Abstract
Purpose: :
To study the effects of dietary n–3 fatty acids, lutein and/or zeaxanthin on lipofuscin accumulation in the retinal pigment epithelium (RPE) of the foveal region.
Methods: :
Rhesus monkeys (7–16 yr, n = 17) were fed xanthophyll–free semipurified diets from birth with either adequate or low n–3 fatty acids. All animals had no observable macular pigment clinically. Chromatographic analyses of the retinas did not found any lutein or zeaxanthin. Five monkeys then were supplemented with lutein and six with zeaxanthin for 6 to 24 months, while six remained xanthophyll–free until death. The retinas were embedded in methacrylate and 2 µm sections were cut along the vertical meridian through the foveas. Images of the RPE were taken at 400 X magnification with a Texas Red filter set (excitation wavelength 465–495 nm, emission wavelength 515–555 nm). Sampling images were collected at 0 and ± 0.69 mm eccentricity along the vertical meridian. The areas occupied by the autofluorescent lipofuscin granules of the RPE were measured by computer software and values were compared with those of the age–matched control monkeys (n = 7) fed a standard laboratory diet.
Results: :
The amount of lipofuscin granules in the RPE showed no significantly difference at sites 0, + 0.69 mm (superiorly) and – 0.69 mm (inferiorly) eccentricity in normal monkey foveas. However, lipofuscin increased significantly at ± 0.69 mm eccentricity in all the experimental groups with or without lutein/zeaxanthin supplementation when compared with controls. The RPE of the animals fed with low n–3 fatty acids had more lipofuscin at ± 0.69 mm eccentricity when compared to animals fed with adequate n–3 fatty acids diet. Monkeys which had xanthophyll–free diet but later supplemented with zeaxanthin or lutein showed greater variability of the increased lipofuscin granules in the RPE.
Conclusions: :
Nutritional manipulations of n–3 fatty acids, lutein and zeaxanthin influence the amount of lipofuscin granules in the RPE of the foveal region. Higher lipofuscin in animals lacking dietary n–3 fatty acids suggests one mechanism that may underlie the observed association of higher n–3 fatty acids intake with lower risk of age–related macular degeneration. The increased variability of lipofuscin in the zeaxanthin/lutein supplemented monkeys suggests that lutein/zeaxanthin may play a role in reduction of lipofuscin in some animals.
Keywords: macular pigment • retinal pigment epithelium • nutritional factors