Aerobic Exercise Preserves Vision in Retinal Degeneration Lab Study

May 04, 2013

Aerobic exercise is well-known for helping people stay trim, stave off heart disease and improve mood, but a study by researchers at Emory University and the Atlanta Veterans Administration Medical Center suggests that it also can preserve vision in those with retinal degenerative diseases. While the investigation was in mice, the scientists believe the results, published in The Journal of Neuroscience, may translate to humans.

The research team, led by Machelle Pardue, Ph.D., and Jeff Boatright, Ph.D., found that mice that exercised on a treadmill five days a week, one hour per day, over a four-week period retained significantly more vision and photoreceptors than inactive mice when exposed to damaging levels of bright light. The exercising mice had about twice the number of photoreceptors and retinal sensitivity after the exposure.

Researchers sometimes use toxic levels of light to quickly simulate the degenerative effects of genetic retinal diseases in mice with normal retinas. To better understand the effects of exercise on other retinal diseases, Drs. Pardue and Boatright are currently studying the impact of aerobic activity in mice that have the same genetic mutations that cause retinal diseases in humans.

“We are excited that exercise may be a low cost, non-invasive intervention for patients with vision loss that could be initiated at the first signs of impairment”, says Dr. Pardue. “Early intervention may preserve vision as well as prevent the sedentary lifestyle that often develops in patients with vision loss.”

The hypothesis for the investigation came from previous studies showing the benefits of aerobic exercise in humans with conditions of the central and peripheral nervous systems, including Alzheimer’s and Parkinson’s diseases and amyotrophic lateral sclerosis. Research has also demonstrated that aerobic activity enhances cognitive function in healthy adults, both young and old.

Scientists have found that aerobic exercise causes production of a protein known as brain-derived neurotrophic factor (BDNF), which, in many laboratory studies, has prevented photoreceptor degeneration and preserved vision in animals with retinitis pigmentosa and related conditions. In the Emory study, the exercising mice had 20 percent more BDNF in their retinas than the inactive mice.

To elucidate BDNF’s role in preserving vision, the Emory researchers injected mice before exercise with a substance that blocks the effects of BDNF. As the scientists expected, blocking BDNF inhibited the therapeutic effect of exercise.

“Though we've demonstrated a role for BDNF, other metabolic pathways are undoubtedly involved, so we're also investigating stress and inflammatory response factors,” says Dr. Boatright.

Study results from an Italian research group published in 2012 showed that environmental enrichment — including exercise, companionship and comfortable nesting material — slowed retinal degeneration in mice with RP. Investigators believe that the increased production of neuroprotective proteins such as BDNF played a major role in vision preservation.