Effect of Subadequate Maternal Vitamin-A Status on Placental Transfer of Retinol and Beta-Carotene to the Human Fetus

Abstract

The placental transfer of retinol and β-carotene was assessed based on maternal serum, cord serum and placental levels at term parturition in women with adequate (n = 15; serum retinol > 20 μg/dl) and subadequate (n = 16; serum retinol ≤ 20 μg/dl) vitamin-A status. There was no difference in retinol and β-carotene levels in placenta and cord serum between these groups. However, differences in the relation of maternal, placental and cord blood components were observed between women with adequate and subadequate vitamin-A status. In women with subadequate status, circulating fetal retinol levels correlated with placental retinol levels, and maternal serum β-carotene correlated with placental retinol. Within this group, maternal serum β-carotene and cord serum retinol correlated significantly in women with serum retinol levels lower than 15 μg/dl. These results suggest that β-carotene may be a precursor of retinol in placenta and that this conversion may depend on the nutritional status of the mother, being particularly effective in a more depleted state.

β-Apo-10′-carotenoids Modulate Placental Microsomal Triglyceride Transfer Protein Expression and Function to Optimize Transport of Intact β-Carotene to the Embryo

“…Indeed, maternal retinoic acid administration can rescue several but not all the developmental defects in mouse mutants for retinoic acid biosynthetic enzymes, such as RALDH2, RALDH3, and RDH10 (36). Also, retinoic acid supplementation never resulted in normal live embryos at term in these strains (37), hence the notions that the placenta favors the transfer of retinol (retinoic acid precursor) versus retinoic acid (51) and that BC could be used as a precursor of retinol in placenta (52). Contrary to this hypothesis, our data suggest that the placenta is equipped with highly regulated molecular machineries that favor the transfer of intact BC (retinoic acid precursor) versus retinoic acid under a normal maternal vitamin A status.…”

Esterification of Vitamin A by the Human Placenta Involves Villous Mesenchymal Fibroblasts

“…This question has been approached in animal models (sheep, mouse, monkey), but the placental metabolism of retinoids is difficult to deduce from studies in the intact animal, and extrapolation of these results to humans is uncertain (11-13). Measurements of human placental, maternal, and cord retinoid concentrations have been reported, but they shed little light on the metabolic pathway (14,15). Experiments using human perfused placenta and full-term human placental tissues in vitro have yielded controversial results concerning retinoid metabolism, especially the ability of the placenta to produce and store retinyl esters from retinol (16,17).…”

Papel da vitamina A na prevenção do estresse oxidativo em recém-nascidos

“…50,51 Em razão desse mecanismo regulatório, as concentrações séricas fetais, tanto de carotenói-des 15,19,51 quanto de retinol, são bastante inferiores quando comparadas às concentrações maternas. 19,51 Segundo Oostenbrug et al 52 os níveis de retinol do RN representam cerca de 55% do valor sérico materno e os carotenóides cerca apenas 17%. Resultados semelhantes são descritos por Baydas et al, 15 Yeum et al 19 Dimenstein et al 51 Tal condição, no entanto, pode ser agravada em gestantes com DVA.…”

“…19,51 Segundo Oostenbrug et al 52 os níveis de retinol do RN representam cerca de 55% do valor sérico materno e os carotenóides cerca apenas 17%. Resultados semelhantes são descritos por Baydas et al, 15 Yeum et al 19 Dimenstein et al 51 Tal condição, no entanto, pode ser agravada em gestantes com DVA. Mesmo que os níveis séricos fetais não sejam gravemente afetados na deficiência subclínica de VA materna, a formação de reservas hepáticas do feto e do recém-nascido pode ser comprometida.…”

“…Mesmo que os níveis séricos fetais não sejam gravemente afetados na deficiência subclínica de VA materna, a formação de reservas hepáticas do feto e do recém-nascido pode ser comprometida. 51,53 O transporte desses nutrientes ocorre predominantemente no terceiro trimestre gestacional, 15,22,24 sendo constatada redução dos níveis séricos maternos de retinol e ß-caroteno durante esse período. 52 Entretanto, as reservas do RN podem ser aumentadas durante o aleitamento materno.…”