The essential fatty acid status of mother and child in pregnancy-induced hypertension: a prospective longitudinal study

BMA-based Mendelian randomization identifies blood metabolites as causal candidates in pregnancy-induced hypertension

Pregnancy-induced hypertension (PIH), a prominent determinant of maternal mortality and morbidity worldwide, is hindered by the absence of efficacious biomarkers for early diagnosis, contributing to suboptimal outcomes. Here, we explored potential causal relationships between blood metabolites and the risk of PIH using Mendelian randomization (MR). We employed a two-sample univariable MR approach to empirically estimate the causal relationships between 249 circulating metabolites and PIH. Inverse variance weighted, MR-egger, weight median, simple mode, and weighted mode methods were used for causal estimates. The exposure-to-outcome directionality was confirmed with the MR Steiger test. The Bayesian model averaging MR (MR-BMA) method was applied to detect the predominant causal metabolic traits with alignment for pleiotropy effects. In the primary analysis, analyzing 249 metabolites, we identified 25 causally linked to PIH, including 11 lipid-related traits and 6 associated with fatty acid (un)saturation. Importantly, MR-BMA analyses corroborated the total concentration of branched-chain amino acids(total-BCAA) to be the highest rank causal metabolite, followed by leucine (Leu), phospholipids to total lipids ratio in medium LDL (M-LDL-PL-pct), and Val (all P < 0.05). The directionality of causality predicted by univariable MR and MR-BMA for these metabolites remained consistent. This study highlights the causal connection between metabolites and PIH risk. It highlighted BCAAs as the strongest causal candidates warranting further investigation. Since PIH typically occurs in the second and third trimesters, extending these findings could inform earlier strategies to reduce its risk. Directed acyclic graph of the MR framework investigating the causal relationship between metabolites and PIH. MR: Mendelian randomization; GIVs: genetic instrument variables; SNPs: single-nucleotide polymorphism; IVW: inverse variance weighted; WM: weighted median; PIH: pregnancy-induced hypertension; SM: significant metabolite; MR-BMA: Bayesian model averaging MR.

Paradoxes: Cholesterol and Hypoxia in Preeclampsia

Preeclampsia, a hypertensive disease of pregnancy of unknown etiology, is intensely studied as a model of cardiovascular disease (CVD) not only due to multiple shared pathologic elements but also because changes that develop over decades in CVD appear and resolve within days in preeclampsia. Those affected by preeclampsia and their offspring experience increased lifetime risks of CVD. At the systemic level, preeclampsia is characterized by increased cellular, membrane, and blood levels of cholesterol; however, cholesterol-dependent signaling, such as canonical Wnt/βcatenin, Hedgehog, and endothelial nitric oxide synthase, is downregulated indicating a cholesterol deficit with the upregulation of cholesterol synthesis and efflux. Hypoxia-related signaling in preeclampsia also appears to be paradoxical with increased Hypoxia-Inducible Factors in the placenta but measurably increased oxygen in maternal blood in placental villous spaces. This review addresses the molecular mechanisms by which excessive systemic cholesterol and deficient cholesterol-dependent signaling may arise from the effects of dietary lipid variance and environmental membrane modifiers causing the cellular hypoxia that characterizes preeclampsia.

A theoretical model of dietary lipid variance as the origin of primary ciliary dysfunction in preeclampsia

Serving as the cell's key interface in communicating with the outside world, primary cilia have emerged as an area of multidisciplinary research interest over the last 2 decades. Although the term "ciliopathy" was first used to describe abnormal cilia caused by gene mutations, recent studies focus on abnormalities of cilia that are found in diseases without clear genetic antecedents, such as obesity, diabetes, cancer, and cardiovascular disease. Preeclampsia, a hypertensive disease of pregnancy, is intensely studied as a model for cardiovascular disease partially due to many shared pathophysiologic elements, but also because changes that develop over decades in cardiovascular disease arise in days with preeclampsia yet resolve rapidly after delivery, thus providing a time-lapse view of the development of cardiovascular pathology. As with genetic primary ciliopathies, preeclampsia affects multiple organ systems. While aspirin delays the onset of preeclampsia, there is no cure other than delivery. The primary etiology of preeclampsia is unknown; however, recent reviews emphasize the fundamental role of abnormal placentation. During normal embryonic development, trophoblastic cells, which arise from the outer layer of the 4-day-old blastocyst, invade the maternal endometrium and establish extensive placental vascular connections between mother and fetus. In primary cilia of trophoblasts, Hedgehog and Wnt/catenin signaling operate upstream of vascular endothelial growth factor to advance placental angiogenesis in a process that is promoted by accessible membrane cholesterol. In preeclampsia, impaired proangiogenic signaling combined with an increase in apoptotic signaling results in shallow invasion and inadequate placental function. Recent studies show primary cilia in preeclampsia to be fewer in number and shortened with functional signaling abnormalities. Presented here is a model that integrates preeclampsia lipidomics and physiology with the molecular mechanisms of liquid-liquid phase separation in model membrane studies and the known changes in human dietary lipids over the last century to explain how changes in dietary lipids might reduce accessible membrane cholesterol and give rise to shortened cilia and defects in angiogenic signaling, which underlie placental dysfunction of preeclampsia. This model offers a possible mechanism for non-genetic dysfunction in cilia and proposes a proof-of-concept study to treat preeclampsia with dietary lipids.

Exploring the role of LC-PUFA metabolism in pregnancy complications

Maternal nutrition during pregnancy plays a significant role in growth and development of the placenta and influencing pregnancy outcome. Suboptimal nutritional status during early gestational period compromises the normal course of pregnancy leading to adverse maternal and fetal outcomes. Omega-3 and omega-6 long chain polyunsaturated fatty acids (LC-PUFA) are important for the growth and development of the placenta. Maternal fatty acids and their metabolites influence the normal course of pregnancy by regulating cell growth and development, cell signaling, regulate angiogenesis, modulate inflammatory responses and influence various structural and functional processes. Alterations in LC-PUFA and their metabolites may result in inadequate spiral artery remodeling or placental angiogenesis leading to structural and functional deficiency of the placenta which contributes to several pregnancy complications like preeclampsia, gestational diabetes mellitus, intrauterine growth restriction, and results in adverse birth outcomes. In this review, we summarize studies examining the role of fatty acids and their metabolites in pregnancy. We also discuss the possible molecular mechanisms through which LC-PUFA influences placental growth and development. Studies have demonstrated that omega-3 fatty acid supplementation lowers the incidence of preterm births, but its effect on reducing pregnancy complications are inconclusive.

Influence of clinical characteristics on maternal DHA and other polyunsaturated fatty acid status in pregnancy: A systematic review

INTRODUCTION

Omega-3 DHA is important for the prevention of preterm birth, however there is limited knowledge of the determinants of omega-3 status during pregnancy. The primary objective of this systematic review was to synthesise data from existing studies assessing relationships between clinical factors and maternal DHA status.

MATERIALS AND METHODS

The Medline, Embase, Amed, and CINAHL databases were searched for studies reporting measures of maternal omega-3 status and one or more clinical characteristics.

RESULTS

Eighteen studies were included in the final analyses. Factors associated with a higher BMI (overweight, higher gestational weight gain, gestational diabetes), or lower parity were each associated with higher omega-3 status in the majority of studies, with mixed findings for other comparisons.

DISCUSSION

Inconsistent findings between studies make it difficult to draw clear conclusions about the relationship between clinical factors and maternal omega-3 DHA status. However, maternal overweight and associated metabolic conditions may increase lipid metabolism.

Gestational age and maternal status of DHA and other polyunsaturated fatty acids in pregnancy: A systematic review

INTRODUCTION

Maternal diet is important in determining omega-3 DHA status however there is limited knowledge of other factors influencing maternal omega-3 concentrations during pregnancy. The primary objective of this systematic review and meta-analysis was to evaluate whether maternal DHA status changed across gestation. Changes in levels of other key polyunsaturated fatty acids were also investigated.

MATERIALS AND METHODS

The Medline, Embase, Amed, and CINAHL databases were searched. Included studies reported measures of maternal omega-3 status in at least two pregnancy trimesters.

RESULTS

Thirteen studies were included in the final analyses. Absolute omega-3 DHA concentrations increased across gestation, but decreased as a proportion of total lipids.

DISCUSSION

Our findings are consistent with previous observations of increases in lipid mobilisation, coupled with preferential transfer of DHA to the fetus, with advancing gestation. However the number of eligible studies was small and further investigations are required.

Maternal long chain polyunsaturated fatty acid status and pregnancy complications

Maternal nutrition plays a crucial role in influencing fetal growth and birth outcome. Any nutritional insult starting several weeks before pregnancy and during critical periods of gestation is known to influence fetal development and increase the risk for diseases during later life. Literature suggests that chronic adult diseases may have their origin during early life - a concept referred to as Developmental Origins of Health and Disease (DOHaD) which states that adverse exposures early in life "program" risks for later chronic disorders. Long chain polyunsaturated fatty acids (LCPUFA), mainly omega-6 and omega-3 fatty acids are known to have an effect on fetal programming. The placental supply of optimal levels of LCPUFA to the fetus during early life is extremely important for the normal growth and development of both placenta and fetus. Any alteration in placental development will result in adverse pregnancy outcome such as gestational diabetes mellitus (GDM), preeclampsia, and intrauterine growth restriction (IUGR). A disturbed materno-fetal LCPUFA supply is known to be linked with each of these pathologies. Further, a disturbed LCPUFA metabolism is reported to be associated with a number of metabolic disorders. It is likely that LCPUFA supplementation during early pregnancy may be beneficial in improving the health of the mother, improving birth outcome and thereby reducing the risk of diseases in later life.

Pregnancy-Related Changes of Amino Acid and Acylcarnitine Concentrations: The Impact of Obesity

Objective Our primary objective was to assess the difference in amino and fatty acid biomarkers throughout pregnancy in women with and without obesity. Interactions between biomarkers and obesity status for associations with maternal and fetal metabolic measures were secondarily analyzed. Methods Overall 39 women (15 cases, 24 controls) were enrolled in this study during their 15- to 20-weeks' visit at the University of Iowa Hospitals and Clinics. We analyzed 32 amino acid and acylcarnitine concentrations with tandem mass spectrometry for differences throughout pregnancy as well as among women with and without obesity (body mass index [BMI] ≥ 35, BMI < 25). Results There were substantial changes in amino acids and acylcarnitine metabolites between the second and third trimesters (nonfasting state) of pregnancy that were significant after correcting for multiple testing (p < 0.002). Examining differences by maternal obesity, C8:1 (second trimester) and C2, C4-OH, C18:1 (third trimester) were higher in women with obesity compared with women without obesity. Several metabolites were marginally (0.002 < p < 0.05) correlated with birth weight, maternal glucose, and maternal weight gain stratified by obesity status and trimester. Conclusions Understanding maternal metabolism throughout pregnancy and the influence of obesity is a critical step in identifying potential mechanisms that may contribute to adverse outcomes in pregnancies complicated by obesity.

Association between prenatal and current exposure to selected LCPUFAs and school performance at age 7

INTRODUCTION

Long-chain polyunsaturated fatty acids (LCPUFAs) are important for brain functioning and might, thus, influence cognition and school performance. However, research investigating LCPUFAs relationships with school performance is limited. The objective of this study was to determine the association between levels of the LCPUFAs docosahexaenoic acid (DHA), arachidonic acid (AA), eicosapentaenoic acid (EPA) and n-6 docosapentaenoic acid (Osbond acid, ObA) at study entry, 22 weeks of pregnancy, 32 weeks of pregnancy, at partus, in umbilical cord plasma and child's plasma at age 7 and school performance scores at age 7.

METHODS

Data from the Maastricht Essential Fatty Acid Birth cohort (MEFAB) were used for this study. Fatty acid levels of plasma phospholipids were measured in maternal blood plasma at study entry, 22 weeks of pregnancy, 32 weeks of pregnancy and partus. Childs fatty acid levels of plasma phospholipids were measured a in umbilical cord blood plasma, and in blood plasma of the child at age 7. Scores on national standardised tests for spelling, reading and arithmetic at age 7 were obtained via the school (scores were available for 149, 159 and 155 children, respectively). Associations between LCPUFA levels and school performance scores were analysed with categorical regression analyses with correction for covariates (smoking, maternal education, sex, breastfeeding, maternal intelligence, birth weight and BMI at age 7).

RESULTS

Significant (p<0.001) associations between DHA level at age 7 and both reading (β=0.158) and spelling (β=0.146) were found. Consistent significant negative associations were observed between all maternal DHA plasma levels and arithmetic scores at age 7 (all p<0.001, all β<-0.019). Additional significant negative associations were observed between maternal LCPUFA plasma levels at study entry and both reading and spelling scores at age 7; these associations were less consistent.

CONCLUSION

Plasma DHA levels at age 7 were positively associated with reading and spelling scores at age 7. Consistent significant negative associations between maternal plasma DHA levels and arithmetic scores of the child at age 7 were found. Although this is an observational study, which cannot proof causality, the consistent negative associations observed between maternal plasma DHA levels and the arithmetic scores of the children at age 7 calls upon prudence when considering DHA supplementation during pregnancy.

Reduced Maternal Erythrocyte Long Chain Polyunsaturated Fatty Acids Exist in Early Pregnancy in Preeclampsia

The present prospective study examines proportions of maternal erythrocyte fatty acids across gestation and their association with cord erythrocyte fatty acids in normotensive control (NC) and preeclamptic pregnancies. We hypothesize that maternal fatty acid status in early pregnancy influences fetal fatty acid stores in preeclampsia. 137 NC women and 58 women with preeclampsia were included in this study. Maternal blood was collected at 3 time points during pregnancy (16-20th weeks, 26-30th weeks and at delivery). Cord blood was collected at delivery. Fatty acids were analyzed using gas chromatography. The proportions of maternal erythrocyte α-linolenic acid, docosahexaenoic acid, nervonic acid, and monounsaturated fatty acids (MUFA) (p < 0.05 for all) were lower while total n-6 fatty acids were higher (p < 0.05) at 16-20th weeks of gestation in preeclampsia as compared with NC. Cord 18:3n-3, 22:6n-3, 24:1n-9, MUFA, and total n-3 fatty acids (p < 0.05 for all) were also lower in preeclampsia as compared with NC. A positive association was observed between maternal erythrocyte 22:6n-3 and 24:1n-9 at 16-20th weeks with the same fatty acids in cord erythrocytes (p < 0.05 for both) in preeclampsia. Our study for the first time indicates alteration in maternal erythrocyte fatty acids at 16th weeks of gestation which is further reflected in cord erythrocytes at delivery in preeclampsia.

Maternal preeclampsia and risk for cardiovascular disease in offspring

Hypertensive disease of pregnancy (HDP) has been associated with elevated lifetime cardiovascular risk, including stroke, myocardial disease, coronary artery disease, and peripheral arterial disease. These two entities share common risk factors such as obesity, insulin resistance, diabetes, and hypertension. This article will evaluate the current literature on the maternal and fetal cardiovascular risks posed by HDP. The landmark study by Barker et al. demonstrated increased cardiovascular risk in growth-restricted infants, which may also be associated with HDP. Research has demonstrated the effects that HDP may have on the vascular and nephron development in offspring, particularly with respect to endothelial and inflammatory markers. In order to control for confounding variables and better understand the relationship between HDP and lifetime cardiovascular risk, future research will require following blood pressure and metabolic profiles of the parturients and their offspring.

Relations of plasma polyunsaturated Fatty acids with blood pressures during the 26th and 28th week of gestation in women of Chinese, Malay, and Indian ethnicity

Observational and intervention studies have reported inconsistent results of the relationship between polyunsaturated fatty acids (PUFAs) and hypertension during pregnancy. Here, we examined maternal plasma concentrations of n-3 and n-6 PUFAs between the 26th and the 28th week of gestation in relation to blood pressures and pregnancy-associated hypertension.We used data from a birth cohort study of 751 Chinese, Malay, and Indian women. Maternal peripheral systolic blood pressure (SBP) and diastolic blood pressure (DBP) were taken from the brachial arm, and central SBP and pulse pressures (PPs) were derived from radial artery pressure waveforms between the 26th and the 28th week of gestation. Pregnancy-associated hypertension (including gestational hypertension and preeclampsia) was ascertained from medical records. Plasma phosphatidylcholine n-3 and n-6 PUFAs were measured by gas chromatography and expressed as percentage of total fatty acids.Peripheral SBP was inversely associated with total n-3 PUFAs [-0.51 (95% confidence interval, CI, -0.89 to -0.13) mm Hg] and long-chain n-3 PUFAs [-0.52 (CI -0.92 to -0.13) mmHg]. Similar but weaker associations were observed for central SBP and PP. Dihomo-γ-linolenic acid was marginally positively associated with peripheral SBP, central SBP, and PP, whereas linoleic acid and total n-6 PUFAs showed no significant associations with blood pressures. We identified 28 pregnancy-associated hypertension cases, and 1% increase in total n-3 PUFAs was associated with a 24% lower odds of pregnancy-associated hypertension (odds ratio 0.76; 95% CI 0.60 to 0.97). Maternal ethnicity modified the PUFAs-blood pressure relations, with stronger inverse associations with n-3 PUFAs in Chinese women, and stronger positive associations with n-6 PUFAs in Indian women (P values for interaction ranged from 0.02 to 0.07).Higher n-3 PUFAs at midgestation are related to lower maternal blood pressures and pregnancy-associated hypertension in Asian women, and the ethnicity-related variation between PUFAs and blood pressures deserves further investigation.

The association between dietary factors and gestational hypertension and pre-eclampsia: a systematic review and meta-analysis of observational studies

BACKGROUND

Dietary factors have been suggested to play a role in the prevention of hypertensive disorders of pregnancy (HDP), including gestational hypertension and pre-eclampsia, but inconsistent findings have been reported. A systematic review and meta-analyses were performed to synthesize evidence from observational studies of reproductive-aged women on the association between dietary factors and HDP.

METHODS

MEDLINE and EMBASE were searched to identify studies published until the end of May 2014. Studies were included if they were observational studies of reproductive-age women and reported results on dietary factors (energy, nutrients, foods or overall dietary patterns, alone or in combination with dietary supplements) and gestational hypertension and/or pre-eclampsia. Studies were excluded if they reported on supplements not in combination with dietary intake, or examined a biomarker of dietary intake. Random effects meta-analyses were performed on calculated weighted mean differences (WMD) of dietary intake between cases and non-cases, and effect estimates were pooled.

RESULTS

In total, 23 cohort and 15 case-control studies were identified for systematic review, of which 16 could be included in the meta-analyses. Based on meta-analyses of cohort studies, unadjusted energy intake was higher for pre-eclampsia cases (WMD 46 kcal/day, 95% confidence interval (CI) -13.80 to 106.23; I 2 = 23.9%, P = 0.26), although this was not statistically significant. Unadjusted intakes of magnesium (WMD 8 mg/day, 95% CI -13.99 to -1.38; I 2 = 0.0%, P = 0.41) and calcium (WMD 44 mg/day, 95% CI -84.31 to -3.62, I 2 = 51.1%, P = 0.03) were lower for the HDP cases, compared with pregnant women without HDP. Higher calcium intake consistently showed lower odds for HDP after adjustment for confounding factors (OR = 0.76, 95% CI 0.57 to 1.01, I 2 = 0.0%, P = 0.79). A few studies examining foods and dietary patterns suggested a beneficial effect of a diet rich in fruit and vegetables on pre-eclampsia, although not all the results were statistically significant.

CONCLUSIONS

Based on a limited number of studies, higher total energy and lower magnesium and calcium intake measured during pregnancy were identified as related to HDP. Further prospective studies are required to provide an evidence base for development of preventive health strategies, particularly focusing on dietary factors during pre-pregnancy and early pregnancy.

Maternal lipids in pre-eclampsia: innocent bystander or culprit?

Pre-eclampsia continues to be a challenge--to understand the underlying pathogenesis and to prevent or treat in the clinical setting. One area of potential therapies opening up is treatment of maternal lipids and clinical trials are underway using statins in early pre-eclampsia. At present, most potential therapies to treat lipids cannot be recommended for general use in pregnancy and if we were to target maternal lipids to reduce rates of pre-eclampsia, very large numbers of women may need to be treated. Prior to reaching that point, we first need to understand whether maternal lipids are pathogenic in the processes underlying pre-eclampsia. The aim of this review is to examine the role of lipids in the pathogenesis and outcomes of pre-eclampsia, how abnormal lipid genes may be implicated and consider whether treatment of hyperlipidemia has a more general place in the prevention or treatment of pre-eclampsia.

Altered maternal proportions of long chain polyunsaturated fatty acids and their transport leads to disturbed fetal stores in preeclampsia

Our previous cross-sectional studies have shown altered proportions of long chain polyunsaturated fatty acids (LCPUFA) in preeclampsia (PE) at the end of pregnancy when the pathology has already progressed. The present longitudinal study for the first time reports fatty acid proportions from 16th week of gestation till delivery and placental transport in PE. This is a hospital based study where women were recruited in early pregnancy. Maternal blood was collected at 3 time points i.e. T1=16-20th week, T2=26-30th week and T3=at delivery. Cord blood and placenta were collected at delivery. This study reports data on 140 normotensive control (NC) and 54 PE women. In PE we report lower proportions of DHA in maternal plasma at T1, cord plasma and placenta (p<0.05 for all). The mRNA levels of placental ∆5 desaturase, fatty acid transport proteins -1, -4, were lower (p<0.05 for all) in PE. There was also a positive association between cord and maternal plasma DHA and total omega-3 fatty acids at T1. This study demonstrates that women with PE have lower fatty acids stores at 16-20th week of gestation and lower placental synthesis and transport. It is likely that supplementation of omega-3 fatty acids during the 16-20th week of gestation may help in improving fatty acid status in infants born to mothers with PE.

Effect of fatty acid status in cord blood serum on children's behavioral difficulties at 10 y of age: results from the LISAplus Study

BACKGROUND

Little is known about the effect of fatty acid (FA) concentrations in cord blood on long-term behavioral outcomes.

OBJECTIVE

We assessed the effect of FAs in cord blood serum on children's behavioral difficulties at the age of 10 y.

DESIGN

A longitudinal study of 416 children from the population-based Influences of Lifestyle-Related Factors on the Immune System and the Development of Allergies in Childhood (LISAplus) birth cohort from Munich was conducted. Individual glycerophospholipid FAs in blood were analyzed in venous cord blood. Data on children's behavior were collected with a parent-reported Strength and Difficulties Questionnaire at 10 y of age. Zero-inflated Poisson regression models were applied and adjusted for sex, parental income, smoking during pregnancy, and dietary intake of arachidonic acid (AA) and DHA at 10 y.

RESULTS

A 1% increase in DHA in cord blood serum was found to decrease total difficulties by (exp)β(adj) = 0.93 (SE = 0.02, P < 0.0001) and hyperactivity or inattention by (exp)β(adj) = 0.94 (SE = 0.03, P < 0.04). Higher long-chain (LC) PUFA concentrations in cord blood serum were associated with fewer emotional symptoms [(exp)β(adj) = 0.95, SE = 0.03, P = 0.01], and similarly higher AA concentrations were associated with fewer emotional symptoms [(exp)β(adj) = 0.94, SE = 0.03, P = 0.03].

CONCLUSION

Increased concentrations of DHA, LC-PUFAs, and AA in cord blood serum were associated with lower scores on a parent-completed behavioral screen. An appropriate FA supply to the developing fetus may be essential for optimal long-term behavioral outcomes in children.

Body mass index and cognitive ability of young children

OBJECTIVE

This study prospectively assessed the association between body mass index (BMI) and cognitive ability of young children, while accounting for confounding factors.

METHODS

The study included 236 children born between 1990 and 1994 participating in a Dutch birth cohort study. Anthropometric data of the children at birth, 4, and 7 years of age were collected from growth records or measured at the Academic Hospital of Maastricht. The Kaufman Assessment Battery for Children (K-ABC) was used to assess cognitive ability at 7 years of age. The association between BMI and cognitive ability was investigated using univariate and multivariate linear regression analyses, including various covariates.

RESULTS

Although the results suggest that cognitive ability at 7 years of age decreased with increasing BMI at 4 years and 7 years of age, this association was not significant in any performed analysis. Multivariate analyses showed that maternal intelligence was strongly associated with all scales of the K-ABC as a significant covariate. Adjusting analyses for physical fitness of the child, maternal education, maternal pre-pregnancy BMI, maternal smoking during pregnancy, and birth weight did not change the results.

CONCLUSION

This study found no evidence for an association between BMI and cognitive ability of school-aged children.

Role of nutrition in the risk of preeclampsia

Preeclampsia (PE) accounts for about one-quarter of the cases of maternal mortality and ranks second among the causes of pregnancy-associated maternal deaths in Canada and worldwide. The identification of an effective strategy to prevent PE is a priority and a challenge for research in obstetrics. Progress has been hampered by inadequate understanding of the underlying etiology of the disease. The role of maternal diet in the etiology of PE has recently received increased attention. The objective of this paper is to provide an overview of the literature concerning 1) the current understanding of the pathogenesis of PE, 2) the biological plausibility and potential mechanisms underlying the associations between maternal dietary exposures, nutrition, and the risk of PE, and 3) the epidemiological findings of maternal nutrient intake in relation to the risk of PE.

Associations between term birth dimensions and prenatal exposure to essential and trans fatty acids

BACKGROUND

Certain essential long-chain polyunsaturated fatty acids (LCPUFAs) are considered important for fetal growth and brain development, whereas industrial trans fatty acids (mainly 18:1trans) have been associated with negative effects. The aim of this study was to investigate associations between term birth dimensions and prenatal exposure to some of these fatty acids, reflected by neonatal fatty acid concentrations at birth.

METHODS

Data of up to 700 infant-mother pairs from the Maastricht Essential Fatty Acid Birth Cohort were used for the present study. Unadjusted and multivariable-adjusted linear regression analyses were performed to investigate associations between birth weight, birth length or head circumference and relative concentrations of docosahexaenoic acid (DHA), arachidonic acid (AA), dihomo-gamma-linolenic acid (DGLA) and trans-octadecenoic acids (18:1t) measured in phospholipids of the walls of umbilical arteries and veins, and in umbilical cord plasma and erythrocytes.

RESULTS

After optimal adjustment, a significant negative association was observed between birth weight and umbilical plasma DHA concentrations. Negative associations were also found for AA concentrations measured in umbilical plasma and in arterial and venous vessel walls. Birth length was negatively related to arterial vessel wall AA concentrations only. A significant negative association was observed for the relationship between 18:1t in cord erythrocytes and birth weight. For DGLA no significant associations were observed.

CONCLUSIONS

Results seem to preclude a role of DHA and AA as growth factors per se. Their negative relationships with birth dimensions may result from a limited maternal-fetal LCPUFA transfer capacity. Potential effects of 18:1t and DGLA on birth dimensions are probably small or non-existing.

Fetal learning and memory: weak associations with the early essential polyunsaturated fatty acid status

To study the potential associations between fetal brain functions and the early essential polyunsaturated fatty acid (ePUFA) status, fetal learning and memory were assessed by repeated habituation rate measurements (HR) in fetuses of 30, 32, 34 or 36 weeks gestational age (GA). HR tests were repeated 10 min later. Both measurements were replicated in a second session at GA 38. Fetal short-term memory (STM) and long-term memory (LTM) were calculated from these habituation rates and related to concentrations of ePUFAs and their status markers, measured in umbilical artery wall phospholipids. The only relevant associations observed were positive trends (0.010<p<0.050) between STM measured before 38 weeks GA and concentrations of the ePUFA status markers Mead acid and Mead acid+dihomo-Mead acid, and between LTM and levels of Osbond acid, a marker of the n-3 LCPUFA status. Although these weak associations may imply some negative relationships between fetal brain functions and the early ePUFA status, we concluded that physiological differences in the availability of these fatty acids may probably not determine the differences in these primitive brain functions during the third trimester of fetal development.

Higher de novo synthesized fatty acids and lower omega3- and omega6-long-chain polyunsaturated fatty acids in umbilical vessels of women with preeclampsia and high fish intakes

Umbilical veins (UV) and arteries (UA) of preeclamptic women in Curaçao harbor lower long-chain polyunsaturated fatty acids (LCP). The present aim was to test these findings in Mwanza (Tanzania), whose inhabitants have high LCPomega3 and LCPomega6 intakes from Lake Victoria fish. Women with preeclampsia (n=28) in Mwanza had lower PUFA and higher 20:0 in UV and UA, compared with normotensive/non-proteinuric controls (n=31). Their UV 22:6omega3, 22:4omega6, LCPomega6, omega6, and LCPomega3+omega6 were lower, while saturated FA, potentially de novo synthesized FA (Sigmade novo) and (Sigmade novo)/(LCPomega3+omega6) ratio were higher. Their UA had higher 16:1omega7, omega7, 18:0, and 16:1omega7/16:0. Umbilical vessels in Mwanza had higher 22:6omega3, LCPomega3, omega3, and 16:0, and lower 22:5omega6, 20:2omega6, 18:1omega9, and omega9, compared to those in Curaçao. Preeclampsia in both Mwanza and Curaçao is characterized by lower LCP and higher Sigmade novo. An explanation of this might be placental dysfunction, while the similarity of umbilical vessel FA-abnormalities in preeclamptic and diabetic pregnancies suggests insulin resistance as a common denominator.

Prenatal arachidonic acid exposure and selected immune-related variables in childhood

Arachidonic acid (AA) is considered essential in fetal development and some of its metabolites are thought to be important mediators of the immune responses. Therefore, we studied whether prenatal exposure to AA is associated with some immune-related clinical conditions and plasma markers in childhood. In 280 children aged 7 years, atopy, lung function and plasma inflammation markers were measured and their relationships with early AA exposure were studied by linear and logistic regression analyses. AA exposure was deduced from AA concentrations in plasma phospholipids of the mothers collected at several time points during pregnancy and at delivery, and in umbilical cord plasma and arterial and venous wall phospholipids. In unadjusted regression analyses, significant positive associations were observed between maternal AA concentrations at 16 and 32 weeks of pregnancy (proxies for fetal AA exposure) and peak expiratory flow decline after maximal physical exercise and plasma fibrinogen concentrations of their children, respectively. However, after correction for relevant covariables, only trends remained. A significant negative relationship was observed between AA concentrations in cord plasma (reflecting prenatal AA exposure) and the average daily amplitude of peak expiratory flow at rest, which lost significance after appropriate adjustment. Because of these few, weak and inconsistent relationships, a major impact of early-life exposure to AA on atopy, lung function and selected plasma inflammation markers of children at 7 years of age seems unlikely.

Maternal docosahexaenoic acid supplementation and fetal accretion

Docosahexaenoic acid (DHA) (22:6n−3) is a polyunsaturated fatty acid that is an essential constituent of membranes, particularly of the nervous system. Infants acquire DHA from their mothers, either prenatally via the placenta or postnatally in milk. The present study aimed to test the hypothesis that maternal supplementation during the second and third trimesters of pregnancy enriches maternal and/or fetal DHA status. In a randomised, prospective, double-blind study 100 mothers received either fish-oil capsules containing 400mg DHA/g (200mg/d) (n50), or placebo containing 810mg oleic acid/g (400mg/d) (n50) from 15 weeks gestation until term. Venous blood samples were obtained from mothers at 15, 28 and 40 weeks, and from the umbilical cord at birth. Total fatty acids in plasma and erythrocytes were analysed by GC–MS. There were no significant differences between maternal groups in baseline DHA, as a proportion of total fatty acids (g/100g total fatty acids) or concentration (nmol/ml), in plasma and erythrocytes. DHA concentrations in plasma at 28 weeks (P=0·02) and erythrocytes at both 28 weeks (P=0·03) and term (P=0·02) were 20% higher in supplemented mothers than the placebo group. DHA accounted for a higher proportion of total fatty acids in erythrocytes of supplemented mothers at 28 weeks (P=0·003) and term (P=0·01). There were no significant differences between groups in DHA (g/100g total fatty acids or nmol/l) in cord blood. Maternal DHA status was maximal in mid-trimester and declined to term, at a lower rate in supplemented compared with unsupplemented mothers. Maternal DHA supplementation significantly increases maternal DHA status and limits the last trimester decline in maternal status, aiding preferential transfer of DHA from mother to fetus.

Relationships between fatty acid status of sow plasma and that of umbilical cord, plasma and tissues of newborn piglets when sows were fed on diets containing tuna oil or soyabean oil in late pregnancy

To investigate the relationships between maternal, umbilical cord and piglet fatty acid status, multiparous sows (six per diet) were fed on diets containing supplements (30 g/kg) of either soyabean oil or tuna oil for the last 21 d of pregnancy. The proportions of most fatty acids differed between diets: in particular, the tuna-oil-containing diet supplied more 22:6n-3 and less 18:2n-6 fatty acids than the soyabean-oil-containing diet. Maternal plasma fatty acid concentrations (mg/l) were greater than those in umbilical plasma and 20:4n-6 and 22:6n-3 fatty acids were present in higher proportions (g/100 g fatty acids) in umbilical than maternal plasma. Feeding tuna oil increased the proportionate amounts (g/100 g fatty acids) of total n-3 fatty acids (particularly 22:6n-3) in umbilical cord, plasma and piglet tissues compared with feeding soyabean oil: in contrast, the proportion of 20:4n-6 was decreased by feeding tuna oil. Changes in piglet fatty acid proportions as a result of oil feeding were not influenced by piglet weight. While proportions of the long-chain n-3 and n-6 polyunsaturated fatty acids in piglet liver, spleen and reproductive tract (ovaries plus uterus of the female, testes of the male) correlated well with those of umbilical plasma, those in brain and retina were poorly correlated. Therefore umbilical plasma cannot be used to predict the fatty acid status of piglet brain.

Nutrient involvement in preeclampsia

Preeclampsia is a pregnancy-specific condition that increases maternal and infant mortality and morbidity. It is diagnosed by new-onset increased blood pressure and proteinuria during gestation; for many years these markers were the sole targets for study. More recently, increased attention to the multisystemic nature of the syndrome with involvement of almost all organs, activation of coagulation and increased sensitivity to pressor agents has expanded understanding of the disorder. The epidemiology of preeclampsia, being more common in poor women, long ago suggested that nutrients might be involved in the disorder. Numerous conflicting hypotheses were advanced but the testing of these hypotheses has either been done poorly or not at all. Review of the available data indicates very few studies that provide useful insights. In many studies the syndrome is poorly defined and in most studies nutritional data (questionnaires or biomarkers) are obtained on women with the clinical syndrome. In overtly preeclamptic women it is impossible to decipher cause from effect. Nonetheless, current concepts of the genesis of preeclampsia that include endothelial dysfunction, inflammatory activation, oxidative stress and predisposing maternal factors provide targets for well-designed nutritional investigation. In this review the current concepts of the pathogenesis of preeclampsia are reviewed and available data are assessed in light of these concepts. Targets for nutritional investigation based on the current knowledge of pathophysiology are suggested.

Alpha-fetoprotein gene expression in early and full-term human trophoblast

Alpha-fetoprotein (AFP) is a major serum glycoprotein synthesized during fetal life mainly by the yolk sac and the fetal liver. At term, it reaches high concentrations in the maternal intervillous blood, which is in direct contact with the placental trophoblastic microvillous membrane, and this suggests the placental origin of the AFP at the fetal-maternal interface. We used several experimental approaches to investigate the expression of AFP gene and fetal protein production in early gestation and term placentas. RT-PCR and immunological studies clearly identified AFP messenger RNA and AFP protein in the placental villi from first trimester of pregnancy. The AFP gene was also expressed in highly purified cytotrophoblasts from early placentas, and enzymo-immunoassay showed that AFP protein was synthesized and secreted by early cytotrophoblasts. AFP was also detected in the cytoplasm of these cells by immuno-cytochemistry. However, none of these methods detected any expression of the AFP gene in full-term placental villi or in cultured trophoblasts. These findings demonstrate that both AFP mRNA and protein are present in trophoblastic cells early in pregnancy. The absence of AFP gene expression in term placental villi also suggests, that the AFP at the fetal-maternal interface is attributable to a notable transplacental passage of AFP from fetal blood in late pregnancy.

Placental regulation of fatty acid delivery and its effect on fetal growth--a review

More than 90 per cent of the fat deposition in the fetus occurs in the last 10 weeks of pregnancy during which it increases exponentially to reach a rate of accretion of around 7 g/day close to term. All of the n -3 and n -6 fatty acid structure acquired by the fetus has to cross the placenta and fetal blood is enriched in long chain polyunsaturated fatty acids (LCPUFA) relative to the maternal supply. The placenta may regulate its own fatty acid substrate supply via the action of placental leptin on maternal adipose tissue. Fatty acids cross the microvillous and basal membranes by simple diffusion and via the action of membrane bound and cytosolic fatty acid binding proteins (FABPs). The direction and magnitude of fatty acid flux is mainly dictated by the relative abundance of available binding sites. The fatty acid mix delivered to the fetus is largely determined by the fatty acid composition of the maternal blood although the placenta is able to preferentially transfer the important PUFA to the fetus as a result of selective uptake by the syncytiotrophoblast, intracellular metabolic channelling of individual fatty acids, and selective export to the fetal circulation. Placental FABP polymorphisms may affect these processes. There is little evidence to suggest that placental delivery of fatty acids limits normal fetal growth although the importance of the in utero supply may be to support post-natal development as most of the LCPUFA accumulated by the fetus is stored in the adipose tissue for use in early post-natal life.

The n-3 and n-6 polyunsaturated fatty acid composition of plasma phospholipids in pregnant women and their infants. relationship with maternal linoleic acid intake

The availability of long-chain polyunsaturated fatty acids during infancy has been related to neonatal growth and development. Fatty acid concentration at birth is an important predictor of postnatal level. The primary aim of this study was to provide a description of the distribution of n-3 and n-6 polyunsaturated fatty acids in the plasma phospholipid fraction of pregnant women remaining on a Western-style diet and their neonates. The plasma phospholipid polyunsaturated fatty acid composition was determined by gas-liquid chromatography in 889 mother-infant pairs. Blood samples were taken during the first, second and third trimester of pregnancy, at delivery, and from the umbilical vein at birth. Mean (+/- SD) fatty acid concentrations are reported in mg/l and as percentage of total fatty acids (% wt/wt). In addition, the 10th, 25th, 50th, 75th and 90th percentiles are given. The distribution of docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6) concentrations in umbilical plasma phospholipids is also reported as a function of gestational age and maternal linoleic acid intake during pregnancy. This data can be be used as a reference for future studies and may aid in identifying term infants with a relatively low long-chain polyene status at birth.

Essential fatty acid composition of plasma phospholipids and birth weight: a study in term neonates

BACKGROUND

Essential fatty acids (EFAs) in umbilical cord blood samples are associated with attained birth weight in premature infants and low-birth-weight neonates.

OBJECTIVE

The objective was to investigate relations between the EFA composition of cord and maternal plasma phospholipids and birth weight in term neonates.

DESIGN

This was a cross-sectional study in 627 singletons born at term. The plasma phospholipid EFA composition of the mothers was determined by gas-liquid chromatography at study entry (< or = 16 wk gestation), at delivery, and in cord plasma at birth. Birth weights were normalized to SD scores.

RESULTS

In cord plasma, the dihomo-gamma-linolenic acid concentration was positively related to weight SD scores. Both arachidonic acid (AA) and docosahexaenoic acid (DHA) were negatively related to weight SD scores. EFA-status indicators showed similar negative associations, whereas eicosatrienoic acid concentrations were positively related to neonatal size. In maternal plasma, proportions of n-3 long-chain polyenes (LCPs) and n-6 LCPs decreased during pregnancy. Larger decreases in AA, DHA, n-3 LCP, and n-6 LCP fractions were observed in mothers of heavier babies. Higher concentrations of LCPs in maternal plasma were, however, not related to a larger infant size at birth.

CONCLUSIONS

A lower biochemical EFA status in umbilical cord plasma and a larger decrease in maternal plasma LCP concentrations are associated with a higher weight-for-gestational-age at birth in term neonates. Our findings do not support a growth-stimulating effect of AA or DHA; however, they do suggest that maternal-to-fetal transfer of EFAs might be a limiting factor in determining neonatal EFA status.

Effects of gestational alcohol exposure on the fatty acid composition of umbilical cord serum in humans

This study examined the effects of maternal periconceptional alcohol intake on polyunsaturated fatty acid (PUFA) concentrations in human neonates. The area percentage of each fatty acid in cord blood serum from 12 infants born to control women (who consumed <2 mL absolute ethanol/d) was compared with that of 9 infants born to women whose periconceptional alcohol intake averaged > or = 30mL absolute ethanol/d. Periconceptional alcohol use was associated with a 30% increase in the proportion of docosahexaenoic acid (22:6n-3) in cord blood (3.0% of total lipid in control infants compared with 3.9% in alcohol-exposed infants; P < 0.01). The rise in the proportion of 22:6n-3 was responsible for increases in the ratio of n-3 to n-6 fatty acids and the ratio of long-chain n-3 to n-6 fatty acids (P < 0.055). Examination of the lipid-class fatty acid profile indicated that serum lipid alterations were localized to the cholesterol esters; 22:6n-3 in the cholesterol esters of alcohol-exposed infants increased 54% (P < 0.011) and arachidonic acid increased 55% (P < 0. 005). The relative fatty acyl composition of maternal serum showed a significant increase in 18:0 fatty acids in the alcohol-exposed group (25%, P < 0.005) but there were no changes in the other fatty acids. The increase in the proportion of 22:6n-3 was unexpected but is consistent with the hypothesis that this essential lipid may be conserved selectively. These results imply that the lifelong neurobehavioral and sensory dysfunction in fetal alcohol syndrome and other alcohol-related neurodevelopmental disorders may be due in part to PUFA dysregulation.

Long-chain polyunsaturated fatty acids, pregnancy, and pregnancy outcome

During pregnancy, essential long-chain polyunsaturated fatty acids (LCPUFAs) play important roles as precursors of prostaglandins and as structural elements of cell membranes. Throughout gestation, accretion of maternal, placental, and fetal tissue occurs and consequently the LCPUFA requirements of pregnant women and their developing fetuses are high. This is particularly true for docosahexaenoic acid (DHA; 22:6n-3). The ratio of DHA to its status marker, docosapentaenoic acid (22:5n-6), in maternal plasma phospholipids decreases significantly during pregnancy. This suggests that pregnancy is associated with maternal difficulty in coping with the high demand for DHA. The DHA status of newborn multiplets is significantly lower than that of singletons; the same is true for infants of multigravidas as compared with those of primigravidas and for preterm compared with term neonates. Because the LCPUFA status at birth seems to have a long-term effect, the fetus should receive an adequate supply of LCPUFAs. Data from an international comparative study indicated that, especially for n-3 LCPUFAs, the fetus is dependent on maternal fatty acid intake; maternal supplementation with LCPUFAs, their precursors, or both increased LCPUFA concentrations in maternal and umbilical plasma phospholipids. However, significant competition between the 2 LCPUFA families was observed, which implies that effective supplementation requires a mixture of n-6 and n-3 fatty acids. Further research is needed to determine whether higher LCPUFA concentrations in plasma phospholipid will have functional benefits for mothers and children.

Long-chain polyunsaturated fatty acids and development of human infants

Human infants require n-6 and n-3 long-chain polyunsaturated fatty acids (LCPUFA), derivatives of the essential fatty acids, linoleate (n-6) and linolenate (n-3), for growth and neural development. Animals fed diets deficient in the essential fatty acids have low neural LCPUFA and behavioral changes that imply adverse effects on brain function. Studies of animals deficient in essential fatty acids have provided the rationale and outcomes for studies to determine whether human infants need dietary LCPUFA. After including n-3 LCPUFA in formula, preterm infants showed higher sensory function (retinal responses to light, visual acuity), visual attention characteristic of higher maturity during infancy, and higher scores on test of global development (6- and 12-mo Bayley Mental Developmental Index). In term infants, some but not all studies found higher visual acuity, 4-mo Brunet-Lezine psychomotor development, and 10-mo means-end problem solving with LCPUFA-containing formulae compared to formulae in general use. Because preterm infants have lower LCPUFA accumulation at birth than term infants, it may be easier to show benefits of dietary LCPUFA for neural development in the former group. In addition to low gestational age, other variables may influence LCPUFA accumulation at birth and determine whether a particular group of infants will respond to dietary LCPUFA. One current challenge is to identify and characterize the effects of those variables. Another is to learn the mechanisms by which LCPUFA status may influence behavior.

Effects of pregnancy-induced hypertension on the essential fatty acid statuses of Ecuadorian and Dutch women

OBJECTIVE

Among white Dutch women pregnancy-induced hypertension was shown to be associated with elevated levels of the long-chain polyenes of 18:2n-6 and 18:3n-3 in combination with reduced levels of those parent essential fatty acids. This observation suggested an enhanced desaturation and elongation of the parent fatty acids. This study was performed to investigate whether this phenomenon also occurs under completely different nutritional and geographic conditions.

STUDY DESIGN

Plasma fatty acids of primiparous Mestizo Ecuadorian women with uncomplicated pregnancies and with pregnancy-induced hypertension were assessed at delivery and compared with similar data from white Dutch women. Neonatal values, as determined in umbilical plasma and umbilical vessel walls, were also compared.

RESULTS

In contrast to the pattern seen among white mothers, pregnancy-induced hypertension did not increase the long-chain polyene status of Mestizo mothers. Despite the absence of this compensatory mechanism, long-chain polyene status was not compromised in Mestizo neonates born after pregnancy-induced hypertension.

CONCLUSION

Additional mechanisms may be active in maintaining the long-chain polyene status of neonates born after pregnancy-induced hypertension.

Polyunsaturated fatty acid status and neurodevelopment: a summary and critical analysis of the literature

The rationale for randomized trials designed to measure the effects of variable docosahexaenoic acid (DHA) status on neurodevelopment in human infants came from earlier studies of neurodevelopment in animals that were deficient in DHA owing to diets low in alpha-linolenic acid. The session on neurodevelopment looked at the results of these animal studies and discussed outcomes that appear to be analogous in human infants with variable DHA status. Presentations focused mainly on measures of development that may be attributed to more specific developmental domains (e.g., visual attention, recognition memory, problem-solving), some of which have been shown to be affected by long-chain polyunsaturated fatty acid (LCPUFA) status. This paper derives from discussions that took place during the session and reviews subsequent developments in this area. Although more difficult to interpret, global measures of infant development (e.g., the Bayley Scales of Infant Development, and Brunet-Lezine) can only suggest a relationship to specific developmental domains, but they have been applied in some randomized trials of LCPUFA and infant development. Those results are also summarized here.

Essential fatty acid status in plasma phospholipids of mother and neonate after multiple pregnancy

During singleton pregnancy, maternal essential fatty acid (EFA) status decreases progressively. After multiple pregnancy it can be expected that the neonatal and maternal EFA status is even lower. To study whether the maternal EFA supply to the fetus is a limiting factor to the neonatal EFA status, we compared the plasma phospholipid EFA status of newborn multiplets (30 pairs of twins and 7 sets of triplets) with that of singletons (n = 89) at birth and that of their mothers at delivery. After correction for gestational age, a slightly lower EFA status was found in maternal and umbilical plasma from multiplets compared to singletons. No relation was found between the difference in birthweight of the smallest and the largest neonate of a set of multiplets and the difference in cord plasma EFA levels. Correlations between maternal and umbilical plasma EFA levels were comparable for multiple and singleton pregnancies. Therefore, adequate dietary intake is required to guarantee an optimal neonatal EFA status, especially during multiple pregnancy.

Essential fatty acid status measured in umbilical vessel walls of infants born after a multiple pregnancy

The essential fatty acid (EFA) status of full-term infants born after an uneventful, singleton pregnancy has been reported to be marginal. If this low EFA status is caused by a limiting maternal EFA supply, the higher total fetal EFA demand associated with a multiple pregnancy would result in an even lower EFA status of the infants born after a multiple pregnancy. Therefore, we compared the EFA status at birth of 30 pairs of twins, seven sets of triplets, and one set of quintuplets with that of 94 infants (51 preterm, 43 full-term) born after a singleton pregnancy. Phospholipid-associated EFA profiles of the umbilical vessel walls, considered a longer-term reflection of the fetal EFA status, were studied. After correction for gestational age at birth, levels of n-6 and n-3 EFAs were generally lower, while levels of EFA-deficiency indicating n-9 polyunsaturated fatty acids were significantly higher both in the draining umbilical arteries and the supplying veins of infants born after a multiple pregnancy. EFA profiles of twins and triplets were similar, but the average EFA status of the set of quintuplets was lower than that of twins and triplets. In conclusion, the observation that the EFA status of infants born after a multiple pregnancy is lower than that of infants born after a singleton pregnancy supports the view that the maternal EFA supply to the fetus is limiting. Considering the importance of EFAs and their longer chain derivatives for proper growth and development, this finding warrants further studies of the adequacy of the maternal EFA intake during pregnancy.