Thermogenic profiling using magnetic resonance imaging of dermal and other adipose tissues
Ildiko Kasza, Diego Hernando, Alejandro Roldán-Alzate, Caroline M. Alexander, Scott B. Reeder
Ildiko Kasza, Diego Hernando, Alejandro Roldán-Alzate, Caroline M. Alexander, Scott B. Reeder
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Research Article Metabolism

Thermogenic profiling using magnetic resonance imaging of dermal and other adipose tissues

Abstract

Dermal white adipose tissue (dWAT) was recently recognized for its potential to modify whole body metabolism. Here, we show that dWAT can be quantified using a high-resolution, fat-specific magnetic resonance imaging (MRI) technique. Noninvasive MRI has been used to describe adipocyte depots for many years; the MRI technique we describe uses an advanced fat-specific method to measure the thickness of dWAT, together with the total volume of WAT and the relative activation/fat depletion of brown adipose tissues (BAT). Since skin-embedded adipocytes may provide natural insulation, they provide an important counterpoint to the activation of thermogenic brown and beige adipose tissues, whereby these distinct depots are functionally interrelated and require simultaneous assay. This method was validated using characterized mouse cohorts of a lipodystrophic, dWAT-deficient strain (syndecan-1 KO) and 2 obese models (diet-induced obese mice and genetically obese animals, ob/ob). Using a preliminary cohort of normal human subjects, we found the thickness of skin-associated fat varied 8-fold, from 0.13–1.10 cm; on average, this depot is calculated to weigh 8.8 kg.

Authors

Ildiko Kasza, Diego Hernando, Alejandro Roldán-Alzate, Caroline M. Alexander, Scott B. Reeder

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Figure 4

Assay of obese mice.

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Assay of obese mice. (A) An expanded sampling scheme was applied to 7-we...
(A) An expanded sampling scheme was applied to 7-week-old female leptin-deficient ob/ob mice (used extensively as a model of obesity). (B) MRI imaging of WT and ob/ob obese mice is shown to illustrate the accumulation of white adipose tissue (WAT) present in these mice. However, the dermal WAT (dWAT) layer is clearly distinguished in central abdominal image sections (shown with red arrow heads). iBAT is outlined in a dotted red line. (C) Comparative histology of skins of control and obese mice, illustrated at low-power magnification, left side (scale bar: 200 μm), and higher power, right side (scale bar: 100 μm). (D) Comparison of relative dWAT thickness in ob/ob mice (n = 4) by MRI and histological assays (left panel, data pooled from assay of ventral, dorsal, anagen, and nonanagen skins). The difference between dorsal and ventral dWAT thickness is shown on right side. Box-and-whisker plots are presented as described in Figure 2E. (E) The average density of fat for WAT (periovarian, intra-abdominal) and mammary gland (MG; s.c., specialized) was measured, together with interscapular brown adipose tissue (iBAT). Dot plots are presented as for Figure 3. Statistical analysis was performed with unpaired 1-tailed t tests using GraphPad Prism software.