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 3

Evaluation of WAT and BAT depots.

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Evaluation of WAT and BAT depots. (A) Lateral views of white adipose tis...
(A) Lateral views of white adipose tissue (WAT) depots are used to delimit the front and rear of each specific depot, to calculate total WAT volumes. Outlines and arrowheads indicate adipose organs (11): A, anterior subcutaneous; B, dermal; C–E, visceral depots (specifically C, retroperitoneal; D, mesenteric; E, abdomino-pelvic); and F, posterior s.c. The lateral views shown here are approximately 5.5 cm actual width. (B) This noninvasive method can be compared with previous studies of WAT volumes and appearance, performed using dissection procedures (11). (C) The relative fat signal from interscapular brown adipose tissue (iBAT) depots (normalized to fat signal from perigonadal WAT) was quantified (20 ROIs each, n = 3) and validated by comparison with the iBAT depots of cold-stressed Sdc1–/– mouse strain, previously shown to have depleted lipid content. The relative signal is reported in arbitrary units. The histological appearance of the iBAT depots illustrates the relative lipid depletion (clear droplets on H&E-stained images); scale bar: 25 μm. (D) Similarly, the relative fat signals from WAT depots (pgWAT and mammary gland [MG]) were compared for control and Sdc1–/– mice (20 voxels selected at random, indicated for this example in red circles; n = 3). They showed no difference, which confirms the histological data; scale bar: 50 μm. Dot plots (C and D) show mean values; error bars indicate ±SEM. Statistical analysis was performed with unpaired 1-tailed t tests using GraphPad Prism software.