P 43 Plant sterol concentrations suggest unaffected materno-placental cholesterol supply to the fetus in IUGR

Introduction Fetal cholesterol levels are low in IUGR. The fetus synthesizes its cholesterol de novo. However, 20–50% of the fetal cholesterol is provided by the mother. Whether low fetal cholesterol levels in IUGR are the result of reduced materno-placental cholesterol supply or of low fetal synthesis rates is a matter of debate. Plant sterol concentrations are dependent on nutritional intake of vegetables, plant oil or nuts by the mother and cannot be synthesized de novo in humans. However, plant sterols have biologic properties similar to cholesterol and are transported by the same transport pathways. Hence, the concentration levels in the fetus are directly related to maternal supply. Objectives We aimed at analyzing fetal plant sterols to gain deeper insights into transplacental cholesterol transport in IUGR. Material and methods Umbilical cord sera were sampled post-partum from fetuses delivered between 24 weeks of gestation till term. 49 IUGR fetuses were matched to 49 adequate for age delivered preterm and term neonates (CTRL) according to gestational age at delivery. Sterols (5a-Cholestanol, Campesterol, Sitosterol) were analyzed by GC–MS. Results Related to total cholesterol concentrations phytosterol concentrations increased with gestational age in the CTRL group. The ratios of phytosterol to cholesterol levels were higher in the IUGR group as compared to the CTRL group (5a-Cholestanol p  = 0.0004, Campesterol p  = 0.0002, Sitosterol p  = 0.0212). The differential potential was pronounced in fetuses delivered before 32 weeks of gestation, especially for sitosterol (before 32nd week: p  = 0.0007, after 32nd p  = 0.9740). Conclusions Increasing ratios of phytosterol levels to total fetal cholesterol levels suggest an increasing maternal contribution to fetal cholesterol pool with gestational age. Hence, decreasing fetal cholesterol concentrations later in pregnancy are rather an effect of decreasing fetal de novo synthesis or increasing turnover rates of fetal cholesterol. Unlike expected in pregnancies with placental insufficiency the ratios of phytosterol concentrations to total cholesterol levels are increased in IUGR as compared to CTRL. Cholesterol deficiency in IUGR is hence the result of diminished fetal de novo synthesis rates rather than low maternal supply.