Meeting Abstract
Glucose is the predominant fuel source for most animal tissues. We employed an experimental approach called glucose oxidation testing to quantify glucose oxidation in real time. Laboratory mice (Mus musculus) were given IP injections of trace amounts of 13C-U-glucose (75-600ug) after which we measured both the rates of CO2 production (VCO2) and the isotopic enrichment of the breath (13CO2) at 1Hz frequency using the new Sable Systems Stable Isotope Gas Analyzer. We conducted dose response (75-600ug) trials at 22°C and fixed-dose (300ug) trials at three temperatures (10, 22, and 30°C) and different nutritional states (fed vs. 24h-fasted). The 13CO2 increased within 90-seconds and peak values occurred approximately 15-30 minutes later. The dose responses were isometric across the range examined suggesting no mass action effects of the tracer. In fed mice we observed lower 13CO2, but the differences were counterbalanced by the increased VCO2 caused by cold temperatures; thus, temperature had no effect on net glucose tracer oxidation rates. Nutritional stress (fasting) generally caused attenuated and protracted oxidation kinetics resulting in a 40% reduction in tracer oxidation in mice exposed to 22°C and 30°C. We expect this approach will be useful to investigate differences in glucose oxidation in various animal models.
