title: Assessment of circadian rhythms in humans: comparison of real-time fibroblast reporter imaging with plasma melatonin.
abstract: We compared the period of the rhythm of plasma melatonin, driven by the hypothalamic circadian pacemaker, to in vitro periodicity in cultured peripheral fibroblasts to assess the effects on these rhythms of a polymorphism of PER3 (rs57875989), which is associated with sleep timing. In vitro circadian period was determined using luminometry of cultured fibroblasts, in which the expression of firefly luciferase was driven by the promoter of the circadian gene Arntl (Bmal1). The period of the melatonin rhythm was assessed in a 9-d forced desynchrony protocol, minimizing confounding effects of sleep-wake and light-dark cycles on circadian rhythmicity. In vitro periods (32 participants, 24.61±0.33 h, mean±SD) were longer than in vivo periods (31 participants, 24.16±0.17 h; P<0.0001) but did not differ between PER3 genotypes (P>0.4). Analyses of replicate in vitro assessments demonstrated that circadian period was reproducible within individuals (intraclass correlation=0.62), but in vivo and in vitro period assessments did not correlate (P>0.9). In accordance with circadian entrainment theory, in vivo period correlated with the timing of melatonin (P<0.05) at baseline and with diurnal preference (P<0.05). Individual circadian rhythms can be reliably assessed in fibroblasts but may not correlate with physiological rhythms driven by the central circadian pacemaker.
authors.affiliation: Surrey Sleep Research Centre, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.
authors.forename: Sibah
authors.initials: S
authors.lastname: Hasan
authors.forename: Nayantara
authors.initials: N
authors.lastname: Santhi
authors.forename: Alpar S
authors.initials: AS
authors.lastname: Lazar
authors.forename: Ana
authors.initials: A
authors.lastname: Slak
authors.forename: June
authors.initials: J
authors.lastname: Lo
authors.forename: Malcolm
authors.initials: M
authors.lastname: von Schantz
authors.forename: Simon N
authors.initials: SN
authors.lastname: Archer
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Johnston
authors.forename: Derk-Jan
authors.initials: DJ
authors.lastname: Dijk
mesh_terms: D056930:ARNTL Transcription Factors / Q000502:physiology*; D000328:Adult; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008297:Male; D008550:Melatonin / Q000097:blood*; D018598:Minisatellite Repeats / Q000235:genetics; D056950:Period Circadian Proteins / Q000235:genetics*; D015203:Reproducibility of Results
chemical_list: D056930:ARNTL Transcription Factors; C538960:BMAL1 protein, human; C512644:PER3 protein, human; D056950:Period Circadian Proteins; D008550:Melatonin