Article pubs.acs.org/jpr
Pregnancy-Induced Metabolic Phenotype Variations in Maternal Plasma Hemi Luan,*,†,‡,# Nan Meng,†,# Ping Liu,†,# Qiang Feng,† Shuhai Lin,‡ Jin Fu,† Robert Davidson,§ Xiaomin Chen,† Weiqiao Rao,† Fang Chen,† Hui Jiang,† Xun Xu,† Zongwei Cai,*,‡ and Jun Wang*,†,∥ †
BGI-Shenzhen, Building No.11, Beishan Industrial Zone, Yantian District, Shenzhen, China Department of Chemistry, Hong Kong Baptist University, 224 Waterloo Road, Kowloon Tong, Hong Kong, China § School of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K. ∥ Department of Biology, University of Copenhagen, Copenhagen DK-2200, Denmark ‡
S Supporting Information *
ABSTRACT: Metabolic variations occur during normal pregnancy to provide the growing fetus with a supply of nutrients required for its development and to ensure the health of the woman during gestation. Mass spectrometry-based metabolomics was employed to study the metabolic phenotype variations in the maternal plasma that are induced by pregnancy in each of its three trimesters. Nontargeted metabolomics analysis showed that pregnancy significantly altered the profile of metabolites in maternal plasma. The levels of six metabolites were found to change significantly throughout pregnancy, with related metabolic pathway variations observed in biopterin metabolism, phospholipid metabolism, amino acid derivatives, and fatty acid oxidation. In particular, there was a pronounced elevation of dihydrobiopterin (BH2), a compound produced in the synthesis of dopa, dopamine, norepinephrine, and epinephrine, in the second trimester, whereas it was markedly decreased in the third trimester. The turnover of BH2 and tryptophan catabolites indicated that the fluctuations of neurotransmitters throughout pregnancy might reveal the metabolic adaption in the maternal body for the growth of the fetus. Furthermore, 11 lipid classes and 41 carnitine species were also determined and this showed variations in the presence of longchain acylcarnitines and lysophospholipids in later pregnancy, suggesting changes of acylcarnitines and lysophospholipids to meet the energy demands in pregnant women. To our knowledge, this work is the first report of dynamic metabolic signatures and proposed related metabolic pathways in the maternal plasma for normal pregnancies and provided the basis for time-dependent metabolic trajectory against which disease-related disorders may be contrasted. KEYWORDS: pregnancy, metabolic phenotype, variations, metabolomics, maternal plasma
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INTRODUCTION During a normal and healthy pregnancy, substantial metabolic changes occur in the maternal body. In early pregnancy, the body may be considered to be in an anabolic state with an increased requirement for nutrients. These nutrients are stored in early gestation and will be used to meet the fetal and maternal demands of late gestation and lactation.1 Protein and nitrogen metabolism play extremely important roles in pregnancy and the development of the fetus. For conservation and accretion of nitrogen in mother and fetal bodies, the integral regulation of whole-body protein and nitrogen metabolism will be started early in gestation.2 The lower rate of urea synthesis and branched-chain amino acid transamination early in gestation may be related with pregnancyinduced resistance to insulin action, although the exact mechanism of these relations remains unclear.3 Insulin sensitivity remains normal or may increase during early pregnancy but decreases progressively during the later pregnancy. Any increased insulin resistance also results in © 2014 American Chemical Society
elevated insulin-mediated glucose and free fatty acid levels, allowing for greater substrate availability for fetal growth. Gradual changes in glucose metabolism over the course of pregnancy have been demonstrated by longitudinal studies in women with normal glucose tolerance.4 The elevation of plasma free fatty acids in early gestation inhibits total body glucose uptake and may also contribute to peripheral insulin resistance during later pregnancy. The reason for these changes in metabolic process is not well understood.5,6 Other reported key changes in prenatal metabolism have included steroid hormones, lactogen, cortisol, and gut microbiota.7−10 These metabolic changes of pregnancy directly influence the health conditions of the mother and the development of the fetus. Clinical monitoring of pregnancy often uses ultrasound testing and may be combined with chorionic villus sampling, amniocentesis, and cordocentesis as well as assays of specific Received: October 25, 2013 Published: January 22, 2014 1527
dx.doi.org/10.1021/pr401068k | J. Proteome Res. 2014, 13, 1527−1536
Journal of Proteome Research
Article
Table 1. The Characteristics of the Study Samplesa first trimester N age (years) BMI (kg/m2) GW (weeks)
second trimester
third trimester
T1
T2
T3
T4
T5
T6
30 32.53 ± 4.89 23.35 ± 5.89 11.85 ± 0.45
30 33.17 ± 5.31 23.34 ± 5.75 15.36 ± 0.92
30 29.60 ± 4.05 21.66 ± 2.98 18.65 ± 0.91
30 28.47 ± 4.69 22.26 ± 4.47 22.02 ± 0.99
30 30.90 ± 4.86 24.56 ± 4.21 25.74 ± 0.65
30 29.63 ± 5.31 27.17 ± 8.63b 31.15 ± 2.04
Values are presented as mean ± standard deviation. BMI, body mass index; GW, gestational weeks. bCalculated by Mann−Whitney test and indicated significant result between third trimester and others (less than 0.05).
a
study was provided by the Institutional Review Board of BGIShenzhen.
maternal plasma markers that are associated with increased risk of chromosomal disorders.11 A suitable method to characterize untargeted time course effects of healthy pregnancies on the metabolite compositions of maternal (e.g., urine, blood) and fetal (e.g., amniotic fluid, umbilical cord blood) biofluids is very critical to cover a wide range of diseases and congenital abnormalities. Metabolomics can be a powerful approach to investigate the low-molecular-weight metabolite profiles present in maternal fluids. Previously, there has been a focus on the study of diseases in pregnancy, including preeclampsia, gestational diabetes, and poor pregnancy outcome.12−15 Meanwhile, the metabolic trajectory for maternal urine from healthy pregnancies has only been evaluated by untargeted nuclear magnetic resonance (NMR) metabolomics and its usefulness has been demonstrated in disease-related deviations of pregnancies.16 The present study is, at least to our knowledge, the first report of using high performance liquid chromatography−mass spectrometry (HPLC−MS) to survey the effects of pregnancy on the metabolite profiles of maternal plasma during the first, second, and third trimester. Shotgun lipidomics and carnitine profiling based on the MS platform were also employed to describe metabolic phenotype variations of this group of compounds in maternal plasma during pregnancy.
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Nontargeted Metabolic Profiling Spectral Acquisition
The low-molecular-weight metabolites (
