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Scientists have discovered that breast tissue ages more rapidly than the rest of the body
Now scientists have discovered that breast tissue does indeed age more rapidly than the rest of the body.
Researchers have uncovered a biological clock embedded in our genomes that sheds light on why people age and on how the process can be slowed.
Experts at the University of California, Los Angeles, found that some parts of the anatomy – like a woman’s breast tissue – age faster than the rest of the body.
‘To fight ageing, we first need an objective way of measuring it. Pinpointing a set of biomarkers that keeps time throughout the body has been a four-year challenge,’ said Steve Horvath, a professor of human genetics at the David Geffen School of Medicine at UCLA and of biostatistics at the UCLA Fielding School of Public Health.
‘My goal in inventing this clock is to help scientists improve their understanding of what speeds up and slows down the human ageing process.’
To create the clock, Professor Horvath focused on methylation, a naturally occurring process that chemically alters DNA.
He sifted through 121 sets of data collected previously by researchers who had studied methylation in both healthy and cancerous human tissue.
Gleaning information from nearly 8,000 samples of 51 types of tissue and cells taken from throughout the body, Professor Horvath charted how age affects DNA methylation levels from pre-birth through 101 years.
To create the clock, he focused on 353 markers that change with age and are present throughout the body.
Professor Horvath tested the clock's effectiveness by comparing a tissue's biological age to its chronological age. When the clock repeatedly proved accurate, he was thrilled—and a little stunned.
‘It's surprising that one could develop a clock that reliably keeps time across the human anatomy,’ he admitted.
‘My approach really compared apples and oranges, or in this case, very different parts of the body: the brain, heart, lungs, liver, kidney and cartilage.’
Researchers have uncovered a biological clock embedded in our genomes that sheds light on why people age and on how the process can be slowed
While most samples' biological ages matched their chronological ages, others diverged significantly.
For example, Professor Horvath discovered that a woman's breast tissue ages faster than the rest of her body.
‘Healthy breast tissue is about two to three years older than the rest of a woman's body,’ said Professor Horvath.
‘If a woman has breast cancer, the healthy tissue next to the tumour is an average of 12 years older than the rest of her body.’
If a woman has breast cancer (pictured), the healthy tissue next to the tumour is an average of 12 years older than the rest of her body
The results may explain why breast cancer is the most common cancer in women. Given that the clock ranked tumour tissue an average of 36 years older than healthy tissue, it could also explain why age is a major risk factor for many cancers in both genders.
Professor Horvath also looked at pluripotent stem cells, adult cells that have been reprogrammed to an embryonic stem cell–like state, enabling them to form any type of cell in the body and continue dividing indefinitely.
‘My research shows that all stem cells are newborns,’ he said. ‘More importantly, the process of transforming a person's cells into pluripotent stem cells resets the cells' clock to zero.’
In principle, the discovery proves that scientists can rewind the body's biological clock and restore it to zero.
‘The big question is whether the biological clock controls a process that leads to ageing,’ Professor Horvath said. ‘If so, the clock will become an important biomarker for studying new therapeutic approaches to keeping us young.’
Finally, Professor 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.’
Professor Horvath’s next studies will examine whether stopping the body's ageing clock halts the ageing process—or increases cancer risk. He'll also explore whether a similar clock exists in mice.
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