Navegando por Palavras-chave "MTHFR"

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    Alzheimer's disease in Brazilian elderly has a relation with homocysteine but not with MTHFR polymorphisms
    (Academia Brasileira de Neurologia - ABNEURO, 2006-12-01) Silva, Vanessa Cavalcante da; Ramos, Flávio José da Costa; Freitas, Elizabete Malaquias; Brito-marques, Paulo Roberto de; Cavalcanti, Márcia Nery de Holanda; D'Almeida, Vânia [UNIFESP]; Cabral-filho, José Eulálio; Muniz, Maria Tereza Cartaxo; Universidade de Pernambuco Instituto de Ciências Biológicas; Universidade de Pernambuco Faculdade de Ciências Médicas Departamento de Neurologia; Universidade Federal de São Paulo (UNIFESP); Instituto Materno-Infantil de Pernambuco
    OBJECTIVE: To investigate the association between total plasma homocysteine concentration, C677T and A1298C polymorphisms in MTHFR gene and Alzheimer's disease (AD) development. METHOD: Forty-three patients with probable (63%) and possible (37%) AD and 50 non-demented controls were evaluated. Groups did not differ as to gender, age, scholar years, diabetes, alcohol and coffee intake and physical activity. Total plasma homocysteine (Hcy) levels were determined by HPLC and genotyping for MTHFR by PCR/RFLP. Mann-Whitney U test was used to compare quantitative variable, Fisher-Freeman-Halton test to compare genotypes and allele proportions and Chi-square test to other qualitative variables. RESULTS: AD patients presented higher total plasma Hcy levels than controls and the difference was statistically significant. No differences in the C677T and A1298C MTHFR polymorphisms distributions were found between patients and controls. Plasma homocysteine concentration did not change with MTHFR genotypes. CONCLUSION: Our data confirms the association between increased plasma Hcy concentration and AD and suggests that neither C677T nor A1298C MTHFR polymorphisms contributed to genetic susceptibility for AD in elderly individuals in the Northeast of Brazil.
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    Do polymorphisms of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene affect the risk of childhood acute lymphoblastic leukemia?
    (Springer, 2006-12-01) Pereira, Tiago Veiga; Rudnicki, Martina; Pereira, Alexandre Costa; Pombo-de-Oliveira, Maria S.; Franco, Rendrik Franca; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP); Inst Nacl Canc; Fleury Res Inst
    Meta-analysis has become an important statistical tool in genetic association studies, since it may provide more powerful and precise estimates. However, meta-analytic studies are prone to several potential biases not only because the preferential publication of positive'' studies but also due to difficulties in obtaining all relevant information during the study selection process. in this letter, we point out major problems in meta-analysis that may lead to biased conclusions, illustrating an empirical example of two recent meta-analyses on the relation between MTHFR polymorphisms and risk of acute lymphoblastic leukemia that, despite the similarity in statistical methods and period of study selection, provided partially conflicting results.
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    Methylenetetrahydrofolate reductase (MTHFR): Incidence of mutations C677T and A1298C in Brazilian population and its correlation with plasma homocysteine levels in spina bifida
    (Wiley-Blackwell, 2003-05-15) Perez, Ana Beatriz Alvarez [UNIFESP]; D'Almeida, Vania [UNIFESP]; Vergani, Naja [UNIFESP]; Oliveira, Allan Chiaratti de [UNIFESP]; Lima, Fernanda Teresa de [UNIFESP]; Brunoni, Decio [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Homocysteine (Hcy) is converted to cysteine or is remethylated to methionine by methylenetetrahydrofolate reductase (MTHFR). MTHFR plays a central role in the metabolism of folate. Two common polymorphisms in the MTHFR gene (C677T and A1298C) have been described and studies suggest that these polymorphisms are positively associated with the occurrence of spina bifida (SB). Among Brazilians, the incidence of 677T allele homozygosity is 4%. We compared Hey levels with the genotypes obtained for the mutations C677T and A1298C in the gene MTHFR. Levels of plasma Hey were higher in children with SB than in controls (average 7.95 vs. 5.55 (mumol/L); P < 0.001). There was no significant difference in the levels of Hey for these childrens's mothers and controls (average 7.76 vs. 8.36 (μmol/L); P = 0.27). Eighty one (61.8%) of the affected children were white and 50 (38.2%) were non-white. A similar ratio was observed in the mothers. in the control group, 51 children (40.5%) were white and 75 (59.5%) were non-white, and 52 mothers (41.3%) were white and 74 (58.7%) were non-white. There was no significant difference in the homozygous frequency for the mutated allele 677T among different racial groups. We obtained a prevalence of TT homozygosity of 10/131 (7.64%) in affected children and 13/126 (10.32%) in controls. With respect to the mutation A1298C, the homozygous prevalence for the wild allele was greater among non-white individuals than in white individuals both in case and control groups. Hyperhomocysteinemia is a risk factor for SB. However, in our population, the increase in plasma levels of Hey is not explained by the presence of the homozygous TT. It is possible that low folic acid intake combined with other genetic factors plays a more important role in the cause of this disease. (C) 2003 Wiley-Liss, Inc.
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    Relationship between polymorphisms in genes involved in homocysteine metabolism and maternal risk for Down syndrome in Brazil
    (Wiley-Blackwell, 2005-06-15) Silva, LRJ da; Vergani, N.; Galdieri, L. D.; Porto, MPR; Longhitano, S. B.; Brunoni, D.; D'Almeida, V; Perez, ABA; Universidade Federal de São Paulo (UNIFESP); Assoc Pais & Amigos Excepcionais
    Associations between specific alleles of genes encoding enzymes in the methionine/homocysteine pathway and plasma homocysteine levels have been examined in different populations. in the present study, we determined polymorphisms of MTHFR A222V (677C > T), MTHFR E429A (1298A > C), MTRR I22M (66A > G), MTR D919G (2756A > G), and CBS 844ins68 and total plasma homocysteine levels (tHcy) among 154 mothers of children with Down syndrome (DS) and 158 control mothers from Brazil. Homocysteine levels were higher among DS mothers compared to control groups (10.437 vs. 8.600 respectively, P = 0.002). Only the 677T allele was associated with altered levels of tHcy in the case group (F(2,153) = 5.300; P = 0.006), primarily when homozygous. in the control group, the association of the TT genotype with higher levels of tHcy showed borderline significance (F(2,157) = 2.974; P = 0.054). All genotype distributions were similar in the two groups (P > 0.05), but the frequency of the 677T allele in the case group was significantly higher (X-2 = 3.862; DF = 1; P = 0.049; OR = 1.437 (1.001-2.062)). Although the 677T allele is associated with increased homocysteine levels, its presence has only a modest impact as an independent risk factor for DS. All the other polymorphisms did not show an association with risk for the syndrome, when evaluated separately (P > 0.05). However, when the presence of 677T, 1298C, 2756G, 66G, and 844ins68 alleles were evaluated together, the mothers of children with DS tend to have a higher number of uncommon alleles than the mothers with no previous affected child. (c) 2005 Wiley-Liss, Inc.
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    Serum total homocysteine levels and the prevalence of folic acid deficiency and C677T mutation at the MTHFR gene in an indigenous population of Amazonia: The relationship of homocysteine with other cardiovascular risk factors
    (Int Soc Hypertension Blacks-ishib, 2004-12-01) Tavares, Edelweiss Fonseca [UNIFESP]; Vieira Filho, João Paulo Botelho [UNIFESP]; Andriolo, Adagmar [UNIFESP]; Perez, Ana Beatriz Alvarez [UNIFESP]; Vergani, Naja [UNIFESP]; Sanudo, Adriana [UNIFESP]; Gimeno, Suely Godoy Agostinho [UNIFESP]; Franco, Laercio Joel [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Hyperhomocysteinemia is a risk factor for cardiovascular disease. C677T mutation at the MTHFR gene and deficiencies of folic acid and vitamin B-12 may account for elevation of total homocysteine (tHcy). Ninety Brazilian Parka-teje Indians (90.0% of the population without admixture, aged greater than or equal to20 years) were studied. Hyperhomocysteinemia was observed in 26.7% of the Indians. No case of vitamin B-12 deficiency was detected. Folic acid deficiency was found in 43.3% of the subjects. Rates of mutated allele 677T and TT genotype were 40.7% and 14.0%, respectively. Prevalence of hypertension, dyslipidemia, smoking, WHIR greater than or equal to0.9, BMI greater than or equal to25 kg/m(2) and chronic alcohol use were 4.4%, 44.4%, 25.6%, 72.2%, 67.8%, and 0.0%, respectively. All creatinine values were normal. Natural logarithmic (In) tHcy showed no correlation with age, but was positively correlated with systolic (r=0.22) and diastolic (r=0.21) blood pressure and triglycerides (r=0.39) and inversely correlated with folic acid (r= -0.40) adjusted for age and sex. Total homocysteine (tHcy) was higher among TT genotype (P<.001). The multiple linear regression model, containing variables for sex, folic acid, TT genotype, and triglycerides, explained 50.0% of the variation of the In tHcy. in summary, high rates of cardiovascular risk factors were discovered. C667T mutation and folic acid deficiency can explain, at least in part, the observed hyperhomocysteinemia.