Measurement of metabolic fluxes using stable isotope tracers in whole animals and human patients

Abstract

Purpose of review Metabolic flux analysis using stable isotope labeled substrates allows for the tracing of carbon, nitrogen, and hydrogen atoms through metabolic pathways and is an invaluable tool for investigating dynamic metabolic changes occurring in health and disease. Studies of flux analysis in vivo are more technically challenging than in vitro or ex vivo but provide a highly detailed view of organ and/or systemic metabolism. We review here recent efforts in studies of diet and nutrition, non-small cell lung cancer, ischemia/reperfusion injury, and hemorrhagic shock where in vivo flux analysis was utilized to analyze metabolic modulation. Recent findings Recent technical strides in the field of metabolomics afford sensitive and quantitative in vivo measurements of metabolic fluxes. Stable isotope tracing with 13C-glucose, 13C, 15N-glutamine, 13C-propionate, and other substrates are used in combination or in parallel to investigate the interplays among central carbon metabolic pathways and many other areas of the metabolome. Summary Stable isotope tracing in vivo provides opportunities to investigate physiological processes in the context of the whole animal. These approaches, often NMR spectroscopy or mass spectrometry (MS)-based, are growing in use and will likely find key applications in studying systemic disease, sports physiology, cancer metabolism, and personalized medicine.

Metabolic Pathways in Alloreactive T Cells

“…In recent years, the repertoire of available technologies for in vivo human work has expanded, making the in vivo study of T cell metabolism during GVHD more feasible than ever. For example, recent publications have used administration of non-radioactive isotope tracers to study tissue metabolism in human patients in real time ( 132 , 133 ). It could be envisioned that using non-radioactive isotope tracing in GVHD patients at the time of diagnosis could help to determine the dynamics of T cell metabolism during an active alloreactive immunologic response in vivo .…”

Cancer Cell Metabolites: Updates on Current Tracing Methods

“…In addition to stable isotope tracing in vivo using NMR and MS methods, a review on flux analysis and its potential use in in vivo physiological processes has been published. [31] Cellular metabolism is a dynamic system that facilitates complex network involving nutrient metabolism and energy production. Experimental computational approach such as 13 C-metabolic flux analysis ( 13 C-MFA), quantitatively measures biochemical reactions in the metabolic network.…”

Metabolic Remodelling: An Accomplice for New Therapeutic Strategies to Fight Lung Cancer

“…In the past decade, stable-isotope tracing with 13 C-glucose became an important tool for the analysis of metabolic pathways that are differentially activated in tumour cells in vivo, both in cancer mouse models and humans [26][27][28][29][30]. Uniformly labelled 13 C-glucose is administered as a bolus by an intraoperative infusion before surgical tumour resection and the distribution of labelled carbons in the various intermediates is analysed by 13 C NMR spectroscopy [31,32].…”