Low cholesterol may add to cataracts risk

Low cholesterol levels may contribute to the development of cataracts, according to a Japanese study.

The researchers warned that the findings could have implications for patients taking statins or other cholesterol-lowering medication, as well as for those with hereditary cholesterol deficiency.

The genetic study looked for the genes responsible for early cataract development in the Shumiya cataract rat, which develops mature cataracts at about 11 weeks of age.

By cross-breeding the rats with another strain with normal eye development they identified a genetic mutation on chromosome 20, which was linked to early cataract formation.

This mutant gene was identified as one that controls the production of lanosterol synthase, which plays a part in the cholesterol biosynthesis pathway.

When the researchers compared the lenses, they found that rats with the genetic mutation predisposing to cataract formation had 43 per cent less cholesterol in their lenses than rats with the normal version of the gene.

The researchers, led by Dr Masayuki Mori at Shinshu University Graduate School of Medicine in Matsumoto, Japan, concluded that cholesterol was required by proliferating epithelial cells in the centre of the lens for normal membrane formation.

They suggested that cholesterol deficiency in the lens could lead to cataract formation and that this mechanism could be responsible for the increased risk of cataracts seen in patients with hereditary defects of cholesterol synthesis, such as those with Smith-Lemli-Opitz syndrome or X-linked dominant chondroplasia punctata.

Although clinical safety trials found no increased risk of cataracts in patients on statins, researchers suggested that those exposed to high doses of the drugs could be more likely to develop cataracts.

This conclusion is supported by research that found a higher risk of cataracts in patients taking simvastatin together with the antibiotic erythromycin which blocks statin metabolism, leading to high serum statin levels.

Patients with a mutation in the genes governing cholesterol biosynthesis could also be at risk of developing cataracts if prescribed statins or other cholesterol-lowering drugs.

www.jci.org

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