Functional VEGF C-634G polymorphism is associated with development of diabetic macular edema and correlated with macular retinal thickness in type 2 diabetes

Association of Vascular Endothelial Growth Factor (VEGF) and Mouse Model Minute 2 (MDM2) Polymorphisms With Diabetic Retinopathy in a Northwest Indian Population: A Case-Control Study

INTRODUCTION

Diabetic retinopathy (DR), a microvascular complication of type 2 diabetes (T2D), results from complex interactions of genetic and environmental factors. Vascular endothelial growth factor (VEGF) and mouse model minute 2 (MDM2)are upregulated in the retina due to diabetes, which increases the risk of DR. VEGFA and MDM2 genetic variations can influence DR risk. The present case-control study was conducted to evaluate the association of VEGFA and MDM2 promoter variants with DR in a population from Punjab, Northwest India.

METHODS

A total of 414 DR patients, 425 T2D patients without DR, and 402 healthy controls were screened for VEGFA -2578C/A (rs699947), VEGFA -2549I/D (rs35569394), VEGFA -7C/T (rs25648), and MDM2 rs3730485 polymorphisms using polymerase chain reaction (PCR)-based methods.

RESULTS

VEGFA -2549 I allele (OR = 1.35 (1.00-1.81), p = 0.043) and II genotype (OR = 1.78 (1.00-3.15), p = 0.047) were significantly associated with increased risk of DR. VEGFA -7 CT genotype conferred reduced risk of DR (OR = 0.28 (0.20-0.38); p = <0.001). VEGFA -2578 and MDM2 rs3730485 showed no significant association with DR. A-I-T (OR = 0.30 (0.20-0.44); p = <0.001) and C-D-T (OR = 0.33 (0.16-0.65); p = 0.002) haplotypes of rs699947-rs35569394-rs25648 polymorphisms showed decreased risk of DR.

CONCLUSIONS

I allele and II genotype of VEGFA -2549, CT genotype of VEGFA -7, and C-I-C and A-D-C haplotypes of rs699947-rs35569394-rs25648 polymorphisms were significantly associated with DR risk in a Northwest Indian population. This is the first study worldwide to report DR risk with VEGFA promoter variants together.

Association of VEGF Gene Polymorphism (rs699947) with Glaucoma and In-Silico Study of Antiglaucoma Bioactive Compounds

Vascular endothelial growth factor (VEGF) is a useful expert in various maturation and other problems such as glaucoma. VEGF gene is located on the short arm of chromosome 6. It has 8 exons and 6 introns. This investigation was planned to check out the relationship of VEGF polymorphism with glaucoma patients and to cause in silico limitation of carbonic anhydrase to diminish the intraocular strain of watery humor to fix glaucoma. In this examination, a large portion of the glaucoma patients (n = 70) were males (66%) when contrasted with females (34%) as the p-value was 0.025 which showed critical outcomes and subsequently demonstrated that the sickness was more predominant in males. Glaucoma for the most part influences people between the ages of 50-60 years followed by the age bunch between 30 and 40 years. Around 36 (51.4%) were experiencing watering in the eyes, 28 (40%) had photophobia, 9 (12.8%) had a hazy cornea, 6 (8.6%) had expanded eye globe, and 15 patients (21.3%) had rosy eyes. Factual tests showed that VEGF quality SNP rs699947 had no huge relationship with glaucoma (POAG). In this study, various carbonic anhydrase inhibitor phytochemicals and synthetic chemicals were screened in silico which may be used as antiglaucoma drugs.

A study of the genotyping and vascular endothelial growth factor polymorphism differences in diabetic and diabetic retinopathy patients

Background

Retinopathy is one of the major causes of visual impairment which is the most severe microvascular complication of diabetes mellitus (DM). The aim of this study was to evaluate the association between diabetic retinopathy (DR) and two SNPs (− 152G > A and − 165C > T) located in the promoter region of the vascular endothelial growth factor (VEGF) gene in a small sample from Egyptian population. One hundred diabetic patients without retinopathy (DWR) and two hundred diabetic patients with retinopathy were included in this study. Genotype analysis for the two SNPs (− 152G > A and − 165C > T) was assessed by using the PCR–RFLP technique. In addition, the serum protein level of VEGF was measured by ELISA assay.

Results

The results showed a significant relationship between − 152G > A (rs13207351) polymorphism and both proliferative and non-proliferative retinopathy in genotypes (GG, GA, AA). The risk factor increment in the mutant heterozygous genotype (GA) was significantly increased in NPDR compared to PDR (OR = 16.3, 95%CI = 0.80–331.7); (OR = 20.4, 95%CI = 1.08–385.3), respectively. There was no significance between VEGF − 165C > T (rs79469752) gene polymorphism and retinopathy. Moreover, the serum protein level of VEGF showed a highly significant increase (P = 0.0001) in PDR (Mean ± SD = 3691 ± 124.9) when compared to both DWR (Mean ± SD = 497.3 ± 18.51) and NPDR (Mean ± SD = 1674.5 ± 771.7). These results were supported by the increased level of VEGF in serum protein which is positively correlated with the severity of retinopathy. Measuring VEGF protein level in DR patients would help as a biomarker in early diagnosis.

Conclusion

The increase in the mutant heterogeneous GA genotype in VEGF − 152G > A SNP could be a risk factor for the progression of severe retinopathy in diabetic patients.

Association of four gene polymorphisms in Chinese Guangxi population with diabetic retinopathy in type 2 diabetic patients

Background

Diabetic retinopathy (DR) is one of the most common chronic microvascular complications of diabetes. Many studies have suggested that genetic factors are important in the context of DR. This study evaluated the associations of GWAS (Genome-wide association study) -identified DR-associated SNPs in a Chinese population in Guangxi Province with type 2 diabetes mellitus (T2DM).

Methods

A total of 386 hospitalized T2DM patients without proliferative diabetic retinopathy (PDR) and 316 hospitalized T2DM patients with PDR were included in this case–control study. Four tag SNPs, including rs1800896 in the IL-10 gene, rs2010963 in the VEGFA gene, rs2070600 in the RAGE gene and rs2910164 in the miR-146a gene, were examined using KASP (kompetitive allele specific PCR) genotyping assays.

Results

There were no significant differences in the genotype or allele frequencies of the miR-146a polymorphism (rs2910164) between subjects with PDR and those without DR. The TC genotype of rs1800896 was determined to be associated with an increased risk of PDR (the odds ratio (OR) was 2.366, with a 95% confidence interval (CI) ranging from 1.144 to 4.894). The CG genotypes of rs2010963 was associated with an decreased risk of PDR (the OR was 0.588, with a 95% CI ranging from 0.366 to 0.946). Regarding rs2070600, 2 genotypes (TT and CT) were associated with a decreased risk of PDR (the OR of the TT genotype was 0.180, with a 95% CI ranging from 0.037 to 0.872, and the OR of the CT genotype was 0.448, with a 95% CI ranging from 0.266 to 0.753).

Conclusions

The rs1800896 polymorphisms in the IL-10 gene, rs2010963 in the VEGFA gene and rs2070600 in the RAGE gene are associated with the risk of PDR in the Han Chinese population of Guangxi Province. Our findings provide suggestive evidence that these polymorphisms may be involved in the pathogenesis of PDR and should be investigated further.

Association of VEGFA promoter polymorphisms rs699947 and rs35569394 with diabetic retinopathy among North-Central Indian subjects: a case-control study

BACKGROUND

Diabetes mellitus type 2 is often described as the global pandemic of the 21^st century with India emerging as its capital. Microvascular complications such as retinopathy associated with diabetes are a serious world health problem, leading to the already existing burden of blindness. The aim of this study was to determine whether VEGF gene polymorphisms rs35569394 and rs699947 are associated with DR in North Indians.

MATERIALS AND METHODS

North Indian subjects, diabetic controls with no retinopathy (DR I, n = 51), subjects with diabetes with mild-moderate retinal changes (DR II, n = 50), and subjects with diabetes with severe retinopathy with/without retinal neovascularization (DR III, n = 55) were recruited for this study. Genotyping of the VEGF gene I/D polymorphism was done by PCR and C/A polymorphism by PCR-RFLP method.

RESULTS

DD-genotype was 2.73 times over expressed among DR III category (p = .02; OR: 2.73; 95% CI: 1.20-6.19) as compared to DR I category among male subgroup. C-allele (rs699947) had 1.66-times more exposure among DR III as compared to DR I (C vs. A allele; p = .063; OR: 1.66; 95% CI: 0.97-2.84), probably due to high linkage disequilibrium between both the polymorphisms.

CONCLUSIONS

Results of our study support the hypothesis that D-allele and DD-genotype of rs35569394 have deleterious effect on the progression of DR. C-allele had skewed frequency towards DR III subjects owing to strong linkage disequilibrium between C-allele (rs699947) and D-allele (rs35569394).

Systemic and ocular diseases associated with the development of diabetic macular edema among Japanese patients with diabetes mellitus

Background

Diabetic macular edema (DME) causes severe vision loss among patients with diabetes mellitus (DM). We aimed to investigate systemic and ocular diseases associated with the development of DME in a Japanese population.

Methods

A total of 3.11 million Japanese subjects who were registered in the database of the Japan Medical Data Center from 2005 to 2014 were analyzed. Subjects with DM were defined as individuals who had been prescribed any therapeutic medications for DM, and associated diseases were analyzed. The periods assessed were one year before the development of DME among patients with DME and one year before the last visit to an ophthalmic clinic among patients without DME.

Results

A total of 17,403 patients with DM satisfied the inclusion and exclusion criteria, and 420 patients developed DME. Univariate analysis revealed significant associations between 55 diseases, including 39 systemic and 16 ocular diseases, and DME development. Logistic analysis identified 21 systemic diseases and 10 ocular diseases as significant factors associated with DME development.

Conclusion

Various types of systemic and ocular diseases are associated with DME development. Subjects with DM who present these risk factors must be carefully monitored to prevent visual impairment.

Association of rs699947 (-2578 C/A) and rs2010963 (-634 G/C) Single Nucleotide Polymorphisms of the VEGF Gene, VEGF-A and Leptin Serum Level, and Cardiovascular Risk in Patients with Excess Body Mass: A Case-Control Study

Background: Two single nucleotide polymorphisms (SNPs) of the VEGF gene, rs699947 and rs2010963, are responsible for differentiated gene expression. A mutual dependence between VEGF and leptin serum level has been observed. This study investigated the associations between the rs699947 and rs2010963 SNPs of VEGF gene, VEGF-A, and leptin serum concentrations, and cardiometabolic risk of body mass excess. Methods: In this case–control study, 212 subjects with excess body mass and 145 normal-weight controls gave blood samples and underwent anthropometric and pulse wave analysis. Genotyping of VEGF gene was carried out to analyze the rs699947 (−2578 C/A) and rs2010963 (−634 G/C) SNPs. (ClinicalTrials.gov ID: NCT04077554). Results: This study showed a significant positive correlation between serum levels of VEGF-A and leptin in individuals with excess body mass possessing the CC genotype of the rs699947 variant of the VEGF gene. It has been registered that an increase in VEGF-A serum level correlates with an increase in arterial stiffness in excess body mass patients harboring AA genotype of the rs699947 (−2578 C/A) variant of the VEGF gene. No differences in VEGF-A and leptin serum concentrations were noted between particular genotypes. Conclusions: The CC genotype of the rs699947 variant of the VEGF gene promotes a positive interdependency between leptin and VEGF-A serum levels in subjects with excess body mass.

Do Genomic Factors Play a Role in Diabetic Retinopathy?

Although there is strong clinical evidence that the control of blood glucose, blood pressure, and lipid level can prevent and slow down the progression of diabetic retinopathy (DR) as shown by landmark clinical trials, it has been shown that these factors only account for 10% of the risk for developing this disease. This suggests that other factors, such as genetics, may play a role in the development and progression of DR. Clinical evidence shows that some diabetics, despite the long duration of their diabetes (25 years or more) do not show any sign of DR or show minimal non-proliferative diabetic retinopathy (NPDR). Similarly, not all diabetics develop proliferative diabetic retinopathy (PDR). So far, linkage analysis, candidate gene studies, and genome-wide association studies (GWAS) have not produced any statistically significant results. We recently initiated a genomics study, the Diabetic Retinopathy Genetics (DRGen) Study, to examine the contribution of rare and common variants in the development of different phenotypes of DR, as well as their responsiveness to anti-VEGF treatment in diabetic macular edema (DME). Our preliminary findings reveal a novel set of genetic variants involved in the angiogenesis and inflammatory pathways that contribute to DR progression or protection. Further investigation of variants can help to develop novel biomarkers and lead to new therapeutic targets in DR.

Identifying Genetic Risk Factors for Diabetic Macular Edema and the Response to Treatment

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus (DM). DR is complex and the term encompasses several clinical subtypes of diabetic eye disease, including diabetic macular edema (DME), the most frequent cause of central vision loss in DR patients. Both genetic and environmental factors contribute to the pathophysiology of DR and its subtypes. While numerous studies have identified several susceptibility genes for DR, few have investigated the impact of genetics on DME susceptibility. This review will focus on the current literature surrounding genetic risk factors associated with DME. We will also highlight the small number of studies investigating the genetics of response to antivascular endothelial growth factor (anti-VEGF) injection, which is used to treat DME.

Genetics of Diabetic Retinopathy

PURPOSE OF REVIEW

The goal of this paper is to review the latest findings in understanding the genetics of diabetic retinopathy. We highlight recent literature using a variety of molecular genetic techniques to identify variants which contribute to genetic susceptibility for diabetic retinopathy.

RECENT FINDINGS

New genome-wide association study (GWAS) and whole-exome sequencing approaches have been utilized to identify both common and rare variants associated with diabetic retinopathy. While variants have been identified in isolated studies, no variants have been replicated across multiple studies. The identification of genetic factors associated with diabetic retinopathy remains elusive. This is due to the multifactorial nature of the disease, small sample sizes for GWAS, and difficulty in controlling covariates of the disease. Larger populations as well as utilization of new sequencing and data analysis techniques may lead to new insights into genetic factors associated with diabetic retinopathy in the future.

A genome-wide association study implicates that the TTC39C gene is associated with diabetic maculopathy with decreased visual acuity

Background: Diabetic maculopathy is a form of diabetic retinopathy. The visual acuity of one third of patients with diabetic maculopathy will be affected. The purpose of this study was to identify genetic contributors of diabetic maculopathy with decreased visual acuity based on a genome-wide association approach using a well-defined Scottish diabetic cohort. Methods: We used linked e-health records of diabetic patients to define our cases and controls. The cases in this study were defined as type 2 diabetic patients who had ever been recorded in the linked e-health records as having maculopathy (observable or referable) in at least one eye and whose visual acuity of the eye was recorded to have decreased between the first and the last visual acuity record of that eye in the longitudinal e-health records. The controls were defined as a type 2 diabetic individual who had never been diagnosed with maculopathy or retinopathy in the linked e-health records. Anyone who had laser photocoagulation treatment was also excluded from the controls. A standard genome-wide association approach was applied. Results: Overall, we identified 469 cases and 1,374 controls within the Genetics of Diabetes Audit and Research in Tayside Scotland (GoDARTS) dataset. We found that the P value of rs9966620 in the TTC39C gene was 4.13x10^-8, which reached genome-wide significance. Conclusions: We suggest that the TTC39C gene is associated with diabetic maculopathy with decreased visual acuity. This needs to be confirmed by further replication studies and functional studies.

Association of 18bp insertion/deletion polymorphism, at -2549 position of VEGF gene, with diabetic vascular complications in type 2 diabetes mellitus

PURPOSE

Diabetes mellitus type 2 (T2DM) and its vascular complications are a serious world health problem. For this reason it is important to look for new diabetes complication risk factors. The aim of this study was to determine whether 18-bp insertion/deletion (I/D) polymorphism at -2549 position of the vascular endothelial growth factor (VEGF) gene is associated with diabetic vascular complications (DVC).

MATERIAL AND METHODS

Caucasian subjects (n = 100) with T2DM were recruited for this study. Genotyping of the VEGF gene I/D polymorphism was done by the polymerase chain reaction (PCR) method. The results were correlated with laboratory and clinical data.

RESULTS

In our population heterozygous of the VEGF gene polymorphism was observed most frequently (57%). DVC were observed in 53 patients. Heterozygous T2DM patients significantly more often suffered from heart failure (HF) and stroke (p = 0.05). Amongst all the DVC, D allele of the VEGF polymorphism had a significantly increased risk of diabetic retinopathy (DR) (OR = 1.31; p = 0.033) irrespective of the duration of diabetes, BMI, the glycemia control expressed by HbA1c, renal function, lipid values or applied treatment. The studied polymorphism did not correlate with coronary heart disease, peripheral vascular disease, cardiovascular death, diabetic kidney disease or applied treatment.

CONCLUSIONS

The multivariate logistic regression analysis showed that the D allele in the promoter region of the VEGF gene is an independent risk factor of DR irrespective of other laboratory and clinical variables in T2DM patients. Our study suggests that I/D allele in the studied gene is associated with HF and strokes.

Association of vascular endothelial growth factor expression and polymorphisms with the risk of gestational diabetes mellitus

OBJECTIVE

To study the associations of vascular endothelial growth factor (VEGF) expression and its gene polymorphisms with the risk of gestational diabetes mellitus (GDM).

METHODS

A total of 239 GDM patients (GDM group) and 275 healthy pregnant women (Control group) were included in this study. VEGF genotypes (including rs2146323, rs2010963, rs3025039, rs3025010, and rs833069) were analyzed by TaqMan assay. ELISA was used to determine the serum VEGF levels. The software SHEsis was performed to analyze haplotypes.

RESULTS

The carrier with the rs2146323 AA, CA+AA genotypes, and A allele, as well as the rs3025039 CT, TT, CT+TT genotypes, and T allele showed the increased risk of GDM (all P < 0.05), but the distributions of genotype and allele at rs2010963, rs3025010, and rs833069 were not significantly different between GDM patients and controls (all P > 0.05). Notably, the frequency of rs2010963-rs833069-rs2146323-rs3025010 haplotypes CAAC, CAAT, CACC, CACT, GACT, and GGCT was found statistically different between GDM patients and controls (all P < 0.05). The patients with rs3025039 CT+TT genotype had higher VEGF levels than those with CC genotype (all P < 0.05). Besides, age, family histories of diabetes, previous GDM, hypertension, pre-pregnancy body mass index, fasting plasma glucose, fasting insulin, homeostasis model assessment (HOMA)-IR, rs2146323 CA+AA, rs3025039 CT+TT, and VEGF expression level were independent risk factors, while HOMA-β was an independent protective factor for GDM (all P < 0.05).

CONCLUSION

VEGF rs2146323 and rs3025039 polymorphisms and its expression were significantly correlated with the risk of GDM, providing a great clinical value for GDM assessment and diagnosis.

Potential Impact of Vascular Endothelial Growth Factor Gene Variation (-2578C>A) on Breast Cancer Susceptibility in Saudi Arabia: a Case-Control Study

Aim:

VEGF gene polymorphisms can induce either increase or inhibition of VEGF secretion, with altered promoter activity. The VEGF rs699947 SNP is located in the promoter region and is associated with susceptibility to breast carcinoma development. Here, we investigated the association of the -2578C>A polymorphism in the VEGF gene with breast cancer risk in Saudi women.

Methodology:

Genotyping of the VEGF-gene variation (-2578A>C) was performed using the amplification refractory mutation system PCR. We investigated the association of VEGF gene variants with different clinicopathological features of breast cancer patients.

Results:

A significant difference was observed in genotype distribution among the breast cancer cases and sex matched healthy controls (p=0.03). The frequencies of the three genotypes CC, CA, AA found in the patient samples were 37%, 45% and 18% and in the healthy controls were 54%,37%, and 09% respectively. An increased risk of developing breast cancer in Saudi women was associated with the VEGF −2578 AA genotype (OR = 2.91, 95 % CI, 1.18-7.20; p = 0.01; RR 1.78 (1.01-3.11 p=0.01), the VEGF −2578 A allele (OR = 1.79, 95 % CI, 1.17-2.73; p = 0.004: RR 1.35 1.07-1.71) and the VEGFR-(CA+ AA) (OR 1.99 1.13-3.51; RR 1.401.0-1.85). Thus the A allele increased the risk of BC when compared with C allele. When we stratified groups of patients according to the status of tumor markers, stage, age and metastasis, statistically significant associations with −2578 C/A SNP were revealed.

Conclusion:

Our data showed a significant association of the VEGF -2578C>A polymorphism with BC susceptibility in Saudi women. The VEGF -2578AA homozygote significantly increases the risk and can be useful as a predisposing genetic marker. Further studies with larger sample sizes are necessary to confirm our findings.

Diabetic macular oedema: under-represented in the genetic analysis of diabetic retinopathy

Diabetic retinopathy, a complication of both type 1 and type 2 diabetes, is a complex disease and is one of the leading causes of blindness in adults worldwide. It can be divided into distinct subclasses, one of which is diabetic macular oedema. Diabetic macular oedema can occur at any time in diabetic retinopathy and is the most common cause of vision loss in patients with type 2 diabetes. The purpose of this review is to summarize the large number of genetic association studies that have been performed in cohorts of patients with type 2 diabetes and published in English-language journals up to February 2017. Many of these studies have produced positive associations with gene polymorphisms and diabetic retinopathy. However, this review highlights that within this large body of work, studies specifically addressing a genetic association with diabetic macular oedema, although present, are vastly under-represented. We also highlight that many of the studies have small patient numbers and that meta-analyses often inappropriately combine patient data sets. We conclude that there will continue to be conflicting results and no meaningful findings will be achieved if the historical approach of combining all diabetic retinopathy disease states within patient cohorts continues in future studies. This review also identifies several genes that would be interesting to analyse in large, well-defined cohorts of patients with diabetic macular oedema in future candidate gene association studies.

Vascular endothelial growth factor gene variations as a risk predictor in disc degeneration

Objective

To evaluate the frequency of polymorphisms in the vascular endothelial growth factor (VEGF) gene, as well as to identify a potential risk haplotype among the polymorphic regions in this gene in patients with disc degeneration and in the Control Group.

Methods

This study analyzed a total of 217 individuals distributed into the Disc Degeneration and Control Groups. Peripheral blood was collected from all patients to detect VEGF gene polymorphisms identified by qPCR (rs699947, rs1570360, rs2010963, rs833061 and rs3025039). All patients presenting disc degeneration had the confirmation by nuclear magnetic resonance test and were rated according to disc degeneration level.

Results

All polymorphisms were in Hardy- Weinberg equilibrium (p>0.05) in the studied population. The genotypic frequency for Disc Degeneration and Control Group were rs699947 p = 0.475, rs1570360 p = 0.862, rs2010963 p = 0.823, rs833061 p=0.596 and rs3025039 p=0.230. In haplotype analysis, the compositions CAGGC (p=0.094) and CCGGC (p=0.054) stood out.

Conclusion

The correlation between VEGF gene polymorphism as a risk predictor for disc degeneration was negative in the studied population. However, the VEGF gene has a large polymorphic region, and it is activated by various catabolic and metabolic factors in the disc degeneration process, which has not been fully elucidated.

VEGF-A gene polymorphisms and responses to intravitreal ranibizumab treatment in patients with diabetic macular edema

PURPOSE

To investigate the association between VEGF gene polymorphisms and the responses to treatment with intravitreal ranibizumab (IVR) in patients with diabetic macular edema (DME).

METHODS

This prospective study, conducted at the Kutahya Dumlupinar University Faculty of Medicine, included 95 patients with DME that were treated with IVR and 32 patients without DME despite proliferative diabetic retinopathy (PDR). The participants were divided into three groups: DME with non-proliferative diabetic retinopathy, DME with PDR, and PDR without DME; patients with DME who were treated with IVR were further divided into two groups based on their response to the treatment. Each patient was genotyped for five single nucleotide variations (SNVs) in VEGF-A: rs2010963, rs2146323, rs10434, rs833069, and rs6921438.

RESULT

There was a statistically significant difference in allelic distribution of VEGF-A rs833069 polymorphism in relation to the severity of diabetic retinopathy (DRP) (p = 0.031). The allelic distribution of VEGF-A rs2146323 polymorphism tended to be associated with the severity of DRP (p = 0.069). There were no statistically significant differences in the allelic distribution of the studied five SNVs in DME patients regarding the patients' responses to IVR therapy.

CONCLUSIONS

There is no association between the studied VEGF-A SNVs and the responses to IVR therapy in DME. However, the VEGF-A rs833069 gene polymorphism has a clear association with the severity of diabetic retinopathy.

VEGF Polymorphisms Among Neovascular Age-Related Macular Degenerative Subjects in a Multiethnic Population

AIM

To determine the association of vascular endothelial growth factor (VEGF) polymorphisms with neovascular age-related macular degeneration (nAMD).

MATERIALS AND METHODS

One hundred thirty-five nAMD patients and 135 controls were recruited to determine the association of the -460 C/T, the -2549 I/D, and the +405 G/C polymorphisms with the VEGF gene. Genotyping was conducted using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach, and association analyses were conducted using chi-square analysis and logistic regression analysis.

RESULTS

A significant association was observed between nAMD and the VEGF +405 G/C genotypes (p = 0.002) and alleles (odds ratio = 1.36, 95% confidence interval = 1.12-1.62, p = < 0.001) compared with the controls. This association was confirmed by logistic regression analyses, using two different genetic models (additive and dominant) resulting in p-values of p = 0.001 and p < 0.001, respectively. In addition, the dominant model of VEGF +405 G/C was also found to be at risk of the CC genotype with nAMD among subjects that were aged ≥60 years, female, of Chinese ethnicity, hypertensive, diabetic, and smokers.

CONCLUSION

With the exception of several limitations, the present study showed evidence of an association between the VEGF +405 G/C polymorphism and nAMD in Malaysian subjects.

Association between the vascular endothelial growth factor single nucleotide polymorphisms and diabetic retinopathy risk: A meta-analysis

BACKGROUND

The aim of the present study was to reveal the relationship between vascular endothelial growth factor (VEGF) single nucleotide polymorphisms (SNPs) and susceptibility to diabetic retinopathy (DR).

METHODS

A literature review was conducted (PubMed, Web of Science, Embase) to identify papers about VEGF SNPs and DR published up to 23 September 2015. The VEGF gene SNPs analyzed with regard to DR susceptibility were rs2010963 (G > C), rs833061 (T > C), rs699947 (C > A), rs3025039 (C > T) and rs1570360 (G > A). Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated, and meta-analyses were performed using fixed or random effects models.

RESULTS

Sixteen studies were included in the meta-analysis. Significant associations between the rs3025039 (C > T) polymorphism and increased DR risk were found in the allele model (T/C; pooled OR 1.60, 95% CI 1.07-2.41, P = 0.02), homozygote model (TT/CC; pooled OR 2.08, 95% CI 1.29-3.35, P = 0.003), heterozygote model (TC/CC; pooled OR 1.68, 95% CI 1.04-2.72, P = 0.04), dominant model (TT+TC/CC; pooled OR 1.72, 95% CI 1.06-2.80, P = 0.03), and recessive model (TT/TC+CC; pooled OR 1.80, 95% CI 1.12-2.90, P = 0.02). For rs833061, a significant association between VEGF SNPs and DR was found only in the allele model (C/T; pooled OR 6.34, 95% CI 2.10-19.14, P = 0.001).

CONCLUSIONS

The rs3025039 and rs833061 SNPs are most likely associated with an increased risk of DR. The T allele in rs3025039 and the C allele in rs833061 are associated with increased DR susceptibility.

SNP and Haplotype Analysis of Vascular Endothelial Growth Factor (VEGF) Gene in Lung Cancer Patients of Kashmir

Vascular endothelial growth factor (VEGF) is a major mediator of angiogenesis involving tumor growth and metastasis. In this large case-control study, we investigated whether functional polymorphisms (+405C>G, +936C>T) in the VEGF gene are associated with the risk of lung cancer. The study investigates the association between variants of VEGF gene and lung cancer. We performed single nucleotide polymorphism (SNP), haplotype and linkage disequilibrium studies on 100 patients and 128 healthy controls with 2 SNPs in the VEGF gene. The results were analyzed using logistic regression models, adjusted for age and sex. No Significant association was detected between individual SNPs and lung cancer using all the models of inheritance (codominant, dominant, recessive, over dominant and additive) for finding an association between genotypes and the cancer risk. The P values obtained for two markers were non-significant (P>0.05). Haplotype analysis produced additional support for the non-association of individual haplotypes/all haplotypes with the cancer risk (Global association P=0.56). Our findings suggest the non-involvement of genetic variants (+405C>G, +936C>T) of the VEGF gene in the etiology of lung cancer.

Diabetic macular oedema: clinical risk factors and emerging genetic influences

Diabetic macular oedema is the major cause of visual impairment in type 1 and type 2 diabetes. As type 2 diabetes becomes more prevalent worldwide, the prevalence of diabetic macular oedema is also expected to rise. Current management of diabetic macular oedema is challenging, expensive and not optimal in a subset of patients. Therefore, it is important to increase our understanding of the risk factors involved and develop preventative strategies. While clinical risk factors for diabetic macular oedema have been identified, few studies have addressed potential genetic risk factors. Epidemiology and family studies suggest genetic influences are of importance. In this review, we summarise known clinical risk factors, as well as discuss the small number of genetic studies that have been performed for diabetic macular oedema.

Angiogenesis-related genes and thalidomide teratogenesis in humans: an approach on genetic variation and review of past in vitro studies

Thalidomide embryopathy (TE) has affected more than 10,000 babies worldwide. The hypothesis of antiangiogenesis as the teratogenic mechanism of thalidomide has been investigated in several experimental models; but, in humans, it has only been accessed by in vitro studies. Here, we hypothesized the effect of thalidomide upon angiogenesis-related molecules or proteins, previously identified in human embryonic cells, through the in silico STRING-tool. We also investigated ten polymorphisms in angiogenesis-related genes in 38 Brazilian TE individuals and 136 non-affected Brazilians. NOS2, PTGS2, and VEGFA polymorphisms were chosen for genotyping. The STRING-tool suggested nitric oxide and β-catenin as the central angiogenesis-related molecules affected by thalidomide's antiangiogenic property. We did not identify a significant difference of allelic, genotypic or haplotypic frequencies between the groups. We could not predict a risk allele or a protective one for TE in NOS2, PTGS2, or VEGFA, although other genes should be analyzed in larger samples. The role of nitric oxide and β-catenin must be further evaluated, regarding thalidomide teratogenesis complex etiology.

Genetic and epigenetic modifications in the pathogenesis of diabetic retinopathy: a molecular link to regulate gene expression

Intensification in the frequency of diabetes and the associated vascular complications has been a root cause of blindness and visual impairment worldwide. One such vascular complication which has been the prominent cause of blindness; retinal vasculature, neuronal and glial abnormalities is diabetic retinopathy (DR), a chronic complicated outcome of Type 1 and Type 2 diabetes. It has also become clear that "genetic" variations in population alone can't explain the development and progression of diabetes and its complications including DR. DR experiences engagement of foremost mediators of diabetes such as hyperglycemia, oxidant stress, and inflammatory factors that lead to the dysregulation of "epigenetic" mechanisms involving histone acetylation and histone and DNA methylation, chromatin remodeling and expression of a complex set of stress-regulated and disease-associated genes. In addition, both elevated glucose concentration and insulin resistance leave a robust effect on epigenetic reprogramming of the endothelial cells too, since endothelium associated with the eye aids in maintaining the vascular homeostasis. Furthermore, several studies conducted on the disease suggest that the modifications of the epigenome might be the fundamental mechanism(s) for the proposed metabolic memory' resulting into prolonged gene expression for inflammation and cellular dysfunction even after attaining the glycemic control in diabetics. Henceforth, the present review focuses on the aspects of genetic and epigenetic alterations in genes such as vascular endothelial growth factor and aldose reductase considered being associated with DR. In addition, we discuss briefly the role of the thioredoxin-interacting protein TXNIP, which is strongly induced by high glucose and diabetes, in cellular oxidative stress and mitochondrial dysfunction potentially leading to chromatin remodeling and ocular complications of diabetes. The identification of disease-associated genes and their epigenetic regulations will lead to potential new drugs and gene therapies as well as personalized medicine to prevent or slow down the progression of DR.

Candidate gene studies of diabetic retinopathy in human

Diabetic retinopathy (DR) is a multifactorial disease with complex pathophysiology. It is the main cause of blindness among the people in productive age. The purpose of this literature review is to highlight recent achievements in the genetics of diabetic retinopathy with particular focus on candidate gene studies. We summarized most of the available published data about candidate genes for diabetic retinopathy with the goal to identify main genetic aspects. We conclude that genetic studies reported contradictory findings and no genetic variants meet criteria of a diagnostic marker, or significantly elucidate the root of DR development. Based on these findings it is important to continue with the research in the field of DR genetics, mainly due to the fact that currently new possibilities and approaches associated with utilization of next-generation sequencing are available.

Association of vascular endothelial growth factor -634G/C and receptor for advanced glycation end products G82S gene polymorphisms with diabetic retinopathy

AIM

To investigate the association of receptor for advanced glycation end products (RAGE) G82S and vascular endothelial growth factor (VEGF) -634 G/C gene polymorphisms with diabetic retinopathy (DR).

METHODS

Our cross-sectional study included 61 diabetic patients, 12 of them had proliferative diabetic retinopathy (PDR), 15 had non proliferative diabetic retinopathy (NPDR), 34 had no diabetic retinopathy (NDR) and 61 healthy controls. Participants were tested for RAGE G82S and VEGF -634 G/C polymorphisms by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

We found a significant association between VEGF -634 G/C polymorphism and PDR as PDR patients had increased incidence of VEGF -634 CC genotype compared to NDR patients [odds ratio for CC vs (GC+GG)=6.5, 95% CI=1.5-27.8, P=0.021]. Also VEGF -634 CC genotype and C allele were significantly higher in the PDR than in NPDR patients, which is a novel finding in our study (P=0.024, 0.009 respectively). The mean triglycerides level was significantly higher in diabetic patients with CC genotype (P=0.01) as compared to patients with other genotypes. All cases and control subjects were of the same heterozygous RAGE 82G/S genotype.

CONCLUSION

Patients carrying VEGF -634 C polymorphism have a higher risk of PDR development, so VEGF -634 G/C polymorphism could be used as a predictive marker for PDR in diabetic patients. We could not find a significant association between RAGE G82S polymorphism and DR.

Vascular Endothelial Growth Factor Gene Polymorphism is not Associated with Diabetic Retinopathy in Egyptian Patients

PURPOSE

Vascular endothelial growth factor (VEGF) was implicated as a major contributor to the development of diabetic retinopathy (DR). This study investigated whether single nucleotide polymorphisms of A allele of rs699947 or G allele of rs10434 in the VEGF gene were associated with DR in Egyptian patients with type 2 diabetes mellitus (DM).

METHODS

This is a case-controlled study which was performed at Cairo University Hospital in 2012 on Egyptian patients with type 2 DM with and without DR. Healthy adults without diabetes comprised the comparison group. Patients underwent an ophthalmological examination and fundus photography. Genotyping was performed for the A allele of rs699947 and the G allele of rs10434 polymorphisms using real-time polymerase chain reaction.

RESULTS

A total of 128 patients were enrolled in this study and divided into three groups: Group A included 46 patients with type 2 DM and DR; Group B included 41 patients with type 2 DM without DR; and Group C included 41 healthy controls. There was no significant association between rs699947 or rs10434 and any of the three groups (P = 0.5, P = 0.7, respectively). Allelic frequency in the three groups was not statistically significant for rs699947 or rs10434 (P = 0.6, P = 0.6, respectively).

CONCLUSION

Rs699947 or rs10434 polymorphism was not associated with the presence of DR in Egyptian patients. Further studies are required before genetic testing for polymorphism can be used clinically to correlate with DR.

Diabetic macular oedema: pathophysiology, management challenges and treatment resistance

Diabetic macular oedema (DMO) is the leading cause of vision loss in patients living with diabetes. DMO results from hyperglycaemia-induced activation of pathways that lead to oxidative stress and release of cytokines, impairing the inner and outer blood-retinal barriers. Improved understanding of the pathophysiological mechanisms leading to DMO have led to the development of effective therapies, including vitreoretinal surgery, laser photocoagulation, intravitreal anti-vascular endothelial growth factor drugs and corticosteroids. Advances in imaging, including fluorescein angiography and optical coherence tomography, have also enhanced diagnosis and management of the condition. Despite these advances, there remain patients who do not respond completely to therapy, reflecting the complex pathophysiology of DMO. These patients may be considered treatment-resistant. In this review, we summarise the pathophysiology of DMO, as well as the available treatments and their mechanism of action. Additionally, we focus on treatment-resistant disease and review the literature on potential options for managing this complication of diabetes.

The role of pharmacogenetics and advances in gene therapy in the treatment of diabetic retinopathy

Diabetic retinopathy (DR) and its complications such as diabetic macular edema continue to remain a major cause for legal blindness in the developed world. While the introduction of anti-tVEGF agents has significantly improved visual outcomes of patients with DR, unpredictable response, largely due to genetic polymorphisms, appears to be a challenge with this therapy. With advances in identification of various genetic biomarkers, novel therapeutic strategies consisting of gene transfer are being developed and tested for patients with DR. Application of pharmacogenetic principles appears to be a promising futuristic strategy to attenuate diabetes-mediated retinal vasculopathy. In this comprehensive review, data from recent studies in the field of pharmacogenomics for the treatment of DR have been provided.

Novel Genetic Actors of Diabetes-Associated Microvascular Complications: Retinopathy, Kidney Disease and Neuropathy

Both type 1 and type 2 diabetes mellitus can lead to the common microvascular complications of diabetic retinopathy, kidney disease, and neuropathy. Diabetic patients do not universally develop these complications. Long duration of diabetes and poor glycemic control explain a lot of the variability in the development of microvascular complications, but not all. Genetic factors account for some of the remaining variability because of the heritability and familial clustering of these complications. There have been a large number of investigations, including linkage studies, candidate gene studies, and genome-wide association studies, all of which have sought to identify the specific variants that increase susceptibility. For retinopathy, several genome-wide association studies have been performed in small or midsize samples, but no reproducible loci across the studies have been identified. For diabetic kidney disease, genome-wide association studies in larger samples have been performed, and loci for this complication are beginning to emerge. However, validation of the existing discoveries, and further novel discoveries in larger samples is ongoing. The amount of genetic research into diabetic neuropathy has been very limited, and much is dedicated to the understanding of genetic risk factors only. Collaborations that pool samples and aim to detect phenotype classifications more precisely are promising avenues for a better explanation of the genetics of diabetic microvascular complications.

Common Sequence Variation in the VEGFC Gene Is Associated with Diabetic Retinopathy and Diabetic Macular Edema

PURPOSE

To investigate associations between single nucleotide polymorphisms (SNPs) in the VEGFC gene and the development of diabetic retinopathy (DR) in white patients with type 1 diabetes mellitus (T1DM) or type 2 diabetes mellitus (T2DM).

DESIGN

Cross-sectional, case control study.

PARTICIPANTS

White patients with T1DM or T2DM (n = 2899) were recruited from ophthalmology and endocrine clinics in Australia and the United Kingdom. Patients with T2DM were required to have diabetes mellitus (DM) for at least 5 years and be receiving oral hypoglycemic treatment or insulin.

METHODS

Participants were categorized according to their worst-ever DR grading, as having "no DR" (no history of nonproliferative DR [NPDR], proliferative DR [PDR], or diabetic macular edema [DME]) or "any DR" (further subclassified as NPDR or PDR, without or with DME). Clinical characteristics, glycemic control (hemoglobin A1c [HbA1c]), and presence of diabetic complications were determined at recruitment. Genotyping was performed for 13 VEGFC tag SNPs.

MAIN OUTCOME MEASURES

Odds ratios (ORs) were determined for associations with DR of VEGFC tag SNPs, individually and within haplotypes. Logistic regression was used to adjust for clinical covariates, including DM type, age, sex, DM duration, hypertension, nephropathy, HbA1c, and smoking.

RESULTS

Participants with DM but "no DR" (n = 980) were compared with 1919 participants with DM and "any DR." Three VEGFC SNPs were associated with DR after logistic regression: rs17697419 (P = 0.001; OR, 0.67; confidence interval [CI], 0.52-0.85), rs17697515 (P = 0.001; OR, 0.62; CI, 0.47-0.81), and rs2333526 (P = 0.005; OR, 0.69; CI, 0.54-0.90). rs17697515 Was also specifically associated with DME in those with T2DM (P = 0.004; OR, 0.53; CI, 0.35-0.82). Haplotype analysis revealed 2 significantly associated haplotypes, both protective against DR development.

CONCLUSIONS

Significant associations were found between VEGFC tag SNPs (individually and within haplotypes) and the presence of any DR or DME in white participants with T1DM and T2DM.

Role of NF-κB activation and VEGF gene polymorphisms in VEGF up regulation in non-proliferative and proliferative diabetic retinopathy

The present study was aimed to investigate the relation between nuclear factor kappa beta (NFκB) activation and downstream up-regulation of vascular endothelial growth factor (VEGF) in diabetic retinopathy (DR). Moreover the study was intended to evaluate the role of VEGF gene single nucleotide polymorphisms (SNPs) in DR occurrence and to investigate the functional relevance of VEGF gene SNPs in terms of VEGF expression in DR. Serum level of VEGF, VEGF R1 (receptor 1), VEGF R 2 (receptor 2) and NFκB (p50/65) activity was measured by enzyme linked immune sorbent assay. Genotyping and allelic composition of different SNPs i.e., rs2010963, rs3025039, rs1570360 and rs 2071559 were investigated by Taqman SNP genotyping assay. VEGF, NFκB p50/p65, and VEGF R1 & R2 gene expressions were quantified by real time quantitative polymerase chain reaction. Increased NFκB p50/p65 activity and expressions were observed in non proliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) subjects compared to type 2 diabetes mellitus without retinopathy (DNR) group. Significantly elevated levels of serum VEGF and highest VEGF expression were found among PDR subjects compared to DNR or NPDR subjects. CC genotype and C allele of rs2010963 and TT genotype and T allele of rs3025039 were significantly over represented among PDR subjects compared to DNR group. Increased activation of NFκβ in NPDR and PDR subjects might involve increased up regulation of VEGF. VEGF SNPs i.e., rs2010963 C allele and rs3025039 T allele might be associated with PDR occurrence and in turn regulates VEGF expression among PDR subjects.

Association of 18bp insertion/deletion polymorphism, at -2549 position of VEGF gene, with diabetic nephropathy in type 2 diabetes mellitus patients of North Indian population

BACKGROUND

Vascular endothelial growth factor (VEGF) is a potent multifunctional cytokine which plays a key role in the pathogenesis of diabetic micro-vascular complications. Human VEGF gene is said to be highly polymorphic. Insertion/deletion (I/D) polymorphism of the 18 bp fragment at -2549 position of the promoter region in VEGF gene is said to be of particular interest. The study was aimed to evaluate association of Insertion/deletion (I/D) polymorphism of the 18 bp fragment at -2549 position of the promoter region in VEGF gene, with diabetic nephropathy in type 2 diabetes mellitus.

METHODS

This cross sectional study enrolled 40 subjects each of diabetic nephropathy (DN), diabetes mellitus without nephropathy (DM) and normal control subjects. DNA was isolated from peripheral blood leukocytes. Genotyping of the VEGF gene insertion/ deletion (I/D) polymorphism was done by the polymerase chain reaction (PCR) methods. The frequency of VEGF alleles and genotype distribution were compared in diabetic nephropathy, uncomplicated diabetic and control groups.

RESULTS

DD genotype and D allele were found to be significantly associated with DN group (p = 0.009 and 0.02 respectively) in comparison to DM group. Also DD genotype conferred significant risk of diabetic nephropathy in DM group (OR = 4.2) (against combined frequency of ID and II genotype) so does D allele 2.09 (against I allele).

CONCLUSION

DD genotype and D allele in I/D polymorphism at -2549 position of VEGF gene is associated with increased susceptibility to diabetic nephropathy in north Indian population.

Diabetic retinopathy: variations in patient therapeutic outcomes and pharmacogenomics

Diabetes and its microvascular complications in patients poses a significant challenge and constitutes a major health problem. When it comes to manifestations in the eye, each case of diabetic retinopathy (DR) is unique, in terms of the phenotype, genotype, and, more importantly, the therapeutic response. It is therefore important to identify factors that distinguish one patient from another. Personalized therapy in DR is a new trend aimed at achieving maximum therapeutic response in patients by identifying genotypic and phenotypic factors that may result in less than optimal response to conventional therapy, and consequently, lead to poorer outcome. With advances in the identification of these genetic markers, such as gene polymorphisms and human leucocyte antigen associations, as well as development of drugs that can target their effects, the future of personalized medicine in DR is promising. In this comprehensive review, data from various studies have been analyzed to present what has been achieved in the field of pharmacogenomics thus far. An insight into future research is also provided.

Human genetics of diabetic retinopathy

There is evidence demonstrating that genetic factors contribute to the risk of diabetic retinopathy (DR). Genetics variants, structural variants (copy number variation, CNV) and epigenetic changes play important roles in the development of DR. Genetic linkage and association studies have uncovered a number of genetic loci and common genetic variants susceptibility to DR. CNV and interactions of gene by environment have also been detected by association analysis. Apart from nucleus genome, mitochondrial DNA plays critical roles in regulation of development of DR. Epigenetic studies have indicated epigenetic changes in chromatin affecting gene transcription in response to environmental stimuli, which provided a large body of evidence of regulating development of diabetes mellitus. Identification of genetic variants and epigenetic changes contributed to risk or protection of DR will benefit uncovering the complex mechanism underlying DR. This review focused on the current knowledge of the genetic and epigenetic basis of DR.

A genome-wide association study for diabetic retinopathy in a Japanese population: potential association with a long intergenic non-coding RNA

Elucidation of the genetic susceptibility factors for diabetic retinopathy (DR) is important to gain insight into the pathogenesis of DR, and may help to define genetic risk factors for this condition. In the present study, we conducted a three-stage genome-wide association study (GWAS) to identify DR susceptibility loci in Japanese patients, which comprised a total of 837 type 2 diabetes patients with DR (cases) and 1,149 without DR (controls). From the stage 1 genome-wide scan of 446 subjects (205 cases and 241 controls) on 614,216 SNPs, 249 SNPs were selected for the stage 2 replication in 623 subjects (335 cases and 288 controls). Eight SNPs were further followed up in a stage 3 study of 297 cases and 620 controls. The top signal from the present association analysis was rs9362054 in an intron of RP1-90L14.1 showing borderline genome-wide significance (P_met = 1.4×10⁻⁷, meta-analysis of stage 1 and stage 2, allele model). RP1-90L14.1 is a long intergenic non-coding RNA (lincRNA) adjacent to KIAA1009/QN1/CEP162 gene; CEP162 plays a critical role in ciliary transition zone formation before ciliogenesis. The present study raises the possibility that the dysregulation of ciliary-associated genes plays a role in susceptibility to DR.

Variants in angiogenesis-related genes and the risk of clear cell renal cell carcinoma

Angiogenesis is fundamentally important to the pathogenesis of clear cell renal cell carcinoma (ccRCC). We investigated the association between variations of genes related to angiogenesis and the risk of ccRCC. In a case-control study of 859 ccRCC patients and 1004 cancer-free subjects, we genotyped 24 potentially functional single nucleotide polymorphisms (SNPs) in seven angiogenesis-related genes (HIF1A, EPAS1, VEGFA, VEGFR1, VEGFR2, VEGFR3 and PDGFRB) using the TaqMan or Snapshot method. Unconditional logistic regression, adjusted for potential confounding factors, was used to assess the risk associations. The functionality of selected SNPs was assessed by real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) and luciferase reporter gene assays. We found two SNPs (VEGFA rs2010963 and VEGFR3 rs448012) that were significantly associated with increased risk of ccRCC, after adjusting for multiple comparisons [rs2010963 CC/GC cf. GG: false discovery rate (FDR) = 0.048, odds ratio (OR) = 1.36, 95% confidence interval (95% CI) = 1.12-1.66; rs448012 CC/GC cf. GG: FDR = 0.048, OR = 1.38, 95% CI =1.13-1.69]. Real-time quantitative PCR revealed that the variant genotypes of rs2010963, but not rs448012, were associated with increased gene expression in normal tissues of ccRCC patients (CC/GC cf. GG: P = 0.036). The luciferase reporter assay showed that the rs2010963 C allele significantly increased luciferase activity over that of the rs2010963 G allele. Our results indicate that VEGFA rs2010963 and VEGFR3 rs448012 are associated with risk of ccRCC. Furthermore, rs2010963 is a functional SNP that may affect ccRCC susceptibility by modulating endogenous VEGFA expression.

Genetics of diabetes complications

Chronic hyperglycemia and duration of diabetes are the major risk factors associated with development of micro- and macrovascular complications of diabetes. Although it is believed that hyperglycemia induces damage to the particular cell subtypes, e.g., mesangial cells in the renal glomerulus, capillary endothelial cells in the retina, and neurons and Schwann cells in peripheral nerves, the exact mechanisms underlying these damaging defects are not yet well understood. Clustering of micro- and macrovascular complications in families of patients with diabetes suggests a strong genetic susceptibility. However, until now only a handful number of genetic variants were reported to be associated with either nephropathy (ACE, ELMO1, FRMD3, and AKR1B1) or retinopathy (VEGF, AKR1B1, and EPO), and only a few studies were carried out for genetic susceptibility to cardiovascular diseases (ADIPOQ, GLUL) in patients with diabetes. It is, therefore, obvious that the accumulation of more data from larger studies and better phenotypically characterized cohorts is needed to facilitate genetic discoveries and unravel novel insights into the pathogenesis of diabetic complications.

Genetics of diabetic retinopathy

Multiple studies have shown that genetic factors may play an important role in determining an individual's risk for the development of diabetic retinopathy (DR) and progression to proliferative DR. However, consistent and definitive genetic associations with DR across broad populations have been not been established. Numerous genes have been studied for their association with DR and the results of these investigations have most specifically pointed to three specific genes that are likely involved in DR development and progression. The gene coding for vascular endothelial growth factor, aldose reductase, and the receptor for advanced glycation end products have been extensively evaluated, and specific polymorphisms of these genes have been suggested to potentially increase the risk of DR development. In this paper, we have reviewed the published literature on the genetics of DR and the potential implications for DR development and progression.

Meta-analysis of association between the -2578C/A polymorphism of the vascular endothelial growth factor and retinopathy in type 2 diabetes in Asians and Caucasians

BACKGROUND AND OBJECTIVES

Vascular endothelial growth factor (VEGF) has been shown to play an important role in the development and progress of diabetic retinopathy (DR). A number of case-control studies focused on the association between VEGF -2578C/A and risk for DR. But the results were not always consistent, so we performed a meta-analysis to evaluate the precise association between this variant and risk for DR.

METHODS

All publications on the association between VEGF -2578C/A polymorphism and DR were searched in the following electronic databases: PubMed, Embase, the Cochrane Library and Chinese Biomedical Literature Database, with the last report up to January 2013. This meta-analysis was assessed by Review Manager 5.1.

RESULTS

A total of 6 studies were involved in this meta-analysis, including 835 cases and 867 controls. Overall, we found a significant association between this polymorphism and DR (A vs. C: OR=1.49, 95% CI=1.26-1.77, p<0.00001; AA vs. CA+CC: OR=1.26, 95% CI=0.94-1.68, p=0.12; AA+CA vs. CC: OR=1.56, 95% CI=1.27-1.91, p<0.00001; AA vs. CC: OR=1.67, 95% CI=1.20-2.32, p=0.003; CA vs. CC: OR=1.51, 95% CI=1.21-1.87, p=0.0002), but we did not find any significant association in Caucasians in subgroup analysis. The results were not materially altered after the studies which did not fulfill the Hardy-Weinberg equilibrium were excluded.

CONCLUSION

Our meta-analysis supports the association between the VEGF -2578C/A polymorphism and DR, but not in the Caucasian population.

A Study of VEGF Gene Polymorphism in Egyptian Patients with Diabetic Retinopathy

BACKGROUND

There are subgroups of patients with diabetes mellitus (DM) in whom diabetic retinopathy (DR) does not develop despite poor long-term control of their disease, while others exercising fairly good control, develop retinopathy. So, we aimed to investigate the association of DR with -2578 polymorphism of the vascular endothelial growth factor (VEGF) gene, which has been reported to be associated with increased VEGF production, in Egyptian diabetic patients.

MATERIALS AND METHODS

This is a case control study in which 148 diabetic patients were enrolled. Among them, 44 subjects had proliferative diabetic retinopathy (PDR), 30 had non-proliferative diabetic retinopathy (NPDR), and 74 individuals without retinopathy served as controls. A single nucleotide polymorphism (SNP) of the VEGF gene, a C→A transversion at -2578 (the C/A polymorphism), was investigated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

We found a higher frequency of the polymorphic genotype in both the NPDR (66.7%) and PDR (72.7%) groups compared to the wild C/C genotype (33.3% in NPDR and 27.3% in PDR), but with no statistically significant difference from the control group. Significant association of the progression of DR to the polymorphic genotype was achieved at diabetes duration more than 20 years.

CONCLUSION

Despite of the higher frequency of both the polymorphic genotype and the A allele in cases with DR compared to the control group, there might be no significant association between the VEGF gene polymorphism and DR per se, unless it is longstanding.

Genetics in diabetic retinopathy: current concepts and new insights

There is emerging evidence which indicates the essential role of genetic factors in the development of diabetic retinopathy (DR). In this regard it should be highlighted that genetic factors account for 25-50% of the risk of developing DR. Therefore, the use of genetic analysis to identify those diabetic patients most prone to developing DR might be useful in designing a more individualized treatment. In this regard, there are three main research strategies: candidate gene studies, linkage studies and Genome-Wide Association Studies (GWAS). In the candidate gene approach, several genes encoding proteins closely related to DR development have been analyzed. The linkage studies analyze shared alleles among family members with DR under the assumption that these predispose to a more aggressive development of DR. Finally, Genome-Wide Association Studies (GWAS) are a new tool involving a massive evaluation of single nucleotide polymorphisms (SNP) in large samples. In this review the available information using these three methodologies is critically analyzed. A genetic approach in order to identify new candidates in the pathogenesis of DR would permit us to design more targeted therapeutic strategies in order to decrease this devastating complication of diabetes. Basic researchers, ophthalmologists, diabetologists and geneticists should work together in order to gain new insights into this issue.

The associations between VEGF gene polymorphisms and diabetic retinopathy susceptibility: a meta-analysis of 11 case-control studies

AIMS. Published data on the associations of VEGF polymorphisms with diabetic retinopathy (DR) susceptibility are inconclusive. A systematic meta-analysis was undertaken to clarify this topic. METHODS. Data were collected from the following electronic databases: PubMed, Embase, OVID, Web of Science, Elsevier Science Direct, Excerpta Medica Database (EMBASE), and Cochrane Library with the last report up to January 10, 2014. ORs and 95% CIs were calculated for VEGF-2578C/A (rs699947), -1154G/A (rs1570360), -460T/C (rs833061), -634G>C (rs2010963), and +936C/T (rs3025039) in at least two published studies. Meta-analysis was performed in a fixed/random effect model by using the software STATA 12.0. RESULTS. A total of 11 studies fulfilling the inclusion criteria were included in this meta-analysis. A significant relationship between VEGF+936C/T (rs3025039) polymorphism and DR was found in a recessive model (OR = 3.19, 95% CI = 1.20-8.41, and P(z) = 0.01) in Asian and overall populations, while a significant association was also found between -460T/C (rs833061) polymorphism and DR risk under a recessive model (OR = 2.12, 95% CI = 1.12-4.01, and P(z) = 0.02). CONCLUSIONS. Our meta-analysis demonstrates that +936C/T (rs3025039) is likely to be associated with susceptibility to DR in Asian populations, and the recessive model of -460T/C (rs833061) is associated with elevated DR susceptibility.

Association of VEGF gene polymorphisms with diabetic retinopathy: a meta-analysis

Background

Studies on the association of vascular endothelial growth factor (VEGF) gene -460T/C and -2578C/A polymorphisms with diabetic retinopathy (DR) have reported conflicting results. The aim of the present study was to assess the association by using meta-analysis.

Methods

A systematic search of electronic databases (PubMed, EMBASE, Elsevier Science Direct, ISI Web of Science, CBM, CNKI and VIP) was carried out until Sept 18, 2013. The pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were used to assess the strength of the association.

Results

Eleven studies (-460T/C: 6 studies including 932 cases and 722 controls; -2578C/A: 6 studies including 1,071 cases and 1,137 controls) were involved in this meta-analysis. Significant association was found for -460T/C polymorphism (C versus T: OR=1.48, 95%CI=1.07–2.05, P=0.02; TC+CC versus TT: OR=1.78, 95%CI=1.02–3.12, P=0.04; CC versus TT+TC: OR=1.76, 95%CI=1.10–2.81, P=0.02), but not for -2578C/A polymorphism (P>0.05). Similar results were found in the subgroup analysis.

Conclusions

This meta-analysis demonstrates that DR is associated with VEGF gene -460T/C polymorphism, but not -2578C/A polymorphism. Further case-control studies based on larger sample size are still needed, especially for -2578C/A polymorphism.

Two polymorphisms (rs699947, rs2010963) in the VEGFA gene and diabetic retinopathy: an updated meta-analysis

Background

The vascular endothelial growth factor (VEGFA) gene has been suggested to play an important role in the pathogenesis of diabetic retinopathy (DR). However, the results have been inconsistent. In this study, we performed a meta-analysis to clarify the associations between VEGFA polymorphisms and DR risk.

Methods

Published literature from PubMed, EMBASE, Web of Science and Google Scholar were retrieved. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using fixed- or random-effects model.

Results

A total of eight studies (1204 cases and 1198 controls) for rs699947 polymorphism and ten studies (1666 cases and 1782 controls) for rs2010963 polymorphism were included in the meta-analysis. The results suggested that rs699947 polymorphism was marginally associated with DR under a homogeneous co-dominant model (AA vs. CC: OR = 1.69, 95% CI = 1.03-2.77, p = 0.040) and a dominant model (AA + AC vs. CC: OR = 1.38, 95% CI = 1.01-1.90, p = 0.040), whereas the association between rs2010963 polymorphism and DR was not significant under all genetic models (all p > 0.05). In the subgroup analysis, the effect size for rs699947 polymorphism was only marginally significant among European populations under a dominant model (OR = 1.47, 95% CI = 1.07–2.02, p = 0.018), but not among East Asians. After exclusion of outliers which were the source of between-study heterogeneity, there was significant association between rs699947 polymorphism and DR under a homogeneous co-dominant model (OR = 1.64, 95% CI = 1.18-2.28, p = 0.003), even after multiple comparison correction.

Conclusions

Our meta-analysis confirmed the significant association between rs699947 polymorphism and DR after exclusion of outliers, and rs2010963 polymorphism might be not associated with DR.

Vascular endothelial growth factor gene polymorphism prevalence in patients with diabetic macular oedema and its correlation with anti-vascular endothelial growth factor treatment outcomes

BACKGROUND

To study the possible association between vascular endothelial growth factor gene polymorphism and diabetic macular oedema, and its correlation to the outcomes of anti-vascular endothelial growth factor treatment.

DESIGN

Prospective study.

PARTICIPANTS

392 diabetic patients were included; 180 patients of them had no retinopathy, 212 patients had diabetic retinopathy. Diabetic retinopathy patients were classified into four groups as defined by the absence or presence of macular oedema or proliferative retinopathy.

METHODS

In all subjects, polymerase chain reaction-restriction fragment length polymorphism was conducted to detect the vascular endothelial growth factor gene C-634G polymorphism. Serum levels of vascular endothelial growth factor were estimated. Changes of visual acuity and central macular thickness after bevacizumab treatment in diabetic macular oedema patients of different genotypes were monitored for 9-12 months.

MAIN OUTCOME MEASURES

Vascular endothelial growth factor C-634G genotypes distribution in different groups; correlation between genotypes, and changes in visual acuity and central macular thickness after intravitreal bevacizumab treatment.

RESULTS

CC genotype was significantly prevalent among diabetic macular oedema patients (P = 0.019). Significant higher serum levels of vascular endothelial growth factor were detected in diabetic retinopathy and diabetic macular oedema patients with CC genotype (P = 0.02, 0.016). After bevacizumab treatment, individuals with genotypes CG and GG have a decreased chance of positive treatment outcomes compared t with CC genotype (P < 0.001).

CONCLUSIONS

Vascular endothelial growth factor C-634G polymorphism (CC genotype) is a genetic risk factor for diabetic macular oedema, and its presence provides significantly better visual outcome following bevacizumab treatment.