Placental release of taurine to both the maternal and fetal circulations in human term pregnancies
Taurine is regarded as an essential amino acid in utero, and fetal taurine supply is believed to rely solely on placental transfer from maternal plasma. Despite its potential role in intrauterine growth restriction and other developmental disturbances, human in vivo studies of taurine transfer between the maternal, placental, and fetal compartments are scarce. We studied placental transfer of taurine in uncomplicated human term pregnancies in vivo in a cross-sectional study of 179 mother-fetus pairs. During cesarean section, we obtained placental tissue and plasma from incoming and outgoing vessels on the maternal and fetal sides of the placenta. Taurine was measured by liquid chromatography–tandem mass spectrometry. We calculated paired arteriovenous differences, and measured placental expression of the taurine biosynthetic enzyme cysteine sulfinic acid decarboxylase (CSAD) with quantitative real-time polymerase chain reaction and western blot. We observed a fetal uptake (p < 0.001), an uteroplacental release (p < 0.001), and a negative placental consumption of taurine (p = 0.001), demonstrating a bilateral placental release to the maternal and fetal compartments. Increasing umbilical vein concentrations and fetal uptake was associated with the uteroplacental release to the maternal circulation (rs = − 0.19, p = 0.01/rs = − 0.24, p = 0.003), but not with taurine concentrations in placental tissue. CSAD-mRNA was expressed in placental tissue, suggesting a potential for placental taurine synthesis. Our observations show that the placenta has the capacity to a bilateral taurine release, indicating a fundamental role of taurine in the human placental homeostasis beyond the supply to the fetus.
KeywordsTaurine Placenta Fetus Transfer Arteriovenous differences CSAD
First, we would like to thank the participating women for contributing to our study. We would also like to acknowledge the anesthesiologists, specialist nurses, obstetricians, and midwives at Oslo University Hospital for offering their time and skills to help us with the sampling procedure. We further thank Trine M. Reine and Anne Randi Enget at the Department of Nutrition at the University of Oslo who performed the qRT-PCR analysis, and Jan Haavik at the Department of Biomedicine at the University of Bergen who generously provided the CSAD antibody for western blot analysis.
This study was funded by grants from the South-Eastern Norway Regional Health Authority, the Throne Holst foundation, the Norwegian National Advisory Unit on Women’s Health, Oslo University Hospital, and the Department of Obstetrics, Oslo University Hospital.
Compliance with ethical standards
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The study was approved by the data protection officials at Oslo University Hospital and the Regional Committee for Medical and Health Research Ethics, Southern Norway 2419/2011.
Informed consent was obtained from all individual participants included in the study.
Conflict of interest
Rune Blomhoff is a chair holder in AS Vitas. Otherwise, the authors declare that they have no conflict of interest.
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