Metabonomics approach to determine metabolic differences between green tea and black tea consumption

Dietary Ascophyllum nodosum increases urinary excretion of tricarboxylic acid cycle intermediates in male Sprague-dawley rats

We used a (1)H NMR-based metabonomics approach to examine the physiological effects of the seaweed Ascophyllum nodosum in a mammalian model, assess the dosage level required to elicit a response in the urinary profile, and identify potential toxic effects. Male Sprague-Dawley rats (n = 6/group) were fed a control or 5, 10, or 15% freeze-dried, ground A. nodosum diet for 4 wk. Urine samples were collected 3 times daily (0-4, 4-8, and 8-24 h) prior to feeding experimental diets and, at the end of the study, were profiled using (1)H NMR spectroscopy. Food intake, weight gain, and serum enzyme (alanine transaminase and aspartate transaminase) levels indicated that seaweed diets were well tolerated. The spectral data and principal component analysis (PCA) revealed that rats fed 5, 10, and 15% seaweed diets had increased urinary excretion of citrate, 2-oxoglutarate, succinate, trimethylamine (TMA), TMA-N-oxide, and malonate and decreased excretion of taurine, creatinine, and acetate compared with the controls. In addition, mannitol was detected in the 8- to 24-h urine samples from seaweed-fed rats. Metabolic responses related to ingestion of seaweed polyphenolics and fiber were not observed in the spectral profiles. Increased seaweed concentration in the diet did not increase the magnitude of the rats' response as detected by (1)H NMR. Visual analysis and PCA of the spectral data for serum samples collected at the end of the study did not show diet-related clustering. The lack of toxicity at 15% seaweed incorporation allows the use of this concentration in future A. nodosum intervention studies.

Characterization of inflammatory bowel disease with urinary metabolic profiling

OBJECTIVES

Distinguishing between the inflammatory bowel disease (IBD), Crohn's disease (CD), and ulcerative colitis (UC) is important for both management and prognostic reasons. Discrimination using noninvasive techniques could be an adjunct to conventional diagnostics. Differences have been shown between the intestinal microbiota of CD and UC patients and controls; the gut bacteria influence specific urinary metabolites that are quantifiable using proton high-resolution nuclear magnetic resonance (NMR) spectroscopy. This study tested the hypothesis that such metabolites differ between IBD and control cohorts, and that using multivariate pattern-recognition analysis, the cohorts could be distinguished by urine NMR spectroscopy.

METHODS

NMR spectra were acquired from urine samples of 206 Caucasian subjects (86 CD patients, 60 UC patients, and 60 healthy controls). Longitudinal samples were collected from 75 individuals. NMR resonances specific for metabolites influenced by the gut microbes were studied, including hippurate, formate, and 4-cresol sulfate. Multivariate analysis of all urinary metabolites involved principal components analysis (PCA) and partial least squares discriminant analysis (PLS-DA).

RESULTS

Hippurate levels were lowest in CD patients and differed significantly between the three cohorts (P<0.0001). Formate levels were higher and 4-cresol sulfate levels lower in CD patients than in UC patients or controls (P=0.0005 and P=0.0002, respectively). PCA revealed clustering of the groups; PLS-DA modeling was able to distinguish the cohorts. These results were independent of medication and diet and were reproducible in the longitudinal cohort.

CONCLUSIONS

Specific urinary metabolites related to gut microbial metabolism differ between CD patients, UC patients, and controls. The emerging technique of urinary metabolic profiling with multivariate analysis was able to distinguish these cohorts.

Characterization of pu-erh tea using chemical and metabolic profiling approaches

In this study, the chemical constituents of pu-erh tea, black tea, and green tea, as well as those of pu-erh tea products of different ages, were analyzed and compared using a chemical profiling approach. Differences in tea processing resulted in differences in the chemical constituents and the color of tea infusions. Human biological responses to pu-erh tea ingestion were also studied by using ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOFMS) in conjunction with multivariate statistical techniques. Metabolic alterations during and after pu-erh tea ingestion were characterized by increased urinary excretion of 5-hydroxytryptophan, inositol, and 4-methoxyphenylacetic acid, along with reduced excretion of 3-chlorotyrosine and creatinine. This study highlights the potential for metabonomic technology to assess nutritional interventions and is an important step toward a full understanding of pu-erh tea and its influence on human metabolism.

Use of conventional and -omics based methods for health claims of dietary antioxidants: a critical overview

This article describes the principles and limitations of methods used to investigate reactive oxygen species (ROS) protective properties of dietary constituents and is aimed at providing a better understanding of the requirements for science based health claims of antioxidant (AO) effects of foods. A number of currently used biochemical measurements aimed of determining the total antioxidant capacity and oxidised lipids and proteins are carried out under unphysiological conditions and are prone to artefact formation. Probably the most reliable approaches are measurements of isoprostanes as a parameter of lipid peroxidation and determination of oxidative DNA damage. Also the design of the experimental models has a strong impact on the reliability of AO studies: the common strategy is the identification of AO by in vitro screening with cell lines. This approach is based on the assumption that protection towards ROS is due to scavenging, but recent findings indicate that activation of transcription factors which regulate genes involved in antioxidant defence plays a key role in the mode of action of AO. These processes are not adequately represented in cell lines. Another shortcoming of in vitro experiments is that AO are metabolised in vivo and that most cell lines are lacking enzymes which catalyse these reactions. Compounds with large molecular configurations (chlorophylls, anthocyans and polyphenolics) are potent AO in vitro, but weak or no effects were observed in animal/human studies with realistic doses as they are poorly absorbed. The development of -omics approaches will improve the scientific basis for health claims. The evaluation of results from microarray and proteomics studies shows that it is not possible to establish a general signature of alterations of transcription and protein patterns by AO. However, it was shown that alterations of gene expression and protein levels caused by experimentally induced oxidative stress and ROS related diseases can be normalised by dietary AO.

Tea and health: preventive and therapeutic usefulness in the elderly?

PURPOSE OF REVIEW

To update the growing literature suggesting that tea and its constituent flavonoids are inversely related to the risk of chronic diseases common among the elderly.

RECENT FINDINGS

Results are provided from recent observational studies and clinical trials on the relationship of tea and tea catechins to body weight control and energy metabolism, impaired glucose tolerance and diabetes, cardiovascular disease, bone mineral density, cognitive function and neurodegenerative disease, and cancer. The evidence for the efficacy and potency of tea and tea extracts in benefiting these outcomes ranges from compelling for cardiovascular disease to equivocal at best for some forms of cancer.

SUMMARY

Although randomized clinical trials of tea have generally been of short duration and with small sample sizes, together with experimental and epidemiological studies, the totality of the data suggests a role for tea in health promotion as a beverage absent in calories and rich in phytochemicals. Further research is warranted on the putative benefits of tea and the potential for synergy among its constituent flavonoids, L-theanine, and caffeine.

Metabolomic analysis of the response of growing pigs to dietary L-arginine supplementation

Arginine plays an important role regulating nutrient metabolism, but the underlying mechanisms are largely unknown. This study was conducted to determine the effect of dietary arginine supplementation on the metabolome in serum of growing pigs using (1)H nuclear magnetic resonance spectroscopy. Sixteen 120-day-old pigs (48 +/- 1 kg) were randomly assigned to one of two groups, representing supplementation with 0 or 1.0% L: -arginine to corn- and soybean meal-based diets. Serum was collected after a 46-day period of treatment. Dietary arginine supplementation decreased fat deposition and increased protein accretion in the body. Principal component analysis showed that serum concentrations of low density lipoprotein, very low density lipoprotein, and urea were lower, but concentrations of creatinine, tricarboxylic acid cycle metabolites, ornithine, lysine and tyrosine were greater in arginine-supplemented than in control pigs. Additionally, the arginine treatment affected serum concentrations of nitrogenous and lipid signaling molecules (glycerophosphorylcholine and myo-inositol) and intestinal bacterial metabolites (formate, ethanol, methylamine, dimethylamine, acetate, and propionate). These novel findings suggest that dietary arginine supplementation alters the catabolism of fat and amino acids in the whole body, enhances protein synthesis in skeletal muscle, and modulates intestinal microbial metabolism in growing pigs.

Multilevel data analysis of a crossover designed human nutritional intervention study

A new method is introduced for the analysis of 'omics' data derived from crossover designed drug or nutritional intervention studies. The method aims at finding systematic variations in metabolic profiles after a drug or nutritional challenge and takes advantage of the crossover design in the data. The method, which can be considered as a multivariate extension of a paired t test, generates different multivariate submodels for the between- and the within-subject variation in the data. A major advantage of this variation splitting is that each submodel can be analyzed separately without being confounded with the other variation sources. The power of the multilevel approach is demonstrated in a human nutritional intervention study which used NMR-based metabolomics to assess the metabolic impact of grape/wine extract consumption. The variations in the urine metabolic profiles are studied between and within the human subjects using the multilevel analysis. After variation splitting, multilevel PCA is used to investigate the experimental and biological differences between the subjects, whereas a multilevel PLS-DA model is used to reveal the net treatment effect within the subjects. The observed treatment effect is validated with cross model validation and permutations. It is shown that the statistical significance of the multilevel classification model ( p << 0.0002) is a major improvement compared to a ordinary PLS-DA model ( p = 0.058) without variation splitting. Finally, rank products are used to determine which NMR signals are most important in the multilevel classification model.

Recent advances in the compound-oriented and pattern-oriented approaches to the quality control of herbal medicines

The current approaches to the quality control of herbal medicines are either compound-oriented or pattern-oriented, the former targeting specific components with some known chemical properties and the latter targeting all detectable components. The marker approach uses specific chemical compounds with known molecular structures, while the multi-compound approach uses both chemical compounds with known structures and those with partial chemical information e.g. retention times, mass spectra and ultraviolet spectra. Apart from chromatographic techniques, new techniques such as oscillating and electrochemistry fingerprints have been developed for quality control. Chemometric resolution methods are widely used for component deconvolution and data comparison. Pattern recognition techniques are used for authentication of herbal medicines.

Metabonomics investigation of human urine after ingestion of green tea with gas chromatography/mass spectrometry, liquid chromatography/mass spectrometry and (1)H NMR spectroscopy

A method using gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS) and (1)H NMR with pattern recognition tools such as principle components analysis (PCA) was used to study the human urinary metabolic profiles after the intake of green tea. From the normalized peak areas obtained from GC/MS and LC/MS and peak heights from (1)H NMR, statistical analyses were used in the identification of potential biomarkers. Metabolic profiling by GC/MS provided a different set of quantitative signatures of metabolites that can be used to characterize the molecular changes in human urine samples. A comparison of normalized metabonomics data for selected metabolites in human urine samples in the presence of potential overlapping peaks after tea ingestion from LC/MS and (1)H NMR showed the reliability of the current approach and method of normalization. The close agreements of LC/MS with (1)H NMR data showed that the effects of ion suppression in LC/MS for early eluting metabolites were not significant. Concurrently, the specificity of detecting the stated metabolites by (1)H NMR and LC/MS was demonstrated. Our data showed that a number of metabolites involved in glucose metabolism, citric acid cycle and amino acid metabolism were affected immediately after the intake of green tea. The proposed approach provided a more comprehensive picture of the metabolic changes after intake of green tea in human urine. The multiple analytical approach together with pattern recognition tools is a useful platform to study metabolic profiles after ingestion of botanicals and medicinal plants.

The relation between green tea consumption and cardiovascular disease as evidenced by epidemiological studies

Although substantial evidence from in vitro and animal studies indicates that green tea preparations inhibit cardiovascular disease processes, the possible protective role of green tea consumption against this disease in humans remains unclear. We conducted a population-based prospective cohort study (the Ohsaki Study) to examine the association between green tea consumption and mortality from cardiovascular disease (CVD), cancer, and all causes with 40,530 persons in Miyagi prefecture, in northern Japan. Previously published work has shown that green tea consumption was inversely associated with mortality from CVD and all causes. The inverse association of mortality from CVD was more pronounced in women (P = 0.08 for interaction with sex). In women, the multivariate hazard ratios (95% confidence intervals) of CVD mortality across increasing green tea consumption categories were 1.00, 0.84 (0.63-1.12), 0.69 (0.52-0.93), 0.69 (0.53-0.90) (P for trend = 0.004). Within CVD mortality, the stronger inverse association was observed for stroke mortality. Because our observational study has found the inverse association, I report here the results of a review of epidemiological evidence from randomized controlled trials (RCT) of the association between green tea or green tea extracts and CVD risk profiles. More than half of the RCT have demonstrated the beneficial effects of green tea on CVD risk profiles. These results from RCT suggest a plausible mechanism for the beneficial effects of green tea and provide substantial support for our observations.

Metabolomics provide new insight on the metabolism of dietary phytochemicals in rats

Foods of plant origin contain a large number of phytochemicals that may positively affect health. Phytochemicals are largely excreted in urine as metabolites that are formed in host tissues or by the microbiota and constitute a great proportion of the urinary metabolome. The latter can be characterized by a metabolomics approach. In this work, we compared the metabolism of lignins to that of the structurally related ferulic acid (FA) and sinapic acid (SA). Five groups of rats (n = 5) were fed for 2 d a purified diet alone [control (C)] or supplemented with lignin-enriched wheat bran (3% of the diet, wt:wt), poplar wood lignins (0.42%), FA (0.42%), or SA (0.42%). The metabolomes of urine samples collected after 1 and 2 d of supplementation were analyzed by high-resolution MS (liquid chromatography/quadrupole time-of-flight). Comparing metabolic fingerprints by gathering semiquantitative information on several hundreds of metabolites and using multivariate statistical analysis (partial least squares for discriminant analysis) showed the similarity between both lignin-supplemented and C groups and confirmed that lignins are largely inert and not absorbed in the body. One the other hand, metabolic fingerprints of the 2 phenolic acid-supplemented groups were clearly distinct from the C group. Differences between the groups were mainly from nonmetabolized FA and SA and metabolites excreted in urine. Thirteen of them were identified as sulfate esters and glucuronide and glycine conjugates of the same phenolic acids, and of dihydrosinapic, vanillic, and benzoic acids. This study shows that metabolomics allows the identification of new metabolites of phytochemicals and can be used to distinguish individuals fed different phytochemical-containing foods.

(1)H NMR metabolite profiling of feces as a tool to assess the impact of nutrition on the human microbiome

Current research increasingly recognizes the human gut microbiome as a metabolically versatile biological 'digester' that plays an essential role in regulating the host metabolome. Gut microbiota recover energy and biologically active molecules from food that would otherwise be washed out of the intestinal tract without benefit. In this study, a protocol for NMR-based metabolite profiling has been developed to access the activity of the microbiome. The physicochemical properties of fecal metabolites have been found to strongly affect the reproducibility and coverage of the profiles obtained. Metabolite profiles generated by water and methanol extraction of lyophilized feces are reproducible and comprise a variety of different compounds including, among others, short-chain fatty acids (e.g. acetate, propionate, butyrate, isobutyrate, isovalerate, malate), organic acids (e.g. succinate, pyruvate, fumarate, lactate), amino acids, uracil, trimethylamine, ethanol, glycerol, glucose, phenolic acids, cholate, and lipid components. The NMR profiling approach was validated on fecal samples from a double-blinded, placebo-controlled, randomized cross-over study, in which healthy human subjects consumed a placebo and either a grape juice extract or a mix of grape juice and wine extract over a period of 4 weeks, each. The considerable inter- and intra-individual variability observed originates in the first instance from variable metabolite concentrations rather than from variable metabolite compositions, suggesting that different colonic flora share general biochemical characteristics metabolizing different substrates to specific metabolic patterns. Whereas the grape juice extract did not induce changes in the metabolite profiles as compared with the placebo, the mixture of grape juice and wine extract induced a reduction in isobutyrate, which may indicate that polyphenols are able to modulate the microbial ecology of the gut.

A liquid chromatography-quadrupole time-of-flight (LC-QTOF)-based metabolomic approach reveals new metabolic effects of catechin in rats fed high-fat diets

Unbalanced diets generate oxidative stress commonly associated with the development of diabetes, atherosclerosis, obesity and cancer. Dietary flavonoids have antioxidant properties and may limit this stress and reduce the risk of these diseases. We used a metabolomic approach to study the influence of catechin, a common flavonoid naturally occurring in various fruits, wine or chocolate, on the metabolic changes induced by hyperlipidemic diets. Male Wistar rats ( n = 8/group) were fed during 6 weeks normolipidemic (5% w/w) or hyperlipidemic (15 and 25%) diets with or without catechin supplementation (0.2% w/w). Urines were collected at days 17 and 38 and analyzed by reverse-phase liquid chromatography-mass spectrometry (LC-QTOF). Hyperlipidic diets led to a significant increase of oxidative stress in liver and aorta, upon which catechin had no effect. Multivariate analyses (PCA and PLS-DA) of the urine fingerprints allowed discrimination of the different diets. Variables were then classified according to their dependence on lipid and catechin intake (ANOVA). Nine variables were identified as catechin metabolites of tissular or microbial origin. Around 1000 variables were significantly affected by the lipid content of the diet, and 76 were fully reversed by catechin supplementation. Four variables showing an increase in urinary excretion in rats fed the high-fat diets were identified as deoxycytidine, nicotinic acid, dihydroxyquinoline and pipecolinic acid. After catechin supplementation, the excretion of nicotinic acid was fully restored to the level found in the rats fed the low-fat diet. The physiological significance of these metabolic changes is discussed.

GC-MS methods for metabolic profiling of microbial fermentation products of dietary polyphenols in human and in vitro intervention studies

Flavonoids, a subclass of polyphenols, are major constituents of many plant-based foods and beverages, including tea, wine and chocolate. Epidemiological studies have shown that a flavonoid-rich diet is associated with reduced risk of cardiovascular diseases. The majority of the flavonoids survive intact until they reach the colon where they are then extensively metabolized into smaller fragments. Here, we describe the development of GC-MS-based methods for the profiling of phenolic microbial fermentation products in urine, plasma, and fecal water. Furthermore, the methods are applicable for profiling products obtained from in vitro batch culture fermentation models. The methods incorporate enzymatic deconjugation, liquid-liquid extraction, derivatization, and subsequent analysis by GC-MS. At the level of individual compounds, the methods gave recoveries better than 80% with inter-day precision being better than 20%, depending on the matrix. Limits of detection were below 0.1 microg/ml for most phenolic acids. The newly developed methods were successfully applied to samples from human and in-vitro intervention trials, studying the metabolic impact of flavonoid intake. In conclusion, the methods presented are robust and generally applicable to diverse biological fluids. Its profiling character is useful to investigate on a large scale the gut microbiome-mediated bioavailability of flavonoids.

Rapid differentiation of tea products by surface desorption atmospheric pressure chemical ionization mass spectrometry

Protonated water molecules generated by an ambient corona discharge were directed to impact tea leaves for desorption/ionization at atmospheric pressure. Thus, a novel method based on surface desorption chemical ionization mass spectrometry (DAPCI-MS) has been developed for rapid analysis of tea products without any sample pretreatment. Under the optimized experimental conditions, DAPCI MS spectra of various tea samples are recorded rapidly, and the resulting mass spectra are chemical fingerprints that characterize the tea samples. On the basis of the mass spectral fingerprints, 40 tea samples including green tea, oolong tea, and jasmine tea were successfully differentiated by principal component analysis (PCA) of the mass spectral raw data. The PCA results were also validated with cluster analysis and supervised PCA analysis. The alteration of signal intensity caused by rough surfaces of tea leaves did not cause failure in the separation of the tea products. The experimental findings show that DAPCI-MS creates ions of both volatile and nonvolatile compounds in tea products at atmospheric pressure, providing a practical and convenient tool for high-throughput differentiation of tea products.

Influence of acute phytochemical intake on human urinary metabolomic profiles

BACKGROUND

Diversity in dietary intake contributes to variation in human metabolomic profiles and artifacts from acute dietary intake can affect metabolomics data.

OBJECTIVE

We investigated the role of dietary phytochemicals on shaping human urinary metabolomic profiles.

DESIGN

First void urine samples were collected from 21 healthy volunteers (12 women, 9 men) following their normal diet (ND), a 2-d low-phytochemical diet (LPD), or a 2-d standard phytochemical diet (SPD). Nutrient intake was assessed during the study. Urine samples were analyzed by using (1)H nuclear magnetic resonance spectroscopy ((1)H NMR) and mass spectrometry (MS), which was followed by multivariate data analysis.

RESULTS

Macronutrient intake did not change throughout the study. Partial least-squares-discriminant analysis indicated a clear distinction between the LPD samples and the ND and SPD samples, relating to creatinine and methylhistidine excretion after the LPD and hippurate excretion after the ND and SPD. The predictive power of the LPD versus the ND model was 74 +/- 3% and 82 +/- 6% with the (1)H NMR and MS data sets, respectively. The predictive power of the LPD versus the SPD model was 83 +/- 8% and 69 +/- 4% for the (1)H NMR and MS data sets respectively. A cross platform comparison of both data sets by co-inertia analysis showed a similar distinction between the LPD and SPD.

CONCLUSIONS

Acute changes in urinary metabolomic profiles occur after the consumption of dietary phytochemicals. Dietary restrictions in the 24 h before sample collection may reduce diversity in phytochemical intakes and therefore reduce variation and improve data interpretation in metabolomics studies using urine.

Nutritional metabonomics: applications and perspectives

Nowadays, nutrition focuses on improving health of individuals through diet. Current nutritional research aims at health promotion, disease prevention, and performance improvement. Modern analytical platforms allow the simultaneous measurement of multiple metabolites providing new insights in the understanding of the functionalities of cells and whole organisms. Metabonomics, "the quantitative measurement of the dynamic multiparametric metabolic response of living systems to pathophysiological stimuli or genetic modifications", provides a systems approach to understanding global metabolic regulations of organisms. This concept has arisen from various applications of NMR and MS spectroscopies to study the multicomponent metabolic composition of biological fluids, cells, and tissues. The generated metabolic profiles are processed by multivariate statistics to maximize the recovery of information to be correlated with well-determined stimuli such as dietary intervention or with any phenotypic data or diet habits. Metabonomics is thus uniquely suited to assess metabolic responses to deficiencies or excesses of nutrients and bioactive components. Furthermore, metabonomics is used to characterize the metabolic phenotype of individuals integrating genetic polymorphism, metabolic interactions with commensal and symbiotic partners such as gut microflora, as well as environmental and behavioral factors including dietary preferences. This paper reports several experimental key aspects in nutritional metabonomics, reviews its applications employing targeted and holistic approach analysis for the study of the metabolic responses following dietary interventions. It also reports the assessment of intra- and inter-individual variability in animal and human populations. The potentialities of nutritional metabonomics for the discovery of new biomarkers and the characterization of metabolic phenotypes are discussed in a context of their possible utilizations for personalized nutrition to provide health maintenance at the individual level.

Metabonomics in pharmaceutical discovery and development

Metabonomics has emerged as a key technology in pharmaceutical discovery and development, evolving as the small molecule counterpart of transcriptomics and proteomics. In drug discovery laboratories, metabonomics aids in target identification, phenotyping, and the understanding of the biochemical basis of disease and toxicity. This review focuses on three areas where metabonomics is used in the industry: (1) analytical considerations, (2) chemometric and statistical concerns, and (3) biological aspects and applications.

1H NMR Monitoring of the Canine Metabolic Profile after Oral Administration of Xenobiotics Using Multivariate Statistics

This study describes a chemometric analysis of 1H NMR spectra of canine plasma following oral single dose administrations of two food components (lycopene and oleuropein) and of two drug products, Fungoral (ketoconazole) and Adalat (nifedipine). Due to the high interday physiological variation, 1H NMR plasma data were first filtered (by applying orthogonal signal correction) and then subjected to principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). A distinct discrimination was achieved between samples obtained with and without administration of xenobiotics using both techniques. According to distance to model criterion and as shown by the Cooman's plots there was no overlap between the four models which proved to be specific for each xenobiotic. Moreover, it was shown that this approach has the potential to recognize subtle variations in the metabolic profile even if the administered xenobiotic itself could not be detected in the canine plasma by conventional HPLC methods.