Emerging Insights and Interventions for Diabetic Retinopathy

CD40 Induces Unfolded Protein Response, Upregulation of VEGF, and Vascular Leakage in Diabetic Retinopathy

The unfolded protein response (UPR) drives events that promote diabetic retinopathy, including vascular endothelial growth factor (VEGF) upregulation in Müller cells. How UPR is activated in vivo in the diabetic retina is not well understood. CD40 is required for development of diabetic retinopathy, but whether CD40 mediates activation of UPR sensors is unknown. CD40 ligation in Müller cells caused phospholipase Cγ1 (PLCγ1)-dependent activation of UPR sensors (PERK, IRE1α, and ATF6α) and VEGF production dependent on PLCγ1 and UPR sensors. Diabetic Cd40-/- mice did not exhibit UPR activation or VEGF upregulation in the retina. These responses were restored in diabetic Cd40-/- mice rescued to express wild-type CD40 in Müller cells but not in mice rescued to express a CD40 mutation unable to recruit TRAF2/3. Intravitreal administration of a cell-permeable CD40-TRAF2/3-disrupting peptide reduced UPR activation, VEGF upregulation, and vascular leakage in diabetic mice. CD40 and TRAF2 in Müller cells from patients with diabetic retinopathy colocalized with activated UPR sensors and VEGF. Our study indicates that CD40 (via TRAF2/3 signaling) is an inducer of UPR activation that triggers VEGF production in Müller cells. This work uncovered inhibition of CD40-TRAF2/3 signaling as a potential approach to impair UPR activation, VEGF upregulation, and vascular leakage in diabetic retinopathy.

ARTICLE HIGHLIGHTS

Downregulation of MerTK in circulating T cells of patients with non-proliferative diabetic retinopathy

Objective

To explore the differential gene expression in peripheral blood immune cells of individuals with type 2 diabetes mellitus (DM), comparing those with and without non-proliferative diabetic retinopathy (NPDR).

Methods

From a pool of 126 potential participants, 60 were selected for detailed analysis. This group included 12 healthy donors (HDs), 22 individuals with DM, and 26 with NPDR. We analyzed peripheral blood mononuclear cells (PBMCs) using RNA sequencing and quantitative PCR (qPCR) to pinpoint differentially expressed genes (DEGs). Western blot and flow cytometry were also employed to evaluate the protein expression of specific genes.

Results

In patients with NPDR compared to those with DM alone, MerTK-a gene implicated in inherited retinal dystrophies due to its mutations-was notably downregulated in PBMCs. Through flow cytometry, we assessed the protein levels and cellular distribution of MerTK, finding a predominant expression in monocytes and myeloid-derived suppressor cells (MDSCs), with a marked reduction in CD4+ and CD8+ T cells, as well as in natural killer T (NKT) cells. Patients with DM demonstrated a significant deviation in the PBMCs composition, particularly in B cells, CD4+ T cells, and NK cells, when compared to HDs.

Conclusions

The study indicates that MerTK expression in T cells within PBMCs could act as a viable blood biomarker for NPDR risk in patients with DM. Furthermore, the regulation of T cells by MerTK might represent a critical pathway through which DM evolves into NPDR.

Associations of retinal neurovascular dysfunction with inner retinal layer thickness in non-proliferative diabetic retinopathy

PURPOSE

Neurovascular coupling impairment and inner retinal layer thinning are early detectable retinal changes in diabetes, and both worsen during progression of diabetic retinopathy (DR). However, direct interactions between these features have not been investigated so far. Therefore, we aimed to analyze associations between the retinal functional hyperemic response to light stimulation and the thickness of individual neuroretinal layers in eyes with early non-proliferative DR.

METHODS

Thirty patients with type 1 diabetes featuring mild (n = 15) or moderate (n = 15) non-proliferative DR and 14 healthy subjects were included in this cross-sectional study. Retinal vessel diameters were measured before and during illumination with flickering light using a dynamic vessel analyzer. Individual layer thickness in the macula was analyzed from spectral domain optical coherence tomography.

RESULTS

Flicker light-induced vessel dilation was significantly reduced in patients compared to healthy controls (veins: 3.0% vs. 6.1%, p < 0.001; arteries: 1.3% vs. 5.1%, p = 0.005). Univariately, the response in retinal veins of diabetes patients correlated significantly with ganglion cell layer (GCL) thickness (r = 0.46, p = 0.010), and negatively with hemoglobin A1c (HbA1c) levels (r=-0.41, p = 0.023) and age (r=-0.38, p = 0.037), but not with baseline diameters, glucose levels, or diabetes duration. In a multiple regression model only GCL thickness (p = 0.017, β = 0.42) and HbA1c (p = 0.045, β=-0.35) remained significantly associated with the vascular flicker light response.

CONCLUSION

The results indicate that thinner GCL and worse glycemic control both contribute to reduced retinal neurovascular coupling in patients with clinical signs of DR. Progression of neurovascular dysfunction in DR might be related to structural degeneration of the neurovascular complex in the inner retina.

Relationship of fibroblast growth factor 21, Klotho, and diabetic retinopathy: a meta-analysis

Background

Diabetic retinopathy (DR) is a serious microvascular complication of diabetes mellitus. Research has identified a close relationship between fibroblast growth factor 21 (FGF21) and DR. FGF21 is a member of the FGF subfamily, which is activated by the Klotho coenzyme involved in the occurrence of DR. However, the association between FGF21, Klotho, and DR remains controversial.

Aim

To assess FGF21 and Klotho levels in patients with DR.

Methods

A literature search of the Web of Science, Wiley Online Library, PubMed, China National Knowledge Infrastructure and Wanfang databases was performed. The title or abstract search terms "diabetic retinopathy" and "DR" were used in combination with "fibroblast growth factor 21", "FGF21", and "Klotho". Meta-analysis results are presented as standardized mean difference (SMD) with corresponding 95% confidence interval (CI).

Results

Fifteen studies were included in this meta-analysis. FGF21 levels in patients with DR were significantly higher than in non-DR patients with diabetes (SMD: 2.12, 95% CI [1.40, 2.84]). Klotho levels in patients with DR were significantly lower than in non-DR patients with diabetes (SMD: -0.63, 95% CI [-1.22, - 0.04]).

Conclusions

This systematic review is the first to evaluate the relationship between FGF21, Klotho levels, and DR. FGF21 levels were significantly higher in patients with DR. Fully elucidating the role of FGF21 will significantly contribute to the treatment of DR.

AAV2-antiVEGFscFv gene therapy for retinal neovascularization

Retinal neovascularization (NV) may lead to irreversible vision impairment, the main treatment for which is the inhibition of vascular endothelial growth factor (VEGF). Existing drugs show limited clinical benefits because of their high prices and short half-lives, which increase the financial burden and medical risks to patients. Gene therapy on the basis of adeno-associated viruses is a promising approach to overcome these limitations because of the nonintegrative nature, low immunogenicity, and potential long-term gene expression of adeno-associated viruses. In this study, we constructed a novel recombinant adeno-associated virus with the single-chain fragment variable (scFv) fragment of the anti-VEGF antibody, AAV2-antiVEGFscFv, consisting of the VH and VL structural domains of IgG. AAV2-antiVEGFscFv effectively inhibited NV, retinal leakage, and retinal detachment in oxygen-induced retinopathy (OIR) mice, Tet/opsin/VEGF double-transgenic mice, and VEGF-induced rabbit NV models. AAV2-antiVEGFscFv also significantly suppressed VEGF-induced inflammation. Furthermore, we showed that AAV2-antiVEGFscFv could be sustainably expressed for a prolonged period and exhibited low immunotoxicity in vivo. This study indicates that AAV2-antiVEGFscFv could be a potential approach for NV treatment and provides strong support for preclinical research.

Aberrant SUMO2/3 modification of RUNX1 upon SENP1 inhibition is linked to the development of diabetic retinopathy in mice

Our previous report established that RUNX family transcription factor 1 (RUNX1) promotes proliferation of mouse retinal microvascular endothelial cells (mRMECs) and exacerbates diabetic retinopathy (DR). However, the mechanism behind the upregulation of RUNX1 remains unclear. This study aims to investigate the possible correlation between histone SUMOylation and RUNX1 in DR, as well as the involved molecules. A mouse model of diabetes was induced by streptozotocin (STZ). These mice had increased retinal thickness and elevated production of inflammatory cytokines. Additionally, they showed elevated levels of SUMO1 and SUMO2/3, but reduced levels of SUMO specific peptidase 1 (SENP1) in retinal tissues. Co-immunoprecipitation and Western blot assays revealed that the RUNX1 protein was primarily modified by SUMO2/3, and SENP1 inhibited SUMO2/3 modification, thereby reducing RUNX1 expression. Overexpression of SENP1 alleviated symptoms in mice and alleviated inflammation. In vitro experiments demonstrated that the SENP1 overexpression suppressed the proliferation, migration, and angiogenesis of high-glucose-induced mRMECs. However, further overexpression of RUNX1 counteracted the alleviating effects of SENP1 both in vivo and in vitro. In conclusion, this study demonstrates that the downregulation of SENP1 in DR leads to SUMO2/3-dependent activation of RUNX1. This activation promotes proliferation of mRMECs and exacerbates DR symptoms in mice.

Dysregulated CD200-CD200R signaling in early diabetes modulates microglia-mediated retinopathy

Diabetic retinopathy (DR) is a neurovascular complication of diabetes. Recent investigations have suggested that early degeneration of the neuroretina may occur prior to the appearance of microvascular changes; however, the mechanisms underlying this neurodegeneration have been elusive. Microglia are the predominant resident immune cell in the retina and adopt dynamic roles in disease. Here, we show that ablation of retinal microglia ameliorates visual dysfunction and neurodegeneration in a type I diabetes mouse model. We also provide evidence of enhanced microglial contact and engulfment of amacrine cells, ultrastructural modifications, and transcriptome changes that drive inflammation and phagocytosis. We show that CD200-CD200R signaling between amacrine cells and microglia is dysregulated during early DR and that targeting CD200R can attenuate high glucose-induced inflammation and phagocytosis in cultured microglia. Last, we demonstrate that targeting CD200R in vivo can prevent visual dysfunction, microglia activation, and retinal inflammation in the diabetic mouse. These studies provide a molecular framework for the pivotal role that microglia play in early DR pathogenesis and identify a potential immunotherapeutic target for treating DR in patients.

Determinants of diabetic retinopathy in Ethiopia: A systematic review and meta-analysis

INTRODUCTION

Diabetic retinopathy (DR) is the primary retinal vascular complication of diabetes mellitus and a leading cause of visual impairment and blindness. It affects the global diabetic population. In Ethiopia, about one-fifth of diabetic patients were affected by DR, but there were inconsistent finding across studies about the determinants factors of DR. Therefore, we aimed to identify the risk factors for DR among diabetic patients.

METHODS

We have accessed previous studies through an electronic web-based search strategy using PubMed, Google (Scholar), the Web of Science, and the Cochrane Library with a combination of search terms. The quality of each included article was assessed using the Newcastle Ottawa Assessment Scale. All statistical analyses were carried out using Stata version 14 software. The odds ratios of risk factors were pooled using a fixed-effect meta-analysis model. Heterogeneity was assessed using the Cochrane Q statistics and I-Square (I2). Furthermore, publication bias was detected based on the graphic asymmetry test of the funnel plot and/or Egger's test (p< 0.05).

RESULTS

The search strategy retrieved 1285 articles. After the removal of duplicate articles, 249 articles remained. Following further screening, about 18 articles were assessed for eligibility, of which three articles were excluded because of reporting without the outcome of interest, poor quality, and not full text. Finally, fifteen studies were reviewed for the final analysis. Co-morbid hypertension (HTN) (AOR 2.04, 95%CI: 1.07, 3.89), poor glycemic control (AOR = 4.36, 95%CI: 1.47, 12.90), and duration of diabetes illness (AOR = 3.83, 95%CI: 1.17, 12.55) were found to be confirmed associated factors of diabetic retinopathy.

CONCLUSION

In this study, co-morbid HTN, poor glycemic control, and longer duration of diabetes illness were found to be the determinant factors of DR. Aggressive treatment of co-morbid HTN and blood glucose, and regular eye screening should be implemented to reduce the occurrence of DR.

TRIAL REGISTRATION

The review protocol was registered in the international prospective register of systematic reviews (PROSPERO) with registration number PROSPERO: CRD42023416724.

New Insights on Dietary Polyphenols for the Management of Oxidative Stress and Neuroinflammation in Diabetic Retinopathy

Diabetic retinopathy (DR) is a neurodegenerative and vascular pathology that is considered one of the leading causes of blindness worldwide, resulting from complications of advanced diabetes mellitus (DM). Current therapies consist of protocols aiming to alleviate the existing clinical signs associated with microvascular alterations limited to the advanced disease stages. In response to the low resolution and limitations of the DR treatment, there is an urgent need to develop more effective alternative therapies to optimize glycemic, vascular, and neuronal parameters, including the reduction in the cellular damage promoted by inflammation and oxidative stress. Recent evidence has shown that dietary polyphenols reduce oxidative and inflammatory parameters of various diseases by modulating multiple cell signaling pathways and gene expression, contributing to the improvement of several chronic diseases, including metabolic and neurodegenerative diseases. However, despite the growing evidence for the bioactivities of phenolic compounds, there is still a lack of data, especially from human studies, on the therapeutic potential of these substances. This review aims to comprehensively describe and clarify the effects of dietary phenolic compounds on the pathophysiological mechanisms involved in DR, especially those of oxidative and inflammatory nature, through evidence from experimental studies. Finally, the review highlights the potential of dietary phenolic compounds as a prophylactic and therapeutic strategy and the need for further clinical studies approaching the efficacy of these substances in DR management.

MG53 represses high glucose-induced inflammation and angiogenesis in human retinal endothelial cells by repressing the EGR1/STAT3 axis

BACKGROUND

Diabetic retinopathy (DR) is a vascular complication of diabetes mellitus that leads to visual injury and blindness. Both angiogenesis and inflammation play an important role in the pathogenesis of DR. Here we aimed to explore the mechanisms of mitsugumin 53 (MG53) in ameliorating the dysfunction induced by high glucose (HG) in humans retinal microvascular endothelial cells (HRECs).

METHODS

HRECs were subjected to HG in the presence or absence of MG53 overexpression. The effect of MG53 on cell viability and inflammatory response in HG-treated HRECs was measured using the Cell Counting Kit-8 and ELISAs, respectively. Expression of MG53, EGR1, p-STAT3, FGF2, TGFB1, and Angiopoietin-1 in HG-treated HRECs was quantified by western blot or quantitative real-time polymerase chain reaction.

RESULTS

HG significantly downregulated MG53 in HRECs, which reduced cell viability while inducing angiogenesis and inflammatory response. Upregulation of MG53 reversed these effects of HG. MG53 directly interacted with EGR1 and repressed its expression, which decreased phosphorylation of STAT3 and downregulated FGF2, TGFB1, and Angiopoietin-1. EGR1 up-regulation or STAT3 activation antagonized the protective effects of MG53.

CONCLUSION

MG53 alleviates HG-induced dysfunction in HRECs by repressing EGR1/STAT3 signaling. Thereby MG53 may have therapeutic potential in DR.

Axon guidance molecules in immunometabolic diseases

The global prevalence of metabolic diseases, such as obesity, diabetes, and atherosclerosis, is rapidly increasing and has now reached epidemic proportions. Chronic tissue inflammation is a characteristic of these metabolic diseases, indicating that immune responses are closely involved in the pathogenesis of metabolic disorders. However, the regulatory mechanisms underlying immunometabolic crosstalk in these diseases are not completely understood. Recent studies have revealed the multifaceted functions of semaphorins, originally identified as axon guidance molecules, in regulating tissue inflammation and metabolic disorders, thereby highlighting the functional coupling between semaphorin signaling and immunometabolism. In this review, we explore how semaphorin signaling transcends beyond merely guiding axons to controlling immune responses and metabolic diseases.

Weight Reduction as an Adjunctive Management Strategy for Diabetic Retinopathy

As rates of global obesity and diabetes increase, diabetic retinopathy continues to grow as a frequent cause of visual impairment. Despite tremendous recent strides in therapy, a significant fraction of patients remain poorly responsive to modern interventions. Adjunctive therapy in such settings could be widely beneficial. A growing body of evidence suggests that weight reduction strategies for obesity-related diabetes have the potential to serve as important supplements to modern ophthalmic care for preservation of vision.

Aqueous angiopoietin-like levels correlate with optical coherence tomography angiography metrics in diabetic macular edema

AIM

To quantitatively detect aqueous levels of angiopoietin-like (ANGPTL)3, ANGPTL4, and ANGPTL6 and investigate their correlation with optical coherence tomography angiography (OCTA) findings in patients with diabetic macular edema (DME).

METHODS

This cross-sectional study included 23 patients (27 eyes) with type 2 diabetes and 16 control subjects (20 eyes). All patients underwent OCTA imaging and ultra-wide field fundus photography. Diabetic patients were categorized into two groups according to the presence or absence of diabetic retinopathy (DME group, 14 patients, 16 eyes); and non-diabetic retinopathy (NDR) group, 9 patients, 11 eyes, respectively. Aqueous levels of ANGPTL3, ANGPTL4, and ANGPTL6 were assessed using suspension array technology, and foveal-centered 3×3 mm² OCTA scans were automatically graded to determine the central, inner, and full vessel density (CVD, IVD, FVD); central, inner, and full perfusion density (CPD, IPD, FPD), foveal avascular zone (FAZ) area, FAZ perimeter, and FAZ circularity index (FAZ-CI) on superficial capillary plexuses. Additionally, central subfield thickness (CST), cube volume (CV), and cube average thickness (CAT) were measured in a model of macular cube 512×128.

RESULTS

Aqueous ANGPTL3 levels were not significantly different among the three groups (P>0.05). ANGPTL4 levels were significantly higher in the DME group than the control and NDR groups (P<0.0001 and P<0.001), while ANGPTL6 levels were significantly higher in the DME group than the control group (P<0.05). In the whole cohort, the aqueous ANGPTL3 levels correlated negatively with the IVD, FVD, IPD, and FPD, and positively with the CV and CAT. The aqueous ANGPTL4 levels correlated negatively with the CVD, IVD, FVD, CPD, IPD, and FPD, and positively with the FAZ perimeter, CST, CV, and CAT. The aqueous ANGPTL6 levels correlated negatively with the IVD, FVD, IPD, FPD, FAZ-CI and positively with CST, CV, CAT.

CONCLUSION

ANGPTL4 and ANGPTL6 may be associated with vascular leakage in DME and may represent good targets for DME therapy. In addition, OCTA metrics may be useful for evaluating macular ischemia in DME.

Pediatric Diabetic Retinopathy: Updates in Prevalence, Risk Factors, Screening, and Management

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus and a major cause of vision loss worldwide. The purpose of this review is to provide an update on the prevalence of diabetic retinopathy in youth, discuss risk factors, and review recent advances in diabetic retinopathy screening.

RECENT FINDINGS

While DR has long been considered a microvascular complication, recent data suggests that retinal neurodegeneration may precede the vascular changes associated with DR. The prevalence of DR has decreased in type 1 diabetes (T1D) patients following the results of the Diabetes Control and Complications Trial and implementation of intensive insulin therapy, with prevalence ranging from 14-20% before the year 2000 to 3.7-6% after 2000. In contrast, the prevalence of diabetic retinopathy in pediatric type 2 diabetes (T2D) is higher, ranging from 9.1-50%. Risk factors for diabetic retinopathy are well established and include glycemic control, diabetes duration, hypertension, and hyperlipidemia, whereas diabetes technology use including insulin pumps and continuous glucose monitors has been shown to have protective effects. Screening for DR is recommended for youth with T1D once they are aged ≥ 11 years or puberty has started and diabetes duration of 3-5 years. Pediatric T2D patients are advised to undergo screening at or soon after diagnosis, and annually thereafter, due to the insidious nature of T2D. Recent advances in DR screening methods including point of care and artificial intelligence technology have increased access to DR screening, while being cost-saving to patients and cost-effective to healthcare systems. While the prevalence of diabetic retinopathy in youth with T1D has been declining over the last few decades, there has been a significant increase in the prevalence of DR in youth with T2D. Improving access to diabetic retinopathy screening using novel screening methods may help improve detection and early treatment of diabetic retinopathy.

Toward a New Staging System for Diabetic Retinopathy Using Wide Field Swept-Source Optical Coherence Tomography Angiography

PURPOSE OF REVIEW

For over 50 years, diabetic retinopathy (DR) has been classified by pathologic features seen on clinical examination and conventional retinal photographs. However, newer technology such as optical coherence tomography angiography (OCTA) now enables rapid acquisition of retinal structural and vascular information in a reliable, non-invasive, high-resolution fashion. Here, we highlight recent studies that have explored wide field swept-source OCTA (WF SS-OCTA) for the diagnosis and management of DR.

RECENT FINDINGS

Multiple studies have demonstrated the utility of WF SS-OCTA for detection of all clinically relevant features of DR. An updated DR staging system is proposed that leverages the advantages of WF SS-OCTA, including the ability to correlate detailed vascular and structural pathology over time with longitudinal imaging. WF SS-OCTA has tremendous potential for evaluating patients with DR. A new WF SS-OCTA-based staging system may be useful in routine clinical practice and for clinical trials.

Glucose-mediated de novo lipogenesis in photoreceptors drives early diabetic retinopathy

Diabetic retinopathy (DR) is an increasingly frequent cause of blindness across populations; however, the events that initiate pathophysiology of DR remain elusive. Strong preclinical and clinical evidence suggests that abnormalities in retinal lipid metabolism caused by diabetes may account for the origin of this disease. A major arm of lipid metabolism, de novo biosynthesis, is driven by elevation in available glucose, a common thread binding all forms of vision loss in diabetes. Therefore, we hypothesized that aberrant retinal lipid biogenesis is an important promoter of early DR. In murine models, we observed elevations of diabetes-associated retinal de novo lipogenesis ∼70% over control levels. This shift was primarily because of activation of fatty acid synthase (FAS), a rate-limiting enzyme in the biogenic pathway. Activation of FAS was driven by canonical glucose-mediated disinhibition of acetyl-CoA carboxylase, a major upstream regulatory enzyme. Mutant mice expressing gain-of-function FAS demonstrated increased vulnerability to DR, whereas those with FAS deletion in rod photoreceptors maintained preserved visual responses upon induction of diabetes. Excess retinal de novo lipogenesis—either because of diabetes or because of FAS gain of function—was associated with modestly increased levels of palmitate-containing phosphatidylcholine species in synaptic membranes, a finding with as yet uncertain significance. These findings implicate glucose-dependent increases in photoreceptor de novo lipogenesis in the early pathogenesis of DR, although the mechanism of deleterious action of this pathway remains unclear.

Neurovascular regulation in diabetic retinopathy and emerging therapies

Diabetic retinopathy (DR) is the leading cause of vision loss in working adults in developed countries. The disease traditionally classified as a microvascular complication of diabetes is now widely recognized as a neurovascular disorder resulting from disruption of the retinal neurovascular unit (NVU). The NVU comprising retinal neurons, glia and vascular cells coordinately regulates blood flow, vascular density and permeability to maintain homeostasis. Disturbance of the NVU during DR can lead to vision-threatening clinical manifestations. A limited number of signaling pathways have been identified for intercellular communication within the NVU, including vascular endothelial growth factor (VEGF), the master switch for angiogenesis. VEGF inhibitors are now widely used to treat DR, but their limited efficacy implies that other signaling molecules are involved in the pathogenesis of DR. By applying a novel screening technology called comparative ligandomics, we recently discovered secretogranin III (Scg3) as a unique DR-selective angiogenic and vascular leakage factor with therapeutic potential for DR. This review proposes neuron-derived Scg3 as the first diabetes-selective neurovascular regulator and discusses important features of Scg3 inhibition for next-generation disease-targeted anti-angiogenic therapies of DR.

KAT1 triggers YTHDF2-mediated ITGB1 mRNA instability to alleviate the progression of diabetic retinopathy

Diabetic retinopathy (DR) is a major complication of diabetes and a leading cause of blindness and visual impairment. This study focuses on the function of lysine acetyltransferase 1 (KAT1) in the progression of DR and the epigenetic mechanism. A mouse model with DR was induced by streptozotocin (STZ). Abundantly expressed genes in STZ-induced mice were analyzed. KAT1 was found to be significantly downregulated in the retinal tissues of model mice. Retinal microvascular endothelial cells (RMECs) and retinal Müller cells (rMCs) were cultured in high-glucose medium for in vitro studies. Upregulation of KAT1 suppressed inflammation, neovascularization, and vascular leakage in mouse retinal tissues, and it reduced the activity and inflammatory responses in rMCs, as well as the proliferation and metastatic potential of RMECs. KAT1 activated the transcription activity of YTHDF2 through histone acetylation of the promoter, and YTHDF2 triggered the instability of ITGB1 mRNA to induce mRNA degradation in an m6A manner. The activities of rMCs and RMECs were increased by sh-YTHDF2 but suppressed by sh-ITGB1. The FAK/PI3K/AKT signaling pathway was suppressed upon ITGB1 silencing. Collectively, this study demonstrated that KAT1 triggers YTHDF2-mediated ITGB1 mRNA instability to alleviate the progression of DR.

Network pharmacology and molecular docking study on the active ingredients of qidengmingmu capsule for the treatment of diabetic retinopathy

Diabetic retinopathy (DR) is a leading cause of irreversible blindness globally. Qidengmingmu Capsule (QC) is a Chinese patent medicine used to treat DR, but the molecular mechanism of the treatment remains unknown. In this study, we identified and validated potential molecular mechanisms involved in the treatment of DR with QC via network pharmacology and molecular docking methods. The results of Ingredient-DR Target Network showed that 134 common targets and 20 active ingredients of QC were involved. According to the results of enrichment analysis, 2307 biological processes and 40 pathways were related to the treatment effects. Most of these processes and pathways were important for cell survival and were associated with many key factors in DR, such as vascular endothelial growth factor-A (VEGFA), hypoxia-inducible factor-1A (HIF-1Α), and tumor necrosis factor-α (TNFα). Based on the results of the PPI network and KEGG enrichment analyses, we selected AKT1, HIF-1α, VEGFA, TNFα and their corresponding active ingredients for molecular docking. According to the molecular docking results, several key targets of DR (including AKT1, HIF-1α, VEGFA, and TNFα) can form stable bonds with the corresponding active ingredients of QC. In conclusion, through network pharmacology methods, we found that potential biological mechanisms involved in the alleviation of DR by QC are related to multiple biological processes and signaling pathways. The molecular docking results also provide us with sound directions for further experiments.

Sodium-glucose co-transporter 2 inhibitors and diabetic retinopathy: insights into preservation of sight and looking beyond

Sodium-glucose co-transporter 2 Inhibitors (SGLT2i) were initially developed as therapeutic options for patients with type 2 diabetes mellitus (T2DM). Recently, randomized clinical trials have investigated their effects in cardiorenal protection through major adverse cardiovascular event reduction and reductions in diabetic nephropathy. While multiple mechanisms are proposed for this protection, microvascular protection is the primary component of their efficacy. While not primarily emphasized in clinical trials, evidence in other studies suggests that SGLT2i may confer retinoprotective effects via some of the same mechanisms in the aforementioned cardiorenal trials. Diabetic patients are susceptible to vision loss with chronic hyperglycemia promoting inflammation, edema, and retinal pathological changes. Targeting these pathways via SGLT2i may represent opportunities for providers to decrease retinopathy in high-risk T2DM patients, reduce disease progression, and lower drug burden in diabetic retinopathy patients. Further comprehensive clinical trials investigating these associations are needed to establish the potential retinoprotective effects of SGLT2i.

Photoreceptor responses to light in the pathogenesis of diabetic retinopathy

Vision loss, among the most feared complications of diabetes, is primarily caused by diabetic retinopathy, a disease that manifests in well-recognized, characteristic microvascular lesions. The reasons for retinal susceptibility to damage in diabetes are unclear, especially considering that microvascular networks are found in all tissues. However, the unique metabolic demands of retinal neurons could account for their vulnerability in diabetes. Photoreceptors are the first neurons in the visual circuit and are also the most energy-demanding cells of the retina. Here, we review experimental and clinical evidence linking photoreceptors to the development of diabetic retinopathy. We then describe the influence of retinal illumination on photoreceptor metabolism, effects of light modulation on the severity of diabetic retinopathy, and recent clinical trials testing the treatment of diabetic retinopathy with interventions that impact photoreceptor metabolism. Finally, we introduce several possible mechanisms that could link photoreceptor responses to light and the development of retinal vascular disease in diabetes. Collectively, these concepts form the basis for a growing body of investigative efforts aimed at developing novel pharmacologic and nonpharmacologic tools that target photoreceptor physiology to treat a very common cause of blindness across the world.

VEGF, apelin and HO-1 in diabetic patients with retinopathy: a correlation analysis

BACKGROUND

It's necessary to analyze the role of VEGF, apelin, and HO-1 in patients with type 2 diabetes (T2DM), and to evaluate its relevance to diabetic retinopathy (DR).

METHODS

T2DM patients who were treated in our hospital from December 1, 2018 to November 30, 2019 were included. T2DM patients were divided into non-DR (NDR) group, non-proliferative DR (NPDR) group, and proliferative DR (PDR) group. and healthy participants were selected as the control group. The value of VEGF, apelin, and HO1 in predicting PDR were analyzed by receiver operating characteristic (ROC) curve, and the relations of VEGF, apelin, HO-1 and clinical factors in PDR patients were analyzed by Pearson correlation analysis.

RESULTS

A total of 295 participants were included. The level of FPG and HbAlc in PDR group were significantly higher than that of other groups (all p < 0.05); the level of VEGF and apelin in PDR group were significantly higher than that of other groups (all p < 0.05), but the level of HO-1 in PDR group were significantly less than that of other groups(p = 0.017); the AUC of VEGF, apelin, HO-1 and combined use was 0.806(95%CI: 0.779-0.861), 0.819(95%CI: 0.765-0.878), 0.808(95%CI: 0.733-0.869) and 0.902(95%CI: 0.822-0.958) respectively, the AUC, sensitivity, specificity of the three combined use was significantly higher than that of single VEGF, apelin, HO-1 use(all p < 0.05). The cutoff values of serum VEGF, apelin, and HO-1 levels for predicting PDR were 163.85 pg/ml, 8.27 ng/ml, and 26.06 mmol/L respectively. Serum VEGF, apelin, and HO-1 in patients with PDR was related to the time course of DM, FPG and HbAlc (all p < 0.05).

CONCLUSIONS

VEGF, apelin and HO-1 are related to the progress of DR, and the combined use of VEGF, apelin and HO-1 is beneficial to the diagnosis and treatment of PDR.

The Role of Semaphorins in Metabolic Disorders

Semaphorins are a family originally identified as axonal guidance molecules. They are also involved in tumor growth, angiogenesis, immune regulation, as well as other biological and pathological processes. Recent studies have shown that semaphorins play a role in metabolic diseases including obesity, adipose inflammation, and diabetic complications, including diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, diabetic wound healing, and diabetic osteoporosis. Evidence provides mechanistic insights regarding the role of semaphorins in metabolic diseases by regulating adipogenesis, hypothalamic melanocortin circuit, immune responses, and angiogenesis. In this review, we summarize recent progress regarding the role of semaphorins in obesity, adipose inflammation, and diabetic complications.

Dysfunctional Nurr1 promotes high glucose-induced Müller cell activation by up-regulating the NF-κB/NLRP3 inflammasome axis

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus (DM). During DR, high glucose levels induce Müller cell gliosis, and the dysfunction of Müller cells further promotes the pathogenesis of DR. Transcription factor nuclear receptor subfamily 4 group A member 2 (Nurr1) inhibits the inflammatory response by suppressing nuclear factor-kappa B (NF-κB) and downregulating the downstream NACHT, LRR and PYD domain-containing protein 3 (NLRP3) inflammasome. This study aimed to investigate whether Nurr1 dysfunction in Müller cells promoted the NF-κB/NLRP3 inflammasome axis during DR. In vitro, Nurr1 expression and nuclear translocation decreased in Müller cells exposed to high glucose levels; therefore, p65 was activated, and the downstream NLRP3 inflammasome was up-regulated via the interaction of p65 with its promoter. These phenomena promoted Müller cell activation and proliferation. Moreover, in vivo, gavage of the Nurr1 agonist C-DIM12 reduced retinal ganglion cell (RGC) loss in a mouse model of streptozotocin (STZ)-induced diabetes. Together, these results showed that Nurr1 played important anti-inflammatory and neuroprotective roles in Müller cells during DR, suggesting that Nurr1 may be a potential molecular target for the treatment of DR.

Diabetic Retinopathy Screening with Automated Retinal Image Analysis in a Primary Care Setting Improves Adherence to Ophthalmic Care

PURPOSE

Retinal screening examinations can prevent vision loss resulting from diabetes but are costly and highly underused. We hypothesized that artificial intelligence-assisted nonmydriatic point-of-care screening administered during primary care visits would increase the adherence to recommendations for follow-up eye care in patients with diabetes.

DESIGN

Prospective cohort study.

PARTICIPANTS

Adults 18 years of age or older with a clinical diagnosis of diabetes being cared for in a metropolitan primary care practice for low-income patients.

METHODS

All participants underwent nonmydriatic fundus photography followed by automated retinal image analysis with human supervision. Patients with positive or inconclusive screening results were referred for comprehensive ophthalmic evaluation. Adherence to referral recommendations was recorded and compared with the historical adherence rate from the same clinic.

MAIN OUTCOME MEASURE

Rate of adherence to eye screening recommendations.

RESULTS

By automated screening, 8.3% of the 180 study participants had referable diabetic eye disease, 13.3% had vision-threatening disease, and 29.4% showed inconclusive results. The remaining 48.9% showed negative screening results, confirmed by human overread, and were not referred for follow-up ophthalmic evaluation. Overall, the automated platform showed a sensitivity of 100% (confidence interval, 92.3%-100%) in detecting an abnormal screening results, whereas its specificity was 65.7% (confidence interval, 57.0%-73.7%). Among patients referred for follow-up ophthalmic evaluation, the adherence rate was 55.4% at 1 year compared with the historical adherence rate of 18.7% (P < 0.0001, Fisher exact test).

CONCLUSIONS

Implementation of an automated diabetic retinopathy screening system in a primary care clinic serving a low-income metropolitan patient population improved adherence to follow-up eye care recommendations while reducing referrals for patients with low-risk features.

Adjuvant Therapies in Diabetic Retinopathy as an Early Approach to Delay Its Progression: The Importance of Oxidative Stress and Inflammation

Diabetes mellitus (DM) is a progressive disease induced by a sustained state of chronic hyperglycemia that can lead to several complications targeting highly metabolic cells. Diabetic retinopathy (DR) is a multifactorial microvascular complication of DM, with high prevalence, which can ultimately lead to visual impairment. The genesis of DR involves a complex variety of pathways such as oxidative stress, inflammation, apoptosis, neurodegeneration, angiogenesis, lipid peroxidation, and endoplasmic reticulum (ER) stress, each possessing potential therapeutic biomarkers. A specific treatment has yet to be developed for early stages of DR since no management is given other than glycemic control until the proliferative stage develops, offering a poor visual prognosis to the patient. In this narrative review article, we evaluate different dietary regimens, such as the Mediterranean diet, Dietary Pattern to Stop Hypertension (DASH) and their functional foods, and low-calorie diets (LCDs). Nutraceuticals have also been assessed in DR on account of their antioxidant, anti-inflammatory, and antiangiogenic properties, which may have an important impact on the physiopathology of DR. These nutraceuticals have shown to lower reactive oxygen species (ROS), important inflammatory factors, cytokines, and endothelial damage biomarkers either as monotherapies or combined therapies or concomitantly with established diabetes management or nonconventional adjuvant drugs like topical nonsteroidal anti-inflammatory drugs (NSAIDs).

Troxerutin downregulates C/EBP-β gene expression via modulating the IFNγ-ERK1/2 signaling pathway to ameliorate rotenone-induced retinal neurodegeneration

Troxerutin, a natural flavonoid guards against oxidative stress and apoptosis with a high capability of passing through the blood-brain barrier. Our aim was to investigate the role of troxerutin in experimentally induced retinal neurodegeneration by modulating the interferon-gamma (IFNγ)-extracellular signal-regulated kinases 1/2 (ERK1/2)-CCAAT enhancer-binding protein β (C/EBP-β) signaling pathway. Three groups of rats (10 each group) were included. Group I (control group), group II (rotenone treated group): the rats were injected subcutaneously with a single rotenone dosage of 3 mg/kg repeated every 48 hours for 60 days to trigger retinal neurodegeneration. Group III (troxerutin-treated group): rats received troxerutin (150 mg/kg/day) by oral gavage 1 hour before rotenone administration. A real-time polymerase chain reaction technique was applied to measure messenger RNA (mRNA) levels of retinal C/EBP-β. Enzyme-linked immunosorbent assay technique was utilized to assay tumor necrosis factor-α (TNF-α), IFNγ, and ERK1/2 levels. Finally, reactive oxygen species (ROS), as well as carbonylated protein (CP) levels, were assessed spectrophotometrically. Improved retinal neurodegeneration by downregulation of C/EBP-β mRNA gene expression, also caused a significant reduction of TNF-α, IFNγ, ERK1/2 as well as ROS and CP levels compared with the diseased group. These findings could hold promise for the usage of troxerutin as a protective agent against rotenone-induced retinal neurodegeneration.

Light deprivation reduces the severity of experimental diabetic retinopathy

Illumination of the retina is a major determinant of energy expenditure by its neurons. However, it remains unclear whether light exposure significantly contributes to the pathophysiology of common retinal disease. Driven by the premise that light exposure reduces the metabolic demand of the retina, recent clinical trials failed to demonstrate a benefit for constant illumination in the treatment of diabetic retinopathy. Here, we instead ask whether light deprivation or blockade of visual transduction could modulate the severity of this common cause of blindness. We randomized adult mice with two different models of diabetic retinopathy to 1-3 months of complete dark housing. Unexpectedly, we find that diabetic mice exposed to short or prolonged light deprivation have reduced diabetes-induced retinal pathology, using measures of visual function, compared to control animals in standard lighting conditions. To corroborate these results, we performed assays of retinal vascular health in diabetic Gnat1^-/- and Rpe65^-/- mice, which lack phototransduction. Both mutants displayed less diabetes-associated retinal vascular disease compared to respective wild-type controls. Collectively, these results suggest that light-induced visual transduction promotes the development of diabetic retinopathy and implicate photoreceptors as an early source of visual pathology in diabetes.