Hyperhomocysteinaemia and MTHFR C677T gene polymorphism in renal transplant recipients

AIM—To study the effect of folate treatment on hyperhomocysteinaemia and the effect of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphism on total homocysteine and folate concentrations after renal transplantation.METHODS—A total of 30 transplanted children and adolescents were investigated for total homocysteine and folate serum concentrations before and after folate treatment, as well as for the presence of the MTHFR C677T polymorphism.RESULTS—The allele frequency of C677T polymorphism in the MTHFR gene in the study population (0.33) was not different to that in controls (0.38). Before folate treatment the homocysteine concentration was raised in all groups; following folate supplementation it was significantly decreased in the CC and CT groups, but not in the TT group. In patients with CC genotype, serum homocysteine correlated with serum creatinine and cholesterol, and time since transplantation before treatment.CONCLUSION—Folate supplementation appears to be an effective strategy to normalise total homocysteine concentration in renal transplanted children and adolescents.     

Anti-Epileptic drug treatment in children: Hyperhomocysteinaemia, B-Vitamins and the 677C→T Mutation of the Methylenetetrahydrofolate Reductase Gene

The aim of the study was to observe the influence of carbamazepine and valproic acid on plasma total homocysteine and B-vitamin status and the gene-drug interaction with the 677C-->T mutation of the methylenetetrahydrofolate reductase (MTHFR) gene. Plasma total homocysteine concentrations were determined in 136 epileptic children taking anti-epileptic drugs as monotherapy. Nutritional (folate, B12 and B6 vitamins) and genetic (MTHFR 677 C-->T) determinants of plasma homocysteine were studied in a random sample of 59 of the 136 epileptic children. Total homocysteine concentrations were significantly increased (p < 0.05) and folate and vitamin B6 levels were significantly decreased (p < 0.01) in the children taking anti-epileptic drugs compared with our reference ranges. In the carbamazepine-treated group, significantly positive correlation was found between duration of treatment and homocysteine concentration (p < 0.01). Homocysteine concentrations showed a significantly negative correlation with vitamin levels (folate: p = 0.002, and vitamin B12: p = 0.017) only in the carbamazepine treated group. In children treated with carbamazepine up to 3 years, total homocysteine concentration correlated negatively only with folate (p = 0.003), while in patients treated for more than 3 years, total homocysteine correlated negatively only with vitamin B12 values (p = 0.007). The lowering action of carbamazepine treatment on folate levels seems to be associated with hyperhomocysteinaemia, which seems to be related to the homozygous condition for the MTHFR 677C-->T mutation. Valproic acid treatment, although also associated with hyperhomocysteinaemia, only shows a lowering effect on vitamin B6 levels, which seems to be independent of the MTHFR genotype.     

Cardiovascular fitness is negatively associated with homocysteine levels in female adolescents

OBJECTIVE: To examine the association between cardiovascular fitness and homocysteine levels in adolescents. DESIGN: Cross-sectional study. SETTING: Madrid, Murcia, Granada, Santander, and Zaragoza, Spain. PARTICIPANTS: One hundred fifty-six Spanish adolescents (76 boys and 80 girls) aged (mean +/- SD) 14.8 +/- 1.4 years. MAIN EXPOSURES: Cardiovascular fitness was measured by the 20-m shuttle run test. Pubertal stage, birth weight, smoking status, and socioeconomic status were determined, and the sum of 6 skinfold thickness measurements, and serum folic acid and vitamin B(12) levels were measured. Methylenetetrahydrofolate reductase (MTHFR; 677C>T genotype) polymorphism was done by DNA sequencing. MAIN OUTCOME MEASURE: Fasting homocysteine levels. RESULTS: Mean values of homocysteine were significantly higher in the MTHFR 677CT and TT genotype subgroups compared with the CC genotype subgroup in adolescent boys, whereas in adolescent girls, mean values of homocysteine were significantly higher in the MTHFR 677CT and TT genotype subgroup compared with the CC and CT genotype subgroups. Multiple regression analyses showed that cardiovascular fitness was significantly associated with homocysteine levels in female adolescents after controlling for potential confounders including the MTHFR 677C>T genotype (beta = -0.40; semipartial correlation = -0.35; P = .007). No associations were found between cardiovascular fitness and homocysteine levels in male adolescents (beta = 0.12; semipartial correlation = 0.08; P = .51). CONCLUSION: The results suggest that cardiovascular fitness is negatively associated with homocysteine levels in female adolescents after controlling for potential cofounders including MTHFR 677C>T genotype.     

MTHFR基因多态性与儿童原发性高血压的相关性研究北大核心CSCD

目的分析原发性高血压儿童亚甲基四氢叶酸还原酶(methylenetetrahydrofolate reductase,MTHFR)基因C677T多态性分布特征,探讨其与儿童H型高血压的相关性。方法回顾性选取2021年1~7月于心血管内科住院、初次诊断未经治疗的121例原发性高血压儿童为研究对象,按基因型分为CC型组(19例)、CT型组(51例)和TT型组(51例);按血清同型半胱氨酸(homocysteine,Hcy)水平分为H型高血压组(47例)和单纯高血压组(74例),比较各组间临床资料差异,分析MTHFR基因C677T多态性与儿童H型高血压的相关性。结果原发性高血压儿童T等位基因突变频率高于北京地区健康成年人群和中国汉族成年人群(P<0.001)。TT型组血清Hcy水平高于CC型组和CT型组(P<0.001)。H型高血压组血清Hcy水平高于单纯高血压组(P<0.001),且MTHFR基因C677T多为TT基因型,TT基因型与H型高血压的发生风险存在关联(OR=12.71,P<0.001)。H型高血压组和单纯高血压组间靶器官损伤发生率差异无统计学意义(P>0.05),但初次诊断时,H型高血压组即可存在多脏器受累情况,占11%(5/47)。结论原发性高血压儿童MTHFR基因C677T的T等位基因突变率高且与血清Hcy水平具有一定关联,TT基因型是儿童H型高血压的独立危险因素,与早期靶器官损伤严重程度可能相关。     

Reduced total plasma homocyst(e)ine in children and adolescents with type 1 diabetes

OBJECTIVES: The objective was to investigate total plasma homocyst(e)ine (tHcy), methylenetetrahydrofolate reductase (MTHFR) genotype, and the contribution of diet to homocysteine values in children and adolescents with type 1 diabetes and a control group. STUDY DESIGN: A total of 78 children with type 1 diabetes and 59 members of an age- and sex-matched control group were recruited. Fasting samples were collected for tHcy, MTHFR genotype, serum vitamin B(12), serum folate, red cell folate, and plasma creatinine. Food frequency questionnaires targeted intake of folate, vitamin B(6), and vitamin B(12). RESULTS: Fasting tHcy was reduced in patients compared with the control group (4.7 vs 5.9 micromol/L, P <.001). Serum folate (P =.002), red cell folate(P <.001), and serum vitamin B(12) (P =.005) were higher, and plasma creatinine was lower. A significant difference in tHcy values between patients and the control group persisted after correction was done for these factors (r = 0.1, P =.02). No difference was seen in the frequency of MTHFR polymorphisms. tHcy was not elevated in those patients with the 677TT or 677T/1298C genotypes, although red cell folate was significantly higher in members of the case (P =.01) and control groups (P =.05) with a 677 TT genotype. Dietary intake of folate correlated with serum folate (r = 0.4,P =.005). CONCLUSION: tHcy values are lower in children and adolescents with type 1 diabetes. Higher serum levels of folic acid and vitamin B(12), reflecting differences in dietary intake between children with diabetes and members of a control group, partially account for this difference.     

Alanine amino transferase concentrations are linked to folate intakes and methylenetetrahydrofolate reductase polymorphism in obese adolescent girls

OBJECTIVE: The objective of this study was to investigate the consequences of low dietary folate intake and the impact of the 677 C-->T methylenetetrahydrofolate reductase (MTHFR) common mutation on liver function in obese adolescents. METHODS: Fifty-seven obese girls (BMI = 36.1 +/- 6.0 kg/m) aged 14.1 +/- 1.5 years were included before starting a weight reduction program. Dietary intakes for folate were assessed by means of an adapted food frequency questionnaire (n = 50). Liver enzymes, plasma lipids, glucose metabolism parameters, ferritin, homocysteine and erythrocyte folate content were measured in plasma or blood obtained under fasting conditions. The MTHFR 677 C-->T polymorphism, which is associated with decreased enzyme activity, was determined using PCR. Body composition was assessed using dual x-ray absorptiometry. RESULTS: Twenty-three subjects were heterozygote (CT) for the mutation and 5 were homozygote (TT). An increase in alanine amino transferase (ALT) and ALT/aspartate aminotransferase ratio was associated with the mutation (F = 4.46, P = 0.016 and F = 5.92, P = 0.0049, respectively). Alanine amino transferase was correlated negatively to folate intake (r = -0.32, P = 0.024) (n = 50) and positively to homocysteine concentrations (r = 0.30, P = 0.025). Body composition was similar among the 3 genotypic groups. Ferritin was also correlated to ALT concentrations of the entire group (P = 0.009). CONCLUSION: Our data suggest that folate intake and the MTHFR polymorphism represent a part of the link between antioxidant status and liver disease in obese adolescent girls.     

Total homocysteine, folate, and cobalamin, and their relation to genetic polymorphisms, lifestyle and body mass index in healthy children and adolescents

We investigated total homocysteine (tHcy) concentrations and relations between tHcy and folate, cobalamin (Cbl), genetic polymorphisms (MTHFR 677C > T, MTHFR 1298A > C, MTHFR 1793G > A), blood pressure (BP), body mass index (BMI), cholesterol, triglycerides, sports activities, family and individual history of cardiovascular disease (CVD) and lifestyle issues in 264 healthy children and adolescents (2-17 y). THcy concentrations significantly increased while folate and Cbl decreased with age without gender differences. Age, folate and Cbl were significant predictors for tHcy concentrations. THcy was higher but within normal ranges in MTHFR 677TT homozygotes (10.6%) and carriers of the MTHFR 1793A allele (8%). Only two individuals (0.8%), both with low tHcy concentrations, were homozygous for MTHFR 1793AA. THcy concentration correlated positively with creatinine, triglycerides, BMI and systolic BP and was not related to cholesterol, sports activities and family history of CVD. In conclusion, tHcy concentrations in this pediatric population were significantly influenced by age, folate and Cbl concentrations. No gender differences for tHcy, folate or Cbl concentrations were observed. Both the MTHFR 677TT genotype and the MTHFR 1793A allele were not associated with hyperhomocysteinemia. The prevalence of the MTHFR 1793AA genotype was too low for meaningful interpretation.     

急性淋巴细胞白血病患儿亚甲基四氢叶酸还原酶基因多态性与大剂量甲氨蝶呤不良反应的相关性

目的探讨急性淋巴细胞白血病(ALL)患儿亚甲基四氢叶酸还原酶(MTHFR)基因677位点多态性与大剂量甲氨蝶呤(HDMTX)体内排泄及不良反应的相关性。方法 2008年3月-2010年2月在本院儿科中心和血液内科住院的完全缓解并接受HDMTX治疗的40例ALL患儿,在接受HDMTX治疗前应用PCR-限制性酶切片段长度多态性(RFLP)技术检测MTHFR基因C677T多态性,在HDMTX静脉输注开始后24 h、48 h应用荧光偏振免疫法(FPIA)测定其血浆MTX水平,密切观察ALL患儿HDMTX化疗后的不良反应,对化疗不良反应进行分级。对MTHFR677的基因多态性与MTX不良反应及HDMTX 48 h的MTX水平(MTX-48 h)的相关性进行分析。结果在有HDMTX相关不良反应的ALL患儿中,肝损害和骨髓抑制发生率最高。MTHFR C677T有肝脏损害的基因型分布频率由低到高为CC型40.0%,TT型60.0%,CT型80.0%,CT基因型者肝脏损害发生的风险是CC基因型者的6倍(OR=6.00,95%CI:1.05～34.32,P=0.044);677CT+TT基因型者肝脏损害发生的风险是CC基因型者的4.13倍(OR=4.13,95%CI:1.02～16.67,P=0.047)。MTHFR C677T基因型与骨髓抑制无明显相关性。携有MTHFR突变基因型(CT+TT)患者的48 hMTX血药质量浓度明显高于携带MTHFR野生型基因CC者(P=0.006)。结论 MTHFR 677位基因型可作为ALL患儿HDMTX化疗不良反应和药物体内排泄的有效预测指标。     

支气管哮喘患儿亚甲基四氢叶酸还原酶基因多态性与血清免疫球蛋白E的关系

目的探讨支气管哮喘(哮喘)患儿亚甲基四氢叶酸还原酶(MTHFR)基因C677位点多态性与血清IgE水平的相关性。方法选择95例哮喘患儿作为病例组,均为急性发作期或临床缓解期哮喘患儿,患病前2周均未使用过肾上腺皮质激素及免疫调节剂。另选择健康儿童113例作为健康对照组。2组儿童年龄及性别比较差异均无统计学意义。采用PCR-限制性片段长度多态性分析法对病例组和健康对照组儿童外周血白细胞MTHFR基因C677位点基因多态性进行研究,应用双抗体夹心ELISA法检测2组儿童血清总IgE水平。结果健康对照组MTHFR 677C/T的3种基因型频率分别CC 35.4%、CT 45.1%、TT 19.5%,病例组分别为CC 24.2%、CT 40.0%、TT 35.8%,677C/T基因型分布频率在哮喘病例组和健康对照组间差异有统计学意义(χ2=7.556 5,P<0.05)。病例组T等位基因的频率为55.3%,健康对照组为42.0%,病例组较健康对照组显著增高,其患哮喘的危险度是健康对照组的1.71倍(χ2=7.254 7,P<0.01;95%CI:1.13～2.57)。病例组血清总IgE水平在各基因型患儿间比较差异有统计学意义(F=3.46,P<0.05),健康对照组血清总IgE水平在各基因型儿童间比较差异无统计学意义(F=0.13,P>0.05)。结论 MTHFRC677位点C→T的基因突变增加了患儿哮喘发病的危险度,TT基因型与哮喘的发生直接相关;哮喘患儿血清总IgE水平升高,该位点基因型并非导致血清总IgE水平升高的直接原因。     

Methylenetetrahydrofolate Reductase TT Genotype as a Predictor of Cardiovascular Risk in Hypertensive Adolescents

Methylenetetrahydrofolate reductase (MTHFR) is associated with homocysteine level. In deficit of MTHFR, cardiovascular risk is increased with hyperhomocysteinemia and hypomethionemia. Mutation of the MTHFR gene is associated with the risk for premature cardiovascular diseases. However, the association between MTHFR mutation and cardiovascular risk is still controversial. The purposes of this study were to determine whether MTHFR genotype is associated with cardiovascular risks in hypertensive adolescents and to investigate the association between MTHFR genotype and carotid intima-media thickness (IMT). Forty-three hypertensive adolescents were included in this study. Serum lipid levels, insulin, vitamin B₁₂, folate, renin, aldosterone, angiotensin converting enzyme, and homocysteine levels were evaluated. The carotid IMT and diameter were estimated by ultrasound. Brachial–ankle pulse wave velocity was also measured. Polymerase chain reaction was conducted to amplify genomic DNA fragment containing C677T position of the MTHFR gene. The height, weight, body mass index, obesity index, arm circumference, fat mass, and fat distribution were significantly greater in patients with C677T mutation. The C677T mutation group showed significantly greater carotid IMT, higher homocysteine, and lower folic acid levels than the normal genotype group. Interpretation of MTHFR genotype might be useful in predicting the development of premature coronary artery disease in hypertensive adolescents.     

Methylenetetrahydrofolate reductase and methionine synthase reductase gene polymorphisms and protection from microvascular complications in adolescents with type 1 diabetes

Abstract:  Folate status has been associated with endothelial dysfunction in adolescents with type 1 diabetes, and elevated total plasma homoocyst(e)ine (tHcy) is a risk for vascular disease in the non-diabetic population. Polymorphisms in genes involved in folate and homocysteine metabolism are implicated in vascular disease. We aimed to determine whether polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) genes are risk factors for early microvascular disease in a large group of adolescents with type 1 diabetes. Four hundred and eighty adolescents were screened annually for retinopathy and microalbuminuria for a median of 4 yr. Molecular analysis for the polymorphisms 677C→T, 1298A→C in MTHFR, and 66A→G in MTRR was performed. The MTRR 66GG genotype reduced the risk for elevated albumin excretion rate (AER) (OR 0.47, CI 0.25, 0.88, p = 0.018) and showed a trend to reduced risk for microalbuminuria (OR 0.27, CI 0.06–1.21, p = 0.09). Survival without elevated AER was increased with the MTRR 66GG genotype (12.4 vs. 9.7 yr, p = 0.04) and with the MTHFR 1298CC genotype (15.2 vs. 10.2 yr, p = 0.007). Conversely, survival without retinopathy was reduced with the MTHFR 677TT and MTRR 66GG combined genotype (6.2 vs. 10.2 yr, p = 0.015). The MTRR 66GG and MTHFR 1298 CC genotypes may confer protection against early nephropathy, possibly because they are associated with lower tHcy. The MTHFR 677 TT was only related to earlier onset retinopathy in combination with MTRR 66GG.     

Methylene tetrahydrofolate reductase mutations as genetic risk factors for neural tube defects (NTF)

Folic acid supplementation before conception and during the first trimester of pregnancy prevents about 70% of all neural tube defects (NTD). Folic acid is a cofactor in the homocysteine metabolism. Its product--S-adenosylmethionine is a major methyl donor for reactions taking place in a cell. The 677 C-->T mutation in the methylene tetrahydrofolate reductase gene leads to thermolability and decreased activity of the enzyme. In the individuals homozygous for that mutation hyperhomocystynemia and lowered plasma folate level are observed. Presence of the MTHFR 677 C-->T mutation increases the requirements for folic acid, especially at the time of rapid foetal growth. Studies showed higher rate of TT homozygotes in people with NTD and their parents compared with the control group. Hyperhomocystynemia has been associated with higher risk of recurrent miscarriages in women. It was also proved that stillbirths are a risk factor associated with NTDs. TT homozygosity varies among different country populations, from 6% to 16%. An additional risk factor for NTD is MTHFR 1298 A-->C mutation. Combined heterozygosity for the 1298 A-->C and 677 C-->T mutations is associated with increased homocysteine and lowered plasma folate levels. This genotype is more frequent in NTD patients compared with controls. Further investigations in the field of genetic aspects of NTD in Poland will be very important for the primary prevention of NTD.     

Genetic determinants of hyperhomocysteinaemia: the roles of cystathionine beta-synthase and 5,10-methylenetetrahydrofolate reductase

Over the last decade mild hyperhomocysteinaemia has widely been recognised as a new risk factor for arteriosclerosis and thrombosis. Main regulating enzymes of homocysteine (Hcy) metabolism are cystathionine beta-synthase (CBS), methionine synthase and methylenetetrahydrofolate reductase (MTHFR). Early studies on patients with vascular disease described elevated Hcy concentrations after methionine loading and decreased CBS activity, resembling heterozygotes for CBS deficiency. Therefore, heterozygosity for CBS deficiency was proposed as the main cause of mild hyperhomocysteinaemia. However, more recent enzymatic and molecular genetic studies have demonstrated that heterozygosity for CBS deficiency is not or only a very minor cause of mild hyperhomocysteinaemia in vascular disease. We discovered two common genetic causes of mild hyperhomocysteinaemia, the 677C > T and the 1298A > C mutations in the coding region of MTHFR. The 677C > T mutation causes reduced enzyme activity with thermolabile protein properties, elevated Hcy and low-normal or decreased plasma folate levels. The 1298A > C mutation relates also to decreased enzyme activity, but not to thermolabile protein, and Hcy and folate levels are not influenced. However, compound heterozygosity for these two mutations, i.e. individuals with the 677CT/1298AC genotype, have elevated Hcy and decreased plasma folate levels. Gene-enviroment interactions between 677C > T and folate is demonstrated in individuals with the 677TT genotype. Those with low-normal folate have elevated Hcy, whereas those with high-normal folate have normal Hcy concentrations. The elevated Hcy levels due to these mutations can be normalised by administration of folate, but whether folate reduces the risk of cardiovascular disease remains to be established. CONCLUSION: Heterozygosity for cystathionine beta-synthase deficiency is a minor cause of hyperhomocysteinaemia. The current data on mutations in the methylenetetrahydrofolate reductase gene do not tell us whether elevated plasma homocysteine plays a causal role in vascular disease. Low cellular vitamin status may be a possible cause and homocysteine may just be a marker for this situation.     

Genetic determinants of hyperhomocysteinaemia: the roles of cystathionine ?-synthase and 5,10-methylenetetrahydrofolate reductase

Over the last decade mild hyperhomocysteinaemia has widely been recognised as a new risk factor for arteriosclerosis and thrombosis. Main regulating enzymes of homocysteine (Hcy) metabolism are cystathionine #-synthase (CBS), methionine synthase and methylenetetrahydrofolate reductase (MTHFR). Early studies on patients with vascular disease described elevated Hcy concentrations after methionine loading and decreased CBS activity, resembling heterozygotes for CBS deficiency. Therefore, heterozygosity for CBS deficiency was proposed as the main cause of mild hyperhomocysteinaemia. However, more recent enzymatic and molecular genetic studies have demonstrated that heterozygosity for CBS deficiency is not or only a very minor cause of mild hyperhomocysteinaemia in vascular disease. We discovered two common genetic causes of mild hyperhomocysteinaemia, the 677C > T and the 1298A > C mutations in the coding region of MTHFR. The 677C > T mutation causes reduced enzyme activity with thermolabile protein properties, elevated Hcy and low-normal or decreased plasma folate levels. The 1298A > C mutation relates also to decreased enzyme activity, but not to thermolabile protein, and Hcy and folate levels are not influenced. However, compound heterozygosity for these two mutations, i.e. individuals with the 677CT/1298AC genotype, have elevated Hcy and decreased plasma folate levels. Gene-enviroment interactions between 677C > T and folate is demonstrated in individuals with the 677TT genotype. Those with low-normal folate have elevated Hcy, whereas those with high-normal folate have normal Hcy concentrations. The elevated Hcy levels due to these mutations can be normalised by administration of folate, but whether folate reduces the risk of cardiovascular disease remains to be established. Conclusion Heterozygosity for cystathionine #-synthase deficiency is a minor cause of hyperhomocysteinaemia. The current data on mutations in the methylenetetrahydrofolate reductase gene do not tell us whether elevated plasma homocysteine plays a causal role in vascular disease. Low cellular vitamin status may be a possible cause and homocysteine may just be a marker for this situation.     

亚甲基四氢叶酸还原酶缺陷导致学童精神分裂症

亚甲基四氢叶酸还原酶（MTHFR）缺陷是一种少见的常染色体隐性遗传性疾病,是高同型半胱氨酸血症的常见类型之一。该文通过对1例MTHFR缺陷导致的精神障碍的临床经过、生化特点、MTHFR 基因突变进行回顾性研究,探讨该病的临床特点与诊疗方法。患儿11岁起出现精神异常,恐惧、幻听、学习困难、入睡困难、脾气暴躁、发呆、傻笑,符合精神分裂症诊断。多种精神科药物治疗无效,休学。13岁时来院就诊,血、尿总同型半胱氨酸明显升高。血浆和脑脊液叶酸均显著降低。血液蛋氨酸水平正常。患儿MTHFR基因存在665C>T纯合突变。经亚叶酸钙、维生素B12、维生素B6、甜菜碱补充治疗1周后,患儿血清及尿液总同型半胱氨酸降至正常,病情逐步改善,3个月后复学。晚发型MTHFR缺陷合并继发性脑叶酸缺乏症的患儿可表现为精神分裂症;血液及尿液总同型半胱氨酸测定、血液氨基酸测定、血清及脑脊液叶酸测定及基因分析对患者的病因诊断非常重要;补充叶酸、维生素B6、维生素B12、甜菜碱治疗有效。     

Methionine synthase deficiency without megaloblastic anaemia

We report findings on a child presenting with neonatal homocystinuria, hypomethioninaemia and severe neurological symptoms, including developmental delay and seizures. Methylmalonic aciduria was not present. The activity of methionine synthase in fibroblasts was severely deficient and formation of methylcobalamin from ⁵⁷Co labelled cyanocobalamin was very low. The patients cells complemented with those of a cblE patient but not with those of two cblG patients. No biochemical or clinical response to injections of hydroxycobalamin was found. Both off treatment and on betaine and methionine supplementation the patient, at age 8 years, has not developed megaloblastic anaemia. In addition, the patient is homozygous for the C677T polymorphism in the 5,10 methylenetetrahydrofolate reductase (MTHFR) gene and the concomitant existence of this mutation with the methionine synthase defect may prevent folate «trapping» and thus anaemia. Conclusion We report the lack of megaloblastic anaemia in a patient with severe methionine synthase deficiency who is also homozygous for C677T in MTHFR, hypothesize that the MTHFR polymorphism protects the patient against anaemia and speculate that homozygosity for MTHFR C677T could cause the dissociation between haematological and neurological disease seen in some patients with vitamin B12 deficiency.     

Methylenetetrahydrofolate reductase C677T polymorphism in patients with Henoch‐Schönlein purpura

Aim: Associations between several vascular diseases such as Kawasaki disease, venous and arterial thromboembolism, cardiovascular disease, diabetic nephropathy, focal segmental glomerulosclerosis and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism have been reported. This is a clinical study designed to investigate the possible effects of MTHFR C677T polymorphism on the development of Henoch‐Schönlein purpura (HSP). Methods: Forty‐one patients with HSP (25 male/16 female) with a mean age of 7.8 ± 2.9 years were included in the study. The control group consisted of 50 healthy children. MTHFR genotypes were determined by polymerase chain reaction and by Hindf I restriction enzyme analysis and subsequent 3% agarose gel electrophoresis techniques. Results: No significant differences were observed in the distribution of MTHFR genotypes or allele frequencies in the HSP cases versus controls. Plasma homocysteine levels and vitamin B₁₂ levels were almost comparable in the HSP patients and control group without a significant difference. Folic acid levels were within normal limits in the HSP cases and the control group, HSP patients' levels being significantly higher than the control group. No significant relationship was present with the MTHFR genotype and plasma homocysteine, vitamin B₁₂ and folic acid levels in HSP patients. Conclusion: No association with MTHFR gene polymorphism and homocysteine plasma levels could be found in patients with HSP. The results of this study indicate that other mechanisms should be operative in the development of HSP.     

Thrombophilia and first arterial ischaemic stroke: a systematic review.

AIMS: To undertake a systematic review of the literature reporting the prevalence of thrombophilia in children with a first arterial ischaemic stroke (AIS). METHODS: Systematic review of case-control studies reporting data for prevalence of protein C, S, and antithrombin (AT) deficiencies, activated protein C resistance (APCr), total plasma homocysteine >95th centile, the thrombophilic mutations factor V1691 GA, prothrombin 20210GA, and MTHFR C677T in children with first, radiologically confirmed, AIS. RESULTS: Of 1437 potentially relevant citations, 18 met inclusion criteria. A total of 3235 patients and 9019 controls had been studied. Results of meta-analyses were expressed as pooled odds ratios (OR) relating the prevalence of the thrombophilic condition in children with AIS to that in controls. The pooled OR (and 95% CI) were: protein C deficiency, 6.49 (2.96 to 14.27); protein S deficiency, 1.14 (0.34 to 3.80); AT deficiency, 1.02 (0.28 to 3.67); APCr, 1.34 (0.16 to 11.52); FV1691 GA, 1.22 (0.80 to 1.87); PT20210GA, 1.10 (0.51 to 2.34); MTHFR C677T, 1.70 (1.23 to 2.34); and total plasma homocysteine >95th centile, 1.36 (0.53 to 3.51). There was no statistical heterogeneity within these data. CONCLUSIONS: All factors examined were more common in children with first AIS than in controls, and significantly so for protein C deficiency and the MTHFR C677T mutation. The implications of thrombophilia for prognosis and recurrence need to be established before clinical recommendations can be made regarding investigation and treatment of children with AIS.     

Thrombophilia and first arterial ischaemic stroke: a systematic review

Aims: To undertake a systematic review of the literature reporting the prevalence of thrombophilia in children with a first arterial ischaemic stroke (AIS). Methods: Systematic review of case-control studies reporting data for prevalence of protein C, S, and antithrombin (AT) deficiencies, activated protein C resistance (APCr), total plasma homocysteine >95th centile, the thrombophilic mutations factor V1691 GA, prothrombin 20210GA, and MTHFR C677T in children with first, radiologically confirmed, AIS. Results: Of 1437 potentially relevant citations, 18 met inclusion criteria. A total of 3235 patients and 9019 controls had been studied. Results of meta-analyses were expressed as pooled odds ratios (OR) relating the prevalence of the thrombophilic condition in children with AIS to that in controls. The pooled OR (and 95% CI) were: protein C deficiency, 6.49 (2.96 to 14.27); protein S deficiency, 1.14 (0.34 to 3.80); AT deficiency, 1.02 (0.28 to 3.67); APCr, 1.34 (0.16 to 11.52); FV1691 GA, 1.22 (0.80 to 1.87); PT20210GA, 1.10 (0.51 to 2.34); MTHFR C677T, 1.70 (1.23 to 2.34); and total plasma homocysteine >95th centile, 1.36 (0.53 to 3.51). There was no statistical heterogeneity within these data. Conclusions: All factors examined were more common in children with first AIS than in controls, and significantly so for protein C deficiency and the MTHFR C677T mutation. The implications of thrombophilia for prognosis and recurrence need to be established before clinical recommendations can be made regarding investigation and treatment of children with AIS.     

Analysis of MTHFR 1298A>C in addition to MTHFR 677C>T polymorphism as a risk factor for neural tube defects in the Turkish population

Maternal folic acid intake in the periconceptional period is strongly related to reduction in recurrence and occurrence of birth defects involving the neural tube. Among the single nucleotide polymorphisms (SNPs) influencing the folate metabolism, the methylenetetrahydrofolate reductase (MTHFR) gene has been the one most exclusively studied. Many studies have reported significant association between MTHFR 677C>T and increased risk of neural tube defects (NTDs). Our previous study did not support this observation. The present study aimed to determine the prevalence of 1298A>C polymorphism in addition to 677C>T in the same Turkish population as a risk factor for NTDs. We genotyped case (95 offspring with NTDs, 80 mothers, 72 fathers) and control (93 healthy children) populations for MTHFR 677C>T and MTHFR 1298 A>C polymorphisms. The comparison demonstrated a significant increase in the 1298AA/677TT genotype frequency among mothers of offspring with NTDs (OR 5.23 [1.06-25.9]; p=0.067). The 677CT genotype was only 1.35 times higher than controls among mothers when 677C>T polymorphism was evaluated alone, while 677CT/1298AC in the current study demonstrated a 3.8 times increase in this risk. These observations led us to conclude that although not statistically significant, MTHFR 1298AC polymorphism might be a risk factor for the occurrence of NTDs in the Turkish population.