Study of Dieting Mice Yields Clues on Longevity
Eating less food may help mice--and possibly people--live longer by reducing the activity of certain damaging genes in their brains, report scientists at the University of Wisconsin.
The findings should help scientists better understand the tantalizing observation that rodents have longer life spans when they’re given less to eat.
The study, published today in the journal Nature Genetics, used high-tech methods to study more than 6,000 genes in elderly mice kept on either normal or restricted diets.
The researchers found that genes involved in inflammation were less active in the brains of old mice that had been fed less throughout their lives. Inflammation is associated with such maladies as Alzheimer’s and Parkinson’s diseases and may play a role in normal changes of aging.
Genes involved in the body’s response to stress were also reduced in the elderly mice that had had their calories restricted. This implies that restricting calories reduces the amount of stress--from such things as damaging free radicals--that the brain is subject to.
The study is a landmark, said Caleb Finch, Arco professor of gerontology and neuroscience at USC, who studies calorie restriction and aging. The findings vastly increase what’s known about the effects of caloric restriction, he said.
Studies show that mice and rats live about 30%-40% longer when their calories are reduced by 30%-40%. However, Finch said, that doesn’t necessarily pertain to our own diets.
“It’s unclear whether this is also applicable to humans, who live vastly longer than the 2-year life span of rodents,” he said. Obese people can certainly increase their life span by eating less, he said, “but whether cutting back daily intake 30%-40% will slow aging in someone in their 30s, 40s or 50s with good general health is completely unknown.”
The study was performed by University of Wisconsin researchers Richard Weindruch, Tomas A. Prolla and Cheol-Koo Lee. It follows a report by the same group last year on the effects that restricting calories have on genes in the muscles of mice.
In the most recent study, the researchers fed one group of mice their usual portions and another group a diet that provided the same amount of protein and nutrients but 26% fewer calories. The mice were fed the diets from youth (2 months) to the ripe old age of 30 months.
Then the scientists harvested two regions of the rodents’ brains--the neocortex, involved in higher thinking, and the cerebellum, involved in coordinated movement--for study. They used “DNA chip” technology, which enables the study of thousands of genes at a time, to pinpoint genes that had different activities in old mice fed either restricted or unrestricted diets.
The study is important because scientists don’t understand aging--nor how restricting calories slows it down, said Anna McCormick, chief of the Genetics and Cell Biology branch of the National Institute on Aging in Bethesda, Md.
“This starts to tell us what might be the important changes of aging and which might be the gray hair changes that aren’t good or bad for you--they just happen,” she said.
Eventually, by understanding how restricting calories allows creatures to live longer, it may be possible to design drugs that can mimic the effect of caloric restriction, McCormick said.
“I can’t imagine we’re going to get people to restrict their calories by 30% or 40% for life,” she said. “But we’d like to find out how it works--understand the pathways--so we could intervene with a drug.”
