Gene Sequence Determines Lifespan, How Fast We Age
Why do some people seem to age faster than others? Scientists believe they have found the answer: a specific gene sequence that determines how fast bodies age. This is the first time researchers have found a link between DNA and human lifespan.
People have both a chronological age and a biological age. Chronological age refers to the actual amount of time a person has lived, and it is considered a crude indication of a person’s probable lifespan. Biological age is determined by a person’s genetic makeup along with lifestyle factors, such as diet, exercise, alcohol use, and smoking. It can be regarded as a more accurate estimation of a person’s position in time relative to his or her potential lifespan. Two people can be chronologically the same age but differ in their biological ages by more than a decade.
In this new study, a team of scientists from the University of Leicester, King’s College London, and University of Groningen in the Netherlands analyzed more than 500,000 genetic variations before they discovered definitive variants associated with biological aging in humans. They discovered a common sequence of DNA was significantly associated with a person’s biological age.
Overall, the scientists evaluated nearly 3,000 people, and about 38 percent had inherited one copy of the gene variant, which meant they were biologically three to four years older than people who had not inherited the sequence. Only 17 percent tested positive for two copies of the DNA sequence, and this meant they were six to seven biological years older. Fifty-five percent of the group studied did not have any copies of the gene variant.
Discovery of the gene sequence could have a significant impact on how clinicians will be able to identify people who are likely to age fast and thus be more susceptible to health problems and age-related diseases, such as cardiovascular problems, early in life. For example, people in their twenties who test positive for the gene variant could begin taking steps to avoid heart disease, such as changing to a low-fat, low-cholesterol diet, losing weight, and stopping smoking.
Cardiologist and Professor Nilesh Samani of the University of Leicester, who co-headed the research, noted that he sees patients who are in their 80s who have high blood pressure and healthy coronary arteries, yet there are patients in their forties who have advanced heart disease but no apparent risk factors. “We think this kind of variability must have something to do with premature ageing,” he is quoted in the Guardian.
Specifically, the scientists found that a certain gene sequence was more common in people who had unusually short telomeres for their age. Telomeres are like protective caps found on either end of the long molecules of DNA called chromosomes. Whenever a cell divides, the telomeres become shorter. Over time, the telomeres become very short, prompting the cell to malfunction and show signs of aging.
Although there is a gene that makes an enzyme that fixes telomeres when they become shorter, the scientists believe that people who have one or two copies of the gene sequence probably make less of the enzyme (telomerase) even before they leave the womb. Thus these individuals are born with shorter telomeres and are more prone to age more quickly, meaning telomere length is considered an indicator of biological aging.
Discovery of the special gene sequence suggests that some individuals are genetically programmed to age faster than others, shortening their lifespan. The scientists note that their findings also raise questions, including whether people who have one or two copies of the variant are at greater risk of developing age-associated diseases.
The Guardian, Feb. 7, 2010
Tinterow MM et al. Townsend Letter for Doctors Feb/March 1993