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Jeremy K Nicholson

Publications and source records attributed to Jeremy K Nicholson.

At least 91 records · Page 5Linked to original sources
PubMed2003

NMR spectroscopic-based metabonomic studies of urinary metabolite variation in acclimatizing germ-free rats.

Understanding metabolic variation in "normal" animals is critical to the evaluation of drug-induced metabolic perturbation related to toxicity or pharmacology. NMR spectroscopic-based metabonomic methods were used to evaluate the acclimatization pathways of germ-free (axenic) rats to standard laboratory conditions concomitant with the associated development of gut microfloral communities. Urine samples from male Fischer 344 germ-free rats were collected over 21 days following introduction to a standard laboratory environment and analyzed using NMR spectroscopy. NMR spectra were data-reduced and analyzed using principal component analysis to visualize the changes in the host metabolic trajectory over the course of the study. At days 2 and 6 of the acclimatization process, there were marked episodes of glycosuria. In comparison to the concentrations in the 0-6 h samples, there was a reduction in the level of the tricarboxylic acid cycle intermediates (citrate, 2-oxoglutarate, and succinate) from 6 h to day 6, after which there was a sustained increase until the end of the study. The concentrations of hippurate and trimethylamine N-oxide increased over the course of the study in comparison to the levels at 0-6 h, with the most pronounced increase in the former between days 17 and 21. Phenylacetylglycine levels increased after 6 h whereas 3-hydroxypropionic acid was observed at day 12 and increased up to day 17. By day 21, the urinary metabolic profile was within the control range when compared to historical data, implying the establishment of a stable gut microflora. Although the metabolic alterations caused by the microbial alterations were not as substantial as those from metabolic dysfunction, their presence does have an effect on the interpretation of the profiles, the state of the animal, and the mechanism for the cause of such alterations. Furthermore, the use of oral drug delivery will have an effect on the microbial state, not only as a direct influence of the drug but also from it's associated vehicle. Such effects are likely to be observed particularly in the area of preclinical investigation where the data from these studies are of particular relevance.

Acclimatization↗
PubMed2003

Application of chemometrics to 1H NMR spectroscopic data to investigate a relationship between human serum metabolic profiles and hypertension.

The application of chemometric methods to 1H NMR spectroscopic data has been documented for pathophysiological processes. In this study we show the application of 1H NMR-based metabonomics to investigate a relationship between serum metabolic profiles and hypertension. Although hypertension can be defined using blood pressure measurements, the underlying aetiology and metabolic effects are not so readily identified. Serum profiles for patients with low/normal systolic blood pressure (SBP < or = 130 mm Hg; n = 28), borderline SBP (131-149 mm Hg; n = 19) and high SBP (> or = 150 mm Hg; n = 17) were acquired using 1H NMR spectroscopy. Orthogonal signal correction followed by principal components analysis were applied to these NMR data in order to facilitate interpretation, and the resulting chemometric models were validated using Soft Independent Modelling of Class Analogy. Using 1H NMR-based metabonomics, it was possible to distinguish low/ normal SBP serum samples from borderline and high SBP samples. Borderline and high SBP samples, however, were indiscriminate from each other. Our preliminary results showed that there was a relationship between serum metabolic profiles and blood pressure which, in part, was due to lipoprotein particle composition differences between the samples. Furthermore, our results indicated that serum pathology associated with blood pressure is apparent at SBP values > 130 mm Hg, which the WHO and ISH currently define as the limit between normal and high-normal.

Coronary Angiography↗
PubMed2003

A metabonomic investigation of hepatotoxicity using diffusion-edited 1H NMR spectroscopy of blood serum.

It has been shown extensively, that chemometric investigations of 1H NMR spectra of rat urine taken from animals dosed with model toxins produce characteristic patterns of metabolic responses and that this permits the identification of biomarkers of toxic response and regeneration. To date, metabonomic methods have been mainly optimised for urine which contains mainly low molecular weight moieties, and thus a conventional 1-dimensional 1H NMR pulse sequence is an efficient means of obtaining information-rich data. In the case of biofluids such as blood plasma or serum, which contain a wide range of macromolecules the resonances of which can overlap with peaks from small molecule metabolites, the information giving rise to sample classification can be concealed in a conventional NMR spectrum andthis presents a different analytical challenge in terms of chemometric analysis of spectral profiles. Here, the use of other types of NMR data have been investigated and it is shown that by using spectra where the peak intensities are edited according to their molecular diffusion coefficients, it is possible to improve differentiation of control animals and those treated with the model hepatotoxin, alpha-naphthylisothiocyanate (ANIT). By using diffusion-edited spectroscopy, plasma lipid moieties are less attenuated than those from small endogenous metabolites and thus the toxin-induced changes to the lipoprotein profiles are more easily detectable.

1-Naphthylisothiocyanate↗
PubMed2002

Rapid and noninvasive diagnosis of the presence and severity of coronary heart disease using 1H-NMR-based metabonomics.

Although a wide range of risk factors for coronary heart disease have been identified from population studies, these measures, singly or in combination, are insufficiently powerful to provide a reliable, noninvasive diagnosis of the presence of coronary heart disease. Here we show that pattern-recognition techniques applied to proton nuclear magnetic resonance (1H-NMR) spectra of human serum can correctly diagnose not only the presence, but also the severity, of coronary heart disease. Application of supervised partial least squares-discriminant analysis to orthogonal signal-corrected data sets allows >90% of subjects with stenosis of all three major coronary vessels to be distinguished from subjects with angiographically normal coronary arteries, with a specificity of >90%. Our studies show for the first time a technique capable of providing an accurate, noninvasive and rapid diagnosis of coronary heart disease that can be used clinically, either in population screening or to allow effective targeting of treatments such as statins.

Coronary Artery Disease↗
PubMed2002

Cryogenic probe 13C NMR spectroscopy of urine for metabonomic studies.

Cryogenic probe technology can significantly compensate for the inherently low sensitivity of natural abundance 13C NMR spectroscopy. This now permits its routine use in NMR spectroscopy of biofluids, such as urine or plasma, with acquisition times that enable a high throughput of samples. Metabonomic studies often generate numerous samples in order to characterize fully the time-dependent biochemical response to stimuli, but until now, they have been largely conducted using 1H NMR spectroscopy because of its high sensitivity and hence efficient data acquisition. Here, we demonstrate that information-rich 13C NMR spectra of rat urine can be obtained using appropriately short acquisition times suitable for biochemical samples when using a cryogenic probe. Furthermore, these data were amenable to automated pattern recognition analysis, which produced a profile of the metabolic response to the model hepatotoxin hydrazine that was consistent with earlier studies. Thus, a new source of detailed and complementary information is available to metabonomics using cryogenic probe 13C NMR spectroscopy.

Animals↗
PubMed2002

NMR and pattern recognition studies on liver extracts and intact livers from rats treated with alpha-naphthylisothiocyanate.

The metabolite profiles from livers of toxin-treated rats were investigated using high resolution 1H NMR spectroscopy of aqueous (acetonitrile/water), lipidic (chloroform/methanol) extracts and magic angle spinning (MAS)-NMR spectroscopy of intact tissue. Rats were treated with the model cholestatic hepatotoxin, alpha-naphthylisothiocyanate (ANIT, 150 mg/kg) and NMR spectra of liver were analysed using principal components analysis (PCA) to extract novel toxicity biomarker information. 1H NMR spectra of control aqueous extracts showed signals from a range of organic acids and bases, amino acids, sugars, and glycogen. Chloroform/methanol extracts showed signals from a range of saturated and unsaturated triglycerides, phospholipids and cholesterol. The MAS 1H NMR spectra of livers showed a composite of signals found in both aqueous and lipophilic extracts. Following ANIT treatment, 1H NMR-PCA of aqueous extracts indicated a progressive reduction in glucose and glycogen, together with increases in bile acid, choline, and phosphocholine signals. 1H NMR-PCA of chloroform/methanol extracts showed elevated triglyceride levels. The 1H MAS-NMR-PCA analysis allowed direct detection of all of the ANIT-induced tissue perturbations revealed by 1H NMR of extracts, enabling metabolic characterisation of the lesion, which included steatosis, bile duct obstruction and altered glucose/glycogen metabolism. MAS-NMR spectroscopy requires minimal sample preparation and, unlike 1H NMR spectroscopy of tissue extracts, does not discriminate metabolites based on their solubility in a particular solvent and so this is a particularly useful exploratory tool in biochemical toxicology.

1-Naphthylisothiocyanate↗
PubMed2002

Earthworm species of the genus Eisenia can be phenotypically differentiated by metabolic profiling.

The universality of low molecular weight metabolites allows rapid and straightforward investigation of the biochemistry of genetically uncharacterised species. Thus ex vivo metabolic profiling in combination with multivariate data analysis (metabonomics) offers great potential in comparative biology. Here we present the first use of high resolution nuclear magnetic resonance (NMR) spectroscopy to distinguish closely related animal species via their metabolic phenotype (metabotype). We have profiled the three Eisenia (Oligochaeta, Lumbricidae) species Eisenia fetida, Eisenia andrei and Eisenia veneta using tissue extracts and coelomic fluid analysis. The low molecular weight biochemical profiles of tissue extracts were highly conserved for all three species, with E. fetida and E. andrei being more similar to each other than to E. veneta. However the metabolic profiles of the coelomic fluid of the different species were highly distinctive - the NMR spectra allowed unequivocal identification of species. Multivariate statistics were also used to quantify these spectral differences and to enable simplified graphical visualisation of species similarity. These results show that two morphologically undistinguishable species (E. fetida and E. andrei) differ markedly in their biochemical profiles despite apparently occupying the same ecological niche, and indicate that metabolic phenotype profiling can be used as a powerful functional genomics tool.

Animals↗
PubMed2002

The comparison of plasma deproteinization methods for the detection of low-molecular-weight metabolites by (1)H nuclear magnetic resonance spectroscopy.

Blood plasma is the major vehicle by which metabolites are transported around the body in mammalian species, and chemical analysis of plasma can provide a wealth of information relating to the biochemical status of an individual and is important for diagnostic purposes. However, plasma is very complex in physicochemical terms because it is composed of a range of organic and inorganic constituents with a wide range of molecular weights and chemical classes and this makes analysis non-trivial. It is now well established that high-resolution (1)H NMR spectroscopy of blood plasma provides useful qualitative and quantitative biochemical information relating to metabolic disorders. However, one of the problems encountered in NMR spectroscopic analysis of blood plasma is the extensive peak overlap or presence of broad macromolecule peaks in the (1)H NMR spectrum, which can severely limit the amount of obtainable information. Even with spectroscopic editing, information relating to low-molecular-weight (MW) metabolites is frequently lost. Therefore, the efficiency of a range of conventional protein removal methods, in combination with the use of one- and two-dimensional NMR spectroscopic methods for evaluation, have been compared for the extraction of NMR-observable low-MW metabolites. It has been shown that these "deproteinization" methods vary considerably in recovery of low MW metabolites and a judicious choice is crucial for optimal extraction of a given analyte. The results presented here show that while ultrafiltration provides the "safest" method of plasma deproteinization, the signal-to-noise ratio of the resultant (1)H NMR spectra is poor. On the other hand, acetonitrile precipitation at physiological pH allows the detection of more low-MW metabolites and at higher concentrations than any other method and provides the further advantages of being a rapid and simple procedure.

Acetaminophen↗
PubMed2002

Spectral profiles of cultured neuronal and glial cells derived from HRMAS (1)H NMR spectroscopy.

In the investigations of brain function and pathology in vivo by magnetic resonance spectroscopy (MRS), a decrease in the relative concentration of N-acetyl aspartate (NAA) has been correlated with neuronal cell damage or loss, while a relative increase in the resonance intensity of creatine has been correlated with gliosis. However, neither metabolite is confined strictly to one cell-type. In this study, pattern recognition of spectra derived from high-resolution magic angle spinning (HRMAS) (1)H NMR spectroscopy was used to distinguish three neural cell types; cortical astrocytes, cerebellar neurones and O-2A progenitors. The intact cells contained significant amounts of lipid resonances (-CH(2)CH(3) and -CH(2)CH(2)CH(2)-) in all three cell-types, even when a T(2)-edited Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was used, selectively attenuating resonances from macromolecules. Creatine was also detected in all three cell types. Principle component analysis (PCA) readily differentiated the NMR spectra, based on the individual metabolic profile derived from the cohort of cell type examined using conventional solvent-suppressed and CPMG pulse sequences. Creatine was not found to contribute to this separation. Moreover, the large lipid content of neuronal cells contributed most to the separation from the other cell types. This suggests that during MRS in vivo, where lipid resonances are commonly 'edited out' by T(2) delays, significant information may be sacrificed concerning relative contribution from individual cell types.

Amino Acids↗
PubMed2002

Quantitation in gradient high performance liquid chromatography/inductively coupled mass spectrometry investigated using diclofenac and chlorpromazine.

The use of directly coupled high performance liquid chromatography/inductively coupled plasma mass spectroscopy (HPLC/ICPMS) employing chlorine ((35)Cl/(37)Cl) detection has been investigated with respect to the detection and quantitation of the drugs diclofenac and chlorpromazine. By integration of peak areas in the 'chloratogram' (the chlorine specific HPLC chromatogram), a calibration curve was constructed, from which the concentrations could be determined. Chlorine detected HPLC/ICPMS is quantitative over a wide range of concentrations of pharmaceutical relevance for metabolite detection and the results reproducible (standard deviation +/- 0.43%) over multiple injections. Application of gradient chromatography and variation in the bulk mobile phase physicochemical properties has little effect on the ICPMS detection response for these compounds. This work indicates that the use of HPLC/ICPMS is likely to be quantitatively reliable for metabolism studies for a range of chlorinated xenobiotics.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2002

NMR-based metabonomic studies on the biochemical effects of commonly used drug carrier vehicles in the rat.

The biochemical effects of a series of commonly used drug carrier vehicles were investigated using (1)H NMR spectroscopic and pattern recognition based metabonomic analysis. Animals were treated by oral gavage with six dosage vehicles: 0.5% (w/v) sodium carboxymethylcellulose/0.2% (v/v)tween; microemulsion (consisting of propylene glycol, ethanol, cremophor, and corn oil glycerides); labrafil [consisting of poly(ethylene glycol) 300 esterified with oleic acid] (30%)/corn oil (70%); 0.1 M sodium phosphate buffered water; poly(ethylene glycol) 300 and 0.5% methocel. Urine samples (n = 7) collected over a 96 h period post administration were analyzed using 600 MHz (1)H NMR spectroscopy, and principal components analysis of the spectral data was used to analyze these data. Of the six vehicles studied, three (labrafil/corn oil, PEG 300 and microemulsion) gave rise to strong vehicle-related signals in the (1)H NMR spectra of urine and were, therefore, deemed to be less suitable for NMR-based toxicity studies. To investigate any biochemical consequences of vehicle dosing, PCA was used to analyze spectral regions that did not contain vehicle-related signals, i.e., the NMR-detectable endogenous metabolite profile. PEG 300 and labrafil/corn oil induced changes in the biochemical composition of urine including increased concentrations of dicarboxylic acids, creatinine, taurine, and sugars, indicating that these vehicles were bioactive in their own right and that this might confound interpretation of biochemical effects of weakly toxic drugs dosed in these carriers. This study shows the importance of selecting appropriate vehicles for NMR-based metabonomic studies with a view to minimizing the possibility of vehicle resonances obscuring endogenous compound peaks. Furthermore, we have shown that at least two of the commonly used drug carrier vehicles caused metabolic perturbations in the urine profile. These alterations in the biochemical profile reflect vehicle-induced changes in the physiological status of the organism that may obscure the pharmacologic or toxicologic effects of drugs.

Administration, Oral↗
PubMed2002

Metabolic profiling of the effects of D-galactosamine in liver spheroids using (1)H NMR and MAS-NMR spectroscopy.

We report here the combined application of (1)H magic angle spinning (MAS) and high-resolution NMR spectroscopy and pattern recognition methods to study the effects of a model toxin (D-galactosamine) in liver spheroid cultures. (1)H NMR spectra of metabolic profiles of spheroids showed closer similarities to intact liver spectra than those of isolated hepatocytes, suggesting their superiority as an in vitro model system. Batches of spheroids were prepared from male Sprague Dawley rat livers and incubated in control hepatocyte medium or medium containing D-galactosamine (4 or 20 mM) for 4 or 24 h. Intact spheroids were packed into rotors and analyzed using MAS-NMR spectroscopy or homogenized and analyzed using conventional (1)H NMR spectroscopy. Principal components analysis, (PCA), of the NMR data revealed separation of control and D-galactosamine-treated spheroids based on changes in the concentrations of the triglycerides and elevations in cholesterol and esters. The absence of cholesterol in hepatocytes and the relative under-representation of the lipid resonances offer an important advantage of spheroids over hepatocytes for the (1)H NMR studies of fatty liver. Orthogonal signal correction (OSC) was used as a data filter to remove non-dose-dependent variation from the NMR spectra, improving the classification of treated spheroids and controls. This work shows that useful metabolic information can be obtained on drug toxicity by the use of combined MAS-NMR and high-resolution NMR of liver spheroids and that such studies may enhance the validation of in vitro techniques against in vivo models for metabolic profiling.

Animals↗
PubMed2002

Analytical reproducibility in (1)H NMR-based metabonomic urinalysis.

Metabonomic analysis of biofluids and tissues utilizing high-resolution NMR spectroscopy and chemometric techniques has proven valuable in characterizing the biochemical response to toxicity for many xenobiotics. To assess the analytical reproducibility of metabonomic protocols, sample preparation and NMR data acquisition were performed at two sites (one using a 500 MHz and the other using a 600 MHz system) using two identical (split) sets of urine samples from an 8-day acute study of hydrazine toxicity in the rat. Despite the difference in spectrometer operating frequency, both datasets were extremely similar when analyzed using principal components analysis (PCA) and gave near-identical descriptions of the metabolic responses to hydrazine treatment. The main consistent difference between the datasets was related to the efficiency of water resonance suppression in the spectra. In a 4-PC model of both datasets combined, describing all systematic dose- and time-related variation (88% of the total variation), differences between the two datasets accounted for only 3% of the total modeled variance compared to ca. 15% for normal physiological (pre-dose) variation. Furthermore, <3% of spectra displayed distinct inter-site differences, and these were clearly identified as outliers in their respective dose-group PCA models. No samples produced clear outliers in both datasets, suggesting that the outliers observed did not reflect an unusual sample composition, but rather sporadic differences in sample preparation leading to, for example, very dilute samples. Estimations of the relative concentrations of citrate, hippurate, and taurine were in >95% correlation (r(2)) between sites, with an analytical error comparable to normal physiological variation in concentration (4-8%). The excellent analytical reproducibility and robustness of metabonomic techniques demonstrated here are highly competitive compared to the best proteomic analyses and are in significant contrast to genomic microarray platforms, both of which are complementary techniques for predictive and mechanistic toxicology. These results have implications for the quantitative interpretation of metabonomic data, and the establishment of quality control criteria for both regulatory agencies and for integrating data obtained at different sites.

Animals↗
PubMed2002

Metabonomics: a platform for studying drug toxicity and gene function.

The later that a molecule or molecular class is lost from the drug development pipeline, the higher the financial cost. Minimizing attrition is therefore one of the most important aims of a pharmaceutical discovery programme. Novel technologies that increase the probability of making the right choice early save resources, and promote safety, efficacy and profitability. Metabonomics is a systems approach for studying in vivo metabolic profiles, which promises to provide information on drug toxicity, disease processes and gene function at several stages in the discovery-and-development process.

Animals↗
PubMed2002

Metabolic trajectory characterisation of xenobiotic-induced hepatotoxic lesions using statistical batch processing of NMR data.

Multivariate statistical batch processing (BP) analysis of 1H NMR urine spectra was employed to establish time-dependent metabolic variations in animals treated with the model hepatotoxin, alpha-naphthylisothiocyanate (ANIT). ANIT (100 mg kg(-1)) was administered orally to rats (n = 5) and urine samples were collected from dosed and matching control rats at time-points up to 168 h post-dose. Urine samples were measured via 1H NMR spectroscopy and partial least squares (PLS) based batch processing analysis was used to interpret the spectral data, treating each rat as an individual batch comprising a series of timed urine samples. A model defining the mean urine profile over the 7 day study period was established, together with model confidence limits (+/-3 standard deviation), for the control group. Samples obtained from ANIT treated animals were evaluated using the control model. Time-dependent deviations from the control model were evident in all ANIT treated animals consisting of glycosuria, bile aciduria, an initial decrease in taurine levels followed by taurinuria and a reduction of tricarboxylic acid cycle intermediate excretion. BP provided an efficient means of visualising the biochemical response to ANIT in terms of both inter-animal variation and net variation in metabolite excretion profiles. BP also allowed multivariate statistical limits for normality to be established and provided a template for defining the sequence of time-dependent metabolic consequences of toxicity in NMR based metabonomic studies.

1-Naphthylisothiocyanate↗
PubMed2002

Metabolic profiling of rodent biological fluids via 1H NMR spectroscopy using a 1 mm microlitre probe.

The application of a 1 mm TXI (1H/13C/15N) microlitre NMR probe with z-gradient for metabolic profiling of biofluids is described. The probe was used to provide spectral profiles for rat blood plasma using only approximately 2 microl of fluid with a range of solvent suppression techniques. Using a similar amount of fluid, spectra were obtained from rat and mouse cerebrospinal fluid, demonstrating that the probe could be used to profile rodents metabolically via biofluids previously inaccessible to NMR analysis without the need for termination.

Animals↗
PubMed2002

Application of orthogonal signal correction to minimise the effects of physical and biological variation in high resolution 1H NMR spectra of biofluids.

1H nuclear magnetic resonance (NMR)-based metabonomics is a well-established technique used to analyse and interpret complex multiparametric metabolic data, and has a wide number of applications in the development of pharmaceuticals. However, interpretation of biological data can be confounded by extraneous variation in the data such as fluctuations in either experimental conditions or in physiological status. Here we have shown the novel application of a data filtering method, orthogonal signal correction (OSC), to biofluid NMR data to minimise the influence of inter- and intra-spectrometer variation during data acquisition, and also to minimise innate physiological variation. The removal of orthogonal variation exposed features of interest in the NMR data and facilitated interpretation of the derived multivariate models. Furthermore, analysis of the orthogonal variation provided an explanation of the systematic analytical/biological changes responsible for confounding the original NMR data.

Blood Chemical Analysis↗