In this subcore, parameters of cellular and tissue metabolic flux are assessed by incorporation of stable isotope labeled tracers (e.g., 13C, 15N, 2D) into metabolism. The CMC uses the targeted mass isotopomer multi-ordinate spectral analysis (MIMOSA) platform to interpret stable isotope labeling patterns for calculation of rates of discrete steps in glycolytic and mitochondrial metabolism. Such measurements can be used to identify differences in fuel usage (e.g., glycolysis vs. beta-oxidation), and non-oxidative (reductive carboxylation, anaplerosis and cataplerosis) contributions to the TCA cycle.