Macular Degeneration, Cholesterol and Treatment Options

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Macular degeneration is a serious eye condition that is the main cause of blindness among older adults in the United States. Now there is evidence that cholesterol buster drugs may stop progression of the disease, which may respond to other treatment options as well.

What’s the role of cholesterol in macular degeneration?

It’s well known that cholesterol can clog your arteries, but it seems it can interfere with your eyes as well. The good news regarding this discovery is that anti-cholesterol drugs may not only benefit people with atherosclerosis but those with the eye problem as well, according to researchers at the Washington University School of Medicine in St. Louis.

Macular degeneration affects approximately 11 million people have some form of macular degeneration in the United States, according to the Bright Focus Foundation. The disease causes individuals to lose their central vision, which is controlled by an area of the retina called the macula, as fatty deposits build up under the retina.

The vast majority (about 90%) of these individuals have the dry form of the disease, which typically progresses at a slow pace. Wet macular degeneration, although less common, is also more serious and often comes on rapidly.

The wet form of macular degeneration is characterized by the formation of new blood vessels under the retina which leak and damage the macula. About 10 percent of people with dry macular degeneration eventually develop the wet form.

While medications can be used to fight cholesterol, the human body is also equipped with its own cholesterol removal system. Players in that system are immune cells called macrophages, and these cells were the target of research by the authors of the new study.

Under the lead of Rajendra S. Apte, senior investigator and a Paul A. Cibis Distinguished Professor of Ophthalmology and Visual Sciences, a research team evaluated cells from mice and humans and showed how cholesterol is involved in both macular degeneration and atherosclerosis. Going a step further, they found that macrophages, which act as cholesterol and fat removal crews, need help from a protein called ABCA1.

But people with macular degeneration don’t have enough ABCA1, which in turn causes macrophages to become overloaded with cholesterol. This process then leads to a process by which new blood vessels are formed that damage the macula, characteristic of the wet form of macular degeneration.

Mice, macular degeneration and men
The researchers used mice and cells from humans and treated the macrophages with a drug that restored ABCA1. After treatment, which was delivered in the form of eye drops for the mice, the cells regained their ability to rid themselves of cholesterol and slow down the growth of new blood vessels.

Apte stated that based on these findings “we need to investigate whether vision loss caused by macular degeneration could be prevented with cholesterol-lowering eye drops or other medications that might prevent the buildup of lipids beneath the retina.”

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Other ways to fight macular degeneration
Until scientists are able to develop a treatment that addresses the buildup of cholesterol in macular degeneration, patients with the eye disease and those at risk need other ways to prevent and fight the disease. One suggestion comes from the results of the National Eye Institute’s Age-Related Eye Disease Study (AREDS).

That study showed how taking specific nutrients could reduce the risk of progressing from dry to wet macular degeneration. Those nutrients include vitamin C (500 mg), vitamin E (400 IU), beta-carotene (15 mg), zinc (80 mg), and copper (2 mg, as cupric oxide).

Additional nutrients, lutein and zeaxanthin, were reported to show evidence “associated with a lower risk of prevalence and incidence” of macular degeneration in a recent systematic review. Several studies have also reported that omega-3 fatty acids may help reduce the risk of the eye disease.

Drugs used to treat wet macular degeneration include a class called angiogenesis inhibitors, which means they help block the proteins that lead to the formation of new abnormal blood vessels (angiogenesis) in the eye, which damage the macula. These drugs include afibercept (EYLEA), ranibizumab (Lucentis), and pegaptanib (Macugen), and all of them are injected into the eye.

Another angiogenesis inhibitor, called bevacizumab (Avastin) is used off-label for macular degeneration. In a head-to-head comparison of Avastin and Lucentis, both drugs were found to be effective in improving macular degeneration, with the main difference being the fact that Lucentis cost 20 to 100 times more than Avastin.

Two other ways to fight wet macular degeneration involve laser treatments. One is photodynamic therapy using a drug called verteporfin (Visudyne) accompanied by laser treatment to destroy abnormal blood vessels. Another treatment is laser photocoagulation, which also destroys abnormal blood vessels, but only those not under the center of the macula, where most of the vessels develop.

Some general guidelines for the prevention of macular degeneration also should be considered. They include:

  • Do not smoke
  • Wear sunglasses and a hat to protect your eyes from sunlight
  • Maintain a healthy blood pressure
  • Eat a low-cholesterol diet; include lots of antioxidant-rich fruits and vegetables and fish rich in omega-3 fatty acids
  • Maintain a healthy weight

The search for effective and safe ways to prevent and treat macular degeneration continues, and cholesterol busters may be one of the next treatments to reach the market. Until then, there are other treatment options for macular degeneration.

Also read: Genes discovered that identify macular degeneration
Artificial retina offers hope for macular degeneration patients

SOURCES:
Bright Focus Foundation
Sene A et al. Impaired cholesterol efflux in senescent macrophages promotes age-related macular degeneration. Cell Metabolism 2013 Apr 2; 17(4): 549-61
Sin HP et al. Lifestyle modification, nutritional and vitamins supplements for age-related macular degeneration. Acta Ophthalmology 2013 Feb; 91(1): 6-11

Image: Morguefile

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