Measurement of metabolite concentrations provides only part of the picture of the metabolic activity of a cell, tissue, or organism. An equally important aspect is the rate of turnover of metabolites, termed metabolic flux. Mass spectrometry provides a convenient way of assessing metabolic flux in a large number of pathways simultaneously via the use of stable isotope labeling experiments, termed "fluxomics". Many of the core lab’s metabolomics services can be adapted to study metabolic flux.
Important note: Once you decide that you want to do a fluxomics experiment, it is necessary to select a targeted assay (or assays) that you want to use to perform the fluxomics study. Fluxomics can be done on many of our targeted assays, depending on the compounds you're looking for. Appropriate design of the biological experiment is especially important in fluxomics studies.
When you're ready to proceed, please follow the steps to submit a project service request here.
Please contact the Managing Director, Maureen Kachman, if you have questions not answered here, or to discuss details.
More background information about fluxomics. Stable isotopes, such as 13C, 15N, 2H, etc., are naturally-occurring, non-radioactive versions of elements which differ in mass from more abundant versions of these atoms (12C, 14N, 1H, etc). Tracer compounds which are enriched in these stable isotopes (such as 13C glucose) are commercially available and can be administered to cultured cells or living organisms. After a determined period of time of exposure to the tracer, the resulting cells, tissues or bio-fluids can be collected and analyzed by mass-spectrometry based metabolomics. The extent of incorporation of stable isotopes into the metabolome can be used to measure the turnover of a wide range of metabolites simultaneously. (1)
Notes on data analysis in flux studies. The data output which the core lab generates from fluxomics studies are "mass isotopomer distributions." These data show the extent of incorporation of stable isotope tracers into a variety of metabolites (determined by the assay type selected). These data can be used in several ways. One possibility is to use mass isotopomer data as an input for a comprehensive computational model of flux in major metabolic pathways. While this approach yields the most information, it requires consultation with experts in computational modeling, and is often not realistic to implement because of the complexity of mammalian metabolic networks and because of the compartmentalization of metabolic reactions (1). An alternative, simpler approach is to compare measured mass isotopomer distributions between different experimental groups via flux ratios or statistics; this approach has been termed stable isotope resolved metabolomics (SIRM) or "fluxomics" (2, 3). Please consult with the core lab to discuss options for analysis and interpretation of fluxomics data.
1. Sauer U. Metabolic networks in motion: 13C-based flux analysis. Molecular Systems Biology. 2006;2. doi: 10.1038/msb4100109.
2. Fan TWM, Lane AN, Higashi RM, Farag MA, Gao H, Bousamra M, Miller DM. Altered regulation of metabolic pathways in human lung cancer discerned by 13C stable isotope-resolved metabolomics (SIRM). Molecular Cancer. 2009;8(1):41. doi: 10.1186/1476-4598-8-41.
3. Godin J-P, Ross AB, Rezzi S, Poussin C, Martin F-P, Fuerholz A, Cleroux M, Mermoud A-F, Tornier L, Vera FA, Pouteau E, Ramadan Z, Kochhar S, Fay L-B. Isotopomics: A Top-Down Systems Biology Approach for Understanding Dynamic Metabolism in Rats Using [1,2-13C2] Acetate. Analytical Chemistry. 2010;82:646-53.