title: Chemical versus dual energy x-ray absorptiometry for detecting age-associated body compositional changes in male rats.
abstract: Aging is associated with increases in body mass and fat mass (FM), whereas fat-free mass (FFM) either decreases or remains unchanged. The purpose of this study was to determine whether dual-energy X-ray absorptiometry (DXA) accurately detects age-associated changes in male Fischer 344 x Brown-Norway rats ages 8, 18, and 28 months. Eviscerated animal carcasses were first examined via the Lunar DPX-IQ DXA (small animal software version 1.0; HiRes (0.6 x 1.2 mm) medium mode). Eviscerated carcasses were then weighed, autoclaved, homogenized, and fat isolated from aliquots of homogenate via methanol/chloroform extraction. In both chemical (CHEM) and DXA analysis, carcass mass (CM), FM, and % fat were significantly higher (P < 0.0001) in the 18 and 28 versus 8-month-old rats. CHEM showed greater FFM in the 18 versus 8 months-old rats but not the 28 months-old animals. DXA was unable to detect the age-associated changes in FFM. Regression analysis showed a strong correlation between CHEM and DXA methods for CM (r = 0.98, P < 0.0001) and FM (r = 0.97, P < 0.0001), but less strong for FFM (r = 0.59, P = 0.0002). In conclusion, compared to CHEM, DXA consistently overestimated CM and FM across the age groups by 9% and 77%, respectively, and underestimated FFM by 5%.
authors.affiliation: Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs Medical Center, University of Michigan, CCGCB, 5302, 1500 East Medical Center Drive, Ann Arbor, MI 48109-0940, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Feely
authors.forename: L M
authors.initials: LM
authors.lastname: Larkin
authors.forename: J B
authors.initials: JB
authors.lastname: Halter
authors.forename: D R
authors.initials: DR
authors.lastname: Dengel
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000033:anatomy & histology; D000375:Aging / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344