Abstract
We examined the precision, accuracy, and capability of detecting changes of Dual-Energy X-ray Absorptiometry (DXA) for the measurements of total-body weight (TBW), total-body fat weight (TBFW), and total-body lean weight (TBLW) in an 8-week follow-up study of rats. Twenty male rats (4-week) were divided into 2 diet groups. For 8 weeks, we measured body composition (TBW, TBFW, TBLW) by DXA and TBW by an electronic scale once a week. In week 8, we measured body composition 5 times by DXA and TBFW by dissecting experiment (EXP) of euthanized rats (12-week). Total-body fat ratio (TBFR) was defined as TBFW/(TBFW+TBLW). The precision of DXA was evaluated by measuring the coefficient of variation (CV) and accuracy was evaluated by comparing DXA-derived data with EXP data. The capability of detecting changes of DXA in follow-up study was verified by analyzing the trend of DXA-derived values over the 8 weeks. For TBW, TBFW, TBLW of DXA, CVs were 0.02 ± 0.01, 0.10 ± 0.05, 0.03 ± 0.02 and errors were − 6.996 ± 3.429 (r = 0.999), + 14.729 ± 3.663 (r = 0.982), − 21.725 ± 4.223 (r = 0.991), respectively. Prediction models were [EXP TBW = − 31.767 + 1.085 (DXA TBW), R2 = 0.998, root mean square error (RMSE) = 1.842] and [EXP TBFR = − 0.056 + 1.177 (DXA TBFR), R2 = 0.948, RMSE = 0.007]. Over 8 weeks, DXA TBW and DXA TBLW steadily increased, DXA TBFW steadily increased followed by saturation or declination, difference of DXA TBFW between 2 diet groups steadily increased. In conclusion, our study verified that DXA (iNSiGHT VET DXA, OsteoSys, Korea) is accurate and precise enough to measure body composition of rats. Additionally, we confirmed the possibility that DXA could be used for the long-term follow-up studies.
Highlights
The World Health Organization (WHO) has acknowledged obesity as one of the most obvious public health problems, and the prevalence of obesity has almost doubled globally in 2008 compared to 1980
Procedure During the feeding period, Total body Weight (TBW), Total Body Bone Weight (TBBW), Total Body Fat Ratio (TBFR), Total Body Fat Weight (TBFW) and Total Body Lean Weight (TBLW) were measured weekly by cone beam flat panel detector Dual-Energy X-ray Absorptiometry (DXA), and total-body weight (TBW) was measured with an electronic scale (Entris, sartorius, Germany)
After 8 weeks of feeding, CO2 gas was used for euthanasia, and all rats was scanned by DXA instrument five times without repositioning (1-min rest between measurements) and their TBW was measured with an electronic scale
Summary
The World Health Organization (WHO) has acknowledged obesity as one of the most obvious public health problems, and the prevalence of obesity has almost doubled globally in 2008 compared to 1980. Studies preparing or treating obesity are actively in progress including clinical trials mainly conducted on mice and rats to analyze the effect of food, medications, and exercise on obesity. In most of these studies, the degree of increase in actual fat weight was estimated with the fat tissue extracted by dissecting experiment [2,3,4,5]. Dissection experiment (EXP) method of a euthanized animal can be relatively accurate compared with the noninvasive methods. EXP method is a limited approach as it cannot estimate the longitudinal change of the fat weight while continuously observing the growth of live animal
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