Henk Russcher

Homocysteine and folate concentrations in early pregnancy and the risk of adverse pregnancy outcomes: The generation R study

Please cite this paper as: Bergen N, Jaddoe V, Timmermans S, Hofman A, Lindemans J, Russcher H, Raat H, Steegers‐Theunissen R, Steegers E. Homocysteine and folate concentrations in early pregnancy and the risk of adverse pregnancy outcomes: the Generation R Study. BJOG 2012;119:739–751.

Glucocorticoid receptor gene and risk of cardiovascular disease

BACKGROUND Genetic variants in immunomodulating genes have been suggested to contribute to the risk of cardiovascular disease. Glucocorticoids are important regulators of inflammatory processes and the immune system. Our aim was to determine the contribution of genetic glucocorticoid receptor variants, with different cortisol sensitivities, to the risk of cardiovascular disease. METHODS The study was conducted in a large (n=7983) population-based, prospective cohort of the Rotterdam Study. The mean duration of follow-up was 8.9 years. Measures of cardiovascular disease were incident myocardial infarction, coronary heart disease, high-sensitivity C-reactive protein level, interleukin 6 level, and arteria carotis intima-media thickness. RESULTS Persons homozygous for haplotype 3, which is a common variant of the glucocorticoid receptor gene, had a more than 2-fold increased risk of myocardial infarction (hazard ratio, 2.1; 95% confidence interval, 1.13-4.07) and an almost 3-fold increased risk of coronary heart disease (hazard ratio, 2.6; 95% confidence interval, 1.40-4.81) compared with nonhomozygous persons. In addition, their C-reactive protein and interleukin 6 levels were higher, and carotis intima-media thickness was greater. No associations were found for the other haplotypes. CONCLUSIONS The glucocorticoid receptor gene haplotype 3 is a common genetic variant and is related to a more active proinflammatory system. This haplotype is associated with the risk of cardiovascular disease and its parameters. These results should be regarded as hypothesis generating until they have been replicated in other studies. Our findings suggest that genetically determined cortisol sensitivity is involved in the pathogenesis of cardiovascular disease and might identify a subgroup at risk.

Multicenter evaluation of the first automated Elecsys sFlt-1 and PlGF assays in normal pregnancies and preeclampsia.

OBJECTIVES Performance evaluation of Elecsys sFlt-1 and PlGF assays. DESIGN AND METHODS Within-, between-run, total imprecision, functional sensitivity, inter-laboratory comparison, method comparison and lot-to-lot reproducibility were evaluated. RESULTS Within- and between-run CVs were below 4% for sFlt-1 >60 and PlGF > 20 pg/mL. Total imprecision CVs were below 4.3%. Functional sensitivity was < 5 pg/mL. Inter-laboratory CVs were <5%. Elecsys correlated well with Quantikine VEGF-R1 (r=0.960) and PlGF (r=0.968). Lot-to-lot comparisons yielded highly correlated results (r>0.999). In healthy pregnancies, the median levels of sFlt-1 remained constant in first (1107 pg/mL) and second trimesters (1437 pg/mL) but increased in the third trimester (2395 pg/mL), while median PlGF levels increased in the first (30 pg/mL) and second trimesters (279 pg/mL) and peaked at 29 to 32 weeks (626 pg/mL) and decreased thereafter (340 pg/mL). The sFlt-1/PlGF ratio is highest in the first trimester (median: 28) but remained constant in the second (median: 4.7) and third trimesters (median: 5.1). In PE/HELPP samples matched for gestational age the sFlt-1 levels were significantly higher (6894-34,624 pg/mL), whereas PlGF levels were lower (9.2-80 pg/mL) and the median sFlt-1/PlGF ratio is much higher (461; range: 121-2614) than in apparently healthy pregnancies (3.6; range: 0.3-105). CONCLUSION The new Roche Elecsys sFlt-1 and PlGF immunoassay showed excellent precision and reliability. There was a clear difference in the Elecsys sFlt-1/PlGF ratio between samples obtained from women with apparently normal pregnancy at the time of blood collection and those diagnosed with PE/HELLP at the same age of gestation.

Air Pollution Exposure and Markers of Placental Growth and Function: The Generation R Study

Background: Air pollution exposure during pregnancy might affect placental growth and function, perhaps leading to pregnancy complications. Objective: We prospectively evaluated the associations of maternal air pollution exposure with markers of placental growth and function among 7,801 pregnant women in the Netherlands. Methods: We estimated levels of particulate matter ≤ 10 µm in aerodynamic diameter (PM10) and nitrogen dioxide (NO2) at the home address for different periods during pregnancy using dispersion modeling techniques. Pro- and anti-angiogenic factors [placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1), respectively] were measured in first- and second-trimester maternal blood and in fetal cord blood samples at delivery. Pulsatility index of the uterine and umbilical arteries was measured by Doppler ultrasound in second and third trimester, and notching was assessed in third trimester. Placenta weight and birth weight were obtained from medical records. Results: Higher PM10 and NO2 exposure levels were associated with lower second-trimester maternal sFlt-1 and PlGF levels. PM10 and NO2 exposures averaged over total pregnancy were associated with higher sFlt-1 and lower PlGF levels in fetal cord blood, consistent with an anti-angiogenic state. PM10 and NO2 exposures were not consistently associated with second- or third-trimester placental resistance indices. NO2 exposure was associated with third-trimester notching (odds ratio 1.33; 95% CI: 0.99, 1.78 per 10-µg/m3 increase in the prior 2 months). PM10 and NO2 exposures were associated with lower placenta weight (–11.8 g; 95% CI: –20.9, –2.7, and –10.7 g; 95% CI: –19.0, –2.4, respectively, per 10-µg/m3 increase in the prior 2 months), but not with placenta to birth weight ratio. Conclusions: Our results suggest that maternal air pollution exposure may influence markers of placental growth and function. Future studies are needed to confirm these findings and explore the maternal and fetal consequences.

Association Studies Suggest a Key Role for Endothelin-1 in the Pathogenesis of Preeclampsia and the Accompanying Renin-Angiotensin-Aldosterone System Suppression

Women with preeclampsia display low renin–angiotensin–aldosterone system activity and a high antiangiogenic state, the latter characterized by high levels of soluble Fms-like tyrosine kinase (sFlt)-1 and reduced placental growth factor levels. To investigate whether renin–angiotensin–aldosterone system suppression in preeclampsia is because of this disturbed angiogenic balance, we measured mean arterial pressure, creatinine, endothelin-1 (ET-1), and renin–angiotensin–aldosterone system components in pregnant women with a high (≥85; n=38) or low (<85; n=65) soluble Fms-like tyrosine kinase-1/placental growth factor ratio. Plasma ET-1 levels were increased in women with a high ratio, whereas their plasma renin activity and plasma concentrations of renin, angiotensinogen, and aldosterone were decreased. Plasma renin activity–aldosterone relationships were identical in both the groups. Multiple regression analysis revealed that plasma renin concentration correlated independently with mean arterial pressure and plasma ET-1. Plasma ET-1 correlated positively with soluble Fms-like tyrosine kinase-1 and negatively with plasma renin concentration, and urinary protein correlated with plasma ET-1 and mean arterial pressure. Despite the lower plasma levels of renin and angiotensinogen in the high-ratio group, their urinary levels of these components were elevated. Correction for albumin revealed that this was because of increased glomerular filtration. Subcutaneous arteries obtained from patients with preeclampsia displayed an enhanced, AT2 receptor-mediated response to angiotensin II. In conclusion, a high antiangiogenic state associates with ET-1 activation, which together with the increased mean arterial pressure may underlie the parallel reductions in renin and aldosterone in preeclampsia. Because ET-1 also was a major determinant of urinary protein, our data reveal a key role for ET-1 in the pathogenesis of preeclampsia. Finally, the enhanced angiotensin responsiveness in preeclampsia involves constrictor AT2 receptors.

Genetic polymorphisms and multifactorial diseases: Facts and fallacies revealed by the glucocorticoid receptor gene

In recent years enormous progress in determining the sequence of the human genome has led to a rapid development of research into polymorphisms in genes involved in complex diseases. It is clear, however, that there are important limitations in many of these association studies. Problems with reliable and reproducible phenotyping, the number of individuals studied, racial heterogeneity, population stratification (founder effect), functionality and multiple testing often mean that studies are not reproducible. In this review we describe a number of the limitations related to this type of research; from both our own experience with studies on polymorphisms in the glucocorticoid receptor gene, and shortcomings and solutions from the literature.

Chronic air pollution exposure during pregnancy and maternal and fetal c-reactive protein levels: The generation R study

Background: Exposure to air pollution has been associated with higher C-reactive protein (CRP) levels, suggesting an inflammatory response. Not much is known about this association in pregnancy. Objectives: We investigated the associations of air pollution exposure during pregnancy with maternal and fetal CRP levels in a population-based cohort study in the Netherlands. Methods: Particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM10) and nitrogen dioxide (NO2) levels were estimated at the home address using dispersion modeling for different averaging periods preceding the blood sampling (1 week, 2 weeks, 4 weeks, and total pregnancy). High-sensitivity CRP levels were measured in maternal blood samples in early pregnancy (n = 5,067) and in fetal cord blood samples at birth (n = 4,450). Results: Compared with the lowest quartile, higher PM10 exposure levels for the prior 1 and 2 weeks were associated with elevated maternal CRP levels (> 8 mg/L) in the first trimester [fourth PM10 quartile for the prior week: odds ratio (OR), 1.32; 95% confidence interval (CI): 1.08, 1.61; third PM10 quartile for the prior 2 weeks: OR, 1.28; 95% CI: 1.06, 1.56]; however, no clear dose–response relationships were observed. PM10 and NO2 exposure levels for 1, 2, and 4 weeks preceding delivery were not consistently associated with fetal CRP levels at delivery. Higher long-term PM10 and NO2 exposure levels (total pregnancy) were associated with elevated fetal CRP levels (> 1 mg/L) at delivery (fourth quartile PM10: OR, 2.18; 95% CI: 1.08, 4.38; fourth quartile NO2: OR, 3.42; 95% CI: 1.36, 8.58; p-values for trend < 0.05). Conclusions: Our results suggest that exposure to air pollution during pregnancy may lead to maternal and fetal inflammatory responses.

C-reactive protein levels in early pregnancy, fetal growth patterns, and the risk for neonatal complications: the Generation R Study

OBJECTIVE We sought to examine the associations of maternal C-reactive protein (CRP) levels with fetal growth and the risks of neonatal complications. STUDY DESIGN CRP levels were measured in early pregnancy in 6016 women. Main outcome measures were fetal growth in each trimester and neonatal complications. RESULTS As compared to the reference group (CRP levels<5 mg/L), elevated maternal CRP levels (≥25 mg/L) were associated with lower estimated fetal weight in third trimester and lower weight at birth (differences: -29 g, 95% confidence interval [CI], -58 to 0 and -128 g, 95% CI, -195 to -60, respectively). Elevated maternal CRP levels were also associated with an increased risk of a small size for gestational age in the offspring (adjusted odds ratio, 2.94; 95% CI, 1.61-5.36). CONCLUSION Maternal CRP levels in early pregnancy are associated with fetal growth restriction and increased risks of neonatal complications.

Angiogenic and fibrinolytic factors in blood during the first half of pregnancy and adverse pregnancy outcomes.

OBJECTIVE: To estimate whether the imbalance of angiogenic factors (soluble fms-like tyrosine kinase-1, placental growth factor) and fibrinolytic factors (plasminogen activator inhibitor-2 [PAI-2]) might affect placentation in early pregnancy. METHODS: We studied the associations of maternal soluble fms-like tyrosine kinase-1, placental growth factor, and PAI-2 concentrations in the first trimester (before 18 weeks of gestation) and soluble fms-like tyrosine kinase-1 and placental growth factor concentrations in the second trimester (18–25 weeks of gestation) with placental function and adverse pregnancy outcomes. This study was embedded in a population-based prospective cohort study. Data were used from 7,519 women. Biomarker concentrations were divided into deciles and evaluated in multivariable linear and logistic regression models. RESULTS: First-trimester high soluble fms-like tyrosine kinase-1 was associated with a 5.2% lower uterine artery index in the second-trimester and a 1.6% higher birth weight (55 g, confidence interval [CI] 15–95). Neither in the first nor in the second trimester were soluble fms-like tyrosine kinase-1 concentrations significantly associated with preeclampsia. First-trimester low placental growth factor was associated with a 6.1% higher uterine artery index and a 3.4% lower birth weight (−115 g, CI −157 to −74). First-trimester low placental growth factor was associated with fetal growth restriction (odds ratio [OR] 2.62, CI 1.68–4.08) and preeclampsia (OR 2.46, CI 1.49–4.08). First-trimester low PAI-2 was associated with a 1.9% higher uterine artery index and a 2.7% lower birth weight (−94 g, CI −136 to −51). First-trimester low PAI-2 was associated with a higher risk of fetal growth restriction (OR 2.22, CI 1.39–3.55). CONCLUSION: First-half-of-pregnancy concentrations of soluble fms-like tyrosine kinase-1, placental growth factor, and PAI-2 are associated with uteroplacental vascular resistance, placental weight, and birth weight. Moreover, first-trimester placental growth factor and PAI-2 are associated with an increased risk of adverse pregnancy outcomes. LEVEL OF EVIDENCE: II

Major dietary patterns and blood pressure patterns during pregnancy: the Generation R Study

OBJECTIVE We sought to evaluate associations between dietary patterns and systolic blood pressure (SBP) and diastolic blood pressure during pregnancy. STUDY DESIGN This was a prospective study of 3187 pregnant women. Participants completed a food-frequency questionnaire in early pregnancy. The Mediterranean dietary pattern, comprising high intake of vegetables, vegetable oils, pasta, fish, and legumes, and the Traditional dietary pattern, comprising high intake of meat and potatoes, were identified using factor analysis. RESULTS A higher SBP was observed among mothers with high Traditional pattern adherence. Low adherence to the Mediterranean pattern was also associated with higher SBP but only in early and mid pregnancy. A higher diastolic blood pressure throughout pregnancy was observed in mothers with high adherence to the Traditional pattern and low adherence to the Mediterranean pattern. These effect estimates were most pronounced in mid pregnancy. CONCLUSION Low adherence to a Mediterranean and high adherence to a Traditional dietary pattern is associated with a higher blood pressure in pregnancy.