The maternal-fetal gradient of free and esterified phytosterols at the time of delivery in humans

Background: High dietary intakes of phytosterols (Phyto), such as those consumed by vegans and vegetarians, are not recommended for cholesterol-lowering in pregnant women (PW) because the safety of their use during pregnancy has not been fully established [1]. Information on Phyto in pregnancy is very limited. Objective: To characterize the maternal-fetal gradient of free and esterified Phyto at the time of delivery in humans. Design: PW who had a term delivery at the Obstetrics and Gynecology Unit of the University Hospital of Padua (Padua, Italy), between November 2016 and March 2017, participated in the study. Fatty acids (FA), cholesterol (Chol), Chol metabolites (7-dehydrocholesterol, 7-DHChol; lathosterol, Latho; 7α-hydroxycholesterol, 7α-OHChol), and Phyto (campesterol, Camp; stigmasterol, Stigma; sitosterol, Sito) were measured in both maternal (MB) and cord blood (CB) at the time of delivery. Non-pregnant adult volunteers (Ref-NA) served as a reference. Results: Thirty-four term PW and 12 Ref-NA signed informed consent and were studied. Plasma total Phyto concentrations in CB were up to 20-fold lower than in MB (p < 0.05). Positive and significant correlations were found between total Phyto of MB-CB pairs (p < 0.01), and between total FA and Camp of MB (p < 0.05). Interestingly, free Chol to Chol ester ratio of CB did not differ from that of MB, and free Phyto to Phyto ester ratios were higher in CB than in MB (p < 0.001). No differences were found between Phyto concentrations of MB and Ref-NA. However, free Chol to Chol ester ratio, and free Phyto to Phyto ester ratios were higher in MB than in Ref-NA (p < 0.05). Chol synthesis, as indicated by 7-DHChol to 7α-OHChol, Latho to 7α-OHChol, and Latho to Sito ratios, was greatest in CB and lowest in Ref-NA. Conclusion: Our data suggest that free Phyto cross the human placenta more easily than Phyto ester. An elevated Stigma to Chol ratio in CB than in MB was also described for the first time. The impact of these findings on the neonatal outcomes remains to be elucidated.