Circadian gene methylation in rotating-shift nurses: a cross-sectional study
Creators: name: Reszka, Edyta
name: Wieczorek, Edyta
name: Przybek, Monika
name: Jabłońska, Ewa
name: Paweł Kałużny
name: Bukowska-Damska, Agnieszka
name: Shanbeh Zienolddiny
name: Pepłońska, Beata
Publisher: name: Taylor & Francis
Year: 2017
Subjects: subject: Genetics
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: Molecular Biology
subject: Neuroscience
subject: Physiology
subject: Biotechnology
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: FOS: Earth and related environmental sciences
subject: 111714 Mental Health
subject: FOS: Health sciences
subject: FOS: Health sciences

description: Investigating the methylation status of the circadian genes may contribute to a better understanding of the shift work-related circadian disruption in individuals exposed to artificial light at night. In the present study, we determined the methylation status of the circadian genes associated with a shift work pattern among nurses and midwives participating in a cross-sectional study in Lodz, Poland. Quantitative methylation polymerase chain reaction assays were used to assess promoter CpG methylation in <i>PER1, PER2, PER3, CRY1, CRY2, BMAL1, CLOCK</i>, and <i>NPAS2</i> in genomic DNA from whole blood of 347 women having a rotating-shift work schedule and 363 women working days only. The percentage of methylated reference (PMR) was assessed using fluorescent probes for <i>PER1, PER2, PER3, CRY1</i>, and <i>NPAS2</i>, and the percentage of gene methylation, as the methylation index (MI), using two sets of primers for <i>BMAL1, CLOCK</i>, and <i>CRY2</i>. We tested the possible association between current and lifetime rotating night-shift work characteristics and circadian gene methylation by using proportional odds regression model with blood DNA methylation, categorized into tertiles, and adjusted for age, current smoking status, folate intake and blood collection time. The findings indicated that CpG methylation in <i>PER2</i> promoter was significantly decreased (<i>P</i> PER2 methylation was associated with a higher monthly frequency of current night duties (2–7 night shifts, and eight or more night shifts per month) (<i>P</i> = 0.012) and was associated at borderline significance (<i>P</i> = 0.092) with the lifetime duration of shift work (&gt;10 ≤ 20 years and &gt;20 ≤ 43 years of rotating-shift work) among nurses and midwives (<i>N</i> = 710). Moreover, women with a longer lifetime duration of shift work presented a lower status of <i>PER1</i> methylation (<i>P</i> = 0.040) than did the women with up to 10 years of rotating-shift work. Long lifetime duration of shift work (&gt; 10 years) among current rotating night-shift workers (<i>N</i> = 347) was associated with <i>BMAL1</i> hypomethylation (<i>P</i> = 0.013). Among eight of the investigated circadian genes, only <i>PER1, PER2</i>, and <i>BMAL1</i> showed differential methylation attributable to the rotating-shift work of nurses and midwives. The findings on blood-based DNA methylation in the circadian genes may provide a better insight into the mechanistic principles underlying the possible health effects of night-shift work but these should be verified in further studies recruiting larger populations of shift workers.