Increased Antioxidant Capacity and Pro-Homeostatic Lipid Mediators in Ocular Hypertension-A Human Experimental Model

Proteomic and Cytokine Profiling in Plasma from Patients with Normal-Tension Glaucoma and Ocular Hypertension

Primary open-angle glaucoma (POAG) is subdivided depending on eye pressure. Patients with normal-tension glaucoma (NTG) have never had high intraocular pressure (IOP) measured while patients with ocular hypertension (OHT) have high eye pressure but no signs of glaucoma. Although IOP is considered to be a risk factor for all glaucoma patients, it is reasonable to assume that other risk factors such as inflammation play a role. We aimed to characterize the proteome and cytokine profile during hypoxia in plasma from patients with NTG (n = 10), OHT (n = 10), and controls (n = 10). Participants were exposed to hypoxia for two hours, followed by 30 min of normoxia. Samples were taken before ("baseline"), during ("hypoxia"), and after hypoxia ("recovery"). Proteomics based on liquid chromatography coupled with mass spectrometry (LC-MS) was performed. Cytokines were measured by Luminex assays. Bioinformatic analyses indicated the involvement of complement and coagulation cascades in NTG and OHT. Regulation of high-density lipoprotein 3 (HDL3) apolipoproteins suggested that changes in cholesterol metabolism are related to OHT. Hypoxia decreased the level of tumor necrosis factor-α (TNF-α) in OHT patients compared to controls. Circulating levels of interleukin-1β (IL-1β) and C-reactive protein (CRP) were decreased in NTG patients compared to controls during hypoxia. After recovery, plasma interleukin-6 (IL-6) was upregulated in patients with NTG and OHT. Current results indicate an enhanced systemic immune response in patients with NTG and OHT, which correlates with pathogenic events in glaucoma. Apolipoproteins may have anti-inflammatory effects, enabling OHT patients to withstand inflammation and development of glaucoma despite high IOP.

Higher vitamin B6 dietary consumption is associated with a lower risk of glaucoma among United States adults

Objective

Although numerous studies have substantiated the neuroprotective effects of vitamin B6 on the optic nerve and its enhancement of visual function, comprehensive data delineating the correlation between vitamin B6 and glaucoma at a national demographic scale remain insufficient. This study is designed to explore the link between the dietary consumption of vitamin B6 and glaucoma.

Methods

This study included 3,850 individuals aged 40 and older from the National Health and Nutrition Examination Survey (NHANES), spanning 2005-2008. Dietary consumption of vitamin B6 was calculated from the average of two 24-h dietary recall interviews. Glaucoma was diagnosed in accordance with the established Rotterdam criteria. To evaluate the relationship between vitamin B6 dietary consumption and the risk of glaucoma, we employed Restricted Cubic Splines and weighted multivariable logistic regression analysis. We employed stratified and three other sensitivity analyses to confirm the robustness of our results, and conducted a preliminary exploration of the potential association between vitamin B6 supplement consumption and glaucoma risk.

Results

After adjusting for covariates, we found a significant inverse correlation between dietary consumption of vitamin B6 and glaucoma risk (p non-linearity = 0.18; p for trend = 0.02). Stratified analysis and three other sensitivity analyses revealed stability in the outcomes (all p for interaction>0.05). Compared to the lowest quartile of consumption (≤1.23 mg/day), individuals in the highest quartile of vitamin B6 consumption (>2.34 mg/day) experienced a 75% reduction in glaucoma risk (OR = 0.25, 95% CI 0.07-0.92). However, the effect of vitamin B6 supplements on glaucoma was inconclusive.

Conclusion

A diet high in vitamin B6 inversely correlates with glaucoma risk, suggesting that increasing dietary intake of vitamin B6 could be a viable preventative strategy against glaucoma among adults in the United States.

Distinct Metabolic Profiles of Ocular Hypertensives in Response to Hypoxia

Glaucoma is a neurodegenerative disease that affects the retinal ganglion cells (RGCs). The main risk factor is elevated intraocular pressure (IOP), but the actual cause of the disease remains unknown. Emerging evidence indicates that metabolic dysfunction plays a central role. The aim of the current study was to determine and compare the effect of universal hypoxia on the metabolomic signature in plasma samples from healthy controls (n = 10), patients with normal-tension glaucoma (NTG, n = 10), and ocular hypertension (OHT, n = 10). By subjecting humans to universal hypoxia, we aim to mimic a state in which the mitochondria in the body are universally stressed. Participants were exposed to normobaric hypoxia for two hours, followed by a 30 min recovery period in normobaric normoxia. Blood samples were collected at baseline, during hypoxia, and in recovery. Plasma samples were analyzed using a non-targeted metabolomics approach based on liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS). Multivariate analyses were conducted using principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA), and univariate analysis using the Wilcoxon signed-rank test and false discovery rate (FDR) correction. Unique metabolites involved in fatty acid biosynthesis and ketone body metabolism were upregulated, while metabolites of the kynurenine pathway were downregulated in OHT patients exposed to universal hypoxia. Differential affection of metabolic pathways may explain why patients with OHT initially do not suffer or are more resilient from optic nerve degeneration. The metabolomes of NTG and OHT patients are regulated differently from control subjects and show dysregulation of metabolites important for energy production. These dysregulated processes may potentially contribute to the elevation of IOP and, ultimately, cell death of the RGCs.

Oxidative Stress: A Suitable Therapeutic Target for Optic Nerve Diseases?

Optic nerve disorders encompass a wide spectrum of conditions characterized by the loss of retinal ganglion cells (RGCs) and subsequent degeneration of the optic nerve. The etiology of these disorders can vary significantly, but emerging research highlights the crucial role of oxidative stress, an imbalance in the redox status characterized by an excess of reactive oxygen species (ROS), in driving cell death through apoptosis, autophagy, and inflammation. This review provides an overview of ROS-related processes underlying four extensively studied optic nerve diseases: glaucoma, Leber's hereditary optic neuropathy (LHON), anterior ischemic optic neuropathy (AION), and optic neuritis (ON). Furthermore, we present preclinical findings on antioxidants, with the objective of evaluating the potential therapeutic benefits of targeting oxidative stress in the treatment of optic neuropathies.

Is fat the future for saving sight? Bioactive lipids and their impact on glaucoma

Glaucoma is characterized by a continuous loss of retinal ganglion cells. The cause of glaucoma is associated with an increase in intraocular pressure (IOP), but the underlying pathophysiology is diverse and, in most cases, unknown. There is an indisputable unmet need to identify new pathways involved in glaucoma pathogenesis. Increasing evidence suggests that bioactive lipids may be critical in the development and progression of glaucoma. Preclinical and clinical bioactive lipid targets exist and are being developed. In this review, we aim to shed light on the potential of bioactive lipids for the prevention, diagnosis, prognosis, and treatment of glaucoma by asking the question "is fat the future for saving sight".

Optic disc drusen in patients diagnosed with normal tension glaucoma

PURPOSE

To investigate the prevalence of optic disc drusen (ODD) and optic nerve head (ONH) morphology in patients diagnosed with normal tension glaucoma (NTG).

METHODS

In this prospective cross-sectional study, we included patients diagnosed with NTG from two glaucoma units. In both eyes, dense enhanced depth imaging optical coherence tomography volume scans of the ONH by means of standardized scanning guidelines were performed to examine for presence of ODD, and radial ONH scans were used for investigating parameters such as scleral canal diameter, cup/disc ratio and cup depth.

RESULTS

We found ODD in 7 (3.6%) of 195 eyes, in 6 (6.1%) out of 98 patients diagnosed with NTG. The ODD were not ophthalmoscopically visible in five out of six patients. Eyes with ODD had lower cup/disc ratio, 0.44 ± 0.4 (p = 0.040), and less-prominent cup depth, 236.6 ± 204.4 μm (p = 0.041) compared to eyes without ODD, 0.81 ± 0.2 and 437.8 ± 139.1 μm, respectively. We found no significant difference in scleral canal diameter between the eyes without (1602.8 ± 193 μm) and those with ODD (1492 ± 123.4 μm, p = 0.057).

CONCLUSION

The prevalence of ODD in patients diagnosed with NTG is substantially higher than in the background population. A low cup/disc ratio correlates with ODD presence. Therefore, due to the challenges associated with NTG diagnosis, we recommend examining the deep layers of the ONH in NTG patients with a cup/disc ratio lower than 0.5 to avoid misdiagnosing ODD as NTG.

Oxidative Stress in Optic Neuropathies

Increasing evidence indicates that changes in the redox system may contribute to the pathogenesis of multiple optic neuropathies. Optic neuropathies are characterized by the neurodegeneration of the inner-most retinal neurons, the retinal ganglion cells (RGCs), and their axons, which form the optic nerve. Often, optic neuropathies are asymptomatic until advanced stages, when visual impairment or blindness is unavoidable despite existing treatments. In this review, we describe systemic and, whenever possible, ocular redox dysregulations observed in patients with glaucoma, ischemic optic neuropathy, optic neuritis, hereditary optic neuropathies (i.e., Leber's hereditary optic neuropathy and autosomal dominant optic atrophy), nutritional and toxic optic neuropathies, and optic disc drusen. We discuss aspects related to anti/oxidative stress biomarkers that need further investigation and features related to study design that should be optimized to generate more valuable and comparable results. Understanding the role of oxidative stress in optic neuropathies can serve to develop therapeutic strategies directed at the redox system to arrest the neurodegenerative processes in the retina and RGCs and ultimately prevent vision loss.