Recent advances in the detection of brown adipose tissue in adult humans: a review

Abstract

The activation of brown adipose tissue (BAT) is associated with reductions in circulating lipids and glucose in rodents and contributes to energy expenditure in humans indicating the potential therapeutic importance of targetting this tissue for the treatment of a variety of metabolic disorders. In order to evaluate the therapeutic potential of human BAT, a variety of methodologies for assessing the volume and metabolic activity of BAT are utilized. Cold exposure is often utilized to increase BAT activity but inconsistencies in the characteristics of the exposure protocols make it challenging to compare findings. The metabolic activity of BAT in response to cold exposure has most commonly been measured by static positron emission tomography of F-fluorodeoxyglucose in combination with computed tomography (F-FDG PET-CT) imaging, but recent studies suggest that under some conditions this may not always reflect BAT thermogenic activity. Therefore, recent studies have used alternative positron emission tomography and computed tomography (PET-CT) imaging strategies and radiotracers that may offer important insights. In addition to PET-CT, there are numerous emerging techniques that may have utility for assessing BAT metabolic activity including magnetic resonance imaging (MRI), skin temperature measurements, near-infrared spectroscopy (NIRS) and contrast ultrasound (CU). In this review, we discuss and critically evaluate the various methodologies used to measure BAT metabolic activity in humans and provide a contemporary assessment of protocols which may be useful in interpreting research findings and guiding the development of future studies.

Association of wrist and ambient temperature with cold-induced brown adipose tissue and skeletal muscle [18F]FDG uptake in young adults

“…For logistical reasons, we were not able to control the clothing of the participants during the measurement of Personal-ET and WT. We performed a personalized cooling protocol, which had several limitations (27). Moreover, we know that during sleep phases, humans can lose at least 25% of their total thermoregulatory capacity.…”

Human Brown Adipose Tissue Estimated With Magnetic Resonance Imaging Undergoes Changes in Composition After Cold Exposure: An in vivo MRI Study in Healthy Volunteers

“…The largest FF decrease we observed (i.e., 3.5%) is in the range of values reported in literature (19,21,23), but also much smaller (22) and larger decreases (25) have been reported. This could be due to the use of different thresholds, but also differences in the cooling protocols can play an important role (54,55). Raising the lower threshold above 34% decreases the extent of FF differences upon cold exposure, as we excluded voxels that fell below the threshold in both the thermoneutral and post-cooling scan in order to avoid partial volume artifacts and to enable volumetric analysis.…”

A decrease in brown adipose tissue activity is associated with weight gain during chemotherapy in early breast cancer patients

“…Feldmann et al drew the same conclusion, showing that UCP1 ablation led to obesity in mice [14]. Studies using fluorine-18 fluorodeoxyglucose ( 18 F-FDG) positron emission tomography (PET) scans have evidenced the presence of BAT in adults [15][16][17][18]. 18 F-FDG is currently used in oncology to mark tumours but it is not specific and has been found in high glucose metabolism organs such as BAT [19][20][21].…”