title: Profiling the human response to physical exercise: a computational strategy for the identification and kinetic analysis of metabolic biomarkers.
abstract: BACKGROUND
  In metabolomics, biomarker discovery is a highly data driven process and requires sophisticated computational methods for the search and prioritization of novel and unforeseen biomarkers in data, typically gathered in preclinical or clinical studies. In particular, the discovery of biomarker candidates from longitudinal cohort studies is crucial for kinetic analysis to better understand complex metabolic processes in the organism during physical activity.
  
  
  RESULTS
  In this work we introduce a novel computational strategy that allows to identify and study kinetic changes of putative biomarkers using targeted MS/MS profiling data from time series cohort studies or other cross-over designs. We propose a prioritization model with the objective of classifying biomarker candidates according to their discriminatory ability and couple this discovery step with a novel network-based approach to visualize, review and interpret key metabolites and their dynamic interactions within the network. The application of our method on longitudinal stress test data revealed a panel of metabolic signatures, i.e., lactate, alanine, glycine and the short-chain fatty acids C2 and C3 in trained and physically fit persons during bicycle exercise.
  
  
  CONCLUSIONS
  We propose a new computational method for the discovery of new signatures in dynamic metabolic profiling data which revealed known and unexpected candidate biomarkers in physical activity. Many of them could be verified and confirmed by literature. Our computational approach is freely available as R package termed BiomarkeR under LGPL via CRAN http://cran.r-project.org/web/packages/BiomarkeR/.
authors.affiliation: Research Group for Clinical Bioinformatics, Institute of Electrical, Electronic and Bioengineering, UMIT, 6060 Hall in Tirol, Austria. christian.baumgartner@umit.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Netzer
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Weinberger
authors.forename: Michael
authors.initials: M
authors.lastname: Handler
authors.forename: Michael
authors.initials: M
authors.lastname: Seger
authors.forename: Xiaocong
authors.initials: X
authors.lastname: Fang
authors.forename: Karl G
authors.initials: KG
authors.lastname: Kugler
authors.forename: Armin
authors.initials: A
authors.lastname: Graber
authors.forename: Christian
authors.initials: C
authors.lastname: Baumgartner