Many people think that sleeping little does not have important consequences, beyond the fact that it causes a feeling of fatigue that can be quite bearable for some people. Nevertheless, lack of sleep causes alterations in brain function which are not always easy to detect but are associated with serious long-term problems.
A recent study carried out at the Polytechnic University of Marche, in Italy, provides relevant information on this fact. According to the authors, little sleep can cause a substance called glia “eat” healthy neuronal connections (the so-called “synapses”), affecting neuronal connectivity and increasing the risk of developing neurological disorders such as dementia. Glia are made up of nervous system cells called glial cells that are normally responsible for making sure everything works as it should, but certain alterations seem to modify their behavior.
In order to understand the discoveries made by this research, it is necessary to be clear about the functions of glial cells in the nervous system. The study focuses specifically on the role of two of them: astrocytes and microglia.
Glial cells or neuroglia They are specialized in providing support to neurons, which are very effective in neuronal transmission but highly limited in other ways. Different types of glia provide a solid structure to neurons, accelerate synaptic connections and maintain the balance of the extracellular environment of the nervous system.
Astrocytes are a type of glia that are located in the central nervous system, that is, in the brain and spinal cord. In addition to being part of the blood-brain barrier that nourishes and protects neurons, astroglia eliminates unnecessary synapses to promote the regeneration of damaged tissues.
Microglial cells or microglia are also located in the central nervous system. They are considered part of the immune system due to their ability to phagocytose (“eat”) waste products and damaged cells, which is very important to protect the body from pathogens, infections and other threats.
The study by Bellesi and collaborators
The research team from the Polytechnic University of Marche, headed by Michele Bellesi, studied the effects of lack of sleep in mice comparing the brains of three sets of experimental subjects using three-dimensional measurement and representation techniques.
The rodents in one of the groups were able to sleep freely. Those in the second had been kept awake for 8 hours when they needed to sleep, while those in the third were deprived of sleep for a period of 5 days. This last group was intended to simulate chronic sleep deprivation.
The study focused on analyzing the differences in glial cell activity depending on the degree of sleep deprivation, particularly that of astrocytes and microglia, which Bellesi’s team and other research groups had previously linked to brain degeneration.
The researchers found that the intensity of phagocytosis increased with that of sleep deficit Thus, while astrocytes were active in 6% of the synapses of the mice that had been able to sleep, they were active in 7% in the mice with mild deprivation and in 13.5% in the lack of sleep group. chronic sleep.
On the other hand, Bellesi and his collaborators also identified an increase in the activity of microglia. This may be even more relevant than the phagocytosis carried out by astrocytes, since the excess function of microglia is related to the development of neurodegenerative diseases as we will explain later.
Previously, Bellesi’s team had found that the genes that lead astrocytes to initiate the phagocytation process are expressed more intensely under conditions of sleep deprivation. However, until now they have not been able to demonstrate a direct connection between the activity of this glial cell and lack of sleep
Studies had also been published, both with rodents and humans, suggesting a causal relationship between insufficient sleep and increased inflammation of the nervous system. The Bellesi team’s research provides the important information that this inflammation is due to an increase in the activity of microglia.
This type of glia has received a lot of attention from the scientific community due to the role of chronic inflammation in different neurodegenerative diseases, particularly Alzheimer’s and Parkinson’s. The functions of microglia they become destructive instead of regenerative when the amount of brain damage is excessive.
Implications of the findings
Briefly, the results of this study suggest that the activity of certain glial cells is intensified under conditions of sleep deprivation. These data in turn connect with the known fact that if astrocytes or microglia act excessively can cause long-term brain damage
In the case of astrocytes, Bellesi’s team found that little sleep can cause them to phagocytose portions of healthy synapses in addition to irrelevant connections and waste products. This leads to a worsening of neuronal transmission that would become more marked the longer the sleep deficit persists.
Excessive microglia activity has been linked to neurodegenerative diseases such as Alzheimer’s dementia. This seems to be due to the fact that the inflammatory responses provoked by this glial cell predispose to the development of greater damage if they are maintained for too long.
