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This study set out to determine the key metabolite changes underlying the pathophysiology of severe preeclampsia (PE) using metabolic analysis. We collected sera from 10 patients with severe PE and from 10 healthy pregnant women of the same trimester and analyzed them using liquid chromatography mass spectrometry. A total of 3,138 differential metabolites were screened, resulting in the identification of 124 differential metabolites. Kyoto encyclopedia of genes and genomes pathway analysis revealed that they were mainly enriched in the following metabolic pathways: central carbon metabolism in cancer; protein digestion and absorption; aminoacyl-transfer RNA biosynthesis; mineral absorption; alanine, aspartate, and glutamate metabolism; and prostate cancer. After analysis of 124 differential metabolites, 2-hydroxybutyric acid was found to be the most critical differential metabolite, and its use allowed the differentiation of women with severe PE from healthy pregnant women. In summary, our analysis revealed that 2-hydroxybutyric acid is a potential key metabolite for distinguishing severe PE from healthy controls and is also a marker for the early diagnosis of severe PE, thus allowing early intervention.

2-hydroxybutyric acid (2HB) serves as an important regulatory factor in a variety of diseases. The circulating level of 2HB in serum is significantly higher in multiple diseases, such as cancer and type 2 diabetes (T2D). However, there is currently no systematic study on 2HB-producing bacteria that demonstrates whether gut bacteria contribute to the circulating 2HB pool. To address this question, we used BLASTP to reveal the taxonomic profiling of 2HB-producing bacteria in the human microbiome, which are mainly distributed in the phylum Proteobacteria and Firmicutes. In vitro experiments showed that most gut bacteria (21/32) have at least one path to produce 2HB, which includes Aspartic acid, methionine, threonine, and 2-aminobutyric acid. Particularly, Fusobacterium nucleatum has the strongest ability to synthesize 2HB, which is sufficient to alter colon 2HB concentration in mice. Nevertheless, neither antibiotic (ABX) nor Fusobacterium nucleatum gavage significantly affected mouse serum 2HB levels during the time course of this study. Taken together, our study presents the profiles of 2HB-producing bacteria and demonstrates that gut microbiota was a major contributor to 2HB concentration in the intestinal lumen but a relatively minor contributor to serum 2HB concentration. [ABSTRACT FROM AUTHOR]

Polysaccharides are widely present in herbs with multiple activities, especially immunity regulation and metabolic benefits for metabolic disorders. However, the underlying mechanisms are not well understood. Functional metabolomics is increasingly used to investigate systemic effects on the host by identifying metabolites with particular functions. This study explores the mechanisms underlying the metabolic benefits of Astragalus polysaccharides (APS) by adopting a functional metabolomics strategy. The effects of APS were determined in eight-week high-fat diet (HFD)-fed obese mice. Then, gas chromatography–time-of-flight mass spectrometry (GC–TOFMS)-based untargeted metabolomics was performed for an analysis of serum and liver tissues, and liquid chromatography–tandem mass spectrometry (LC–MS/MS)-based targeted metabolomics was performed. The potential functions of the metabolites were tested with in vitro and in vivo models of metabolic disorders. Our results first confirmed the metabolic benefits of APS in obese mice. Then, metabolomics analysis revealed that APS supplementation reversed the HFD-induced metabolic changes, and identified 2-hydroxybutyric acid (2-HB) as a potential functional metabolite for APS activity that was significantly decreased by a HFD and reversed by APS. Further study indicated that 2-HB inhibited oleic acid (OA)-induced triglyceride (TG) accumulation. It was also found to stimulate the expression of proteins in lipid degradation in hepatocytes and TG lipolysis in 3T3-L1 cells. Moreover, it was found to reduce serum TG and regulate the proteins involved in lipid degradation in high-fat and high-sucrose (HFHS)-fed mice. In conclusion, our study demonstrates that the metabolic benefits of APS are at least partially due to 2-HB generation, which modulated lipid metabolism both in vitro and in vivo. Our results also highlight that functional metabolomics is practical for investigating the mechanism underlying the systemic benefits of plant polysaccharides.

2-hydroxybutyric acid (2HB) serves as an important regulatory factor in a variety of diseases. The circulating level of 2HB in serum is significantly higher in multiple diseases, such as cancer and type 2 diabetes (T2D). However, there is currently no systematic study on 2HB-producing bacteria that demonstrates whether gut bacteria contribute to the circulating 2HB pool. To address this question, we used BLASTP to reveal the taxonomic profiling of 2HB-producing bacteria in the human microbiome, which are mainly distributed in the phylum Proteobacteria and Firmicutes. In vitro experiments showed that most gut bacteria (21/32) have at least one path to produce 2HB, which includes Aspartic acid, methionine, threonine, and 2-aminobutyric acid. Particularly, Fusobacterium nucleatum has the strongest ability to synthesize 2HB, which is sufficient to alter colon 2HB concentration in mice. Nevertheless, neither antibiotic (ABX) nor Fusobacterium nucleatum gavage significantly affected mouse serum 2HB levels during the time course of this study. Taken together, our study presents the profiles of 2HB-producing bacteria and demonstrates that gut microbiota was a major contributor to 2HB concentration in the intestinal lumen but a relatively minor contributor to serum 2HB concentration.

Liver injury caused by acetaminophen (AP) overdose is a leading public health problem. Although AP-induced liver injury is well recognized as the formation of N-acetyl-p-benzoquinone (NAPQI), a toxic metabolite of AP, resulting in cell damage, emerging evidence indicates that AP-induced liver injury is also associated with gut microbiota. However, the gut microbiota-involved mechanism remains largely unknown. In our study, we found that vancomycin (Vac) pretreatment (100 mg/kg, twice a day for 4 days) attenuated AP-induced liver injury, altered the composition of gut microbiota, and changed serum metabolic profile. Moreover, we identified Vac pretreatment elevated cecum and serum 2-hydroxybutyric acid (2-HB), which ameliorated AP-induced cell damage and liver injury in mice by reducing AP bioavailability and elevating GSH levels. Our current results revealed the novel role of 2-HB in protecting AP-induced liver injury and add new evidence for gut microbiota in affecting AP toxicity.

Liver injury caused by acetaminophen (AP) overdose is a leading public health problem. Although AP-induced liver injury is well recognized as the formation of N-acetyl-p-benzoquinone (NAPQI), a toxic metabolite of AP, resulting in cell damage, emerging evidence indicates that AP-induced liver injury is also associated with gut microbiota. However, the gut microbiota-involved mechanism remains largely unknown. In our study, we found that vancomycin (Vac) pretreatment (100 mg/kg, twice a day for 4 days) attenuated AP-induced liver injury, altered the composition of gut microbiota, and changed serum metabolic profile. Moreover, we identified Vac pretreatment elevated cecum and serum 2-hydroxybutyric acid (2-HB), which ameliorated AP-induced cell damage and liver injury in mice by reducing AP bioavailability and elevating GSH levels. Our current results revealed the novel role of 2-HB in protecting AP-induced liver injury and add new evidence for gut microbiota in affecting AP toxicity. Image 1 • Vac pretreatment attenuated AP-induced liver injury in rats. • Vac pretreatment elevated metabolite 2-HB both in cecum and serum. • 2-HB attenuated the AP-induced hepatotoxicity both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Paraquat (PQ) is a widely used herbicide which can cause high mortality to humans. However, relatively few studies focus on metabolic feature of PQ intoxication for investigating the underlying mechanisms. Here we performed non-targeted metabolomics profiling of serum samples from acute and chronic PQ intoxicated mouse models by gas chromatography time-of-flight mass spectrometry (GC–TOF/MS) to identify metabolic feature and characteristic metabolites of acute and chronic PQ intoxication. Results showed that 3-indolepropionic acid (IPA) and pathway of glycine, serine, and threonine metabolism were significantly altered after acute PQ intoxication; 2-hydroxybutyric acid and the ratio of L-serine/glycine were of significance between acute and chronic PQ intoxication. Then targeted metabolomics profiling was conducted by liquid chromatography–mass spectrometry (LC–MS) analysis to confirm the changes of IPA after acute PQ intoxication. Moreover, IPA-producing gut bacteria in feces were quantified by qRT-PCR to explain the varied IPA serum concentration. Clostridium botulinum and Peptostreptococcus anaerobius were significantly suppressed after acute PQ intoxication. The data suggested that PQ caused oxidative damage partially through suppression of anti-oxidative metabolite producing gut bacteria. In conclusion, we identified characteristic metabolites and pathway of acute and chronic PQ intoxication which could be potential biomarkers and therapeutic targets.

Type 2 Diabetes Mellitus (T2D) is defined as a chronic condition caused by beta cell loss and/or dysfunction and insulin resistance (IR). The discovering of novel biomarkers capable of identifying T2D and other metabolic disorders associated with IR in a timely and accurate way is critical. In this review, 2-hydroxybutyric acid (2HB) is presented as that upheaval biomarker with an unexplored potential ahead. Due to the activation of other metabolic pathways during IR, 2HB is synthesized as a coproduct of protein metabolism, being the progression of IR intrinsically related to the increasing of 2HB levels. Hence, the focus of this review will be on the 2HB metabolite and its involvement in glucose homeostasis. A literature review was conducted, which comprised an examination of publications from different databases that had been published over the previous ten years. A total of 19 articles fulfilled the intended set of criteria. The use of 2HB as an early indicator of IR was separated into subjects based on the number of analytes examined simultaneously. In terms of the association between 2HB and IR, it has been established that increasing 2HB levels can predict the development of IR. Thus, 2HB has demonstrated considerable promise as a clinical monitoring molecule, not only as an IR biomarker, but also for disease follow-up throughout IR treatment.

Paraquat (PQ) is a widely used herbicide which can cause high mortality to humans. However, relatively few studies focus on metabolic feature of PQ intoxication for investigating the underlying mechanisms. Here we performed non-targeted metabolomics profiling of serum samples from acute and chronic PQ intoxicated mouse models by gas chromatography time-of-flight mass spectrometry (GC–TOF/MS) to identify metabolic feature and characteristic metabolites of acute and chronic PQ intoxication. Results showed that 3-indolepropionic acid (IPA) and pathway of glycine, serine, and threonine metabolism were significantly altered after acute PQ intoxication; 2-hydroxybutyric acid and the ratio of L-serine/glycine were of significance between acute and chronic PQ intoxication. Then targeted metabolomics profiling was conducted by liquid chromatography–mass spectrometry (LC–MS) analysis to confirm the changes of IPA after acute PQ intoxication. Moreover, IPA-producing gut bacteria in feces were quantified by qRT-PCR to explain the varied IPA serum concentration. Clostridium botulinum and Peptostreptococcus anaerobius were significantly suppressed after acute PQ intoxication. The data suggested that PQ caused oxidative damage partially through suppression of anti-oxidative metabolite producing gut bacteria. In conclusion, we identified characteristic metabolites and pathway of acute and chronic PQ intoxication which could be potential biomarkers and therapeutic targets. [ABSTRACT FROM AUTHOR]

Highlights • This is the first report of a decline in 2-hydroxybutyric acid in response to bariatric surgery. Correlation between insulin resistance and 2-hydroxybutyric acid suggests the utility of the latter as an excellent biomarker for tracking glycemic improvement, and offers further insight into the pathways that control diabetes. Abstract Background Gastric bypass surgery for weight reduction often corrects dysglycemia in diabetic patients, but a full understanding of the underlying biochemical pathways continues to be investigated. Objectives To explore the effects of weight loss by surgical and dietary interventions on plasma metabolites using both targeted and discovery-oriented metabolomics platforms. Setting An academic medical center in the United States. Methods Improvement in homeostatic model assessment for insulin resistance (HOMA-IR), as an index of insulin resistance, was compared at 6 months in 11 patients that underwent Roux-en-Y gastric bypass against 11 patients that were matched for weight loss in the Weight Loss Maintenance (WLM) program. Metabolites in plasma were evaluated by nontargeted gas chromatography/mass spectrometry for the potential detection of >1100 biochemical markers. Results Among multiple metabolites detected, 2-hydroxybutyric acid (2-HBA) declined most significantly after 6 months in comparing patients that underwent Roux-en-Y gastric bypass with those in WLM (P <.001), corresponding with declines in HOMA-IR (P =.025). Baseline levels of 2-HBA for all patients were correlated with preintervention levels of HOMA-IR (R2 =.565, P <.001). Moreover, the changes in 2-HBA after 6 months were correlated with changes in HOMA-IR (R2 =.399, P =.0016). Conclusions Correlation between insulin resistance and 2-HBA suggests the utility of the latter as an excellent biomarker for tracking glycemic improvement, and offers further insight into the pathways that control diabetes. This is the first report of a decline in 2-HBA in response to bariatric surgery. [ABSTRACT FROM AUTHOR]

2-Hydroxybutyric acid appears at high concentrations in situations related to deficient energy metabolism (e.g., birth asphyxia) and also in inherited metabolic diseases affecting the central nervous system during neonatal development, such as "cerebral" lactic acidosis, glutaric aciduria type II, dihydrolipoyl dehydrogenase (E3) deficiency, and propionic acidemia. The present study was carried out to determine the effect of 2-hydroxybutyric acid at various concentrations (1-10 mM) on CO2 production and lipid synthesis from labeled substrates in cerebral cortex of 30-day-old Wistar rats in vitro. CO2 production was significantly inhibited (30-70%) by 2-hydroxybutyric acid in cerebral cortex prisms, in total homogenates and in the mitochondrial fraction. We also demonstrated a significant inhibition of lipid synthesis (20-45%) in cerebral cortex prisms and total homogenates in the presence of 2-hydroxybutyric acid. However, no inhibition of lipid synthesis occurred in homogenates free of nuclei and mitochondria. The results indicate an impairment of mitochondrial energy metabolism caused by 2-hydroxybutyric acid, a fact that may secondarily lead to reduction of lipid synthesis. It is possible that these findings may be associated with the neuropathophysiology of the situations where 2-hydroxybutyric acid is accumulated.

[Display omitted] • Microbial cell factory for whole cell bioconversion of threonine to 2-hydroxybutyric acid developed. • Three enzymes, threonine dehydratase (TD), lactate dehydrogenase (LDH) and formate dehydrogenase (FDH), overexpressed. • Seven genes (tdh , ilvIH , aceE , poxB , pflB, lldD, dld) in competing pathways removed. • UTR and protein engineering of FDH improved NADH regeneration. • 650 mM 2-hydroxybutyric acid with ∼ 0.95 mol/mol threonine resulted. Production of 2-hydroxybutyric acid (2-HBA) was attempted in recombinant Escherichia coli W3110 Δ tdh Δ ilvIH (over)expressing a homologous and mutated threonine dehydratase (ilvA *) and a heterologous 2-ketobutyric acid (2-KBA) reductase from Alcaligenes eutrophus H16 (Ae _ ldh). To prevent the degradation of 2-KBA, the aceE , poxB and pflB genes were deleted, and for blocking the 2-HBA degradation, the lldD and dld genes were disrupted. In addition, for efficient NADH regeneration/supply, a heterologous formate dehydrogenase from Candida boidinii (Cb _ fdh) was overexpressed. Under anaerobic condition, E. coli W3110 Δ tdh Δ ilvIH Δ aceE Δ poxB Δ lldD Δ dld Δ pflB could produce > 400 mM 2-HBA in 33 h with the yield of ∼ 0.95 mol/mol. Furthermore, by enhancing the expression of a mutant Cb_fdh , the titer could be increased to ∼ 650 mM in 33 h. This study provides an efficient microbial cell factory for the bioconversion of threonine to 2-HBA with a high yield. [ABSTRACT FROM AUTHOR]

Type 2 Diabetes Mellitus (T2D) is defined as a chronic condition caused by beta cell loss and/or dysfunction and insulin resistance (IR). The discovering of novel biomarkers capable of identifying T2D and other metabolic disorders associated with IR in a timely and accurate way is critical. In this review, 2-hydroxybutyric acid (2HB) is presented as that upheaval biomarker with an unexplored potential ahead. Due to the activation of other metabolic pathways during IR, 2HB is synthesized as a coproduct of protein metabolism, being the progression of IR intrinsically related to the increasing of 2HB levels. Hence, the focus of this review will be on the 2HB metabolite and its involvement in glucose homeostasis. A literature review was conducted, which comprised an examination of publications from different databases that had been published over the previous ten years. A total of 19 articles fulfilled the intended set of criteria. The use of 2HB as an early indicator of IR was separated into subjects based on the number of analytes examined simultaneously. In terms of the association between 2HB and IR, it has been established that increasing 2HB levels can predict the development of IR. Thus, 2HB has demonstrated considerable promise as a clinical monitoring molecule, not only as an IR biomarker, but also for disease follow-up throughout IR treatment. [ABSTRACT FROM AUTHOR]

• A GC–MS method for simultaneous analysis of the seven metabolites in the plasma samples was developed and validated. • The method optimization studies were performed to increase peak intensity at the same time lower analysis time. • The validation study results showed that stable, linear, sensitive, accurate, precision, selective, robust and rugged. • The method was applied to the analysis of the metabolites in plasma samples of Down Syndrome and euploid fetuses. • A statistical difference was found between Down Syndrome and euploid fetuses and these metabolites may be used as biomarker. Down Syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. Metabolomics is identification and quantification of small-molecule metabolites (molecular weight <1000 Da) in tissues, cells and physiological fluids within a certain period time. Metabolites are intermediate products of various types of biochemical reactions that participate in bonding metabolic pathways. In this study, metabolites such as 2-Hydroxybutyric acid, 3-Hydroxybutyric acid, β-Hydroxyisovaleric acid, Uracil, Glutamic acid, Maltose and Melezitose were chosen as the possible determinants/markers for the prenatal screening of Down Syndrome. Quantitative analysis of the metabolites conducted by GC MS method using 5 % phenyl / 95 % dimethylpolysiloxane (30 m ×0.25 mm, 0.25 μm film thickness) capillary column. The oven temperature was held constant at 60 °C for 1 min and ramped at 10 °C /min to 200 °C then ramped at 30 °C/min to 320 °C and hold for 6 min before cool-down, as helium mobile phase and flow rate of 2.8 mL/min and adding Myristic acid-d27 as an internal standard. Our method was validated by parameters of system suitability, stability, linearity, sensitivity, accuracy, precision, selectivity, robustness and ruggedness. The developed and validated method was applied to plasma samples taken from pregnant women with Down Syndrome (study group) and euploid fetuses (healthy group). The levels of these seven metabolites are statistically different (p < 0.05 for all) between the groups. It can be concluded that these relevant metabolites might be used for the prenatal screening of Down Syndrome. [ABSTRACT FROM AUTHOR]

Blood biomarkers may help to predict pregnancy in recipients of in vitro produced (IVP) embryos. Using 1H nuclear magnetic resonance, we quantified 36 metabolites in the blood plasma of recipients (90% heifers, healthy, 1.95 years on average at the time of 1st embryo transfer –ET-) collected at Day-0 (estrus) and Day-7 (before ET time). First, IVP embryos were transferred to Asturiana de los Valles recipients as fresh (F) (N = 26) and vitrified/warmed (V / W) (N = 48) (discovery groups). Only at estrus, we discovered 4, 11, and 5 (F-ET), and 2, 2, and 4 (V / W -ET) metabolites that predicted pregnancy on Day-40, Day-62 and calving time, respectively (ROC-AUC > 0.700; P <.05). Thereafter, validation was performed in independent samples (N = 67 F and N = 63 V / W) of three cattle breeds by an index of overall classification accuracy (OCA>0.650, P <.05). The numbers of candidate biomarkers validated were 2, 9 and 1 (F-ET) and 2, 2, and 3 (V / W -ET) on Day 40, Day-62 and calving time. Relevant metabolites were validated at the three (2-Oxoglutaric acid (F-ET), and 2-Hydroxybutyric acid and Dimethylamine (V / W -ET)) and two pregnancy endpoints (Ketoleucine (F-ET); Day-40 and Day-62) analysed. Fatty acid degradation and oxidative metabolism were enriched in pregnant recipients. The candidate biomarkers identified can improve embryo-recipient selection. We identified, for the first time, reliable pregnancy and birth candidate metabolite biomarkers for fresh and vitrified IVP embryos in blood of beef cattle recipients. Our findings can help to improve embryo-recipient selection, which is usually carried out in a way that females that will not become pregnant are not well differentiated. Unlabelled Image • Candidate biomarkers identified by 1HNMR can efficiently predict pregnancy, diagnosed at Day-62 and to term, in beef cattle. • Metabolic traits in recipients for fresh and vitrified/warmed embryo transfer depict distinct recipient populations. • Recipient fitness for pregnancy involves different regulation in oxidative and lipid metabolism. [ABSTRACT FROM AUTHOR]