RESUMO
To prevent neuronal damage, patients with ataxia with isolated vitamin E deficiency need lifelong supplementation with high doses of vitamin E. Short interruptions of therapy, such as occur in malcompliance, do not lead to clinical symptoms. However, the authors show that even short withdrawals may cause a prolonged decrease of the total radical trapping capacity of plasma; its major contributors, such as urate and sulfhydryl groups, fail to compensate for the missing vitamin E.
Assuntos
Ataxia/metabolismo , Recusa do Paciente ao Tratamento , Deficiência de Vitamina E/tratamento farmacológico , Deficiência de Vitamina E/metabolismo , Vitamina E/uso terapêutico , Adolescente , Adulto , Ataxia/genética , Feminino , Humanos , Masculino , Linhagem , Deficiência de Vitamina E/genéticaRESUMO
Patients with alpha-tocopherol transfer protein (alpha-TTP) defects experience neurological symptoms characteristic of vitamin E deficiency and depend on continuous high alpha-tocopherol supplements. We investigated the excretion of 2,5,7, 8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC), a urinary metabolite of alpha-tocopherol, as a putative marker for the alpha-tocopherol status of alpha-TTP-deficient patients and control subjects. In three patients vitamin E supplementation was stopped for short periods of time, during which plasma alpha-tocopherol concentrations and urinary alpha-CEHC excretion were measured. In the patients, plasma alpha-tocopherol decreased below normal (<5 micromol/l) but alpha-CEHC excretion remained above the range of unsupplemented control subjects (0.118-0.306 mg/day, n = 6). In healthy subjects, however, alpha-CEHC excretion was increased only after surpassing a plasma alpha-tocopherol threshold of 30-40 micromol/l. Such a threshold did not exist in patients. The general mechanism of alpha-tocopherol degradation did not appear to differ between patients and control subjects. The presumed mechanism of omega- and subsequent beta-oxidation was supported by the detection of alpha- CPHC, an alpha -CEHC homolog with a side chain longer by 3 carbon atoms, both in supplemented patients and in control subjects.
Assuntos
Proteínas de Transporte/genética , Vitamina E/metabolismo , Adolescente , Adulto , Ataxia/genética , Ataxia/metabolismo , Cromanos/química , Cromanos/urina , Suplementos Nutricionais , Feminino , Humanos , Masculino , Espectrometria de Massas , Oxirredução , Ácidos Pentanoicos/química , Ácidos Pentanoicos/urina , Propionatos/urina , Vitamina E/administração & dosagem , Vitamina E/sangue , Deficiência de Vitamina E/genética , Deficiência de Vitamina E/metabolismoRESUMO
Dysfunction of the alpha-tocopherol transfer protein causes ataxia with isolated vitamin E deficiency. A 14-year-old male patient presented with ataxia and mental symptoms caused by a homozygous (552G-->A) alpha-tocopherol transfer protein mutation. After initiation of high-dosage alpha-tocopherol therapy, the organic mental syndrome disappeared and cognitive function improved rapidly. Neurologic recovery, however, was slow and incomplete.
Assuntos
Ataxia/etiologia , Proteínas de Transporte/genética , Deficiência de Vitamina E/complicações , Adolescente , Ataxia/tratamento farmacológico , DNA/análise , Humanos , Masculino , Mutação , Vitamina E/uso terapêutico , Deficiência de Vitamina E/tratamento farmacológico , Deficiência de Vitamina E/genéticaRESUMO
NADH:ubiquinone oxidoreductase (complex I) is an extremely complicated multiprotein complex located in the inner mitochondrial membrane. Its main function is the transport of electrons from NADH to ubiquinone, which is accompanied by translocation of protons from the mitochondrial matrix to the intermembrane space. Human complex I appears to consist of 41 subunits of which 34 are encoded by nDNA. Here we report the cDNA sequences of the hitherto uncharacterized 8 nuclear encoded subunits, all located within the hydrophobic protein (HP) fraction of complex I. Now all currently known 41 proteins of human NADH:ubiquinone oxidoreductase have been characterized and reported in literature, which enables more complete mutational analysis studies of isolated complex I-deficient patients.