Specific cells located in a region of the brain have been found to help control a person's appetite and weight gain. The discovery raises hope for the development of better obesity treatments.
Past studies have shown that our appetite is controlled by a molecule known as leptin, a hormone that is produced by fat cells and delivered to the brain as a signal to stop us from eating and indicate that we are full.
However, although leptin receptors were discovered in the hypothalamus -- the brain region that regulates body weight and food intake -- scientists have yet to fully understand how leptin is exactly detected.
In 2012, a team of scientists led by Dr. Maia Kokoeva began to examine which brain cells might have an influence in leptin sensing and weight gain.
Now, in a new report published in the journal Cell Metabolism, the researchers explain that the answer lies in median eminence.
These Brain Cells Are Extremely Vital
Likened to a marketplace where molecules and hormones travel in different directions between the bloodstream and the brain, the median eminence is found at the base of the hypothalamus.
Kokoeva and her colleagues, most of which are from McGill University, found that without a particular group of cells called NG2-glia cells in the median eminence, the brain's leptin receptors will never receive the signals from the body that tells it is sated.
"Most of the brain is a well-protected fortress," said Kokoeva, adding that it shelters delicate nerve cells.
However, the median eminence is separate from this protection, so the region can be a dangerous place for leptin-detecting neurons.
With that, Kokoeva said they believe that NG2-glia cells shelter and support the neurons, allowing them to instruct the body when to stop eating.
How The Median Eminence Influences Weight Gain
Unlike most neurons, NG2-glia cells constantly divide during our adult lives. This occurs most actively in the median eminence, said Tina Djogo, one of the lead study authors.
Although these cells were first described three decades ago, Djogo said it has been difficult to pinpoint their exact functions.
The research team wondered whether NG2-glia cells might play a role in detecting leptin and appetite control, so they used a drug to deactivate these cells located in the median eminence of several lab mice.
Three days after the mice received the drug, some of the "gainers" started to eat more compared with the mice control group that did not receive it. By about 30 days, the weight of some of the lab mice doubled - from 25 grams (0,.05 pound) to 50 grams (0.11 pound).
Sarah Robins, another lead author of the study, said what was most interesting was the fact that when the cells were removed from the median eminence, there was a clear increase in body weight.
In Relation To Brain Tumor Patients
The McGill researchers corroborated the role of NG2-glia cells in appetite control through experiments with genetically-altered lab mice and irradiation.
This suggests a possible explanation as to why people undergoing brain tumor treatments often become overweight, Kokoeva said. Their findings indicate that weight gain may be due to the loss of NG2-glia cells in the median eminence as an effect of radiation.
Photo: Colin Zhu | Flickr