Breath water-based doubly labelled water method for the noninvasive determination of CO_2 production and energy expenditure in mice

摘要

We explored a novel doubly labelled water (DLW) method based on breath water (BW-DLW) in mice to determine whole body CO2 production and energy expenditure noninvasively. The BW-DLW method was compared to the DLW based on blood plasma. Mice (n = 11, 43.5 +/- 4.6 g body mass (BM)) were administered orally a single bolus of doubly labelled water (1.2 g (H2O)-O-18 kg BM-1 and 0.4 g (H2O)-H-2 kg BM-1, 99 atom% (AP) O-18 or H-2). To sample breath water, the mice were placed into a respiration vessel. The exhaled water vapour was condensed in a cold-trap. The isotope enrichments of breath water were compared with plasma samples. The H-2/H-1 and O-18/O-16 isotope ratios were measured by means of isotope ratio mass spectrometry. The CO2 production (RCO2) was calculated from the H-2 and O-18 enrichments in breath water and plasma over 5 days. The isotope enrichments of breath water vs. plasma were correlated (R-2 = 0.89 for H-2 and 0.95 for O-18) linearly. The RCO2 determined based on breath water and plasma was not different (113.2 +/- 12.7 vs. 111.4 +/- 11.0 mmol d(-1)), respectively. In conclusion, the novel BW-DLW method is appropriate to obtain reliable estimates of RCO2 avoiding blood sampling.