Promethion multiplexed metabolic cage system

The major determinants of whole-body energy balance were assessed in the Sable Systems Promethion Multi-plexed Metabolic cage system. Mice were individually housed in a home cage setting for 72 hours during which feeding, activity, energy expenditure and respiratory exchange ratio were continuously monitored. The first 24 h were considered acclimation and not included in the analysis such that data shown represent 48 h of data beginning on day two of housing. Body composition was measured by EchoMRI.
Glucose tolerance tests were performed after a 6 h morning fast (7am-1pm). Following collection of a basal blood sample (t = 0) by tail bleed, mice received an intraperitoneal bolus injection of glucose at 1.5 g/kg body weight followed by blood sampling at set intervals (15, 30, 45, 60 and 120 min) for blood glucose measurements and plasma insulin determination. Blood glucose was measured using a Bayer Contour Next glucometer and plasma insulin measured by chemiluminescence ELISA (Stellux, ALPCO).

Indirect calorimetry was performed using the Promethion Multiplexed Metabolic Cage System (Sable Systems) by the University of Pittsburgh Center for Metabolism and Mitochondrial Medicine. Animals were placed individually in chambers for 24 hours to acclimate followed by 48 hours at ambient room temperature with 12-hour light/12-hour dark cycles for analysis. Animals had free access to food and water. Respiratory measurements (VO₂/VCO₂) were made at 5-minute intervals. Food intake was measured in metabolic chambers during the 48-hour period. Body composition including fat and LM was determined using by EchoMRI. Mice were weighed twice per month to determine weight increases over time on SFD and HFD.