
Do
you think we will be able to live forever in the near future?
I
think there's a possibility that we may have an indefinite lifespan.
I think that's a possibility. At the end of our chromosomes of every
cell, there's something called the telomeres. And the telomeres are
like a clock. They get shorter every time a cell reproduces. And when
the telomere gets so short, it frays, falls apart, and you die. So we
have a time limit. We've also discovered telomerase, a chemical that
stops the clock. There's a clock in our body that tracks how long
we're going to live and there's something called telomerase which
stops the clock, so the question is... can we live forever? In our
discovery, we also found that cancer uses telomeres and telomerase to
live forever. So cancer is immortal in principle and could live
forever. So the secret of immortality is tantalizing close. We know
that there are cells that make immortality possible, but there's a
price to pay. The price to pay is you don't want cancers to also
follow you. We have a whole bunch of top people in the sciences and
medicine looking for ways to extend the human lifespan without waking
up the cancers that cut it short.
~
Michio Kaku, world-renowned physicist
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
secrets to how we age and 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. So
telomeres also have been compared with a bomb fuse.
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 cancer
As a
cell begins to become cancerous, it divides more often, and its
telomeres become very short. If its telomeres get too short, the cell
may die. Often times, these cells escape death by making more
telomerase enzyme, which prevents the telomeres from getting even
shorter. Many cancers have shortened telomeres, including pancreatic,
bone, prostate, bladder, lung, kidney, and head and neck.
Measuring
telomerase may be a way to detect cancer. And if scientists can learn
how to stop telomerase, they might be able to fight cancer by making
cancer cells age and die. In one experiment, researchers blocked
telomerase activity in human breast and prostate cancer cells growing
in the laboratory, prompting the tumor cells to die. But there are
risks. Blocking telomerase could impair fertility, wound healing, and
production of blood cells and immune system cells.
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.
If we
used telomerase to "immortalize" human cells, we may be
able to mass produce cells for transplantation, including
insulin-producing cells to cure diabetes, muscle cells for treating
muscular dystrophy, cartilage cells for certain kinds of arthritis,
and skin cells for healing severe burns and wounds. An unlimited
supply of normal human cells grown in the laboratory would also help
efforts to test new drugs and gene therapies.
How
big is the role of telomeres 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 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. So
what causes the other 63%?
A
major cause of aging is "oxidative stress." It is the
damage to DNA, proteins, and lipids (fats) caused by oxidants, which
are highly reactive substances containing oxygen. These oxidants are
produced normally when we breathe, and also result from inflammation,
infection, and consumption of alcohol and cigarettes. In one study,
scientists exposed worms to two substances that neutralize oxidants,
and the worms' lifespan increased an average 44%.
Another
factor in aging is "glycation." It happens when glucose,
the main sugar we use as energy, binds to some of our DNA, proteins,
and lipids, leaving them unable to do their jobs. The problem becomes
worse as we get older, causing body tissues to malfunction, resulting
in disease and death. Glycation may explain why studies in laboratory
animals indicate that restricting calorie intake extends lifespan.
Most
likely oxidative stress, glycation, telomere shortening, and
chronological age along with various genes all work together to
cause aging. Cawthon says that if all processes of aging could be
eliminated and oxidative stress damage could be repaired, "one
estimate is people could live 1,000 years."
What
are the prospects for human immortality?
Human
lifespan has increased considerably since the 1600s, when the average
lifespan was 30 years. By 2012, the average US life expectancy was
nearly 79. Reasons for the increase include sewers and other
sanitation measures, antibiotics, clean water, refrigeration,
vaccines and other medical efforts to prevent children and babies
from dying, improved diets, and better health care.
Some
scientists predict average life expectancy will continue to increase,
although many doubt the average will ever be much higher than 90. But
a few say vastly longer lifespans are possible.
How
you can lengthen and protect your telomeres
The
good news is that you have a lot of control over the wear-and-tear of
your telomeres. And even if you have shorter telomeres, it’s not a
done deal — you can lengthen them with certain habits and
behaviors. Here’s how to do it:
Since
how you perceive your stress counts, finding ways to feel more in
control is key. Meditation gives you that time and space to sort out
your thoughts, so you can recognize which worries are valid, and
which are not. This changes your perception and experience of stress.
A 2009 paper suggests that mindfulness meditation lowers stress,
which in turn could preserve telomeres. Another study found that
women who practiced loving kindness meditation (a technique that
encourages compassion) had longer telomeres than women who didn’t.
Carve out time each day (put it in the calendar if you have to) to
quieten your thoughts and focus on your breath. Even a quick
five-minute meditation in the middle of your workday can calm your
nervous system and do wonders for your sense of well-being.
Limit
exposure to air pollution. If you live near a highway or have a long
commute, this one could be hard. But air pollution does affect
telomere length. One study found that traffic officers had shorter
telomeres than people who worked in an office. Consider investing in
a high-efficiency particulate (HEPA) air filter, and sleep with your
windows closed if you live near a busy road.
Get
active. Yet another benefit of exercise — it reduces oxidative
stress and boosts proteins that help stabilize telomeres. In one
study, men and women who didn’t exercise much or at all were
biologically older by 10 years than those who were very active. But
you don’t need to run a marathon or put in hours each day at the
gym. People who do moderate aerobic exercise just 45 minutes, three
times a week, have telomeres similar in length to marathon runners.
According to Dr. Eric Berg the best exercises to slow telomere
shortening are high-intensity exercises and aerobic exercises. But
take note office workers: “It’s not just how active you are,”
says Epel, “it’s really how much sitting you do, so people like
me are in trouble. I exercise every day, but I sit on my butt for
hours the rest of the time.” Get up regularly from your desk — at
least once every hour — and walk around or do some stretching. A
standing desk, although pricey, is a great long-term investment in
your health.
Maintain
a healthy weight. Obesity causes telomeres to wear down quicker. One
study found that the loss of telomeres in obese people was equivalent
to 9 years of life. One way to keep your weight steady is to practice
intermittent fasting — when you cycle in and out of periods of
eating and not eating. Intermittent fasting not only boosts weight
loss, it makes cells more resilient and promotes cellular repair. It
also lowers oxidative stress — when free radicals overpower the
antioxidants in the body. Since oxidative stress shortens telomeres,
reducing this type of stress will help preserve them.
Boost
your NAD+ levels. Nicotinamide adenine dinucleotide (known as NAD+)
is a coenzyme, found in every cell, that rewires your metabolism and
activates sirtuins — proteins that help maintain the length of your
telomeres. Since NAD+ levels drop as you get older, consider taking
supplements of this coenzyme or practice intermittent fasting, which
increases NAD+ supplies.
Load
up on healthy fats and veggies. One study found that telomeres didn’t
shorten as quickly in people with high levels of omega-3 fatty acids
than people with low levels of the fats. Another study found that
women with shorter telomeres and lower levels of vitamin C, vitamin
E, and beta carotene had an increased risk of developing breast
cancer. Eat plenty of lightly cooked leafy greens and broccoli,
berries, wild salmon, and other fatty fish. “Eat your damn
vegetables,” says Michael Fossel, MD, PhD, author of “The
Telomerase Revolution”. “It’s really not rocket science when it
comes to maintaining telomeres.” But he emphasizes that moderation
is key: “You need a good diet, but if what you do is end up
stressing yourself worrying about it the whole time, you’ll just
undercut yourself. Chill out, relax, go meditate.”
Give
TA-65 supplements a try. Made from a Chinese root, this supplement
claims to activate telomerase — the enzyme that rebuilds telomeres.
A 2009 study found that TA-65 increased telomere length and lessened
DNA damage in mice. But before you rush out to buy it, it doesn’t
come cheap — expect to shell out $600 for a three-month supply. A
slightly cheaper option is cycloastragenol — believed to be the
active ingredient of TA-65. One study found that, like TA-65, it
activated telomerase in mice.
Test
your telomeres at home. You can now order telomeres testing kits in
the mail. With the prick of a finger or swab of a cheek, companies
like TeloYears and Titanova tell you how your telomeres compare in
length to others your age. Whether the information is accurate is
another story — people have received conflicting results when
trying different tests. Most scientists agree that while knowing your
telomere length could nudge you to adopt healthier habits, there are
still too many unknowns. For instance, it’s not clear whether
telomeres are the same length throughout all tissues and cells of the
body. So a test that analyses telomeres in saliva may be offering
just a small snapshot of the bigger picture. Tests typically cost
around $100 a pop — money perhaps better spent on a fresh farmer’s
market haul or new walking shoes.
from
learn.genetics.utah.edu and daveasprey.com/telomeres-aging