Modeling non-linear kinetics of hyperpolarized [1-13 C] pyruvate in the crystalloid-perfused rat heart

TY - JOUR

T1 - Modeling non-linear kinetics of hyperpolarized [1-13 C] pyruvate in the crystalloid-perfused rat heart

AU - Mariotti, Erika

AU - Orton, Matthew R.

AU - Eerbeek, Otto

AU - Ashruf, J.F.

AU - Zuurbier, Coert J

AU - Southworth, Richard

AU - Eykyn, Thomas Roger

PY - 2016/1/18

Y1 - 2016/1/18

N2 - Hyperpolarized 13 C MR measurements have the potential to display non-linear kinetics. We have developed an approach to describe possible non-first-order kinetics of hyperpolarized [1-13 C] pyruvate employing a system of differential equations that agrees with the principle of conservation of mass of the hyperpolarized signal. Simultaneous fitting to a second-order model for conversion of [1-13 C] pyruvate to bicarbonate, lactate and alanine was well described in the isolated rat heart perfused with Krebs buffer containing glucose as sole energy substrate, or glucose supplemented with pyruvate. Second-order modeling yielded significantly improved fits of pyruvate-bicarbonate kinetics compared with the more traditionally used first-order model and suggested time-dependent decreases in pyruvate-bicarbonate flux. Second-order modeling gave time-dependent changes in forward and reverse reaction kinetics of pyruvate-lactate exchange and pyruvate-alanine exchange in both groups of hearts during the infusion of pyruvate; however, the fits were not significantly improved with respect to a traditional first-order model. The mechanism giving rise to second-order pyruvate dehydrogenase (PDH) kinetics was explored experimentally using surface fluorescence measurements of nicotinamide adenine dinucleotide reduced form (NADH) performed under the same conditions, demonstrating a significant increase of NADH during pyruvate infusion. This suggests a simultaneous depletion of available mitochondrial NAD+ (the cofactor for PDH), consistent with the non-linear nature of the kinetics. NADH levels returned to baseline following cessation of the pyruvate infusion, suggesting this to be a transient effect

AB - Hyperpolarized 13 C MR measurements have the potential to display non-linear kinetics. We have developed an approach to describe possible non-first-order kinetics of hyperpolarized [1-13 C] pyruvate employing a system of differential equations that agrees with the principle of conservation of mass of the hyperpolarized signal. Simultaneous fitting to a second-order model for conversion of [1-13 C] pyruvate to bicarbonate, lactate and alanine was well described in the isolated rat heart perfused with Krebs buffer containing glucose as sole energy substrate, or glucose supplemented with pyruvate. Second-order modeling yielded significantly improved fits of pyruvate-bicarbonate kinetics compared with the more traditionally used first-order model and suggested time-dependent decreases in pyruvate-bicarbonate flux. Second-order modeling gave time-dependent changes in forward and reverse reaction kinetics of pyruvate-lactate exchange and pyruvate-alanine exchange in both groups of hearts during the infusion of pyruvate; however, the fits were not significantly improved with respect to a traditional first-order model. The mechanism giving rise to second-order pyruvate dehydrogenase (PDH) kinetics was explored experimentally using surface fluorescence measurements of nicotinamide adenine dinucleotide reduced form (NADH) performed under the same conditions, demonstrating a significant increase of NADH during pyruvate infusion. This suggests a simultaneous depletion of available mitochondrial NAD+ (the cofactor for PDH), consistent with the non-linear nature of the kinetics. NADH levels returned to baseline following cessation of the pyruvate infusion, suggesting this to be a transient effect

U2 - 10.1002/nbm.3464

DO - 10.1002/nbm.3464

M3 - Article

SN - 0952-3480

JO - NMR in Biomedicine

JF - NMR in Biomedicine

ER -