UPTON, NY -- A brain-imaging study of genetically obese rats conducted at the U.S. Department of Energy's Brookhaven National Laboratory provides more evidence that dopamine - a brain chemical associated with reward, pleasure, movement, and motivation - plays a role in obesity. The scientists found that genetically obese rats had lower levels of dopamine D2 receptors than lean rats. They also demonstrated that restricting food intake can increase the number of D2 receptors, partially attenuating a normal decline associated with aging.
"This research corroborates brain-imaging studies conducted at Brookhaven that found decreased levels of dopamine D2 receptors in obese people compared with normal-weight people," said Brookhaven neuroscientist Panayotis (Peter) Thanos, lead author of the current study, which will be published in the journal Synapse and is now available online.
It's not clear whether reduced receptor levels are a cause or consequence of obesity: Overeating may chronically reduce receptor levels, which, over the long term, could eventually contribute to obesity. But having genetically low receptor levels may also lead to obesity by predisposing the individual to overeating in an attempt to stimulate a "blunted" reward system. Either way, revving up receptor levels by restricting food intake could enhance the impact of this common strategy for combating obesity.
"Consuming fewer calories is obviously important for people trying to lose weight, plus improving the brain's ability to respond to rewards other than food may help prevent overeating," Thanos said. Because food intake can have such a dramatic effect on dopamine receptor levels, "this study also provides further evidence for the interplay of genetic factors with the environment in the development of obesity in our society," he said.
The finding that food restriction can attenuate the effects of aging on the brain's ability to respond to dopamine may also h
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DOE/Brookhaven National Laboratory