Neuroprotection- Exercise to Protect Dopamine Nerve Cells
Neuroprotection-exercise to protect dopamine nerve cells
What is neuroprotection?
Neuroprotection refers to mechanisms within the central nervous system that protect neurons from degeneration or death. In the case of Parkinson’s disease, neuroprotection refers to the protection of dopamine producing cells within the basal ganglia from cellular damage. In other words, a treatment that is Neuroprotective in Parkinson’s would reduce cell damage or death in the vulnerable dopamine nerve cells that degenerate or die as the disease progresses. Think of this as a process that puts the ‘breaks on’ or slows the changes of Parkinson’s over time. Recently, Dr. Warren Olanow wrote, “Neuroprotection is the single most important unmet medical need in Parkinson’s disease.”
What is the evidence for the neuroprotective effect of exercise in Parkinson’s? In rodents, exercise has been shown to have neuroprotective qualities. In these studies, rodents that had free access to a running wheel exhibited less degeneration of dopamine producing neurons, compared to sedentary rodents, in the substantia nigra following the administration of a toxin that selectively destroys dopamine cells. The substantia nigra is the site of dopamine nerve cells that is lost over time in Parkinson’s. Similar neuroprotective effects have been shown in rodents during treadmill running. More recent studies indicate that aerobic exercise is neuroprotective in non-human primates. Monkeys that exercised prior to an injection of a neurotoxin which causes Parkinson’s symptoms exhibited decreased loss dopamine compared to sedentary monkeys. Currently, there have not been any human studies or clinical trials conducted to determine if exercise is neuroprotective for Parkinson’s disease. However, a number of studies have been completed that indicate exercise can reduce the motor symptoms associated with Parkinson’s. The most common type of effective exercise has been those exercises that are aerobic in nature.
Does the kind of exercise matter? My lab recently published a study indicating that Parkinson’s motor function improved nearly 35% after eight-weeks of tandem bicycle riding. This study was conducted as a result of my personal observations during a cross-state bicycle ride in which I noticed that Parkinson’s patients symptoms appeared to decrease after riding on a tandem bicycle with me. Initially, I thought these patients exposure to my wonderful sense of humor while riding with me was the likely explanation for improved motor functions as we all know that “laughter is medicine,” my colleagues, spouse, children and lab personnel were highly doubtful this was the case. In our study, we showed that the tandem could be used to assist the Parkinson’s patients in pedaling at a greater rate than they could achieve on their own, based on data from the animal studies exercise rate and intensity appear to be critical factors if neuroprotection is to occur and the degree of motor improvement has been related to exercise rate in these animal studies.
Since publishing this paper, I have received hundreds of emails from patients engaging in all different types of exercises, ranging from cycling to rowing to boxing to running on a treadmill to jumping rope. At this point, we do not have enough data to recommend one specific exercise over another. My recommendation is to find a mode of exercise that you enjoy (so you will not be dreading your exercise routine) and exercise at relatively high aerobic intensities (you should not be able to hold a conversation comfortably while exercising). Find an exercise partner, possibly a spouse or a friend, as that will decrease the likelihood of skipping sessions. And of course, before starting any exercise program consult with your physician or cardiologist, however as my friend and colleague Dr. Lee Dibble has commented, you really should have to get a prescription to be sedentary from your doctor, rather than get a prescription for something healthy such as exercise.
Will this benefit apply to other areas? Parkinson’s patients will derive all of the same benefits of exercise as people without Parkinson’s. Namely, helps in maintaining a healthy weight, improves mood, promotes better sleep and boosts your overall energy level. Specific exercise programs to combat loss of speech projection have been shown effective in some studies, however, typically there is little of no change in other motor symptoms following these specific targeted approaches. We have had a surprise finding in our subsequent studies, following high intensity aerobic exercise some Parkinson’s patients report improvements in the sense of smell.
What unanswered question(s) is research now focusing on? The $64,000 dollar question that remains to be answered in human PD patients: is exercise neuroprotective which will allow for a slowing or altering the progression of the disease. We are part of a group that will be submitting a multi-site clinical trial to address this question. Other questions being researched by various groups around the country relate to the specifics of exercise prescription for PD patients, namely, what is the ideal intensity, frequency and exercise mode. In the meantime, I sincerely believe there is enough scientific evidence to support that recommendation that Parkinson’s patients should engage in some level of physical activity and that exercise really is medicine for the brain. However, it is important to do so safely so speak to your health care provider and consider an evaluation with a physical therapist to get started.
Author: Jay L. Alberts, Ph.D., Asst. Staff, Center for Neurological Restoration and Dept. of Biomedical Engineering, Cleveland Clinic, Principal Investigator, Louis Stokes VA Medical Center, Cleveland, OH