Published: July 1st, 2021
Functional imaging and quantitation of thermogenic adipose depots in mice using a micro-PET/MR imaging-based approach.
Brown and beige adipocytes are now recognized as potential therapeutic targets for obesity and metabolic syndromes. Non-invasive molecular imaging methods are essential to provide critical insights into these thermogenic adipose depots. Here, the protocol presents a PET/MR imaging-based method to evaluate the activity of brown and beige adipocytes in mouse interscapular brown adipose tissue (iBAT) and inguinal subcutaneous white adipose tissue (iWAT). Visualization and quantification of the thermogenic adipose depots were achieved using [18F]FDG, the non-metabolizable glucose analog, as the radiotracer, when combined with the precise anatomical information provided by MR imaging. The PET/MR imaging was conducted 7 days after cold acclimation and quantitation of [18F]FDG signal in different adipose depots was conducted to assess the relative mobilization of thermogenic adipose tissues. Removal of iBAT substantially increased cold-evoked [18F]FDG uptake in iWAT of the mice.
In response to changing nutritional needs, adipose tissue serves as an energy cache to adopt either lipid storage or mobilization mode to meet the needs of the body1. Moreover, adipose tissue also plays a key function in thermoregulation, via a process called non-shivering thermogenesis, also called facultative thermogenesis. This is typically achieved by the brown adipose tissue (BAT), which expresses abundant level of mitochondria membrane protein uncoupling protein 1 (UCP1). As a proton carrier, UCP1 generates heat by uncoupling the proton transport and ATP production2. Upon cold stimulation, thermogenesis in BAT is s....
The protocol described below follows the animal care guidelines of The University of Hong Kong. The animals used in the study were 8-week-old C57BL/6J mice.
1. Animal surgical procedures and cold challenge
Three groups of mice (n = 3 per group) underwent micro-PET/MR imaging in this study, where they were housed at either thermoneutrality (30 °C) or cold (6 °C) for 7 days. One group of mice (n = 3) had their iBAT removed (iBATx) prior to cold treatment (Figure 1A). This method led to an alteration to the white adipose tissue activity in all three mice. In particular, a remarkable increase in [18F]FDG uptake was observed in iWAT using micro-PET/MR imaging (
In this study, a PET/MR -based imaging and quantification of functional brown and beige adipose tissue in small animal was described. This method uses the non-metabolizable glucose analog [18F]FDG as an imaging biomarker so as to identify the adipose tissues with high glucose-demand in a non-invasive manner. MR offers good soft tissue contrast and can better differentiate adipose fat tissues from the neighboring soft tissues and muscle. When combined with PET, this enables imaging and quantifying of the activa.......
We thank the support of National Natural Science Foundation of China (NSFC) - Excellent Young Scientists Fund (Hong Kong and Macau) (81922079), Hong Kong Research Grants Council General Research Fund (GRF 17121520 and 17123419), and Hong Kong Research Grants Council Collaborative Research Fund (CRF C7018-14E) for small animal imaging experiments.....
|0.9% sterile saline
|0.9% sodium chloride intravenous infusion, 500 mL
|5 mL syringe
|5 mL syringe Luer Lock
|Sterile ocular lubricant ointment, 3.5 g
|1 mL insulin syringe with needle
|InterView Fusion software
|Post-processing and image analysis software
|Iso-Vet, inhalation anesthetic, 250 mL
|Alfasan International B.V.
|Ketamine 10% injection solution, 10 mL
|compressed gas, 99.5% purity
|5 mg/mL Meloxicam solution for injection for dogs and cats, 10 mL
|nanoScan PET/MR Scanner
|3 Tesla MR
|Nucline nanoScan software
|Scanner operating software
|7mm Stainless steel wound clips, 20 clips
|Alfasan International B.V.
|Xylazine 2% injection solution, 30 mL
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