p53 and brown adipose tissue under fasting

Active thermogenic adipocytes voraciously consume energy substrates like fatty acids and glucose to maintain body temperature upon cold exposure. Despite strong evidence for the involvement of brown adipose tissue (BAT) in controlling systemic energy homeostasis upon nutrient excess, it is unclear how the activity of brown adipocytes is regulated in times of nutrient scarcity. Therefore, this study aimed to scrutinize factors that modulate BAT activity upon fasting to balance thermogenic and energetic needs. For an unbiased view we performed transcriptomic and miRNA sequencing analysis of BAT from acutely fasted mice under mild cold exposure. Combining these data with in-depth bioinformatic analyses and in vitro experiments, we defined a previously undescribed axis of p53 and miR-92a-1-5p that is highly upregulated by fasting in thermogenic adipocytes. p53, a fasting-responsive transcription factor, was previously shown to control genes involved in the thermogenic program and miR-92a-1-5p was found to negatively correlate with human BAT activity. Here, we elucidated fructose transporter Slc2a5 as one direct downstream target of this axis and show that fructose can be taken up by and metabolized in brown adipocytes. In sum, this study delineates a fasting-induced pathway involving p53 and miR-92a-1-5p impinging on Slc2a5 and suggest a contribution of fructose as an energy substrate in thermogenic adipocytes.