Aging
| A UCLA study has uncovered a biological clock embedded in our genomes that may shed light on why our bodies age and how we can slow the process. The findings could offer valuable insights into cancer and stem cell research. |
An American scientist has discovered an internal body clock based on DNA that measures the biological age of our tissues and organs.
This 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 unravelling 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.
The research has been published in the journal Genome Biology.
"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 showed that the biological clock was reset to zero when cells plucked from an adult were reprogrammed back to a stem-cell-like state.
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.
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"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. Female breast tissue aged faster than the rest of the body, on average appearing two years older.
Diseased tissues also aged at different rates, with cancers speeding up the clock by an average of 36 years. Some brain cancer tissues taken from children had a biological age of more than 80 years.
"Female breast tissue, even healthy tissue, seems to be older than other tissues of the human body. That's interesting in the light that breast cancer is the most common cancer in women. Also, age is one of the primary risk factors of cancer, so these types of results could explain why cancer of the breast is so common," Horvath said.
Healthy tissue surrounding a breast tumour was on average 12 years older than the rest of the woman's body, the scientist's tests revealed.
"It provides a proof of concept that one can reset the clock," said Horvath. The scientist now wants to run tests to see how neurodegenerative and infectious diseases affect, or are affected by, the biological clock.
Horvath discovered that the clock’s rate speeds up or slows down depending on a person’s age.
“The clock’s ticking rate isn’t constant,” he explained. “It ticks much faster when we’re born and growing from children into teenagers, then slows to a constant rate when we reach 20.”
In an unexpected finding, the cells of children with progeria, a genetic disorder that causes premature aging, appeared normal and reflected their true chronological age.
SOURCE The Guardian, UCLA via Newswise
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