RESUMO
BACKGROUND: Folate status has been positively associated with cognitive function in many studies; however, some studies have observed associations of poor cognitive outcomes with high folate. In search of an explanation, we hypothesized that the association of folate with cognition would be modified by the interaction of high-folate status with a common 19-bp deletion polymorphism in the dihydrofolate reductase (DHFR) gene. To our knowledge, the cognitive effects of this gene have not been studied previously. OBJECTIVE: We examined the association between cognitive outcomes with the 19-bp deletion DHFR polymorphism, folate status, and their interaction with high or normal plasma folate. DESIGN: This was a pooled cross-sectional study of the following 2 Boston-based cohorts of community living adults: the Boston Puerto Rican Health Study and the Nutrition, Aging, and Memory in Elders study. Individuals were genotyped for the DHFR 19-bp deletion genotype, and plasma folate status was determined. Cognitive outcomes included the Mini-Mental State Examination, Center for Epidemiologic Studies Depression Scale, and factor scores for the domains of memory, executive function, and attention from a set of cognitive tests. RESULTS: The prevalence of the homozygous deletion (del/del) genotype was 23%. In a multivariable analysis, high folate status (>17.8 ng/mL) was associated with better memory scores than was normal-folate status (fourth-fifth quintiles compared with first-third quintiles: ß ± SE = -0.22 ± 0.06, P < 0.01). Carriers of the DHFR del/del genotype had worse memory scores (ß ± SE = -0.24 ± 0.10, P < 0.05) and worse executive scores (ß = -0.19, P < 0.05) than did those with the del/ins and ins/ins genotypes. Finally, we observed an interaction such that carriers of the del/del genotype with high folate had significantly worse memory scores than those of both noncarriers with high-folate and del/del carriers with normal-folate (ß-interaction = 0.26 ± 0.13, P < 0.05). CONCLUSIONS: This study identifies a putative gene-nutrient interaction that, if confirmed, would predict that a sizable minority carrying the del/del genotype might not benefit from high-folate status and could see a worsening of memory. An understanding of how genetic variation affects responses to high-folate exposure will help weigh risks and benefits of folate supplementation for individuals and public health.
Assuntos
Deficiência de Ácido Fólico/genética , Deleção de Genes , Transtornos da Memória/etiologia , Estado Nutricional , Polimorfismo Genético , Tetra-Hidrofolato Desidrogenase/genética , Negro ou Afro-Americano , Idoso , Idoso de 80 Anos ou mais , Boston/epidemiologia , Estudos de Coortes , Estudos Transversais , Feminino , Ácido Fólico/intoxicação , Deficiência de Ácido Fólico/enzimologia , Deficiência de Ácido Fólico/fisiopatologia , Estudos de Associação Genética , Hispânico ou Latino , Humanos , Masculino , Transtornos da Memória/epidemiologia , Pessoa de Meia-Idade , Nutrigenômica/métodos , Prevalência , Porto Rico/etnologia , Tetra-Hidrofolato Desidrogenase/metabolismo , População BrancaRESUMO
BACKGROUND: A large body of evidence links plasma concentrations of homocysteine and cardiovascular disease. Several genetic and environmental variables may modulate such relationship. We investigated the influence of methylenetetrahydrofolate reductase (MTHFR) gene variants C677T, A1298C, and T1317C on homocysteine, folate, and cobalamin concentrations in a sample of individuals from a mild folate deficiency population to better clarify the complex interactions existing among these variables. METHODS: In the present study, 209 individuals belonging to an admixed urban population characterized by mild folate deficiency were investigated. MTHFR gene variants C677T, A1298C, and T1317C were genotyped and homocysteine-, folate-, and cobalamin-determined for each individual. RESULTS: Univariate analyses showed a significant association between the C677T variant with homocysteine (P<0.001) and cobalamin (P=0.005) as well as a significant relationship between the T allele and serum folate concentrations (P<0.05). The TT genotype of the C677T polymorphism remained significantly associated with log-transformed homocysteine even after adjustment for age, sex, smoking status, ethnicity, folate, and cobalamin concentrations (P<0.01). Both univariate and multivariate analysis have failed to show any effect of the A1298C and T1317C genetic variants in homocysteine concentrations in this population. Finally, a significant interaction between folate and C677T polymorphism in the determination of homocysteine was also disclosed (P<0.005). CONCLUSIONS: Taken together, these results demonstrate a significant interaction between serum folate and MTHFR genotype in predicting homocysteine concentrations. One may consider that a differential response of homocysteine to folic acid supplementation may depend on MTHFR genotype which may have important implications when attempting to lower homocysteine concentrations in populations with mild folate deficiency.
Assuntos
Deficiência de Ácido Fólico/sangue , Deficiência de Ácido Fólico/enzimologia , Ácido Fólico/sangue , Homocisteína/sangue , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Metilenotetra-Hidrofolato Redutase (NADPH2)/metabolismo , Polimorfismo Genético/genética , Adulto , Feminino , Deficiência de Ácido Fólico/genética , Deficiência de Ácido Fólico/metabolismo , Genótipo , Humanos , Masculino , Vitamina B 12/sangueRESUMO
BACKGROUND: Neural tube defects (NTDs) have been associated with biochemical factors involved in the conversion of homocysteine to methionine as folate deficiency and the mutation 677T in the N(5),N(10)-methylenetetrahydrofolate reductase gene (MTHFR). METHODS: A case-control study was performed to detect this mutation in 38 unrelated women with NTD deceased products and 31 mothers without antecedents of NTD offspring. All products were born in Nuevo León (northeastern Mexico) during 1997. Erythrocyte and plasmatic folate levels and the genotype of the 677 polymorphism at the MTHFR locus were analyzed in both groups. RESULTS: Although no significant differences were found in mean blood folate levels, the percentage of women in the case group with erythrocyte folate levels <160 ng/mL was significantly higher than in the control group (75 vs. 51.2%, p <0.05). The proportion of women with plasma folate levels <3.5 ng/mL was higher in the case group (16.2 vs. 0%, p <0.01). Genotype analysis demonstrated a significantly higher proportion of 677T homozygous mothers with NTD products (39.6 vs. 9.1%, p <0.05). Allele frequencies for the 677T mutation were 0.55 and 0.36 for cases and controls, respectively. The odds ratio (OR) for having a NTD product was 6.1 (95%, CI 1.56-23.6) for homozygous 677T mothers vs. homozygous 677C and heterozygous mothers. Significantly low levels of erythrocyte folate were found in the 677C homozygous case group and in plasma folate in the 677C/677T heterozygous case mothers. CONCLUSIONS: Our study suggests that folate deficiency and MTHFR unfavorable genotype in mothers are important risk factors for severe NTD phenotype in our population.