title: DNA methylation and body-mass index: a genome-wide analysis.
abstract: BACKGROUND
  Obesity is a major health problem that is determined by interactions between lifestyle and environmental and genetic factors. Although associations between several genetic variants and body-mass index (BMI) have been identified, little is known about epigenetic changes related to BMI. We undertook a genome-wide analysis of methylation at CpG sites in relation to BMI.
  
  
  METHODS
  479 individuals of European origin recruited by the Cardiogenics Consortium formed our discovery cohort. We typed their whole-blood DNA with the Infinium HumanMethylation450 array. After quality control, methylation levels were tested for association with BMI. Methylation sites showing an association with BMI at a false discovery rate q value of 0·05 or less were taken forward for replication in a cohort of 339 unrelated white patients of northern European origin from the MARTHA cohort. Sites that remained significant in this primary replication cohort were tested in a second replication cohort of 1789 white patients of European origin from the KORA cohort. We examined whether methylation levels at identified sites also showed an association with BMI in DNA from adipose tissue (n=635) and skin (n=395) obtained from white female individuals participating in the MuTHER study. Finally, we examined the association of methylation at BMI-associated sites with genetic variants and with gene expression.
  
  
  RESULTS
  20 individuals from the discovery cohort were excluded from analyses after quality-control checks, leaving 459 participants. After adjustment for covariates, we identified an association (q value ≤0·05) between methylation at five probes across three different genes and BMI. The associations with three of these probes--cg22891070, cg27146050, and cg16672562, all of which are in intron 1 of HIF3A--were confirmed in both the primary and second replication cohorts. For every 0·1 increase in methylation β value at cg22891070, BMI was 3·6% (95% CI 2·4-4·9) higher in the discovery cohort, 2·7% (1·2-4·2) higher in the primary replication cohort, and 0·8% (0·2-1·4) higher in the second replication cohort. For the MuTHER cohort, methylation at cg22891070 was associated with BMI in adipose tissue (p=1·72 × 10(-5)) but not in skin (p=0·882). We observed a significant inverse correlation (p=0·005) between methylation at cg22891070 and expression of one HIF3A gene-expression probe in adipose tissue. Two single nucleotide polymorphisms--rs8102595 and rs3826795--had independent associations with methylation at cg22891070 in all cohorts. However, these single nucleotide polymorphisms were not significantly associated with BMI.
  
  
  CONCLUSIONS
  Increased BMI in adults of European origin is associated with increased methylation at the HIF3A locus in blood cells and in adipose tissue. Our findings suggest that perturbation of hypoxia inducible transcription factor pathways could have an important role in the response to increased weight in people.
  
  
  BACKGROUND
  The European Commission, National Institute for Health Research, British Heart Foundation, and Wellcome Trust.
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester, UK.
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Dick
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester, UK.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Nelson
authors.affiliation: Human Genetics, Wellcome Trust Sanger Institute, Hinxton, UK; ISPAR Institute, University of Bedforshire, Bedford, UK.
authors.forename: Loukia
authors.initials: L
authors.lastname: Tsaprouni
authors.affiliation: Human Genetics, Wellcome Trust Sanger Institute, Hinxton, UK; Department of Medical Sciences, Molecular Medicine and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Johanna K
authors.initials: JK
authors.lastname: Sandling
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1166, F-75013, Paris, France; INSERM, UMR_S 1166, F-75013, Paris, France; ICAN Institute for Cardiometabolism And Nutrition, F-75013, Paris, France.
authors.forename: Dylan
authors.initials: D
authors.lastname: Aïssi
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany; Research Unit of Molecular Epidemiology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany; Institute of Epidemiology II, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Wahl
authors.affiliation: Human Genetics, Wellcome Trust Sanger Institute, Hinxton, UK.
authors.forename: Eshwar
authors.initials: E
authors.lastname: Meduri
authors.affiliation: INSERM, UMR_S 1062, Aix-Marseille University, Marseille, France.
authors.forename: Pierre-Emmanuel
authors.initials: PE
authors.lastname: Morange
authors.affiliation: Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
authors.forename: France
authors.initials: F
authors.lastname: Gagnon
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany; Research Unit of Molecular Epidemiology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany; Institute of Epidemiology II, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Grallert
authors.affiliation: Research Unit of Molecular Epidemiology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany; Institute of Epidemiology II, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Waldenberger
authors.affiliation: Research Unit of Molecular Epidemiology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany; Institute of Epidemiology II, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany; German Centre for Cardiovascular Research, Munich Heart Alliance, Munich, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
authors.affiliation: Institut für Integrative und Experimentelle Genomik, Universität zu Lübeck, Lübeck, Germany; German Centre for Cardiovascular Research, Hamburg/Kiel/Lübeck, Germany.
authors.forename: Jeanette
authors.initials: J
authors.lastname: Erdmann
authors.affiliation: German Centre for Cardiovascular Research, Munich Heart Alliance, Munich, Germany; Deutsches Herzzentrum München, Technische Universität München, Munich, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Hengstenberg
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1166, F-75013, Paris, France; INSERM, UMR_S 1166, F-75013, Paris, France; ICAN Institute for Cardiometabolism And Nutrition, F-75013, Paris, France.
authors.forename: Francois
authors.initials: F
authors.lastname: Cambien
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester, UK.
authors.forename: Alison H
authors.initials: AH
authors.lastname: Goodall
authors.affiliation: Human Genetics, Wellcome Trust Sanger Institute, Hinxton, UK; Department of Haematology, University of Cambridge, Cambridge, UK; National Health Service Blood and Transplant, Cambridge, UK.
authors.forename: Willem H
authors.initials: WH
authors.lastname: Ouwehand
authors.affiliation: German Centre for Cardiovascular Research, Munich Heart Alliance, Munich, Germany; Deutsches Herzzentrum München, Technische Universität München, Munich, Germany.
authors.forename: Heribert
authors.initials: H
authors.lastname: Schunkert
authors.affiliation: Department of Health Sciences, University of Leicester, Leicester, UK.
authors.forename: John R
authors.initials: JR
authors.lastname: Thompson
authors.affiliation: Department of Twin Research and Genetic Epidemiology, King's College London, London, UK.
authors.forename: Tim D
authors.initials: TD
authors.lastname: Spector
authors.affiliation: Institute of Genetic Epidemiology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Gieger
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1166, F-75013, Paris, France; INSERM, UMR_S 1166, F-75013, Paris, France; ICAN Institute for Cardiometabolism And Nutrition, F-75013, Paris, France.
authors.forename: David-Alexandre
authors.initials: DA
authors.lastname: Trégouët
authors.affiliation: Human Genetics, Wellcome Trust Sanger Institute, Hinxton, UK; William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK; Princess Al-Jawhara Al-Brahim Centre of Excellence in Research of Hereditary Disorders, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Panos
authors.initials: P
authors.lastname: Deloukas
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester, UK. Electronic address: njs@le.ac.uk.
authors.forename: Nilesh J
authors.initials: NJ
authors.lastname: Samani
mesh_terms: D051017:Apoptosis Regulatory Proteins; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D015992:Body Mass Index; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics; D002888:Chromosomes, Human, Pair 19 / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D005260:Female; D055106:Genome-Wide Association Study; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012097:Repressor Proteins
chemical_list: D051017:Apoptosis Regulatory Proteins; D051792:Basic Helix-Loop-Helix Proteins; D012097:Repressor Proteins; C116973:HIF3A protein, human