Nicotine treatment 'could control obesity'
Scientists have identified a group of neurons in the brain responsible for smokers' lack of appetite.
In an article in the journal Science, Yale University researchers describe experiments on mice which found nicotine activates neurons to send signals the body has had enough to eat.
However they are not the same neurons which trigger a craving for tobacco.
As a result, the researchers say nicotine-based treatments could help control obesity.
A research team from Yale University School of Medicine and Baylor College of Medicine in Houston performed a combination of molecular, pharmacological, behavioural and genetic experiments on mice.
They 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 also found that these receptors were of a different type to those known to trigger tobacco craving in smokers.
Marina Picciotto, senior 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."
Prof Picciotto 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."
And it could also have an impact on other groups, she says.
"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."
Amanda Sandford, research manager for ASH, Action on Smoking and Health, said it was already known that pure nicotine could be safely used to wean smokers off their tobacco habit.
"If nicotine could also be used to tackle obesity then it could be a valuable tool in tackling two of the most critical public health problems that we face today," she said.