Good fitness before a stroke could reduce brain damage


Here’s reason No. 101 to do those jumping jacks in the morning: The brain housed in a well-conditioned body is far more able to respond to the challenge of a stroke than the brain housed in an out-of-shape body, new research out of the Health Science Center suggests.

“Ten years ago, no one believed exercise before a stroke could reduce brain damage,” said Yuchuan Ding, M.D., Ph.D., associate professor and director of research in the department of neurosurgery at the Health Science Center. “But our study showed that the brains of preconditioned rats formed significantly more new blood vessels to compensate for stroke damage than the brains of rats that were not preconditioned.”

This formation of new blood vessels is called angiogenesis.

Dr. Ding hypothesizes that the new blood vessels reduce the damage from lack of oxygen by stimulating a molecular pathway called the tumor necrosis factor signaling pathway. His work is funded by the American Heart Association.

Rats in the intervention group were exercised for one to three weeks. Half of the rats exercised on a treadmill – simple motor exercise – while the other half raced on a running wheel, complex movement that requires motor balance and coordination. Rats in the control group were inactive for the entire period.

Stroke was induced in all the rats. “Three weeks of preconditioning made a significant difference in neuroprotection,” Dr. Ding said. “One week even made a difference in molecular changes, compared to the control group.”

In addition to testing whether exercise before a stroke would reduce brain damage thereafter, the researchers also tested whether exercise after a stroke would improve functional recovery. They found that it did, and that running wheel exercise was more effective. “Our study suggests that complex exercise may have a better effect on functional recovery after stroke, because more brain areas are involved in this type of exercise, and that simple exercise has better effect on neuroprotection at the time of stroke, because of more angiogenesis,” Dr. Ding said.

The research team now wants to not only test the function of the newly formed blood vessels, but also to figure out why the new vessels are able to resist ischemia/reperfusion insult in stroke. Ischemia is lack of oxygen in tissue due to obstruction of arterial blood. Reperfusion is restoration of blood flow to an organ or tissue. Restoring blood flow to stroke-affected tissue can result in reperfusion injury, which researchers continue to investigate.

“Our study, while constrained to rats, suggests that if you exercise, you not only reduce body weight and blood pressure, but you cause some biochemical reactions in your brain, making it healthier and more resistant to possible damage from stroke,” Dr. Ding said.

“Dr. Ding showed that if you exercise a rat with a good regimen, then put it through an ischemic event, this exercise protects the brain,” said David F. Jimenez, M.D., F.A.C.S., professor and chairman of the department of neurosurgery at the Health Science Center. “This is a totally new concept. The implications for humans are fantastic.”

The finding provides a clue for studies of potential stroke therapies, Dr. Ding said.

Stroke is the third leading cause of death in the U.S., according to Heart Disease and Stroke Statistics – 2005 Update, a publication of the American Heart Association. Stroke strikes about 700,000 people a year, either for the first time or as a recurrence. The lifetime risk of stroke among people 55 or older is greater than 1 in 6.

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