The big biome news of the week was a study out of the University of Illinois at Urbana-Champaign that found a 3-way communication process between gut bacteria, cortisol (our “stress hormone”) and brain metabolites (which can greatly alter brain development).[i] The findings are early stage but may be of particular importance in that, the chemicals in the brain affected by changes in the gut bacteria are also ones found distinctly altered in autism.
“Changes in neurometabolites during infancy can have profound effects on brain development and it is possible that the microbiome – or collection of bacteria, fungi, and viruses inhabiting our gut – plays a role in this process…”
The researchers examined the feces of 1 month old piglets (which are apparently very similar to human infants in terms of brain development and the gut microbiome) and found that Bacteroides and Clostridum bacteria in the animals’ feces predicted higher levels of a metabolite called myo-inositol in the brain (and which plays a role in cell signaling), and Bacteroides and predicted a higher brain quantity of creatine, an amino acid like compound.
Another bacteria though, Butyricimonas, predicted higher levels of the amino acid, n-acetylaspartate (NAA) while Ruminococcus bacteria predicted lower levels of NAA. Previous research has shown that abnormal levels of NAA are correlated to the development of autism, and researchers have long suspected that microbiome alterations are a leading cause of the development of autism – but this was the first time that research showed that gut bacteria affected NAA levels in the brain.
The researchers went on to look at whether or not these gut bacteria could predict levels of various compounds in the blood. A blood test is a simple way of testing for autism risk, for example, as opposed to brain scans. They were shocked to find that cortisol appears to indirectly influence the relationship between Ruminoccus in gut and NAA in the brain. “This mediation finding is interesting, in that it gives us insight into one way that the gut microbiota may be communicating with the brain…”
Says one of the researchers, “Alterations in serum serotonin and cortisol, as well as fecal Bacteroides and Ruminococcus levels, have been described in ASD individuals.”[ii]
In fact, in 2015, a research study[iii] showed that in lower functioning children with autism, cortisol levels were significantly higher. And high levels of inflammation stimulate hormones from the brain’s hypothalamus which in turn stimulates the pituitary gland which in turn stimulates the release of cortisol from the adrenal glands….
It’s all a bit chicken and the egg at the moment – what comes first? Is it abnormalities in the gut microbiota or the immune system…or in the brain, which sends abnormal signals to the endocrine system or the gut or….????
I’m looking forward to finding out.