Sexual Dimorphisms in Adult Human Brown Adipose Tissue.

ABSTRACT

OBJECTIVE: This study aimed to quantify and compare the amount, activity, and anatomical distribution of cold-activated brown adipose tissue (BAT) in healthy, young, lean women and men. METHODS: BAT volume and 18 F-fluorodeoxyglucose uptake were measured by positron emission tomography and computerized tomography in 12 women and 12 men (BMI 18.5-25 kg/m2 , aged 18-35 years) after 5 hours of exposure to their coldest temperature before overt shivering. RESULTS: Women had a lower detectable BAT volume than men (P = 0.03), but there was no difference after normalizing to body size. The mean BAT glucose uptake and relative distribution of BAT did not differ by sex. 18 F-fluorodeoxyglucose uptake consistent with BAT was observed in superficial dorsocervical adipose tissue of 6 of 12 women but only 1 of 12 men (P = 0.02). This potential BAT depot would pose fewer biopsy risks than other depots. CONCLUSIONS: Despite differences in adiposity and total BAT volume, we found that healthy, lean, young women and men do not differ in the relative amount, glucose uptake, and distribution of BAT. Dorsocervical 18 F-fluorodeoxyglucose uptake was more prevalent in women and may be a remnant of interscapular BAT seen in human newborns. Future studies are needed to discern how BAT contributes to whole-body thermal physiology and body weight regulation in women and men.