Fasting and Postprandial Activity of Brown Adipose Tissue in Healthy Men

Abstract

The role of brown adipose tissue (BAT) in adult metabolism is poorly understood. This study aimed to examine the differential effects of an overnight fast and the postprandial state on BAT activity. Methods: We included 10 healthy, lean male volunteers. BAT uptake of glucose was visualized using ¹⁸F-FDG PET/CT during mild cold exposure. Each subject underwent PET/CT twice. The first scan was obtained after an overnight fast; the second after a standardized meal. Results: ¹⁸F-FDG uptake in BAT was observed in 6 of 10 volunteers. These subjects were found to have a higher maximal standardized uptake value when fasting (median, 13.1 g/mL; range, 6.1–27.6 g/mL) than when in the postprandial state (median, 6.8 g/mL; range, 2.1–13.4 g/mL) (P = 0.03). Conclusion: Cold-stimulated ¹⁸F-FDG uptake by BAT in humans is more pronounced during fasting. The lower maximal standardized uptake value in the postprandial state may be explained by increased insulin-stimulated glucose uptake in muscle.