Metabolite profiling of fecal water extracts from human colorectal cancer

Identification of biomarkers for apoptosis in cancer cell lines using metabolomics: tools for individualized medicine

BACKGROUND

Metabolomics is a versatile unbiased method to search for biomarkers of human disease. In particular, one approach in cancer therapy is to promote apoptosis in tumour cells; this could be improved with specific biomarkers of apoptosis for monitoring treatment. We recently observed specific metabolic patterns in apoptotic cell lines; however, in that study, apoptosis was only induced with one pro-apoptotic agent, staurosporine.

OBJECTIVE

The aim of this study was to find novel biomarkers of apoptosis by verifying our previous findings using two further pro-apoptotic agents, 5-fluorouracil and etoposide, that are commonly used in anticancer treatment.

METHODS

Metabolic parameters were assessed in HepG2 and HEK293 cells using the newborn screening assay adapted for cell culture approaches, quantifying the levels of amino acids and acylcarnitines with mass spectrometry.

RESULTS

We were able to identify apoptosis-specific changes in the metabolite profile. Moreover, the amino acids alanine and glutamate were both significantly up-regulated in apoptotic HepG2 and HEK293 cells irrespective of the apoptosis inducer.

CONCLUSION

Our observations clearly indicate the potential of metabolomics in detecting metabolic biomarkers applicable in theranostics and for monitoring drug efficacy.

Review article: small intestinal bacterial overgrowth--prevalence, clinical features, current and developing diagnostic tests, and treatment

BACKGROUND

The symptoms and signs of small intestinal bacterial overgrowth (SIBO) are often identical to a variety of diseases and can lead to diagnostic confusion.

AIMS

To review the diagnostic options for SIBO and present new investigative options for the condition.

METHODS

A literature search was performed on MEDLINE, EMBASE and Web of Science for English articles and abstracts. Search terms included free text words and combinations of the following terms 'small intestinal bacterial overgrowth', 'small bowel bacterial overgrowth', 'diagnostic tests', 'treatment', 'antibiotics', 'probiotics', 'metabonomics', 'proton nuclear magnetic resonance spectroscopy', 'electronic nose' and 'field asymmetric ion mobility spectrometry'.

RESULTS

All of the available methods to test for SIBO have inherent limitations and no 'gold-standard' diagnostic test for the condition exists. Accurate diagnosis of SIBO requires identification of bacterial species growing inappropriately within the small intestine and symptom response to antibiotics. Proton nuclear magnetic resonance spectroscopy, electronic nose technology and/or field asymmetric ion mobility spectrometry may represent better investigative options for the condition.

CONCLUSIONS

Novel diagnostic options are needed to supplement or replace available tests.

Metabolomic profiling in colorectal cancer: opportunities for personalized medicine

Colorectal cancer (CRC) is one of the most common types of cancer in the world, with high prevalence and mortality. Understanding the alterations of cancer metabolism and identifying reliable biomarkers would facilitate the development of novel technologies of CRC screening and early diagnosis, as well as new approaches to providing personalized medicine. Metabolomics, as an emerging molecular phenotyping approach, provides a clinical platform technology with an unprecedented amount of metabolic readout information, which is ideal for theranostic biomarker discovery. Metabolic signatures can link the unique pathophysiological states of patients to personalized health monitoring and intervention strategies. This article presents an overview of the metabolomic studies of CRC with a focus on recent advances in the biomarker discovery in serum, urine, fecal water and tissue samples for cancer diagnosis. The development and application of metabolomics towards personalized medicine, including early diagnosis, cancer staging, treatment and drug discovery are also discussed.

Global gas chromatography/time-of-flight mass spectrometry (GC/TOFMS)-based metabonomic profiling of lyophilized human feces

Gas chromatography mass spectrometry (GC/MS)-based fecal metabonomics represents a powerful systems biology approach for elucidating metabolic biomarkers of lower gastrointestinal tract (GIT) diseases. Unlike metabolic profiling of fecal water, the profiling of complete fecal material remains under-explored. Here, a gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) method was developed and validated for the global metabonomic profiling of human feces. Fecal and fecal water metabotypes were also profiled and compared. Additionally, the unclear influence of blood in stool on the fecal metabotype was investigated unprecedentedly. Eighty milligram of lyophilized feces was ultrasonicated with 1mL of methanol:water (8:2) for 30min, followed by centrifugation, drying of supernatant, oximation and trimethylsilylation for 45min. Lyophilized feces demonstrated a more comprehensive metabolic coverage than fecal water, based on the number of chromatographic peaks. Principal component analysis (PCA) indicated occult blood (1mgHb/g feces) exerted a negligible effect on the fecal metabotype. Conversely, a unique metabotype related to feces spiked with gross blood (100mgHb/g feces) was revealed (PCA, R(2)X=0.837, Q(2)=0.794), confirming the potential confounding effect of gross GIT bleeding on the fecal metabotype. This pertinent finding highlights the importance of prudent interpretation of fecal metabonomic data, particularly in GIT diseases where bleeding is prevalent.

Metabolomics approaches for characterizing metabolic interactions between host and its commensal microbes

It is increasingly evident that the gut microbiota is involved in the regulation of multiple mammalian metabolic pathways through a series of interactive host-microbiota metabolic, signaling, and immune-inflammatory axes that physiologically connect the gut, liver, brain, and other organs. Correlation of the metabotypes with the gut microbial profiles derived from culture-independent molecular techniques is increasingly useful for deciphering inherent and intimate host-microbe relationships. Real-time analysis of the small molecule metabolites derived from gut microbial-host co-metabolism is essential for understanding the metabolic functions of the gut microbiome and has tremendous implications for personalized healthcare strategies. Metabolomics, an array of analytical techniques that includes high resolution NMR spectroscopy and chromatography-MS in conjunction with chemometrics and bioinformatics tools, enables characterization of the metabolic footprints of mammalian hosts that correlate with the microbial community in the intestinal tract. The metabolomics approach provides important information of a complete spectrum of metabolites produced from the gut microbial-mammalian co-metabolism and is improving our understanding of the molecular mechanisms underlying multilevel host-microbe interactions. In this review, the interactions of gut microbiota with their host are discussed and some examples of NMR- or MS-based metabolomics applications for characterizing the metabolic footprints of gut microbial-host co-metabolism are described. Advances in the metabolomic analysis of bile acids, short-chain fatty acids, and choline metabolism are also summarized.

Stool microbiome and metabolome differences between colorectal cancer patients and healthy adults

In this study we used stool profiling to identify intestinal bacteria and metabolites that are differentially represented in humans with colorectal cancer (CRC) compared to healthy controls to identify how microbial functions may influence CRC development. Stool samples were collected from healthy adults (n = 10) and colorectal cancer patients (n = 11) prior to colon resection surgery at the University of Colorado Health-Poudre Valley Hospital in Fort Collins, CO. The V4 region of the 16s rRNA gene was pyrosequenced and both short chain fatty acids and global stool metabolites were extracted and analyzed utilizing Gas Chromatography-Mass Spectrometry (GC-MS). There were no significant differences in the overall microbial community structure associated with the disease state, but several bacterial genera, particularly butyrate-producing species, were under-represented in the CRC samples, while a mucin-degrading species, Akkermansia muciniphila, was about 4-fold higher in CRC (p<0.01). Proportionately higher amounts of butyrate were seen in stool of healthy individuals while relative concentrations of acetate were higher in stools of CRC patients. GC-MS profiling revealed higher concentrations of amino acids in stool samples from CRC patients and higher poly and monounsaturated fatty acids and ursodeoxycholic acid, a conjugated bile acid in stool samples from healthy adults (p<0.01). Correlative analysis between the combined datasets revealed some potential relationships between stool metabolites and certain bacterial species. These associations could provide insight into microbial functions occurring in a cancer environment and will help direct future mechanistic studies. Using integrated “omics” approaches may prove a useful tool in identifying functional groups of gastrointestinal bacteria and their associated metabolites as novel therapeutic and chemopreventive targets.

The future of NMR metabolomics in cancer therapy: towards personalizing treatment and developing targeted drugs?

There has been a recent shift in how cancers are defined, where tumors are no longer simply classified by their tissue origin, but also by their molecular characteristics. Furthermore, personalized medicine has become a popular term and it could start to play an important role in future medical care. However, today, a "one size fits all" approach is still the most common form of cancer treatment. In this mini-review paper, we report on the role of nuclear magnetic resonance (NMR) metabolomics in drug development and in personalized medicine. NMR spectroscopy has successfully been used to evaluate current and potential therapies, both single-agents and combination therapies, to analyze toxicology, optimal dose, resistance, sensitivity, and biological mechanisms. It can also provide biological insight on tumor subtypes and their different responses to drugs, and indicate which patients are most likely to experience off-target effects and predict characteristics for treatment efficacy. Identifying pre-treatment metabolic profiles that correlate to these events could significantly improve how we view and treat tumors. We also briefly discuss several targeted cancer drugs that have been studied by metabolomics. We conclude that NMR technology provides a key platform in metabolomics that is well-positioned to play a crucial role in realizing the ultimate goal of better tailored cancer medicine.

Ageing and gut microbes: perspectives for health maintenance and longevity

The ageing process affects the human gut microbiota phylogenetic composition and its interaction with the immune system. Age-related gut microbiota modifications are associated with immunosenescence and inflamm-ageing in a sort of self-sustaining loop, which allows the placement of gut microbiota unbalances among both the causes and the effects of the inflamm-ageing process. Even if, up to now, the link between gut microbiota and the ageing process is only partially understood, the gut ecosystem shows the potential to become a promising target for strategies able to contribute to the health status of older people. In this context, the consumption of pro/prebiotics may be useful in both prevention and treatment of age-related pathophysiological conditions, such as recovery and promotion of immune functions, i.e. adjuvant effect for influenza vaccine, and prevention and/or alleviation of common "winter diseases", as well as constipation and Clostridium difficile-associated diarrhoea. Moreover, being involved in different mechanisms which concur in counteracting inflammation, such as down-regulation of inflammation-associated genes and improvement of colonic mucosa conditions, probiotics have the potentiality to be involved in the promotion of longevity.

(1)H NMR-based metabolomics exploring biomarkers in rat cerebrospinal fluid after cerebral ischemia/reperfusion

In our study, metabolomics was used to investigate biochemical changes in the early stages of rats focal cerebral ischemia/reperfusion (I/R) injury. Cerebrospinal fluid (CSF) samples at 0, 0.5, 1, 3, and 6 h of reperfusion (n = 10), based on (1)H NMR spectroscopy and multivariate data analyses, were tested to analyze the changing of metabolites during the early disease process. Partial least squares-discriminant analysis scores plots of the (1)H NMR data revealed clear differences among the experiment groups. Combining the results of the loading plot and t-test, we found that twenty-seven metabolites were changed significantly (p < 0.05) in the CSF samples among the different groups. Among that, the potential biomarkers in CSF of ischemic rats were: acetic acid, 3-hydroxyisovaleric acid, 3-hydroxybutyric acid, choline, l-alanine, creatine, creatinine, glycine, pyruvic acid, glycerol, glutamic acid, d-fructose, l-lactic acid and acetone. These findings help us understand the biochemical metabolite changes in CSF of I/R rats in early stages. What's more, metabolomics may, therefore, have the potential to be developed into a clinically useful diagnostic tool of ischemic brain injury.

Metabolomics of human intestinal transplant rejection

Surveillance endoscopy with biopsy is the standard method to monitor intestinal transplant recipients but it is invasive, costly and prone to sampling error. Early noninvasive biomarkers of intestinal rejection are needed. In this pilot study we applied metabolomics to characterize the metabolomic profile of intestinal allograft rejection. Fifty-six samples of ileostomy fluid or stool from 11 rejection and 45 nonrejection episodes were analyzed by ultraperformance liquid chromatography in conjunction with Quadrupole time-of-flight mass spectrometry (UPLC-QTOFMS). The data were acquired in duplicate for each sample in positive ionization mode and preprocessed using XCMS (Scripps) followed by multivariate data analysis. We detected a total of 2541 metabolites in the positive ionization mode (mass 50-850 Daltons). A significant interclass separation was found between rejection and nonrejection. The proinflammatory mediator leukotriene E4 was the metabolite with the highest fold change in the rejection group compared to nonrejection. Water-soluble vitamins B2, B5, B6, and taurocholate were also detected with high fold change in rejection. The metabolomic profile of rejection was more heterogeneous than nonrejection. Although larger studies are needed, metabolomics appears to be a promising tool to characterize the pathophysiologic mechanisms involved in intestinal allograft rejection and potentially to identify noninvasive biomarkers.

Metabolic profiling, a noninvasive approach for the detection of experimental colorectal neoplasia

Colorectal cancer is the second leading cause of cancer-related deaths in the United States. Although noninvasive stool-based screening tests are used for the early detection of colorectal neoplasia, concerns have been raised about their sensitivity and specificity. A metabolomics-based approach provides a potential noninvasive strategy to identify biomarkers of colorectal carcinogenesis including premalignant adenomas. Our primary objective was to determine whether a distinct metabolic profile could be found in both feces and plasma during experimental colorectal carcinogenesis. Feces, plasma as well as tumor tissue and normal colorectal mucosa were obtained from A/J mice at several time points following administration of azoxymethane or saline. Ultra-performance liquid chromatography tandem mass spectroscopy and gas chromatography mass spectroscopy were used to quantify metabolites in each of these matrices. Here, we show that colorectal carcinogenesis was associated with significant metabolic alterations in both the feces and plasma, some of which overlap with metabolic changes in the tumor tissue. These consisted of 33 shared changes between feces and tumor, 14 shared changes between plasma and tumor, and 3 shared changes across all 3 matrices. For example, elevated levels of sarcosine were found in both tumor and feces whereas increased levels of 2-hydroxyglutarate were found in both tumor and plasma. Collectively, these results provide evidence that metabolomics can be used to detect changes in feces and plasma during azoxymethane-induced colorectal carcinogenesis and thus provide a strong rationale for future studies in humans.

Expanding the reach of cancer metabolomics

Metabolism is again emerging as a key property that differentiates normal cells from neoplastic tissues. The coupling of this phenomenon with advanced bioanalytic methods may now open new avenues for diagnostics in cancer via discovery of chemical biomarkers. In this issue of Cancer Prevention Research, Montrose and colleagues apply metabolic profiling to a model of chemically induced colorectal cancer and describe the metabolomic landscape of colorectal tumors and associated biofluids in great detail. Their analysis of plasma and fecal metabolites provides inroads into the noninvasive detection of colorectal cancer using biochemical markers, as some conserved metabolic changes were altered across tumors, plasma, and feces. Meanwhile, the specific alterations identified in this study offer insights into potential metabolic drivers of colorectal cancer. For example, elevated sarcosine and 2-hydroxyglutarate were detected in these induced tumors, implicating their respective metabolic pathways and downstream interactions in colorectal cancer progression. This work highlights the potential value of cancer metabolomics for the noninvasive analysis of colorectal neoplasias while underscoring the importance of profiling diverse sample sets and metabolites in relevant cancer models to identify and validate such findings.

Gut microbial activity, implications for health and disease: the potential role of metabolite analysis

Microbial metabolism of proteins and amino acids by human gut bacteria generates a variety of compounds including phenol, indole, and sulfur compounds and branched chain fatty acids, many of which have been shown to elicit a toxic effect on the lumen. Bacterial fermentation of amino acids and proteins occurs mainly in the distal colon, a site that is often fraught with symptoms from disorders including ulcerative colitis (UC) and colorectal cancer (CRC). In contrast to carbohydrate metabolism by the gut microbiota, proteolysis is less extensively researched. Many metabolites are low molecular weight, volatile compounds. This review will summarize the use of analytical methods to detect and identify compounds in order to elucidate the relationship between specific dietary proteinaceous substrates, their corresponding metabolites, and implications for gastrointestinal health.

The Warburg effect dictates the mechanism of butyrate-mediated histone acetylation and cell proliferation

Widespread changes in gene expression drive tumorigenesis, yet our knowledge of how aberrant epigenomic and transcriptome profiles arise in cancer cells is poorly understood. Here, we demonstrate that metabolic transformation plays an important role. Butyrate is the primary energy source of normal colonocytes and is metabolized to acetyl-CoA, which was shown to be important not only for energetics but also for HAT activity. Due to the Warburg effect, cancerous colonocytes rely on glucose as their primary energy source, so butyrate accumulated and functioned as an HDAC inhibitor. Although both mechanisms increased histone acetylation, different target genes were upregulated. Consequently, butyrate stimulated the proliferation of normal colonocytes and cancerous colonocytes when the Warburg effect was prevented from occurring, whereas it inhibited the proliferation of cancerous colonocytes undergoing the Warburg effect. These findings link a common metabolite to epigenetic mechanisms that are differentially utilized by normal and cancerous cells because of their inherent metabolic differences.

Metabolomics of urinary tract infection: a new uroscope in town

Urinary tract infection (UTI) is a potentially life-threatening infectious disease. For rapid directed therapy of UTIs, it is essential to determine the causative microorganism. To date, there is no single test that has been proven to reliably, rapidly and accurately identify the etiologic organism in UTI. The molecular methods for diagnosing the cause of UTI and prognostic development of clinically important metabolomic evaluations and their limitations for use in the diagnosis and monitoring of infections are discussed in this review article. The application of the emerging investigative device NMR spectroscopy as a surrogate method for the diagnosis of UTI is also addressed.

Development of an untargeted metabolomics method for the analysis of human faecal samples using Cryptosporidium-infected samples

Faecal metabolite profiling, though in its infancy, allows for investigation of complex metabolic interactions between gastrointestinal infections or diseases and host health. In the present study, we describe a faecal metabolite extraction method for untargeted gas chromatography-mass spectrometry (GC-MS) analysis using Cryptosporidium positive and negative human faecal samples. The extraction method takes into account the varying faecal consistencies and quantities received for clinical diagnosis. Optimisation was carried out using different extraction solvents and on three different faecal quantities to determine the minimum amount of faecal sample required. The method was validated by untargeted GC-MS analysis on 8 Cryptosporidium positive and 8 Cryptosporidium negative human faecal samples, extracted using the optimised conditions. The method showed good extraction reproducibility with a relative standard deviation of 9.14%. Multivariate analysis of the GC-MS generated dataset showed distinct differences between profiles of Cryptosporidium positive and Cryptosporidium negative samples. The most notable differences included changes in amino acid, nitrogen and energy metabolism, demonstrating the association of infection with Cryptosporidium and altered permeability of the small intestine.

Recent advances in metabolomics in oncology

The burden of cancer is growing worldwide and with it a more desperate need for better tools to detect, diagnose and monitor the disease is required. It is well recognized that cancer cells are characterized by distinct metabolic perturbations. The metabolomics approach involves the comprehensive profiling of the full complement of low MW compounds in a biological system. By applying advanced analytical and statistical tools, the 'metabolome' is mined for biomarkers that are associated with the state of cancer. This review presents an introduction to the main analytical platforms used in metabolomics analyses, such as NMR spectroscopy and MS, as well as the statistical tools used to mine these datasets. The discussion focuses on 'state-of-the-art' investigations on the four cancer types that have received the most study by metabolomics, namely breast, prostate, colorectal and liver cancer.

Metabolomic study of serum from rabbits with acute acalculous cholecystitis

OBJECTIVES

(1)H-NMR is a powerful approach of metabolomics. This study aimed to apply it to detect the serum metabolites in rabbits with acute acalculous cholecystitis (AAC), and to analyze their potential roles in AAC.

METHODS

Fourteen rabbits were randomly divided into two groups, the AAC group and the CON group. In the AAC rabbit model, Escherichia coli solution was injected into the gallbladder, while same volume of saline, instead of E. coli solution, was injected into the gallbladder of the CON rabbit. General morphological, light microscopic and transmission electron microscopic observations were used to evaluate the model. Metabolic profiles of serum from rabbits with AAC were investigated through (1)H-NMR spectroscopy coupled with multivariate statistical analysis, such as principal components analysis and orthogonal partial least-squares discriminant analysis.

RESULTS

The pathohistology of gallbladders showed a significant difference between the two groups, proving the successful induction of inflammation in the gallbladders of the AAC group. The serum concentration of lipids (LDL and VLDL) increased during AAC, while the concentrations of phospholipids, lactic acid, 3-hydroxybutyric acid, lysine, citric acid, asparagine, histidine, glucose and some other small molecular metabolites decreased.

CONCLUSION

The profiling of serum metabolites in rabbits with acute acalculous cholecystitis changed significantly. These changes referred to the metabolic disturbance of carbohydrate, amino acids and lipids, inhibition of immunological functions and inflammation reaction.

Metabolomic applications to decipher gut microbial metabolic influence in health and disease

Dietary preferences and nutrients composition have been shown to influence human and gut microbial metabolism, which ultimately has specific effects on health and diseases’ risk. Increasingly, results from molecular biology and microbiology demonstrate the key role of the gut microbiota metabolic interface to the overall mammalian host’s health status. There is therefore raising interest in nutrition research to characterize the molecular foundations of the gut microbial–mammalian cross talk at both physiological and biochemical pathway levels. Tackling these challenges can be achieved through systems biology approaches, such as metabolomics, to underpin the highly complex metabolic exchanges between diverse biological compartments, including organs, systemic biofluids, and microbial symbionts. By the development of specific biomarkers for prediction of health and disease, metabolomics is increasingly used in clinical applications as regard to disease etiology, diagnostic stratification, and potentially mechanism of action of therapeutical and nutraceutical solutions. Surprisingly, an increasing number of metabolomics investigations in pre-clinical and clinical studies based on proton nuclear magnetic resonance (¹H NMR) spectroscopy and mass spectrometry provided compelling evidence that system wide and organ-specific biochemical processes are under the influence of gut microbial metabolism. This review aims at describing recent applications of metabolomics in clinical fields where main objective is to discern the biochemical mechanisms under the influence of the gut microbiota, with insight into gastrointestinal health and diseases diagnostics and improvement of homeostasis metabolic regulation.

Biofluid metabonomics using (1)H NMR spectroscopy: the road to biomarker discovery in gastroenterology and hepatology

Metabolic profiling or 'metabonomics' is an investigatory method that allows metabolic changes associated with the presence of an underlying pathological process to be investigated. Various biofluids can be utilized in the process but urine, serum and fecal extract are most pertinent to the investigation of gastrointestinal and hepatological disease. Nuclear magnetic resonance spectroscopy-based metabonomic research has the potential to generate novel noninvasive diagnostic tests, based on biomarkers of disease, which are simple and cost effective yet retain high sensitivity and specificity characteristics. The process involves a number of key steps, including sample collection, data acquisition, chemometric techniques and, finally, validation. This technique-driven review aims to demystify the metabonomics pathway, while also illustrating the potential of this technique with recent examples of its application in hepato-gastroenterological disease.

Analytical metabolomics: nutritional opportunities for personalized health

Nutrition is the cornerstone of health; survival depends on acquiring essential nutrients, and dietary components can both prevent and promote disease. Metabolomics, the study of all small molecule metabolic products in a system, has been shown to provide a detailed snapshot of the body's processes at any particular point in time, opening up the possibility of monitoring health and disease, prevention and treatment. Metabolomics has the potential to fundamentally change clinical chemistry and, by extension, the fields of nutrition, toxicology and medicine. Technological advances, combined with new knowledge of the human genome and gut microbiome, have made and will continue to make possible earlier, more accurate, less invasive diagnoses, all while enhancing our understanding of the root causes of disease and leading to a generation of dietary recommendations that enable optimal health. This article reviews the recent contributions of metabolomics to the fields of nutrition, toxicology and medicine. It is expected that these fields will eventually blend together through development of new technologies in metabolomics and genomics into a new area of clinical chemistry: personalized medicine.

Understanding the role of gut microbiome-host metabolic signal disruption in health and disease

There is growing awareness of the importance of the gut microbiome in health and disease, and recognition that the microbe to host metabolic signalling is crucial to understanding the mechanistic basis of their interaction. This opens new avenues of research for advancing knowledge on the aetiopathologic consequences of dysbiosis with potential for identifying novel microbially-related drug targets. Advances in both sequencing technologies and metabolic profiling platforms, coupled with mathematical integration approaches, herald a new era in characterizing the role of the microbiome in metabolic signalling within the host and have far reaching implications in promoting health in both the developed and developing world.

Identification of metabolites in the normal ovary and their transformation in primary and metastatic ovarian cancer

In this study, we characterized the metabolome of the human ovary and identified metabolic alternations that coincide with primary epithelial ovarian cancer (EOC) and metastatic tumors resulting from primary ovarian cancer (MOC) using three analytical platforms: gas chromatography mass spectrometry (GC/MS) and liquid chromatography tandem mass spectrometry (LC/MS/MS) using buffer systems and instrument settings to catalog positive or negative ions. The human ovarian metabolome was found to contain 364 biochemicals and upon transformation of the ovary caused changes in energy utilization, altering metabolites associated with glycolysis and β-oxidation of fatty acids--such as carnitine (1.79 fold in EOC, p<0.001; 1.88 fold in MOC, p<0.001), acetylcarnitine (1.75 fold in EOC, p<0.001; 2.39 fold in MOC, p<0.001), and butyrylcarnitine (3.62 fold, p<0.0094 in EOC; 7.88 fold, p<0.001 in MOC). There were also significant changes in phenylalanine catabolism marked by increases in phenylpyruvate (4.21 fold; p = 0.0098) and phenyllactate (195.45 fold; p<0.0023) in EOC. Ovarian cancer also displayed an enhanced oxidative stress response as indicated by increases in 2-aminobutyrate in EOC (1.46 fold, p = 0.0316) and in MOC (2.25 fold, p<0.001) and several isoforms of tocopherols. We have also identified novel metabolites in the ovary, specifically N-acetylasparate and N-acetyl-aspartyl-glutamate, whose role in ovarian physiology has yet to be determined. These data enhance our understanding of the diverse biochemistry of the human ovary and demonstrate metabolic alterations upon transformation. Furthermore, metabolites with significant changes between groups provide insight into biochemical consequences of transformation and are candidate biomarkers of ovarian oncogenesis. Validation studies are warranted to determine whether these compounds have clinical utility in the diagnosis or clinical management of ovarian cancer patients.

Analysis of metabolic and gene expression changes after hydrodynamic DNA injection into mouse liver

The hydrodynamic injection in mice tail vein of a plasmid (40 µg DNA) bearing the human α1-antitrypsin gene mediates: a) good liver gene transfer resulting in therapeutic plasma levels of human protein (1 mg/ml, approximately) from days 1-10 after injection; b) low liver injury as demonstrated by a poor and transient increase of aspartate aminotransferase (AST) and alanine transaminase (ALT) in mouse plasma; 3) limited expression and metabolic changes in host liver genes and metabolites as evaluated on days 2 and 10 after injection. Groups of three mice were uninjected (control) or hydrodynamically injected with saline or plasmid DNA and then sacrificed on days 2 and 10 after injection. The results of principal component analysis (PCA) show, both in expression microarray and metabolomic analysis, that changes between control and hydrodynamically injected groups are not dramatic and tend to normalize after 10 d. The differences are even smaller between DNA and saline hydrodynamically injected mice. Hydrodynamic injection induces a complex but limited gene expression and metabolic change which includes variations in molecules related to energy metabolism and stress response. The results contribute to support that hydrodynamic method is a safe procedure of liver gene transfer but the long-term effect of hydrodynamic gene transfer procedure, remains to be studied.

Prediction of gastric cancer metastasis through urinary metabolomic investigation using GC/MS

AIM: To gain new insights into tumor metabolism and to identify possible biomarkers with potential diagnostic values to predict tumor metastasis.

METHODS: Human gastric cancer SGC-7901 cells were implanted into 24 severe combined immune deficiency (SCID) mice, which were randomly divided into metastasis group (n = 8), non-metastasis group (n = 8), and normal group (n = 8). Urinary metabolomic information was obtained by gas chromatography/mass spectrometry (GC/MS).

RESULTS: There were significant metabolic differences among the three groups (t test, P < 0.05). Ten selected metabolites were different between normal and cancer groups (non-metastasis and metastasis groups), and seven metabolites were also different between non-metastasis and metastasis groups. Two diagnostic models for gastric cancer and metastasis were constructed respectively by the principal component analysis (PCA). These PCA models were confirmed by corresponding receiver operating characteristic analysis (area under the curve = 1.00).

CONCLUSION: The urinary metabolomic profile is different, and the selected metabolites might be instructive to clinical diagnosis or screening metastasis for gastric cancer.

Metabolomics and detection of colorectal cancer in humans: a systematic review

Metabolomics represents one of the new omics sciences and capitalizes on the unique presence and concentration of small molecules in tissues and body fluids to construct a 'fingerprint' that can be unique to the individual and, within that individual, unique to environmental influences, including health and disease states. As such, metabolomics has the potential to serve an important role in diagnosis and management of human conditions. Colorectal cancer is a major public health concern. Current population-based screening methods are suboptimal and whether metabolomics could represent a new tool of screening is under investigation. The purpose of this systematic review is to summarize existing literature on metabolomics and colorectal cancer, in terms of diagnostic accuracies and distinguishing metabolites. Eight studies are included. A total of 12 metabolites (taurine, lactate, choline, inositol, glycine, phosphocholine, proline, phenylalanine, alanine, threonine, valine and leucine) were found to be more prevalent in colorectal cancer and glucose was found to be in higher proportion in control specimens using tissue metabolomics. Serum and urine metabolomics identified several other differential metabolites between controls and colorectal cancer patients. This article highlights the novelty of the field of metabolomics in colorectal oncology.

Metabolomics and surgical oncology: Potential role for small molecule biomarkers

Metabolomics, the newest of the "omics" sciences, has brought much excitement to the field of oncology as a potential new translational tool capable of bringing the molecular world of cancer care to the bedside. While still early in its development, metabolomics could alter the scope and role of surgery in the multidisciplinary treatment of cancer. This review examines potential roles of metabolomics in areas of early cancer detection, personalized therapeutics and tumorigenesis.

Linking obesity to colorectal cancer: application of nutrigenomics

Diet is one of the most affective environmental factors in cancer development. Due to complicated nature of the diet, it has been very difficult to provide clear explanations for the role of dietary components in carcinogenesis. However, as high-throughput omics techniques became available, researchers are now able to analyze large sets of gene transcripts, proteins, and metabolites to identify molecules involved in disease development. Bioinformatics uses these data to perform network analyses and suggest possible interactions between metabolic processes and environmental factors. Obesity is known as one of the most closely related risk factors of colorectal cancer (CRC). Metabolic disturbances due to a positive energy balance may trigger and accelerate CRC development. In this review, we have summarized reports on genes, proteins and metabolites that are related to either obesity or CRC, and suggested candidate molecules linking obesity and CRC based on currently available literature. Possible application of bioinformatics for a large scale network analysis in studying cause-effect relationship between dietary components and CRC are suggested.

Profiling of phenols in human fecal water after raspberry supplementation

The phenolic compositions of fecal water samples from ten free-living human subjects without marked dietary restrictions were monitored before and after intake of raspberry puree (200 g/day, 4 days) using gas chromatography-mass spectrometry. No single phenolic component was increased in all subjects after intake, but a majority of subjects had significant elevations in phenylacetic acid (7/10), 4-hydroxyphenylacetic acid (6/10), 3-hydroxyphenylacetic acid (5/10), 3-phenylpropionic acid and 3-(4-hydroxyphenyl)propionic acid. The levels of 3,4-dihydroxbenzoic acid were elevated in 8/10 subjects, significantly for 6 subjects (p < 0.05), and not significantly reduced in the other 2 subjects. In addition, unlike most other fecal metabolites, the increase was always >2-fold. This metabolite may be representative of the increased colonic dose of cyanidin anthocyanins. The colonic microbiota varied greatly between individuals, and supplementation with raspberries did not produce any statistically significant alterations in the profile of colonic bacteria, nor was a common pattern revealed to account for the interindividual variations observed in the fecal water phenolic profiles.

The interaction of large bowel microflora with the colonic mucus barrier

The colonic mucus barrier is the first line of defence that the underlying mucosa has against the wide range of potentially damaging agents of microbial, endogenous, and dietary origin that occur within the colonic lumen. The functional component of mucus is the secreted, polymeric glycoprotein mucin. The mucus barrier can either act as an energy source or a support medium for growth to the intestinal microflora. The mucus barrier appears to effectively partition the vast number of microbial cells from the underlying epithelium. The normal functionality and biochemistry of this mucus barrier appears to be lost in diseases of the colorectal mucosa. Germ-free animal studies have highlighted the necessity of the presence of the colonic microflora to drive the maturation of the colonic mucosa and normal mucus production. A number of by-products of the microflora have been suggested to be key luminal drivers of colonic mucus secretion.

Systems level studies of mammalian metabolomes: the roles of mass spectrometry and nuclear magnetic resonance spectroscopy

The study of biological systems in a holistic manner (systems biology) is increasingly being viewed as a necessity to provide qualitative and quantitative descriptions of the emergent properties of the complete system. Systems biology performs studies focussed on the complex interactions of system components; emphasising the whole system rather than the individual parts. Many perturbations to mammalian systems (diet, disease, drugs) are multi-factorial and the study of small parts of the system is insufficient to understand the complete phenotypic changes induced. Metabolomics is one functional level tool being employed to investigate the complex interactions of metabolites with other metabolites (metabolism) but also the regulatory role metabolites provide through interaction with genes, transcripts and proteins (e.g. allosteric regulation). Technological developments are the driving force behind advances in scientific knowledge. Recent advances in the two analytical platforms of mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy have driven forward the discipline of metabolomics. In this critical review, an introduction to metabolites, metabolomes, metabolomics and the role of MS and NMR spectroscopy will be provided. The applications of metabolomics in mammalian systems biology for the study of the health-disease continuum, drug efficacy and toxicity and dietary effects on mammalian health will be reviewed. The current limitations and future goals of metabolomics in systems biology will also be discussed (374 references).

Urinary metabolic profiling of colorectal carcinoma based on online affinity solid phase extraction-high performance liquid chromatography and ultra performance liquid chromatography-mass spectrometry

Colorectal carcinoma (CRC) is the third most commonly encountered cancer and fourth cause of cancer-associated death worldwide. Abundant studies have demonstrated that one of the best effective therapies for enhancing the 5-year survival rate of patients is to diagnose the disease at an early stage. Urine metabonomics is widely being utilized as an efficient platform to investigate the metabolic changes and discover the potential biomarkers of malignant diseases. In this study both ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and online affinity solid phase extraction-high performance liquid chromatography (SPE-HPLC) were used to analyze the urinary metabolites from 34 healthy volunteers, 34 benign colorectal tumor and 50 colorectal carcinoma patients to produce comprehensive metabolic profiling data. A reliable separation between the control and disease groups as well as significantly changed metabolites were obtained from orthogonal signal correction partial least squares models which were built based on the two separate data sets from UPLC-MS and affinity SPE-HPLC, respectively. 15 metabolites, showing the metabolic disorders of CRC, were identified finally. These metabolites were found to be related to glutamine metabolism, fatty acid oxidation, nucleotide biosynthesis and protein metabolism.

Metabolomics: towards understanding host-microbe interactions

Metabolomics employs an array of analytical techniques, including high-resolution nuclear magnetic resonance spectroscopy and mass spectrometry, to simultaneously analyze hundreds to thousands of small-molecule metabolites in biological samples. In conjunction with chemoinformatics and bioinformatics tools, metabolomics enables comprehensive characterization of the metabolic phenotypes (metabotypes) of the human, and other mammalian, hosts that have co-evolved with a large number of diverse commensal microbes, especially in the intestinal tract. Correlation of the metabotypes with the microbial profiles derived from culture-independent molecular techniques is increasingly helping to decipher inherent and intimate host-microbe relationships. This integrated, systems biology approach is improving our understanding of the molecular mechanisms underlying multilevel host-microbe interactions, and promises to elucidate the etiologies of human disorders resulting from unfavorable human-microbial associations, including enteric infections.

An optimised sample preparation method for NMR-based faecal metabonomic analysis

Faecal metabonomic NMR analysis plays an essential role in investigating the interactions between mammalian metabolism and symbiotic gut microbiota. However, the faecal metabolite extraction method remains to be optimised and standardised to take into consideration signal-to-noise ratios, pH and chemical shift consistency. In the current investigation, we compared extraction consistency of three homogenisation methods including manual ultrasonication, automatic homogenization with tissuelyser and their combination, and systematically optimised faecal metabolite extraction parameters, including the faeces-to-buffer ratio (W(f) : V(b)), extraction repetition times and duration. We found that automatic homogenisation with tissuelyser was the choice of extraction method owning to its good metabolite extraction consistency and high throughput. We also recommend W(f) : V(b) of 1 : 10 (mg microl(-1)) and use of the combined first two extracts as the resultant samples to represent faecal metabolite composition. Such recommendation is based on considerations of maximisation of the spectral signal-to-noise ratio, pH and chemical shift consistency, completeness of metabolite extraction and sample preparation throughput so that the method is suitable for analysing a large number of samples especially in human population studies.

MR metabolomics of fecal extracts: applications in the study of bowel diseases

NMR-based metabolomics is becoming a useful tool in the study of body fluids and has a strong potential to contribute to disease diagnosis. While applications on urine and serum have been the focus to date, there are a number of other body fluids that are readily available and could potentially be used for metabolomics-based disease diagnosis. One such body fluid is stool or fecal extract. Given its contact with and transient stay in the colon and rectum, stool carries a lot of useful information regarding the health/disease status of both the colon and the rectum. This could be particularly useful for the non-invasive diagnosis of colorectal cancer and inflammatory bowel disease--the two bowel diseases that are very common and pose significant public health problems. Different methodological considerations including the collection of sample, the storage of sample, the preparation of sample, NMR acquisition parameters, experimental conditions and data analysis methods are discussed. Results obtained in the detection of colorectal cancer and in the differentiation of the two major forms of inflammatory bowel disease (i.e. ulcerative colitis and Crohn's disease) are presented. This is concluded with a brief discussion on the future of MR metabolomics of fecal extracts.

Chemometrics in metabolomics--a review in human disease diagnosis

Metabolomics is a post genomic research field concerned with developing methods for analysis of low molecular weight compounds in biological systems, such as cells, organs or organisms. Analyzing metabolic differences between unperturbed and perturbed systems, such as healthy volunteers and patients with a disease, can lead to insights into the underlying pathology. In metabolomics analysis, large amounts of data are routinely produced in order to characterize samples. The use of multivariate data analysis techniques and chemometrics is a commonly used strategy for obtaining reliable results. Metabolomics have been applied in different fields such as disease diagnosis, toxicology, plant science and pharmaceutical and environmental research. In this review we take a closer look at the chemometric methods used and the available results within the field of disease diagnosis. We will first present some current strategies for performing metabolomics studies, especially regarding disease diagnosis. The main focus will be on data analysis strategies and validation of multivariate models, since there are many pitfalls in this regard. Further, we highlight the most interesting metabolomics publications and discuss these in detail; additional studies are mentioned as a reference for the interested reader. A general trend is an increased focus on biological interpretation rather than merely the ability to classify samples. In the conclusions, the general trends and some recommendations for improving metabolomics data analysis are provided.

Combining nuclear magnetic resonance spectroscopy and mass spectrometry in biomarker discovery

Metabolic profiling of biological specimens is emerging as a promising approach for discovering specific biomarkers in the diagnosis of a number of diseases. Amongst many analytical techniques, nuclear magnetic resonance spectroscopy and mass spectrometry are the most information-rich tools that enable high-throughput and global analysis of hundreds of metabolites in a single step. Although only one of the two techniques is utilized in a majority of metabolomics applications, there is a growing interest in combining the data from the two methods to effectively unravel the mammoth complexity of biological samples. In this article, current developments in nuclear magnetic resonance, mass spectrometry and multivariate statistical analysis methods are described. While some general applications that utilize the combination of the two analytical methods are presented briefly, the emphasis is laid on the recent applications of nuclear magnetic resonance and mass spectrometry methods in the studies of hepatopancreatobiliary and gastrointestinal malignancies.

Metabolomics: moving to the clinic

Assessment of a biological system by means of global and non-targeted metabolite profiling--metabolomics or metabonomics--provides the investigator with molecular information that is close to the phenotype in question in the sense that metabolites are an ultimate product of gene, mRNA, and protein activity. Over the last few years, there has been a rapidly growing number of metabolomics applications aimed at finding biomarkers which could assist diagnosis, provide therapy guidance, and evaluate response to therapy for particular diseases. Also, within the fields of drug discovery, drug toxicology, and personalized pharmacology, metabolomics is emerging as a powerful tool. This review seeks to update the reader on analytical strategies, biomarker findings, and implications of metabolomics for the clinic. Particular attention is paid to recent biomarkers found related to neurological, cardiovascular, and cancer diseases. Moreover, the impact of metabolomics in the drug discovery and development process is examined.