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In a study which can have far reaching consequences, scientists from the Washington University School of Medicine in St. Louis have found that drugs commonly employed to lower the levels of cholesterol can be effectively used to treat macular degeneration, an age related blindness. The research has been published in the journal Cell Metabolism and was led by Rajendra S. Apte, a Paul A. Cibis Distinguished Professor of Ophthalmology and Visual Sciences, along with his colleagues.
Macular degeneration is one of the commonest causes of blindness in American people beyond the age of 50. Studies done in the past have shown that both atherosclerosis and macular degeneration are a result of the same disease process. In both the conditions, the underlying pathology is the inability of the body to clear fat and cholesterol deposition. Researchers associated with the present study, tried to find out whether medicines used for treating atherosclerosis would be beneficial in treatment of macular degeneration as well.
The two types of macular degeneration
Macular degeneration is basically of two types- the dry form and the wet form. In the dry form of macular degeneration, there is a collection of lipids beneath the retina in the eye. As the deposits increase in size, they start interfering with the vision. The result is gradual loss of vision, particularly in the central part of the eye. In a normal individual, the lipid collection is cleared by the macrophages. But in elderly people, where the macrophages are not working to their optimal capacity, the lipids are not cleared completely. On the contrary, the macrophages meant to remove them get filled with cholesterol and become sluggish. Their collection gives rise to an inflammatory process which, in turn, leads to the formation of new blood vessels. This neo-vascularization is characteristic of the wet form of macular degeneration and results in further impairment of vision. This is because the development of these abnormal new blood vessels is associated with bleeding and formation of scar tissue.
As a part of their study, the researchers analyzed the macrophages in humans and mice. They noticed that the macrophages need a protein, called as ABCA1, to clear cholesterol and fats. With the aging process, the level of this protein becomes insufficient in the macrophages. Therefore, the efficiency of macrophages in clearing cholesterol decreases. With low levels of ABCA1, the macrophages are no longer able to transport cholesterol outside the cells. This leads to an accumulation of cholesterol inside the macrophages.