Nutritional manipulation of primate retinas, II: effects of age, n-3 fatty acids, lutein, and zeaxanthin on retinal pigment epithelium.

Purpose: To study the effects of age and of n-3 fatty acids, lutein, and zeaxanthin on the retinal pigment epithelium (RPE).

Methods: Rhesus monkeys (age range, 7-17 years; n = 18) were fed xanthophyll-free semipurified diets from birth. The diets had either low or adequate amounts of n-3 fatty acids. Six monkeys remained xanthophyll-free until death. Six received supplements of pure lutein and six of pure zeaxanthin for 6 to 24 months. The central retina was serially sectioned, and the number of RPE cells were counted in an 8-microm strip along the vertical meridian. Cell counts were compared with data from control monkeys (n = 15) fed a standard laboratory diet.

Results: Foveal and parafoveal RPE cell densities increased with age. Xanthophyll-free monkeys had a dip in the RPE cell density profile at the foveal center, rather than the normal peak. After supplementation with xanthophylls, the RPE profile of animals low in n-3 fatty acids no longer had a dip at the foveal center but became asymmetric, with higher densities in the inferior retina. In animals with adequate n-3 fatty acid levels, xanthophyll supplementation did not restore the foveal peak, and resulted in an asymmetric profile with higher densities in the superior retina.

Conclusions: RPE cells are sensitive to the absence of macular pigment. Supplemental xanthophylls interact with n-3 fatty acid levels to produce asymmetries in the RPE profile. Xanthophylls and n-3 fatty acids are essential for the development and/or maintenance of a normal distribution of RPE cells.