Glial cells control the appetite and feeding behavior. MIT neuroscientists have discovered the role of brain cells called glial cells in appetite control in a recent study. The researchers found that glial cells activation leads to overeating and the suppression of these cells, suppress appetite in mice.
The results of this study might help scientists for developing drugs against obesity and other appetite-related problems. This study is considered to be the latest one on glial cells in important brain functions. Earlier the role of glial cells was considered as supporting neurons.
“In the last few years, abnormal glial cell activities have been strongly implicated in neurodegenerative disorders. There is more and more evidence to point to the importance of glial cells in modulating neuronal function and in mediating brain disorders,” mentions Guoping Feng, the James W. and Patricia Poitras Professor of Neuroscience. Feng is also a member of MIT’s McGovern Institute for Brain Research and the Stanley Center for Psychiatric Research at the Broad Institute.
Feng and Weiping Han are the senior authors of this study; Weiping serves as head of the Laboratory of Metabolic Medicine at the Singapore Bioimaging Consortium in Singapore. Naiyan Chen,
The lead author Naiyan Chen is a postdoc at the Singapore Bioimaging Consortium and the McGovern Institute.
Role in appetite
The hypothalamus, an almond-sized structure located deep within the brain, controls appetite in addition to energy expenditure, body temperature, and circadian rhythms as well as sleep cycles. While doing studies on glial cells in other parts of the brain, Chen found that the hypothalamus also showed a lot of glial cell activity.
Chen noted that, “I was very curious at that point what glial cells would be doing in the hypothalamus, since glial cells have been shown in other brain areas to have an influence on regulation of neuronal function,”.
Scientists have recognized two major groups of neurons that control appetite, known as AgRP neurons and POMC neurons inside the hypothalamus. AgRP neurons stimulate feeding, while POMC neurons suppress appetite.
There were no techniques for silencing or stimulating these glial cells in earlier days; so it was difficult to study the role of glial cells in controlling appetite or any other brain function. Glial cells are about the half of brain cells count, they have more supporting roles like cushioning neurons and connecting neurons with one another.
A new technique developed at the University of North Carolina to study a type of glial cell known as an astrocyte, used for this study. With the help of this strategy researchers can engineer specific cells to make a surface receptor that binds to CNO, a derivative chemical compound of clozapine. Then, when CNO is given, it will activate the glial cells.
The MIT research team found that turning on astrocyte activity with only a single dose of CNO had a notable effect on feeding behavior.
“When we gave the compound that specifically activated the receptors, we saw a robust increase in feeding,” Chen describes. “Mice are not known to eat very much in the daytime, but when we gave drugs to these animals that express a particular receptor, they were eating a lot.”
The researchers also found that in a short period of three days, the mice did not gain extra weight, although they were eating more.
“This raises the possibility that glial cells may also be modulating neurons that control energy expenditures, to compensate for the increased food intake,” Chen says. “They might have multiple neuronal partners and modulate multiple energy homeostasis functions all at the same time.”
When the researchers muted the activity in astrocytes, they found that the mice ate less than normal
How astrocytes interact?
Still unknown is how the astrocytes apply their effects on neurons. As per some recent studies, glial cells can secrete chemical messengers such as glutamate and ATP; if so, these “gliotransmitters” could control neuron activity.
Another hypothesis is that instead of secreting chemicals, astrocytes exert their effects by controlling the uptake of neurotransmitters from the space surrounding neurons, thereby influencing neuron activity indirectly.
Now Feng plans to create new research tools that could facilitate scientists to learn more about astrocyte-neuron interactions and how astrocytes play their role in modulation of appetite and feeding. He also hopes to learn more about whether there are different types of astrocytes that may contribute differently to feeding behavior, especially abnormal behavior.
Feng stated that, “We really know very little about how astrocytes contribute to the modulation of appetite, eating, and metabolism. In the future, dissecting out these functional difference will be critical for our understanding of these disorders.”