Ocular Anti-VEGF therapy for diabetic retinopathy: the role of VEGF in the pathogenesis of diabetic retinopathy

Metabolic reprogramming and interventions in angiogenesis

BACKGROUND

Endothelial cell (EC) metabolism plays a crucial role in the process of angiogenesis. Intrinsic metabolic events such as glycolysis, fatty acid oxidation, and glutamine metabolism, support secure vascular migration and proliferation, energy and biomass production, as well as redox homeostasis maintenance during vessel formation. Nevertheless, perturbation of EC metabolism instigates vascular dysregulation-associated diseases, especially cancer.

AIM OF REVIEW

In this review, we aim to discuss the metabolic regulation of angiogenesis by EC metabolites and metabolic enzymes, as well as prospect the possible therapeutic opportunities and strategies targeting EC metabolism.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we discuss various aspects of EC metabolism considering normal and diseased vasculature. Of relevance, we highlight that the implications of EC metabolism-targeted intervention (chiefly by metabolic enzymes or metabolites) could be harnessed in orchestrating a spectrum of pathological angiogenesis-associated diseases.

Biochemical Changes in Anterior Chamber of the Eye in Diabetic Patients-A Review

This article aims to provide a comprehensive review of the biochemical changes observed in the anterior chamber of the eye in diabetic patients. The increased levels of inflammatory markers, alterations in antioxidant defense mechanisms, and elevated levels of advanced glycation end products (AGEs) in the aqueous humor (AH) are explored. Additionally, the impact of these biochemical changes on diabetic retinopathy progression, increased intraocular pressure, and cataract formation is discussed. Furthermore, the diagnostic and therapeutic implications of these findings are presented. This study explores potential biomarkers for detecting diabetic eye disease at an early stage and monitoring its progression. An investigation of the targeting of inflammatory and angiogenic pathways as a potential treatment approach and the role of antioxidant agents in managing these biochemical changes is performed.

Investigating the impact of empagliflozin on the retina of diabetic mice

BACKGROUND

Diabetic retinopathy (DR) frequently results in compromised visual function, with hyperglycemia-induced disruption of the blood-retinal barrier (BRB) through various pathways as a critical mechanism. Existing DR treatments fail to address early and potentially reversible microvascular alterations. This study examined the effects of empagliflozin (EMPA), a selective Sodium-glucose transporter 2 (SGLT2) inhibitor, on the retina of db/db mice. The objective of this study is to investigate the potential role of EMPA in the prevention and delay of DR.

METHODS

db/db mice were randomly assigned to either the EMPA treatment group (db/db + Emp) or the model group (db/db), while C57 mice served as the normal control group (C57). Mice in the db/db + Emp group received EMPA for eight weeks. Body weight, fasting blood glucose (FBG), and blood VEGF were subsequently measured in all mice, along with the detection of specific inflammatory factors and BRB proteins in the retina. Retinal SGLT2 protein expression was compared using immunohistochemical analysis, and BRB structural changes were observed via electron microscopy.

RESULTS

EMPA reduced FBG, blood VEGF, and retinal inflammatory factors TNF-α, IL-6, and VEGF levels in the eye tissues of db/db mice. EMPA also increased Claudin-1, Occludin-1, and ZO-1 levels while decreasing ICAM-1 and Fibronectin, thereby preserving BRB function in db/db mice. Immunohistochemistry revealed that EMPA reduced SGLT2 expression in the retina of diabetic mice, and electron microscopy demonstrated that EMPA diminished tight junction damage between retinal vascular endothelial cells and prevented retinal vascular basement membrane thickening in diabetic mice.

CONCLUSION

EMPA mitigates inflammation and preserves BRB structure and function, suggesting that it may prevent DR or serve as an effective early treatment for DR.

GBP2 inhibits pathological angiogenesis in the retina via the AKT/mTOR/VEGFA axis

Pathological retinal angiogenesis is not only the hallmark of retinopathies, but also a major cause of blindness. Guanylate binding protein 2 (GBP2) has been reported to be associated with retinal diseases such as diabetic retinopathy and hypoxic retinopathy. However, GBP2-mediated pathological retinal angiogenesis remains largely unknown. The present study aimed to investigate the role of GBP2 in pathological retinal angiogenesis and its underlying molecular mechanism. In this study, we established oxygen-induced retinopathy (OIR) mice model for in vivo study and hypoxia-induced angiogenesis in ARPE-19 cells for in vitro study. We demonstrated that GBP2 expression was markedly downregulated in the retina of mice with OIR and ARPE-19 cells treated with hypoxia, which was associated with pathological retinal angiogenesis. The regulatory mechanism of GBP2 in ARPE-19 cells was studied by GBP2 silencing and overexpression. The regulatory mechanism of GBP2 in the retina was investigated by overexpressing GBP2 in the retina of OIR mice. Mechanistically, GBP2 downregulated the expression and secretion of vascular endothelial growth factor (VEGFA) in ARPE-19 cells and retina of OIR mice. Interestingly, overexpression of GBP2 significantly inhibited neovascularization in OIR mice, conditioned medium of GBP2 overexpressing ARPE-19 cells inhibited angiogenesis in human umbilical vein endothelial cells (HUVECs). Furthermore, we confirmed that GBP2 downregulated VEGFA expression and angiogenesis by inhibiting the AKT/mTOR signaling pathway. Taken together, we concluded that GBP2 inhibited pathological retinal angiogenesis via the AKT/mTOR/VEGFA axis, thereby suggesting that GBP2 may be a therapeutic target for pathological retinal angiogenesis.

Statins as a risk factor for diabetic retinopathy: a Mendelian randomization and cross-sectional observational study

BACKGROUND

Diabetic retinopathy (DR) is the foremost cause of vision loss among the global working-age population, and statins are among the most frequently prescribed drugs for lipid management in patients with DR. The exact relationship between statins and DR has not been determined. This study sought to validate the causal association between statins usage and diabetic retinopathy.

METHODS

The summary-data-based Mendelian randomization (SMR) method and inverse-variance-weighted Mendelian randomization (IVW-MR) were used to identify the causal relationship between statins and DR via the use of expression quantitative trait loci (eQTL) data for 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) (31,684 blood samples), low density lipoprotein cholesterol-related GWAS data (sample size: 440,546), and DR-related GWAS data (14,584 cases and 176,010 controls). Additionally, a cross-sectional observational study based on the data from the National Health and Nutrition Examination Survey (NHANES) was conducted to supplement the association between DR and statins (sample size: 106,911). The odds ratios (ORs) with corresponding 95% confidence intervals (CIs) was employed to evaluate the results.

RESULTS

Based on the results of the MR analysis, HMGCR inhibitors were causally connected with a noticeably greater incidence of DR (IVW: OR = 0.54, 95% CI [0.42, 0.69], p = 0.000002; SMR: OR = 0.66, 95% CI [0.52, 0.84], p = 0.00073). Subgroup analysis revealed that the results were not affected by the severity of DR. The sensitivity analysis revealed the stability and reliability of the MR analysis results. The results from the cross-sectional study based on NHANES also support the association between not taking statins and a decreased risk of DR (OR = 0.54, 95% CI [0.37, 0.79], p = 0.001).

CONCLUSIONS

This study revealed that a significant increase in DR risk was causally related to statins use, providing novel insights into the role of statins in DR. However, further investigations are needed to verify these findings.

Parallelism and non-parallelism in diabetic nephropathy and diabetic retinopathy

Diabetic nephropathy (DN) and diabetic retinopathy (DR), as microvascular complications of diabetes mellitus, are currently the leading causes of end-stage renal disease (ESRD) and blindness, respectively, in the adult working population, and they are major public health problems with social and economic burdens. The parallelism between the two in the process of occurrence and development manifests in the high overlap of disease-causing risk factors and pathogenesis, high rates of comorbidity, mutually predictive effects, and partial concordance in the clinical use of medications. However, since the two organs, the eye and the kidney, have their unique internal environment and physiological processes, each with specific influencing molecules, and the target organs have non-parallelism due to different pathological changes and responses to various influencing factors, this article provides an overview of the parallelism and non-parallelism between DN and DR to further recognize the commonalities and differences between the two diseases and provide references for early diagnosis, clinical guidance on the use of medication, and the development of new drugs.

Bibliometric and visualized analysis of diabetic macular edema

PURPOSE

Our aim was to identify recent research trends on diabetic macular edema (DME) and focus on publications from different countries, institutions, and authors.

METHODS

We retrieved and analyzed data from January 1, 2003 to December 31, 2022 on the DME research field from the Web of Science Core Collection (WoSCC) database. Microsoft Excel and VOSviewer were applied to perform visualization analysis and evaluate the trends.

RESULTS

A total of 4482 publications were identified, and the annual global publications increased steadily, from 36 to 390, during this period. The United States (1339 publications, 71,754 citations), Johns Hopkins University (176 publications, 17,015 citations), and Bressler NM (76 publications, 9621 citations) were the most influential and productive countries, institutions, and authors, respectively. The top 100 keywords were classified into five clusters: (1) therapy and adverse effects of DME; (2) clinical biomarkers of DME; (3) mechanistic research on DME; (4) improving bioavailability and efficacy; and (5) early diagnosis of diabetic complications. "Diabetic macular edema," "retinopathy," "ranibizumab," and "optical coherence tomography angiography" were the most frequent keywords. Regarding the average appearing years (AAYs) of the keywords, "deep learning" (AAY:2020.83), "optical coherence tomography angiography" (AAY:2019.59), "intravitreal Aflibercept" (AAY:2019.29), and "dexamethasone implant" (AAY:2019.20) were recognized as the hotspots of the DME research area in the short run.

CONCLUSION

In the past two decades, the United States was in master status in DME research. Although intravitreal drug injection has been the mainstream therapy for a long time, the effectiveness of different drugs, such as dexamethasone, new solutions for drug delivery, such as intravitreal implantation, and more accurate tools for the classification and follow-up of DME patients, such as deep learning systems, are still research hotspots.

Diabetic retinopathy: emerging concepts of current and potential therapy

Diabetic retinopathy (DR) is one of the leading causes of permanent central blindness worldwide. Despite the complexity and inadequate understanding of DR pathogenesis, many of the underlying pathways are currently partially understood and may offer potential targets for future treatments. Anti-VEGF medications are currently the main medication for this problem. This article provides an overview of the established pharmacological treatments and those that are being developed to cure DR. We firstly reviewed the widely utilized approaches including pan-retinal photocoagulation therapy, anti-VEGF therapy, corticosteroid therapy, and surgical management of DR. Next, we discussed the mechanisms of action and prospective benefits of novel candidate medications. Current management are far from being a perfect treatment for DR, despite mild-term favorable efficiency and safety profiles. Pharmacological research should work toward developing longer-lasting treatments or new drug delivery systems, as well as on identifying new molecular targets in the pathogenetical mechanism for DR. In order to find a treatment that is specifically designed for each patient, it is also necessary to properly characterize patients, taking into account elements like hereditary factors and intraretinal neovascularization stages for effective utilization of drugs. The current and potential approaches for diabetic retinopathy. Image was constructed using Biorender.com.

Blocking Hemopexin With Specific Antibodies: A New Strategy for Treating Diabetic Retinopathy

Hemopexin (HPX) is overexpressed in the retina of patients with diabetes and induces the breakdown of the blood-retinal barrier in vitro. The aim of this study was to evaluate whether HPX blockade by specific antibodies (aHPX) could avoid vascular leakage in vivo and microvascular angiogenesis in vitro and ex vivo. For this purpose, the effect of intravitreal (IVT) injections of aHPX on vascular leakage was evaluated in db/db mice and rats with streptozotocin-induced diabetes using the Evans Blue method. Retinal neurodegeneration and inflammation were also evaluated. The antiangiogenic effect of aHPX on human retinal endothelial cells (HRECs) was tested by scratch wound healing and tube formation using standardized methods, as well as by choroidal sprouting assays from retinal explants obtained in rats. We found that IVT injection of aHPX significantly reduced vascular leakage, retinal neurodegeneration, and inflammation. In addition, treatment with aHPX significantly reduced HREC migration and tube formation induced by high glucose concentration and suppressed choroidal sprouting even after vascular endothelial growth factor stimulation, with this effect being higher than obtained with bevacizumab. The antipermeability and antiangiogenic effects of IVT injection of aHPX suggest the blockade or inhibition of HPX as a new strategy for the treatment of advanced stages of diabetic retinopathy.

ARTICLE HIGHLIGHTS

Hemopexin (HPX) is the best-characterized permeability factor in steroid-sensitive nephrotic syndrome. We have previously reported that HPX is overexpressed in the retina of patients with diabetes and induces the breakdown of the blood-retinal barrier in vitro. Here, we report that intravitreal injection of anti-HPX antibodies significantly reduces vascular leakage, retinal neurodegeneration, and inflammation in diabetic murine models and that the immunoneutralization of HPX exerts a significant antiangiogenic effect in vitro and in retinal explants. The blockade of HPX can be considered as a new therapy for advanced stages of diabetic retinopathy.

Use of Yamane technique for secondary intraocular lens implantation following open globe injury

A woman in her 50s presented with suspected open globe injury (OGI) of the right eye after being hit with a high velocity piece of plastic. Visual acuity at the time of presentation was counting fingers in the affected eye. Slit lamp examination revealed a full thickness laceration of the cornea and a traumatic cataract. Primary corneal repair was performed and the patient was left aphakic after cataract removal. Secondary intraocular lens placement was deferred for 2 years, after which time a scleral-fixated intraocular lens was implanted using the Yamane technique. Postoperative visual acuity of 20/50 was achieved, with the vision limited by persistent diabetic macular oedema. Thus, this case of successful implantation of a secondary lens using the Yamane technique in a patient with prior corneal laceration and traumatic cataract highlights that the Yamane technique can result in visual improvement in patients with prior OGI.

Single-cell transcriptomics analysis of proliferative diabetic retinopathy fibrovascular membranes reveals AEBP1 as fibrogenesis modulator

The management of preretinal fibrovascular membranes, a devastating complication of advanced diabetic retinopathy (DR), remains challenging. We characterized the molecular profile of cell populations in these fibrovascular membranes to identify potentially new therapeutic targets. Preretinal fibrovascular membranes were surgically removed from patients and submitted for single-cell RNA-Seq (scRNA-Seq). Differential gene expression was implemented to define the transcriptomics profile of these cells and revealed the presence of endothelial, inflammatory, and stromal cells. Endothelial cell reclustering identified subclusters characterized by noncanonical transcriptomics profile and active angiogenesis. Deeper investigation of the inflammatory cells showed a subcluster of macrophages expressing proangiogenic cytokines, presumably contributing to angiogenesis. The stromal cell cluster included a pericyte-myofibroblast transdifferentiating subcluster, indicating the involvement of pericytes in fibrogenesis. Differentially expressed gene analysis showed that Adipocyte Enhancer-binding Protein 1, AEBP1, was significantly upregulated in myofibroblast clusters, suggesting that this molecule may have a role in transformation. Cell culture experiments with human retinal pericytes (HRP) in high-glucose condition confirmed the molecular transformation of pericytes toward myofibroblastic lineage. AEBP1 siRNA transfection in HRP reduced the expression of profibrotic markers in high glucose. In conclusion, AEBP1 signaling modulates pericyte-myofibroblast transformation, suggesting that targeting AEBP1 could prevent scar tissue formation in advanced DR.

Microinvasive pars plana vitrectomy combined with internal limiting membrane peeling versus anti-VEGF intravitreal injection for treatment-naïve diabetic macular edema (VVV-DME study): study protocol for a randomized controlled trial

BACKGROUND

Diabetic macular edema (DME) is the main cause of vision loss in diabetic patients. Currently, anti-vascular endothelial growth factor (VEGF) intravitreal injection stands as the first-line therapy for DME. However, some patients exhibit insufficient response to anti-VEGF agents and often require multiple injections, imposing psychological and economic burdens. While microinvasive pars plana vitrectomy (PPV) has been shown to be safe and effective in treating refractory DME, scant research has explored its application to treatment-naïve DME. The purpose of this study is to determine whether early PPV combined with internal limiting membrane (ILM) peeling can lessen the therapeutic burden of DME patients, prevent vision loss, and maintain long-term stabilization of diabetic retinopathy.

METHODS

This is a single-center, prospective, parallel-group, non-inferiority randomized controlled trial involving 102 DME participants. Participants will be randomly assigned to either the study group (PPV combined with ILM peeling) or the control group (conbercept intravitreal injection (IVC)) at a 1:1 ratio, with a scheduled follow-up at 12 months post-operation. Comparative analysis of results between the two groups will be conducted at months 1, 3, 6, and 12 after the intervention. The primary outcomes involve evaluating the changes in central subfield thickness (CST) and best corrected visual acuity (BCVA). The secondary outcomes include assessment of optical coherence tomography (OCT) and OCT angiography (OCTA) biomarkers, re-treatment and adverse events rates, diabetic retinopathy (DR) development, cost-effectiveness analysis, and vision-related quality of life (VRQL).

DISCUSSION

Some patients do not respond well to anti-VEGF drugs and repeated intravitreal injections increase the treatment burden for patients. The VVV study aims to explore whether PPV combined with ILM peeling could become an initial treatment option for treatment-naïve DME patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05728476. Registered on 15 February 2023.

Limited Hyperoxia-Induced Proliferative Retinopathy (LHIPR) as a Model of Retinal Fibrosis, Angiogenesis, and Inflammation

The progression to fibrosis and traction in retinopathy of prematurity (ROP) and other ischemic retinopathies remains an important clinical and surgical challenge, necessitating a comprehensive understanding of its pathogenesis. Fibrosis is an unbalanced deposition of extracellular matrix components responsible for scar tissue formation with consequent tissue and organ impairment. Together with retinal traction, it is among the main causes of retinal detachment and vision loss. We capitalize on the Limited Hyperoxia Induced Retinopathy (LHIPR) model, as it reflects the more advanced pathological phenotypes seen in ROP and other ischemic retinopathies. To model LHIPR, we exposed wild-type C57Bl/6J mouse pups to 65% oxygen from P0 to P7. Then, the pups were returned to room air to recover until later endpoints. We performed histological and molecular analysis to evaluate fibrosis progression, angiogenesis, and inflammation at several time points, from 1.5 months to 9 months. In addition, we performed in vivo retinal imaging by optical coherence tomography (OCT) or OCT Angiography (OCTA) to follow the fibrovascular progression in vivo. Although the retinal morphology was relatively preserved, we found a progressive increase in preretinal fibrogenesis over time, up to 9 months of age. We also detected blood vessels in the preretinal space as well as an active inflammatory process, altogether mimicking advanced preretinal fibrovascular disease in humans.

SRY-box transcription factor 9 modulates Müller cell gliosis in diabetic retinopathy by upregulating TXNIP transcription

Diabetic retinopathy (DR), a common complication of diabetes, involves excessive proliferation and inflammation of Muller cells and ultimately leads to vision loss and blindness. SRY-box transcription factor 9 (SOX9) has been reported to be highly expressed in Müller cells in light-induced retinal damage rats, but the functional role of SOX9 in DR remains unclear. To explore this issue, the DR rat model was successfully constructed via injection with streptozotocin (65 mg/kg) and the retinal thicknesses and blood glucose levels were evaluated. Müller cells were treated with 25 mmol/l glucose to create a cell model in vitro. The results indicated that SOX9 expression was significantly increased in DR rat retinas and in Müller cells stimulated with a high glucose (HG) concentration. HG treatment promoted the proliferation and migration capabilities of Müller cells, whereas SOX9 knockdown reversed those behaviors. Moreover, SOX9 knockdown provided protection against an HG-induced inflammatory response, as evidenced by reduced tumor necrosis factor-α, IL-1β, and IL-6 levels in serum and decreased NLRP3 inflammasome activation. Notably, SOX9 acted as a transcription factor that positively regulated thioredoxin-interacting protein (TXNIP), a positive regulator of Müller cells gliosis under HG conditions. A dual-luciferase assay demonstrated that SOX9 could enhance TXNIP expression at the transcriptional level through binding to the promoter of TXNIP. Moreover, TXNIP overexpression restored the effects caused by SOX9 silencing. In conclusion, these findings demonstrate that SOX9 may accelerate the progression of DR by promoting glial cell proliferation, metastasis, and inflammation, which involves the transcriptional regulation of TXNIP, providing new theoretical fundamentals for DR therapy.

Correlation of hemoglobin levels with diabetic retinopathy in US adults aged ≥40 years: the NHANES 2005-2008

Purpose

The aim of this study was to explore the connection between hemoglobin levels and diabetic retinopathy (DR).

Methods

Cross-sectional research used data from the National Health and Nutrition Examination Survey (NHANES) 2005-2008. A multiple logistic regression analysis was performed to investigate the association between DR and hemoglobin levels. Additionally, generalized additivity models and smoothed curve fitting were carried out.

Results

After adjusting for several covariates, there was a negative association between hemoglobin levels and DR in the study, which included 837 participants. The negative association between hemoglobin levels and DR was present in men and women, the obese (BMI > 30), and 60- to 69-year-olds in subgroup analyses stratified by sex, BMI, and age. The association between hemoglobin levels and DR in the normal weight group (BMI < 25) displayed an inverted U-shaped curve with an inflection point of 13.7 (g/dL).

Conclusion

In conclusion, our research reveals that high hemoglobin levels are related to a decreased risk of DR. Ascertaining the hemoglobin levels ought to be regarded as an integral facet of the monitoring regimen for patients with diabetic complications and that the risk of DR is reduced through the detection and management of hemoglobin levels.

Diabetic complications and prospective immunotherapy

The incidence of Diabetes Mellitus is increasing globally. Individuals who have been burdened with diabetes for many years often develop complications as a result of hyperglycemia. More and more research is being conducted highlighting inflammation as an important factor in disease progression. In all kinds of diabetes, hyperglycemia leads to activation of alternative glucose metabolic pathways, resulting in problematic by-products including reactive oxygen species and advanced glycation end products. This review takes a look into the pathogenesis of three specific diabetic complications; retinopathy, nephropathy and neuropathy as well as their current treatment options. By considering recent research papers investigating the effects of immunotherapy on relevant conditions in animal models, multiple strategies are suggested for future treatment and prevention of diabetic complications with an emphasis on molecular targets associated with the inflammation.

Implications of Caspase 1/ Interleukin-1 Beta (IL-1β) Signaling and Hypoxia-Inducible Factor 1-Alpha (HIF-1α) on Diabetic Retinopathy Pathology

Diabetic retinopathy (DR) is the leading cause of adult blindness and partial vision loss in modern society for hyperglycemic patients. Accordingly, new treatment options are imperative to the overall reduction of DR prevalence and the ongoing progression of already affected candidates. There are many diseases that are the direct result of specific inflammatory processes. In this literature, DR is looked at as a potential disease that can be alleviated by targeting caspase 1/ interleukin-1 beta (IL-1β), and hypoxia-inducible factor 1-alpha (HIF-1α) signaling pathways and reducing cytokine mobilization within retinal tissues. Caspase-1 is thought to be upregulated during retinal capillary degeneration and other ocular complications. Hypoxia-inducible factor 1-alpha (HIF-1α) is implicated in its role in neovascularization and cell apoptosis within a retinal cell line. Both of these proteins are shown to be significantly elevated in hyperglycemic and galactosemic mice and, when knocked out, seem to have the reverse effect, showing that there is room for potential non-invasive therapy involving these proteins in the future. Vascular endothelial growth factor-alpha (VEGF-A) is also examined as a main signaling protein involved in the manifestation of DR.

The Association of Intravitreal Injections of Different Anti-Vascular Endothelial Growth Factor with Systemic Outcomes in Diabetic Patients

This retrospective cohort study aimed to assess the systemic effects of three commonly available anti-vascular endothelial growth factor intravitreal injections in patients with diabetes, using data taken from a multi-institutional database in Taiwan. Patient data were sourced from the multi-institutional Chang Gung Research Database. Participants were divided into groups based on treatment with bevacizumab, ranibizumab, or aflibercept. Baseline characteristics were matched among the groups by the inverse probability of treatment weighting. The incidence rate of outcome events was calculated as the number of events divided by 100 person-years of follow-up. The cumulative incidence function was used to estimate the incidence rate of the outcome events among groups. The incidence of ischemic stroke was higher in the ranibizumab group than the bevacizumab and aflibercept groups (1.65, 0.92, and 0.61 per 100 person-years, respectively). The incidence of major adverse lower-limb events was higher in the bevacizumab group (2.95), followed by ranibizumab (2.00) and aflibercept (0.74). Major bleeding was relatively higher in bevacizumab (12.1) compared to ranibizumab (4.3) and aflibercept (3.8). All-cause death was higher for both bevacizumab (3.26) and aflibercept (2.61) when compared to ranibizumab (0.55), and all-cause admission was found to be highest with bevacizumab (58.6), followed by aflibercept (30.2), and ranibizumab (27.6). The bevacizumab group demonstrated a greater decrease in glycated hemoglobin compared to the baseline level (-0.33%). However, a few differences in the clinical condition between the groups were still observed after matching. In conclusion, this study suggests that different anti-vascular endothelial growth factor agents may be associated with various and differing systemic adverse events. The differences might also be attributed to differences in patient characteristics and clinical status.

Neuroinflammation and neovascularization in diabetic eye diseases (DEDs): identification of potential pharmacotherapeutic targets

The goal of this review is to increase public knowledge of the etiopathogenesis of diabetic eye diseases (DEDs), such as diabetic retinopathy (DR) and ocular angiosarcoma (ASO), and the likelihood of blindness among elderly widows. A widow's life in North India, in general, is fraught with peril because of the economic and social isolation it brings, as well as the increased risk of death from heart disease, hypertension, diabetes, depression, and dementia. Neovascularization, neuroinflammation, and edema in the ocular tissue are hallmarks of the ASO, a rare form of malignant tumor. When diabetes, hypertension, and aging all contribute to increased oxidative stress, the DR can proceed to ASO. Microglia in the retina of the optic nerve head are responsible for causing inflammation, discomfort, and neurodegeneration. Those that come into contact with them will get blind as a result of this. Advanced glycation end products (AGE), vascular endothelial growth factor (VEGF), protein kinase C (PKC), poly-ADP-ribose polymerase (PARP), metalloproteinase9 (MMP9), nuclear factor kappaB (NFkB), program death ligand1 (PDL-1), factor VIII (FVIII), and von Willebrand factor (VWF) are potent agents for ocular neovascularisation (ONV), neuroinflammation and edema in the ocular tissue. AGE/VEGF, DAG/PKC, PARP/NFkB, RAS/VEGF, PDL-1/PD-1, VWF/FVIII/VEGF, and RAS/VEGF are all linked to the pathophysiology of DEDs. The interaction between ONV and ASO is mostly determined by the VWF/FVIII/VEGF and PDL-1/PD-1 axis. This study focused on retinoprotective medications that can pass the blood-retinal barrier and cure DEDs, as well as the factors that influence the etiology of neovascularization and neuroinflammation in the eye.

L-type calcium channel blocker increases VEGF concentrations in retinal cells and human serum

OBJECTIVE

Vascular endothelial growth factor (VEGF) plays a key role in diabetic retinopathy (DR). Previously, we have reported an association between mutations in a gene coding for the L-type calcium channel subunit, VEGF and DR. L-type calcium channel blockers (LTCCBs) have been widely used as antihypertensive medication (AHM), but their association with VEGF and DR is still unclear. Therefore, we explored the effect of LTCCBs compared to other AHMs on VEGF concentrations in retinal cells and human serum. Furthermore, we evaluated the association between the use of LTCCBs and the risk of severe diabetic eye disease (SDED).

RESEARCH DESIGN AND METHODS

Müller cells (MIO-M1) were cultured as per recommended protocol and treated with LTCCBs and other AHMs. VEGF secreted from cells were collected at 24 hours intervals. In an interventional study, 39 individuals received LTCCBs or other AHM for four weeks with a four-week wash-out placebo period between treatments. VEGF was measured during the medication and placebo periods. Finally, we evaluated the risk of SDED associated with LTCCB usage in 192 individuals from the FinnDiane Study in an observational setting.

RESULTS

In the cell cultures, the medium VEGF concentration increased time-dependently after amlodipine (P<0.01) treatment, but not after losartan (P>0.01), or lisinopril (P>0.01). Amlodipine, but no other AHM, increased the serum VEGF concentration (P<0.05) during the interventional clinical study. The usage of LTCCB was not associated with the risk of SDED in the observational study.

CONCLUSIONS

LTCCB increases VEGF concentrations in retinal cells and human serum. However, the usage of LTCCBs does not appear to be associated with SDED in adults with type 1 diabetes.

MicroRNA-150 (miR-150) and Diabetic Retinopathy: Is miR-150 Only a Biomarker or Does It Contribute to Disease Progression?

Diabetic retinopathy (DR) is a chronic disease associated with diabetes mellitus and is a leading cause of visual impairment among the working population in the US. Clinically, DR has been diagnosed and treated as a vascular complication, but it adversely impacts both neural retina and retinal vasculature. Degeneration of retinal neurons and microvasculature manifests in the diabetic retina and early stages of DR. Retinal photoreceptors undergo apoptosis shortly after the onset of diabetes, which contributes to the retinal dysfunction and microvascular complications leading to vision impairment. Chronic inflammation is a hallmark of diabetes and a contributor to cell apoptosis, and retinal photoreceptors are a major source of intraocular inflammation that contributes to vascular abnormalities in diabetes. As the levels of microRNAs (miRs) are changed in the plasma and vitreous of diabetic patients, miRs have been suggested as biomarkers to determine the progression of diabetic ocular diseases, including DR. However, few miRs have been thoroughly investigated as contributors to the pathogenesis of DR. Among these miRs, miR-150 is downregulated in diabetic patients and is an endogenous suppressor of inflammation, apoptosis, and pathological angiogenesis. In this review, how miR-150 and its downstream targets contribute to diabetes-associated retinal degeneration and pathological angiogenesis in DR are discussed. Currently, there is no effective treatment to stop or reverse diabetes-caused neural and vascular degeneration in the retina. Understanding the molecular mechanism of the pathogenesis of DR may shed light for the future development of more effective treatments for DR and other diabetes-associated ocular diseases.

Anti-RAGE (Receptor Advanced Glycation End products) Antibody Improves Diabetic Retinopathy in Rats via Hypoglycemic and Anti-inflammatory Mechanism

Background

Receptor advanced glycation end products (RAGE) activation plays an essential role in diabetic retinopathy (DR) progression. This study was aimed to explore the role of anti-RAGE antibodies (RAGE antagonists) in inhibiting DR progression through their hypoglycemic and anti-inflammatory mechanism in diabetic retinopathy induced rats.

Methods

A total of 30 male Wistar rats were randomly divided into five group. The group was consisted of normal control group, DR group without treatment, DR group with anti-RAGE 1 ηg/kg BW, 10 ηg/kg BW, and 100 ηg/kg BW. To assess the diabetic retinopathy, fundus photographs were taken every week using a camera with 16x magnification placed in front of the rat's eyes. Blood glucose was checked by the glucose oxidase-peroxidase method. Retinal TNF-α levels and VEGF were examined using an enzyme-linked immunosorbent assay (ELISA) kit.

Results

The finding of this study showed that anti-RAGE treatment at dose of 10 and 100 ηg/kg BW, HbA1c levels were significantly higher (p< 0.05) compared to the normal control group but significantly lower (p< 0.05) than in the diabetes group. The mean blood vessel diameter in the DR+anti-RAGE 10 and 100 ηg/kg BW groups was significantly lower than in the diabetic retinopathy group (p< 0.05). The administration of anti-RAGE 10 and 100 ηg/kg BW showed the ability to significantly reduce VEGF levels compared to the DR group (p< 0.05).

Discussion

This study revealed at doses of 10 and 100 ηg/kg BW, anti-RAGE antibodies improved diabetic retinopathy in Wistar rats through hypoglycemic effects and anti-inflammatory mechanisms.

Cytokine levels in the aqueous humor of young and senior patients with proliferative diabetic retinopathy

OBJECTIVE

To evaluate the aqueous humor levels of vascular endothelial growth factor (VEGF), connective tissue growth factor (CTGF), and tumor necrosis factor α (TNF-α) as biomarkers of the severity of proliferative diabetic retinopathy (PDR) in young and senior patients.

METHODS

This was a prospective clinical study. From October 2020 to June 2021, 37 patients (37 eyes) who were diagnosed with PDR and received pars plana vitrectomy (PPV) at Tianjin Medical University Eye Hospital were recruited and allocated to either the young (16 patients, 16 eyes) or senior subgroup (21 patients, 21 eyes). Twelve patients with cataracts (12 eyes) who underwent phacoemulsification combined with intraocular lens (IOL) implantation during the same period were recruited in the control group. The fibrovascular proliferation (FVP) grade and PDR severity scores were recorded during PPV. Enzyme-linked immunosorbent assay was used to detect the levels of VEGF, CTGF, and TNF-α in the aqueous humor.

RESULTS

(1) Young patients with PDR had a higher FVP grade and PDR severity score (P = 0.037, = 0.009); (2) The levels of the three cytokines in the study group were all significantly higher than in the control group (all P < 0.001); (3) The CTGF level in the young subgroup (2239.55 ± 167.32 pg/mL) was significantly higher than that in the senior subgroup (2114.49 ± 102.04 pg/mL) (P = 0.025). The VEGF level in the young subgroup (311.09 ± 10.74 pg/mL) was significantly lower than that in the senior subgroup (324.85 ± 14.97 pg/mL) (P = 0.004). The TNF-α level was not statistically different between the two subgroups (P = 0.382); (4) The CTGF/VEGF ratio in the young subgroup (7.20 ± 0.54) was significantly higher than in the senior subgroup (6.52 ± 0.39) (P < 0.001); (5) The CTGF/VEGF ratio was positively correlated with the FVP grades (R = 0.377, P = 0.022) and with the PDR severity scores (R = 0.354, P = 0.032) in patients with PDR.

CONCLUSION

The aqueous humor CTGF/VEGF ratio was positively correlated with the severity of PDR. A higher CTGF/VEGF ratio in the aqueous humor proved that neovascular fibrosis was more serious in young patients when they received PPV.

Plumbagin Suppresses Breast Cancer Progression by Downregulating HIF-1α Expression via a PI3K/Akt/mTOR Independent Pathway under Hypoxic Condition

Hypoxia-inducible factor-1α (HIF-1α) is a major transcriptional regulator that plays a crucial role in the hypoxic response of rapidly growing tumors. Overexpression of HIF-1α has been associated with breast cancer metastasis and poor clinical prognosis. Plumbagin, the main phytochemical from Plumbago indica, exerts anticancer effects via multiple mechanisms. However, its precise mechanisms on breast cancer cells under hypoxic conditions has never been investigated. This study aims to examine the anticancer effect of plumbagin on MCF-7 cell viability, transcriptional activity, and protein expression of HIF-1α under normoxia and hypoxia-mimicking conditions, as well as reveal the underlying signaling pathways. The results demonstrate that plumbagin decreased MCF-7 cell viability under normoxic conditions, and a greater extent of reduction was observed upon exposure to hypoxic conditions induced by cobalt chloride (CoCl₂). Mechanistically, MCF-7 cells upregulated the expression of HIF-1α protein, mRNA, and the VEGF target gene under CoCl₂-induced hypoxia, which were abolished by plumbagin treatment. In addition, inhibition of HIF-1α and its downstream targets did not affect the signaling transduction of the PI3K/Akt/mTOR pathway under hypoxic state. This study provides mechanistic insight into the anticancer activity of plumbagin in breast cancer cells under hypoxic conditions by abolishing HIF-1α at transcription and post-translational modifications.

The pathophysiological mechanisms underlying diabetic retinopathy

Diabetic retinopathy (DR) is the most common complication of diabetes mellitus (DM), which can lead to visual impairment and even blindness in severe cases. DR is generally considered to be a microvascular disease but its pathogenesis is still unclear. A large body of evidence shows that the development of DR is not determined by a single factor but rather by multiple related mechanisms that lead to different degrees of retinal damage in DR patients. Therefore, this article briefly reviews the pathophysiological changes in DR, and discusses the occurrence and development of DR resulting from different factors such as oxidative stress, inflammation, neovascularization, neurodegeneration, the neurovascular unit, and gut microbiota, to provide a theoretical reference for the development of new DR treatment strategies.

Urolithin A ameliorates diabetic retinopathy via activation of the Nrf2/HO-1 pathway

Diabetic retinopathy (DR) is a progressive microvascular complication of diabetes mellitus and is characterised by excessive inflammation and oxidative stress. Urolithin A (UA), a major metabolite of ellagic acid, exerts anti-inflammatory and antioxidant functions in various human diseases. This study, for the first time, uncovered the role of UA in DR pathogenesis. Streptozotocin-induced diabetic rats were used to determine the effects of UA on blood glucose levels, retinal structures, inflammation, and oxidative stress. High glucose (HG)-induced human retinal endothelial cells (HRECs) were used to elucidate the anti-inflammatory and antioxidant mechanisms of UA in DR in vitro. The in vivo experiments demonstrated that UA injection reduced blood glucose levels, decreased albumin and vascular endothelial growth factor concentrations, and ameliorated the injured retinal structures caused by DR. UA administration also inhibited inflammation and oxidative damage in the retinal tissues of diabetic rats. Similar anti-inflammatory and antioxidant effects of UA were observed in HRECs induced by HG. Furthermore, we found that UA elevated the levels of nuclear Nrf2 and HO-1 both in vivo and in vitro. Nrf2 silencing reversed the inhibitory effects of UA on inflammation and oxidative stress during DR progression. Together, our findings indicate that UA can ameliorate DR by repressing inflammation and oxidative stress via the Nrf2/HO-1 pathway, which suggests that UA could be an effective drug for clinical DR treatment.

New Insights into Treating Early and Advanced Stage Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of preventable blindness in the working-age population. The disease progresses slowly, and we can roughly differentiate two stages: early-stage (ESDR), in which there are mild retinal lesions and visual acuity is generally preserved, and advanced-stage (ASDR), in which the structural lesions are significant and visual acuity is compromised. At present, there are no specific treatments for ESDR and the current recommended action is to optimize metabolic control and maintain close control of blood pressure. However, in the coming years, it is foreseeable that therapeutic strategies based in neuroprotection will be introduced in the clinical arena. This means that screening aimed at identifying patients in whom neuroprotective treatment might be beneficial will be crucial. Regarding the treatment of ASDR, the current primary course is based on laser photocoagulation and intravitreal injections of anti-angiogenic factors or corticosteroids. Repeated intravitreal injections of anti-VEGF agents as the first-line treatment would be replaced by more cost-effective and personalized treatments based on the results of “liquid biopsies” of aqueous humor. Finally, topical administration (i.e., eye drops) of neuroprotective, anti-inflammatory and anti-angiogenic agents will represent a revolution in the treatment of DR in the coming decade. In this article, all these approaches and others will be critically discussed from a holistic perspective.

The association between the use of sodium glucose cotransporter 2 inhibitor and the risk of diabetic retinopathy and other eye disorders: a systematic review and meta-analysis

OBJECTIVE

To assess the association between the use of sodium-glucose cotransporter 2 inhibitor (SGLT2i) and the incidence of diabetic retinopathy (DR).

RESEARCH DESIGN AND METHODS

Pubmed, Medline, Embase, the Cochrane Central Register of Controlled Trials and Clinicaltrial.gov were searched from inception to October 2021. Randomized controlled trials (RCTs) with reports of incidence of DR and other eye disorders between SGLT2i users and non-SGLT2i users with type 2 diabetes mellitus were included.

RESULTS

In general, the incidences of DR were comparable between SGLT2i users and non-SGLT2i users (OR=0.80, 95%CI 0.61 to 1.06, P=0.12). However, compared with non-SGLT2i users, the incidence of DR was significantly reduced in SGLT2i users with diabetes duration less than 10 years (OR=0.32, 95%CI 0.13 to 0.76, P=0.01). Weight reduction in SGLT2i users was associated with the decreased risk of retinal detachment. Moreover, longer study duration was associated with lower incidence of cataract and retinal vasculopathy in SGLT2i users.

CONCLUSIONS

In general, the use of SGLT2i was not associated with the incidence of DR. However, a reduced risk of DR was observed in SGLT2i users with diabetes duration less than 10 years. An early initiation of SGLT2i might be more likely to provide with ocular benefits.

Experiment-Based Interventions to Diabetic Retinopathy: Present and Advances

Diabetic retinopathy is the major blinding disease among working-age populations, which is becoming more significant due to the growth of diabetes. The metabolic-induced oxidative and inflammatory stress leads to the insult of neovascular unit, resulting in the core pathophysiology of diabetic retinopathy. Existing therapies focus on the inflammation, oxidation, and angiogenesis phenomena of diabetic retinopathy, without effect to radically cure the disease. This review also summarizes novel therapeutic attempts for diabetic retinopathy along with their advantages and disadvantages, mainly focusing on those using cellular and genetic techniques to achieve remission on a fundamental level of disease.

Association Between Increased Lipid Profiles and Risk of Diabetic Retinopathy in a Population-Based Case-Control Study

Purpose

We aimed to investigate the association between lipid profiles and diabetic retinopathy (DR).

Patients and Methods

This case-control study, which was conducted between November 2019 and August 2021, comprised 309 patients with DR, 186 patients with diabetes mellitus, and 172 healthy controls. Serum cholesterol (CHOL), triglyceride (TRIG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), small dense LDL-C (SDLDL-C), apolipoprotein A (APOA), APOB, APOE and lipoprotein (a)(LPA) levels were assessed. Patients were divided into two groups according to median age and glycated hemoglobin (HbA1c) level. Linear and logistic regression analyses were performed to assess the association between lipid levels and DR.

Results

CHOL, TRIG, HDL-C, APOB, APOE, and SDLDL-C levels were significantly higher in the DR group than in the healthy control group, and TRIG levels were lower in the DR group than in the DM group (P < 0.05), especially in the ≤57-year-old and the HbA1c ≤7.2% subgroups. Linear regression analyses showed that CHOL, TRIG, APOA, APOB, APOE, and SDLDL-C levels were associated with HbA1c levels. Multivariable logistic regression analyses indicated that CHOL (odds ratio [OR] = 1.32, 95% confidence interval [CI] = 1.112–1.566), TRIG (OR = 1.269, 95% CI = 1.030–1.563), HDL-C (OR = 43.744, 95% CI = 17.12–111.769), APOB (OR = 7.037, 95% CI = 3.370–14.695), APOE (OR = 1.057, 95% CI = 1.038–1.077), and SDLDL-C (OR = 14.719, 95% CI = 8.304–26.088) levels were risk factors for DR (P < 0.05).

Conclusion

Increased lipid levels were risk factors for DR, and lipid level control should be strengthened, especially in younger adults or in patients with HbA1c ≤7.2%.

The effects of vitamin E on non-proliferative diabetic retinopathy in type 2 diabetes mellitus: Are they sustainable with 12 months of therapy

Introduction:

Prolonged uncontrolled hyperglycaemia has shown to cause oxidative stress, inflammation, thrombosis and upregulation of angiogenesis in diabetics, which all contributes to diabetic retinopathy development and progression. Vitamin E is found to have anti-inflammatory, anti-oxidative, anti-thrombogenic and anti-angiogenesis which could play an important role in early treatment of diabetic retinopathy. This study aims to investigate the effect of Tocotrienol-rich vitamin E (Tocovid) on the progression of retinal microhaemorrhages and diabetic macular oedema in patients with diabetic retinopathy.

Method:

This is a multi-centred, randomized, double-blinded, placebo-controlled trial which involved 55 eligible participants. The participants in the treatment group (n = 22) received Tocovid 200 mg twice daily while those in the placebo group (n = 23) would receive placebo twice daily. Both groups will be on the treatment for a total duration of 12 months. Both retinal signs will be assessed at baseline, 2 months, 6 months and 12 months of treatment to determine the progression of diabetic retinopathy. Serum vascular endothelial growth factor which reflects on the angiogenesis process in the eye was analysed as well at similar time points as the retinal findings.

Results:

After 12 months of treatment, the placebo group had a significant increase of 23.42% in retinal microhaemorrhages (p < 0.05), but the Tocovid group had no significant changes. Moreover, the Tocovid group showed a significant decrease of 48.38% in area of diabetic macular oedema over the 12 months period (p < 0.05), but the placebo group had no significant changes. Meanwhile, there was no significant difference in serum vascular endothelial growth factor level when comparing between both groups.

Conclusion:

These findings could indicate that Tocovid has an important role in preventing early diabetic retinopathy progression.

Intravitreal aflibercept for diabetic macular edema in real-world clinical practice in Japan: 24-month outcomes

Purpose

To report the safety and effectiveness of intravitreal aflibercept (IVT-AFL) for diabetic macular edema (DME) in the real-world clinical practice setting in Japan.

Methods

In this prospective, multicenter, observational, post-marketing surveillance, patients with DME newly receiving IVT-AFL were enrolled. During a 24-month follow-up, the primary outcome was the occurrence of safety events. Other pre-specified endpoints were effectiveness indicators, such as best-corrected visual acuity (BCVA), central retinal thickness, and injection frequency.

Results

In total, 646 patients administered at least one IVT-AFL injection were included in the safety analysis. During the follow-up period, adverse events occurred in 42 patients (6.50%), whereas adverse drug reactions occurred in 12 (1.86%). In the 12 patients who had adverse drug reactions, seven events occurred in seven patients within the first month of the most recent injection. In addition, 622 patients were included in the effectiveness analysis set. The number of injections over 24 months was 3.6 ± 3.0 (mean ± standard deviation [SD]). BCVA (logarithm of the minimum angle of resolution) was 0.437 ± 0.362 (mean ± SD) (n = 622) at baseline and 0.321 ± 0.348 (n = 177) after 24 months of treatment with IVT-AFL. Central retinal thickness was 440.8 ± 134.2 μm (mean ± SD) (n = 444) at baseline and 355.5 ± 126.4 μm (n = 140) at 24 months.

Conclusion

Routine administration of IVT-AFL for DME was not associated with new safety concerns, and BCVA outcomes were maintained over 24 months in the real-world setting. Nonetheless, patients in this real-world setting received fewer injections than those in clinical trials, suggesting that a margin for improvement exists in clinical practice.

Trial registration

ClinicalTrials.gov: NCT02425501.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-022-05703-9.

Inhibition of vascular endothelial growth factor alleviates neovascular retinopathy with regulated neurotrophic/proinflammatory cytokines through the modulation of DBI-TSPO signaling

Diazepam binding inhibitor (DBI)-translocator protein (18kDa) (TSPO) signaling in the retina was reported to possess coordinated macroglia-microglia interactions. We investigated DBI-TSPO signaling and its correlation with vascular endothelial growth factor (VEGF), neurotrophic or inflammatory cytokines in neovascular retinopathy, and under hypoxic conditions. The vitreous expression of DBI, VEGF, nerve growth factor (NGF), and interleukin-1beta (IL-1β) were examined in proliferative diabetic retinopathy (PDR) patients with or without anti-VEGF therapy and nondiabetic controls. Retinal DBI-TSPO signaling and the effect of the anti-VEGF agent were evaluated in a mouse model of oxygen-induced retinopathy (OIR). Interactions between Müller cell-derived VEGF and DBI, as well as cocultured microglial cells under hypoxic conditions, were studied, using Western blot, real-time RT-PCR, enzyme-linked immunosorbent assay (ELISA), flow cytometry, and immunofluorescent labeling. Results showed that vitreous levels of DBI, VEGF, NGF, and IL-1β were significantly higher in PDR patients compared with controls, which further changed after anti-VEGF therapy. A statistical association was found between vitreous DBI and VEGF, NGF, IL-1β, and age. The application of the anti-VEGF agent in the OIR model induced retinal expression of DBI and NGF, and attenuated inflammation and microglial cell activation. Inhibition of Müller cell-derived VEGF could increase its DBI expression under hypoxic conditions, while the DBI-TSPO signaling pathway is essential for anti-VEGF agents exerting anti-inflammatory and neuroprotective effects, as well as limiting inflammatory magnitude, promoting its neurotrophin production and anti-inflammatory (M2) polarization in microglial cells. These findings suggest the beneficial effect of anti-VEGF therapy on inflammation and neurotrophy of retinal glial cells through modulation of the DBI-TSPO signaling pathway.

Busulfan Treatment for Myeloproliferative Disease may Reduce Injection Burden in Vascular Endothelial Growth Factor-Driven Retinopathy

Purpose

Methods

Results

Conclusions and importance

Correlation between the progression of diabetic retinopathy and inflammasome biomarkers in vitreous and serum – a systematic review

Activation of the NOD-like receptor protein 3 (NLRP3) inflammasome pathway has been implicated in Diabetic retinopathy (DR) pathogenesis, but its impact on DR development and progression remains unclear. Therefore, the primary aim of this systematic literature review was to determine the role of the inflammasome in DR development. Furthermore, the secondary aim was to determine whether systemic inflammasome activity can be used to predict DR progression. Studies measuring vitreous and/or serum inflammasome biomarkers in DR patients with Type 2 Diabetes Mellitus (T2DM) were searched systematically using online databases EMBASE, PubMed and Web of Science with the last search conducted on 29^th of September 2021. The risk of bias was assessed using the Newcastle Ottawa Scale and 20 studies were eligible for narrative analysis. Limitations included the heterogeneity in detection assays used, the small and uneven sample size, a lack of vitreous data in earlier disease stages, and not accounting for patients with other systemic co-morbidities. Analysis showed that inflammasome biomarkers IL-1β and IL-18 increased significantly from non-proliferative DR to proliferative DR in both vitreous and serum, suggesting the inflammasome pathway is activated as DR progresses and that serum inflammasome levels could be explored as potential biomarkers for DR progression.

Neuronal Dysfunction Is Linked to the Famine-Associated Risk of Proliferative Retinopathy in Patients With Type 2 Diabetes

Persons with type 2 diabetes born in the regions of famine exposures have disproportionally elevated risk of vision-threatening proliferative diabetic retinopathy (PDR) in adulthood. However, the underlying mechanisms are not known. In the present study, we aimed to investigate the plausible molecular factors underlying progression to PDR. To study the association of genetic variants with PDR under the intrauterine famine exposure, we analyzed single nucleotide polymorphisms (SNPs) that were previously reported to be associated with type 2 diabetes, glucose, and pharmacogenetics. Analyses were performed in the population from northern Ukraine with a history of exposure to the Great Ukrainian Holodomor famine [the Diagnostic Optimization and Treatment of Diabetes and its Complications in the Chernihiv Region (DOLCE study), n = 3,583]. A validation of the top genetic findings was performed in the Hong Kong diabetes registry (HKDR, n = 730) with a history of famine as a consequence of the Japanese invasion during WWII. In DOLCE, the genetic risk for PDR was elevated for the variants in ADRA2A, PCSK9, and CYP2C19*2 loci, but reduced at PROX1 locus. The association of ADRA2A loci with the risk of advanced diabetic retinopathy in famine-exposed group was further replicated in HKDR. The exposure of embryonic retinal cells to starvation for glucose, mimicking the perinatal exposure to famine, resulted in sustained increased expression of Adra2a and Pcsk9, but decreased Prox1. The exposure to starvation exhibited a lasting inhibitory effects on neurite outgrowth, as determined by neurite length. In conclusion, a consistent genetic findings on the famine-linked risk of ADRA2A with PDR indicate that the nerves may likely to be responsible for communicating the effects of perinatal exposure to famine on the elevated risk of advanced stages of diabetic retinopathy in adults. These results suggest the possibility of utilizing neuroprotective drugs for the prevention and treatment of PDR.

Insulin like growth factor-1 works synergistically with dopamine to attenuate diabetic retinopathy by downregulating vascular endothelial growth factor

AIM

Levels of Insulin-like growth factor-1 (IGF-1), a proangiogenic growth factor is elevated and dopamine downregulated in proliferative diabetic retinopathy (PDR). This study aims to investigate whether IGF-1 with dopamine can together modulate vascular endothelial growth factor (VEGF) to prevent proliferative diabetic retinopathy while also attenuating angiogenic effects of IGF-1.

METHODS

Effect of combination of levodopa L-Dopa with IGF-1 was tested on normal retinal pigment epithelium cells (ARPE-19) and human umbilical vein endothelial cells (HUVEC), followed by tube formation. Invivo analysis of anti-angiogenic potential assessed by chick chorioallantoic membrane (CAM) assay. Diabetes induction in wistar rats at two time points, 12 and 16 weeks, treated with L-Dopa+IGF-1 and analysed for morphological variations, serum and tissue dopamine levels, gene expression by real-time PCR and western blot assay.

RESULTS

L-Dopa+IGF-1 on ARPE-19 cells caused no toxicity and worked synergistically. Reduced number of vessels observed. Significant improvement in inner retina thickness (*p < 0.05) was observed when L-Dopa was given alone and/or with IGF-1. Dopamine levels improved significantly in both serum and tissue (*p < 0.05). Levels of VEGF and IGF-1 receptors reduced significantly in 12 weeks. Western studies suggest that L-Dopa+IGF-1 modulates its effects via Akt/ERK dependent pathway.

CONCLUSION

First ever report on synergistic effect of L-Dopa+IGF-1 in a rat model of diabetic retinopathy. Even though the effect of L-Dopa in combination with IGF-1 is comparable to levels of L-Dopa alone, this study presents an interesting finding of neuroprotective function of IGF-1, which has been studied in disease models of Parkinson's but not diabetes.

Osteopontin-induced vascular hyperpermeability through tight junction disruption in diabetic retina

Diabetic retinopathy is a major cause of blindness in developed countries, and is characterized by deterioration of barrier function causing vascular hyperpermeability and retinal edema. Vascular endothelial growth factor (VEGF) is a major mediator of diabetic macular edema. Although anti-VEGF drugs are the first-line treatment for diabetic macular edema, some cases are refractory to anti-VEGF therapy. Osteopontin (OPN) is a phosphoglycoprotein with diverse functions and expressed in various cells and tissues. Elevated OPN level has been implicated in diabetic retinopathy, but whether OPN is involved in hyperpermeability remains unclear. Using streptozotocin-induced diabetic mice (STZ mice) and human retinal endothelial cells (HRECs), we tested the hypothesis that up-regulated OPN causes tight junction disruption, leading to vascular hyperpermeability. The serum and retinal OPN concentrations were elevated in STZ mice compared to controls. Intravitreal injection of anti-OPN neutralizing antibody (anti-OPN Ab) suppressed vascular hyperpermeability and prevented decreases in claudin-5 and ZO-1 gene expression levels in the retina of STZ mice. Immunohistochemical staining of retinal vessels in STZ mice revealed claudin-5 immunoreactivity with punctate distribution and attenuated ZO-1 immunoreactivity, and these changes were prevented by anti-OPN Ab. Intravitreal injection of anti-OPN Ab did not change VEGF gene expression or protein concentration in retina of STZ mice. In an in vitro study, HRECs were exposed to normal glucose or high glucose with or without OPN for 48 h, and barrier function was evaluated by transendothelial electrical resistance and Evans blue permeation. Barrier function deteriorated under high glucose condition, and was further exacerbated by the addition of OPN. Immunofluorescence localization of claudin-5 and ZO-1 demonstrated punctate appearance with discontinuous junction in HRECs exposed to high glucose and OPN. There were no changes in VEGF and VEGF receptor-2 expression levels in HRECs by exposure to OPN. Our results suggest that OPN induces tight junction disruption and vascular hyperpermeability under diabetic conditions. Targeting OPN may be an effective approach to manage diabetic retinopathy.

Determining the role of SGLT2 inhibition with Empagliflozin in the development of diabetic retinopathy

Diabetes mellitus is a chronic metabolic disease that occurs when the pancreas is not producing enough insulin or when the insulin that it does produce is not able to be used effectively in the body. This results in hyperglycemia and if the blood sugars are not controlled, then it can lead to serious damage of various body systems, especially the nerves and the blood vessels. Uncontrolled diabetes is a major cause of kidney failure, heart attacks, stroke and amputation. One of the most devastating complications for patients is diabetic retinopathy (DR) which represents the leading cause of preventable vision loss in people between 20 and 65 years of age. Sodium glucose transporter 2 (SGLT2) inhibitors have been shown to reduce the risk for cardiovascular and renal events, however literature highlighting their potential role to prevent DR is limited. We therefore used a relevant mouse model (Akimba) to explore the effects of the SGLT2 inhibitor, Empagliflozin (EMPA), on the development of diabetic retinal changes. Here we show that when given in the early stages of type 1 diabetes (T1D), EMPA reduced the weight loss usually associated with T1D, decreased diabetes-associated polydipsia, lowered fasting blood glucose levels, decreased kidney-to-body weight ratios and, most importantly in the current context, substantially reduced retinal abnormalities associated with DR. We show that EMPA reduces vascular leakage indicated by lower albumin staining in the vitreous humor and diminishes expression of the pathogenic factor VEGF in the retina. Additionally, EMPA significantly alters the retinal genetic signature. Our findings suggest that SGLT2 inhibition may be a useful therapeutic approach to prevent the development of DR and its severity if given early in the disease process.

Contribution of Müller Cells in the Diabetic Retinopathy Development: Focus on Oxidative Stress and Inflammation

Diabetic retinopathy is a neurovascular complication of diabetes and the main cause of vision loss in adults. Glial cells have a key role in maintenance of central nervous system homeostasis. In the retina, the predominant element is the Müller cell, a specialized cell with radial morphology that spans all retinal layers and influences the function of the entire retinal circuitry. Müller cells provide metabolic support, regulation of extracellular composition, synaptic activity control, structural organization of the blood–retina barrier, antioxidant activity, and trophic support, among other roles. Therefore, impairments of Müller actions lead to retinal malfunctions. Accordingly, increasing evidence indicates that Müller cells are affected in diabetic retinopathy and may contribute to the severity of the disease. Here, we will survey recently described alterations in Müller cell functions and cellular events that contribute to diabetic retinopathy, especially related to oxidative stress and inflammation. This review sheds light on Müller cells as potential therapeutic targets of this disease.

Steroid Treatment in Macular Edema: A Bibliometric Study and Visualization Analysis

The use of steroids to treat macular edema (ME) is a research hotspot in ophthalmology. We utilized CiteSpace and VOSviewer software to evaluate the Web of Science Core Collection publications and to build visualizing maps to describe the research progress in this topic. There were 3,252 publications for three decades during 1988–2021. The number of studies was low during the first 14 years but has risen consistently in the following two decades. The average publications per year were only 4.8 during 1988–2002, which jumped to 113 per year during 2003–2012, and 227 per year during 2013–2021. These publications came from 83 countries/regions, with the United States, Germany, and Italy leading positions. Most studies were published in Investigative Ophthalmology Visual Science, and Ophthalmology was the most cited journal. We found 9,993 authors, with Bandello F having the most publications and Jonas JB being the most frequently co-cited. According to our research, the most popular keyword is triamcinolone acetonide (TA). Macular edema, diabetic macular edema (DME), retinal vein occlusion (RVO), dexamethasone (DEX), fluocinolone acetonide (FA), and some other keywords were commonly studied in this field. In conclusion, the bibliometric analysis provides a comprehensive overview of steroid hotspots and developmental tendencies in the macular edema study. While anti-VEGF therapy is the first-line treatment for DME and RVO-induced macular edema, steroids implant is a valid option for these DME patients not responding to anti-VEGF therapy and non-DME patients with macular edema. Combined therapy with anti-VEGF and steroid agents is vital for future research.

Evaluation of Microvascular and Visual Acuity Changes in Patients with Early Diabetic Retinopathy: Optical Coherence Tomography Angiography Study

Purpose

Comparison of early microvascular changes detected by optical coherence tomography angiography (OCTA) in patients with mild non-proliferative diabetic retinopathy (NPDR) with healthy volunteers.

Patients and Methods

Forty-four eyes of 44 type-2 diabetic patients with mild non-proliferative diabetic retinopathy and 30 eyes of 30 age-matched healthy controls were imaged using OCTA to quantify microvascular changes and the FAZ quantitative parameters (area, perimeter, and circularity index); the values of patients and controls were then compared.

Results

Macular vessel density, perfusion index, and circularity index values were reduced and positively correlated with visual acuity in patients (15.4 ± 2.6, 38.0 ± 6.7, 0.6 ± 0.06 and p = 0.003, 0.001, and 0.003, respectively). However, FAZ area and perimeter were found to be larger in patients than controls (0.30 ± 0.08, 2.5 ± 0.3 and p < 0.001).

Conclusion

OCTA quantified vessel density and perfusion density were found to be correlated with visual acuity and FAZ parameters in patients with early NPDR; this could help in detecting early disease progression and modifying treatment decisions.

Perspectives on diabetic retinopathy from advanced retinal vascular imaging

Diabetic retinopathy (DR) is a microvascular complication of diabetes and the most common cause of acquired vision loss in adults worldwide. DR is associated with long-term chronic hyperglycaemia and its detrimental effects on the neurovascular structure and function of the retina. Direct imaging of the retinal vasculature and staging of DR has been traditionally based on fundoscopy and fluorescein angiography, which provide only 2D views of the retina, and in the case of fluorescein angiography, requires an invasive dye injection. In contrast, advanced retinal imaging modalities like optical coherence tomography angiography (OCTA) and adaptive optics (AO) are non-invasive and provide depth-resolved, 3D visualization of retinal vessel structure as well as blood flow. Recent studies utilizing these imaging techniques have shown promise in evaluating quantitative vascular parameters that correlate tightly to clinical DR staging, elucidating functional changes in early diabetes, and monitoring DR treatment response. In this article, we discuss and synthesize the results of advanced retinal imaging studies in DR and their implications for our clinical and pathophysiologic understanding of the disease. Based on the recent literature, we also propose a model to describe the differential changes in vascular structure and flow that have been described on advanced retinal imaging as DR progresses. Future studies of these imaging modalities in larger and more diverse populations, as well as corroboration with histological and functional studies, will be important to further our understanding of DR.

Inflammation in obesity, diabetes, and related disorders

Obesity leads to chronic, systemic inflammation and can lead to insulin resistance (IR), β-cell dysfunction, and ultimately type 2 diabetes (T2D). This chronic inflammatory state contributes to long-term complications of diabetes, including non-alcoholic fatty liver disease (NAFLD), retinopathy, cardiovascular disease, and nephropathy, and may underlie the association of type 2 diabetes with other conditions such as Alzheimer's disease, polycystic ovarian syndrome, gout, and rheumatoid arthritis. Here, we review the current understanding of the mechanisms underlying inflammation in obesity, T2D, and related disorders. We discuss how chronic tissue inflammation results in IR, impaired insulin secretion, glucose intolerance, and T2D and review the effect of inflammation on diabetic complications and on the relationship between T2D and other pathologies. In this context, we discuss current therapeutic options for the treatment of metabolic disease, advances in the clinic and the potential of immune-modulatory approaches.

CD8+T Cell-Related Gene Biomarkers in Macular Edema of Diabetic Retinopathy

BACKGROUND

CD8+T lymphocytes have a strong pro-inflammatory effect in all parts of the tissue, and some studies have demonstrated that its concentration in the vitreous increased significantly, suggesting that CD8+T cells play a pivotal role in the inflammatory response of diabetic retinopathy (DR). However, the infiltration of CD8+T cells in the DR retina, especially in diabetic macular edema (DME), and its related genes are still unclear.

METHODS

Download the GSE16036 dataset from the Gene Expression Omnibus (GEO) database. The ImmuCellAI program was performed to evaluate the abundance of 24 immune cells including CD8+T cells. The CD8+T cell-related genes (DECD8+TRGs) between non-proliferative diabetic retinopathy (NPDR) and DME were detected via difference analysis and correlation analysis. Enrichment analysis and protein-protein interaction (PPI) network mapping were implemented to explore the potential function of DECD8+TRGs. Lasso regression, support vector machine recursive feature elimination (SVM-RFE), CytoHubba plug-in and MCODE plug-in in Cytoscape software, and Weighted Gene Co-Expression Network Analysis (WGCNA) were performed to comprehensively analyze and obtain Hub DECD8+TRGs. Hub DECD8+TRGs expression patterns were further validated in other two DR-related independent datasets. The CD8+TRG score was defined as the genetic characterization of Hub DECD8+TRGs using the GSVA sample scoring method, which can be administered to distinguish early and advanced diabetic nephropathy (DN) as well as normal and DN. Finally, the transcription level of DECD8+TRGs in DR model mouse were verified by quantitative real-time PCR (qPCR).

RESULTS

A total of 371 DECD8+TRGs were identified, of which 294 genes were positively correlated and only 77 genes were negatively correlated. Eight genes (IKZF1, PTPRC, ITGB2, ITGAX, TLR7, LYN, CD74, SPI1) were recognized as Hub DECD8+TRGs. DR and DN, which have strong clinical correlation, have been proved to be associated with CD8+T cell-related hub genes by multiple independent data sets. Hub DECD8+TRGs can not only distinguish PDR from normal and DN from normal, but also play a role in the early and progressive stages of the two diseases (NPDR vs DME, Early DN vs Advanced DN). The qPCR transcription level and trend of Hub DECD8+TRGs in DR mouse model was basically the same as that in human transcriptome.

CONCLUSION

This study not only increases our understanding of the molecular mechanism of CD8+T cells in the progression of DME, but also expands people's cognitive vision of the molecular mechanism of crosstalk of CD8+T cells in the eyes and kidneys of patients with diabetes.

Animal models of diabetic microvascular complications: Relevance to clinical features

Diabetes has become more common in recent years worldwide, and this growth is projected to continue in the future. The primary concern with diabetes is developing various complications, which significantly contribute to the disease's mortality and morbidity. Over time, the condition progresses from the pre-diabetic to the diabetic stage and then to the development of complications. Years and enormous resources are required to evaluate pharmacological interventions to prevent or delay the progression of disease or complications in humans. Appropriate screening models are required to gain a better understanding of both pathogenesis and potential therapeutic agents. Different species of animals are used to evaluate the pharmacological potentials and study the pathogenesis of the disease. Animal models are essential for research because they represent most of the structural, functional, and biochemical characteristics of human diseases. An ideal screening model should mimic the pathogenesis of the disease with identifiable characteristics. A thorough understanding of animal models is required for the experimental design to select an appropriate model. Each animal model has certain advantages and limitations. The present manuscript describes the animal models and their diagnostic characteristics to evaluate microvascular diabetic complications.

The tumour neovasculature-homing dimeric peptide GX1 demonstrates antiangiogenic activity in the retinal neovasculature

Identification of molecules specific to the retinal neovasculature will promote antiangiogenic therapy with enhanced targeting ability. The specificity of phage-displayed peptide GX1 (a cyclic 7-mer peptide motif CGNSNPKSC) to gastric cancer neovasculature has been extensively confirmed both in vitro and in vivo. To investigate the potential application of GX1 in antiangiogenic therapy targeting retinal angiogenesis-related diseases, we performed immunohistochemistry and immunofluorescence analyses. GX1 demonstrated positive staining in the retinal neovasculature in an oxygen-induced mouse model of retinopathy (OIR) as well as in rat retinal microvasculature endothelial cells (RMECs), confirming the major role of the GX1 receptor during retinal angiogenesis. Dimeric GX1 was synthesized to increase the binding affinity to the GX1 receptor, and the antiangiogenic effects were examined in RMECs in vitro and the retinal neovasculature in the OIR in vivo. Cell proliferation was evaluated using a Cell Counting Kit-8 (CCK-8) assay, revealing that compared with the GX1 monomer, dimeric GX1 significantly inhibited RMEC proliferation (P < 0.05). This finding may be attributed to the enhanced (P < 0.05) apoptosis induced by dimeric GX1 in RMECs based on results obtained from TUNEL, flow cytometric and cell cycle analyses. In RMECs, in vitro cell migration and tube formation were significantly inhibited following exposure to dimeric GX1. Intravitreal administration of dimeric GX1 resulted in a greater reduction in the retinal neovascularization in vivo than administration of the GX1 monomer (P < 0.05). In conclusion, dimeric GX1 showed greater inhibition of angiogenesis than monomeric GX1 and could be a promising agent for antiangiogenic therapy in retinal angiogenesis-related diseases.

Intravitreal corticosteroids for diabetic macular edema: a network meta-analysis of randomized controlled trials

BACKGROUND

To evaluate the efficacy and safety of different intravitreal corticosteroids for treating diabetic macular edema (DME).

METHODS

Four databases were systematically searched for randomized controlled trials comparing different intravitreal corticosteroids for treating DME. The primary outcome was the change in best-corrected visual acuity (BCVA) within 6 months after the first injection (short-term BCVA). Secondary outcomes were the change in BCVA over 1 year (long-term BCVA) and changes in central macular thickness (CMT) and intraocular pressure (IOP) within 6 months after the first injection. Network meta-analysis was performed to aggregate the results from the individual studies.

RESULTS

Nineteen trials involving 2839 eyes were included. Intravitreal triamcinolone acetonide (TA) injections (≥ 8 mg and 4-8 mg), fluocinolone acetonide (FA) implants (0.5 µg/day) and dexamethasone (DEX) implants (700 µg) improved short-term BCVA (mean changes in logMAR [95% confidence interval] - 0.27 [- 0.40, - 0.15]; - 0.12 [- 0.18, - 0.06]; - 0.10 [- 0.21, - 0.01]; and - 0.06 [- 0.11, - 0.01]). Intravitreal TA injections (4 mg, multiple times), FA implants (0.5 µg/day and 0.2 µg/day), and DEX implants (350 µg) improved long-term BCVA (mean changes in logMAR [95% confidence interval] - 0.11 [- 0.21, - 0.02]; - 0.09 [- 0.15, - 0.03]; - 0.09 [- 0.14, - 0.02]; and - 0.04 [- 0.07, - 0.01]). All intravitreal corticosteroids reduced CMT, and different dosages of TA did not show significant differences in increasing IOP.

CONCLUSIONS

Intravitreal corticosteroids effectively improved BCVA in DME patients, with higher dosages showing greater efficacies. TA was not inferior to FA or DEX and may be considered a low-cost alternative choice for DME patients. The long-term efficacy and safety of different corticosteroids deserve further investigation. Trial registration Prospectively registered: PROSPERO, CRD42020219870.

Inhibition of APE1/Ref-1 for Neovascular Eye Diseases: From Biology to Therapy

Proliferative diabetic retinopathy (PDR), neovascular age-related macular degeneration (nvAMD), retinopathy of prematurity (ROP) and other eye diseases are characterized by retinal and/or choroidal neovascularization, ultimately causing vision loss in millions of people worldwide. nvAMD and PDR are associated with aging and the number of those affected is expected to increase as the global median age and life expectancy continue to rise. With this increase in prevalence, the development of novel, orally bioavailable therapies for neovascular eye diseases that target multiple pathways is critical, since current anti-vascular endothelial growth factor (VEGF) treatments, delivered by intravitreal injection, are accompanied with tachyphylaxis, a high treatment burden and risk of complications. One potential target is apurinic/apyrimidinic endonuclease 1/reduction-oxidation factor 1 (APE1/Ref-1). The multifunctional protein APE1/Ref-1 may be targeted via inhibitors of its redox-regulating transcription factor activation activity to modulate angiogenesis, inflammation, oxidative stress response and cell cycle in neovascular eye disease; these inhibitors also have neuroprotective effects in other tissues. An APE1/Ref-1 small molecule inhibitor is already in clinical trials for cancer, PDR and diabetic macular edema. Efforts to develop further inhibitors are underway. APE1/Ref-1 is a novel candidate for therapeutically targeting neovascular eye diseases and alleviating the burden associated with anti-VEGF intravitreal injections.

Chitosan coated nanoparticles for efficient delivery of bevacizumab in the posterior ocular tissues via subconjunctival administration

In several ocular diseases, vascular endothelial growth factor (VEGF) level has been found to be unregulated. Bevacizumab, an anti-VEGF drug, is the most commonly used off level drug for diabetic retinopathy (DR). The present study was to evaluate the chitosan-coated poly (lactide-co-glycolic acid) nanoparticles (CS-PLGA NPs) for sustained and effective delivery of bevacizumab to posterior ocular tissues. The penetration of NP through sclera was studied by confocal laser scanning microscopy (CLSM). For pharmacokinetic study, bevacizumab loaded NPs were administered into the rat eye through subconjunctival injection (SCJ) and pharmacokinetic parameters were compared to drug solution. CLSM and pharmacokinetic study showed better penetration of formulation and higher concentration of bevacizumab in posterior ocular tissues. In retinopathy model, CS-PLGA NPs by SCJ route showed more reduction of VEGF level in retina than the topical and intravitreal administration of formulation. Thus, CS-coated PLGA NPs can be potentially useful as carriers to target retina.