Mechanisms of β-carotene transfer from placenta to embryo in mammals (LB406)

Vitamin A is an essential nutrient for mammalian embryonic development. The most abundant precursor of vitamin A in the human diet is β-carotene (BC). The enzyme β-carotene 15-15’-monooxygenase (CMOI) cleaves BC to form retinaldehyde which is oxidized to form retinoic acid, the biologically active form of vitamin A. BC can be cleaved by β-carotene 9’-10’-monooxygenase (CMOII) to form apocarotenoids which can function as retinoid precursors. The mammalian embryo obtains BC from the maternal circulation and converts it to retinaldehyde via CMOI. However, BC transfer across the maternal-fetal barrier is not fully understood. We demonstrated that embryos from wild-type dams on high vitamin A diet (220 IU/g) and treated with BC at 13.5 dpc, had lower BC levels compared to embryos from wild-type dams on vitamin A sufficient diet (14 IU/g). Regulatory mechanisms involving regulation of placental BC secretion may therefore prevent embryonic retinoid toxicity. Ex vivo placenta culture and in vivo placenta injectio...