RESUMEN
OBJECTIVES: Folate status and/or genes have been linked to depression in a number of studies. This may be via a direct action (or actions) on neuronal membranes or indirect effects through the metabolism of methyl groups involved in neurotransmitter synthesis. This study examines folate and related thiol metabolism that might underpin either phenomenon. DESIGN: Cohort study describing the relationship between several genetic and nutritional aspects of folic acid homeostasis and depression assessed by the HADS psychometric index in an elderly cohort. SETTING: New South Wales (Australia) retirement village. PARTICIPANTS: 118 elderly participants (age 65-90 years). RESULTS: Stepwise multiple regression was used to determine the best statistical model to predict depression; C677T-MTHFR (p=0.0103) was found to be positively associated with depression, while the thiol dipeptide Cys-Gly was negatively associated (p=0.0403). The statistical models used accounted for the major folate related indices (genetic and biochemical) that are most often evaluated in the context of health and disease. When only genetic data were examined for interactions, C677T-MTHFR was found to be negatively associated with the HADS Depression Index Score (p=0.0191). CONCLUSION: The potential influence of Cys-Gly on this phenotype is novel, and of considerable interest given that it has been linked to altered spontaneous activity and sedation in an animal model. Cys-Gly is a recognised ligand at the N-methyl-D-aspartatic acid (NMDA) subclass of glutamate receptor, a system associated with depression. In addition, the C677T-MTHFR association adds further support to existing findings underscoring the potential role of folate in depression.
Asunto(s)
Depresión/epidemiología , Depresión/genética , Dipéptidos/sangre , Ácido Fólico/metabolismo , Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Anciano , Anciano de 80 o más Años , Australia/epidemiología , Estudios de Cohortes , Depresión/sangre , Dieta , Femenino , Ácido Fólico/administración & dosificación , Ácido Fólico/sangre , Deficiencia de Ácido Fólico/epidemiología , Estudios de Asociación Genética , Homeostasis , Viviendas para Ancianos , Humanos , Masculino , Polimorfismo de Nucleótido Simple , Escalas de Valoración Psiquiátrica , Encuestas y CuestionariosRESUMEN
BACKGROUND: Elevated plasma homocysteine (Hcy) is a recognized risk factor for cardiovascular disease (CVD) and other defects. Biochemical and genetic studies have characterized molecular determinants contributing to alter Hcy metabolism. The vitamin B12 dependent enzyme methionine synthase (MTR) regulates de novo production of methionine from homocysteine. Defects in the activity of this enzyme may possibly predispose to higher plasma Hcy concentrations. STUDY DESIGN: We examined the associations between plasma Hcy concentrations and a single nucleotide polymorphism (SNP) in the MTR gene (MTR 2756A>G), and plasma folate concentrations, in 71 women (Caucasian and South Asian) attending a fertility clinic. We also determined the ethnic variations in the frequencies of the 3 genotypes of the MTR 2756 A>G gene. RESULTS: The frequency of the variant G allele was similar in the Caucasians and the South Asians (OR: 1.83; 95% CI: 0.79-4.23, p=0.2). The frequency was also similar in the PCOS and non-PCOS groups (OR: 0.88; 95% CI: 0.39-1.99). Plasma Hcy levels were significantly higher in women with PCOS compared with non-PCOS controls (p=0.05) and in Caucasian women with PCOS compared with Caucasian controls (p=0.04) in the presence of the MTR 2756 AA genotype (wild type). After adjusting for age, BMI, waist circumference and ethnicity, the significant predictors of plasma Hcy concentrations were plasma LDL, whole blood folate concentrations and a clinical diagnosis of PCOS. CONCLUSIONS: The important predictors of plasma Hcy concentration in women of reproductive age are whole blood folate concentrations, a background of PCOS and plasma LDL concentrations. The SNP 2756 A>G in the MTR gene does not appear to influence the plasma Hcy levels.
Asunto(s)
5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/genética , Homocisteína/sangre , Síndrome del Ovario Poliquístico/genética , Polimorfismo de Nucleótido Simple , Adulto , Femenino , Ácido Fólico/sangre , Humanos , Lipoproteínas LDL/sangre , Proyectos Piloto , Síndrome del Ovario Poliquístico/sangre , Estudios ProspectivosRESUMEN
UNLABELLED: Polycystic ovary syndrome (PCOS), insulin resistance and overall mortality due to diabetes and coronary artery disease are higher in South Asians than in Caucasians. AIMS: We compared the prevalence of the C677T and A1298C single nucleotide polymorphisms in the methylenetetrahydrofolate reductase gene in South Asian and Caucasian women, its association with folate and homocysteine (Hcy) metabolism, and its relevance to future atherogenic events. METHODS AND RESULTS: 71 women were recruited for the study: South Asian PCOS (21) plus controls (9) and Caucasian PCOS (25) plus controls (16). Anthropometric and laboratory parameters were compared. South Asian PCOS women were significantly hyperandrogenic and exhibited a greater degree of insulin resistance. Caucasian PCOS women had higher plasma Hcy concentrations with a 1.9 times higher frequency of the T allele than the South Asian PCOS group. In the presence of this variant allele, plasma Hcy levels appear to be higher in both PCOS groups. The South Asians had a 1.8 times higher frequency of the C allele than the Caucasians; however, the overall frequency was comparable in the two PCOS groups. The frequency of homozygosity, i.e. TT677 and CC1298, was 7.2% and 4.9% in the Caucasians and 0% and 16.6% in the South Asian recruits, respectively. Dietary inadequacies in the South Asian women can influence their plasma folate and B12 concentrations resulting in hyperhomocysteinemia which, in combination with dyslipidaemia and insulin resistance, can lead to long-term atherogenic consequences. CONCLUSIONS: Current data suggests that the mechanisms of atherothrombosis have separate pathways in the two ethnic groups. Larger studies exploring the current theme need to be carried out in the PCOS groups to obtain adequate insight.
Asunto(s)
Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Síndrome del Ovario Poliquístico/enzimología , Polimorfismo de Nucleótido Simple/genética , Adulto , Antropometría , Asia Sudoriental , Pueblo Asiatico/genética , Femenino , Frecuencia de los Genes , Genotipo , Homocisteína/sangre , Humanos , Resistencia a la Insulina , Proyectos Piloto , Síndrome del Ovario Poliquístico/genética , Complejo Vitamínico B/sangre , Población Blanca/genéticaRESUMEN
The aim of this study was to determine if fetal C677T methylenetetrahydrofolate reductase (MTHFR) genotype contributes to low birth weight. The study group consisted of 243 term babies with a birth weight<10th centile for gestational age, with subgroup analyses for those <1st centile. The control group consisted of 132 term babies with a birth weight 3.3-3.8 kg. Odds ratio analyses with 95% confidence intervals (CI) were calculated for carriage of the t allele and overall genotype frequencies. There was no significant difference in carriage of the t allele between study and control groups, odds ratio (OR) 0.79 (95% CI, 0.57-1.09). No differences were observed for frequencies of heterozygote and recessive homozygote genotypes for the two populations. In the subgroup analyses, no statistical differences were observed in the t allele frequency, frequency of the heterozygote or homozygote genotype. Trends were seen and the study suggests that fetal C677T MTHFR genotype may be a factor contributing to birth weight. The potential may exist to influence clinical outcome by maternal folate supplementation.
Asunto(s)
Peso al Nacer/genética , Recién Nacido de Bajo Peso/fisiología , Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Estudios de Casos y Controles , Predisposición Genética a la Enfermedad/genética , Heterocigoto , Humanos , Recién Nacido , Polimorfismo Genético , Nacimiento a TérminoRESUMEN
BACKGROUND: Folylpoly-gamma-glutamate synthetase (FPGS) converts intracellular folates and antifolates (for example, methotrexate (MTX)) to polyglutamates. Polyglutamylated folates and antifolates are retained in cells longer and are better substrates than their monoglutamate counterparts for enzymes involved in one carbon transfer. Polyglutamylation of intracellular 5,10-methylenetetrahydrofolate may also enhance the cytotoxicity of 5-fluorouracil (5-FU) by allowing more efficient formation and stabilisation of the inhibitory ternary complex involving thymidylate synthase and a 5-FU metabolite. AIM: We investigated the effects of FPGS modulation on the chemosensitivity of colon cancer cells to 5-FU and MTX. METHODS: Human HCT116 colon cancer cells were stably transfected with the sense or antisense FPGS cDNA or blank (control). FPGS protein expression and enzyme activity, growth rate, intracellular folate content and composition, and in vitro chemosensitivity to 5-FU and MTX were determined. RESULTS: Compared with cells expressing endogenous FPGS, those overexpressing FPGS had significantly faster growth rates and higher concentrations of total folate and long chain folate polyglutamates while antisense FPGS inhibition produced opposite results. FPGS overexpression significantly enhanced, whereas FPGS inhibition decreased, chemosensitivity to 5-FU. No significant difference in chemosensitivity to MTX was observed. CONCLUSIONS: These data provide functional evidence that FPGS overexpression and inhibition modulate chemosensitivity of colon cancer cells to 5-FU by altering intracellular folate polyglutamylation, providing proof of principle. Thus FPGS status may be an important predictor of chemosensitivity of colon cancer cells to 5-FU based chemotherapy, and FPGS gene transfer may increase the sensitivity of colon cancer cells to 5-FU-based chemotherapy.
Asunto(s)
Adenocarcinoma/patología , Antimetabolitos Antineoplásicos/farmacología , Neoplasias del Colon/patología , Fluorouracilo/farmacología , Metotrexato/farmacología , Péptido Sintasas/metabolismo , Adenocarcinoma/enzimología , División Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Neoplasias del Colon/enzimología , Relación Dosis-Respuesta a Droga , Humanos , Péptido Sintasas/antagonistas & inhibidores , Péptido Sintasas/genética , Transfección , Células Tumorales CultivadasRESUMEN
The effect of four polymorphic genes of folate-dependent methionine biosynthesis have been investigated in mothers affected by a neural tube defect pregnancy (NTD) and matched controls. The influence of the various genotypes on total red cell 5-methyl-H(4)folate,5,10-methenyl-H(4)folate, and 5-formyl-H(4)folate is reported, as is the effect on homocysteine and radioassay folate in both serum and red cells. All of the single nucleotide polymorphisms studied would seem to contribute to the cellular folate profile in some way. From the data presented, and from the work of others, it is likely that C677T 5,10-methylenetetrahydrofolate reductase is the most important of these polymorphisms. Control mother folate profiles seem reasonably predictive of any given methionine cycle mutation, but profiles in NTD mothers do not. On this basis, it seems likely that some other, as yet unidentified folate lesion is causal for NTD. In NTD-C677T 5,10-methylenetetrahydrofolate reductase in particular, indexes of folate depletion such as high-performance liquid chromatography (HPLC) folate level, oligo-gamma-glutamyl chain length, homocysteine, and radioassay folate values all seem to deteriorate with increased mutant allele carriage. This indicates that this folate polymorphism may provide a critical threshold effect that helps to promote NTD occurrence in the presence of another, as yet unidentified folate-related factor. In more general terms, on a by genotype basis, all 11 genotypes studied give NTD mothers a higher homocysteine compared to controls. Furthermore, a trend that is less universal indicates that NTD mothers have higher 5,10-methenyl-H(4)folate and 5-methyl-H(4)folate levels and lower 5-formyl-H(4)folate and H(4)PteGlu(1) levels than do controls. One of the most consistent, and possibly specific, differences between participant groups is a statistically significant elevation of 5,10-methenyl-H(4)folate in NTD mothers (affects three genotypes). Possible interpretations of this finding are discussed.
Asunto(s)
Ácido Fólico/metabolismo , Mutación/genética , Polimorfismo Genético/genética , Disrafia Espinal/genética , Disrafia Espinal/metabolismo , Adulto , Alelos , Inglaterra , Eritrocitos/enzimología , Eritrocitos/metabolismo , Femenino , Ácido Fólico/análogos & derivados , Ácido Fólico/sangre , Frecuencia de los Genes , Humanos , Metionina/biosíntesis , Metionina/metabolismo , Metilación , Ácido Poliglutámico/metabolismo , Polimorfismo de Nucleótido Simple/genética , Embarazo , Ácidos Pteroilpoliglutámicos/metabolismo , Disrafia Espinal/sangre , Disrafia Espinal/enzimología , Vitamina B 12/metabolismoRESUMEN
Periconceptional folate prevents spina bifida although the mechanisms involved are unclear. We present the genotype frequency for the 677 ct methylenetetrahydrofolate reductase (MTHFR) and 2756ag methionine synthase (MetSyn) polymorphisms. Calculated odds ratios (OR) show that neither the homozygous recessive genotype, carriage of the mutant allele, nor frequency of the mutant allele represent significantly increased risk for neural tube defect (NTD). This is true for both polymorphisms. Simultaneous carriage of t and g alleles is also not a significantly increased risk for NTD. OR and 95% CI for carriage of (i) t allele, (ii) g allele, and (iii) simultaneous carriage of t and g alleles in NTD are 0.89 (0.28-2.82), 0.97 (0.28-3.30), and 0.61 (0.11-3.52), respectively. OR and 95% CI for frequency of t and g alleles are 0.94 (0.42-2.13) and 0.88 (0. 29-2.67), respectively. Unlike some previous studies, we could not detect a significantly increased risk for NTD conferred by the 677ct MTHFR tt genotype; OR 0.98 (0.19-6.49). Differences were found to exist in the circulating whole blood folate profile: total formyl-H(4)PteGlu was significantly higher than total 5-methyl-H(4)PteGlu in control (P = 0.036) but not NTD blood. When broken down into the various 677 ct MTHFR and 2756ag MetSyn genotypes, carriage of the 677ct MTHFR allele appears to affect formyl-H(4)PteGlu metabolism in non-NTD mothers. In addition, NTD mothers exhibited noticeably lower formyl-H(4)PteGlu levels compared to controls; these effects, however, were not significant. 2756ag MetSyn is similarly associated with an altered formyl-H(4)PteGlu disposition. The ag genotype had significantly more formyl-H(4)PteGlu relative to 5-methyl-H(4)PteGlu than wildtype 2756ag MetSyn (P = 0.024). This heterozygous increase in the relative formyl-H(4)PteGlu level holds true for controls only; no such relationship occurred in NTD samples. Folyl hexaglutamates are the active cellular coenzyme forms. We showed that where 5-methyl-H(4)PteGlu(6) predominates, Hcy levels are highest. As the relative abundance of formyl-H(4)PteGlu(6) increased, so Hcy decreased, presumably due to increased Hcy remethylation, a process in which 5-methyl-H(4)PteGlu(6) is demethylated and downstream folates like formyl-H(4)PteGlu(6) are produced. The negative linear association between the hexaglutamate ratio (formyl-H(4)PteGlu(6)/5-methyl-H(4)PteGlu(6)) and Hcy is significant for control (r = -0.64, P = 0.003) but not NTD samples. This effect, centering on Hcy remethylation, is supported by a statistically elevated formyl-H(4)PteGlu(6) to 5-methyl-H(4)PteGlu(6) level in controls relative to NTDs (P = 0.047). The overall (polymorphism independent) effect of exogenous 5,10-methenyl-H(4)PteGlu(1) substrate on the cellular folate profile was to preferentially increase formyl-H(4)PteGlu, while exogenous 5-methyl-H(4)PteGlu(1) substrate dramatically increased metabolic production of 5, 10-methylene-H(4)PteGlu. The following differences were observed between NTD and control samples: (i) a reduced expansion of the formyl-H(4)PteGlu(6) pool in NTD with exogenous 5, 10-methenyl-H(4)PteGlu(1) (P = 0.0005 for control expansion, NS for NTD increase); (ii) a reduced initial expansion of the 5, 10-methylene-H(4)PteGlu pool in NTD following treatment with exogenous 5-methyl-H(4)PteGlu(1) substrate (difference between subject groups; P = 0.031). In addition, taking polymorphisms into account, lysate from NTD-MTHFR wildtypes utilized less exogenous 5-methyl-H(4)PteGlu(1) substrate than control-MTHFR wildtypes in the short (P = 0.011) and long term (P = 0.036). Commensurate with this latter effect, the initial production of 5,10-methylene-H(4)PteGlu due to exogenous 5-methyl-H(4)PteGlu(1) substrate was significantly reduced in the NTD-MTHFR wildtype (P = 0.037). These two MTHFR wildtype effects imply that the 677 ct polymorphism is not the only mutation affecting folate metabolism in NTD mothers. (ABSTRACT TRUNCATED)
Asunto(s)
Ácido Fólico/metabolismo , Complicaciones del Embarazo , Disrafia Espinal/metabolismo , 5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/genética , 5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/metabolismo , Cromatografía Líquida de Alta Presión , Femenino , Ácido Fólico/sangre , Frecuencia de los Genes , Genotipo , Humanos , Metilenotetrahidrofolato Reductasa (NADPH2) , Oxidorreductasas actuantes sobre Donantes de Grupo CH-NH/genética , Oxidorreductasas actuantes sobre Donantes de Grupo CH-NH/metabolismo , Polimorfismo Genético , Embarazo , Ácidos Pteroilpoliglutámicos/metabolismo , Disrafia Espinal/enzimología , Disrafia Espinal/genética , Especificidad por SustratoRESUMEN
OBJECTIVES: To develop a non-invasive method for determining fetal RhD status in order to provide improved care for women most at risk. DESIGN: A prospective study. METHODS: Fetal erythroblasts were enriched from the peripheral circulation of 96 RhD negative women with pregnancies at various stages in gestation using discontinuous density gradients. Amplification of RhD-specific mRNAs was carried out by reverse transcription-polymerase chain reaction assay. RNA, rather than DNA, was selected for amplification because it rarely contaminates samples, thus resulting in fewer false positives; moreover, its presence in multiple copies per cell should enhance the sensitivity of the assay, resulting in fewer false negatives. The study was prospective, relying on postnatal serological confirmation of RhD phenotype. RESULTS: The assay was 75% accurate at predicting fetal RhD status, comparing favourably with standard genomic DNA-based assays. However, we found that accuracy dropped from 85% (29/34) in the third trimester of pregnancy, to 82% (32/39) in the second and 48% (11/23) in the first trimester. Discordant data were due to false negatives in the majority (78%) of cases. CONCLUSIONS: We suggest that reverse transcription may be a useful and perhaps more sensitive alternative to standard genomic polymerase chain reaction in the majority of cases. However, under certain circumstances the absence or reduction of fetal erythroblasts or possibly RhD mRNA in some preparations may compromise the accuracy of the assay.
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Eritroblastosis Fetal/diagnóstico , Globulina Inmune rho(D)/análisis , Biomarcadores/sangre , ADN Complementario/análisis , Femenino , Humanos , Recién Nacido , Embarazo , Diagnóstico Prenatal/métodos , Estudios Prospectivos , ARN Mensajero/análisis , Globulina Inmune rho(D)/genética , Sensibilidad y EspecificidadRESUMEN
Immunoglobulin class switching occurs as a result of recombination between pairs of switch region sequences located 5' to each constant heavy chain gene except Cdelta. In the B cell neoplasm multiple myeloma, tumour cells have generally undergone class switching and often contain oncogenic sequences translocated into switch regions, presumably as a result of aberrant switch recombination. We have developed a method (LDV-PCR) which combines long distance PCR with one-sided vectorette PCR that is capable of detecting and isolating both normal and aberrant switch recombination breakpoints from multiple myeloma cell lines and primary multiple myeloma tumour material. Using LDV-PCR we have directly cloned the translocation breakpoints present in two multiple myeloma cell lines and isolated a normal productive switch recombination event from a primary tumour. Furthermore, we have isolated a novel translocation t(14;22)(q32;q12) from a primary tumour sample and have demonstrated that internal deletions within switch regions can occur in multiple myeloma cells. Compared to a Southern blotting approach, LDV-PCR is simpler and more rapid to perform, allows the simultaneous detection and isolation of recombination events, and can also be applied to amounts of DNA which are too low to permit the conventional cloning of recombination breakpoints.