First use of triply labelled water analysis for energy expenditure measurements in mice

Abstract

The doubly labelled water (DLW) method is widely used to determine energy expenditure. In this work, we demonstrate the addition of the third stable isotope, 17O, to turn it into triply labelled water (TLW), using the three isotopes measurement of optical spectrometry. We performed TLW (2H, 18O and17O) measurements for the analysis of the CO2 production (rCO2) of mice on different diets for the first time. Triply highly enriched water was injected into mice, and the isotope enrichments of the distilled blood samples of one initial and two finals were measured by an off-axis integrated cavity output spectroscopy instrument. We evaluated the impact of different calculation protocols and the values of evaporative water loss fraction. We found that the dilution space and turnover rates of 17O and 18O were equal for the same mice group, and that values of rCO2 calculated based on 18O–2H, or on 17O–2H agreed very well. This increases the reliability and redundancy of the measurements and it lowers the uncertainty in the calculated rCO2 to 3% when taking the average of two DLW methods. However, the TLW method overestimated the rCO2 compared to the indirect calorimetry measurements that we also performed, much more for the mice on a high-fat diet than for low-fat. We hypothesize an extra loss or exchange mechanism with a high fractionation for 2H to explain this difference.

The absolute δ18O value for SLAP with respect to VSMOW reveals a much lower value than previously established

“…Finally, in fields where VSMOW–SLAP‐scaled δ 18 O values are converted into absolute abundances and vice versa, our new δ 18 O value for SLAP does matter. An example of such a field is energy expenditure measurements using doubly labeled water, in which the used enriched reference waters will change their delta value (Guidotti et al, 26 Wang et al, 27 and Faghihi et al 14 ).…”

“…However, the large difference between the consensus value and our value for δ 18 O of SLAP could also be caused by a bias in the determination of the absolute 18 with phosphoric acid (McCrea, 25 Meijer, 16 and Hillaire-Marcel et al 20 The difference between VSMOW-CO 2 and VPDB-CO 2 on the two value for SLAP does matter. An example of such a field is energy expenditure measurements using doubly labeled water, in which the used enriched reference waters will change their delta value (Guidotti et al, 26 Wang et al, 27 and Faghihi et al 14 ).…”

Assessing daily energy intake in adult women: validity of a food-recognition mobile application compared to doubly labelled water

“…Isotope analyses of the urine samples were performed at the Centre for Isotope Research (CIO), University of Groningen, Netherlands using an optical spectrometer (LGR LWIA 912–0050, ABB Ltd. – Los Gatos Research, San Jose, California, United States). The measurement analysis (including the sample memory correction) and the calculation of isotopic abundances of 2 H and 18 O were done according to the isotope measurement method described by Wang et al – although in the present study limited to DLW ( 53 ). Reference waters (DLW) of the International Atomic Energy Agency (IAEA) were used for calibration ( 54 ).…”

“…TDEE gives an estimation of the daily energy intake under the hypothesis of energy balance, and therefore body weight stability, during the 7 days of the two-point protocol. The use of the coefficients used in the calculations have also been explained by Wang et al ( 53 ).…”