Less sugar, more neurons: how glucose inhibits neurogenesis

Packets of biscuits, chocolate bars or bags of candy, sodas, fruit juices… Our cupboards and refrigerators are overflowing with sweet foods and drinks, and we love them. Although it is certainly an essential energy substrate for the brain, in large quantities it poses a problem. Researchers from Boston University have demonstrated that regular consumption of sugary drinks, in addition to increasing the risk of stroke, led to a reduction in the size of the hippocampus, a key brain region for learning and memory. Additionally, among the 4,000 study participants, those who drank the most soda or fruit juice performed worse on memory tests. And that’s not all: in people with a genetic risk of developing Alzheimer’s disease, the probability of developing symptoms for good increases if they consume a sweet snack daily…

For all these reasons, excess sugar seems to be accompanied by a series of negative effects on the functioning of our brain. But how is this possible, given that glucose is precisely essential for its proper functioning, and that our neurons even need more than 20% of all the glucose that we absorb, while they only represent 2% of our body mass?

​​​​​​Glucose in chaos…

Recently, a study published in the journal Nature came to shed light on this phenomenon on the scale of the functioning of brain cells. These experiments, currently carried out on mice, reveal that excess glucose hinders the production of new neurons. Normally, the brain continually produces new neurons from a special type of stem cells called neural stem cells. But as we age, this phenomenon of neurogenesis diminishes, which contributes to memory problems and the emergence of neurodegenerative diseases such as Alzheimer’s or Parkinson’s disease.

American researchers from Stanford University, under the direction of neuroscientist Tyzon Ruetz, wanted to understand why neurogenesis decreases with age. Initially, they looked for genes that might impact neurogenesis. To do this, they inactivated hundreds of genes in stem cells from aged mice using a genetic manipulation technique known as the CRISPR-Cas9 method. Surprise: when they blocked the action of a gene – called GLUT4 – the stem cells began to produce twice as many neurons. This gene allows glucose to enter cells, and scientists have observed that as they age, the gene is more and more active and brings in more and more glucose!

Which is rather good news. Because it would be enough to inactivate the GLUT4 gene to stimulate neurogenesis. A cutting-edge solution, which could only be possible in therapy in the distant future… This is why, in the meantime, another solution is temporary glucose fasting: because in their experiments, the researchers demonstrated that by withdrawing for forty- eight hours glucose from the stem cell culture medium, they began to divide and produce new neurons.

This effect remains to be confirmed in humans. But in the meantime, this does not prevent you from limiting your sugar consumption now, as a precaution: while reducing the risk of developing cardiovascular diseases, obesity or diabetes, this habit could well earn you later a small reserve of neurons very useful to prevent brain decline.