Intra-abdommal fat burden discriminated in vivo using proton magnetic resonance spectroscopy

Objective: To assess proton magnetic resonance spectroscopy (H-1-MRS) as a means to distinguish among mice with disparate intra-abdominal body fat compositions, and to measure changes in intra-abdominal fat burden during weight loss and regain. Research Methods and Procedures: Intra-abdominal fat burden was analyzed as a ratio of integrated areas under the curves of fat to water H-1-MRS signals collected from a region of interest standardized across B6.V-Lep(ob) C57BL/6, and A-ZIP/F mice that exhibited various genotypically related body fat compositions, ranging from obese (B6.V-Lep(ob) ) to minimal body fat (A-ZIP/F). H-1-MRS analysis of fat burden was compared with intra-abdominal fat volume and with a single cross-sectional intra-abdominal fat area calculated from segmented magnetic resonance images. Similar measurements were made from obese B6.VLep(ob) mice before, during, and after they were induced to lose weight by leptin administration. Results: Relative amounts of intra-abdominal fat analyzed by H-1-MRS differed significantly according to body composition and genotype of the three strains of mice (p < 0.05). Intra-abdominal fat assessed by H-1-MRS correlated with both intra-abdominal fat volume (r = 0.88, p < 0.001) and body weight (r = 0.82, p < 0.001) among, but not within, all three genotypes. During weight loss and regain, there was a significant overall pattern of changes in intraabdominal fat quantity that occurred, which was reflected by H-1-MRS (p = 0.006). Discussion: Results support the use of localized H-1-MRS for assessing differences in intra-abdominal fat. Refinements in H-1-MRS voxel region of interest size and location as well as instrument precision may result in improved correlations within certain body compositions.