A Fuel Sensor in the Brain

According to a report in the 12 May 2006 issue of the journal Science, scientists have identified a new component of the brain system that regulates body weight. A select population of neurons in the brain's hypothalamus senses changes in the body's fuel availability and, in turn, influences appetite and metabolism.

In addition to monitoring levels of carbohydrates and fat, this circuitry also responds to amino acids, the building blocks of proteins, according to Daniela Cota and colleagues. Scientists had previously determined that, outside of the brain, the so-called “mTOR signaling pathway” integrates nutrient signals with hormonal signals to control growth and development. They had also learned that the amino acid leucine increases mTOR signaling.

In this study, when the researchers injected leucine into the brains of rodents, this activated hypothalamic mTOR signaling and decreased food intake and body weight. The authors speculate that imbalances between the fuel-sensing pathways in the brain and the rest of the body may predispose people toward obesity or diabetes. A related “Perspective” discusses the study.

Kathy Wren

12 May 2006