Researchers at Albert Einstein College of Medicine of Yeshiva University have found that overactivity of a brain enzyme may play a role in preventing weight gain and obesity.
The findings were reported in 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, researchers at Einstein focused on an enzyme called p70 S6 Kinase 1, or 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 principal investigator, Gary J. Schwartz, Ph.D., professor of medicine and neuroscience at Einstein. "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 [small chains of amino acids] that normally stimulate feeding," says Dr. Schwartz. "When we lowered S6K activity, we saw essentially the opposite response."