The regulation of central and peripheral circadian clocks in humans.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing circadian clock mechanisms and monitoring techniques without a systematic review methodology
PubMed 19849799 · doi:10.1111/j.1467-789X.2009.00660.x
What was done
This narrative review outlines methods for assessing central and peripheral circadian clocks in humans. It discusses monitoring clock gene expression in peripheral tissues—including white blood cells, skin, oral mucosa, colon cells, adipose tissue, and post-mortem brain tissue—in comparison with central clock markers (melatonin, cortisol, core body temperature), referencing protocols examining peripheral entrainment during simulated night shifts with bright light therapy.
What was found
The abstract reports no numerical values, effect sizes, or statistical metrics. It qualitatively describes that clock gene expression can be tracked across various peripheral human tissues and notes that bright light treatment efficiently resets the central circadian clock in simulated shift-work protocols.
Why it matters
Establishing accessible peripheral biomarkers of circadian rhythms allows researchers to evaluate circadian misalignment and potential chronobiological interventions in shift workers.
Limits
As a narrative review, the abstract provides no specific sample sizes, statistical outcomes, detailed protocol parameters, or systematic evaluation of evidence.
Cited by
- contradicts A drop in core body temperature triggers the brain to release melatonin, and core body temperature begins rising again between 1:00 AM and 3:00 AM in all humans.