Kathryn J. Gray

Integration of metabolomic and transcriptomic networks in pregnant women reveals biological pathways and predictive signatures associated with preeclampsia

IntroductionPreeclampsia is a leading cause of maternal and fetal mortality worldwide, yet its exact pathogenesis remains elusive.ObjectivesThis study, nested within the Vitamin D Antenatal Asthma Reduction Trial (VDAART), aimed to develop integrated omics models of preeclampsia that have utility in both prediction and in the elucidation of underlying biological mechanisms.MethodsMetabolomic profiling was performed on first trimester plasma samples of 47 pregnant women from VDAART who subsequently developed preeclampsia and 62 controls with healthy pregnancies, using liquid-chromatography tandem mass-spectrometry. Metabolomic profiles were generated based on logistic regression models and assessed using Received Operator Characteristic Curve analysis. These profiles were compared to profiles from generated using third trimester samples. The first trimester metabolite profile was then integrated with a pre-existing transcriptomic profile using network methods.ResultsIn total, 72 (0.9%) metabolite features were associated (p < 0.01) with preeclampsia after adjustment for maternal age, race, and gestational age. These features had moderate to good discriminatory ability; in ROC curve analyses a summary score based on these features displayed an area under the curve (AUC) of 0.794 (95%CI 0.700, 0.888). This profile retained the ability to distinguish preeclamptic from healthy pregnancies in the third trimester [AUC: 0.762 (95% CI 0.663, 0.860)]. Additionally, metabolite set enrichment analysis identified common pathways, including glycerophospholipid metabolism, at the two time-points. Integration with the transcriptomic signature refined these results suggesting a particular role for lipid imbalance, immune function and the circulatory system.ConclusionsThese findings suggest it is possible to develop a predictive metabolomic profile of preeclampsia. This profile is characterized by changes in lipid and amino acid metabolism and dysregulation of immune response and can be refined through interaction with transcriptomic data. However validation in larger and more diverse populations is required.

Management of a Woman With Maple Syrup Urine Disease During Pregnancy, Delivery, and Lactation

Maple syrup urine disease (MSUD) is an inherited disorder of metabolism of the branched-chain amino acids leucine, isoleucine, and valine. Complications of acute elevation in plasma leucine include ketoacidosis and risk of cerebral edema, which can be fatal. Individuals with MSUD are at risk of metabolic crisis throughout life, especially at times of physiological stress. We present a case of successful management of a woman with MSUD through pregnancy, delivery, postpartum, and lactation, including nutrition therapy using modified parenteral nutrition.

Applications of metabolomics in the study and management of preeclampsia: a review of the literature

IntroductionPreeclampsia represents a major public health burden worldwide, but predictive and diagnostic biomarkers are lacking. Metabolomics is emerging as a valuable approach to generating novel biomarkers whilst increasing the mechanistic understanding of this complex condition.ObjectivesTo summarize the published literature on the use of metabolomics as a tool to study preeclampsia.MethodsPubMed and Web of Science were searched for articles that performed metabolomic profiling of human biosamples using either Mass-spectrometry or Nuclear Magnetic Resonance based approaches and which included preeclampsia as a primary endpoint.ResultsTwenty-eight studies investigating the metabolome of preeclampsia in a variety of biospecimens were identified. Individual metabolite and metabolite profiles were reported to have discriminatory ability to distinguish preeclamptic from normal pregnancies, both prior to and post diagnosis. Lipids and carnitines were among the most commonly reported metabolites. Further work and validation studies are required to demonstrate the utility of such metabolites as preeclampsia biomarkers.ConclusionMetabolomic-based biomarkers of preeclampsia have yet to be integrated into routine clinical practice. However, metabolomic profiling is becoming increasingly popular in the study of preeclampsia and is likely to be a valuable tool to better understand the pathophysiology of this disorder and to better classify its subtypes, particularly when integrated with other omic data.

Have we done our last amniocentesis? Updates on cell-free DNA for Down syndrome screening

Prenatal aneuploidy screening changed significantly in 2012 when cell-free fetal deoxyribonucleic acid (DNA) was introduced as a noninvasive prenatal test. A noninvasive prenatal test detects cell free fragments of fetal DNA from the placenta circulating in maternal blood that coexist with cell-free DNA (cfDNA) of maternal origin. Using next-generation sequencing, the noninvasive prenatal test compares maternal and fetal cfDNA ratios for chromosomes of interest (i.e., 21, 18, 13, X, and Y) to assess chromosomal aneuploidy. Compared to traditional screening using ultrasound and serum markers, the noninvasive prenatal test has superior test characteristics, including a higher detection rate and positive predictive value, and a lower false-positive rate. The noninvasive prenatal test is already used for primary screening in high-risk women and is rapidly expanding to all women. Given its increasing use, understanding the noninvasive prenatal test’s limitations is critical. Discordant results (i.e. noninvasive prenatal test is positive for aneuploidy with a normal fetal karyotype) can occur because of biological processes such as aneuploidy confined to the placenta, a vanished twin, maternal aneuploidy or maternal cancer. Use of the noninvasive prenatal test for screening beyond the most common aneuploidies is not recommended. The noninvasive prenatal test is a major advance in prenatal aneuploidy screening but it is not diagnostic and does not replace invasive testing (i.e. chorionic villous sampling or amniocentesis) for confirmation of fetal chromosomal disorders.

Placental Complications Associated With Psychostimulant Use in Pregnancy

OBJECTIVE To evaluate whether psychostimulants used to treat attention-deficit/hyperactivity disorder (ADHD) are associated with risk of adverse placental-associated pregnancy outcomes including preeclampsia, placental abruption, growth restriction, and preterm birth. METHODS We designed a population-based cohort study in which we examined a cohort of pregnant women and their liveborn neonates enrolled in Medicaid from 2000 to 2010. Women who received amphetamine-dextroamphetamine or methylphenidate monotherapy in the first half of pregnancy were compared with unexposed women. We considered atomoxetine, a nonstimulant ADHD medication, as a negative control exposure. To assess whether the risk period extended to the latter half of pregnancy, women who continued stimulant monotherapy after 20 weeks of gestation were compared with those who discontinued. Risk ratios and 95% CIs were estimated with propensity score stratification to control for confounders. RESULTS Pregnancies exposed to amphetamine-dextroamphetamine (n=3,331), methylphenidate (n=1,515), and atomoxetine (n=453) monotherapy in early pregnancy were compared with 1,461,493 unexposed pregnancies. Among unexposed women, the risks of the outcomes were 3.7% for preeclampsia, 1.4% for placental abruption, 2.9% for small for gestational age, and 11.2% for preterm birth. The adjusted risk ratio for stimulant use was 1.29 for preeclampsia (95% CI 1.11-1.49), 1.13 for placental abruption (0.88-1.44), 0.91 for small for gestational age (0.77-1.07), and 1.06 for preterm birth (0.97-1.16). Compared with discontinuation (n=3,527), the adjusted risk ratio for continuation of stimulant use in the latter half of pregnancy (n=1,319) was 1.26 for preeclampsia (0.94-1.67), 1.08 for placental abruption (0.67-1.74), 1.37 for small for gestational age (0.97-1.93), and 1.30 for preterm birth (1.10-1.55). Atomoxetine was not associated with the outcomes studied. CONCLUSION Psychostimulant use during pregnancy was associated with a small increased relative risk of preeclampsia and preterm birth. The absolute increases in risks are small and, thus, women with significant ADHD should not be counseled to suspend their ADHD treatment based on these findings.

Pregnancy outcomes in inherited bone marrow failure syndromes

To the editor: Inherited bone marrow failure syndromes include entities such as Fanconi anemia, Diamond-Blackfan anemia, Shwachman-Diamond syndrome, severe congenital neutropenia, and telomere biology disorders/dyskeratosis congenita (TBDs/DKC). These are potentially devastating conditions that

Genetic predisposition to preeclampsia is conferred by fetal DNA variants near FLT1 , a gene involved in the regulation of angiogenesis

Preeclampsia risk is influenced by both the mothers genetic background and the genetics of her fetus; however, the specific genes responsible for conferring preeclampsia risk have largely remained elusive. Evidence that preeclampsia has a genetic predisposition was first detailed in the early 1960s, and overall preeclampsia heritability is estimated at ∼55%. Many traditional gene discovery approaches have been used to investigate the specific genes that contribute to preeclampsia risk, but these have largely not been successful or reproducible. Over the past decade, genome-wide association studies have allowed for significant advances in the understanding of the genetic basis of many common diseases. Genome-wide association studies are predicated on the idea that the genetic basis of many common diseases are complex and polygenic with many variants, each with modest effects that contribute to disease risk. Using this approach in preeclampsia, a large genome-wide association study recently identified and replicated the first robust fetal genomic region associated with excess risk. A screen of >7 million genetic variants in 2658 offspring from preeclamptic women and 308,292 population controls identified a single association signal close to the Fms-like tyrosine kinase 1 gene, on chromosome 13. Fms-like tyrosine kinase 1 encodes soluble Fms-like tyrosine kinase 1, a splice variant of the vascular endothelial growth factor receptor that exerts antiangiogenic activity by inhibiting signaling of proangiogenic factors. The Fms-like tyrosine kinase 1 pathway is central in preeclampsia pathogenesis because excess circulating soluble Fms-like tyrosine kinase 1 in the maternal plasma leads to the hallmark clinical features of preeclampsia, including hypertension and proteinuria. The success of this landmark fetal preeclampsia genome-wide association study suggests that well-powered, larger maternal and fetal genome-wide association study will be fruitful in identifying additional common variants that implicate causal preeclampsia genes and pathways. Such efforts will rely on the continued development of large preeclampsia consortia focused on preeclampsia genetics to obtain adequate sample sizes, detailed clinical phenotyping, and matched maternal-fetal samples. In summary, the fetal preeclampsia genome-wide association study represents an exciting advance in preeclampsia biology, suggesting that dysregulation at the Fms-like tyrosine kinase 1 locus in the fetal genome (likely in the placenta) is a fundamental molecular defect in preeclampsia.

Anticonvulsants and the risk of perinatal bleeding complications: A pregnancy cohort study

Objective To examine the risk of postpartum hemorrhage (PPH) and neonatal bleeding complications associated with late-pregnancy exposure to anticonvulsant drugs (ACDs) that induce cytochrome P450 enzymes (ACDi) and alter the metabolism of vitamin K compared to other ACDs. Methods We used a population-based cohort study stemming from a nationwide sample of publicly insured pregnant women with a liveborn infant from the 2000 to 2010 Medicaid Analytic eXtract. ACDi (carbamazepine, phenobarbital, phenytoin, oxcarbazepine, topiramate) were compared to other ACDs dispensed during the last month of pregnancy. Relative risks (RRs) and 95% confidence intervals (CIs) of PPH and neonatal bleeding complications were estimated using generalized linear models with fine stratification on the propensity score to control for indication and other potential confounders. Results Among 11,572 women with an ACD prescription overlapping delivery, 2.6% (135/5,109) in the ACDi group and 3.6% (231/6,463) in the other ACDs group had a diagnosis of PPH: unadjusted RR 0.74 (95% CI 0.60–0.91), adjusted RR 0.77 (95% CI 0.58–1.00). The prevalence of neonatal bleeding complications was 3.1% (157/5,109) in the ACDi group and 3.5% (229/6,463) in the other ACDs group: unadjusted RR 0.87 (95% CI 0.71–1.06), adjusted RR 0.83 (95% CI 0.64–1.08). Conclusions Evidence from this large observational study suggests that use of ACDi near delivery does not increase the risk of bleeding complications compared to other ACDs in clinical settings where neonatal intramuscular or oral vitamin K administration is considered standard of care. These findings provide reassurance for clinicians and pregnant women successfully treated with ACDi.

Gene-Centric Analysis of Preeclampsia Identifies Maternal Association at PLEKHG1Novelty and Significance

The genetic susceptibility to preeclampsia, a pregnancy-specific complication with significant maternal and fetal morbidity, has been poorly characterized. To identify maternal genes associated with preeclampsia risk, we assembled 498 cases and 1864 controls of European ancestry from preeclampsia case-control collections in 5 different US sites (with additional matched population controls), genotyped samples on a cardiovascular gene-centric array composed of variants from ≈2000 genes selected based on prior genetic studies of cardiovascular and metabolic diseases and performed case-control genetic association analysis on 27 429 variants passing quality control. In silico replication testing of 9 lead signals with P<10−4 was performed in independent European samples from the SOPHIA (Study of Pregnancy Hypertension in Iowa) and Inova cohorts (212 cases, 456 controls). Multiethnic assessment of lead signals was then performed in samples of black (26 cases, 136 controls), Hispanic (132 cases, 468 controls), and East Asian (9 cases, 80 controls) ancestry. Multiethnic meta-analysis (877 cases, 3004 controls) revealed a study-wide statistically significant association of the rs9478812 variant in the pleiotropic PLEKHG1 gene (odds ratio, 1.40 [1.23–1.60]; Pmeta=5.90×10−7). The rs9478812 effect was even stronger in the subset of European cases with known early-onset preeclampsia (236 cases diagnosed <37 weeks, 1864 controls; odds ratio, 1.59 [1.27–1.98]; P=4.01×10−5). PLEKHG1 variants have previously been implicated in genome-wide association studies of blood pressure, body weight, and neurological disorders. Although larger studies are required to further define maternal preeclampsia heritability, this study identifies a novel maternal risk locus for further investigation.

AP39, a modulator of mitochondrial bioenergetics, reduces anti-angiogenic response and oxidative stress in hypoxia-exposed trophoblasts: relevance for preeclampsia pathogenesis

Although the cause of preeclampsia, a pregnancy complication with significant maternal and neonatal morbidity, has not been fully characterized, placental ischemia attributable to impaired spiral artery remodeling and abnormal secretion of antiangiogenic factors are thought to be important in the pathogenesis of the disease. Placental ischemia could impair trophoblast mitochondrial function and energy production, leading to the release of reactive oxygen species (ROS). ROS have been shown to stabilize hypoxia-inducible factor (HIF)-1α, which, in turn, may induce transcription of antiangiogenic factors, soluble fms-like tyrosine kinase 1 (sFLT1), and soluble endoglin in trophoblasts. Herein, we tested whether the angiogenic imbalance and oxidative stress in the preeclamptic placenta may be prevented by improving mitochondrial function. First, to evaluate the cause-effect relationship between mitochondrial function and sFLT1 production, a human trophoblast primary cell culture model was established in which hypoxia induced mitochondrial ROS production and concurrent sFLT1 increase. Second, treatment with AP39, a novel mitochondria-targeted hydrogen sulfide donor, prevented ROS production, reduced HIF-1α protein levels, and diminished sFLT1 production. Finally, AP39, a modulator of mitochondrial bioenergetics enhanced cytochrome c oxidase activity, reversed oxidative stress and antiangiogenic response in hypoxic trophoblasts. These results suggest that placental hypoxia induces ROS production, HIF-1α stabilization, and sFLT1 up-regulation; these pathophysiological alterations can be attenuated by mitochondrial-targeted antioxidants.