Metabolomics: Metabolome measurement in human plasma

Objectives: Metabolomics is a new approach to precisely phenotype individuals and identify potentially novel biomarkers. Although GC- and LC-MS/MS based metabolomics has been established to determine the metabolome in plants, these techniques have not yet been evaluated in human plasma. We therefore aimed to analyze the reproducibility of measurements under various conditions. Methods: The analytical variability was investigated by repeated measurement of EDTA-plasma samples. Stability of the metabolome was analyzed by investigating samples after different periods at room temperature until freezing. In addition the effects of repeated Freeze-thawing cycles were analysed. GC-MS/MS and LC-MS/MS methods were adapted to the measurement in human plasma. Results: Up to 230 metabolites were detected per sample. About 120 of these metabolites were unknown. Analytical variability was rather low, as shown by intraindividual coefficients of variance (CV) between 0.9 and 56.1%. As expected, preanalytical factors had a higher influence on metabolite variability with preanalytical CVs up to 165.4%. Principal component analysis revealed that interindividual differences of cluster driving metabolites were far larger than analytical and preanalytical effects. Good correlations between conventionally determined metabolites and the here described metabolome measurements were observed. Conclusion: We demonstrate the feasibility of metabolome measurement by GC- and LC-MS/MS. The influence of preanalytical factors is far less than the individual metabolic character of a person. Therefore the presented techniques could be useful tool for further research of the human metabolome.