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

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