Nutrition for the eye: different susceptibility of the retina and the lacrimal gland to dietary omega-6 and omega-3 polyunsaturated fatty acid incorporation.

The purpose of this study was to compare the susceptibility of the retina and the exorbital lacrimal gland to dietary supplies of long-chain omega-3 (omega3) and omega-6 (omega6) polyunsaturated fatty acids (LC-PUFAs). Male Wistar rats were fed a 5% lipid diet containing: (1) 10% eicosapentaenoic acid (EPA) and 7% docosahexaenoic acid (DHA), or (2) 10% gamma-linolenic acid (GLA), or (3) 10% EPA, 7% DHA and 10% GLA or (4) a balanced diet deprived of EPA, DHA and GLA for 3 months. Lipids were extracted from plasma phospholipids, retina and exorbital lacrimal gland, and fatty acid composition was determined by gas chromatography. Dietary supplementation with EPA and DHA increased omega3 PUFA levels in plasma phospholipids as well as in the retina and the exorbital lacrimal gland. By contrast, GLA supplementation favored omega6 PUFA incorporation, and particularly the incorporation of the end-chain omega6 product, docosapentaenoic acid (DPA), into all tissues. Supplementation with EPA, DHA and GLA increased the levels of DHA, EPA and dihomo-GLA (dGLA), whereas arachidonic acid (AA) was unchanged and DPA decreased in the retina and the lacrimal gland. The ability of both tissues to incorporate PUFAs from blood was evaluated. The results showed that the retina was more selective than the lacrimal gland for EPA. In spite of the different susceptibility of the retina and the lacrimal gland to dietary PUFAs, these results suggest that the concomitant use of dietary omega3 and omega6 PUFAs may be useful in modulating inflammation in both tissues.