October 22, 2013 - A U.S. scientist has discovered an internal body clock
based on DNA
that measures the biological age of our tissues and organs.
The clock shows that while many healthy tissues age at the same rate as the body as a whole, some of them age much faster or slower. The age of diseased organs varied hugely, with some many tens of years “older” than healthy tissue in the same person, according to the clock.
Researchers say that unraveling the mechanisms behind the clock will help them understand the ageing process and hopefully lead to drugs and other interventions that slow it down.
Therapies that counteract natural ageing are attracting huge interest from scientists because they target the single most important risk factor for scores of incurable diseases that strike in old age.
“Ultimately, it would be very exciting to develop therapy interventions to reset the clock and hopefully keep us young,” said Steve Horvath, professor of genetics and biostatistics at the University of California in Los Angeles. Horvath
looked at the DNA
of nearly 8,000 samples of 51 different healthy and cancerous cells and tissues. Specifically, he looked at how methylation, a natural process that chemically modifies DNA, varied with age.
Horvath found that the methylation of 353 DNA
markers varied consistently with age and could be used as a biological clock. The clock ticked fastest in the years up to around age 20, then slowed down to a steadier rate. Whether the DNA
changes cause ageing or are caused by ageing is an unknown that scientists are now keen to work out.
“Does this relate to something that keeps track of age, or is a consequence of age? I really don’t know,” Horvath told the Guardian. “The development of grey hair is a marker of ageing, but nobody would say it causes ageing,” he said.
The clock has already revealed some intriguing results. Tests on healthy heart tissue showed that its biological age – how worn out it appears to be – was around nine years younger than expected.