Isotopic Labeling Assisted Metabolomics

The analysis of relative and absolute amounts of metabolites in a given sample can answer a lot of research questions. Yet, neither one can be used to draw conclusion on metabolic turnover rates (fluxes) or the direction of such a flux, as a change in pool size can be caused by either changed production or consumption of the respective compound. A tool box of isotopic labelling assisted metabolomics can be used to overcome this limitation. 

13C- based Metabolic Flux analysis is probably the most elaborate of the approaches. It requires the analysis of labelling patterns in intracellular metabolite pools resulting from the metabolization of 13C labeled substrates, as well as the determination of metabolic secretion and uptake rates. The combination of this experimental data with a biochemical reaction network that needs to be known in advance, makes it possible to computationally estimate metabolic fluxes, and even to predict the networks response upon introduction of modifications. Unfortunately, applying the method in practice is time and data-intensive.

While we aim to establish formal 13C-based metabolomic flux analysis as a standard workflow in the future, we mainly focus on the analysis of mass distribution vectors in the moment. In many cases, this direct interpretation of 13C-labelling patters can offer sufficient information to answer research questions in the context of relative pathway activities, qualitative changes in pathway contributions (alternative metabolic routs), and the contribution and integration of substrates into metabolite pools.