Among the carotenoids in the diet, lutein, zeaxanthin, and meso-zeaxanthin can be found in the macular region of the retina, where they contribute to eye health by filtering blue light and serving antioxidant functions. Together these compounds contribute to macular pigment optical density (MPOD), and consumption of these compounds is needed to maintain MPOD status, as de novo synthesis of carotenoids does not occur. In addition to the eye, lutein is also found in all cortices of the brain, yet the function of lutein in the brain is not yet known, even though elevated MPOD is associated with better executive functioning, visuospatial thinking, and global intelligence in children. Existing literature documents an association between MPOD in adults and genetic variations, but this association has not been studied in children. Liu and colleagues conducted a study to determine if differences in child MPOD status were explained by the genetic variances observed in adults. They report their results in the September 2021 issue of The Journal of Nutrition.
Subjects for this study were participants (n=134) in the Fitness Improves Thinking in Kids study. The children were between 7 and 9 years of age at the time that MPOD was measured, whole-body and visceral adiposity was determined, and DNA samples were collected from saliva to genotype the subjects for specific single nucleotide polymorphisms and ancestry markers. Habitual diet was estimated using a 3 day food log prepared by their parents.
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The presence of more than 1 minor allele on b-carotene-15,15’-monooxygenase-rs7501331(T allele), cluster of differentiation 36(CD36)-rs1527483 (T allele), or CD36-rs3173798 (C allele) was found to occur in children with lower MPOD than those children who were homozygous for the major allele. When adjusted for dietary lutein and zeaxanthin intake, the MPOD differences based on the CD36-rs3173798 allele remained significant. The authors concluded that the genetic variations in b-carotene-15,15’-monooxygenase and CD36 in children contribute to their MPOD levels, with the variation in CD36-rs3173798 remaining a determinant even after dietary intake was included in the model.
In a commentary, Handelman and Handelman discuss the importance of the rs3173798 SNP for CD36, as it is an expression quantitative trait locus, which can play a role in differential RNA abundance in tissues. Some studies have noted that certain SNP’s may result in a strong association with a phenotype in one population but less in another. They discuss the need for further studies using populations with specific ancestries, as the presence of this SNP is different for certain populations. They suggest the possibility of recalling subjects where existing genotypic data exist in order to make MPOD measurements to strengthen the confidence in the association between this SNP and MPOD levels.
References
Liu R, Hannon BA, Robinson KN, Raine LB, Hammond BR, Renzi-Hammond LM, Cohen NJ, Kramer AF, Hillman CH, Teran-Garcia M, Khan NA. Single nucleotide polymorphisms in CD36 are associated with macular pigment among children. Journal of Nutrition, Volume 151, Issue 9, September 2021, Pages 2533–2540, https://doi.org/10.1093/jn/nxab153.
Handelman GJ, Handelman SK. Single-nucleotide polymorphisms in CD36 are associated with macular pigment among children. Journal of Nutrition, Volume 151, Issue 9, September 2021, Pages 2507–2508, https://doi.org/10.1093/jn/nxab242.
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