Beschreibung:
<jats:title>Abstract</jats:title><jats:sec><jats:title>Introduction</jats:title><jats:p>Relative oxidation of different metabolic substrates in the heart varies both physiologically and pathologically, in order to meet metabolic demands under different circumstances.<jats:sup>13</jats:sup>C labelled substrates have become a key tool for studying substrate use—yet an accurate model is required to analyse the complex data produced as these substrates become incorporated into the Krebs cycle.</jats:p></jats:sec><jats:sec><jats:title>Objectives</jats:title><jats:p>We aimed to generate a network model for the quantitative analysis of Krebs cycle intermediate isotopologue distributions measured by mass spectrometry, to determine the<jats:sup>13</jats:sup>C labelled proportion of acetyl-CoA entering the Krebs cycle.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>A model was generated, and validated ex vivo using isotopic distributions measured from isolated hearts perfused with buffer containing 11 mM glucose in total, with varying fractions of universally labelled with<jats:sup>13</jats:sup>C. The model was then employed to determine the relative oxidation of glucose and triacylglycerol by hearts perfused with 11 mM glucose and 0.4 mM equivalent Intralipid (a triacylglycerol mixture).</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The contribution of glucose to Krebs cycle oxidation was measured to be 79.1 ± 0.9%, independent of the fraction of buffer glucose which was U-<jats:sup>13</jats:sup>C labelled, or of which Krebs cycle intermediate was assessed. In the presence of Intralipid, glucose and triglyceride were determined to contribute 58 ± 3.6% and 35.6 ± 0.8% of acetyl-CoA entering the Krebs cycle, respectively.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>These results demonstrate the accuracy of a functional model of Krebs cycle metabolism, which can allow quantitative determination of the effects of therapeutics and pathology on cardiac substrate metabolism.</jats:p></jats:sec>