Challenges in elucidating the genetics of diabetic retinopathy

Exploring the Associated Genetic Causes of Diabetic Retinopathy as a Model of Inflammation in Retinal Diseases

To investigate potential biomarkers and biological processes associated with diabetic retinopathy (DR) using transcriptomic and proteomic data. The OmicsPred PheWAS application was interrogated to identify genes and proteins associated with DR and diabetes mellitus (DM) at a false discovery rate (FDR)-adjusted p-value of <0.05 and also <0.005. Gene Ontology PANTHER analysis and STRING database analysis were conducted to explore the biological processes and protein interactions related to the identified biomarkers. The interrogation identified 49 genes and 22 proteins associated with DR and/or DM; these were divided into those uniquely associated with diabetic retinopathy, uniquely associated with diabetes mellitus, and the ones seen in both conditions. The Gene Ontology PANTHER and STRING database analyses highlighted associations of several genes and proteins associated with diabetic retinopathy with adaptive immune response, valyl-TRNA aminoacylation, complement activation, and immune system processes. Our analyses highlight potential transcriptomic and proteomic biomarkers for DR and emphasize the association of known aspects of immune response, the complement system, advanced glycosylation end-product formation, and specific receptor and mitochondrial function with DR pathophysiology. These findings may suggest pathways for future research into novel diagnostic and therapeutic strategies for DR.

Correlation Between Thyroid-Related Hormones and Diabetic Retinopathy in Type 2 Diabetes Mellitus Patients with Normal Thyroid Function: A Retrospective Study

Purpose

To investigate the correlation between thyroid-related hormones and diabetic retinopathy (DR) in euthyroid patients with type 2 diabetes mellitus (T2DM).

Patients and Methods

Patients with T2DM admitted to our hospital between January 2023 and June 2023 were retrospectively analyzed. The patients were divided into DR and non-diabetic retinopathy (NDR) groups according to whether DR occurred. Thyroid function-related hormones (TSH, FT3, and FT4), blood glucose indices (FBG and HbA1c), and blood lipid indices (HDL-C, LDL-C, TC, and TG) of the two groups were analyzed by univariate and multivariate logistic regression to explore the risk factors for DR. Pearson correlation analysis and multiple stepwise regression analysis were used to investigate the correlation of TSH or FT3 with FBG, HbA1c, and TG in DR patients.

Results

Of the 286 patients with T2DM included in this study, 101 (35.31%) developed DR and 185 (64.69%) did not. High TG, FBG, HbA1c, and TSH and low FT3 levels were independent risk factors for DR in T2DM patients. TSH positively correlated with TG, whereas FT3 negatively correlated with TG and HbA1c in T2DM patients with DR.

Conclusion

Higher TSH and lower FT3 in T2DM patients with normal thyroid function may affect glucose and lipid metabolism, thereby increasing the risk of DR.

Diabetic Retinopathy: Clinical Features, Risk Factors, and Treatment Options

Diabetic retinopathy is a common complication of diabetes that affects the eyes and can lead to severe vision loss or blindness if left untreated. Chronic hyperglycemia destroys the blood vessels in the retina, resulting in diabetic retinopathy. The damage can lead to leakage of fluid and blood into the retina, causing edema, hemorrhages, and ischemia. A thorough evaluation by an ophthalmologist is necessary to determine the most appropriate course of treatment for each patient with diabetic retinopathy. The article discusses various surgical treatment options for diabetic retinopathy, including vitrectomy, scleral buckling, epiretinal membrane peeling, retinal detachment repair, and the risk factors of diabetic retinopathy. These surgical techniques can help to address the underlying causes of vision loss and prevent further complications from developing or worsening. To avoid complications and maintain vision, this review emphasizes the significance of early detection and treatment of diabetic retinopathy. Patients with diabetic retinopathy can improve their eyesight and quality of life with the help of some surgical treatments. The article also highlights some case studies in the field of diabetic retinopathy.

The Role of Genetic Polymorphisms in Diabetic Retinopathy: Narrative Review

Diabetic retinopathy (DR) is renowned as a leading cause of visual loss in working-age populations with its etiopathology influenced by the disturbance of biochemical metabolic pathways and genetic factors, including gene polymorphism. Metabolic pathways considered to have an impact on the development of the disease, as well as genes and polymorphisms that can affect the gene expression, modify the quantity and quality of the encoded product (protein), and significantly alter the metabolic pathway and its control, and thus cause changes in the functioning of metabolic pathways. In this article, the screening of chromosomes and the most important genes involved in the etiology of diabetic retinopathy is presented. The common databases with manuscripts published from January 2000 to June 2023 have been taken into consideration and chosen. This article indicates the role of specific genes in the development of diabetic retinopathy, as well as polymorphic changes within the indicated genes that may have an impact on exacerbating the symptoms of the disease. The collected data will allow for a broader look at the disease and help to select candidate genes that can become markers of the disease.

Risk Factors for Diabetic Retinopathy in Chinese Patients with Different Diabetes Duration: Association of C-Peptide and BUN/Cr Ratio with Type 2 Diabetic Retinopathy

Background and Aim

Controlling the risk factors was the most effective strategy to prevent diabetic retinopathy (DR). This study aimed to recognize the risk factors of DR, and explores whether the effect of those factors is modified by diabetes mellitus (DM) duration.

Methods

A total of 1058 DM patients with information about DR assessment were included. DR was measured by a complete ophthalmic examination and was classified as having one or more distinct microaneurysms in the eyes. Data from the lab and clinical factors were gathered. Multivariate logistic analysis was used to examine the risk factors, and the best-fitting model was selected by a backward stepwise based on A1C.

Results

In the current study, 274 (25.9%) patients developed DR. In the entire subjects, baseline age, the level of C-peptide, and urinary creatinine were all presented as protective effects of DR, whose odds ratios (ORs) and 95% confidence intervals (CIs) were 0.79 (0.62, 0.99), 0.75 (0.61, 0.91), and 0.70 (0.52, 0.93), respectively. Conversely, systolic pressure (SBP), urinary albumin, and BUN/Cr ratio were the important risk factors for DR with ORs (95% CIs) 1.21 (1.01, 1.46), 1.55 (1.30, 1.84), and 1.33 (1.11, 1.59), respectively. In stratification analysis, females with higher SBP would be more likely to develop DR in the short-duration group, while C-peptide and urinary creatinine showed protective effects in the long-duration group. BUN/Cr ratio all presented as a risk factor, with ORs 1.38 (p = 0.041) and 1.33 (p = 0.014) in short- and long-duration groups, respectively.

Conclusion

Although renal functions presented a significant association with DR in all DM patients, the risk factors of DR varied widely in different disease-duration subjects. Target strategies to prevent DR should be put forward individually, considering the patient's DM duration. Improving the BUN/Cr ratio may be beneficial to delaying DR.

Novel risk score model for non-proliferative diabetic retinopathy based on untargeted metabolomics of venous blood

Background and Purpose

Nonproliferative diabetic retinopathy (NPDR) occurs in the early stages of Diabetic retinopathy (DR), and the study of its metabolic markers will help to prevent DR. Hence, we aimed to establish a risk score based on multiple metabolites through untargeted metabolomic analysis of venous blood from NPDR patients and diabetic non-DR patients.

Experimental Approach

Untargeted metabolomics of venous blood samples from patients with NPDR, diabetes melitus without DR were performed using high-performance liquid chromatography-mass spectrometry.

Results

Detailed metabolomic evaluation showed distinct clusters of metabolites in plasma samples from patients with NPDR and diabetic non-DR patients. NPDR patients had significantly higher levels of phenylacetylglycine, L-aspartic acid, tiglylglycine, and 3-sulfinato-L-alaninate, and lower level of indolelactic acid, threonic acid, L-arginine (Arg), and 4-dodecylbenzenesulfonic acid compared to control. The expression profiles of these eight NPDR risk-related characteristic metabolites were analyzed using Cox regression to establish a risk score model. Subsequently, univariate and multivariate Cox regression analyses were used to determine that this risk score model was a predictor of independent prognosis for NPDR.

Conclusions

Untargeted metabolome analysis of blood metabolites revealed unreported metabolic alterations in NPDR patients compared with those in diabetic non-DR patients or MH. In the venous blood, we identified depleted metabolites thA and Arg, indicating that they might play a role in NPDR development.

Diabetic Retinopathy – Diagnostics and Treatment Guidelines

Diabetic retinopathy is one of the most common complications of diabetes mellitus and represents a serious health, social and economic problem. With the expected increase in the number of patients with diabetes, it is becoming the leading cause of severe vision loss in the working-age population.  The presented guidelines summarize the current knowledge about this disease in order to standardize and update the procedures for the diagnosis, classification and treatment of diabetic retinopathy.

A Guide to Genome-Wide Association Study Design for Diabetic Retinopathy

Diabetic retinopathy (DR) is the most common microvascular complication related to diabetes. There is evidence that genetics play an important role in DR pathogenesis, but the complexity of the disease makes genetic studies a challenge. This chapter is a practical overview of the basic steps for genome-wide association studies with respect to DR and its associated traits. Also described are approaches that can be adopted in future DR studies. This is intended to serve as a guide for beginners and to provide a framework for further in-depth analysis.

Genome-wide DNA methylation analysis of extreme phenotypes in the identification of novel epigenetic modifications in diabetic retinopathy

Background

Aberrant epigenetic modifications such as DNA methylation may contribute to the pathogenesis of DR. We aimed at elucidating the role of novel DNA methylation modifications in diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM) using an extreme phenotypic design.

Methods/results

Two consecutive studies were conducted. A cross-sectional study using an extreme phenotypic design was conducted to identify rare methylation modifications that might contribute to DR pathogenesis. A 2-year longitudinal nested case–control study was conducted to validate the results and assess whether these novel methylation modifications could be used as biomarkers for predicting DR onset. A large number of differentially methylated CpG sites were identified in the cross-sectional study, and two (cg12869254 and cg04026387) corresponding to known genes were replicated in the longitudinal study. Higher methylation of cg12869254 significantly correlated with macular RNFL thinning in the superior and nasal subregions, and that of cg04026387 correlated with reduced deep capillary plexus VD in the superior and inferior subregions after adjusting for covariates.

Conclusions

Cg12869254 and cg04026387 hypermethylation may complement the known risk factors that contribute to the pathogenesis of DR and as novel biomarkers for disease prediction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01354-z.

The relationship between the neutrophil-to-lymphocyte ratio and diabetic retinopathy in adults from the United States: results from the National Health and nutrition examination survey

Background

Diabetic retinopathy (DR) is a common complication of diabetes mellitus (DM). Systemic inflammation is intimately associated with DR. The neutrophil-to-lymphocyte ratio (NLR) index is a relatively new indicator of inflammation.

Methods

This cross-sectional study was carried out among adults with DM based on the National Health and Nutrition Examination Survey (NHANES) from 2009 to 2016. NLR was presented as absolute neutrophil counts/ absolute lymphocyte counts. The relationship of NLR levels to DR was analyzed using multivariable logistic regression.

Results

There were 2772 eligible subjects extracted from the NHANES. In the multivariate analysis, NLR was related to the risk of DR after adjustment for potential confounders. The association between NLR levels and DR was nonlinear, with an inflection point of 4.778. Compared with the baseline values, NLR was not statistically significant on the right side of the inflection point (1.000, 0.914 to 1.094, 0.9974) but was positively associated with DR on the left side (1.236, 1.132 to 1.349, < 0.0001).

Conclusions

NLR reflects systemic inflammation that may increase the risk of DR. NLR positively correlates with DR when its value is less than 4.778.

Association of MMP-2 genes variants with diabetic retinopathy in Tunisian population with type 2 diabetes

AIMS

Few studies investigated the association of genetic difference in metalloproteinase-2 (MMP-2) gene with diabetic retinopathy but with mixed outcome. To investigate the association between a set of MMP-2 genetic variants and the risk of diabetic retinopathy in an Arab Tunisian population with type 2 diabetes.

SUBJECTS AND METHODS

A retrospective case-control study comprising a total of 779 type 2 diabetes patients with or without diabetic retinopathy was conducted. Genotyping was prepared by TaqMan® SNP genotyping qRT-PCR. The variants used were rs243865 (C/T), rs243864 (T/G), rs243866 (G/T) and rs2285053 (C/T).

RESULTS

The minor allele frequency (MAF) of the rs243864 MMP-2 variant was significantly higher among diabetic retinopathy patients. Setting homozygous wild type genotype carrier as reference, the rs243864T/G allele was associated with increased risk of diabetic retinopathy under the dominant, recessive, and additive models which persisted when key covariates were controlled for, while a reduced risk of diabetic retinopathy progression was seen after adjustment between non-proliferative and proliferative diabetic patients. Furthermore, the heterozygous genotype GT of the rs243866 variant is positively associated with the risk of proliferative diabetic retinopathy in the additive model. A limited linkage disequilibrium (LD) was revealed between the four-matrix metalloproteinase-2 variants. Four-loci haplotype analysis identified, GCTC, TTTC, and GCTT haplotypes to be positively associated with the risk of diabetic retinopathy.

CONCLUSION

Our findings demonstrate that the MMP-2 variant rs243864 and 243866 are related to the susceptibility to diabetic retinopathy and the progression of the disease in an Arab Tunisian population with type 2 diabetes.

Improving the screening of risk factors in diabetic retinopathy

INTRODUCTION

In 2002, Diabetic Retinopathy was reported as the leading cause of blindness in the working age group. The introduction of systematic screening programs in the UK has reduced visual loss and blindness due to diabetic retinopathy, but it does still occur with catastrophic consequences for the individual.

AREAS COVERED

The author conducted an ongoing search for articles relating to diabetic retinopathy since 2000 utilizing Zetoc Alert with keywords and contents page lists from relevant journals. This review covers the risk factors for loss of vision due to diabetic retinopathy and discusses ways in which the awareness of these risk factors can be used to further reduce visual loss. Some risk factors such as glycemic and B/P control are well known from landmark trials. This review has included these factors but concentrated more on the evidence behind those risk factors that are not so clearly defined or so well known.

EXPERT OPINION

The major risk factors are well known, but one continues to find that people with diabetes lose vision in situations in which a better awareness of the risks by both the individual with diabetes and the health workers involved may have prevented the visual loss.

Single nucleotide variants of receptor for advanced glycation end-products (AGER) gene: is it a new opening in the risk assessment of diabetic retinopathy?-a review

Background

Diabetic retinopathy (DR) is a common microvascular complication of diabetes. There is strong evidence suggesting that DR has an inheritable component. The interaction between advanced glycation end products (AGEs) and their receptor is integral in the pathogenesis of diabetic retinopathy and its various complications, retinopathy being one of them.

Overview and methodology

This review discusses the existing literature on the association between single nucleotide variants (SNV) of AGER gene and the risk of DR. It also discusses the current understanding of the AGE-AGER pathway in diabetic retinopathy. Through our article we have tried to consolidate all the available information about these SNVs associated with diabetic retinopathy in a succinct tabular form. Additionally, a current understanding of the AGE-AGER interaction and its deleterious effects on the cells of the retina has been discussed in detail to provide comprehensive information about the topic to the reader. A literature review was performed on PubMed, Cochrane Library, and Google Scholar for studies to find existing literature on the association between AGER gene SNVs and the risk, progression and severity of developing DR. This article will encourage scientific communication and discussion about possibly devising genetic markers for an important cause of blindness both in developed and developing countries, i.e., diabetic retinopathy.

Result

Based on genetic studies done in Indian and Chinese population G82S(rs2070600) was positively associated with Diabetic Retinopathy. Patients of diabetic retinopathy in Caucasian population had −T374A(rs1800624) polymorphism. + 20T/A was found to be associated with the disease in a study done in UK. Association with G1704T(rs184003) was seen in Chinese and Malaysian population. A Chinese study found its association with CYB242T. -T429C(rs1800625) SNV was not associated with DR in any of the studies. G2245A(rs55640627) was positively associated with the disease process in Malaysian population. It was not associated in Malaysian and Chinese population. Promoter variant rs1051993 has also been found to a susceptible SNV in the Chinese population.

Conclusion

While providing a comprehensive review of the existing information, we would like to emphasize on a large, multi-centric, trial with a much larger and varied population base to definitely determine these single nucleotide variants predisposing diabetic individuals.

Diabetic retinopathy risk prediction in patients with type 2 diabetes mellitus using a nomogram model

BACKGROUND

This study aims to develop a diabetic retinopathy (DR) hazard nomogram for a Chinese population of patients with type 2 diabetes mellitus (T2DM).

METHODS

We constructed a nomogram model by including data from 213 patients with T2DM between January 2019 and May 2021 in the Affiliated Hospital of Zunyi Medical University. We used basic statistics and biochemical indicator tests to assess the risk of DR in patients with T2DM. The patient data were used to evaluate the DR risk using R software and a least absolute shrinkage and selection operator (LASSO) predictive model. Using multivariable Cox regression, we examined the risk factors of DR to reduce the LASSO penalty. The validation model, decision curve analysis, and C-index were tested on the calibration plot. The bootstrapping methodology was used to internally validate the accuracy of the nomogram.

RESULTS

The LASSO algorithm identified the following eight predictive variables from the 16 independent variables: disease duration, body mass index (BMI), fasting blood glucose (FPG), glycated hemoglobin (HbA1c), homeostatic model assessment-insulin resistance (HOMA-IR), triglyceride (TG), total cholesterol (TC), and vitamin D (VitD)-T3. The C-index was 0.848 (95% CI: 0.798-0.898), indicating the accuracy of the model. In the interval validation, high scores (0.816) are possible from an analysis of a DR nomogram's decision curve to predict DR.

CONCLUSION

We developed a non-parametric technique to predict the risk of DR based on disease duration, BMI, FPG, HbA1c, HOMA-IR, TG, TC, and VitD.

The role of hesperidin in ameliorating retinal changes in rats with experimentally induced type 1 diabetes mellitus and the active role of vascular endothelial growth factor and glial fibrillary acidic protein

Patients with type 1 diabetes mellitus (T₁DM) are vulnerable to developing diabetic retinopathy even under insulin therapy. Thus, this study was designed to evaluate the efficacy of hesperidin and insulin in rats with T₁DM compared with insulin alone in improving diabetic retinal changes. Eighty rats were divided into four equal groups: group I, control rats without diabetes; group II, untreated rats with diabetes; group III, rats with diabetes treated daily with subcutaneous (SC) doses of long-acting insulin; and group IV, a rat with diabetes in which hesperidin was orally administered with SC insulin. The animals were assessed histologically, morphometrically, and biochemically. In group II, the thickness of all retinal layers decreased histologically. Ultrastructurally, degenerated retinal neurons and congested blood vessels were observed. Immunostaining detected elevated gene expression of advanced glycation end products. Gene expression of vascular endothelial growth factor, and glial fibrillary acidic protein were elevated. In this study, hesperidin supplementation with insulin significantly improved the retinal histological changes, supported by morphometric findings, compared with insulin alone. Moreover, treatment with hesperidin significantly reduced malondialdehyde and elevated serum antioxidant markers, including superoxide dismutase and catalase; furthermore, glutathione peroxidase decreased. Hesperidin might be an effective supplement for improving diabetic retinal complications occurring even with insulin treatment.

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.

Human Leukocyte Antigens class II (HLA II) gene profile from an admixed population of patients with type 1 diabetes with severe diabetic retinopathy: a nested case-control study in Brazil

BACKGROUND

Although the well-established role of the HLA genes on the predisposition of type 1 diabetes (T1D), its contribution to the development and progression of diabetic retinopathy is still unclear, especially in admixed populations. We aimed to study the relationship between HLA alleles and severe diabetic retinopathy in a highly admixed population of T1D patients.

METHODS

This was a nested case-control study based on a cross-sectional, nationwide survey conducted in Brazil. We included 117 patients with severe diabetic retinopathy and 117 random controls composed of T1D patients without retinopathy, matched for diabetes duration. HLA-class II genes (HLA-DRB1, -DQA1, and -DQB1) were genotyped using the SSO and NGS methods.

RESULTS

Haplotypes HLA-DRB1*04:05 ~ DQA1*03:01 g ~ DQB1*03:02 (OR 1.75, CI 0.97-3.16, p value 0.058) and HLA-DRB1*13:02 ~ DQA1*01:02 ~ DQB1*06:04 (OR 5.18, CI 1.12-23.09, p value 0.019) were more prevalent on the severe DR group but they did not present statistically difference after Bonferroni correction. The most frequent haplotype on both groups was HLA-DRB1*03:01 ~ DQA1*05:01 g ~ DQB1*02:01 (29.6% on severe DR and 33.33% on the control group).

CONCLUSIONS

Our study showed no influence of HLA genes on the development of DR. Further longitudinal data is needed to better understand the role of genetic factors on this multifactorial significant microvascular complication.

Association of periodontitis and diabetic macular edema in various stages of diabetic retinopathy

OBJECTIVES

Periodontitis and diabetes are known to have a bidirectional relationship. Diabetic macular edema is a complication of diabetes that is strongly influenced by inflammatory pathways. However, it remains to be established whether inflammation at other locations, such as periodontitis, affects diabetic macular edema. Here, we investigated the prevalence of periodontitis in patients treated for diabetic macular edema.

MATERIALS AND METHODS

Patients with diabetic macular edema were recruited for this cross-sectional study at the Medical University of Graz. Macular edema was documented by optical coherence tomography. Periodontal status was assessed by computerized periodontal probing and panoramic X-ray imaging. Bleeding on probing, clinical attachment level, probing pocket depth, and plaque index were compared between different stages of diabetic retinopathy.

RESULTS

Eighty-three eyes of 45 patients with diabetic macular edema were enrolled. Forty-four eyes (53.0%) had early stages of diabetic retinopathy (mild and moderate), and 39 eyes (47.0%) had late stages (severe and proliferative). Patients with mild or moderate DR were more likely to have more severe periodontal conditions than patients with severe or proliferative DR. Fourteen patients with mild DR (82.4%), 7 patients with moderate DR (87.5%), 4 patients with severe DR (100.0%), and 15 patients with proliferative DR (93.8%) had some degree of PD. The periodontal inflamed surface areas and the percentages of tooth sites that bled on probing were significantly higher in patients with early stages of diabetic retinopathy than in those with late stages of the disease (p < 0.05). Patients with periodontal inflamed surface areas of more than 500 mm² required significantly more intravitreal injections in the last year than those with milder forms of periodontitis (n = 6.9 ± 3.1 versus n = 5.0 ± 3.5, p = 0.03).

CONCLUSION

In patients with diabetic macular edema, periodontitis is more prevalent in early stages of diabetic retinopathy. We suggest regular dental check-ups for diabetic patients, especially when diabetic macular edema is already present.

CLINICAL RELEVANCE

Patients with diabetic macular edema should be screened for periodontitis and vice versa, particularly early in the course of diabetes.

Diabetic retinopathy and diabetic macular oedema pathways and management: UK Consensus Working Group

The management of diabetic retinopathy (DR) has evolved considerably over the past decade, with the availability of new technologies (diagnostic and therapeutic). As such, the existing Royal College of Ophthalmologists DR Guidelines (2013) are outdated, and to the best of our knowledge are not under revision at present. Furthermore, there are no other UK guidelines covering all available treatments, and there seems to be significant variation around the UK in the management of diabetic macular oedema (DMO). This manuscript provides a summary of reviews the pathogenesis of DR and DMO, including role of vascular endothelial growth factor (VEGF) and non-VEGF cytokines, clinical grading/classification of DMO vis a vis current terminology (of centre-involving [CI-DMO], or non-centre involving [nCI-DMO], systemic risks and their management). The excellent UK DR Screening (DRS) service has continued to evolve and remains world-leading. However, challenges remain, as there are significant variations in equipment used, and reproducible standards of DMO screening nationally. The interphase between DRS and the hospital eye service can only be strengthened with further improvements. The role of modern technology including optical coherence tomography (OCT) and wide-field imaging, and working practices including virtual clinics and their potential in increasing clinic capacity and improving patient experiences and outcomes are discussed. Similarly, potential roles of home monitoring in diabetic eyes in the future are explored. The role of pharmacological (intravitreal injections [IVT] of anti-VEGFs and steroids) and laser therapies are summarised. Generally, IVT anti-VEGF are offered as first line pharmacologic therapy. As requirements of diabetic patients in particular patient groups may vary, including pregnant women, children, and persons with learning difficulties, it is important that DR management is personalised in such particular patient groups. First choice therapy needs to be individualised in these cases and may be intravitreal steroids rather than the standard choice of anti-VEGF agents. Some of these, but not all, are discussed in this document.

Knockdown of Malat1 alleviates high-glucose-induced angiogenesis through regulating miR-205-5p/VEGF-A axis

Diabetic retinopathy (DR), characterized by intraretinal vessel formation, is a major complication in diabetes. Neovascularization is an important characteristic of DR, but its formation mechanism remains unclear. In this research, Malat1, miR-205-5p, and VEGF-A levels in high glucose (HG) treat-human retinal microvascular endothelial cells (hRMECs) was detected with qRT-PCR. CCK-8 assay, transwell assay, and tube formation assay was applied to access hRMEC viability, migration, and angiogenesis. Expression level of endothelial-mesenchymal transition (EndMT) markers (VE-cadherin, FSP1, and α-SMA) was detected by western blotting assay. Interaction among Malat1, miR-205-5p, and VEGF-A was confirmed by dual-luciferase reporter assay. Furthermore, in vivo DR mouse model was induced, and the effect of Malat1 on DR and EndMT markers was confirmed through hematoxylin-eosin (HE) staining and western blotting. As a result, Malat1 and VEGF-A was upregulated while miR-205-5p was suppressed under HG conditions. Malat1 could sponge miR-205-5p to regulate VEGF-A expression. Malat1 knockdown inhibited hRMEC proliferation, migration, and tube formation by targeting miR-205-5p under HG conditions. Furthermore, inhibition of Malat1 prevented the HG-induced EndMT process. In summary, Malat1 knockdown diminished hRMEC dysfunctions by regulating miR-205-5p/VEGF-A, providing a useful insight for exploring new therapeutic target for DR.

Biomarkers for Progression in Diabetic Retinopathy: Expanding Personalized Medicine through Integration of AI with Electronic Health Records

The goal of personalized diabetes eye care is to accurately predict in real-time the risk of diabetic retinopathy (DR) progression and visual loss. The use of electronic health records (EHR) provides a platform for artificial intelligence (AI) algorithms that predict DR progression to be incorporated into clinical decision-making. By implementing an algorithm on data points from each patient, their risk for retinopathy progression and visual loss can be modeled, allowing them to receive timely treatment. Data can guide algorithms to create models for disease and treatment that may pave the way for more personalized care. Currently, there exist numerous challenges that need to be addressed before reliably building and deploying AI algorithms, including issues with data quality, privacy, intellectual property, and informed consent.

Mechanistic dissection of diabetic retinopathy using the protein-metabolite interactome

Purpose

The current study aims to determine the molecular mechanisms of diabetic retinopathy (DR) using the protein-protein interactome and metabolome map. We examined the protein network of novel biomarkers of DR for direct (physical) and indirect (functional) interactions using clinical target proteins in different models.

Methods

We used proteomic tools including 2-dimensional gel electrophoresis, mass spectrometry analysis, and database search for biomarker identification using in vivo murine and human model of diabetic retinopathy and in vitro model of oxidative stress. For the protein interactome and metabolome mapping, various bioinformatic tools that include STRING and OmicsNet were used.

Results

We uncovered new diabetic biomarkers including prohibitin (PHB), dynamin 1, microtubule-actin crosslinking factor 1, Toll-like receptor (TLR 7), complement activation, as well as hypothetical proteins that include a disintegrin and metalloproteinase (ADAM18), vimentin III, and calcium-binding C2 domain-containing phospholipid-binding switch (CAC2PBS) using a proteomic approach. Proteome networks of protein interactions with diabetic biomarkers were established using known DR-related proteome data. DR metabolites were interconnected to establish the metabolome map. Our results showed that mitochondrial protein interactions were changed during hyperglycemic conditions in the streptozotocin-treated murine model and diabetic human tissue.

Conclusions

Our interactome mapping suggests that mitochondrial dysfunction could be tightly linked to various phases of DR pathogenesis including altered visual cycle, cytoskeletal remodeling, altered lipid concentration, inflammation, PHB depletion, tubulin phosphorylation, and altered energy metabolism. The protein-metabolite interactions in the current network demonstrate the etiology of retinal degeneration and suggest the potential therapeutic approach to treat DR.

The Risk Factors for Diabetic Retinopathy in a Chinese Population: A Cross-Sectional Study

AIMS

Epidemiological data on diabetic retinopathy (DR) in Chinese population is still rather scarce, and risk factors for diabetic retinopathy are inconsistent because of study designs, grading standards, and population samples.

MATERIALS AND METHODS

This hospital-based retrospective study included 1052 type 2 diabetes patients. Diabetic retinopathy was diagnosed by nonmydriatic fundus photography and/or fundus examination apparatus. Logistic regression analysis was performed to evaluate the risk of diabetic retinopathy.

RESULTS

A total of 352 (33.5% prevalence) subjects were diagnosed with diabetic retinopathy based on our population. The patients in the DR group not only had significantly higher hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), urinary microalbumin-creatinine ratio (ACR), and systolic blood pressure but also had higher follicle-stimulating hormone (FSH), luteinizing hormone (LH), and sex hormone-binding globulin (SHBG) levels compared to those in the non-DR group. Moreover, we confirmed that diabetes duration and HbA1c are strongly associated with DR risk. We also found that serum LH was an independent risk factor in male diabetic retinopathy patients (OR = 1.086, 95% CI 1.024-1.152), and the levels of LH were significantly associated with diabetic retinopathy prevalence (P = 0.018).

CONCLUSIONS

Our study strengthens the argument that diabetes duration and HbA1c are risk factors for patients with DR. Additionally; we firstly confirmed that serum LH was an independent risk factor in male diabetic retinopathy patients.

Genotypes and Phenotypes: A Search for Influential Genes in Diabetic Retinopathy

Although gene–environment interactions are known to play an important role in the inheritance of complex traits, it is still unknown how a genotype and the environmental factors result in an observable phenotype. Understanding this complex interaction in the pathogenesis of diabetic retinopathy (DR) remains a big challenge as DR appears to be a disease with heterogenous phenotypes with multifactorial influence. In this review, we examine the natural history and risk factors related to DR, emphasizing distinct clinical phenotypes and their natural course in retinopathy. Although there is strong evidence that duration of diabetes and metabolic factors play a key role in the pathogenesis of DR, accumulating new clinical studies reveal that this disease can develop independently of duration of diabetes and metabolic dysfunction. More recently, studies have emphasized the role of genetic factors in DR. However, linkage analyses, candidate gene studies, and genome-wide association studies (GWAS) have not produced any statistically significant results. Our recently initiated genomics study, the Diabetic Retinopathy Genomics (DRGen) Study, aims to examine the contribution of rare and common variants in the development DR, and how they can contribute to clinical phenotype, rate of progression, and response to available therapies. Our preliminary findings reveal a novel set of genetic variants associated with proangiogenic and inflammatory pathways that may contribute to DR pathogenesis. Further investigation of these variants is necessary and may lead to development of novel biomarkers and new therapeutic targets in DR.

Design and baseline data of a population-based metabonomics study of eye diseases in eastern China: the Yueqing Ocular Diseases Investigation

Background

China is undergoing a massive transition toward an urban and industrial economy. These changes will restructure the demographics and economy which will eventually influence the future patterns of disease. The risk factors of vision-impairing eye diseases remain ambiguous and poorly understood. Metabolomics is an ideal tool to understand and shed light on the ocular disease mechanisms for earlier treatment. This article aims to describe the design, methodology and baseline data of the Yueqing Ocular Diseases Investigation (YODI), a developed county population-based study to determine the prevalence and primary causes of visual impairment; also with metabonomics analysis we aimed to identify, predict and suggest some preventive biomarkers that cause blindness.

Methods

A population-based, cross-sectional study. Randomized clustering sampling was used to identify adults aged 50 years and older in Xiangyang Town, Yueqing county-level City. The interviews covered demographic, behavioral, ocular risk factors and mental health state. The ocular examination included visual acuity, autorefraction, intraocular pressure, anterior and posterior segment examinations, fundus photography, retinal tomography and angiography, and visual field testing. Anthropometric measurements included height and weight, waist and hip circumference, blood pressure, pulse rate, electrocardiogram, and abdominal ultrasound scan. A venous blood sample was collected for laboratory tests and metabonomics studies.

Results

Of the 5319 individuals recruited for the YODI, 4769 (89.7%) subjects were enrolled for analyses. The median age was 62.0 years, and 45.6% were male. The educational level of illiteracy or semi-illiteracy, primary, middle and high school or above was 29.8%, 45.5%, 20.1%, and 3.3%, respectively. Majority of the participants were female, younger, and less educated when compared with nonparticipants. The average body mass index and waist-hip ratios were 24.4 ± 3.4 kg/m² and 0.9 ± 0.1 respectively. Blood sample collection reached a sample size of 1909 (479 from subjects with self-reported diabetes and 1430 from one-third of the 4290 subjects without self-reported diabetes).

Conclusions

The YODI provides population-based data with a high response rate (89.7%) on the prevalence and primary causes of major vision-impairing eye diseases in developed county areas in eastern China. Metabonomics analysis from YODI will provide further association of metabolic characteristics with the visual impairment eye diseases. The risk prediction model could be created and has the potential to be generalized to developed eastern areas in China for prevention.

Knockdown of MALAT1 attenuates high-glucose-induced angiogenesis and inflammation via endoplasmic reticulum stress in human retinal vascular endothelial cells

Diabetic retinopathy (DR) is one of the most severe complications of diabetes mellitus, and retinal endoplasmic reticulum stress (ERS) plays an important role in the pathogenesis of DR. However, the exact mechanisms by which ERS mediates DR remain unclear. In this study, human retinal vascular endothelial cells (RVECs) were cultured in high-glucose (HG) medium to mimic the environment of DR. The expression of long non-coding RNA (lncRNA)-metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) was determined by quantitative real time PCR. ERS markers (glucose-regulated protein 78 [GRP78] and C/EBP homologous protein [CHOP]) were measured by immunofluorescence and western blotting. Cell viability was analyzed by the CCK-8 assay. The angiogenesis of RVECs was evaluated by tube formation assays. The levels of pro-inflammation cytokines TNF-α and IL-6 in RVECs were determined by ELISA assays. We found that exposure to HG levels upregulated MALAT1 and GRP78 expression in RVECs. While, GRP78 overexpression strengthened CHOP expression, cell proliferation suppression, capillary morphogenesis and inflammation in HG-treated RVECs. Importantly, knockdown of MALAT1 reversed HG-induced cell proliferation suppression, inhibited capillary morphogenesis, and inflammation in RVECs, and those effects were reversed by GRP78 overexpression. These results suggest that MALAT1 promotes HG-induced angiogenesis and inflammation in RVECs by upregulating ER stress, and might be target for treating DR.

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.

Association between neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and diabetic retinopathy among diabetic patients without a related family history

BACKGROUND

Diabetic retinopathy (DR) is a specific neurovascular complication of diabetes mellitus (DM). Clinically, family history is a widely recognized risk factor for DR, assisting diagnosis and risk strata. However, among a great amount of DR patients without hereditary history like hypertension and diabetes, direct and simple risk factors to assist clinical decisions are still required. Herein, we intend to investigate the associated risk factors for these DR patients based on systemic inflammatory response indexes, neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR).

METHODS

We consecutively enrolled 1030 patients with a definite diagnosis of type 2 diabetes mellitus (T2DM) from the endocrinology department of the Second hospital of People in Yun Nan. Based on funduscopy and family history checking, we excluded patients with a family history of hypertension and diabetes and finally enrolled 264 patients with DR and 206 patients with non-diabetic retinopathy (NDR). Through correlation analysis, univariate and multivariate regression, we further explore the association between NLR, PLR, and DR. On top of that, we investigate the effect of NLR and PLR on risk reclassification of DR.

RESULTS

Compared with NDR patients, NLR and PLR levels are significantly higher among DR patients (NLR: 2.36 ± 1.16 in DR group versus 1.97 ± 1.06 in NDR group, p < 0.001; PLR: 11.62 ± 4.55 in DR group versus10.56 ± 4.45 in NDR group, p = 0.012). According to univariate analysis, NLR and PLR add risks to DR. After fully adjusting co-founders, NLR, as both continuous and categorical variate, remains an independent risk factor for DR (OR (95%CI): 1.37 (1.06, 1.78) P = 0.018). And though PLR was not independently associated with DR as a continuous variable (OR (95%CI) 1.05 (0.99, 1.11) p = 0.135), the highest quantile of PLR add two-fold increased risk (OR (95%CI) 2.20 (1.05, 4.59) p = 0.037) in the fully adjusted model for DR. In addition, addition of PLR and NLR to the established factor hemoglobin (Hb) improved the discriminability of the model and assisted the reclassification of DR. After combining PLR and NLR the Area under curve (AUC) of Hb based model raised from 0.76 to 0.78, with a category-free net reclassification improvement (NRI) of 0.532 (p < 0.001) and integrated discrimination improvement (IDI) of 0.029 (p < 0.001).

CONCLUSIONS

Systemic inflammatory response indexes NLR and PLR were associated with the presence of DR among patients without associated family history and contributed to improvements in reclassification of DR in addition to Hb.

Clinical Predictors of Diabetic Retinopathy Progression; A Systematic Review

OBJECTIVE

This study was conducted to discuss the clinical value of published Diabetic Retinopathy Progression determinants.

METHODS

The data for systematic review was collected from the published studies through PubMed and Medline. These studies discussed the clinical predictors of Diabetic Retinopathy (DR) progression. The common keywords used were diabetic Retinopathy, diabetes mellitus, systolic blood pressure, hemoglobin, and albuminuria.

RESULTS

Diabetic Retinopathy is one of the common causes of irreversible visual impairment among adults. Poor glycemic control, systemic hypertension, diabetes duration, dyslipidemia, and microalbuminuria are the major risk factors for the development and progression of diabetic retinopathy. Recently, increased aortic stiffness has been identified as a prognostic marker of diabetic retinopathy and peripheral neuropathy.

CONCLUSION

Certain groups of diabetic individuals are at higher risk to have progressive diabetic retinopathy and eventually visual impairment. Clinical determinants and predictors are considered as prognostic markers and could help physicians to develop an effective risk-based screening program for this condition.

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.

Plasma metabolomic profiling of proliferative diabetic retinopathy

Background

Proliferative diabetic retinopathy (PDR), a sight-threatening retinopathy, is the leading cause of irreversible blindness in adults. Despite strict control of systemic risk factors, a fraction of patients with diabetes develop PDR, suggesting the existence of other potential pathogenic factors underlying PDR. This study aimed to investigate the plasma metabotype of patients with PDR and to identify novel metabolite markers for PDR. Biomarkers identified from this study will provide scientific insight and new strategies for the early diagnosis and intervention of diabetic retinopathy.

Methods

A total of 1024 patients with type 2 diabetes were screened. To match clinical parameters between case and control subjects, patients with PDR (PDR, n = 21) or those with a duration of diabetes of ≥10 years but without diabetic retinopathy (NDR, n = 21) were assigned to the present case-control study. Distinct metabolite profiles of serum were examined using liquid chromatography-mass spectrometry (LC-MS).

Results

The distinct metabolites between PDR and NDR groups were significantly enriched in 9 KEGG pathways (P < 0.05, impact > 0.1), namely, alanine, aspartate and glutamate metabolism, caffeine metabolism, beta-alanine metabolism, purine metabolism, cysteine and methionine metabolism, sulfur metabolism, sphingosine metabolism, and arginine and proline metabolism. A total of 63 altered metabolites played important roles in these pathways. Finally, 4 metabolites were selected as candidate biomarkers for PDR, namely, fumaric acid, uridine, acetic acid, and cytidine. The area under the curve for these biomarkers were 0.96, 0.95, 1.0, and 0.95, respectively.

Conclusions

This study suggested that impairment in the metabolism of pyrimidines, arginine and proline were identified as metabolic dysregulation associated with PDR. And fumaric acid, uridine, acetic acid, and cytidine might be potential biomarkers for PDR. Fumaric acid was firstly reported as a novel metabolite marker with no prior reports of association with diabetes or diabetic retinopathy, which might provide insights into potential new pathogenic pathways for diabetic retinopathy.

Diabetic macular edema: Evidence-based management

Diabetic macular edema (DME) is the most common cause of vision loss in patients with diabetic retinopathy with an increasing prevalence tied to the global epidemic in type 2 diabetes mellitus. Its pathophysiology starts with decreased retinal oxygen tension that manifests as retinal capillary hyperpermeability and increased intravascular pressure mediated by vascular endothelial growth factor (VEGF) upregulation and retinal vascular autoregulation, respectively. Spectral domain optical coherence tomography (SD-OCT) is the cornerstone of clinical assessment of DME. The foundation of treatment is metabolic control of hyperglycemia and blood pressure. Specific ophthalmic treatments include intravitreal anti-VEGF drug injections, intravitreal corticosteroid injections, focal laser photocoagulation, and vitrectomy, but a substantial fraction of eyes respond incompletely to all of these modalities resulting in visual loss and disordered retinal structure and vasculature visible on SD-OCT and OCT angiography. Efforts to close the gap between the results of interventions within randomized clinical trials and in real-world contexts, and to reduce the cost of care increasingly occupy innovation in the social organization of ophthalmic care of DME. Pharmacologic research is exploring other biochemical pathways involved in retinal vascular homeostasis that may provide new points of intervention effective in those cases unresponsive to current treatments.

Mitochondrial haplogroups are not associated with diabetic retinopathy in a large Australian and British Caucasian sample

Mitochondrial haplogroups H1, H2 and UK have previously been reported to be associated with proliferative diabetic retinopathy (PDR) in Caucasian patients with diabetes. We aimed to replicate this finding with a larger sample and expand the analysis to include different severities of DR, and diabetic macular edema (DME). Caucasian participants (n = 2935) with either type 1 or type 2 diabetes from the Australian Registry of Advanced Diabetic Retinopathy were enrolled in this study. Twenty-two mitochondrial single nucleotide polymorphisms were genotyped by MassArray and haplogroups reconstructed using Haplogrep. Chi square tests and logistic regressions were used to test associations between haplogroup and DR phenotypes including any DR, non-proliferative DR (NPDR), proliferative DR (PDR) and DME. After stratifying the samples in type 1 and type 2 diabetes groups, and adjusting for sex, age, diabetes duration, concurrent HbA1c and hypertension, neither haplogroups H1, H2, UK, K or JT were associated with any DR, NPDR, PDR or DME.

Multilocus genetic risk score for diabetic retinopathy in the Han Chinese population of Taiwan

The aim of this study is to explore the effect of genetic variation on diabetic retinopathy (DR) risk in a Taiwanese population. The logistic regression model was used to evaluate the relationship between DR status and risk factors, including the conventional parameters and genetic risk score (GRS). Candidate single nucleotide polymorphisms (SNPs) in GRS were selected based on previous reports with a combined P < 10^-4 (genome-wide association) and P < 0.05 (meta-analysis). In total, 58 SNPs in 44 susceptibility loci were selected, and four were used to calculate GRS. After adjustment for age, systolic blood pressure, diabetes duration, and HbA1c, the DR risk was 4.95 times higher for patients in the top GRS third tile than for those in the bottom third tile (95% CI = 2.99-8.18; P < 0.001). The addition of genetic information improved DR prediction, increasing the area under the curve (AUC) from 0.72 to 0.77 (P = 0.0024) and improving the sensitivity of the model such that 40 more subjects were reclassified into DR status. The developed multivariate logistic regression model combining conventional risk factors and the multilocus GRS can predict DR, thus enabling timely treatment to reduce blindness in T2D patients.

MicroRNA-384-3p inhibits retinal neovascularization through targeting hexokinase 2 in mice with diabetic retinopathy

Diabetic retinopathy (DR) presents a microvascular complication of diabetes, which may contribute to visual impairment. The treatment of DR is still controversial. Accumulating studies have reported the role of microRNAs (miRs) in DR. This study aims to explore the functions of microRNA-384-3p (miR-384-3p) in retinal neovascularization by targeting hexokinase 2 (HK2) in mice with DR. A total of 43 C57BL/6 male mice were selected and divided into normal ( n = 16) and DR ( n = 27) groups. Retinal microvascular endothelial cells (RMECs) were collected from the normal and DR mice and mainly treated with a miR-384-3p mimic, a miR-384-3p inhibitor, small interfering RNA (siRNA) against HK2 and HK2 overexpression plasmids to understand the underlying regulatory mechanisms of miR-384-3p. The relationship between miR-384-3p and HK2 was determined by dual-luciferase reporter assay. The miR-384-3p expression and the mRNA and the protein expressions of HK2 and CD31 in retinal tissues and cells were evaluated using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot assay. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Tube formation was observed by conducting a tube formation experiment. HK2 is a target gene of miR-384-3p. The DR mice showed higher expression of HK2 and CD31 but lower expression of miR-384-3p. The miR-384-3p mimic and siRNA-HK2 reduced the expression of HK2, decreased cell proliferation and tube formation of RMECs, whereas the miR-384-3p inhibitor could reverse these trends. Our study demonstrates that overexpression of miR-384-3p inhibits retinal neovascularization in DR mice via inhibition of HK2.

Remodeling of Retinal Architecture in Diabetic Retinopathy: Disruption of Ocular Physiology and Visual Functions by Inflammatory Gene Products and Pyroptosis

Diabetic patients suffer from a host of physiological abnormalities beyond just those of glucose metabolism. These abnormalities often lead to systemic inflammation via modulation of several inflammation-related genes, their respective gene products, homocysteine metabolism, and pyroptosis. The very nature of this homeostatic disruption re-sets the overall physiology of diabetics via upregulation of immune responses, enhanced retinal neovascularization, upregulation of epigenetic events, and disturbances in cells' redox regulatory system. This altered pathophysiological milieu can lead to the development of diabetic retinopathy (DR), a debilitating vision-threatening eye condition with microvascular complications. DR is the most prevalent cause of irreversible blindness in the working-age adults throughout the world as it can lead to severe structural and functional remodeling of the retina, decreasing vision and thus diminishing the quality of life. In this manuscript, we attempt to summarize recent developments and new insights to explore the very nature of this intertwined crosstalk between components of the immune system and their metabolic orchestrations to elucidate the pathophysiology of DR. Understanding the multifaceted nature of the cellular and molecular factors that are involved in DR could reveal new targets for effective diagnostics, therapeutics, prognostics, preventive tools, and finally strategies to combat the development and progression of DR in susceptible subjects.

The genetics of retinopathy of prematurity: a model for neovascular retinal disease

TOPIC

Retinopathy of prematurity (ROP) is a proliferative retinal vascular disease in premature infants, and is a major cause of childhood blindness worldwide. In addition to known clinical risk factors such as low birth weight and gestational age, there is a growing body of evidence supporting a genetic basis for ROP.

CLINICAL RELEVANCE

While comorbidities and environmental factors have been identified as contributing to ROP outcomes in premature infants, most notably gestational age and oxygen, some infants progress to severe disease despite absence of these clinical risk factors. The contribution of genetic factors may explain these differences and allow better detection and treatment of infants at risk for severe ROP.

METHODS

To comprehensively review genetic factors that potentially contribute to the development and severity of ROP, we conducted a literature search focusing on the genetic basis for ROP. Terms related to other heritable retinal vascular diseases like "familial exudative vitreoretinopathy", as well as to genes implicated in animal models of ROP, were also used to capture research in diseases with similar pathogenesis to ROP in humans with known genetic components.

RESULTS

Contributions across several genetic domains are described including vascular endothelial growth factor, the Wnt signaling pathway, insulin-like growth factor 1, inflammatory mediators, and brain-derived neurotrophic factor.

CONCLUSIONS

Most candidate gene studies of ROP have limitations such as inability to replicate results, conflicting results from various studies, small sample size, and differences in clinical characterization. Additional difficulty arises in separating the contribution of genetic factors like Wnt signaling to ROP and prematurity. Although studies have implicated involvement of multiple signaling pathways in ROP, the genetics of ROP have not been clearly elucidated. Next-generation sequencing and genome-wide association studies have potential to expand future understanding of underlying genetic risk factors and pathophysiology of ROP.

Metabolomics of Diabetic Retinopathy

PURPOSE OF REVIEW

Metabolomics is the study of dysregulated metabolites in biological materials. We reviewed the use of the technique to elucidate the genetic and environmental factors that contribute to the development of diabetic retinopathy.

RECENT FINDINGS

With regard to metabolomic studies of diabetic retinopathy, the field remains in its infancy with few studies published to date and little replication of results. Vitreous and serum samples are the main tissues examined, and dysregulation in pathways such as the pentose phosphate pathway, arginine to proline pathway, polyol pathway, and ascorbic acidic pathways have been reported. Few studies have examined the metabolomic underpinnings of diabetic retinopathy. Further research is required to replicate findings to date and determine longitudinal associations with disease.

CDKAL1 rs7756992 is associated with diabetic retinopathy in a Chinese population with type 2 diabetes

Diabetic retinopathy (DR) is a major microvascular complication of diabetes. Susceptibility genes for type 2 diabetes may also impact the susceptibility of DR. This case-control study investigated the effects of 88 type 2 diabetes susceptibility loci on DR in a Chinese population with type 2 diabetes performed in two stages. In stage 1, 88 SNPs were genotyped in 1,251 patients with type 2 diabetes, and we found that ADAMTS9-AS2 rs4607103, WFS1 rs10010131, CDKAL1 rs7756992, VPS26A rs1802295 and IDE-KIF11-HHEX rs1111875 were significantly associated with DR. The association between CDKAL1 rs7756992 and DR remained significant after Bonferroni correction for multiple comparisons (corrected P = 0.0492). Then, the effect of rs7756992 on DR were analysed in two independent cohorts for replication in stage 2. Cohort (1) consisted of 380 patients with DR and 613 patients with diabetes for ≥5 years but without DR. Cohort (2) consisted of 545 patients with DR and 929 patients with diabetes for ≥5 years but without DR. A meta-analysis combining the results of stage 1 and 2 revealed a significant association between rs7756992 and DR, with the minor allele A conferring a lower risk of DR (OR 0.824, 95% CI 0.743–0.914, P = 2.46 × 10⁻⁴).

Clinical worthlessness of genetic prediction of common forms of diabetes mellitus and related chronic complications: A position statement of the Italian Society of Diabetology

AIM

We are currently facing several attempts aimed at marketing genetic data for predicting multifactorial diseases, among which diabetes mellitus is one of the more prevalent. The present document primarily aims at providing to practicing physicians a summary of available data regarding the role of genetic information in predicting diabetes and its chronic complications.

DATA SYNTHESIS

Firstly, general information about characteristics and performance of risk prediction tools will be presented in order to help clinicians to get acquainted with basic methodological information related to the subject at issue. Then, as far as type 1 diabetes is concerned, available data indicate that genetic information and counseling may be useful only in families with many affected individuals. However, since no disease prevention is possible, the utility of predicting this form of diabetes is at question. In the case of type 2 diabetes, available data really question the utility of adding genetic information on top of well performing, easy available and inexpensive non-genetic markers. Finally, the possibility of using the few available genetic data on diabetic complications for improving our ability to predict them will also be presented and discussed. For cardiovascular complication, the addition of genetic information to models based on clinical features does not translate in a substantial improvement in risk discrimination. For all other diabetic complications genetic information are currently very poor and cannot, therefore, be used for improving risk stratification.

CONCLUSIONS

In all, nowadays the use of genetic testing for predicting diabetes and its chronic complications is definitively of little value in clinical practice.

Common variants of HNF1A gene are associated with diabetic retinopathy and poor glycemic control in normal-weight Japanese subjects with type 2 diabetes mellitus

AIM

This study investigated the associations between the common hepatocyte nuclear factor-1A (HNF1A) variants and the risk of diabetic retinopathy (DR) in relation to the glycemic control and weight status.

METHODS

A retrospective longitudinal analysis was conducted among 354 Japanese patients with type 2 diabetes mellitus (T2DM) (mean follow-up duration: 5.8±2.5 years). The multivariable-adjusted hazard ratio (HR) for the cumulative incidence of DR was calculated using a Cox proportional hazard model. During the observation period, the longitudinal associations of the HNF1A diplotypes with the risk of DR and the clinical parameters were also analyzed using the generalized estimating equations approach.

RESULTS

The combination of risk variants, i.e., rs1169288-C, rs1183910-A and rs2464196-A, was defined as the H1 haplotype. The incidence of DR was higher in the H1/H1 diplotype cases than in the others (HR 2.75 vs. non-H1/non-H1; p=0.02). Only in normal-weight subjects, the risks of DR and poor glycemic control were higher in the H1/H1 diplotype cases than in the others [odds ratio 4.08 vs. non-H1/non-H1, p=0.02; odds ratio 3.03, p=0.01; respectively].

CONCLUSIONS

This study demonstrated that the common HNF1A diplotype of three risk variants may be an independent risk factor for the development of DR resulting from poor glycemic control in normal-weight patients with T2DM. These results need to be replicated in larger and more varied study populations.

Gene therapy for diabetic retinopathy: Are we ready to make the leap from bench to bedside?

Diabetic retinopathy (DR), a chronic and progressive complication of diabetes mellitus, is a sight-threatening disease characterized in the early stages by neuronal and vascular dysfunction in the retina, and later by neovascularization that further damages vision. A major contributor to the pathology is excess production of vascular endothelial growth factor (VEGF), a growth factor that induces formation of new blood vessels and increases permeability of existing vessels. Despite the recent availability of effective treatments for the disease, including laser photocoagulation and therapeutic VEGF antibodies, DR remains a significant cause of vision loss worldwide. Existing anti-VEGF agents, though generally effective, are limited by their short therapeutic half-lives, necessitating frequent intravitreal injections and the risk of attendant adverse events. Management of DR with gene therapies has been proposed for several years, and pre-clinical studies have yielded enticing findings. Gene therapy holds several advantages over conventional treatments for DR, such as a longer duration of therapeutic effect, simpler administration, the ability to intervene at an earlier stage of the disease, and potentially fewer side-effects. In this review, we summarize the current understanding of the pathophysiology of DR and provide an overview of research into DR gene therapies. We also examine current barriers to the clinical application of gene therapy for DR and evaluate future prospects for this approach.