February 12, 2014
Retinal Degeneration May Be Slowed By Moderate Exercise
Brett Smith for redOrbit.com - Your Universe Online
While it may seem unrelated to eye function, physical exercise can actually help to protect the structure and function of nerve cells in the retina after injury – according to a new study in The Journal of Neuroscience.
The study indicated that exercising may be able to hamper the advancement of retinal degenerative diseases, such as age-related macular degeneration.
“This is the first report of simple exercise having a direct effect on retinal health and vision,” said study author Machelle Pardue, an associate professor in the Department of Ophthalmology at Emory University. “This research may one day lead to tailored exercise regimens or combination therapies in treatments of blinding diseases.”
In the study, scientists regularly ran mice on a treadmill for two weeks prior to and after exposing them to a light that causes retinal degeneration. The exercise regimens consisted of one hour per day, five days per week.
The study team discovered that the regular running maintained photoreceptors and retinal cell function in the rodents. More specifically, they found that the exercise group lost only half the number of photoreceptor cells as the rodents that spent a comparable amount of time on a stationary treadmill.
The scientists also learned that the retinal cells of the exercise group were more responsive to light and had higher levels of a beneficial protein called brain-derived neurotrophic factor (BDNF), which previous reports have linked to the useful effects of exercise. When the scientists blocked the receptors for BDNF in the exercise group, they saw that retinal function in these mice was as poor as in the inactive mice, effectively removing the mitigating effects of the aerobic exercise.
"One point to emphasize is that the exercise the animals engaged in is really comparable to a brisk walk," Pardue said. "One previous study that examined the effects of exercise on vision in humans had examined a select group of long distance runners. Our results suggest it's possible to attain these effects with more moderate exercise."
Michelle Ploughman, who studies the effects of exercise on the brain at Memorial University of Newfoundland in Canada and who was not involved with the study, said the findings advance the current understanding of both the neuroprotective effects of aerobic exercise and the role of BDNF.
“People who are at risk of macular degeneration or have early signs of the disease may be able to slow down the progression of visual impairment,” she added.
Pardue said she is currently working on determining the potential benefits of other exercise regimens and if exercise is beneficial might be beneficial for other retinal diseases, such as glaucoma and diabetic retinopathy.
"Possibly in the near future, ophthalmologists could be prescribing exercise as a low-cost intervention to delay vision loss,” she said.
In September, medical researchers at the University of North Carolina revealed a promising new treatment for macular degeneration.
Also based on experiments with laboratory mice, the UNC study found that a group of drugs known as MDM2 inhibitors is exceedingly effective at mitigating the abnormal blood vessels responsible for the vision loss linked to the disease.