It's a wake-up call for the rest of us to get some regular exercise, the researchers say.
"The concept is emerging that exercise is not only good for the heart and body weight, but also good for the brain," senior researcher Michael J. Zigmond, PhD, co-director of the Center for Neurosciences at the University of Pittsburgh School of Medicine, tells WebMD.
Zigmond heads the team presenting this newest report at the Society for Neuroscience annual meeting, held in San Diego this week.
"Studies show consistently that people who lead active lives — who exercise and walk every day — are less likely to get Parkinson's disease," Zigmond says. "Studies are also under way to identify individuals with Parkinson's disease, put them on an exercise regimen, to see if it is preventive. In the next few years, we should have a real handle on that."
Parkinson's disease is a mystery, its cause unknown but the symptoms unmistakable. The progression of this brain-wasting disease causes uncontrollable tremors, rigidity of limbs, slow movements, and stooped posture. This results from the slow breakdown of nerve cells in the brain that produce dopamine, a chemical that helps control movement.
While some medications or surgery help relieve symptoms, researchers have searched for ways to prevent the downward spiral of Parkinson's disease. This newest study offers hope for an extremely doable alternative, says Zigmond.
Simulating Parkinson's Disease
In their study, the Pittsburgh researchers first put a cast on a lab rat's forearm and forced the rat to exercise the other "good arm" for seven days. Researchers then removed the cast, and — to simulate Parkinson's disease — injected one side of the rat's brain (the same side as the casted limb) with a toxin that triggers brain cell loss, mimicking what is seen in Parkinson's disease.
The side of the brain that was injected was chosen because it controls movement in the free limb. By casting the opposite limb, the researchers were hoping to force exercise in the limb that should have had its movement destroyed by the brain toxin.
Animals that exercised their free limb lost significantly fewer brain cells that contain dopamine— just 6 percent of these brain cells. Another group of rats that also received the toxin but were not forced to exercise lost 87 percent of their brain cells. Parkinson's disease is caused by the destruction of dopamine-producing brain cells.
Two days after the toxin was given, the "exercised" rats still had brain cells that appeared healthy.
Previous research has shown a similar pattern — that people who lead active lives, who exercise and walk every day, are less likely to get degenerative brain disorders like Parkinson's disease, Zigmond says.
In fact, just last month two studies showed that exercise helps prevent or delay onset of Alzheimer's disease, which also involves brain cell death, Zigmond tells WebMD. Those studies showed that "the more active you are, the older you were when you developed it, and the less severe it was."
Studies have also shown that exercise stimulates production of key proteins — specifically a nerve growth factor called GDNF that is important for survival of brain cells, he explains.
"Exercise increases concentrations of growth factors that reduce the rate at which nerve cells die," Zigmond explains. "We've known that these growth factors are very important during a child's early years. But now we realize that they can become important again in adulthood."
Several small pilot studies are under way involving patients diagnosed with Parkinson's disease, he says. Researchers plan to enroll 20 patients in a 60-minute exercise program that meets three times a week.
Preventing, Slowing Parkinson's Disease May Be Possible
Zigmond's study is "exciting, very interesting," Spyridon Papapetropoulos, MD, PhD, professor of neurology at the University of Miami School of Medicine, tells WebMD. "All our efforts up to now have been in preventing further degeneration of these nerve cells or restoring brain cells with embryonic stem cells. If exercise can prevent loss, that's very exciting."
However, he advises against getting overly excited about the research just yet. "It's too early to know whether this works in humans. By the time that Parkinson's disease is diagnosed, people have already lost 60 percent to 80 percent of their dopamine-producing neurons. One can speculate that if it's caught early enough, it's possible to salvage [brain cells] that have survived."
"It's an intriguing finding. ... We're all looking for interventions to prevent these degenerative diseases, and this growth factor GDEF has looked promising," Burton Scott, MD, professor of neurology at the Duke University Movement Disorders Center, tells WebMD. "But how to deliver this growth factor so it works in patients hasn't been determined. So far, those efforts have been unsuccessful. This study presents another avenue to explore."
SOURCES: Neuroscience 2004, San Diego, Oct. 23-27, 2004. Michael J. Zigmond, PhD, co-director, Center for Neurosciences, University of Pittsburgh School of Medicine. Spyridon Papapetropoulos, MD, PhD, professor of neurology, University of Miami School of Medicine. Burton Scott, MD, professor of neurology, Duke University Movement Disorders Center.
By Jeanie Lerche Davis
Reviewed by Brunilda Nazario, MD
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