Objectives: Xanthophyll pigments lutein and zeaxanthin cross the blood-retina barrier to preferentially accumulate in the macular region of the neural retina. There they form macular pigment, protecting the retina from blue light damage and oxidative stress. Lutein and zeaxanthin also accumulate in brain tissue. The objective of the study was to evaluate the relationship between retinal and brain levels of these xanthophylls in non-human primates.
Methods: Study animals included rhesus monkeys reared on diets devoid of xanthophylls that were subsequently fed pure lutein or pure zeaxanthin (both at 3.9 µmol/kg per day, n = 6/group) and normal rhesus monkeys fed a stock diet (0.26 µmol/kg per day lutein and 0.24 µmol/kg per day zeaxanthin, n = 5). Retina (4 mm macular punch, 4-8 mm annulus, and periphery) and brain tissue (cerebellum, frontal cortex, occipital cortex, and pons) from the same animals were analyzed by reverse-phase high-performance liquid chromatography.
Results: Lutein in the macula and annulus was significantly related to lutein levels in the cerebellum, occipital cortex, and pons, both in bivariate analysis and after adjusting for age, sex and n-3 fatty acid status. In the frontal cortex the relationship was marginally significant. Macular zeaxanthin was significantly related to zeaxanthin in the cerebellum and frontal cortex, while the relationship was marginally significant in the occipital cortex and pons in a bivariate model.
Discussion: An integrated measure of total macular pigment optical density, which can be measured non-invasively, has the potential to be used as a biomarker to assess brain lutein and zeaxanthin status.