Can Telomeres Be The Key To Aging And Cancer?

Telomeres

In the core or nucleus of any cell, our genes are situated on twisted, double-stranded molecules of DNA called chromosomes. At the ends of the chromosomes are usually stretches of DNA called telomeres, which shield each of our genetic data, make it easy for cells to divide, and hold some encoded information the way you age and acquire cancer.

Telomeres are already in comparison with the plastic tips on shoelaces because they prevent chromosome ends from wearing and sticking with each other, that would mix up an organism’s genetic information to result in cancer, other health problems or death.

 

Yet, every time a cell divides, the telomeres get shorter.

Whenever they get too short, the cell will no longer be able to divide and becomes inactive or “senescent” or dies. The process is part of aging, cancer plus a greater risk of death. So telomeres in addition have been compared with a bomb fuse.

What are telomeres?

Like the remainder of a chromosome as well as its genes, telomeres are sequences of DNA – sequence of chemical code. Like other DNA, they are made of 4 nucleic acid bases: G for guanine, A for adenine, T for thymine and C for cytosine.

Telomeres are constructed with repeating sequences of TTAGGG on a single strand of DNA attached to AATCCC on the other strand. Thus, one component of telomere is really a “repeat” created from half a dozen “base sets.”

In cells within human blood, the length of telomeres ranges from 8,000 base pairs at birth to three thousand base sets as people age and as little as 1,500 in elderly people. (An entire chromosome has about 150 million base sets.) Whenever a cell divides, the average person loses thirty to two hundred base pairs on the ends of that cell’s telomeres.

Cells normally can divide just about fifty to seventy times, with telomeres becoming progressively shorter till the cells become senescent, die or sustain genetic damage that could cause cancer.

Telomeres usually do not shorten with age in tissues like heart muscle in which cells will not continually divide.

Why do chromosomes have telomeres?

Without telomeres, the principle section of the chromosome – the section containing genes essential for life – would get shorter every time a cell divides. So telomeres permits cells to divide without dropping genes. Cell division is necessary so we can grow brand new skin, blood, bone along with other cells as required.

Without having telomeres, chromosome ends could fuse together and degrade the cell’s genetic blueprint, causing the cell malfunction, become cancerous or die. Because broken DNA is dangerous, a cell has got the power to sense and repair chromosome damage. With no telomeres, the ends of chromosomes would look like broken DNA, and the cell would try to fix something which wasn’t broken. That also will make them stop dividing and eventually die.

So why do telomeres get shorter whenever a cell divides?

Prior to the cell could separate , the chromosomes inside of it are duplicated making sure that both of the two brand new cells contains identical genetic substance. A chromosome’s 2 strands of DNA must unwind and split. An enzyme (DNA polymerase) then begins to make 2 fresh lengths of DNA to match each of the two unwound strands. It lets you do this with the help of short components of RNA. When each fresh corresponding strand is finished, it’s a bit reduced than the original string because of the room needed right at the end by this small piece of RNA. It is as if a person that paints herself in a corner and can’t paint the corner.

Can anything combat telomere shortening?

The enzyme known as telomerase adds bases on the ends of telomeres. In new cells, telomerase keeps telomeres from breaking down too much. But as cells split frequently, there is not enough telomerase, therefore the telomeres grow reduced and the cells grow older.

Telomerase stays active in sperm and eggs, which are passed from one generation to the next. If reproductive cells would not possess telomerase to maintain the length of their telomeres, any organism with such cells soon would not exist.

Is there a role that telomeres play in cancer?

When a cell starts to become cancerous, it divides more frequently, and its telomeres become short quicker. If its telomeres get short, the cell may die. It could possibly escape this fate by being a cancer cell and activating an enzyme called telomerase, which usually inhibits the telomeres from getting even shorter.

Investigation has found shortened telomeres in many cancers, which includes pancreatic, bone, prostate, bladder, lung, kidney, and neck and head.

Measuring telomerase can be a innovative strategy to discover cancer. When scientists can learn to stop telomerase, they might be in a position to battle cancer by making cancer cells in order to grow older as well as die . In one experiment, researchers blocked telomerase activity in human breast and prostate cancer cells growing within the laboratory, prompting the tumor cells to die. But there are risks. Blocking telomerase could hinder fertility, wound healing, and output of blood cells and body’s defence mechanism cells.

What about 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, does that raise a risk the telomerase also will cause cancer?

Scientists are not yet sure. But they have been able to use telomerase to make human cells keep dividing far beyond their normal limit in laboratory experiments, and the cells do not become cancerous.

If telomerase could be used routinely to “immortalize” human cells, it would be theoretically possible to mass produce any human cell for transplantation, including insulin-producing cells to cure diabetes patients, muscle cells for muscular dystrophy, cartilage cells for people with certain kinds of arthritis, and skin cells for people with severe burns and wounds. Efforts to test new drugs and gene therapies also would be helped by an unlimited supply of normal human cells grown in the laboratory.

How big a role do telomeres play in aging?

Some long-lived species like humans have telomeres that are much shorter than species like mice, which live only a few years. Nobody yet knows why. But it’s evidence that telomeres alone do not dictate lifespan.

Cawthon’s study found that whenever persons are broken into a couple of groups based on telomere lengths, the fifty percent with longer telomeres lives five years longer than others with shorter telomeres. That suggests lifetime could possibly be improved 5yrs by improving the length of telomeres in people who have shorter ones.

Individuals with longer telomeres continue to experience telomere shortening while they age. The number of years might be added to our life expectancy by completely ending telomere shortening? Cawthon believes a decade and perhaps 3 decades.

After a person becomes over the age of sixty, their chance of passing away doubles with each and every eight years of age. So a person sixty eight years old has two times the potential risk of dying inside a year in contrast to a sixty year old. Cawthon’s study discovered that differences in telomere size included only 4% of that difference. And while intuition informs us older people employ a higher risk of death, only another 6% is due purely to chronological age. When telomere length, chronological age and gender are combined (women live longer than men), those factors are the reason for thirty seven% of the variation in the risk of death after 60 years old. So what on earth causes the other 63%?

A major source of aging is “oxidative stress.” It is the injury to DNA, proteins and lipids (fatty substances) brought on by oxidants, that are highly reactive substances containing oxygen. These types of oxidants are produced commonly when we breathe, and in addition be a consequence of inflammation, infection and consumption of alcohol and cigarettes. In one study, scientists exposed worms to two substances that counteract oxidants, and the worms’ lifespan increased a typical 44%.

Another element in aging is “glycation.” It takes place when glucose sugar from the food we eat binds to alot of our DNA, proteins and lipids, leaving them unable to do their jobs. The issue becomes worse as we mature, causing body tissues to fail to function properly, leading to sickness and death. This may explain why studies in numerous laboratory animals indicate that restricting calorie consumption extends lifespan.

It’s possible oxidative stress, glycation, telomere shortening and chronological age – in addition to various genes – all interact to cause aging.

What are the prospects for human life extension?

The lifespan of humans has increased considerably since the 1600s, when the average lifespan was thirty years. By 1998, the life expectancy of the average American was 76. The reasons included sewers and also other sanitation measures, antibiotics, clean water, refrigeration, vaccines and other medical efforts to prevent youngsters from dying, improved diets and better health care.

A number of scientists believe that average life expectancy will continue to improve, although few believe the typical will grow past ninety. But a few predict significantly lengthier lifespans are achievable.

Cawthon says that if all processes of growing older might be removed and oxidative stress damage might be mended, “one scientific estimate says that people could live 1,000 years.”

Telomeres