Gray hair and wrinkles are only the external signs of aging, which are often not sufficient to determine the exact age of the person. A scientist from the University of California found that the “biological clock” embedded in our genes can define much more precise age of human cells and tissues. Perhaps it would help understand why some tissues age faster than the rest, and which ones are more prone to cancer.
“In order to fight aging, we have to find an objective way to measure this process. My mission is to help scientists understand what exactly makes the rate of aging reduce and increase,” says Steve Horvath, bioinformatician of the University of California.
During the study, he focused on methylation, or chemical modification of the DNA molecule which does not disturb the sequence of nucleotides. In particular, the scientist made an outline of how the rates of DNA methylation vary in different tissues from birth to old age.
To develop these ‘clock’, the scientist processed data on nearly 8,000 DNA samples of 51 types of tissues and cells, including the ones of the brain and major organs like the liver and kidney. Having noted 353 points of methylation, which change with age and are found in all cells, Horvath compared them the biological age of tissues. To his surprise, this «biological clock» showed high accuracy in the tissues of most organs.
Amazingly, the scientist found that the breast tissue ages much faster than the others. Breast health is 2-3 years older than the other tissues of the female body. If a woman suffers from breast cancer, the healthy tissue around the affected area ages by leaps and bounds, getting 12 years older than other tissues. On average, the tumor tissue is 36 years older than the healthy one; therefore, not without reason age is a key risk factor for cancer.
Steve Horvath hopes that his discovery will help better understand the factors that have impact on the rate of aging. He himself plans to explore the possibility of delaying aging and reducing the risk of cancer through the manipulations of the “biological clock”.