[Show abstract][Hide abstract] ABSTRACT: Objective:
Metabolomics is a promising approach to the identification of biomarkers in plasma. Here, we performed a population-based, cross-sectional study to identify potential biomarkers of alcohol intake and alcohol-induced liver injury by metabolomic profiling using capillary electrophoresis-mass spectrometry (CE-MS).
Fasting plasma samples were collected from 896 Japanese men who participated in the baseline survey of the Tsuruoka Metabolomics Cohort Study, and 115 polar metabolites were identified and absolutely quantified by CE-MS. Information on daily ethanol intake was collected through a standardized, self-administered questionnaire. The associations between ethanol intake and plasma concentration of metabolites were examined. Relationships between metabolite concentrations or their ratios and serum liver enzyme levels in the highest ethanol intake group (>46.0 g/day) were then examined by linear regression analysis. Replication analysis was conducted in 193 samples collected from independent population of this cohort.
Nineteen metabolites were identified to have an association with daily alcohol consumption both in the original and replication population. Three of these metabolites (threonine, glutamine, and guanidinosuccinate) were found to associate well with elevated levels of serum liver enzymes in the highest ethanol intake group, but not in the non-drinker group. We also found that the glutamate/glutamine ratio had a much stronger relation to serum γ-glutamyltransferase, aspartate transaminase, and alanine transaminase than glutamate or glutamine alone (standardized beta = 0.678, 0.558, 0.498, respectively).
We found 19 metabolites associated with alcohol intake, and three biomarker candidates (threonine, guanidinosuccinate and glutamine) of alcohol-induced liver injury. Glutamate/glutamine ratio might also be good biomarker.
Environmental Health and Preventive Medicine 10/2015; DOI:10.1007/s12199-015-0494-y
[Show abstract][Hide abstract] ABSTRACT: Intravenous administration of high-dose vitamin C has recently attracted attention as a cancer therapy. High-dose vitamin C induces pro-oxidant effects and selectively kills cancer cells. However, the anticancer mechanisms of vitamin C are not fully understood. Here, we analyzed metabolic changes induced by vitamin C in MCF7 human breast adenocarcinoma and HT29 human colon cancer cells using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). The metabolomic profiles of both cell lines were dramatically altered after exposure to cytotoxic concentrations of vitamin C. Levels of upstream metabolites in the glycolysis pathway and tricarboxylic acid (TCA) cycle were increased in both cell lines following treatment with vitamin C, while adenosine triphosphate (ATP) levels and adenylate energy charges were decreased concentration-dependently. Treatment with N-acetyl cysteine (NAC) and reduced glutathione (GSH) significantly inhibited vitamin C-induced cytotoxicity in MCF7 cells. NAC also suppressed vitamin C-dependent metabolic changes, and NAD treatment prevented vitamin C-induced cell death. Collectively, our data suggests that vitamin C inhibited energy metabolism through NAD depletion, thereby inducing cancer cell death.
[Show abstract][Hide abstract] ABSTRACT: Unlike bacteria such as Escherichia coli and Bacillus subtilis, several species of freshwater cyanobacteria are known to contain multiple chromosomal copies per cell, at all stages of their cell cycle. We have characterized the replication of multi-copy chromosomes in the cyanobacterium Synechococcus elongatus PCC 7942 (hereafter Synechococcus 7942). In Synechococcus 7942, the replication of multi-copy chromosome is asynchronous, not only among cells but also among multi-copy chromosomes. This suggests that DNA replication is not tightly coupled to cell division in Synechococcus 7942. To address this hypothesis, we analysed the relationship between DNA replication and cell doubling at various growth phases of Synechococcus 7942 cell culture. Three distinct growth phases were characterised in Synechococcus 7942 batch culture: lag phase, exponential phase, and arithmetic (linear) phase. The chromosomal copy number was significantly higher during the lag phase than during the exponential and linear phases. Likewise, DNA replication activity was higher in the lag phase cells than in the exponential and linear phase cells, and the lag phase cells were more sensitive to nalidixic acid, a DNA gyrase inhibitor, than cells in other growth phases. To elucidate physiological differences in Synechococcus 7942 during the lag phase, we analysed the metabolome at each growth phase. In addition, we assessed the accumulation of central carbon metabolites, amino acids, and DNA precursors at each phase. The results of these analyses suggest that Synechococcus 7942 cells prepare for cell division during the lag phase by initiating intensive chromosomal DNA replication and accumulating metabolites necessary for the subsequent cell division and elongation steps that occur during the exponential growth and linear phases.
PLoS ONE 09/2015; 10(9):e0136800. DOI:10.1371/journal.pone.0136800 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Reduced expression of microRNA122 (miR122), a liver-specific microRNA, is frequent in hepatocellular carcinoma (HCC). However, its biological significances remain poorly understood. Because deregulated amino acid levels in cancers can affect their biological behavior, we determined the amino acid levels in miR122-silenced mouse liver tissues, in which intracellular arginine levels were significantly increased. The increased intracellular arginine levels were through upregulation of the solute carrier family 7 (SLC7A1), a transporter of arginine and a direct target of miR122. Arginine is the substrate for nitric oxide (NO) synthetase, and intracellular NO levels were increased in miR122-silenced HCC cells, with increased resistance to sorafenib, a multikinase inhibitor. Conversely, maintenance of the miR122-silenced HCC cells in arginine-depleted culture media, as well as overexpression of miR122 in miR122-low-expressing HCC cells, reversed these effects and rendered the cells more sensitive to sorafenib. Using a reporter knock-in construct, chemical compounds were screened, and Wee1 kinase inhibitor was identified as upregulators of miR122 transcription, which increased the sensitivity of the cells to sorafenib. These results provide an insight into sorafenib resistance in miR122-low HCC, and suggest that arginine depletion or a combination of sorafenib with the identified compound may provide promising approaches to managing this HCC subset.
[Show abstract][Hide abstract] ABSTRACT: In the present study, prior to the establishment of a method for the clinical diagnosis of chronic fatigue in humans, we validated the utility of plasma metabolomic analysis in a rat model of fatigue using capillary electrophoresis-mass spectrometry (CE-MS). In order to obtain a fatigued animal group, rats were placed in a cage filled with water to a height of 2.2 cm for 5 days. A food-restricted group, in which rats were limited to 10 g/d of food (around 50% of the control group), was also assessed. The food-restricted group exhibited weight reduction similar to that of the fatigued group. CE-MS measurements were performed to evaluate the profile of food intake-dependent metabolic changes, as well as the profile in fatigue loading, resulting in the identification of 48 metabolites in plasma. Multivariate analyses using hierarchical clustering and principal component analysis revealed that the plasma metabolome in the fatigued group showed clear differences from those in the control and food-restricted groups. In the fatigued group, we found distinctive changes in metabolites related to branched-chain amino acid metabolism, urea cycle, and proline metabolism. Specifically, the fatigued group exhibited significant increases in valine, leucine, isoleucine, and 2-oxoisopentanoate, and significant decreases in citrulline and hydroxyproline compared with the control and food-restricted groups. Plasma levels of total nitric oxide were increased in the fatigued group, indicating systemic oxidative stress. Further, plasma metabolites involved in the citrate cycle, such as cis-aconitate and isocitrate, were reduced in the fatigued group. The levels of ATP were significantly decreased in the liver and skeletal muscle, indicative of a deterioration in energy metabolism in these organs. Thus, this comprehensive metabolic analysis furthered our understanding of the pathophysiology of fatigue, and identified potential diagnostic biomarkers based on fatigue pathophysiology.
PLoS ONE 03/2015; 10(3):e0120106. DOI:10.1371/journal.pone.0120106 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The development of high throughput metabolite measurement technologies has enabled the use of metabolomics for epidemiologic studies by profiling metabolite concentrations in large cohorts of human blood samples. Standard protocols are necessary to obtain unbiased profiles through multiple runs over long periods of time and to allow reliable statistical analyses. This study assessed the effects of sampling procedures and storage conditions on the stability of metabolomic profiles in blood and serum. Charged metabolomic profiles were determined by capillary electrophoresis-mass spectrometry (CE-MS) and compared by multivariate analyses. The effects of pre-analytical procedures, including times for clotting and incubation of serum and plasma, respectively; incubation temperatures; and number of freeze-thaw cycles, were assessed. Overall, inter-individual differences in profiles were larger than intra-individual differences, and profiles in plasma showed better stability than those in serum. These quantified datasets of metabolites, along with their stability and variation, may help in interpreting data from long-term cohort studies. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Capillary electrophoresis-mass spectrometry (CE-MS) has proven to be useful for metabolomics studies. Charged metabolites are first separated by CE based on charge and size and are subsequently selectively detected using MS. The major advantages of CE-MS are its high resolution and the fact that almost any charged species can be analyzed by two methods, both cationic and anionic. This technique can readily be applied to various types of biological samples originating from bacteria, plants, mammals, and body fluids. This chapter highlights detailed practical procedures for using this technology.
[Show abstract][Hide abstract] ABSTRACT: The biochemistry of cancer cells diverges significantly from normal cells as a result of a comprehensive reprogramming of metabolic pathways. A major factor influencing cancer metabolism is hypoxia, which is mediated by HIF1α and HIF2α. HIF1α represents one of the principal regulators of metabolism and energetic balance in cancer cells through its regulation of glycolysis, glycogen synthesis, Krebs cycle and the pentose phosphate shunt. However, less is known about the role of HIF1α in modulating lipid metabolism. Lipids serve cancer cells to provide molecules acting as oncogenic signals, energetic reserve, precursors for new membrane synthesis and to balance redox biological reactions. To study the role of HIF1α in these processes, we used HCT116 colorectal cancer cells expressing endogenous HIF1α and cells in which the hif1α gene was deleted to characterize HIF1α-dependent and independent effects on hypoxia regulated lipid metabolites. Untargeted metabolomics integrated with proteomics revealed that hypoxia induced many changes in lipids metabolites. Enzymatic steps in fatty acid synthesis and the Kennedy pathway were modified in a HIF1α-dependent fashion. Palmitate, stearate, PLD3 and PAFC16 were regulated in a HIF-independent manner. Our results demonstrate the impact of hypoxia on lipid metabolites, of which a distinct subset is regulated by HIF1α.
[Show abstract][Hide abstract] ABSTRACT: Serum γ-glutamyl di- and tripeptides have proven to be useful biomarkers to accurately predict nine different forms of liver disease. Using liquid chromatography–tandem mass spectrometry (LC–MS/MS) with multiple reaction monitoring (MRM), serum and liver samples spiked with γ-glutamyl peptide standards were analyzed to estimate accuracy. Unexpectedly, the recovery rates for several γ-glutamyl peptides in the serum samples were quite low, whereas values for some γ-glutamyl peptides in the liver samples were highly elevated. Most of these peptides were barely retained on the reverse-phase column, resulting in significant ion suppression or enhancement. In contrast, a capillary electrophoresis tandem mass spectrometry (CE-MS/MS) method with MRM was minimally affected by matrix effects. Of the 39 tested compounds, most of γ-glutamyl peptides that did not contain a thiol substituent in its structure gave acceptable recoveries (70–120%), and limits of detection for the analytes were between 3.6 and 800 nmol/l with pressure injection at 5 kPa for 10 s (ca. 10 nl). The CE-MS/MS method provided high resolution and proved to be highly selective and sensitive, its utility being demonstrated by the determination of γ-glutamyl di- and tripeptides in serum and liver samples.
Journal of Chromatography A 11/2014; 1369. DOI:10.1016/j.chroma.2014.10.007 · 4.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Quinonoid dihydropteridine reductase (QDPR) catalyzes the regeneration of tetrahydrobiopterin (BH4), a cofactor for monoamine synthesis, phenylalanine hydroxylation and nitric oxide production. Here, we produced and analyzed a transgenic Qdpr(-/-) mouse model. Unexpectedly, the BH4 contents in the Qdpr(-/-) mice were not decreased and even increased in some tissues, whereas those of the oxidized form dihydrobiopterin (BH2) were significantly increased. We demonstrated that unlike the wild-type mice, dihydrofolate reductase regenerated BH4 from BH2 in the mutants. Furthermore, we revealed wide alterations in folate-associated metabolism in the Qdpr(-/-) mice, which suggests an interconnection between folate and biopterin metabolism in the transgenic mouse model.
[Show abstract][Hide abstract] ABSTRACT: Unlabelled:
L-cysteine is essential for virtually all living organisms, from bacteria to higher eukaryotes. Besides having a role in the synthesis of virtually all proteins and of taurine, cysteamine, glutathione, and other redox-regulating proteins, L-cysteine has important functions under anaerobic/microaerophilic conditions. In anaerobic or microaerophilic protozoan parasites, such as Entamoeba histolytica, L-cysteine has been implicated in growth, attachment, survival, and protection from oxidative stress. However, a specific role of this amino acid or related metabolic intermediates is not well understood. In this study, using stable-isotope-labeled L-cysteine and capillary electrophoresis-time of flight mass spectrometry, we investigated the metabolism of L-cysteine in E. histolytica. [U-(13)C3, (15)N]L-cysteine was rapidly metabolized into three unknown metabolites, besides L-cystine and L-alanine. These metabolites were identified as thiazolidine-4-carboxylic acid (T4C), 2-methyl thiazolidine-4-carboxylic acid (MT4C), and 2-ethyl-thiazolidine-4-carboxylic acid (ET4C), the condensation products of L-cysteine with aldehydes. We demonstrated that these 2-(R)-thiazolidine-4-carboxylic acids serve for storage of L-cysteine. Liberation of L-cysteine occurred when T4C was incubated with amebic lysates, suggesting enzymatic degradation of these L-cysteine derivatives. Furthermore, T4C and MT4C significantly enhanced trophozoite growth and reduced intracellular reactive oxygen species (ROS) levels when it was added to cultures, suggesting that 2-(R)-thiazolidine-4-carboxylic acids are involved in the defense against oxidative stress.
Amebiasis is a human parasitic disease caused by the protozoan parasite Entamoeba histolytica. In this parasite, L-cysteine is the principal low-molecular-weight thiol and is assumed to play a significant role in supplying the amino acid during trophozoite invasion, particularly when the parasites move from the anaerobic intestinal lumen to highly oxygenated tissues in the intestine and the liver. It is well known that E. histolytica needs a comparatively high concentration of L-cysteine for its axenic cultivation. However, the reason for and the metabolic fate of L-cysteine in this parasite are not well understood. Here, using a metabolomic and stable-isotope-labeled approach, we investigated the metabolic fate of this amino acid in these parasites. We found that L-cysteine inside the cell rapidly reacts with aldehydes to form 2-(R)-thiazolidine-4-carboxylic acid. We showed that these 2-(R)-thiazolidine-4-carboxylic derivatives serve as an L-cysteine source, promote growth, and protect cells against oxidative stress by scavenging aldehydes and reducing the ROS level. Our findings represent the first demonstration of 2-(R)-thiazolidine-4-carboxylic acids and their roles in protozoan parasites.
[Show abstract][Hide abstract] ABSTRACT: The structural dynamics of chromatin have been implicated in the regulation of fundamental eukaryotic processes, such as DNA transcription, replication and repair. Although previous studies have revealed that the chromatin landscape, nucleosome remodeling and histone modification events are intimately tied into cellular energetics and redox state, few studies undertake defined time-resolved measurements of these state variables. Here, we use metabolically synchronous, continuously-grown yeast cultures to measure DNA occupancy and track global patterns with respect to the metabolic state of the culture. Combined with transcriptome analyses and ChIP-qPCR experiments, these paint an intriguing picture where genome-wide nucleosome focusing occurs during the recovery of energy charge, followed by clearance of the promoter regions and global transcriptional slowdown , thus indicating a nucleosome-mediated " reset point " for the cycle. The reset begins at the end of the catabolic and stress-response transcriptional programs and ends prior to the start of the anabolic and cell-growth transcrip-tional program, and the histones on genes from both the catabolic and ana-bolic superclusters are deacetylated.
[Show abstract][Hide abstract] ABSTRACT: Gastric mucosal ulceration and gastric hemorrhage are frequently associated with treatment by non-steroid anti-inflammatory drugs (NSAIDs); however, no convenient biomarker-based diagnostic methods for these adverse reactions are currently available, requiring the use of endoscopic evaluation. We recently reported five biomarker candidates in serum which predict gastric injury induced by NSAIDs in rats, but were unable to clarify the mechanism of change in the levels of these biomarker candidates. In this study, we performed capillary electrophoresis–mass spectrometry-based metabolomic profiling in stomach and serum from rats in which gastric ulcer was induced by aspirin and prevented by co-administration of omeprazole and famotidine. Results showed drug-induced decreases in the levels of citrate, cis-aconitate, succinate, 3-hydroxy butanoic acid, and O-acetyl carnitine in all animals administered aspirin. In contrast, aspirin-induced decreases in the level of 4-hydroxyproline were suppressed by co-administration of omeprazole and famotidine. We consider that these changes were due to the prevention of gastric ulcer and decrease in the amount of collagen in stomach tissue by omeprazole and famotidine, without prevention of the NSAID-induced depression of mitochondrial function. In addition, the decreases in 4-hydroxyproline in the stomach was also detectable as changes in the serum. While further study is needed to clarify limitations of indications and extrapolation to humans, this new serum biomarker candidate of gastric injury may be useful in the monitoring of NSAID-induced tissue damage.
[Show abstract][Hide abstract] ABSTRACT: Capillary electrophoresis-mass spectrometry (CE-MS) has emerged as a powerful new tool for comprehensive analysis of charged compounds. In this review, we provide a general description of the application of CE-MS in metabolome analysis, including the separation modes of CE, various interfaces and the mass spectrometers used. We also discuss strategies for sample pretreatment, data processing and peak identification, which are important processes in metabolome analysis. In addition, we highlight a number of new techniques to improve metabolite extraction, peak resolution and sensitivity. Finally, we provide some general conclusions and future perspectives.
[Show abstract][Hide abstract] ABSTRACT: Ezrin is a membrane-associated cytoplasmic protein that serves to link cell-membrane proteins with the actin-based cytoskeleton, and also plays a role in regulation of the functional activities of some transmembrane proteins. It is expressed in placental trophoblasts. We hypothesized that placental ezrin is involved in the supply of nutrients from mother to fetus, thereby influencing fetal growth. The aim of this study was firstly to clarify the effect of ezrin on fetal growth and secondly to determine whether knockout of ezrin is associated with decreased concentrations of serum and placental nutrients. Ezrin knockout mice (Ez-/-) were confirmed to exhibit fetal growth retardation. Metabolome analysis of fetal serum and placental extract of ezrin knockout mice by means of capillary electrophoresis-time-of-flight mass spectrometry revealed a markedly decreased concentration of hypotaurine, a precursor of taurine. However, placental levels of cysteine and cysteine sulfinic acid (precursors of hypotaurine) and taurine were not affected. Lack of hypotaurine in Ez-/- mice was confirmed by liquid chromatography with tandem mass spectrometry. Administration of hypotaurine to heterogenous dams significantly decreased the placenta-to-maternal plasma ratio of hypotaurine in wild-type fetuses but only slightly decreased it in ezrin knockout fetuses, indicating that the uptake of hypotaurine from mother to placenta is saturable and that disruption of ezrin impairs the uptake of hypotaurine by placental trophoblasts. These results indicate that ezrin is required for uptake of hypotaurine from maternal serum by placental trophoblasts, and plays an important role in fetal growth.
PLoS ONE 08/2014; 9(8):e105423. DOI:10.1371/journal.pone.0105423 · 3.23 Impact Factor