Smoking affects DNA methylation

Shannon Loftus
Science & Tech Correspondent

According to new findings from a study published in “Circulation: Cardiovascular Genetics” by the American Heart Association, smoking leaves a footprint in the human genome through DNA methylation, a process by which cells control gene activity. These findings may now help researchers develop new therapies as well as provide a way to assess a person’s smoking history and risk factors.

DNA methylation is one way our cells can control which genes are turned on and which are turned off. Even after a person has stopped smoking, researchers found that DNA was still impacted. The genes found to be affected in a smoker have implications for the development of smoking diseases, which makes this an important finding in the development of therapies for such diseases.

Smoking remains the leading cause of preventable death throughout the world, although levels have declined steadily due to consistent findings on its negative health implications and aggressive anti-smoking campaigns. Fewer adolescents now begin the habit of smoking compared to years past, but anyone who has walked through campus probably knows that it is still present in people our age.

These findings may have important implications for those on campus who are smokers, and those who smoke would be well advised to pay attention and look at the risk factors researchers have found to be associated with smoking.
Researchers conducted an analysis of DNA methylation sites across the human genome using blood taken from nearly 16,000 people in the sample population, including those who were current smokers, former smokers and nonsmokers. Findings from the studies include more than 7,000 DNA methylation sites associated with smoking, the return of levels seen in nonsmokers within five years of quitting smoking, and some DNA methylation sites that persisted after 30 years of quitting.

The most significant sites of DNA methylation were genes that are strongly linked to the formation of smoking-related diseases.
Although the study found most methylation sites were returned to nonsmoker levels after five years of quitting, it seems that some sites continue to be affected for many more years, which researchers think can be important for former smokers to realize. Even long after quitting, former smokers may still be at an increased risk for developing smoking-related diseases, so the best way to help prevent these diseases is to simply never begin to smoke.

However, it is promising for those who already smoke that most sites do return to normal within five years, so quitting can make a big impact on your risk of developing preventable diseases, such as cardiovascular diseases, certain cancers and COPD.
This study provides researchers with much more information than before on how smoking can affect the human genome in long-lasting ways. Now that researchers have identified the most important methylation sites, the next step is to look at how these can be used as biomarkers to assess a patient’s smoking history as well as begin to develop therapies targeted at repairing these methylation sites.

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