For Chromosomes, Size Does Matter

DNA bounty. Longer protective caps on chromosomes, known as telomeres (yellow), are associated with healthier aging.

Want to live longer? Eat your vegetables, don't smoke, and don't play in traffic. And according to a new study, you should hope you're endowed with ample stretches of DNA called telomeres at the ends of your chromosomes. The study is the first to link telomere length to longevity in humans and could yield new strategies for combating age-related ills.

Telomeres--repeating segments of DNA on the ends of chromosomes--are often likened to the plastic caps that prevent shoelaces from fraying. The molecules don't contain genes, but they protect chromosomes from damage. Telomeres' initial length varies among individuals, but in everyone, they become shorter over time. Cell-culture studies show that when telomeres can no longer shield chromosomes from damage, cells stop dividing or become unstable. And recently, researchers have learned that people with a genetic disorder that accelerates aging have abnormally short telomeres, further implicating telomeres in aging.

But do longer telomeres mean longer life in normal circumstances? To find out, geneticist Richard Cawthon and colleagues at the University of Utah in Salt Lake City examined telomere lengths in 143 elderly men and women who had provided blood samples more than 15 years earlier. In the 1 February issue of The Lancet, the team reports that participants with shorter-than-average telomeres died 4 to 5 years younger than did those with longer telomeres and were more than three times as likely to have died from heart disease. Participants with the shortest telomeres (the bottom 25%) were more than eight times as likely to die of infectious disease as those with longer telomeres.

This is "the first hint that telomeres might limit people's lives, says molecular biologist Jerry Shay of the University of Texas Southwestern Medical Center in Dallas. Still, he cautions that more research--using many more participants--is needed to understand the link. For instance, Cawthon points out, it's important to learn whether telomere shortening actually causes disease or is just a side-effect of something else. Resolving that question, he says, will likely help researchers identify and thwart processes that cause age-related illness.

Related sites
Richard Cawthon's Web site
Basic introduction to telomeres and telomerase
American Federation for Aging Research

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