Vitamin C Prevents Offspring DNA Methylation Changes Associated with Maternal Smoking in Pregnancy.

RATIONALE: Infants whose mothers smoked during pregnancy demonstrate lifelong decreases in pulmonary function. DNA methylation changes associated with maternal smoking during pregnancy have been described in placenta and cord blood at delivery, in fetal lung, and in buccal epithelium and blood during childhood. We demonstrated in a randomized clinical trial ( ClinicalTrials.gov identifier, NCT00632476) that vitamin C supplementation to pregnant smokers can lessen the impact of maternal smoking on offspring pulmonary function and decrease the incidence of wheeze at 1 year of age. OBJECTIVES: To determine whether vitamin C supplementation reduces changes in offspring methylation in response to maternal smoking and whether methylation at specific CpGs is also associated with respiratory outcomes. METHODS: Targeted bisulfite sequencing was performed with a subset of placentas, cord blood samples, and buccal samples collected during the NCT00632476 trial followed by independent validation of selected cord blood differentially methylated regions, using bisulfite amplicon sequencing. MEASUREMENTS AND MAIN RESULTS: The majority (69.03%) of CpGs with at least 10% methylation difference between placebo and nonsmoker groups were restored (by at least 50%) toward nonsmoker levels with vitamin C treatment. A significant proportion of restored CpGs were associated with phenotypic outcome with greater enrichment among hypomethylated CpGs. CONCLUSIONS: We identified a pattern of normalization in DNA methylation by vitamin C supplementation across multiple loci. The consistency of this pattern across tissues and time suggests a systemic and persistent effect on offspring DNA methylation. Further work is necessary to determine how genome-wide changes in DNA methylation may mediate or reflect persistent effects of maternal smoking on lung function.

Vitamin C to Decrease the Effects of Smoking in Pregnancy on Infant Lung Function (VCSIP): Rationale, design, and methods of a randomized, controlled trial of vitamin C supplementation in pregnancy for the primary prevention of effects of in utero tobacco smoke exposure on infant lung function and respiratory health.

Despite strong anti-smoking efforts, at least 12% of American women cannot quit smoking when pregnant resulting in >450,000 smoke-exposed infants born yearly. Smoking during pregnancy is the largest preventable cause of childhood respiratory illness including wheezing and asthma. Recent studies have shown a protective effect of vitamin C supplementation on the lung function of offspring exposed to in utero smoke in a non-human primate model and an initial human trial. Vitamin C to Decrease the Effects of Smoking in Pregnancy on Infant Lung Function (VCSIP) is a randomized, double-blind, placebo-controlled trial to evaluate pulmonary function at 3months of age in infants delivered to pregnant smokers randomized to 500mg/day of vitamin C versus placebo during pregnancy. Secondary aims evaluate the incidence of wheezing through 12months and pulmonary function testing at 12months of age. Women are randomized between 13 and 23weeks gestation from clinical sites in Portland, Oregon at Oregon Health & Science University and PeaceHealth Southwest Medical Center and in Indianapolis, Indiana at Indiana University and Wishard Hospital. Vitamin C supplementation occurs from randomization to delivery. Monthly contact with participants and monitoring of medical records is performed to document medication adherence, changes in smoking and medical history, and adverse events. Pulmonary function testing of offspring occurs at 3 and 12months of age and incidence of wheezing and respiratory illness through 12months is captured via at least quarterly questionnaires. Ancillary studies are investigating the impact of vitamin C on placental blood flow and DNA methylation.