Metabonomics, defined

Metabonomics in the context of this chapter aims to define the status and changes of the endogenous metabolite profile in biofluids or tissues of animals or in in vitro systems in response to toxic insults. The most commonly applied... 

The success of the project to describe the human genome along with progress in the definition of polymorphisms in human xenobiotic-metabolizing enzymes and other proteins will certainly lead to the ability to define populations and individuals at increased risk from a particular chemical insult. This ability will be extended and put on a more mechanistic basis by advances in the new disciplines of proteomics and metabonomics. 

Metabolism is considered to be a phenotype. It integrates all the factors from nutrition to environment to genetics assessing one s current state of health. Metabolomics arose from metabolic control theory and was originally based on the metabolome, which is defined as the metabolic composition of a cell and is analogous to the genome or proteome. In metabonomics, static cellular and biofluid concentrations of endogenous metabolites are evaluated over a time-course. 

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... 

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