Irvine, Calif., May 16, 2002 — That daily jog may do more than keep you fit-it also might prevent the deterioration of brain cells that can lead to Alzheimer's disease, according to researchers at UC Irvine's College of Medicine.
The researchers' work indicates that regular exercise controls the expression of genes in an area of the brain important for memory and maintaining healthy cells in the brain; this maintenance breaks down in cases of Alzheimer's. Their study appears in the June edition of Trends in Neurosciences.
Carl Cotman, director of the Institute for Brain Aging and Dementia, and Nicole Berchtold, a researcher at the institute, found in rats that after three weeks of wheel-running, their brains had increased expression of some genes and decreased expression of others. Many of these genes are responsible for helping the brain respond to stress, learning and a wide range of other outside influences.
"Studies have indicated the benefits of exercise in preventing Alzheimer's disease, but none have shown how-and why-exercise might help the brain prevent the cell degradation that can lead to the disease," Cotman said. "Our studies demonstrate for the first time a connection between the genes that control growth hormones and other important molecules and the genes' ability to be stimulated by exercise. We think this may show us a way to determine how much and what types of exercise may help reduce the risk of cognitive impairment and perhaps Alzheimer's disease."
Alzheimer's disease affects more than four million Americans and is a debilitating, progressive disorder, marked by increasing losses in memory and cognitive function. Its cause is unknown, and researchers are looking at a wide range of options for treating and preventing the disease. Scientists only recently have looked at exercise as a possible prevention of Alzheimer's, Cotman and Berchtold note in their Trends paper.
Using sophisticated microarray, or "gene chip," techniques, Cotman and Berchtold found that after three weeks of running on their cage wheels, rats had changed the expression, or activity, of genes in an area of the brain called the hippocampus, a structure usually associated with higher cognitive functions like memory, thinking and learning. These broad changes in gene expression could make the hippocampus more able to respond to outside influences, enabling the brain to be more adaptable to changing circumstances.
"We were surprised to find the concentration of activity in the hippocampus. We presumed that exercise principally would affect motor areas and not areas of higher function in the brain," Berchtold said. "We also found a wide variety in the types of genes that were affected, indicating that exercise is a powerful regulator of brain activity."
Other researchers' work has shown that learning, a high-level brain activity, can affect the productivity of a wide variety of genes, including those that:
* Produce a chemical called BDNF, short for brain-derived neurotrophic factor, which helps amplify nerve signals important in maintaining a healthy nervous system;
* Code for IGF-1, part of the immune system that helps in the growth of new nerve cells and aids in protection of cells from injury;
* Regulate energy metabolism in cells, and even estrogen production.
Studies also have shown that running increases the growth factor levels in rat brains and improves the rats' learning ability in mazes.
The researchers are now looking at the complex interactions of the various genes in the hippocampus that appear to be controlled by exercise, in search of more evidence of how physical activity can affect brain functions during the aging process and could play a role in preventing Alzheimer's disease.
UCI's Institute for Brain Aging and Dementia brings together scientists, nurses, clinicians, technicians and students from a variety of disciplines to study the causes, treatments and prevention of Alzheimer's and other disorders of the brain called dementias. The Institute also is an Alzheimer's Disease Research Center, which provides clinical assessments for patients suspected of having Alzheimer's, and supports community education, research and training.
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