title: The association between personal sun exposure, serum vitamin D and global methylation in human lymphocytes in a population of healthy adults in South Australia.
abstract: BACKGROUND
  There is a positive association between solar UV exposure and micronucleus frequency in peripheral blood lymphocytes (PBL) and this association may be stronger when serum vitamin D (25(OH)D) levels are insufficient (<50 nmol/L). Micronucleus formation can result from global hypomethylation of DNA repeat sequences. The aim of this analysis was to evaluate the relationship between solar UV exposure and methylation pattern in LINE-1 repetitive elements in PBL DNA and to see if serum 25(OH)D levels modify it.
  
  
  METHODS
  Personal solar UV exposure was estimated from hours of outdoor exposure over 6 weeks recalled at the time of blood collection in 208 male and female participants living in South Australia. Methylation in LINE-1 repetitive elements was assessed in PBL using pyrosequencing.
  
  
  RESULTS
  Methylation in LINE-1 decreased with increasing solar UV exposure (% decrease = 0.5% per doubling of sUV; 95%CI: -0.7 to -0.2 p(value) = 0.00003). Although there was no correlation between LINE-1 methylation and micronucleus frequency, there was a 4.3% increase (95%CI: 0.6-8.1 p-value = 0.02) in nucleoplasmic bridges and a 4.3% increase in necrosis (CI: 1.9-6.8 p-value = 0.0005) for every 1% increase in LINE-1 methylation. Serum 25(OH)D was not associated with DNA methylation; or did it modify the association of solar UV with DNA methylation.
  
  
  CONCLUSIONS
  Exposure to solar UV radiation may reduce DNA methylation in circulating lymphocytes. This association does not appear to be influenced or mediated by vitamin D status.
authors.affiliation: Cancer Research Division, Cancer Council New South Wales, Australia. Electronic address: visalinin@nswcc.org.au.
authors.forename: Visalini
authors.initials: V
authors.lastname: Nair-Shalliker
authors.affiliation: CSIRO Food and Nutritional Sciences, Australia.
authors.forename: Varinderpal
authors.initials: V
authors.lastname: Dhillon
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Sweden.
authors.forename: Mark
authors.initials: M
authors.lastname: Clements
authors.affiliation: Sydney School of Public Health, University of Sydney, Australia.
authors.forename: Bruce K
authors.initials: BK
authors.lastname: Armstrong
authors.affiliation: CSIRO Food and Nutritional Sciences, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Fenech
mesh_terms: D000328:Adult; D001315:Australia; D002112:Calcifediol / Q000097:blood*; D019175:DNA Methylation / Q000528:radiation effects*; D005260:Female; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D048629:Micronuclei, Chromosome-Defective / Q000528:radiation effects; D008875:Middle Aged; D013472:Sunlight; D014466:Ultraviolet Rays
chemical_list: D002112:Calcifediol
keywords: DNA damage; Global methylation; LINE-1 repetitive elements; Solar UV exposure; Vitamin D