Using [1-13C]lactic acid for hyperpolarized 13C MR cardiac studies

PurposeHyperpolarized [1-C-13]lactate in solution may be a clinically relevant and safe substrate for real time MR investigations of key metabolic pathways. The potential of using hyperpolarized [1-C-13]lactate for magnetic resonance studies of cardiac metabolism in vivo was explored. MethodsNeat [1-C-13]lactic acid was hyperpolarized using the dynamic nuclear polarization process. Cardiac MR spectroscopy experiments were performed in vivo using hyperpolarized [1-C-13]lactate and [1-C-13]pyruvate in solutions. ResultsA high degree of polarization was achieved for [1-C-13]lactate in solution (16.7%). C-13-bicarbonate was observed in rat hearts in vivo after either hyperpolarized [1-C-13]lactate or hyperpolarized [1-C-13]pyruvate was infused, but lower C-13-bicarbonate to substrate ratio was observed with hyperpolarized [1-C-13]lactate infusions. The response of C-13-bicarbonate signal as a function of hyperpolarized [1-C-13]lactate doses was also investigated and a saturation of C-13-bicarbonate signal was observed at the highest dose of [1-C-13]lactate used (0.69 mmol/kg). ConclusionThis study demonstrated that the use of neat [1-C-13]lactic acid as the DNP sample is a potential alternative to [1-C-13]pyruvic acid for cardiac hyperpolarized C-13 MR studies. Hyperpolarized [1-C-13]lactate may enable noninvasive assessment of cardiac PDH flux in cardiac patients in the near future. Magn Reson Med, 2014. (c) 2014 Wiley Periodicals, Inc. Magn Reson Med 73:2087-2093, 2015. (c) 2014 Wiley Periodicals, Inc.