The presence of active brown adipose tissue determines cold-induced energy expenditure and oxylipin profiles in humans.

Accumulating evidence links brown adipose tissue (BAT) to increased cold-induced energy expenditure (CIEE) and regulation of lipid metabolism in humans. BAT has also been proposed as a novel source for biologically active lipid mediators including polyunsaturated fatty acids (PUFAs) and oxylipins. However, little is known about cold-mediated differences in energy expenditure and various lipid species between individuals with detectable BAT (BATpos) and those without (BATneg).Here we investigated a unique cohort of matched BATpos and BATneg individuals identified by [18F]-FDG PET/CT. BAT function, CIEE and circulating oxylipins, were analyzed before and after short-term cold exposure using [18F]-FDG PET/CT, indirect calorimetry and high-resolution mass spectrometry, respectively.We found that active BAT is the major determinant of cold-induced energy expenditure since only BATpos individuals experienced significantly increased energy expenditure in response to cold. A single bout of moderate cold exposure resulted in the dissipation of additional 20kcal excess energy in BATpos but not in BATneg individuals. The presence of BAT was associated with a unique systemic PUFA and oxylipin profile characterized by increased levels of anti-inflammatory ω3 fatty acids as well as cytochrome P450 products but decreased concentrations of some pro-inflammatory hydroxyeicosatetraenoic acids when compared to BATneg individuals. Notably, cold exposure raised circulating levels of various lipids, including the recently identified BATokines DiHOME and 12-HEPE, only in BATpos subjects.In summary, our data emphasize that BAT in humans is a major contributor towards cold-mediated energy dissipation and a critical organ in the regulation of the systemic lipid pool.

Click here to read the full article @ The Journal of clinical endocrinology and metabolism