`Nicotine-based treatment may control obesity`

London: Scientists have identified some brain neurons responsible for the lack of appetite in smokers, a finding they say could lead to nicotine-based treatments to combat obesity.

In experiments on mice, researchers at Yale University School of Medicine in Houston found that nicotine activates some neurons to send signals the body has had enough to eat.

However, they found that those neurons are not the same neurons that trigger a craving for tobacco, meaning nicotine-based treatments could help control obesity, the BBC reported.

After doing a series of molecular, pharmacological, behavioural and genetic experiments on mice, the researchers found that nicotine influences a collection of central nervous system circuits, known as the body`s hypothalamic melanocortin system, by activating certain receptors.

These receptors, in turn, increase the activity of pro-opiomelanocortin (POMC) neurons, known for their effects on obesity in humans and animals.

When subjected to nicotine, mice lacking the POMC pathway did not lose weight, but mice with the pathway did.

The researchers, who detailed their findings in the journal Science, also found that these receptors were of a different type to those known to trigger tobacco craving in smokers.

Marina Picciotto, study researcher and professor of psychiatry at Yale University, said the research could be beneficial.

"Imagine a nicotine-based medicine which could only target those cells which stop eating and not trigger the need for tobacco," she said.

"This suggests it is possible to get the effect of appetite suppression without also triggering the brain`s reward centres," she added.

Prof Picciotto, however, cautioned that the impact of a nicotine-based medication would be limited because smokers who are leaner when they give up smoking only gain 2.5 kilos of weight on average.

Clinical trials in humans would also be necessary to explore the side effects on blood pressure.

She said: "It could perhaps motivate smokers who are afraid to quit because of fears of putting on weight."

"There are some groups of people who take up smoking to control their weight. It is tragic to think people would take up smoking for this reason."