JaxCC1 project protocol for procedure: body composition

Multisystem phenotyping of 18 Collaborative Cross strains   (2018)

The Jackson Laboratory

See also: JaxCC1 animal documentation         All protocol docs for JaxCC1


See JAX Pipeline on the IMPC website for order of tasks for all mice tested

Project protocol: Dual Energy X-ray Absorptiometry (DXA)



Introduction

DXA is used to measure bone mineral content and density as well as to assess body composition. DXA uses an X-ray generator of high stability to produce photons over a broad spectrum of energy levels. Its photon output is filtered to produce the two distinct peaks necessary to distinguish bone from soft tissue.



Study design

  • Paradigm: Baseline study
  • Panel: Collaborative Cross
  • Number of strains: 18
  • Sex: Both
  • Age: 13-15 wks
  • Sample size: Seven mice per sex from at least two litters
  • Number of cohorts: 1



    Workflow

    Step Description Equipment Data collected
    1 Anesthetize mice - -

    2

    Weigh mice, measure length Balance, ruler Body weight, body length
    3 Measure bone mineral content and density, and determine body composition DXA Bone mineral content, bone mineral density, fat mass, lean mass, bone area


    Equipment, software and supplies


    Procedure

    1. The volume of anesthetic solution (Avertin) required for i.p. injection is calculated and recorded.
    2. Mice are anesthetized.
    3. Mice are weighed and length is measured (nose to beginning of tail).
    4. Each unconscious mouse is placed in the DXA analyzer.
    5. A scout-scan is performed.
    6. The area of interest is optimized and a measure-scan performed.
    7. The standard analysis is a whole body analysis, excluding the head.
    8. Remove mouse once image is captured. Place on heated mat set at 37°C, in a cage and monitor closely until consciousness is regained.

     

    Data QC: Calibration of the system is done in daily intervals using the phantoms provided by the manufacturer.

    Formulas and derivations: Fat mass = TTM x percent fat / 100. Lean mass = TTM - fat mass.

     


    Measurements

    LIMS field name MPD variable name Description Units Series Primary measurement Series order MPD computed Calculation Method Data type
    Body weight body_weight body weight g           DXA

    Float

    Fat mass

    fat fat tissue mass of whole body scan, head excluded g           DXA Float
    Lean mass lean lean tissue mass of whole body scan, head excluded g           DXA Float
    Bone mineral density BMD bone mineral density of whole body scan, head excluded g/cm2           DXA Float
    Bone mineral content BMC bone mineral content of whole body scan, head excluded g           DXA Float
    Body length body_length body length cm           DXA Float
    BMC/Body weight BMC_adj bone mineral content to body weight ratio ratio           DXA Float
    Lean/Body weight lean_adj lean tissue mass to body weight ratio ratio           DXA Float
    Fat/Body weight fat_adj fat tissue mass to body weight ratio ratio           DXA Float
    Bone area bone_area bone area, whole body scan, head excluded cm2           DXA Float
    % fat pct_fat percent fat, whole body scan, head excluded %           DXA Float
    TTM TTM total tissue mass, whole body scan, head excluded g           DXA Float


    Experimental and technical parameters

    Equipment name Dual Energy X-ray Absorptiometry Analyzer
    Equipment manufacturer GE Medical Systems
    Equipment model Lunar Piximus II
    Anesthesia Avertin