U.S. researchers have found that over activity of a brain enzyme may play a role in preventing weight gain and obesity.
The findings were reported Friday in the journal Cell Metabolism.
To understand what drives hunger and causes metabolic disease, many scientists have focused on the hypothalamus, an almond-sized structure located deep within the brain that controls body temperature, hunger, and thirst.
Specialized nerve cells in the hypothalamus sense whether the body contains adequate amounts of nutrients and stored body fat. The cells then send out signals telling other parts of the brain to adjust food intake, metabolic rates, and physical activity accordingly -- keeping the body's caloric intake in balance with calories burned.
To learn more about these nutrient-sensing pathways and how they go awry in metabolic disorders, the research team focused on an enzyme called S6K, which plays a role in regulating the growth and proliferation of all cells, including nerve cells.
"It turns out that this enzyme, and the pathway it regulates, is nutrient sensitive -- that is, S6K activity increases in the presence of carbohydrates and protein," says the study's principalinvestigator Gary Schwartz.
"This led us to believe that S6K might not only be involved in maintaining the structure and function of individual cells, but also in regulating the energy balance of the whole body."
To test this hypothesis, the researchers injected rats with special viruses that selectively raise or lower S6K activity. The viruses were injected directly into the lower-middle, or mediobasal, portion of the hypothalamus, an area rich in nutrient-sensing nerve cells.
"When we raised the activity of the enzyme, we saw reductions in food intake, in body weight, and in production of peptides that normally stimulate feeding," says Schwartz. "When we lowered S6K activity, we saw essentially the opposite response."
Overall, the study shows that S6K acts as a kind of food-sensing thermostat in mammals, increasing or decreasing feeding behavior and metabolism to maintain a normal energy balance.
"These findings show that it may be possible to control obesity and other human metabolic disorders by developing drugs that regulate S6K activity," says Schwartz.
Source:Xinhua
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