It is widely reported that BAT is more frequently observed in patients during the winter season, and its activities could vary significantly under different conditions. However, whether this phenomenon is entirely caused by low temperature or other factors is not very clear. In this study, we tried to explore the seasonal fluctuation of FDG-PET BAT using mouse models that were from the same genetic breed and raised in a well-controlled environment. We also compared these variations with the effects of fasting and cold stimulation on BAT activities in these mice. In overnight fasted mice, the FDG-PET BAT was the highest in standardized uptake value (SUV) in the winter season. The values were much lower in all other seasons, especially in the summer. Compared to regular feeding, overnight fasting reduced BAT SUV, and refeeding after fasting could fully recover BAT activities. Fasted mice also did not respond to cold environment stimulation. After refeeding, their BAT thermogenic activities became normal. These results suggest that BAT FDG-PET SUV measurements vary significantly with the season and highlight the importance of taking into account the seasonal effect and fasting status in BAT evaluation studies using FDG-PET imaging.
Keywords: Brown Adipose tissue; Dietary state; Micro-PET/CT; Seasonal change.
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