Metabolomic profiling of serum and tongue coating of pregnant women with intrahepatic cholestasis in pregnancy.

Intrahepatic cholestasis of pregnancy (ICP) is associated with an increased risk of cesarean section and adverse fetal outcomes. Currently, ICP diagnosis depends largely on serum levels of bile acids and lacks sensitivity and specificity for accurate diagnosis. Tongue diagnosis is an important diagnostic tool in traditional Chinese medicine (TCM) and is used in our clinic as complementary treatment and personalized medicine for ICP. However, the molecular basis of the manifestation of greasy white tongue coatings in ICP remains unknown. In this study, we performed untargeted metabolomic profiling of the serum, tongue coating, and saliva of 66 pregnant women, including 22 with ICP. The metabolomic profiles of the serum and tongue coatings showed marked differences between the two clinical groups. Forty-six differentially abundant metabolites were identified, and their relative concentrations correlated with total bile acid levels. These differential metabolites included bile acids, lipids, microbiota- and diet-related metabolites, and exposomes. Conventional biochemical markers, including serum aminotransferases and bilirubin, were not significantly increased in the ICP group, whereas the total cholesterol and triglyceride levels were significantly increased as early as the first trimester. Our data provide insights into the pathophysiology of ICP and implicate the gut-liver axis and environmental exposure. Tongue coating has the potential to be a non-invasive diagnostic approach. Further studies are required to validate the clinical utility of these findings.

A Novel Approach to Characterize the Lipidome of Marine Archaeon Nitrosopumilus maritimus by Ion Mobility Mass Spectrometry.

Archaea are differentiated from the other two domains of life by their biomolecular characteristics. One such characteristic is the unique structure and composition of their lipids. Characterization of the whole set of lipids in a biological system (the lipidome) remains technologically challenging. This is because the lipidome is innately complex, and not all lipid species are extractable, separable, or ionizable by a single analytical method. Furthermore, lipids are structurally and chemically diverse. Many lipids are isobaric or isomeric and often indistinguishable by the measurement of mass or even their fragmentation spectra. Here we developed a novel analytical protocol based on liquid chromatography ion mobility mass spectrometry to enhance the coverage of the lipidome and characterize the conformations of archaeal lipids by their collision cross-sections (CCSs). The measurements of ion mobility revealed the gas-phase ion chemistry of representative archaeal lipids and provided further insights into their attributions to the adaptability of archaea to environmental stresses. A comprehensive characterization of the lipidome of mesophilic marine thaumarchaeon, Nitrosopumilus maritimus (strain SCM1) revealed potentially an unreported phosphate- and sulfate-containing lipid candidate by negative ionization analysis. It was the first time that experimentally derived CCS values of archaeal lipids were reported. Discrimination of crenarchaeol and its proposed stereoisomer was, however, not achieved with the resolving power of the SYNAPT G2 ion mobility system, and a high-resolution ion mobility system may be required for future work. Structural and spectral libraries of archaeal lipids were constructed in non-vendor-specific formats and are being made available to the community to promote research of Archaea by lipidomics.

Characterization of the Exometabolome of Nitrosopumilus maritimus SCM1 by Liquid Chromatography-Ion Mobility Mass Spectrometry.

Marine Thaumarchaeota (formerly known as the marine group I archaea) have received much research interest in recent years since these chemolithoautotrophic organisms are abundant in the subsurface ocean and oxidize ammonium to nitrite, which makes them a major contributor to the marine carbon and nitrogen cycles. However, few studies have investigated the chemical composition of their exometabolome and their contributions to the pool of dissolved organic matter (DOM) in seawater. This study exploits the recent advances in ion mobility mass spectrometry (IM-MS) and integrates this instrumental capability with bioinformatics to reassess the exometabolome of a model ammonia-oxidizing archaeon, Nitrosopumilus maritimus strain SCM1. Our method has several advantages over the conventional approach using an Orbitrap or ion cyclotron resonance mass analyzer and allows assignments or annotations of spectral features to known metabolites confidently and indiscriminately, as well as distinction of biological molecules from background organics. Consistent with the results of a previous report, the SPE-extracted exometabolome of N. maritimus is dominated by biologically active nitrogen-containing metabolites, in addition to peptides secreted extracellularly. Cobalamin and associated intermediates, including α-ribazole and α-ribazole 5'-phosphate, are major components of the SPE-extracted exometabolome of N. maritimus. This supports the proposition that Thaumarchaeota have the capacity of de novo biosynthesizing cobalamin. Other biologically significant metabolites, such as agmatidine and medicagenate, predicted by genome screening are also detected, which indicates that Thaumarchaeota have remarkable metabolic potentials, underlining their importance in driving elemental cycles critical to biological processes in the ocean.

Metabolomics in gestational diabetes.

Gestational diabetes mellitus (GDM) is a form of diabetes that is first diagnosed during pregnancy in the absence of existing type 1 or type 2 diabetes. Early screening tools for GDM are currently unavailable, but metabolomics is a promising approach for detecting biomarkers of GDM. This review evaluates recent GDM studies employing metabolomic techniques, highlighting the challenges in those studies and envisions the future directions for metabolomic study of GDM. A diverse range of predictive markers and dysregulated metabolic pathways have been associated with the pathogenesis of GDM, but these findings have lacked reproducibility among studies. The case-control study design has been most frequently employed in the studies of GDM, and most of them used specimens acquired in mid-pregnancy. However, this approach might not be adequate to recognise the complexity of the condition. The sample size in some of the studies is limited, and this may result in findings from a participant set that is not representative of the general population. Therefore, we propose that future metabolomic studies pertaining to GDM use a cross-platform approach employing unified diagnostic criteria, a longitudinal cohort, and innovative data processing methods to allow for full-scale identification and comprehensive coverage of the metabolome. In addition, the relationship between the exposure to environmental chemicals such as endocrine disruptors and the development of GDM should be further investigated in future studies.

Analytical challenges of untargeted GC-MS-based metabolomics and the critical issues in selecting the data processing strategy.

Background: A challenge of metabolomics is data processing the enormous amount of information generated by sophisticated analytical techniques. The raw data of an untargeted metabolomic experiment are composited with unwanted biological and technical variations that confound the biological variations of interest. The art of data normalisation to offset these variations and/or eliminate experimental or biological biases has made significant progress recently. However, published comparative studies are often biased or have omissions. Methods: We investigated the issues with our own data set, using five different representative methods of internal standard-based, model-based, and pooled quality control-based approaches, and examined the performance of these methods against each other in an epidemiological study of gestational diabetes using plasma. Results: Our results demonstrated that the quality control-based approaches gave the highest data precision in all methods tested, and would be the method of choice for controlled experimental conditions. But for our epidemiological study, the model-based approaches were able to classify the clinical groups more effectively than the quality control-based approaches because of their ability to minimise not only technical variations, but also biological biases from the raw data. Conclusions: We suggest that metabolomic researchers should optimise and justify the method they have chosen for their experimental condition in order to obtain an optimal biological outcome.

Tryptophan and purine metabolites are consistently upregulated in the urinary metabolome of patients diagnosed with gestational diabetes mellitus throughout pregnancy: A longitudinal metabolomics study of Chinese pregnant women part 2.

BACKGROUND: Gestational diabetes mellitus (GDM) is a pathological state of glucose intolerance associated with adverse pregnancy outcomes and an increased risk of developing maternal type 2 diabetes later in life. The mechanisms underlying GDM development are not fully understood. We examined the pathophysiology of GDM through comprehensive metabolic profiling of maternal urine, using participants from a longitudinal cohort of normal pregnancies and pregnancies complicated by GDM. METHODS: Based on ultra-performance liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry, an untargeted metabolomics study was performed to explore the differences in the urinary metabolome of GDM cases and healthy controls over the course of pregnancy. Multilevel statistical approaches were employed to address the complex metabolomic data obtained from a longitudinal cohort. RESULTS: The results indicated that tryptophan and purine metabolism was associated with GDM. The tryptophan-kynurenine pathway was activated in the GDM subjects before placental hormones or the fetoplacental unit could have produced any physiological effect. Hypoxanthine, xanthine, xanthosine, and 1-methylhypoxanthine were all elevated in the urine metabolome of subjects with GDM. Catabolism of purine nucleosides leads ultimately to the production of uric acid, which discriminated the subjects with GDM from controls. CONCLUSIONS: The results support the notion that GDM may be a predisposed condition, or prediabetic state, which is manifested during pregnancy. This challenges the conventional view of the pathogenesis of GDM, which assumes placental hormones are the major causes of insulin resistance in GDM.

The pathogenesis and pathophysiology of gestational diabetes mellitus: Deductions from a three-part longitudinal metabolomics study in China.

Gestational diabetes mellitus (GDM) is a form of diabetes that is first recognised during pregnancy, with no evidence of pre-existing type 1 or type 2 diabetes. The prevalence of GDM has been rising steadily over the past few decades, coinciding with the ongoing epidemic of obesity and type 2 diabetes. Although GDM normally disappears after delivery, women who have been previously diagnosed with GDM are at a greater risk of developing gestational diabetes in subsequent pregnancies, and type 2 diabetes later in life. Infants born to mothers with GDM also have a higher risk of developing type 2 diabetes in their teens or early adulthood. There are many possible causes of insulin resistance, and multiple metabolic aberrants are known to be involved in the development of different forms of diabetes. Increasing evidence suggests that different forms of diabetes share common pathogenesis and pathophysiological dysregulation resulting from a progressive ß-cell demise or dysfunction. The outcome manifests clinically as hyperglycaemia. The development of GDM may represent a very early stage of the progression to type 2 diabetes that is being manifested under the stresses of pregnancy. However, the exact mechanisms of GDM development are not clearly understood. Based on the results of a three-part longitudinal metabolomics study of Chinese pregnant women, in combination with the current literature, a new model of GDM development is proposed to outline the biomolecular mechanisms underpinning GDM. A possible cause of GDM is obesity, which is an important clinical risk factor for the development of diabetes. Women who develop GDM generally have higher body mass indices when compared with healthy pregnant women, and obesity can induce low-grade inflammation. Chronic low-grade inflammation induces the synthesis of xanthurenic acid, which is known to be associated with the development of type 2 diabetes, pre-diabetes and GDM. Hyperglycaemia accelerates purine nucleotide synthesis, which in turn stimulates nucleotide breakdown and increases the concentration of nucleotide degradation products, including superoxide molecules and uric acid. Reactive oxygen species and excessive intracellular uric acid may also have direct effects on the development of the disease or further deterioration of the condition.

Unsaturated plasma phospholipids are consistently lower in the patients diagnosed with gestational diabetes mellitus throughout pregnancy: A longitudinal metabolomics study of Chinese pregnant women part 1.

BACKGROUND: Gestational diabetes mellitus (GDM) is a milder degree of hyperglycaemia diagnosed during pregnancy that can lead to serious, long-term consequences for both mother and foetus. The pathophysiology of GDM is not fully understood. The number of pregnant women diagnosed with GDM has been steadily increasing, but effective screening tools for early risk stratification are still missing. The emerging field of metabolomics has the potential to provide new insights and as a result is increasingly being used in studies of GDM. However, no study to date has investigated the longitudinal changes associated with GDM as pregnancy progresses. We investigated maternal plasma of a longitudinal cohort of normal pregnancies and pregnancies complicated by GDM. METHODS: Based on ultra-performance hydrophilic interaction liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry, an untargeted metabolomics study was performed to explore the changes in the plasma metabolome of GDM cases and healthy controls. Innovative sample preparation and multilevel statistical methods were employed to enhance our ability to analyse the longitudinal plasma samples by LC-MS. RESULTS: A number of polyunsaturated or chemically modified phospholipids were significantly lower in the plasma of pregnant women that developed GDM when compared to healthy controls, while no difference was observed for the saturated phospholipids. The reduction of these lipid species in the participants that developed GDM could be detected as early in the first trimester and the changes were independent of the stage of gestation and the steroid hormones in the plasma. CONCLUSIONS: These differences observed in our study were detected well before the onset of GDM, and might provide further insights into the etiology or pathophysiology of GDM.

Mass spectrometry-based proteomics for pre-eclampsia and preterm birth.

Pregnancy-related complications such as pre-eclampsia and preterm birth now represent a notable burden of adverse health. Pre-eclampsia is a hypertensive disorder unique to pregnancy. It is an important cause of maternal death worldwide and a leading cause of fetal growth restriction and iatrogenic prematurity. Fifteen million infants are born preterm each year globally, but more than one million of those do not survive their first month of life. Currently there are no predictive tests available for diagnosis of these pregnancy-related complications and the biological mechanisms of the diseases have not been fully elucidated. Mass spectrometry-based proteomics have all the necessary attributes to provide the needed breakthrough in understanding the pathophysiology of complex human diseases thorough the discovery of biomarkers. The mass spectrometry methodologies employed in the studies for pregnancy-related complications are evaluated in this article. Top-down proteomic and peptidomic profiling by laser mass spectrometry, liquid chromatography or capillary electrophoresis coupled to mass spectrometry, and bottom-up quantitative proteomics and targeted proteomics by liquid chromatography mass spectrometry have been applied to elucidate protein biomarkers and biological mechanism of pregnancy-related complications. The proteomes of serum, urine, amniotic fluid, cervical-vaginal fluid, placental tissue, and cytotrophoblastic cells have all been investigated. Numerous biomarkers or biomarker candidates that could distinguish complicated pregnancies from healthy controls have been proposed. Nevertheless, questions as to the clinically utility and the capacity to elucidate the pathogenesis of the pre-eclampsia and preterm birth remain to be answered.