Development of novel hyperpolarized magnetic resonance techniques and compounds for perfused organs

Hyperpolarization via the Dynamic Nuclear Polarization (DNP) technique has revolutionized our ability to study metabolic changes in real time. The aim of this thesis was to build upon previous work centered around the use of DNP within the isolated perfused rat heart, a well established model system for the study of cardiac metabolism, to enhance the information that can be obtained through the combination of DNP with perfused organs. Initially this was done by using the widely studied DNP probe, [1-13C]pyruvate, to generate images of metabolism within the isolated perfused rat heart. The developed technique was then successfully demonstrated in two models of myocardial infarction. The thesis then proceeds to develop an understanding of how the supra-physiological concentrations of [1-13C]pyruvate commonly used in DNP experiments can affect metabolism in the isolated perfused rat heart, and the way in which the myocardium responds to those changes if it is not adequately supplied with substrates ordinarily present in vivo, namely fatty acids. New methods of providing the heart with these required substrates were developed, without significant interference to the biochemical information acquired from DNP experiments. As [1-13C]pyruvate only provides information on a small subset of carbohydrate metabolism, the next chapter develops new compounds to be used with DNP, which would allow the exploration of short chain fatty acid metabolism (butyrate) as well as ketone body metabolism (β-hydroxybutyrate and acetoacetate), and other aspects of carbohydrate metabolism (lactate and alanine). These compounds were developed and then tested for their potential usefulness in the isolated perfused heart. Finally, as the isolated perfused rat heart lacks the diversity of genetic disease models available in the mouse, the final chapter expanded the use of DNP to the isolated perfused mouse heart with all the size challenges that this entails, and makes the transition from the heart to the liver, in order to provide an alternative metabolic viewpoint on the biochemistry of disease models. This thesis thereby permits studies involving isolated perfused organs to be carried out whilst exploiting all the tools that DNP has to offer and consequentially, allows for a vast array of physiologically derived information to help us better understand metabolic diseases.