Companies are offering tests to gauge the length of telomeres, which they say may
foretell our health. But some researchers question how useful they will be
Can the length of our telomeres, the protective caps at the ends of chromosomes that
wear down as we get old, predict how well
our bodies will age and our vulnerability to
chronic diseases? Two new companies, both
with heavyweight academic backing, are
betting on it and have started or are planning to start performing telomere tests for
the general public this year. But other leading telomere scientists say such tests are
premature, if not virtually useless. On opposite sides of the issue are former collaborators Elizabeth Blackburn and Carol Greider,
who, along with Jack Szostak of Harvard
Medical School in Boston, shared the 2009
Nobel Prize in physiology or medicine for
their telomere discoveries.
“Telomeres are an integrative indicator of health,” says Blackburn, a molecular biologist at the University of California,
San Francisco (UCSF), who co-founded
one of the companies, Telome Health in
Menlo Park, California. Its Web site boasts
that by knowing how long your telomeres
are, you—and your doctor—might be able
gauge your vulnerability to aging-related illnesses like heart disease and cancer and possibly tailor your lifestyle to improve the odds
of staying healthy.
Greider and other critics disagree. “Do I
think it’s useful to have a bunch of companies offering to measure telomere length so
people can find out how old they are? No,”
says Greider, who was a graduate student in
Blackburn’s lab in the mid-1980s and is now
a molecular biologist at Johns Hopkins University (JHU) School of Medicine in Baltimore, Maryland.
Telomeres perform a vital cellular job:
preventing chromosomes from sticking to
each other. But their notoriety stems from
their putative role in aging. Each time a
cell divides, its telomeres typically shrink a
little. Over many years and divisions, they
can dwindle to nubs, spurring the cell to
kill itself or stop dividing and enter a semi-
retired state called replicative senescence.
As more and more cells die or senesce, the
skin, the lining of the intestines, and other
tissues can gradually lose the capacity to
replenish themselves. By curtailing tissue
self-renewal, worn-down telomeres might
promote the senescence of our bodies—
although how much has been controversial.
The length of our telomeres could serve as
a life-span clock that reveals our biologi-
cal age, providing a better indicator of our
Going public. Maria Blasco is a co-founder of one
of two new companies offering tests of telomere
length to patients.
Telltale tips. The glowing caps on these chromo- somes are telomeres, which wear down as we get old.
physical deterioration than does our chronological age. Telomeres are “the best bio-marker of aging we have,” says Jerry Shay,
a cell biologist at the University of Texas
Southwestern Medical Center in Dallas.
For some diseases, telomere measurements are already helping doctors tailor
treatments and save lives, says cancer biologist and physician Mary Armanios of JHU
School of Medicine. The beneficiaries are
people who suffer from telomeropathies,
inherited diseases that result in stumpy
telomeres. Along with the rare dyskerato-sis congenita, the telomeropathies include
some cases of the blood disorder aplastic
anemia and of idiopathic pulmonary fibrosis, progressive lung scarring that kills up to
40,000 people a year in the United States.
More uncertain is what value these tests
will have for the general population—and
whether doctors will be able to interpret the
results. Right now, Telome Health is offering the service only to academic researchers,
according to Calvin Harley, the company’s
president and chief scientific officer. He was
formerly chief scientific officer at Geron
Corp., a biotech company that has been trying to develop telomere-lengthening drugs
since the early 1990s. Harley says that later
this year, individuals will be able to find out
how long their telomeres are, probably by
having their doctors submit a blood sample to Telome Health for analysis. The second company, Life Length of Madrid, also
measures telomeres for researchers and has
already launched patient testing, says co-founder Maria Blasco, a molecular biologist
at the Spanish National Cancer Research
Centre in Madrid.
What the measurements furnish, according to the companies, is a readout of a
patient’s overall risk of developing age-related chronic diseases. Studies have
linked undersized telomeres to cardiovascular disease, diabetes, Alzheimer’s disease, and cancer, among other chronic diseases. Although telomeres don’t necessarily
foretell when we’ll die, Blackburn and colleagues reported in 2009 that their length
correlates with the number of years elderly
people remain healthy.
Very short telomeres might signal a
health problem, Blasco says. They can also
suggest who would profit from treatment.
As an example, Harley points to the West
of Scotland Primary Prevention Study,
which for 20 years has been investigating