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Underactive Dorsal Striatum May Play Role in Overeating

Compromised dopamine signaling in brain areas linked to food reward may also raise obesity risk

FRIDAY, Oct. 16 (HealthDay News) -- Obese individuals may overeat to compensate for a decreased response to food reward in the dorsal striatum, especially those individuals with genetic polymorphisms that may lower dopamine signaling in this area, according to research published in the Oct. 17 issue of Science.

Eric Stice, Ph.D., of the Oregon Research Institute in Eugene, and colleagues discuss the results of two studies. In one, 43 young women underwent functional MRI while viewing pictures of a milkshake and a glass of water, and tasting a milkshake or flavorless solution. The second study, with 33 adolescent girls, was similar, but the visual cues were geometric shapes.

In both studies, obese subjects compared to lean subjects had a lower striatal response to the milkshake, particularly in the individuals with the A1 allele of the TaqIA restriction fragment length polymorphism, the investigators found. This allele has been associated with compromised striatal dopamine signaling. In each study, the A1 allele moderated the negative relation between body mass index and activation in the left caudate nucleus when subjects drank the milkshake compared to the flavorless solution, the report indicates.

"In conclusion, the present results strongly suggest that individuals who show blunted striatal activation during food intake are at risk for obesity, particularly those at genetic risk for compromised dopamine signaling in brain regions implicated in food reward. Thus, behavioral or pharmacologic interventions that remedy striatal hypofunctioning may assist in the prevention and treatment of this pernicious health problem," the authors conclude.

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