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

Explore the Role of the rs1801133-PPARG Pathway in the H-type Hypertension

Both rs1801133 mutation on Methylenetetrahydrofolate reductase (MTHFR) gene and transcription factor peroxisome proliferator-activated gamma (PPARG) have been associated with plasma homocysteine (Hcy) levels and hypertension. However, their role in H-type hypertension remains unclear. In this study, we first tested the association between rs1801133 genotypes and Hcy level in H-type hypertension using clinical profiles collected from 203 patients before and after the treatment using enalapril maleate and folic acid tablets (EMFAT). Then, we constructed a literature-based pathway analysis to explore the role of the rs1801133-PPARG signaling pathway in H-type hypertension and its treatment. Although presented similar blood pressure, the patients with TT genotype of rs1801133 were much younger ( $p$ value <0.05) and significantly higher in Hcy levels ( $x^2=6.11$ and $p<0.005$ ) than that in the CC and CT genotype groups. Pathway analysis showed that T-allele of rs1801133 could inhibit the expression of PPARG through the downregulation of folate levels and upregulation of Hcy levels, which increased the risk of hypertension and hyperhomocysteinemia. Treatment using EMFAT led to similarly decreased Hcy levels for all patients with different genotypes ( $x^2=86.00$ ; $p<0.36$ ), which may occur partially through the activation of PPARG. Moreover, even after treatment, the patients with TT genotype still presented significantly higher Hcy levels ( $x^2=7.87$ and $p<0.001$ ). Our results supported that rs1801133 mutation could play a role in H-type hypertension, which might be partially through the downregulation of PPARG. Moreover, PPARG might also be involved in treating H-type hypertension using EMFAT.

Association of Novel Single Nucleotide Polymorphisms of Genes Involved in Cell Functions with Male Infertility: A Study of Male Cases in Northwest Iran

Background

Infertility is a global health problem caused by various environmental and genetic factors. Male infertility accounts for 40-50% of all cases of infertility and approximately half of them are grouped as idiopathic with no definitive causes. Previous studies have suggested an association between some SNPs and infertility in men. In this study, an attempt was made to investigate the association of 7 different SNPs of 4 genes involved in common cell functions with male infertility.

Methods

MTHFR rs1801131 (T>G), MTHFR rs2274976 (G>A), FASLG rs80358238 (A>G), FASLG rs12079514 (A>C), GSTM1 rs1192077068 (G>A), BRCA2 rs4987117 (C>T), and BRCA2 rs11571833 (A>T) were genotyped in 120 infertile men with idiopathic azoospermia or severe oligospermia and 120 proven fertile controls using ARMS-PCR methods. Next, 30% of SNPs were regenotyped to confirm the results. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using SPSS statistical software to evaluate the strength of association. The p<0.05 were considered statistically significant.

Results

Statistical analysis revealed significant association between MTHFR rs-2274976 AA variant (OR: 10.00, CI: 3.203-31.225), FASLG rs12079514 AC variant (OR: 0.412, CI: 0.212-0.800), and BRCA2 rs11571833 TT variant OR: 6.233, CI: 3.211-12.101) with male infertility, but there was no significant difference between case and control groups in MTHFR rs1801131 (p= 0.111), GSTM1 rs1192077068 (p=0.272), BRCA2 rs4987117 (p=0.221), and FASLG rs80358238 (p=0.161).

Conclusion

Our findings suggested that some novel polymorphisms including MTHFR rs2274976, FASLG rs12079514, and BRCA2 rs11571833 might be the possible predisposing risk factors for male infertility in cases with idiopathic azoospermia.

Association of paternal MTHFR polymorphisms (C677T) with clinical outcomes in ICSI treatment

PURPOSE

This study aims to investigate the association between paternal methylenetetrahydrofolate reductase (MTHFR) polymorphisms (C677T) and embryonic development, pregnancy, and neonatal outcomes in intracytoplasmic sperm injection (ICSI) treatment.

METHODS

A total of 191 infertile men undergoing ICSI treatment at the Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, were recruited between January 2020 and June 2021. The MTHFR C677T polymorphism genotyping was evaluated in these male patients, and they were stratified into three groups according to genotyping results: Control (CC), heterozygote mutated (CT), and mutated homozygote (TT). In addition, we conducted a comparative analysis of embryonic development, pregnancy, and neonatal outcomes among these three groups.

RESULTS

The embryonic development (including normal fertilization rate (80.14% vs. 83.06% vs. 85.10%; p = 0.37), high-quality embryo rate (45.26% vs. 43.69% vs. 46.04%; p = 0.72), blastocyst formation rate (42.47% vs. 43.18% vs. 39.38%; p = 0.62), implantation rate (42.47% vs. 36.25% vs. 41.22%; p = 0.62), and clinical pregnancy rate (64.71% vs. 58.75% vs. 66.67%; p = 0.59) were not comparable among these three groups. Moreover, no significant difference was observed in terms of pregnancy outcomes (including miscarriage rate (24.24% vs. 12.77% vs. 22.5%; p = 0.35) and live birth rate (49.02% vs. 51.25% vs. 51.66%; p = 0.96)). Additionally, no marked difference was observed in terms of neonatal outcome (including, preterm delivery rate (24% vs. 14.63% vs. 9.67%; p = 0.35), birth height (p = 0.75), birth weight (p = 0.35), neonatal sex (p = 0.48), gestational age at delivery (p = 0.24), Apgar score (p = 0.34), and birth defects (0% vs. 2% vs. 9%; p = 0.23) among the study groups.

CONCLUSION

The paternal MTHFR C677T polymorphism is not associated with embryo quality, pregnancy, or neonatal outcomes in ICSI treatment. Therefore, in our population, MTHFR polymorphisms do not provide helpful information in explaining ICSI failure.

Methylenetetrahydrofolate reductase C677T gene polymorphism and the association with dyslipidemia in type 2 diabetic Palestinian patients

BACKGROUND

Dyslipidemia in diabetes is common and characterized by hypertriglyceridemia with decreased levels of high-density lipoprotein. The objective of this study was to assess the prevalence of MTHFR C677T polymorphism in Palestinian T2DM patients and to investigate the association between this polymorphism and lipid profile in diabetic patients with and without dyslipidemia.

METHODS

A total of 208 T2DM patients including 98 with dyslipidemia and 110 without dyslipidemia were enrolled in this study. The MTHFR C677T genotyping was conducted by PCR-RFLP followed by agarose gel electrophoresis.

RESULTS

There were no significant differences in either the genotype distribution or allele frequency in T2DM patients with or without dyslipidemia (37.8% CC, 54% CT, 8.2% TT vs. 48.2% CC, 41.8% CT, 11% TT; p = 0.209). However, among the dyslipidemic group, the TT carriers have a higher HDL level (46.8 ± 17.8) compared to (CC+CT) carriers (34.68 + 11.9) (p = 0.01). In the group without dyslipidemia, there was a significant elevation in diastolic blood pressure (DBP) among the CC carriers (83.6 ± 10.6) compared to those who carried at least one mutant allele (CT+TT) (78.1 ± 11.1) (p = 0.009).

CONCLUSIONS

The study shows that in our Palestinian population the MTHFR 677TT genotype lowers DBP significantly in patients without dyslipidemia and is related to increased level of HDL in diabetic dyslipidemia patients.

Lack of association between single polymorphic variants of the mitochondrial nicotinamide adenine dinucleotide dehydrogenase 3, and 4L (MT-ND3 and MT-ND4L) and male infertility

Male infertility is a multifactorial condition associated with different genetic abnormalities in at least 15%-30% of cases. The purpose of this study was to identify suspected correlations between infertility and polymorphisms in mitochondrial NADH dehydrogenase subunits 3 and 4L (MT-ND3 and MT-ND4L) in subfertile male spermatozoa. Sanger sequencing of the mitochondrial DNA target genes was performed on 68 subfertile and 44 fertile males. Eight single nucleotide polymorphisms (SNPs) in MT-ND3 (rs2853826, rs28435660, rs193302927, rs28358278, rs41467651, rs3899188, rs28358277 and rs28673954) and seven SNPs in MT-ND4L (rs28358280, rs28358281, rs28358279, rs2853487, rs2853488, rs193302933 and rs28532881) were detected and genotyped. The genotypes and allele frequencies of the study population have shown a lack of statistically significant association between MT-ND3 and MT-ND4L SNPs and male infertility. However, no statistically significant association was found between the asthenozoospermia, oligozoospermia, teratozoospermia, asthenoteratozoospermia, oligoasthenoteratozoospermia and oligoteratozoospermia subgroups of subfertile males. However, rs28358278 genotype of the MT-ND3 gene was reported in the subfertile group but not in the fertile group, which implies a possible role of this SNP in male infertility. In conclusion, the investigated polymorphic variants in the MT-ND3 and MT-ND4L genes did not show any significant association with the occurrence of male infertility. Further studies are required to evaluate these findings. Moreover, the subfertile individuals who exhibit a polymorphism at rs28358278 require further monitoring and evaluation.

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.

A posteriori dietary patterns and risk of inflammatory bowel disease: a meta-analysis of observational studies

Abstract. Inflammatory bowel disease (IBD) is a chronic inflammatory disorder which affects the gastrointestinal tract. Many factors, such as genetics, stress, and dietary patterns have been related to the risk of this disease. Adherence to a prudent/healthy dietary pattern, due to its antioxidant and anti-inflammatory properties, help to reduce the risk of many chronic diseases such as IBD. The results from previous studies regarding the association between dietary patterns and risk of IBD, including Crohn’s disease (CD) and ulcerative colitis (UC), are inconsistent. This meta-analysis was performed to evaluate the potential relations between dietary patterns and risk of CD and UC. PubMed and Scopus were searched up to October 2017 for eligible studies. Random-effects or fixed-effects models were used to pool the estimated risks for the highest versus the lowest category of extracted dietary patterns. A total of six studies, including four case-control and two cohort studies with 1099 cases and 263112 controls/participants were included in the meta-analysis. A decreased risk of CD was seen for the highest compared with the lowest categories of healthy dietary pattern (OR/RR = 0.39, 95%CI = 0.16–0.62), while no significant association with western dietary pattern was observed (OR/RR = 0.78, 95% CI: 0.51–1.04). Furthermore, no significant relationship was found between healthy (OR/RR = 0.61, 95%CI = 0.04–1.18, random effects) and western/unhealthy (OR/RR = 0.97, 95% CI: 0.67–1.26) dietary patterns and risk of UC. The results of the current meta-analysis showed that a healthy dietary pattern is associated with a lower risk of CD. Further studies are warranted to confirm these findings.

Effects of folic acid on oligozoospermia with MTHFR polymorphisms in term of seminal parameters, DNA fragmentation, and live birth rate: a double-blind, randomized, placebo-controlled trial

BACKGROUND

It has been reported that paternal folic acid deficiency is correlated with male infertility and increased birth defects in the offspring. However, there are few data concerning the influence of folic acid supplementation on male-factor infertility with MTHFR gene polymorphisms.

OBJECTIVES

To evaluate whether folic acid supplementation has a beneficial effect on oligozoospermia with MTHFR gene polymorphisms in Chinese infertility population.

MATERIALS AND METHODS

The infertile men suffering oligozoospermia with MTHFR gene polymorphisms were randomly divided into the folic acid treatment groups receiving folic acid 0.8 mg daily for 3 months and the placebo groups receiving placebo for 3 months. Semen parameters, seminal MDA, and DNA fragmentation were measured. Furthermore, spontaneous pregnancy rate and live birth rate were evaluated.

RESULTS

Administration of folic acid for 3 months could significantly improve the seminal parameters in patients with MTHFR 677 TT genotype in comparison with that receiving placebo. Moreover, seminal MDA and sperm DNA fragmentation index in patients with MTHFR 677 TT genotype significantly declined at the end of treatment. Spontaneous pregnancy rate and live birth rate tended to be significantly higher in couples in which the men with MTHFR 677 TT genotype receiving folic acid than that receiving placebo. However, folic acid treatment did not exhibit any advantage in MTHFR 677 CT, 1298 AC, 1298 CC, 1793 GA, or combined 677 CT/1298 AC genotype.

DISCUSSION

The anti-oxidation function of folic acid is one of possible mechanisms invovled in improving seminal parameters and pregnancy outcome.

CONCLUSIONS

Folic acid supplementation has a beneficial effect on oligozoospermia with MTHFR 677 TT genotype in term of seminal parameters, seminal MDA, sperm DNA fragmentation, and pregnancy outcome.

The relation of healthy and Western dietary patterns to the risk of endometrial and ovarian cancers: a systematic review and meta-analysis

Dietary patterns have been used to explore the association between dietary factors and risk of endometrial (EC) and ovarian cancer (OC); however, the results are inconclusive. This meta-analysis aimed to analyze these associations. Methods: Pertinent studies published prior to March 2016 were systematically searched. The common dietary patterns were selected and adjusted risk estimates were derived by comparing the highest with the lowest categories of dietary pattern scores. Results: A total of 8 studies, 5 for endometrial cancer (1 cohort and 4 case-control studies including 2617 cases and 78082 participants/controls) and 3 for ovarian cancer (1 cohort and 2 case-control studies with 2025 cases and 101482 participants/controls) were included in this meta-analysis. A lower risk of EC was shown for the highest compared with the lowest category of the healthy dietary pattern (OR = 0.84, 95% CI: 0.72-0.98; P for heterogeneity = 0.10), whereas the Western dietary pattern was related to the higher risk of EC (OR = 1.19, 95% CI: 1.01-1.41; P for heterogeneity = 0.35). No significant relationship was found between the healthy dietary pattern (OR = 1.03, 95% CI: 0.69-1.53; P for heterogeneity = 0.01) and OC, while, adherence to the western pattern was associated with a 73% higher risk of OC (OR = 1.73, 95% CI: 1.08-2.37; P for heterogeneity = 0.06). Conclusion: A Western dietary pattern might be associated with a higher risk of endometrial and ovarian cancer.

MTHFR polymorphisms as risk for male infertility in Pakistan and its comparison with socioeconomic status in the world

Aim: 5,10-MTHFR-single nucleotide polymorphisms are important for normal functioning of the enzyme that plays a key role in DNA synthesis, folate metabolism and methylation reactions. Methodology & results: Male infertility association of C665T and A1298C polymorphisms was explored, this topic is still debatable. Infertile men (232) and controls (114) were genotyped and statistically analyzed. Comparison of patients (6180) and controls (5744) of Caucasian populations was performed by meta-analysis. Pooled results showed A1298C minor allele and homozygous genotype to be of a significantly higher frequency in the low-income group. Increase in per capita income has shown an increasing trend in the minor allele frequency in various world populations, potentially due to dietry-folate compensation. Conclusion: A1298C seems more relevant marker than C665T for infertility association in Caucasian populations and may be addressed by improving dietary folate.

Synergistic effects of TIMP2-418G/C and MMP9-1562C/T variants on the male infertility risk

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) involve in the degradation of the extracellular matrix (ECM) that imbalances their activity and may lead to various diseases. The present study aims to evaluate the association between MMP9-1562C/T and TIMP2-418G/C variants and synergistic effects of both variants on male infertility in an Iranian population. We analyzed these polymorphisms in 101 infertile men and 106 fertile men as a control group using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Based on the obtained results, no considerable association was observed in MMP9-1562C/T polymorphism frequency between infertile men and controls while frequencies of TIMP2-418G/C variant were significantly different in infertile and control groups (P = 0.028). Men with CC, GC and CC + GC genotypes for TIMP2-418G/C polymorphism had an increased risk of infertility compared to men with GG genotype [OR = 1.85, 95% CI (0.917-3.734, P = 0.086), OR = 1.94, 95% CI (1.098-3.437, P = 0.023) and OR = 2.053 95% CI (1.179-3.577, P = 0.011), respectively]. Also, in the presence of both TIMP2-418C and MMP9-1562T alleles the male infertility risk was significantly increased (P = 0.032). The current study suggests that the variation of TIMP2 gene and its interaction with MMP9 gene might be associated with male infertility. However, to confirm these findings, further studies are required in different ethnicities and with a larger sample size.

Strong association of SLC1A1 and DPF3 gene variants with idiopathic male infertility in Han Chinese

Male infertility is a multifactorial syndrome encompassing a wide variety of disorders. In recent years, several genome-wide single-nucleotide polymorphism (SNP) association studies (GWAS) have been performed on azoospermia and/or oligozoospermia in different populations including two GWAS on nonobstructive azoospermia in China; however, the association of SNPs with idiopathic male infertility, especially asthenozoospermia and oligozoospermia, and their correlation with semen parameters are still not clear. To investigate genetic variants associated with idiopathic male infertility (asthenozoospermia, oligozoospermia, and oligoasthenozoospermia) in Chinese Han people, 20 candidate SNPs were selected from GWAS results and genotyped using the Sequenom MassARRAY assay. A total of 136 subfertile men and 456 healthy fertile men were recruited. rs6476866 in SLC1A1 (P = 1.919E-4, OR = 0.5905, 95% CI: 0.447–0.78) and rs10129954 in DPF3 (P = 0.0023, OR = 2.199, 95% CI: 1.311–3.689) were strongly associated with idiopathic male infertility. In addition, positive associations were observed between asthenozoospermia and rs215702 in LSM5 (P = 0.0016, OR = 1.479, 95% CI: 1.075–2.033) and between oligoasthenozoospermia and rs2477686 in PEX10 (P = 0.0011, OR = 2.935, 95% CI: 1.492–5.775). In addition, six SNPs (rs215702 in LSM5, rs6476866 in SLC1A1, rs10129954 in DPF3, rs1801133 in MTHFR, rs2477686 in PEX10, and rs10841496 in PED3A) were significantly correlated with semen quality alterations. Our results suggest that idiopathic male infertility in different ethnic groups may share the same mechanism or pathway. Cohort expansion and further mechanistic studies on the role of genetic factors that influence spermatogenesis and sperm progressive motility are suggested.

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 Methylenetetrahydrofolate Reductase C677T and A1298C Gene Polymorphisms With Recurrent Pregnancy Loss in Syrian Women

C677T polymorphism of the methylenetetrahydrofolate reductase ( MTHFR) gene was a risk factor for recurrent pregnancy loss (RPL), but few studies have confirmed a possible role of MTHFR A1298C polymorphism in RPL risk. This study was carried out to determine the influence of the MTHFR gene polymorphisms in RPL Syrian women. A case-control study was performed on 2 groups (106 healthy and 100 RPL women). The frequency of the MTHFR gene polymorphisms was determined by polymerase chain reaction based on restriction fragment length gene polymorphism. In the RPL group, the genotype frequencies of MTHFR C677T were CC (41%), CT (41%), and TT (18%), and in the control group, the frequencies were CC (62.2%), CT (36.7%), and TT (1%). Statistical analysis showed a homozygous TT genotype and T allele were significantly different in the RPL group ( P = .000003 and P = .000019, respectively). The genotype frequencies of MTHFR A1298C were AA (53%), AC (44%), and CC (8%) in the RPL group, whereas in the control group, these were AA (61.3%), AC (37.8%), and CC (1%). A significant difference in the CC genotype and C allelic frequencies in the RPL women was observed ( P = .014 and P = .064, respectively). The patients having compound heterozygous (677 CT/1298AC) were associated with an estimated 4.86-fold increase in risk of pregnancy loss compared to individuals with a wild type ( P = .012). Our findings indicate that RPL women with homozygous genotype for (C677T and A1298C) either alone or compound heterozygous genotypes have a high risk of pregnancy loss in Syrian women.

Single gene defects leading to sperm quantitative anomalies

Azoospermia, defined by the absence of sperm in the ejaculate, is estimated to affect up to 1% of men in the general population. Assisted reproductive technologies have revolutionized the treatment of infertility, and some azoospermic men, those with a post-meiotic defect, can conceive following the use of viable spermatoza recovered from testicular or epididymal biopsies. Although male infertility is a multifactorial disease, it is believed that genetic factors are predominant in the etiology of azoospermia and severe oligozoospermia. Despite that assumption, substantiated by the high number of infertile knockout (KO) mice and the even higher number of genes expressed essentially in the testis, little is known about the pathophysiology of reduced sperm production, its primary causes or the genetic and epigenetic consequences for the gamete and the future conceptus. The identification of genetic abnormalities is therefore paramount to understand spermatogenesis, to adopt the best course of action for the patient and to provide adequate genetic counseling. We provide here a review of the recent literature on the genetics of azoospermia and oligozoospermia, focusing on defects directly altering sperm production. New sequencing technologies are contributing to the rapid evolution of the recent field of infertility genetics.

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.

C667T and A1298C polymorphisms of methylenetetrahydrofolate reductase gene and susceptibility to myocardial infarction: A systematic review and meta-analysis

MTHFR C677T and A1298C polymorphisms have been reported to be associated with the risk of myocardial infarction (MI), although the results of previous studies have been inconsistent. The aim of this study was to explore whether these polymorphisms play a role in the genetic susceptibility to MI. A comprehensive search of MEDLINE and EMBASE databases was conducted for studies evaluating the association between the C667T and A1298C polymorphisms and MI risk. Odds ratios (OR) with 95% confidence intervals (CIs) were calculated to assess the strength of association in the dominant model, recessive model, allelic model, and genotypes contrast. A total of 47 studies were finally included in this meta-analysis. Overall, the results showed no statistically significant association between C667T and A1298C polymorphisms and MI risk. However, in subgroup analysis by ethnicity, the T allele of C677T polymorphism was associated with a 63% increased risk of MI compared with the C allele (T vs. C, OR=1. 63, 95%CI=1.15-2.10, fixed effects) in African populations, while compared to wild homozygote genotype, CT genotype was associated with a decreased risk of MI in North American populations (CT vs. CC, OR=0.81, 95%CI=0.64-0.98, fixed effects). Moreover, C677T polymorphism had a protective effect against MI risk under the dominant model (OR=0.93, 945%CI=0.87-0.99, fixed effects) in elderly (≥50) population. The A1298C polymorphism was not significantly associated with MI risk. Unlike A1298C polymorphism, C677T polymorphism was associated with risk of MI in African, North American, and elderly populations.

The "omics" of human male infertility: integrating big data in a systems biology approach

Spermatogenesis is a complex process in which >2300 genes are temporally and spatially regulated to form a terminally differentiated sperm cell that must maintain the ability to contribute to a totipotent embryo which can successfully differentiate into a healthy individual. This process is dependent on fidelity of the genome, epigenome, transcriptome, and proteome of the spermatogonia, supporting cells, and the resulting sperm cell. Infertility and/or disease risk may increase in the offspring if abnormalities are present. This review highlights the recent advances in our understanding of these processes in light of the "omics revolution". We briefly review each of these areas, as well as highlight areas of future study and needs to advance further.

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.

Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism: epidemiology, metabolism and the associated diseases

The Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is associated with various diseases (vascular, cancers, neurology, diabetes, psoriasis, etc) with the epidemiology of the polymorphism of the C677T that varies dependent on the geography and ethnicity. The 5,10-Methylenetetrahydrofolate reductase (MTHFR) locus is mapped on chromosome 1 at the end of the short arm (1p36.6). This enzyme is important for the folate metabolism which is an integral process for cell metabolism in the DNA, RNA and protein methylation. The mutation of the MTHFR gene which causes the C677T polymorphism is located at exon 4 which results in the conversion of valine to alanine at codon 222, a common polymorphism that reduces the activity of this enzyme. The homozygous mutated subjects have higher homocysteine levels while the heterozygous mutated subjects have mildly raised homocysteine levels compared with the normal, non-mutated controls. Hyperhomocysteinemia is an emerging risk factor for various cardiovascular diseases and with the increasing significance of this polymorphism in view of the morbidity and mortality impact on the patients, further prevention strategies and nutritional recommendations with the supplementation of vitamin B12 and folic acid which reduces plasma homocysteine level would be necessary as part of future health education. This literature review therefore focuses on the recent evidence-based reports on the associations of the MTHFR C677T polymorphism and the various diseases globally.

Methylenetetrahydrofolate Reductase C677T and A1298C Polymorphism in Iranian Women With Idiopathic Recurrent Pregnancy Losses

BACKGROUND

Recurrent pregnancy loss (RPL) is a serious problem for pregnancy. There is evidence that vascular complications play a principal role in RPL. Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism. Polymorphisms (C677T, A1298C) of MTHFR gene are associated with decreased MTHFR activity.

OBJECTIVES

The aim of this study was to determine the association between MTHFR polymorphisms (C677T and A1298C) and recurrent pregnancy loss (RPL) in Iranian women.

MATERIALS AND METHODS

In this case-control study, blood samples were obtained from patients who had three or more consecutive pregnancy losses before the 22(nd) week of pregnancy (n = 204). The control group consisted of 116 age-matched women with at least one alive child and without any history of pregnancy loss or other gestational complications (n = 116). Following DNA extraction, samples were tested for MTHFR C677T and A1298C polymorphisms using the reverse hybridization method.

RESULTS

The prevalence of 677TT mutation was 8.8% (18/204) in the patient group and 8.6% (10/116) in the control group (P = 0.434). The prevalence of 1298CC mutation was 12.3 % (25/204) in the patient group and 8% (9/116) in the control group (P = 0.155). Investigation of the distributions of various genotypes of MTHFR C677T and A1298C did not indicate a significant difference between patients with RPL and healthy control subjects.

CONCLUSIONS

The results suggest that MTHFR mutations might not be associated with RPL in the examined population.

Genetic susceptibility to male infertility: news from genome-wide association studies

A thorough understanding of the genetic basis of male infertility has eluded researchers in spite of significant efforts to identify novel genetic causes of the disease, particularly over the past decade. Approximately half of male factor infertility cases have no known cause; however, it is likely that the majority of idiopathic male factor infertility cases have some unidentified genetic basis. Well-established genetic causes of male infertility are limited to Y chromosome microdeletions and Klinefelter's syndrome, together accounting for 10-20% of cases of severe spermatogenic failure. In addition to these, several genetic polymorphisms have been demonstrated to be significantly associated with male infertility. The discovery of new genetic associations with male infertility has been hampered by two primary factors. First, most studies are underpowered because of insufficient sample size and ethnic and phenotypic heterogeneity. Second, most studies evaluate a single gene, an approach that is very inefficient in the context of male infertility, considering that many hundreds of genes are involved in the process of testicular development and spermatogenesis. Significant recent advances in microarray and next-generation sequencing technologies have enabled the application of whole-genome approaches to the study of male infertility. We recently performed a pilot genome-wide association study (GWAS) for severe spermatogenic failure, and several additional male infertility GWAS have since been published. More recently, genomic microarray tools have been applied to the association of copy number variants with male infertility. These studies are beginning to shed additional light on the genetic architecture of male infertility, and whole-genome studies have proven effective in identifying novel genetic causes of the disease. This review will discuss some of the recent findings of these whole-genome studies as well as future directions for this research that will likely be the most productive moving forward.

Is methylenetetrahydrofolate reductase (MTHFR) gene A1298C polymorphism related with varicocele risk?

Varicocele is one of the main reasons for male infertility the exact aetiology of which remains unclear. Methylenetetrahydrofolate reductase (MTHFR) is important for DNA synthesis and methylation, which has a key role during spermatogenesis. Numerous literature suggests that the MTHFR polymorphism may be genetic risk factors for male infertility. In this study, we evaluated C677T and A1298C MTHFR gene polymorphism frequency in patients with varicocele and normal men. A total of 107 varicocele patients and 109 fertile healthy individuals were included. Genotyping of the MTHFR gene in C677T and A1298C base pairs carried out by using real-time PCR technique and afterwards, the statistical analysis accomplished. There is a statistical difference for the frequency of 1298AA genotype in patients with varicocele compared with normal controls (P = 0.0051, OR = 2.2750). Instead, subsequently, 1298/A allel frequency in patient group was significantly higher in comparison with control group (P = 0.0174). According to our results, 1298AA genotype in MTHFR gene raises the risk of varicocele approximately 2.3 times more compared with men carrying other genotypes. The results show that genetic factors have an important role in the molecular basis of varicocele.

Associations of variants in MTHFR and MTRR genes with male infertility in the Jordanian population

Folate pathway is expected to play an important role in spermatogenesis since it is involved in DNA synthesis, repair and methylation. The purpose of this study was to examine the association between male infertility and the MTHFR (C677T and A1298C) and MTRR (A66G) polymorphisms. A group of 300 males was recruited in this study from different Jordanian infertility clinics. Of these, 150 cases of infertile men that included oligozoospermia cases (n=45), severe oligozoospermia (n=71) and azoospermia (n=34) were studied. The other 150 males were age matched fertile controls. Genotyping of MTHFR and MTRR polymorphisms was performed using PCR-RFLP technique. The results showed an association between MTHFR 677TT genotype and male infertility (P<0.05). However, the distribution of MTHFR A1298C and MTRR A66G genotypes were not different between the fertile and infertile groups (P>0.05). In addition, none of the examined polymorphisms was related to any of the semen parameters in the infertile group. In conclusion, this study showed that MTHFR C677T polymorphism is associated with male infertility in Jordanians.

Significant impact of the MTHFR polymorphisms and haplotypes on male infertility risk

Background

Methylenetetrahydrofolate reductase (MTHFR) converts 5,10-methylene tetrahydrofolate to 5-methyl tetrahydrofolate and affects the activity of cellular cycles participating in nucleotide synthesis, DNA repair, genome stability, maintenance of methyl pool, and gene regulation. Genetically compromised MTHFR activity has been suggested to affect male fertility. The objective of the present study was to find the impact on infertility risk of c.203G>A, c.1298A>C, and c.1793G>A polymorphisms in the MTHFR gene.

Methods

PCR-RFLP and DNA sequencing were used to genotype the common SNPs in the MTHFR gene in 630 infertile and 250 fertile males. Chi-square test was applied for statistical comparison of genotype data. Linkage disequilibrium between the SNPs and the frequency of common haplotypes were assessed using Haploview software. Biochemical levels of total homocysteine (tHcy) and folic acid were measured. Meta-analysis on c.1298A>C polymorphism was performed using data from ten studies, comprising 2734 cases and 2737 controls.

Results

c.203G>A and c.1298A>C were found to be unrelated to infertility risk. c.1793G>A was protective against infertility (P = 0.0008). c.677C>T and c.1793G>A were in significant LD (D’ = 0.9). Folic acid and tHcy level did not correlate with male infertility. Pooled estimate on c.1298A>C data from all published studies including our data showed no association of this polymorphism with male infertility (Odds ratio = 1.035, P = 0.56), azoospermia (Odds ratio = 0.97, P = 0.74), or oligoasthenoteratozoospermia (Odds ratio = 0.92, p = 0.29). Eight haplotypes with more than 1% frequency were detected, of which CCGA was protective against infertility (p = 0.02), but the significance of the latter was not seen after applying Bonferroni correction.

Conclusion

Among MTHFR polymorphisms, c.203G>A and c.1298A>C do not affect infertility risk and c.1793G>A is protective against infertility. Haplotype analysis suggested that risk factors on the MTHFR locus do not extend too long on the DNA string.

Association of the MTHFR A1298C variant with unexplained severe male infertility

The methylenetetrahydrofolate reductase (MTHFR) gene is one of the main regulatory enzymes involved in folate metabolism, DNA synthesis and remethylation reactions. The influence of MTHFR variants on male infertility is not completely understood. The objective of this study was to analyze the distribution of the MTHFR C677T and A1298C variants using PCR-Restriction Fragment Length Polymorphism (RFLP) in a case group consisting of 344 men with unexplained reduced sperm counts compared to 617 ancestry-matched fertile or normozoospermic controls. The Chi square test was used to analyze the genotype distributions of MTHFR polymorphisms. Our data indicated a lack of association of the C677T variant with infertility. However, the homozygous (C/C) A1298C polymorphism of the MTHFR gene was present at a statistically high significance in severe oligozoospermia group compared with controls (OR = 3.372, 95% confidence interval CI = 1.27–8.238; p = 0.01431). The genotype distribution of the A1298C variants showed significant deviation from the expected Hardy-Weinberg equilibrium, suggesting that purifying selection may be acting on the 1298CC genotype. Further studies are necessary to determine the influence of the environment, especially the consumption of diet folate on sperm counts of men with different MTHFR variants.

Genetic causes of spermatogenic failure

Approximately 10%-15% of couples are infertile, and a male factor is involved in almost half of these cases. This observation is due in part to defects in spermatogenesis, and the underlying causes, including genetic abnormalities, remain largely unknown. Until recently, the only genetic tests used in the diagnosis of male infertility were aimed at detecting the presence of microdeletions of the long arm of the Y chromosome and/or chromosomal abnormalities. Various other single-gene or polygenic defects have been proposed to be involved in male fertility. However, their causative effects often remain unproven. The recent evolution in the development of whole-genome-based techniques and the large-scale analysis of mouse models might help in this process. Through knockout mouse models, at least 388 genes have been shown to be associated with spermatogenesis in mice. However, problems often arise when translating this information from mice to humans.