MS-based metabonomics

Williams RE, Lenz EM, Evans JA, Wilson ID, Granger JH, Plumb RS, Stumpf CL. A combined (1)H NMR and HPLC-MS-based metabonomic study of urine from obese (fa/fa) Zucker and normal 48. Wistar-derived rats. J. Pharm. Biomed. Anal. 2005 38 465-471. 

Interestingly, the number of examples of toxicity biomarkers discovered using nuclear magnetic resonance (NMR)-based and MS-based metabonomics is quite impressive. In metabonomics studies in which a severe toxicity is observed, almost always the relative urinary concentrations of Krebs cycle intermediates are decreased and a concomitant decrease in urinary levels of hippuric acid is observed. These compounds have been proposed to be nonspecific markers of toxicity as they reflect a combination of complex changes in an organism [11,48-51], Taurine has been known to be a specific marker for liver toxicity as its urinary levels are typically increased with necrosis and fatty liver. Several bile acids in the serum such as cholic, glycolic, and taurocholic acids have also been demonstrated to be sensitive markers of liver dysfunction [50], In the literature, there are a few preclinical and clinical examples of... 

Along with advances in various ionization sources, significant improvements have been made in the area of mass analyzers. Mass analyzers can be differentiated based on several attributes such as scan speed, duty cycle, mass resolution, mass range, and cost [126], The most common analyzers used for metabonomics analyses include the quadrupole and TOF-based analyzers [125-127], Some other analyzers that have been reported for use in MS-based metabonomics analyses are the ion traps, Orbitraps, and Fourier transform mass spectrometers [128,129],... 

Sun J, Von Tungeln LS, Hines W, Beger RD. Identification of metabolite profiles of the catechol-O-methyl transferase inhibitor tolcapone in rat urine using LC/MS-based metabonomics analysis. J Chromatogr B Anal Technol Biomed Life Sci 2009 877 2557-2565. 

Lu X, et al. LC-MS-based metabonomics analysis. J Chromatogr B Anal Technol Biomed Life Sci 2008b 866 64—76. 

Sangster T, et al. A pragmatic and readily implemented quality control strategy for HPLC-MS and GC-MS-based metabonomic analysis. Analyst 2006 131 1075-1078. 

The focus of this chapter is to review the progress that has been made in the area of mass spectrometry (MS)-based nontargeted metabonomics research in the context of... 

Luc et al. [86] evaluated a number of different columns and gradients for LC-MS-based nontargeted metabonomics analyses of rat plasma and urine samples. The authors compared equivalent UPLC and HPLC columns of the same size and with the same packing material. The only difference was in the particle size, which was 1.7 and 3.5 pm for UPLC and HPLC columns, respectively. Luc et al. concluded that although the UPLC peaks had improved peak widths (FWHM) and overall intensity,... 

Luc, C.E. et al., Evaluation of columns and gradients for LC/MS-based non-targeted metabonomics. Proceedings of the 56th ASMS Conference, Denver, CO, 2008. 

Gika, H.G. et al., Within-day reproducibility of an HPLC-MS-based method for metabonomic analysis Application to human urine, J. Proteome Res., 6(8), 3291, 2007. 

Theodoridis, G., Gika, H.G., and Wilson, I.D., LC-MS based methodology for global metabolite profiling in metabonomics/metabolomics, Trends Anal. Chem., 27(3), 251, 2008. 

This approach differs from those discussed above in that measured analytes have been selected a priori, usually to address certain specific biological questions within a study. Furthermore, since the exact analytes are known, it is possible and desirable to measure their absolute concentrations with appropriate use of internal standards and calibration curves. The lines between targeted metabolomics and traditional LC—MS-based assay development are arguably ill defined. Certainly, no one would equate an MS assay developed to measure alanine with targeted metabonomics. However, a multiplex assay to measure 13 or 14 organic acids in a urine sample probably qualifies. Often, targeted approaches can be developed for specific compoimd classes such as... 

Michopoulos F, et al. UPLC-MS-based analysis of human plasma for metabonomics using solvent precipitation or solid phase extraction. J Proteome Res 2009 8 2114-2121. 

Moreover, there are a number of publicly available free and commercial spectral (e.g., MS- and NMR-based), chemical, and biochemical/metabolic pathway databases that can be useful in identification and characterization of metabolites, as well as interpretation of metabonomics data at a biochemical pathway level. Examples of such databases are listed in Table 10.4. In a very recent publication, Loftus et al. [150] provided an example in which unknown analytes in complex biological matrices can be detected and characterized using high mass accuracy ESI MS" and formula prediction software, as well as by comparison to mass spectral databases, rather than by following the standard identification route via comparison to an authentic standard. This seems to be an attractive and a promising alternative for future profiling studies. 

As described in more detail in Section 13.3.2, the main analytical techniques that are employed for metabonomic studies are based on nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). The latter technique requires a preseparation of the metabolic components using either gas chromatography (GC) after chemical derivatization or liquid chromatography (LC), with the newer method of ultra-high-pressure LC (UPLC) being used increasingly. The use of capillary electrophoresis (CE) coupled to MS has also shown promise. Other more specialized techniques such as Fourier transform infrared spectroscopy and arrayed electrochemical detection have been used in some cases. 

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