VOA标准英语2013--生物钟提供衰老的线索（在线收听）

Body Clock Provides Clues to Aging 生物钟提供衰老的线索

If you’re searching for the fountain of youth, you might find it in  your DNA. That’s according to a new study that sheds light on the  biological clock ticking in our genomes, why our bodies age and how we  can slow down the process.

如果你正在寻找青春之泉,你可能会发现它在你的DNA里面。这是根据一项新的研 究,我们的基因组结识了为什么我们的身体年龄和我们如何可以减缓衰老过程。

University of California genetics professor Steve Horvath has created a  new tool that can accurately measure the aging body. 

“Basically I developed a way of predicting age based on DNA," Horvath  said. "To achieve this goal I identified 353 markers on the DNA which  measure DNA methylation levels.” 

Methylation is a naturally occurring epigenetic - or gene altering -  process that chemically modifies the DNA and is critical in the  development of every organism. Horvath and his colleagues gleaned  information from 8,000 samples to chart methylation in healthy and  diseased organs, tissues and cells, from fetuses to centenarians.

“For one thing, I find that this epigenetic clock ticks fastest during  development, and after age 20 it slows down to a constant ticking  rate," he said. "But also I find that cancer tissue is on average 36  years older than healthy tissue and I observed that effect in all 20  cancer types that I studied.”   

In other words, some cells age faster than others.

Horvath notes that while most biological samples matched their  chronological age, some diverged significantly. The average human  heart, for example, appears to be 12 years younger than its  chronological age, and a woman’s healthy breast tissue ages faster  than the rest of her body.   

“So it is possible that the cancer that is adjacent to this tissue  accelerates the age," he said. "Having said this, I had one data set  that was composed of truly healthy breast tissue and even there I  observed a significant age acceleration.”

The results may explain why breast cancer is the most common cancer in  women. 

Remarkably, Horvath says the clock kept reliable time across the human  anatomy, irrespective of where the DNA came from.

“This new epigenetic clock really frees us up from focusing on one  tissue at a time because it really works in most tissues and organs and  cell types, and the great advantage is that we now can compare the ages  of different tissues and organs from the same individual,” he said.

Horvath says the work holds promise for studying human development,  aging and disease, but also shows potential for rejuvenating tissues.

"Of course it has been a long-standing hope to find therapies or  compounds that keep us young, and if this epigenetic clock measures a  process that causes aging, then we will have a tool that allows us to  evaluate compounds that keep us young,” he said

So has Horvath found the Fountain of Youth?

"I have unfortunately no data that would support that,” he said with a  laugh.