Polymorphisms in folate-metabolizing genes and risk of idiopathic male infertility: a study on a Russian population and a meta-analysis

Do aluminum, boron, arsenic, cadmium, lipoperoxidation, and genetic polymorphism determine male fertility?

Male infertility is a world multifactorial problem modulated by environmental and genetic factors. Male aspects account for 20-50 % of infertility cases. Our results are unique because they treat the importance of components participating in the determination of male infertility (environmental and immunogenetic determinants, seminological analysis, lipoperoxidation, genetic determinants, role of aluminum, arsenic, cadmium and boron). We analyzed agents affecting male reproductive potential (aluminum, boron, cadmium, arsenic, lipid peroxidation, gene polymorphisms (MTHFRv.C677T (rs1801133) (chromosome-1) and IL-4v.C589T (rs2243250) (chromosome-5) in men with semen disorders (n=76) and with normozoospermia (n=87) from Central Poland. Polymorphisms of MTHFRv.C677T and IL-4v.C589T genes indirectly shape toxic metals concentration and lipoperoxidation but do not exert direct influence on male fertility disorders (monomorphism and lack of differences in genotypes frequency). Men with genotype TT or CC (IL-4v.C589T) show some differentiation in elements concentration and intensity of lipoperoxidation. Analysis of TT or CC (IL-4v.C589T) genotype brought correlations with B, Al, Cd, and lipoperoxidation (P<0.05) and suggesting that mentioned factors jointly shape male reproductive capability. Toxic metals may play an important role in shaping of men genetic polymorphisms, since Cd was identified as a factor increasing risk of qualification to infertile group, predisposing to fertility disorders. B, Al and Cd may be considered as important modulators of reproductive condition. However, lipoperoxidation as an isolated predictive parameter does not produce convincing results in male reproductive potential (higher MDA concentration in healthy men). Our results may be helpful in the diagnosis of male infertility, in the reduction of idiopathic cases of unknown origin and in implementation of targeted and more effective treatment (pharmacological, hormonal). Identification of environmental stressors and their correlations with fertility disorders can help to eliminate or reduce the impact of factors unfavorable to fertility. Our results highlight the importance of environmental and immunogenetic factors in shaping of defensive potential against destruction of spermatozoa and infer a role of oxidative stress in the induction of gene polymorphisms, affecting male fertility.

Correlation of MTHFR C677T Polymorphism with Male Infertility among Indian Population: Case-Control Study

This case-control study investigated the correlation between male infertility in India and the methylenetetrahydrofolate reductase (MTHFR) C677T variant. Infertile males were utilized as the case group in the study, whereas fertile individuals served as the control group. The C677T polymorphism was genotyped using PCR-RFLP analysis (polymerase chain reaction-restriction fragment length polymorphism). The Chi-square test and odds ratio calculation were implemented in the statistical analysis method for assessing the correlation between the C677T mutation and infertility. The results of this study revealed that the case group (9.4%) had a substantially greater prevalence of the C677T variation than the control group (1.6%). The C677T variation is significantly associated with male infertility by the Chi-square test (P value: 0.006). According to these results, the MTHFR gene›s C677T variation may increase the incidence of male infertility in the Indian population. Additional evaluations were also conducted to investigate the association between the C677T variation and particular infertility indicators. The C677T variation has been demonstrated to have been significantly correlated with a low or missing sperm count (p 0.05). These findings highlight the potential function of the MTHFR gene in reproductive health and advance our understanding of the genetic underpinnings of male infertility. It is encouraged to investigate the underlying mechanisms and additional investigation of the underlying mechanisms and to support the creation of individualized approaches to diagnosing and managing male infertility.

Role of MDR1 Gene Polymorphisms in Human Male Infertility: A Meta-Analysis

The present meta-analysis is performed to determine the association of C1236T and C3435T polymorphisms in the MDR1 gene. Google Scholar, PubMed, and Science Direct were searched. A total of 47 studies were retrieved, of which only three case-control studies, consisting of 490 cases and 423 controls, met the selection criteria. Odds ratios (ORs) for MDR1 C1236T were as follows: Allelic model (T vs. C): OR = 1.06 [0.83, 1.35]; Additive model (TT vs. CC): OR = 0.91 [0.53, 1.56]; Dominant model (TT+CT vs. CC): OR = 0.83 [0.55, 1.24]; and Recessive model (TT vs. CT+CC): OR = 1.43 [0.95, 2.17]. However, for MDR1 C3435T: Allelic model (T vs. C): OR = 1.06 [0.83, 1.35]; Additive model (TT vs. CC): OR = 1.18 [0.75, 1.88]; Dominant model (TT+CT vs. CC): OR = 1.42 [0.99, 2.04]; and Recessive model (TT vs. CT+CC): OR = 0.90 [0.61, 1.33]. None of the four models presented a significant association of either polymorphism with the risk of infertility in men (p >.05). The present study indicates that MDR1 gene polymorphisms might not be a risk factor for male infertility. Further studies with a larger sample size are needed to be conducted to confirm the findings of the present study.

Genetic variations as molecular diagnostic factors for idiopathic male infertility: current knowledge and future perspectives

INTRODUCTION

Infertility is a major health problem, worldwide, which affects 10-15% of couples. About half a percent of infertility cases are related to male-related factors. Male infertility is a complex disease that is the result of various insults as lifestyle issues, genetics, and epigenetic factors. Idiopathic infertility is responsible for 30% of total cases. The genetic factors responsible for male infertility include chromosomal abnormalities, deletions of chromosome Y, and mutations and genetic variations of key genes.

AREAS COVERED

In this review article, we aim to narrate performed studies on polymorphisms of essential genes involved in male infertility including folate metabolizing genes, oxidative stress-related genes, inflammation, and cellular pathways related to spermatogenesis. Moreover, possible pathophysiologic mechanisms responsible for genetic polymorphisms are discussed.

EXPERT OPINION

Analysis and assessment of these genetic variations could help in screening, diagnosis, and treatment of idiopathic male infertility.

A Association of MTHFR C677T and MTRR A66G Gene Polymorphisms with Iranian Male Infertility and Its Effect on Seminal Folate and Vitamin B12

Background

The relation between key enzymes in regulation of folate metabolism and male infertility is the subject of numerous studies. We aimed to determine whether 5, 10-methylenetetrahydrofolate reductase (MTHFR) C677T and methionine synthase reductase (MTRR) A66G genotypes are associated with male infertility in Iranian men and to evaluate its effect on seminal levels of folate and vitamin B12.

Materials and Methods

In this retrospective study, semen and peripheral blood samples were collected from 254 men with oligoasthenoteratozoospermia (OAT) and 77 normozoospermic men who attended Avicenna infertility clin- ic. Single nucleotide polymorphism (SNP) analysis was carried out in genomic DNA by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for MTHFR C677T and MTRR A66G gene poly- morphisms.

Results

In MTHFR C677T, our founding showed that T carrier was conversely lower in OAT than normozoospermic men (χ²-test=7.245, P=0.02) whereas in MTRR A66G, A and G carrier showed no significant difference between the two groups (χ²-test=1.079, P=0.53). The concentration of seminal folate was not different between normozoospermic (18.83 ± 17.1 ng/ ml) and OAT (16.96 ± 14.2 ng/ml) men (P=0.47). The concentration of vitamin B₁₂ was slightly higher in normozospermic men (522.6 ± 388.1 pg/ml) compared to OAT men (412.9 ± 303.6 pg/ml, P=0.058).

Conclusion

The MTHFR C677T and MTRR A66G have no effect on the concentrations of seminal folate and vitamin B₁₂. The present study showed that two SNPs of MTRR A66G and MTHFR C677T cannot be seen as a risk factor for male factor subfertility.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and male infertility risk: An updated meta-analysis

BACKGROUND

18 previous meta-analyses have been published on the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms with male infertility risk. However, results of the previous meta-analyses were still inconsistent. Moreover, their meta-analyses did not assess false-positive report probabilities except one study. Furthermore, many new studies have been published, and therefore an updated meta-analysis and re-analysis of systematic previous meta-analyses were performed to further explore these issues.

OBJECTIVES

To determine the association between MTHFR C677T and A1298C polymorphisms and male infertility risk.

METHODS

Crude odds ratios and their 95% confidence intervals were used to assess the association between MTHFR C677T and A1298C polymorphisms and male infertility risk. We used the Bayesian false discovery probability (BFDP) to assess the credibility of statistically significant associations.

RESULTS

Fifty-nine studies were included concerning the MTHFR C677T and 28 studies were found on the MTHFR A1298C with male infertility risk. Overall, the MTHFR C677T was associated with increased male infertility risk in overall populations, Africans, East Asians, West Asians, South Asians, azoospermia, and Oligoasthenoteratozoospermia (OAT). In further sensitivity analysis and BFDP test, the positive results were only considered as "noteworthy" in the overall population (TT vs CC: BFDP = 0.294, CT + TT vs CC: BFDP = 0.300, T vs C: BFDP = 0.336), East Asians (TT vs CC: BFDP = 0.089, TT vs CT + CC: BFDP = 0.020, T vs C: BFDP < 0.001), West Asians (TT vs CC: BFDP = 0.584), hospital-based studies (TT vs CC: BFDP = 0.726, TT vs CT + CC: BFDP = 0.126), and OAT (TT vs CT + CC: BFDP = 0.494) for MTHFR C677T. In addition, a significantly increased male infertility risk was found in East Asians and population-based studies for MTHFR A1298C. However, we did not find that the positive results were considered as "noteworthy" in the overall and all subgroup analyses for MTHFR A1298C.

CONCLUSIONS

In summary, this study indicates that the MTHFR C677T is associated with increased male infertility risk in East Asians, West Asians, and OAT. No significant association was observed on the MTHFR A1298C with male infertility risk.

Association of the MTHFR 677C>T and 1298A>C polymorphisms and male infertility risk: a meta-analysis

BACKGROUND AND OBJECTIVES

One of the possible male sterility risk factors are polymorphisms of Methylenetetrahydrofolate reductase (MTHFR). However, the epidemiologic investigations described inconsistent results regarding MTHFR polymorphism and the risk of male infertility. For that reason, we carried out a meta-analysis of published case-control studies to re-examine the controversy.

METHODS

Electronic searches of Cochrane, EMBASE, Google Scholar, and PubMed were conducted to select eligible studies for this meta-analysis (updated to May 2019). According to our exclusion and inclusion criteria, only high-quality studies that remarked the association between MTHFR polymorphisms and male infertility risk were included. The Crude odds ratio (OR) with a confidence interval of 95% (CI) was used to assess the relationship between MTHFR polymorphism and male infertility risk.

RESULTS

Thirty-four case-control studies with 9662 cases and 9154 controls concerning 677C/T polymorphism and 22 case-control studies with 5893 cases and 6303 controls concerning 1298A/C polymorphism were recruited. Both MTHFR polymorphisms had significant associations with male infertility risk (CT + TT vs. CC: OR = 1.37, 95% CI: 1.21-1.55, P = 0.00, I² = 41.9%); (CC vs. CA + AA: OR = 0.82, 95% CI: 0.52-1.30, P = 0.04, I² = 50.1%). Further, when stratified by ethnicity, the significant association results were observed in Asians and Caucasians for 677C/T and just Asians for 1298A/C.

CONCLUSIONS

Some of MTHFR polymorphisms like MTHFR 677C > T are associated with an elevated male infertility risk. To confirm our conclusion and to provide more accurate and complete gene-environment communication with male infertility risk, more analytical studies are needed.

Contribution of MTR A2756G polymorphism and MTRR A66G polymorphism to the risk of idiopathic male infertility

BACKGROUND

Methionine synthase reductase gene (MTRR A66G) polymorphism and methionine synthase gene (MTR A2756G) polymorphism have shown an association with idiopathic male infertility risk in several ethnic populations. However, their small sample sizes and inconsistent outcomes have prevented strong conclusions. We performed a meta-analysis with published studies to evaluate the associations of the 2 single nucleotide polymorphisms (SNPs) and idiopathic male infertility risk.

METHODS

A thorough literature search was performed up to Jun 21, 2019 with Medline, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), China Biology Medical literature (CBM), China Science and Technology Journal Database (VIP), and Chinese literature (Wan Fang) databases. Odds ratio (OR) and 95% confidence interval (95% CI) were used to assess the strength of associations.

RESULTS

Seventeen studies including 3269 cases and 3192 controls met the inclusion criteria. Our meta-analysis showed that the MTR A2756G mutation may contribute to genetic susceptibility to the risk of idiopathic male infertility in Non-Asians, but not to Asian population, whereas the MTRR A66G polymorphism may be unrelated to idiopathic male infertility in both Non-Asian and Asian populations. In the stratified analysis by infertility type, the MTR A2756G polymorphism was a risk factor for both non-obstructive azoospermia (NOA) and oligoasthenoteratozoospermia (OAT) patients. However, the MTRR A66G polymorphism is associated with risk for OAT in Asian, but not in Non-Asian population.

CONCLUSION

This meta-analysis suggested that the MTR A2756G and MTRR A66G polymorphisms were risk factors for idiopathic male infertility. Studies with larger sample sizes and representative population-based cases and well-matched controls are needed to validate our results.

Investigation of the association of idiopathic male infertility with polymorphisms in the methionine synthase (MTR) gene

OBJECTIVE

Spermatogenesis is a complex process that is regulated by a number of genes, some of which are involved in folate-dependent 1-carbon metabolism. Methionine synthase (encoded by MTR) is a key enzyme participating in this pathway. This study aimed to investigate the relationship of the MTR 2756A > G polymorphism with idiopathic male fertility in the Iranian population.

METHODS

The participants of this study included 100 men with idiopathic infertility and 100 healthy men as the control group. Genotyping of MTR 2756A > G was performed using the polymerase chain reaction and restriction fragment length polymorphism technique. The obtained data were analyzed using SPSS ver. 20.0 with a level of confidence of p< 0.05.

RESULTS

The frequencies of the A and G alleles at this locus were 77% and 23% in infertile patients and 84% and 16% in the control group, respectively. The frequencies of the GG, GA, and AA genotypes were 5%, 36%, and 59% in the infertile patients versus 3%, 27%, and 70% in the control group, respectively. No significant difference was observed in any genetic models.

CONCLUSION

In general, the findings of this study suggest that the MTR 2756A > G single-nucleotide polymorphism is not a predisposing factor for idiopathic infertility in men.

The relevance of MTHFR C677T, A1298C, and MTRR A66G polymorphisms with response to male infertility in Asians: A meta-analysis

Although published studies have reported the association between MTHFR C677T (rs 1801133), A1298C (rs 1801131), and MTRR A66G (rs1801394) polymorphisms and male infertility in Asian populations, the results are conflicting. In order to accurately evaluate the relevance, a meta-analysis was performed.We searched for potential studies in 4 databases, containing PubMed, ScienceDirect, China National Knowledge Infrastructure (CNKI), and Wanfang database until May 31, 2018. The summarized odds ratio (OR) with 95% confidence intervals (95% CI) were calculated to evaluate the relevance in 5 genetic models. The heterogeneity test, sensitivity analysis, and publication bias test was performed by Review Manager 5.3 software.Overall, 22 case-control studies with 5049 cases and 4157 controls were included in this meta-analysis, which contained 20 studies of MTHFR C677T polymorphism, 12 studies of MTHFR A1298C polymorphism and 4 studies of MTRR A66G polymorphism. The results indicated that MTHFR C677T, A1298C, and MTRR A66G polymorphisms were significantly associated with male infertility in Asian populations (Dominant model: MTHFR CC + CT vs TT: OR = 0.60, 95% CI (0.53, 0.67), P <.00001; MTHFR AA + AC vs CC: OR = 0.62, 95% CI (0.49, 0.79), P = .0001; MTRR AA + AG vs GG: OR = 0.60, 95% CI (0.45, 0.81), P = .001. Recessive model: MTHFR CC vs CT + TT: OR = 0.67, 95% CI (0.61, 0.74), P <.00001; MTHFR AA vs AC + CC: OR = 0.79, 95% CI (0.70, 0.88), P <.0001; MTRR AA vs AG + GG: OR = 0.70, 95% CI (0.56, 0.88), P = .002. Heterozygote model: MTHFR CC vs CT: OR = 0.74, 95% CI (0.67, 0.82), P <.00001; MTHFR AA vs AC: OR = 0.83, 95% CI (0.73, 0.93), P = .002; MTRR AA vs AG: OR = 0.76, 95% CI (0.60, 0.92), P = .02. Homozygote model: MTHFR CC vs TT: OR = 0.48, 95% CI (0.41, 0.56), P <.00001; MTHFR AA vs CC: OR = 0.61, 95% CI (0.39, 0.93), P = .02; MTRR AA vs GG: OR = 0.51, 95% CI (0.36, 0.72), P = .0001. Allele model: MTHFR C vs T: OR = 0.70, 95% CI (0.66, 0.75), P <.00001; MTHFR A vsC: OR = 0.82, 95% CI (0.71, 0.95), P = .01; MTRR A vs G: OR = 0.76, 95% CI (0.66, 0.88), P = .00003). Stratified analyses by geographical location and source of controls showed the same results. Sensitivity analyses indicated that the final consequences of this meta-analysis were stable, and the publication biases test had not found obvious asymmetry.This meta-analysis indicates that MTHFR C677T, A1298C, and MTRR A66G polymorphisms are the risk factors with susceptibility to male infertility in Asians.

Effect of folate deficiency on promoter methylation and gene expression of Esr1, Cav1, and Elavl1, and its influence on spermatogenesis

This study aims to investigate the effect of folate deficiency on the male reproductive function and the underlying mechanism. A total of 269 screened participants from 421 recruitments were enrolled in this study. An animal model of folate deficiency was constructed. Folate concentration was measured in the ejaculate, and its association with semen parameters was then determined. The expression and promoter methylation status of ESR1, CAV1, and ELAVL1 were also evaluated. Results showed that seminal plasma folate level was significantly lower among subjects with azoospermia than those with normozoospermia. Low folate level was significantly correlated with low sperm concentration in men with normozoospermia. Folate deficiency significantly reduced the expression of ESR1, CAV1, and ELAVL1, which are critical to spermatogenesis. However, low folate levels did not increase the methylation levels of the promoter regions of ESR1, CAV1, and ELAVL1 in human sperm DNA. Thus, folate deficiency impairs spermatogenesis may partly due to inhibiting the expression of these genes. Thus future research should determine the significance of sufficient folate status in male fertilization and subsequent pregnancy outcomes.

The methylenetetrahydrofolate reductase c.c.677 C>T and c.c.1298 A>C polymorphisms in reproductive failures: Experience from an RSA and RIF study on a Polish population

Almost 1600 individuals from the Polish population were recruited to this study. Among them 319 were fertile couples, 289 were recurrent spontaneous abortion (RSA) couples, and 131 were in the group of recurrent implantation failure (RIF) following in vitro fertilization. The aim of this study was to evaluate the MTHFR c.c.677 C>T and c.c.1298 A>C polymorphisms’ association with RSA and RIF. We used PCR-RFLP with HinfI (677 C>T) and MboII (1298 A>C) digestion. We observed a protective effect of the female AC genotype (OR = 0.64, p = 0.01) and the C allele (AC+CC genotypes; OR = 0.65, p = 0.009) against RSA. Moreover, 1298 AA/677 CT women were more frequent in RSA (31.14%) and RIF (25.20%) groups in comparison to fertile women (22.88%), although this difference was significant only in the case of RSA (p = 0.022, OR = 1.52). Male combined genotype analysis revealed no association with reproductive failure of their partners. Nevertheless, the female/male combination AA/AC of the 1298 polymorphism was more frequent in RSA couples (p = 0.049, OR = 1.49). However, the significant results became insignificant after Bonferroni correction. In addition, analysis of haplotypes showed significantly higher frequency of the C/C haplotype (1298 C/677 C) in the female control group than in the female RSA group (p = 0.03, OR = 0.77). Moreover, the association between elevated homocysteine (Hcy) level in plasma of RSA and RIF women and MTHFR polymorphisms was investigated but did not reveal significant differences. In conclusion, for clinical practice, it is better to check the homocysteine level in plasma and, if the Hcy level is increased, to recommend patients to take folic acid supplements rather than undergo screening of MTHFR for 1298 A>C and 677 C>T polymorphisms.

Associations of C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR) gene with male infertility risk: A meta-analysis

PURPOSE

Methylenetetrahydrofolate reductase is one of the key enzymes in folate metabolism. But the association between polymorphism and the risk of male infertility is still controversial. Therefore, this study used a meta-analysis on the collection of data to analyze MTHFR gene C677T polymorphism (known as c.665 C>T, rs1801133, p.Ala222Val).

METHODS

PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), and Wan fang. Data were searched to identify eligible studies. We sifted the data collection by Hardy-Weinberg equilibrium calculator and used odds ratios (ORs) and 95% confidence intervals (95% CIs) to conduct data through RevMan5.0 and StataSE12.0 software.

RESULTS

A total of 15 studies have 3853 patients with infertility and 3613 healthy controls in this meta-analysis. Our results showed that T variant of MTHFR C677T gene polymorphism was significantly associated with an increased risk of male infertility (forT vs. C: OR=1.38, 95% CI=1.18-1.63; for TT vs. CC: OR=1.86, 95% CI=1.36-2.54; for CT vs. CC: OR=1.34, 95% CI=1.03-1.74; for TT vs. CT: OR=1.52, 95% CI=1.26-1.84; for TT vs. CT+CC: OR=1.42, 95% CI=1.19-1.70; for TT+CT versus CC: OR=1.46, 95%CI=1.05-2.04). In addition, the results indicated that T allele had the positive association which was driven by East-asian populations (random: OR=1.44, 95% CI=1.2-1.74; fixed: OR=1.39, 95% CI=1.20-1.61), Middle-eastern populations (random: OR=1.30, 95% CI=1.05-1.63; fixed: OR=1.30, 95% CI=1.05-1.63) and Mixed-race (random: OR=1.96, 95% CI=1.35-2.85; fixed: OR=1.31, 95% CI=1.20-1.43).

CONCLUSION

This meta-analysis suggests that MTHFR C677T polymorphism is associated with male infertility.

MTHFR C677T, A1298C and MS A2756G Gene Polymorphisms and Male Infertility Risk in a Chinese Population: A Meta-Analysis

Background

Methylenetetrahydrofolate reductase gene (MTHFR C677T and A1298C) and methionine synthase gene (MS A2756G) polymorphisms have shown an association with male infertility risk in several ethnic populations. Although several studies have evaluated these associations in Chinese populations, their small sample sizes and inconsistent outcomes have prevented strong conclusions. Therefore, the present meta-analysis was performed with published studies to evaluate the associations of the three single nucleotide polymorphisms (SNPs) and male infertility in a Chinese population.

Methods

We conducted a search of PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure (CNKI), China biology medical literature (CBM), VIP, and Chinese literature (Wan Fang) databases up to May 31, 2016. Odds ratios (ORs) and 95% confidence intervals (95%CIs) were used to assess the strength of associations with a random-effect model or a fixed-effect model based on the heterogeneity analysis results. Sensitivity analysis was used to confirm the reliability and stability of the meta-analysis.

Results

A total of nine studies, including 1,713 cases and 1,104 controls, were included in the meta-analysis. The pooled results indicated that the MTHFR C667T polymorphism was significantly associated with increased risk of male infertility in the Chinese population in the allele model (T vs. C: OR = 1.47, 95%CI = 1.32–1.63), the dominant model (TT + CT vs. CC: OR = 1.51, 95%CI = 1.30–1.77), the additive model (TT vs. CC: OR = 2.08, 95%CI = 1.68–2.58) and the recessive model (TT vs. CT+CC: OR = 1.58, 95%CI = 1.31–1.90), whereas the MTHFR A1298C and MS A2756G polymorphisms were not risk factors. There was no significant heterogeneity in any genotype contrasts among the studies. The sensitivity analysis indicated that the results of this meta-analysis were relatively stable.

Conclusion

This study suggests that the MTHFR C667T polymorphism may contribute to the genetic susceptibility to male infertility in the Chinese population, whereas MTHFR A1298C and MS A2756G polymorphisms may be unrelated to male infertility. Studies with larger sample sizes and representative population-based cases and well-matched controls are needed to validate our results.

Association of the MTHFR C677T (rs1801133) polymorphism with idiopathic male infertility in a local Pakistani population

The present study determined an association between idiopathic sperm disorders in a local Pakistani infertile male population and the MTHFR C677T polymorphism. After ruling out non genetic factors, a total of 437 idiopathic infertile men including 57 azoospermic, 66 oligospermic, 44 asthenozoospermic, 29 teratozoospermic, 20 oligoasthenospermic and 221 infertile normospermic men were recruited. Furthermore, 218 normospermic fertile men, who had two children (or more) were included as controls. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to determine MTHFR C677T (rs1801133) polymorphism. A significant association of the minor MTHFR 677T allele with male infertility was observed (p <0.05). In addition, men with MTHFR 677 CT and TT genotypes were at a greater risk [odds ratio (OR): 1.81, 95% confidence interval (95% CI): 1.17-2.80, p = 0.008 and OR: 9.24, 95% CI: 1.20-70.92, p = 0.032, respectively] of infertility. All the subgroups of male infertility (azoospermic, oligospermic, asthenospermic, oligoasthenoteratospermic (OAT) and normospermic infertile) had significantly (p <0.05) higher frequencies of CT and TT genotypes when compared to fertile men. The combined genotypes (CT + TT) were also found significantly (OR: 2.01, 95% CI: 1.31-3.08, p <0.001) associated with male infertility. The results suggest that the polymorphism might be a factor of male infertility in the Pakistani population.

Genetics of male infertility: from research to clinic

Male infertility is a multifactorial complex disease with highly heterogeneous phenotypic representation and in at least 15% of cases, this condition is related to known genetic disorders, including both chromosomal and single-gene alterations. In about 40% of primary testicular failure, the etiology remains unknown and a portion of them is likely to be caused by not yet identified genetic anomalies. During the last 10 years, the search for 'hidden' genetic factors was largely unsuccessful in identifying recurrent genetic factors with potential clinical application. The armamentarium of diagnostic tests has been implemented only by the screening for Y chromosome-linked gr/gr deletion in those populations for which consistent data with risk estimate are available. On the other hand, it is clearly demonstrated by both single nucleotide polymorphisms and comparative genomic hybridization arrays, that there is a rare variant burden (especially relevant concerning deletions) in men with impaired spermatogenesis. In the era of next generation sequencing (NGS), we expect to expand our diagnostic skills, since mutations in several hundred genes can potentially lead to infertility and each of them is likely responsible for only a small fraction of cases. In this regard, system biology, which allows revealing possible gene interactions and common biological pathways, will provide an informative tool for NGS data interpretation. Although these novel approaches will certainly help in discovering 'hidden' genetic factors, a more comprehensive picture of the etiopathogenesis of idiopathic male infertility will only be achieved by a parallel investigation of the complex world of gene environmental interaction and epigenetics.

Polymorphisms in the MTHFR and MTR genes and the risk of varicose veins in ethnical Russians

OBJECTIVES

The objective of this study was to study the association of polymorphisms MTHFR C677T (rs1801133) and MTR A2756G (rs1805087) with the risk of varicose veins in ethnical Russians.

METHODS

We genotyped 475 patients with varicose veins, 168 individual without chronic venous disease, and the population-based group of 896 subjects. Association was studied using logistic regression analysis adopting co-dominant, additive, recessive, and dominant models of inheritance.

RESULTS

None of the polymorphisms showed a statistically significant association with the risk of varicose veins.

CONCLUSIONS

Our results provide evidence that the studied polymorphisms do not contribute to genetic susceptibility to varicose veins in ethnical Russians.

Methionine synthase A2756G transition might be a risk factor for male infertility: Evidences from seven case-control studies

Methionine synthase (MTR) has a crucial role in DNA synthesis and methylation reactions. The aim of this study was to investigate the association of the MTR-A2756G polymorphism with idiopathic male infertility. Blood samples were collected from 217 idiopathic infertile- and 233 healthy-men, and MTR-A2756G genotyping was performed by PCR-RFLP. Meta-analysis was conducted by pooling our data with the data obtained from 6 previous studies. Also, the effects of this substitution on protein structure were evaluated by bioinformatics tools. Our study revealed the association of AG-genotype, GG-genotype, and G-allele with male infertility. Meta-analysis showed a significant association between A2756G transition and male infertility. In addition, structural analysis of the transition effect on protein revealed a significant influence on MTR function (with score: 38; expected accuracy: 66%). These findings suggest that the A2756G substitution might be a genetic risk factor and a potential biomarker for idiopathic male infertility.

Role of genetic mutations in folate-related enzyme genes on Male Infertility

Several studies showed that the genetic mutations in the folate-related enzyme genes might be associated with male infertility; however, the results were still inconsistent. We performed a meta-analysis with trial sequential analysis to investigate the associations between the MTHFR C677T, MTHFR A1298C, MTR A2756G, MTRR A66G mutations and the MTHFR haplotype with the risk of male infertility. Overall, a total of 37 studies were selected. Our meta-analysis showed that the MTHFR C677T mutation was a risk factor for male infertility in both azoospermia and oligoasthenoteratozoospermia patients, especially in Asian population. Men carrying the MTHFR TC haplotype were most liable to suffer infertility while those with CC haplotype had lowest risk. On the other hand, the MTHFR A1298C mutation was not related to male infertility. MTR A2756G and MTRR A66G were potential candidates in the pathogenesis of male infertility, but more case-control studies were required to avoid false-positive outcomes. All of these results were confirmed by the trial sequential analysis. Finally, our meta-analysis with trial sequential analysis proved that the genetic mutations in the folate-related enzyme genes played a significant role in male infertility.

MTHFR 677C>T polymorphism increases the male infertility risk: a meta-analysis involving 26 studies

Background and Objectives

Methylenetetrahydrofolate reductase (MTHFR) polymorphism may be a risk factor for male infertility. However, the epidemiologic studies showed inconsistent results regarding MTHFR polymorphism and the risk of male infertility. Therefore, we performed a meta-analysis of published case-control studies to re-examine the controversy.

Methods

Electronic searches of PubMed, EMBASE, Google Scholar and China National Knowledge Infrastructure (CNKI) were conducted to select eligible literatures for this meta-analysis (updated to June 19, 2014). According to our inclusion criteria and the Newcastle-Ottawa Scale (NOS), only high quality studies that observed the association between MTHFR polymorphism and male infertility risk were included. Crude odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of association between the MTHFR polymorphism and male infertility risk.

Results

Twenty-six studies involving 5,575 cases and 5,447 controls were recruited. Overall, MTHFR 677C>T polymorphism showed significant associations with male infertility risk in both fixed effects (CT+TT vs. CC: OR = 1.34, 95% CI: 1.23–1.46) and random effects models (CT+TT vs. CC: OR = 1.39, 95% CI: 1.19–1.62). Further, when stratified by ethnicity, sperm concentration and control sources, the similar results were observed in Asians, Caucasians, Azoo or OAT subgroup and both in population-based and hospital-based controls. Nevertheless, no significant association was only observed in oligo subgroup.

Conclusions

Our results indicated that the MTHFR polymorphism is associated with an increased risk of male infertility. Further well-designed analytical studies are necessary to confirm our conclusions and evaluate gene-environment interactions with male infertility risk.

Lack of association between genetic polymorphisms in three folate-related enzyme genes and male infertility in the Chinese population

PURPOSE

This study explored the possible association of four single nucleotide polymorphisms (SNPs) of the three folate-related enzyme genes: MTHFR C677T and A1298C, MTR A2756G and MTRR A66G, with male infertility in the Chinese population.

METHODS

The polymorphic distributions of the four SNPs (MTHFR C677T and A1298C, MTR A2756G and MTRR A66G) were investigated by the method of SNaPshot in a Chinese cohort including 296 idiopathic infertile males with azoospermia or oligozoospermia and 204 fertile males.

RESULTS

We found no evidence for an association between any of these variants (MTHFR C677T and A1298C, MTR A2756G and MTRR A66G) and male infertility.

CONCLUSIONS

There is no evidence for an association between male infertility and polymorphism of the three folate-related enzyme genes in the Chinese population.

Association study of folate-related enzymes (MTHFR, MTR, MTRR) genetic variants with non-obstructive male infertility in a Polish population

Spermatogenesis is a process where an important contribution of genes involved in folate-mediated one-carbon metabolism is observed. The aim of the present study was to investigate the association between male infertility and the MTHFR (677C > T; 1298A > C), MTR (2756A > G) and MTRR (66A > G) polymorphisms in a Polish population. No significant differences in genotype or allele frequencies were detected between the groups of 284 infertile men and of 352 fertile controls. These results demonstrate that common polymorphisms in folate pathway genes are not major risk factors for non-obstructive male infertility in the Polish population.