Elevated aqueous endothelin-1 concentrations in advanced diabetic retinopathy

Increased aqueous humor levels of endothelin-1 in patients with open angle glaucoma

BACKGROUND

Endothelin is a potent vasoconstrictor and contributes to the regulation of vascular perfusion. Aberrant endothelin-1 (ET-1) levels in aqueous humor have been reported across a variety of vascular diseases of the eye, including glaucoma. These findings suggest that dysregulation of ET-1 production may contribute to glaucoma pathophysiology. In this study, aqueous humor from patients undergoing ocular surgery was assayed for ET-1 abundance and related to the presence of glaucoma.

PATIENTS

Open angle glaucoma patients (n=62 total) from the ophthalmology clinics of the University of Iowa Hospitals and Clinics were enrolled in this study and organized into three distinct cohorts based on their diagnostic criteria, including those with primary open angle glaucoma (POAG, n=25 patients), normal tension glaucoma (NTG, n=17 patients), exfoliation glaucoma (XFG, n=8 patients), and normal controls (n=12 patients).

METHODS

Aqueous humor was collected intraoperatively from patients undergoing surgeries for glaucoma (including minimally invasive glaucoma surgeries, trabeculectomy, or glaucoma drainage device implantation) for samples in the glaucoma cohorts and cataract extraction for those in the control cohort. Aqueous humor was assayed by ELISA to measure and compare ET-1 abundance between the glaucoma cohorts and control cohort. ET-1 levels were also analyzed with linear regression to control for the covariates of age and sex.

RESULTS

ET-1 was significantly elevated in the aqueous humor of patients in the POAG (mean ± SD: 7.8 ± 5.1 pg/mL; p = 0.002) and NTG cohorts (6.1 ± 3.0 pg/mL; p = 0.030) compared to the control (4.0 ± 1.9 pg/mL). No significant difference in aqueous ET-1 was detected in the XFG cohort (6.2 ± 4.5 pg/mL; p = 0.230) compared to the control. Significantly higher ET-1 levels were detected in a merged grouping of all glaucoma cohorts (POAG, NTG, XFG) relative to controls (p = 0.021). Analysis of covariance indicated neither age nor sex was associated with ET-1 level (p = 0.60 and p = 0.27), respectively. Controlling for age and sex had minimal influence on the comparison of ET-1 levels in the POAG versus control cohort (p = 0.018) and nominal influence on the comparisons between the NTG (p = 0.089) or XFG cohort (p = 0.15) relative to the control.

CONCLUSIONS

Elevated ET-1 in aqueous humor was associated with POAG and NTG compared to controls amongst cohorts of patients at the University of Iowa. These data suggest that dysregulation of vascular perfusion may have a role in the pathophysiology of POAG. The analyses of NTG and XFG samples were limited by the relatively small sample sizes.

Relationship between Biochemical Pathways and Non-Coding RNAs Involved in the Progression of Diabetic Retinopathy

Diabetic retinopathy (DR) is a progressive blinding disease, which affects the vision and quality of life of patients, and it severely impacts the society. This complication, caused by abnormal glucose metabolism, leads to structural, functional, molecular, and biochemical abnormalities in the retina. Oxidative stress and inflammation also play pivotal roles in the pathogenic process of DR, leading to mitochondrial damage and a decrease in mitochondrial function. DR causes retinal degeneration in glial and neural cells, while the disappearance of pericytes in retinal blood vessels leads to alterations in vascular regulation and stability. Clinical changes include dilatation and blood flow changes in response to the decrease in retinal perfusion in retinal blood vessels, leading to vascular leakage, neovascularization, and neurodegeneration. The loss of vascular cells in the retina results in capillary occlusion and ischemia. Thus, DR is a highly complex disease with various biological factors, which contribute to its pathogenesis. The interplay between biochemical pathways and non-coding RNAs (ncRNAs) is essential for understanding the development and progression of DR. Abnormal expression of ncRNAs has been confirmed to promote the development of DR, suggesting that ncRNAs such as miRNAs, lncRNAs, and circRNAs have potential as diagnostic biomarkers and theranostic targets in DR. This review provides an overview of the interactions between abnormal biochemical pathways and dysregulated expression of ncRNAs under the influence of hyperglycemic environment in DR.

Advances and Perspectives in Relation to the Molecular Basis of Diabetic Retinopathy-A Review

Diabetes mellitus (DM) is a growing problem nowadays, and diabetic retinopathy (DR) is its predominant complication. Currently, DR diagnosis primarily relies on fundoscopic examination; however, novel biomarkers may facilitate that process and make it widely available. In this current review, we delve into the intricate roles of various factors and mechanisms in DR development, progression, prediction, and their association with therapeutic approaches linked to the underlying pathogenic pathways. Specifically, we focus on advanced glycation end products, vascular endothelial growth factor (VEGF), asymmetric dimethylarginine, endothelin-1, and the epigenetic regulation mediated by microRNAs (miRNAs) in the context of DR.

Diabetic retinopathy as the leading cause of blindness and early predictor of cascading complications-risks and mitigation

Proliferative diabetic retinopathy (PDR) the sequel of diabetic retinopathy (DR), a frequent complication of diabetes mellitus (DM), is the leading cause of blindness in the working-age population. The current screening process for the DR risk is not sufficiently effective such that often the disease is undetected until irreversible damage occurs. Diabetes-associated small vessel disease and neuroretinal changes create a vicious cycle resulting in the conversion of DR into PDR with characteristic ocular attributes including excessive mitochondrial and retinal cell damage, chronic inflammation, neovascularisation, and reduced visual field. PDR is considered an independent predictor of other severe diabetic complications such as ischemic stroke. A "domino effect" is highly characteristic for the cascading DM complications in which DR is an early indicator of impaired molecular and visual signaling. Mitochondrial health control is clinically relevant in DR management, and multi-omic tear fluid analysis can be instrumental for DR prognosis and PDR prediction. Altered metabolic pathways and bioenergetics, microvascular deficits and small vessel disease, chronic inflammation, and excessive tissue remodelling are in focus of this article as evidence-based targets for a predictive approach to develop diagnosis and treatment algorithms tailored to the individual for a cost-effective early prevention by implementing the paradigm shift from reactive medicine to predictive, preventive, and personalized medicine (PPPM) in primary and secondary DR care management.