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 2

Validation of dWAT imaging.

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Validation of dWAT imaging. (A) The sampling procedure is illustrated, t...
(A) The sampling procedure is illustrated, together with the voxel dimensions used for this study. Typical mouse skin fat layers are less than 1 voxel thick; thus, thickness is calculated based on signal intensity (referenced to a nearby white adipose tissue [WAT] depot) and related to thickness by a volume/thickness calculation (as described in Methods). ROI, region of interest. (B) The histological appearance of skin samples from control and dermal WAT–deficient (dWAT-deficient; Sdc1–/–) mouse strains. Comparative views at low-power (scale bar: 500 μm) and high-power (scale bar: 200 μm). (C) Relative dWAT thickness, calculated from MRI data, was compared with data for Sdc1–/– (n = 4) and control mice (n = 4) derived by histological assay. To compare data from MRI and histological analysis, ventral, dorsal, anagen, and nonanagen skins were pooled. (D) Thickness of dWAT varies with different factors, one of which is body site; here, dorsal (back skin) or ventral (belly skin) are assayed by MRI. (E) A benefit of histological analysis is that dWAT can be measured separately for skin patches in the growth phase of folliculogenesis (anagen, accompanied by the ingression of hair follicles through the dermis and into the dWAT). For the box-and-whisker plots shown in C–E, the box indicates 25%–75%, the line is placed at the median, and the whiskers indicate 5%–95%. There were no significant outliers (determined by Grubbs’ test). Statistical analysis was performed with unpaired 1-tailed t tests using GraphPad Prism software.