Researchers from the University of Warwick in England have found that specific cells in the brain can both stimulate and reduce appetite.
Tanycytes are glial cells located in the center of the brain. They are responsible for body weight and energy levels. Researchers have found that they do this by responding to amino acids in foods via the tongue's receptors that detect which amino acids are present in food as it is being eaten.
Since finding this out, scientists wondered whether tanycytes could pass this information about nutrients on to nearby neurons that regulate appetite. They also wanted to know how much energy would be spent by the activity and in the production of body heat.
Thus, researchers from Warwick set up an experiment. They first got the tanycytes to express a light-sensitive ion channel. In doing so, they were able to determine they could activate nearby neurons. Examining the neurons' identities, the researchers noticed that the tanycytes were able to switch on two different pathways known to control appetite.
While one pathway is linked to an increased urge to eat, the other is connected to a reduced urge to eat and a more significant loss in energy.
The researchers also studied how stimulation of tanycytes changes appetite. In particular, they noticed that stimulating the cells leads to a short-term increase in appetite. Opposite to what the researchers suspected, they say they are yet to understand how the cells contribute to body weight control in the longer term.
"Neuronal mechanisms controlling appetite have been studied for decades. Our discovery has added an unexpected new player into this neural circuit. Our important finding is that tanycytes have an active role in increasing appetite. In the future, these cells could become potential targets to reduce or increase food intake for therapeutic purposes." says Dr Matei Bolborea, first author of the study.