RESUMO
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.
RESUMO
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.
