MRI characteristics of supraclavicular brown adipose tissue in relation to cold-induced thermogenesis in healthy human adults

Abstract

Background: Brown adipose tissue (BAT) has been proposed as a target to treat obesity and metabolic disease. Currently, ¹⁸ F-Fluordeoxyglucose positron emission tomography (FDG-PET) is the standard for BAT-imaging. MRI might be a promising alternative, as it is not associated with ionizing radiation, offers a high resolution, and allows to discriminate different types of soft tissue.

Purpose: We sought to evaluate whether supraclavicular BAT (scBAT) volume, fat-fraction (FF), and relaxation rate (R2*) determined by MRI can predict its metabolic activity, which was assessed by measurement of cold-induced thermogenesis (CIT).

Study type: Prospective cohort study.

Subjects: Twenty healthy volunteers (9 female, 11 male), aged 18-47 years, with a body mass index (BMI) of 18-30 kg/m² .

Field strength/sequence: Multiecho gradient MRI for water-fat separation was used on a 3T device to measure the FF and T₂ * of BAT.

Assessment: Prior to imaging, CIT was determined by measuring the difference in energy expenditure (EE) during warm conditions and after cold exposure. Volume, FF, and R2* of scBAT was assessed and compared with CIT. In 11 participants, two MRI sessions with and without cold exposure were performed and the dynamic changes in FF and R2* assessed.

Statistical tests: Linear regression was used to evaluate the relation of MRI measurements and CIT. P-values below 0.05 were considered significant; data are given as mean ± SD.

Results: R2* correlated positively with CIT (r = 0.64, R² = 0.41 P = 0.0041). Volume and FF did not correlate significantly with CIT. After mild cold exposure EE increased significantly (P = 0.0002), with a mean CIT of 147 kcal/day. The mean volume of scBAT was 72.4 ± 38.4 ml, mean FF was 74.3 ± 5.8%, and the mean R2* (1/T₂ *) was 33.5 ± 12.7 s^-1 .

Data conclusion: R2* of human scBAT can be used to estimate CIT. FF of scBAT was not associated with CIT.

Level of evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1160-1168.

Keywords: brown adipose tissue; cold induced thermogenesis; magnetic resonance imaging; multi-echo Dixon imaging; thermogenesis.