AP0103 - Measurement of Peripheral Adipose in Small ... - Bruker

Application Note # AP0103 Jan 2011Dual Energy X-ray Method for Direct Visualization andQuantitative Measurement of Peripheral Adipose in SmallAnimalsSarah E. Chapman 1 , Sean P. Orton 2 , Douglas Vizard 2 , William McLaughlin 2 , Spencer Proctor 3 and,W. Matthew Leevy 3Author Information: 1- Freimann Life Science Center, University of Notre Dame, 400 Galvin Life Science, Notre Dame, IN 46556;2- Bruker BioSpin, 15 Fortune Drive, Billerica, MA 01821; 3- Alberta Institute for Human Nutrition, Division of Human Nutrition, C/O4-10 Agriculture/Forestry Centre, University of Alberta, Edmonton, Alberta, Canada T6G-2P5;4- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556Application OverviewObesity is a medical condition in which an individual isoverweight to such an extent that both health and qualityof life are acutely diminished. It increases the risk ofdeveloping serious diseases, like Type II diabetes andcoronary heart disease. 1 Further, individuals that areseverely overweight may suffer negative social andeconomic effects. 2 According to the World HealthOrganization, approximately 300 million people in theworld are affected by obesity, including children,adolescents, and adults. 1 Thus, a significant researcheffort is underway to discover the genetic andphysiological factors contributing to weight disorders.For years, transgenic mice have been utilized as amodel to study obesity. In just a short time, gene defectsresulting in obesity have been cloned. 3 Traditionalstrategies for investigating obesity include molecularbiological techniques, quantitative trait loci, genemapping, chromosomal scanning, and the study ofcandidate gene. 4 A critical component to executing preclinicalobesity research is to measure murine bodycomposition, including fat content, lean content, andbone density, under a number of genetic and biologicalconditions. These key metrics allow investigators toquantitatively assess the biological and environmentalfactors that contribute to obesity and subsequentlymeasure treatment efficacy. 5anatomical features. A common technique for determiningwhole-body and regional bone, fat, and fat-free, mineral-freesoft tissue masses in both humans and mice utilizes a dualenergyX-ray absorptiometry (DXA) scan. 6 This methodutilizes X-ray images at different energy levels: one lowenergyX-ray to image soft tissue, and one higher energyX-ray to capture bone. These images are then input intoa calibrated set of equations to output absolute bodycomposition percentages including the body fat percent ofan animal. Unfortunately, literature reports have raisedquestions about the ability of DXA algorithms to reliablygenerate absolute values of body composition. 7,8Here we propose a simplified X-ray strategy for directobservation and enumeration of peripheral fat in smallanimals. One of the underlying merits of our method is thatthe prone placement of a rodent under its own weightextrudes the peripheral fat in the torso, revealing the fat tounobstructed imaging.First, we utilize two X-rays acquired at different energies,and divide them to yield a ratiometric X-ray image that canbe thresholded to highlight areas of peripheral adipose, aswell as lean and bone features. Next, this methodintroduces two new metrics, Net Peri Fat Area and Peri FatArea Percentage, to monitor relative, as opposed toabsolute, changes in fat composition in cohorts of rats andmice during longitudinal studies.X-ray imaging provides a safe, convenient, and noninvasivemeans for the direct visualization of murine

within animal cohorts during longitudinal studies.In order to maintain maximal objectivity, a researcherblinded to the experimental protocol should draw theabove ROIs. In addition, if this method were applied tomice, higher throughput could likely be achieved as aresult of the larger imaging area of up to 20 x 20 cm inthe In-Vivo MS FX PRO or the In-Vivo DXS PRO. Thislarger imaging area would allow for up to five mice to bestudied at one time.ConclusionHere we describe an approach to facilitate directobservation and quantification of peripheral fat withinsmall animals. A ratiometric X-ray image is acquired toenable robust contrast of peripheral fat and lean/bonecomponents. These anatomical features can bedelineated and measured by straightforward ROIanalysis of the circumscribed areas. These areas are auseful metric on their own and also upon conversion toarea percentages.Based on these results, different cohorts of fat and leananimals may be readily compared using visual inspectionand quantitative analysis. These same parameters shouldenable facile analysis of cohorts during longitudinal studiesin which body fat changes over time under variousexperimental conditions.References1) Brockman G, Bevova M, TRENDS in Genetics 2002,18(7), 367-376.2) Clarke PJ, O'Malley PM, Schulenberg JE, JohnstonLD. Am. J. Epidemiol. 2010 Jul 7.3) Bray GA, J. Nutr. 1997, 127(5 Suppl), 940S-942S.Review.4) Bray GA, Bouchard C, FASEB J. 1997, 11, 937-945.5) Carroll L, Voisey J, Van Daal A, Clin. Dermatol. 2004,22, 345-349.6) Lukaski H, J. Nutr. 1993, 123(2 Suppl), 438-43.Review.7) Johnston, S. L. et al. Obes. Res. 2005, 13(9), 1558-1565.8) Nagy, T. R. et al. Obes. Res. 2000, 8(5), 392-398.For more information, contact yourBruker BioSpin dealer, or contact us directly at:Telephone:Call 1-978-667-9580 and select Option 4.Mon. through Fri., 8:00 a.m. – 6:00 p.m. ESTE-mail:molecularsupport@bruker.comWeb:http://www.bruker.comBruker BioSpin is a division of Bruker, Inc. and is atrademark of Bruker, Inc. All other products or namebrands are trademarks of their respective holders.© Bruker BioSpin, 2012. All rights are reserved. Nosection of this document may be photocopied,reproduced, translated to another language, stored in aretrieval system, or transmitted in any form without theprior written consent of Bruker BioSpin.The information contained in this document is subject tochange without notice. Bruker BioSpin makes nowarranty of any kind with regard to this written material.Bruker BioSpin assumes no responsibility for any errorsthat may appear in this document.4