Excessive growth of blood vessels beneath the retina is a proximate cause of blindness in conditions such as macular degeneration. Researchers here provide evidence for physical activity to be influential in the pace at which this process of tissue damage takes place. The usual conclusion to such research is provided, which is to head off into the space of developing pharmaceuticals to mimic some fraction of the effects of exercise on metabolism. Given that calorie restriction mimetic research has been ongoing for more than 20 years, with all too little to show for it, no-one should be holding their breath awaiting viable exercise mimetic drugs with meaningfully large effect sizes.
Exercise reduced the harmful overgrowth of blood vessels in the eyes of lab mice by up to 45%. This tangle of blood vessels is a key contributor to macular degeneration and several other eye diseases. The study represents the first experimental evidence showing that exercise can reduce the severity of macular degeneration, a leading cause of vision loss. "There has long been a question about whether maintaining a healthy lifestyle can delay or prevent the development of macular degeneration. The way that question has historically been answered has been by taking surveys of people, asking them what they are eating and how much exercise they are performing. That is basically the most sophisticated study that has been done. The problem with that is that people are notoriously bad self-reporters - and that can lead to conclusions that may or not be true. This study offers hard evidence from the lab for very first time."
Enticingly, the research found that the bar for receiving the benefits from exercise was relatively low - more exercise didn't mean more benefit. "Mice are like people in that they will perform a spectrum of exercise. As long as they had a wheel and ran on it, there was a benefit. The benefit that they obtained is saturated at low levels of exercise." An initial test comparing mice that voluntarily exercised versus those that did not found that exercise reduced the blood vessel overgrowth by 45%. A second test, to confirm the findings, found a reduction of 32%.
The scientists aren't certain exactly how exercise is preventing the blood vessel overgrowth. There could be a variety of factors at play, including increased blood flow to the eyes. "It is fairly well known that as people's eyes and vision deteriorate, their tendency to engage in physical activity also goes down. It can be a challenging thing to study in older people. How much of that is one causing the other? The next step is to look at how and why this happens, and to see if we can develop a pill or method that will give you the benefits of exercise without having to exercise."