Time of feeding and the intrinsic circadian clock drive rhythms in hepatic gene expression.
Level 5 - mechanism / opinion, no new human data
Preclinical animal model study (CEBM Level 5 for bench and animal research)
PubMed 19940241 · doi:10.1073/pnas.0909591106
What was done
Researchers subjected wild-type (WT) and circadian clock-deficient mice to distinct feeding and fasting paradigms under controlled lighting conditions. They tracked the temporal patterns of food intake and measured hepatic transcription to evaluate the phase, amplitude, and repertoire of rhythmic gene expression.
What was found
The abstract reports that up to 15% of expressed transcripts in WT mouse liver show circadian rhythmicity under constant darkness, but gives no other specific numerical values or sample counts. Fasting restricted rhythmic oscillation to only a small subset of transcripts in WT mice, whereas temporally restricted feeding restored rhythmic transcription in hundreds of genes in clock-deficient mice.
Why it matters
The findings demonstrate that rhythmic liver transcription is an emergent property shaped by both cell-autonomous circadian clocks and systemic feeding cues, establishing meal timing as a key driver of peripheral circadian biology.
Limits
This is an animal study in mice, limiting direct translation to human circadian rhythms and metabolic health. The abstract omits sample sizes, specific genetic knockout details, and statistical significance values, and it does not report downstream protein translation or physiological metabolic outcomes.
Cited by
- supports Between 3,000 and 5,000 genes in the liver (representing nearly 30% of the expressed genome) are cyclically turned on and off depending on time of day.
- supports The timing of food intake, rather than light-dark cycles, sets the phase of cycling genes in the mammalian liver.