Those with schizophrenia have completely different intestinal bacteria
It’s a connection between what’s going on in billions of bacteria in the gut and what’s going on in the brain, and research these days is working to map this out.
The bacterial composition of the intestine can have an effect on mental health. Now a Danish study sharpens the suspicion that it is called the intestinal microbiome may be associated with mental illness.
The new study examines the bacterium in the gut in people with schizophrenia and the researchers find that they are quite different than in healthy controls.
The intestinal microbiome is less diverse, but at the same time contains some types of bacteria that are rarely found in healthy people.
The researchers behind the studies also find indications for a continuous disorder in the intestinal microbiome and the patient’s cognitive functions, it will be a process in the brain that has to do with, among other things, learning, memory, overview, mental pace and problem solving.
The study, published in the journal Biological Psychiatry Global Open Science, has been conducted over 10 years.
The work has taken place under the direction of Professor Oluf Borbye Pedersen at the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen.
– One third of the approximately 600 different bacterial species we have studied differ in patients with schizophrenia, and it is first and foremost the lack of health-promoting intestinal bacteria that is striking. It is a reduced quantity and a reduced diversity, says Pedersen.
– It is especially the intestinal bacteria’s ability to form health-promoting substances such as butyric acid and neurotransmitters that is different.
Smsyre protects, among other things, against inflammation in the brain, and neurotrans are signal substances that have been identified for the brain’s functions, including communication, memory and processing of sensory impressions. Seven of the known neurotransmitters, including glutamate, dopamine and serotonin, are formed by bacteria in the gut.
– We can not say whether the reduced ability to form neurotransmitters is related to the mental illness, but we have some hypotheses that intestinal bacteria are probably involved in regulating the signals that are sent from the intestine to the brain. So when there are imbalances in the intestinal bacteria, it is possible that it contributes to mental disorders, Pedersen says.
He emphasizes that studying is an observational study which can therefore not be certain about causal relationships. The communication between brain and intestine goes both ways, he points out.
The same is pointed out by Peter Leutscher, clinical professor at Aalborg University:
– You must always ask yourself if it is the hen or the egg that has come first. Is it the bacteria in the gut that causes the patient to develop schizophrenia, or is it diet or help for patients with schizophrenia that changes the bacterial composition?
However, Leutscher believes that this is something that is being researched a lot.
He himself has researched the connection between intestinal bacteria and mental health. The new studies, he says, go even deeper.
– It is a fantastic study shows that people with schizophrenia have a completely different bacterial composition, he says.
This is what the researchers have done
The study is a case-control study. That is, one has compared a patient group with different control groups to look at similarities and differences.
The patient group consists of 132 people who have been recruited from the Psychiatric Center Copenhagen and the Research Unit for Psychosis at Aarhus University. All had been diagnosed with schizophrenia.
With advanced DNA technology and supercomputer power, patients’ gut bacteria have been mapped and compared with gut bacteria from control groups:
- One control group consisted of 132 healthy individuals
- The other consisted of 132 people suffering from metabolic syndrome
The metabolic syndrome is a condition which, among other things, affects the body’s ability to metabolize nutrients. People who have metabolic syndrome are often overweight, have increased blood pressure and blood sugar and a reduced sensitivity to insulin, explains Oluf Borbye Pedersen.
Many people who suffer from schizophrenia also suffer from metabolic syndrome. It is not known why, but it may be due to side effects from medications, such as increased appetite and lethargy.
By combining a control group with people who have the metabolic syndrome, but not schizophrenia, the researchers were able to filter the effect of the metabolic syndrome. When they did, they saw massive changes in the intestinal microbiome in the patient group with schizophrenia.
The researchers behind the studies have also developed and advanced mathematical model to filter out the effect of drugs, and they have conducted some very precise assessments of the patient’s mental skills using cognitive tests.
Bacteria have a «contributing meaning»
In the group of people with schizophrenia, the researchers find, among other things, disturbances in the intestinal bacteria’s ability to form various neurotransmitters, and they show that the amino acid tyrosine, which is a precursor to the neurotransmitter dopamine, is directly linked to the patient’s mental skills.
Exactly how this is connected, we do not know, Peter Leutscher explains. Some may be predisposed to schizophrenia, and then there are some changes in the intestinal microbiome that cause it to break out later in life.
– We have not found evidence that this is the cause, but the bacterium has a contributing effect on how the patient feels, among other things when it comes to cognition and probably also other important mental functions, he says.
Sources:
Alteration of intestinal microbiome in patients with schizophrenia indicates links between bacterial tyrosine biosynthesis and cognitive dysfunction, Biological Psychiatry Global Open Science (2022). DOI: 10.1016 / j.bpsgos.2022.01.009.