Untargeted metabolomic analysis and pathway discovery in perinatal asphyxia and hypoxic-ischaemic encephalopathy

Serum metabolism alteration behind different etiology, diagnosis, and prognosis of disorders of consciousness

BACKGROUND

Patients with disorders of consciousness (DoC) exhibit varied revival outcomes based on different etiologies and diagnoses, the mechanisms of which remain largely unknown. The fluctuating clinical presentations in DoC pose challenges in accurately assessing consciousness levels and prognoses, often leading to misdiagnoses. There is an urgent need for a deeper understanding of the physiological changes in DoC and the development of objective diagnostic and prognostic biomarkers to improve treatment guidance.

METHODS

To explore biomarkers and understand the biological processes, we conducted a comprehensive untargeted metabolomic analysis on serum samples from 48 patients with DoC. Patients were categorized based on etiology (TBI vs. non-TBI), CRS-R scores, and prognosis. Advanced analytical techniques, including PCA and OPLS-DA models, were employed to identify differential metabolites.

RESULTS

Our analysis revealed a distinct separation in metabolomic profiles among the different groups. The primary differential metabolites distinguishing patients with varying etiologies were predominantly phospholipids, with a notable decrease in glycerophospholipids observed in the TBI group. Patients with higher CRS-R scores exhibited a pattern of impaired carbohydrate metabolism coupled with enhanced lipid metabolism. Notably, serum concentrations of both LysoPE and PE were reduced in patients with improved outcomes, suggesting their potential as prognostic biomarkers.

CONCLUSIONS

Our study underscores the critical role of phospholipid metabolism in the brain's metabolic alterations in patients with DoC. It identifies key biomarkers for diagnosis and prognosis, offering insights that could lead to novel therapeutic targets. These findings highlight the value of metabolomic profiling in understanding and potentially treating DoC.

In situ analysis of metabolic changes under hypoxic-ischemic encephalopathy via MALDI mass spectrometry imaging

Hypoxic-ischemic encephalopathy (HIE) is a leading cause of neurological disability and even more serious fetal or neonatal asphyxia death. As the therapeutic time window is limited and timely intervention could have a better prognosis, elucidating the mechanisms underlying HIE and developing novel therapeutic strategies is of great importance. In the present study, 1, 5-Diaminonaphthalene hydrochloride (1, 5-DANHCl) assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) was applied to the neonatal rat model of HIE to investigate metabolic changes during hypoxic-ischemic period. Seventy-three metabolites involved in various metabolic pathways such as glycolysis, tricarboxylic acid (TCA) cycle, nucleoside metabolism, lipid metabolism, oxidative stress and ionic homeostasis demonstrated significant changes. It is worth mentioning that we have detected neutral triglycerides (TGs) that are difficult to ionize and observed their accumulation in the ischemic region, which has been rarely reported in previous studies. The results not only help us discover biomarkers but also provide new insights into its mechanism for us to understand the pathological and physiological processes of the disease.

Differential Effects of Hypothermia and SZR72 on Cerebral Kynurenine and Kynurenic Acid in a Piglet Model of Hypoxic-Ischemic Encephalopathy

Kynurenic acid (KYNA), an endogenous neuroprotectant with antiexcitotoxic, antioxidant, and anti-inflammatory effects, is synthesized through the tryptophan-kynurenine (KYN) pathway. We investigated whether brain KYN or KYNA levels were affected by asphyxia in a translational piglet model of hypoxic-ischemic encephalopathy (HIE). We also studied brain levels of the putative blood-brain barrier (BBB) permeable neuroprotective KYNA analogue SZR72, and whether SZR72 or therapeutic hypothermia (TH) modified KYN or KYNA levels. KYN, KYNA, and SZR72 levels were determined using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry in five brain regions 24 h after 20 min of asphyxia in vehicle-, SZR72- and TH-treated newborn piglets (n = 6-6-6) and naive controls (n = 4). Endogenous brain KYN levels (median range 311.2-965.6 pmol/g) exceeded KYNA concentrations (4.5-6.0 pmol/g) ~100-fold. Asphyxia significantly increased cerebral KYN and KYNA levels in all regions (1512.0-3273.9 and 16.9-21.2 pmol/g, respectively), increasing the KYN/Tryptophan-, but retaining the KYNA/KYN ratio. SZR72 treatment resulted in very high cerebral SZR72 levels (13.2-33.2 nmol/g); however, KYN and KYNA levels remained similar to those of the vehicle-treated animals. However, TH virtually ameliorated asphyxia-induced elevations in brain KYN and KYNA levels. The present study reports for the first time that the KYN pathway is altered during HIE development in the piglet. SZR72 readily crosses the BBB in piglets but fails to affect cerebral KYNA levels. Beneficial effects of TH may include restoration of the tryptophan metabolism to pre-asphyxia levels.

Preservation of Biomarkers Associated with Alzheimer's Disease (Amyloid Peptides 1-38, 1-40, 1-42, Tau Protein, Beclin 1) in the Blood of Neonates after Perinatal Asphyxia

Perinatal asphyxia is a complex disease involving massive death of brain cells in full-term newborns. The most impressive consequence of perinatal asphyxia is a neurodegenerative brain injury called hypoxic-ischemic encephalopathy. Management of newborns after perinatal asphyxia is very difficult due to the lack of measurable biomarkers that would be able to assess the severity of the brain injury in the future, help in the selection of therapy, assess the results of treatment and determine the prognosis for the future. Thus, these limitations make long-term neurodevelopmental outcomes unpredictable during life. Quantifying biomarkers that can detect subclinical changes at a stage where routine brain monitoring or imaging is still mute would be a major advance in the care of neonates with brain neurodegeneration after asphyxia. Understanding the effect of perinatal asphyxia on changes in blood neurodegenerative biomarkers over time, which would be commonly used to assess the severity of postpartum encephalopathy, would be an important step in developing precision in predicting the consequences of brain injuries. We urgently need more accurate early predictive markers to guide clinicians when to use neuroprotective therapy. The needed neurodegenerative biomarkers may represent neuronal pathological changes that can be recognized by new technologies such as genomic and proteomic. Nevertheless, the simultaneous blood tau protein and various amyloid changes with the addition of an autophagy marker beclin 1 after perinatal asphyxia have not been studied. We decided to evaluate serum biomarkers of neuronal injury characteristic for Alzheimer's disease such as amyloid peptides (1-38, 1-40 and 1-42), tau protein and beclin 1, which can predict the progression of brain neurodegeneration in future. In this paper, we report for the first time the significant changes in the above molecules in the blood after asphyxia compared to healthy controls during the 1-7, 8-14 and 15+ days ELISA test.

Advances in Ultra-High-Resolution Mass Spectrometry for Pharmaceutical Analysis

Pharmaceutical analysis refers to an area of analytical chemistry that deals with active compounds either by themselves (drug substance) or when formulated with excipients (drug product). In a less simplistic way, it can be defined as a complex science involving various disciplines, e.g., drug development, pharmacokinetics, drug metabolism, tissue distribution studies, and environmental contamination analyses. As such, the pharmaceutical analysis covers drug development to its impact on health and the environment. Moreover, due to the need for safe and effective medications, the pharmaceutical industry is one of the most heavily regulated sectors of the global economy. For this reason, powerful analytical instrumentation and efficient methods are required. In the last decades, mass spectrometry has been increasingly used in pharmaceutical analysis both for research aims and routine quality controls. Among different instrumental setups, ultra-high-resolution mass spectrometry with Fourier transform instruments, i.e., Fourier transform ion cyclotron resonance (FTICR) and Orbitrap, gives access to valuable molecular information for pharmaceutical analysis. In fact, thanks to their high resolving power, mass accuracy, and dynamic range, reliable molecular formula assignments or trace analysis in complex mixtures can be obtained. This review summarizes the principles of the two main types of Fourier transform mass spectrometers, and it highlights applications, developments, and future perspectives in pharmaceutical analysis.

The Oxygen Cascade from Atmosphere to Mitochondria as a Tool to Understand the (Mal)adaptation to Hypoxia

Hypoxia is a life-threatening challenge for about 1% of the world population, as well as a contributor to high morbidity and mortality scores in patients affected by various cardiopulmonary, hematological, and circulatory diseases. However, the adaptation to hypoxia represents a failure for a relevant portion of the cases as the pathways of potential adaptation often conflict with well-being and generate diseases that in certain areas of the world still afflict up to one-third of the populations living at altitude. To help understand the mechanisms of adaptation and maladaptation, this review examines the various steps of the oxygen cascade from the atmosphere to the mitochondria distinguishing the patterns related to physiological (i.e., due to altitude) and pathological (i.e., due to a pre-existing disease) hypoxia. The aim is to assess the ability of humans to adapt to hypoxia in a multidisciplinary approach that correlates the function of genes, molecules, and cells with the physiologic and pathological outcomes. We conclude that, in most cases, it is not hypoxia by itself that generates diseases, but rather the attempts to adapt to the hypoxia condition. This underlies the paradigm shift that when adaptation to hypoxia becomes excessive, it translates into maladaptation.

Brain Injury in Infants Evaluated for, But Not Treated with, Therapeutic Hypothermia

Defining neonatal encephalopathy clinically to qualify for therapeutic hypothermia is challenging. This study examines magnetic resonance imaging outcomes of 39 infants who were evaluated and not cooled using criteria inclusive of mild encephalopathy. Infants evaluated for therapeutic hypothermia are at risk for brain injury and may benefit from neuroimaging and follow-up.

Microbiota independent effects of oligosaccharides on Caco-2 cells -A semi-targeted metabolomics approach using DI-FT-ICR-MS coupled with pathway enrichment analysis

Milk oligosaccharides (MOS) and galactooligosaccharides (GOS) are associated with many benefits, including anti-microbial effects and immune-modulating properties. However, the cellular mechanisms of these are largely unknown. In this study, the effects of enriched GOS and MOS mixtures from caprine and bovine milk consisting mainly 6'-galactosyllactose, 3'-sialyllactose, and 6'-sialyllactose on Caco-2 cells were investigated, and the treatment-specific metabolomes were described. In the control, the cells were treated with a sugar mix consisting of one-third each of glucose, galactose and lactose.

A local metabolomics workflow with pathway enrichment was established, which specifically addresses DI-FT-ICR-MS analyses and includes adaptations in terms of measurement technology and sample matrices. By including quality parameters, especially the isotope pattern, we increased the precision of annotation. The independence from online tools, the fast adaptability to changes in databases, and the specific adjustment to the measurement technology and biomaterial used, proved to be a great advantage.

For the first time it was possible to find 71 active pathways in a Caco-2 cell experiment. These pathways were assigned to 12 main categories, with amino acid metabolism and carbohydrate metabolism being the most dominant categories in terms of the number of metabolites and metabolic pathways. Treatment of Caco-2 cells with high GOS and glucose contents resulted in significant effects on several metabolic pathways, whereas the MOS containing treatments resulted only for individual metabolites in significant changes. An effect based on bovine or caprine origin alone could not be observed. Thus, it was shown that MOS and GOS containing treatments can exert microbiome-independent effects on the metabolome of Caco-2 cells.

Diagnostic and Therapeutic Roles of the “Omics” in Hypoxic–Ischemic Encephalopathy in Neonates

Perinatal asphyxia and neonatal encephalopathy remain major causes of neonatal mortality, despite the improved availability of diagnostic and therapeutic tools, contributing to neurological and intellectual disabilities worldwide. An approach using a combination of clinical data, neuroimaging, and biochemical parameters is the current strategy towards the improved diagnosis and prognosis of the outcome in neonatal hypoxic–ischemic encephalopathy (HIE) using bioengineering methods. Traditional biomarkers are of little use in this multifactorial and variable phenotype-presenting clinical condition. Novel systems of biology-based “omics” approaches (genomics, transcriptome proteomics, and metabolomics) may help to identify biomarkers associated with brain and other tissue injuries, predicting the disease severity in HIE. Biomarker studies using omics technologies will likely be a key feature of future neuroprotective treatment methods and will help to assess the successful treatment and long-term efficacy of the intervention. This article reviews the roles of different omics as biomarkers of HIE and outlines the existing knowledge of our current understanding of the clinical use of different omics molecules as novel neonatal brain injury biomarkers, which may lead to improved interventions related to the diagnostic and therapeutic aspects of HIE.

Recent advances in diagnostics of neonatal hypoxic ischemic encephalopathy

The prognosis in neonatal hypoxic ischemic encephalopathy (HIE) depends on early differential diagnosis for justified administration of emergency therapeutic hypothermia. The moment of therapy initiation directly affects the long-term neurological outcome: the earlier the commencement, the better the prognosis. This review analyzes recent advances in systems biology that facilitate early differential diagnosis of HIE as a pivotal complement to clinical indicators. We discuss the possibilities of clinical translation for proteomic, metabolomic and extracellular vesicle patterns characteristic of HIE and correlations with severity and prognosis. Identification and use of selective biomarkers of brain damage in neonates during the first hours of life is hindered by systemic effects of hypoxia. Chromatography– mass spectrometry blood tests allow analyzing hundreds and thousands of metabolites in a small biological sample to identify characteristic signatures of brain damage. Clinical use of advanced analytical techniques will facilitate the accurate and timely diagnosis of HIE for enhanced management.

Noninvasive monitoring of evolving urinary metabolic patterns in neonatal encephalopathy

BACKGROUND

Infants with moderate and severe neonatal encephalopathy (NE) frequently suffer from long-term adverse outcomes. We hypothesize that the urinary metabolome of newborns with NE reflects the evolution of injury patterns observed with magnetic resonance imaging (MRI).

METHODS

Eligible patients were newborn infants with perinatal asphyxia evolving to NE and qualifying for therapeutic hypothermia (TH) included in the HYPOTOP trial. MRI was employed for characterizing brain injury. Urine samples of 55 infants were collected before, during, and after TH. Metabolic profiles of samples were recorded employing three complementary mass spectrometry-based assays, and the alteration of detected metabolic features between groups was assessed.

RESULTS

The longitudinal assessment revealed significant perturbations of the urinary metabolome. After 24 h of TH, a stable disease pattern evolved characterized by the alterations of 4-8% of metabolic features related to lipid metabolism, metabolism of cofactors and vitamins, glycan biosynthesis and metabolism, amino acid metabolism, and nucleotide metabolism. Characteristic metabolomic fingerprints were observed for different MRI injury patterns.

CONCLUSIONS

This study shows the potential of urinary metabolic profiles for the noninvasive monitoring of brain injury of infants with NE during TH.

IMPACT

A comprehensive approach for the study of the urinary metabolome was employed involving a semi-targeted capillary electrophoresis-time-of-flight mass spectrometry (TOFMS) assay, an untargeted ultra-performance liquid chromatography (UPLC)-quadrupole TOFMS assay, and a targeted UPLC-tandem MS-based method for the quantification of amino acids. The longitudinal study of the urinary metabolome identified dynamic metabolic changes between birth and until 96 h after the initiation of TH. The identification of altered metabolic pathways in newborns with pathologic MRI outcomes might offer the possibility of developing noninvasive monitoring approaches for personalized adjustment of the treatment and for supporting early outcome prediction.

Inside the Alterations of Circulating Metabolome in Antarctica: The Adaptation to Chronic Hypoxia

Although the human body may dynamically adapt to mild and brief oxygen shortages, there is a growing interest in understanding how the metabolic pathways are modified during sustained exposure to chronic hypoxia. Located at an equivalent altitude of approximately 3,800 m asl, the Concordia Station in Antarctica represents an opportunity to study the course of human adaption to mild hypoxia with reduced impact of potentially disturbing variables else than oxygen deprivation. We recruited seven healthy subjects who spent 10 months in the Concordia Station, and collected plasma samples at sea level before departure, and 90 days, 6 months, and 10 months during hypoxia. Samples were analyzed by untargeted liquid chromatography high resolution mass spectrometry to unravel how the non-polar and polar metabolomes are affected. Statistical analyses were performed by clustering the subjects into four groups according to the duration of hypoxia exposure. The non-polar metabolome revealed a modest decrease in the concentration of all the major lipid classes. By contrast, the polar metabolome showed marked alterations in several metabolic pathways, especially those related to amino acids metabolism, with a particular concern of arginine, glutamine, phenylalanine, tryptophan, and tyrosine. Remarkably, all the changes were evident since the first time point and remained unaffected by hypoxia duration (with the exception of a slight return of the non-polar metabolome after 6 months), highlighting a relative inability of the body to compensate them. Finally, we identified a few metabolic pathways that emerged as the main targets of chronic hypoxia.

Neuroprotective strategies of cerebrolysin for the treatment of infants with neonatal hypoxic-ischemic encephalopathy

BACKGROUND

Perinatal asphyxia (PA) is a devastating neonatal condition characterized by a lack of oxygen supporting the organ systems. PA can lead to hypoxic-ischemic encephalopathy (HIE), a brain dysfunction due to oxygen deprivation with a complex neurological sequela. The pathophysiology of HIE and PA is not entirely understood, with therapeutic hypothermia being the standard treatment with only limited value. However, alternative neuroprotective therapies can be a potential treatment modality.

METHODS

In this review, we will characterize the biochemical mechanisms of PA and HIE, while also giving insight into cerebrolysin, a neuroprotective treatment used for HIE and PA.

RESULTS

We found that cerebrolysin has up to 6-month treatment window post-ischemic insult. Cerebrolysin injections of 0.1 ml/kg of body weight twice per week were found to provide gross motor and speech deficit improvement.

CONCLUSION

Our literature search emphasizes the positive effects of cerebrolysin for general improvement outcomes. Nevertheless, biomarker establishment is warranted to improve patient outcomes.

Cytokine and chemokine responses to injury and treatment in a nonhuman primate model of hypoxic-ischemic encephalopathy treated with hypothermia and erythropoietin

Predicting long-term outcome in infants with hypoxic-ischemic encephalopathy (HIE) remains an ongoing clinical challenge. We investigated plasma biomarkers and their association with 6-month outcomes in a nonhuman primate model of HIE with or without therapeutic hypothermia (TH) and erythropoietin (Epo). Twenty-nine Macaca nemestrina were randomized to control cesarean section (n = 7) or 20 min of umbilical cord occlusion (UCO, n = 22) with either no treatment (n = 11) or TH/Epo (n = 11). Initial injury severity was scored using 30-min arterial pH, base deficit, and 10-min Apgar score. Twenty-four plasma cytokines, chemokines, and growth factors were measured 3, 6, 24, 72, and 96 h after UCO. Interleukin 17 (IL-17) and macrophage-derived chemokine (MDC) differentiated the normal/mild from moderate/severe injury groups. Treatment with TH/Epo was associated with increased monocyte chemotactic protein-4 (MCP-4) at 3 h-6h, and significantly lower MCP-4 and MDC at 24 h-72h, respectively. IL-12p40 was lower at 24 h-72h in animals with death/cerebral palsy (CP) compared to survivors without CP. Baseline injury severity was the single best predictor of death/CP, and predictions did not improve with the addition of biomarker data. Circulating chemokines associated with the peripheral monocyte cell lineage are associated with severity of injury and response to therapy, but do not improve ability to predict outcomes.

Neonatal encephalopathy: Focus on epidemiology and underexplored aspects of etiology

Neonatal Encephalopathy (NE) is a neurologic syndrome in term and near-term infants who have depressed consciousness, difficulty initiating and maintaining respiration, and often abnormal tone, reflexes and neonatal seizures in varying combinations. Moderate/severe NE affects 0.5-3/1000 live births in high-income countries, more in low- and middle-income countries, and carries high risk of mortality or disability, including cerebral palsy. Reduced blood flow and/or oxygenation around the time of birth, as with ruptured uterus, placental abruption or umbilical cord prolapse can cause NE. This subset of NE, with accompanying low Apgar scores and acidemia, is termed Hypoxic-Ischemic Encephalopathy. Other causes of NE that can present similarly, include infections, inflammation, toxins, metabolic disease, stroke, placental disease, and genetic disorders. Aberrant fetal growth and congenital anomalies are strongly associated with NE, suggesting a major role for maldevelopment. As new tools for differential diagnosis emerge, their application for prevention, individualized treatment and prognostication will require further systematic studies of etiology of NE.

Blood Plasma Metabolic Profile of Newborns with Hypoxic-Ischaemic Encephalopathy by GC-MS

Background

Early diagnosis of hypoxic-ischaemic encephalopathy (HIE) is crucial in preventing neurodevelopmental disabilities and reducing morbidity and mortality. The study was to investigate the plasma metabolic signatures in the peripheral blood of HIE newborns and explore the potential diagnostic biomarkers.

Method

In the present study, 24 newborns with HIE and 24 healthy controls were recruited. The plasma metabolites were measured by gas chromatography-mass spectrometry (GC-MS), and the raw data was standardized by the EigenMS method. Significantly differential metabolites were identified by multivariate statistics. Pathway enrichment was performed by bioinformatics analysis. Meanwhile, the diagnostic value of candidate biomarkers was evaluated.

Result

The multivariate statistical models showed a robust capacity to distinguish the HIE cases from the controls. 52 metabolites were completely annotated. 331 significantly changed pathways were enriched based on seven databases, including 33 overlapped pathways. Most of them were related to amino acid metabolism, energy metabolism, neurotransmitter biosynthesis, pyrimidine metabolism, the regulation of HIF by oxygen, and GPCR downstream signaling. 14 candidate metabolites showed great diagnostic potential on HIE. Among them, alpha-ketoglutaric acid has the potential to assess the severity of HIE in particular.

Conclusion

The blood plasma metabolic profile could comprehensively reflect the metabolic disorders of the whole body under hypoxia-ischaemic injury. Several candidate metabolites may serve as promising biomarkers for the early diagnosis of HIE. Further validation based on large clinical samples and the establishment of guidelines for the clinical application of mass spectrometry data standardization methods are imperative in the future.

Exploring metabolic alterations associated with death from asphyxia and the differentiation of asphyxia from sudden cardiac death by GC-HRMS-based untargeted metabolomics

The determination of cause of death is one of the most important tasks in forensic practice. However, asphyxia is a difficult cause of death to determine, especially when the deceased has an underlying disease that can lead to a sudden unexpected death, such as coronary atherosclerotic heart disease (CAHD, which is the leading cause of sudden cardiac death, SCD), because its determination is currently still based on an exclusion strategy. In this study, gas chromatography coupled with high-resolution mass spectrometry (GC-HRMS)-based untargeted metabolomics was employed to obtain the pulmonary metabolic profiles of rats who died from asphyxia and SCD. First, fourteen metabolites were identified to investigate the mechanism of death from asphyxia, and we proposed some explanations that may account for these metabolic alterations, including the perturbation of amino acid metabolism, lipid metabolism, and energy metabolism (TCA cycle). Second, we discovered eight potential biomarkers to differentiate between asphyxia and SCD as the cause of death. The excellent classification performances of the eight individual biomarkers and their combination in fresh lung tissue were observed. Third, we also explored the relative change in the concentration of the eight metabolites and their classification performance in decomposed tissue (at 24 h postmortem). Lactic acid, pantothenic acid, and the combination of the eight biomarkers can be recognized as perfect classifiers to discriminate asphyxia from SCD even when decomposition has occurred. Our results showed that GC-HRMS-based untargeted metabolomics can be used as a promising tool to explore the metabolic alterations of the death process and to determine the cause of death.

Improvement in the Prediction of Neonatal Hypoxic-Ischemic Encephalopathy with the Integration of Umbilical Cord Metabolites and Current Clinical Makers

OBJECTIVE

To validate our previously identified candidate metabolites, and to assess the ability of these metabolites to predict hypoxic-ischemic encephalopathy (HIE) both individually and combined with clinical data.

STUDY DESIGN

Term neonates with signs of perinatal asphyxia, with and without HIE, and matched controls were recruited prospectively at birth from 2 large maternity units. Umbilical cord blood was collected for later batch metabolomic analysis by mass spectroscopy along with clinical details. The optimum selection of clinical and metabolites features with the ability to predict the development of HIE was determined using logistic regression modelling and machine learning techniques. Outcome of HIE was determined by clinical Sarnat grading and confirmed by electroencephalogram grade at 24 hours.

RESULTS

Fifteen of 27 candidate metabolites showed significant alteration in infants with perinatal asphyxia or HIE when compared with matched controls. Metabolomic data predicted the development of HIE with an area under the curve of 0.67 (95% CI, 0.62-0.71). Lactic acid and alanine were the primary metabolite predictors for the development of HIE, and when combined with clinical data, gave an area under the curve of 0.96 (95% CI, 0.92-0.95).

CONCLUSIONS

By combining clinical and metabolic data, accurate identification of infants who will develop HIE is possible shortly after birth, allowing early initiation of therapeutic hypothermia.

A Metabolomic Approach in Search of Neurobiomarkers of Perinatal Asphyxia: A Review of the Current Literature

Perinatal asphyxia and the possible sequelae of hypoxic-ischemic encephalopathy (HIE), are associated with high morbidity and mortality rates. The use of therapeutic hypothermia (TH) commencing within the first 6 h of life-currently the only treatment validated for the management of HIE-has been proven to reduce the mortality rate and disability seen at follow up at 18 months. Although there have been attempts to identify neurobiomarkers assessing the severity levels in HIE; none have been validated in clinical use to date, and the lack thereof limits the optimal treatment for these vulnerable infants. Metabolomics is a promising field of the "omics technologies" that may: identify neurobiomarkers, help improve diagnosis, identify patients prone to developing HIE, and potentially improve targeted neuroprotection interventions. This review focuses on the current evidence of metabolomics, a novel tool which may prove to be a useful in the diagnosis, management and treatment options for this multifactorial complex disease. Some of the most promising metabolites analyzed are the group of acylcarnitines: Hydroxybutyrylcarnitine (Malonylcarnitine) [C3-DC (C4-OH)], Tetradecanoylcarnitine [C14], L-Palmitoylcarnitine [C16], Hexadecenoylcarnitine [C16:1], Stearoylcarnitine [C18], and Oleoylcarnitine [C18:1]. A metabolomic "fingerprint" or "index," made up of 4 metabolites (succinate × glycerol/(β-hydroxybutyrate × O-phosphocholine)), seems promising in identifying neonates at risk of developing severe HIE.

Metabolomic analysis and mass spectrometry imaging after neonatal stroke and cell therapies in mouse brains

Ischemic brain injury provokes complex, time-dependent downstream pathways that ultimately lead to cell death. We aimed to demonstrate the levels of a wide range of metabolites in brain lysates and their on-tissue distribution following neonatal stroke and cell therapies. Postnatal day 12 mice underwent middle cerebral artery occlusion (MCAO) and were administered 1 × 10⁵ cells after 48 h. Metabolomic analysis of the injured hemisphere demonstrated that a variety of amino acids were significantly increased and that tricarboxylic acid cycle intermediates and some related amino acids, such as glutamate, were decreased. With the exception of the changes in citric acid, neither mesenchymal stem/stromal cells nor CD34⁺ cells ameliorated these changes. On-tissue visualization with matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) imaging revealed that the signal intensity of glutamate was significantly decreased in the infarct area, consistent with the metabolomic analysis, while its intensity was significantly increased in the peri-infarct area after MCAO. Although cell therapies did not ameliorate the changes in metabolites in the infarct area, mesenchymal stem cells ameliorated the increased levels of glutamate and carnitine in the peri-infarct area. MALDI-MS imaging showed the location-specific effect of cell therapies even in this subacute setting after MCAO. These methodologies may be useful for further investigation of possible treatments for ischemic brain injury.

Biological Filtering and Substrate Promiscuity Prediction for Annotating Untargeted Metabolomics

Mass spectrometry coupled with chromatography separation techniques provides a powerful platform for untargeted metabolomics. Determining the chemical identities of detected compounds however remains a major challenge. Here, we present a novel computational workflow, termed extended metabolic model filtering (EMMF), that aims to engineer a candidate set, a listing of putative chemical identities to be used during annotation, through an extended metabolic model (EMM). An EMM includes not only canonical substrates and products of enzymes already cataloged in a database through a reference metabolic model, but also metabolites that can form due to substrate promiscuity. EMMF aims to strike a balance between discovering previously uncharacterized metabolites and the computational burden of annotation. EMMF was applied to untargeted LC-MS data collected from cultures of Chinese hamster ovary (CHO) cells and murine cecal microbiota. EMM metabolites matched, on average, to 23.92% of measured masses, providing a > 7-fold increase in the candidate set size when compared to a reference metabolic model. Many metabolites suggested by EMMF are not catalogued in PubChem. For the CHO cell, we experimentally confirmed the presence of 4-hydroxyphenyllactate, a metabolite predicted by EMMF that has not been previously documented as part of the CHO cell metabolic model.

Metabolic basis of neuronal vulnerability to ischemia; an in vivo untargeted metabolomics approach

Understanding the root causes of neuronal vulnerability to ischemia is paramount to the development of new therapies for stroke. Transient global cerebral ischemia (tGCI) leads to selective neuronal cell death in the CA1 sub-region of the hippocampus, while the neighboring CA3 sub-region is left largely intact. By studying factors pertaining to such selective vulnerability, we can develop therapies to enhance outcome after stroke. Using untargeted liquid chromatography-mass spectrometry, we analyzed temporal metabolomic changes in CA1 and CA3 hippocampal areas following tGCI in rats till the setting of neuronal apoptosis. 64 compounds in CA1 and 74 in CA3 were found to be enriched and statistically significant following tGCI. Pathway analysis showed that pyrimidine and purine metabolism pathways amongst several others to be enriched after tGCI in CA1 and CA3. Metabolomics analysis was able to capture very early changes following ischemia. We detected 6 metabolites to be upregulated and 6 to be downregulated 1 hour after tGCI in CA1 versus CA3. Several metabolites related to apoptosis and inflammation were differentially expressed in both regions after tGCI. We offer a new insight into the process of neuronal apoptosis, guided by metabolomic profiling that was not performed to such an extent previously.

Small molecule biomarkers for neonatal hypoxic ischemic encephalopathy

Hypoxic Ischemic Encephalopathy (HIE) is one of the most deleterious conditions in the perinatal period and the access to small molecule biomarkers aiding accurate diagnosis and disease staging, progress monitoring, and early outcome prognosis could provide relevant advances towards the development of personalized therapies. The emergence of metabolomics, the "omics" technology enabling the holistic study of small molecules, for biomarker discovery employing different analytical platforms, animal models and study populations has drastically increased the number and diversity of small molecules proposed as candidate biomarkers. However, the use of very few compounds has been implemented in clinical guidelines and authorized medical devices. In this work we review different approaches employed for discovering HIE-related small molecule biomarkers. Their role in associated biochemical disease mechanisms as well as the way towards their translation into the clinical practice are discussed.

Metabolic Phenotypes of Hypoxic-Ischemic Encephalopathy with Normal vs. Pathologic Magnetic Resonance Imaging Outcomes

Hypoxic-Ischemic Encephalopathy (HIE) is one of the most relevant contributors to neurological disability in term infants. We hypothesized that clinical outcomes of newborns with (HIE) can be associated with changes at plasma metabolic level enabling the detection of brain injury. Plasma samples of a cohort of 55 asphyxiated infants who evolved to moderate/severe HIE were collected between birth and completion of therapeutic hypothermia (TH). Samples were analyzed employing a quantitative gas chromatography–mass spectrometry method for the determination of lactate and pyruvate and an untargeted liquid chromatography–time-of-flight mass spectrometry method for metabolic fingerprinting. Brain injury was assessed employing magnetic resonance imaging (MRI). A critical assessment of the usefulness of lactate, pyruvate, and pyruvate/lactate for outcome prediction was carried out. Besides, metabolic fingerprinting identified a dynamic perturbation of eleven metabolic pathways, including amino acid and purine metabolism, and the steroid hormone biosynthesis, in newborns with pathologic MRI outcomes. Although data suggest the usefulness of lactate and pyruvate monitoring during 72 h for discerning outcomes, only the steroid hormone biosynthesis pathway was significantly altered in early plasma samples (i.e., before the initiation of TH). This study highlights pathways that might potentially be targeted for biomarker discovery or adjuvant therapies to be combined with TH.

Association between newborn screening analytes and hypoxic ischemic encephalopathy

Hypoxic ischemic encephalopathy (HIE) is a major cause of neonatal mortality and morbidity. Our study sought to examine whether patterns of newborn screening analytes differed between infants with and without neonatal HIE in order to identify opportunities for potential use of these analytes for diagnosis in routine clinical practice. We linked a population-based newborn screening registry with health databases to identify cases of HIE among term infants (≥37 weeks' gestation) in Ontario from 2010-2015. Correlations between HIE and screening analytes were examined using multivariable logistic regression models containing clinical factors and individual screening analytes (acyl-carnitines, amino acids, fetal-to-adult hemoglobin ratio, endocrine markers, and enzymes). Among 731,841 term infants, 3,010 were diagnosed with HIE during the neonatal period. Multivariable models indicated that clinical variables alone or in combination with hemoglobin values were not associated with HIE diagnosis. Although the model was improved after adding acyl-carnitines and amino acids, the ability of the model to identify infants with HIE was moderate. Our findings indicate that analytes associated with catabolic stress were altered in infants with HIE; however, future research is required to determine whether amino acid and acyl-carnitine profiles could hold clinical utility in the early diagnosis or clinical management of HIE. In particular, further research should examine whether cord blood analyses can be used to identify HIE within a clinically useful timeframe or to guide treatment and predict long-term health outcomes.

[Application of metabolomics in neonatal clinical practice]

Metabolomics is an emerging and popular subject in the post-genome era, and a large number of studies have been noted on the application of metabolomics in health evaluation, growth and development evaluation, disease diagnosis, and therapeutic efficacy evaluation. As a special period of life, the neonatal period is characterized by rapid cell renewing, consumption of a lot of energy and materials, and changes in metabolic pathways, all of which affect the level of metabolites. However, there is still no reference standard for metabolic level and profile in neonates. This article reviews the current status of metabolic research on neonatal growth and development and common diseases and related clinical application of metabolomics, so as to provide new ideas for nutrition guidance and evaluation, selection of therapeutic regimens, and new drug research in neonates.

Integrated Proteomics and Metabolomic Analyses of Plasma Injury Biomarkers in a Serious Brain Trauma Model in Rats

Diffuse axonal injury (DAI) is a prevalent and serious brain injury with significant morbidity and disability. However, the underlying pathogenesis of DAI remains largely unclear, and there are still no objective laboratory-based tests available for clinicians to make an early diagnosis of DAI. An integrated analysis of metabolomic data and proteomic data may be useful to identify all of the molecular mechanisms of DAI and novel potential biomarkers. Therefore, we established a rat model of DAI, and applied an integrated UPLC-Q-TOF/MS-based metabolomics and isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis to obtain unbiased profiling data. Differential analysis identified 34 metabolites and 43 proteins in rat plasma of the injury group. Two metabolites (acetone and 4-Hydroxybenzaldehyde) and two proteins (Alpha-1-antiproteinase and Alpha-1-acid glycoprotein) were identified as potential biomarkers for DAI, and all may play important roles in the pathogenesis of DAI. Our study demonstrated the feasibility of integrated metabolomics and proteomics method to uncover the underlying molecular mechanisms of DAI, and may help provide clinicians with some novel diagnostic biomarkers and therapeutic targets.

Melatonin in Hypoxic-Ischemic Brain Injury in Term and Preterm Babies

Melatonin may serve as a potential therapeutic free radical scavenger and broad-spectrum antioxidant. It shows neuroprotective properties against hypoxic-ischemic brain injury in animal models. The authors review the studies focusing on the neuroprotective potential of melatonin and its possibility of treatment after perinatal asphyxia. Melatonin efficacy, low toxicity, and ability to readily cross through the blood-brain barrier make it a promising molecule. A very interesting thing is the difference between the half-life of melatonin in preterm neonates (15 hours) and adults (45-60 minutes). Probably, the use of synergic strategies-hypothermia coupled with melatonin treatment-may be promising in improving antioxidant action. The authors discuss and try to summarize the evidence surrounding the use of melatonin in hypoxic-ischemic events in term and preterm babies.

Biomarkers in neonatal hypoxic-ischemic encephalopathy-Review of the literature to date and future directions for research

The widespread introduction of therapeutic hypothermia as a standard of care in hypoxic-ischemic encephalopathy (HIE) has brought increasing pressure on clinicians to make an early and accurate assessment of the degree of hypoxic injury (HI) that has occurred and the severity of the encephalopathy that will ensue. No single blood-based marker is currently robust enough to detect significant HI or predict outcome. However, research in the field has been active in the last 10 years and we know that HIE is associated with predictable alterations in the expression of a number of inflammatory proteins, neuron-specific proteins, metabolite pathways, and microRNA. These alterations evolve quickly over the first hours and days of life. Predictive power varies depending on the timing of measurement of the biomarker, the sample type, and the case mix of the cohort examined. Combining clinical data with biochemical measurements is currently the most likely path toward improved detection and prediction of outcome in neonatal HIE.

Blood biomarkers for evaluation of perinatal encephalopathy: state of the art

PURPOSE OF REVIEW

The rapid progress in biomarker science is on the threshold of significantly changing clinical care for infants in the neonatal ICU. Infants with neonatal brain injuries will likely be the first group whose management is dramatically altered with point-of-care, rapidly available brain biomarker analysis. Providing an interim update on progress in this area is the purpose of this review.

RECENT FINDINGS

Highlighted findings from the past 18 months of publications on biomarkers in neonatal brain injury include; Specific nonbrain markers of cardiac health and global asphyxia continue to provide information on brain injury after hypoxic-ischemic encephalopathy (HIE). Prediction of injury in the piglet hypoxia-ischemia model is improved with the use of a combination score of plasma metabolites. In a neonatal piglet model of perinatal hypoxia-ischemia, a systemic proinflammatory surge of cytokines has been identified after rewarming from therapeutic hypothermia. New biomarkers identified recently include osteopontin, activin A, neutrophil gelatinase-associated lipocalin, secretoneurin, Tau and neurofilament light protein. Brain-based biomarkers differ in their ability to predict short-term in-hospital outcomes and long-term neurologic deficits.

SUMMARY

Neonatal brain biomarker research is currently in its very early development with major advances still to be made.

Understanding neonatal hypoxic-ischemic encephalopathy with metabolomics

BACKGROUND

 Hypoxic-ischemic encephalopathy (HIE), a serious complication of perinatal asphyxia, is commonly associated with an unfavorable outcome. In-depth research is important not only for the interpretation of the underlying biological alternations but may also provide the basis for the development of novel diagnostic and therapeutic tools. The application of metabolomics in perinatal asphyxia/HIE is a relatively new approach.

METHODS

 We performed a narrative, non-systematic review in the literature of metabolomic studies involving newborn animals and humans exposed to hypoxia-ischemia or developing perinatal asphyxia/HIE.

RESULTS

 Fifteen animal studies, nine studies in human neonates, and two review articles were evaluated. Changes in the metabolomic profile of newborn animals exposed to hypoxia-ischemia and of asphyxiated neonates with HIE are presented in relation to the underlying pathophysiology. The clinical relevance of these findings is further discussed in a comprehensible to the bedside clinician manner.

CONCLUSIONS

 Metabolomics may provide an explanation for the various metabolic alternations occurring in perinatal asphyxia/HIE, elucidate the biological background of the applied therapeutic interventions and promote the development of novel diagnostic-prognostic biomarkers of the disease. HIPPOKRATIA 2017, 21(3): 115-123.

Urine metabolomic profile in neonates with hypoxic-ischemic encephalopa-thy

BACKGROUND

Metabolomics could provide valuable insights into hypoxemic-ischemic encephalopathy (HIE) revealing new disease-associated biochemical derangements. The study aimed to investigate urine metabolic changes in neonates with HIE compared to healthy controls, using targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS).

PATIENTS AND METHODS

In this prospective, single-center study we enrolled neonates born at ≥ 36 weeks gestation with HIE (HIE group) and healthy controls (control group). We collected urine samples for metabolomic analysis on days one, three, and nine of life.

RESULTS

Twenty-one full-term newborns were studied, 13 in the HIE group and eight in the control group. Six of the affected neonates had moderate/severe HIE and seven mild HIE. Therapeutic hypothermia was applied only in four neonates with moderate/severe HIE. Multivariate and univariate statistical analysis showed a clear separation between the HIE and the control groups. Discriminant metabolites involved pyruvic acid, amino acids, acylcarnitines, inositol, kynurenine, hippuric acid, and vitamins.

CONCLUSIONS

We have identified a specific metabolic profile in neonates with HIE, adding to the existing knowledge on the disease biochemistry that may potentially help in biomarker development. HIPPOKRATIA 2017, 21(2): 80-84.