Effectiveness Differences of Ranibizumab and Aflibercept Action in the Treatment of Diabetic Retinopathy.

Objective: To compare the difference in the effectiveness of ranibizumab (LU) and aflibercept (AF) in the treatment of diabetic retinopathy (DR). Methods: Ninety-four patients with DR admitted to Sunshine Union Hospital from August 2020 to February 2022 were selected for the study and were divided into LU group (n = 47) and AF group (n = 47) according to the random number table method. Both groups underwent 25G vitrectomy in our hospital, with LU injected into the vitreous before surgery in the LU group and AF in the AF group. Vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in the pre-and post-injection atrial water were compared between the two groups, and the operative time, intraoperative bleeding, and the occurrence of medically induced fissures were recorded in both groups. In addition, the expression of best corrected visual acuity (BCVA), Central Macular Thickness (CMT), and inflammatory factors were compared before and after surgery. Finally, patients were counted for adverse reactions and prognosis of DR recurrence during treatment. Results: After injection, VEGF decreased and PEDF increased in both groups (P < .001). There were no differences in operative time (P = .604), intraoperative bleeding rate (P = .694), the incidence of medically induced fissure (P = .557), BCVA [P = .665 (T0), P > .999 (T1), P = .727 (T2)], and CMT [P = .688 (T0), P = .065 (T1), P = .148 (T2)] between the two groups, while IL-6, IL-8, and MMP-9 were lower in the AF group than in the LU group at 2 months after surgery (P < .001). Finally, there was no difference between both groups in terms of adverse effects and prognosis of DR recurrence rate (P = 1.000, .478). Conclusion: Both vitreous cavity injections of LU and AF can effectively reduce the expression of vascular-related factors in the atrial fluid of DR patients, but AF has a more significant inhibitory effect on the level of inflammatory factors in patients in the short term after treatment.

Applications of nanomaterials in anti-VEGF treatment for ophthalmic diseases.

Angiogenesis has been determined to be essential in the occurrence and metastasis of diabetic retinopathy (DR), age-related macular degeneration (AMD), retinal vein occlusion (RVO), choroidal neovascularization (CNV), retinopathy of prematurity (ROP), tumor, etc. However, the clinical use of anti-vascular endothelial growth factors (VEGF) drugs is currently limited due to its high cost, potential side effects, and need for repeated injections. In recent years, nanotechnology has shown promising results in inhibiting neovascularization and reducing reactive oxygen species (ROS) or inflammatory factors. Some nanomaterials can also act as vehicles for drug delivery, such as lipid nanoparticles and PLGA. The process of angiogenesis and its molecular mechanism are discussed in this article. At the same time, this study aims to systematically review the research progress of nanotechnology and offer more treatment options for neovascularization-related diseases in clinical ophthalmology.

Modified early intensive and treat-and-extend regimen of anti-vascular endothelial growth factor for diabetic macular edema in Taiwan.

Given the rising prevalence of patients with diabetes and increasing treatment burden for patients with vision-threatening diabetic macular edema (DME), we aimed to explore the efficacy of modified early intensive and treat-and-extend regimen of anti-vascular endothelial growth factor (VEGF) therapy under the Taiwan National Insurance Bureau reimbursement policy. We obtained data on 69 eyes treated with initial 4-monthly intravitreal injections of aflibercept or ranibizumab, plus individualized treat-and-extend regimen. At 12 months, the mean (SD) change in LogMAR best corrected visual acuity from baseline was - 0.28 (0.31) in all eyes, while that in the aflibercept and ranibizumab groups were - 0.30 (0.34) and - 0.25 (0.28), respectively. Central retinal thickness decreased by 137.2 (122.4) in all eyes, 138.1 (134.2) in the aflibercept group, and 136.2 (110.9) in the ranibizumab group. Additionally, the aflibercept group had a lower mean number of injections than the ranibizumab group (8.5 vs. 8.7). The last extended dosing interval of > 12 weeks was 31.0% and 16.7% of the eyes in the aflibercept and ranibizumab groups, respectively. The modified anti-VEGF regimens effectively managed DME in terms of functional and anatomical outcomes, and efficiently reduced the healthcare burden by reducing the number of injections and extending treatment intervals within 12 months.

Acute Kidney Injury from Intravitreal Anti-vascular Endothelial Growth Factor Drugs: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

BACKGROUND: Several observational studies have reported acute kidney injury from intravitreal anti-vascular endothelial growth factor (anti-VEGF) drugs for retinal diseases. However, systematic reviews and meta-analyses of randomized controlled trials on this critical topic are scant. OBJECTIVE: To evaluate acute kidney injury risk associated with intravitreal anti-VEGF drugs in patients with retinal diseases. METHODS: We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials on 12 July, 2023, and included randomized controlled trials reporting acute kidney injury between anti-VEGF drugs (e.g., aflibercept, bevacizumab, brolucizumab, and ranibizumab) and controls for retinal diseases (e.g., age-related macular degeneration, polypoidal choroidal vasculopathy, diabetic retinopathy/diabetic macular edema, retinal vein occlusion, and myopic choroidal neovascularization). Data were synthesized by a fixed-effects model for pooling odds ratios (ORs) using the Peto method. RESULTS: We included 13 randomized controlled trials (four and nine trials for aflibercept and ranibizumab, respectively) with a total of 4282 participants. The meta-analysis indicated intravitreal anti-VEGF drugs did not increase the acute kidney injury risk, compared with controls (odds ratio [OR]: 1.00, 95% confidence interval [CI] 0.49-2.04, I2: 0%), and no differences in the acute kidney injury risk were observed between different anti-VEGF drugs (OR: 1.10, 95% CI 0.27-4.43, I2: 0% for aflibercept; OR: 0.97, 95% CI 0.42-2.22, I2: 0% for ranibizumab) and between different retinal diseases (OR: 4.61, 95% CI 0.07-284.13, I2: not applicable for age-related macular degeneration; OR: 0.90, 95% CI 0.42-1.93, I2: 0% for diabetic retinopathy/diabetic macular edema; OR: 1.57, 95% CI 0.16-15.88, I2: 0% for retinal vein occlusion). CONCLUSIONS: Intravitreal anti-VEGF drugs were not associated with an acute kidney injury risk, regardless of which anti-VEGF drugs (aflibercept or ranibizumab) or retinal diseases (age-related macular degeneration, diabetic retinopathy/diabetic macular edema, or retinal vein occlusion) were involved. SYSTEMATIC REVIEW PROTOCOL REGISTRATION: PROSPERO CRD42021267854.

Evaluating initial responses to brolucizumab in patients undergoing conventional anti-VEGF therapy for diabetic macular edema: a retrospective, single-center, observational study.

Our retrospective, single-center, observational study aimed to evaluate the initial responses to intravitreal injection of brolucizumab (IVBr) in patients undergoing anti-vascular endothelial growth factor (VEGF) therapy for diabetic macular edema (DME). In total, 23 eyes of 20 patients with DME treated with at least one intravitreal injection of ranibizumab or aflibercept within one year and then switched to IVBr were included. Best corrected visual acuity (BCVA), central macular thickness (CMT), and macular volume (MV) on optical coherence tomography images were evaluated just before the most recent conventional anti-VEGF (ranibizumab/aflibercept) injection therapy (V1), one month after the most recent traditional anti-VEGF therapy (V2), just before the first IVBr (V3), and one month after the first IVBr (V4). BCVA, CMT, MV, and presence of intraocular inflammation (IOI) were evaluated at each visit. Anterior chamber flare values were also examined at V3 and V4. BCVA showed significant improvement at V2 (0.30 ± 0.23) than V1 (0.39 ± 0.29) and at V4 (0.34 ± 0.26) than V3 (0.48 ± 0.34) (P = 0.002, P < 0.001). However, no significant difference was observed between V2 and V4 (P = 0.257). CMT was significantly thinner at V2 (346.8 ± 90.2 µm) than V1 (495.5 ± 123.8 µm), and at V4 (322.2 ± 95.7 µm) than V3 (536.5 ± 166.0 µm) (P < 0.001, P < 0.001), but no significant difference was observed between V2 and V4 (P = 0.140). MV was significantly smaller at V2 (11.6 ± 2.0 mm3) than V1 (12.6 ± 1.9 mm3) and at V4 (11.2 ± 2.0 mm3) than V3 (12.6 ± 2.0 mm3) (P < 0.001, P < 0.001), and even significantly smaller at V4 than V2 (P = 0.009). No patient had IOI. No significant changes were observed in anterior chamber flare values between V3 and V4 (25.6 ± 14.6 vs. 24.0 ± 11.5 photon count/ms; P = 0.543). Both CMT and MV significantly reduced without any adverse events one month after switching from conventional anti-VEGF to IVBr therapy for DME, including IOI. MV was significantly lower for IVBr than anti-VEGF therapy after one month of treatment. Therefore, brolucizumab may be a viable treatment option for DME patients considering switching from conventional anti-VEGF agents for various reasons, such as poor response or inability to extend dosing intervals.

Efficacy and safety profile of intravitreal dexamethasone implant versus antivascular endothelial growth factor treatment in diabetic macular edema: a systematic review and meta-analysis.

To better understand the efficacy of intravitreal dexamethasone implant (Ozurdex) versus antivascular endothelial growth factor (anti-VEGF) treatment in patients with diabetic macular edema (DME). A systematic review and meta-analysis. The study included randomized control trials (RCTs) and non-randomized control trials (Non-RCTs) before December 2021 that compare the efficacy of Ozurdex-related therapyand anti-VEGF therapy. We searched PubMed, Cochrane Library, and EMBASE. The quality of the included studies was assessed carefully. 30 studies were included. Regarding BCVA change, the overall result revealed no significant differences between Ozurdex and anti-VEGF therapies in patients with nonresistant DME, but Ozurdex group had significantly more VA improvement than anti-VEGF therapies in patients with resistant DME (MD 0.12, 95% CI 0.02-0.21). In terms of central retinal thickness (CRT) decrease, there was a significant difference between Ozurdex therapy and anti-VEGF therapy in patients with nonresistant DME (MD 48.10, 95% CI 19.06-77.13) and resistant DME (MD 65.37, 95% CI 3.62-127.13). Overall, Ozurdex therapy resulted in significantly greater VA improvement and CRT decrease than anti-VEGF therapy in resistant DME patients. Ozurdex therapy was not inferior to anti-VEGF therapy in patients with nonresistant DME.

Safety and tolerability of semaglutide across the SUSTAIN and PIONEER phase IIIa clinical trial programmes.

AIM: Glucagon-like peptide-1 receptor agonists improve glycaemic control: some are now available as oral and subcutaneous formulations, and some have indications for reducing cardiovascular risk. The expanded scope for these therapies warrants comprehensive safety evaluations. We report the safety/tolerability of subcutaneous and oral semaglutide from the SUSTAIN and PIONEER clinical trial programmes, respectively. MATERIALS AND METHODS: Adverse events (AEs) from 16 randomized placebo- or active-controlled phase IIIa trials in patients with type 2 diabetes (n = 11 159) including once-weekly subcutaneous semaglutide (n = 3150; SUSTAIN trials) or once-daily oral semaglutide (n = 4116; PIONEER trials) were analysed. Data pools were analysed for each programme, with separate analyses of cardiovascular outcomes trials (CVOTs; n = 6480). RESULTS: In the phase IIIa pools, gastrointestinal disorders were reported in 41.9%/39.1% of patients with subcutaneous/oral semaglutide, respectively (most prevalent during initiation/escalation) versus 22.0%/24.8% with comparators. Rates of kidney disorders, acute pancreatitis, malignant neoplasms, hypoglycaemia, diabetic retinopathy, heart failure and other cardiovascular events were similar for semaglutide versus comparators. Cholelithiasis incidence was higher with subcutaneous and oral semaglutide versus placebo. Diabetic retinopathy incidence was higher with subcutaneous semaglutide versus placebo in SUSTAIN 6. Small pulse rate increases occurred with both formulations; there was no increased rate of arrhythmias. Fatal AE incidence was similar between semaglutide and comparators. Versus placebo, CVOTs showed a reduced risk of major adverse cardiovascular events with subcutaneous semaglutide and non-inferiority criteria were met with oral semaglutide. CONCLUSIONS: The most common AEs with semaglutide were gastrointestinal disorders, which decreased with continued therapy. These comprehensive safety/tolerability data may better inform patient selection and guidance in care.

A systematic review and meta-analysis of the effect of intravitreal VEGF inhibitors on cardiorenal outcomes.

BACKGROUND: Vascular endothelial growth factor inhibitors (VEGFis) have transformed the treatment of many retinal diseases, including diabetic maculopathy. Increasing evidence supports systemic absorption of intravitreal VEGFi and development of significant cardiorenal side effects. METHODS: We conducted a systematic review and meta-analysis (PROSPERO: CRD42020189037) of randomised controlled trials of intravitreal VEGFi treatments (bevacizumab, ranibizumab and aflibercept) for any eye disease. Outcomes of interest were cardiorenal side effects (hypertension, proteinuria, kidney function decline and heart failure). Fixed effects meta-analyses were conducted where possible. RESULTS: There were 78 trials (81 comparisons; 13 175 participants) that met the criteria for inclusion: 47% were trials in diabetic eye disease. Hypertension (29 trials; 8570 participants) was equally common in VEGFi and control groups {7.3 versus 5.4%; relative risk [RR] 1.08 [95% confidence interval (CI) 0.91-1.28]}. New or worsening heart failure (10 trials; 3384 participants) had a similar incidence in VEGFi and control groups [RR 1.03 (95% CI 0.70-1.51)]. Proteinuria (5 trials; 1902 participants) was detectable in some VEGFi-treated participants (0.2%) but not controls [0.0%; RR 4.43 (95% CI 0.49-40.0)]. Kidney function decline (9 trials; 3471 participants) was similar in VEGFi and control groups. In participants with diabetic eye disease, the risk of all-cause mortality was higher in VEGFi-treated participants [RR 1.62 (95% CI 1.04-2.46)]. CONCLUSION: In trials of intravitreal VEGFi, we did not identify an increased risk of cardiorenal outcomes, although these outcomes were reported in only a minority of cases. There was an increased risk of death in VEGFi-treated participants with diabetic eye disease. Additional scrutiny of post-licensing observational data may improve the recognition of safety concerns in VEGFi-treated patients.

Results of intravitreal dexamethasone implant (Ozurdex®) for retinal vascular diseases with macular edema: An observational study of real-life situations.

To evaluate the efficacy of intravitreal dexamethasone implants (Ozurdex®) for the treatment of macular edema (ME) associated with retinal vascular diseases in real-life situations. This retrospective study included patients with ME associated with retinal vascular occlusion (RVO) or diabetic macular edema (DME) treated with dexamethasone implants. Demographic data, best-corrected visual acuity (BCVA), and central retinal thickness (CRT) at baseline and at 1, 3, and 6 months postoperatively were collected and analyzed, and the adverse events were recorded. Forty-four eyes, 42 patients were included in the study. The mean logMAR BCVA improved from 0.79 ± 0.38 at baseline to 0.60 ± 0.34 (P < 0.001), 0.72 ± 0.38 (P = .002), and 0.72 ± 0.37 (P = .002) at 1, 3, and 6 months, respectively. The CRT decreased from 526.70 ± 159.58 µm at baseline to 279 ± 66.23, 422.91 ± 206.99, and 350.23 ± 151.51 µm at 1, 3, and 6 months, respectively (P < 0.001, all visits). The average number of injections was 1.43 ± 0.5. Nineteen eyes (43.18%) received second injections at an interval of 4.20 ± 0.61 months. The mean logMAR BCVA was greater in RVO than in DME patients and in treatment-naïve eyes than in previously treated ones. The baseline CRT of the reinjection group was significantly higher than that of the single-injection group for both the RVO (P < 0.001) and DME groups (P = .002). Nine eyes (20.45%) with increasing intraocular pressure (IOP) were well controlled with medication, and cataract progression was observed in five eyes (21.73%) during follow-up. The dexamethasone implant was effective for the treatment of macular edema secondary to RVO and DME in terms of visual acuity and CRT improvement over 6 months. The visual acuity was greater in the RVO and treatment-naïve eyes. Reinjection may be associated with a high baseline CRT. The increase in the occurrence of IOP and cataract progression was similar to that reported in previous studies.

Effect Modification by Indication to the Risks of Major Thromboembolic Adverse Events in Patients Receiving Intravitreal Anti-Vascular Endothelial Growth Factor Treatment: A Population-Based Retrospective Cohort Study.

BACKGROUND: The association between intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment and the risk of major thromboembolic adverse events (TAEs) remains under debate. This study aimed to examine associated risks of TAEs in patients receiving intravitreal anti-VEGF treatment, and effect modification by different indications. METHODS: This retrospective cohort study analyzed Taiwan's National Health Insurance Database during 2011-2017 to identify neovascular age-related macular degeneration (nAMD) or diabetic macular edema (DME) patients newly receiving intravitreal aflibercept or ranibizumab. We followed up patients for 2 years, or until the occurrence of TAEs, including ischemic heart disease, ischemic stroke, transient ischemic attack, deep vein thrombosis, and pulmonary embolism, death, or the end of the study period (i.e., 31 December 2018). We compared the risk of TAEs between patients with aflibercept and ranibizumab using Cox-proportional hazard models. We examined statistical interactions between the anti-VEGF treatment (i.e., ranibizumab and aflibercept) and indications (i.e., nAMD and DME) with regard to the outcome of TAEs. RESULTS: We included 12,215 nAMD and 7532 DME patients. Among nAMD patients, those receiving aflibercept had lower risk of TAEs (adjusted hazard ratio [HR] 0.85; 95% CI 0.77-0.94) compared with those receiving ranibizumab. However, among DME patients, those receiving aflibercept had no differences in the risk of TAEs (1.14; 0.97-1.35) compared with those receiving ranibizumab. Among patients treated with ranibizumab, the DME group had a higher risk of TAEs than the nAMD group (HR 1.15; 95% CI 1.03-1.28); similar results were observed in patients treated with aflibercept (HR 1.53; 95% CI 1.27-1.85). When DME patients were treated with aflibercept, the risk of TAEs was 31% higher than when nAMD patients were treated with ranibizumab (HR 1.31; 95% CI 1.09-1.56; p < 0.05). The p-value for statistical interaction between the anti-VEGF treatment and indications was 0.0033. CONCLUSIONS: Patients treated with aflibercept or ranibizumab for different indications may be associated with varying risk of TAEs. The findings provide evidence to support treatment selection, taking indications and TAE risk into consideration.

Semaglutide and Diabetic Retinopathy Risk in Patients with Type 2 Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trials.

BACKGROUND: Semaglutide is a recently approved glucagon-like peptide-1 receptor agonist used to treat patients with type 2 diabetes mellitus (T2DM). The SUSTAIN 6 trial found a significantly higher rate of retinopathy complications in the semaglutide-treated group compared with the placebo group. OBJECTIVE: This study aimed to evaluate the association between semaglutide and the risk of retinopathy in patients with T2DM. METHODS: Electronic databases were systematically searched up to April 2021 to identify randomized controlled trials that reported diabetic retinopathy (DR) events in semaglutide-treated and control groups. A meta-analysis was conducted using Review Manager 5.4 software to calculate the risk ratio (RR) and 95% confidence intervals (CIs). RESULTS: A total of 23 randomized trials involving 22,096 patients with T2DM were included. There were 730 incident DR cases-463 in the semaglutide group and 267 in the control group. Overall, semaglutide was not associated with increased DR risk compared with controls when all trials were combined (RR 1.14, 95% CI 0.98-1.33). Subgroup analysis showed that semaglutide was associated with an increased risk of DR compared with placebo (RR 1.24, 95% CI 1.03-1.50). Moreover, patient age ≥ 60 years and diabetes duration ≥ 10 years were also factors for increased risk of DR when using semaglutide (RR 1.27, 95% CI 1.02-1.59; RR 1.28, 95% CI 1.04-1.58, respectively). CONCLUSIONS: Semaglutide was not associated with an increased risk of DR; however, caution regarding DR risk is needed for older patients or those with long diabetes duration when taking semaglutide.

Early Microglial Changes Associated with Diabetic Retinopathy in Rats with Streptozotocin-Induced Diabetes.

Although morphological changes in microglia have been reported to be associated with diabetic retinopathy, little is known about the early changes in the microglia and macrophages during the progression of this condition. The present study was aimed at characterizing retinal microglial activation in the early stages of experimental diabetic retinopathy. Toward this end, a model of diabetic retinopathy was generated by intraperitoneally injecting male Sprague-Dawley rats with streptozotocin. No apparent histological changes were observed during the early stages of experimental diabetic retinopathy. However, at 4 to 16 weeks after the onset of diabetes, the retinas from diabetic rats exhibited higher density of microglia than those from age-matched normal controls, with microglial density peaking at 12 weeks. In particular, the proportion of the activated microglia increased significantly in the diabetic rats, specifically in the nerve fiber and ganglion cell layers, whereas it decreased in the inner plexiform layer within 12 weeks. Furthermore, the resident retinal microglial cells were activated immediately after diabetes induction, peaked at 12 weeks, and remained for up to 16 weeks after disease onset. Thus, experimental diabetic retinopathy causes gradual hypoxia and neuroinflammation, followed by the activation of microglia and the migration of macrophages. The distribution and density of retinal microglial activation changed typically with the progression of the disease in early-stage diabetic rats.

Berberine improves insulin-induced diabetic retinopathy through exclusively suppressing Akt/mTOR-mediated HIF-1α/VEGF activation in retina endothelial cells.

Background: Insulin therapy is the major treatment of glycaemic control in type I diabetes mellitus (DM) and advanced type II DM patients who fail to respond to oral hypoglycemic agents. Nonetheless, insulin therapy is deemed unsuccessful in controlling the incidence of diabetic retinopathy (DR) and is likely a risk factor. Berberine, an isoquinoline alkaloid, has caught great attention towards its anti-diabetic mechanisms. This study aims to investigate the effect of berberine in decelerating DR progression in insulin-treated DM. Methods: To better understand the therapeutic potential of berberine in the presence of insulin, we elaborated the action of mechanism whether berberine inhibited retinal expression of HIF-1α and VEGF through regulating AKT/mTOR pathway. Suppression of insulin-induced neovasculature of retina endothelial cells by berberine was also studied. Lastly, the in vivo efficacy and safety of berberine as adjuvant therapy for the treatment of DR were systemically investigated in experimental type I and type II DM mice with insulin treatment. Results: Among various types of retinal cells, the activity of HIF-1α and VEGF in retinal endothelial cells could be particularly and exclusively stimulated by insulin intervention, which could be inhibited by berberine treatment in a dose- and time-dependent manner. Berberine suppressed Akt/mTOR activity in these cells, and restoration of Akt/mTOR signalling attenuated berberine's inhibition on HIF-1α and VEGF expression. Berberine suppressed the progression of DR in experimental type I and type II diabetic mice receiving insulin therapy. Conclusion: Berberine improves insulin-induced diabetic retinopathy in type I and II diabetes through inhibiting insulin-induced activation of retinal endotheliocytes via Akt/mTOR/ HIF-1α/VEGF pathway.

Retinoprotective effect of agmatine in streptozotocin-induced diabetic rat model: avenues for vascular and neuronal protection : Agmatine in diabetic retinopathy.

Diabetic retinopathy (DR) is the most common diabetic neurovascular complication, and the leading cause of preventable blindness among working-age individuals. Recently, agmatine, the endogenous decarboxylated L-arginine, has gained attention as a pleiotropic agent that modulates the diabetes-associated decline in quality of life, and exhibited varied protective biological effects. Diabetes was induced by a single streptozotocin (STZ, 50 mg/kg, i.p.) injection. When diabetes was verified, the animals were randomly allocated into three groups (16 rat each); diabetic, agmatine-treated diabetic (1 mg/kg, daily, for 12 weeks), and control group. Blood glucose homeostasis, retinal redox status, apoptotic parameters, nitric oxide synthase (NOS), nitric oxide (NO), vascular endothelial growth factor (VEGF), glutamate, glutamine, glutamine synthase (GS) activity, nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), and mitogen-activated protein kinase (MAPKs) pathways were assayed biochemically. Retinal vascular permeability was measured. Retinal morphology was evaluated by hematoxylin and eosin staining. Retinal N-methyl-D-aspartic acid receptor1 (NMDAR1) and glutamate aspartate transporter (GLAST) mRNA were quantified. Glucose transporter 1, pro-caspase3, and glial fibrillary acidic protein (GFAP) expression were quantified by immunohistochemistry. Chronic agmatine treatment abrogated STZ-induced retinal neurodegeneration features including gliosis, and neuronal apoptosis, restored retinal vascular permeability, mostly through antioxidant, anti-apoptotic capacity, abolishing glutamate excitotoxicity, modulating the activity of NMDARs, MAPKs/NFκB, and NOS/NO pathways. By restoring the molecular and functional background of retinal neurovascular homeostatic balance, agmatine would be appropriate therapeutic option acting upstream of the DR, impeding its progression.

Hypoglycemia Induces Mitochondrial Reactive Oxygen Species Production Through Increased Fatty Acid Oxidation and Promotes Retinal Vascular Permeability in Diabetic Mice.

Aims: Hypoglycemia is associated with increased reactive oxygen species (ROS) production and vascular events. We have previously reported that low-glucose (LG) conditions induce mitochondrial ROS (mtROS) production in aortic endothelial cells (ECs). However, the mechanism by which hypoglycemia promotes diabetic retinopathy (DR) is unclear. Blood-retinal barrier (BRB) disruption occurs in the early stages of DR. We hypothesized that the mechanisms underlying hypoglycemia-induced DR are associated with BRB breakdown due to mtROS generation during hypoglycemia. Here, we aimed to determine whether hypoglycemia exacerbated mtROS production and induced BRB disruption. Results: We observed that hypoglycemia induced mtROS production by increasing fatty acid oxidation (FAO), which was suppressed by overexpression of mitochondrial-specific manganese superoxide dismutase (MnSOD) in retinal ECs. Furthermore, FAO blockade decreased the hypoglycemia-induced mtROS production. Recurrent hypoglycemia increased albumin leak in diabetic mice retina, which was suppressed in diabetic vascular endothelial cell-specific MnSOD transgenic (eMnSOD-Tg) mice. Pharmacological FAO blockade also reduced mtROS production, reduced vascular endothelial growth factor (VEGF) production during hypoglycemia, and prevented retinal vascular permeability in diabetic mice. MnSOD overexpression or carnitine palmitoyltransferase I (CPT1) blockade suppressed vascular endothelial-cadherin phosphorylation under LG in retinal ECs. Innovation and Conclusion: Reduction of mtROS and VEGF production via pharmacological FAO and/or CPT1 blockade may prevent hypoglycemia-induced worsening of DR.

MiR-19a inhibitor improves diabetic retinopathy in rats through PTEN/Akt/P-Akt signaling pathway.

The aim of this study is to explore the regulatory effect of micro ribonucleic acid (miR)-19a on diabetic retinopathy (DR) through mediating the phosphatase and tensin homolog deleted on chromosome ten (PTEN)/protein kinase B (Akt) signaling pathway. Thirty male Sprague-Dawley rats were first divided into Healthy group, DR group and miR-19a inhibitor group. The DR model was induced by intraperitoneal injection of streptozotocin (STZ) (60 mg/kg). The retinal tissues were dissected and RGCs were isolated. The expression level of miR-19a therein was determined using quantitative polymerase chain reaction (qPCR). The pathological changes were observed through hematoxylin-eosin staining (HE) staining. The apoptosis was detected by flow cytometry. PTEN was predicted as a target gene of miR-19a through TargetScan biological software. The protein expression of PTEN was detected via immunofluorescence assay. The changes in the phosphatidylinositol 3-hydroxy kinase (PI3K)/Akt pathway-associated proteins were detected using Western blotting. The expression of miR-19a declined substantially in DR rats injected with miR-19a inhibitor (P<0.05). RGCs were arranged regularly, showing apoptosis and milder necrosis in miR-19a inhibitor group. The proportion of apoptotic cells was substantially decreased in miR-19a inhibitor group (P<0.05). It was found that miR-19a inhibitor group exhibited an evidently lower protein expression of PTEN and a higher activation degree of the Akt pathway than DR group (P<0.05). MiR-19a binds to PTEN protein in a targeted manner to mediate the PI3K/Akt pathway, thereby affecting the progression of DR.

Epigenetics and Mitochondrial Stability in the Metabolic Memory Phenomenon Associated with Continued Progression of Diabetic Retinopathy.

Retinopathy continues to progress even when diabetic patients try to control their blood sugar, but the molecular mechanism of this 'metabolic memory' phenomenon remains elusive. Retinal mitochondria remain damaged and vicious cycle of free radicals continues to self-propagate. DNA methylation suppresses gene expression, and diabetes activates DNA methylation machinery. Our aim was to investigate the role of DNA methylation in continued compromised mitochondrial dynamics and genomic stability in diabetic retinopathy. Using retinal endothelial cells, incubated in 20 mM glucose for four days, followed by 5 mM glucose for four days, and retinal microvessels from streptozotocin-induced diabetic rats in poor glycemia for four months, followed by normal glycemia for four additional months, DNA methylation of mitochondrial fusion and mismatch repair proteins, Mfn2 and Mlh1 respectively, was determined. Retinopathy was detected in trypsin-digested microvasculature. Re-institution of good glycemia had no beneficial effect on hypermethylation of Mfn2 and Mlh1 and retinal function (electroretinogram), and the  retinopathy continued to progress. However, intervention of good glycemia directly with DNA methylation inhibitors (Azacytidine or Dnmt1-siRNA), prevented Mfn2 and Mlh1 hypermethylation, and ameliorated retinal dysfunction and diabetic retinopathy. Thus, direct regulation of DNA methylation can prevent/reverse diabetic retinopathy by maintaining mitochondrial dynamics and DNA stability, and prevent retinal functional damage.

Protective Effect of Palm Oil-Derived Tocotrienol-Rich Fraction Against Retinal Neurodegenerative Changes in Rats with Streptozotocin-Induced Diabetic Retinopathy.

: Oxidative stress plays an important role in retinal neurodegeneration and angiogenesis associated with diabetes. In this study, we investigated the effect of the tocotrienol-rich fraction (TRF), a potent antioxidant, against diabetes-induced changes in retinal layer thickness (RLT), retinal cell count (RCC), retinal cell apoptosis, and retinal expression of vascular endothelial growth factor (VEGF) in rats. Additionally, the efficacy of TRF after administration by two different routes was compared. The diabetes was induced in Sprague-Dawley rats by intraperitoneal injection of streptozotocin. Subsequently, diabetic rats received either oral or topical treatment with vehicle or TRF. Additionally, a group of non-diabetic rats was included with either oral or topical treatment with a vehicle. After 12 weeks of the treatment period, rats were euthanized, and retinas were collected for measurement of RLT, RCC, retinal cell apoptosis, and VEGF expression. RLT and RCC in the ganglion cell layer were reduced in all diabetic groups compared to control groups (p < 0.01). However, at the end of the experimental period, oral TRF-treated rats showed a significantly greater RLT compared to topical TRF-treated rats. A similar observation was made for retinal cell apoptosis and VEGF expression. In conclusion, oral TRF supplementation protects against retinal degenerative changes and an increase in VEGF expression in rats with streptozotocin-induced diabetic retinopathy. Similar effects were not observed after topical administration of TRF.

Taxifolin Shows Anticataractogenesis and Attenuates Diabetic Retinopathy in STZ-Diabetic Rats via Suppression of Aldose Reductase, Oxidative Stress, and MAPK Signaling Pathway.

BACKGROUND: Due to the increased prevalence of diabetes-associated complications of the eye like diabetic retinopathy and cataract, the need for a novel therapeutic agent is urgent. Due to the advantages that the polyphenolic compounds enjoy in diabetes and associated complications, we postulated that Taxifolin (TXF), a poly-phenolic flavanol, could show anti-retinopathic and anti-cataract effect in diabetes-induced rats. METHODS: TXF at a dose of 10, 25, and 50 mg/kg was given by oral route to STZ mediated diabetic rats for a time period of 10 weeks. The opacity of lens was studied after every 7 days of treatment till 10 weeks; evaluation of the severity of cataract and changes in the histology of lens as well as retina was done. Tissue homogenates of lens isolated after the end of the study were evaluated for markers of oxidative stress, levels of aldose reductase, p38MAPK, VEGF, and ERK1/2. RESULTS: Outcomes suggested that TXF improved retinopathy and cataract in diabetes-induced rats. The treatment of TXF also improved the status of oxidative stress and inhibited the levels of p38MAPK, VEGF, and ERK1/2. The treatment also improved the lens opacity in diabetic rats. The results suggest that the protective effect of TXF against cataract and retinopathy may be due to the anti-oxidative potential of TXF and its inhibiting effect on VEGF, ERK1/2, p38MAPK, and aldose reductase. CONCLUSION: The study confirms that TXF is a potential candidate showing a protective effect against diabetic induced retinopathy and cataract.

Long noncoding RNA MALAT1 participates in the pathological angiogenesis of diabetic retinopathy in an oxygen-induced retinopathy mouse model by sponging miR-203a-3p.

Diabetic retinopathy (DR) is a devastating complication of diabetes. The aim of the present study is to investigate the exact role and mechanism of long noncoding RNA MALAT1 (MALAT1) in the progress of DR. An oxygen-induced retinopathy (OIR) mouse model and high glucose (HG) stimulated human retinal microvascular endothelial cells (HRMECs) were employed to mimic the pathological statues of DR. Quantitative real-time PCR (qRT-PCR) and Western blot results showed that MALAT1, VEGFA, and HIF-1α levels were increased in DR retinal tissues and HG-stimulated HRMECs, whereas the expression of miR-203a-3p was decreased. Knockdown of MALAT1 or upregulation of miR-203a-3p both suppressed HG-induced proliferation, migration, and tube formation of HRMECs. A dual-luciferase reporter assay showed that miR-203a-3p could bind to the predicted seed regions of MALAT1 as evidenced by the reduced luciferase activity. Furthermore, enforced downregulation of miR-203a-3p abolished the suppressive effect of MALAT1 silencing on HRMEC cell migration and tube formation. In conclusion, these data demonstrated that MALAT1 may affect angiogenesis by sponging miR-203a-3p in DR, suggesting that MALAT1 may act as a novel therapeutic target for the treatment of DR.