RESUMO
PURPOSE: Hyperhomocysteinemia is commonly associated with polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene. The level of homocysteine can be lowered by dietary intake of folate. A protective effect of folate supplementation has been reported against cataract. Here we investigate MTHFR polymorphisms in human cataract. DESIGN: Retrospective case-control association study. METHODS: Patients with nuclear (n = 77), cortical (n = 155), posterior subcapsular (n = 119), and mixed (n = 151) cataract, and 187 controls were analyzed for the MTHFR 677C-->T and 1298A-->C polymorphisms using minisequencing technique. RESULTS: The wild-type MTHFR 677CC/1298AA genotype was strongly overrepresented among cataract cases (P = .003). This effect was most pronounced in the mixed cataract group (P < .001). Hyperhomocysteinemia-associated genotypes had similar frequencies in cataract and control groups. CONCLUSIONS: The previously reported protective effect of folate against cataract is not due to overrepresentation of hyperhomocysteinemia-associated MTHFR genotypes. Instead, the strong predominance of wild-type MTHFR in cataract may suggest impaired DNA synthesis as a cataractogenic factor.
Assuntos
Catarata/genética , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Polimorfismo Genético , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Catarata/enzimologia , Análise Mutacional de DNA , Feminino , Frequência do Gene , Genótipo , Humanos , Hiper-Homocisteinemia/genética , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Análise de Sequência de DNARESUMO
Feeding experimental animals (19 pigs) with surplus sucrose and salt (NaCl) caused cataractous changes in lens tissue and triggered the formation of pseudoexfoliative material on the lens capsule. In the control animals (15 pigs) pseudoexfoliative material was absent. The avidin-biotin complex immunohistochemical method was applied to the pseudoexfoliative material obtained from 15 porcine experimental precataractous lenses and 1 spontaneously cataractous eye and revealed crystallins as a component of the intraocular pseudoexfoliative material. To prevent the development of both intraocular pseudoexfoliative material and crystallin-dependent glaucomatous changes in the trabecular meshwork of the eye, it is important to avoid any cataractogenic insult, including surplus sucrose and salt consumption, causing crystallin leakage from the lens.
