Search of the Secrets of Aging
Condensed from the Government Report by the National Institute
and twenty years, as far as we know, is the longest that anyone
has ever lived. A man in Japan, Shirechiyo Izumi, reached the
age of 120 years, 237 days in 1986, according to documents that
most experts think are authentic. He died after developing pneumonia.
Long lives always make us wonder: What is the secret? Does it
lie in the genes? Is it where people live or the way they live
-- something they do or do not do? Eat or do not eat? Most of
the scientists who study aging, gerontologists, say the secret
probably lies in all of the above -- heredity, environment, and
also ask other and more difficult questions. For example, if the
120-year-old had not finally succumbed to illness, could he have
lived on and on? Or was he approaching some built-in, biological
limit? Is there a maximum human life span beyond which we cannot
live no matter how optimal our environment or favorable our genes?
not there is such a limit, what happens as we age? What are the
dynamics of this process and how do they make life spans short,
average, or long? Once we understand these dynamics, could they
be used to extend everyone's life span to 120 or even, as some
scientists speculate, to much greater ages?
for all of us, the most important question: How can insights into
longevity be used to fight the diseases and disabilities associated
with old age to make sure this period of life is healthy, active,
span and life expectancy in the United States have grown dramatically
in this century, from about 47 years in 1900 to about 75 years
in 1990. This advance is mostly due to improvements in sanitation,
the discovery of antibiotics, and medical care. Now, as scientists
make headway against chronic diseases like cancer and heart disease,
some think it can be extended even further.
life span seems to be another matter. There is no evidence that
it has changed for thousands of years despite fabled fountains
of youth and biblical tales of long-lived patriarchs. However,
very recently, the dream of extending life span has shifted from
legend to laboratory. As gerontologists explore the genes, cells,
and organs involved in aging, they are uncovering more and more
of the secrets of longevity. As a result, life extension may now
be more than the stuff of myth and the retardation of disease
and disability, realistic goals.
In 1989, at
Veterans Administration hospitals in Milwaukee and Chicago, a
small group of men aged 60 and over began receiving injections
three times a week that dramatically reversed some signs of aging.
The injections increased their lean body (and presumably muscle)
mass, reduced excess fat, and thickened skin. When the injections
stopped, the men's new strength ebbed and signs of aging returned.
What the men
were taking was recombinant human growth hormone (GH), a synthetic
version of the hormone that is produced in the pituitary gland
and plays a critical part in normal childhood growth and development.
Now researchers are learning that GH, or the decline of GH, seems
also to play a role in the aging process in at least some individuals.
The idea that
hormones are linked to aging is not new. We have long known that
some hormones decline with age. Human growth hormone levels decrease
in about half of all adults with the passage of time. Production
of the sex hormones estrogen and testosterone tends to fall off.
Hormones with less familiar names, like melatonin and thymosin,
are also not as abundant in older as in younger adults.
unexplored or only sketchily mapped, lies ahead. As gerontologists
isolate and characterize more and more longevity- and aging-related
genes in laboratory animals, insights into genes and gene products
important in human aging will emerge. Comparable human genes will
be identified and mapped to chromosomes.
will be useful in designing both genetic and non-genetic interventions
to slow or even reverse some aging-related changes. Already, for
example, a study by Helen Blau of Stanford University has shown
that muscle cells can be genetically modified and injected into
muscle where they will produce and secrete human growth hormone.
Non-genetic strategies will include the development of interventions
to reduce damage to cellular components, such as proteins, nucleic
acids, and lipids.
will be more closely defined. For instance, at NIA's Gerontology
Research Center, the behavior of the cells that line blood vessels
during aging is now providing clues to the stiffening of blood
vessels that occurs with age as well as insights into vascular
disease. As key biomarkers of aging are identified, researchers
will be able to use them to test interventions to slow aging.
Studies will begin to delve more deeply into differences in aging
between the sexes and among ethnic groups.
gerontologists will be charting the paths and intersections of
genetic, biochemical, and physiologic aging. What they find will
reveal some of the secrets of aging. It may lead to extended life
spans. It will very certainly contribute to better health, less
disability, and more independence in the second fifty years of
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© 2000 BIE Health.