Researchers at the Helmholtz Zentrum München have discovered a new brain sugar switch operated by support cells other than neurons and regulating sugar intake into the brain.
Prior to this, most scientists believed that the transportation of sugar into the brain – which has the highest sugar consumption of all organs and also controls hunger feelings – was a purely passive process.
The study findings, reported in the journal Cell, show that sugar intake into the brain is actually highly regulated by support cells called glial cells.
Glial cells such as astrocytes, which surround neurons, participate among other things in forming what is known as the blood-brain barrier, which selectively allows only certain substances through to the nerve cells.
Previous research had already shown that these glial cells react to lepti, an important metabolic hormone that controls satiety. The German team has now been able to prove that astrocytes can also be influenced by insulin.
This suggests that glial cells or astrocytes control the energy sources reaching neurons by regulating insulin signalling pathways and therefore could be more important adjustors of metabolism than previously suspected.
Matthias Tschöp, Director of the Helmholtz Diabetes Center (HDC), and his colleagues first thought that the process of providing the brain with sufficient sugar occurred passively since it wasn’t controlled by nerve cells.
But, when they examined the activity of insulin receptors on the surface of astrocytes, they found that if this receptor was missing on certain astrocytes the result was less activity in (proopiomelanocortin) neurons that curb food uptake and sugar intake became impaired.
Without insulin receptors, astrocytes became particularly less efficient in overseeing the transport of glucose in the area of the satiety centres located in the hypothalamus.
Advanced imaging technologies like positron emission tomography, which showed that insulin and leptin act specifically on glial cells like a sugar switch, confirmed their observations.
These findings reinforced the idea that essential metabolic and behavioural processes are not regulated by neuronal cells alone but that other cell types in the brain, such as glial cells play a crucial role.

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