Lf50 body composition analyzer

Mice were generated through heterozygous breeding of Snap25^+/Δ3 mice on a C57BL/6 background as described previously (16 (link)) and were housed at Vanderbilt University unless otherwise stated. Mice were maintained on 12-hour light/12-hour dark cycles with 3–5 animals per cage except during food intake monitoring, at which times they were singly housed. Mice were housed at standard housing room temperature (~22°C) or in thermoneutral housing conditions (~29.5°C) when indicated. Mice were maintained ad libitum on chow (13.5% calories from fat: 5001; LabDiet) or a HFD (60% calories from fat; 3282, Bio-Serv) when indicated. Weights and body composition measurements using the LF50 Body Composition Analyzer (Bruker) were done at the Vanderbilt Mouse Metabolic Phenotyping Center (VMMPC). All studies were performed with littermates of the appropriate genotypes. Mice were fasted for 5 hours and then euthanized by isoflurane overdose or CO₂ asphyxiation and exsanguination via cardiac puncture at the end of the study for collection of blood and tissues. Data from one mouse was excluded from all studies due to hydronephrosis.

As described previously [23 (link)], mouse body weight was monitored weekly for 28 weeks. Metabolic monitoring was assessed in a resting state using the PhenoMaster System (TSE systems GmbH, Bad Homburg, Germany). Energy expenditures including CO₂ production (VCO₂) and O₂ consumption (VO₂) were monitored for 48 h. The mice were free to consume food and water. The respiratory exchange ratio (RER) was defined as the ratio of carbon dioxide volume versus oxygen volume (VCO₂/VO₂). Food uptake and locomotor activity were also measured. An LF50 body composition analyzer (Bruker, Germany) was used to determine body composition (lean body mass, total body fat, and fluid) in mice. Animals were given 4–6 h to acclimate to the metabolic caging prior to beginning data collection, which took place over a 24 h period. Data collected (respiratory exchange ratio (RER), VO₂, VCO₂, energy expenditure (EE), food uptake, drinking, and activity) were separately averaged over the light and dark periods. Animals were maintained on a 12 h light–dark cycle, continued to consume a standard rodent chow diet, and were provided with water ad libitum. All procedures were approved and ethical consent was provided by the Animal Care Committee at Seoul University College of Veterinary Medicine, Korea Mouse Phenotyping Center (KMPC).

Mouse body weight was monitored every week for 28 weeks. An LF50 body composition analyzer (Bruker Co., Billerica, MA, USA) was used to determine body composition (lean body mass, total body fat, and fluid) in mice. This analyzer is based on Time Domain Nuclear Magnetic Resonance (TD-NMR) technology. The animal was loaded into the sample holder (animal restrainer not to limit movement of the animal). The animal holder was inserted into the instrument LF50 for analysis. Results are displayed and stored on a PC.