In vivo phenotyping of the ob/ob mouse by magnetic resonance imaging and 1H-magnetic resonance spectroscopy.

OBJECTIVE: We studied ob/ob and wild-type (WT) mice to characterize the adipose tissues depots and other visceral organs and to establish an experimental paradigm for in vivo phenotyping. RESEARCH METHODS AND PROCEDURES: An in vivo evaluation was conducted using magnetic resonance imaging and 1H-magnetic resonance spectroscopy (1H-MRS). We used T1-weighted images and three-dimensional spin echo T1-weighted images for the morphological analysis and 1H-MRS spectra on all body mass, as well as 1H-MRS spectra focalized on specific lipid depots [triglyceride (TG) depots] for a molecular analysis.
RESULTS: In ob/ob mice, three-dimensional evaluation of the trunk revealed that approximately 64% of the volume consists of white adipose tissue, which is 72% subcutaneous and 28% visceral. In vivo 1H-MRS showed that 20.00 +/- 6.92% in the WT group and 58.67 +/- 6.65% in the ob/ob group of the total proton content is composed of TG protons. In in vivo-localized spectra of ob/ob mice, we found a polyunsaturation degree of 0.5247 in subcutaneous depots. In the liver, we observed that 48.7% of the proton signal is due to water, whereas in the WT group, the water signal amounted to 82.8% of the total proton signal. With the sequences used, the TG amount was not detectable in the brain or kidneys. DISCUSSION: The present study shows that several parameters can be obtained by in vivo examination of ob/ob mice by magnetic resonance imaging and 1H-MRS and that the accumulated white adipose tissue displays low polyunsaturation degree and low hydrolipidic ratio. Relevant anatomical alterations observed in urinary and digestive apparatuses should be considered when ob/ob mice are used in experimental paradigms.