Dietary ω-3 deficiency and IOP insult are additive risk factors for ganglion cell dysfunction

Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA): A Targeted Antioxidant Strategy to Counter Oxidative Stress in Retinopathy

Omega-3 fatty acids are critical components of cell membranes, including those in the retina. Specifically, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the primary omega-3 fatty acids that have been studied for their potential benefits in retinal health, preventing the progression of retinopathy. Several studies have shown that a higher intake of omega-3 fatty acids is associated with a lower risk of developing diabetic retinopathy and age-related macular degeneration (AMD). Reviewing clinical trials and observational studies that support the protective role of omega-3s in retinal disorders is essential. This comprehensive review aims to evaluate the current literature on the role of omega-3 fatty acids, exploring their mechanisms of action and anti-inflammatory, anti-angiogenic, and neuroprotective roles in the retina. Omega-3s have been shown to inhibit abnormal blood vessel growth in the retina, which is a significant factor in proliferative diabetic retinopathy and neovascular AMD. Furthermore, omega-3 fatty acids are often studied with other nutrients, such as lutein, zeaxanthin, and vitamins, for their synergistic effects on retinal health. Reviewing these combinations can help understand how omega-3s can be part of a comprehensive approach to preventing or treating retinopathies, especially in diabetic patients. This review emphasizes the preventive function of EPA and DHA in alleviating oxidative stress-related damage in retinal diseases, concentrating on their antioxidative mechanisms.

The potential impact of a vegetarian diet on glaucoma

Treatment of primary open-angle glaucoma has centered on the lowering of intraocular pressure that damages the optic nerve; however, this strategy is not uniformly successful, especially in normal tension glaucoma, and there is interest in antioxidant, anti-inflammatory, and other neuroprotective strategies. Vegetarian diets are known to be rich in antioxidant and anti-inflammatory components and have a number of established health benefits. Thus, it would be reasonable to assume that vegetarian diets would be beneficial in glaucoma, but this approach has not been well studied. We examine the possible role of vegetarian diets and their components in the incidence and progression of glaucoma.

Exploring the Potential of Wild Olive (Acebuche) Oil as a Pharm-Food to Prevent Ocular Hypertension and Fibrotic Events in the Retina of Hypertensive Mice

SCOPE

Our laboratory has previously described the antioxidant and anti-inflammatory potential of a wild olive (acebuche, ACE) oil against hypertension-associated vascular retinopathies. The current study aims to analyze the antifibrotic effect of ACE oil on the retina of hypertensive mice.

METHODS AND RESULTS

Mice are rendered hypertensive by administration of NG-nitro-L-arginine-methyl-ester (L-NAME) and simultaneously subjected to dietary supplementation with ACE oil or a reference extra virgin olive oil (EVOO). Intraocular pressure (IOP) is measured by rebound tonometry, and retinal vasculature/layers are analyzed by fundus fluorescein angiography and optical coherence tomography. Different fibrosis-related parameters are analyzed in the retina and choroid of normotensive and hypertensive mice with or without oil supplementation. Besides preventing the alterations found in hypertensive animals, including increased IOP, reduced fluorescein signal, and altered retinal layer thickness, the ACE oil-enriched diet improves collagen metabolism by regulating the expression of major fibrotic process modulators (matrix metalloproteinases, tissue inhibitors of metalloproteinases, connective tissue growth factor, and transforming growth factor beta family).

CONCLUSION

Regular consumption of EVOO and ACE oil (with better outcomes in the latter) might help reduce abnormally high IOP values in the context of hypertension-related retinal damage, with significant reduction in the surrounding fibrotic process.

Nutritional Factors: Benefits in Glaucoma and Ophthalmologic Pathologies

Glaucoma is a chronic optic neuropathy that can lead to irreversible functional and morphological damage if left untreated. The gold standard therapeutic approaches in managing patients with glaucoma and limiting progression include local drops, laser, and/or surgery, which are all geared at reducing intraocular pressure (IOP). Nutrients, antioxidants, vitamins, organic compounds, and micronutrients have been gaining increasing interest in the past decade as integrative IOP-independent strategies to delay or halt glaucomatous retinal ganglion cell degeneration. In our minireview, we examine the various nutrients and compounds proposed in the current literature for the management of ophthalmology diseases, especially for glaucoma. With respect to each substance considered, this minireview reports the molecular and biological characteristics, neuroprotective activities, antioxidant properties, beneficial mechanisms, and clinical studies published in the past decade in the field of general medicine. This study highlights the potential benefits of these substances in glaucoma and other ophthalmologic pathologies. Nutritional supplementation can thus be useful as integrative IOP-independent strategies in the management of glaucoma and in other ophthalmologic pathologies. Large multicenter clinical trials based on functional and morphologic data collected over long follow-up periods in patients with IOP-independent treatments can pave the way for alternative and/or coadjutant therapeutic options in the management of glaucoma and other ocular pathologies.

Deuterated polyunsaturated fatty acids provided protection against oxidative stress in ocular fibroblasts derived from glaucoma patients

Glaucoma is a complex neurodegenerative disease of the optic nerve that leads to irreversible sight loss. Lowering intraocular pressure (IOP) medically or surgically represents the mainstay of treatment but despite adequate treatment optic nerve function can continue to deteriorate leading to blindness. There is significant clinical and experimental evidence that oxidative stress is involved in the pathogenesis of glaucoma. Decreasing the formation of lipid peroxidation products or scavenging them chemically could be beneficial in limiting the deleterious effects of oxidative stress in glaucoma. A solution to control the susceptibility of PUFAs to noxious lipid peroxidation reactions is by regioselective deuteration. Deuterium incorporated into PUFAs at bis-allylic positions (D-PUFAs) inhibits the rate-limiting step of lipid peroxidation. In this study, we have shown that Tenon's ocular fibroblasts from glaucoma patients have significantly increased basal oxidative stress compared to non-glaucomatous control patients. Furthermore, we have shown that deuterated polyunsaturated fatty acids (D-PUFAs) provide an enhanced rescue of menadione induced lipid peroxidation in both non-glaucomatous and glaucomatous Tenon's ocular fibroblasts using malondialdehyde (MDA) levels as a marker. Our study suggests that D-PUFAs may provide a potentially safe and effective method to reduce cytotoxic oxidative stress in glaucoma.

Circulating fatty acids and risk of primary open-angle glaucoma: A mendelian randomization study

PURPOSE

The relationship between fatty acids (FAs) and glaucoma remains controversial despite several observational studies. We organized a mendelian randomization (MR) study to determine the genetic causal association between circulating FAs and primary open-angle glaucoma (POAG).

METHODS

The two-sample MR method was used to acquire causal estimates. Fourteen distinct single nucleotide polymorphisms (SNPs) of ten FAs were chosen as instrumental variables (IVs) at a genome-wide significance level (p < 5 × 10^-8). Summary statistics for POAG were available from a genome-wide association meta-analysis of 216,257 individuals of European ancestry (16,677 cases, 199,580 controls). The inverse-variance weighted (IVW) method was adopted to evaluate the causality of FAs and POAG. Multiple sensitivity analyses were applied to avoid pleiotropy.

RESULTS

The IVW method suggested no evidence to support causal effects of ten FAs on POAG. The odds ratio (OR) per one SD increment of each FA was OR_ALA = 1.64 (95% CI, 0.441-6.098, p = 0.46), OR_EPA = 0.815 (95% CI, 0.604-1.101, p = 0.182), OR_DPA = 0.896 (95% CI, 0.669-1.198, p = 0.458), OR_DHA = 1.014 (95% CI, 0.801-1.283, p = 0.91), OR_LA = 1.008 (95% CI, 0.971-1.045, p = 0.683), OR_AA = 0.993 (95% CI, 0.973-1.013, p = 0.483), OR_POA = 0.731 (95% CI, 0.261-2.048, p = 0.551), OR_OA = 1.048 (95% CI, 0.934-1.175, p = 0.425), OR_PA = 1.039 (95% CI, 0.903-1.196, p = 0.593), OR_SA = 0.967 (95% CI, 0.879-1.062, p = 0.477). Moreover, Sensitivity analysis indicated no pleiotropy.

CONCLUSION

This MR study does not support causal associations between ten FAs and POAG.

Non-drug interventions in glaucoma: Putative roles for lifestyle, diet and nutritional supplements

Glaucoma is a major ocular neurodegenerative disease characterized by progressive retinal ganglion cells degeneration and sight loss. Current treatment options have been limited to reducing intraocular pressure (IOP), known as the leading risk factor for this disease; however, glaucoma can develop even with low or normal IOP and progress despite controlling IOP values. Lifestyle, dietary habits, and supplementation may influence some of the risk factors and pathophysiological mechanisms underlying glaucoma development and progression; thus, the role of this complementary and alternative medicine in glaucoma has received great interest from both patients and ophthalmologists. We provide a summary of the current evidence concerning the relationship between lifestyle, dietary habits, and effects of supplements on the incidence and progression of glaucoma and their targets and associated mechanisms. The data suggest the existence of a therapeutic potential that needs to be further explored with both preclinical and rigorous clinical studies.

Plasma fatty acids and primary open-angle glaucoma in the elderly: the Montrachet population-based study

Background

To compare plasma fatty acids (FAs) between participants with primary open-angle glaucoma (POAG) and participants without neuropathy in an elderly population and to investigate specific FAs pattern in POAG.

Methods

We conducted a population-based study in participants older than 75 years. Participants underwent a comprehensive eye examination with optic nerve photographs, visual field test and optic nerve OCT with RNFL thickness measurement. Glaucomatous status was defined according to the International Society for Epidemiologic and Geographical Ophthalmology classification. Lipids were extracted from plasma and FAs methylesters prepared and analyzed by gas chromatography-mass spectrometry.

Results

Among the 1153 participants of the Montrachet study 810 were retained for analysis and 68 had POAG. The mean age was 82.11 ± 3.67. In multivariable analysis FAs levels were not different between POAG participants and controls (P = 0.078). A FAs pattern characterized by high negative weight of gamma-linoleic acid, eicosapentaenoic acid polyunsaturated FAs (PUFAs), Cis-7 hexadecenoic acid monounsaturated FAs (MUFAs) and high positive weight of eicosadienoic acid, docosatetraenoic acid, docosapentaenoic n-6, alpha linoleic acid PUFAs, eicosenoic acid MUFAs, margaric acid and behenic acid saturated FAs was positively associated with POAG. After adjustment for major confounders, individuals in the upper tertile of FAs pattern scores compared with those in the lower tertile were more likely to present POAG (OR = 3.09 [95% CI 1.29–7.40] P = 0.013).

Conclusions

We found no significant difference regarding isolated plasma FAs between participants with POAG and participants without neuropathy in elderly but specific FAs pattern might be associated with POAG.

Antioxidant Activity and Neuroprotective Role of Docosahexaenoic Acid (DHA) Supplementation in Eye Diseases That Can Lead to Blindness: A Narrative Review

The objective of this narrative review is to provide updated evidence, based on data from experimental and clinical studies, of the prominent role of omega-3 polyunsaturated fatty acids (n-3 PUFAs) for a number of crucial mechanisms involved in counteracting cell damage induced by oxidative stress in eye diseases. This article is focused on the antioxidant and neuroprotective effects of docosahexaenoic acid (DHA), which have been assessed in different experimental models and clinical studies, particularly in proliferative diabetic retinopathy, age-related macular degeneration and glaucoma that are the most common eye diseases leading to severe vision loss. The mechanisms involved in the role of DHA in protecting human retinal pigment epithelial cells from oxidative stress as well as the interaction with glutathione (GSH) are also described. The review is intended to provide novel and salient findings supporting the rationale of the use of dietary supplementation with high-dose DHA (1050 mg/day) in the form of triglyceride as a potent antioxidant compound for improving the eye health. However, the overall clinical evidence for the use of dietary strategies based on supplementation with n-3 PUFAs in eye diseases linked to oxidative stress other than high-dose DHA triglyceride is both limited and inconsistent.

Natural Products: Evidence for Neuroprotection to Be Exploited in Glaucoma

Glaucoma, a leading cause of irreversible blindness worldwide, is an optic neuropathy characterized by the progressive death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is recognized as the main risk factor. Despite effective IOP-lowering therapies, the disease progresses in a significant number of patients. Therefore, alternative IOP-independent strategies aiming at halting or delaying RGC degeneration is the current therapeutic challenge for glaucoma management. Here, we review the literature on the neuroprotective activities, and the underlying mechanisms, of natural compounds and dietary supplements in experimental and clinical glaucoma.

Effect of dietary modification and antioxidant supplementation on intraocular pressure and open-angle glaucoma

Primary open-angle glaucoma (POAG) is an age-dependent, intraocular pressure (IOP)-related degeneration of the retinal ganglion cells (RGC). At present, IOP is the only modifiable factor that has been identified to prevent glaucomatous vision loss. Though the pathogenesis of glaucomatous optic neuropathy is still not well understood, increasing evidence suggests oxidative stress may contribute to the induction and progression of glaucoma. Furthermore, antioxidant use may be protective against glaucoma through various mechanisms, including reducing IOP, preserving vascular health, and preventing ganglion cell loss. This article provides a comprehensive review of the effect of oxidative stress, diet, and antioxidant therapy on IOP and open-angle glaucoma.

Effects of Oral Supplementation with Docosahexaenoic Acid (DHA) plus Antioxidants in Pseudoexfoliative Glaucoma: A 6-Month Open-Label Randomized Trial

PURPOSE

To assess the effects of antioxidant oral supplementation based on docosahexaenoic acid (DHA) in pseudoexfoliative (PEX) glaucoma.

PATIENTS AND METHODS

A prospective 6-month open-label randomized controlled trial was conducted in patients with PEX glaucoma and adequate intraocular pressure (IOP) control. Patients in the DHA group received a high-rich DHA (1 g) nutraceutical formulation. Ophthalmological examination, DHA erythrocyte membrane content (% total fatty acids), plasma total antioxidant capacity (TAC), plasma malondialdehyde (MDA), and plasma IL-6 levels were assessed.

RESULTS

Forty-seven patients (DHA group 23, controls 24; mean age 70.3 years) were included. In the DHA group, the mean IOP in the right eye decreased from 14.7 [3.3] mmHg at baseline to 12.1 [1.5] mmHg at 6 months (P=0.01). In the left eye, IOP decreased from 15.1 [3.3] mmHg at baseline to 12.2 [2.4] mmHg at 6 months (P=0.007). DHA erythrocyte content increased in the DHA group, with significant differences versus controls at 3 months and 6 months (8.1% [0.9] vs. 4.4% [0.7]; P < 0.0001). At 6 months and in the DHA group only, TAC levels as compared with baseline increased significantly (919.7 [117.9] vs. 856.9 [180.3] µM copper-reducing equivalents; P=0.01), and both MDA (4.4 [0.8] vs. 5.2 [1.1] nmol/mL; P  =  0.02) and IL-6 (2.8 [1.3] vs. 4.7 [2.3] pg/mL; P=0.006) levels were lower than in controls.

CONCLUSIONS

Targeting pathophysiology mechanisms of PEX glaucoma by reducing oxidative stress and inflammation with a high-rich DHA supplement might be an attractive therapeutic approach. Despite the short duration of treatment, decrease in IOP supports the clinical significance of DHA supplementation.

Rational Basis for Nutraceuticals in the Treatment of Glaucoma

BACKGROUND

Glaucoma, the second leading cause of blindness worldwide, is a chronic optic neuropathy characterized by progressive retinal ganglion cell (RGC) axons degeneration and death. Primary open-angle glaucoma (OAG), the most common type, is often associated with increased intraocular pressure (IOP), however other factors have been recognized to partecipate to the patogenesis of the optic neuropathy. IOP-independent mechanisms that contribute to the glaucoma-related neurodegeneration include oxidative stress, excitotoxicity, neuroinflammation, and impaired ocular blood flow. The involvement of several and diverse factors is one of the reasons for the progression of glaucoma observed even under efficient IOP control with the currently available drugs.

METHODS

Current research and online content related to the potential of nutritional supplements for limiting retinal damage and improving RGC survival is reviewed.

RESULTS

Recent studies have suggested a link between dietary factors and glaucoma risk. Particularly, some nutrients have proven capable of lowering IOP, increase circulation to the optic nerve, modulate excitotoxicity and promote RGC survival. However, the lack of clinical trials limit their current therapeutic use. The appropriate use of nutraceuticals that may be able to modify the risk of glaucoma may provide insight into glaucoma pathogenesis and decrease the need for, and therefore the side effects from, conventional therapies.

CONCLUSION

The effects of nutrients with anti-oxidant and neuroprotective properties are of great interest and nutraceuticals may offer some therapeutic potential although a further rigorous evaluation of nutraceuticals in the treatment of glaucoma is needed to determine their safety and efficacy.

Omega-3 fatty acids protect retinal neurons in the DBA/2J hereditary glaucoma mouse model

The purpose of this study was to evaluate the neuroprotective effects of omega-3 polyunsaturated fatty acid (ω3-PUFA) supplementation, alone or in combination with timolol eye drops, in a mouse model of hereditary glaucoma. DBA/2J mice (8.5-month-old) were assigned to an ω3-PUFAs + timolol, ω3-PUFAs only, timolol only, or an untreated group. Treated mice received a daily gavage administration of eicosapentaenoic acid (EPA) and docosahexaenoic acid and/or topical instillation of timolol (0.5%) once a day for 3 months. Blood was analysed regularly to determine ω3-PUFA levels and retinas were histologically analysed. Real-time PCR and Western blot were performed for retinal pro-inflammatory cytokines and macrophages. Blood arachidonic acid/EPA ratio gradually decreased and reached the desired therapeutic range (1-1.5) after 4 weeks of daily gavage with ω3-PUFAs in the ω3-PUFAs + timolol and ω3-PUFAs only groups. Retinal ganglion cell densities were significantly higher in the ω3-PUFAs + timolol (1303.77 ± 139.62/mm²), ω3-PUFAs only (768.40 ± 52.44/mm²) and timolol only (910.57 ± 57.28/mm²) groups than in the untreated group (323.39 ± 95.18/mm²). ω3-PUFA supplementation alone or timolol alone, significantly increased protein expression levels of M1 macrophage-secreted inducible nitric oxide synthase and M2 macrophage-secreted arginase-1 in the retina, which led to significant decreases in the expression levels of tumour necrosis factor-α (TNF-α). ω3-PUFA supplementation alone also resulted in significantly reduced expression of interleukin-18 (IL-18). ω3-PUFA + timolol treatment had no effect on the expression level of any of the aforementioned mediators in the retina. Supplementation with ω3-PUFAs has neuroprotective effect in the retinas of DBA/2J mice that is enhanced when combined with timolol eye drops. The continued inflammation following ω3-PUFAs + timolol treatment suggests that downregulation of IL-18 and TNF-α may not be the only factors involved in ω3-PUFA-mediated neuroprotection in the retina.

Oxidative stress and mitochondrial failure in the pathogenesis of glaucoma neurodegeneration

This review focuses on oxidative stress and mitochondrial failure for understanding mechanisms of optic nerve damage in primary open-angle glaucoma. The chapter shows scientific evidence for the role of mitochondrial disbalance and reactive oxygen species in glaucoma neurodegeneration. Mitochondria regulate important cellular functions including reactive oxygen species generation and apoptosis. Mitochondrial alterations result from a wide variety of damaging sources. Reactive oxygen species formed by the mitochondria can act as signaling molecules, inducing lipid peroxidation and/or excitotoxicity with the result of cell lesion and death. Antioxidants may help to counteract oxidative stress and to promote neuroprotection. We provide information that may lead to a new way for diagnosing and treating glaucoma patients.

A two-year follow-up of oral antioxidant supplementation in primary open-angle glaucoma: an open-label, randomized, controlled trial

PURPOSE

To evaluate the effect of oral antioxidant supplementation (OAS) on primary open-angle glaucoma (POAG) over a 2-year follow-up period.

PATIENTS AND METHODS

In this open-label, randomized controlled trial, 117 eyes of 117 patients with mild or moderate POAG and intraocular pressure under control with topical antiglaucoma medications were recruited and randomly divided into three groups according to supplementation: (1) OAS with (ICAPS R(®) - Alcon Laboratories, n = 26); (2) OAS without ω-3 fatty acids (OFTAN MACULA(®) - Laboratorios Esteve, n = 28); and (3) a control group without OAS (n = 63). They all underwent visual field (VF) tests (Humphrey 24-2) and scans using a Fourier-domain optical coherence tomography (FD-OCT) device (RTVue-100) at the beginning of the study and 2 years later. Mean deviation (MD), standard pattern deviation (PSD), peripapillary retinal nerve fibre layer (RNFL) and macular ganglion cell complex (GCC) parameters were considered for the analysis. Patients were also classified according to MD deterioration (fast deterioration vs. slow deterioration).

RESULTS

Visual field global indices, peripapillary RNFL thickness and macular GCC thickness showed no differences among the groups at the beginning and end of the follow-up. Besides all the comparisons among groups for differences before and after the follow-up of the MD, PSD, RNFL and GCC parameters were also non-significant. The proportions of patients according to MD deterioration were similar among the groups and subgroups (p > 0.05 for all the comparisons).

CONCLUSION

Oral antioxidant supplementation with or without ω-3 fatty acids does not appear useful as an adjuvant treatment of mild/moderate POAG in the short term.