Methylenetetrahydrofolate Reductase Genetic Polymorphisms in Patients with Primary Open-Angle Glaucoma

Association of MTHFR C677T polymorphism with primary open angle glaucoma: a Meta-analysis based on 18 case-control studies

AIM

To systematically understand the genetic association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and primary open angle glaucoma (POAG).

METHODS

A comprehensive literature search in Google Scholar, PubMed, Science Citation Index, Foreign Medical Literature Retrieval Service, Chinese National Knowledge Infrastructure and Wanfang Databases was performed to collect all eligible studies up to August 2019. Study selection, data abstraction and study quality evaluation were performed by two independent investigators. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the association.

RESULTS

Eighteen case-control studies including 2156 cases and 2201 controls were identified. There was no significant difference in the terms of MTHFR C677T polymorphism and POAG in the Caucasian population (for T vs C OR=1.11, 95%CI: 0.88 to 1.39; for TT vs CC OR=1.01, 95%CI: 0.76 to 1.36; for TT+TC vs CC OR=1.15, 95%CI: 0.84 to 1.58 and for TT vs TC+CC OR=1.02, 95%CI: 0.78 to 1.33). However, a significant effect was revealed in the Asian population (for T vs C OR=1.34, 95%CI: 1.12 to 1.59; for TT+TC vs CC OR=1.41, 95%CI: 1.14 to 1.76).

CONCLUSION

Based on 18 eligible studies, we provide a correlation between MTHFR C677T polymorphism and POAG among the Asians subgroup indicating that the T allele or TT +TC genotype may play a critical role in POAG development in Asians.

Association of the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism with primary glaucoma in Saudi population

Background

Methylenetetrahydrofolate reductase (MTHFR), a critical enzyme in folate metabolism is involved in DNA synthesis, DNA repair and DNA methylation. The functional polymorphism of MTHFR gene, C677T has been shown to impact various diseases and implicated as a risk factor for the development of various neurodegenerative disorders including glaucoma.

Methods

We investigated MTHFR C677T genotypes and alleles frequencies in primary glaucoma [primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG)] patients and matched healthy controls in a case-control study. Two hundred ten primary glaucoma cases were studied for MTHFR C677T polymorphism and compared with 280 controls taken from the healthy population, employing the polymerase chain reaction-restriction fragment length polymorphism technique (PCR-RFLP). The MTHFR gene was amplified using specific primers. The PCR products (294 bp) was subsequently digested with HinfI (New England Biolabs) at 37 °C for 12 h, separated by electrophoresis on 2 % agarose gels, and visualized with ethidium bromide staining. The restriction digestion yielded 168 and 126 bp fragments for TT, 294, 168 and 126 bp fragments for CT and undigested PCR product 294 bp indicating CC genotype.

Results

We found the frequency of the genotypes and alleles of MTHFR C677T differ significantly between cases and controls. The frequencies of allele T and genotype CT were significantly higher while the frequencies of allele C and genotype CC were lower in primary glaucoma patients as compared to controls (p <0.05). Upon stratification of our results into POAG and PACG, significantly higher frequencies of allele T (19.44 %) and genotype CT (38.89 %) were found in POAG patients compared to controls (12.5 % and 25 % respectively). The frequencies of alleles and genotypes were almost similar in PACG and controls (p = 0.8).

Conclusion

This study indicates that the allele T and genotype CT of MTHFR C677T polymorphism are significantly associated with POAG while allele C and CC genotype may be protective for it. We conclude that the MTHFR C677T polymorphism increases the risk for POAG development in Saudi population and can be a genetic marker however, further studies are needed with multiple-ethnic populations affected with POAG to strengthen these findings.

Hereditary Thrombophilic Factors in Glaucoma

PURPOSE

To evaluate the hereditary thrombophilic factors in patients with primary open-angle glaucoma, exfoliative glaucoma, and exfoliation syndrome and to compare their results with those of healthy control subjects.

MATERIALS AND METHODS

The study included 75 patients [25 patients with primary open-angle glaucoma (group I), 25 patients with exfoliative glaucoma (group II), and 25 patients with exfoliation syndrome (group III)] and 25 healthy control subjects (group IV). Well-known hereditary thrombophilic factors including methylenetetrahydrofolate reductase (MTHFR) gene C677T mutation, prothrombin G20210A mutation, factor V Leiden mutation, activated protein C resistance, protein S, protein C, and antithrombin III activities, and homocysteine levels were measured in venous blood samples of all subjects.

RESULTS

Fifty-one males and 49 females were included in the study. The mean age of the patients was 67.8 ± 8.7 years (range, 46 to 87 y). There was no statistically significant difference with regard to the mean age (P=0.057) and distribution of sex (P=0.391) between the study groups. The difference of homocysteine, folate, vitamin B12, antithrombin III activity, protein C activity, free protein S activity, and activated protein C resistance were not statistically significant; and the number of subjects with MTHFR C677T, prothrombin G20210A, and factor V Leiden mutations were similar between the study groups.

CONCLUSION

Our results suggest that there is no significant difference between the prothrombotic inherited risk factors of glaucomatous and nonglaucomatous subjects.

The effect of MTHFR ala222val polymorphism on open-angle glaucoma: a meta-analysis

Glaucoma is the second leading cause of irreversible blindness worldwide, among which primary open-angle glaucoma (POAG) is the most common form of glaucoma in some populations. To date, published data on the association between MTHFR (Ala222Val) polymorphism and POAG risk are still inconclusive. In this work, we performed a meta-analysis of available case-control study in order to assess the association between MTHFR (Ala222Val) polymorphism and POAG susceptibility. In total we compiled 13 studies (1970 POAG patients and 1712 control subjects) into the meta-analysis. Overall, no obvious associations between MTHFR (Ala222Val) polymorphism and POAG susceptibility was found under all four genetic models (Val/Val versus Ala/Ala: OR = 1.05, 95% CI = 0.77-1.43; Ala/Val versus Ala/Ala: OR = 1.05, 95% CI = 0.86-1.26; Ala/Val + Val/Val versus Ala/Ala: OR = 1.08, 95% CI = 0.87-1.34; Val/Val versus Ala/Val + Ala/Ala: OR = 1.14, 95% CI = 0.67-1.92). In the stratified analysis by ethnicity, significant associations were still not observed in all genetic models. In conclusion, based on 13 eligible studies, the result provided strong evidences that MTHFR Ala222Val polymorphism is not associated with POAG.

MTHFR C677T predisposes to POAG but not to PACG in a North Indian population: a case control study

Hyperhomocysteinemia induced by the C677T genetic variant in MTHFR (methylenetetrahydrofolate reductase) has been implicated in neuronal cell death of retinal ganglion cells (RGC), which is a characteristic feature of glaucoma. However, association of MTHFR C677T with glaucoma has been controversial because of inconsistent results across association studies. Association between MTHFR C677T and glaucoma has not been reported in Indian population. Therefore, with a focus on neurodegenerative death of RGC in glaucoma, the current study aimed to investigate association of MTHFR C677T with Primary Open Angle Glaucoma (POAG) and Primary Angle Closure Glaucoma (PACG) in a North Indian population. A total of 404 participants (231 patients and 173 controls) were included in this study. Genotyping was performed by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism. A few random samples were also tested by direct sequencing. Genotypic and allelic distributions of the POAG and PACG cohorts were compared to that of controls by chi-square test and odds ratios were reported with 95% confidence intervals. Genotypic and allelic distributions between POAG cases and controls were significantly different (p = 0.03 and p = 0.01 respectively). Unlike POAG, we did not find significant difference in the genotypic and allelic distributions of C677T between PACG cases and controls (p>0.05). We also observed a higher proportion of TT associated POAG in females than that in males. However, this is a preliminary indication of gender specific risk of C677T that needs to be replicated in a larger cohort of males and females. The present investigation on MTHFR C677T and glaucoma reveals that the TT genotype and T allele of this polymorphism are significant risk factors for POAG but not for PACG in North Indian population. Ours is the first report demonstrating association of MTHFR C677T with POAG but not PACG in individuals from North India.

Association study of multiple gene polymorphisms with the risk of adult-onset primary open-angle glaucoma in a Mexican population

The aim of this study was to investigate the association of multiple primary open-angle glaucoma (POAG)-risk alleles in a Mexican population for the first time. Genotyping was performed for a total of 26 previously associated alleles located in 11 different genes, including MYOC, CYP1B1, OPTN, IL1A, TNF, OPA1, EDNRA, AGTR2, MTHFR, GSTM1, and GSTT1. The frequencies of these variants were compared in a group of 218 individuals (118 with POAG and 100 adult controls without the disease). Genomic DNA was extracted from blood leukocytes, and genotyping was performed using PCR followed by direct sequencing. GSTM1 and GSTT1 deletion variants were screened by agarose gel analysis. Individual SNP analysis showed that no specific variants conferred an elevated risk for developing POAG. However, the CG genotype for rs5335 polymorphism in EDNRA showed a protective effect against the development of POAG, as it provides an estimated odds ratio of 0.5 (95% CI, 0.3-0.9; p = 0.03). Moreover, one haplotype consisting of rs1056827 and rs100012 in CYP1B1 gene was significantly associated with a protective effect against POAG (p = 0.0045; OR = 0.3; 95% CI, 0.1-0.7). This is the first case-control investigation of POAG-risk alleles in multiple genes in a Latino population. Although our results support that the analyzed variants are not major risk factors for POAG in this ethnic group, they also point toward a protective effect conferred by EDNRA rs5335, as well as by a CYP1B1 haplotype consisting of rs1056827 and rs100012. Our study emphasizes the importance of genotyping ethnic groups with a complex admixture of ancestral populations for contributing to dissecting the genetics of POAG.

Association between MTHFR C677T polymorphism and primary open-angle glaucoma: a meta-analysis

Epidemiological studies have evaluated the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and primary open-angle glaucoma (POAG) risk. However, the results remain conflicting. The aim of this study was to investigate the association between MTHFRC677T polymorphism and POAG risk. All genetic association studies on MTHFR C677T polymorphism and POAG were systematically searched by the electronic databases PubMed, Embase and Web of Science. Study selection, data abstraction and study quality evaluation were conducted in duplicate independently. The strength of association between MTHFR C677T polymorphism and POAG was measured by odds ratios (ORs) and 95% confidence intervals (CIs). Publication bias was tested by Begg's funnel plot and Egger's regression test. A total of 10 studies including 1224 cases and 1105 controls were included in our final meta-analysis. There was no evidence of significant association of the overall population (for allelic model: OR=1.17, 95% CI=0.94-1.46; for additive model: OR=1.15, 95% CI=0.85-1.57; for dominant model: OR=1.19, 95% CI=0.92-1.55 and for recessive model: OR=1.11, 95% CI=0.83-1.49). Significant associations were found between MTHFR C677T polymorphisms and POAG in allelic model (OR=1.39, 95% CI=1.05-1.83) and additive model (OR=1.88, 95% CI=1.04-3.43) for population-based (PB) subgroup. This meta-analysis suggested that there were significant associations between MTHFR C677T polymorphism and POAG in allelic model and additive model for PB subgroup which indicated that the T allele or TT genotype might increase the risk of POAG, whereas no evidence of significant association was shown of the overall studied population. However, this conclusion should be interpreted cautiously. More large sample-size and multi-ethnicity studies with well-defined POAG patients and well-study design are needed in the future study.