Mouse Study Reveals How Smoking Helps Keep People Thin

Findings hint at possible targets for weight-loss strategies down the line

By Amanda Gardner
HealthDay Reporter

THURSDAY, June 9 (HealthDay News) -- The notion that smoking somehow helps keep smokers thin has gotten new support from a study in mice -- and the finding might one day be parlayed into new drugs to control weight gain.

It's always a leap to extrapolate from animal experiments, one expert said, but this new research does open up interesting possibilities.

"Humans have basically the receptors as mice," noted Ursula Winzer-Serhan, an associate professor of neuroscience and experimental therapeutics at the Texas A&M Health Science Center College of Medicine in Bryan. "There is good evidence that what happens in mice also happens in humans."

Winzer-Serhan was not involved with the study, which appears in the June 10 issue of Science.

"We have to be very cautious," added study author Yann Mineur, but the basic biology, "as far as we can tell, is fairly similar to what's happening in humans."

It's well known that people who smoke tend to be skinnier, even if their lives tend to be shorter than those of nonsmokers.

"All animal studies show that nicotine reduces body weight by reducing food intake and increasing energy expenditure," said Winzer-Serhan. "That is one of the few facts in science there is not a lot of controversy about."

But the new study goes deeper than that. Mineur, an associate research scientist in psychiatry at Yale School of Medicine, stumbled upon the compound used in the study, cytisine, while looking into possible drugs for depression.

The smoking-cessation drug Chantix (varenicline) is a derivative of cytisine.

In experiments with mice, cytisine prevented weight gain by activating the same set of neurons in the hypothalamus as nicotine does. This neurological pathway is also involved in appetite and metabolism, the researchers said.

However, even though the idea of targeting nicotine receptors to control weight has been around a long time, the problem is that nicotine receptors are located all over the body, explained William Tank, chair of pharmacology and physiology at the University of Rochester Medical Center.

That means that any drug developed to control weight via nicotinic receptors would have to be very targeted, otherwise it could have effects on other parts of the body, including memory, blood pressure and heart beat, explained Winzer-Serhan.

Cytisine, which Mineur says is already used in some Eastern European countries as a smoking-cessation aid, is fairly selective, targeting receptors in the peripheral nervous system.

In the meantime, the current findings should not be used to encourage smoking as a weight-loss tool, given the habit's deadly effects.

Certain nicotine-based, smoking-cessation techniques, such as patches, could potentially limit weight gain, Mineur says, but smoking is not the way to go.

Mineur also pointed out that there are many other factors associated with post-smoking weight gain, such as munching on candy because you miss the cigarette.

"The idea of there being a therapeutic use of nicotine agonists is . . . a great idea," said Tank. "[But] this is a very complicated set of physiologies and nicotine is an extraordinarily complicated drug."

More information

For help on quitting smoking, head to the American Lung Association.

SOURCES: Yann Mineur, Ph.D., associate research scientist in psychiatry, Yale School of Medicine, New Haven, Conn.; William Tank, Ph.D., professor and chair, pharmacology and physiology, University of Rochester Medical Center; Ursula Winzer-Serhan, Ph.D., associate professor, neuroscience and experimental therapeutics, Texas A&M Health Science Center College of Medicine, Bryan; June 10, 2011, Science

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