Genetic susceptibility of diabetic retinopathy

Association Between VEGF-460C/T Gene Polymorphism and Risk of Diabetic Retinopathy in Type 2 Diabetes Mellitus: A Meta-Analysis

The aim of the study was to investigate the relationship between VEGF-460C/T polymorphism and susceptibility to diabetic retinopathy (DR) in type 2 diabetes mellitus (T2DM) by meta-analysis. A comprehensive search was conducted across six databases until September 2023 to identify studies examining the association between VEGF-460C/T polymorphism and susceptibility to DR. Data process was performed by Stata 15.0 software. Eight studies were included, involving 1463 patients with DR. In the overall analysis, the difference was statistically significant only in the homozygous model (CC vs. TT: OR=1.86, p=0.048). A subgroup analysis of 6 papers with genotype frequency satisfying HWE in the control group indicated significant differences among the allele (C vs. T: OR=1.34, p=0.037), recessive (CC vs. CT+TT: OR=1.96, p=0.022) and homozygous (CC vs. TT: OR=2.28, p=0.015) models. However, in the dominant and heterozygous models, the difference was not statistically significant. The sensitivity of the HWE-based subgroup analysis showed that the conclusions in other gene models except the heterozygote model were not robust. This meta-analysis indicated that VEGF-460C/T gene polymorphism is associated with susceptibility to DR in T2DM. Allele C and genotype CC at the VEGF-460C/T locus are associated with an increased risk of DR in T2DM. However, considering that the results are not robust, more trials involving more rigorous design are needed to verify the findings of this review in the future.

Assessment of MIR200B Polymorphisms Association with Sight-Threatening Diabetic Retinopathy

Purpose

To assess the possible association between MIR200B variations and sight-threatening diabetic retinopathy (STDR).

Methods

A total number of 141 diabetes mellitus patients were enrolled in the study and divided into two groups including 76 patients diagnosed with STDR assigned to the case group, and 65 subjects without STDR considered in the control group. Peripheral blood specimens were used to extract the DNA content, and the primary MIR200B encoding sequence was amplified using a polymerase chain reaction. Then, the amplified DNA was sequenced by the Sanger method. The sequences were compared to the MIR200B reference sequence to find sequence variations. RNAfold, miRVaS, and Mfold bioinformatics web servers were employed to predict the potential effects of the identified variations on RNA structure.

Results

Two MIR200B gene variants were identified. Although both variations were found more frequent in cases than controls, statistical analysis of allelic and genotypic features did not reach statistical significance.

Conclusions

In silico analysis showed mild changes in MIR200B secondary structure and increased free energy in the presence of one of the identified variants (g.1167183G>A; rs72563729). Increasing the sample size in future studies may help a more accurate interpretation of the allelic association of MIR200B variations with STDR.

Nanomedicine and drug delivery to the retina: current status and implications for gene therapy

Blindness affects more than 60 million people worldwide. Retinal disorders, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma, are the leading causes of blindness. Finding means to optimize local and sustained delivery of drugs or genes to the eye and retina is one goal to advance the development of new therapeutics. Despite the ease of accessibility of delivering drugs via the ocular surface, the delivery of drugs to the retina is still challenging due to anatomic and physiologic barriers. Designing a suitable delivery platform to overcome these barriers should enhance drug bioavailability and provide a safe, controlled, and sustained release. Current inventions for posterior segment treatments include intravitreal implants and subretinal viral gene delivery that satisfy these criteria. Several other novel drug delivery technologies, including nanoparticles, micelles, dendrimers, microneedles, liposomes, and nanowires, are now being widely studied for posterior segment drug delivery, and extensive research on gene delivery using siRNA, mRNA, or aptamers is also on the rise. This review discusses the current state of retinal drug/gene delivery and highlights future therapeutic opportunities.

Identification of new candidate genes for retinopathy in type 2 diabetics. Valencia Study on Diabetic Retinopathy (VSDR). Report number 3

OBJECTIVE

To identify genes involved in the pathogenic mechanisms of non-proliferative diabetic retinopathy (NPDR), among which include oxidative stress, extracellular matrix changes, and/or apoptosis, in order to evaluate the risk of developing this retinal disease in a type2 diabetic (DM2) population.

MATERIAL AND METHODS

A case-control study was carried out on 81 participants from the Valencia Study on Diabetic Retinopathy (VSDR) of both genders, with ages 25-85years. They were classified into: (i)DM2 group (n=49), with DR (+DR; n=14) and without DR (-DR; n=35), and (ii)control group (GC; n=32). The protocols included a personal interview, standardised ophthalmological examination, and blood collection (to analyse the DNA for determining the gene expression (TP53, MMP9, and SLC23A2) in the study groups. Statistical analyses were performed using the SPSS v22.0 program.

RESULTS

The TP53 and MMP9 genes showed a higher expression in the DM2 group compared to the GC, although the difference was only significant for the MMP9 gene (TP53: 10.40±1.20 vs. 8.23±1.36, P=.084; MMP9: 1.45±0.16 vs. 0.95±0.16, P=.036), and the SLC23A2 gene showed a significant lower expression in the DM2 vs CG (5.58±0.64 vs. 11.66±1.90, P=.026). When sub-dividing the DM2 group according to the presence of retinopathy, the expression of the TP53, MMP9 and SLC23A2 genes showed significant differences between the DM2-RD, DM2+RD and GC groups (TP53: 9.95±1.47 vs. 11.52±2.05 vs. 8.23±1.36, P=.038; MMP9: 1.47±0.20 vs. 1.41±0.27 vs. 0.95±0.16, P=.021; SLC23A2: 5.61±0.77 vs. 5.51±1.21 vs. 11.66±1.90, P=.018).

CONCLUSIONS

Genes involved in extracellular matrix integrity (MMP9) and/or apoptosis (TP53), could be considered potential markers of susceptibility to the development/progression of NPDR. Interestingly, the SLC232A2 gene (ascorbic acid transporter) can be considered a protector of the risk of the development/progression of the retinopathy.

Recent Update on the Role of Chinese Material Medica and Formulations in Diabetic Retinopathy

Diabetes mellitus is one of the most frequent endocrine disorders, affecting populations worldwide. Diabetic retinopathy (DR) is the most frequent microvascular complication of diabetes in patients aged 20 and over. Major complications of DR include intraocular neovascularization, inter-retinal edema, hemorrhage, exudates and microaneurysms. Therefore, timely medical attention and prevention are required. At present, laser-assisted therapy and other operational procedures are the most common treatment for DR. However, these treatments can cause retinal damage and scarring. Also, use of the majority of traditional medicines is not supported by clinical evidence. However, due to accumulating scientific evidence, traditional natural medications may assist in delaying or preventing the progression of DR. This review focuses on evidence for the role of traditional natural medicines and their mechanisms of action and pharmacological test results in relation to the progression of DR.

The role of NOS2A -954G/C and vascular endothelial growth factor +936C/T polymorphisms in type 2 diabetes mellitus and diabetic nonproliferative retinopathy risk management

Type 2 diabetes mellitus (T2DM) remains one of the major health problems in Europe. Retinopathy is one of the major causes of morbidity in T2DM, strongly influencing the evolution and prognosis of these patients. In the last 2 decades, several studies have been conducted to identify the possible genetic susceptibility factors involved in the pathogenesis of the disease. However, there is little data related to the involvement of vascular endothelial growth factor (VEGF) and nitric oxide synthase (NOS) gene polymorphisms in the T2DM Caucasian population. The objective of this study was to identify a possible connection between NOS2A -954G/C (rs2297518) and VEGF +936C/T (rs3025039) polymorphisms and the risk of developing T2DM and nonproliferative diabetic retinopathy in a Caucasian population group. We investigated 200 patients diagnosed with T2DM and 208 controls. Genotypes were determined by multiplex polymerase chain reaction-restriction fragment length polymorphism. Statistical and comparative analyses (Fisher's exact test) for dominant and recessive models of NOS2A -954G/C and VEGF +936C/T polymorphisms revealed an increased risk of T2DM (χ (2)=8.14, phi =0.141, P=0.004, odds ratio [OR] =2.795, 95% confidence interval [CI] =1.347-5.801; χ (2)=18.814, phi =0.215, P<0.001, OR =2.59, 95% CI =1.675-4.006, respectively). Also, comparative analysis for the recessive model (using Pearson's chi-square test [χ (2)] and the phi coefficient [phi]) reveals that the variant CC genotype of NOS2A gene is more frequently associated with T2DM without retinopathy (χ (2)=3.835, phi =-0.138, P=0.05, OR =0.447, 95% CI =0.197-1.015). In conclusion, the results of the study place VEGF +936C/T polymorphisms among the genetic risk factor for T2DM, whereas NOS2A -954G/C polymorphisms act like a protective individual factor for nonproliferative retinopathy.

Epidemiology of diabetic retinopathy, diabetic macular edema and related vision loss

Diabetic retinopathy (DR) is a leading cause of vision-loss globally. Of an estimated 285 million people with diabetes mellitus worldwide, approximately one third have signs of DR and of these, a further one third of DR is vision-threatening DR, including diabetic macular edema (DME). The identification of established modifiable risk factors for DR such as hyperglycemia and hypertension has provided the basis for risk factor control in preventing onset and progression of DR. Additional research investigating novel risk factors has improved our understanding of multiple biological pathways involved in the pathogenesis of DR and DME, especially those involved in inflammation and oxidative stress. Variations in DR prevalence between populations have also sparked interest in genetic studies to identify loci associated with disease susceptibility. In this review, major trends in the prevalence, incidence, progression and regression of DR and DME are explored, and gaps in literature identified. Established and novel risk factors are also extensively reviewed with a focus on landmark studies and updates from the recent literature.

Epidemiology of diabetic retinopathy, diabetic macular edema and related vision loss

Diabetic retinopathy (DR) is a leading cause of vision-loss globally. Of an estimated 285 million people with diabetes mellitus worldwide, approximately one third have signs of DR and of these, a further one third of DR is vision-threatening DR, including diabetic macular edema (DME). The identification of established modifiable risk factors for DR such as hyperglycemia and hypertension has provided the basis for risk factor control in preventing onset and progression of DR. Additional research investigating novel risk factors has improved our understanding of multiple biological pathways involved in the pathogenesis of DR and DME, especially those involved in inflammation and oxidative stress. Variations in DR prevalence between populations have also sparked interest in genetic studies to identify loci associated with disease susceptibility. In this review, major trends in the prevalence, incidence, progression and regression of DR and DME are explored, and gaps in literature identified. Established and novel risk factors are also extensively reviewed with a focus on landmark studies and updates from the recent literature.

Epidemiology of diabetic retinopathy, diabetic macular edema and related vision loss

Diabetic retinopathy (DR) is a leading cause of vision-loss globally. Of an estimated 285 million people with diabetes mellitus worldwide, approximately one third have signs of DR and of these, a further one third of DR is vision-threatening DR, including diabetic macular edema (DME). The identification of established modifiable risk factors for DR such as hyperglycemia and hypertension has provided the basis for risk factor control in preventing onset and progression of DR. Additional research investigating novel risk factors has improved our understanding of multiple biological pathways involved in the pathogenesis of DR and DME, especially those involved in inflammation and oxidative stress. Variations in DR prevalence between populations have also sparked interest in genetic studies to identify loci associated with disease susceptibility. In this review, major trends in the prevalence, incidence, progression and regression of DR and DME are explored, and gaps in literature identified. Established and novel risk factors are also extensively reviewed with a focus on landmark studies and updates from the recent literature.

Effects of vitamin D receptor gene polymorphism and clinical characteristics on risk of diabetic retinopathy in Han Chinese type 2 diabetes patients

PURPOSE

The purpose of this study was to investigate the association of VDR polymorphism with development of retinopathy in a Han Chinese population with type 2 diabetes mellitus.

MATERIALS AND METHODS

A total of 204 T2DM patients were subdivided into groups without diabetic retinopathy (NDR, n=110) and those with DR (n=94). VDR rs2228570 (FokI:C>T), rs1544410 (BsmI:G>A), and rs7975232 (Apal:A>C) polymorphism was assayed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Diabetes duration (10.0 vs. 5.0 years, P<0.01) was longer, systolic blood pressure (143.98 ± 24.31 vs. 135.11 ± 15.23, P<0.01), and HbA1c (9.2 ± 2.06 vs. 8.35 ± 1.62, P<0.01) were higher in DR than in NDR patients. Distribution frequencies of the rs2228570, rs1544410, and rs7975232 genotypes followed the Hardy-Weinberg equilibrium. VDR rs2228570 TT genotype frequency was significantly higher in DR (n=30; 31.9%) than in NDR patients (n=14; 12.7%; P<0.01). DR patients carried more rs2228570 T alleles (n=113; 60.1%) than did NDR patients (n=89; 40.5%; P<0.01). Genotype frequencies of rs1544410 and rs7975232 in NDR and DR patients were not different. Logistic analysis confirmed that diabetes duration (odds ratio (OR) 1.108, P<0.01), SBP (OR 1.022, P<0.05), HbA1c (OR 1.267, P<0.05), and the VDR rs2228570 T allele (OR 1.467, P<0.01) were independently associated with DR risk. TAA haplotype frequency was significantly higher in DR (24.0%) than in NDR (16.1%) patients (P<0.05).

CONCLUSIONS

Diabetes duration, SBP, HbA1c, and the rs2228570 T allele were associated with increased risk of DR. VDR rs2228570 might be good candidate biomarker of DR in Han Chinese T2DM patients.

Association of platelet glycoprotein receptor alpha2beta1 integrin and glycoprotein IIIa gene polymorphisms with diabetic retinopathy: evidence from 3007 subjects

PURPOSE

Many epidemiological studies have evaluated associations of platelet glycoprotein receptor alpha2beta1 integrin (ITGA2) and glycoprotein IIIa (ITGB3) gene polymorphisms with diabetic retinopathy (DR), but the published data are inconclusive. The aim of the present study was to assess the associations by using meta-analysis.

METHODS

A comprehensive electronic search (PubMed, EMBASE, Elsevier Science Direct, CNKI and Wanfang) was carried out until 31 August 2013. Odds ratios (ORs) and its 95% confidence intervals (CIs) were used to assess the strength of the associations.

RESULTS

Nine studies including 1678 cases and 1329 controls were included in the meta-analysis. Meta-analysis was performed for ITGA2 gene BgI II polymorphism (7 studies including 758 cases and 570 controls) and ITGB3 gene PlA1/A2 polymorphism (4 studies including 1047 cases and 861 controls). Significant associations were found for BgI II (+ versus -: OR = 1.42, 95% CI = 1.06-1.90, p = 0.02; +/- + +/+ versus -/-: OR = 1.46, 95% CI = 0.99-2.15, p = 0.06; +/+ versus -/- + +/-: OR = 1.90, 95% CI = 1.35-2.67, p = 0.0003) and PlA1/A2 (A2 versus A1: OR = 0.74, 95% CI = 0.52-1.07, p = 0.11; A1A2 + A2A2 versus A1A1: OR = 0.80, 95% CI = 0.64-0.99, p = 0.04; A2A2 versus A1A1 + A1A2: OR = 0.45, 95% CI = 0.27-0.75, p = 0.002) polymorphisms.

CONCLUSION

This meta-analysis demonstrates that DR is associated with ITGA2 BgI II and ITGB3 PlA1/A2 polymorphisms.

Genome-wide association studies: applications and insights gained in Ophthalmology

Genome-wide association studies (GWAS) use high-throughput genotyping technologies to genotype thousands of single-nucleotide polymorphisms (SNPs) and relate them to the development of clinical and quantitative traits. Their use has been highly successful in the field of ophthalmology, and since the advent of GWAS in 2005, many genes not previously suspected of having a role in disease have been identified and the findings replicated. We conducted an extensive literature review and describe the concept, design, advantages, and limitations of GWAS and provide a detailed description of the applications and discoveries of GWAS in the field of eye disease to date. There have been many novel findings revealing previously unknown biological insights in a diverse range of common ocular conditions. GWAS have been a highly successful modality for investigating the pathogenesis of a wide variety of ophthalmic conditions. The insights gained into the pathogenesis of disease provide not only a better understanding of underlying disease mechanism but also offer a rationale for targeted treatment and preventative strategies. Expansive international collaboration and standardised phenotyping will permit the continued success of this investigative technique.

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.

Candidate genes for proliferative diabetic retinopathy

Several candidate genes have been so far implicated in the pathogenesis of proliferative diabetic retinopathy (PDR) in subjects with type 2 diabetes. Since the principal pathogenetic mechanisms for diabetic retinopathy (DR) and PDR are different, the main pathogenetic mechanism in DR is increased vascular permeability, whereas in PDR the crucial pathogenetic mechanisms are fibrosis and neoangiogenesis. Due to that fact, different candidate genes are expected to be involved in the development of either DR or PDR. None of the candidate genes, however, can be fully and solely responsible for the development of PDR and for DR progression into PDR. Epigenetic mechanisms are expected to be involved in the pathogenesis of PDR as well. Gene polymorphisms responsible for PDR and epigenetic mechanisms responsible for PDR are reviewed in this paper.

Retinopathy in diabetes

With the incidence, and prevalence of diabetes mellitus increasing worldwide, diabetic retinopathy is expected to reach epidemic proportions. The aim of this chapter is to introduce diabetic retinopathy, a leading cause of blindness in people of the working age. The clinical course of retinopathy, anatomical changes, its pathogenesis and current treatment are described, followed by an overview of the emerging drug therapies for the potential treatment of this sight-threatening complication of diabetes.

Ophthalmic drug discovery: novel targets and mechanisms for retinal diseases and glaucoma

Blindness affects 60 million people worldwide. The leading causes of irreversible blindness include age-related macular degeneration, retinal vascular diseases and glaucoma. The unique features of the eye provide both benefits and challenges for drug discovery and delivery. During the past decade, the landscape for ocular drug therapy has substantially changed and our knowledge of the pathogenesis of ophthalmic diseases has grown considerably. Anti-angiogenic drugs have emerged as the most effective form of therapy for age-related macular degeneration and retinal vascular diseases. Lowering intraocular pressure is still the mainstay for glaucoma treatment but neuroprotective drugs represent a promising next-generation therapy. This Review discusses the current state of ocular drug therapy and highlights future therapeutic opportunities.

Nitric oxide synthase 3 (NOS3) 4b/a, T-786C and G894T polymorphisms in association with diabetic retinopathy susceptibility: a meta-analysis

AIMS

To assess the association between the NOS3 4b/a, T-786C and G894T polymorphisms and diabetic retinopathy (DR) susceptibility.

MATERIALS AND METHODS

Twenty-one studies covering 8,111 subjects were included. The fixed or random effect model used was based on heterogeneity.

RESULTS

A significant association of the intron 4a allele in the NOS3 4b/a polymorphism with reduced risk of DR was found in dominant (OR 0.778, 95% CI 0.654-0.926) and additive (OR 0.809, 95% CI 0.698-0.937) models. Subgroup analysis revealed that the intron 4a allele additive model (OR 0.807, 95% CI 0.697-0.935) was associated with DR risk in type 2 diabetic patients. We also found a marginally significant association of the C allele in the T-786C polymorphism with reduced risk of proliferative DR. In contrast, no statistically significant association was observed between the G894T polymorphism and DR risk, either in the overall or subgroup analyses.

CONCLUSIONS

The intron 4a allele of the 4b/a polymorphism in the eNOS gene has protective effects against DR, especially in type 2 diabetic patients. The C allele of the T-786C polymorphism may be a protective factor for proliferative DR. However, the G894T polymorphism does not appear to influence the development of DR. This conclusion warrants confirmation by further studies.

Individualized optimization of the screening interval for diabetic retinopathy: a new model

INTRODUCTION

Screening programmes for diabetic retinopathy follow guidelines that ensure that vision-threatening complications are detected even when the disease progression is fast. This implies that patients with slow disease progression will be recommended examinations more often than needed.

METHOD

On the basis of previously defined individual risk factors, multiple logistic regression was used to develop a model for individualized determination of the screening interval in diabetic retinopathy, while adjusting for the fact that in the data set used to construct the model, the screening interval acted as a time-dependent confounder. The model was tested on 1372 patients screened during year 2000.

RESULTS

It was possible to construct a model for calculating the optimal screening interval in low-risk patients in whom the recommended screening interval was longer than 12 months. When the probability of reaching a treatment requiring event was set to 0.5%, none of the patients reached a treatment end-point in a validation of the model, and the screening interval was prolonged on average 2.9 times in patients with type 1 diabetes and 1.2 times in those with type 2 diabetes. The predictive strength of the model depended on the number of variables included.

CONCLUSIONS

It is possible to construct a model for optimizing the examination interval during screening for diabetic retinopathy in low-risk patients. The model can potentially be improved by identifying unknown or unmeasured confounders and by including knowledge of risk factors before and after the examination on the basis of which the prediction is made.

The 4a/4a genotype of the VNTR polymorphism for endothelial nitric oxide synthase (eNOS) gene predicts risk for proliferative diabetic retinopathy in Slovenian patients (Caucasians) with type 2 diabetes mellitus

Thus far only a limited number of studies examined the association between endothelial nitric oxide synthase (eNOS) polymorphisms and proliferative diabetic retinopathy (PDR). In this report, two polymorphisms in the eNOS gene have been investigated, namely the 894G>T (Glu298Asp) and a 27 bp VNTR (4b/4a), to assess their possible relationships to PDR among Slovenian (Caucasians) type 2 diabetic patients. This cross-sectional case-control study enrolled 577 unrelated Slovenian subjects (Caucasians) with type 2 diabetes mellitus. The case group consisted of 172 patients with PDR and the control group had 405 patients who had no clinical signs of diabetic retinopathy (DR) but did have type 2 diabetes for more than 10 years' duration. Genotyping of eNOS polymorphisms was carried out with conventional and real-time PCR assays. A significantly higher frequency of the eNOS minor "4a" allele was found in patients with PDR than in controls (23.6 versus 17.7%, p = 0.01). Moreover, the univariate analysis showed a significant association of the 27 bp VNTR 4a/4a genotype and PDR in the recessive model. The odds ratio (OR) of PDR for the 4a/4a genotype to 4b/4a plus 4b/4b was 2.9 (95% CI 1.3-6.2, p = 0.005). Further, the presence of 4a/a genotype was associated with a 3.4-fold (95% CI 1.4-8.6, p = 0.009) increased risk for PDR while adjusted for other risk factors. This is the first study to implicate eNOS 4a/4a homozygous deletion, and hence the "4a" allele, as the genetic risk factors for PDR in Caucasians.

Diabetic retinopathy: pathogenic mechanisms and current treatments

Since diabetes is now a global epidemic, the incidence of retinopathy, a leading cause of blindness in patients aged 20-74 years, is also expected to rise to alarming levels. The risk of development and progression of diabetic retinopathy is closely associated with the type and duration of diabetes, blood glucose, blood pressure and possibly lipids. It is an unmet medical need that can lead to severe and irreversible loss of vision in people of working age worldwide. The aim of this review is to give an overview of the clinical and anatomical changes during the progression of retinopathy, the underlying pathogenic mechanisms that link hyperglycemia with retinal tissue damage, current treatments, and the emerging pharmacological therapies for this sight-threatening complication of diabetes.

Association between the -634C/G polymorphisms of the vascular endothelial growth factor and retinopathy in type 2 diabetes: a meta-analysis

AIMS

To investigate the association of vascular endothelial growth factor (VEGF) -634C/G polymorphism with retinopathy in type 2 diabetes.

METHODS

8 studies with 1183 cases and 1057 controls were included. Allelic and genotypic comparisons between cases and controls were evaluated.

RESULTS

Our meta-analysis did not suggest a significant association of the -634C/G polymorphism with diabetic retinopathy (DR) and proliferative diabetic retinopathy (PDR) (P>0.05). The pooled odds ratios (ORs) for allelic frequency comparison, recessive model comparison, dominant model comparison, and additive model showed that the -634C/G polymorphism is significantly associated with nonproliferative diabetic retinopathy (NPDR): OR=1.61 [95% confidence interval (CI, 1.23, 2.10)], P=0.0005, P(heterogeneity)=0.38, OR=2.24 [95% CI (1.15, 4.39)], P=0.02, P(heterogeneity)=0.24, OR=1.87 [95% CI (1.01, 3.48)], P=0.05, P(heterogeneity)=0.16, and OR=2.91 [95% CI (1.33, 6.39)], P=0.008, P(heterogeneity)=0.26, respectively. However, in sensitivity analyses, we only detected a marginally significant association of the C allele with NPDR: OR=1.54 [95% CI (1.00, 2.39)], P=0.05, P(heterogeneity)=0.17.

CONCLUSIONS

Our meta-analysis does not support the association of the VEGF -634C/G polymorphism with DR and PDR. Significant association between this polymorphism and NPDR was detected in this meta-analysis. However, this association is not robust and could be due to chance.

Cannabidiol As a Putative Novel Therapy for Diabetic Retinopathy: A Postulated Mechanism of Action as an Entry Point for Biomarker-Guided Clinical Development

Diabetic retinopathy is a leading cause of blindness in the Western world. However, treatment options for diabetic retinopathy are limited and display poor efficacy with marked patient-to-patient variation in therapeutic outcomes. Discovery of new molecular entities acting on mechanistically novel biological pathways remains as one of the key research priorities in diabetic retinopathy. Moreover, given the variable success of the existing treatment modalities, a targeted and personalized drug development strategy could be more fruitful for rational and successful transition of preclinical discoveries to the clinical realm. This review is focused on cannabidiol, a non-psychoactive native cannabinoid, as an emerging and novel therapeutic modality based on systematic studies in animal models of inflammatory retinal diseases including diabetic retinopathy - one of the retinal diseases associated with vascular neuroinflammation. We present the postulated and preclinically documented novel mechanisms that may underlie cannabidiol mode of action in diabetic retinopathy. We discuss the interindividual variation in pharmacokinetic pathways as well as in the SLC29A1 gene, a molecular target for cannabidiol. We emphasize that the novel mode of action of cannabidiol and the previous failures with nontargeted interventions in diabetic retinopathy collectively demand a more rational and personalized clinical development strategy for compounds that have shown promise at the preclinical stage. Moreover, it is noteworthy that ophthalmology, as a medical specialty, has fewer examples (e.g., compared to oncology) of personalized medicine and biomarker applications thus far. Understanding the biological action of cannabidiol in preclinical studies is therefore a rational first step to proactively map the pertinent biomarker strategies in clinical proof of concept studies in diabetic retinopathy, and to allow advances at the hitherto neglected intersection of personalized medicine and ophthalmology.