'Statins in retinal disease'

Next generation therapeutics for retinal neurodegenerative diseases

Neurodegenerative diseases affecting the visual system encompass glaucoma, macular degeneration, retinopathies, and inherited genetic disorders such as retinitis pigmentosa. These ocular pathologies pose a serious burden of visual impairment and blindness worldwide. Current treatment modalities include small molecule drugs, biologics, or gene therapies, most of which are administered topically as eye drops or as injectables. However, the topical route of administration faces challenges in effectively reaching the posterior segment and achieving desired concentrations at the target site, while injections and implants risk severe complications, such as retinal detachment and endophthalmitis. This necessitates the development of innovative therapeutic strategies that can prolong drug release, deliver effective concentrations to the back of the eye with minimal systemic exposure, and improve patient compliance and safety. In this review, we introduce retinal degenerative diseases, followed by a discussion of the existing clinical standard of care. We then delve into detail about drug and gene delivery systems currently in preclinical and clinical development, including formulation and delivery advantages/drawbacks, with a special emphasis on potential for clinical translation.

The Effect of Systemic Parameters and Baseline Characteristics in Short-Term Response Analysis with Intravitreal Ranibizumab in Treatment-Naive Patients with Neovascular Age-Related Macular Degeneration

Anti-vascular endothelial growth factor drugs keep being the main therapy for neovascular age-related macular degeneration (AMD). Possible predictive parameters (demographic, biochemical and/or inflammatory) could anticipate short-term treatment response with ranibizumab. 46 treatment-naive patients were included in a prospective observational study. They underwent three monthly injections of intravitreal ranibizumab for neovascular AMD and the clinical examination was made at baseline and one month after the third injection. Demographic characteristics, co-morbidities and concomitant treatments were recorded at the baseline visit. Biochemical parameters, complete blood count and inflammation biomarkers were also measured at these times. Uric Acid was found to be statistically significant with a one-point difference between good and poor responders in both basal and treated patients, but only in basal parameters was statistical significance reached (p = 0.007 vs. p = 0.071 in treated patients). Cholesterol and inflammatory parameters such as white blood cell count and neutrophils were significantly reduced over time when treated with intravitreal ranibizumab. On the other hand, women seemed to have a worse prognosis for short-term response to intravitreal ranibizumab treatment. Uric acid may help identify possible non-responders before initial treatment with ranibizumab, and cholesterol and white blood cells could be good candidates to monitor short-term response to ranibizumab treatment.

Association between Antihyperlipidemic Agent Use and Age-Related Macular Degeneration in Patients with Hyperlipidemia: A Population-Based Retrospective Cohort Study

Several studies have indicated that lipoproteins might contribute to the pathogenesis of age-related macular degeneration (AMD). In this population-based retrospective cohort study, patients with hyperlipidemia were divided into two groups (study groups I and II) based on whether or not they were receiving antihyperlipidemic agents. The comparison group included patients without hyperlipidemia who were randomly selected and matched with study group II patients. A Cox proportional hazard model was used to evaluate the risk of AMD among the groups. Patients with hyperlipidemia receiving antihyperlipidemic agents (study group I, n = 15,482) had a significantly increased AMD risk (adjusted hazard ratio (HR) = 1.23, 95% confidence interval (CI) = 1.04-1.45) compared to those not receiving antihyperlipidemic agents (study group II, n = 15,482). However, with an increase in cumulative exposure, a reduced risk of AMD was observed in patients using a defined daily dose of more than 721, with an adjusted HR of 0.34 (95% CI = 0.22-0.53, p < 0.001). Additionally, the adjusted HR of AMD for study group II was 1.40 (95% CI = 1.20-1.63, p < 0.001) relative to the comparison group (n = 61,928). In conclusion, the study results indicated that patients with hyperlipidemia have a higher AMD risk than patients without hyperlipidemia. Furthermore, patients with hyperlipidemia who received antihyperlipidemic agents had a significantly increased AMD risk. However, a dose-dependent reduction in the risk of AMD was observed in patients with hyperlipidemia using statins or/and fibrates.

Chronic Kidney Disease as A Potential Risk Factor for Uveitis: A 13-Year Nationwide Population-Based Cohort Study in Taiwan

PURPOSE

To investigate whether patients with chronic kidney disease (CKD) are at increased risk of uveitis.

METHODS

Data was collected from the Taiwan National Health Insurance system and included patients newly diagnosed with CKD between 2000 and 2012. The endpoint of interest was a diagnosis of uveitis.

RESULTS

30,256 CKD patients and 121,024 matched comparisons were analyzed. CKD patients were found to have a significantly higher cumulative uveitis incidence. Through multivariate Cox regression analysis, the CKD group was found to have higher risk of developing uveitis (adjusted hazard ratio 1.51). After stratified by gender, age, and comorbidities (hypertension, diabetes, and hyperlipidemia), the increased risk of uveitis in CKD patients remained significant.

CONCLUSIONS

Patients with CKD were found to have higher risk of developing uveitis. For patients over 18 years old and with hypertension, diabetes, or hyperlipidemia, the presence of CKD was demonstrated as an additional crucial factor for uveitis development.

Statin Use and the Risk of Progression to Vision Threatening Diabetic Retinopathy

PURPOSE

This study aims to assess the effect of statins on progression from nonproliferative diabetic retinopathy (NPDR) to vision-threatening diabetic retinopathy (VTDR), proliferative diabetic retinopathy (PDR) or diabetic macular edema (DME).

METHODS

Two cohort studies using a U.S. medical claims database from 2002 to 2019 including NPDR patients 18 years or older. A risk factor analysis performed a time-updating cox regression model assessing statin usage. A second new-user active comparator design analysis replicating a previously published study. Main outcomes included a new diagnosis of VTDR (composite of either PDR or DME) or DME and PDR individually for the risk factor study and included additional outcomes of new DR, NPDR, vitreous hemorrhage (VH) and tractional retinal detachment (TRD) for the new user study.

RESULTS

Risk factor analysis included 66 617 statin users with NPDR at baseline and 83 365 nonstatin users. Of these, 27 325 (18.2%) progressed to VTDR, 4086 (2.71%) progressed to PDR, and 22 750 (15.1%) progressed to DME. After multivariable analysis, no protective effect of statin use was found for progression to VTDR, PDR, or DME (HR = 1.01-3, p >0.33 for all comparisons). Replicated new user design analysis also showed no protective effect for statins on risk of development of DR (HR = 1.03, 95% CI: 0.99-1.07, p = 0.13), PDR (HR = 0.89, 95% CI: 0.79-1.02, p = 0.09), DME (HR = 0.94, 95% CI: 0.86-1.03, p = 0.21), VH (HR = 1.00, 95% CI: 0.86-1.16, p = 0.99), and TRD (HR = 1.11, 95% CI: 0.89-1.38, p = 0.36).

CONCLUSION

Statin use was found not to be protective for progression of DR regardless of study methodology. These results suggest that the specifics of the population studied rather than differing study methodology are important in assessing the effect of statins on DR progression.

Association between Statins and Retinal Vascular Occlusion: A Population-Based Cohort Study

Retinal vascular occlusion (RVO), including retinal arterial occlusion and retinal vein occlusion, is a common retinal vascular disease that causes visual disturbance. The exact pathogenesis of RVO remains unclear. In all types of RVO patients, hyperlipidemia is more than twofold more common than in controls. Statins have been used to control blood cholesterol levels and have been found to reduce the risk of cardiovascular morbidity and mortality. Moreover, the immunomodulatory functions of statins may play a role in treating inflammatory diseases. This study aimed to evaluate whether patients taking statins have a lower risk of developing RVO compared to patients not taking statins. Adult patients with statins usage on the index date identified from the Taiwan National Health Insurance Research Database (NHIRD) between 2000 and 2013 were included. A threefold matched group was selected using age, sex, and year of index date for comparison. During the mean follow-up period of 12.87 ± 1.88 years, the cumulative incidence of RVO was significantly lower in the statin-user group (29.96 per 105 person-years [PYs]) than in the non-statin-user group (39.35 per 105 PYs). The results showed a lower cumulative incidence rate of RVO in patients prescribed statins than in those not prescribed statins (log-rank test, p = 0.020). The adjusting hazard ratio (HR) was significantly greater for RVO in the statin-user group (adjusted HR, 0.704; 95% CI, 0.591-0.873). Statin users had a decreased risk for all types of RVO development, including central retinal artery occlusion, arterial branch occlusion, central retinal vein occlusion, and branch retinal vein occlusion. In conclusion, patients undergoing statin treatment have a lower risk of developing RVO compared to patients not taking statins.

Lipid profile and serum folate, vitamin B12 and homocysteine levels in patients with retinal vein occlusion

BACKGROUND

Retinal vein occlusion (RVO) is mainly related with vascular risk factors (VRF).

OBJECTIVES

To analyze the lipid profile and serum folate, vitamin B₁₂ and homocysteine levels, in patients with RVO and a population-based control group.

PATIENTS AND METHODS

Case-control study. Patients with RVO were assessed during an 11-year period.

RESULTS

We included 368 patients and 325 controls of similar age and sex. HDL cholesterol and folate levels were lower (52 [43-63] mg/dL vs. 55 [46-66]; p = 0.016 and 7 [5-10] ng/mL vs. 9 [7-13]; p < 0.0001, respectively) and non-HDL cholesterol and homocysteine levels higher (148.9 ± 37.3 mg/dL vs. 142.9 ± 34.5; p = 0.03 and 13.4 [11.2-18.2] μmol/L vs. 11.1 [9.0-14.4]; p < 0.001) in patients with RVO than controls. Although total cholesterol, LDL-C, and triglyceride levels were higher and serum vitamin B₁₂ levels were lower in RVO patients, these differences did not reach statistical significance.

CONCLUSIONS

RVO-patients have lower serum HDL-C and folate levels and higher non-HDL-C and serum homocysteine levels than population-based controls of similar age and sex. In patients with RVO, apart from the lipid profile, determination of serum homocysteine, folate and vitamin B₁₂ levels might be useful, as well as the treatment of their alterations.

Preliminary Investigation on Simvastatin-Loaded Polymeric Micelles in View of the Treatment of the Back of the Eye

There is increasing consensus in considering statins beneficial for age-related macular degeneration and in general, for immune and inflammatory mediated diseases affecting the posterior segment of the eye. However, all available data relate to oral administration, and safety and effectiveness of statins directly administered to the eye are not yet known, despite their ophthalmic administration could be beneficial. The aim was the development and the characterization of polymeric micelles based on TPGS or TPGS/poloxamer 407 to increase simvastatin solubility and stability and to enhance the delivery of the drug to the posterior segment of the eye via trans-scleral permeation. Simvastatin was chosen as a model statin and its active hydroxy acid metabolite was investigated as well. Results demonstrated that polymeric micelles increased simvastatin solubility at least 30-fold and particularly TPGS/poloxamer 407 mixed micelles, successfully stabilized simvastatin over time, preventing the hydrolysis when stored for 1 month at 4 °C. Furthermore, both TPGS (1.3 mPas) and mixed micelles (33.2 mPas) showed low viscosity, suitable for periocular administration. TPGS micelles resulted the best performing in delivery simvastatin either across conjunctiva or sclera in ex vivo porcine models. The data pave the way for a future viable ocular administration of statins.

Effect of a TSPO ligand on retinal pigment epithelial cholesterol homeostasis in high-fat fed mice, implication for age-related macular degeneration

Age-related Macular Degeneration (AMD) is a major cause of sight impairment in the elderly with complex aetiology involving genetics and environment and with limited therapeutic options which have limited efficacy. We have previously shown in a mouse-model of the condition, induced by feeding a high fat diet, that adverse effects of the diet can be reversed by co-administration of the TSPO activator, etifoxine. We extend those observations showing improvements in retinal pigment epithelial (RPE) cells with decreased lipids and enhanced expression of cholesterol metabolism and transport enzymes. Further, etifoxine decreased levels of reactive oxygen species (ROS) in RPE and inflammatory cytokines in RPE and serum. With respect to gut microbiome, we found that organisms abundant in the high fat condition (e.g. in the genus Anaerotruncus and Oscillospira) and implicated in AMD, were much less abundant after etifoxine treatment. The changes in gut flora were associated with the predicted production of metabolites of benefit to the retina including tryptophan and other amino acids and taurine, an essential component of the retina necessary to counteract ROS. These novel observations strengthen earlier conclusions that the mechanisms behind improvements in etifoxine-induced retinal physiology involve an interaction between effects on the host and the gut microbiome.

Extracellular Vesicles and MicroRNA: Putative Role in Diagnosis and Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is a complex, progressive, and heterogenous retinal degenerative disease associated with diabetes duration. It is characterized by glial, neural, and microvascular dysfunction, being the blood-retinal barrier (BRB) breakdown a hallmark of the early stages. In advanced stages, there is formation of new blood vessels, which are fragile and prone to leaking. This disease, if left untreated, may result in severe vision loss and eventually legal blindness. Although there are some available treatment options for DR, most of them are targeted to the advanced stages of the disease, have some adverse effects, and many patients do not adequately respond to the treatment, which demands further research. Oxidative stress and low-grade inflammation are closely associated processes that play a critical role in the development of DR. Retinal cells communicate with each other or with another one, using cell junctions, adhesion contacts, and secreted soluble factors that can act in neighboring or long-distance cells. Another mechanism of cell communication is via secreted extracellular vesicles (EVs), through exchange of material. Here, we review the current knowledge on deregulation of cell-to-cell communication through EVs, discussing the changes in miRNA expression profiling in body fluids and their role in the development of DR. Thereafter, current and promising therapeutic agents for preventing the progression of DR will be discussed.

Relationship between Uveitis and Thyroid Disease: A 13-Year Nationwide Population-based Cohort Study in Taiwan

PURPOSE

To investigate whether patients with thyroid disease are at increased risk of uveitis.

METHODS

Data was collected from the Taiwan National Health Insurance system and included patients newly diagnosed with thyroid disease from 2000 to 2012. The endpoint of interest was a diagnosis of uveitis.

RESULTS

In analyzing 21,396 patients with thyroid disease, yielding 85,584 matched comparisons, patients with thyroid disease to have a significantly higher cumulative incidence of uveitis when compared to the control cohort with the Kaplan-Meier analysis. This result was further confirmed by Cox regression analysis. The increased risk was persistent in both genders. The association between thyroid disease and uveitis was stronger in patients without diabetes or hypertension.

CONCLUSION

Patients with thyroid disease were found to have a higher risk for uveitis. For certain age groups or patients without diabetes or hypertension, the role of thyroid disease might be more crucial for uveitis development.

Oxidative Stress and Microvascular Alterations in Diabetic Retinopathy: Future Therapies

Diabetes is a disease that can be treated with oral antidiabetic agents and/or insulin. However, patients' metabolic control is inadequate in a high percentage of them and a major cause of chronic diseases like diabetic retinopathy. Approximately 15% of patients have some degree of diabetic retinopathy when diabetes is first diagnosed, and most will have developed this microvascular complication after 20 years. Early diagnosis of the disease is the best tool to prevent or delay vision loss and reduce the involved costs. However, diabetic retinopathy is an asymptomatic disease and its development to advanced stages reduces the effectiveness of treatments. Today, the recommended treatment for severe nonproliferative and proliferative diabetic retinopathy is photocoagulation with an argon laser and intravitreal injections of anti-VEGF associated with, or not, focal laser for diabetic macular oedema. The use of these therapeutic approaches is severely limited, such as uncomfortable administration for patients, long-term side effects, the costs they incur, and the therapeutic effectiveness of the employed management protocols. Hence, diabetic retinopathy is the widespread diabetic eye disease and a leading cause of blindness in adults in developed countries. The growing interest in using polyphenols, e.g., resveratrol, in treatments related to oxidative stress diseases has spread to diabetic retinopathy. This review focuses on analysing the sources and effects of oxidative stress and inflammation on vascular alterations and diabetic retinopathy development. Furthermore, current and antioxidant therapies, together with new molecular targets, are postulated for diabetic retinopathy treatment.

Lipid-Lowering Medications Are Associated with Lower Risk of Retinopathy and Ophthalmic Interventions among United States Patients with Diabetes

PURPOSE

To evaluate the impact of lipid-lowering medications on diabetic retinopathy and diabetic complications requiring intervention in the US population.

DESIGN

Retrospective cohort analysis.

METHODS

Administrative insurance claims were drawn from the Truven MarketScan Commercial Claims and Encounters databases. Population consisted of beneficiaries with type 2 diabetes mellitus (T2DM). Main outcome measurements were any signs of diabetic retinopathy, as measured by diagnosis codes for nonproliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR), or diabetic macular edema (DME) and procedure codes for retinopathy treatments (anti-VEGF injections, laser therapy, and vitrectomy).

RESULTS

A population of 269,782 patients diagnosed with T2DM between 2008 and 2015 were analyzed. A total of 99,233 patients (37%) were undergoing treatment with lipid-lowering medications. Approximately 6% of patients taking lipid-lowering medications had a diagnosis code for NPDR, PDR, or DME or a procedural code for intravitreal injections, pars plana vitrectomy (PPV) or laser treatment in their record following diagnosis with diabetes compared to 6.5% of patients who did not take lipid-lowering medications (P < 0.01). In adjusted time-to-event analyses, patients who took lipid-lowering medications prior to diagnosis of T2DM were less likely to progress to any retinopathy diagnosis (hazard ratio [HR], 0.60; 95% confidence interval [CI], 0.55-0.65) and less likely to receive any treatment for retinopathy (HR, 0.81; 95% CI, 0.78-0.84). These findings were significant at the aggregate level, at the individual level of diagnosis (NPDR HR, 0.63; 95% CI, 0.57-0.69; PDR HR, 0.45; 95% CI, 0.37-0.54; and DME HR, 0.39; 95% CI, 0.33-0.45), and at the level of each treatment category (anti-VEGF injection HR, 0.81; 95% CI, 0.78-0.84; laser HR, 0.62; 95% CI, 0.47-0.81; and vitrectomy HR, 0.71; 95% CI, 0.59-0.85).

CONCLUSIONS

This study found consistent evidence that patients taking lipid-lowering medications were less likely to develop NPDR, PDR, or DME and modest evidence that these patients are less likely to receive intravitreal injections of anti-VEGF medication, laser treatments, or vitrectomy. The study validates the findings of studies that have used claims databases in East Asia in relatively homogeneous populations to estimate an association between statin use and retinopathy, replicating them in a US context in a large commercial claims database.

Dietary Polyphenols in Age-Related Macular Degeneration: Protection against Oxidative Stress and Beyond

Age-related macular degeneration (AMD) is a multifactorial disease of the retina featured by degeneration and loss of photoreceptors and retinal pigment epithelium (RPE) cells with oxidative stress playing a role in its pathology. Although systematic reviews do not support the protective role of diet rich in antioxidants against AMD, dietary polyphenols (DPs) have been reported to have beneficial effects on vision. Some of them, such as quercetin and cyanidin-3-glucoside, can directly scavenge reactive oxygen species (ROS) due to the presence of two hydroxyl groups in their B ring structure. Apart from direct ROS scavenging, DPs can lower oxidative stress in several other pathways. Many DPs induce NRF2 (nuclear factor, erythroid 2-like 2) activation and expression of phase II enzymes that are under transcriptional control of this factor. DPs can inhibit A2E photooxidation in RPE cells, which is a source of oxidative stress. Anti-inflammatory action of DPs in RPE cells is associated with regulation of various interleukins and signaling pathways, including IL-6/JAK2 (Janus kinase 2)/STAT3. Some DPs can improve impaired cellular waste clearance, including AMD-specific deficient phagocytosis of the Aβ42 peptide and autophagy.