Abstract
ObjectivesTo evaluate whether a water-fat magnetic resonance imaging (MRI) cooling-reheating protocol could be used to detect changes in lipid content and perfusion in the main human brown adipose tissue (BAT) depot after a three-hour long mild cold exposure.Materials and MethodsNine volunteers were investigated with chemical-shift-encoded water-fat MRI at baseline, after a three-hour long cold exposure and after subsequent short reheating. Changes in fat fraction (FF) and R2*, related to ambient temperature, were quantified within cervical-supraclavicular adipose tissue (considered as suspected BAT, denoted sBAT) after semi-automatic segmentation. In addition, FF and R2* were quantified fully automatically in subcutaneous adipose tissue (not considered as suspected BAT, denoted SAT) for comparison. By assuming different time scales for the regulation of lipid turnover and perfusion in BAT, the changes were determined as resulting from either altered absolute fat content (lipid-related) or altered absolute water content (perfusion-related).ResultssBAT-FF decreased after cold exposure (mean change in percentage points = -1.94 pp, P = 0.021) whereas no change was observed in SAT-FF (mean = 0.23 pp, P = 0.314). sBAT-R2* tended to increase (mean = 0.65 s-1, P = 0.051) and SAT-R2* increased (mean = 0.40 s-1, P = 0.038) after cold exposure. sBAT-FF remained decreased after reheating (mean = -1.92 pp, P = 0.008, compared to baseline) whereas SAT-FF decreased (mean = -0.79 pp, P = 0.008, compared to after cold exposure).ConclusionsThe sustained low sBAT-FF after reheating suggests lipid consumption, rather than altered perfusion, as the main cause to the decreased sBAT-FF. The results obtained demonstrate the use of the cooling-reheating protocol for detecting changes in the cervical-supraclavicular fat depot, being the main human brown adipose tissue depot, in terms of lipid content and perfusion.
Highlights
There are two main types of mammal adipose tissue: white adipose tissue (WAT) and brown adipose tissue (BAT), formed by white and brown adipocytes, respectively
Results sBAT-fat fraction (FF) decreased after cold exposure whereas no change was observed in subcutaneous adipose tissue (SAT)-FF. sBATR2* tended to increase and SAT-R2* increased after cold exposure. sBAT-FF remained decreased after reheating whereas SAT-FF decreased
The results obtained demonstrate the use of the cooling-reheating protocol for detecting changes in the cervical-supraclavicular fat depot, being the main human brown adipose tissue depot, in terms of lipid content and perfusion
Summary
There are two main types of mammal adipose tissue: white adipose tissue (WAT) and brown adipose tissue (BAT), formed by white and brown adipocytes, respectively. It is well established that BAT is prevalent in young adults (in the twenties and thirties) [1], with the main depot being the cervical-supraclavicular, and can be activated to contribute to non-shivering thermogenesis during cold exposure [2]. Being essentially non-invasive and providing high sensitivity in detecting active BAT, research with PET/CT is restricted due to exposure to ionizing radiation. In this context, magnetic resonance imaging (MRI) has been proposed as a non-ionizing imaging alternative and complement to PET/CT [9,10,11,12,13,14,15,16]. As the cervical BAT depot in human adults has been observed to contain a mixture of brown adipocytes and white adipocytes [17], BAT imaging is expected to be challenged by partial volume effects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
