Lutein, a xanthophyll with antioxidant properties, preferentially accumulates in primate brain. Brain concentrations of lutein are associated with higher cognitive test scores and supplementation with lutein improves cognitive performance in older adults. The mechanism underlying this beneficial effect, however, remains unknown.

Recent studies suggest the association between brain lutein and cognition may be dependent on brain docosahexaenoic acid (DHA) levels, which are also related to better cognitive function. Furthermore, supplementation with both lutein and DHA has been shown to provide additional cognitive benefits in older adults compared to supplementation with either alone. Therefore, lutein and DHA may function together to influence cognition.

Given that both compounds accumulate in membranes, the objective of this study was to determine the co-localization of lutein and DHA in membranes of brain regions controlling different domains of cognitive function in adult rhesus monkeys (age 7–20 y; n=11). Nuclear, myelin, mitochondrial, and neuronal plasma membranes were isolated from prefrontal cortex, cerebellum and striatum tissue using differential centrifugation with a Ficoll density gradient. Lutein and DHA were measured using high performance liquid chromatography and gas chromatography, respectively.

Results document that both lutein and DHA were differentially distributed among nuclear, myelin, mitochondrial, and neuronal plasma membranes, with levels being the lowest in mitochondrial membranes (one-way ANOVA with Tukey HSD, P<0.05). Both followed a similar distribution pattern in the prefrontal cortex and striatum, but not cerebellum. In the prefrontal cortex, age adjusted lutein and DHA levels were inversely associated in myelin membranes only (r = −0.73, P<0.03), while in the striatum, lutein and DHA were positively related in nuclear (r = 0.77, P<0.02) and mitochondrial membranes (r = 0.88, P<0.004). Co-localization of lutein and DHA in some membranes and regions, but not others, may be indicative of varied, and specific, functions of lutein in different brain regions.

Results from this study provide the first steps toward understanding lutein’s mechanism of action in the brain and its relationship to DHA.