Homocysteine, MTHFR C677T gene polymorphism, folic acid and vitamin B 12 in patients with retinal vein occlusion

PON1, APOE and SDF-1 Gene Polymorphisms and Risk of Retinal Vein Occlusion: A Case-Control Study

Numerous studies have tried to evaluate the potential role of thrombophilia-related genes in retinal vein occlusion (RVO); however, there is limited research on genes related to different pathophysiological mechanisms involved in RVO. In view of the strong contribution of oxidative stress and inflammation to the pathogenesis of RVO, the purpose of the present study was to investigate the association of inflammation- and oxidative-stress-related polymorphisms from three different genes [apolipoprotein E (APOE), paraoxonase 1 (PON1) and stromal cell-derived factor 1 (SDF-1)] and the risk of RVO in a Greek population. Participants in this case-control study were 50 RVO patients (RVO group) and 50 healthy volunteers (control group). Blood samples were collected on EDTA tubes and genomic DNA was extracted. Genotyping of rs854560 (L55M) and rs662 (Q192R) for the PON1 gene, rs429358 and rs7412 for the APOE gene and rs1801157 [SDF1-3'G(801)A] for SDF-1 gene was performed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Multiple genetic models (codominant, dominant, recessive, overdominant and log-additive) and haplotype analyses were performed using the SNPStats web tool to assess the correlation between the genetic polymorphisms and the risk of RVO. Binary logistic regression analysis was used for the association analysis between APOE gene variants and RVO. Given the multifactorial nature of the disease, our statistical analysis was adjusted for the most important systemic risk factors (age, hypertension and diabetes mellitus). The dominant genetic model for the PON1 Q192R single nucleotide polymorphism (SNP) of the association analysis revealed that there was a statistically significant difference between the RVO group and the control group. Specifically, after adjusting for age and hypertension, the PON1 192 R allele (QR + RR) was found to be associated with a statistically significantly higher risk of RVO compared to the QQ genotype (OR = 2.51; 95% CI = 1.02-6.14, p = 0.04). The statistically significant results were maintained after including diabetes in the multivariate model in addition to age and hypertension (OR = 2.83; 95% CI = 1.01-7.97, p = 0.042). No statistically significant association was revealed between the other studied polymorphisms and the risk of RVO. Haplotype analysis for PON1 SNPs, L55M and Q192R, revealed no statistically significant correlation. In conclusion, PON1 192 R allele carriers (QR + RR) were associated with a statistically significantly increased risk of RVO compared to the QQ homozygotes. These findings suggest that the R allele of the PON1 Q192R is likely to play a role as a risk factor for retinal vein occlusion.

Highlights on Genetic Polymorphism Associated with Thromboembolic Risk; Implications in Ophthalmic and Autoimmune Disorders—A Review

The present paper explores genetic polymorphism and its association with thromboembolic retinal venous disorders, such as central/hemi-retinal vein occlusion, as well as possible correlations with other ocular findings, such as closed angle glaucoma, but also with autoimmune general disorders. In this review, we are highlighting the importance of establishing a correspondence between all of the above, since they all have complex etiopathogeneses; sometimes, when all coexist together, they could generate effects that may be very difficult to manage. There are studies supporting that genetic polymorphism, such as the variant MTHFR A1298C, may increase the risk for developing glaucoma, especially in the heterozygote model. Being aware of all these aspects may prove to be useful in patients with several associated diseases, as a combined effort between several medical specialties may prove to the benefit of these patients. Our review, completed with an exemplifying clinical case, shows that it is necessary to raise awareness of all aspects of a complex medical situation, including the genetic one, of a patient being at risk for thromboembolic episodes, for preventing them or managing them promptly and properly in the future.

Vitamin B12 and Folate as Risk Factors for Retinal Vein Occlusion: A Meta-Analysis

PURPOSE

To evaluate the association between serum vitamin B12/folate and retinal vein occlusion (RVO).

METHODS

A comprehensive search of the PubMed database was performed, which identified 271 abstracts to be screened. Ten studies met our inclusion criteria and a meta-analysis of these comparative case-control studies was performed on the mean ± standard deviation serum vitamin B12 and folate levels, without language restrictions. Nine studies with 720 patients with RVO and 613 controls were included in the meta-analysis for vitamin B12, and 10 studies with 784 patients with RVO and 677 controls in the meta-analysis for folate.

RESULTS

There was no statistically significant difference between patients with RVO and controls in serum vitamin B12 levels (mean difference: - 40.25 pg/mL, p = 0.28), either central RVO (mean difference: - 18.24 pg/mL, p = 0.71) or branch RVO (mean difference: - 23.56 pg/mL, p = 0.48). On the contrary, the plasma folate level was significantly lower in RVO patients than in controls (mean difference: - 1.34 ng/mL, p = 0.001), as well as in patients with CRVO compared to controls (mean difference: - 1.48 ng/mL, p = 0.006), but not in BRVO patients (mean difference: - 0.72 ng/mL, p = 0.11).

CONCLUSIONS

RVO is associated with low serum folate levels, but not with serum vitamin B12 levels.

Methylenetetrahydrofolate reductase polymorphisms as risk factors for retinal venous occlusive disease: A literature review

The role of polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene in retinal vein occlusion (RVO) is a theme of discussion since the first reports of RVO in patients with MTHFR C677T mutation and without classic acquired risk factors for retinal vascular disease. The association between MTHFR polymorphisms and RVO has been studied over the last 20 years producing conflicting results. This review aims to summarize the literature concerning the role MTHFR polymorphisms as risk factors for RVO.

Thrombophilic and cardiovascular risk factors for retinal vein occlusion

BACKGROUND

The role of thrombophilic and cardiovascular risk factors in different manifestations of retinal vein occlusion (RVO), i.e., central or branch RVO, and at different ages is still debated.

AIMS

To evaluate the association between thrombophilic and cardiovascular risk factors and the risk of RVO (overall, separately for central and branch RVO, and at different ages).

METHODS

Case-control study on 313 patients with a first objectively-confirmed RVO (216 central and 97 branch RVO) and 415 healthy individuals.

RESULTS

Antithrombin, protein C or protein S deficiency (adjusted odds ratio [95%CI]: 15.60 [2.01-121]; p=0.009), hyperhomocysteinemia (HHCy; 3.22 [1.38-7.49]; p=0.007), high factor VIII (FVIII) levels (3.08 [1.20-7.89]; p=0.019), factor V Leiden (2.93 [0.97-8.86]; p=0.058) and the presence of at least one cardiovascular risk factor (1.79 [1.00-3.23]; p=0.050) were associated with an increased risk of branch RVO. The association was weaker for central RVO, and limited to HHCy (2.15 [1.09-4.24]; p=0.027) and high FVIII (1.99 [0.90-4.42]; p=0.091). For HHCy, high FVIII and cardiovascular risk factors the association with the risk of RVO was stronger at an age>50years (3.41[1.29-8.99], p=0.013; 2.57[1.00-6.68], p=0.050; and 2.03[1.16-3.56], p=0.013, respectively) than ≤50years (1.93[0.85-4.36], p=0.114; 1.67[0.54-5.12], p=0.371; and 1.22[0.73-2.03], p=0.454, respectively), whereas classic inherited thrombophilia (antithrombin, protein C or protein S deficiencies, factor V Leiden and prothrombin G20210A mutation) was slightly more prevalent at an age≤50years (1.62 [0.76-3.45], p=0.210) than >50years (1.11[0.44-2.79], p=0.833).

CONCLUSIONS

Thrombophilic and cardiovascular risk factors are associated with RVO, particularly branch RVO. The risk of RVO associated with HHCy, high FVIII and cardiovascular risk factors is higher at an older age.

Association of retinal vein occlusion, homocysteine, and the thrombophilic mutations in a Turkish population: A case-control study

PURPOSE

To compare homocysteine and thrombophilic mutations for the methylenetetrahydrofolate reductase (MTHFR) C677T, factor V Leiden, and prothrombin G20210A between retinal vein occlusion (RVO) and healthy controls in a Turkish population.

MATERIALS AND METHODS

Forty-nine subjects with RVO were compared for homocysteine status and the MTHFR C677T, prothrombin G20210A, and factor V Leiden mutations with those of 68 healthy controls. Then, the groups were subdivided into two subgroups according to age (less than 50 years old, equal to or more than 50 years old) and were further compared.

RESULTS

Mean plasma level of homocysteine was similar, but the frequency of hyperhomocysteinemia was significantly higher in the RVO group when compared with the control group (22.5% and 8.8%, respectively, p = 0.037). The frequency of all thrombophilic mutations was similar between the groups (p > 0.05). The frequency of all thrombophilic mutations and homocysteine levels was also similar between age subgroups (p > 0.05). Only hyperhomocysteinemia was significantly different between subgroups (p = 0.037); the frequency of hyperhomocysteinemia was significantly different in RVO patients less than 50 years old (22.7%) from that in healthy controls less than 50 years old (11.1%). Two RVO patients (4.1%) with bilateral involvement had MTHFR C677T mutation.

CONCLUSIONS

Screening for thrombophilic mutations such as MTHFR C677T, factor V Leiden, and prothrombin G20210A in RVO patients at all ages seems to be unnecessary and not cost-effective. However, thrombophilic disorders should be screened selectively, focusing on young individuals, especially with bilateral involvement, without additional cardiovascular risk factors, or a family history of thrombosis.

Multidisciplinary approach and anesthetic management of a surgical cancer patient with methylene tetrahydrofolate reductase deficiency: a case report and review of the literature

Introduction

Hyperhomocysteinemia is a known risk factor for myocardial infarction, stroke, peripheral vascular disease, and thrombosis. Elevated plasma homocysteine levels have been demonstrated in patients with recurrent episodes or a single episode of thrombosis. Here we describe the development of cardiovascular disease as a complication of a surgical intervention in a patient with colorectal cancer and hyperhomocysteinemia.

Case presentation

A 65-year-old Caucasian man complained of pain and constipation, attributed to previously diagnosed adenocarcinoma (stage IIB) of the hepatic flexure. An anamnestic investigation showed that he had undergone two surgical interventions. During both, he suffered thrombotic postoperative complications, a deep vein thrombosis of the upper extremity after the first operation and retinal vein occlusion after the second. He was diagnosed with hyperhomocysteinemia associated with a homozygous C677T mutation of the gene encoding the enzyme methylenetetrahydrofolate reductase. Our patient was initially treated with folic acid and high-dose B vitamins. On day 7 he underwent a right hemicolectomy. Anesthesia was performed with sevoflurane in 40% O₂ and without the use of nitrous oxide. Postoperatively, our patient remained on folic acid and B vitamins and was without immediate or subsequent complications.

Conclusions

Neoplastic disease and related surgery followed by the administration of chemotherapeutic drugs alter the hemostatic balance in cancer patients. Those suspected of also having a thrombophilic disease require a thorough laboratory diagnostic workup, including a molecular analysis aimed at identifying the genetic mutation responsible for the hyperhomocysteinemia, as indicated. The case described in this report highlights the importance of a multidisciplinary approach that includes expertise in peri-operative anesthesia, surgery, oncology, and hematology.

Homocysteine, methylenetetrahydrofolate reductase C677T polymorphism, and risk of retinal vein occlusion: an updated meta-analysis

Background

To evaluate the role of plasma total homocysteine (tHcy) and homozygosity for the thermolabile variant of the methylenetetrahydrofolate reductase (MTHFR) C677T genotype in the risk of retinal vein occlusion (RVO).

Methods

Relevant studies were selected through an extensive search of PubMed, EMBASE, and the Web of Science databases. Summary weighted mean differences (WMDs) or odds ratios (ORs) and 95% confidence intervals (CI) were calculated with a random-effects model.

Results

Forty-two studies with 6445 participants were included in this updated systematic review and meta-analysis. The mean plasma tHcy level in the RVO patients was significantly higher than in the controls (WMD =2.13 μmol/L; 95% CI: 1.29 to 2.98, P < 0.001), but there was evidence of between-study heterogeneity (P < 0.001). No significant association between MTHFR C677T genotype and RVO was found under all genetic models.

Conclusion

There was some evidence that plasma tHcy is associated with an increased risk of RVO. There was no evidence to suggest an association between homozygosity for the MTHFR C677T genotype and RVO.

Thrombophilic Mutations as Risk Factor for Retinal Vein Occlusion

Background:

Retinal vein occlusion (RVO) is the second most common retinal vein disease and an important cause of blindness and visual morbidity. Many conditions are associated with RVO but the real role of the thrombophilic mutations is still unclear.

Aim:

To evaluate the potential role of thrombophilic mutations in RVO.

Methods:

We have evaluated 113 patients with RVO and compared with 104 volunteer controls. The controls were all healthy blood donors without previous venous thromboembolism episode or arterial thromboembolism episode. All patients were tested for 5 gene variants (here all named as mutations): factor V ( FV) Leiden (G1691A), factor II ( FII; G20210A), 5,1-methylenetetra-hydrofolate reductase ( MTHFR; C677T), plasminogen activator inhibitor 1 ( PAI-1; 4G/5G), and angiotensin-converting enzyme ( ACE; Del/Ins). Statistical analysis were performed by the 2-tailed chi-square test.

Results:

Statistical test showed that TT homozygous patients of the MTHFR C677T mutation ( P = .017) and heterozygous GA patients of the FII G20210A mutation ( P = .018) were significantly higher than that in controls. For FV Leiden, even if the values were higher in patients than in controls, P value was not statistically significant. Conversely, for the ACE (Ins/Del) and PAI-1 (4G/5G) mutations, no difference was observed among genotypes of patients with RVO and control participants.

Conclusions:

In our study, the FII G20210A and the MTHFR C677T mutations resulted significantly higher in patients than in controls; in contrast, thrombophilic mutation of FV, ACE, and PAI-1 genes was not statistically correlated with RVO. In spite of having found an association between some thrombophilic mutations and RVO, more studies with a major number of patients are necessary to determine the final role of these gene variants.

Methylenetetrahydrofolate reductase C677T mutation and risk of retinal vein thrombosis

BACKGROUND

Elevated plasma homocysteine (Hcy) level has been established as a significant risk factor for venous thrombosis and cardiovascular disease. Homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation has been associated with elevated plasma Hcy concentration and may contribute to retinal vein thrombosis (RVT) development. The aim of the present study was to investigate whether the hyperhomocysteinemia and/or homozygosity for the MTHFR C677T mutation are associated with an increased risk for RVT.

MATERIALS AND METHODS

Our study population consisted of 73 consecutive patients (50-78 years old) with RVT and 73 control subjects (51-80 years old), matched for age and sex. Genotyping for the MTHFR C677T mutation was performed by polymerase chain reaction-restriction fragment length polymorphism technique and Hcy level was determined by an enzyme immunoassay kit.

RESULTS

The prevalence of 677TT genotype was higher in patients than control subjects, but the difference in frequency didn't reach a significant value (P = 0.07). The frequency of the 677T allele was 26% and 21.2% in patients and controls, respectively and did not differ significantly between the two groups (odds ratio = 1.3, 95% confidence interval (0.75-2.24), P = 0.33). Fasting plasma total Hcy level was significantly higher in patients than controls (P = 0.001).

CONCLUSION

Our study demonstrated that hyperhomocysteinemia, but not the MTHFR C677T mutation, is associated with RVT.

Association between B-group vitamins and venous thrombosis: systematic review and meta-analysis of epidemiological studies

A homocysteine-independent role for B-group vitamins on venous thrombosis (VT) development has been reported. However, related research findings remain inconsistent. PUBMED, EMBASE, and COCHRANE databases were searched to collect information on all eligible studies to make a meta-analysis about the relationship between B-group vitamins and VT. Literature search results did not suggest a correlation between thiamin, pantothenic acid, niacin, or riboflavin with VT. Based on their correlations in the literature, folic acid, vitamin B12, B6 were considered in the meta-analysis and systematic review. Significant standardized mean differences were obtained for plasma folic acid (-0.55; 95% CI, -0.75 to -0.36) and vitamin B12 (-0.34; 95% CI, -0.55 to -0.13). Reduced levels of folic acid and vitamin B12 may be independent risk factors of VT. Moreover, a qualitative systematic review indicated that low level of vitamin B6 was an independent risk factor of VT. Randomized clinical studies of B-group vitamins supplementation showed varying results on VT prevention. Multivitamin supplementation for VT prevention, regardless of homocysteine level, would be of interest. Further prospective clinical studies are needed to provide additional evidence on the clinical benefits of B-group vitamin supplementation for VT.

Genetic polymorphisms associated with endothelial function in nonarteritic anterior ischemic optic neuropathy

PURPOSE

To examine the relationship between nonarteritic anterior ischemic optic neuropathy (NAION) and genetic polymorphisms of enzymes influencing endothelial function.

METHODS

The subjects were 34 patients with NAION (mean age, 62.4 years old; 59% male) and 102 controls (mean age, 63.8 years old; 66% male). Genetic polymorphisms were investigated in three candidate genes associated with endothelial function: endothelin-1 (ET-1), angiotensin-converting enzyme (ACE), and methylenetetrahydrofolate reductase (MTHFR). The genotype distributions in the patients with NAION were compared with those in the controls.

RESULTS

There were no significant differences in the genotype distributions of the ACE I/D and MTHFR C677T polymorphisms between the NAION and control groups (p=0.261 and p=0.354, respectively), whereas the genotype distribution of the G/T (Lys198Asn) polymorphism of the ET-1 gene varied significantly between the groups (p=0.009). After adjusting for covariates, individuals with the TT genotype of the Lys198Asn polymorphism were more likely to develop NAION compared with those with the GG genotype (odds ratio=4.43, 95% confidence interval 1.33-14.73, p=0.015).

CONCLUSIONS

We found an increased prevalence of a G/T polymorphism of the ET-1 gene in patients with NAION. Our data suggest that this polymorphism may be an important risk factor in developing NAION in the Japanese population.

Thrombophilia and retinal vascular occlusion

Purpose

The purpose of this research was to assess associations of thrombophilia with central retinal vein occlusion (CRVO), central retinal artery occlusion (CRAO), and amaurosis fugax (AF); to evaluate outcomes of normalizing high homocysteine; and to study CRVO, CRAO, and AF developing in estrogens/estrogen agonists in women subsequently shown to have thrombophilia.

Methods

Measures of thrombophilia–hypofibrinolysis were obtained in 132 CRVO cases, 15 CRAO cases, and 17 AF cases. Cases were compared to 105 healthy control subjects who did not differ by race or sex and were free of any ophthalmologic disorders. All cardiovascular disease (CVD) risk factors were compared to healthy general populations.

Main outcome measures

The main outcome measure of this study was thrombophilia.

Results

CRVO cases were more likely than controls to have high homocysteine (odds ratio [OR] 8.64, 95% confidence intervals [CI]: 1.96–38), high anticardiolipin immunoglobulin M (IgM; OR 6.26, 95% CI: 1.4–28.2), and high Factor VIII (OR 2.47, 95% CI: 1.31–7.9). CRAO-AF cases were more likely than controls to have high homocysteine (OR 14, 95% CI: 2.7–71.6) or the lupus anticoagulant (OR 4.1, 95% CI: 1.3–13.2). In four of 77 women with CRVO (two found to have high homocysteine, two with inherited high Factor XI), CRVO occurred after starting estrogen–progestins, estrogen–testosterone, or estrogen agonists. In one of eight women with CRAO found to have high anticardiolipin antibody IgG, CRAO occurred after starting conjugated estrogens, and AF occurred after starting conjugated estrogens in one of eleven women with AF (inherited protein S deficiency). Therapy for medians of 21 months (CRVO) and 6 months (CRAO-AF) was 5 mg folic acid, 100 mg B6, and 2000 mcg/day B12 normalized homocysteine in 13 of 16 (81%) CRVO cases and all five CRAO-AF cases with pretreatment hyperhomocysteinemia. The CRVO cases had an excess of hypertension; CRAO-AF cases had an excess of type 2 diabetes and hypertension.

Conclusion

Treatable thrombophilia, hyperhomocysteinemia in particular, is more common in RVO cases than in normal controls. RVO occurs after estrogens or estrogen agonists were administered in women subsequently shown to have thrombophilia.

Extra-abdominal venous thromboses at unusual sites

Venous thrombosis typically involves the lower extremities. Rarely, it can occur in cerebral, splanchnic, or renal veins, with a frightening clinical impact. Other rare manifestations are upper-extremity deep vein thrombosis, that can complicate with pulmonary embolism and post-thrombotic syndrome, and retinal vein occlusion, significantly affecting the quality of life. This review is focused on venous thromboses at unusual extra-abdominal sites. Local infections or cancer are frequent in cerebral sinus-venous thrombosis. Upper-extremity deep vein thrombosis is mostly due to catheters or effort-related factors. Common risk factors are inherited thrombophilia and oral contraceptive use. Acute treatment is based on heparin; in cerebral sinus-venous thrombosis, local or systemic fibrinolysis should be considered in case of clinical deterioration. Vitamin-K antagonists are recommended for 3-6 months; indefinite anticoagulation is suggested for recurrent thrombosis or unprovoked thrombosis and permanent risk factors. However, such recommendations mainly derive from observational studies; there are no data about long-term treatment of retinal vein occlusion.

Atherosclerotic and thrombophilic risk factors in patients with ischemic central retinal vein occlusion

PURPOSE

To investigate atherosclerotic and thrombophilic risk factors in patients affected by acute ischemic and nonischemic central retinal vein occlusions (CRVOs).

METHODS

One hundred and three patients with acute unilateral CRVO (41 ischemic and 62 nonischemic) were studied. The frequency of traditional cardiovascular risk factors was assessed, and the plasma levels of a variety of thrombophilic markers were measured. Univariate logistic regression was performed to determine risk factors for ischemic CRVO.

RESULTS

Arterial hypertension, hypercholesterolemia, postmethionine hyperhomocysteinemia (HHcy), elevated factor VIII, and reduced folic acid and B6 plasma levels were more frequent in patients with ischemic CRVO than in those with nonischemic CRVO (P = 0.030, P = 0.025, P = 0.011, P < 0.001, P < 0.001, and P = 0.044, respectively). Risk factors for ischemic CRVO were arterial hypertension (odds ratio [OR], 3.22; 95% confidence interval [CI], 1.13-9.21; P = 0.037), hypercholesterolemia (OR, 3.03; 95% CI, 1.06-8.65; P = 0.042), reduced folic acid levels (OR, 6.77; 95% CI, 1.59-28.79; P = 0.011), and elevated FVIII levels (OR, 6.17; 95% CI, 2.56-14.82; P < 0.001). Postmethionine HHcy was associated with low folic acid levels (r = -0.413; P = 0.007; OR, 9.33; 95% CI, 2.06-42.18; P = 0.005).

CONCLUSION

The results of the present study suggest that some atherosclerotic and thrombophilic risk factors may increase the risk of having an ischemic form of CRVO.

Retinal vein occlusions: a review for the internist

Retinal vein occlusion (RVO) is a disease that is often associated with a variety of systemic disorders including arterial hypertension, diabetes mellitus, dyslipidemia and systemic vasculitis. There are various types of RVO, categorized on the basis of the site of occlusion and on the type of consequent vascular damage. Central retinal vein occlusion (CRVO) is the most clinically relevant type of RVO. In addition to well-known classical risk factors, new thrombophilic factors have been investigated in patients with RVO. Data concerning a number of the parameters remain contradictory; yet, hyperhomocysteinemia and vitamins involved in methionine metabolism appear to play a significant role in the pathogenesis of this disease. Alterations in the fibrinolysis pathway (elevated levels of PAI-1 and Lipoprotein (a)), together with haemorheologic modifications have been recently consistently associated with the disease. Medical treatment includes identification and correction of vascular risk factors. In addition, LMWHs appear to be the best therapeutic approach even if based on a limited number of trials, conducted on a limited number of patients. No data are available on the possible role of antithrombotic strategies in the long-term prevention of recurrent RVO or vascular events.

Hyperhomocysteinemia and C677T MTHFR genotype in patients with retinal vein thrombosis

INTRODUCTION

Elevated homocysteine (Hcy) is associated with the risk of deep vein thrombosis, pulmonary embolism, ischemic heart disease, and stroke. Several studies have suggested that hyperhomocysteinemia (HHcy) may predispose to retinal vein thrombosis (RVT) development. The aim of this study is to investigate the relationship between Hcy, C677T methylenetetrahydrofolate reductase (MTHFR) genotype, and RVT in patients compared with controls.

MATERIALS AND METHODS

We evaluated the Hcy plasma level of 3114 consecutive participants in 2 Italian centers during a 2-year period. Hyperhomocysteinemia was found in 99 patients and 136 healthy participants. Of the 99 patients, 20 had RVT with a high prevalence of HHcy in the RVT subgroup (20.2%). This result suggested a possible relationship between HHcy and RVT development. We investigated 105 consecutive patients with recent diagnosis of RVT, and we compared them with 226 healthy controls to evaluate whether HHcy may be a risk factor for RVT.

RESULTS

the prevalence of HHcy was higher in patients compared with controls (34.3% vs 14.2%; P < .001). The MTHFR C677T genotype was found in 69 of 105 (65.7%) patients with RVT (heterozygosity: 40 of 105 and homozygosity: 29 of 105). The control group showed the presence of MTHFR C677T genotype in 169 of 226 participants (74.8%; heterozygosity: 100 of 226 and homozygosity: 69 of 226) without difference between the 2 groups (P = .08).

CONCLUSION

our study suggests that HHcy is a possible risk factor for RVT development, while no association was found between RVT and the C677T MTHFR genotype.

Homocysteine, methylenetetrahydrofolate reductase C677T polymorphism, and risk of retinal vein occlusion: a meta-analysis

OBJECTIVE

To assess the role of plasma total homocysteine (tHcy) concentrations and homozygosity for the thermolabile variant of the methylenetetrahydrofolate reductase (MTHFR) C677T gene as risk factors for retinal vascular occlusive disease.

DESIGN

Retinal vein occlusion (RVO) is an important cause of vision loss. Early meta-analyses showed that tHcy was associated with an increased risk of RVO, but a significant number of new studies have been published.

PARTICIPANTS AND/OR CONTROLS

RVO patients and controls.

METHODS

Data sources included MEDLINE, Web of Science, and PubMed searches and searching reference lists of relevant articles and reviews. Reviewers searched the databases, selected the studies, and then extracted data. Results were pooled quantitatively using meta-analytic methods.

MAIN OUTCOME MEASURES

tHcy concentrations and MTHFR genotype.

RESULTS

There were 25 case-control studies for tHcy (1533 cases and 1708 controls) and 18 case-control studies for MTHFR (1082 cases and 4706 controls). The mean tHcy was on average 2.8 micromol/L (95% confidence interval [CI], 1.8-3.7) greater in the RVO cases compared with controls, but there was evidence of between-study heterogeneity (P<0.001, I(2) = 93%). There was funnel plot asymmetry suggesting publication bias. There was no evidence of association between homozygosity for the MTHFR C677T genotype and RVO (odds ratio [OR] 1.20; 95% CI, 0.84-1.71), but again marked heterogeneity (P = 0.004, I(2) = 53%) was observed.

CONCLUSIONS

There was some evidence that elevated tHcy was associated with RVO, but not homozygosity for the MTHFR C677T genotype. Both analyses should be interpreted cautiously because of marked heterogeneity between the study estimates and possible effect of publication bias on the tHcy findings.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Central retinal vein thrombosis and hyperhomocysteinemia in a young patient with renal transplantation

A 28-year-old woman was admitted with a sudden loss of vision in the right eye. She underwent renal transplantation in June 1999 for chronic renal failure secondary to amyloidosis. Upon ophthalmologic examination, the patient was diagnosed with central retinal vein occlusion. Physical and laboratory examinations failed to disclose any remarkable pathology except for high homocysteine levels. Hyperhomocysteinemia has been reported as a potential risk factor requiring treatment and a significant association has been found between this condition and central retinal vein thrombosis.

Comparative analysis of homocysteine concentrations in patients with retinal vein occlusion versus thrombotic and atherosclerotic disorders

The objectives of the present study were to determine the concentrations of plasma homocysteine in a large (n = 562) cohort of patients with retinal vein occlusion (RVO) and to compare them with the values observed in other vascular thrombotic and atherosclerotic conditions. Results were compared with those observed in patients with deep vein thrombosis (n = 1700), pulmonary embolism (n = 542), transient ischemic attack (n = 1301), cerebrovascular accident (n = 1299), myocardial infarction (n = 3087), as well as peripheral artery occlusive disease (n = 1946). No differences were found between the age-adjusted estimated marginal mean +/- SE for homocysteine concentrations in individuals with RVO and in those who had other atherosclerotic and atherothrombotic diseases The respective concentrations for RVO, deep vein thrombosis, pulmonary embolism, transient ischemic attack, cerebrovascular accident, myocardial infarction, and peripheral artery occlusive disease were 13.8 +/- 0.4, 14.7 +/- 0.3, 14.3 +/- 0.5, 14.2 +/- 0.3,14.6 +/- 0.3, 13.8 +/- 0.2, 14.4 +/- 0.2 pmol/l for men and 11.4 +/- 0.4, 10.7 +/- 0.2, 10.8 +/- 0.3, 10.8 +/- 0.2, 11.8 +/- 0.2, 11.2 +/- 0.2 pmol/l for women. In conclusion, the concentrations of homocysteine observed in patients with RVO are similar to those detected in other thrombotic and atherosclerotic vascular disorders. In view of the fact that this is a common disorder of the elderly, increased homocysteine concentrations often reported in patients with RVO could reflect the underlying atherothrombotic condition and might not necessarily be specifically related to the RVO per se. This information is relevant in researching the potential etiopathologic role, if any, of increased homocysteine concentrations in RVO.

Atherosclerotic and thrombophilic risk factors in patients with recurrent central retinal vein occlusion

PURPOSE

Atherosclerotic and thrombophilic risk factors may be causes of central retinal vein occlusion (CRVO). The aim of this study was to evaluate the prevalence of the aforesaid risk factors in patients with recurrent CRVOs and patients with a single episode of CRVO.

METHODS

Seventeen patients with recurrent CRVO and 30 with a single episode of CRVO were enrolled. The atherosclerotic risk factors investigated were hypertension, diabetes, smoking, and dyslipidemia. Specific laboratory tests for the following thrombophilic markers were performed: homocystinemia (Hcy), lipoprotein (a), factor VIII, factor II G20210A and factor V G1691A polymorphisms, lupus anticoagulant, anticardiolipin antibodies, plasminogen activator inhibitor-1, and deficit of vitamins B6, B12, and folic acid. A multivariate analysis, adjusted for age, gender, traditional and thrombophilic risk factors, was performed. Statistical significance was set at p<or=0.05.

RESULTS

Hypercholesterolemia, hypertriglyceridemia, fasting, and postmethionine hyperhomocysteinemia (HHcy) were more prevalent in recurrent CRVO patients (p<0.001, p<0.001, p=0.006, and p=0.005, respectively). At multivariate analysis, hypercholesterolemia (OR: 5.04, 95% CI 1.39-18.17; p=0.025), hypertriglyceridemia (OR: 5.60, 95% CI 1.52-20.61; p=0.017), fasting HHcy (OR: 5.77, 95% CI 1.39-23.89; p=0.028), and postmethionine HHcy (OR: 10.88, 95% CI 2.50-47.42; p=0.002) were found to be significantly associated with recurrent CRVO.

CONCLUSIONS

Dyslipidemia and hyperhomocysteinemia are independent risk factors for the occurrence of recurrent CRVO. A complete assessment of atherosclerotic and thrombophilic risk factors in CRVO patients. In addition, the need for a specific treatment is suggested.

Distinct association of SLC19A1 polymorphism -43T>C with red cell folate levels and of MTHFR polymorphism 677C>T with plasma folate levels

OBJECTIVES

The role of SLC19A1 -43T>C, MTHFR 677C>T and MS 2756A>G polymorphisms on red cell and plasma folate levels.

DESIGN AND METHODS

Genotype analysis of the three polymorphisms. Red cell and plasma folate measurements in 64 patients with coronary artery disease.

RESULTS

The non-wild type allele of SLC19A1 polymorphism -43T>C was associated with low red cell folate levels and the non-wild type allele of MTHFR polymorphism 677C>T with low plasma folate levels.

CONCLUSION

SLC19A1 and MTHFR genes are differently associated with red cell and plasma folate levels.

Low vitamin B6 and folic acid levels are associated with retinal vein occlusion independently of homocysteine levels

Retinal vein occlusion (RVO) is one of the most common retinal vascular disorders. During the last years, high levels of homocysteine (Hcy) have been demonstrated to be an independent risk factor for RVO. Aim of this study was to investigate the association among circulating B-group vitamins, Hcy and RVO. Thus, we studied 262 RVO patients and 262 age- and sex-comparable healthy subjects. Serum vitamin B6 was measured by HPLC, serum folic acid and vitamin B12 by radioimmunoassay and plasma Hcy by FPIA. Blood levels of vitamin B6, folate and Hcy, but not of vitamin B12, were found to be significantly different in patients as compared to healthy subjects. At the univariate analysis, the lowest tertile of vitamin B6 [odds ratio (OR) 4.03; 95% confidence interval (CI) 2.58-6.31; P<0.0001)] and folate (OR 6.13; 95% CI 3.85-9.76, P<0.0001), and the highest tertile of Hcy (OR 8.08; 95% CI 5.05-12.92, P<0.0001) were found to be significantly associated with RVO. Moreover, at multivariate analysis, after adjustment for traditional cardiovascular risk factors, Hcy, and circulating levels of vitamins, respectively, the lowest tertile of vitamin B6 (OR 3.29; 95% CI 1.89-5.70, P<0.0001) and folate (OR 5.41; 95% CI 3.08-9.51, P<0.0001) and the highest tertile of Hcy (OR 2.58; 95% CI 1.12-5.94, P<0.0001) maintained their significant association with RVO. In conclusion, the present study documents, on a large sample of patients, that low vitamin B6 levels, low folic acid levels and elevated Hcy levels are each independently associated with RVO.

Hyperhomocysteinemia and central retinal vein occlusion in Iranian population

PURPOSE

To evaluate total plasma homocysteine level during the acute phase of central retinal vein occlusion (CRVO) in the Iranian population and determine whether hyperhomocysteinemia is also a risk factor for CRVO.

METHODS

Fifty-four patients with recently diagnosed CRVO were studied. Their fasting total plasma homocysteine level was compared with a matched control group of 51 patients evaluated in the same clinic for a non-retinal disease diagnosis.

RESULTS

The mean total plasma homocysteine level was 14.76+/-7.67 micromol/l in cases, and 11.42+/-3.74 micromol/l in control subjects. It showed a significant difference (P=0.005) in mean plasma homocysteine level between cases and control group. Odds ratio of CRVO for individuals with hyperhomocysteinemia was 2.88 (95% CI=1.08-7.71 and P=0.03). The overall multivariable-adjusted odds of CRVO in participants with plasma homocysteine level above 15 micromol/l was 4.71 (95% CI=1.46-15.19 and P=0.009) Hyperhomocysteinemia was not statistically different in each age group (<60 years: 27%, 61-70 years: 33.3%, 71-80 years: 31.6%, >81 years: 33.3%, Chi-square test, P=0.98).

CONCLUSION

Elevated total plasma homocysteine level is an independent risk factor for CRVO in Iranian population. In addition to an evaluation of all conventional cardiovascular risk factors, measurement of total homocysteine for evidence of hyperhomocysteinemia may be important in the initial investigation and management of patients with CRVO.