Introduction:
The timing of food intake is a critical determinant of metabolic health, with misaligned feeding schedules contributing to obesity, cardiovascular disease, and type-2 diabetes. While the suprachiasmatic nucleus (SCN) is well established as the master circadian pacemaker, emerging evidence highlights the importance of extra-SCN clocks in metabolic regulation. In our work, we have identified the dorsal vagal complex (DVC)—a brainstem satiety hub composed of the area postrema (AP), nucleus of the solitary tract (NTS), and dorsal motor nucleus of the vagus (DMV)—as a previously unrecognised site of autonomous circadian timekeeping. The DVC integrates visceral and hormonal signals to control feeding and energy balance, and we hypothesised that it may play a role in encoding daily patterns of food intake. Here, we investigated whether and how feeding schedules entrain circadian gene expression in the DVC.

Methods:
Adult C57BL/6J mice (8–12 weeks, both sexes) were housed under a 12:12h light-dark cycle and assigned to one of four time-restricted feeding (TRF) conditions: ad-libitum or 6-hour feeding windows during the early light (ZT0–6), late light (ZT6–12), or early dark phase (ZT12–18) for a week. Animals were then culled at 4 or 6h intervals over a 24h period. The DVC was isolated and analysed using qPCR, NanoString nCounter, and RNAscope in situ hybridisation to assess rhythmic expression of clock genes and neurotransmitter receptor genes. Rhythmicity and phase shifts were analysed using sine wave fitting. All experimental procedures were approved by the University of Bristol Animal Welfare and Ethical Review Body and conducted under the UK Animals (Scientific Procedures) Act 1986, under a valid Home Office project licence.

Results:

Under ad-libitum conditions, 23 and 32 transcripts (out of 84 tested) showed significant 24h rhythmicity in the AP and NTS, respectively (n=5/each of 6 timepoints; p<0.05). TRF (n=16 per feeding condition) caused robust phase shifts in clock gene expression across DVC subregions, aligning with feeding time rather than the light-dark cycle. Notably, rhythmic expression of key neurotransmitter receptor genes also followed the timing of food availability. The precision of food entrainment was significantly greater in the NTS compared to the AP (p=0.0223, paired t-test), suggesting regional differences in metabolic clock plasticity. Altogether, these results indicate that feeding time is a dominant cue for circadian programming in the DVC.

Conclusion:
We demonstrate that circadian timekeeping in the brainstem satiety and timekeeping centre is malleable and entrainable by meal timing. This newly discovered circadian node may be an essential component of the broader food-entrainable oscillator network, acting independently of the SCN. Our findings have implications for the design of chrono-nutrition strategies, suggesting that aligning feeding schedules with endogenous brainstem clocks may help optimise satiety signalling and metabolic health. Ongoing behavioural studies are investigating whether this mechanism contributes to food anticipatory activity and exploring neural mechanisms of DVC’s food entrainment.