Cholesterol-lowering eye drops could be used to treat a common cause of blindness, research suggests.
Scientists found a link between high cholesterol levels in immune system cells and age-related macular degeneration (AMD).
In experiments with mice, they were able to control the key cause of AMD with eye drops containing cholesterol-regulating agents.
AMD, the leading cause of blindness among older people in the western world, occurs when the over-growth of blood vessels produce bleeding and scarring in the eye. Eventually, the central part of the eye responsible for fine-detail vision is destroyed.
Previous studies have shown that macrophages, white blood cells which form part of the immune system, play a key role in AMD.
Macrophages promote the abnormal blood vessel growth linked to the condition, but it has not been clear how.
The new research shows that high levels of cholesterol building up in the macrophages block the normal inhibition of new blood vessels.
"Our increased understanding of cholesterol's role in the growth of ocular (eye) blood vessels helped us identify therapeutically modifiable pathways, opening up avenues for new treatments that may help us prevent blindness caused by macular degeneration," said Dr Rajendra Apte, from Washington University School of Medicine in the US.
Ageing mice were treated with two drugs designed to aid the transport of cholesterol out of the cells. They experienced a reduction in the growth of blood vessels in their eyes.
The findings, published in the journal Cell Metabolism, have implications that go beyond AMD, the researchers believe.
"Abnormal blood vessel growth is a characteristic of not only AMD, but also diverse disease processes outside the eye, including cancers and atherosclerosis, which are both associated with significant morbidity and mortality," said Dr Apte.
"Our findings may have significant relevance in our understanding of the pathobiology of these conditions."
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Kale, Spinach And Collards
Lutein and zeaxanthin are antioxidants that protect and maintain healthy cells -- and they're abundant in these dark, leafy greens, Caplan explains. She quotes <a href="http://www.aoa.org/" target="_hplink">The American Optometric Association,</a> which has reportedly said they act like "internal sunglasses" that can "filter harmful blue waves." Another bonus? "These [greens] are also high in vitamin A, which is good for the eyes," Caplan said.
Zinc deficiency has been linked to impaired vision and poor night vision, as well as cloudy cataracts, Caplan says. But getting plenty of of the nutrient can work wonders, slowing the progression of age-related macular degeneration, which is <a href="http://www.nei.nih.gov/health/maculardegen/armd_facts.asp#1" target="_hplink">a common condition in adults age 50</a> and older. Oysters are a great source of zinc, Caplan explains. And if they're not exactly your thing, she suggests trying lobster, salmon, beef or milk instead.
Apricots are a good source of beta carotene and lycopene, both carotenoids that can help promote good vision, explains Elisa Zied, an author and registered dietitian. Indeed, the <a href="http://www.maculardegenerationassociation.org/resources/information.aspx?post=98fede9b-f533-4530-9c69-a7d159063010" target="_hplink">Macular Degeneration Association explains</a> that the body converts beta carotene into vitamin A, which resists damage to cells and tissues, including the eye lens. "Continued oxidative stress may result in the development of cataracts or damage the blood supply to the eyes and lead to macular degeneration," the <a href="http://www.maculardegenerationassociation.org/resources/information.aspx?post=98fede9b-f533-4530-9c69-a7d159063010" target="_hplink">organization says.</a>
"It's prudent for people to follow current Dietary Guidelines for Americans, consuming at least three-and-a-half or four cups of produce each day," Zied says. And she recommends that people pay particular attention to eating plenty of fruits and veggies that are rich in vitamins C and A -- which is why sweet potatoes are high on her eye-health list. In fact, <a href="http://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2667/2" target="_hplink">a one-cup serving of sweet potato</a> has more than the full daily requirement for vitamin A. And yes, there is another orange, vitamin A-rich option that's more commonly associated with protecting our peepers: Zied also recommends good ol' carrots.
Eggs are another food that's relatively high in zinc, Caplan explains. They're also a good source of Omega 3 fatty acids <em>and</em> lutein. As Tufts nutritional biochemist <a href="http://www.fitsugar.com/Eating-Eggs-Can-Benefit-Eye-Health-882515" target="_hplink">told FitSugar, </a>eggs don't contain as much of that particular carotenoid as the leafy greens that are also on this list, but "the body is able to absorb these antioxidants better from eggs," <a href="http://www.fitsugar.com/Eating-Eggs-Can-Benefit-Eye-Health-882515" target="_hplink">she says.</a>
"Vitamin E might slow macular degeneration [and can also] decrease risk of cataracts," Caplan says (<a href="http://www.webmd.com/vitamins-and-supplements/lifestyle-guide-11/supplement-guide-vitamin-e" target="_hplink">although WebMD cautions</a> that studies looking at possible benefits for cataracts have been inconclusive). She recommends wheat germ as her top source for vitamin E, as well as other tasty options like almonds, sunflower seeds, peanut butter and the aforementioned sweet potato.