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Sept. 20, 2007 -- Scientists may have a new clue about how calorie restriction may lengthen life.
Previous research has linked calorie restriction to longevity, though many of those studies have been done in rodents and other short-lived species including worms, flies, and yeast.
Certain genes may be the link between calorie restriction and cell survival, a new study shows. Those genes, called SIRT3 and SIRT4, might eventually be targets for drugs to treat age-related diseases, according to Harvard Medical School's David Sinclair, PhD.
Sinclair's team studied?a complex chemical chain reaction in which these genes?nudge cells to live longer in the face of stress.
That stress came in the form of a two-day fast for rats studied by Sinclair and colleagues.
After the rats finished fasting, the researchers studied the rats' livers. They noticed that a protein called NAD+ was present at higher-than-normal levels in the rats' cellular powerhouses (mitochondria).
In earlier lab tests, the scientists had already linked increased NAD+ levels to the SIRT3 and SIRT4 genes.
Basically, those genes boost production of another chemical, which in turn boosts NAD+ levels -- and the whole process hinges on the cells being stressed (in this case, by the rats' fasting).
The study, published in the journal Cell, doesn't prove that a two-day fast -- or lengthier calorie restriction -- will extend human life span. But the findings may help explain the inner workings of cells during calorie restriction.
"Theoretically, we can envision a small molecule that can increase levels of NAD, or SIRT3 and SIRT4 directly, in the mitochondria," Sinclair states in a Harvard Medical School news release. "Such a molecule could be used for many age-related diseases."
Sinclair is a co-founder of Sirtris Pharmaceuticals, which is developing drugs that target SIRT genes.
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