Peripheral circadian oscillators in mammals: time and food.
Level 5 - mechanism / opinion, no new human data
Narrative review of animal and in vitro laboratory mechanisms without human data.
PubMed 12828282 · doi:10.1177/0748730403018003007
What was done
This narrative review examined the mechanisms by which non-photic cues entrain mammalian peripheral circadian oscillators, synthesizing evidence on the roles of feeding time, body temperature rhythms, and systemic chemical signaling (such as glucocorticoid receptor agonists) in synchronizing peripheral tissue clocks relative to the central suprachiasmatic nucleus (SCN) pacemaker.
What was found
The abstract reports no numerical values or statistical metrics. It describes that daytime feeding of nocturnal rodents completely inverts the phase of circadian gene expression in peripheral tissues—including the liver, heart, kidney, and pancreas—without altering the SCN pacemaker. Furthermore, while SCN light responsiveness is gated exclusively to the night, peripheral oscillators can be chemically phase-shifted across the full 24-hour cycle (e.g., dexamethasone injection resets liver circadian gene expression at any time of day).
Why it matters
This review establishes feeding timing as the dominant zeitgeber for peripheral organs, demonstrating that metabolic cues can drive peripheral tissue rhythms independently of the central light-driven master clock.
Limits
The abstract provides no quantitative data, sample sizes, or formal search methodology. Findings rely exclusively on rodent models and in vitro cell culture systems, limiting direct extrapolation to human circadian physiology.
Cited by
- supports Food intake is the primary signal that resets peripheral circadian clocks in organs such as the liver, whereas light resets the master clock in the suprachiasmatic nucleus.