Polycystic ovary syndrome and the single nucleotide polymorphisms of methylenetetrahydrofolate reductase: a pilot observational study

Potential environmental toxicant exposure, metabolizing gene variants and risk of PCOS-A systematic review

Exposure of environmental toxicants such as potentially toxic metals and pesticides have largely been attributed to produce adverse effects on general women's health and to be more precise on the reproductive system. In order to explore exposure of toxicants and metabolizing gene variants as risk factor for polycystic ovarian syndrome (PCOS), literature search was carried out using the databases PubMed, Central Cochrane Library, Google Scholar, Science Direct with appropriate keywords upto 6 December 2020. While most of the studies indicate higher serum Cu concentration and lower concentration of Mn as risk factor, studies also report presence of higher pesticide concentration in PCOS women. Genes such as MTHFR, CYPs participate in the metabolism of toxicants and may show different response due to underlying genetic variants. Thus, toxicant exposure are to some extent responsible for the pathogenesis of syndrome through oxidative stress and endocrine disruption, but the susceptibility may vary due to the underlying genetic polymorphism of the exposed population.

Methylenetetrahydrofolate reductase gene polymorphisms in the risk of polycystic ovary syndrome and ovarian cancer

Polymorphisms of methylenetetrahydrofolate reductase (MTHFR) in hormone metabolism pathways might cause metabolic disturbances and contribute to the development of polycystic ovary syndrome (PCOS) and ovarian cancer, but the published studies were inconsistent. The aim of the present study was to evaluate the MTHFR C677T (rs1801133) and A1298C (rs1801131) gene polymorphisms in the risk of PCOS and ovarian cancer by meta-analysis. A comprehensive electronic search was conducted in databases for studies published from 1995 to 2020. The pooled ORs were calculated by Revman 5.2 software. Twenty-nine articles including 45 case–control studies were included. We found that MTHFR C677T polymorphisms were correlated with elevated PCOS risk (TT vs. CT+CC: OR = 1.41, 95%CI = 1.20–1.67; TT+CT vs. CC: OR = 1.54, 95%CI = 1.07–2.22; CT vs. CC+TT: OR = 1.18, 95%CI 1.04–1.33; TT vs. CC: OR = 1.47, 95%CI = 1.03–2.11; T vs. C: OR = 1.25, 95%CI = 1.06–1.47), which were more obvious in Middle Eastern subgroup. MTHFR A1298C polymorphisms were also associated with overall PCOS susceptibility (CC vs. AC+AA: OR = 2.55, 95% CI = 1.61–4.03; CC+AC vs. AA: OR = 1.84, 95%CI = 1.04–3.28; CC vs. AA: OR = 2.66, 95%CI = 1.68–4.22; C vs. A: OR = 1.67, 95%CI = 1.03–2.71), which were mainly reflected in Asian subjects. For ovarian cancer, MTHFR C677T polymorphisms were only related with elevated ovarian cancer risk in Asian population, while no significant association was found for A1298C polymorphisms. This meta-analysis suggested that MTHFR C677T and MTHFR A1298C polymorphisms were correlated with elevated PCOS risk. MTHFR C667T only posed a higher risk for ovarian cancer in Asians instead of other populations, while MTHFR A1298C polymorphisms were not related to ovarian cancer risk. Further studies are needed to validate the conclusion.

Significant association between methylenetetrahydrofolate reductase gene C677T polymorphism with polycystic ovary syndrome risk: A meta-analysis update

The methylenetetrahydrofolate reductase (MTHFR) may play a pathological role in polycystic ovary syndrome (PCOS). However, the conclusions of published reports on the relationship between the MTHFR C677T polymorphism and PCOS risk remain controversial.To derive a more precise estimation we performed a metaanalysis based on 22 studies that together included 2405 cases and 2419 controls. PubMed, EMBASE, WanFang and the Chinese National Knowledge Infrastructure databases were used to retrieve articles up to up to October 28, 2019. The crude odds ratios (ORs) with 95% confidence intervals (95% CI) were calculated to evaluate the association.Metaanalysis results showed a significant association between the MTHFR C677T polymorphism and PCOS risk in 3 genetic models (allele model: OR = 1.40, 95% CI = 1.27-1.53; dominant model: OR = 1.47, 95% CI = 1.17-1.85); homozygous model: OR = 1.90, 95% CI = 1.55-2.32). Moreover, significant associations were observed when stratified by ethnicity, source of controls, etiology, and genotype methods.This metaanalysis suggests that the T-allele of the MTHFR C677T polymorphism is associated with an increased risk of PCOS, especially in Asians further studies with larger population sizes are needed to confirm these results.

Can the genetic polymorphisms of the folate metabolism have an influence in the polycystic ovary syndrome?

OBJECTIVE

To investigate the association of the genetic variants of the folate metabolism genes (MTHFR C677T; MTHFR A1298C; MTR A2756G; MTRR A66G and RFC-1 A80G) with the development of polycystic ovary syndrome (PCOS).

SUBJECTS AND METHODS

This study included 203 women (99 women with PCOS and 104 controls). The genotyping was performed by PCR-RFLP. Chi-squared test and multiple logistic regression were used in the statistical analysis. Haplotype analysis was conducted using the SNPstat program. The results were presented in odds ratio (OR) and confidence interval of 95% (CI-95%), with a significance level of 5% (p ≤ 0.05).

RESULTS

The genotypic distribution of the RFC-1 A80G polymorphism showed significant difference between the two groups, showing that the heterozygous genotype (AG genotype) was most frequent in controls. The polymorphic homozygous (GG genotype) of MTRR A66G polymorphism were most frequent in controls. The T-C haplotype MTHFR C677T and A1298C polymorphisms were more frequent in the control group (OR = 0.19; CI 95% - 0.04 to 0.93 e p = 0.042). The multivariate analysis evidenced that family history of PCOS was more frequent in the PCOS group (OR = 3.29; CI 95% - 1.48 to 7.31; p = 0.003).

CONCLUSION

In our casuistry, the polymorphic homozygous of MTRR A66G polymorphism gene and heterozygous of RFC-1 A80G polymorphism gene, the haplotype T-C C677T and A1298C polymorphisms of MTHFR gene, can be associated with protective factors for the disease.

Potential genetic polymorphisms predicting polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogenous endocrine disorder with typical symptoms of oligomenorrhoea, hyperandrogenism, hirsutism, obesity, insulin resistance and increased risk of type 2 diabetes mellitus. Extensive evidence indicates that PCOS is a genetic disease and numerous biochemical pathways have been linked with its pathogenesis. A number of genes from these pathways have been investigated, which include those involved with steroid hormone biosynthesis and metabolism, action of gonadotropin and gonadal hormones, folliculogenesis, obesity and energy regulation, insulin secretion and action and many others. In this review, we summarize the historical and recent findings in genetic polymorphisms of PCOS from the relevant publications and outline some genetic polymorphisms that are potentially associated with the risk of PCOS. This information could uncover candidate genes associating with PCOS, which will be valuable for the development of novel diagnostic and treatment platforms for PCOS patients.

Methylenetetrahydrofolate reductase C677T polymorphism and the risks of polycystic ovary syndrome: an updated meta-analysis of 14 studies

Some studies have reported an association between the Methylenetetrahydrofolate reductase (MTHFR) C667T genetic variant and risk of polycystic ovary syndrome (PCOS), although the results remain controversial. A systematic search was conducted on PubMed, Web of Science, EMBASE, Ovid, Chinese National Knowledge Databases and WanFang databases with relevant keywords. Fourteen studies of sixteen distinct populations involving 1478 PCOS cases and used to conduct a meta-analysis. The T allele was not significantly associated with increased risk of PCOS [OR: 1.08; 95% CI: 0.96–1.21]. In the stratified analysis by ethnicity, the T allele significantly increases risks for the Asian [OR = 1.31; 95% CI: 1.09–1.58] population. No significant associations were detected for the Middle Eastern population [OR = 1.26; 95% CI: 0.96–1.67] and the T allele was found to be protective in the Caucasian population [OR = 0.82; 95% CI: 0.68–0.99]. In conclusion, this meta-analysis suggests that MTHFR C667T variant can increase, decrease, or have no effect on the risks of PCOS depending on the ethnicity.

Association of the Pro12Ala Polymorphism with the Metabolic Parameters in Women with Polycystic Ovary Syndrome

AIM:

To investigate the association of peroxisome proliferator-activated receptor gamma (PPARG) Pro12Ala polymorphism with polycystic ovary syndrome (PCOS) and its effect on the metabolic parameters in PCOS women.

METHODS:

The study used PCR to identify the presence of the PPARG Pro12Ala polymorphism in 100 PCOS women and 120 age-matched healthy women. All participants were subjected to anthropometry, biochemical and metabolic evaluation.

RESULTS:

Significant difference in the genotypes distributions of PPARG Pro12Ala polymorphism was observed among PCOS women and controls (p = 0.03). The frequency of the polymorphic allele Ala was significantly higher in PCOS cases than that in the controls (OR = 2.01, p = 0.01). The carries of the variant allele Ala in PCOS women showed significant higher values in body mass index (BMI), systolic and diastolic blood pressure, waist circumference, waist to hip ratio, sum of skin folds, fasting blood glucose, fasting blood insulin, HOMA-IR, fasting triglycerides, total cholesterol and low-density lipoprotein than non-carriers.

CONCLUSION:

The PPARG Pro12Ala polymorphism might contribute to the risk of PCOS and abnormal metabolic parameters and could be considered as a biomarker for early diagnosis and clinic prediction of metabolic complications.

Association between High Serum Homocysteine Levels and Biochemical Characteristics in Women with Polycystic Ovarian Syndrome: A Systematic Review and Meta-Analysis

Background

Elevated homocysteine levels have been observed in previous studies of PCOS; however, the nature of the associations between high homocysteine levels and the biochemical characteristics of polycystic ovarian syndrome (PCOS)—such as obesity, insulin resistance (IR), and androgen levels—is still uncertain.

Methods

A systematic search was conducted electronically up to December 28, 2015 using specific eligibility criteria. Standardized mean difference (SMD) and the corresponding 95% confidence intervals (95% CIs) were used as a measure of effect size.

Results

A total of 34 studies (with 1,718 cases and 1,399 controls) of homocysteine levels in PCOS were pooled in this meta-analysis. Significantly lower homocysteine levels were found in controls than in PCOS patients (SMD = 0.895, 95% CI = 0.643–1.146, P<0.001; I² = 90.4% and P<0.001 for heterogeneity), regardless of the degree of obesity, IR, or androgen levels. Homocysteine levels in non-IR PCOS patients were significantly lower than those of PCOS patients with IR (SMD = 0.69, 95% CI = 0.37–1.01, P<0.01; I² = 0% and P = 0.50 for heterogeneity). However, metformin treatment did not appear to cause any significant change in the homocysteine levels of PCOS patients (SMD = –0.17, 95% CI = –1.10–0.75, P = 0.71; I² = 92% and P<0.01 for heterogeneity).

Conclusions

High homocysteine levels in women with PCOS are not related to degree of obesity, IR, or androgen levels. Metformin treatment cannot decrease the homocysteine levels in PCOS patients.

Is MTHFR 677 C>T Polymorphism Clinically Important in Polycystic Ovarian Syndrome (PCOS)? A Case-Control Study, Meta-Analysis and Trial Sequential Analysis

BACKGROUND

Optimum efficiency of the folate pathway is considered essential for adequate ovarian function. 677 C>T substitution in the 5, 10-methylene tertrahydrofolatereductase (MTHFR) gene compromises activity of the MTHFR enzyme by about 50%. The significance of correlation between 677C>T substitution and PCOS remains dubious due to the low power of published studies.

METHODS AND RESULTS

We analyzed MTHFR 677 C>T site in ethnically two different PCOS case-control groups (total 261 cases and 256 controls) from India. The data analysis revealed a lack of association between this polymorphism and PCOS [OR = 1.11 (95%CI = 0.71-1.72), P = 0.66]. Group-wise analysis on the basis of ethnicity also revealed no association in any of the ethnic groups [Indo-Europeans, P = 1; Dravidians, P = 0.70]. Homocysteine levels did not differ significantly between cases (15.51 μmol/L, SD = 2.89) and controls (15.89 μmol/L, SD = 2.23). We also undertook a meta-analysis on 960 cases and 1028 controls, which suggested a significant association of the substitution with PCOS in the dominant model of analysis (OR = 1.47 (95%CI = 1.04-2.09), P = 0.032]. Trial sequential analysis corroborated findings of the traditional meta-analysis. However, we found that the conclusions of meta-analysis were strongly influenced by studies that deviated from the Hardy Weinberg equilibrium. A careful investigation of each study and a trial sequential analysis suggested that 677 C>T substitution holds no clinical significance in PCOS in most of the populations.

CONCLUSION

In conclusion, MTHFR 677 C>T polymorphism does not affect PCOS risk in India. The association seen in the meta-analysis is due to an outlier study and studies showing deviation from the Hardy Weinberg equilibrium.

Circulating markers of oxidative stress and polycystic ovary syndrome (PCOS): a systematic review and meta-analysis

BACKGROUND Oxidative stress might be associated with polycystic ovary syndrome (PCOS), but relatively small studies published to date do not permit reaching a definitive conclusion. We aimed at conducting a systematic review and meta-analysis of studies evaluating circulating markers of oxidative stress in patients with PCOS. METHODS We conducted a systematic review of studies reporting circulating markers of oxidative stress in women with PCOS and controls published up to June 2012, using Entrez PubMed and EMBASE online facilities. Meta-analysis calculated standardized mean differences (SMDs) and 95% confidence intervals (95CI). RESULTS From 1633 potential studies identified electronically, 68 studies, including 4933 PCOS patients and 3671 controls, were selected. For each of nine circulating markers of oxidative stress, an individual meta-analysis was conducted. Compared with control women, patients with PCOS presented higher circulating concentrations of homocysteine (23% increase, SMD 0.6, 95CI, 0.4-0.8), malondialdehyde (47% increase, SMD 1.9, 95CI 1.2-2.6) and asymmetric dimethylarginine (36% increase, SMD 1.1, 95CI 0.6-1.6), and increased superoxide dismutase activity (34% increase, SMD 1.0, 95CI 0.5-1.4) and decreased glutathione levels (50% decrease, SMD -3.7, 95CI -6.2 to -1.2) and paraoxonase-1 activity (32% decrease, SMD -0.9, 95CI -1.3 to -0.4). Similar results were found when restricting the analyses to studies in which patients and controls were matched for age and body mass index. CONCLUSIONS Circulating markers of oxidative stress are abnormal in women with PCOS independent of weight excess. This finding suggests that oxidative stress may participate in the pathophysiology of this common disorder.

A meta-analysis on the association between PPAR-γ Pro12Ala polymorphism and polycystic ovary syndrome

PURPOSE

To investigate the influence of the peroxisome proliferator activated receptor gamma (PPAR-γ) Pro12Ala polymorphism on the susceptibility of polycystic ovary syndrome (PCOS) and body mass index (BMI), fast insulin levels, homeostasis model assessment of insulin resistance (HOMA-IR) in PCOS patients.

METHODS

PubMed, EMBASE, MEDLINE and CENTRAL databases were searched to identify eligible studies. We then conducted a meta-analysis to examine the association between Pro12Ala polymorphism and PCOS.

RESULTS

Seventeen eligible studies, including 2,149 patients and 2,124 controls were enrolled in this meta-analysis. Pro12Ala polymorphism was significantly associated with the susceptibility of PCOS (odds ratio [OR] 0.74, 95 % confidence interval [CI] [0.61, 0.90] for allele; OR 0.70, 95 % CI [0.57, 0.86] for genotype). In the European subgroup of PCOS, the X/Ala genotype was associated with lower BMI (mean difference [MD] -1.08, 95 % CI [-2.08, -0.09]) and fast insulin levels (MD -19.82, 95 % CI [-34.07, -5.58]). However, this polymorphism did not display an impact on HOMA-IR in PCOS patients.

CONCLUSIONS

Ala variant would decrease the risk of PCOS and result in lower BMI and fast insulin levels in a European population, but had no impact on HOMA-IR in PCOS patients. Further studies are required to elucidate these associations more clear.

Association of angiotensin converting enzyme (ACE) gene I/D polymorphism and polycystic ovary syndrome (PCOS)

This study was conducted in Turkish patients with polycystic ovary syndrome to determine the frequency of I/D polymorphism genotypes of angiotensin converting enzyme gene, and to examine the role of this polymorphism in polycystic ovary syndrome development. Genomic DNA obtained from 200 persons (100 patients with polycystic ovary syndrome and 100 healthy controls) was used in the study. DNA was multiplied by polymerase chain reaction using I and D allele-specific primers. Polymerase chain reaction products were assessed with a charge coupled device (CCD) camera by being exposed to 2% agarose gel electrophoresis. There was statistically significant difference between the groups with respect to genotype distribution (p<0.001). The D allele frequency was indicated as 68% and I allele was as 32% in the patients, whereas it was 51.5-48.5% respectively in the control group. As a result of our study we may assert that angiotensin converting enzyme gene I/D polymorphism DD genotype should be considered as a genetic marker in polycystic ovary syndrome development in this Turkish study population.

Meta-analysis of cardiovascular disease risk markers in women with polycystic ovary syndrome

BACKGROUND

The relation between polycystic ovary syndrome (PCOS) and cardiovascular disease (CVD) remains unclear. In an attempt to provide high-quality evidence on the relation between PCOS and CVD, relevant literature for CVD risk markers [C-reactive protein (CRP), homocysteine (Hcy), tumor necrosis factor-alpha (TNF-α), plasminogen activator inhibitor-1 (PAI-1), lipoprotein (a) [Lp(a)], advanced glycation end-products (AGEs), vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), asymmetric dimethylarginine (ADMA), endothelin-1 (ET-1) and fibrinogen] in women with PCOS was reviewed and analyzed.

METHODS

A systematic search was conducted electronically using specific eligibility criteria. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated and combined appropriately. To ensure synthesis of the best available evidence, sensitivity analyses were performed. RESULTS A total of 130 data sets were included in 11 different outcomes, involving 7174 and 5076 CVD markers in women with PCOS and controls, respectively. Women with PCOS demonstrated significantly elevated CRP [WMD (95% CI) 0.99 (0.77-1.21)], Hcy [2.25 (1.46-3.03)], PAI-1 antigen [16.96 (7.25-26.28)], PAI-1 activity [0.71 (0.18-1.23)], VEGF [1.72 (0.96-2.48)], ADMA [0.19 (0.08-0.3)], AGEs [3.91 (2.36-5.45)] and Lp(a) [0.81 (0.58-1.04)] concentrations compared with controls, yet with significant between-study heterogeneity. Borderline significance (not robust in the sensitivity analyses) was detected for TNF-α [0.75 (0.07-1.44)], ET-1 [1.06 (0.52-1.59)] and fibrinogen [0.20 (0.01-0.39)], whereas no difference was detected for IL-6 [0.71 (-0.16 to 1.59)]. CONCLUSIONS Women with PCOS have increased serum concentrations of CVD risk markers compared with controls. Whether this apparent risk is translated into increased incidence of CVD in later life remains to be elucidated.

Methylenetetrahydrofolate reductase C677T gene polymorphism in Turkish patients with polycystic ovary syndrome

Higher Levels of Hcy are associated with several clinical conditions, among them non-insulin-dependent diabetes mellitus, endometrial dysplasia and hypertension with insulin resistance, and polycystic ovary syndrome. The purpose of this study was to investigate the serum homocystein levels and other metabolic parameters in relationship with the MTHFR C677T gene polymorphism in patients with PCOS. Our study included 86 young women with PCOS constituting the study group and 70 healthy women constituting the control group. Homocystein levels, metabolic, and hormonal parameters were measured, and genetic analysis of the MTHFR C677T gene polymorphism was performed in all the subjects. A statistically significant difference was observed in mean homocystein levels between patients with PCOS when compared to the control group. The MTHFR 677 CC genotypes had significantly higher proportions in the control group compared to the PCOS patients (χ(2) = 21.381, P < 0.001). Our data show that homocystein levels were higher than normal subjects in patients with PCOS and that the MTHFR C677T gene polymorphism does not influence homocystein levels of patients with PCOS.

Association between a single nucleotide polymorphism in MTHFR gene and polycystic ovary syndrome

OBJECTIVE

The aim of the present study was to investigate whether there is an association between the C677T polymorphism in MTHFR and PCOS in a Korean population.

STUDY DESIGN

The prevalence of MTHFR gene was compared between women with PCOS (n=227) and normal patients (n=115) using restriction fragment length polymorphism (RFLP) analysis. The HapAnalyzer was used to analyze the genotype of MTHFR polymorphism in PCOS and control subjects. We considered a p-value less than 0.05 as statistically significant.

RESULTS

The frequency of C/C, C/T, and T/T genotype showed similar proportion between PCOS and control subjects. In addition, the frequencies of co-dominant (p-value=0.8334, odds ratio (OR)=1.04), dominant (p-value=0.8749, OR=0.96) and recessive alleles (p-value=0.5574, OR=1.22) did not show any association between PCOS and control subjects.

CONCLUSION

Our data demonstrate that the C677T polymorphism of MTHFR gene is not associated with PCOS in a Korean population, suggesting that the C677T polymorphism in MTHFR may have different influences in various ethnic groups and diseases.