Year: 2008
Abstract Number: 310-OR
Authors: MATTHEW E. MERRITT, CRYSTAL HARRISON, SHAWN C. BURGESS, A D. SHERRY, CRAIG R. MALLOY, Dallas, TX
Institutions: Dallas, TX
Results: Poorly regulated hepatic gluconeogenesis is a hallmark feature of obesity, insulin resistance and all forms of diabetes. Detection of abnormal gluconeogenesis requires sophisticated tracer regiments involving several hours to implement and at least some degree of fasting intervention. Currently there are no approaches to monitor gluconeogenesis on shorter time scales allowing real-time serial measurements, measurements under conditions when tracer recycling is problematic (i.e. insulin clamp, fed state) or impromptu measurements during a clinical crisis (e.g. ketoacidosis, heart failure, sepsis etc.). Among approaches used to measure gluconeogenesis and other hepatic fluxes, NMR in combination with stable isotope tracers is popular because of its ability to detect the simultaneous incorporation of multiple tracers into a metabolite pool without interference between tracers. However, compared to other approaches, such as radioisotope tracers or mass analysis by mass spectrometry, NMR is sensitivity limited. Dynamic nuclear polarization (DNP) enhances the sensitivity of NMR detection >10,000 fold allowing this technology to be applied to previously infeasible experimental situations. We used the DNP process to hyperpolarize [1-13C] pyruvate and followed its incorporation into hepatic metabolites in real time by 13C NMR in isolated perfused mouse liver. Incorporation of tracer into hepatic metabolites of the TCA cycle was observed over 90 seconds in WT and liver pck KO mice. Livers from KO mice had normal lactate and alanine production, but substantially less incorporation of tracer into peaks reflective of TCA cycle intermediates (181.4, 180.8, 179.3 and 175.3 ppm), accurately reflecting impaired gluconeogenesis in these livers. This very first application of hyperpolarized 13C NMR spectroscopy in the liver illustrates that this technique can be used to monitor in vivo gluconeogenesis on the time scale of seconds and provides impetus for using this technology in more advanced imaging studies (MRS) to investigate the state of hepatic gluconeogenesis during a variety of pathophysiologies.[figure1]
Category: Clinical Therapeutics/New Technology - Glucose Monitoring and Sensing
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