Original Research Folic Acid Effects on S-Adenosylmethionine, S-Adenosylhomocysteine, and DNA Methylation in Patients with Intermediate Hyperhomocysteinemia Francesca Pizzolo, MD, PhD, Henk J. Blom, PhD, Sang W. Choi, MD, PhD, Domenico Girelli, MD, PhD, Patrizia Guarini, PhD, Nicola Martinelli, MD, Anna Maria Stanzial, MD, Roberto Corrocher, MD, Oliviero Olivieri, MD, and Simonetta Friso, MD, PhD Department of Medicine, University of Verona School of Medicine, Verona, ITALY (F.P., D.G., P.G., N.M., A.S., R.C., O.O., S.F.), The Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center, Amsterdam, THE NETHERLANDS (H.J.B.), Vitamins and Carcinogenesis Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts (S.W.C.) Key words: one-carbon metabolism, folic acid supplementation, DNA methylation Objective: Folic acid (FA) supplementation decreases homocysteine (tHcy) levels. However, little is known about the effects of FA treatment on DNA methylation or plasma S-adenosylmethionine (AdoMet) and S- adenosylhomocysteine (AdoHcy) concentrations. The purpose of this study was to investigate the effects of FA supplementation on AdoMet, AdoHcy, and genomic DNA methylation in hyperhomocysteinemic subjects without end-stage renal disease. Methods: To evaluate the effects of 5 mg FA/d for 8 weeks, we recruited 7 hyperhomocysteinemic MTHFR677TT patients (tHcy .30 lmol/L) with normal renal function. Results: FA supplementation induced a decrease in tHcy (from 51.1 6 21 at baseline to 26.1 6 27 lmol/L after folate supplementation; p , 0.01). A parallel increase was seen in plasma AdoMet concentrations and the AdoMet/AdoHcy ratio ( p , 0.05). However, FA supplementation had no effect on global DNA methylation levels in the present study. Conclusions: Supraphysiologic FA supplementation can modulate biochemical markers in one-carbon metabolism such as tHcy, AdoMet, and the AdoMet/AdoHcy ratio in hyperhomocysteinemic subjects. However, the reduction in homocysteinemia and the increased availability of methyl compounds provided by vitamin supplementation may not be sufficient to affect genomic DNA methylation. INTRODUCTION Folic acid (FA) plays a pivotal function in homocysteine metabolism [1,2], being the most important dietary deter- minant of plasma total homocysteine (tHcy) concentra- tions [3]. Daily supplementation with 0.5–5 mg of FA has typically been shown to lower plasma homocysteine by about 25% [4]. By lowering tHcy, FA supplementation is also expected to modify S-adenosylmethionine (AdoMet) and S-adenosylhomo- cysteine (AdoHcy), as well as the AdoMet/AdoHcy ratio, thereby potentially affecting DNA methylation status. Within the homocysteine-methionine cycle, methionine is converted to AdoMet, which serves as a methyl donor for numerous methyl acceptors, including DNA, RNA, and proteins [2]. As a result of the transfer of methyl groups, a reaction that is catalyzed by a number of methyltransferases, AdoMet is converted to AdoHcy. The AdoMet/AdoHcy ratio is an indicator of the flow of methyl groups from the universal methyl donor, AdoMet, to methyl acceptors [5], and a Address reprint requests to: Simonetta Friso, MD, PhD, University of Verona School of Medicine, Department of Medicine, Policlinico ‘‘G. B. Rossi,’’ P.le L.A. Scuro 10, 37134 Verona, ITALY. E-mail: simonetta.friso@univr.it This work has been supported by grants from the Ministry of the University and Scientific and Technological Research (O.O.), the Veneto Region Department of Health (O.O.), and Cariverona Foundation (S.F.). No potential conflicts of interest nor competing financial interests are related to this work. Journal of the American College of Nutrition, Vol. 30, No. 1, 11–18 (2011) Published by the American College of Nutrition 11