title: The impact of sleep deprivation and nighttime light exposure on clock gene expression in humans.
abstract: OBJECTIVE
  To examine the effect of acute sleep deprivation under light conditions on the expression of two key clock genes, hPer2 and hBmal1, in peripheral blood mononuclear cells (PBMC) and on plasma melatonin and cortisol levels.
  
  
  METHODS
  Blood samples were drawn from 6 healthy individuals at 4-hour intervals for three consecutive nights, including a night of total sleep deprivation (second night). The study was conducted in April-June 2006 at the University Medical Centre Ljubljana.
  
  
  RESULTS
  We found a significant diurnal variation in hPer2 and hBmal1 expression levels under baseline (P<0.001, F=19.7, df=30 for hPer2 and P<0.001, F=17.6, df=30 for hBmal1) and sleep-deprived conditions (P<0.001, F=9.2, df=30 for hPer2 and P<0.001, F=13.2, df=30 for hBmal1). Statistical analysis with the single cosinor method revealed circadian variation of hPer2 under baseline and of hBmal1 under baseline and sleep-deprived conditions. The peak expression of hPer2 was at 13:55 ± 1:15 hours under baseline conditions and of hBmal1 at 16:08 ± 1:18 hours under baseline and at 17:13 ± 1:35 hours under sleep-deprived conditions. Individual cosinor analysis of hPer2 revealed a loss of circadian rhythm in 3 participants and a phase shift in 2 participants under sleep-deprived conditions. The plasma melatonin and cortisol rhythms confirmed a conventional alignment of the central circadian pacemaker to the habitual sleep/wake schedule.
  
  
  CONCLUSIONS
  Our results suggest that 40-hour acute sleep deprivation under light conditions may affect the expression of hPer2 in PBMCs..
authors: 1Institute of Clinical Neurophysiology, Division of Neurology, University Medical Centre, Ljubljana, Slovenia. pavel.kavcic@gmail.com
authors: Pavel
authors: P
authors: Kavcic
authors: Bojan
authors: B
authors: Rojc
authors: Leja
authors: L
authors: Dolenc-Groselj
authors: Bruno
authors: B
authors: Claustrat
authors: Kristina
authors: K
authors: Fujs
authors: Mario
authors: M
authors: Poljak
mesh_terms: D056930:ARNTL Transcription Factors / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D000328:Adult; D002940:Circadian Rhythm; D015870:Gene Expression; D006801:Humans; D008027:Light; D008297:Male; D056950:Period Circadian Proteins / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D012892:Sleep Deprivation / Q000378:metabolism*
chemical_list: D056930:ARNTL Transcription Factors; C538960:BMAL1 protein, human; C421902:PER2 protein, human; D056950:Period Circadian Proteins