Measuring glutamate metabolism in vivo in tumors using Dynamic Nuclear Polarization

Introduction Dynamic Nuclear Polarisation (DNP) has recently been shown to increase the sensitivity of C magnetic resonance spectroscopy (MRS) by several orders of magnitude [1]. The number of metabolites that can be hyperpolarized using this technique is increasing; here we show that [1-C]glutamic acid can also be polarized using DNP. The metabolism of hyperpolarized glutamate to αketoglutarate, catalyzed by the enzyme alanine transaminase (ALT), was detected in vitro and in vivo in tumor models. As nonpolarized α-ketoglutarate is below the threshold for MRS detection, this presents a new method for probing tumor metabolism.