he said.
Other recent studies have associated epigenetic drift with age-related disorders and diseases like cancer. However, further studies on epigenetic drift need to be conducted before researchers can fully grasp its inner workings or establish effective methods for controlling it, especially in human test subjects.
"Our lab was the first to propose the idea of modifying epigenetic drift as a way of modifying disease risk. But why epigenetic drift occurs faster in some people and slower in others is still unclear,” said Issa.