Supplementary Material for: Smoking and Promoter-Specific Deoxyribonucleic Acid Methylation of the Atrial Natriuretic Peptide Gene: Methylation of Smokers and Non-Smokers Differs Significantly during Withdrawal

<b><i>Background:</i></b> Atrial natriuretic peptide (ANP) is well known in psychiatric disorders to modulate hypothalamic-pituitary-adrenal axis activity. Disturbances of ANP have been described in early abstinent alcohol-dependent patients. This is the first longitudinal investigation on cytosine-phosphatidyl-guanine (CpG)-island promoter methylation of the <i>ANP</i> gene in the blood of tobacco-dependent patients. <b><i>Methods:</i></b> In a longitudinal approach, we investigated whether changes in ANP serum levels correlated to CpG methylation of the respective gene promoters on days 1, 7, and 14 of tobacco withdrawal. <b><i>Results</i></b> <b><i>and Conclusion:</i></b> Compared to non-smokers, promoter-related deoxyribonucleic acid methylation of the ANP promoter was significantly elevated on days 7 and 14 of withdrawal in tobacco-dependent patients. Baseline methylation status of the ANP promoter was not significantly different from controls, arguing for an impaired regulation during withdrawal.