Abstract 946: Effects of maternal and postweaning folic acid supplementation on gene-specific DNA methylation in the offspring

Abstract

Abstract Background: Folate is an important co-factor in the transfer of one-carbon moieties essential in DNA methylation reactions, aberrations of which have been implicated in several chronic diseases including cancer. Previous studies have demonstrated that in utero supplementation of methyl donors, including folic acid (FA), can affect DNA methylation with permanent and heritable phenotypic changes in the offspring. Recently, we observed that maternal and postweaning FA supplementation significantly decreased global DNA methylation in the liver of the offspring. We investigated the effect of maternal and postweaning FA supplementation on gene-specific methylation in the offspring. Methods: Female Sprague-Dawley rats were placed on a control diet (2 mg FA/kg diet) or supplemented (5 mg) diet for 3 weeks prior to breeding and throughout pregnancy and lactation. At weaning, pups were randomized to the control or supplemented diet until 14 weeks of age. At necropsy, plasma folate and homocysteine (Hcy; an accurate inverse indicator of tissue folate status), and liver folate concentrations of the pups were determined. Site-specific methylation of the promoter region of the Pparγ, p16 and ER and intraexonic regions of the p53 (exons 6 & 7) and Apc (exon 15) was determined in the liver at weaning and at 14 weeks of age using methylation-sensitive PCR following restriction endonuclease digestion. DNA methyltransferase (DNMT) activity in the liver was also determined at both time points. Results: At weaning and 14 weeks of age, plasma and liver folate concentrations accurately reflected dietary FA levels and were higher in the supplemented FA groups (p<0.001). Plasma Hcy was significantly lower in pups supplemented with FA (p<0.001). At weaning, maternal FA supplementation was associated with significant hypomethylation of the Pparγ, ER, p53, and Apc genes (p<0.05). At 14 weeks of age, however, maternal and postweaning FA supplementation increased methylation of the Pparγ, p53, and p16 genes (p<0.05) and postweaning FA supplementation independently increased methylation of the ER and Apc genes (p<0.05). No interactions between maternal or postweaning diets on gene-specific methylation were observed. FA supplementation also decreased DNMT activity at both time points (p<0.05). Conclusions: Our data suggest that FA supplementation during the intrauterine, perinatal and postweaning periods significantly modulates DNA methylation of critical genes with tumor suppressor or transcription regulation functions in the liver of offspring at weaning and 14 weeks of age. Given the drastically increased FA intake and blood measurements in women at childbearing age in North America, in part due to widespread FA supplementation and mandatory fortification, whether or not FA can influence cancer risk in the offspring via epigenetic mechanisms warrants further investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 946.