Dietary docosahexaenoic acid protects against N-methyl- N-nitrosourea-induced retinal degeneration in rats

Abstract

The effect of dietary intake of specific types of fatty acids on retinal degeneration due to N-methyl- N-nitrosourea (MNU)-induced photoreceptor cell apoptosis was evaluated. Fifty-day-old female Sprague–Dawley rats were given a single intraperitoneal injection of 50 mg kg −1 body weight of MNU, and were then switched to one of five different diets containing the following fatty acids at the following weight percentages: 10% linoleic acid (LA); 9·5% palmitic acid (PA) and 0·5% LA; 9·5% eicosapentaenoic acid (EPA) and 0·5% LA; 4·75% EPA, 4·75% docosahexaenoic acid (DHA) and 0·5% LA; or 9·5% DHA and 0·5% LA. When rats developed MNU-induced mammary tumors with a diameter of ≧1 cm, or at the termination of the experiment (20 weeks after MNU injection), retinal tissue samples were obtained and examined. Incidence and severity of retinal damage were compared by histologic examination. MNU-induced retinal degeneration was prevented in rats fed the diet containing 9·5% DHA (4·75% DHA was less effective), whereas it was accelerated in rats fed the 10% LA diet. Over the course of the 20-week experimental period, the fatty acid composition of serum reflected differences in dietary fatty acids. The present results indicate that a diet containing 9·5% DHA can counteract MNU retinotoxicity in the rat retina. DHA may play a role in protection against MNU-induced photoreceptor cell apoptosis in the rat retina.