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Obesity is associated with brain’s neurotransmitters

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Researchers at Aalto University and University of Turku have revealed how obesity is associated with altered opioid neurotransmission in the brain.

New research reveals how obesity is associated with altered functioning of brain’s opioid system, which is intimately involved in generating pleasurable sensations.  Researchers found that obesity was associated with significantly lowered number of opioid receptors in the brain. However, no changes were observed in the dopamine neurotransmitter system, which regulates motivational aspects of eating.

Obesity is a great challenge to human health worldwide because it is associated with serious medical conditions such as type 2 diabetes, coronary heart disease, and stroke. Even though it is well known that unhealthy eating habits are the major cause for obesity, people have often problems with restraining their eating.  

The findings, published in The Journal of Neuroscience, highlight how obesity is associated with brain-level molecular changes. It is possible that the lack of brain’s opioid receptors predisposes the obese individuals to overeating to compensate decreased hedonic responses in this system, say professor Lauri Nummenmaa and researcher Henry Karlsson.

The findings have major implications for understanding the causes of obesity and the mechanisms involved in overeating, and provide insight into behavioral and pharmacological treatment and prevention of obesity. However, it is not yet known whether the altered brain neurochemistry is a cause or consequence of obesity.

The researchers measured availability of mu-opioid and type 2 dopamine receptors in normal-weight and obese individuals’ brains using positron emission tomography at the Turku PET Centre.

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Aalto University   press release


Henry K. Karlsson, Lauri Tuominen, Jetro J. Tuulari, Jussi Hirvonen, Riitta Parkkola, Semi Helin, Paulina Salminen, Pirjo Nuutila, Lauri Nummenmaa. Obesity Is Associated with Decreased μ-Opioid But Unaltered Dopamine D2 Receptor Availability in the Brain.  The Journal of Neuroscience, Published March 4 2015. doi: 10.1523/JNEUROSCI.4744-14.2015