Lipid and lipoprotein concentrations in pregnancies complicated by intrauterine growth restriction

Periconceptional Mediterranean diet during pregnancy on children's health

During pregnancy, rapid and subtle physiological changes are observed from conception to birth. Nutrition and other lifestyle factors before and during pregnancy have been shown in the literature to influence the health of both mother and child. A healthy and varied diet during pregnancy can provide adequate energy and nutrients for both the mother and the growing fetus. Current research focuses on the periconceptional phase, which includes the early processes of gametogenesis, embryogenesis and placentation. A variety of abnormalities and pregnancy-related problems occur during this period, including congenital defects, fetal loss, miscarriage and preterm birth. A varied and balanced diet during periconception is important to maintain fetal development and growth. To date, numerous studies have been conducted to investigate the effects of consuming different nutrients, foods or food groups during pregnancy on the health of mother and child. For example, the Mediterranean diet is considered as a balanced, nutrient-rich diet due to the low consumption of meat products and fatty foods and the high consumption of vegetables, cheese, olive oil, fish, shellfish and little meat. While many studies have been conducted in the literature to investigate the effects of a Mediterranean diet during pregnancy on fetal health, the results have been inconclusive. The aim of this article is to review the current literature on the Mediterranean diet during pregnancy.

Maternal lipid profile in pregnancy and embryonic size: a population-based prospective cohort study

Background

Lipids are crucial for fetal growth and development. Maternal lipid concentrations are associated with fetal growth in the second and third trimester of pregnancy and with birth outcomes. However, it is unknown if this association starts early in pregnancy or arises later during fetal development. The aim of this study was to investigate the association between the maternal lipid profile in early pregnancy and embryonic size.

Methods

We included 1474 women from the Generation R Study, a population based prospective birth cohort. Both embryonic size and the maternal lipid profile were measured between 10 weeks + 1 day and 13 weeks + 6 days gestational age. The maternal lipid profile was defined as total cholesterol, triglycerides (TG), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), remnant cholesterol, non-high-density (non-HDL-c) lipoprotein cholesterol concentrations and the triglycerides/high-density lipoprotein (TG/HDL-c) ratio. Additionally, maternal glucose concentrations were assessed. Embryonic size was assessed using crown-rump length (CRL) measurements. Associations were studied with linear regression models, adjusted for confounding factors: maternal age, pre-pregnancy body mass index (BMI), parity, educational level, ethnicity, smoking and folic acid supplement use.

Results

Triglycerides and remnant cholesterol concentrations are positively associated with embryonic size (fully adjusted models, 0.17 SDS CRL: 95% CI 0.03; 0.30, and 0.17 SDS: 95% CI 0.04; 0.31 per 1 MoM increase, respectively). These associations were not present in women with normal weight (triglycerides and remnant cholesterol: fully adjusted model, 0.44 SDS: 95% CI 0.15; 0.72). Associations between maternal lipid concentrations and embryonic size were not attenuated after adjustment for glucose concentrations. Total cholesterol, HDL-c, LDL-c, non-HDL-c concentrations and the TG/HDL-c ratio were not associated with embryonic size.

Conclusions

Higher triglycerides and remnant cholesterol concentrations in early pregnancy are associated with increased embryonic size, most notably in overweight women.

Trial registration

The study protocol has been approved by the Medical Ethics Committee of the Erasmus University Medical Centre (Erasmus MC), Rotterdam (MEC-2007-413). Written informed consent was obtained from all participants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04647-6.

Maternal and neonatal outcomes in women with disorders of lipid metabolism

OBJECTIVES

The effects of lipid metabolism disorders (LMD) on pregnancy outcomes is not well known. The purpose of this study is to evaluate the impact of LMD on maternal and fetal outcomes.

METHODS

Using the Healthcare Cost and Utilization Project - National Inpatient Sample from the United States, we carried out a retrospective cohort study of all births between 1999 and 2015 to determine the risks of complications in pregnant women known to have LMDs. All pregnant patients diagnosed with LMDs between 1999 and 2015 were identified using the International Classification of Disease-9 coding, which included all patients with pure hypercholesterolemia, pure hyperglyceridemia, mixed hyperlipidemia, hyperchylomicronemia, and other lipid metabolism disorders. Adjusted effects of LMDs on maternal and newborn outcomes were estimated using unconditional logistic regression analysis.

RESULTS

A total of 13,792,544 births were included, 9,666 of which had an underlying diagnosis of LMDs for an overall prevalence of 7.0 per 10,000 births. Women with LMDs were more likely to have pregnancies complicated by diabetes, hypertension, and premature births, and to experience myocardial infarctions, venous thromboembolisms, postpartum hemorrhage, and maternal death. Their infants were at increased risk of congenital anomalies, fetal growth restriction, and fetal demise.

CONCLUSIONS

Women with LMDs are at significantly higher risk of adverse maternal and newborn outcomes. Prenatal counselling should take into consideration these risks and antenatal care in specialized centres should be considered.

Dysregulated Autophagy Leads to Oxidative Stress and Aberrant Expression of ABC Transporters in Women with Early Miscarriage

Early miscarriage (EMC) is a devastating obstetrical complication. ATP-binding cassette (ABC) transporters mediate cholesterol transfer across the placenta and enhance cell survival by effluxing substrates from target cells in the presence of stressors. Recent evidence reports an intricate interplay between autophagy and ABC transporters. We hypothesized that dysregulated autophagy and oxidative stress (OS) in the placenta leads to abnormal expression of membrane transporters contributing to poor pregnancy survival in EMC. We determined mRNA and protein expression of autophagy genes (Beclin-1/Bcl-2/LC3I/LC3II/p62) and ABC transporters (ABCA1/ABCG1/ABCG2) in placentae from EMC patients (n = 20), term controls (n = 19), first trimester (n = 6), and term controls (n = 5) controls. Oxidative/antioxidant status and biomarkers of oxidative damage were evaluated in maternal serum and placentae from EMC and healthy controls. In EMC, placental expression of LC3II/LC3I as well as of the key autophagy regulatory proteins Beclin-1 and Bcl-2 were reduced, whereas p62 was increased. Both in the serum and placentae of EMC patients, total OS was elevated reflected by increased oxidative damage markers (8-OHdG/malondialdehyde/carbonyl formation) accompanied by diminished levels of total antioxidant status, catalase, and total glutathione. Furthermore, we found reduced ABCG1 and increased ABCG2 expression. These findings suggest that a decreased autophagy status triggers Bcl-2-dependent OS leading to macromolecule damage in EMC placentae. The decreased expression of ABCG1 contributes to reduced cholesterol export to the growing fetus. Increasing ABCG2 expression could represent a protective feedback mechanism under inhibited autophagy conditions. In conclusion, dysregulated autophagy combined with increased oxidative toxicity and aberrant expression of placental ABC transporters affects materno-fetal health in EMC.

Low CETP activity and unique composition of large VLDL and small HDL in women giving birth to small-for-gestational age infants

Cholesteryl ester transfer protein (CETP) regulates high density lipoproteins (HDL)-cholesterol (C) and HDL-C is essential for fetal development. We hypothesized that women giving birth to large-for-gestational-age (LGA) and small-for-gestational age (SGA) infants differed in longitudinal changes in lipoproteins, CETP activity and HDL-C and that placentas from women with higher or lower circulating HDL-C displayed differential expression of mRNAs involved in cholesterol/nutrient transport, insulin signaling, inflammation/ extracellular matrix (ECM) remodeling. Circulating lipids and CETP activity was measured during pregnancy, NMR lipidomics in late pregnancy, and associations with LGA and SGA infants investigated. RNA sequencing was performed in 28 placentas according to higher and lower maternal HDL-C levels. Lipidomics revealed high triglycerides in large VLDL and lipids/cholesterol/cholesteryl esters in small HDL in women giving birth to SGA infants. Placentas from women with higher HDL-C had decreased levels of CETP expression which was associated with mRNAs involved in cholesterol/nutrient transport, insulin signaling and inflammation/ECM remodeling. Both placental and circulating CETP levels were associated with growth of the fetus. Low circulating CETP activity at 36–38 weeks was associated with giving birth to SGA infants. Our findings suggest a link between increased maternal HDL-C levels, low CETP levels both in circulation and placenta, and SGA infants.

Higher Peripheral Cholesterol and a Positive Correlation With Risk for Large-For-Gestational-Age Neonates in Pre-Pregnancy Underweight Women

OBJECTIVE

As the high proportion of underweight pregnant women, omission of their weight gain and blood lipids management during gestation might lead to adverse pregnancy outcomes. This study aimed to determine the relationship between lipid profile and risks for adverse pregnancy outcomes in pre-pregnancy underweight women.

METHODS

This study was part of an ongoing cohort study including Chinese gravidas delivered from January 2015 to December 2016. Included subjects were grouped into underweight, normal-weight, and overweight by BMI before conception. Logistic regression was used to assess the association between lipid profiles during second trimester and adverse obstetric outcomes in each group. A subgroup analysis according to the gestational weight gain, in which subjects in each group were divided into above and within the Institute of Medicine (IOM) recommendations, was performed.

RESULTS

A total of 6, 223 women were included. The proportion of underweight (19.3%) was similar to that of overweight women (19.4%) in South China. Peripheral total cholesterol (TC) level in underweight women was significantly higher than that in overweight women (P <0.001). After adjusting maternal age, TC level was positively correlated to the risk for large-for-gestational-age (LGA) [aOR =2.24, 95%CI (1.08, 4.63)], and negatively related to the risk for small-for-gestational age (SGA) [aOR =0.71, 95%CI (0.59, 0.85)] in underweight women, but not in normal-weight or overweight women. The subgroup analysis showed that maternal TC level was positively correlated with the risk of LGA only in underweight women who gained weight more than the IOM recommendations.

CONCLUSION

Underweight pregnant women with high TC levels had a higher risk for LGA, especially among women whose gestational weight gain were above the IOM recommendations. Therefore, clinical management of lipids and weight gain during gestation should also be recommended for underweight women.

Using a two-sample Mendelian randomization design to investigate a possible causal effect of maternal lipid concentrations on offspring birth weight

Background

The intrauterine environment is critical for fetal growth and development. However, observational associations between maternal gestational lipid concentrations and offspring birth weight (BW) have been inconsistent and ascertaining causality is challenging.

Methods

We used a novel two-sample Mendelian randomization (MR) approach to estimate the causal effect of maternal gestational high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride concentrations on offspring BW. Single nucleotide polymorphisms (SNPs) associated with serum HDL-C, LDL-C and triglyceride concentrations identified in the Global Lipids Genetics Consortium genome-wide association study meta-analysis (n = 188 577 European-ancestry individuals; sample 1) were selected as instrumental variables. The effects of these SNPs on offspring BW were estimated using a structural equation model in the UK Biobank and Early Growth Genetics consortium (n = 230 069 European-ancestry individuals; sample 2) that enabled partitioning of the genetic associations into maternal- (intrauterine) and fetal-specific effects.

Results

We found no evidence for a causal effect of maternal gestational HDL-C, LDL-C or triglyceride concentrations on offspring BW [standard deviation change in BW per standard deviation higher in HDL-C = −0.005 (95% confidence interval: −0.039, 0.029), LDL-C = 0.014 (−0.017, 0.045), and triglycerides = 0.014 (−0.025, 0.052)].

Conclusions

Our findings suggest that maternal gestational HDL-C, LDL-C and triglyceride concentrations play a limited role in determining offspring BW. However, we cannot comment on the impact of these and other lipid fractions on fetal development more generally. Our study illustrates the power and flexibility of two-sample MR in assessing the causal effect of maternal environmental exposures on offspring outcomes.

[Does Apolipoprotein B Level in Early Pregnancy Predict Excessive Gestational Weight Gain and Adverse Pregnancy Outcome?]

INTRODUCTION

Excessive maternal gestational weight gain (GWG) is a risk factor for maternal and fetal complications. The lipid profile changes physiologically during pregnancy. Weight gain can affect lipid metabolism. The hypothesis of the study was that apoB levels early in pregnancy are associated with excessive GWG and predictive for adverse outcomes.

METHODS

Out of 547 patients there were 95 women with inadequate GWG, 171 with adequate GWG, and 281 with excessive GWG. Out of 581 patients there were 14 patients with pregnancy-induced hypertonus/pre-eclampsia, 67 with small-for-gestational-age (SGA) infants, and 7 with fetal growth restriction (FGR). ApoB levels were measured by ELISA.

RESULTS

There was no significant difference in apoB levels between the different GWG groups. We found significantly higher levels of apoB in overweight and obese patients compared to those with normal BMI. Smoking was correlated with higher apoB levels. There were no differences either between women with PIH/PE and normotensive women or between SGA/IUGR and pregnancies without. Women with pre-existing hypertension showed significantly higher apoB levels than the control group.

CONCLUSIONS

ApoB cannot be used as a marker for identifying the risk of excessive GWG or adverse pregnancy outcomes early in pregnancy. However, it may be involved in the pathophysiology of adverse pregnancy outcomes in high-risk patients.

Maternal preconception lipid profile and gestational lipid changes in relation to birthweight outcomes

In 575 women with 1–2 prior pregnancy losses; total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) were evaluated preconception and throughout pregnancy to evaluate whether previously observed associations between third trimester maternal lipid profile and birthweight outcomes are driven by preconception lipids or lipid changes during pregnancy. Lipid trajectories were compared by pre-pregnancy body mass index (BMI) <25 or ≥25 kg/m²; logistic regression models evaluated preconception lipid concentration and change from preconception to 28 weeks with adjusted odds of large- or small-for-gestational age (LGA or SGA) neonate by BMI group. Preconception lipid concentrations and gestational lipid trajectories varied by BMI group (P < 0.001). Preconception lipids were not associated with LGA or SGA in either group. A 10 mg/dL increase in HDL-C change from preconception to 28 weeks was associated with decreased odds of LGA (odds ratio (OR) = 0.63, 95% confidence interval (CI): 0.46, 0.86) and 10 mg/dL increase in TG change associated with increased odds of LGA (OR = 1.05, 95% CI: 1.01, 1.1) overall. For ≥25 BMI only, 10 mg/dL increase in HDL-C change was associated with decreased SGA odds (OR = 0.35, 95% CI: 0.19, 0.64). Gestational lipid trajectories differed by BMI group and were differentially associated with birthweight outcomes, with HDL-C more strongly associated with healthy birthweight in women with BMI ≥25.

Race-ethnic differences in the associations of maternal lipid trait genetic risk scores with longitudinal fetal growth

BACKGROUND

Fetal growth, an important predictor of cardiometabolic diseases in adults, is influenced by maternal and fetal genetic and environmental factors.

OBJECTIVE

We investigated the association between maternal lipid genetic risk score (GRS) and fetal growth among 4 US racial-ethnic populations (Whites, Blacks, Hispanics, and Asians).

METHODS

We extracted genotype data for 2008 pregnant women recruited in the National Institute of Child Health and Human Development Fetal Growth Studies-Singleton cohort with up to 6 standardized ultrasound examinations. GRS was calculated using 240 single-nucleotide polymorphisms previously associated with higher total cholesterol (GRSTChol), low-density lipoprotein cholesterol (GRSLDLc), and triglycerides (GRSTG) and lower high-density lipoprotein cholesterol (GRSHDLc).

RESULTS

At 40 weeks' gestation, a unit increase in GRSTG was associated with 11.4 g higher fetal weight (95% confidence interval [CI] 2.8-20.0 g) among normal-weight Whites, 26.3 g (95% CI 6.0-46.6 g) among obese Blacks, and 30.8 g (95% CI 6.3-55.3 g) among obese Hispanics. Higher GRSHDLc was associated with increased fetal weight across 36 to 40 weeks among normal-weight Whites and across 13 to 20 weeks among normal-weight Asians, but with decreased fetal weight across 26 to 40 weeks among normal-weight Hispanics. Higher GRSTChol was suggestively associated with increased fetal weight in males and decreased in females. Associations remained consistent after adjustment for serum lipids.

CONCLUSION

Associations between fetal weight and maternal lipid GRS appear to vary by maternal race-ethnic group, obesity status, and offspring sex. Genetic susceptibility to unfavorable lipid profiles contributes to fetal growth differences even among normal-weight women suggesting a potential future application in predicting aberrant fetal growth.

Physiology and Pathophysiology of Steroid Biosynthesis, Transport and Metabolism in the Human Placenta

The steroid hormones progestagens, estrogens, androgens, and glucocorticoids as well as their precursor cholesterol are required for successful establishment and maintenance of pregnancy and proper development of the fetus. The human placenta forms at the interface of maternal and fetal circulation. It participates in biosynthesis and metabolism of steroids as well as their regulated exchange between maternal and fetal compartment. This review outlines the mechanisms of human placental handling of steroid compounds. Cholesterol is transported from mother to offspring involving lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SRB1) as well as ATP-binding cassette (ABC)-transporters, ABCA1 and ABCG1. Additionally, cholesterol is also a precursor for placental progesterone and estrogen synthesis. Hormone synthesis is predominantly performed by members of the cytochrome P-450 (CYP) enzyme family including CYP11A1 or CYP19A1 and hydroxysteroid dehydrogenases (HSDs) such as 3β-HSD and 17β-HSD. Placental estrogen synthesis requires delivery of sulfate-conjugated precursor molecules from fetal and maternal serum. Placental uptake of these precursors is mediated by members of the solute carrier (SLC) family including sodium-dependent organic anion transporter (SOAT), organic anion transporter 4 (OAT4), and organic anion transporting polypeptide 2B1 (OATP2B1). Maternal-fetal glucocorticoid transport has to be tightly regulated in order to ensure healthy fetal growth and development. For that purpose, the placenta expresses the enzymes 11β-HSD 1 and 2 as well as the transporter ABCB1. This article also summarizes the impact of diverse compounds and diseases on the expression level and activity of the involved transporters, receptors, and metabolizing enzymes and concludes that the regulatory mechanisms changing the physiological to a pathophysiological state are barely explored. The structure and the cellular composition of the human placental barrier are introduced. While steroid production, metabolism and transport in the placental syncytiotrophoblast have been explored for decades, few information is available for the role of placental-fetal endothelial cells in these processes. With regard to placental structure and function, significant differences exist between species. To further decipher physiologic pathways and their pathologic alterations in placental steroid handling, proper model systems are mandatory.

Metabolic profiling and targeted lipidomics reveals a disturbed lipid profile in mothers and fetuses with intrauterine growth restriction

Fetal growth may be impaired by poor placental function or maternal conditions, each of which can influence the transfer of nutrients and oxygen from the mother to the developing fetus. Large-scale studies of metabolites (metabolomics) are key to understand cellular metabolism and pathophysiology of human conditions. Herein, maternal and cord blood plasma samples were used for NMR-based metabolic fingerprinting and profiling, including analysis of the enrichment of circulating lipid classes and subclasses, as well as the number of sub-fraction particles and their size. Changes in phosphatidylcholines and glycoproteins were prominent in growth-restricted fetuses indicating significant alterations in their abundance and biophysical properties. Lipoprotein profiles showed significantly lower plasma concentrations of cholesterol-intermediate density lipoprotein (IDL), triglycerides-IDL and high-density lipoprotein (HDL) in mothers of growth-restricted fetuses compared to controls (p < 0.05). In contrast, growth-restricted fetuses had significantly higher plasma concentrations of cholesterol and triglycerides transporting lipoproteins [LDL, IDL, and VLDL, (p < 0.005; all)], as well as increased VLDL particle types (large, medium and small). Significant changes in plasma concentrations of formate, histidine, isoleucine and citrate in growth-restricted fetuses were also observed. Comprehensive metabolic profiling reveals that both, mother and fetuses of pregnancies complicated with fetal growth restriction have a substantial disruption in lipid metabolism.

Studies in genetically modified mice implicate maternal HDL as a mediator of fetal growth

Studies in humans have shown a direct association between maternal plasma cholesterol concentrations and infant birthweight. Similarly, previous studies in our laboratory have shown that chow-fed mice lacking apolipoprotein (apo) A-I, the major protein in HDL, have low HDL-cholesterol (HDL-C) concentrations and smaller fetuses in midgestation. In the current study, we measured fetal weights in mice with varying levels of apoA-I gene dose (knockout, wild-type, and transgenic) and examined metabolic pathways known to affect fetal growth. As expected, we found the differences in apoA-I expression led to changes in HDL particle size and protein cargo as well as plasma cholesterol concentrations. Fetal masses correlated directly with maternal plasma cholesterol and apoA-I concentrations, but placental masses and histology did not differ between groups of mice. There was no significant difference in glucose or amino acid transport to the fetus or in expression levels of the glucose (glucose transporter 1 and 2) or amino acid (sodium-coupled neutral amino acid transporter 1 and 2) transporters in whole placentas, although there was a trend for greater uptake of both nutrients in the whole fetal unit (fetus + placenta) of mice with greater apoA-I levels; significant differences in transport rates occurred when mice without apoA-I (knockout) vs. mice with apoA-I (wild-type and transgenic) were compared. Glucose tolerance tests were improved in the mice with the highest level of apoA-I, suggesting increased insulin-induced uptake of glucose by tissues of apoA-I transgenic mice. Thus, maternal HDL is associated with fetal growth, an effect that is likely mediated by plasma cholesterol or other HDL-cargo, including apolipoproteins or complement system proteins. A direct role of enhanced glucose and/or amino acid transport cannot be excluded.-Rebholz, S. L., Melchior, J. T., Davidson, W. S., Jones, H. N., Welge, J. A., Prentice, A. M., Moore, S. E., Woollett, L. A. Studies in genetically modified mice implicate maternal HDL as a mediator of fetal growth.

Lipoprotein Heterogeneity Early in Pregnancy and Preterm Birth

Background

The concentration and size of lipoprotein particles are associated with race, inflammation and disease. When triglycerides are high, as in pregnancy, lipoprotein particle size may have physiologic importance beyond conventional lipid measurements. We considered that lipoprotein particles may be related to preterm birth (PTB), and explored race differences.

Methods

Samples were collected at 9 weeks gestation (22 PTB [<37 weeks]; 42 term births [≥37 weeks]). Lipids were assayed using standard techniques. Concentrations of high-density lipoprotein, low-density lipoprotein, very low-density lipoprotein particles (HDL-P, LDL-P, and VLDL-P) and markers of systemic inflammation were quantified using NMR spectroscopy and related to PTB.

Results

Women with PTB had lower VLDL-P (−10.66 nmol/L, p=0.03) and higher systemic inflammation (+19.2 μmol/L, p=0.02) compared to women with term births, independent of race, pre-pregnancy BMI and smoking. Black vs. White women had lower VLDL-P and higher HDL-cholesterol (both p<0.05). Race-specific results indicated that large HDL-P and inflammation (GlycB) were higher with PTB vs. term birth among black women only.

Conclusion

Women with PTB had lower VLDL-P early in pregnancy, which may represent impaired lipid response. Black-White differences in the lipoprotein profile are similar to non-pregnant adults, but race-specific lipoprotein and inflammation associations with PTB warrant further study.

Maternal 27-hydroxycholesterol concentrations during the course of pregnancy and in pregnancy pathologies

Background

The oxysterol 27-hydroxycholesterol (27-OHC) plays an important role in the regulation of cholesterol homeostasis. Pregnancy pathologies like preeclampsia (PE), HELLP-syndrome (HELLP), intrauterine growth restriction (IUGR) and intrahepatic cholestasis in pregnancy (ICP) are linked to disturbances in lipid metabolism. In the present study, we hypothesized a specific gestational regulation of 27-OHC and compromised 27-OHC levels due to placental and hepatic diseases in pregnancy resulting in a dysregulation of lipid metabolism.

Methods

The 27-OHC was measured by gas-chromatography-mass spectrometry (GC-MS) and related to cholesterol concentrations. In the longitudinal cohort, a complete set of samples of healthy patients (n = 33) obtained at three different time points throughout gestation and once post-partum was analyzed. In the cross sectional cohort, patients with pregnancy pathologies (IUGR n = 14, PE n = 14, HELLP n = 7, ICP n = 7) were matched to a control group (CTRL) of equal gestational ages.

Results

The 27-OHC levels already increased in the first trimester despite lower TC concentrations (p < 0.05). During the course of pregnancy, a subtle rise in 27-OHC concentrations results in an overall decrease of 27-OHC/TC ratio in between the first (p < 0.05) and second trimester. The ratio remains stable thereafter including the post-partum period. No significant differences have been observed in pregnancy pathologies as compared to the CTRL group.

Conclusion

In conclusion, 27-OHC may have a compensatory role in cholesterol metabolism early in pregnancy. The conserved 27-OHC/TC ratio in pregnancy pathologies suggest that neither the placenta nor the liver is majorly involved in the regulation of 27-OHC metabolism.

Fetal gender and gestational age differentially affect PCSK9 levels in intrauterine growth restriction

BACKGROUND

Maternal and fetal Low Density Lipoprotein-Cholesterol (LDL-C) concentrations are compromised in intrauterine growth restriction (IUGR). Generally, LDL-C catabolism is under control of PCSK9 by binding to the LDL-receptor leading to its degradation. Hence, we hypothesized a role for PCSK9 in the modulation of lipid metabolism and placental transport in IUGR.

METHODS

172 women, 70 IUGR and 102 controls were included in the study. Maternal and fetal serum PCSK9 levels and lipid profiles including LDL-C were measured. Placental LDL-receptor and PCSK9 expressions were estimated by tissue microarray immunohistochemistry, and analyzed by two blinded observers using an immunoreactivity score. Non-parametric tests and multivariate regression analyses were used for statistical estimations.

RESULTS

PCSK9 levels in the maternal and fetal compartment independently predicted LDL-C levels (maternal compartment: adjusted R 2 = 0.2526; coefficient b i  = 0.0938, standard error s bi =0.0217, rpartial = 0.4420, t-value = 4.323, p < 0.0001; fetal compartment: adjusted R 2 = 0.2929; b i  = 0.1156, s bi =0.020, rpartial = 0.5494, t-value = 5.81, p < 0.0001). We did not find significant differences in maternal PCSK9 concentrations between IUGR and controls. However, we found lower fetal serum PCSK9 concentrations in IUGR than in controls (IUGR median 137.1 ng/mL (95% CI 94.8-160.0) vs. controls 176.8 (154.6-202.5), p = 0.0005). When subgrouping according to early onset, late onset IUGR, and fetal gender differences remained consistent only for male neonates born before 34 weeks of gestation. In the placenta we found no correlation between PCSK9 and LDL-receptor expression patterns. However, the LDL-receptor was significantly upregulated in IUGR when compared to controls (p = 0.0063).

CONCLUSIONS

Our results suggest that PCSK9 play a role in impaired fetal growth by controlling fetal LDL-C metabolism, which seems to be dependent on gestational age and fetal gender. This underlines the need to identify subgroups of IUGR that may benefit from individualized and gender-specific pharmacotherapy in future studies.

Maternal Serum Lipid, Estradiol, and Progesterone Levels in Pregnancy, and the Impact of Placental and Hepatic Pathologies

OBJECTIVE

Lipids and steroid hormones are closely linked. While cholesterol is the substrate for (placental) steroid hormone synthesis, steroid hormones regulate hepatic lipid production. The aim of this study was to quantify circulating steroid hormones and lipid metabolites, and to characterize their interactions in normal and pathological pregnancies with a focus on hepatic and placental pathologies.

METHODS

A total of 216 serum samples were analyzed. Group A consisted of 32 patients with uncomplicated pregnancies who were analyzed at three different time-points in pregnancy (from the first through the third trimester) and once post partum. Group B consisted of 36 patients (24th to 42nd week of gestation) with pregnancy pathologies (IUGR n = 10, preeclampsia n = 13, HELLP n = 6, intrahepatic cholestasis n = 7) and 31 controls with uncomplicated pregnancies. Steroid profiles including estradiol, progesterone, and dehydroepiandrosterone were measured by GC-MS and compared with lipid concentrations.

RESULTS

In Group A, cholesterol and triglycerides correlated positively with estradiol (cholesterol ρ = 0.50, triglycerides ρ = 0.57) and progesterone (ρ = 0.49, ρ = 0.53) and negatively with dehydroepiandrosterone (ρ = - 0.47, ρ = - 0.38). Smoking during pregnancy affected estradiol concentrations, leading to lower levels in the third trimester compared to non-smoking patients (p < 0.05). In Group B, cholesterol levels were found to be lower in IUGR pregnancies and in patients with HELLP syndrome compared to controls (p < 0.05). Steroid hormone concentrations of estradiol (p < 0.05) and progesterone (p < 0.01) were lower in pregnancies with IUGR.

DISCUSSION

Lipid and steroid levels were affected most in IUGR pregnancies, while only minor changes in concentrations were observed for other pregnancy-related disorders. Each of the analyzed entities displayed specific changes. However, since the changes were most obvious in pregnancies complicated by IUGR and only minor changes were observed in pregnancies where patients had impaired liver function, our data suggests that placental rather than maternal hepatic function strongly determines lipid and steroid levels in pregnancy.

Maternal apolipoprotein E genotype as a potential risk factor for poor birth outcomes: The Bogalusa Heart Study

OBJECTIVE

The objective of this study was to assess the association between apolipoprotein E (apoE) genotype and preterm birth (PTB) and small for gestational age (SGA).

STUDY DESIGN

ApoE phenotyping was performed on 680 women linked to 1065 births. Allele frequencies were compared and PTB and SGA risk was estimated using log-binomial regression.

RESULTS

The ɛ2 allele was more common in SGA births (P<0.01). SGA risk was increased among ɛ2 carriers compared with genotype ɛ3/ɛ3, though associations were attenuated following adjustment for maternal age, education, race, smoking and prenatal visits. Stronger associations were observed for term SGA (first birth: adjusted relative risk (aRR)=1.78, 95% confidence interval (CI) 1.06 to 2.98; any birth: aRR=1.52, 95% CI 0.96 to 2.40) and among whites specifically (first: aRR=2.88, 95% CI 1.45 to 5.69; any: aRR=2.75, 95% CI 1.46 to 5.22).

CONCLUSIONS

Associations between maternal apoE genotype and SGA may represent decreased fetal growth in women with lower circulating cholesterol levels.

Revisiting Human Cholesterol Synthesis and Absorption: The Reciprocity Paradigm and its Key Regulators

Hypercholesterolemia is a major risk factor for cardiovascular disease. Cholesterol homeostasis in the body is governed by the interplay between absorption, synthesis, and excretion or conversion of cholesterol into bile acids. A reciprocal relationship between cholesterol synthesis and absorption is known to regulate circulating cholesterol in response to dietary or therapeutic interventions. However, the degree to which these factors affect synthesis and absorption and the extent to which one vector shifts in response to the other are not thoroughly understood. Also, huge inter-individual variability exists in the manner in which the two systems act in response to any cholesterol-lowering treatment. Various factors are known to account for this variability and in light of recent experimental advances new players such as gene-gene interactions, gene-environmental effects, and gut microbiome hold immense potential in offering an explanation to the complex traits of inter-individual variability in human cholesterol metabolism. In this context, the objective of the present review is to provide an overview on cholesterol metabolism and discuss the role of potential factors such as genetics, epigenetics, epistasis, and gut microbiome, as well as other regulators in modulating cholesterol metabolism, especially emphasizing the reciprocal relationship between cholesterol synthesis and absorption. Furthermore, an evaluation of the implications of this push-pull mechanism on cholesterol-lowering strategies is presented.

Revisiting Human Cholesterol Synthesis and Absorption: The Reciprocity Paradigm and its Key Regulators

Hypercholesterolemia is a major risk factor for cardiovascular disease. Cholesterol homeostasis in the body is governed by the interplay between absorption, synthesis, and excretion or conversion of cholesterol into bile acids. A reciprocal relationship between cholesterol synthesis and absorption is known to regulate circulating cholesterol in response to dietary or therapeutic interventions. However, the degree to which these factors affect synthesis and absorption and the extent to which one vector shifts in response to the other are not thoroughly understood. Also, huge inter-individual variability exists in the manner in which the two systems act in response to any cholesterol-lowering treatment. Various factors are known to account for this variability and in light of recent experimental advances new players such as gene-gene interactions, gene-environmental effects, and gut microbiome hold immense potential in offering an explanation to the complex traits of inter-individual variability in human cholesterol metabolism. In this context, the objective of the present review is to provide an overview on cholesterol metabolism and discuss the role of potential factors such as genetics, epigenetics, epistasis, and gut microbiome, as well as other regulators in modulating cholesterol metabolism, especially emphasizing the reciprocal relationship between cholesterol synthesis and absorption. Furthermore, an evaluation of the implications of this push-pull mechanism on cholesterol-lowering strategies is presented.

The -93T/G LPL Promoter Polymorphism Is Associated With Lower Third-Trimester Triglycerides in Pregnant African American Women

BACKGROUND

Hypertriglyceridemia is a risk factor for cardiovascular disease and several pregnancy complications. Lipoprotein lipase (LPL) genetic variation modulates nonpregnancy plasma triglycerides, but its effects during pregnancy are unknown. The G allele of the LPL -93T/G promoter polymorphism is 16-23 times more prevalent in Blacks than in Whites, contributing to lower triglycerides in nonpregnant African Americans by increasing LPL expression.

PURPOSE

This study investigated whether the triglyceride-lowering effect of -93G is observed in African Americans during pregnancy.

METHODS

Genotyping was performed on 124 African American women with uncomplicated pregnancies for common functional LPL polymorphisms/mutations (-93T/G, D9N, N291S, and S447X). Third-trimester plasma triglyceride, high- and low-density lipoprotein cholesterol, apolipoprotein B, and free fatty acid concentrations were measured with colorimetric assays. Clinical characteristics and lipid values were compared across the -93T/G genotypes.

RESULTS

Triglycerides were significantly lower in women with the -93GG compared to the -93TT genotype, both with (n = 124, p = .02) and without (n = 108, p = .03) inclusion of participants with other LPL variant alleles. Triglyceride differences persisted after adjustment for prepregnancy body mass index, gestational age at delivery, and smoking. There were no significant differences in the other lipids or apolipoprotein B by -93T/G genotype.

CONCLUSIONS

Despite the considerable metabolic changes accompanying pregnancy, the triglyceride-lowering effect associated with the -93GG LPL genotype in African Americans persists during late pregnancy. The -93GG genotype might protect against pregnancy complications stemming from hypertriglyceridemia, but the overall increased risk of pregnancy complications in African American women points to complex, multifactorial relationships among risk factors, race, and adverse pregnancy outcomes.

Pregnancy characteristics and women's future cardiovascular health: an underused opportunity to improve women's health?

Growing evidence indicates that women with a history of common pregnancy complications, including fetal growth restriction and preterm delivery (often combined as low birth weight), hypertensive disorders of pregnancy, and gestational diabetes, are at increased risk for cardiovascular disease later in life. The purpose of this paper was to review the associations of parity and these 4 pregnancy complications with cardiovascular morbidity and mortality; to review the role of cardiovascular risk factors before, during, and after pregnancy complications in explaining these associations; and to explore the implications of this emerging science for new research and policy. We systematically searched for relevant cohort and case-control studies in Medline through December 2012 and used citation searches for already published reviews to identify new studies. The findings of this review suggest consistent and often strong associations of pregnancy complications with latent and future cardiovascular disease. Many pregnancy complications appear to be preceded by subclinical vascular and metabolic dysfunction, suggesting that the complications may be useful markers of latent high-risk cardiovascular trajectories. With further replication research, these findings would support the utility of these prevalent pregnancy complications in identifying high-risk women for screening, prevention, and treatment of cardiovascular disease, the leading cause of morbidity and mortality among women.

Sex and breed-dependent organ development and metabolic responses in foetuses from lean and obese/leptin resistant swine

The present study aimed to determine the effects of breed and sex on growth patterns and metabolic features of advanced-pregnancy foetuses exposed to the same environmental conditions. Thus, at Day 62 of pregnancy, swine foetuses from an obese breed with leptin resistance (Iberian breed) were compared to lean crossbred foetuses (25% Large White ×25% Landrace ×50% Pietrain). There were differential developmental patterns in foetuses with leptin resistance, mainly a higher relative weight of the brain resembling “brain-sparing effect”. Prioritization of brain growth may be protective for the adequate growth and postnatal survival of the Iberian individuals, an ancient breed reared in extensive semi-feral conditions for centuries. There were also clear sex-related differences in foetal development and metabolism in the Iberian breed. Female Iberian foetuses were similar in size and weight to male littermates but had a significantly higher relative liver to body weight ratio resembling “liver-sparing effect” and a trend for a higher relative intestine to body ratio. Moreover, the availability of triglycerides, cholesterol and IL-6 in female Iberian foetuses was similar to that of lean crossbred foetuses. Overall, these features may favour a better postnatal survival and development of females, the sex more critical for the species survival. These findings set the basis for future translational studies aimed at increasing the knowledge on the interaction between genetic and environmental factors in the early programming of the adult phenotype.

Maternal lipids at mid-pregnancy and the risk of preterm delivery

OBJECTIVE

This study examined associations between maternal lipid levels at mid-pregnancy and preterm delivery, medically indicated or spontaneous.

DESIGN

Prospective cohort study.

SETTING

Women were recruited from 52 clinics in five Michigan, USA communities (1998-2004).

POPULATION

Pregnant women were enrolled at 15-27 weeks' gestation and followed to delivery (n=3019).

METHODS

A single blood sample was obtained at study enrollment. Blood lipids, i.e. total cholesterol (TC), high-density lipoprotein (HDLc), low-density lipoprotein (LDLc) cholesterol, and triglycerides (TG), were measured on a sub-cohort (n=1309).

MAIN OUTCOME MEASURES

There were 221 spontaneous, 100 medically indicated preterm deliveries and 988 term deliveries. Polytomous logistic regression models examined relationships among cholesterol levels (Low: <10(th) percentile, Referent: 10(th) -<70(th) percentile, High: ≥70(th) percentile), quartiles of TG (Referent: first quartile) and delivery outcome (Referent: term).

RESULTS

Odds of medically indicated preterm delivery were increased among women with low TC (adjusted odds ratio (aOR)=2.04, 95% confidence interval (CI): 1.12, 3.72), low HDLc (aOR=1.89, 95%CI: 1.04, 3.42) or low LDLc (aOR=1.96, 95%CI: 1.09, 3.54). Odds of spontaneous preterm delivery were increased among women with high TC (aOR=1.51, 95%CI: 1.06, 2.15), high LDLc (aOR=1.42, 95%CI: 0.99, 2.04) or high TG (aOR=1.90, 95%CI: 1.21, 2.97 and aOR=1.72, 95%CI: 1.06, 2.78 for third and fourth quartiles, respectively).

CONCLUSIONS

Extremely low TC, HDLc, and LDLc were associated with a modest increase in risk of medically indicated preterm delivery, whereas high TC, LDLc and TG modestly increased the risk of spontaneous preterm delivery. Further research is needed to uncover explanations for these associations and to identify optimal ranges for maternal lipids.

Review: Transport of maternal cholesterol to the fetal circulation

Data obtained from recent studies in humans, rodents, and cell culture demonstrate that circulating maternal cholesterol can be transported to the fetus. The two major cell types responsible for the transport are trophoblasts and endothelial cells of the fetoplacental vasculature. Maternal lipoprotein-cholesterol is initially taken up by trophoblasts via receptor-mediated and receptor-independent processes, is transported by any number of the sterol transport proteins expressed by cells, and is effluxed or secreted out of the basal side via protein-mediated processes or by aqueous diffusion. This cholesterol is then taken up by the endothelium and effluxed to acceptors within the fetal circulation. The ability to manipulate the mass of maternal cholesterol that is taken up by the placenta and crosses to the fetus could positively impact development of fetuses affected with the Smith-Lemli-Opitz Syndrome (SLOS) that have reduced ability to synthesize cholesterol and possibly impact growth of fetuses unaffected by SLOS but with low birthweights.

Prepregnancy lipids related to preterm birth risk: the coronary artery risk development in young adults study

CONTEXT

Preterm birth is associated with maternal cardiovascular risk, but mechanisms are unknown.

OBJECTIVE

We considered that dyslipidemia may predispose women to both conditions and that prepregnancy lipids may be related to preterm birth risk. We hypothesized that low or high prepregnancy plasma lipids would be associated with preterm birth.

DESIGN, SETTING, AND PARTICIPANTS

A total of 1010 women (49% black) enrolled in the multicenter, prospective Coronary Artery Risk Development in Young Adults study with at least one singleton birth during 20 yr of follow-up were evaluated.

MAIN OUTCOME MEASURE

Postbaseline preterm births less than 34 wk or 34 to less than 37 wk vs. greater than 37 wk gestation.

RESULTS

We detected a U-shaped relationship between prepregnancy cholesterol concentrations and preterm birth risk. Women with prepregnancy cholesterol in the lowest quartile compared with the second quartile (<156 vs. 156-171 mg/dl) had an increased risk for preterm birth 34 to less than 37 wk (odds ratio 1.86; 95% confidence interval 1.10, 3.15) and less than 34 wk (odds ratio 3.04; 1.35, 6.81) independent of race, age, parity, body mass index, hypertension during pregnancy, physical activity, and years from measurement to birth. Prepregnancy cholesterol in the highest quartile (>195 mg/dl) was also associated with preterm birth less than 34 wk among women with normotensive pregnancies (odds ratio 3.80; 95% confidence interval 1.07, 7.57). There were no associations between prepregnancy triglycerides, low-density lipoprotein cholesterol, or high-density lipoprotein cholesterol and preterm birth.

CONCLUSIONS

Both low and high prepregnancy cholesterol were related to preterm birth risk. These may represent distinct pathways to the heterogeneous outcome of preterm birth. Additional studies are needed to elucidate mechanisms that link low or high cholesterol to preterm birth and later-life sequelae.

Interactions between smoking and weight in pregnancies complicated by preeclampsia and small-for-gestational-age birth

Cigarette smoking protects against preeclampsia but increases the risk of small-for-gestational-age birth (SGA). Regarding body weight, the converse is true: obesity elevates rates of preeclampsia but reduces rates of SGA. The authors assessed the combined effects of smoking and weight among US women developing preeclampsia or SGA, studying 7,757 healthy, primigravid women with singleton pregnancies in 1959-1965. Smoking (never, light, heavy), stratified by prepregnancy body mass index (BMI (weight (kg)/height (m)(2)); underweight, overweight, obese), was examined in relation to preeclampsia and SGA. Among underweight (BMI <18.5) and normal-weight (BMI 18.5-24.9) women, smoking decreased the risk of preeclampsia (for heavy smoking, light smoking, nonsmoking, test for trend p = 0.002 for underweight and p = 0.009 for normal weight) after adjustment for age, race, and socioeconomic status. However, among overweight/obese women (BMI >or=25), this trend was not apparent (p = 0.4). Among both underweight and overweight women, smoking significantly increased SGA risk (trend p < 0.001 for underweight and p = 0.02 for overweight/obese). Obesity eliminated the inverse association between smoking and preeclampsia but did not substantially alter the positive association between smoking and SGA. A possible unifying biologic explanation is discussed in this paper.

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.