How does the brain know that the stomach is full?

You don't need a new brain surgeon to know when you've eaten enough. However, a group of neuroscientists from Canada and Germany have now discovered how the stomach communicates with the central nervous system to tell us how to stop consuming more food.

The first breakthrough in this issue dates back to the 1990s, when researchers discovered leptin , a hormone secreted by the fat cells in the blood to signal the stomach is full. Until now, however, they have solved the mystery of how leptin from the blood into the brain remains a mystery to researchers.

The main meeting point between the bloodstreams in the body and the hypothalamus - the area of ​​the brain that controls appetite , is called the midlevel (ME) . Here, blood compounds come into contact with nerve cells, although the process may be risky, because blood also contains waste products and other toxic substances, potentially damaging. these neurons.

NG2-glia exists in the ME region more than anywhere else in the brain.

Fortunately, the ME region is full of a cell called NG2-glia , which helps protect nerve cells by stimulating the production of myelin sheaths that cover them. Realizing that NG2-glia existed in the ME region more than anywhere else in the brain, the researchers began to speculate that this substance plays a key role in ensuring safe contact between leptin and the neurons of the brain region under the hill.

To validate this hypothesis, the team disabled NG2-glia cells in the ME region of the mouse chemically. They found that the move immediately caused the animals to eat insatiable, doubling the weight in just one month.

In the next step, the team modified the gene so that mice lacking microglia, another type of brain cell that is also responsible for protecting nerve cells. Realizing that the move did not affect the weight or eating habits of mice, they were able to make sure that NG-glia itself, not microglia, helped neurons to receive leptin.

It's NG-glia, not microglia, that helps neurons to receive leptin.

In order to reinforce the findings, the team then used X-ray irradiation techniques (similar to radiotherapy to kill human brain tumors) to attack the rat NG2-glia. Again, this move causes mice to lose control of their diet and become obese.

According to researcher Maia Kokoeva, "people who receive radiation to prevent proliferation of cells in brain cancer tumors often become overweight". The new finding could therefore help explain this phenomenon, implying that weight gain may be due to the loss of NG2-glia radiation in the ME region.