Measurement of interscapular brown adipose tissue of mice in differentially housed temperatures by chemical‐shift–encoded water–fat MRI

Abstract

PurposeTo determine differences in fat‐signal fraction (FF) from chemical‐shift–encoded water–fat MRI of interscapular BAT in mice housed at different ambient temperatures (Ta).Materials and MethodsC57BL/6J male mice (8 weeks old) were singly housed at 16°C, 23°C, or 30°C (n = 16/group) for 4 weeks. Measures included food intake, body weight (both measured weekly) and body composition (at baseline, 2, and 4 weeks post‐thermal exposure); chemical‐shift–encoded water–fat MRI was performed on a 9.4 Tesla Bruker magnet with respiratory gating and anesthesia at 4 weeks post‐thermal exposure.ResultsA significant inverse relationship between food intake and Ta was evidenced (P < 0.0001). Lean mass was similar among groups, while total fat mass was significantly different among groups ([mean ± SE]: 30°C = 5.10 ± 0.19 g; 23°C = 4.18 ± 0.16 g; 16°C = 3.48 ± 0.54 g; P < 0.0001). Mean BAT‐FF was positively related to Ta (means: 30°C = 79.4%; 23°C = 61.8%; 16°C = 50.9%; P < 0.0001).ConclusionThese cross‐sectional results demonstrate that MRI measurement of FF within the interscapular BAT in mice reflects recent functional status of the tissue, with a lower Ta leading to a significantly reduced BAT‐FF, indicative of the tissue's involvement in thermogenesis. J. Magn. Reson. Imaging 2013;38:1425–1433. © 2013 Wiley Periodicals, Inc.