Modulation of Apolipoprotein D levels in human pregnancy and association with gestational weight gain

Abstract

Background: Apolipoprotein D (ApoD) is a lipocalin involved in several processes including lipid transport, but its modulation during human pregnancy was never examined.

Methods: We investigated the changes in the levels of ApoD in the plasma of pregnant women at the two first trimesters of gestation and at delivery as well as in the placenta and in venous cord blood. These changes were studied in 151 women classified into 9 groups in relation to their prepregnancy body mass index (BMI) and gestational weight gain (GWG).

Results: Plasma ApoD levels decrease significantly during normal uncomplicated pregnancy. ApoD is further decreased in women with excessive GWG and their newborns. In these women, the ApoD concentration was tightly associated with the lipid parameters. However, the similar ApoD levels in low cholesterol (LC) and high cholesterol (HC) women suggest that the plasma ApoD variation is not cholesterol dependant. A tight regulation of both placental ApoD transcription and protein content is most probably at the basis of the low circulating ApoD concentrations in women with excessive GWG. After delivery, the plasma ApoD concentrations depended on whether the mother was breast-feeding or not, lactation favoring a faster return to baseline values.

Conclusion: It is speculated that the decrease in plasma ApoD concentration during pregnancy is an adaptive response aimed at maintaining fetal lipid homeostasis. The exact mechanism of this adaptation is not known.

Figure 1

Plasma ApoD levels during pregnancy. ApoD levels were measured in women with a BMI of 20-26 kg/m² and a GWG of 11-18 kg at the two first trimesters of pregnancy (1^st and 2^nd) and at delivery. ApoD levels in the venous cord blood were also measured. Data are expressed as means ± SEM. * indicates significant differences compared to the first trimester (p < 0.001). # indicates significant differences compared to the second trimester (p < 0.001). & indicates significant differences compared to the pregnant groups and to cord blood (p < 0.001).

Figure 2

ApoD levels in placenta according to pre-pregnancy BMI and GWG. (A) The level of apoD mRNA expression was measured by qRT-PCR using specific primers for apoD. Data are expressed as the normalized ratio of apoD mRNA to 18S RNA (means ± SEM). (B) The placental ApoD protein content was measured by ELISA. The values (means ± SEM) were normalized by the total protein content. * indicates significant differences (p < 0.01) from the normal control group (BMI 20-26 kg/m², GWG 11-18 kg). # indicates significant differences (p < 0.01) from the group of similar GWG and normal BMI (20-26 kg/m²).

Figure 3

The effect of breast- and bottle-feeding on plasma ApoD levels. ApoD concentration was measured in mothers two months after delivery (women with a BMI of 20-26 kg/m² and a GWG of 11-18 kg) and compared with levels at delivery and in non-pregnant women (BMI 20-26 kg/m²). Data are expressed as means ± SEM. * indicates significant differences compared to non-pregnant women (p < 0.001). # indicates significant differences compared to breast-feeding women (p < 0.001).