Formate: The Neglected Member of One-Carbon Metabolism

Metabolic profiling of CD19+ cells in chronic lymphocytic leukemia by single-cell mass spectrometry imaging

BACKGROUND AND AIMS

Modern mass spectrometry imaging (MSI) enables single cells' metabolism exploration. Aims of this study were development of the single-cell MSI of human CD19+ lymphocytes and metabolic profiling of chronic lymphocytic leukemia (CLL).

MATERIALS AND METHODS

Blood donor (BD) samples were used for the optimization of CD19+ lymphocyte isolation and single-cell matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) MSI. Independent set of 200 CD19+ lymphocytes coming from 5 CLL patients and 5 BD was used for the CD19+ lymphocytes classification assessment and the untargeted metabolic profiling. CLL vs BD lymphocyte classification was performed using partial least squares-discriminant analysis (PLS-DA) using normalized single-cell mass spectra recorded in 300-600 and 600-950 Da ranges was applied.

RESULTS

Accuracy assessed by 10-fold cross-validation of CD19+ lymphocyte PLS-DA classification reached >90.0 %. Volcano plots showed 106 significantly altered m/z signals in CLL of which 9 were tentatively annotated. Among tentatively annotated m/z signals formaldehyde and glutathione metabolites and tetrahydrofolate stand out.

CONCLUSION

A method for single-cell MALDI TOF MSI of CD19+ lymphocytes was successfully developed. The method confirmed the significance of oxidative stress and single-carbon metabolism, pyruvate and fatty acid metabolism and apoptosis in CLL and it provided metabolic candidates for diagnostic applications.

Dynamic evolution of the mTHF gene family associated with primary metabolism across life

BACKGROUND

The folate cycle of one-carbon (C1) metabolism, which plays a central role in the biosynthesis of nucleotides and amino acids, demonstrates the significance of metabolic adaptation. We investigated the evolutionary history of the methylenetetrahydrofolate dehydrogenase (mTHF) gene family, one of the main drivers of the folate cycle, across life.

RESULTS

Through comparative genomic and phylogenetic analyses, we found that several lineages of Archaea lacked domains vital for folate cycle function such as the mTHF catalytic and NAD(P)-binding domains of FolD. Within eukaryotes, the mTHF gene family diversified rapidly. For example, several duplications have been observed in lineages including the Amoebozoa, Opisthokonta, and Viridiplantae. In a common ancestor of Opisthokonta, FolD and FTHFS underwent fusion giving rise to the gene MTHFD1, possessing the domains of both genes.

CONCLUSIONS

Our evolutionary reconstruction of the mTHF gene family associated with a primary metabolic pathway reveals dynamic evolution, including gene birth-and-death, gene fusion, and potential horizontal gene transfer events and/or amino acid convergence.

Cycling back to folate metabolism in cancer

Metabolic changes contribute to cancer initiation and progression through effects on cancer cells, the tumor microenvironment and whole-body metabolism. Alterations in serine metabolism and the control of one-carbon cycles have emerged as critical for the development of many tumor types. In this Review, we focus on the mitochondrial folate cycle. We discuss recent evidence that, in addition to supporting nucleotide synthesis, mitochondrial folate metabolism also contributes to metastasis through support of antioxidant defense, mitochondrial protein synthesis and the overflow of excess formate. These observations offer potential therapeutic opportunities, including the modulation of formate metabolism through dietary interventions and the use of circulating folate cycle metabolites as biomarkers for cancer detection.

A Transfer Hydrogenation Approach to Activity-Based Sensing of Formate in Living Cells

Formate is a major reactive carbon species in one-carbon metabolism, where it serves as an endogenous precursor for amino acid and nucleic acid biosynthesis and a cellular source of NAD(P)H. On the other hand, aberrant elevations in cellular formate are connected to progression of serious diseases, including cancer and Alzheimer's disease. Traditional methods for formate detection in biological environments often rely on sample destruction or extensive processing, resulting in a loss of spatiotemporal information. To help address these limitations, here we present the design, synthesis, and biological evaluation of a first-generation activity-based sensing system for live-cell formate imaging that relies on iridium-mediated transfer hydrogenation chemistry. Formate facilitates an aldehyde-to-alcohol conversion on various fluorophore scaffolds to enable fluorescence detection of this one-carbon unit, including through a two-color ratiometric response with internal calibration. The resulting two-component probe system can detect changes in formate levels in living cells with a high selectivity over potentially competing biological analytes. Moreover, this activity-based sensing system can visualize changes in endogenous formate fluxes through alterations of one-carbon pathways in cell-based models of human colon cancer, presaging the potential utility of this chemical approach to probe the continuum between one-carbon metabolism and signaling in cancer and other diseases.

Whole-body metabolic modelling reveals microbiome and genomic interactions on reduced urine formate levels in Alzheimer's disease

In this study, we aimed to understand the potential role of the gut microbiome in the development of Alzheimer's disease (AD). We took a multi-faceted approach to investigate this relationship. Urine metabolomics were examined in individuals with AD and controls, revealing decreased formate and fumarate concentrations in AD. Additionally, we utilised whole-genome sequencing (WGS) data obtained from a separate group of individuals with AD and controls. This information allowed us to create and investigate host-microbiome personalised whole-body metabolic models. Notably, AD individuals displayed diminished formate microbial secretion in these models. Additionally, we identified specific reactions responsible for the production of formate in the host, and interestingly, these reactions were linked to genes that have correlations with AD. This study suggests formate as a possible early AD marker and highlights genetic and microbiome contributions to its production. The reduced formate secretion and its genetic associations point to a complex connection between gut microbiota and AD. This holistic understanding might pave the way for novel diagnostic and therapeutic avenues in AD management.

Association between gut health and gut microbiota in a polluted environment

Animals host complex bacterial communities in their gastrointestinal tracts, with which they share a mutualistic interaction. The numerous effects these interactions grant to the host include regulation of the immune system, defense against pathogen invasion, digestion of otherwise undigestible foodstuffs, and impacts on host behaviour. Exposure to stressors, such as environmental pollution, parasites, and/or predators, can alter the composition of the gut microbiome, potentially affecting host-microbiome interactions that can be manifest in the host as, for example, metabolic dysfunction or inflammation. However, whether a change in gut microbiota in wild animals associates with a change in host condition is seldom examined. Thus, we quantified whether wild bank voles inhabiting a polluted environment, areas where there are environmental radionuclides, exhibited a change in gut microbiota (using 16S amplicon sequencing) and concomitant change in host health using a combined approach of transcriptomics, histological staining analyses of colon tissue, and quantification of short-chain fatty acids in faeces and blood. Concomitant with a change in gut microbiota in animals inhabiting contaminated areas, we found evidence of poor gut health in the host, such as hypotrophy of goblet cells and likely weakened mucus layer and related changes in Clca1 and Agr2 gene expression, but no visible inflammation in colon tissue. Through this case study we show that inhabiting a polluted environment can have wide reaching effects on the gut health of affected animals, and that gut health and other host health parameters should be examined together with gut microbiota in ecotoxicological studies.

Mitochondrial One-Carbon Metabolism is Required for TGF-β-Induced Glycine Synthesis and Collagen Protein Production

A hallmark of Idiopathic Pulmonary Fibrosis is the TGF-β-dependent activation of lung fibroblasts, leading to excessive deposition of collagen proteins and progressive scarring. We have previously shown that synthesis of collagen by lung fibroblasts requires de novo synthesis of glycine, the most abundant amino acid in collagen protein. TGF-β upregulates the expression of the enzymes of the de novo serine/glycine synthesis pathway in lung fibroblasts through mTORC1 and ATF4-dependent transcriptional programs. SHMT2, the final enzyme of the de novo serine/glycine synthesis pathway, transfers a one-carbon unit from serine to tetrahydrofolate (THF), producing glycine and 5,10-methylene-THF (meTHF). meTHF is converted back to THF in the mitochondrial one-carbon (1C) pathway through the sequential actions of MTHFD2 (which converts meTHF to 10-formyl-THF), and either MTHFD1L, which produces formate, or ALDH1L2, which produces CO2. It is unknown how the mitochondrial 1C pathway contributes to glycine biosynthesis or collagen protein production in fibroblasts, or fibrosis in vivo. Here, we demonstrate that TGF-β induces the expression of MTHFD2, MTHFD1L, and ALDH1L2 in human lung fibroblasts. MTHFD2 expression was required for TGF-β-induced cellular glycine accumulation and collagen protein production. Combined knockdown of both MTHFD1L and ALDH1L2 also inhibited glycine accumulation and collagen protein production downstream of TGF-β; however knockdown of either protein alone had no inhibitory effect, suggesting that lung fibroblasts can utilize either enzyme to regenerate THF. Pharmacologic inhibition of MTHFD2 recapitulated the effects of MTHFD2 knockdown in lung fibroblasts and ameliorated fibrotic responses after intratracheal bleomycin instillation in vivo. Our results provide insight into the metabolic requirements of lung fibroblasts and provide support for continued development of MTHFD2 inhibitors for the treatment of IPF and other fibrotic diseases.

Activation of the integrated stress response rewires cardiac metabolism in Barth syndrome

Barth Syndrome (BTHS) is an inherited cardiomyopathy caused by defects in the mitochondrial transacylase TAFAZZIN (Taz), required for the synthesis of the phospholipid cardiolipin. BTHS is characterized by heart failure, increased propensity for arrhythmias and a blunted inotropic reserve. Defects in Ca2+-induced Krebs cycle activation contribute to these functional defects, but despite oxidation of pyridine nucleotides, no oxidative stress developed in the heart. Here, we investigated how retrograde signaling pathways orchestrate metabolic rewiring to compensate for mitochondrial defects. In mice with an inducible knockdown (KD) of TAFAZZIN, and in induced pluripotent stem cell-derived cardiac myocytes, mitochondrial uptake and oxidation of fatty acids was strongly decreased, while glucose uptake was increased. Unbiased transcriptomic analyses revealed that the activation of the eIF2α/ATF4 axis of the integrated stress response upregulates one-carbon metabolism, which diverts glycolytic intermediates towards the biosynthesis of serine and fuels the biosynthesis of glutathione. In addition, strong upregulation of the glutamate/cystine antiporter xCT increases cardiac cystine import required for glutathione synthesis. Increased glutamate uptake facilitates anaplerotic replenishment of the Krebs cycle, sustaining energy production and antioxidative pathways. These data indicate that ATF4-driven rewiring of metabolism compensates for defects in mitochondrial uptake of fatty acids to sustain energy production and antioxidation.

Formate Might Be a Novel Potential Serum Metabolic Biomarker for Type 2 Diabetic Peripheral Neuropathy

Background

As one of the most frequent complications of type 2 diabetes mellitus (T2DM), diabetic peripheral neuropathy (DPN) shows a profound impact on 50% of patients with symptoms of neuropathic pain, numbness and other paresthesia. No valid serum biomarkers for the prediction of DPN have been identified in the clinic so far. This study is to investigate the potential serum biomarkers for DPN firstly based on 1H-Nuclear Magnetic Resonance (1H-NMR)-based metabolomics technique.

Methods

Thirty-six patients enrolled in this study were divided into two groups: 18 T2DM patients without DPN (T2DM group) and 18 T2DM patients with DPN (DPN group). Serum metabolites were measured via 1H-NMR spectroscopy. Bioinformatic approaches including principal component analysis (PCA), orthogonal partial least squares-discriminant analysis (OPLS-DA), independent sample t-test, Fisher's test, Pearson and Spearman correlation analysis, Stepwise multiple linear regression analysis and receiver operating characteristic (ROC) curve analysis were used to identify the potential altered serum biomarkers.

Results

A total of 20 metabolites were obtained and further analyzed. Formate was identified as the only potential biomarker that decreased in the DPN group with statistical significance after multiple comparisons (p<0.05). Formate also displayed a negative relationship with some elevated clinical markers in DPN. ROC curve analysis showed a good discriminative ability for formate in DPN with an area under the curve (AUC) value of 0.981.

Conclusion

Formate could be considered a potential serum metabolic biomarker for DPN. The reduced level of formate in DPN may be associated with mitochondrial dysfunction and gut microbiota alteration. Monitoring the level of serum formate would be an important strategy for the early diagnosis of DPN and a supplement of formate may be a promising treatment for DPN in the future.

Formate promotes invasion and metastasis in reliance on lipid metabolism

Metabolic rewiring is essential for cancer onset and progression. We previously showed that one-carbon metabolism-dependent formate production often exceeds the anabolic demand of cancer cells, resulting in formate overflow. Furthermore, we showed that increased extracellular formate concentrations promote the in vitro invasiveness of glioblastoma cells. Here, we substantiate these initial observations with ex vivo and in vivo experiments. We also show that exposure to exogeneous formate can prime cancer cells toward a pro-invasive phenotype leading to increased metastasis formation in vivo. Our results suggest that the increased local formate concentration within the tumor microenvironment can be one factor to promote metastases. Additionally, we describe a mechanistic interplay between formate-dependent increased invasiveness and adaptations of lipid metabolism and matrix metalloproteinase activity. Our findings consolidate the role of formate as pro-invasive metabolite and warrant further research to better understand the interplay between formate and lipid metabolism.

Modulation of DNA methylation by one-carbon metabolism: a milestone for healthy aging

Healthy aging can be defined as an extended lifespan and health span. Nutrition has been regarded as an important factor in healthy aging, because nutrients, bioactive food components, and diets have demonstrated beneficial effects on aging hallmarks such as oxidative stress, mitochondrial function, apoptosis and autophagy, genomic stability, and immune function. Nutrition also plays a role in epigenetic regulation of gene expression, and DNA methylation is the most extensively investigated epigenetic phenomenon in aging. Interestingly, age-associated DNA methylation can be modulated by one-carbon metabolism or inhibition of DNA methyltransferases. One-carbon metabolism ultimately controls the balance between the universal methyl donor S-adenosylmethionine and the methyltransferase inhibitor S-adenosylhomocysteine. Water-soluble B-vitamins such as folate, vitamin B6, and vitamin B12 serve as coenzymes for multiple steps in one-carbon metabolism, whereas methionine, choline, betaine, and serine act as methyl donors. Thus, these one-carbon nutrients can modify age-associated DNA methylation and subsequently alter the age-associated physiologic and pathologic processes. We cannot elude aging per se but we may at least change age-associated DNA methylation, which could mitigate age-associated diseases and disorders.

Homocysteine-a retrospective and prospective appraisal

The biologically important amino acid homocysteine links sulfur, methionine, and one-carbon metabolism. This review describes its initial discovery, the identification of the clinical condition of "homocystinuria" and the recognition of its close relationship to folate and vitamin B12 metabolism. It discusses the history behind its current association with diverse diseases including neural tube defects, cardio- and cerebrovascular disease and, more recently, dementia and Alzheimer's Disease. It also explores current controversies and considers potential future research directions. It is intended to give a general overview of homocysteine in relation to health and disease.

Allantoic fluid metabolome reveals specific metabolic signatures in chicken lines different for their muscle glycogen content

Nutrient availability in eggs can affect early metabolic orientation in birds. In chickens divergently selected on the Pectoralis major ultimate pH, a proxy for muscle glycogen stores, characterization of the yolk and amniotic fluid revealed a different nutritional environment. The present study aimed to assess indicators of embryo metabolism in pHu lines (pHu+ and pHu-) using allantoic fluids (compartment storing nitrogenous waste products and metabolites), collected at days 10, 14 and 17 of embryogenesis and characterized by 1H-NMR spectroscopy. Analysis of metabolic profiles revealed a significant stage effect, with an enrichment in metabolites at the end of incubation, and an increase in interindividual variability during development. OPLS-DA analysis discriminated the two lines. The allantoic fluid of pHu- was richer in carbohydrates, intermediates of purine metabolism and derivatives of tryptophan-histidine metabolism, while formate, branched-chain amino acids, Krebs cycle intermediates and metabolites from different catabolic pathways were more abundant in pHu+. In conclusion, the characterization of the main nutrient sources for embryos and now allantoic fluids provided an overview of the in ovo nutritional environment of pHu lines. Moreover, this study revealed the establishment, as early as day 10 of embryo development, of specific metabolic signatures in the allantoic fluid of pHu+ and pHu- lines.

Changes in the Urine Metabolomic Profile in Patients Recovering from Severe COVID-19

Metabolomics is a relatively new research area that focuses mostly on the profiling of selected molecules and metabolites within the organism. A SARS-CoV-2 infection itself can lead to major disturbances in the metabolite profile of the infected individuals. The aim of this study was to analyze metabolomic changes in the urine of patients during the acute phase of COVID-19 and approximately one month after infection in the recovery period. We discuss the observed changes in relation to the alterations resulting from changes in the blood plasma metabolome, as described in our previous study. The metabolome analysis was performed using NMR spectroscopy from the urine of patients and controls. The urine samples were collected at three timepoints, namely upon hospital admission, during hospitalization, and after discharge from the hospital. The acute COVID-19 phase induced massive alterations in the metabolic composition of urine was linked with various changes taking place in the organism. Discriminatory analyses showed the feasibility of successful discrimination of COVID-19 patients from healthy controls based on urinary metabolite levels, with the highest significance assigned to citrate, Hippurate, and pyruvate. Our results show that the metabolomic changes persist one month after the acute phase and that the organism is not fully recovered.

FMO rewires metabolism to promote longevity through tryptophan and one carbon metabolism in C. elegans

Flavin containing monooxygenases (FMOs) are promiscuous enzymes known for metabolizing a wide range of exogenous compounds. In C. elegans, fmo-2 expression increases lifespan and healthspan downstream of multiple longevity-promoting pathways through an unknown mechanism. Here, we report that, beyond its classification as a xenobiotic enzyme, fmo-2 expression leads to rewiring of endogenous metabolism principally through changes in one carbon metabolism (OCM). These changes are likely relevant, as we find that genetically modifying OCM enzyme expression leads to alterations in longevity that interact with fmo-2 expression. Using computer modeling, we identify decreased methylation as the major OCM flux modified by FMO-2 that is sufficient to recapitulate its longevity benefits. We further find that tryptophan is decreased in multiple mammalian FMO overexpression models and is a validated substrate for FMO-2. Our resulting model connects a single enzyme to two previously unconnected key metabolic pathways and provides a framework for the metabolic interconnectivity of longevity-promoting pathways such as dietary restriction. FMOs are well-conserved enzymes that are also induced by lifespan-extending interventions in mice, supporting a conserved and important role in promoting health and longevity through metabolic remodeling.

The ovine conceptus utilizes extracellular serine, glucose, and fructose to generate formate via the one carbon metabolism pathway

Highly proliferative cells rely on one carbon (1C) metabolism for production of formate required for synthesis of purines and thymidine for nucleic acid synthesis. This study was to determine if extracellular serine and/or glucose and fructose contribute the production of formate in ovine conceptuses. Suffolk ewes (n = 8) were synchronized to estrus, bred to fertile rams, and conceptuses were collected on Day 17 of gestation. Conceptuses were either snap frozen in liquid nitrogen (n = 3) or placed in culture in medium (n = 5) containing either: 1) 4 mM D-glucose + 2 mM [U-¹³C]serine; 2) 6 mM glycine + 4 mM D-glucose + 2 mM [U-¹³C]serine; 3) 4 mM D-fructose + 2 mM [U-¹³C]serine; 4) 6 mM glycine + 4 mM D-fructose + 2 mM [U-¹³C]serine; 5) 4 mM D-glucose + 4 mM D-fructose + 2 mM [U-¹³C]serine; or 6) 6 mM glycine + 4 mM D-glucose + 4 mM D-fructose + 2 mM [U-¹³C]serine. After 2 h incubation, conceptuses in their respective culture medium were homogenized and the supernatant analyzed for ¹²C- and ¹³C-formate by gas chromatography and amino acids by high performance liquid chromatography. Ovine conceptuses produced both ¹³C- and ¹²C-formate, indicating that the [U-¹³C]serine, glucose, and fructose were utilized to generate formate, respectively. Greater amounts of ¹²C-formate than ¹³C-formate were produced, indicating that the ovine conceptus utilized more glucose and fructose than serine to produce formate. This study is the first to demonstrate that both 1C metabolism and serinogenesis are active metabolic pathways in ovine conceptuses during the peri-implantation period of pregnancy, and that hexose sugars are the preferred substrate for generating formate required for nucleotide synthesis for proliferating trophectoderm cells.

Untargeted NMR Metabolomics Reveals Alternative Biomarkers and Pathways in Alkaptonuria

Alkaptonuria (AKU) is an ultra-rare metabolic disease caused by the accumulation of homogentisic acid (HGA), an intermediate product of phenylalanine and tyrosine degradation. AKU patients carry variants within the gene coding for homogentisate-1,2-dioxygenase (HGD), which are responsible for reducing the enzyme catalytic activity and the consequent accumulation of HGA and formation of a dark pigment called the ochronotic pigment. In individuals with alkaptonuria, ochronotic pigmentation of connective tissues occurs, leading to inflammation, degeneration, and eventually osteoarthritis. The molecular mechanisms underlying the multisystemic development of the disease severity are still not fully understood and are mostly limited to the metabolic pathway segment involving HGA. In this view, untargeted metabolomics of biofluids in metabolic diseases allows the direct investigation of molecular species involved in pathways alterations and their interplay. Here, we present the untargeted metabolomics study of AKU through the nuclear magnetic resonance of urine from a cohort of Italian patients; the study aims to unravel molecular species and mechanisms underlying the AKU metabolic disorder. Dysregulation of metabolic pathways other than the HGD route and new potential biomarkers beyond homogentisate are suggested, contributing to a more comprehensive molecular signature definition for AKU and the development of future adjuvant treatment.

Radiosynthesis, Preclinical, and Clinical Positron Emission Tomography Studies of Carbon-11 Labeled Endogenous and Natural Exogenous Compounds

The presence of positron emission tomography (PET) centers at most major hospitals worldwide, along with the improvement of PET scanner sensitivity and the introduction of total body PET systems, has increased the interest in the PET tracer development using the short-lived radionuclides carbon-11. In the last few decades, methodological improvements and fully automated modules have allowed the development of carbon-11 tracers for clinical use. Radiolabeling natural compounds with carbon-11 by substituting one of the backbone carbons with the radionuclide has provided important information on the biochemistry of the authentic compounds and increased the understanding of their in vivo behavior in healthy and diseased states. The number of endogenous and natural compounds essential for human life is staggering, ranging from simple alcohols to vitamins and peptides. This review collates all the carbon-11 radiolabeled endogenous and natural exogenous compounds synthesised to date, including essential information on their radiochemistry methodologies and preclinical and clinical studies in healthy subjects.

Adaptive and Pathological Outcomes of Radiation Stress-Induced Redox Signaling

Significance: Ionizing radiation can damage cells either directly or through oxidative damage caused by ionization. Although radiation exposure from natural sources is very limited, ionizing radiation in nuclear disaster zones and long spaceflights causes inconspicuous, yet measurable physiological effects in men and animals, whose significance remains poorly known. Understanding the physiological impacts of ionizing radiation has a wide importance due to the increased use of medical imaging and radiotherapy. Recent Advances: Radiation exposure has been traditionally investigated from the perspective of DNA damage and its consequences. However, recent studies from Chernobyl as well as spaceflights have provided interesting insights into oxidative stress-induced metabolic alterations and disturbances in the circadian regulation. Critical Issues: In this review, we discuss the physiological consequences of radiation exposure in the light of oxidative stress signaling. Radiation exposure likely triggers many converging or interconnecting signaling pathways, some of which mimic mitochondrial dysfunction and might explain the observed metabolic changes. Future Directions: Better understanding of the different radiation-induced signaling pathways might help to devise strategies for mitigation of the long-term effects of radiation exposure. The utility of fibroblast growth factor 21 (FGF21) as a radiation exposure biomarker and the use of radiation hormesis as a method to protect astronauts on a prolonged spaceflight, such as a mission to Mars, should be investigated. Antioxid. Redox Signal. 37, 336-348.

Tumor Necrosis Factor Alpha and the Gastrointestinal Epithelium: Implications for the Gut-Brain Axis and Hypertension

The colonic epithelium is the site of production and transport of many vasoactive metabolites and neurotransmitters that can modulate the immune system, affect cellular metabolism, and subsequently regulate blood pressure. As an important interface between the microbiome and its host, the colon can contribute to the development of hypertension. In this critical review, we highlight the role of colonic inflammation and microbial metabolites on the gut brain axis in the pathology of hypertension, with special emphasis on the interaction between tumor necrosis factor α (TNFα) and short chain fatty acid (SCFA) metabolites. Here, we review the current literature and identify novel pathways in the colonic epithelium related to hypertension. A network analysis on transcriptome data previously generated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats reveals differences in several pathways associated with inflammation involving TNFα (NF-κB and STAT Expression Targets) as well as oxidative stress. We also identify down-regulation of networks associated with gastrointestinal function, cardiovascular function, enteric nervous system function, and cholinergic and adrenergic transmission. The analysis also uncovered transcriptome responses related to glycolysis, butyrate oxidation, and mitochondrial function, in addition to gut neuropeptides that serve as modulators of blood pressure and metabolic function. We present a model for the role of TNFα in regulating bacterial metabolite transport and neuropeptide signaling in the gastrointestinal system, highlighting the complexity of host-microbiota interactions in hypertension.

Electrospun Silk Fibroin Scaffolds for Tissue Regeneration: Chemical, Structural, and Toxicological Implications of the Formic Acid-Silk Fibroin Interaction

The dissolution of Bombyx mori silk fibroin (SF) films in formic acid (FA) for the preparation of electrospinning dopes is widely exploited to produce electrospun SF scaffolds. The SILKBridge^® nerve conduit is an example of medical device having in its wall structure an electrospun component produced from an FA spinning dope. Though highly volatile, residual FA remains trapped into the bulk of the SF nanofibers. The purpose of this work is to investigate the type and strength of the interaction between FA and SF in electrospun mats, to quantify its amount and to evaluate its possible toxicological impact on human health. The presence of residual FA in SF mats was detected by FTIR and Raman spectroscopy (new carbonyl peak at about 1,725 cm⁻¹) and by solid state NMR, which revealed a new carbonyl signal at about 164.3 ppm, attributed to FA by isotopic ¹³C substitution. Changes occurred also in the spectral ranges of hydroxylated amino acids (Ser and Thr), demonstrating that FA interacted with SF by forming formyl esters. The total amount of FA was determined by HS-GC/MS analysis and accounted for 247 ± 20 μmol/g. The greatest part was present as formyl ester, a small part (about 3%) as free FA. Approximately 17% of the 1,500 μmol/g of hydroxy amino acids (Ser and Thr) theoretically available were involved in the formation of formyl esters. Treatment with alkali (Na₂CO₃) succeeded to remove the greatest part of FA, but not all. Alkali-treated electrospun SF mats underwent morphological, physical, and mechanical changes. The average diameter of the fibers increased from about 440 nm to about 480 nm, the mat shrunk, became stiffer (the modulus increased from about 5.5 MPa to about 7 MPa), and lost elasticity (the strain decreased from about 1 mm/mm to about 0.8 mm/mm). Biocompatibility studies with human adult dermal fibroblasts did not show significant difference in cell proliferation (313 ± 18 and 309 ± 23 cells/mm² for untreated and alkali-treated SF mat, respectively) and metabolic activity. An in-depth evaluation of the possible toxicological impact of residual FA was made using the SILKBridge^® nerve conduit as case study, following the provisions of the ISO 10993-1 standard. The Potential Patient Daily Intake, calculated from the total amount of FA determined by HS-GC/MS, was 2.4 mg/day and the Tolerable Exposure level was set to 35.4 mg/day. This allowed to obtain a value of the Margin of Safety of 15, indicating that the amount of FA left on SF mats after electrospinning does not raise concerns for human health.

Oncogenic Ras expression increases cellular formate production

One-carbon units, critical intermediates for cell growth, may be produced by a variety of means, one of which is via the production of formate. Excessive formate accumulation, known as formate overflow and a characteristic of oxidative cancer, has been observed in cancer cells. However, the basis for this high rate of formate production is unknown. We examined the effect of elevated expression of oncogenic Ras (RasV12), on formate production in NIH-3T3 cells (mouse fibroblasts) cultured with either labelled ¹³C-serine or ¹³C-glycine. Formate accumulation by the fibroblasts transformed by RasV12 was increased two-threefold over those by vector control (Babe) cells. The production of formate exceeded the rate of utilization in both cell types. ¹³C-formate was produced almost exclusively from the #3 carbon of ¹³C-serine. Virtually no labelled formate was produced from either the #2 carbon of serine or the #2 carbon of glycine. The increased formate production by RasV12 cells was associated with increased mRNA abundances for enzymes of formate production in both the mitochondria and the cytosol. Thus, we find the oncogenic RasV12 significantly increases formate overflow and may be one way for tumor cells to produce one-carbon units required for enhanced proliferation of these cells and/or for other processes which have not been identified.

NADPH debt drives redox bankruptcy: SLC7A11/xCT-mediated cystine uptake as a double-edged sword in cellular redox regulation

Cystine/glutamate antiporter solute carrier family 7 member 11 (SLC7A11; also known as xCT) plays a key role in antioxidant defense by mediating cystine uptake, promoting glutathione synthesis, and maintaining cell survival under oxidative stress conditions. Recent studies showed that, to prevent toxic buildup of highly insoluble cystine inside cells, cancer cells with high expression of SLC7A11 (SLC7A11^high) are forced to quickly reduce cystine to more soluble cysteine, which requires substantial NADPH supply from the glucose-pentose phosphate pathway (PPP) route, thereby inducing glucose- and PPP-dependency in SLC7A11^high cancer cells. Limiting glucose supply to SLC7A11^high cancer cells results in significant NADPH “debt”, redox “bankruptcy”, and subsequent cell death. This review summarizes our current understanding of NADPH-generating and -consuming pathways, discusses the opposing role of SLC7A11 in protecting cells from oxidative stress–induced cell death such as ferroptosis but promoting glucose starvation–induced cell death, and proposes the concept that SLC7A11-mediated cystine uptake acts as a double-edged sword in cellular redox regulation. A detailed understanding of SLC7A11 in redox biology may identify metabolic vulnerabilities in SLC7A11^high cancer for therapeutic targeting.

A Systematic Review of Metabolomic Biomarkers for the Intake of Sugar-Sweetened and Low-Calorie Sweetened Beverages

Intake of added sugars (AS) is challenging to assess compared with total dietary sugar because of the lack of reliable assessment methods. The reliance on self-reported dietary data in observational studies is often cited as biased, with evidence of AS intake in relation to health outcomes rated as low to moderate quality. Sugar-sweetened beverages (SSBs) are a major source of AS. A regular and high intake of SSBs is associated with an overall poor diet, weight gain, and cardiometabolic risks. An elevated intake of low-calorie sweetened beverages (LCSBs), often regarded as healthier alternatives to SSBs, is also increasingly associated with increased risk for metabolic dysfunction. In this review, we systematically collate evidence and provide perspectives on the use of metabolomics for the discovery of candidate biomarkers associated with the intake of SSBs and LCSBs. We searched the Medline, Embase, Scopus, and Web of Science databases until the end of December 2020. Seventeen articles fulfilled our inclusion criteria. We evaluated specificity and validity of the identified biomarkers following Guidelines for Biomarker of Food Intake Reviews (BFIRev). We report that the ¹³C:¹²C carbon isotope ratio (δ¹³C), particularly, the δ¹³C of alanine is the most robust, sensitive, and specific biomarker of SSBs intake. Acesulfame-K, saccharin, sucralose, cyclamate, and steviol glucuronide showed moderate validity for predicting the short-term intake of LCSBs. More evidence is required to evaluate the validity of other panels of metabolites associated with the intake of SSBs.

The two faces of cyanide: an environmental toxin and a potential novel mammalian gasotransmitter

Cyanide is traditionally viewed as a cytotoxic agent, with its primary mode of action being the inhibition of mitochondrial Complex IV (cytochrome c oxidase). However, recent studies demonstrate that the effect of cyanide on Complex IV in various mammalian cells is biphasic: in lower concentrations (nanomolar to low micromolar) cyanide stimulates Complex IV activity, increases ATP production and accelerates cell proliferation, while at higher concentrations (high micromolar to low millimolar) it produces the previously known (‘classic’) toxic effects. The first part of the article describes the cytotoxic actions of cyanide in the context of environmental toxicology, and highlights pathophysiological conditions (e.g., cystic fibrosis with Pseudomonas colonization) where bacterially produced cyanide exerts deleterious effects to the host. The second part of the article summarizes the mammalian sources of cyanide production and overviews the emerging concept that mammalian cells may produce cyanide, in low concentrations, to serve biological regulatory roles. Cyanide fulfills many of the general criteria as a ‘classical’ mammalian gasotransmitter and shares some common features with the current members of this class: nitric oxide, carbon monoxide, and hydrogen sulfide.

The Incoherent Fluctuation of Folate Pools and Differential Regulation of Folate Enzymes Prioritize Nucleotide Supply in the Zebrafish Model Displaying Folate Deficiency-Induced Microphthalmia and Visual Defects

Objective

Congenital eye diseases are multi-factorial and usually cannot be cured. Therefore, proper preventive strategy and understanding the pathomechanism underlying these diseases become important. Deficiency in folate, a water-soluble vitamin B, has been associated with microphthalmia, a congenital eye disease characterized by abnormally small and malformed eyes. However, the causal-link and the underlying mechanism between folate and microphthalmia remain incompletely understood.

Methods

We examined the eye size, optomotor response, intracellular folate distribution, and the expression of folate-requiring enzymes in zebrafish larvae displaying folate deficiency (FD) and ocular defects.

Results

FD caused microphthalmia and impeded visual ability in zebrafish larvae, which were rescued by folate and dNTP supplementation. Cell cycle analysis revealed cell accumulation at S-phase and sub-G1 phase. Decreased cell proliferation and increased apoptosis were found in FD larvae during embryogenesis in a developmental timing-specific manner. Lowered methylenetetrahydrofolate reductase (mthfr) expression and up-regulated methylenetetrahydrofolate dehydrogenase (NADP⁺-dependent)-1-like (mthfd1L) expression were found in FD larvae. Knocking-down mthfd1L expression worsened FD-induced ocular anomalies; whereas increasing mthfd1L expression provided a protective effect. 5-CH₃-THF is the most sensitive folate pool, whose levels were the most significantly reduced in response to FD; whereas 10-CHO-THF levels were less affected. 5-CHO-THF is the most effective folate adduct for rescuing FD-induced microphthalmia and defective visual ability.

Conclusion

FD impeded nucleotides formation, impaired cell proliferation and differentiation, caused apoptosis and interfered active vitamin A production, contributing to ocular defects. The developmental timing-specific and incoherent fluctuation among folate adducts and increased expression of mthfd1L in response to FD reflect the context-dependent regulation of folate-mediated one-carbon metabolism, endowing the larvae to prioritize the essential biochemical pathways for supporting the continuous growth in response to folate depletion.

Methyl-Donor Micronutrient for Gestating Sows: Effects on Gut Microbiota and Metabolome in Offspring Piglets

This study aimed to investigate the effects of maternal methyl-donor micronutrient supplementation during gestation on gut microbiota and the fecal metabolic profile in offspring piglets. Forty-three Duroc × Erhualian gilts were assigned to two dietary groups during gestation: control diet (CON) and CON diet supplemented with MET (folic acid, methionine, choline, vitamin B6, and vitamin B12). The body weights of offspring piglets were recorded at birth and weaning. Besides this, fresh fecal samples of offspring piglets were collected at 7, 14, and 21 days. The gut microbiota composition, metabolic profile, and short-chain fatty acid (SCFA) profiles in the fecal samples were determined using 16S rDNA sequencing, liquid chromatography-mass spectrometry metabolomics, and gas chromatography methods, respectively. The results showed that maternal methyl-donor micronutrient supplementation increased the microbiota diversity and uniformity in feces of offspring piglets as indicated by increased Shannon and Simpson indices at 7 days, and greater Simpson, ACE, Chao1 and observed species indices at 21 days. Specifically, at the phylum level, the relative abundance of Firmicutes and the Firmicutes to Bacteroidetes ratio were elevated by maternal treatment. At the genus level, the relative abundance of SCFA-producing Dialister, Megasphaera, and Turicibacter, and lactate-producing Sharpea as well as Akkermansia, Weissella, and Pediococcus were increased in the MET group. The metabolic analyses show that maternal methyl-donor micronutrient addition increased the concentrations of individual and total SCFAs of 21-day piglets and increased metabolism mainly involving amino acids, pyrimidine, and purine biosynthesis. Collectively, maternal methyl-donor micronutrient addition altered gut microbiota and the fecal metabolic profile, resulting in an improved weaning weight of offspring piglets.

Combined effects of arsenic and palmitic acid on oxidative stress and lipid metabolism disorder in human hepatoma HepG2 cells

The toxicity of arsenic (As) can be influenced by many nutrients in food. However, the combined effects and underlying mechanisms of As and palmitic acid (PA) are still unclear. Here, cell viability, oxidative stress, lipids accumulation, gene expression profiles, and metabolome profiles of human hepatoma HepG2 cells exposed to As, PA, and As + PA were analyzed and compared. Results showed that co-exposure of 100 μM PA and 2 μM As induced lower cell viability, higher intracellular reactive oxygen species level, more lipid droplet accumulation, and more intracellular triglyceride contents than As alone or PA alone exposure. High-throughput quantitative PCR and ¹H NMR-based metabolomics analysis showed that co-exposure of As and PA caused all toxic effects on gene expression and metabolome profiles induced by As alone or PA alone exposure, and showed higher toxicities. Gene expression profiles in the As + PA group had higher similarity with those in the As group than the PA group. However, PA played a more important role in metabolism disorder than As in their interactive effects. Oxidative stress and lipid metabolism disorder were found to be the main toxic effects in the As + PA group. Several differentially expressed genes (such as OXR1, OXSR1, INSR, and PPARA) and changed metabolites (such as pyruvate, acetate, and L-phenylalanine) were involved in the combined toxicity of As and PA. This study provides basic information on the interactive effects of As and PA, which is useful for the health risk assessment of As and FFA.

The cellular function and molecular mechanism of formaldehyde in cardiovascular disease and heart development

As a common air pollutant, formaldehyde is widely present in nature, industrial production and consumer products. Endogenous formaldehyde is mainly produced through the oxidative deamination of methylamine catalysed by semicarbazide-sensitive amine oxidase (SSAO) and is ubiquitous in human body fluids, tissues and cells. Vascular endothelial cells and smooth muscle cells are rich in this formaldehyde-producing enzyme and are easily damaged owing to consequent cytotoxicity. Consistent with this, increasing evidence suggests that the cardiovascular system and stages of heart development are also susceptible to the harmful effects of formaldehyde. Exposure to formaldehyde from different sources can induce heart disease such as arrhythmia, myocardial infarction (MI), heart failure (HF) and atherosclerosis (AS). In particular, long-term exposure to high concentrations of formaldehyde in pregnant women is more likely to affect embryonic development and cause heart malformations than long-term exposure to low concentrations of formaldehyde. Specifically, the ability of mouse embryos to effect formaldehyde clearance is far lower than that of the rat embryos, more readily allowing its accumulation. Formaldehyde may also exert toxic effects on heart development by inducing oxidative stress and cardiomyocyte apoptosis. This review focuses on the current progress in understanding the influence and underlying mechanisms of formaldehyde on cardiovascular disease and heart development.

Application of Metabolomics in Pediatric Asthma: Prediction, Diagnosis and Personalized Treatment

Asthma in children remains a significant public health challenge affecting 5–20% of children in Europe and is associated with increased morbidity and societal healthcare costs. The high variation in asthma incidence among countries may be attributed to differences in genetic susceptibility and environmental factors. This respiratory disorder is described as a heterogeneous syndrome of multiple clinical manifestations (phenotypes) with varying degrees of severity and airway hyper-responsiveness, which is based on patient symptoms, lung function and response to pharmacotherapy. However, an accurate diagnosis is often difficult due to diversities in clinical presentation. Therefore, identifying early diagnostic biomarkers and improving the monitoring of airway dysfunction and inflammatory through non-invasive methods are key goals in successful pediatric asthma management. Given that asthma is caused by the interaction between genes and environmental factors, an emerging approach, metabolomics—the systematic analysis of small molecules—can provide more insight into asthma pathophysiological mechanisms, enable the identification of early biomarkers and targeted personalized therapies, thus reducing disease burden and societal cost. The purpose of this review is to present evidence on the utility of metabolomics in pediatric asthma through the analysis of intermediate metabolites of biochemical pathways that involve carbohydrates, amino acids, lipids, organic acids and nucleotides and discuss their potential application in clinical practice. Also, current challenges on the integration of metabolomics in pediatric asthma management and needed next steps are critically discussed.

Primary Metabolism co-Opted for Defensive Chemical Production in the Carabid Beetle, Harpalus pensylvanicus

Of the approximately one million described insect species, ground beetles (Coleoptera: Carabidae) have long captivated the attention of evolutionary biologists due to the diversity of defensive compounds they synthesize. Produced using defensive glands in the abdomen, ground beetle chemicals represent over 250 compounds including predator-deterring formic acid, which has evolved as a defensive strategy at least three times across Insecta. Despite being a widespread method of defense, formic acid biosynthesis is poorly understood in insects. Previous studies have suggested that the folate cycle of one-carbon (C1) metabolism, a pathway involved in nucleotide biosynthesis, may play a key role in defensive-grade formic acid production in ants. Here, we report on the defensive gland transcriptome of the formic acid-producing ground beetle Harpalus pensylvanicus. The full suite of genes involved in the folate cycle of C1 metabolism are significantly differentially expressed in the defensive glands of H. pensylvanicus when compared to gene expression profiles in the rest of the body. We also find support for two additional pathways potentially involved in the biosynthesis of defensive-grade formic acid, the kynurenine pathway and the methionine salvage cycle. Additionally, we have found an array of differentially expressed genes in the secretory lobes involved in the biosynthesis and transport of cofactors necessary for formic acid biosynthesis, as well as genes presumably involved in the detoxification of secondary metabolites including formic acid. We also provide insight into the evolution of the predominant gene family involved in the folate cycle (MTHFD) and suggest that high expression of folate cycle genes rather than gene duplication and/or neofunctionalization may be more important for defensive-grade formic acid biosynthesis in H. pensylvanicus. This provides the first evidence in Coleoptera and one of a few examples in Insecta of a primary metabolic process being co-opted for defensive chemical biosynthesis. Our results shed light on potential mechanisms of formic acid biosynthesis in the defensive glands of a ground beetle and provide a foundation for further studies into the evolution of formic acid-based chemical defense strategies in insects.

Pre-implantation exogenous progesterone and pregnancy in sheep: I. polyamines, nutrient transport, and progestamedins

Background

Administration of exogenous progesterone (P4) to ewes during the pre-implantation period advances conceptus development and implantation. This study determined effects of exogenous P4 on transport of select nutrients and pathways that enhance conceptus development. Pregnant ewes (n = 38) were treated with either 25 mg P4 in 1 mL corn oil (P4, n = 18) or 1 mL corn oil alone (CO, n = 20) from day 1.5 through day 8 of pregnancy and hysterectomized on either day 9 or day 12 of pregnancy. Endometrial expression of genes encoding enzymes for synthesis of polyamines, transporters of glucose, arginine, and glycine, as well as progestamedins was determined by RT-qPCR.

Results

On day 12 of pregnancy, conceptuses from P4-treated ewes had elongated while those from CO-treated ewes were spherical. The mRNA expression of AZIN2, an arginine decarboxylase, was lower in endometria of P4-treated than CO-treated ewes on day 9 of pregnancy. Expression of FGF10, a progestamedin, was greater in endometria of CO and P4-treated ewes on day 12 of gestation in addition to P4-treated ewes necropsied on day 9 of gestation. Treatment with P4 down-regulated endometrial expression of amino acid transporter SLC1A4 on day 12 of pregnancy.

Conclusions

Results indicated that administration of exogenous P4 during the pre-implantation period advanced the expression of FGF10, which may accelerate proliferation of trophectoderm cells, but also was correlated with decreased expression of glycine and serine transporters and polyamine synthesis enzyme AZIN2. Further research with increased sample sizes may determine how differential expression affects endometrial functions and potentially embryonic loss.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00554-6.

The emerging role of one-carbon metabolism in T cells

One-carbon metabolism (1CM) supports multiple biological functions, providing 1C units for nucleotide synthesis, epigenetic maintenance, and redox regulation. Although much has been deciphered about the relationship between disruption of 1CM and various diseases, our understanding of 1CM's involvement in the regulation of the immune system is only now evolving. In this review, we summarize key checkpoints of 1CM pathways that govern cellular activities. We also report on recent findings regarding the role of 1CM in T cells and discuss several promising avenues requiring future investigation.

The conversion of formate into purines stimulates mTORC1 leading to CAD-dependent activation of pyrimidine synthesis

BACKGROUND

Mitochondrial serine catabolism to formate induces a metabolic switch to a hypermetabolic state with high rates of glycolysis, purine synthesis and pyrimidine synthesis. While formate is a purine precursor, it is not clear how formate induces pyrimidine synthesis.

METHODS

Here we combine phospho-proteome and metabolic profiling to determine how formate induces pyrimidine synthesis.

RESULTS

We discover that formate induces phosphorylation of carbamoyl phosphate synthetase (CAD), which is known to increase CAD enzymatic activity. Mechanistically, formate induces mechanistic target of rapamycin complex 1 (mTORC1) activity as quantified by phosphorylation of its targets S6, 4E-BP1, S6K1 and CAD. Treatment with the allosteric mTORC1 inhibitor rapamycin abrogates CAD phosphorylation and pyrimidine synthesis induced by formate. Furthermore, we show that the formate-dependent induction of mTOR signalling and CAD phosphorylation is dependent on an increase in purine synthesis.

CONCLUSIONS

We conclude that formate activates mTORC1 and induces pyrimidine synthesis via the mTORC1-dependent phosphorylation of CAD.

Metabolic Potential of Cancer Cells in Context of the Metastatic Cascade

The metastatic cascade is a highly plastic and dynamic process dominated by cellular heterogeneity and varying metabolic requirements. During this cascade, the three major metabolic pillars, namely biosynthesis, RedOx balance, and bioenergetics, have variable importance. Biosynthesis has superior significance during the proliferation-dominated steps of primary tumour growth and secondary macrometastasis formation and only minor relevance during the growth-independent processes of invasion and dissemination. Consequently, RedOx homeostasis and bioenergetics emerge as conceivable metabolic key determinants in cancer cells that disseminate from the primary tumour. Within this review, we summarise our current understanding on how cancer cells adjust their metabolism in the context of different microenvironments along the metastatic cascade. With the example of one-carbon metabolism, we establish a conceptual view on how the same metabolic pathway can be exploited in different ways depending on the current cellular needs during metastatic progression.

Impact of Formate Supplementation on Body Weight and Plasma Amino Acids

Current nutritional recommendations are focused on energy, fat, carbohydrate, protein and vitamins. Less attention has been paid to the nutritional demand of one-carbon units for nucleotide and methionine synthesis. Here, we investigated the impact of sodium formate supplementation as a nutritional intervention to increase the dietary intake of one-carbon units. A cohort of six female and six male mice received 125 mM of sodium formate in the drinking water for three months. A control group of another six female and six male mice was also followed up for the same period of time. Tail vein blood samples were collected once a month and profiled with a haematology analyser. At the end of the study, blood and tissues were collected for metabolomics analysis and immune cell profiling. Formate supplementation had no significant physiological effect on male mice, except for a small decrease in body weight. Formate supplementation had no significant effect on the immune cell counts during the intervention or at the end of the study in either gender. In female mice, however, the body weight and spleen wet weight were significantly increased by formate supplementation, while the blood plasma levels of amino acids were decreased. Formate supplementation also increased the frequency of bifidobacteria, a probiotic bacterium, in the stools of female mice. We conclude that formate supplementation induces physiological changes in a gender-specific manner.

Nutrients, Mitochondrial Function, and Perinatal Health

Mitochondria are active independent organelles that not only meet the cellular energy requirement but also regulate central cellular activities. Mitochondria can play a critical role in physiological adaptations during pregnancy. Differences in mitochondrial function have been found between healthy and complicated pregnancies. Pregnancy signifies increased nutritional requirements to support fetal growth and the metabolism of maternal and fetal tissues. Nutrient availability regulates mitochondrial metabolism, where excessive macronutrient supply could lead to oxidative stress and contribute to mitochondrial dysfunction, while micronutrients are essential elements for optimal mitochondrial processes, as cofactors in energy metabolism and/or as antioxidants. Inadequate macronutrient and micronutrient consumption can result in adverse pregnancy outcomes, possibly through mitochondrial dysfunction, by impairing energy supply, one-carbon metabolism, biosynthetic pathways, and the availability of metabolic co-factors which modulate the epigenetic processes capable of establishing significant short- and long-term effects on infant health. Here, we review the importance of macronutrients and micronutrients on mitochondrial function and its influence on maternal and infant health.

Respiratory metabolites in bronchoalveolar lavage fluid (BALF) and exhaled breath condensate (EBC) can differentiate horses affected by severe equine asthma from healthy horses

BACKGROUND

The use of an untargeted metabolomic approach to investigate biofluids of respiratory origin is of increasing interest in human and veterinary lung research. Considering the high incidence of equine asthma (> 14%) within horse population and the importance of this animal model for human disease, we aimed to investigate the metabolomic profile of bronchoalveolar lavage fluid (BALF) and exhaled breath condensate (EBC) in healthy and asthmatic horses.

RESULTS

On the basis of clinical, endoscopic and BALF cytology findings, 6 horses with severe asthma (Group A) and 6 healthy horses (Group C) were included in the study. 1H-NMR analysis was used to identified metabolites in BALF and EBC samples. Metabolomic analysis allowed to identify and quantify 12 metabolites in BALF and seven metabolites in EBC. Among respiratory metabolites, myo-inositol, formate, glycerol and isopropanol in BALF, and methanol and ethanol in EBC, differed between groups (p < 0.05).

CONCLUSIONS

The application of metabolomic studies to investigate equine asthma using minimally invasive diagnostic methods, such as EBC metabolomics, provided promising results. According to our research, the study of selective profiles of BALF and EBC metabolites might be useful for identifying molecules like myo-inositol and methanol as possible biomarkers for airways diseases in horses.

One-Carbon Metabolism in Fatty Liver Disease and Fibrosis: One-Carbon to Rule Them All

Nonalcoholic fatty liver disease (NAFLD) is a term used to characterize a range of disease states that involve the accumulation of fat in the liver but are not associated with excessive alcohol consumption. NAFLD is a prevalent disease that can progress to organ damage like liver cirrhosis and hepatocellular carcinoma. Many animal models have demonstrated that one-carbon metabolism is strongly associated with NAFLD. Phosphatidylcholine is an important phospholipid that affects hepatic lipid homeostasis and de novo synthesis of this phospholipid is associated with NAFLD. However, one-carbon metabolism serves to support all cellular methylation reactions and catabolism of methionine, serine, glycine, choline, betaine, tryptophan, and histidine. Several different pathways within one-carbon metabolism that play important roles in regulating energy metabolism and immune function have received less attention in the study of fatty liver disease and fibrosis. This review examines what we have learned about hepatic lipid metabolism and liver damage from the study of one-carbon metabolism thus far and highlights unexplored opportunities for future research.

Glycine Enhances Satellite Cell Proliferation, Cell Transplantation, and Oligonucleotide Efficacy in Dystrophic Muscle

The need to distribute therapy evenly systemically throughout the large muscle volume within the body makes Duchenne muscular dystrophy (DMD) therapy a challenge. Cell and exon-skipping therapies are promising but have limited effects, and thus enhancing their therapeutic potency is of paramount importance to increase the accessibility of these therapies to DMD patients. In this study, we demonstrate that co-administered glycine improves phosphorodiamidate morpholino oligomer (PMO) potency in mdx mice with marked functional improvement and an up to 50-fold increase of dystrophin in abdominal muscles compared to PMO in saline. Glycine boosts satellite cell proliferation and muscle regeneration by increasing activation of mammalian target of rapamycin complex 1 (mTORC1) and replenishing the one-carbon unit pool. The expanded regenerating myofiber population then results in increased PMO uptake. Glycine also augments the transplantation efficiency of exogenous satellite cells and primary myoblasts in mdx mice. Our data provide evidence that glycine enhances satellite cell proliferation, cell transplantation, and oligonucleotide efficacy in mdx mice, and thus it has therapeutic utility for cell therapy and drug delivery in muscle-wasting diseases.

Formate metabolism in health and disease

BACKGROUND

Formate is a one-carbon molecule at the crossroad between cellular and whole body metabolism, between host and microbiome metabolism, and between nutrition and toxicology. This centrality confers formate with a key role in human physiology and disease that is currently unappreciated.

SCOPE OF REVIEW

Here we review the scientific literature on formate metabolism, highlighting cellular pathways, whole body metabolism, and interactions with the diet and the gut microbiome. We will discuss the relevance of formate metabolism in the context of embryonic development, cancer, obesity, immunometabolism, and neurodegeneration.

MAJOR CONCLUSIONS

We will conclude with an outlook of some open questions bringing formate metabolism into the spotlight.

An emerging perspective on sex differences: Intersecting S-nitrosothiol and aldehyde signaling in the heart

Cardiovascular disease is the leading cause of the death for both men and women. Although baseline heart physiology and the response to disease are known to differ by sex, little is known about sex differences in baseline molecular signaling, especially with regard to redox biology. In this review, we describe current research on sex differences in cardiac redox biology with a focus on the regulation of nitric oxide and aldehyde signaling. Furthermore, we argue for a new perspective on cardiovascular sex differences research, one that focuses on baseline redox biology without the elimination or disruption of sex hormones.

Formate and its role in amino acid metabolism

PURPOSE OF REVIEW

The aim of this report is to examine critical relationships between amino acid and formate metabolism with particular reference to the production of formate, and to review novel functions of formate.

RECENT FINDINGS

In addition to well established mechanisms in one-carbon metabolism, formate may play an important role in early pregnancy by preventing the onset of neural tube defects in sensitive strains of mice, including mice with deficiencies in MTHFD1L, the glycine cleavage system and the mitochondrial folate transporter. Markedly elevated, circulating levels of formate are found in late pregnancy, including in cord blood, as well as elevated levels of amino acid precursors. These are consistent with specific roles for formate in late pregnancy. Serine metabolism may reduce NADP to NADPH and permit the use of NADPH in reductive reactions. Novel, noncanonical functions of formate include high rates of formate production from serine in cells and in cancers.

SUMMARY

Novel, noncanonical functions of formate continue to be discovered. Integrating their functions with well established elements of one-carbon metabolism remains an important future objective.

NMR-based metabolomics analysis identifies discriminatory metabolic disturbances in tissue and biofluid samples for progressive prostate cancer

BACKGROUND

Prostate cancer (PCa) is one of the most common cancers in men, but its metabolic characteristics during tumor progression are still far from being fully understood.

METHODS

The metabolic profiles of matched tissue, serum and urine samples from the same patients were analyzed using a ¹H NMR-based metabolomics approach. We identified several important metabolites that significantly altered at different stages of PCa, including benign prostatic hyperplasia (BPH), early PCa (EPC), advanced PCa (APC), metastatic PCa (MPC) and castration-resistant PCa (CRPC). Metabolic correlation networks among tissue, serum and urine samples were examined using Pearson's correlation.

RESULTS

The changes in metabolic phenotypes during the progression of PCa were more noticeable in tissue samples when compared with serum and urine samples. Herein we identified a series of important metabolic disturbances, including decreased trends of citrate, creatinine, acetate, leucine, valine, glycine, lysine, histidine, glutamine and choline as well as increased trends of uridine and formate. These metabolites are mainly implicated in energy metabolism, amino acid metabolism, choline and fatty acid metabolism as well as uridine metabolism. We also found that energy metabolism in tumor tissues was positively associated with amino acid metabolism in serum and urine. Additionally, CRPC patients had a peculiar metabolic phenotype, especially decreased amino acid metabolism in serum.

CONCLUSIONS

The present study characterizes metabolic disturbances in both tissue and biofluid samples during PCa progression and provides potential diagnostic biomarkers and therapeutic targets for PCa.

Formate concentrations in maternal plasma during pregnancy and in cord blood in a cohort of pregnant Canadian women: relations to genetic polymorphisms and plasma metabolites

BACKGROUND

One-carbon metabolism, responsible for purine and thymidylate synthesis and transmethylation reactions, plays a critical role in embryonic and fetal development. Formate is a key player in one-carbon metabolism. In contrast to other one-carbon metabolites, it is not linked to tetrahydrofolate, is present in plasma at appreciable concentrations, and may therefore be distributed to different tissues.

OBJECTIVE

The study was designed to determine the concentration of formate in cord blood in comparison with maternal blood taken earlier in pregnancy and at delivery and to relate formate concentrations to potential precursors and key fetal genotypes.

METHODS

Formate and amino acids were measured in plasma during early pregnancy (12-16 wk), at delivery (37-42 wk), and in cord blood samples from 215 mothers, of a prospective cohort study. Three fetal genetic variants in one-carbon metabolism were assessed for their association with cord plasma concentrations of formate.

RESULTS

The formate concentration was ∼60% higher in the cord blood samples than in mothers' plasma. The maternal formate concentrations did not differ between the early pregnancy samples and those taken at delivery. Plasma concentrations of 4 formate precursors (serine, glycine, tryptophan, and methionine) were increased in cord blood compared with the maternal samples. Cord blood formate was influenced by fetal genotype, being ∼12% higher in infants harboring the MTHFR A1298C (rs1801131) AC or CC genotypes and 10% lower in infants harboring the MTHFD1 G1958A (rs2236225) GA or AA genotypes.

CONCLUSIONS

The increased formate concentrations in cord blood may support the increased activity of one-carbon metabolism in infants. As such, it would support increased rates of purine and thymidylate synthesis and the provision of methionine for methylation reactions.