Associação entre a homocisteína e os polimorfismos do gene da MTHFR em mulheres brasileiras obesas / Association between homocysteine and polymorphisms in MTHFR in Brazilian obese women

Fundamentos: Pesquisas nacionais brasileiras indicam aumento da obesidade e doenças cardiovasculares em mulheres. Objetivo: Determinar a frequência dos polimorfismos 677C>T e 1298A>C do gene da metilenotetra-hidrofolato redutase (MTHFR) em mulheres brasileiras obesas e avaliar sua associação com as concentrações séricas de homocisteína (Hcy),folato e cobalamina, no período após a fortificação das farinhas de trigo e milho com ácido fólico no Brasil. Métodos: Estudo transversal realizado no período de 2008 a 2009, com 133 mulheres obesas. Kits comerciais foramutilizados para realizar análises laboratoriais, incluindo mensuração de lipídeos e glicose por métodos enzimáticos; Hcy total e o folato plasmático, utilizando um imunoensaio competitivo; e cobalamina baseado em quimiluminescência. A genotipagem foi realizada por PCR, seguido por fragmento de restrição enzimática. Resultados: A média de idade dos participantes foi 39,0±4,4 anos e o índice de massa corporal, 32,5±2,1 kg/m². Distribuições dos genótipos encontradas: CC (47%), CT (44%) e TT (9%) para a posição 677 da MTHFR e AA (60%), AC (35%), e CC (5%) para a posição 1298. As concentrações de Hcy correlacionaram-se negativamente com a concentração de folato plasmático no grupo exibindo os genótipos 677CT, 1298AC ou 1298CC (r=0,554, p<0,01). Conclusão: Mulheres brasileiras obesas com genótipos 677TT estudadas apresentaram maiores concentrações de Hcy do que aquelas que apresentaram os genótipos 677CT e 677CC. Além disso, genótipos 1298CC mostraram associação com concentrações de Hcy maiores do que os genótipos 1298AC e 1298AA.

Background: Brazilian national surveys have indicated a rise in obesity and cardiovascular disease in women.Objective: To determine the frequency of 677C>T and 1298A>C polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene in obese Brazilian women and to assess the potential association of these polymorphisms with serum concentrations of homocysteine (Hcy), folate and cobalamin after fortification of wheat and corn flour with folic acid in Brazil. Methods: A cross-sectional study was conducted from 2008 to 2009 with 133 obese women. Commercial kits were employed to perform laboratory analyses including measurement of lipids and glucose using enzymatic methods, total Hcy and serum folate using a competitive immunoassay and cobalamin based on chemiluminescence. Genotyping was performed by PCR, followed by restriction fragment lengthpolymorphism analysis. Results: The average age of participants was 39.0±4.4 years and mean body mass index was 32.5±2.1kg/m². The distributions of the genotypeswere CC (47%), CT (44%), and TT (9%) for the position MTHFR 677 and AA (60%), AC (35%), and CC (5%) for the position 1298. Hcy levels correlated negatively with serum folate in the group displaying the 677CT, 1298AC, or 1298CC genotypes (r=-0.554, p<0.01). Conclusion: Our findings suggest that obese Brazilian women with genotypes 677TT have higher Hcy concentrations than those carrying the genotypes 677CT and 677CC. Additionally, genotypes 1298CC are associated with higher Hcy concentrations than genotypes 1298AC and 1298AA.

Glutamate carboxypeptidase II (GCPII) genetic variants as determinants of hyperhomocysteinemia: Implications in stroke susceptibility.

The rationale of this case-control study is to ascertain whether glutamate carboxypeptidase II (GCPII) variants serve as determinants of hyperhomocysteinemia and contribute to the etiology of stroke. Hyperhomocysteinemia was observed in stroke cases compared to controls (14.09 ± 7.62 mmol/L vs. 8.71 ± 4.35, P<0.0001). GCPII sequencing revealed two known variants (R190W and H475Y) and six novel variants (V108A, P160S, Y176H, G206R, G245S and D520E). Among the haplotypes of GCPII, all wild-haplotype H0 showed independent association with stroke risk (OR: 9.89, 95% CI: 4.13-23.68), while H2 representing P160S variant showed reduced risk (OR: 0.17, 95% CI: 0.06-0.50). When compared to subjects with H2 haplotype, H0 haplotype showed elevated homocysteine levels (18.26 ± 4.31 mmol/L vs. 13.66 ± 3.72 mmol/L, P = 0.002) and reduced plasma folate levels (7.09 ± 1.19 ng/ml vs. 8.21 ± 1.14 ng/ml, P = 0.007). Using GCPII genetic variants, dietary folate and gender as predictor variables and homocysteine as outcome variable, a multiple linear regression model was developed. This model explained 36% variability in plasma homocysteine levels. To conclude, GCPII haplotypes influenced susceptibility to stroke by influencing homocysteine levels.

Factores genéticos del sistema hemostático en pacientes jóvenes con infarto agudo del miocardio / Genetic factors of the hemostatic system in young patients with myocardial infarction

La enfermedad arterial coronaria (EAC) es la primera causa de muerte en todo el mundo y representa un problema de salud pública en México. El infarto agudo del miocardio (IAM) representa la principal complicación trombótica de la EAC. Aproximadamente 9 % de los nuevos casos está constituido por sujetos menores de 45 años. El IAM se produce por el desarrollo de un trombo en el sitio de la placa aterosclerosa, generando oclusión arterial súbita con isquemia y muerte celular. El IAM resulta de la interacción entre factores genéticos y ambientales. Existen diversos factores de riesgo modificables como la hipertensión arterial, la diabetes mellitus, el tabaquismo, la obesidad y la hipercolesterolemia asociados con el IAM. Sin embargo, numerosos pacientes con IAM no presentan factores de riesgo modificables. En la última década se han identificado variantes genéticas en las proteínas relacionadas con los sistemas de coagulación y fibrinólisis, receptores plaquetarios, disfunción endotelial, flujo sanguíneo anormal, metabolismo de la homocisteína, estrés oxidativo, los cuales se asocian a desarrollo del IAM. La identificación de los polimorfismos asociados a la enfermedad arterial coronaria permitirá desarrollar mejores estrategias de tratamiento e identificación de individuos con alto riesgo para EAC y medidas preventivas en etapas tempranas.

BACKGROUND: Coronary artery disease (CAD) is the first cause of death worldwide and represents a public health issue in our country. Acute myocardial infarction (AMI) represents the main thrombotic complication of CAD. Approximately 9% of the new events of MI occur in patients <45 years of age. DISCUSSION: AMI is produced by development of a thrombus at the site of an atherosclerotic plaque that initiates abrupt arterial occlusion, with ischemia and cell death. AMI results from the interaction of gene-environment factors. There are several modifiable factors such as hypertension, diabetes, smoking, obesity, and hypercholesterolemia associated with AMI. However, in a large number of patients with AMI, modifiable risk factors are not present. In the last decade, several genetic variants (polymorphisms) have been identified associated with AMI in genes related to coagulation proteins, fibrinolytic system, platelet receptors, homocysteine metabolism, endothelial dysfunction, abnormal blood flow and oxidative stress. CONCLUSIONS: Identifying the genes associated with CAD will allow us to develop more efficacious treatment strategies and will also help to identify at-risk subjects, thereby enabling the introduction of early preventive measures. Thus, many research efforts continue to address the identification of acquired and inherited risk factors of this complex disease.

Genetics of homocysteine metabolism and associated disorders

Homocysteine is a sulfur-containing amino acid derived from the metabolism of methionine, an essential amino acid, and is metabolized by one of two pathways: remethylation or transsulfuration. Abnormalities of these pathways lead to hyperhomocysteinemia. Hyperhomocysteinemia is observed in approximately 5 percent of the general population and is associated with an increased risk for many disorders, including vascular and neurodegenerative diseases, autoimmune disorders, birth defects, diabetes, renal disease, osteoporosis, neuropsychiatric disorders, and cancer. We review here the correlation between homocysteine metabolism and the disorders described above with genetic variants on genes coding for enzymes of homocysteine metabolism relevant to clinical practice, especially common variants of the MTHFR gene, 677C>T and 1298A>C. We also discuss the management of hyperhomocysteinemia with folic acid supplementation and fortification of folic acid and the impact of a decrease in the prevalence of congenital anomalies and a decline in the incidence of stroke mortality.

Hiper-homocisteinemia e risco cardiometabólico: [revisão] / Hyperhomocysteinemia and cardiometabolic risk: [review]

A hiper-homocisteinemia, quando considerada como fator causal de doenças vasculares, tem suscitado muitas discussões. Estudos caso-controle, retrospectivos e prospectivos têm identificado relação entre concentrações plasmáticas elevadas de homocisteína e doenças vasculares. Na presente revisão, objetivou-se compreender melhor a inter-relação entre as concentrações plasmáticas de homocisteína e doenças vasculares, além do envolvimento de fatores de risco clássicos para a doença: os genéticos, como as mutações em genes que codificam as enzimas envolvidas no metabolismo da homocisteína, e os nutricionais, como a deficiência de vitaminas do complexo B. Foram consultadas as publicações das principais bases de dados em saúde, no período de 1962 a 2009. O mecanismo pelo qual a hiper-homocisteinemia atua como fator de risco para doenças vasculares ainda não está totalmente esclarecido; entretanto, sugere-se o envolvimento da disfunção endotelial e da peroxidação lipídica. O tratamento da hiper-homocisteinemia fundamenta-se na suplementação alimentar e medicamentosa, com ácido fólico e vitaminas B6 e B12.

Hyperhomocysteinemia, when considered as a causal factor of vascular diseases, has been subject of much discussion. Case-control, retrospective and prospective studies have identified a relationship between high plasma concentrations of homocysteine and vascular disease. The aim of the present review was to better understand the interrelation between plasma concentrations of homocysteine and vascular diseases, as well as the involvement of classical risk factors for the disease: genetic factors, such as mutations in the genes that codify the enzymes involved in the metabolism of homocysteine, and nutritional factors, such as complex B vitamin deficiency. The publications of the main databases in health were consulted for the period 1962 to 2009. The mechanism by which hyperhomocysteinemia acts as a risk factor for vascular diseases still has not been fully clarified, but involvement of endothelial dysfunction and lipid peroxidation is suggested. The treatment of hyperhomocysteinemia is based on food supplements and medication, with folic acid and vitamins B6 and B12.

Nutri-genetic determinants of neural tube defects in India.

Justification: Neural tube defects (NTDs) are one of the commonest birth defects with a high incidence in India. However, few studies have systematically looked into the etio-pathogeneis of NTDs, which mainly includes nutritional deficiencies and genetic predisposition. Efforts are afoot for universal food fortification with folic acid in the hope of preventing NTDs, without factual evidence of folate deficiency in the target population. Evidence acquisition: We conducted a review of Indian literature on NTDs focusing on the role of folate and vitamin B12 nutrition and common genetic polymorphisms in 1-carbon metabolism. We performed a literature search of Medline and Indian Medlars (www. indmed.nic.in) for articles using following search terms: Neural tube defect and India, published up to November 2008, on human subjects. We did not include individual case reports and case series describing surgical and medical management, genetic syndromes where NTD was only one of the features or unusual associations of NTDs with other clinical findings. Results: Absence of a nationally representative large study, lack of interventional studies and methodological differences were conspicuous during this review. Larger studies are, therefore, urgently needed to delineate gene-nutrient interactions in association with NTDs in India. We urge that caution should be exercised before widespread folic acid fortification of food, without addressing the issue of concurrent B12 deficiency.

Plasma homocysteine levels & 677C-->T methylenetetrahydrofolate reductase gene polymorphism in patients with coronary artery disease of different severity.

BACKGROUND & OBJECTIVE: Numerous studies have identified hyperhomocysteinemia as an independent risk factor for coronary artery disease (CAD). Furthermore, influences of polymorphysim of methylenetetrahydrofolate reductase (MTHFR) on homocysteine levels are documented. However, the relationship between severity of CAD and polymorphism of MTHFR has not been systematically evaluated. The present study was undertaken to evaluate this relationship in patients undergoing coronary artery bypass surgery. METHODS: Serum homocysteine and MTHFR polymorphism in relation to severity of CAD was examined in 113 male patients, who all underwent coronary artery bypass surgery. The prevalences of 677 C-->T transition of the MTHFR gene were determined in these patients. Two groups were compared according to GENSINI coronary score : mild atherosclerosis (CAD stenosis < 30) and severe atherosclerosis (CAD stenosis > 30). RESULTS: Patients with CAD showed a significantly higher serum concentration of homocysteine than control subjects (P < 0.01). The serum homocysteine level was significantly higher in patients with increased scores than in patients with mild CAD (Gensini score < 30) both with and without the MTHFR polymorphism. INTERPRETATION & CONCLUSION: The findings of our study showed that hyperhomocysteinemia was significantly related to the severity of CAD independent on MTHFR polymorphism.

Presença de hiper-homocisteinemia em pacientes portadores de três fatores de risco para doença cardiovascular: hipertensão, tabagismo e histórico familiar / The presence of homocysteinemia in patients carrying three risk factors for cardiovascular diseases: hypertension, smoking habit and family history

A hiper-homocisteinemia é um fator de risco independente para desenvolvimento de doença cardiovascular e na presença de outros fatores de risco (FR) poderá acarretar em risco adicional para o surgimento do evento. Foram realizadas dosagens séricas de homocisteína e creatinina em 146 pacientes (51 homens e 95 mulheres) cadastrados no programa HIPERDIA/MS sendo todos portadores de três FR associados: hipertensão, tabagismo e histórico familiar para doença cardiovascular. A média geral foi de 14,48 µmol/L ± 5,98 (15,38 µmol/L ± 6,77 e 13,99 µmol/L ± 5,48, homens e mulheres respectivamente). A hiper-homocisteinemia esteve presente em 34,90% (39,20% e 32,60%, homens e mulheres respectivamente), de acordo com o intervalo de referência entre 5 - 15 µmol/L. Entretanto, segundo recomendações da DACH-LIGA Homocysteine, valores entre 12 - 30 µmol/L são considerados como moderada hiper-homocisteinemia. O estudo revelou que 60,30% (70,60% e 54,70%, homens e mulheres respectivamente) estavam acima de 12 µmol/L. Na avaliação do estudo, a dosagem de homocisteína sérica deve ser realizada em pacientes cadastrados no programa HIPERDIA/MS, pois além de hipertensos e/ou diabéticos, a presença de hiper-homocisteinemia pode ser um risco adicional para o desenvolvimento de doença cardiovascular.

Hiper-homocysteinemia is an independent risk factor in the development of cardiovascular diseases and in the presence of other risk factors (RF) may bring about an additional risk for the occurrence of the event. Serum dosages of homocysteine and creatinine in 146 patients (51 men and 95 women), registered at the HIPERDIA/MS Program, all presenting three associated RF's; hypertension, smoking habit and family history for cardiovascular diseases. The general average has been 14.48 µmol/L ± 5,98 (15,38 µmol/L ±6,77 and 13,99 µmol/L ± 5,48, for men and women respectively). Hiper-homocysteinemia had been present in 34.90% (39.20% and 32.60%, men and women, respectively), according to the reference interval between 5 - 15 µmol/L. Although, according to Homocysteine DACH-LIGA recommendations, values between 12 - 30 µmol/L are considered being a moderate hiper-homocysteinemia. The study has revealed that 60.30% (70.60% and 54.70%, men and women, respectively) had been above 12 µmol/L. In the evaluation of the study, the serum dosage of homocysteine has to be performed in patients registered at the HIPERDIA/MS Program for, besides being hypertense and/or diabetic, the presence of hiper-homocisteinemia may be an additional risk for the development of cardiovascular disease.

Hyperhomocystinemia in patients with coronary artery disease

Hyperhomocystinemia has been related to an increased risk of cardiovascular disease in several studies. The C677T polymorphism for the gene that encodes the methylenetetrahydrofolate reductase enzyme (MTHFR) and low plasma folate levels are common causes of hyperhomocystinemia. Due to differences in nutritional patterns and genetic background among different countries, we evaluated the role of hyperhomocystinemia as a coronary artery disease (CAD) risk factor in a Brazilian population. The relation between homocysteine (Hcy) and the extent of CAD, measured by an angiographic score, was determined. A total of 236 patients referred for coronary angiography for clinical reasons were included. CAD was found in 148 (62.7 percent) patients and 88 subjects had normal or near normal arteries. Patients with CAD had higher Hcy levels [mean (SD)] than those without disease (14 (6.8) vs 12.5 (4.0) æM; P = 0.04). Hyperhomocystinemia (Hcy >17.8 æM) prevalence was higher in the CAD group: 31.1 vs 12.2 percent (P = 0.01). After adjustment for major risk factors, we found an independent association between hyperhomocystinemia and CAD (OR = 2.48; 95 percent CI = 1.02-6.14). Patients with a more advanced coronary score had a higher frequency of hyperhomocystinemia and tended to have higher mean Hcy levels. An inverse relation between plasma folate and Hcy levels was found (r = -0.14; P = 0.04). Individuals with the MTHFR C677T polymorphism had a higher prevalence of hyperhomocystinemia than those without the mutated allele. We conclude that hyperhomocystinemia is independently associated with CAD, with a positive association between Hcy level and disease severity.

Homozygous VN (677C to T) and d/D (2756G to A) variants in the methylenetetrahydrofolate and methionine synthase genes in a case of hyperhomocysteinemia with stroke at young age

Hyperhomocysteinemia is known to be associated with an increased risk of myocardial infarction, stroke, peripheral arterial disease, and venous thrombosis. Gene polymorphisms in methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MS) may account for reduced enzyme activity and hyperhomocysteinemia. A recent study has documented evidence of polygenic regulation of plasma homocyteine. We report here on a case of occlusive stroke at young age and hyperhomocysteinemia with homozygous VN (677C to T) variant in the MTHFR gene as well as homozygous D/D (2756G to A) variant in the MS gene.