Quitting Smoking Without Gaining Weight

Quitting Smoking Without Gaining Weight

  3:41:00 PM    Science Lover

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Smokers tend to die young, but they tend to die thinner than non-smokers. A team of scientists led by Yale School of Medicine has discovered exactly how nicotine suppresses appetite -- findings that suggest that it might be possible to develop a drug that would help smokers, and non-smokers, stay thin.

Scientists have discovered exactly how nicotine suppresses appetite -- findings that suggest that it might be possible to develop a drug that would help smokers, and non-smokers, stay thin.

Nicotine activates a small set of neurons in a section of the hypothalamus that signals the body has had enough to eat, the researchers report in the June 10 issue of the journal Science. Nicotine accomplishes this trick by activating a different set of receptors on the surface of neurons than those that trigger a craving for tobacco.

"Unfortunately, smoking does keep weight off," said Marina Picciotto, the Charles B.G. Murphy Professor of Psychiatry, professor of neurobiology and pharmacology and senior author of the paper. "Many people say they won't quit smoking because they'll gain weight. Ultimately, we would like to help people maintain their body weight when they kick the habit and perhaps help non-smokers who are struggling with obesity."

Picciotto is an expert on the function of nicotine receptors located on the surface of neurons. Nicotinic acetylcholine receptors have many functions, and in the brain are the primary targets of nicotine. Yann Mineur, an associate research scientist in her lab, was investigating a potential drug for depression that acts upon these receptors when he noticed that mice given the drug ate less than those not on the medication. With the help of researchers at Carleton University in Ottawa and the University of Hawaii, they decided to investigate why.

In a variety of experiments, the researchers found that the experimental drug activated a specific type of nicotine receptor, which in turn activated the subset of neurons in the hypothalamus, called pro-opiomelanocortin or POMC cells. The team also found that when subjected to nicotine, mice lacking the POMC pathway did not lose weight, unlike mice with the pathway intact. Intriguingly, they also showed that these receptors were of a different type than those known to trigger tobacco craving in smokers.

"This suggests it is possible to get the effect of appetite suppression without also triggering the brain's reward centers," Picciotto said. Baylor College of Medicine contributed to the study. Other Yale authors are Yan Rao, Ralph J. DiLeone, Sabrina Diano, Tamas L. Horvath and Xiao-Bing Gao.

The study was funded by the National Institutes of Health.

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Brain Cells : Not Lack of Willpower : Determine Obesity, Study Finds

Brain Cells : Not Lack of Willpower : Determine Obesity, Study Finds

  9:35:00 PM    Science Lover

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An international study has discovered the reason why some people who eat a high-fat diet remain slim, yet others pile on the weight.

The study, led in Australia by the Monash Obesity and Diabetes Institute (MODI) at Monash University, found a high-fat diet causes brain cells to become insulated from the body preventing vital signals, which tell the body to stop eating and to burn energy, from reaching the brain efficiently.

Professor Michael Cowley discovered that a high-fat 
diet caused brain cells to become insulated from the 
body, rendering the cells unable to detect signals of 
fullness to stop eating. (Credit: Image courtesy of 
Monash University)

MODI director and Australian Life Scientist of the Year Professor Michael Cowley said there were two clear outcomes from the findings.

'We discovered that a high-fat diet caused brain cells to become insulated from the body, rendering the cells unable to detect signals of fullness to stop eating," Professor Cowley said.

"Secondly, the insulation also created a further complication in that the body was unable to detect signals to increase energy use and burn off calories/kilojoules."

The research showed that support cells in the brain developed overgrowth in a high-fat diet. This prevented the regular brain cells (the melanocortin system or POMC neurons) from connecting with other neural mechanisms, which determine appetite and energy expenditure.

Professor Cowley said the study findings provide a critical link in addressing the obesity epidemic.

"These neuronal circuits regulate eating behaviours and energy expenditure and are a naturally occurring process in the brain. The circuits begin to form early in life so that people may have a tendency towards obesity even before they eat their first meal," Professor Cowley said.

Eating a high fat diet causes more "insulation" in the nerve cells, and makes it even harder for the brain to help a person lose weight.

"Obese people are not necessarily lacking willpower. Their brains do not know how full or how much fat they have stored, so the brain does not tell the body to stop refuelling. Subsequently, their body's ability to lose weight is significantly reduced."

Professor Cowley and fellow MODI researcher Dr Pablo Enriori collaborated with Research Chair and Professor of Comparative Medicine and Professor of Neurobiology Tamas Horvath and his team at the Yale School of Medicine in the United States, together with teams of scientists in Cincinnati, New Jersey, Mexico and Spain.

For a period of four months, the researchers monitored the eating and body composition of groups of mice and rats and found that those with a neural predisposition to obesity gained 30 per cent more weight compared to six per cent of the group with obesity-resistant cells.

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Monash University.

Journal Reference:
T. L. Horvath, B. Sarman, C. Garcia-Caceres, P. J. Enriori, P. Sotonyi, M. Shanabrough, E. Borok, J. Argente, J. A. Chowen, D. Perez-Tilve, P. T. Pfluger, H. S. Bronneke, B. E. Levin, S. Diano, M. A. Cowley, M. H. Tschop. Synaptic input organization of the melanocortin system predicts diet-induced hypothalamic reactive gliosis and obesity. Proceedings of the National Academy of Sciences, 2010; 107 (33): 14875 DOI: 10.1073/pnas.1004282107

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