title: The effects of long-term daily folic acid and vitamin B12 supplementation on genome-wide DNA methylation in elderly subjects.
abstract: BACKGROUND
  Folate and its synthetic form folic acid function as donor of one-carbon units and have been, together with other B-vitamins, implicated in programming of epigenetic processes such as DNA methylation during early development. To what extent regulation of DNA methylation can be altered via B-vitamins later in life, and how this relates to health and disease, is not exactly known. The aim of this study was to identify effects of long-term supplementation with folic acid and vitamin B12 on genome-wide DNA methylation in elderly subjects. This project was part of a randomized, placebo-controlled trial on effects of supplemental intake of folic acid and vitamin B12 on bone fracture incidence (B-vitamins for the PRevention Of Osteoporotic Fractures (B-PROOF) study). Participants with mildly elevated homocysteine levels, aged 65-75 years, were randomly assigned to take 400 μg folic acid and 500 μg vitamin B12 per day or a placebo during an intervention period of 2 years. DNA was isolated from buffy coats, collected before and after intervention, and genome-wide DNA methylation was determined in 87 participants (n = 44 folic acid/vitamin B12, n = 43 placebo) using the Infinium HumanMethylation450 BeadChip.
  
  
  RESULTS
  After intervention with folic acid and vitamin B12, 162 (versus 14 in the placebo group) of the 431,312 positions were differentially methylated as compared to baseline. Comparisons of the DNA methylation changes in the participants receiving folic acid and vitamin B12 versus placebo revealed one single differentially methylated position (cg19380919) with a borderline statistical significance. However, based on the analyses of differentially methylated regions (DMRs) consisting of multiple positions, we identified 6 regions that differed statistically significantly between the intervention and placebo group. Pronounced changes were found for regions in the DIRAS3, ARMC8, and NODAL genes, implicated in carcinogenesis and early embryonic development. Furthermore, serum levels of folate and vitamin B12 or plasma homocysteine were related to DNA methylation of 173, 425, and 11 regions, respectively. Interestingly, for several members of the developmental HOX genes, DNA methylation was related to serum levels of folate.
  
  
  CONCLUSIONS
  Long-term supplementation with folic acid and vitamin B12 in elderly subjects resulted in effects on DNA methylation of several genes, among which genes implicated in developmental processes.
authors.affiliation: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Dieuwertje E G
authors.initials: DE
authors.lastname: Kok
authors.affiliation: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Rosalie A M
authors.initials: RA
authors.lastname: Dhonukshe-Rutten
authors.affiliation: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Carolien
authors.initials: C
authors.lastname: Lute
authors.affiliation: Department of Clinical Chemistry, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Sandra G
authors.initials: SG
authors.lastname: Heil
authors.affiliation: Genetic Laboratory Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands ; Department of Epidemiology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: André G
authors.initials: AG
authors.lastname: Uitterlinden
authors.affiliation: Genetic Laboratory Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands ; Department of Internal Medicine, Section of Geriatrics, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Nathalie
authors.initials: N
authors.lastname: van der Velde
authors.affiliation: Genetic Laboratory Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Joyce B J
authors.initials: JB
authors.lastname: van Meurs
authors.affiliation: Department of Epidemiology and Biostatistics, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Natasja M
authors.initials: NM
authors.lastname: van Schoor
authors.affiliation: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Guido J E J
authors.initials: GJ
authors.lastname: Hooiveld
authors.affiliation: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Lisette C P G M
authors.initials: LC
authors.lastname: de Groot
authors.affiliation: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Ellen
authors.initials: E
authors.lastname: Kampman
authors.affiliation: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Wilma T
authors.initials: WT
authors.lastname: Steegenga
keywords: B-vitamins; Cancer; DNA methylation; Development; Elderly; Epigenetics; Folic acid; Infinium 450k BeadChip; Intervention trial; One-carbon metabolism; Vitamin B12