Body Composition Analysis
The Mouse Metabolic Function and Phenotyping Core has provided equipment and training for DRC investigators to measure body composition of mice. Traditionally dual energy X-ray absorbance (DEXA) nuclear magnetic resonance imaging (MRI) analysis have been the most commonly used. Each system offers relative advantages and disadvantages. MRI measurements can quantify fat mass, lean mass, and water; an MRI scan is conducted in fewer than 60 seconds and can therefore be carried out on mice without sedated; and by our measures MRI analyses provide more precisely reproducible results. However, the MRI instrument is not readily portable and requires a 45 minute “cool” down period during which the MRI magnets are cooled but data cannot be collected. DEXA measurements include fat mass, lean mass, and bone density, and the DEXA scanner is smaller and mobile, but it requires ~5 minutes to scan a single mouse and therefore requires mice be anesthetized. A new system to replace the PIXImus one is expected to be available by the end of 2022.
Equipment and Location
The Body Composition Facility has operated a PIXImus II DEXA scanner (GE Lunar, Fitchburg WI) and a miniSpec NMR analyzer (Buker, Woodlands TX). The miniSpec MRI scanner is located in Room 738 within the mouse barrier facility of the Berrie Pavilion.
Individual investigators are trained in using the body composition equipment, including calibration and quality assurance. Training is schedule with Eleanor Ables and once completed provides access to the the online calendar to schedule use of the equipment.
There are three methods of quality control employed by the Mouse Phenotyping Core. First, a quality assessment query is sent by email to users who have operated the machine on any given day. These are quick and simple and are reviewed by the facility staff. Second, a senior technician runs weekly calibrations protocols for each machine and measures standards/phantoms. If proper calibration cannot be achieved or measurement of the standards/phantoms is outside the acceptable accuracy, the machine is scheduled for maintenance. Third, we compare the body composition data obtained for one lean and one obese mouse measured using the DEXA scanner and MRI on a bimonthly basis. This provides cross validation of each platform with actual mice.