title: Validity of the doubly labeled water method for estimating CO2 production in mice under different nutritional conditions.
abstract: The doubly labeled water (DLW) technique is used to assess metabolic rate (MR) in free-living conditions. We investigated whether differences in the nutritional and body adiposity status affect validity of the assessment of CO2 production (rCO2) by the DLW technique. To serve this purpose, we compared calculated rCO2 by the DLW method to actual CO2 production concomitantly measured in an indirect calorimetry setup over a 3-day period in mice fed with a low-fat (LF) diet or an obesogenic high-fat/high-sucrose (HF) diet. To uncover a potential effect of body composition on DLW accuracy, the HF-fed group was further subdivided in a diet-induced obesity-prone (DIO) and diet-induced obesity-resistant (DR) group. Furthermore, we assessed the influence of different sampling protocols, duration, and methodology of calculation. An excellent match was found between rCO2 assessed by the two methods in the LF-fed mice (least discrepancy -0.5 ± 1.1%). In contrast, there was a consistent overestimation of rCO2 by the DLW technique in the HF-fed animals compared with actual CO2 production independent from body mass gain (least discrepancy DR +15.9 ± 2.2%, DIO +18.5 ± 3.2%). The least discrepancies were found when two-pool model equations and the intercept method were used to calculate the body water pool. Furthermore, the HF group presented different equilibration kinetics of (2)H and (18)O and a lower dilution space ratio between the two. We recommend particular caution when using the DLW method for MR assessment in HF-fed animals and potentially humans because of the overestimation of rCO2.
authors.affiliation: Center for Isotope Research, Energy and Sustainability Research Institute Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Stefano
authors.initials: S
authors.lastname: Guidotti
authors.forename: Harro A J
authors.initials: HA
authors.lastname: Meijer
authors.forename: Gertjan
authors.initials: G
authors.lastname: van Dijk
mesh_terms: D000465:Algorithms; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition; D002138:Calibration; D002153:Calorimetry, Indirect; D002245:Carbon Dioxide / Q000378:metabolism*; D003903:Deuterium; D018752:Diet, Fat-Restricted; D059305:Diet, High-Fat; D004734:Energy Metabolism; D007553:Isotope Labeling / Q000379:methods*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009752:Nutritional Status; D009765:Obesity / Q000378:metabolism; D010103:Oxygen Isotopes; D011865:Radioisotope Dilution Technique; D015203:Reproducibility of Results; D014867:Water
chemical_list: D010103:Oxygen Isotopes; D014867:Water; D002245:Carbon Dioxide; D003903:Deuterium
keywords: body composition; diet-induced obesity; doubly labeled water; metabolic rate; validation