In 2009 the Nobel Prize in Physiology or Medicine was awarded jointly to Elizabeth Blackburn, Carol Greider and Jack Szostak for their discovery of how chromosomes are protected (1). The importance of this finding underlies the award and it’s relevance to DNA and its role in aging. As each of our cells divide their DNA gets packaged into 23 pairs of chromosomes so that they get evenly distributed between the dividing cells.
Each time a cell divides, however, they lose a little bit of DNA at the tips of the chromosomes which are called telomeres. After many cell divisions if the telomeres are not rebuilt the DNA becomes unstable which will cause the cell to stop dividing and become senescent or possibly die in a process called apoptosis or even become cancerous (2). The Nobel Prize mentioned above was won for the discovery of the enzyme that repairs the tips of chromosomes called telomerase. Telomerase activity leads to more youthful, active and healthy cells by restoring the tips of chromosomes which restores the stability of the cell’s DNA. Unfortunately, not every cell has telomerase.
As we age telomeres shorten leading to unstable DNA. The rate at which telomeres shorten, however, is variable and depends on your lifestyle (smoking, excessive alcohol, stress, poor diet, being sedentary, etc.). There are multiple studies that bear this out particularly with smoking and obesity (3, 4, 5).
“Those who do not find time for exercise will have to find time for illness.”
Edward Smith-Stanley
As our bodies get older our cells divide to create new cells often from stem cells. Eventually the supply of these cells run out and the cells go into a state of senescence. This is a state where the cell fails to do all the things it was supposed to do and errors occur. These senescent cells instead release inflammatory molecules that cause our bodies to age faster, hence all the articles on eating anti-inflammatory diets. When a cell has reached its limit to divide we call that the “Hayflick limit”.
Dr. Hayflick in 1961 did a series of experiments that demonstrated that normal human cells have a limited number of cell divisions, between 40 and 60 times in cell culture (2). After a cell reached its limit the cell goes into a state of senescence where it can no longer divide. The reason why this happens is felt to be due to progressive shortening of the DNA at the end of the telomeres. If the cell has telomerase then the telomeres can be repaired if not then the cell goes into senescence and stops functioning properly. Senescent cells not only stop working properly but also cause other nearby cells to stop working properly. They do this by secreting multiple factors that get taken up by other cells and cause them also to not work properly (3) which is referred to as SASP (senescent associated secretory phenotype). In this case one rotten apple surely spoils the bunch. As we get older this becomes a rapidly progressive event that shortens healthspan and lifespan.
So what can we do about it? Is this inevitable for all of us? There are actually a lot of things we can do to help our telomeres. Several studies have shown improvement in telomere length with a healthy diet (4) and regular exercise (5) along with avoiding smoking (6) and excess alcohol (7). There are also several supplements that have also been shown to improve telomere length such as vitamin D, omega-3 fatty acids, Aswagandah, Danazol (4) and TA-65 have been shown to increase telomere length in clinical studies 4,).
Telomere attrition is only one of the 9 hallmarks of aging but it is an important one that should be a part of anyone’s plan for maintaining your health for 100 plus years.