Capsinoids only increased EE in BAT-positive participants, which suggests that BAT mediates EE evoked by capsinoids. This implies that capsinoids stimulate BAT to a lesser degree than cold exposure as evidenced by 18F-FDG uptake below the presently accepted SUV thresholds defining BAT activation. This trial was registered at www.clinicaltrials.gov as NCT02964442.
Objective
This study aimed to compare the associations of positron emission tomography (PET), magnetic resonance (MR), and infrared thermography (IRT) imaging modalities with energy expenditure (EE) after brown adipose tissue (BAT) activation using capsinoid ingestion and cold exposure.
Methods
Twenty participants underwent PET‐MR, IRT imaging, and whole‐body calorimetry after capsinoid ingestion and cold exposure. Standardized uptake values (SUV) and the fat fraction (FF) of the supraclavicular brown adipose tissue regions were estimated. The anterior supraclavicular temperature (Tscv) from IRT at baseline and postintervention was measured. Two‐hour post–capsinoid ingestion EE and post–cold exposure EE served as a reference to correlate fluorodeoxyglucose uptake, FF, and Tscv for BAT assessment. IRT images were geometrically transformed to overlay on PET‐MR for visualization of the hottest regions.
Results
The supraclavicular hot spot identified on IRT closely corresponded to the area of maximal fluorodeoxyglucose uptake on PET images. Controlling for body weight, post–cold exposure Tscv was a significant variable associated with EE (P = 0.025). The SUV was significantly inversely correlated with FF (P = 0.012) and significantly correlated with peak of Tscv during cold exposure in BAT‐positive participants (P = 0.022).
Conclusions
Tscv correlated positively with EE and was also significantly correlated with SUV after cold exposure. Both IRT and MR FF are promising methods to study BAT activity noninvasively.
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