Antioxidants and Aging

New Evidence Found for "Oxidative Stress" Theory of Aging
Researchers have uncovered strong evidence for the long-held theory that the very oxygen we require to live is a contributor to aging, and antioxidant molecules can offset these effects.

The support for the "oxidative stress" model of aging comes from experiments that boosted fruit fly life spans in direct proportion to antioxidant production from manipulated genes. Researchers from the University of Southern California (USC) and University of California at Irvine reported their findings in the June 19 issue of the journal Genetics. The study was funded in part by NSF.

Many researchers believe that antioxidant substances such as vitamins C and E protect cells from the damaging effects of oxidation by neutralizing free-radicals - charged molecules that cells produce when they burn oxygen fuel. To test this theory directly, the researchers created fruit flies that had an extra copy of either of two antioxidant-producing genes known as superoxide dismutases, or SODs.

In control fruit flies, the researchers left the extra SOD genes inactive. Unsurprisingly, these flies lived a normal life span. In the experimental flies, the researchers activated the extra copy, causing the flies' cells to produce far more antioxidant enzymes than normal. These flies enjoyed a longevity boost of up to 40 percent, says lead researcher John Tower, a biologist at USC. And the magnitude of the boost was exactly proportional to the amount of extra SOD production, suggesting that the antioxidants were directly responsible, Tower says.

"It demonstrates that antioxidant activity is a rate-limiting factor for fly lifespan," he says. "There was no negative effect on metabolism from the SOD over-expression. So we're extending life span without some kind of trade-off or deficit in the creatures' metabolism," says Tower.

But now at least, says Tower, it's known that the beneficial effects of antioxidants occur when the genes are made to supply the substance. Drugs or gene therapy might some day be used to stimulate human cells to over-express SOD or similar genes, though it won't happen soon, he says.

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