Methylenetetrahydrofolate reductase 677 C-T and homocysteine levels in Turkish patients with pseudoexfoliation

Relationship between homocysteine levels, anterior chamber depth, and pseudoexfoliation glaucoma in patients with pseudoexfoliation

PURPOSE

This study investigates the relationship between plasma homocysteine levels, anterior chamber depth (ACD), and pseudoexfoliation glaucoma (PEXG) in patients with pseudoexfoliation syndrome.

METHODS

Sixty patients (F:M = 35:25) with pseudoexfoliation (PEX) were divided into two groups based on their plasma homocysteine levels; group 1 (< 20 µmol/L, normal) and group 2 (≥ 20 µmol/L, high). Intraocular pressure (IOP) and ACD values as well as plasma homocysteine levels were compared between the two groups. Moreover, the mean values for ACD and IOP were compared between patients stratified according to the reference upper limit for the homocysteine level (above and below 14 μmol/L), and the prevalence of high IOP was estimated.

RESULTS

Groups 1 and 2 showed no statistically significant differences in the mean ACD (3.04 ± 0.28 vs. 3.07 ± 0.31 mm, respectively) and mean IOP (20.63 ± 10.22 vs. 21.67 ± 7.55 mmHg, respectively). Patients with PEX and homocysteine levels > 14 μmol/L had a significantly increased prevalence (P < 0.05) of high IOP (≥ 22 mmHg).

CONCLUSIONS

Patients with PEX and high homocysteine levels have an increased prevalence of high IOP. No relationship exists between plasma homocysteine levels and ACD. Thus, PEXG should be suspected in patients with PEX and high plasma homocysteine levels. Plasma homocysteine levels could be helpful for the diagnosis of PEXG, although larger sample studies are required to confirm this finding.

Clinical and Laboratory Biomarkers for Pseudoexfoliation Syndrome

In this review, we present an update on biomarkers (both clinical and laboratory) on the basis of recent peer-reviewed publications relating to pseudoexfoliation syndrome and pseudoexfoliation glaucoma.

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.

Plasma homocysteine and genetic variants of homocysteine metabolism enzymes in patients from central Greece with primary open-angle glaucoma and pseudoexfoliation glaucoma

BACKGROUND

The purpose of this study was to investigate plasma homocysteine levels and polymorphisms in genes encoding enzymes in the metabolic pathway of homocysteine in association with primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PXFG).

METHODS

A total of 156 glaucoma patients (76 with POAG and 80 with PXFG) and 135 controls matched for age and sex were enrolled in this study. Plasma homocysteine levels were measured using a commercially available enzyme-linked immunosorbent assay kit. DNA was extracted from peripheral blood leukocytes and real-time polymerase chain reaction was performed for genotyping of the samples. Patients were genotyped using predesigned TaqMan(®) single nucleotide polymorphism genotyping assays for two exon variations (rs1801131, rs1801133) in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene and one intron variation (rs8006686) in the methylenetetrahydrofolate dehydrogenase (MTHFD1) gene.

RESULTS

Homocysteine levels were slightly higher in the patient group (POAG and PXFG) compared with controls, but the difference did not reach statistical significance. The minor alleles of the MTHFR single nucleotide polymorphisms showed a protective effect for POAG and showed an increased risk for PXFG, but none of these associations reached statistical significance (P>0.05). The minor allele of MTHFD1 rs8006686 showed a trend for increased risk of both POAG and PXFG (P>0.05). No statistically significant interaction was seen between the genetic variants and homocysteine levels (P>0.05).

CONCLUSION

Our results show that neither the examined single nucleotide polymorphisms from genes involved in the pathway of homocysteine metabolism nor the measured homocysteine levels were associated with POAG or PXFG in our study cohort.

Pseudoexfoliation syndrome and cardiovascular diseases

Pseudoexfoliation (PEX) syndrome is a well-recognized late-onset disease caused by a generalized fibrillopathy. It is linked to a broad spectrum of ocular complications including glaucoma and perioperative problems during cataract surgery. Apart from the long-known intraocular manifestations, PEX deposits have been found in a variety of extraocular locations and they appear to represent a systemic process associated with increased cardiovascular and cerebrovascular morbidity. However, as published results are inconsistent, the clinical significance of the extraocular PEX deposits remains controversial. Identification of PEX deposits in the heart and the vessel wall, epidemiologic studies, as well as, similarities in pathogenetic mechanisms have led to the hypothesis of a possible relation between fibrillar material and cardiovascular disease. Recent studies suggest that PEX syndrome is frequently linked to impaired heart and blood vessels function. Systemic and ocular blood flow changes, altered parasympathetic vascular control and baroreflex sensitivity, increased vascular resistance and decreased blood flow velocity, arterial endothelial dysfunction, high levels of plasma homocysteine and arterial hypertension have all been demonstrated in PEX subjects. Common features in the pathogenesis of both atherosclerosis and PEX, like oxidative stress and inflammation and a possible higher frequency of abdominal aorta aneurysm in PEX patients, could imply that these grey-white deposits and cardiovascular disorders are related or reflect different manifestations of the same process.

Pseudoexfoliation syndrome, a systemic disorder with ocular manifestations

Pseudoexfoliation syndrome (PXS) is a systemic condition with eye manifestations. In the eye, pseudoexfoliation material deposits on various structures of the anterior segment. The nature of this material is mostly fibrillar with fibers made up of microfibrils and coated with amorphous material. The composition of these fibrils is diverse and includes basement membrane components as well as enzymes involved in extracellular matrix maintenance. Pseudoexfoliation is the most common cause of secondary open-angle glaucoma (pseudoexfoliation glaucoma, PXG) worldwide. The goal of this review is to summarize our knowledge on the genetics of this systemic disorder and its resultant ocular manifestations. PXS familial aggregation suggests genetic inheritance. PXS has been strongly associated with single nucleotide polymorphisms (SNPs) of the lysyl oxidase-like 1 (LOXL1) gene on chromosome 15q24.1. Two of these SNPs confer a higher than 99% population attributable risk for PXS and PXG in the Nordic population; however, they carry different risks in different populations. The high risk haplotypes also vary among different populations. LOXL1 is one of group of the enzymes involved in the cross-linking of collagen and elastin in the extracellular matrix. Its function in connective tissue maintenance has been confirmed in mice; however, its actual role in PXS remains unclear. Contactin-associated protein-like 2 also has a strong genetic association with PXS in a German cohort and is an attractive candidate molecule. It encodes for a protein involved in potassium channel trafficking. Other candidate genes linked to PXS include lysosomal trafficking regulator, clusterin, adenosine receptors, matrix metalloproteinase-1 (MMP1), and glutathione transferase. These genes may be modifying genes for development of PXS and PXG.

Levels of plasma homocysteine in pseudoexfoliation glaucoma

BACKGROUND

To examine levels of serum homocysteine (Hcy), vitamin B12 and folic acid in patients with pseudoexfoliation glaucoma (PEXG), primary open-angle glaucoma (POAG), and healthy control subjects.

METHODS

This study included 36 patients with PEXG, 40 with POAG, and 40 age-matched healthy subjects. Fasting plasma Hcy concentrations and levels of serum vitamin B12 and folic acid were measured using competitive chemiluminescent enzyme immunoassay; values exceeding 14 μm/l were considered elevated.

RESULTS

Mean plasma Hcy was significantly higher in PEXG (16.55 ± 7.23 μm/l) compared with POAG (13.91 ± 3.61 μm/l) and controls (13.12 ± 5.13 μm/l) (p = 0.03 and p = 0.0007 respectively). There were no statistical differences in serum vitamin B12 and folic acid levels among PEXG, POAG and control subjects (p > 0.05). A moderate, although statistically significant, relationship between Hcy and folic acid levels was found in the PEXG group (R(2) = 0.23, p = 0.003). Hcy levels were found not to be related with folic acid or vitamin B12 in either POAG or control subjects.

CONCLUSIONS

In this study, plasma Hcy is significantly higher in PEXG group than the POAG and control groups. Hyper-Hcy might play a role in the pathogenesis of PEXG. Hyper-Hcy may be an independent factor stressing vasculopathy in addition to pseudoexfoliation, so might be a modifiable risk factor for PEXG.

Levels of circulating homocysteine, vitamin B6, vitamin B12, and folate in different types of open-angle glaucoma

OBJECTIVE

To compare the levels of plasma homocysteine (Hcy), vitamin B6 (vit-B6), serum vitamin B12 (vit-B12), and folate in healthy individuals and in patients with normal tension glaucoma (NTG), pseudoexfoliative glaucoma (PXG), or primary open-angle glaucoma (POAG).

STUDY DESIGN

A prospective controlled trial.

PARTICIPANTS AND METHODS

Forty healthy subjects, 48 patients with NTG, 38 patients with PXG, and 34 patients with POAG were included in the study. Those who used vitamin supplements or medications affecting Hcy and vitamin levels were excluded from the study. The levels of Hcy and vit-B6 were measured by High Performance Liquid Chromatography (HPLC). The levels of serum vit-B12 and folic acid were measured by competitive chemiluminescent enzyme immunoassay (CEI). One-way analysis if variance (ANOVA), analysis of covariance (ANCOVA), and the Tukey honestly significant difference test were used for statistical analysis.

RESULTS

The mean Hcy level of the PXG group was 15.46+/-9.27 micromol/L which was significantly higher (P=0.03) than that of the control group. There were no statistical differences in serum vit-B12 and folate levels among control subjects and NTG, PXG and POAG groups (P>0.05). It was found that the mean plasma vit-B6 level was significantly higher in subjects with NTG (P=0.03) and POAG (P=0.025) versus controls. Mean vit-B6 levels in NTG and POAG were 30.50+/-11.29 microg/L and 30+/-12.15 microg/L, respectively.

CONCLUSIONS

The plasma level of Hcy was found to be increased only in PXG patients and the plasma levels of vit-B6 were found to increase in the NTG and POAG sample groups. Using homocysteine and vit-B6 levels as the determinants of hyperhomocysteinemia still needs further research.

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

PURPOSE

Hyperhomocysteinemia has been found in patients with primary open-angle glaucoma. The purpose of the present study was to determine if hyperhomocysteinemia-associated polymorphisms of the methylenetetrahydrofolate reductase gene (MTHFR) are overrepresented in primary open-angle glaucoma.

METHODS

Patients with primary open-angle glaucoma (n = 243) and controls (n = 187) were analyzed for the MTHFR 677 C > T and 1298 A > C polymorphisms using minisequencing technique.

RESULTS

No significant differences were observed in allele and genotype frequencies of the MTHFR 677C > T and 1298A > C polymorphisms between controls and the primary open-angle glaucoma group.

CONCLUSIONS

If hyperhomocysteinemia is important in the pathogenesis of glaucoma, this study does not support a role for MTHFR polymorphisms in this context.

Plasma homocysteine, MTHFR gene mutation, and open-angle glaucoma

OBJECTIVE

Elevated plasma homocysteine has been associated with an increased risk of cardiovascular disease. The association between open-angle glaucoma and cardiovascular disease has recently stimulated interest in the role of homocysteine in the pathogenesis of glaucoma. Some studies report elevated plasma homocysteine in patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma (PXFG), but have not found this association consistently in other types of open-angle glaucoma. In this study, we have measured plasma homocysteine and C677T methylenetetrahydrofolate reductase (MTHFR) mutation, the commonest genetic cause of elevated plasma homocysteine, in patients with PXFG, primary open-angle glaucoma (POAG), and normal tension glaucoma (NTG).

DESIGN

Prospective cross-sectional cohort study.

PARTICIPANTS

Forty-eight patients with PXFG, 36 patients with POAG, 34 patients with NTG, and 42 controls without glaucoma.

METHODS

Fasting venous blood samples from each participant were analyzed for plasma homocysteine and the C677T MTHFR gene mutation. MAIN OUTCOME OF INTEREST: Mean plasma homocysteine levels, number of individuals with homocysteine above the reference range, and percentage of individuals with heterozygous or homozygous C677T MTHFR gene mutations.

RESULTS

Mean plasma homocysteine was significantly higher in PXFG (11.77+/-4.18 micromol/L), POAG (11.21+/-2.84 micromol/L), and NTG (11.74+/-3.79 micromol/L) compared with control (9.82+/-1.75 micromol/L). Hyperhomocysteinemia was found in 27.1% of PXFG patients, 30.6% of POAG patients, and 29.4% of NTG patients. There was no significant difference in frequency of MTHFR C677T gene mutation between groups.

CONCLUSIONS

Plasma homocysteine was elevated in PXFG, POAG, and NTG. Elevated plasma homocysteine seems to be associated with glaucoma in these patients.

Single Nucleotide Polymorphisms That Affect Homocysteine Levels in Turkish Population

In this study, single nucleotide polymorphisms (SNPs) involved in homocysteine metabolism such as CT replacement in the 677th nucleotide in 5,10-methylenetetrahydrofolate reductase (MTHFR) enzyme; 68-bp insertion in the 844th nucleotide of cystathionine β-synthase (CBS) enzyme; 6-bp insertion/deletion in the region of 3′UTR in thymidylate synthase (TYMS) enzyme and 19-bp deletion in dihydrofolate reductase (DHFR) enzyme were investigated. The effects of these mutations on homocysteine levels were studied. As a result; we found that TT genotype of MTHFR 677 CT is an influencing factor on homocysteine levels in Turkish population. Furthermore, there seems to be another MTHFR 677 TT haplotype, which does not have an effect on homocysteine levels .Our data revealed that other SNPs did not have any influence on homocysteine levels.

Investigation of the association between 677C>T and 1298A>C 5,10-methylenetetra- hydrofolate reductase gene polymorphisms and normal-tension glaucoma

PURPOSE

Homozygous polymorphism of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene and resultant hyperhomocysteinaemia have been established as an independent risk factor for vascular diseases. There are evidences that vascular abnormalities are involved in the pathogenesis and progression of normal-tension glaucoma (NTG). In the present study, we were to find out the associations between 677C>T and 1298A>C polymorphisms of the MTHFR gene and NTG.

METHODS

This was a retrospective, case-controlled study enrolling 78 NTG patients and 100 controls. DNA from peripheral blood lymphocytes was extracted and the genotypes of polymorphisms (677C>T and 1298A>C) in the MTHFR gene were determined using PCR followed by restriction enzyme digestion. The frequencies of the polymorphic genotypes in the patients with NTG and controls were compared.

RESULTS

The frequencies of the polymorphisms of the MTHFR gene (677C>T and 1298A>C) in the NTG patients were not significantly different from those of controls. But the younger NTG patients (age at diagnosis < or = 45 years) showed significantly higher prevalence of 677C>T polymorphism than the older NTG patients (age at diagnosis > 45 years) (TT genotype, 38.9 vs 11.9%, P=0.006, OR=4.71, 95% CI=1.49-14.9) and than the younger control subgroup (TT genotype, 38.9 vs 6.1%, P=0.001, OR=9.86, 95% CI=2.23-42.4).

CONCLUSIONS

The 677C>T polymorphism was significantly associated with NTG in the younger patients, while 1298A>C polymorphism was not. This suggests that 677C>T polymorphism of the MTHFR gene can be a genetic risk factor of NTG in Korean population.

Asymmetric dimethylarginine is not elevated in exfoliation syndrome but symmetric dimethylarginine is related to exfoliative glaucoma

BACKGROUND

Hyperhomocysteinemia (HH), oxidative stress and endothelial dysfunction are all implicated as possible pathogenetic factors in exfoliation syndrome (XFS) and exfoliative glaucoma (XFG). Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of endothelial nitric oxide and plasma level of ADMA is often elevated in HH. Thus the present study was undertaken to study plasma levels of ADMA with concomitant measurement of symmetric dimethylarginine (SDMA) and L-arginine (L-Arg) in XFS and XFG.

METHODS

This cross-sectional, prospective study involved 36 XFS patients, 11 of them having XFG, and 36 age- and gender-matched controls. Fasting plasma ADMA, SDMA and L-Arg levels of participants were determined. A special view was created how plasma L-Arg, ADMA and SDMA correlate to plasma homocysteine (P-Hcy). In addition, the influence of P-Hey values derived from our previous study on the above mentioned parameters were evaluated by cut-off values of P-Hcy, 12 micromol/l for women and 14.5 micromol/l for men. RESULTS The mean plasma ADMA, SDMA and L-Arg levels were 0.41, 0.49 and 62.9 micromol/l in the XFS/XFG group, and 0.41, 0.44 and 69.7 micromol/l in the control group, respectively. As all parameters within the XFS and control group were compared, no statistical significance was stated. On the other hand, a positive correlation was observed between plasma SDMA and P-Hcy in XFGs (P = 0.002), and additionally, also a statistically significant difference was in plasma SDMA between the two groups sorted by cut-off levels of P-Hcy 0.49 +/- 0.15 vs. 0.36 +/- 0.04 micromol/l, above and below cut-off levels, respectively (P = 0.001), but not between ADMA in a respective assay. The mean values of L-Arg were 64.6 +/- 17.2 vs. 74.8 +/- 13.3 microg/l, respectively (P = 0.031). In the XFS subgroup, on the contrary, there was no positive correlation between P-Hcy and plasma SDMA.

CONCLUSIONS

A positive correlation of plasma SDMA in respect to P-Hcy in XFGs and increase of SDMA in mild or intermediate hyperhomocysteinemia may indicate SDMA as a marker of developing XFG in hyperhomocysteinemic