Cigarette smoking and heavy alcohol use cause epigenetic changes to DNA that reflect accelerated biological aging in distinct, measurable ways, according to research presented on Thursday, October 8, at the American Society of Human Genetics (ASHG) 2015 Annual Meeting n Baltimore, Maryland. Using data from the publicly available Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/), Robert A. Philibert, M.D., Ph.D., and colleagues at the University of Iowa, and other institutions, analyzed patterns of DNA methylation, a molecular modification to DNA that affects when and how strongly a gene is expressed. Prior research had shown that methylation patterns change in predictable ways as people age, as well as in response to environmental exposures, such as cigarette smoke and alcohol. In these earlier studies, Dr. Philibert’s laboratory identified two specific locations in the genome, base pairs cg05575921 on the AHRR gene and cg23193759 on chromosome 10, at which methylation levels were highly associated with smoking and alcohol consumption, respectively. In fact, they showed, DNA methylation levels at these two locations were a better measure of substance use than people’s self-reported estimates. Thus, in this follow-up study, described at the ASHG meeting in a presentation delivered by Meeshanthini Dogan (photo), M.S.,on Thursday, October 8, Ms. Dogan and Dr. Philibert used methylation levels as a proxy for tobacco and alcohol consumption. They estimated each person’s biological age using a previously validated epigenetic “clock” based on methylation levels at 71 locations in the genome, as measured by the widely used Infinium HumanMethylation450 BeadChip Kit from Illumina (http://www.illumina.com/products/methylation_450_beadchip_kits.html).
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