Association of the methylenetetrahydrofolate reductase gene C677T polymorphism with the risk of male infertility: a meta-analysis

Several molecular epidemiological studies have been conducted to examine the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and male infertility susceptibility, but the results remain inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. In this meta-analysis, a total of 26 case–control studies including 5659 infertility cases and 5528 controls were selected to evaluate the possible association. The pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were used to assess the strength of association of C677T polymorphism with male infertility in the additive model, dominant model, recessive model and allele-frequency genetic model. In the overall analysis, the frequency of the 677T allele was significantly associated with male infertility susceptibility (OR?=?2.32, 95%CI?=?2.04–2.65 for TT vs. CC genotype; OR?=?1.09, 95%CI?=?1.00–1.19 for CT vs. CC genotype; OR?=?1.19, 95%CI?=?1.10–1.29 for CT/TT vs. CC genotype; OR?=?1.54, 95%CI?=?1.36–1.74 for TT vs. CC/TT genotype; OR?=?1.22, 95%CI?=?1.15–1.30 for T vs. C allele). A subgroup analysis of the subjects showed that significantly strong association between MTHFR C677T polymorphism and male infertility was present only in Asians, but not in Caucasians. Additionally, MTHFR C677T was associated with a significant increase in the risk of azoospermia in all genetic models. Meanwhile, no significantly increased risks of oligoasthenotertozoospermia (OAT) were found in most of the genetic models. In conclusion, this meta-analysis is in favor that the MTHFR C677T polymorphism is capable of causing male infertility susceptibility, especially in Asians and the subgroup of azoospermia.     

Methylenetetrahydrofolate reductase C677T polymorphism is not associated with male infertility in a South Indian population

Previous studies have revealed that genetic factors may be involved in regulating the mechanism of infertility, e.g., MTHFR gene polymorphism in the development of male infertility. The aim of this study is to examine whether an association exists between MTHFR C677T polymorphism and male infertility. The study was carried out by means of a PCR-RFLP assay in 206 infertile men and 230 ethnically matched controls. The statistical analysis using two-sided Fisher's exact test and Pearson chi-squared test showed CT genotype is associated nonsignificantly with male infertility (OR = 1.19, 95% CI = 0.71-1.97). Because of the lack of TT homozygotes in the controls, a combined odds ratio of CT and TT homozygotes against the control has been calculated (OR = 1.36, 95% CI = 0.83-2.22), and the same was insignificant. The overall results of the study indicate that MTHFR C677T polymorphism is not associated with male infertility.     

Single nucleotide polymorphism C677T in the methylenetetrahydrofolate reductase gene might be a genetic risk factor for infertility for Chinese men with azoospermia or severe oligozoospermia

Aim： To analyze the distribution of the single nucleotide polymorphism （SNP） C677T in the methylenetetrahydrofolate reductase （MTHFR） gene in 355 infertile Chinese patients with idiopathic azoospermia or severe oligozoospermia and 252 fertile Chinese men as controls to explore the possible association of the SNP and male infertility. Methods： Using the polymerase chain reaction （PCR）-restriction fragment length polymorphism technique, the allele and genotype distribution of SNP C677T in the MTHFR gene were investigated in both patients and controls. Results： The frequencies of allele T （40.9% vs 30.4%, P = 0.002, odds ration [OR] = 1.58, 95% confidence interval [CI]： 1.24-2.02） and mutant homozygote （TT） （18.3% vs. 11.5%, P = 0.023, OR = 1.72, 95% CI： 1.07-2.76） as well as carrier with allele （TT ＋ CT） （63.4% vs. 49.2%, P = 0.0005, OR = 1.79, 95% CI： 1.29-2.48） in infertile patients were significantly higher than those in controls. After patient stratification, the significant differences in distribution of the SNP between each patient subgroup and control group still remained. Conclusion： Our findings indicate that there is an association of SNP C677T in the MTHFR gene with male infertility, suggesting that this polymorphism might be a genetic risk factor for male infertility in Chinese men.     

Methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism and diabetic nephropathy susceptibility in patients with type 2 diabetes mellitus

Abstract

Methylenetetrahydrofolate reductase (MTHFR) is a crucial enzyme that regulates nucleotide synthesis and DNA methylation. The MTHFR C677T gene polymorphism (rs1801133), a C?→?T transition at nucleotide 677 in exon 4, is a common gene variant of MTHFR and has been implicated in diabetic nephropathy, albeit with inconsistent results. Here, we performed a meta-analysis to assess the common effect size of this polymorphism on DN susceptibility. Case–control studies on the association of the MTHFR C677T gene polymorphism with DN risk were retrieved from databases up to August 1, 2013, and eligible studies were recruited into the meta-analysis and further analyzed. Of 132 studies, 33 were identified as suitable for this analysis. The results showed that T allele and TT genotype were distinctly associated with DN susceptibility in the overall population and Asians, and might be a risk factor in Caucasians and Africans (T allele: Overall population: p?<?0.00001, Asians: p?=?0.0002, Caucasians: p?=?0.02, Africans: p?<?0.00001; TT genotype: Overall population: p?<?0.00001, Asians: p?=?0.0003, Caucasians: p?=?0.008, Africans: p?=?0.0003). Furthermore, the analysis suggested that the CC genotype might play a protective role against DN onset in patients with type 2 diabetes for the overall population, Asians, Caucasian and Africans. However, due to the limited sample size in the African population, these results should be interpreted with care. In conclusion, the MTHFR C677T T allele or TT genotype might be a significant genetic molecular marker to determine the risk of DN in patients with type 2 diabetes and help to develop suitable disease prevention and management strategies.     

MTHFR基因C677T多态性与蒙古族中老年男性骨质疏松的相关性

目的 探讨本地区蒙古族中老年男性亚甲基四氢叶酸还原酶（methylenetetrahydrofolate reductase ,MTHFR ）基因的多态性位点C677T基因多态性与内蒙古地区蒙古族中老年男性骨质疏松症(osteoporosis,OP)遗传易感性的关系。方法 收集门诊及住院蒙古族骨质疏松（包括骨质疏松性骨折）男性患者135例。对照组为按年龄配比的门诊体检内蒙古籍蒙古族中老年男性180例。入选者全部行腰椎（L2-L4）及股骨近端股骨颈骨密度扫查,并排除骨代谢疾病的影响,并进行MTHFR基因多态性检测。结果 骨质疏松组MTHFR基因受体C677T基因型CC、CT、TT频率分别为CC 25.2％、CT 40.0％和TT 34.8％;对照组基因型CC、CT、TT频率分别为31.2%,54.5%和14.3%,两组差别有统计学意义（P<0.05）。骨松组中的T等位基因频率为54.8%,显著高于对照组(41.6%,P<0.05),提示T是骨质疏松发生的危险因素(OR=1.70,95% CI=1.24～2.34,P=0.001)。与CC基因型相比,TT基因型携带者的骨松发生风险增加至2.97倍(95％ CI=2.57～5.65,P=0.001)。 结论 MTHFR基因型分布频率均符合 Hardy-Weinberg定律,T等位基因可以增加蒙古族中老年人骨折发生风险,MTHFR C677T基因变异与内蒙古地区蒙古族中老年男性骨质疏松易感性明显相关。     

Association of a common polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene with bone phenotypes depends on plasma folate status.

A study of a polymorphism in the MTHFR gene, plasma folate, and bone phenotypes in 1632 individuals revealed that the genotype effect on BMD and quantitative ultrasound was dependent on the level of folate. Our findings support the hypothesis that the association between an MTHFR polymorphism and bone phenotypes depends on folate status. INTRODUCTION: Genome-wide screens using quantitative ultrasound (QUS) and BMD phenotypes have shown suggestive linkage on chromosome 1pter-1p36.3, a region containing the methylenetetrahydrofolate reductase (MTHFR) gene. Individuals homozygous (TT) for the MTHFR C677T polymorphism who have low plasma folate concentrations exhibit elevated plasma homocysteine (tHcy) concentrations that may compromise bone quality. We hypothesized that folate status might modify an association between the C677T polymorphism and bone, possibly by influencing homocysteine concentrations. MATERIALS AND METHODS: QUS (broadband ultrasound attenuation [BUA], speed of sound, and quantitative ultrasound index) of the heel and BMD of the hip and spine were measured in 1632 male and female members of the Framingham Offspring Study (1996-2001). Participants were assessed for plasma folate concentration and genotyped for the MTHFR C677T polymorphism. TT participants were compared with individuals in the CC + CT group using analysis of covariance. RESULTS: Adjusted mean QUS and BMD measures did not differ between C677T groups. Although all participants with plasma folate concentrations > or =4 ng/ml had approximately 2% higher QUS and BMD than those with folate <4 ng/ml, the association disappeared after controlling for tHcy. Suggestive interactions between folate status and the C677T group (CC + CT versus TT) were found for hip BMD (p < or = 0.05) and BUA (p = 0.11). Compared with CC + CT participants, TT individuals had lower mean BUA (p = 0.06) and Ward's area BMD (p = 0.08) within the folate <4 ng/ml group and significantly higher hip BMD (p < or = 0.05) within the folate > or =4 ng/ml group. For both folate groups, TT participants had higher age-adjusted mean plasma tHcy versus CC + CT participants. Controlling for tHcy in these models did not affect the statistical significance of the interaction effects. CONCLUSIONS: Our findings support the hypothesis that the association between the C677T MTHFR polymorphism and bone phenotypes depends on folate status. The mechanism mediating the association, however, remains unclear, but may be partially caused by homocysteine effects on bone.     

Association of transforming growth factor-β1 polymorphisms with the risk of chronic kidney diseases

Abstract

The association of transforming growth factor-β1 (TGF-β1) polymorphisms with the risk of chronic kidney diseases (CKD) remains elusive. We aimed to perform a meta-analysis to evaluate the relationship between TGF-β1 polymorphisms and the susceptibility to CKD. Association studies were searched according to a defined criteria using electronic databases. The strength of association between TGF-β1 polymorphisms and CKD risk was evaluated by odds ratio (OR) with the corresponding 95% confidence interval (CI). Nine case–control studies were identified. T allele at the +869 T/C polymorphism was associated with a lower risk of CKD in Asians (p?=?0.003). TT genotype at the +869 T/C polymorphism was associated with a lower risk of CKD in overall populations and Asians (p?=?0.007 and <10^?4, respectively). CC genotype at the +869 T/C polymorphism was associated with the risk of CKD in Asians (p?=?0.002). T allele at the ?509 T/C polymorphism was associated with the risk of CKD in overall populations and Asians (p?=?0.044 and 0.050, respectively). TT genotype at the ?509 T/C polymorphism was associated with CKD risk in overall populations, Caucasians and Asians (p?<?10^?4, <10^?4, and <10^?4, respectively). No evidence of significant publication bias was noted. In conclusion, T allele at the +869 T/C polymorphism may be a protective factor against CKD risk in Asians. TT genotype at the +869 T/C polymorphism may be an indicator of lower risk of CKD in overall populations and Asians. CC genotype at the +869 T/C polymorphism may predict the susceptibility to CKD in Asians. T allele at the ?509 T/C polymorphism may be an indicator of CKD risk in overall populations and Asians. TT genotype at the ?509 T/C polymorphism was a risk factor for CKD onset in overall populations, Caucasians and Asians.     

Association between MTHFR C677T polymorphism and diabetic nephropathy in the Chinese population: An updated meta‐analysis and review

To clarify the effects of MTHFR C677T polymorphism on the risk of diabetic nephropathy (DN) in the Chinese population, an updated meta‐analysis was performed. Related studies were identified from PubMed, Springer Link, Ovid and Chinese Databases up to 24 February 2015. A total of 15 studies including 1227 DN cases, 586 healthy controls and 1277 diabetes mellitus (DM) controls were involved in this meta‐analysis. Overall, a significantly elevated risk of DN was associated with all variants of MTHFR C677T when compared with the healthy group (T vs C, odds ratio (OR) = 2.22, 95% confidence interval (CI) = 1.88–2.61; TT vs CC, OR = 4.22, 95% CI = 3.02–5.90; TT + CT vs CC, OR = 2.62, 95% CI = 2.07–3.31; TT vs CC + CT, OR = 2.81, 95% CI = 2.08–3.81) or DM (T vs C, OR = 1.78, 95% CI = 1.59–2.00; TT vs CC, OR = 2.95, 95% CI = 2.33–3.73; TT + CT vs CC, OR = 1.93, 95% CI = 1.63–2.29; TT vs CC + CT, OR = 2.31, 95% CI = 1.87–2.84). In subgroup analyses stratified by ethnicity and geographic areas, it revealed the significant results in Chinese Han, in North and South China. The risk conferred by MTHFR C677T polymorphism is higher in North China than in South China. This meta‐analysis showed that the MTHFR C677T variants may influence DN risk in Chinese, and further studies with gene–gene and gene–environment interactions are required for definite conclusions.     

Effect of MTHFR 677C>T on plasma total homocysteine levels in renal graft recipients

BACKGROUND: Hyperhomocysteinemia is an established, independent risk factor for vascular disease morbidity and mortality. The 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphism C677T has been shown to result in increased total homocysteine concentrations on the basis of low folate levels caused by a decreased enzyme activity. The effect of this polymorphism on total homocysteine and folate plasma levels in renal transplant patients is unknown. METHODS: We screened 636 kidney graft recipients for the presence of the MTHFR C677T gene polymorphism. The major determinants of total homocysteine and folate plasma concentrations of 63 patients, who were identified to be homozygous for this gene polymorphism compared with heterozygotes (N = 63), and patients with wild-type alleles (N = 63), who were matched for sex, age, glomerular filtration rate (GFR), and body mass index, were identified by analysis of covariance. The variables included sex, age, GFR, body mass index, time since transplantation, folate and vitamin B12 levels, the use of azathioprine, and the MTHFR genotype. To investigate the impact of the kidney donor MTHFR genotype on total homocysteine and folate plasma concentrations, a similar model was applied in 111 kidney graft recipients with stable graft function, in whom the kidney donor C677T MTHFR gene polymorphism was determined. RESULTS: The allele frequency of the C677T polymorphism in the MTHFR gene was 0.313 in the whole study population [wild-type (CC), 301; heterozygous (CT), 272; and homozygous mutant (TT), 63 patients, respectively] and showed no difference in the patient subgroups with various renal diseases. The MTHFR C677T gene polymorphism significantly influenced total homocysteine and folate plasma concentrations in renal transplant recipients (P = 0.0009 and P = 0.0002, respectively). Furthermore, a significant influence of the GFR (P = 0.0001), folate levels (P = 0.0001), age (P = 0.0001), body mass index (P = 0.0001), gender (P = 0.0005), and vitamin B12 levels (P = 0.004) on total homocysteine concentrations was observed. The donor MTHFR gene polymorphism had no influence on total homocysteine and folate levels. Geometric mean total homocysteine levels in patients homozygous for the mutant MTHFR allele were 18.6 micromol/liter compared with 14.6 micromol/liter and 14.9 micromol/liter in patients heterozygous for the MTHFR gene polymorphism and those with wild-type alleles (P < 0.05 for TT vs. CT and CC). Geometric mean folate levels were lower in CT and TT patients (11.2 and 10.2 nmol/liter) compared with CC patients (13.6 nmol/liter, P < 0.05 vs. CT and TT). CONCLUSIONS: This study demonstrates that homozygosity for the C677T polymorphism in the MTHFR gene significantly increases total homocysteine concentrations and lowers folate levels in kidney graft recipients, even in patients with excellent renal function (GFR more than median). These findings have important implications for risk evaluation and vitamin intervention therapy in these patients who carry an increased risk for the development of cardiovascular disease.     

Association of Megsin 2093C/T, 2180C/T and C25663G gene polymorphism with the risk of IgA nephropathy

The association between megsin 2093C/T, 2180C/T and C25663G gene polymorphisms and IgA nephropathy (IgAN) risk remains unclear. We aimed to evaluate the association between megsin 2093C/T, 2180C/T and C25663G gene polymorphisms and IgAN risk by performing a meta-analysis. Eligible studies were searched according to predefined criteria by using electronic databases. Six articles were identified for the analysis of the association between megsin 2093C/T, 2180C/T and C25663G gene polymorphisms and IgAN risk. 2093C/T C allele was associated with IgAN risk in overall populations and Asians (overall populations: p?=?0.014, Asians: p?=?0.037). 2093C/T CC/TT genotype was not associated with IgAN risk in overall populations, Caucasians and Asians. 2180C/T C allele was correlated with IgAN risk in Caucasians (p?=?0.024). 2180C/T CC/TT genotype was not associated with IgAN risk in overall populations, Caucasians and Asians. C25663G gene polymorphism was not associated with IgAN onset in Asians. In conclusion, megsin 2093C/T C allele may be genetic marker for IgAN susceptibility in overall populations and Asians. 2180C/T C allele may be risk factor for IgAN onset in Caucasians. However, more studies should be performed in the future.     

亚甲基四氢叶酸还原酶基因多态性及同型半胱氨酸水平与冠心病关系的研究

目的：探讨亚甲基四氢叶酸还原酶（MTHFR）C677T基因多态性、血清同型半胱氨酸（Hcy）水平与冠心病发生的关系。方法：收集解放军总医院第一附属医院收治的冠心病患者172例和健康体检者（正常对照组）160例的空腹静脉血,应用基因芯片技术联合检测MTHFR基因C677T多态性位点,并比较冠心病患者和健康体检者的MTHFR基因型及不同MTHFR基因型冠心病患者中血清Hcy水平的变化。结果：①冠心病组与正常对照组MTHFR基因C677T分布频率分别为CC型20.3%比32.5%（P〈0.05）、CT型44.8%比43.1%（P〉0.05）和TT型34.9%比24.3%（P〈0.05）;②冠心病组血清Hcy水平与正常对照组水平之间存在明显差异（P〈0.05）;③冠心病的TT基因型组的Hcy水平明显高于CC基因型组和CT基因型组,差异具有统计学意义（P〈0.05）。结论：冠心病组MTHFR C677T基因TT型分布频率及Hcy水平均高于正常对照组,MFHFR基因C677T TT型与冠心病的发生有关。     

Polymorphism in methylenetetrahydrofolate reductase gene: its impact on plasma homocysteine levels and carotid atherosclerosis in ESRD patients receiving hemodialysis

The methylenetetrahydrofolate reductase (MTHFR) gene polymorphism has been shown to be associated with cardiovascular disease in healthy subjects as well as in patients with end-stage renal disease (ESRD). In this study, we examined the allelic frequency and genotype distribution of the MTHFR gene in 151 Chinese ESRD patients receiving hemodialysis and 135 healthy controls. In addition, we investigated the relationship between the MTHFR gene polymorphism and the plasma homocysteine (Hcy) level as well as the intima-media thickness of common carotid artery (CC-IMT) in these patients. The allelic frequency of the MTHFR gene with the C677T mutation in ESRD patients was 24.5% and that in healthy controls was 23%. Mean plasma Hcy level of the ESRD patients (23.1 +/- 7.4 micromol/l) was significantly higher than that of the controls (10.1 +/- 5.0 micromol/l), but did not correlate with vitamin B(6) and vitamin B(12) status. Moreover, the extent of hyperhomocysteinemia was genetically affected by the C677T mutation of the MTHFR gene. The plasma Hcy levels for the patients with the CC, CT and TT genotypes of the MTHFR gene were 22.3 +/- 6.8, 22.8 +/- 7.3, and 28.3 +/- 2.8 micromol/l, respectively. In addition, we found that the patients bearing the TT genotype had the highest CC-IMT (0.93 +/- 0.07 mm), whereas the lowest values (0.79 +/- 0.13 mm) were observed in those who had the CC genotype. One-way ANOVA showed that the CC-IMT in the patients with the TT genotype was significantly greater than that of the patients with the CC genotype (p < 0.05). Moreover, the mean CC-IMT of the patients carrying either TT or CT genotype of the MTHFR gene was significantly higher than that of the patients bearing the CC genotype (0.86 +/- 0.14 vs. 0.79 +/- 0.13 mm, p = 0.002). Multiple regression analysis, in which the change in CC-IMT was used as the dependent variables, identified age, smoking, the MTHFR genotype (CC = 0, CT = 1, TT = 2) and diabetes mellitus as the independent variables significantly associated with the increase of CC-IMT (p < 0.001). These risk factors jointly explained 43.9% of the CC-IMT variation and age explained most of the variation (R(2) = 0.34). We conclude that both the TT genotype and the T allele of the MTHFR gene are associated with the increase of CC-IMT in hemodialysis patients. The C677T mutation of the MTHFR gene may be an independent risk factor that predicts the development of carotid atherosclerosis in ESRD patients.     

DNA损伤修复基因XRCC1 Arg194Trp基因多态性与中国人群结直肠癌易感性的Meta分析

【摘要】 目的 探讨DNA损伤修复基因XRCC1 Arg194Trp基因多态性与中国人群结直肠癌易感性的关系。方法 按照制定的检索策略,通过计算机和手工检索相关数据库,收集有关XRCC1 Arg194Trp基因多态性与中国人群结直肠癌易感性的病例对照研究,按照纳入标准筛选文献、并从纳入文献中提取相关数据,以病例组和对照组基因型分布的比值比(OR)为效应指标,应用Stata12.0软件进行异质性检验,对各研究原始数据进行Meta合并,并行敏感性分析和发表偏倚的评估。结果〓本Meta分析共纳入11项病例对照研究,累积病例2710例,对照3567例。根据各研究间的异质性,采用不同的模型进行合并效应量。在等位基因比较(T vs C) [OR(95%CI)=1.18(1.01-1.39),P=0.036],纯合子比较模型(TT vs CC) [OR (95%CI)=1.39(1.02-1.90),P=0.038],显性模型(CT/TT vs CC) [OR(95%CI)=2.24(1.78-2.82),P<0.001] 以及隐性模型 (TT vs CT/CC) [OR(95%CI)=1.23(1.02-1.49),P=0.030]均存在显著的统计学差异。发表偏倚评估均未见明显偏倚。结论〓在中国人群中,携带突变等位基因T或突变纯合子TT的人群罹患CRC的风险有所升高,而在显性遗传模型中,携带有CT/TT基因型的人群其CRC的易感性明显升高。     

The SPO11-C631T gene polymorphism and male infertility risk: a meta-analysis

To evaluate the association between the SPO11 gene C631T polymorphism and the risk of male infertility. We conducted a search on PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure (CNKI), China biology medical literature database (CBM), VIP, and Chinese literature database (Wan Fang) on 31 March 2016. Odds ratio (OR) and 95% confidence interval (95%CI) were used to assess the strength of associations. A total of five studies including 542 cases and 510 controls were involved in this meta-analysis. The pooled results indicated that the SPO11 gene C631T polymorphism was significantly associated with increased risk of male infertility (TT?+?CT vs. CC: OR?=?4.14, 95%CI?=?2.48–6.89; CT vs. CC: OR?=?4.34, 95%CI?=?2.56–7.34; T vs. C: OR?=?4.35, 95%CI?=?2.58–7.34). Subgroup analysis of different countries proved the relationship between SPO11 gene C631T polymorphism and male infertility risk in Chinese, but not in Iranian peoples. In conclusion, this study suggested that SPO11 gene C631T polymorphism may contribute as a genetic factor susceptible to cause male infertility. Furthermore, more large sample and representative population-based cases and well-matched controls are needed to validate our results.     

Association of methylenetetrahydrofolate reductase genetic polymorphisms with atlantoaxial dislocation

OBJECT: Genetic mechanisms of atlantoaxial dislocation (AAD) have not previously been elucidated. The authors studied association of polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, which encodes enzymes of the folate pathway (implicated in causation of neural tube defects [NTDs]), in patients with AAD. METHODS: Molecular analysis of MTHFR polymorphisms (677C-->T, cytosine to thymine and, 1298A-->C, adenine to cytosine, substitutions) was carried out using polymerase chain reaction and restriction enzyme digestion in 75 consecutive patients with AAD and in their reducible (nine patients, 12%) and irreducible (66 patients, 88%) subgroups. Controls were 60 age- and sex-matched patients of the same ethnicity. Comparisons of genotype and allele frequencies were performed using a chi-square test (with significance at p < 0.05). RESULTS: The CT genotype frequency of MTHFR 677C-->T polymorphism was significantly increased in the full group of patients with AAD (odds ratio [OR] 3.00, 95% confidence interval [CI] 1.28-7.14, p = 0.005) as well as in the irreducible subgroup (OR 2.81, 95% CI 1.17-6.86, p = 0.01). The frequency of T alleles was also higher in the AAD group (25.3%) than in controls (15%). The comparison of the combined frequency of CT and TT genotypes with the frequency of the CC genotype again showed significant association in AAD (OR 2.63, 95% CI 1.98-5.90, p = 0.009) and the irreducible (OR 2.5, 95% CI 1.1-5.74, p = 0.016) subgroup. There was, however, no significant association of MTHFR 1298A-->C polymorphism with AAD. CONCLUSIONS: Both MTHFR 677C-->T polymorphism and higher T allele frequency have significant associations with AAD, especially the irreducible variety. Perhaps adequate supplementation of periconceptional folic acid to circumvent effects of this missense mutation (as is done for prevention of NTDs) would reduce the incidence of AAD.     

血管内皮生长因子936C／T基因多态性与结直肠腺瘤易感性的关系

目的探讨血管内皮生长因子（VEGF）1498C／T、936C／T基因多态性与结直肠腺瘤易感性的关系。方法对224份结直肠腺瘤及200份正常对照标本进行研究．应用TaqMa。探针法检测VEGF1498C／T、936C／T基因型,搜集相对应的临床病理资料。结果与VEGF936CC基因型相比．CT基因型和CT＋TT基因型患者结直肠腺瘤的发生危险显著增加（DR=2．00,95％CI：1．23—3．25,P=0．006;OR=2．04,95％C1：1．28—3．26,P=0．003）;与VEGF936-C等位基因相比,T等位基因携带者结直肠腺瘤的发生危险亦显著增加（DR=1．91,95％CI：1．25—2．91．P=0．003）。结直肠腺瘤患者为VEGF936CT＋TT基因型或携带T等位基因,其病理类型倾向于绒毛状腺瘤（OR=2．54,95％CI：1．12—5．75,P：0．040;OR=3．08,95％CI：1．64-5．80,P=0．001）。VEGF1498C／T基因多态性在腺瘤组与对照组间的差异无统计学意义（19〉0．05）。结论VEGF936C／T基凶多态性与结直肠腺瘤易感性密切相关。     

Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is associated with osteoporotic vertebral fractures, but is a weak predictor of BMD

Osteoporosis is a common disease with a strong genetic component. Linkage studies have suggested linkage between BMD and loci on chromosome 1. The MTHFR gene is located on chromosome 1. MTHFR catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methylenetetrahydrofolate, which is used for homocysteine methylation to methionine. The rare genotype (TT) of the C677T polymorphism has previously been demonstrated to be associated with increased plasma homocysteine levels in individuals with inadequate plasma folate levels. Recently, the TT genotype has been found to be associated with reduced bone mass. We therefore examined if the C677T polymorphism in the MTHFR gene is associated with changes in bone mass and risk of osteoporotic fractures in 388 osteoporotic patients and 336 normal individuals. The distributions of the genotypes CC, CT and TT in women with osteoporotic vertebral fractures and normal controls were 43.5%, 42.2% and 14.3% and 52.0%, 42.0% and 8.0%, respectively, ²=5.62, P=0.06. Since studies of the functionality of this polymorphism have revealed that only the TT genotype is associated with biochemical changes, we also compared the prevalence of the TT genotype versus the CT- and CC genotypes in patients and controls and found that the TT genotype is significantly more common in women with vertebral fractures (14.3%) compared with normal controls (8.0%), ²=4.31, P<0.05. Logistic regression analysis demonstrated that vertebral fractures were significantly associated with BMD (lumbar spine) and height but only marginally with the MTHFR genotype (P=0.06). Multiple linear regression analysis revealed that weight, age and the MTHFR polymorphism were predictors of lumbar spine BMD in women. However, age- and gender-corrected BMD of the lumbar spine and the hip was not significantly different between MTHFR genotypes. Furthermore, individuals with the TT genotype did not have BMD significantly lower than the combined group of individuals with the CT- or CC genotypes. In conclusion, we have demonstrated that the rare TT genotype of the C677T polymorphism in the MTHFR gene is associated with increased risk of osteoporotic fractures in women and a weak predictor of lumbar spine BMD.     

Insertion/deletion (I/D) polymorphism of angiotensin-converting enzyme gene in steroid-resistant nephrotic syndrome for children: a genetic association study and meta-analysis

An assessment of the association of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism with steroid-resistant nephrotic syndrome (SRNS) risk in children is still controversial. A meta-analysis was performed to evaluate the relation between ACE gene polymorphisms and SRNS susceptibility. The relevant studies were screened from electronic database and eligible investigations were synthesized using meta-analysis methods. Seven investigations were identified for the analysis of association between ACE I/D gene polymorphism and SRNS risk in children, including five in Asians, one in Caucasians, and one in Africans. There was not a markedly positive association between D allele or DD genotype and SRNS susceptibility in Asians (OR = 1.60, p = 0.26; OR = 1.90, p = 0.38) and for Caucasian population (OR = 0.92, p = 0.86; OR = 0.27, p = 0.22). However, an association of D allele with SRNS susceptibility was observed (OR = 4.67, p = 0.003) in Africans, but not for DD genotype (OR = 6.00, p = 0.05). Interestingly, II genotype seemed to play a positive role against SRNS onset for Asians and African children (OR = 0.51, p = 0.02; OR = 0.07, p = 0.02), but not for Caucasians (OR = 0.33, p = 0.30). In conclusion, our results indicate that D allele or DD homozygous might not be a significant genetic molecular marker for the development of SRNS in Asians and Caucasian children. However, D allele seemed be associated with SRNS risk for Africans but DD genotype did not.     

Effects of the C677T and A1298C polymorphisms of the MTHFR gene on the genetic predisposition for diabetic nephropathy.

BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) is a regulatory enzyme of homocysteine metabolism. The C677T polymorphism of the MTHFR gene has been reported to be associated with elevated plasma homocysteine in patients with low folic acid intake. A recently reported second common polymorphism, A1298C, may increase homocysteine, but only in individuals carrying the T677 allele. This study aimed to investigate the influence of the C677T and A1298C polymorphisms of the MTHFR gene on the development of diabetic nephropathy in Caucasian patients with type 2 diabetes. METHODS: We genotyped 429 type 2 diabetic patients for the C677T and A1298C polymorphisms using standard PCR-based protocols, and divided them into three groups based on renal status: 159 patients with normoalbuminuria, 149 with microalbuminuria, and 121 with persistent proteinuria and chronic renal failure (CRF). The C677T and A1298C genotype frequencies were compared among the three groups. RESULTS: Although the frequencies of the CT and TT genotypes of the C677T polymorphism tended to increase with each stage of diabetic nephropathy (53, 56 and 63% in normoalbuminuria, microalbuminuria and proteinuria/CRF, respectively), these differences were not significant. When male and female patients were analysed separately, the effect was seen only in males. The CT + TT genotype was present in 46% of male patients with normoalbuminuria, in 57% with microalbuminuria and in 68% with proteinuria/CRF (OR = 2.46; 95% CI 1.13-5.38). There were no differ-ences in the A1298C polymorphism among the three groups. CONCLUSIONS: These findings indicate that the C677T polymorphism is a risk factor for diabetic nephrop-athy in male patients with type 2 diabetes.     

Association of a common allelic polymorphism (C677T) in the methylene tetrahydrofolate reductase gene with a reduced risk of osteoporotic fractures. A case control study in Danish postmenopausal women

Twin studies indicate a substantial genetic component in the development of osteoporosis. One of the latest studied candidate genes is the one coding for methylene tetrahydrofolate reductase (MTHFR) (C677T) in which a point mutation gives rise to a thermolabile variant of MTHFR. The aim of this study was to investigate the influence of this mutation on peripheral measures of bone density and on the odds ratios (OR) for hip and lower forearm fracture in a case control study of Danish postmenopausal women. A total of 74 women with lower forearm fracture, 41 women with hip fracture, and 207 age-matched controls were included. All had broadband ultrasound attenuation (BUA) and speed of sound (SOS) measured at the heel as well as bone mineral density (BMD) measured by dual X-ray absorptiometry at the distal forearm. The MTHFR (C677T) genotypes were determined using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Only 2 of 21 individuals with the TT genotype had sustained a fracture as opposed to 46 of 142 with the CT genotype and 67 of 159 with the CC genotype (P = 0.007). Using logistic regression, the following odds ratios were found when comparing the individuals homozygotic for the C-allele with those homozygotic for the T-allele: lower forearm fracture OR = 3.93 (1.25; 12.40, P = 0.02), hip fracture OR = 6.99 (l.35; 36.92, P = 0.02) and the fractures combined OR = 4.33 (1.73; 10.81, P = 0.002). In this study, the MTHFR (C677T) genotypes were not significantly associated with BMD at the lower forearm or with ultrasound parameters measured at the calcaneus. However, a significant increase in the odds ratio of fracture was found for the wild-type C-allele.