In the early 1960s, scientists discovered
that fruit flies exposed to a burst of heat
produced proteins that helped their cel s
they are particularly prone to free radical
survive the temperature change. Over the
damage. As damage mounts, mitochondria
years, scientists have found these “heat
may become less efficient, progressively
shock proteins” in virtual y every living
generating less energy and more free radicals.
organism, including plants, bacteria, worms,
Scientists study whether the accumulation
mice, and even humans. Scientists have
of oxidative (free radical) damage in our cells
learned that, despite their name, heat shock
and tissues over time might be responsible for
proteins are produced when cel s are ex-
many of the changes we associate with aging.
posed to a variety of stresses, not just heat.
Free radicals are already implicated in many
The proteins can be triggered by oxidative
disorders linked with advancing age, includ-
stress and by exposure to toxic substances
ing cancer, atherosclerosis, cataracts, and
(for example, some chemicals). When heat
neurodegeneration.
shock proteins are produced, they help cel s
Fortunately, free radicals in the body do
dismantle and dispose of damaged proteins
not go unchecked. Cells use substances called
and help other proteins keep their structure
antioxidants to counteract them. Antioxidants
and not become unraveled by stress. They
include nutrients, such as vitamins C and E, as
also facilitate making and transporting new
well as enzyme proteins produced naturally in
proteins in the body.
the cell, such as superoxide dismutase (SOD),
Heat shock response to stress changes
catalase, and glutathione peroxidase.
with age. Older animals have a higher every-
Many scientists are taking the idea that anti-
day level of heat shock proteins, indicating
oxidants counter the negative effects of oxygen
that their bodies are under more biological
free radicals a step further. Studies have tested
stress than younger animals. On the other
whether altering the antioxidant defenses of the
hand, older animals are unable to produce
cell can affect the lifespan of animal models.
an adequate amount of heat shock proteins
These experiments have had conflicting results.
to cope with fleeting bouts of stress from
NIA-supported researchers found that insert-
the environment.
ing extra copies of the SOD gene into fruit flies
Heat shock proteins are being consid-
extended the fruit flies’ average lifespan by as
ered as a possible aging biomarker—
much as 30 percent. Other researchers found
something that could predict lifespan or
that immersing roundworms in a synthetic
development of age-related problems—
form of SOD and catalase extended their
in animal models like worms and fruit flies.
lifespan by 44 percent. However, in a com-
However, the exact role heat shock proteins
prehensive set of experiments, increasing or
play in the human aging process is not yet clear.
decreasing antioxidant enzymes in laboratory
mice had no effect on lifespan. Results from a
BIOLOGY OF AGING: RESEARCH TODAY FOR A HEALTHIER TOMORROW 25
limited number of human clinical trials involv-
diet will support longer life. Antioxidant
ing antioxidants generally have not supported
supplementation remains a topic of
the premise that adding antioxidants to the
continuing investigation.
THE FUTURE OF AGING RESEARCH