Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and susceptibility to diabetic nephropathy in Chinese type 2 diabetic patients: a meta-analysis

Abstract

The association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and diabetic nephropathy (DN) or diabetes mellitus (DM) risk has been widely reported, but the results are still debatable. To investigate the role of MTHFR C677T polymorphism on DM or DN, 13 separate studies in the Chinese population on the relation between MTHFR C677T polymorphism and DM or DN were analyzed by a meta-analysis. Five genetic models were used to estimate the association between MTHFR C677T polymorphism and the risk of DM or DN. Overall, our meta-analysis for DN versus healthy controls produced significant results for all genetic contrasts except for the co-dominant model (allele contrast: OR?=?2.24, 95%CI: 1.88–2.65, p?<?0.00001, P_{heterogeneity}?=?0.49). However, the meta-analysis for DM versus healthy controls produced non-significant results for all contrasts (allele contrast: OR?=?1.12, 95%CI: 0.92–1.35, p?=?0.25, P_{heterogeneity}?=?0.07). In addition, the meta-analysis for DM versus DN produced significant results for all contrasts (allele contrast: OR?=?1.88, 95%CI: 1.65–2.15, p?<?0.00001, P_{heterogeneity}?=?0.83). The current meta-analysis suggested that MTHFR C677T polymorphism might influence DN risk, but not for DM in the Chinese population.     

Methylenetetrahydrofolate reductase polymorphism (MTHFR C677T) and bone mineral density in Chinese men and women

The relationship between MTHFR (C677T) genotypes of the methylenetetrahydrofolate reductase, bone mineral density (BMD), and vertebral fracture was studied in 657 Chinese men and women. No association between MTHFR (C677T) and BMD was found in postmenopausal women (aged 55–59 years, n = 178), elderly women (aged 70–79 years, n = 247), or elderly men (aged 70–79 years, n = 232) at the hip, spine, or total body (P > 0.05 by ANCOVA). In all study groups, there was no effect of an interaction between MTHFR (C677T) and daily dietary calcium intake on BMD (P > 0.05 for the interaction effects by two-way ANCOVA). No statistically significant association was observed between MTHFR (C677T) genotypes and vertebral fracture. The MTHFR (C677T) genotypes for CC, CT, and TT among elderly women with or without vertebral fracture were 5%, 33%, 62%; 6%, 37%, and 57%, respectively, and those for elderly men with and without vertebral fracture were 9%, 31%, 60%; 5%, 35%, and 60%, respectively. The prevalence of TT in our study group was 5% compared to 8% in the Danish or 18.6% in the Japanese. We found no association between MTHFR (C677T) and BMD of Chinese men or women. It would be interesting to study the interactions with folate, B12, and homocysteine.     

Relationship between methylenetetrahydrofolate reductase (MTHFR) A1298C gene polymorphism and type 2 diabetic nephropathy risk: a meta-analysis

Relationship between methylenetetrahydrofolate reductase (MTHFR) A1298C gene polymorphism and type 2 diabetic nephropathy (T2DN) risk is still unclear. This study was performed to evaluate if there is an association between the MTHFR A1298C gene polymorphism and T2DN risk using meta-analysis. The relevant reports were searched and identified from PubMed, Cochrane Library on 1 October 2013, and eligible studies were included and synthesized. Eight reports were recruited into this meta-analysis for the association of the MTHFR A1298C gene polymorphism with T2DN risk. The MTHFR A1298C C allele or CC genotype was shown to be not associated with T2DN risk (C allele: OR?=?0.76, 95% CI: 0.43–1.34, p?=?0.34; CC genotype: OR?=?1.18, 95% CI: 0.63–2.22, p?=?0.60). Interestingly, AA genotype was associated with the T2DN risk (OR?=?0.68, 95% CI: 0.49–0.96, p?=?0.03). In the sensitivity analysis according to the Hardy–Weinberg equilibrium (HWE), the results were consistent with those in non-sensitivity analysis. However, in the sensitivity analysis according to the control source from hospital, sample size of case (≥100), sample size of case (<100), the MTHFR A1298C gene polymorphism was not associated with T2DN risk. In conclusion, the MTHFR A1298C gene polymorphism was not associated with T2DN risk. However, additional studies are required to firmly establish a correlation between the MTHFR A1298C gene polymorphism and T2DN risk.     

Effect of MTHFR C677T genotype on survival in type 2 diabetes patients with end-stage diabetic nephropathy.

BACKGROUND: The MTHFR C677T single nucleotide polymorphism TT genotype is associated with increased levels of plasma homocysteine and possibly an effect on cardiovascular mortality. We evaluated the effect of C677T genotype on mortality in a large end-stage renal disease (ESRD) cohort. METHODS: C677T genotype was determined in 439 Caucasians with end-stage diabetic nephropathy (DNP) (cases) recruited from 30 dialysis centres in Southern Germany. A total of 482 type 2 diabetes patients without DNP (no microalbuminuria) at inclusion served as a genotype control collective. Patients were prospectively followed for 4 years. Primary endpoint was all-cause mortality. RESULTS: In contrast to controls, the genotype distribution in cases was not in Hardy-Weinberg equilibrium (HWE, P = 0.003), due to a less than expected number of patients with the TT genotype. The requirements of HWE were met in cases with < 2 years dialysis therapy prior to study inclusion (n = 219). TT genotype was associated with a decreased body mass index (P = 0.002) and long diabetes duration in dialysis patients (P = 0.03). However, TT genotype was not associated with an increased risk of all-cause or cardiac mortality in the total dialysis collective or the subgroup. Also, we observed no association of MTHFR genotype with cardiovascular morbidity in cases or controls (P > 0.05), or with an increased rate of progression to novel microalbuminuria. CONCLUSION: MTHFR 677TT genotype was significantly underrepresented in patients with ESRD in our study, but was not associated with premature mortality in these patients. We found no evidence for survival bias due to C677T genotype in the ESRD cohort, or bias due to genetically determined accelerated progression to novel microalbuminuria in the controls. However, we cannot exclude that the TT genotype protects from progression from microalbuminuria to more advanced stages of DNP, or that TT genotype is associated with premature mortality before a patient progresses to ESRD.     

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.     

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.     

The synergistic effect of bone mineral density and methylenetetrahydrofolate reductase (MTHFR) polymorphism (C677T) on fractures

A functional polymorphism in methylenetetrahydrofolate reductase (MTHFR) has been identified at codon 677 (C677T). The T-allele variant (valine type) has lower enzyme activity than the wild type (C-allele or alanine type), resulting in a slightly elevated homocysteine level, which has been recently recognized as a risk factor for fracture. However, whether subjects bearing the T allele have higher susceptibility to fractures is still controversial. We have investigated the effects of MTHFR polymorphism on fracture susceptibility in Japanese postmenopausal women. A total of 502 postmenopausal ambulatory Japanese women were followed up for 5.1 ± 3.4 (mean ± SD) years, and a total of 155 patients with incident fractures (121 patients with vertebral fractures and 34 cases with fractures at other sites) were recorded. When compared with the patients without any fractures, the patients with incident fractures were older, had more prevalent fractures, had higher urinary levels of bone turnover markers as well as plasma homocysteine level, but were shorter in body height and had lower bone mineral density. The prevalence of the TT genotype of MTHFR was significantly higher in the patients with incident fractures compared to the other genotypes. The subjects with the TT genotype had a higher incidence rate of fracture and higher plasma level of homocysteine than the subjects bearing the non-TT genotype. This relationship was observed in both osteoporotic and nonosteoporotic groups. The hazard ratio for TT genotype without osteoporosis, non-TT genotype with osteoporosis, and TT genotype with osteoporosis was 1.49 (0.91–2.45), 3.64 (2.50–5.29), and 7.21 (4.34–11.97), respectively, compared to the non-TT genotype without osteoporosis. A higher hazard ratio for the TT genotype with osteoporosis was still apparent after adjustment for age, body size, and number of prevalent vertebral fractures. These results indicate that the TT genotype of MTHFR may be a risk factor for future fracture in addition to the traditional risk factors.     

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.     

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 A1298C polymorphism and diabetes risk: evidence from a meta-analysis

Aim: The relationship between the methylenetetrahydrofolate reductase (MTHFR) A1298C polymorphism and the susceptibility of diabetes remains inclusive or controversial. For better understanding of the influence of MTHFR A1298C polymorphism on diabetes risk, we performed this meta-analysis. Methods: All related articles were identified through a search of PubMed, Embase, Chinese Biomedical Literature Database (CBM, Chinese), China National Knowledge Infrastructure (CNKI), and Wangfang Database (Chinese). The relationship between the MTHFR A1298C polymorphism and diabetes susceptibility was conducted by odds ratios (ORs) and 95% confidence intervals. Results: Total of six studies with 897 cases and 852 controls were included in our meta-analysis. Overall, the significance associated was found between MTHFR A1298C polymorphism and the susceptibility of diabetes under recessive model (CC vs. AC/AA: OR?=?1.70, 95% CI?=?1.18–2.45, p?=?0.004). On the subgroup analysis according to ethnicity, the results indicated that MTHFR A1298C polymorphism has a significant association with diabetes in Asian population under dominant model (CC/AC vs. AA: OR?=?1.31, 95% CI?=?1.003–1.72, p?=?0.047). However, there was no association found between MTHFR A1298C polymorphism and diabetes susceptibility in Caucasians. Conclusions: The results indicated that the MTHFR A1298C polymorphism is a dangerous factor for diabetes, especially for Asians.     

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.     

Angiotensinogen gene M235T polymorphism is not associated with diabetic nephropathy

BACKGROUND.: There is agreement that a family history of hypertension (HT),is a predictor for the risk of diabetic nephropathy (DN) inpatients with type 2 diabetes, and possibly also type 1 diabetes.It follows that genes related to the risk of hypertension mustalso be considered candidate genes for DN. The 235T allele ofthe angiotensinogen gene was found to be related to primaryHT. METHODS.: To examine whether it is predictive for DN as well, we examinedthe angiotensinogen gene polymorphism in 230 healthy local controls,423 patients with type 1 diabetes (n=180 with DN; n=243 withoutDN) and 663 patients with type 2 diabetes (n=310 with DN; n=353without DN). The angiotensinogen gene M235T polymorphism wasdetermined using PCR amplification. RESULTS.: The following results were obtained (i) no significant differenceof genotype distribution (type 1: MM/MT/TT(%) 27.6/57.2/15.2vs. 27.2/56.1/16.7 (P=0.92); type 2: MM/MT/TT (%) 31.7/48.2/20.1vs. 32.9/46.8/20.3 (P=0.93)) or allele frequencies (type 1:M 0.56 vs. 0.55 (P=0.795); type 2: M 0.56 vs. 0.56 (P=0.86))was found, between diabetic patients with or without DN, (ii)no difference was found between normotensive and hypertensivediabetic patients. CONCLUSION.: The data argue against a role of the angiotensinogen gene M235Tpolymorphism in the manifestation of diabetic nephropathy orhypertension in diabetic patients.     

The ACACB gene rs2268388 polymorphism is associated with nephropathy in Caucasian patients with diabetes: a meta-analysis

Abstract

To date, case–control studies on the association between a single-nucleotide polymorphism (SNP), rs2268388, in the acetyl-coenzyme A carboxylase beta (ACACB) gene and diabetic nephropathy have provided controversial results. To clarify the effect of rs2268388 on the risk of diabetic nephropathy, a meta-analysis of all case–control studies was performed. The fixed effects and random effects models showed that the C allele was associated with a decreased susceptibility risk of diabetic nephropathy compared with the T allele among Caucasian patients with diabetes. The contrast of the recessive model produced the same pattern of results as the allele contrast. Our pooled data suggest a significant association exists between rs2268388 and diabetic nephropathy among Caucasian patients with diabetes.     

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.     

Genetic susceptibility to nephropathy in Pima Indians with type 2 diabetes mellitus

Summary: In Pima Indians, the incidence of end-stage renal disease, nearly all of which is attributable to type 2 diabetes mellitus, is more than 20 times that in the general United States population. Studies in the Pimas indicate that factors other than diabetes per se enhance susceptibility to the development of diabetic nephropathy. Aggregation of renal disease in families, a relationship between parental blood pressure and diabetic nephropathy in the offspring, and an association between higher prediabetic blood pressure and the occurrence of renal disease after the onset of diabetes all point to individual differences in susceptibility. Although clustering of environmental exposures may be responsible for these findings, they may also represent genetic transmission of susceptibility to renal disease. Recently, linkage analyses were performed in 98 diabetic sib-pairs, both affected by diabetic nephropathy. Two adjacent markers on chromosome 7 met the criteria for suggestive linkage with two-point analysis. Positioned between these markers is the gene coding for aldose reductase. Polymorphisms of this locus are associated with diabetic microvascular complications in other populations. Linkage studies provide evidence that familial aggregation of diabetic renal disease reflects, in part, genetic transmission of susceptibility that appears to be independent of the transmission of diabetes.