Drastically reducing calorie intake, or caloric restriction, is known to extend the lifespan of species including yeast, worms and rodents. Previous research linked a gene called Sir2 with lifespan extension due to caloric restriction, but worms and yeast that lack Sir2 also live longer when put on a tough diet, showing that some other genes must be at work.

Researchers led by David Sinclair at Harvard Medical School and Su-Ju Lin at UC Davis' Center for Genetics and Development and Section of Microbiology screened for other life-extending genes in yeast. They found a gene called Hst2 that accounts for most of the difference.

Deleting Hst2 and Sir2 blocked most of the beneficial effect of caloric restriction. When Hst2 was overexpressed, so that the gene was more active than normal, the yeast lived longer than normal. A third gene, Hst1, appears to act when both Sir2 and Hst2 are missing.

Sir2 and the newly identified Hst genes account for all of the life-prolonging effects of caloric restriction in yeast, Lin said.

In yeast, the effects of aging seem to be due to a build-up of toxic circular DNA molecules that accidentally get copied out of ribosomal DNA, an unstable area of the yeast genome that contains hundreds of repeated sequences.

The researchers showed that caloric restriction drastically reduces recombination of ribosomal DNA, and that deleting Hst2 and Sir2 blocks this effect.

Very similar genes are found in widely different animals including worms, flies and rodents. But the targets of these genes are likely to be different, as the toxic DNA circles have not been identified in more advanced organisms, Lin said.

The work was published in Science.

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The March of Dimes survey on folic acid has been conducted nine times since 1995. In 2005, 2,647 women between the ages of 18 and 45 were asked about their awareness and knowledge of the benefits of folic acid and their use of vitamins. For results based on samples of this size, one can say with 95 percent confidence that the error attributable to sampling and other random effects could be plus or minus two percentage points.

The also survey found:

Nearly 90 percent of women surveyed believe there are things they can do to prevent births defects. These women cited avoiding alcohol and drugs and not smoking as the top two things that could be done to prevent birth defects, followed by proper diet and vitamins. Only 9 percent of the women mentioned folic acid. Folic acid use declined to 33 percent in 2005, down from 40 percent in 2004. However the 2005 rate is consistent with years prior to 2004. Only 24 percent of younger women (age 18-24) take a vitamin containing folic acid daily compared to 36 percent of older women (age 25 to 45). Only 7 percent of women surveyed knew folic acid should be taken before pregnancy. Of women who didn't take a multivitamin daily, 28 percent said it was because they forget, 16 percent said they don't need them, and 9 percent said they get the nutrients and vitamins they need from food.

marchofdimes/