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. Author manuscript; available in PMC: 2019 Jun 1.
Published in final edited form as: Arch Biochem Biophys. 2018 Apr 11;647:33–40. doi: 10.1016/j.abb.2018.04.008

Figure 2. Maternal-fetal transfer of carotenoids.

Figure 2

Proposed model for maternal fetal transfer of β-carotene (β-car): intact β-carotene from the maternal bloodstream is taken up by the syncytiotrophoblast cells of placenta, likely through the action of the lipoprotein receptors LRP1 and VLDLR, at least under a condition of vitamin A sufficiency. Placental β-carotene 9′,10′-oxygenase (BCO2) cleaves the provitamin A carotenoid asymmetrically to generate β-apo-10′carotenal (apo10AL). This metabolite then increases the transcription and activity of placental microsomal triglyceride transfer protein (MTP) which in turn stimulates lipoproteins biosynthesis. Thus, β-carotene is transported toward the fetal circulation in association with lipoproteins, assembled within and secreted from the placenta syncytiotrophoblast cells. Whether or not lutein and zeaxanthin (L/Z) are transferred across the maternal-fetal barrier with similar molecular mechanisms remains to be established. apoB, apolipoprotein B100; CE, cholesteryl esters; TG, triglycerides.