Hyperpolarized 13C imaging allows real-time in vivo measurements of metabolite levels. Quantification of metabolite conversion between [1-13C]pyruvate and downstream metabolites [1-13C]alanine, [1-13C]lactate, and [13C]bicarbonate can be achieved through kinetic modeling. Since pyruvate interacts dynamically and simultaneously with its downstream metabolites, the purpose of this work is the determination of parameter values through a multisite, dynamic model involving possible biochemical pathways present in MR spectroscopy. Kinetic modeling parameters were determined by fitting the multisite model to time-domain dynamic metabolite data. The results for different pyruvate doses were compared with those of different two-site models to evaluate the hypothesis that for identical data the uncertainty of a model and the signal-to-noise ratio determine the sensitivity in detecting small physiological differences in the target metabolism. In comparison to the two-site exchange models, the multisite model yielded metabolic conversion rates with smaller bias and smaller standard deviation, as demonstrated in simulations with different signal-to-noise ratio. Pyruvate dose effects observed previously were confirmed and quantified through metabolic conversion rate values. Parameter interdependency allowed an accurate quantification and can therefore be useful for monitoring metabolic activity in different tissues. 1. Introduction While 13C magnetic resonance spectroscopy (MRS) has been utilized for in vivo imaging and spectroscopy of metabolism [1] for a long time, only the development of dynamic nuclear polarization (DNP) helped to overcome the inherent sensitivity limit; as through hyperpolarization using DNP followed by rapid dissolution, the 13C MR signal can be amplified by more than 10,000-fold [2]. One of the most common and viable agents for in vivo use is 1-13C]pyruvate (PYR) [3]. After intravenous injection, it is transported to the observed tissue or organ under observation, where it is enzymatically metabolized to its downstream metabolites 1-13C]alanine (ALA) by alanine transaminase (ALT), 1-13C]lactate (LAC) by lactate dehydrogenase (LDH), and 13C]bicarbonate (BC) by pyruvate dehydrogenase (PDH) to varying extent, depending on tissue type and predominant metabolic activity. At the same time PYR is in chemical exchange with 1-13C]pyruvate-hydrate (PYRH). As part of gluconeogenesis, PYR may also be carboxylated to oxaloacetate [4]. In order to quantify the metabolic exchange between PYR and its downstream metabolites, MRS data acquired over a certain
References
[1]
K. M. Brindle, “NMR methods for measuring enzyme kinetics in vivo,” Progress in Nuclear Magnetic Resonance Spectroscopy, vol. 20, no. 3, pp. 257–293, 1988.
[2]
J. H. Ardenkj?r-Larsen, B. Fridlund, A. Gram et al., “Increase in signal-to-noise ratio of >10,000 times in liquid-state NMR,” Proceedings of the National Academy of Sciences of the United States of America, vol. 100, no. 18, pp. 10158–10163, 2003.
[3]
K. Golman, R. In 't Zandt, and M. Thaning, “Real-time metabolic imaging,” Proceedings of the National Academy of Sciences of the United States of America, vol. 103, no. 30, pp. 11270–11275, 2006.
[4]
M. E. Bizeau, C. Short, J. S. Thresher, S. R. Commerford, W. T. Willis, and M. J. Pagliassotti, “Increased pyruvate flux capacities account for diet-induced increases in gluconeogenesis in vitro,” American Journal of Physiology, vol. 281, no. 2, pp. R427–R433, 2001.
[5]
M. A. Janich, M. I. Menzel, F. Wiesinger, et al., “Effects of pyruvate dose on in vivo metabolism and quantification of hyperpolarized 13C spectra,” NMR in Biomedicine, vol. 25, no. 1, pp. 142–151, 2012.
[6]
H. J. Atherton, M. A. Schroeder, M. S. Dodd et al., “Validation of the in vivo assessment of pyruvate dehydrogenase activity using hyperpolarised 13C MRS,” NMR in Biomedicine, vol. 24, no. 2, pp. 201–208, 2011.
[7]
S. E. Day, M. I. Kettunen, F. A. Gallagher, et al., “Detecting tumor response to treatment using hyperpolarized 13C magnetic resonance imaging and spectroscopy,” Nature Medicine, vol. 13, no. 11, pp. 1382–1387, 2007.
[8]
M. L. Zierhut, Y.-F. Yen, A. P. Chen et al., “Kinetic modeling of hyperpolarized 13C1-pyruvate metabolism in normal rats and TRAMP mice,” Journal of Magnetic Resonance, vol. 202, no. 1, pp. 85–92, 2010.
[9]
D. M. Spielman, D. Mayer, Y.-F. Yen, J. Tropp, R. E. Hurd, and A. Pfefferbaum, “In vivo measurement of ethanol metabolism in the rat liver using magnetic resonance spectroscopy of hyperpolarized [1-13C]pyruvate,” Magnetic Resonance in Medicine, vol. 62, no. 2, pp. 307–313, 2009.
[10]
O. Khegai, R. F. Schulte, M. A. Janich, et al., “Apparent rate constant mapping using hyperpolarized [1–13C]pyruvate,” NMR in Biomedicine, vol. 27, no. 10, pp. 1256–1265, 2014.
[11]
J. M. Park, S. Josan, T. Jang et al., “Metabolite kinetics in C6 rat glioma model using magnetic resonance spectroscopic imaging of hyperpolarized [1-13C]pyruvate,” Magnetic Resonance in Medicine, vol. 68, no. 6, pp. 1886–1893, 2012.
[12]
S. Josan, D. Spielman, Y.-F. Yen, R. Hurd, A. Pfefferbaum, and D. Mayer, “Fast volumetric imaging of ethanol metabolism in rat liver with hyperpolarized [1-13C]pyruvate,” NMR in Biomedicine, vol. 25, no. 8, pp. 993–999, 2012.
[13]
M. I. Kettunen, D.-E. Hu, T. H. Witney et al., “Magnetization transfer Measurements of exchange between hyperpolarized [1-13C]pyruvate and [1-13C]lactate in a murine lymphoma,” Magnetic Resonance in Medicine, vol. 63, no. 4, pp. 872–880, 2010.
[14]
P. E. Z. Larson, A. B. Kerr, C. Leon Swisher, J. M. Pauly, and D. B. Vigneron, “A rapid method for direct detection of metabolic conversion and magnetization exchange with application to hyperpolarized substrates,” Journal of Magnetic Resonance, vol. 225, pp. 71–80, 2012.
[15]
C. Harrison, C. Yang, A. Jindal, et al., “Comparison of kinetic models for analysis of pyruvate-to-lactate exchange by hyperpolarized 13C NMR,” NMR in Biomedicine, vol. 25, no. 11, pp. 1286–1294, 2012.
[16]
D. K. Hill, M. R. Orton, E. Mariotti et al., “Model free approach to kinetic analysis of real-time hyperpolarized 13C magnetic resonance spectroscopy data,” PLoS ONE, vol. 8, no. 9, Article ID e71996, 2013.
[17]
L. Z. Li, S. Kadlececk, H. N. Xu et al., “Ratiometric analysis in hyperpolarized NMR (I): test of the two-site exchange model and the quantification of reaction rate constants,” NMR in Biomedicine, vol. 26, no. 10, pp. 1308–1320, 2013.
[18]
F. A. Gallagher, M. I. Kettunen, and K. M. Brindle, “Biomedical applications of hyperpolarized 13C magnetic resonance imaging,” Progress in Nuclear Magnetic Resonance Spectroscopy, vol. 55, no. 4, pp. 285–295, 2009.
[19]
M. F. Santarelli, V. Positano, G. Giovannetti et al., “How the signal-to-noise ratio influences hyperpolarized 13C dynamic MRS data fitting and parameter estimation,” NMR in Biomedicine, vol. 25, no. 7, pp. 925–934, 2012.
[20]
M. E. Merritt, C. Harrison, C. Storey, F. M. Jeffrey, A. D. Sherry, and C. R. Malloy, “Hyperpolarized 13C allows a direct measure of flux through a single enzyme-catalyzed step by NMR,” Proceedings of the National Academy of Sciences of the United States of America, vol. 104, no. 50, pp. 19772–19777, 2007.
[21]
S. M. Kazan, S. Reynolds, A. Kennerley et al., “Kinetic modeling of hyperpolarized 13C pyruvate metabolism in tumors using a measured arterial input function,” Magnetic Resonance in Medicine, vol. 70, no. 4, pp. 943–953, 2013.
[22]
C. Yang, C. Harrison, E. S. Jin et al., “Simultaneous steady-state and dynamic 13C NMR can differentiate alternative routes of pyruvate metabolism in living cancer cells,” The Journal of Biological Chemistry, vol. 289, no. 9, pp. 6212–6224, 2014.
[23]
F. Wiesinger, I. Miederer, M. I. Menzel et al., “Metabolic rate constant mapping of hyperpolarized 13C pyruvate,” ISMRM 3282, 2010.
[24]
L. Vanhamme, A. van den Boogaart, and S. van Huffel, “Improved method for accurate and efficient quantification of mrs data with use of prior knowledge,” Journal of Magnetic Resonance, vol. 129, no. 1, pp. 35–43, 1997.
[25]
T. Harris, G. Eliyahu, L. Frydman, and H. Degani, “Kinetics of hyperpolarized 13C1-pyruvate transport and metabolism in living human breast cancer cells,” Proceedings of the National Academy of Sciences of the United States of America, vol. 106, no. 43, pp. 18131–18136, 2009.
[26]
T. Xu, D. Mayer, M. Gu et al., “Quantification of in vivo metabolic kinetics of hyperpolarized pyruvate in rat kidneys using dynamic 13C MRSI,” NMR in Biomedicine, vol. 24, no. 8, pp. 997–1005, 2011.
[27]
J. D. Shearer, G. P. Buzby, J. L. Mullen, E. Miller, and M. D. Caldwell, “Alteration in pyruvate metabolism in the liver of tumor-bearing rats,” Cancer Research, vol. 44, no. 10, pp. 4443–4446, 1984.
[28]
D. M. Bates and D. G. Watts, Nonlinear Regression Analysis and Its Applications, John Wiley & Sons, New York, NY, USA, 2008.
[29]
O. Warburg, “On the origin of cancer cells,” Science, vol. 123, no. 3191, pp. 309–314, 1956.
[30]
H. Lu, R. A. Forbes, and A. Verma, “Hypoxia-inducible factor 1 activation by aerobic glycolysis implicates the Warburg effect in carcinogenesis,” The Journal of Biological Chemistry, vol. 277, no. 26, pp. 23111–23115, 2002.
[31]
W. Droge, H.-P. Eck, H. Kriegbaum, and S. Mihm, “Release of L-alanine by tumor cells,” The Journal of Immunology, vol. 137, no. 4, pp. 1383–1386, 1986.
[32]
L. Brennan, C. Hewage, J. P. G. Malthouse, and G. J. McBean, “Gliotoxins disrupt alanine metabolism and glutathione production in C6 glioma cells: a 13C NMR spectroscopic study,” Neurochemistry International, vol. 45, no. 8, pp. 1155–1165, 2004.
[33]
H. R. Harding, F. Rosen, and C. A. Nichol, “Depression of Alanine Transaminase Activity in the Liver of Rats Bearing Walker Carcinoma 256,” Cancer Research, vol. 24, pp. 1318–1323, 1964.
[34]
S. M. Ronen, A. Volk, and J. Mispelter, “Comparative NMR study of a differentiated rat hepatoma and its dedifferentiated subclone cultured as spheroids and as implanted tumors,” NMR in Biomedicine, vol. 7, no. 6, pp. 278–286, 1994.