RESUMO
MTHFR (methylenetetrahydrofolate reductase) catalyses the synthesis of 5-methyltetrahydrofolate, the folate derivative utilized in homocysteine remethylation to methionine. A severe deficiency of MTHFR results in hyperhomocysteinaemia and homocystinuria. Betaine supplementation has proven effective in ameliorating the biochemical abnormalities and the clinical course in patients with this deficiency. Mice with a complete knockout of MTHFR serve as a good animal model for homocystinuria; early postnatal death of these mice is common, as with some neonates with low residual MTHFR activity. We attempted to rescue Mthfr-/- mice from postnatal death by betaine supplementation to their mothers throughout pregnancy and lactation. Betaine decreased the mortality of Mthfr-/- mice from 83% to 26% and significantly improved somatic development from postnatal day 1, compared with Mthfr-/- mice from unsupplemented dams. Biochemical evaluations demonstrated higher availability of betaine in suckling pups, decreased accumulation of homocysteine, and decreased flux through the trans-sulphuration pathway in liver and brain of Mthfr-/- pups from betaine-supplemented dams. We observed disturbances in proliferation and differentiation in the cerebellum and hippocampus in the knockout mice; these changes were ameliorated by betaine supplementation. The dramatic effects of betaine on survival and growth, and the partial reversibility of the biochemical and developmental anomalies in the brains of MTHFR-deficient mice, emphasize an important role for choline and betaine depletion in the pathogenesis of homocystinuria due to MTHFR deficiency.
Assuntos
Betaína/uso terapêutico , Homocistinúria/tratamento farmacológico , Homocistinúria/enzimologia , Metilenotetra-Hidrofolato Redutase (NADPH2)/deficiência , Animais , Animais Lactentes/metabolismo , Betaína/metabolismo , Peso Corporal/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Encéfalo/embriologia , Modelos Animais de Doenças , Feminino , Genótipo , Homocisteína/metabolismo , Homocistinúria/embriologia , Homocistinúria/genética , Lactação/metabolismo , Fígado/efeitos dos fármacos , Masculino , Troca Materno-Fetal , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Camundongos , Camundongos Knockout , Tamanho do Órgão/efeitos dos fármacos , GravidezRESUMO
A 20-year-old woman with untreated homocystinuria was examined when she was 18 weeks' pregnant. Amniocentesis was performed and raised levels of homocystine and methionine were present in the amniotic fluid. Assay of cystathionine synthetase activity in cultured amniotic fluid cells showed the carrier state for homocystinuria. An abortion was performed because of the possible adverse effects of continuing the pregnancy both for the mother and the fetus. No pathological abnormality was found in the aborted fetus. Further data are needed to assess the possible teratogenic effects of maternal homocystinuria and the adverse consequences of pregnancy in the affected mother.
