Inside the nucleus of a cell, our genes are arranged along twisted, double-stranded molecules of DNA called chromosomes. At the ends of the chromosomes are stretches of DNA called telomeres, which protect our genetic data, make it possible for cells to divide, and hold some of the secrets to how we age and also possibly get cancer.
Telomeres have been compared with the plastic tips on shoelaces, because they keep chromosome ends from fraying and sticking to each other, which would destroy or scramble an organism's genetic information. Yet, each time a cell divides, the telomeres get shorter. When they get too short, the cell can no longer divide; it becomes inactive or "senescent" or it dies. This shortening process is associated with aging, cancer, and a higher risk of death.
More on Telomere
What are telomeres?
Like the rest of a chromosome, including its genes, telomeres are sequences of DNA — chains of chemical code. Like all DNA, they are made of four nucleic acid bases: G for guanine, A for adenine, T for thymine, and C for cytosine.
Telomeres are made of repeating sequences of TTAGGG on one strand paired with AATCCC on the other strand. Thus, one section of telomere is a "repeat" made of six "base pairs."
In white blood cells, the length of telomeres ranges from 8,000 base pairs in newborns to 3,000 base pairs in adults and as low as 1,500 in elderly people. (An entire chromosome has about 150 million base pairs.) Each time it divides, an average cell loses 30 to 200 base pairs from the ends of its telomeres.
Cells normally can divide only about 50 to 70 times, with telomeres getting progressively shorter until the cells become senescent or die.
Telomeres do not shorten in tissues where cells do not continually divide, such as heart muscle.
Why do chromosomes have telomeres?
Without telomeres, the main part of the chromosome — the part with genes essential for life — would get shorter each time a cell divides. So telomeres allow cells to divide without losing genes. Cell division is necessary for growing new skin, blood, bone, and other cells.
Without telomeres, chromosome ends could fuse together and corrupt the cell's genetic blueprint, possibly causing malfunction, cancer, or cell death. Because broken DNA is dangerous, a cell has the ability to sense and repair chromosome damage. Without telomeres, the ends of chromosomes would look like broken DNA, and the cell would try to fix something that wasn't broken. That also would make them stop dividing and eventually die.
Why do telomeres get shorter each time a cell divides?
Before a cell can divide, it makes copies of its chromosomes so that both new cells will have identical genetic material. To be copied, a chromosome's two DNA strands must unwind and separate. An enzyme (DNA polymerase) then reads the existing strands to build two new strands. It begins the process with the help of short pieces of RNA. When each new matching strand is complete, it is a bit shorter than the original strand because of the room needed at the end for this small piece of RNA. It is like someone who paints himself into a corner and cannot paint the corner.
Telomerase counteracts telomere shortening
An enzyme named telomerase adds bases to the ends of telomeres. In young cells, telomerase keeps telomeres from wearing down too much. But as cells divide repeatedly, there is not enough telomerase, so the telomeres grow shorter and the cells age.
Telomerase remains active in sperm and eggs, which are passed from one generation to the next. If reproductive cells did not have telomerase to maintain the length of their telomeres, any organism with such cells would soon go extinct.
Telomeres and aging
Geneticist Richard Cawthon and colleagues at the University of Utah found shorter telomeres are associated with shorter lives. Among people older than 60, those with shorter telomeres were three times more likely to die from heart disease and eight times more likely to die from infectious disease.
While telomere shortening has been linked to the aging process, it is not yet known whether shorter telomeres are just a sign of aging — like gray hair — or actually contribute to aging.
If telomerase makes cancer cells immortal, could it prevent normal cells from aging? Could we extend lifespan by preserving or restoring the length of telomeres with telomerase? If so, would that increase our risk of getting cancer?
Scientists are not yet sure. But they have been able to use telomerase in the lab to keep human cells dividing far beyond their normal limit, and the cells do not become cancerous.
Some long-lived species like humans have telomeres that are much shorter than species like mice, which live only a few years. Nobody knows why. But it's evidence that telomeres alone do not dictate lifespan.
Cawthon's study found that when people are divided into two groups based on telomere length, the half with longer telomeres lives an average of five years longer than those with shorter telomeres. This study suggests that lifespan could be increased five years by increasing the length of telomeres in people with shorter ones.
People with longer telomeres still experience telomere shortening as they age. How many years might be added to our lifespan by completely stopping telomere shortening? Cawthon believes 10 years and perhaps 30 years.
After age 60, the risk of death doubles every 8 years. So a 68-year-old has twice the chance of dying within a year compared with a 60-year-old. Cawthon's study found that differences in telomere length accounted for only 4% of that difference. And while intuition tells us older people have a higher risk of death, only 6% is due purely to chronological age. When telomere length, chronological age, and gender are combined (women live longer than men), those factors account for 37% of the variation in the risk of dying over age 60.
An enzyme called telomerase can slow, stop or perhaps even reverse the telomere shortening that happens as we age. The amount of telomerase in our bodies declines as we get older.
In 2009, the Nobel Prize for Physiology/Medicine was awarded to three scientists who discovered how telomerase impacts telomere length. Their work explained how the ends of DNA strands are protected by telomeres, and that telomeres are built by telomerase.
Exposing human cells to telomerase slows cell aging and allows cells to begin copying again.Activating telomerase can:
Address telomere shortening and cell aging
Help cells live longer and continue to function properly
Make old cells function as they did when they were younger (by changing gene expression to a younger phenotype)
There are other things we can do that might help restore telomere length or at least slow the loss of telomere length:
reduce body fat percentage
A natural substance whoes main component , astragaloside IV, is thought to be effective as a Telomerase Activator
Astagalus membranaceus is an important herb in Traditional Chinese Medicine. It has been used in a wide variety of herbal blends and ‘natural’ remedies, including Dang-gui buxue tang, which is Astragalus membranaceus paired with Angelicae Sinensis.
Astragalus membranaceus has been researched for its cardioprotective, anti-inflammatory, and longevity effects. Astragalus membranaceus supplementation has been shown to reduce the metabolic and physical complications of aging,
The flavonoid content of Astragalus membranaceus may also contribute to its cardioprotective effects. Its polysaccharide content also protects the heart because it is a potent anti-inflammatory agent, and it is able to reduce cholesterol levels,
The main mechanism of Astragalus membranaceus is a result of its active ingredients. The main component is astragaloside IV, which has been extracted. Unfortunately, astragaloside IV has a low bioavailability, meaning it doesn’t circulate well through the body after being ingested. This means it can only be present in the body at low concentrations.
Whole Astragalus membranaceus supplementation may prove to have higher bioavailability and also provide a variety of other health benefits,
Like Resveratrol, Astragalus membranaceus is a compound that may adds life to your years, rather than adding years to your life.