Smoking 'Leaves Footprint on Our DNA'

Peter Russell

September 23, 2016

Smoking cigarettes can alter genes and may have a long-lasting effect on our DNA, according to new research.

The study in 'Circulation: Cardiovascular Genetics' could cast new light on why smoking increases the risk of so many diseases.

The US researchers investigated how tobacco use can trigger a process known as DNA methylation which has previously been linked to the development of coronary heart disease.

Turning Genes On and Off

"These results are important because methylation, as one of the mechanisms of the regulation of gene expression, affects what genes are turned on, which has implications for the development of smoking-related diseases," says co-author Dr Stephanie London from the National Institutes of Health in North Carolina. "Equally important is our finding that even after someone stops smoking, we still see the effects of smoking on their DNA."

The researchers compared blood samples from 15,907 people who were either smokers, former smokers or people who had never smoked. They found that:

Smoking-related methylation was associated with more than 7,000 genes, or one-third of known human genes

  • In former smokers, the majority of DNA methylation sites returned to levels seen in those who had never smoked within 5 years of quitting smoking

  • Some people showed signs of DNA methylation 30 years after quitting smoking.

Heart Disease and Cancers

The study also revealed that the most statistically significant methylation sites were linked to genes associated with a number of smoking-related diseases including heart disease and some cancers.

Co-author Roby Joehanes from Harvard Medical School in Boston says in a statement: "Our study has found compelling evidence that smoking has a long-lasting impact on our molecular machinery, an impact that can last more than 30 years. The encouraging news is that once you stop smoking, the majority of DNA methylation signals return to never smoker levels after 5 years, which means your body is trying to heal itself of the harmful impacts of tobacco smoking."

The researchers say their findings may contribute to future treatments that could be targeted at DNA methylation sites.

Smoking: 'Better Not to Start'

Commenting on the findings in an emailed statement, Professor Jeremy Pearson, associate medical director at the British Heart Foundation, says: "Epigenetics – the science seeking to understand how our environment affects the ways our genes are switched on and off – is an exciting new research field. Research funded by the BHF in this area is helping us to better understand how the environment affects the development of heart disease.

"This large and well performed study extends previous findings that smoking leads to modifications in DNA, by showing that while many of these changes are reversible, some are very long lasting and may affect risk of future disease even though the person has stopped smoking.

"It further emphasises the point that while giving up smoking is a very important way to reduce risk of serious disease, it is even better to not start at all."

SOURCES:

Epigenetic Signatures of Cigarette Smoking, R Joehanes et al, Circulation: Cardiovascular Genetics

Press release, American Heart Association

British Heart Foundation

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