New treatments for diabetic retinopathy

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.

Therapeutic potential of flavopiridol in diabetic retinopathy: Targeting DDX58

Diabetic retinopathy (DR), a common complication of diabetes, is characterized by inflammation and neovascularization, and is intricately regulated by the ubiquitin-proteasome system (UPS). Despite advancements, identifying ubiquitin-related genes and drugs specifically targeting DR remains a significant challenge. In this study, bioinformatics analyses and the Connectivity Map (CMAP) database were utilized to explore the therapeutic potential of genes and drugs for DR. Through these methodologies, flavopiridol was identified as a promising therapeutic candidate. To evaluate flavopiridol's therapeutic potential in DR, an in vitro model using Human Umbilical Vein Endothelial Cells (HUVECs) induced by high glucose (HG) conditions was established. Additionally, in vivo models using mice with streptozotocin (STZ)-induced DR and oxygen-induced retinopathy (OIR) were employed. The current study reveals that flavopiridol possesses robust anti-inflammatory and anti-neovascularization properties. To further elucidate the molecular mechanisms of flavopiridol, experimental validation and molecular docking techniques were employed. These efforts identified DDX58 as a predictive target for flavopiridol. Notably, our research demonstrated that flavopiridol modulates the DDX58/NLRP3 signaling pathway, thereby exerting its therapeutic effects in suppressing inflammation and neovascularization in DR. This study unveils groundbreaking therapeutic agents and innovative targets for DR, and establishes a progressive theoretical framework for the application of ubiquitin-related therapies in DR.

Advances in Research Related to MicroRNA for Diabetic Retinopathy

Diabetic retinopathy (DR) is a severe microvascular complication of diabetes and is one of the primary causes of blindness in the working-age population in Europe and the United States. At present, no cure is available for DR, but early detection and timely intervention can prevent the rapid progression of the disease. Several treatments for DR are known, primarily ophthalmic treatment based on glycemia, blood pressure, and lipid control, which includes laser photocoagulation, glucocorticoids, vitrectomy, and antivascular endothelial growth factor (anti-VEGF) medications. Despite the clinical efficacy of the aforementioned therapies, none of them can entirely shorten the clinical course of DR or reverse retinopathy. MicroRNAs (miRNAs) are vital regulators of gene expression and participate in cell growth, differentiation, development, and apoptosis. MicroRNAs have been shown to play a significant role in DR, particularly in the molecular mechanisms of inflammation, oxidative stress, and neurodegeneration. The aim of this review is to systematically summarize the signaling pathways and molecular mechanisms of miRNAs involved in the occurrence and development of DR, mainly from the pathogenesis of oxidative stress, inflammation, and neovascularization. Meanwhile, this article also discusses the research progress and application of miRNA-specific therapies for DR.

The glucocorticoid receptor as a master regulator of the Müller cell response to diabetic conditions in mice

Diabetic retinopathy (DR) is considered a primarily microvascular complication of diabetes. Müller glia cells are at the centre of the retinal neurovascular unit and play a critical role in DR. We therefore investigated Müller cell-specific signalling pathways that are altered in DR to identify novel targets for gene therapy. Using a multi-omics approach on purified Müller cells from diabetic db/db mice, we found the mRNA and protein expression of the glucocorticoid receptor (GR) to be significantly decreased, while its target gene cluster was down-regulated. Further, oPOSSUM TF analysis and ATAC- sequencing identified the GR as a master regulator of Müller cell response to diabetic conditions. Cortisol not only increased GR phosphorylation. It also induced changes in the expression of known GR target genes in retinal explants. Finally, retinal functionality was improved by AAV-mediated overexpression of GR in Müller cells. Our study demonstrates an important role of the glial GR in DR and implies that therapeutic approaches targeting this signalling pathway should be aimed at increasing GR expression rather than the addition of more ligand.

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.

A Nonrandomized Phase 2 Trial of EG-Mirotin, a Novel, First-in-Class, Subcutaneously Deliverable Peptide Drug for Nonproliferative Diabetic Retinopathy

Background and objectives: EG-Mirotin (active ingredient EGT022) targets nonproliferative diabetic retinopathy (NPDR), the early stage of retinopathy. EG-Mirotin reverses capillary damage before NPDR progresses to an irreversible stage. EG-Mirotin safety and efficacy were investigated in patients with type 1 or type 2 diabetes mellitus and moderate to severe NPDR. Methods: In this open-label, single-arm, single-center, exploratory phase II study, 10 patients (20 eyes) received EG-Mirotin once a day (3 mg/1.5 mL sterile saline) for 5 days and were evaluated for ischemic index changes and safety. End of study was approximately 8 ± 1 weeks (57 ± 7 days) after the first drug administration. Results: EG-Mirotin injections were well tolerated, with no dose-limiting adverse events, serious adverse events, or deaths. Four treatment-emergent adverse events (TEAEs) unrelated to the investigational drug were observed in 2 out of 10 participants (20%) who had received the investigational drug. The overall average percent change in ischemic index at each evaluation point compared with baseline was statistically significant (Greenhouse-Geisser F = 9.456, p = 0.004 for the main effect of time), and a larger change was observed when the baseline ischemic index value was high (Greenhouse-Geisser F = 10.946, p = 0.002 for time × group interaction). Conclusions: The EG-Mirotin regimen established in this study was shown to be feasible and safe and was associated with a trend toward potential improvement in diabetes-induced ischemia and retinal capillary leakage.

Acylcarnitines in Ophthalmology: Promising Emerging Biomarkers

Several common ocular diseases are leading causes of irreversible visual impairment. Over the last decade, various mainly untargeted metabolic studies have been performed to show that metabolic dysfunction plays an important role in the pathogenesis of ocular diseases. A number of metabolites in plasma/serum, aqueous or vitreous humor, or in tears have been found to differ between patients and controls; among them are L-carnitine and acylcarnitines, which are essential for mitochondrial fatty acid oxidation. The metabolic profile of carnitines regarding a variety of diseases has attracted researchers' interest. In this review, we present and discuss recent advances that have been made in the identification of carnitines as potential metabolic biomarkers in common ocular diseases, such as age-related macular degeneration, diabetic retinopathy, retinopathy of prematurity, central retinal vein occlusion, primary open-angle glaucoma, rhegmatogenous retinal detachment, and dry eye syndrome.

Th22 cells induce Müller cell activation via the Act1/TRAF6 pathway in diabetic retinopathy

T helper 22 (Th22) cells have been implicated in diabetic retinopathy (DR), but it remains unclear whether Th22 cells involve in the pathogenesis of DR. To investigate the role of Th22 cells in DR mice, the animal models were established by intraperitoneal injection of STZ and confirmed by fundus fluorescein angiography and retinal haematoxylin-eosin staining. IL-22BP was administered by intravitreal injection. IL-22 level was measured by ELISA in vivo and in vitro. The expression of IL-22Rα1 in the retina was assessed by immunofluorescence. We assessed GFAP, VEGF, ICAM-1, inflammatory-associated factors and the integrity of blood-retinal barrier in control, DR, IL-22BP, and sham group. Müller cells were co-cultured with Th22 cells, and the expression of the above proteins was measured by immunoblotting. Plasmid transfection technique was used to silence Act1 gene in Müller cells. Results in vivo and in vitro indicated that Th22 cells infiltrated into the DR retinal and IL-22Rα1 expressed in Müller cells. Th22 cells promoted Müller cells activation and inflammatory factor secretion by secreting IL-22 compared with high-glucose stimulation alone. In addition, IL-22BP ameliorated the pathological alterations of the retina in DR. Inhibition of the inflammatory signalling cascade through Act1 knockdown alleviated DR-like pathology. All in all, the results suggested that Th22 cells infiltrated into the retina and secreted IL-22 in DR, and then IL-22 binding with IL-22Rα1 activated the Act1/TRAF6 signal pathway, and promoted the inflammatory of Müller cells and involved the pathogenesis of DR.

Berberis dictyophylla F. inhibits angiogenesis and apoptosis of diabetic retinopathy via suppressing HIF-1α/VEGF/DLL-4/Notch-1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Xiao Bopi (XBP, སྐྱེར་བའི་བར་ཤུན།), as a classical Tibetan medicinal plant in China, which derived from the stem bark of Berberis dictyophylla F., has the function of "clearing heat and decreasing mKhris-pa". And it traditionally is utilized to treat the diabetes mellitus and its complications, such as diabetic retinopathy (DR). However, its underlying mechanisms remain unclear.

AIM OF THE STUDY

The purpose of this study aimed to explore the microvascular protection of water extract of XBP against the spontaneous retinal damage of db/db mice. Meanwhile, the underlying mechanisms of XBP on angiogenesis and apoptosis were further interpreted.

MATERIALS AND METHODS

We firstly used high-performance liquid chromatography to detected the representative chemical ingredients in the water extract of XBP. The DR model of db/db mice was then randomly divided into five groups: model group, calcium dobesilate (0.23 g/kg) group, and the water extract of XBP (0.375, 0.75 and 1.5 g/kg, respectively) groups. After 8 weeks of continuous administration, the parameters including body weight, fasting blood glucose, oral glucose tolerance test and insulin tolerance test were measured. The pathological changes and abnormal angiogenesis of the retina were detected by optical coherence tomography, HE, periodic acid-Schiff staining and transmission electron microscopy. Simultaneously, molecular docking was used to predict the potential connections between representative ingredients in XBP and angiogenesis/apoptosis-related proteins. The level of angiogenesis-related proteins and gene hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth (VEGF), delta-like ligand 4 (DLL-4) and Notch-1 were estimated by immunofluorescence analyses and real time-PCR. Further, TUNEL staining and immunofluorescence analyses were performed to investigate the apoptotic phenomenon and the expression of Bax, Bcl-2, Apaf-1, Cyto-c and cleaved caspase-3 and cleaved caspase-9 in the retina.

RESULTS

Phytochemical analysis revealed that magnoflorine, jatrorrhizine, palmatine and berberine were principally representative ingredients in XBP. The results demonstrated that XBP effectively increased glucose tolerance and insulin sensitivity, whereas no effect on body weight of DR mice. Moreover, retinal thickening, pathological and retinal ultrastructure changes in DR mice were evidently ameliorated by XBP. The molecular docking results demonstrated that the main components of XBP and the protein of angiogenesis and apoptosis had a potential bind. XBP restrained the gene and protein levels of HIF-1α, VEGF, DLL-4 and Notch-1 in retina. Additionally, the TUNEL-positive cell rate and the down-regulated proteins of Bax, Apaf-1, Cyto-c, cleaved Caspase-3 and cleaved Caspase 9 and increased Bcl-2 level were revised by XBP.

CONCLUSIONS

To sum up, the results suggested that XBP against DR could attribute to alleviating angiogenesis and apoptosis by suppressing the HIF-1α/VEGF/DLL-4/Notch-1 pathway. This evidence sheds a new light on the potential mechanisms of XBP in the treatment of DR.

Advances in cell therapies using stem cells/progenitors as a novel approach for neurovascular repair of the diabetic retina

BACKGROUND

Diabetic retinopathy, a major complication of diabetes mellitus, is a leading cause of sigh-loss in working age adults. Progressive loss of integrity of the retinal neurovascular unit is a central element in the disease pathogenesis. Retinal ischemia and inflammatory processes drive interrelated pathologies such as blood retinal barrier disruption, fluid accumulation, gliosis, neuronal loss and/or aberrant neovascularisation. Current treatment options are somewhat limited to late-stages of the disease where there is already significant damage to the retinal architecture arising from degenerative, edematous and proliferative pathology. New preventive and interventional treatments to target early vasodegenerative and neurodegenerative stages of the disease are needed to ensure avoidance of sight-loss.

MAIN BODY

Historically, diabetic retinopathy has been considered a primarily microvascular disease of the retina and clinically it is classified based on the presence and severity of vascular lesions. It is now known that neurodegeneration plays a significant role during the pathogenesis. Loss of neurons has been documented at early stages in pre-clinical models as well as in individuals with diabetes and, in some, even prior to the onset of clinically overt diabetic retinopathy. Recent studies suggest that some patients have a primarily neurodegenerative phenotype. Retinal pigment epithelial cells and the choroid are also affected during the disease pathogenesis and these tissues may also need to be addressed by new regenerative treatments. Most stem cell research for diabetic retinopathy to date has focused on addressing vasculopathy. Pre-clinical and clinical studies aiming to restore damaged vasculature using vasoactive progenitors including mesenchymal stromal/stem cells, adipose stem cells, CD34+ cells, endothelial colony forming cells and induced pluripotent stem cell derived endothelial cells are discussed in this review. Stem cells that could replace dying neurons such as retinal progenitor cells, pluripotent stem cell derived photoreceptors and ganglion cells as well as Müller stem cells are also discussed. Finally, challenges of stem cell therapies relevant to diabetic retinopathy are considered.

CONCLUSION

Stem cell therapies hold great potential to replace dying cells during early and even late stages of diabetic retinopathy. However, due to the presence of different phenotypes, selecting the most suitable stem cell product for individual patients will be crucial for successful treatment.

Intravitreal administration of recombinant human opticin protects against hyperoxia-induced pre-retinal neovascularization

Opticin is an extracellular glycoprotein present in the vitreous. Its antiangiogenic properties offer the potential for therapeutic intervention in conditions such as proliferative diabetic retinopathy and retinopathy of prematurity. Here, we investigated the hypothesis that intravitreal administration of recombinant human opticin can safely protect against the development of pathological angiogenesis and promote its regression. We generated and purified recombinant human opticin and investigated its impact on the development and regression of pathological retinal neovascularization following intravitreal administration in murine oxygen-induced retinopathy. We also investigated its effect on normal retinal vascular development and function, following intravitreal injection in neonatal mice, by histological examination and electroretinography. In oxygen-induced retinopathy, intravitreal administration of human recombinant opticin protected against the development of retinal neovascularization to similar extent as aflibercept, which targets VEGF. Opticin also accelerated regression of established retinal neovascularization, though the effect at 18 h was less than that of aflibercept. Intravitreal administration of human recombinant opticin in neonatal mice caused no detectable perturbation of subsequent retinal vascular development or function. In summary we found that intraocular administration of recombinant human opticin protects against the development of pathological angiogenesis in mice and promotes its regression.

MicroRNA-139-5p Alleviates High Glucose-Triggered Human Retinal Pigment Epithelial Cell Injury by Targeting LIM-Only Factor 4

Diabetic retinopathy (DR) is a type of diabetes complication, which can result in loss of vision in adults worldwide. Increasing evidence has revealed that microRNAs (miRs) can regulate DR progression. Thus, the present study was aimed at assessing the possible mechanism of miR-139-5p in high glucose- (HG-) incubated retinal pigment epithelial (ARPE-19) cells. The present results demonstrated that miR-139-5p expression was notably reduced in the serum samples of patients with DR, as well as in ARPE-19 cells treated with HG in a time-dependent manner. Moreover, miR-139-5p was markedly overexpressed by transfection of miR-139-5p mimics into ARPE-19 cells. Overexpression of miR-139-5p markedly induced cell viability and repressed HG-triggered apoptosis. Furthermore, overexpression of miR-139-5p relived HG-enhanced oxidative stress injury. It was found that HG induced malondialdehyde levels but decreased superoxide dismutase and glutathione peroxidase activities in ARPE-19 cells. In addition, overexpression of miR-139-5p could markedly decrease intracellular stress. The results demonstrated that overexpression of miR-139-5p effectively repressed HG-activated inflammation, as indicated by the upregulation of inflammation cytokines, including TNF-α, IL-6, and Cox-2, in ARPE-19 cells. Subsequently, it was identified that LIM-only factor 4 (LMO4) could act as a downstream target for miR-139-5p. LMO4 expression was significantly increased in patients with DR and HG-treated ARPE-19 cells. Mechanistically, knockdown of LMO4 reversed the biological role of miR-139-5p in proliferation, apoptosis, oxidative stress, and release of inflammation factors in vitro. Collectively, these results suggested that miR-139-5p significantly decreased ARPE-19 cell injury caused by HG by inducing proliferation and suppressing cell apoptosis, oxidant stress, and inflammation by modulating LMO4.

High-risk coronary artery plaque in asymptomatic patients with type 2 diabetes: clinical risk factors and coronary artery calcium score

BACKGROUND

High-risk coronary artery plaque (HRP) is associated with increased risk of acute coronary syndrome. We aimed to investigate the prevalence of HRP in asymptomatic patients with type 2 diabetes (T2D), and its relation to patient characteristics including cardiovascular risk factors, diabetes profile, and coronary artery calcium score (CACS).

METHODS

Asymptomatic patients with T2D and no previous coronary artery disease (CAD) were studied using coronary computed tomography angiography (CCTA) in this descriptive study. Plaques with two or more high-risk features (HRP) defined by low attenuation, positive remodeling, spotty calcification, and napkin-ring sign were considered HRP. In addition, total atheroma volume (TAV), proportions of dense calcium, fibrous, fibrous-fatty and necrotic core volumes were assessed. The CACS was obtained from non-enhanced images by the Agatston method. Cardiovascular and diabetic profiles were assessed in all patients.

RESULTS

In 230 patients CCTA was diagnostic and 161 HRP were detected in 86 patients (37%). Male gender (OR 4.19, 95% CI 1.99-8.87; p < 0.01), tobacco exposure in pack years (OR 1.02, 95% CI 1.00-1.03; p = 0.03), and glycated hemoglobin (HbA1c) (OR 1.04, 95% CI 1.02-1.07; p < 0.01) were independent predictors of HRP. No relationship was found to other risk factors. HRP was not associated with increased CACS, and 13 (23%) patients with zero CACS had at least one HRP.

CONCLUSION

A high prevalence of HRP was detected in this population of asymptomatic T2D. The presence of HRP was associated with a particular patient profile, but was not ruled out by the absence of coronary artery calcium. CCTA provides important information on plaque morphology, which may be used to risk stratify this high-risk population. Trial registration This trial was retrospectively registered at clinical trials.gov January 11, 2017 trial identifier NCT03016910.

Systematic review and Meta-analysis of 26 randomized controlled clinical trials of Compound Danshen Dripping Pill for non-proliferating diabetic retinopathy

Objective

Methods

Results

Conclusion

Hub Genes Associated with the Diagnosis of Diabetic Retinopathy

Purpose

This study aimed to identify genes that may be effective in diagnosing or treating diabetic retinopathy (DR), the most common complication of diabetes mellitus (DM).

Methods

Differentially expressed genes (DEGs) were identified between DR and DM in GSE146615 dataset. DEGs that were consistently up- or down-regulated under both standard glucose and high glucose conditions were identified as common genes and used to generate a protein-protein interaction network and modules. The module genes were assessed for the area under the receiver operating characteristic curve (AUC), leading to the identification of hub genes. Differentially methylated probes in GSE76169 were also compared with common DEGs to identify specific methylation markers of DR. Enrichment analysis was used to explore the biological characteristics. The Short Time-series Expression Miner algorithm was used to identify genes that were progressively dysregulated in the sequence: healthy controls < DM < DR.

Results

A total of 1917 common genes were identified for seven modules. The eight genes with AUC > 0.8 under high glucose and standard glucose conditions were considered as hub genes. The module genes were significantly enriched during vascular smooth muscle cell development and regulation of oxygen metabolism, while 92 methylation markers were involved in the similar terms. Among the progressively dysregulated genes, three intersection genes under both standard glucose and high glucose conditions were found to be module genes and were considered as key genes.

Conclusion

We identified eight potential DR-specific diagnostic and therapeutic genes, whose abnormal expression can cause oxidative stress, thus favoring the course of the disease.

Sequoyitol Alleviates High Glucose-Induced Inflammation, Oxidative Stress and Apoptosis of Retina Epithelial Cells

Diabetic retinopathy (DR) is a serious microvascular complication of diabetes, contributing to visual impairment and blindness. Sequoyitol (Seq), a form of inositol derivatives, has been demonstrated to be a therapeutic potential for diabetes and diabetic nephropathy. The aim of this study is to explore the effects of Seq on DR. ARPE-19 cells were cultured in high glucose (HG) condition to simulate DR in vitro. Seq (1,10 and 20 µM) was applied for treatment. CCK-8 assay was performed to detect cell viability. Flow cytometry analysis was conducted to determine cell apoptosis rate. The production level of inflammatory cytokines and oxidative stress-related factors were determined using their commercial kits. The protein expressions of corresponding genes were detected using western blotting. The results revealed that Seq significantly increased cell viability and protein expression of PCNA and Ki67 which were decreased after HG induction. HG promoted cell apoptosis by decreasing protein expression of Bcl-2 and increasing protein expression of Bax and cleaved caspase-3, which was then reversed by Seq treatment. Besides, Seq abolished the promoting effects of HG on the production of pro-inflammatory cytokines and oxidative stress-related factors. Furthermore, Seq suppressed the promoting effect of HG on the activation of NF-κB signaling by inhibiting phosphorylation of kBa and NF-κB nucleus translocation. These results indicated that Seq might protect ARPE-19 cells against HG-induced cell viability, apoptosis, inflammation and oxidative stress by regulating NF-κB signaling, providing evidence for the potential application of Seq in the therapy of DR.

Non-invasive multimodal imaging of Diabetic Retinopathy: A survey on treatment methods and Nanotheranostics

Diabetes Retinopathy (DR) is one of the most prominent microvascular complications of diabetes. It is one of the pre-eminent causes for vision impairment followed by blindness among the working-age population worldwide. The de facto cause for DR remains challenging, despite several efforts made to unveil the mechanism underlying the pathology of DR. There is quite less availability of the low cost pre-emptive theranostic imaging tools in terms of in-depth resolution, due to the multiple factors involved in the etiology of DR. This review work comprehensively explores the various reports and research works on all perspectives of diabetic retinopathy (DR), and its mechanism. It also discusses various advanced non-destructive imaging modalities, current, and future treatment approaches. Further, the application of various nanoparticle-based drug delivery strategies used for the treatment of DR are also discussed. In a nutshell, the present review work bolsters the pursuit of the development of an advanced non-invasive optical imaging modal with a nano-theranostic approach for the future diagnosis and treatment of DR and its associated ocular complications.

Metabolic Dysregulation and Neurovascular Dysfunction in Diabetic Retinopathy

Diabetic retinopathy is a major cause of ocular complications in patients with type 1 and type 2 diabetes in developed countries. Due to the continued increase in the number of people with obesity and diabetes in the United States of America and globally, the incidence of diabetic retinopathy is expected to increase significantly in the coming years. Diabetic retinopathy is widely accepted as a combination of neurodegenerative and microvascular changes; however, which change occurs first is not yet understood. Although the pathogenesis of diabetic retinopathy is very complex, regulated by numerous signaling pathways and cellular processes, maintaining glucose homeostasis is still an essential component for normal physiological functioning of retinal cells. The maintenance of glucose homeostasis is finely regulated by coordinated interplay between glycolysis, Krebs cycle, and oxidative phosphorylation. Glycolysis is the most conserved metabolic pathway in biology and is tightly regulated to maintain a steady-state concentration of glycolytic intermediates; this regulation is called scheduled or regulated glycolysis. However, an abnormal increase in glycolytic flux generates large amounts of intermediate metabolites that can be shunted into different damaging pathways including the polyol pathway, hexosamine pathway, diacylglycerol-dependent activation of the protein kinase C pathway, and Amadori/advanced glycation end products (AGEs) pathway. In addition, disrupting the balance between glycolysis and oxidative phosphorylation leads to other biochemical and molecular changes observed in diabetic retinopathy including endoplasmic reticulum-mitochondria miscommunication and mitophagy dysregulation. This review will focus on how dysregulation of glycolysis contributes to diabetic retinopathy.

Diabetic Retinopathy: Important Biochemical Alterations and the Main Treatment Strategies

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by impaired glucose homeostasis, insulin resistance and hyperglycemia. Among its serious multisystemic complications is diabetic retinopathy (DR), which develops slowly and often insidiously. This disorder-the most common cause of vision loss in working-age adults-is characterized by functional and morphological changes in the retina. It results from the exacerbation of ischemic and inflammatory conditions prompted by alterations in the blood vessels, such as the development of leukostasis, thickening of the basement membrane, retinal neovascularization and fibrovascular tissue formation at the vitreoretinal interface. The pathogenic alterations are usually triggered at the biochemical level, involving a greater activity in 4 pathways: the polyol pathway, the hexosamine pathway, the formation of advanced glycation end-products and the activation of protein kinase C isoforms. When acting together, these pathways give rise to increased levels of reactive oxygen species and decreased levels of endogenous antioxidant agents, thus generating oxidative stress. All current therapies are aimed at the later stages of DR, and their application implies side effects. One possible strategy for preventing the complications of DM is to counteract the elevated superoxide production stemming from a high level of blood glucose. Accordingly, some treatments are under study for their capacity to reduce vascular leakage and avoid retinal ischemia, retinal neovascularization and macular edema. The present review summarizes the biochemical aspects of DR and the main approaches for treating it.

Z-Ligustilide Ameliorates Diabetic Rat Retinal Dysfunction Through Anti-Apoptosis and an Antioxidation Pathway

Background

Diabetic retinopathy (DR) is one of the major causes of vision impairment. Z-ligustilide (3-butylidene-4,5-dihydrophthalide; Z-LIG) is an important volatile oil from the Chinese herb Angelica sinensis (Oliv.) Diels. It has been extensively studied and reportedly has anti-inflammatory, antioxidant, antitumor, analgesic, vasodilatory, and neuroprotective effects. Its effects on DR, however, remain obscure. In this study, we attempted to explore the protective effects of Z-LIG on retinal dysfunction and the potential underlying mechanisms.

Material/Methods

A diabetic rat model was constructed with streptozotocin injection. Three study groups were constituted: control (CON), diabetic model (DM), and DM+Z-LIG. The DM+Z-LIG group was injected intraperitoneally with 10 mg/kg of Z-LIG. The other groups received the same volume of 3% solution of polysorbate 80. After a 12-week intervention, a series of assessments were performed, including tests for retinal function, morphology, and molecular biology.

Results

Z-LIG treatment significantly elevated b-wave and OPs2-wave amplitude and thickened the inner layer of the nucleus of the retina, and the outer plexiform and nuclear layers (INL+OPL+ONL). Moreover, the rate of apoptosis and expression of bcl-2- associated X protein (BAX) and cleaved-Caspase-3 were clearly reduced, and the expression of bcl-2 was raised by Z-LIG in retinas of diabetic mice. In addition, the levels of retinal proinflammatory cytokines interleukin-1 and tumor necrosis factor-α were downregulated by Z-LIG. Furthermore, Z-LIG inhibited expression of vascular endothelial growth factor-α (VEGF-α) at the mRNA and protein levels.

Conclusions

Z-LIG can inhibit inflammatory response and cell apoptosis in retinas of diabetic rats by repressing the VEGF-α pathway. Therefore, it may serve as a potential therapeutic agent for DR.

Formulation of PPAR-gamma agonist as surface modified PLGA nanoparticles for non-invasive treatment of diabetic retinopathy: in vitro and in vivo evidences

Diabetic retinopathy is one of the worst complications of diabetes and it is treated by invasive method. We prepared a surface modified poly (D, L-lactide-co-glycolide) i.e. PLGA nanoparticles for delivery of pioglitazone-a peroxisome proliferator-activated receptor-gamma agonist to posterior segment of the eye by topical administration. The present study investigated two grades of PLGA viz. 75:25 and 50:50. Surface modification was performed using polysorbate 80. Nanoparticles were prepared by single emulsion solvent evaporation method and optimized by using 3-factor 3-level Box-Behnken statistical design. Mean particle size, PDI and entrapment efficiency for optimized batch of PLGA 75:25 was found to be 163.23 nm, 0.286 and 91%, whereas; for PLGA 50:50 it was 171.7 nm, 0.280 and 93% respectively. DSC confirms the molecular dispersion of drug in polymer. In vitro release study showed biphasic drug release pattern with 58.48 ± 1.38% and 74.17 ± 1.38% cumulative drug release by PLGA 75:25 and 50:50 nanoparticles at the end of 10h. The release profile of pioglitazone from nanoparticles appeared to fit best with Higuchi model. In vivo study on rat showed dose dependent reduction in vascular endothelial growth factor concentration in vitreous fluid. The study reveals significance of peroxisome proliferator-activated receptor-gamma in management of diabetic retinopathy.

Ginsenoside Re Attenuates High Glucose-Induced RF/6A Injury via Regulating PI3K/AKT Inhibited HIF-1α/VEGF Signaling Pathway

Hyperglycaemia-induced retinal microvascular endothelial cell apoptosis is a critical and principle event in diabetic retinopathy (DR), which involves a series of complex processes such as mitochondrial dysfunction and oxidative stress. Ginsenoside Re (Re), a key ingredients of ginseng, is considered to have various pharmacologic functions, such as antioxidative, inhibition of inflammation and anti-apoptotic properties. However, the effects of Re in DR and the related mechanisms of endothelial cell injury induced by high glucose (HG) exposure remain unclear. The present study was designed to investigate and evaluate the ability of Re to ameliorate HG-induced retinal endothelial RF/6A cell injury and the potential mechanisms involved in the hypoxia-inducible factor-1-alpha (HIF-1α)/vascular endothelial growth factor (VEGF) signaling regulated by phosphoinositide 3-kinase (PI3K)/AKT pathway. Our results showed that preincubation with Re exerted cytoprotective effects by reversing the HG-induced decrease in RF/6A cell viability, downregulation of apoptosis rate and inhibition of oxidative-related enzymes, thereby reducing the excess intracellular reactive oxygen species (ROS) and HG-triggered RF/6A cell injury. In addition, Western blot analysis results showed ginsenoside Re significantly increased HIF-1α expression in the cytoplasm but decreased its expression in the nucleus, suggesting that it reduced the translocation of HIF-1α from the cytoplasm to the nucleus, and downregulated VEGF level. Moreover, this effect is involved in the activation of the PI3K/Akt pathway. LY294002, a PI3K inhibitor, was used to block the Akt pathway. Afterwards, the effects of Re on the regulation of apoptotic related proteins, VEGF and HIF-1α nuclear transcription was partially reversed. These findings suggested the exerting protective effects of ginsenoside Re were associated with regulating of PI3K/AKT and HIF-1α/VEGF signaling pathway, which indicates that ginsenoside Re may ameliorates HG-induced retinal angiogenesis and suggests the potential for the development of Re as a therapeutic for DR.

Xueshuantong for Injection (Lyophilized, ) Alleviates Streptozotocin-Induced Diabetic Retinopathy in Rats

OBJECTIVE

To investigate the ameliorate effect and underlying mechanism of Xueshuantong for Injection (Lyophilized, , XST) in streptozocin (STZ)-induced diabetic retinopathy (DR) rats.

METHODS

Diabetes mellitus (DM) model was induced by intraperitoneal (i.p.) injection of STZ (60 mg/kg) in Sprague-Dawley rats. Diabetic rats were randomized into 3 groups (n=10) according to a random number table, including DM, XST50 and XST100 groups. XST treatment groups were daily i.p. injected with 50 or 100 mg/kg XST for 60 days, respectively. The control and DM groups were given i.p. injection with saline. Blood glucose level and body weight were recorded every week. Histological changes in the retina tissues were observed with hematoxylin-eosin staining. Apoptosis and inflammation related factors, including cleaved caspase-3, glial fifibrillary acidic protein (GFAP), tumor necrosis factor-α (TNF-α) and intercellular cell adhesion molecule-1 (ICAM-1) were detected by Western blot or real-time polymerase chain reaction. Then, the levels of advanced glycation end product (AGE) and its receptor (RAGE) were investigated. Tight junctions proteins (Zonula occludens-1 (ZO-1), Occludin and Claudin-5) of blood-retinal barrier were detected by Western blot. The levels of retinal fifibrosis, transforming growth factor-β1 (TGF-β1)-Smad2/3 signaling pathway were evaluated at last.

RESULTS

There was no signifificant difference in the body weight and blood glucose level between XST and DM groups (P>0.05). Compared with the DM group, XST treatment signifificantly increased the retinal thickness of rats (P<0.05 or P<0.01), and suppressed cleaved caspase-3 expression (P<0.01). XST increased the protein expressions of ZO-1, Occludin and Claudin-5 and decreased the mRNA expressions of matrix metalloproteinase 2 (MMP-2) and MMP-9 (P<0.05 or P<0.01). Moreover, XST signifificantly reduced the productions of AGE and RAGE proteins in the retina of rats (P<0.05 or P<0.01), suppressed the over-expression of TNF-α, and decreased the elevated level of ICAM-1 in retina of rats (P<0.05 or P<0.01). XST signifificantly reduced the levels of α-smooth muscle actin (α-SMA), connective tissue growth factor (CTGF), TGF-β1 and phosphorylation of Smad2/3 protein in rats (P<0.05 or P<0.01).

CONCLUSIONS

XST had protective effects on DR with possible mechanisms of inhibiting the inflammation and apoptosis, up-regulating the expression of tight junction proteins, suppressing the productions of AGE and RAGE proteins, and blocking the TGF-β/Smad2/3 signaling pathway. XST treatment might play a role for the future therapeutic strategy against DR.

Transcriptomics analysis of pericytes from retinas of diabetic animals reveals novel genes and molecular pathways relevant to blood-retinal barrier alterations in diabetic retinopathy

Selective pericyte loss, the histological hallmark of early diabetic retinopathy (DR), enhances the breakdown of the blood-retinal barrier (BRB) in diabetes. However, the role of pericytes on BRB alteration in diabetes and the signaling pathways involved in their effects are currently unknown. To understand the role of diabetes-induced molecular alteration of pericytes, we performed transcriptomic analysis of sorted retinal pericytes from mice model of diabetes. Retinal tissue from non-diabetic and diabetic (duration 3 months) mouse eyes (n = 10 in each group) were used to isolate pericytes through fluorescent activated cell sorting (FACS) using pericyte specific fluorescent antibodies, PDGFRb-APC. For RNA sequencing and qPCR analysis, a cDNA library was generated using template switching oligo and the resulting libraries were sequenced using paired-end Illumina sequencing. Molecular functional pathways were analyzed using differentially expressed genes (DEGs). Differential expression analysis revealed 217 genes significantly upregulated and 495 genes downregulated, in pericytes isolated from diabetic animals. These analyses revealed a core set of differentially expressed genes that could potentially contribute to the pericyte dysfunction in diabetes and highlighted the pattern of functional connectivity between key candidate genes and blood retinal barrier alteration mechanisms. The top up-regulated gene list included: Ext2, B3gat3, Gpc6, Pip5k1c and Pten and down-regulated genes included: Notch3, Xbp1, Gpc4, Atp1a2 and AKT3. Out of these genes, we further validated one of the down regulated genes, Notch 3 and its role in BRB alteration in diabetic retinopathy. We confirmed the downregulation of Notch3 expression in human retinal pericytes exposed to Advanced Glycation End-products (AGEs) treatment mimicking the chronic hyperglycemia effect. Exploration of pericyte-conditioned media demonstrated that loss of NOTCH3 in pericyte led to increased permeability of endothelial cell monolayers. Collectively, we identify a role for NOTCH3 in pericyte dysfunction in diabetes. Further validation of other DEGs to identify cell specific molecular change through whole transcriptomic approach in diabetic retina will provide novel insight into the pathogenesis of DR and novel therapeutic targets.

Calcitriol and non-calcemic vitamin D analogue, 22-oxacalcitriol, attenuate developmental and pathological choroidal vasculature angiogenesis ex vivo and in vivo

Aberrant ocular angiogenesis can underpin vision loss in leading causes of blindness, including neovascular age-related macular degeneration and proliferative diabetic retinopathy. Current pharmacological interventions require repeated invasive administrations, may lack efficacy and are associated with poor patient compliance and tachyphylaxis. Vitamin D has de novo anti-angiogenic properties. Here, our aim was to validate the ocular anti-angiogenic activity of biologically active vitamin D, calcitriol, and selected vitamin D analogue, 22-oxacalcitriol. Calcitriol induced a significant reduction in ex vivo mouse choroidal fragment sprouting. Viability studies in a human RPE cell line suggested non-calcemic vitamin D analogues including 22-oxacalcitriol have less off-target anti-proliferative activity compared to calcitriol and other analogues. Thereafter, the anti-angiogenic activity of 22-oxacalcitriol was demonstrated in an ex vivo mouse choroidal fragment sprouting assay. In zebrafish larvae, 22-oxacalcitriol was found to be anti-angiogenic, inducing a dose-dependent reduction in choriocapillaris development. Subcutaneously administered calcitriol failed to attenuate mouse retinal vasculature development. However, calcitriol and 22-oxacalcitriol administered intraperitoneally, significantly attenuated lesion volume in the laser-induced choroidal neovascularisation mouse model. In summary, calcitriol and 22-oxacalcitriol attenuate ex vivo and in vivo choroidal vasculature angiogenesis. Therefore, vitamin D may have potential as an interventional treatment for ophthalmic neovascular indications.

Visual Acuity Outcomes after Cataract Extraction with Intraocular Lens Implantation in Eyes with Diabetic Retinopathy

PURPOSE

To evaluate change in best-corrected visual acuity (BCVA) in patients with diabetes and diabetic retinopathy (DR) after cataract extraction (CE).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Diabetic eyes of patients 18 years of age or older that underwent CE at the Cleveland Clinic from 2012 through 2018.

METHODS

Chart review examining visual acuities from patient visits before and after surgery, as well as OCT images. Statistical analysis was carried out using multiple linear regression models.

MAIN OUTCOME MEASURES

The primary end point was change in BCVA during the first postoperative year. The secondary end point was the association of central subfield thickness at baseline with change in BCVA. Additional preoperative factors examined were age, race, gender, laterality, insulin use, hemoglobin A1c, creatinine, blood urea nitrogen, and estimated glomerular filtration rate.

RESULTS

Diabetic eyes without DR (n = 138) and eyes with mild/moderate nonproliferative DR (NPDR; n = 125), severe NPDR (n = 20), and proliferative DR (PDR; n = 72) were included. A year after surgery, eyes without DR gained a median of 11.0 Early Treatment Diabetic Retinopathy Study (ETDRS) letters (interquartile range [IQR], 5.0-20.0) from 65.0 (IQR, 58.0-70.0) before surgery, eyes with mild or moderate DR gained 10.0 letters (IQR, 5.0-22.0) from 65.0 (IQR, 58.0-76.0), eyes with severe NPDR gained 20.5 letters (IQR, 8.0-28.5) from 55.0 (IQR, 26.0-65.0), and eyes with PDR gained 15.0 letters (IQR, 6.0-29.5) from 55.0 (IQR, 35.0-61.0). Eyes without DR or mild or moderate NPDR showed significantly greater improvements in VA 1 year after surgery compared with eyes with severe NPDR or PDR when controlling for baseline visual acuity (VA), with eyes with more severe DR showing less expected VA gain (P < 0.001). Length of disease most strongly related to baseline DR severity (ρ = 0.431; P < 0.001).

CONCLUSIONS

Cataract surgery is beneficial in most patients with DR without severe concurrent macular pathologic features. However, preoperative VA and the severity of DR can limit visual outcomes.

The role of Müller cell glucocorticoid signaling in diabetic retinopathy

Diabetic retinopathy (DR) is a sight-threatening complication associated with the highly prevalent diabetes disorder. Both the microvascular damage and neurodegeneration detected in the retina caused by chronic hyperglycemia have brought special attention to Müller cells, the major macroglia of the retina that are responsible for retinal homeostasis. Given the role of glucocorticoid signaling in anti-inflammatory responses and the almost exclusive expression of glucocorticoid receptors (GRs) in retinal Müller cells, administration of corticosteroid agonists as a potential treatment option has been widely studied. Although these approaches have been moderately efficacious in treating or de-escalating DR pathomechanisms, there are various side effects and gaps of knowledge with regard to introducing exogenous glucocorticoids to the diseased retina. In this paper, we provide a review of the literature concerning the available evidence for the role of Müller cell glucocorticoid signaling in DR and we discuss previously investigated approaches in modulating this system as possible treatment options. Furthermore, we propose a novel alternative to the available choices of treatment by using gene therapy as a tool to regulate the expression of GR in retinal Müller cells. Upregulating GR expression allows for induced glucocorticoid signaling with more enduring effects compared to injection of agonists. Hence, repetitive injections would no longer be required. Lastly, side effects of glucocorticoid therapy such as glucocorticoid resistance of GR following chronic exposure to excess ligands or agonists can be avoided.

[Effect of intravitreal injections of ranibizumab and aflibercept on the retinal nerve fiber layer in patients with concomitant neovascular age-related macular degeneration and glaucoma]

PURPOSE

To study the effect of ranibizumab and aflibercept on the thickness of retinal nerve fiber layer (RNFL) in patients with neovascular age-related macular degeneration (nAMD) and primary open-angle glaucoma (POAG).

MATERIAL AND METHODS

The study included 62 patients (62 eyes) with nAMD and comorbid POAG. Patients were divided into two groups depending on the anti-VEGF treatment. The first group included 42 patients (42 eyes) who received injections of ranibizumab. The second group consisted of 20 patients (20 eyes) who received aflibercept. All patients received three injections of ranibizumab or aflibercept with one-month intervals. In addition to standard ophthalmic examination, patients underwent optical coherence tomography of the macular area and peripapillary RNFL.

RESULTS

After anti-VEGF treatment, patients of both groups exhibited improvements expressed in reduced macular edema, increased visual acuity and absence of intraocular pressure (IOP) changes, as well as no statistically significant changes in the width and depth of excavation. There was a statistically significant decrease of peripapillary RNFL thickness in the temporal quadrant after treatment.

CONCLUSION

The decrease of peripapillary RNFL thickness in the temporal quadrant occurs due to resorption of macular edema. In the absence of statistically significant changes in IOP, width and depth of excavation, intravitreal injections of ranibizumab and aflibercept can be considered safe treatment options for patients with concomitant nAMD and POAG.

Challenges and opportunities for drug delivery to the posterior of the eye

Drug delivery to the posterior segment of the eye remains challenging even though the eye is readily accessible. Its unique and complex anatomy and physiology contribute to the limited options for drug delivery via non-invasive topical treatment, which is the prevalent ophthalmic treatment. To treat the most common retinal diseases, intravitreal (IVT) injection has been a common and effective therapy. With the advancement of nanotechnologies, novel formulations and drug delivery systems are being developed to treat posterior segment diseases. Here, we discuss the recent advancement in ocular delivery systems, including-sustained release formulations, IVT implants, and preclinical topical formulations, and the challenges faced in their clinical translation.

Modulation of three key innate immune pathways for the most common retinal degenerative diseases

This review highlights the role of three key immune pathways in the pathophysiology of major retinal degenerative diseases including diabetic retinopathy, age‐related macular degeneration, and rare retinal dystrophies. We first discuss the mechanisms how loss of retinal homeostasis evokes an unbalanced retinal immune reaction involving responses of local microglia and recruited macrophages, activity of the alternative complement system, and inflammasome assembly in the retinal pigment epithelium. Presenting these key mechanisms as complementary targets, we specifically emphasize the concept of immunomodulation as potential treatment strategy to prevent or delay vision loss. Promising molecules are ligands for phagocyte receptors, specific inhibitors of complement activation products, and inflammasome inhibitors. We comprehensively summarize the scientific evidence for this strategy from preclinical animal models, human ocular tissue analyses, and clinical trials evolving in the last few years.

Therapeutic regulation of VE-cadherin with a novel oligonucleotide drug for diabetic eye complications using retinopathy mouse models

AIMS/HYPOTHESIS

A major feature of diabetic retinopathy is breakdown of the blood-retinal barrier, resulting in macular oedema. We have developed a novel oligonucleotide-based drug, CD5-2, that specifically increases expression of the key junctional protein involved in barrier integrity in endothelial cells, vascular-endothelial-specific cadherin (VE-cadherin). CD5-2 prevents the mRNA silencing by the pro-angiogenic microRNA, miR-27a. CD5-2 was evaluated in animal models of ocular neovascularisation and vascular leak to determine its potential efficacy for diabetic retinopathy.

METHODS

CD5-2 was tested in three mouse models of retinal dysfunction: conditional Müller cell depletion, streptozotocin-induced diabetes and oxygen-induced retinopathy. Vascular permeability in the Müller cell-knockout model was assessed by fluorescein angiography. The Evans Blue leakage method was used to determine vascular permeability in streptozotocin- and oxygen-induced retinopathy models. The effects of CD5-2 on retinal neovascularisation, inter-endothelial junctions and pericyte coverage in streptozotocin- and oxygen-induced retinopathy models were determined by staining for isolectin-B4, VE-cadherin and neural/glial antigen 2 (NG2). Blockmir CD5-2 localisation in diseased retina was determined using fluorescent in situ hybridisation. The effects of CD5-2 on VE-cadherin expression and in diabetic retinopathy-associated pathways, such as the transforming growth factor beta (TGF-β) and wingless/integrated (WNT) pathway, were confirmed using western blot of lysates from HUVECs, a mouse brain endothelial cell line and a VE-cadherin null mouse endothelial cell line.

RESULTS

CD5-2 penetrated the vasculature of the eye in the oxygen-induced retinopathy model. Treatment of diseased mice with CD5-2 resulted in reduced vascular leak in all three animal models, enhanced expression of VE-cadherin in the microvessels of the eye and improved pericyte coverage of the retinal vasculature in streptozotocin-induced diabetic models and oxygen-induced retinopathy models. Further, CD5-2 reduced the activation of retinal microglial cells in the streptozotocin-induced diabetic model. The positive effects of CD5-2 seen in vivo were further confirmed in vitro by increased protein expression of VE-cadherin, SMAD2/3 activity, and platelet-derived growth factor B (PDGF-B).

CONCLUSIONS/INTERPRETATION

CD5-2 has therapeutic potential for individuals with vascular-leak-associated retinal diseases based on its ease of delivery and its ability to reverse vascular dysfunction and inflammatory aspects in three animal models of retinopathy.

Proteinuria and Renal Dysfunction after Intravitreal Injection of Bevacizumab in Patients with Diabetic Nephropathy: A Prospective Observational Study

Background:

Proliferative diabetic retinopathy (PDR) is one of the most important microvascular complications among the patients with diabetes. Intravitreal anti-vascular endothelial growth factor (anti-VEGF) agent enacts a key role in PDR. Some studies have dealt with the systemic exposure to these agents after intravitreal administration. However, renal dysfunction following this therapy has scarcely been reported. Hence, this study aimed to determine the effect of intravitreal bevacizumab treatment on the deterioration of renal function and proteinuria.

Materials and Methods:

This present prospective observational study was performed on 40 patients with diabetic nephropathy and PDR and/or significant diabetic macular edema as the candidates for receiving intravitreal injection of bevacizumab. To evaluate renal function, changes in the urinary albumin-to-creatinine ratio (UACR), serum creatinine (SCr), and estimated glomerular filtration rate (eGFR) one month after injection were measured. Also, changes in systolic and diastolic blood pressures (BPs), plasma VEGF level, platelet, white blood cell (WBC) counts, and hemoglobin (Hb) level were measured at the baseline and one month after treatment.

Results:

The mean age of the patients was 60.3 ± 9.2 years, and 33 patients were female. The decrease in the plasma VEGF level and platelet count, as well as the increase in diastolic BP, and Hb level were significant. However, systolic BP and WBC count remained unchanged. There were no significant changes in UACR, SCr, and eGFR after the injection as compared to baseline (P>0.05).

Conclusion:

Our study indicated that intravitreal bevacizumab injection was not associated with renal dysfunction and proteinuria in patients with diabetic nephropathy. Nevertheless, diastolic BP and Hb level could increase after one month.

Lipid-lowering medication is associated with decreased risk of diabetic retinopathy and the need for treatment in patients with type 2 diabetes: A real-world observational analysis of a health claims database

AIMS

Fenofibrate and statins reduced the need for diabetic retinopathy (DR)-related treatment in clinical trials. We aimed to determine whether use of lipid-lowering medication reduces the risk of DR and the need for treatment in patients with type 2 diabetes using a real-world health claims database.

METHODS

This was an observational analysis using a nation-wide health claims database of the Japan Medical Data Center (JMDC). Type 2 diabetes was defined according to ICD-10 codes for use of glucose-lowering medication. Use of lipid-lowering medication for at least 1 year was confirmed by the Anatomical Therapeutic Chemical Classification System. DR and diabetic macular edema (DME) were determined by ICD-10 codes. DR-related treatments were determined by health insurance claims. A propensity score for use of lipid-lowering medication was estimated, and a doubly robust estimator, using the inverse probability weighting model with regression adjustment, was obtained to determine odds ratios (OR) with 95% confidence interval (95% CI) for cumulative incidence of DR and its treatments over 3 years.

RESULTS

There were 69 070 individuals with type 2 diabetes at baseline, among whom DR developed in 5687 over a period of 3 years. Use of lipid-lowering medication was associated with decreased risk of incidence of DR (OR, 0.772; 95% CI, 0.720-0.827; P < .001). Use of lipid-lowering medication was also associated with decreased incidence of DME, any treatments for DR, laser photocoagulation and vitrectomy in patients with DR at baseline.

CONCLUSIONS

In a population of patients with type 2 diabetes with a variety of risk profiles, use of lipid-lowering medication reduced the risk of DR and thus the risks involved in treatment with laser photocoagulation and vitrectomy.

Increased serum periostin concentrations are associated with the presence of diabetic retinopathy in patients with type 2 diabetes mellitus

PURPOSE

To determine the association between serum periostin and the presence of diabetic retinopathy (DR).

METHODS

Serum periostin was detected in 114 healthy subjects, 122 patients with type 2 diabetes mellitus (T2DM) and 159 patients with DR and compared among groups. Clinical data and other laboratory measurements such as glycated hemoglobin (HbA1c), lipid profiles, serum creatinine (Cr) and high-sensitivity CRP (hsCRP) were also collected and compared among groups. For subgroup analysis, patients with DR were divided into a non-proliferated diabetic retinopathy (NPDR) group and a proliferated diabetic retinopathy (PDR) group. Multivariate analysis was performed using logistic regression models.

RESULTS

The serum periostin level was significantly higher in patients with diabetic retinopathy compared with healthy subjects and patients with T2DM (both P < 0.001, respectively). Also, the periostin level was significantly higher in the PDR group compared to the NPDR group (P = 0.044). Multivariate logistic regression revealed that serum periostin was independently associated with the presence of DR in patients with T2DM (P < 0.001). The receiver operating characteristic (ROC) curves for DR development using serum periostin showed that the area under the receiver operating characteristic curves (AUC) was 0.838 (P < 0.001).

CONCLUSIONS

The current study demonstrated that serum periostin is significantly associated with the presence of DR in patients with T2DM and is an independent risk factor of DR.

The Role of Microglia in Diabetic Retinopathy: Inflammation, Microvasculature Defects and Neurodegeneration

Diabetic retinopathy is a common complication of diabetes mellitus, which appears in one third of all diabetic patients and is a prominent cause of vision loss. First discovered as a microvascular disease, intensive research in the field identified inflammation and neurodegeneration to be part of diabetic retinopathy. Microglia, the resident monocytes of the retina, are activated due to a complex interplay between the different cell types of the retina and diverse pathological pathways. The trigger for developing diabetic retinopathy is diabetes-induced hyperglycemia, accompanied by leukostasis and vascular leakages. Transcriptional changes in activated microglia, mediated via the nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) and extracellular signal–regulated kinase (ERK) signaling pathways, results in release of various pro-inflammatory mediators, including cytokines, chemokines, caspases and glutamate. Activated microglia additionally increased proliferation and migration. Among other consequences, these changes in microglia severely affected retinal neurons, causing increased apoptosis and subsequent thinning of the nerve fiber layer, resulting in visual loss. New potential therapeutics need to interfere with these diabetic complications even before changes in the retina are diagnosed, to prevent neuronal apoptosis and blindness in patients.

Pathogenic Role of microRNA-21 in Diabetic Retinopathy Through Downregulation of PPARα

Fenofibrate, a specific agonist of peroxisome proliferator-activated receptor-α (PPARα), displays robust therapeutic effects on diabetic retinopathy (DR) in patients with type 2 diabetes. Our recent studies have shown that PPARα is downregulated in the diabetic retina, which contributes to the pathogenesis of DR. However, the mechanism for diabetes-induced downregulation of PPARα remains unknown. We investigated the role of microRNA-21 (miR-21) in regulating PPARα in DR. miR-21 was overexpressed, while PPARα levels were decreased in the retina of db/db mice, a model of type 2 diabetes. Such alterations were also observed in palmitate-treated retinal endothelial cells. miR-21 targeted PPARα by inhibiting its mRNA translation. Knockout of miR-21 prevented the decrease of PPARα, alleviated microvascular damage, ameliorated inflammation, and reduced cell apoptosis in the retina of db/db mice. Intravitreal injection of miR-21 inhibitor attenuated PPARα downregulation and ameliorated retinal inflammation in db/db mice. Further, retinal miR-21 levels were increased, while PPARα levels were decreased in oxygen-induced retinopathy (OIR). Knockout of miR-21 prevented PPARα downregulation and ameliorated retinal neovascularization and inflammation in OIR retinas. In conclusion, diabetes-induced overexpression of miR-21 in the retina is at least partly responsible for PPARα downregulation in DR. Targeting miR-21 may represent a novel therapeutic strategy for DR.

The pathology associated with diabetic retinopathy

This review summarizes the pathological features of diabetic retinopathy. The lesions occurring in the diabetic retina have been described over many decades using descriptive and experimental approaches based on clinical studies on patients, human post-mortem material, animal models and various in vitro systems. We have also accumulated a wealth of knowledge about basic molecular mechanisms and key pathogenic processes that drive these abnormalities in diabetic retina. Despite these advances, there are still limited therapeutic options for diabetic retinopathy with those currently available only addressing late-stage disease. With a particular focus on the earlier stages of diabetes, there is growing appreciation the complex neuronal, glial and microvascular abnormalities which progressively disrupt retinal function. This is especially true from the perspective of the neurovascular unit during health and disease. Based on a strong appreciation of cellular and molecular pathology that underpins diabetic retinopathy, further advances are anticipated as we drive towards development of efficacious therapeutic options that can address all stages of disease.

Plasma level of miR-93 is associated with higher risk to develop type 2 diabetic retinopathy

PURPOSE

MicroRNA-93 (miR-93) usually acts as a promoter of tumor progression in several human carcinomas. It has been found distinctly high in eyes with proliferative diabetic retinopathy (DR). The present study aims to investigate the role of plasma miR-93 in the progression of type 2 diabetic retinopathy (T2DR).

METHODS

Our study subjects were made up of 140 type 2 diabetes mellitus (T2DM) patients who were assigned into DR (DR patients, n = 75), NDR (non-DR patients, n = 65), and control (healthy individuals, n = 127) groups. Levels of fasting blood glucose (FBG), fasting plasma glucose (FPG), triglyceride (TG), glycosylated hemoglobin (HbA1c), total cholesterol (TC), blood urea nitrogen (BUN), creatinine (Cr), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and fasting insulin (FIsn) were detected by automatic biochemical analyzer. Enzyme-linked immunosorbent assay (ELISA) was performed for the levels of interleukin (IL)-1, IL-6, tumor necrosis factor (TNF)-α and vascular endothelial growth factor (VEGF), qRT-PCR for the miR-93 expression in plasma, and mRNA expressions of IL-1, IL-6, TNF-α and VEGF; receiver operating characteristic (ROC) curve for the diagnostic performance of miR-93 to T2DR, Pearson correlation analysis for correlation analysis between miR-93 and other indexes detected before and multivariate logistic regression analyses for the risk factors for T2DR.

RESULTS

The DR and NDR groups exhibited elevated course of disease, and decreased levels of FBG, FPG, TG, HbA1c, TC, BUN, Cr, HDL-C, FIsn, IL-1, IL-6, TNF-α and VEGF but declined LDL-C level as compared to the control group. The course of disease was longer and the levels of FBG, FPG, HbA1c, IL1, IL6 and VEGF were higher in the DR group than those in the NDR group (all P < 0.05). The miR-93 expression and RNA expressions of IL-1, IL-6, TNF-α and VEGF were higher in the DR group than those in the NDR group (P < 0.05). The best cutoff for miR-93 to assess T2DR was 1.31, with a Youden index of 0.63, sensitivity of 73.33%, specificity of 89.24%, and area under the curve (AUC) of 0.866. Pearson correlation analysis indicated that miR-93 expression was positively associated with course of disease, the levels of FPG, HbA1c, TNF-α and VEGF. T2DM patients with longer disease course, higher levels of FBG, HbA1c, VEGF and miR-93 expression were risk factors for developing DR.

CONCLUSION

Our study demonstrates that plasma miR-93 is associated with the progression of T2DR and it can sever as a diagnostic marker for T2DR.

Morphological Plasticity of Emerging Purkinje Cells in Response to Exogenous VEGF

Vascular endothelial growth factor (VEGF) is well known as the growth factor with wide-ranging functions even in the central nervous system (CNS). Presently, most attention is given to the investigation of its role in neuronal protection, growth and maturation processes, whereby most effects are mediated through VEGF receptor 2 (VEGFR-2). The purpose of our current study is to provide new insights into the impact of VEGF on immature and mature Purkinje cells (PCs) in accordance with maturity and related receptor expression. Therefore, to expand our knowledge of VEGF effects in PCs development and associated VEGFR-2 expression, we used cultivated organotypic cerebellar slice cultures in immunohistochemical or microinjection studies, followed by confocal laser scanning microscopy (CLSM) and morphometric analysis. Additionally, we incorporated in our study the method of laser microdissection, followed by quantitative polymerase chain reaction (qPCR). For the first time we could show the age-dependent VEGF sensitivity of PCs with the largest promoting effects being on dendritic length and cell soma size in neonatal and juvenile stages. Once mature, PCs were no longer susceptible to VEGF stimulation. Analysis of VEGFR-2 expression revealed its presence in PCs throughout development, which underlined its mediating functions in neuronal cells.

Diabetic Retinopathy: Animal Models, Therapies, and Perspectives

Diabetic retinopathy (DR) is one of the major complications of diabetes. Although great efforts have been made to uncover the mechanisms underlying the pathology of DR, the exact causes of DR remain largely unknown. Because of multifactor involvement in DR etiology, currently no effective therapeutic treatments for DR are available. In this paper, we review the pathology of DR, commonly used animal models, and novel therapeutic approaches. Perspectives and future directions for DR treatment are discussed.

Global metabolomics reveals metabolic dysregulation in ischemic retinopathy

Proliferative diabetic retinopathy (PDR) is the most severe form of diabetic retinopathy and, along with diabetic macular edema, is responsible for the majority of blindness in adults below the age of 65. Therapeutic strategies for PDR are ineffective at curtailing disease progression in all cases; however a deeper understanding of the ocular metabolic landscape in PDR through metabolomic analysis may offer new therapeutic targets. Here, global and targeted mass spectrometry-based metabolomics were used to investigate metabolism. Initial analyses on vitreous humor from patients with PDR (n = 9) and non-diabetic controls (n = 11) revealed an increase of arginine and acylcarnitine metabolism in PDR. The oxygen-induced-retinopathy (OIR) mouse model, which exhibits comparable pathological manifestations to human PDR, revealed similar increases of arginine and other metabolites in the urea cycle, as well as downregulation of purine metabolism. We validated our findings by targeted multiple reaction monitoring and through the analysis of a second set of patient samples [PDR (n = 11) and non-diabetic controls (n = 20)]. These results confirmed a predominant and consistent increase in proline in both the OIR mouse model and vitreous samples from patients with PDR, suggesting that over activity in the arginine-to-proline pathway could be used as a therapeutic target in diabetic retinopathy.

Neuroinflammatory responses in diabetic retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes and has been recognized as a vascular dysfunction leading to blindness in working-age adults. It becomes increasingly clear that neural cells in retina play an important role in the pathogenesis of DR. Neural retina located at the back of the eye is part of the brain and a representative of the central nervous system. The neurosensory deficits seen in DR are related to inflammation and occur prior to the clinically identifiable vascular complications. The neural deficits are associated with abnormal reactions of retina glial cells and neurons in response to hyperglycemia. Improper activation of the innate immune system may also be an important contributor to the pathophysiology of DR. Therefore, DR manifests characteristics of both vasculopathy and chronic neuroinflammatory diseases. In this article, we attempt to provide an overview of the current understanding of inflammation in neural retina abnormalities in diabetes. Inhibition of neuroinflammation may represent a novel therapeutic strategy to the prevention of the progression of DR.

Beta-adrenergic receptor agonist decreases VEGF levels through altered eNOS and PKC signaling in diabetic retina

Vascular endothelial cell growth factor (VEGF) is increased in diabetic macular edema. Compound 49b, a novel β-adrenergic receptor agonist, is protective in a type 1 diabetic rat model. We questioned whether Compound 49b could decrease VEGF levels, suggesting that Compound 49b may be effective against edema. Two-month diabetic rats received topical Compound 49b for 7 days only and/or insulin-like growth factor binding protein 3 (IGFBP-3) siRNA. We also measured endothelial nitric oxide synthase (eNOS) and protein kinase C (PKC)ζ and PKCδ phosphorylation. Retinal endothelial cells (RECs) cultured in high glucose were treated with Compound 49b and IGFBP-3 siRNA for evaluation of the same signaling pathways. Compound 49b significantly decreased VEGF through increased IGFBP-3 in the diabetic retina. Compound 49b also reduced eNOS, PKCζ and PKCδ phosphorylation in the diabetic retina and REC. Compound 49b regulated a number of proteins involved in REC barrier properties.