FOR IMMEDIATE RELEASE
November 18, 2008
Contact: Christine Guilfoy
Office: (301) 634-7253
cguilfoy@the-aps.org
Exercise Helps Increase Production of Neural
Stem Cells in Mice Brains
Research
finds exercise increases brain growth factor and receptors, preventing
dramatic stem cell drop usually seen by middle age
BETHESDA, Md. (Nov. 18, 2008)
− A new study confirms that exercise can reverse the age-related
decline in the production of neural stem cells in the hippocampus of the
mouse brain, and suggests that this happens because exercise restores a
brain chemical which promotes the production and maturation of new stem
cells.
Neural stem cells and progenitor cells differentiate
into a variety of mature nerve cells which have different functions, a
process called neurogenesis. There is evidence that when fewer new stem or
progenitor cells are produced in the hippocampus, it can result in
impairment of the learning and memory functions. The hippocampus plays an
important role in memory and learning.
The study, “Exercise enhances the proliferation of
neural stem cells and neurite growth and survival of neuronal progenitor
cells in dentate gyrus of middle-aged mice,” was carried out by Chih-Wei Wu,
Ya-Ting Chang, Lung Yu, Hsiun-ing Chen, Chauying J. Jen, Shih-Ying Wu, Chen-Peng
Lo, Yu-Min Kuo, all of the National Cheng Kung University Medical College in
Taiwan. The study appears in the November issue of the Journal of Applied
Physiology, published by The American Physiological Society.
Rise in corticosterone or fall in nerve growth
factor?
The researchers built on earlier studies that found
that the production of stem cells in the area of the hippocampus known as
the dentate gyrus drops off dramatically by the time mice are middle age and
that exercise can slow that trend. In the current study, the researchers
wanted to track these changes in mice over time, and find out why they
happen.
One hypothesis the researchers investigated is that the
age-related decline in neurogenesis is tied to a rise in corticosterone in
middle age. Elevation of corticosterone has been associated with a drop in
the production of new stem cells in the hippocampus.
The second hypothesis is that nerve growth factors --
which encourage new neural cell growth but which decrease with age --
account for the drop in neurogenesis. Specifically, the study looked at
whether a decrease in brain-derived neurotrophic growth factor leads to a
decline in new neural stem cells.
Variables studied
The researchers trained young (3 months), adult (7
months), early middle-aged (9 months), middle-aged (13 months) and old (24
months) mice to run a treadmill for up to one hour a day.
The study tracked neurogenesis, age, exercise, serum
corticosterone levels and brain-derived neurotrophic factor (BDNF) and its
receptor TrkB levels in the hippocampus. The researchers focused on middle
age as a critical stage for the decline of neurogenesis in the mice.
As expected, the study found that neurogenesis drops
off sharply in middle-aged mice. For example, the number of neural
progenitor and mitotic (dividing) cells in the hippocampus of middle-aged
mice was only 5% of that observed in the young mice.
The researchers also found that exercise significantly
slows down the loss of new nerve cells in the middle-aged mice. They found
that production of neural stem cells improved by approximately 200% compared
to the middle-aged mice that did not exercise. In addition, the survival of
new nerve cells increased by 170% and growth by 190% compared to the
sedentary middle-aged mice. Exercise also significantly enhanced stem cell
production and maturation in the young mice. In fact, exercise produced a
stronger effect in younger mice compared to the older mice.
How does this happen?
Based on these results, it appears that nerve growth
factor has more to do with these findings than the corticosterone:
-
The middle-aged exercisers had more brain-derived
neurotrophic factor and its receptor, TrkB, compared to the middle-aged
mice that did not exercise. This suggests that exercise promotes the
production of brain-derived neurotrophic factor which, in turn, promotes
differentiation and survival of new brain cells in the hippocampus.
-
Exercise did not change the basal level of serum
corticosterone in middle-aged mice. This suggests that the reduction of
neurogenesis during aging is not due to the drop in corticosterone
levels.
NOTE TO EDITORS: To interview Dr. Kuo, please
contact Christine Guilfoy at (301) 634-7253 or at
cguilfoy@the-aps.org. Because of the time difference between the U.S.
and Taiwan, e-mail interviews may work best for reporters in the U.S. and
Canada.
Funding: National Science Council of Taiwan
***
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society (www.The-APS.org/press)
has been an integral part of this discovery process since it was established
in 1887.
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