Science/Tech

Why Breast Tissue Ages Faster Than Other Body Parts: Scientists Discover ‘Biological Clock’ May Control Aging Process

Breast
A UCLA study found that breast tissue ages faster than the rest of the body. Lou Varone, Creative Commons

How can we halt aging? It's a question that has riddled humans since the beginning of existence, and continues to confound scientists. Researchers at UCLA have recently discovered a new ‘biological clock,’ or biomarker, that can keep track of aging in human tissues. The biomarker is a chemical process called methylation, which naturally modifies one of the four blocks of DNA. Steve Horvath, lead author of the study, found that methylation was a sort of timekeeping tool for the body that could match both the chronological and biological age of tissues, charting age “across the human anatomy,” he notes in a press release about the study.

"To fight aging, 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," Horvath, a professor of human genetics at the David Geffen School of Medicine at UCLA, said in the press release. "My goal in inventing this age-predictive tool is to help scientists improve their understanding of what speeds up and slows down the human aging process."

Horvath studied how age impacts DNA methylation levels from pre-birth to over 100 years. Most of the samples he took showed that the biological ages matched their chronological age, but some — including breast tissue — showed that they mismatched. “Healthy breast tissue is about two to three years older than the rest of a woman’s body,” Horvath said. “If a woman has breast cancer, the healthy tissue next to the tumor is an average of 12 years older than the rest of her body.” Horvath also discovered that the “clock” ticked, or aged, faster during childhood and teenage years, but began to slow down to an even rate again around age 20.

The American Federation for Aging Research (AFAR) notes that “some physicians assert that a person’s biological age, rather than their chronological age, is a more important indicator of health and potential lifespan.” AFAR notes that past research into biomarkers of aging has pinpointed senescence, a condition where old cells remain alive but stop producing, as a possible area to research more deeply. Menopause, the central nervous system, saliva, and telomeres have all been studied in the past as potential biomarkers.

Fighting Age

Perhaps the most fascinating and relevant aspect of Horvath’s study is the hinting at the potential to slow down biological aging, keeping cells young. Horvath hopes to continue research on this biomarker, and test whether stopping the “clock” can also halt aging. "The big question is whether the underlying biological clock controls a process that leads to aging," Horvath said in the press release. "If so, the clock will become an important biomarker for studying new therapeutic approaches to keeping us young." Hovarth also looked at pluripotent stem cells, which are adult cells that have been turned into embryonic stem cells — they had the biological age of newborn cells, meaning that in theory, "the discovery proves that scientists can rewind the body's biological clock and restore it to zero," Horvath said.

Veryan Cod, a researcher of biological aging in cardiovascular disease at Leicester University who was not involved in Horvath's study, told the Guardian that the study "will be important to determine whether the accelerated ageing, as described here, is associated with other age-related diseases and if it is a causal factor in, or a consequence of, disease development."

One of the most well-researched ways to fight biological age, and improve health on a molecular level, is exercise. In 2010, a German study measuring the differences between people who exercise and those who are sedentary found that white blood cells’ telomeres, the caps on the end of DNA strands, were shortened by a much smaller amount if a person was active as they grew older. Telomeres shrink as we age, and if they become too short, the cell “either dies or enters a kind of suspended state,” Stephen Roth of the University of Maryland, who is studying exercise and telomeres, told the New York Times.

What the German scientists found was “striking,” according to Dr. Christian Werner; not only were the telomeres of middle-aged runners longer than those of sedentary people their age, but many of the middle-aged athletes also had a much younger appearance than same-aged sedentary control subjects. The telomeres of active middle-aged people were not much shorter than those of young people. As Gretchen Reynolds writes in the New York Times, “The young never appreciate robust telomere length until they’ve lost it."

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