Diabetic Retinopathy-Update on Prevention Techniques, Present Therapies, and New Leads

Knowledge about age-related eye diseases in the general population in Germany

BACKGROUND

With a rising prevalence of age-related eye diseases, prevention and early diagnosis of these conditions are key goals of public eye health. Disease-related knowledge in the general public supports these goals but there is little data available. Thus, we have assessed knowledge of cataract, glaucoma, age-related macular degeneration (AMD) and diabetic eye disease in the German adult general population in a cross-sectional study and identified target groups for health education interventions.

METHODS

Knowledge assessment content was identified based on a literature review, expert input, and a list of items was generated after a qualitative selection process. The resulting 16-item instrument (4 items per condition) was administered to 1,008 participants from a survey panel, demographically representative of the adult German population. Test properties were evaluated based on a Rasch model and multiple correspondence analysis (MCA). Binary-logistic regression analysis was performed to investigate associations with age, sex, education level, employment status, marital status, income, reported health status, visual difficulties, and recent general practitioner (GP) and ophthalmologist consultations.

RESULTS

Replies were correct for a median of 9 out of 16 (range 2 - 16) items, which differed between conditions (p < 0.0001). Most responses were correct for cataract items (median: 3 / 4) and least were correct for AMD items (median: 2 / 4). 27%, 9%, 1% and 19% of respondents replied correctly to all cataract, glaucoma, AMD and diabetic eye disease-related items, respectively. Rasch analysis suggested an adequate targeting of items and in MCA, no evidence of multidimensionality was present. Older age, being retired, decreased general health and recent GP or ophthalmology consultations were significantly associated with more knowledge about common eye conditions (p ≤ 0.005). GP or ophthalmology consultations remained significant in a multivariable model (p ≤ 0.011).

CONCLUSIONS

Knowledge gaps regarding eye health are considerable in the German general population and should therefore be addressed in educational interventions targeting the public. Special attention when designing such campaigns needs to be paid to infrequent users of the healthcare system. Knowledge of AMD seems to be poorer compared to other eye conditions.

Internalization of Angiotensin-(1-12) in Adult Retinal Pigment Epithelial-19 Cells

Purpose: Angiotensin-(1-12) [Ang-(1-12)] serves as a primary substrate to generate angiotensin II (Ang II) by angiotensin-converting enzyme and/or chymase suggests it may be an unrecognized source of Ang II-mediated microvascular complication in hypertension-mediated retinopathy. We investigated Ang-(1-12) expression and internalization in adult retinal pigment epithelial-19 (ARPE-19) cultured cells. We performed the internalization of Ang-(1-12) in ARPE-19 cells in the presence of a highly specific monoclonal antibody (mAb) developed against the C-terminal end of the Ang-(1-12) sequence. Methods: All experiments were performed in confluent ARPE-19 cells (passage 28-35). We employed high-performance liquid chromatography to purify radiolabeled, 125I-Ang-(1-12) and immuno-neutralization with Ang-(1-12) mAb to demonstrate Ang-(1-12)'s internalization in ARPE-19 cells. Internalization was also demonstrated by immunofluorescence (IF) method. Results: These procedures revealed internalization of an intact 125I-Ang-(1-12) in ARPE-19 cells. A significant reduction (∼53%, P < 0.0001) in 125I-Ang-(1-12) internalization was detected in APRE-19 cells in the presence of the mAb. IF staining experiments further confirms internalization of Ang-(1-12) into the cells from the extracellular culture medium. No endogenous expression was detected in the ARPE-19 cells. An increased intensity of IF staining was detected in cells exposed to 1.0 μM Ang-(1-12) compared with 0.1 μM. Furthermore, we found hydrolysis of Ang-(1-12) into Ang II by ARPE-19 cells' plasma membranes. Conclusions: Intact Ang-(1-12) peptide is internalized from the extracellular spaces in ARPE-19 cells and metabolized into Ang II. The finding that a selective mAb blocks cellular internalization of Ang-(1-12) suggests alternate therapeutic approaches to prevent/reduce the RPE cells Ang II burden.

Diabetic Retinopathy: An Overview of Treatments

Diabetic retinopathy (DR), substantially impacts the quality of life of diabetic patients, it remains, in developed countries, the leading cause of vision loss in working-age adults (20-65 years). Currently, about 90 million diabetics suffer from DR. DR is a silent complication that in its early stages is asymptomatic. However, over time, chronic hyperglycemia can lead to sensitive retinal damage, leading to fluid accumulation and retinal haemorrhage (HM), resulting in cloudy or blurred vision. It can, therefore, lead to severe visual impairment or even blindness if left untreated. It can be classified into nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). NPDR is featured with intraretinal microvasculature changes and can be further divided into mild, moderate, and severe stages that may associate with diabetic macular oedema (DME). PDR involves the formation and growth of new blood vessels (retinal neovascularisation) under low oxygen conditions. Early identification and treatment are key priorities for reducing the morbidity of diabetic eye disease. In the early stages of DR, a tight control of glycemia, blood pressure, plasma lipids, and regular monitoring can help prevent its progression to more advanced stages. In advanced stages, the main treatments of DR include intraocular injections of anti-vascular endothelial growth factor (VEGF) antibodies, laser treatments, and vitrectomy. The aim of this review is to provide a comprehensive overview of the published literature pertaining to the latest progress in the treatment of DR.

Intravitreal injection of adenosine A2A receptor antagonist reduces neuroinflammation, vascular leakage and cell death in the retina of diabetic mice

Diabetic retinopathy is a major complication of diabetes mellitus and a leading cause of blindness. The pathogenesis of diabetic retinopathy is accompanied by chronic low-grade inflammation. Evidence shows that the blockade of adenosine A_2A receptors (A_2AR) affords protection to the retina through the control of microglia-mediated neuroinflammation. Herein, we investigated the therapeutic potential of an antagonist of A_2AR in a model of diabetic retinopathy. Type 1 diabetes was induced in 4–5 months old C57BL/6 J mice with a single intraperitoneal injection streptozotocin. Animals were treated one month after the onset of diabetes. The A_2AR antagonist was delivered by intravitreal injection once a week for 4 weeks. Microglia reactivity and inflammatory mediators were increased in the retinas of diabetic animals. The treatment with the A_2AR antagonist was able to control microglial reactivity and halt neuroinflammation. Furthermore, the A_2AR antagonist rescued retinal vascular leakage, attenuated alterations in retinal thickness, decreased retinal cell death and the loss of retinal ganglion cells induced by diabetes. These results demonstrate that intravitreal injection of the A_2AR antagonist controls inflammation, affords protection against cell loss and reduces vascular leakage associated with diabetes, which could be envisaged as a therapeutic approach for the early complications of diabetes in the retina.

German Diabetes Study - Baseline data of retinal layer thickness measured by SD-OCT in early diabetes mellitus

PURPOSE

Recent studies highlighted that early diabetic neurodegeneration is present before microvascular changes are visible. Retinal neurodegeneration can decrease retinal layer thickness. We aimed to determine whether decreased retinal layer thickness is present already in the early time course of disease.

METHODS

A cross-sectional analysis of patients and healthy adults from the German Diabetes Study (GDS, ClinicalTrials.gov Identifier number: CT01055093, https://clinicaltrials.gov/ct2/show/NCT01055093). Inclusion criteria were a diagnosis of diabetes mellitus (DM) within the last 12 months. Retinal layers thickness in the nasal pericentral segment was measured by spectral domain ocular coherence tomography (SD-OCT). For statistical analysis proc mixed (sas-version 9.4) was used.

RESULTS

One hundred and seventy-eight eyes of 89 patients with type 1 DM (58 males, age 36 ± 11 years, BMI 25.5 ± 4.2 kg/m²) and 242 eyes of 121 patients with type 2 DM (84 males, age 53 ± 10 years, BMI 31.9 ± 6.3 kg/m²) with a disease duration of less than 1 year were compared to 76 eyes of 38 controls (27 males, age 41 ± 16 years, BMI 27.3 ± 6.4 kg/m²). Analysis of retinal layer thickness and visual function did not reveal a significant difference between patients and controls.

CONCLUSION

In the early course of DM potential, neurodegeneration does not relate to measureable changes of retinal layer thickness.

Typhae pollen polysaccharides ameliorate diabetic retinal injury in a streptozotocin-induced diabetic rat model

ETHNOPHARMACOLOGICAL RELEVANCE

According to ancient traditional Chinese medicine, Typhae Pollen (TP) is commonly used to treat fundus haemorrhage because it improves blood circulation.

AIMS OF THE STUDY

This study evaluated the role of the main TP component, polysaccharides (TPP), on diabetic retinopathy (DR) and its possible mechanisms of inhibiting inflammation and improving blood circulation.

MATERIALS AND METHODS

After successful establishment of a diabetic rat model, TPP was administered to diabetic rats for treatment, and the rats were sacrificed at 12 weeks. Retinal electrophysiology and ultrastructures were observed, and serum interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) levels were also measured. Changes in the retinal expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were examined by immunofluorescence. A mouse model of acute blood stasis was then established, and the effects of TPP on haemorheology were observed. The anti-inflammatory effect of TPP was analysed based on the changes in abdominal capillary permeability and the degree of auricle swelling in the mice.

RESULTS

In streptozotocin (STZ)-induced DR rats, TPP (0.4 g/kg) treatment restored electrophysiology indexes and retinal ultrastructures, reduced serum IL-6 and TNF-α levels, decreased VEGF and bFGF expression in retinal tissues, and improved haemorheology indexes. Moreover, TPP reduced abdominal capillary permeability and relieved auricle swelling in a dose-dependent manner.

CONCLUSIONS

TPP treatment ameliorated DR by inhibiting inflammation and improving blood circulation.

Heat shock protein-70 and hypoxia inducible factor-1α in type 2 diabetes mellitus patients complicated with retinopathy

PURPOSE

To elucidate the role of heat shock protein-70 (HSP70) and hypoxia inducible factor-1α (HIF-1α) in diabetic retinopathy (DR) patients.

DESIGN AND METHODS

A comparative study was done on the serum level of both HSP70 and HIF-1α in 50 patients with type 2 diabetes mellitus (T2DM) without DR, 50 patients with T2DM and DR and 70 healthy control subjects.

RESULTS

HSP70 and HIF-1α were significantly increased in T2DM patients compared to controls and increased in patients with T2DM & DR compared to T2DM patients without DR (p < 0.0001). HSP70 did not differ among the patients with different stages of DR, while HIF-1α increased significantly in grades 3 and 4 DR patients compared to grades 1 and 2 DR patients. A strong correlation was found between HIF-1α and the development of DR (r = 0.835, p = 0.00) but not with HSP70. HIF-1α can be used as a predictor for development of DR but not HSP70.

CONCLUSIONS

Our study was the first that investigated both HSP70 and HIF-1α in humans and was the first that measured their levels in serum of patients with DR. The study suggested that HSP70 might have a protective function in T2DM patients rather than a therapeutic function. HIF-1α had an upper hand in the development and progression of DR. Induction of HSP70 and blockage of HIF-1α could lead to the development of novel prophylactic and therapeutic strategies for DR and potentially other diabetic complications.

Aflibercept: A Review of Its Use in the Management of Diabetic Eye Complications

Aflibercept is the most recently approved vascular endothelial growth factor (anti-VEGF) inhibitor for the management of diabetic macular edema and diabetic retinopathy. The purpose of this article is to review the efficacy and safety of aflibercept in the management of diabetic eye complications and to describe its place in therapy. Anti-VEGF agents have been noted in clinical trials to be superior to laser photocoagulation, the standard therapy ( P < .0001, P ≤ .0085, respectively). Aflibercept has been comparatively studied with other anti-VEGF agents, namely, bevacizumab and ranibizumab, and noted to be equally efficacious and safe in patients with mild visual acuity loss ( P > .50). However, in the treatment of patients with diabetic macular edema having moderate to severe visual acuity loss, aflibercept outperformed the other 2 anti-VEGF agents (aflibercept vs bevacizumab, P < .001; aflibercept vs ranibizumab, P = .003). However, additional studies are needed to fully appreciate the long-term safety and efficacy of aflibercept and the anti-VEGF therapy class.

Ranibizumab: A Review of Its Use in the Treatment of Diabetic Retinopathy in Patients With Diabetic Macular Edema

Objective: To evaluate the pharmacotherapy role of ranibizumab, a vascular endothelial growth factor (VEGF) inhibitor, for the treatment of diabetic retinopathy (DR) in patients with diabetic macular edema (DME). Data Sources: PubMed, Science Direct, Google Scholar, and ClinicalTrials.gov searches (January 2000-May 2015) were conducted for articles published in English, and limited to clinical trials using the key words ranibizumab, DR, DME, anti-VEGF, and DR treatment. Study Selection and Data Extraction: Following PubMed, Science Direct, Google Scholar, and ClinicalTrials.gov searches, 4 clinical trials were identified and included in this review. Phase III/IV studies evaluating the clinical efficacy of ranibizumab versus placebo, ranibizumab versus laser, and ranibizumab versus other anti-VEGF agents were selected and evaluated. Data Synthesis: Ranibizumab administered to patients with DME for 12 to 36 months improved and prevented worsening of visual acuity. At month 36 the ranibizumab-treated eyes had a >2 or >3 step DR improvement compared with the sham crossover eyes. Ranibizumab was also found to be superior to laser treatment. Patients receiving ranibizumab gained 6.0 letters, improved tritan and protan color contrast thresholds, and demonstrated improved retinal sensitivity versus the subjects receiving laser treatment who lost 0.9 letters. When ranibizumab was compared with other anti-VEGF agents (aflibercept, pegaptanib, and bevacizumab), it was not always demonstrated to be significantly superior. Conclusion: Ranibizumab has been shown to be safe and efficacious for use in the treatment of DR in patients with DME. Thus, it is an alternative treatment approach to laser photocoagulation therapy.

Association of bilirubin and malondialdehyde levels with retinopathy in type 2 diabetes mellitus

INTRODUCTION

Bilirubin as an antioxidant and malondialdehyde (MDA) as an oxidant have been shown to be associated with various complications of type 2 diabetes mellitus (DM).

AIMS AND OBJECTIVES

The aim was to measure the levels of serum bilirubin and MDA in type 2 DM patients with and without diabetic retinopathy (DR) and to correlate them with severity of DR.

MATERIALS AND METHODS

A total number of 120 subjects out of which 40 were controls without type 2 DM and the rest 80 were type 2 DM patients were included in the study. Of those 80 diabetics, 44 patients did not have DR and 36 patients had DR.

RESULTS

The total bilirubin, direct bilirubin, indirect bilirubin were higher in controls as compared to cases (P = 0.017, 0.033, 0.024). Serum MDA levels were found to be higher in diabetics as compared to controls (P = 0.00). The values of all the three parameters, that is, total bilirubin, direct bilirubin and indirect bilirubin were lower in patients with retinopathy as compared to those without retinopathic changes (P = 0.00, 0.020, and 0.007). Subjects were assigned to quartiles based on serum total bilirubin concentration. The prevalence of DR was significantly lower among persons with the highest bilirubin quartile compared to those with the lowest quartile. The severity of DR was inversely proportional to the total bilirubin levels (P = 0.001). The multiple logistic regression analysis showed total bilirubin to be associated with prevalence of DR (P = 0.035).

CONCLUSIONS

The levels of total bilirubin were significantly lower in patients with DR and also in the late stages of retinopathy as compared to those without retinopathy and in controls but MDA levels did not show any association with DR.