The Role of Genetic Variants (rs869109213 and rs2070744) Of theeNOSGene andBglII in the α2Subunit of the α2β1Integrin Gene in Diabetic Retinopathy in a Tunisian Population

Association of the endothelial nitric oxide synthase (eNOS) 4a/b polymorphism with the risk of incident diabetic retinopathy in patients with type 2 diabetes mellitus: a systematic review and updated meta-analysis

OBJECTIVE

To conduct a systematic review and updated meta-analysis on the potential association between endothelial nitric oxide synthase (eNOS) 4a/b polymorphism and the risk of developing diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM) and to identify possible clinical biomarkers for early screening of DR.

MATERIALS AND METHODS

A meta-analysis based on case-control or cross-sectional studies was conducted to examine the correlation between eNOS 4a/b polymorphism and DR. Pooled odds ratio (OR) and 95% confidence interval (CI) were used to estimate the association strength.

RESULTS

We included 19 studies, covering 7838 subjects. An association was observed in Caucasians (allelic model: OR = 1.273, 95% CI: 1.006-1.610, p = .045; recessive model: OR = 0.575, 95% CI: 0.371-0.892, p = .014; dominant model: OR = 1.268, 95% CI: 1.052-1.528, p = .013; homozygote model: OR = 1.833, 95% CI: 1.176-2.856, p = .007). Moreover, population-based studies have indicated an association between eNOS 4a/b polymorphism and DR susceptibility.

CONCLUSIONS

The present study showed that intron 4a allele of eNOS 4a/b is a risk factor for DR in Caucasians with T2DM. Thus, eNOS 4a/b may be used as a biomarker for the early screening and diagnosis of DR in Caucasian T2DM patients.Key messagesEndothelial nitric oxide synthase 4a/b gene polymorphism is not associated with the risk of developing diabetic retinopathy in the overall population, Asians, or Chinese Han patients with type 2 diabetes. However, 4a is a risk factor for the development of diabetic retinopathy in Caucasians.Endothelial nitric oxide synthase 4a/b gene polymorphism is not associated with the type of diabetic retinopathy.

ITGA2 Gene Polymorphism Is Associated with Type 2 Diabetes Mellitus in the Kazakhstan Population

Background and Objectives: Nowadays, every tenth adult in the world suffers from diabetes mellitus (DM). Diabetic retinopathy (DR) is the most common microvascular complication of type 2 DM (T2DM) and a leading cause of acquired blindness in middle-aged individuals in many countries. Previous studies have identified associations of several gene polymorphisms with susceptibility to microvascular complications of DM in various worldwide populations. In our study, we aimed to test the hypothesis of the associations of single nucleotide polymorphisms (SNP) of the VEGF (−2549I/D), RAGE (−429T/C and −374T/A), TCF7L2 (rs7903146), and ITGA2 (BglII) genes with a predisposition to DR among T2DM patients in the Kazakhstan population. Materials and Methods: We conducted a case–control study comparing the genotype distribution and allele frequencies between groups of DR patients (N = 94), diabetic patients without DR (N = 94), and healthy controls (N = 51). Genotypes were identified using the PCR-RFLP method. Results: In all cases, the genotype distribution corresponded to the Hardy–Weinberg equilibrium. The groups of diabetic patients with and without DR did not significantly differ in the genotype distribution of the SNPs studied. Differences between both groups of diabetic patients and healthy controls in four out of five SNPs were also not significant. At the same time, both groups of diabetic patients differed significantly from healthy controls in genotype distribution (p = 0.042 and 0.005, respectively) and allele frequencies (p = 0.021 and 0.002, respectively) of the BglII polymorphism in the ITGA2 gene. After adjusting for multiple comparisons, the differences between the group of diabetic patients without DR and the control group remained significant (pBonf = 0.027 for genotypes and pBonf = 0.009 for alleles). The BglII− allele was associated with diabetes: OR = 1.81 [1.09–2.99] for DR patients, and OR = 2.24 [1.34–3.75] for diabetic patients without DR. The association was also observed in the subset of Kazakhs. Conclusions: This study shows that the BglII polymorphism in the ITGA2 gene can be associated with T2DM but not with DR. According to our data, the risk allele for diabetes is the wild BglII− allele, and not the minor BglII+, which is considered as risky for DR.

The association of T786C and G894T polymorphisms of eNOS gene with diabetic retinopathy in Greece

PURPOSE

To investigate whether eNOS T786C (rs2070744) and G894T (rs1799983) gene polymorphisms are associated with diabetic retinopathy in Greek diabetic patients.

MATERIALS

271 patients with type-2 diabetes mellitus participated in our study; 130 suffered from diabetic retinopathy and 141 not. All the patients underwent a complete ophthalmological examination, while clinical and demographic data were assessed. Furthermore, they were genotyped for rs2070744 and rs1799983 single nucleotide polymorphisms of eNOS gene.

RESULTS

Regarding the clinical and demographic data, no significant differences were detected between the studied groups, except for hemoglobin A1c levels and the frequency of insulin treatment (higher in patients with diabetic retinopathy). The frequency of rs1799983 GT genotype was significantly elevated in patients with diabetic retinopathy (55% vs. 40%, P = 0.011) and was associated with a 2-fold increased risk of developing retinopathy (OR 1.92, 95% CI 1.16-3.17). Furthermore, we demonstrated that the aforementioned genotype was significantly and independently associated with increased odds for retinopathy onset in diabetic subjects (OR 2.23, 95% CI 1.28-3.90, P = 0.005), regardless of the impact of other confounders.

CONCLUSIONS

We documented that rs1799983 GT genotype could be recognized as an independent risk factor of retinopathy in Greek patients with type-2 diabetes mellitus, while no role for rs2070744 polymorphism was identified. Further research in different ethnic groups will clarify the exact association of these polymorphisms with the risk for diabetic retinopathy development.

Genetics of Diabetic Retinopathy, a Leading Cause of Irreversible Blindness in the Industrialized World

Diabetic retinopathy (DR) is a chronic complication of diabetes and a leading cause of blindness in the industrialized world. Traditional risk factors, such as glycemic control and duration of diabetes, are unable to explain why some individuals remain protected while others progress to a more severe form of the disease. Differences are also observed in DR heritability as well as the response to anti-vascular endothelial growth factor (VEGF) treatment. This review discusses various aspects of genetics in DR to shed light on DR pathogenesis and treatment. First, we discuss the global burden of DR followed by a discussion on disease pathogenesis as well as the role genetics plays in the prevalence and progression of DR. Subsequently, we provide a review of studies related to DR’s genetic contribution, such as candidate gene studies, linkage studies, and genome-wide association studies (GWAS) as well as other clinical and meta-analysis studies that have identified putative candidate genes. With the advent of newer cutting-edge technologies, identifying the genetic components in DR has played an important role in understanding DR incidence, progression, and response to treatment, thereby developing newer therapeutic targets and therapies.

The association of OPG polymorphisms with diabetic retinopathy in Chinese population

PURPOSE

Genetic factors have been studied to be associated with diabetic retinopathy (DR). This study aimed to investigate the association between the polymorphisms in the osteoproterin (OPG) gene and DR in a Han Chinese population.

METHODS

There were 475 patients with diabetic retinopathy (DR), 478 type 2 diabetes mellitus without retinopathy (DNR) and 469 healthy controls collected in this study. OPG single-nucleotide polymorphisms (SNPs) rs2073618 and rs3134069 were genotyped by Mass ARRAY MALDI-TOF system. The genotype and allele frequencies were evaluated using the χ² tests. Odds ratio (OR) and 95% confidence intervals (95% CI) were calculated for the risk of genotype and allele.

RESULTS

There was a statistically significant difference for OPG SNP rs3134069 between DR cases and healthy controls in the allelic model (P = .036, OR = 1.33, 95% CI = 1.02-1.73). The C allele frequency of this polymorphism was 0.154 in the DR cases, whereas it was 0.120 in healthy controls, suggesting a risk effect for DR. SNP rs3134069 had a significant association with DR in the dominant model (P = .038, OR = 1.37, 95% CI = 1.02-1.84), indicating that the CC/AC genotype was more likely to suffer from DR. For rs2073618, no significant difference was identified in the allelic model (P = .632, OR = 0.95, 95% CI = 0.78-1.16) and the four genetic models.

CONCLUSIONS

This study showed that OPG SNP rs3134069 was associated with DR in the dominant model, suggesting that the OPG gene variant may be involved in the development of DR.

Targeting RGD-binding integrins as an integrative therapy for diabetic retinopathy and neovascular age-related macular degeneration

Integrins are a class of transmembrane receptors that are involved in a wide range of biological functions. Dysregulation of integrins has been implicated in many pathological processes and consequently, they are attractive therapeutic targets. In the ophthalmology arena, there is extensive evidence suggesting that integrins play an important role in diabetic retinopathy (DR), age-related macular degeneration (AMD), glaucoma, dry eye disease and retinal vein occlusion. For example, there is extensive evidence that arginyl-glycyl-aspartic acid (Arg-Gly-Asp; RGD)-binding integrins are involved in key disease hallmarks of DR and neovascular AMD (nvAMD), specifically inflammation, vascular leakage, angiogenesis and fibrosis. Based on such evidence, drugs that engage integrin-linked pathways have received attention for their potential to block all these vision-threatening pathways. This review focuses on the pathophysiological role that RGD-binding integrins can have in complex multifactorial retinal disorders like DR, diabetic macular edema (DME) and nvAMD, which are leading causes of blindness in developed countries. Special emphasis will be given on how RGD-binding integrins can modulate the intricate molecular pathways and regulate the underlying pathological mechanisms. For instance, the interplay between integrins and key molecular players such as growth factors, cytokines and enzymes will be summarized. In addition, recent clinical advances linked to targeting RGD-binding integrins in the context of DME and nvAMD will be discussed alongside future potential for limiting progression of these diseases.

Association between endothelial nitric oxide synthase (NOS3) rs2070744 and the risk for migraine

Because nitric oxide could play an important role in the pathogenesis of migraine (suggested by experimental, neuropathological, biochemical, and pharmacological data), and a recent meta-analysis showed an association between the single-nucleotide polymorphism (SNP) rs2070744 in the endothelial nitric oxide synthase (eNOS or NOS3) gene (chromosome 7q36.1) and the risk for migraine in Caucasians, we attempted to replicate the possible association between this SNP and the and the risk for migraine in the Caucasian Spanish population. The frequencies for the NOS3 rs2070744 genotypes and allelic variants were assessed in 283 migraine patients and 287 healthy controls with a TaqMan-based qPCR Assay. The putative influence on genotype frequency of age at onset of migraine attacks, gender, family history of migraine, absence or presence of aura, and triggering of migraine attacks by ethanol, were also analyzed. The frequencies of NOS3 rs2070744 genotypes and allelic variants were not associated with the risk for migraine (OR [95%] CI for the minor allele = 0.91 [0.72-1.15]) and were not influenced by age at onset of migraine, gender, presence of aura, or triggering of migraine attacks by ethanol. NOS3 rs2070744CC genotypes were significantly more frequent in patients with a family history of migraine. NOS3 rs2070744 SNP is not associated with the risk for migraine in Caucasian Spanish people although it might be related to family history.