Spectral Unmixing Imaging for Differentiating Brown Adipose Tissue Mass and Its Activation.

Jing Yang,Chongzhao Ran,Jian Yang

doi:10.1155/2018/6134186

Abstract

Recent large-scale clinical analysis indicates that brown adipose tissue (BAT) mass levels inversely correlate with body-mass index (BMI), suggesting that BAT is associated with metabolic disorders such as obesity and diabetes. PET imaging with 18F-FDG is the most commonly used method for visualizing BAT. However, this method is not able to differentiate between BAT mass and BAT activation. This task, in fact, presents a tremendous challenge with no currently existing methods to separate BAT mass and BAT activation. Our previous results indicated that BAT could be successfully imaged in mice with near infrared fluorescent (NIRF) curcumin analogues. However, the results from conventional NIRF imaging could not reflect what portion of the NIRF signal from BAT activation contributed to the signal observed. To solve this problem, we used spectral unmixing to separate/unmix NIRF signal from oil droplets in BAT, which represents its mass and NIRF signal from blood, which represents BAT activation. In this report, results from our proof-of-concept investigation demonstrated that spectral unmixing could be used to separate NIRF signal from BAT mass and BAT activation.

Highlights

Brown adipose tissue (BAT) has been considered as “good fat,” due to its function of dissipating large amounts of chemical/food energy as heat to maintain the energy balance of the whole body [1,2,3]
We demonstrated that spectral unmixing could be used to dissect near infrared fluorescent (NIRF) signal from BAT mass and NIRF signal from blood flow [59]
With conventional NIRF imaging, we demonstrated that CRANAD-29 had significant selectivity for BAT over WAT and could be used to monitor BAT activation and BAT mass changes [52]

Summary

Introduction

Brown adipose tissue (BAT) has been considered as “good fat,” due to its function of dissipating large amounts of chemical/food energy as heat to maintain the energy balance of the whole body [1,2,3]. Via conventional NIRF imaging with CRANAD29, BAT mass change in a streptozotocin-induced diabetic mouse model and BAT activation under cold exposure could be reported. To the best of our knowledge, there is no available imaging method for differentiating BAT mass and activation The key to this challenge is to dissect BAT mass measurement from BAT physiology status (activated or suppressed). We demonstrated that spectral unmixing could be used to dissect NIRF signal from BAT mass and NIRF signal from blood flow [59]. With this technique, it is feasible to accurately report BAT mass and BAT activation/physiological status

Methods and Materials

Results and Discussions

Conclusion