Washington, Sept. 9 (Reuters): Smoking causes damage throughout the body by lowering levels of an enzyme key to physical and mental health, US researchers reported yesterday.
Smoking is known to damage the lungs, heart and arteries, but PET scans showed it affected these organs as well as the kidneys and spleen by its impact on monoamine oxidase B, the researchers said.
“When we think about smoking and the harmful effects of smoke, we usually think of the lungs and of nicotine,” Nora Volkow, director of the National Institute on Drug Abuse and a researcher on the study, said in a statement.
“But here we see a marked effect on a major body enzyme in sites far removed from the lungs that we know is due to a substance other than nicotine. This alerts us to the fact that smoking, which is highly addictive, exposes the whole body to the thousands of compounds in tobacco smoke.”
MAO-B breaks down chemicals used by nerve cells to communicate and regulate blood pressure. Reducing MAO-B levels thus keeps some of these chemicals active in the body longer than normal.
Joanna Fowler and colleagues at the Brookhaven National Laboratory in New York had earlier used PET scans to show smoking affected levels of MAO-B in the brain. PET, or positron emission tomography, uses radioactive compounds to look at cell processes inside a living animal. Special computer technology translates the signal from the compounds into a visual image. “Since smoking exposes the entire body to the tobacco compounds that inhibit MAO-B, we believed it had the potential to limit MAO-B activity throughout the body,” said Fowler.
Writing in the Proceedings of the National Academy of Sciences, the researchers said they studied 12 smokers and eight non-smokers.
They performed whole-body PET scans to measure the level of MAO-B in various organs, and found reduced activity by the enzyme in the heart, lungs, kidneys and spleen — anywhere between 33 per cent and 46 per cent lower — in the smokers.
“The consequences of these reduced MAO-B levels need to be examined in greater detail, but, at the very least, it is clear that enzyme levels in smokers’ peripheral organs are significantly impacted by their habit,” Fowler said. Specifically, MAO-B breaks down compounds that raise blood pressure. It also helps break down chemicals called tyramines found in certain foods like cheese and wine, as well as some of the chemicals released by nicotine.
It is involved in the “cheese effect” — when certain foods such as cheeses and cured meats raise blood pressure when people eat them. Some researchers believe MAO-B may be involved in the addictive properties of smoking — especially in the ability of a cigarette to make a smoker feel good.
“With the whole body exposed to the thousands of compounds in tobacco smoke, we need to be aware that these may contribute to the physiological effects of smoking,” Fowler said.