title: Tobacco smoking is associated with DNA methylation of diabetes susceptibility genes.
abstract: OBJECTIVE
  Tobacco smoking, a risk factor for diabetes, is an established modifier of DNA methylation. We hypothesised that tobacco smoking modifies DNA methylation of genes previously identified for diabetes.
  
  
  METHODS
  We annotated CpG sites available on the Illumina Human Methylation 450K array to diabetes genes previously identified by genome-wide association studies (GWAS), and investigated them for an association with smoking by comparing current to never smokers. The discovery study consisted of 630 individuals (Bonferroni-corrected p = 1.4 × 10(-5)), and we sought replication in an independent sample of 674 individuals. The replicated sites were tested for association with nearby genetic variants and gene expression and fasting glucose and insulin levels.
  
  
  RESULTS
  We annotated 3,620 CpG sites to the genes identified in the GWAS on type 2 diabetes. Comparing current smokers to never smokers, we found 12 differentially methylated CpG sites, of which five replicated: cg23161492 within ANPEP (p = 1.3 × 10(-12)); cg26963277 (p = 1.2 × 10(-9)), cg01744331 (p = 8.0 × 10(-6)) and cg16556677 (p = 1.2 × 10(-5)) within KCNQ1 and cg03450842 (p = 3.1 × 10(-8)) within ZMIZ1. The effect of smoking on DNA methylation at the replicated CpG sites attenuated after smoking cessation. Increased DNA methylation at cg23161492 was associated with decreased gene expression levels of ANPEP (p = 8.9 × 10(-5)). rs231356-T, which was associated with hypomethylation of cg26963277 (KCNQ1), was associated with a higher odds of diabetes (OR 1.06, p = 1.3 × 10(-5)). Additionally, hypomethylation of cg26963277 was associated with lower fasting insulin levels (p = 0.04).
  
  
  CONCLUSIONS
  Tobacco smoking is associated with differential DNA methylation of the diabetes risk genes ANPEP, KCNQ1 and ZMIZ1. Our study highlights potential biological mechanisms connecting tobacco smoking to excess risk of type 2 diabetes.
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, P. O. Box 2040, 3000 CA, Rotterdam, the Netherlands.
authors.forename: Symen
authors.initials: S
authors.lastname: Ligthart
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, P. O. Box 2040, 3000 CA, Rotterdam, the Netherlands.
authors.forename: Rebecca V
authors.initials: RV
authors.lastname: Steenaard
authors.affiliation: Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, the Netherlands.|The Netherlands Genomics Initiative-sponsored Netherlands Consortium for Healthy Aging (NGI-NCHA), Leiden/ Rotterdam, the Netherlands.
authors.forename: Marjolein J
authors.initials: MJ
authors.lastname: Peters
authors.affiliation: Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, the Netherlands.|The Netherlands Genomics Initiative-sponsored Netherlands Consortium for Healthy Aging (NGI-NCHA), Leiden/ Rotterdam, the Netherlands.
authors.forename: Joyce B J
authors.initials: JB
authors.lastname: van Meurs
authors.affiliation: Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, the Netherlands.
authors.forename: Eric J G
authors.initials: EJ
authors.lastname: Sijbrands
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, P. O. Box 2040, 3000 CA, Rotterdam, the Netherlands.|Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, the Netherlands.|The Netherlands Genomics Initiative-sponsored Netherlands Consortium for Healthy Aging (NGI-NCHA), Leiden/ Rotterdam, the Netherlands.
authors.forename: André G
authors.initials: AG
authors.lastname: Uitterlinden
authors.affiliation: Department of Genetics, University of Groningen, University Medical Centre Groningen, Groningen, the Netherlands.
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Bonder
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, P. O. Box 2040, 3000 CA, Rotterdam, the Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, P. O. Box 2040, 3000 CA, Rotterdam, the Netherlands.
authors.forename: Oscar H
authors.initials: OH
authors.lastname: Franco
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, P. O. Box 2040, 3000 CA, Rotterdam, the Netherlands. a.dehghan@erasmusmc.nl.|The Netherlands Genomics Initiative-sponsored Netherlands Consortium for Healthy Aging (NGI-NCHA), Leiden/ Rotterdam, the Netherlands. a.dehghan@erasmusmc.nl.
authors.forename: Abbas
authors.initials: A
authors.lastname: Dehghan
mesh_terms: D000368:Aged; D019175:DNA Methylation / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D005260:Female; D055106:Genome-Wide Association Study; D006801:Humans; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000009:adverse effects*
keywords: DNA methylation; Gene expression; Tobacco smoking; Type 2 diabetes
references.citation: Hum Mol Genet. 2013 Mar 1;22(5):843-51
references.pmid: 23175441
references.citation: Epigenetics. 2013 Aug;8(8):802-6
references.pmid: 23811543
references.citation: Diabetes. 2015 Apr;64(4):1484-91
references.pmid: 25392243
references.citation: Acta Pharmacol Sin. 2009 Jun;30(6):784-7
references.pmid: 19434055
references.citation: BMC Genomics. 2013;14:293
references.pmid: 23631413
references.citation: Trends Mol Med. 2008 Aug;14(8):361-71
references.pmid: 18603472
references.citation: Bioinformatics. 2014 Dec 1;30(23):3435-7
references.pmid: 25147358
references.citation: Epigenetics. 2011 Jun;6(6):692-702
references.pmid: 21593595
references.citation: PLoS Genet. 2014 Mar;10(3):e1004160
references.pmid: 24603685
references.citation: PLoS One. 2012;7(12):e50938
references.pmid: 23236413
references.citation: Hum Mol Genet. 2014 Mar 1;23(5):1186-201
references.pmid: 24163245
references.citation: Nat Genet. 2010 Jul;42(7):579-89
references.pmid: 20581827
references.citation: Am J Hum Genet. 2013 Nov 7;93(5):876-90
references.pmid: 24183450
references.citation: Am J Hum Genet. 2011 Apr 8;88(4):450-7
references.pmid: 21457905
references.citation: Curr Diab Rep. 2014;14(11):551
references.pmid: 25344220
references.citation: Epigenetics. 2014 Oct;9(10):1382-96
references.pmid: 25424692
references.citation: BMC Bioinformatics. 2012;13:86
references.pmid: 22568884
references.citation: Lancet. 2014 Jun 7;383(9933):1990-8
references.pmid: 24630777
references.citation: Diabetes. 2014 Sep;63(9):2962-76
references.pmid: 24812430
references.citation: PLoS One. 2013;8(5):e63812
references.pmid: 23691101
references.citation: Nat Genet. 2008 May;40(5):638-45
references.pmid: 18372903
references.citation: Clin Epigenetics. 2015 May 14;7:54
references.pmid: 26015811
references.citation: Epigenetics. 2011 May;6(5):623-9
references.pmid: 21739720
references.citation: Epigenetics. 2013 Feb;8(2):203-9
references.pmid: 23314698
references.citation: Hum Mol Genet. 2014 May 1;23(9):2290-7
references.pmid: 24334605
references.citation: Nat Genet. 2012 Sep;44(9):981-90
references.pmid: 22885922
references.citation: JAMA. 2007 Dec 12;298(22):2654-64
references.pmid: 18073361
references.citation: Epigenetics. 2013 Aug;8(8):816-26
references.pmid: 23903776
references.citation: Nat Genet. 2013 Oct;45(10):1238-43
references.pmid: 24013639
references.citation: Eur J Epidemiol. 2015 Aug;30(8):661-708
references.pmid: 26386597
references.citation: Nat Rev Genet. 2012 Jul;13(7):484-92
references.pmid: 22641018