Homocysteine, vitamin B12, and folate circulating levels in women with and without polycystic ovary syndrome: A systematic review and meta-analysis

BACKGROUND

Some studies have reported that homocysteine, vitamin B12, and folic acid levels are associated with polycystic ovary syndrome (PCOS), whereas other studies yielded controversial results.

OBJECTIVES

This study aimed to systematize the available evidence of homocysteine, vitamin B12, and folate levels in women with and without PCOS.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES AND METHODS

A systematic search without language restrictions was performed on PubMed, Ovid/Medline, Scopus, Embase, and Web of Science. In addition, the reference lists of the selected studies were reviewed. The Newcastle-Ottawa Scale was employed to evaluate the quality of studies. The means and standard deviations of the outcomes were pooled as standardized mean differences (SMDs) with 95% confidence intervals (CI). Furthermore, the DerSimonian and Laird method was employed for the quantitative synthesis.

RESULTS

A total of 75 studies met the eligibility criteria for at least one outcome. Patients with PCOS had higher circulating homocysteine levels than those without (SMD: 0.82; 95% CI: 0.62-1.02, n = 70 studies, p < 0.001). This trend remained in the sensitivity and subgroup analyses by world regions of studies, assay methods, and insulin resistance. No significant differences were observed in circulating vitamin B12 (SMD: -0.11; 95% CI: -0.25 to 0.03; n = 17 studies, p = 0.13) and folate levels (SMD: -0.2; 95% CI: -0.68 to 0.27; n = 17 studies, p = 0.41) between patients with and without PCOS.

CONCLUSIONS

(i) Patients with PCOS exhibited significantly higher homocysteine levels than those without, and (ii) no significant differences were observed in both vitamin B12 and folate levels in women with and without PCOS.

REGISTRATION

PROSPERO ID (CRD42023432883).

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.

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.

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.

Association between the SERPINE1 (PAI-1) 4G/5G insertion/deletion promoter polymorphism (rs1799889) and pre-eclampsia: a systematic review and meta-analysis

The SERPINE1 -675 4G/5G promoter region insertion/deletion polymorphism (rs1799889) has been implicated in the pathogenesis of pre-eclampsia (PE), but the genetic association has been inconsistently replicated. To derive a more precise estimate of the association, a systematic review and meta-analysis was conducted. This study conformed to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed (MEDLINE), Scopus and HuGE Literature Finder literature databases were systematically searched for relevant studies. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for the allelic comparison (4G versus 5G) and genotypic comparisons following the co-dominant (4G/4G versus 5G/5G and 4G/5G versus 5G/5G), dominant (4G/4G+4G/5G versus 5G/5G) and recessive (4G/4G versus 4G/5G+5G/5G) genetic models. Between-study heterogeneity was quantified by I(2) statistics and publication bias was appraised with funnel plots. Sensitivity analysis was conducted to evaluate the robustness of meta-analysis findings. Meta-analysis of 11 studies involving 1297 PE cases and 1791 controls found a significant association between the SERPINE1 -675 4G/5G polymorphism and PE for the recessive genetic model (OR = 1.36, 95% CI: 1.13-1.64, P = 0.001), a robust finding according to sensitivity analysis. A low level of between-study heterogeneity was detected (I(2) = 20%) in this comparison, which may be explained by ethnic differences. Funnel plot inspection did not reveal evidence of publication bias. In conclusion, this study provides a comprehensive examination of the available literature on the association between SERPINE1 -675 4G/5G and PE. Meta-analysis results support this polymorphism as a likely susceptibility variant for PE.

Homocysteine metabolism in polycystic ovary syndrome

Homocysteine, a sulfur-containing amino acid formed during the metabolism of methionine, exert cytotoxic effects on vascular endothelium. Molecular mechanisms of homocysteine-induced cellular dysfunction include increased inflammatory cytokine expression, altered nitric oxide bioavailability, induction of oxidative stress, activation of apoptosis and defective methylation. Hyperhomocysteinemia is associated with an increased risk of atherosclerotic and thromboembolic disorders, as well as hyperinsulinemia and may partially account for increased risk of cardiovascular disease associated with insulin resistance. Women with PCOS are more likely to develop components of the metabolic syndrome such as disturbances of carbohydrate metabolism, obesity, hypertension and dyslipidemia, which in turn are risk factors for cardiovascular disease. A number of studies confirmed the presence of increased serum homocysteine concentration in PCOS patients and the possible determinants of this observation are still debated. PCOS treatment options can influence homocysteine levels.

Genetic polymorphisms associated with steroids metabolism and insulin action in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is an endocrinopathy associated with infertility, diabetes and cardiovascular events. This study aimed to correlate polymorphisms of genes involved in the biosynthesis and metabolism of steroids and insulin action (CYP17A1, CYP19A1, AR, ESR1, ESR2, INSR, IGF2 and PAI1) with clinical and biochemical parameters of PCOS. DNA was extracted from peripheral blood samples obtained from 117 PCOS and 105 healthy women. The PAI1 insertion/deletion (-675 ins/delG) polymorphism (rs1799768) was genotyped by PCR-SSCP. CYP19A1 [TTTA](n), AR [CAG](n), ESR1 [TA](n), and ESR2 [CA](n) genes were evaluated by PCR-based GeneScan analysis, while CYP17A1 5'UTR (rs743572), INSR 1058 CT (rs1799817), and IGF2 3'UTR GA (rs680) polymorphisms were evaluated by PCR-RFLP. The results showed a prevalence of PAI1 4G5G+4G4G genotypes in PCOS (p = 0.025). Younger PCOS women showed a predominance of CT+TT, GA+AA and 4G5G+4G4G genotypes of INSR, IGF2, and PAI1 (p = 0.0499, p = 0.0300, p = 0.0350, respectively). AR shorter alleles (≤ 20 repeats) were significantly associated with higher serum levels of total testosterone (TT, p = 0.0086). In conclusion, PAI1 polymorphism seems to be associated with the risk of PCOS development. Younger PCOS women had specific genotypes of INSR, IGF2 and PAI1 genes. AR shorter alleles can be associated with higher serum levels of TT in PCOS patients.

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.

Polymorphisms of the insulin receptor and the insulin receptor substrates genes in polycystic ovary syndrome: a Mendelian randomization meta-analysis

Polycystic ovary syndrome (PCOS) is a heterogeneous condition with unknown aetiology which is considered to be the most common endocrine disorder in women of reproductive age. In this work we investigated the association of insulin receptor (IotaNSR) and insulin receptor substrates (IRSs) polymorphisms with the risk of developing PCOS. The meta-analysis of eleven studies (889 cases, 1303 controls) yielded a significant association for IRS-1 Gly972Arg (G972R) polymorphism concerning the GR vs. GG genotype (OR: 1.77, 95% CI: 1.28, 2.45), with no between-studies heterogeneity. Concerning IotaNSR His1058 C/T, the meta-analysis of eight studies (795 cases, 576 controls) found no significant evidence for association with PCOS (OR for the TT+CT vs. CC comparison equal to 1.28 with 95% CI: 0.88, 1.85) and a moderate between studies variability (I(2)=44.6%). No evidence for publication bias was found in these meta-analyses. Following a multivariate Mendelian randomization approach, the overall OR was unaffected but the overall mean difference of fasting insulin levels between carriers of GR and RR genotypes in controls was significant (2.18, 95% CI: 0.36, 4.01). These results suggest that IRS-1 Gly972Arg polymorphism is significantly associated with the risk of developing PCOS and that this association is primarily mediated by increasing the levels of fasting insulin. The particular polymorphism is located in a region nearby two phosphorylation sites that interact physically with INSR and PI 3-kinase and there is enough evidence from the literature suggesting that the Arg972 variant is associated with decreased PI 3-kinase activity and impaired insulin-stimulated signaling.