Smoking Leaves Historical ‘Footprint’ in DNA

Cigarette smoke not only directly harms the pulmonary function, it also damages the DNA. Until now, researchers have primarily concentrated on changes in the sequence of the bases, the so-called mutations. Helmholtz Zentrum München is one of the participants in a large study that now shows that there are also a number of changes "on" the DNA. These epigenetic patterns can still be seen after 30 years in some cases.

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Cigarette smoke can change methylation patterns of more than 1000 genes. Source: Fotolia / Rumkugel

As a part of the study, which was published in ‘Circulation: Cardiovascular Genetics‘, numerous international scientists evaluated blood samples from just under 16,000 individuals: roughly 2,400 active smokers, 6,500 former smokers and almost 7,000 people who had never smoked. The Germans contributed data collected from 1,800 participants in the Augsburg KORA study.*

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Dr. Rui Wang-Sattler und Dr. Melanie Waldenberger, Quelle: Helmholtz Zentrum München

“By analyzing this large volume of data we were able to show that smoking leaves a type of epigenetic** fingerprint behind that can still be detected years later,” Dr. Melanie Waldenberger reports. She is a group leader in the Research Unit of Molecular Epidemiology at the Helmholtz Zentrum München and was involved in the study. According to the authors, some of these changes could even still be detected 30 years after the test subject had quit smoking. “Seen at the molecular level, this fingerprint involves methyl groups that are added to individual bases where they can influence the activity of the genes below.”

The scientists determined that this was the case for more than 1,000 genes, or about every 20th of the roughly 20,000 currently known. According to the authors, these include numerous genes that are relevant for pulmonary function and that also play a role in cancer, cardiovascular diseases and inflammation. “Some of these had already been associated with smoking, while others were new in this context,” says Prof. Annette Peters, Director of the Institute of Epidemiology. “Our hope is that it will be possible to derive disease mechanisms and consequently to create new treatments.”

The authors also have some encouraging news for those who would like to quit smoking: “Five years after smoking cessation, the majority of the methylation signals return to the levels of those who have never smoked,” says Dr. Rui Wang-Sattler, also a group leader in the Research Unit of Molecular Epidemiology.

Further information

*Key topics of the KORA studies are issues regarding the genesis and progress of chronic diseases, particularly cardiac infarction and diabetes mellitus. Risk factors from the area of health-related behaviour (such as smoking, nutrition, and physical activity), environmental factors (including air and noise pollution) and genetics are investigated for this purpose. From the point of view of care research, issues of the utilization and costs of healthcare are examined. Overall, the KORA research is intended to serve the development of new approaches in the area of chronic disease prevention and the improvement of healthcare.

** Epigenetics: In contrast to genetics, the term epigenetics refers to the inheritance of traits that are not determined in the primary sequence of the DNA (the genes). So far, RNA transcripts and chemical modifications of the chromatin (e.g. on the DNA or the histones) have been considered as carriers of this epigenetic information.

Original Publication: Joehanes, R. et al. (2016): Epigenetic Signatures of Cigarette Smoking. Circulation: Cardiovascular Genetics, doi: 10.1161/CIRCGENETICS.116.001506