Metabolic Disorders:
Body Fat and Bone Mineral Density
A DEXA instrument (Lunar Piximus) is used to record bone mineral density, bone mineral content, percent body fat, lean body mass, and total tissue mass (Nagy et al, 2000; Punyanitya et al. 2000). Although primarily aimed at metabolic and osteoporotic conditions, DEXA is a sensitive measure of all-round wellbeing and often contributes to diagnosis in other therapeutic areas. DEXA has been used successfully to identify increased total body fat in melanocortin-3 receptor knockout mice (Butler et al. 2000) and decreased total body fat in melanin concentrating hormone 1 receptor knockout mice; the latter observation was confirmed by direct analysis of fat pad weights (Marsh et al. 2002).
Image of mouse taken with PIXImus DEXA (GE Medical Systems, New York, NY)
Animals are maintained on normal chow (Purina 5001) from weaning until DEXA scan is performed at 14 weeks of age.
Displayed below is a sample graph of how DEXA scan observations are presented. In comprehensive phenotypic data packages graphs are interactive. Raw or calculated data and statistics can be seen by clicking on points in the graph.
Figure represents total tissue mass (TTM; top left), lean body mass (LBM; top center) percentage of body fat (FAT%; top right), total fat in grams (FATg; middle left), bone mineral content (BMC; middle center), percentage of lean body mass that is bone mineral content (BMC/LBM; middle right), volumetric bone mineral density (vBMD; bottom left), and bone mineral density (BMD; bottom right) of wild type littermates (green circle), heterozygous (blue triangle), homozygous (red diamond), and recent historical wild type (purple line) mice plotted against long-term historical values (± 2 standard deviations) for wild type animals (green shading). Recent wild type values are calculated from data collected within 60 days of current measures and long-term historical values are derived from data collected on more than 10,000 wild type mice.
References
Butler AA, Kesterson RA, Khong K, Cullen MJ, Pelleymounter MA, et al. (2000) A unique metabolic syndrome causes obesity in the melanocortin-3 receptor deficient mouse, Endocrinology, 141:3518-3521.
Marsh DJ, Weingarth DT, Novi DE, Chen HY, Trumbauer ME, Chen AS, Guan XM, et al. (2002) Melanin-concentrating hormone 1 receptor-deficient mice are lean, hyperactive, and hyperphagic and have altered metabolism, Proc Natl Acad Sci USA, 99:3240-3245.
Nagy TR, Clair AL. (2000) Precision and accuracy of dual-energy X-ray absorptiometry for determining in vivo body composition of mice, Obes Res, 8:392-398.
Punyanitya M, Leibel RL, Heymsfield SB, Boozer CN. (2000) Evaluation of a new dual-energy x-ray absorptiometry technique for in vivo body composition measurements in mice, FASEB J, 14:497.