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Obesity is associated with decreased μ-opioid but unaltered dopamine D2 receptor availability in the brain

Henry K Karlsson1, Lauri Tuominen2, Jetro J Tuulari3

  • 1Turku PET Centre, and lauri.nummenmaa@aalto.fi hekrka@utu.fi.

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience
|March 6, 2015
PubMed

Insights

Obese individuals have lower brain opioid receptor availability, suggesting a link to overeating similar to opioid addiction. Dopamine receptor levels did not differ significantly between obese and non-obese groups.

Area of Science:

  • Neuroscience
  • Obesity Research
  • Addiction Studies

Background:

  • Pathological overeating and obesity neurochemical pathways are not well understood.
  • Previous research indicates altered μ-opioid receptor (MOR) and dopamine D2 receptor (D2R) availability in addiction, but their role in human obesity is unclear.

Purpose of the Study:

  • To investigate the role of μ-opioid receptor (MOR) and dopamine D2 receptor (D2R) availability in the brains of morbidly obese women compared to non-obese controls.
  • To explore the association between brain receptor availability, body mass index (BMI), and eating behaviors.

Main Methods:

  • Positron Emission Tomography (PET) with selective radioligands [(11)C]carfentanil and [(11)C]raclopride was used to measure brain MOR and D2R availability in 13 morbidly obese women and 14 age-matched non-obese women.
  • Quantitative meta-analytic techniques were employed to synthesize existing evidence on D2R availability in obesity.

Main Results:

  • Morbidly obese subjects exhibited significantly lower MOR availability in reward-related brain regions (ventral striatum, insula, thalamus) compared to controls.
  • BMI negatively correlated with MOR availability in these regions.
  • Striatal MOR availability was negatively associated with self-reported food addiction and restrained eating patterns. No significant differences in D2R availability were found between groups, and meta-analysis showed modest evidence for altered D2R in obesity.

Conclusions:

  • Obesity shares neurobiological underpinnings with opioid addiction, characterized by reduced MOR availability in reward pathways.
  • Low MOR availability may drive overeating as a compensatory mechanism for reduced hedonic responses.
  • Targeting the opioid system through behavioral or pharmacological interventions could be crucial for managing obesity.
Keywords:
dopamineobesityopioidspositron emission tomographyreceptorsreward

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