Study Finds Genetic Factor in Vulnerability to Nicotine
A new study has found that a person’s vulnerability to nicotine addiction appears to have a genetic basis. Researchers from the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch, Germany, have shown that a region in the midbrain called the habenula plays an important role in this process.
Tobacco use kills more than 5 million people each year worldwide, according to the World Health Organization, and many of them die from lung cancer. Lead author Dr. Inés Ibañez-Tallon said that two years ago, studies indicated that genetic variations in a specific gene cluster are risk factors for nicotine dependence and lung cancer.
Dr. Ibañez-Tallon and her team, collaborating with researchers from the Pasteur Institute in Paris, France and the Russian Academy of Sciences in Moscow, examined a receptor for the neurotransmitter acetylcholine, which is activated by nicotine and encoded by a specific gene cluster. Dr. Ibañez-Tallon said that although this gene cluster is present in the DNA of every cell, the receptor is only expressed in a few places in the brain, one of which is the habenula.
The researchers from MDC examined this receptor in egg cells of the African clawed frog and in transgenic mice. Dr. Ibañez-Tallon said that a large percentage of heavy smokers carry a mutation in this gene, and thus have an increased risk of becoming addicted to nicotine and developing lung cancer than those without the mutation.
The MDC researchers showed that transgenic mice expressing high levels of beta4, a gene in the cluster that encodes the receptor, were more sensitive to nicotine than mice with lower levels of the gene, and had a strong aversion to drinking water that contained nicotine. This could help explain why some people have a higher aversion to nicotine than others.
However, when the researchers expressed the mutated variant of the alpha5 gene, another gene in the cluster, the mice began showing a preference for nicotine after only two weeks.
Dr. Ibañez-Tallon and colleagues conclude that balanced activity of these two genes can reduce nicotine use.
Source: Science Daily, Vulnerability to Nicotine Addiction Appears to Have a Genetic Basis, Study Suggests, May 13, 2011
