Study on effects of anti-obesity drug paves way for more effective treatments
27 October 2010
Researchers at the University of Cambridge discovered that the anti-obesity drug sibutramine reduced responses in certain regions of the brain, which are known to be important in appetite control and eating behaviour. Their findings are reported today in 'The Journal of Neuroscience'.
Professor Paul Fletcher said: "Currently, there are few drugs that effectively help patients lose weight. Developing new pharmaceuticals is expensive and risky. However, our findings suggest that we may be able to use brain imaging and psychological tests to make better predictions of which drugs are likely to work."
Using functional magnetic resonance imaging (fMRI), the researchers measured brain activity while obese volunteers viewed pictures of appetising high-calorie foods, like chocolate cake, or pictures of low-calorie foods, like broccoli. The scans were carried out after two weeks of treatment with a placebo or two weeks of sibutramine treatment.
The placebo treatment showed that simply seeing pictures of appetising foods caused greater activation of many regions of the brain that are known to be important for reward processing. The sibutramine treatment, however, reduced brain responses to the appetising foods in two regions of the volunteers' brain- the hypothalamus and the amygdala. People who had the greatest reduction of brain activation following drug treatment tended to eat less and lose more weight.
Professor Ed Bullmore, Director of the GlaxoSmithKline (GSK) Clinical Unit in Cambridge, said: "Our results help us to understand more precisely how anti-obesity drugs work in the brain to change eating behaviour and hence, ultimately assist people in losing weight.
"The most exciting aspect of these results is that they help us to see that brain and behaviour are fundamental to understanding and treating obesity. Simply because obesity involves major changes in body weight and body composition, it is easy to imagine that it is entirely 'a body problem'. These results remind us that the major cause of obesity in the West is over-eating, and this behaviour is regulated by reward and satiety processing circuits in the brain."
Sibutramine, which is manufactured by Abbott Laboratories, was licensed for treatment of obesity at the time the study was conducted, but its marketing licence has since been withdrawn due to concerns about cardiovascular risk. There were no cardiovascular or other adverse events in the course of this study.
The study was sponsored by GSK. Additional funding was provided by the Wellcome Trust, the Medical Research Council, Bernard Wolfe Health Neuroscience Fund, and the National Institute for Health Research Cambridge Biomedical Research Centre.
Image: Teenage girl eating and watching the television. Credit: Anne-Katrine Purkiss, Wellcome Images
Reference
Fletcher PC et al. Distinct modulatory effects of satiety and sibutramine on brain responses to food images in humans: a double dissociation across hypothalamus, amygdala and ventral striatum. J Neurosci 2010.