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Editors Selection IGR 11-3

Basic Research: Omega-3 and -6 fatty acids and prevention retinal structural losses

Comment by Lori Ventura on:

24155 A dietary combination of omega-3 and omega-6 polyunsaturated fatty acids is more efficient than single supplementations in the prevention of retinal damage induced by elevation of intraocular pressure in rats, Schnebelen C; Pasquis B; Salinas-Navarro M et al., Graefe's Archive for Clinical and Experimental Ophthalmology, 2009; 247: 1191-1203

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Despite millions of US dollars spent each year on complementary therapies, there is a paucity of well-designed, well-controlled research on the efficacy of nutraceuticals in general, and particularly with respect to ocular disease. Schnebelen et al. (1240) are to be commended for having undertaken this question since the use of PUFA supplements for other conditions is widespread, and the effects in glaucoma are unknown. In this study, Schnebelen et al. compared a six-month supplementation of either omega-6 fatty acid (gamma linolenic acid, GLA) alone, omega-3 fatty acids (eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA) alone, and a combination of omega-6 and omega-3 (GLA + EPA + DHA) in the prevention of retinal damage secondary to laser-induced IOP elevation (49 ± 7 mmHg) in rats. While no significant protection of any of the retinal layers was noted for omega-6 or omega-3 fatty acids when administered alone, the authors conclude that a combination of omega-6 and omega-3 decreased glial cell activation and prevented retinal structural losses induced by the elevation of IOP in rats, but did not protect against dysfunction as measured by scotopic ERG and Flourogold retrograde staining. While the results suggest that there may be a potential benefit in glaucoma, there are a few issues which may limit enthusiasm for this paper. Firstly, the authors acknowledge that the IOP elevation in their model was very high resulting in a drastic reduction of the ERG-a and -b wave amplitudes which is more representative of ischemia. The relevance of this model for glaucoma, where selective inner retinal losses are seen, is questionable. Secondly, the main histological evidence (spared retinal thickness) supporting a protective role of combined omega-6 and omega-3 PUFA therapy against IOP elevation was obtained in only three animals, and there was no mention of the corresponding IOP exposures. In contrast, this same combined treatment neither spared the ERG, nor Flourogold-stained RGCs, the latter representing a more specific marker for glaucoma. Similarly, the evidence supporting a protective role for combined therapy against retinal stress, as measured by glial activation, is based on only three animals without mention of the corresponding IOP exposures. A recent study published by Gu et al. (Mol Cell Proteomics 8(6): 1338) from the Cole Eye Institute, indicates that carboxyethylpyrrole (CEP) adducts are uniquely generated from the oxidation of DHA-containing lipids which are abundant in the retina. The question arises whether the supplementation of DHA in this study would have been more efficacious in preserving structure and function were it administered in combination with an antioxidant such as vitamin C. It is hoped that the authors will continue to pursue this line of research in a non-ischemic glaucoma model to further investigate whether function as well as structure may be preserved with polyunsaturated fatty acid therapy.

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