Abstract
Purpose :
To examine correlates of macular pigment optical density (MPOD) in rhesus monkey infants.
Methods :
Rhesus macaque infants were breastfed and mother-reared (n=8, BF) or nursery-reared and fed human infant formulas (n=15, FF) that either were supplemented with carotenoids, including lutein (L) at the level in rhesus breastmilk and zeaxanthin (Z) at 18% of breastmilk levels (n=8, SF), or were unsupplemented (n=7, UF). Retinal imaging at 4, 8, 16 and 24 weeks included 2-wavelength reflectometry of MPOD, sdOCT to determine retinal layer thicknesses, and axial length measurements. Carotenoids were determined by HPLC in serum and macular retina at 24 weeks. Total and HDL cholesterol and apolipoproteins were measured in serum, and mRNA expression of carotenoid transporters, binding proteins, and cleavage enzymes (CD36, SCARB1, SCARB2, LDLR, STARD3, GSTP1, BCO1, BCO2 and RPE65) were determined in macular retina. Pearson correlation coefficients and group comparisons are described if p<0.05.
Results :
Peak MPOD increased from 8 to 24 weeks in BF but not FF groups, and MPOD peak and volume were higher in BF than FF groups at 16 and 24 weeks. Foveal thickness of the inner/outer segment layer (IS/OS) was lower in FF than BF groups at 8 and 16 weeks but values converged by 24 weeks. At 24 weeks, MPOD was not correlated with thickness of foveal IS/OS, outer nuclear layer or total retina; axial length was greater in BF than in FF infants, and within the BF group was correlated with MPOD. Serum L was ~5-fold lower in SF than in BF infants despite similar L intakes; serum Z fell to 0 by 12 weeks in both FF groups. Macular L and Z at 24 weeks were ~25-30% of BF in both FF groups. MPOD levels were highly correlated with serum and macular L and Z. MPOD was correlated with ApoA1 (the major protein of HDL) and ApoB100 (the major protein of LDL), both of which were higher in BF than FF infants. Among carotenoid-related genes, MPOD was significantly correlated with expression of SCARB1 and SCARB2, scavenger receptors involved in retinal lutein uptake from the circulation.
Conclusions :
Although MPOD accumulation during primate eye development is dependent on the dietary supply of L and Z, the bioavailability of L for MPOD accretion differs several-fold between breast milk and infant formulas. This difference may be associated with levels of apolipoproteins and the expression of scavenger receptors.
This is a 2020 ARVO Annual Meeting abstract.