Supraclavicular skin temperature measured by iButtons and ¹⁸F-fluorodeoxyglucose uptake by brown adipose tissue in adults

Currently, 18 [F]-Fluorodeoxyglucose (¹⁸F-FDG) in combination with a positron emission tomography/computed tomography (PET/CT) scan analysis is the most commonly used method to quantify human BAT volume and activity. However, this technique presents several drawbacks which negatively affect participant's health. The aim of the present work is to determine whether supraclavicular skin temperature can be used as an indirect marker of cold-induced BAT and skeletal muscle ¹⁸F-FDG uptake in adults, while taking into account body composition. We performed a personalized cooling protocol just before an ¹⁸F-FDG-PET/CT scan, and we measured supraclavicular skin temperature before (in warm conditions) and after the cooling protocol in 88 adults (n = 57 women, mean age: 21.9 ± 2.1 years old, body mass index: 24.5 ± 4.3 km/m²). We found that supraclavicular skin temperature at the warm and cold periods was weakly and positively associated with BAT activity (SUV_mean and SUV_peak: β = 3.000; R² = 0.072; P = 0.022 and β = 2.448; R² = 0.060; P = 0.021), but not with skeletal muscle ¹⁸F-FDG uptake, after controlling for body composition. We performed further analyses and the positive associations persisted only in the group of women. In conclusion, supraclavicular skin temperature in warm and cold conditions seems to be related with cold-induced ¹⁸F-FDG uptake by BAT only in women, although the low explained variance of these associations means that there are other factors involved in the supraclavicular skin temperature.