Role of human brown adipose tissue in adaptive thermogenesis

Individual variation in cold adaptive thermogenesis can potentially be attributed to sympathetic nervous innervation of brown adipose tissue (BAT). In humans BAT was thought to be present only in infants. Recent results from PET‐CT scans indicate that adults may have significant amounts of active BAT. The objective is to study the relation between presence and activity of BAT and the level of cold induced thermogenesis in humans. Male volunteers (age: 24.3±3.5 y; length: 181±5.5 cm; weight: 75±4.3) were examined for presence and/or activity (standardized uptake value) of BAT during cold exposure by means of 18F‐FDG PET‐CT. In a climate chamber thermoneutral (1 h; 22 °C) condition is compared to mild cold (2 h; 16 °C). Increase in resting metabolic rate (RMR) as measured by indirect calorimetry is compared to the BAT data. Six subjects have currently been measured. RMR (mean 4.07±0.42 kJ/min) increased between 1.5 and 25 %, depending on the subject. Five subjects showed significant amounts of BAT, especially in the supra‐clavicular region. One showed no sign of BAT. This study shows high prevalence of BAT in young adult human males and will relate cold induced thermogenesis to BAT activity.