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(Ivanhoe Newswire) -- A sixth sense in the brain may help explain some of the causes of obesity.
Scientists at Duke University Medical Center have discovered this sixth sense and say in mice, it can sense the calories in food.
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Researchers genetically altered mice to make them sweet-blind, meaning the animals could not detect the sweet taste. They then compared normal mice to sweet-blind ones in their preference for sugar solutions and those with the non-calorie sweetener sucralose. They found sweet-blind mice preferred calorie-containing sugar water based on the calorie content, not on their ability to taste.
When scientists analyzed the brains of the sweet-blind mice, they found the animals reward system and neurons in the food-reward region were switched on by caloric intake and did not depend on the mices ability to taste. And the levels of the brain chemical dopamine -- key in activating the reward circuitry -- increased with the intake of calories.
There was another significant discovery -- researchers found a preference for sucrose over sucralose developed only after ten minutes of a one-hour feeding session. Neurons in the reward region also had the same delay in responding.
Researchers say the findings are important in understanding what causes obesity. For example, the results suggest why high-fructose corn syrup -- a common sweetener in foods -- might contribute to the problem.
It may be that fructose produces stronger activation of the reward system and that removing high-fructose corn syrup as a sweetener will curb some desire for these products, write the authors. Regardless, the present study alone will further galvanize the scientific community to understand how higher cognitive centers in the brain control food intake and body weight regulation.
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SOURCE: Neuron, 2008;57:930-941
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