Association of serum levels of anti-myeloperoxidase antibody with retinal photoreceptor ellipsoid zone disruption in diabetic retinopathy

External Limiting Membrane, Photoreceptor Ellipsoid Zone Disruption, and Retinal Pigment Epithelium Alterations in Diabetic Retinopathy

Objective Diabetic retinopathy (DR), a microvascular complication of diabetes, is a leading cause of preventable blindness. Spectral domain optical coherence tomography (SD-OCT) provides cross-sectional and topographical imaging of the retina. SD-OCT resolves outer retinal layers into three hyperreflective bands—external limiting membrane (ELM), ellipsoid zone (EZ), and retinal pigment epithelium (RPE). In this article, we have studied the role of these outer retinal layers in structural and molecular changes taking place in DR.

Materials and Methods Articles with clinical features, pathogenesis, diagnosis, and treatment of DR were thoroughly studied. Articles were searched on PubMed, MEDLINE, and Cochrane Library from 2000 to 2020. Studies focusing on the role of ELM, EZ, and RPE in pathogenesis of DR based on SD-OCT were included.

Results The long-standing hyperglycemia leads to protein glycosylation resulting in formation of advanced glycation end products (AGEs). AGEs have an impact through their effect on retinal microvasculature, vascular endothelial growth factor (VEGF), intercellular adhesion molecule-1, nitrosative and oxidative stress, and vitamin D and calcium metabolism. All these factors have been linked with disruption of outer retinal layers. AGEs lead to vascular endothelial dysfunction and release of proangiogenic factors by increasing the expression of VEGF in retinal pericytes and RPE cells. This leads to leakage and fluid accumulation resulting in diabetic macular edema (DME). In DME, there is sequential disruption of ELM and EZ and decrease in visual acuity (VA). The RPE alterations have been reported to be associated with the severity of DR and decrease in VA. Anti-VEGF therapy, most common treatment of DME, leads to restoration of barrier effect of ELM, it was found to be restored first followed by EZ restoration. Newer anti-AGEs agents and their receptor blockers are being developed which have a positive effect on maintaining the health of RPE.

Conclusion A complex molecular association exists between the structural changes in ELM, EZ, and RPE in DR. SD-OCT is an indispensable tool to study these changes as integrity of these outer layers of retina is essential for maintaining visual function of retina in DR.

Elevated advanced glycation end products are associated with subfoveal ellipsoid zone disruption in diabetic macular edema

Purpose:

Advanced glycation end products (AGEs), due to increased production and a slow turnover rate, serve as mediators of “metabolic memory” even after the resolution of hyperglycemia. A prospective study was undertaken to evaluate the association of AGEs with subfoveal ellipsoid zone (EZ) disruption in diabetic macular edema (DME).

Methods:

A tertiary-care-center-based cross-sectional study included 40 consecutive cases with DME and 20 healthy controls in the age group of 40–65 years. All the study subjects underwent spectral-domain optical coherence tomography (SD-OCT) for cross-sectional imaging of the retina. The EZ was defined as a hyperreflective band below the external limiting membrane. The disruption of EZ was graded as intact EZ and disrupted EZ. Serum AGEs were assessed by assay of N^ε-carboxymethyl-lysine (N^ε-CML) using the standard protocol. Data were analyzed statistically.

Results:

Subfoveal EZ disruption was noted in 80% (32/40) of the cases of DME. In the cases without EZ disruption, visual acuity (LogMAR VA) was 0.60 ± 0.52, whereas in cases with EZ disruption, LogMAR VA was 0.96 ± 0.56 (P < 0.001). In the cases without EZ disruption, N^ε-CML was 94.31 ± 57 ng/mL, whereas in cases with EZ disruption N^ε-CML was 120.64 ± 71.98 ng/mL (P < 0.001).

Conclusion:

In DME, increased levels of AGEs are significantly associated with EZ disruption on SD-OCT.

Aqueous Cytokine Expression and Higher Order OCT Biomarkers: Assessment of the Anatomic-Biologic Bridge in the IMAGINE DME Study

PURPOSE

To identify biomarkers for predicting response to anti-vascular endothelial growth factor (VEGF) therapy in diabetic macular edema (DME) and evaluate any links between cytokine expression and optical coherence tomography (OCT) phenotype.

DESIGN

The IMAGINE is a post hoc image analysis and cytokine expression assessment of the Efficacy & Safety Trial of Intravitreal Injections Combined With PRP for CSME Secondary to Diabetes Mellitus (DAVE) randomized clinical trial.

METHODS

Subjects were categorized as anatomical responders or nonresponders, and within the responder group as rebounders and non-rebounders based on quantitative, longitudinal OCT criteria. Retinal layer and fluid features were extracted using an OCT machine-learning augmented segmentation platform. Responders were further sub-classified by rapidity of response. Aqueous concentrations of 54 cytokines were measured at multiple timepoints. Expression was compared between responder groups and correlated with OCT imaging biomarkers.

RESULTS

Of the 24 eyes studied, 79% were anatomical responders with 38% super responders, 17% early responders, and 25% slow responders. Twenty-one percent were nonresponders. Super responders had increased baseline vascular endothelial growth factor (VEGF) (880.0 pg/mL vs 245.4 pg/mL; P = .012) and decreased monocyte chemotactic protein-1 (MCP-1) (513.3 pg/mL vs 809.5 pg/mL; P = .0.042) concentrations compared with nonresponders. Interleukin-6 (-24.9 pg/mL vs 442.8 pg/mL; P = .032) concentrations increased among nonresponders during therapy. VEGF concentrations correlated with central subfield thickness (r = 0.49; P = .01). Panmacular retinal volume correlated with increased interleuckin-6 (r = 0.47; P = .02) and decreased MCP-1 (r = -0.45; P = .03). Matrix metallopeptidase-1 correlated with subretinal fluid volume (r = 0.50; P = .01).

CONCLUSIONS

OCT imaging biomarkers correlated with both intraocular cytokines and responsiveness to anti-VEGF therapy, which indicated a possible link to underlying pathways and their relevance to DME prognosis. Baseline concentrations of VEGF and MCP-1 are associated with anatomic response to anti-VEGF therapy.

Serum vitamin D is a biomolecular biomarker for proliferative diabetic retinopathy

BACKGROUND

Vitamin D is a multi-functional fat-soluble metabolite essential for a vast number of physiological processes. Non-classical functions are gaining attention because of the close association of vitamin D deficiency with diabetes, and its complications. The present study was undertaken to evaluate the role of vitamin D as a biomarker for proliferative diabetic retinopathy.

METHODS

A tertiary care center based cross-sectional study was undertaken. Seventy-two consecutive cases of type 2 diabetes mellitus were included. Diagnosis of diabetes mellitus was made using American Diabetes Association guidelines. Study subjects included: diabetes mellitus with no retinopathy (No DR) (n = 24); non-proliferative diabetic retinopathy (n = 24); and proliferative diabetic retinopathy (n = 24) and healthy controls (n = 24). All of the study subjects underwent complete ophthalmological evaluation. Best Corrected Visual Acuity (BCVA) was measured on the logarithm of the minimum angle of resolution (logMAR) scale. Serum 25-OH Vitamin D assay was done using chemiluminescent microparticle immunoassay technology. Diagnostic accuracy of vitamin D was assessed using receiver operating characteristics curve analysis and area under curve (AUC) was determined for the first time.

RESULTS

ANOVA revealed a significant decrease in serum vitamin D levels with severity of diabetic retinopathy (F = 8.95, p < 0.001). LogMAR BCVA was found to increase significantly with the severity of DR (F = 112.64, p < 0.001). On AUC analysis, a cut off value of 18.6 ng/mL for Vitamin D was found to be significantly associated with proliferative diabetic retinopathy [sensitivity = 86.36% (95% CI 65.1-96.9); specificity = 81.82% (95% CI 59.7-94.7); AUC = 0.91 (excellent); and Z value = 8.17].

CONCLUSIONS

Serum vitamin D levels of ≤ 18.6 ng/mL serve as sensitive and specific indicator for proliferative disease, among patients of DR.