Intestinal clock shapes sleep-wake cycle via sustaining glutamine homeostasis

The intestinal clock plays a role in transmitting feeding signals and generating circadian events, but how this clock system may time homeostatic processes related to sleep-wake regulation is unknown. Our functional dissections of the circadian clock in intestinal epithelial cells (IECs) demonstrate that its integrity is required for maintenance of the diurnal sleep-wake cycle. In IECs, BMAL1 generates diurnal rhythmic SLC6A19 expression that promotes intestinal absorption of glutamine during the active phase, which enhances glutamatergic neuron activities in hypothalamic nuclei and contributes to increased wakefulness and decreased sleep. The involvement of glutamine homeostasis in sleep-wake regulation is also pronounced during the rest phase, as an elevation of glutamine in the rest phase caused by IEC deficiency of REV-ERBα is causally linked to sleep abnormalities characterized by reduced sleep. Overall, the intestinal clock shapes the diurnal sleep-wake cycle through temporally gating glutamine homeostasis and serves as a potential target for boosting the sleep rhythm and for managing sleep disorders.