Out of sight. people with advanced macular degeneration ( right ) have difficulty seeing objects in the center of their field of vision.
National Eye Institute, National Institutes of Health
Two genetic studies involving thousands of participants suggest that macular degeneration, a common eye disease the elderly, is linked to a gene that helps regulate "good" cholesterol. The studies present the first genetic evidence of a link between cholesterol and disease, and may lead scientists to identify new targets for therapy.
macular degeneration is the leading cause of blindness in the elderly in the United States. Lesions form behind the retina, preventing the center of the field of view of an individual. A link between cholesterol and eye disease may seem strange, but scientists have known for years that cholesterol can accumulate in the back of the eye in the context of aging. Furthermore, cholesterol is a major component of macular lesions. What is the role cholesterol plays in the eye, however, remains uncertain.
In the new work, the researchers compared the genomes of people who have macular degeneration with the genomes of healthy individuals looking for genetic variants that occur more frequently in one or another group.
In the first study, Johanna Seddon, genetic epidemiologist at Tufts University in Boston and colleagues scanned the genomes of 979 people with advanced degeneration and 1709 healthy people. The researchers found a strong association with a gene variant hepatic lipase ( LIPC ). LIPC encodes an enzyme involved in the metabolism of HDL, or "good" cholesterol. People with this variant have a reduced risk of getting the disease by 18%. An analysis of 4337 and 2077 other cases, controls yielded the same result. The researchers also found weaker associations with three other genes involved in HDL pathway: ABCA1 CETP and LPL . These weaker associations did not meet the strict criteria required in this type of study to reach statistical significance.
In the second study, a team led by Anand Swaroop, a molecular geneticist at the National Eye Institute in Bethesda, Maryland, confirmed the same link between macular degeneration and LIPC . The researchers also connected independently disease ABCA1 , CETP and LPL when scanned genomes 2157 people with macular degeneration and 1150 controls. Both studies appear online today in Proceedings of the National Academy of Sciences .
These results indicate a relationship between HDL pathway and the risk of macular degeneration, but they do not explain this connection. An idea, Seddon said, is that HDL can act as a transport system for the eye, conveying in nutrients that protect the retina from the bloodstream.
There is a plausible mechanism, said Christine Curcio, a pathologist at the University of Alabama, Birmingham, who was not involved in the work. "If there is a variant that causes [that nutrition system] to be less effective," she said, "which could have a long term effect on susceptibility to disease of the eyes."
provides Curcio these documents will require more research to understand the role of cholesterol in the eye, which could help scientists identify potential drug targets. pharmaceutical companies can not necessarily develop new drugs, however. Curcio said existing cholesterol drugs delivered locally to the eye may benefit patients. "We can piggyback on decades of hard work in the service of understanding of heart disease," she said.
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