An Adipose Tissue Atlas: An Image-Guided Identification of Human-like BAT and Beige Depots in Rodents

Abstract

[¹⁸F]Fluorodeoxyglucose-PET/CT (¹⁸F-FDG-PET/CT) imaging has been invaluable for visualizing metabolically active adipose tissues in humans with potential anti-diabetic and anti-obesity effects. To explore whether mice display human-like fat depots in anatomically comparable regions, we mapped fat depots using glucose or fatty acid imaging tracers, such as ¹⁸F-FDG through PET/CT or [^123/125I]-β-methyl-p-iodophenyl-pentadecanoic acid with SPECT/CT imaging, to analogous depots in mice. Using this type of image analysis with both probes, we define a large number of additional areas of high metabolic activity corresponding to novel fat pads. Histological and gene expression analyses validate these regions as bona fide fat pads. Our findings indicate that fat depots of rodents show a high degree of topological similarity to those of humans. Studies involving both glucose and lipid tracers indicate differential preferences for these substrates in different depots and also suggest that fatty acid-based visualized approaches may reveal additional brown adipose tissue and beige depots in humans.

Keywords: BAT; PET/CT; SPECT/CT; beige; bona fide thermogenic fat tissues; glucose or fatty acid imaging tracers; human-like; imaging; marker genes; morphology.