Intrauterine growth restriction is associated with alterations in placental lipoprotein receptors and maternal lipoprotein composition

Among other factors, fetal growth requires maternal supply of cholesterol. Cellular cholesterol uptake is mainly mediated by the LDL receptor (LDL-R) and the scavenger receptor family. We hypothesized that expression levels of key receptors of these families were regulated differently in placentas from IUGR pregnancies with varying degrees of severity. Third-trimester placentas from IUGR pregnancies with (IUGR-S) and without (IUGR-M) fetal hemodynamic changes and from control (AGA) pregnancies were studied. LDL-R, LDL-R-related protein (LRP-1), and scavenger receptor class B type I (SR-BI) mRNA and protein levels were measured. Cholesterol concentration and composition of lipoproteins were analyzed enzymatically and by lipid electrophoresis, respectively, in maternal and umbilical cord blood. LDL-R mRNA levels in IUGR- M were similar to AGA but lower ( P < 0.05) in IUGR- S. In contrast, LDL-R protein was twofold ( IUGR- M) and 1.8-fold ( IUGR- S) higher ( P < 0.05) than in the AGA group. LRP-1 mRNA and protein levels were not altered in the IUGR cases. SR-BI mRNA was unchanged in IUGR, but protein levels were lower ( P < 0.05) in IUGR- S than in the other groups. Maternal plasma concentrations of LDL cholesterol were higher ( P < 0.05) in the AGA group ( 188.5 +/- 23.6 mg/dl) than in the IUGR- S group (154.2 +/- 26.1). Electrophoretic mobility of the LDL fraction in maternal plasma demonstrated significant changes in migration toward higher values ( AGA 0.95 +/- 0.06, IUGR- M 1.12 +/- 0.11, P < 0.001; IUGR- S 1.28 +/- 0.20, P = 0.002). We conclude that LDL-R and SR-BI levels are altered in IUGR pregnancies. These differences were associated with changes in LDL, but not HDL, mobility and cholesterol concentration in maternal circulation.