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Gene Jack WANG Brain imaging of overeating behavior and drug addiction.

Abstract :

The increasing number of obese individuals in many countries around the world adds urgency to understand the mechanisms underlying pathological overeating. Brain imaging studies in humans implicate the involvement of dopamine (DA) modulated circuits in pathological eating behaviour(s). Food cues increase striatal extracellular DA, providing evidence for the involvement of DA in the non-hedonic motivational properties of food. Food cues also increase metabolism in the orbitofrontal cortex indicating the association of this region with the motivation for food consumption. Similar to drug-addicted subjects, striatal DA D2 receptor availability is reduced in obese subjects, which may predispose obese subjects to seek food as a means to temporarily compensate for understimulated reward circuits. Decreased DA D2 receptors in the obese subjects is also associated with decreased metabolism in prefrontal regions involved in inhibitory control, which may underlie their inability to control food intake. Gastric stimulation in obese subjects activates cortical and limbic regions involved with self-control, motivation, and memory. These brain regions are also activated during drug craving in drug-addicted subjects. Obese subjects have increased metabolism in the somatosensory cortex, which suggests an enhanced sensitivity to the sensory properties of food. The reduction in DA D2 receptors in obese subjects coupled with the enhanced sensitivity to food palatability could make food their most salient reinforcer putting them at risk for compulsive eating and obesity. The studies from our laboratory provide evidence that multiple but similar brain circuits (reward, motivation, learning, inhibitory control) are disrupted in drug addiction and obesity. The results implicate the need for a multimodal approach in the treatment of obesity.

Selected publications

Wang G-J, Volkow ND, Thanos PK, Fowler JS. Brain Imaging of Dopamine: Implications for Understanding Obesity. Journal of Addiction Medicine 2009; 3(1): 8-18.    
Wang GJ, Volkow ND, Telang F, Jayne M, Ma Y, Pradhan K, Zhu W, Wong CT, Thanos PK, Geliebter A, Biegon A, Fowler JS. Evidence of gender differences in the ability to inhibit brain activation elicited by food stimulation. PNAS 2009, 106:1249-54.
Volkow ND, Wang GJ, Telang F, Fowler JS, Goldstein RZ, Alia-Klein N, Logan J, Wong C, Thanos PK, Ma Y, Pradhan K. Inverse association between BMI and prefrontal metabolic activity in healthy adults. Obesity 2009, 17:60-5.