Metabolomics is the analysis of metabolite profiles in biological samples.They are considered to serve as unique chemical fingerprints and represent the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. Those are diveded into primary metabolites which are directly involved in normal growth, development, body maintanance and reproduction of an organism and secondary metabolites not directly involved in those processes, but usually important for ecological functions.

METABOLOMICS & MORE

The Munich Functional Metabolomics Initiative will organize its 1st International Metabolomics Conference in the Munich vicinity (Weihenstephan) in March 2010 together with the TUM Center Institute on Nutrition and Food Science and the Helmholtz Zentrum München (German Research Center for Environmental Health). For more information visit the symposium website!

The most important techniques for metabolomics in human biofluids are gas chromatography (GC) or liquid chromatography (LC) coupled to mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy. Each of these platforms has its advantages and limitations. To obtain the most valuable information of the metabolome, a combination of the different techniques appears necessary as each technique  covers different mass and concentration ranges. GC-MS is mainly applied to identify and quantify low molecular weight metabolites with masses of up to about 1000 Da. Applied to human biofluids this method has been used in toxicology and pharmacology as well as newborn screening, where usually only a few selected metabolites are analyzed. LC-MS seems better suited for the analysis of labile and higher molecular weight compounds. It is the most global of the techniques and can be used to determine a raw metabolite profile as well as to identify and quantify specific compounds. Absolute quantification, however, requires reliable internal standards, and better results for identification can be obtained using tandem MS (LC-MS/MS).

High-resolution 1H-NMR spectroscopy can in principle detect any proton-containing metabolite present in a sample above a certain threshold concentration. Thus, 1-dimensional 1H-NMR techniques are mainly used for metabolic fingerprinting of raw samples without identifying the individual metabolites. After chromatographic separation or by using 2-dimensional techniques, NMR can also be used to characterise specific compounds or to obtain valuable structural information. NMR-techniques have been used successfully to analyze metabolite changes in human and animal body fluids and tissue extracts. The huge amount of data generated with the described metabolomics technologies then have to be processed and analyzed using appropriate chemometrics methods. After the necessary pre-processing of the spectra, relevant information is usually extracted and visualized by multivariate analysis methods like hierarchical cluster analysis, principal components analysis or discriminate analysis. Various efforts are currently undertaken to standardize metabolomics experiments and build databases that will facilitate the identification of metabolites.