A new study has revealed that the voices inside people's head that tells them to eat or stop eating are actually a cluster of about 10,000 specialized brain cells.
The international team of scientists has found tiny triggers inside those cells that give rise to this "voice," and keep it speaking throughout life.
The new research, done in fish and mice, can't yet be applied to humans who eat too much or too little. But it revealed how tiny bits of DNA can have a big influence on how the body regulates appetite and weight. It's the first documentation of exactly how a brain cell gene involved in weight regulation was controlled.
The team reports their discoveries on genetic factors key to the brain cells, or neurons, called POMC cells.
Located deep inside the brain, in a structure called the hypothalamus, the cluster of POMC neurons act as a control center for feelings of fullness or hunger. They take in signals from the body, and send out chemical signals to regulate appetite and eating.
When POMC neurons are absent, or not working correctly, animals and humans grow dangerously obese. Now, the new findings show in animals that the same thing happens when certain genetic triggers inside the POMC cells aren't working.
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The researchers were also able to show the importance of Islet 1 in zebrafish, which also fail to develop POMC neurons when the transcription factor was blocked early in development. Since zebrafish use different gene enhancers to regulate the reading of the Pomc gene, this shows the true importance of Islet 1 by itself.
So far, genome-wide studies of humans have not shown any relationship between obesity and changes in the Isl1 gene. Brain imaging that tracks the binding of signals to and from POMC cells could reveal further clues. And in theory, it could be possible to find drugs to increase the production of Pomc gene products, or to grow replacement cells for malfunctioning POMC cells.
The paper is published in PLoS Genetics.