title: Anxiety is associated with higher levels of global DNA methylation and altered expression of epigenetic and interleukin-6 genes.
abstract: OBJECTIVE
  Anxiety is associated with elevated levels of the inflammatory cytokine interleukin-6 (IL-6) and an increased risk for diseases with an inflammatory aetiology. In cancer, higher levels of IL-6 have been associated with increased expression of the epigenetic enzymes DNMT1 and Enhancer of Zeste Homolog 2 (EZH2). However, the relationship between IL-6 and DNA methyltransferases (DNMTs) and EZH2 expression has not previously been examined in anxious individuals.
  
  
  METHODS
  Global DNA methylation levels were measured using the Methylflash Methylated DNA Quantification Kit and gene expression levels of the DNMT and EZH2 genes in anxious (n=25) and nonanxious individuals (n=22) were compared using quantitative real-time PCR. Specifically, we investigated whether global DNA methylation or aberrant expression of these genes was correlated with IL-6 mRNA and protein serum levels in anxious individuals.
  
  
  RESULTS
  Anxious participants had significantly higher levels of global DNA methylation compared with controls (P=0.001). There were no differences in the mean mRNA expression levels of the DNMT1/3A/3B, EZH2 and IL-6 genes in anxious individuals compared with controls. However, the expression of DNMT1/3A, EZH2 and IL-6 genes increases with increasing Hospital Anxiety and Depression Scale-Anxiety scores in the anxious cohort only. Interestingly, IL-6 gene expression was correlated strongly with DNMT1/3A/3B and EZH2 expression, highlighting a potential relationship between IL-6 and important epigenetic regulatory enzymes.
  
  
  CONCLUSIONS
  This study provides novel insight into the relationship between anxiety, epigenetics and IL-6. Moreover, our findings support the hypothesis that changes in DNA methylation profiles may contribute to the biology of anxiety.
authors.affiliation: aMedical School, University of Exeter, Royal Devon and Exeter Hospital, Exeter, UK bDepartment of Psychiatry, San Francisco & San Francisco VA Medical Center, University of California, USA cDepartment of Psychiatry and Mental Health Research, Education and Research Centre, St. Vincent's University Hospital dThe UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, UCD School of Medicine and Medical Science, Dublin eSchool of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Therese M
authors.initials: TM
authors.lastname: Murphy
authors.forename: Aoife
authors.initials: A
authors.lastname: O'Donovan
authors.forename: Niamh
authors.initials: N
authors.lastname: Mullins
authors.forename: Cliona
authors.initials: C
authors.lastname: O'Farrelly
authors.forename: Amanda
authors.initials: A
authors.lastname: McCann
authors.forename: Kevin
authors.initials: K
authors.lastname: Malone
mesh_terms: D000328:Adult; D001007:Anxiety / Q000097:blood / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis / Q000097:blood / Q000235:genetics*; D008297:Male; D008347:Manifest Anxiety Scale; D063151:Polycomb Repressive Complex 2 / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D000097584:DNA Methyltransferase 3B
chemical_list: D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D000071221:Enhancer of Zeste Homolog 2 Protein; D015850:Interleukin-6; D063151:Polycomb Repressive Complex 2; D000097584:DNA Methyltransferase 3B; C000717967:DNMT3A protein, human; C508600:IL6 protein, human; C000619380:DNMT1 protein, human; C498409:EZH2 protein, human