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December 1, 2004
Chronic Stress Accelerates Aging As Measured By Telomere LengthTopics: Medicine
FuturePundit has an interesting post how stress
Increasing scientific evidence suggests that prolonged psychological stress takes its toll on the body, but the exact mechanisms by which stress influences disease processes have remained elusive. Now, scientists report that psychological stress may exact its toll, at least in part, by affecting molecules believed to play a key role in cellular aging and, possibly, disease development.
In the study, published in the November 30 issue of Proceedings of the National Academy of Sciences, the UCSF-led team determined that chronic stress, and the perception of life stress, each had a significant impact on three biological factors -- the length of telomeres, the activity of telomerase, and levels of oxidative stress -- in immune system cells known as peripheral blood mononucleocytes, in healthy premenopausal women.
Telomeres are DNA-protein complexes that cap the ends of chromosomes and promote genetic stability. Each time a cell divides, a portion of telomeric DNA dwindles away, and after many rounds of cell division, so much telomeric DNA has diminished that the aged cell stops dividing. Thus, telomeres play a critical role in determining the number of times a cell divides, its health, and its life span. These factors, in turn, affect the health of the tissues that cells form. Telomerase is an enzyme that replenishes a portion of telomeres with each round of cell division, and protects telomeres. Oxidative stress, which causes DNA damage, has been shown to hasten the shortening of telomeres in cell culture.
The results of the study -- which involved 58 women, ages 20-50, all of whom were biological mothers either of a chronically ill child (39 women, so-called "caregivers") or a healthy child (19 women, or "controls") -- were dramatic.
As expected, most women who cared for a chronically ill child reported that they were more stressed than women in the control group, though, as a group, their biological markers were not different from those of the controls. However, in one of the study's key findings, the duration of caregiving -- after controlling for the age of the women -- proved critical: The more years of care giving, the shorter the length of the telomeres, the lower the telomerase activity, and the greater the oxidative stress.
Moreover, the perception of being stressed correlated in both the caregiver and control groups with the biological markers. In fact, in the most stunning result, the telomeres of women with the highest perceived psychological stress -- across both groups -- had undergone the equivalent of approximately 10 years of additional aging, compared with the women across both groups who had the lowest perception of being stressed. The highest-stress group also had significantly decreased telomerase activity and higher oxidative stress than the lowest-stress group.
"The results were striking," says co-author Elizabeth Blackburn, PhD, Morris Herzstein Professor of Biology and Physiology in the Department of Biochemistry and Biophysics at UCSF. "This is the first evidence that chronic psychological stress -- and how a person perceives stress -- may damp down telomerase and have a significant impact on the length of telomeres, suggesting that stress may modulate the rate of cellular aging."
The link from mind to body
"Numerous studies have solidly demonstrated a link between chronic psychological stress and indices of impaired health, including cardiovascular disease and weakened immune function," says lead author Elissa Epel, PhD, UCSF assistant professor of psychiatry. "The new findings suggest a cellular mechanism for how chronic stress may cause premature onset of disease. Anecdotal evidence and scientific evidence has have suggested that chronic stress can take years off your life; the implications of this study are that this is true at the cellular level. Chronic stress appears to have the potential to shorten the life of cells, at least immune cells."
While it is not yet clear how psychological stress impacts telomeres, the team suspects stress hormones may play a role.
The next investigative steps
A next step in the research will be determining if prolonged
psychological stress has an impact on telomeres in other types of
cells, such as cells of the lining of the cardiovascular system.
A futurePundit reader comments that the molecule is called a Nanog, and writes:
Age-associated Characteristics of Murine Hematopoietic Stem Cells
"An important question that should be addressed is how HSCs become defective with time. It has been suggested that the length of telomeres limits a life-span of normal somatic cells (20) (21), including HSCs (13). Correlation of telomerase activity and self-renewal potential has been suggested for hematopoietic cells (22). Telomere length can be an indicator of replicative history for HSCs. However, aging in HSCs may be not related solely to shortening of telomeres, since, as shown in this study, aging preferentially affects the lymphoid differentiation potential of HSCs but does not affect their myeloid differentiation potential nor their self-renewal potential."
Scientists have identified a molecule that allows special cells from embryos, called stem cells, to multiply without limit.
This article looks at the regenerative ability of HSC's. HSC's from
adult mice were used to reconstruct the blood stem cells of young mice.
After the young mice aged, the HSC's were again transplanted. The HSC's
retained their regenerative abilities through several generations.
HSC article Here...
There is evidence that telomerase is active in some stem cells. There is also evidence that chronic diseases can lead to stem cells with shortened telomeres and less regenerative ability.
The BBC May 30, 2003 article the reader refers to is entitled "Super cell discovery raises hopes." It gives us the reason behind the name, Nanog, and more:
The UK researchers have dubbed the molecule Nanog, after the mythological Celtic land of the ever young.
Stem cells found in embryos are special because they can turn into almost any type of cell in the body, whether it is a heart cell, skin cell or brain cell.
Research into these cells is expected to lead to revolutionary new treatments for a range of conditions from Parkinson's Disease to heart failure and diabetes.
But the work is controversial because it involves using cells taken from embryos.
This discovery by a team at the Institute for Stem Cell Research at Edinburgh University could help to overcome that problem.
Their finding could ultimately enable scientists to
transform stem cells from adults into cells that have all the
characteristics of those taken from embryos. Read More...
Posted by Hyscience at December 1, 2004 1:30 PM
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