Scientists Find Link Between Dopamine and Obesity
Scientists Find Link Between Dopamine and Obesity
UPTON, NY -- Dopamine, a brain chemical associated with addiction to cocaine, alcohol, and other drugs, may also play an important role in obesity. According to a study by scientists at the U.S. Department of Energy's Brookhaven National Laboratory, obese people have fewer receptors for dopamine, a neurotransmitter that helps produce feelings of satisfaction and pleasure. The findings, which will appear in the February 3, 2001 issue of The Lancet, imply that obese people may eat more to try to stimulate the dopamine "pleasure" circuits in their brains, just as addicts do by taking drugs.
"The results from this study suggest that strategies aimed at improving dopamine function might be beneficial in the treatment of obese individuals," says physician Gene-Jack Wang, the lead scientist on the study.
Brookhaven scientists have done extensive research showing that dopamine plays an important role in drug addiction. Among other things, they¹ve found that addictive drugs increase the level of dopamine in the brain, and that addicts have fewer dopamine receptors than normal subjects.
"Since eating, like the use of addictive drugs, is a highly reinforcing behavior, inducing feelings of gratification and pleasure, we suspected that obese people might have abnormalities in brain dopamine activity as well," says psychiatrist Nora Volkow, who was also involved in the study.
The lower PET scan images, labeled FDG, show glucose metabolism in the brains of obese and control (comparison) subjects. There are no differences. The upper PET scans show where the radiotracer C-11 raclopride binds to dopamine receptors. These images show that obese subjects have fewer dopamine receptors than control subjects.
To test this hypothesis, the scientists measured the number of dopamine receptors in the brains of ten severely obese individuals and ten normal controls. Their method consisted of giving each volunteer subject an injection containing a radiotracer, a radioactive chemical "tag" designed to bind to dopamine receptors in the brain. Then, the researchers scanned the subjects' brains using a positron emission tomography (PET ) camera. The PET camera picks up the radioactive signal of the tracer and shows where it is bound to dopamine receptors in the brain. The strength of the signal indicates the number of receptors.
Obese individuals, the scientists found, had fewer dopamine receptors than normal-weight subjects. And within the obese group, the number of dopamine receptors decreased as the subjects' body mass index, an indicator of obesity, increased. That is, the more obese the individual, the lower the number of receptors.
"It's possible that obese people have fewer dopamine receptors because their brains are trying to compensate for having chronically high dopamine levels, which are triggered by chronic overeating," says Wang. "However, it's also possible that these people have low numbers of dopamine receptors to begin with, making them more vulnerable to addictive behaviors including compulsive food intake."
You know, this makes alot of sense too. I've been theorizing that insulin insensitivity causes dopamine problems. For instance, insulin lowers dopamine levels. But it's also possible that low dopamine, which means less of the reward chemicals in the brain, also called reward deficiency syndrome, causes people with low dopamine to eat more, and/or do drugs and stuff. Could also be both, in a vicious cycle.
Scientists Find Link Between Dopamine and Obesity
UPTON, NY -- Dopamine, a brain chemical associated with addiction to cocaine, alcohol, and other drugs, may also play an important role in obesity. According to a study by scientists at the U.S. Department of Energy's Brookhaven National Laboratory, obese people have fewer receptors for dopamine, a neurotransmitter that helps produce feelings of satisfaction and pleasure. The findings, which will appear in the February 3, 2001 issue of The Lancet, imply that obese people may eat more to try to stimulate the dopamine "pleasure" circuits in their brains, just as addicts do by taking drugs.
"The results from this study suggest that strategies aimed at improving dopamine function might be beneficial in the treatment of obese individuals," says physician Gene-Jack Wang, the lead scientist on the study.
Brookhaven scientists have done extensive research showing that dopamine plays an important role in drug addiction. Among other things, they¹ve found that addictive drugs increase the level of dopamine in the brain, and that addicts have fewer dopamine receptors than normal subjects.
"Since eating, like the use of addictive drugs, is a highly reinforcing behavior, inducing feelings of gratification and pleasure, we suspected that obese people might have abnormalities in brain dopamine activity as well," says psychiatrist Nora Volkow, who was also involved in the study.
The lower PET scan images, labeled FDG, show glucose metabolism in the brains of obese and control (comparison) subjects. There are no differences. The upper PET scans show where the radiotracer C-11 raclopride binds to dopamine receptors. These images show that obese subjects have fewer dopamine receptors than control subjects.
To test this hypothesis, the scientists measured the number of dopamine receptors in the brains of ten severely obese individuals and ten normal controls. Their method consisted of giving each volunteer subject an injection containing a radiotracer, a radioactive chemical "tag" designed to bind to dopamine receptors in the brain. Then, the researchers scanned the subjects' brains using a positron emission tomography (PET ) camera. The PET camera picks up the radioactive signal of the tracer and shows where it is bound to dopamine receptors in the brain. The strength of the signal indicates the number of receptors.
Obese individuals, the scientists found, had fewer dopamine receptors than normal-weight subjects. And within the obese group, the number of dopamine receptors decreased as the subjects' body mass index, an indicator of obesity, increased. That is, the more obese the individual, the lower the number of receptors.
"It's possible that obese people have fewer dopamine receptors because their brains are trying to compensate for having chronically high dopamine levels, which are triggered by chronic overeating," says Wang. "However, it's also possible that these people have low numbers of dopamine receptors to begin with, making them more vulnerable to addictive behaviors including compulsive food intake."
You know, this makes alot of sense too. I've been theorizing that insulin insensitivity causes dopamine problems. For instance, insulin lowers dopamine levels. But it's also possible that low dopamine, which means less of the reward chemicals in the brain, also called reward deficiency syndrome, causes people with low dopamine to eat more, and/or do drugs and stuff. Could also be both, in a vicious cycle.
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