As a saying goes, you're only as old as you feel, but what if different parts of your body aged at different speeds? It turns out they do. The study about the age of our bodies shows that different tissues（组织）inside us are effectively different ages. In 2012, Professor Steve Horvath at the University of California, Los Angeles, looked at something new—DNA methylation（甲基化）, a naturally occurring process in which DNA is chemically changed over time.
Horvath analyzed the DNA in 8,000 tissue samples from different parts of the body in different people to study these markers. What he found was striking—the amount of methylation in cells from most parts of the body was a good predictor of the person's age. But there were inconsistencies. Breast tissue, for instance, ages rapidly, whereas muscle ages slowly. The rates of ageing are also different in men and women. "There are many medical implications, from cancer to premature ageing diseases," says Horvath. It has already been established that tissue that looks significantly older could be cancerous. Horvath's study found that cancerous tissue has a biological age on average 36 years older than a subject's actual age.
Could this knowledge help us live longer? "If the markers relate to a process that causes ageing, then it would be theoretically possible to slow down ageing by carefully targeting DNA methylation," says Horvath. But before scientists got to work on dealing with methylation, they first needed to establish whether these changes were the cause of ageing or just a byproduct of another process. Now, a 2023 study from the University of Michigan has backed up Professor Horvath's findings, which means they can safely make further studies of methylation.
"Our main aim was to see whether biological age acceleration measured from DNA methylation was predictive of health outcomes and death," said research associate professor Jessica Faul. "It turned out that it is largely the case. You can use certain DNA methylation markers to predict age and age-related outcomes quite well."
