Measuring changes in substrate utilization in the myocardium in response to fasting using hyperpolarized [1-13C]butyrate and [1-13C]pyruvate

• Published in: Scientific reports Vol. 6; no. 1; p. 25573
• Main Authors: Bastiaansen, Jessica A. M., Merritt, Matthew E., Comment, Arnaud
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.05.2016; Nature Publishing Group
• Subjects: 631/1647/320; 692/4019/592; Bicarbonates; Carbohydrate metabolism; Fasting; Fatty acids; Heart diseases; Humanities and Social Sciences; Ketogenesis; Ketones; Magnetic resonance spectroscopy; Metabolic flux; Metabolism; Mitochondria; multidisciplinary; Myocardium; Oxidation; Pyruvic acid; Rodents; Science; Spectroscopy
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep25573

Cardiac dysfunction is often associated with a shift in substrate preference for ATP production. Hyperpolarized (HP) 13 C magnetic resonance spectroscopy (MRS) has the unique ability to detect real-time metabolic changes in vivo due to its high sensitivity and specificity. Here a protocol using HP [1- 13 C]pyruvate and [1- 13 C]butyrate is used to measure carbohydrate versus fatty acid metabolism in vivo . Metabolic changes in fed and fasted Sprague Dawley rats (n = 36) were studied at 9.4 T after tail vein injections. Pyruvate and butyrate competed for acetyl-CoA production, as evidenced by significant changes in [ 13 C]bicarbonate (−48%), [1- 13 C]acetylcarnitine (+113%) and [5- 13 C]glutamate (−63%), following fasting. Butyrate uptake was unaffected by fasting, as indicated by [1- 13 C]butyrylcarnitine. Mitochondrial pseudoketogenesis facilitated the labeling of the ketone bodies [1- 13 C]acetoacetate and [1- 13 C]β-hydroxybutyryate, without evidence of true ketogenesis. HP [1- 13 C]acetoacetate was increased in fasting (250%) but decreased during pyruvate co-injection (−82%). Combining HP 13 C technology and co-administration of separate imaging agents enables noninvasive and simultaneous monitoring of both fatty acid and carbohydrate oxidation. This protocol illustrates a novel method for assessing metabolic flux through different enzymatic pathways simultaneously and enables mechanistic studies of the changing myocardial energetics often associated with disease.