- Silvana Teresa Tapia Paniagua
- The Conversation*
We are not alone. Just because we don’t fully see or know our invisible life partners doesn’t mean they don’t exist. They are there and, without them, our existence would be much more complicated, and even impossible.
For a few years now and thanks to the development of new technologies, what surrounds us and what lives with us, inside and outside of our organism, is being known in greater depth.
The microbiota (with r) is the term used to refer to all these microscopic beings that house in a certain place, be it a lake, our intestine or the surface of a rock.
Today, the study of the microbiota is of great relevance. Researchers wonder who its components are and what consequences their presence has where they are.
You have probably heard this concept on several occasions. It has become popular thanks to recent studies that have found relationship between its components and diseases such as Parkinson’s, depression, aging and even the way we respond to covid-19.
Among the microorganisms there are also fungi
The mycobiota (without r) refers to the analysis of the fungi that are part of the microbiota. That is, they are one more component along with bacteria, archaea, viruses and protozoa.
Traditionally, the study focused on the analysis of bacteria, which covers almost 99% of the scientific work that has been published on the microbiota.
The elimination of the “r”, or mycobiota, implies studying a less diverse and abundant group than that of bacteria. This group constitutes among the 0.1 and 1% of the total microorganisms existing in humans.
However, its properties are extraordinary. Fungi are capable of producing a wide variety of substances of interest. What’s more, contribute to myriad biological processes and interactions.
Like the rest of the components of the microbiota, these are also found in appropriate types and proportions that do not affect the health of the host, since any change that alters it could have serious consequences for the host. In balance is virtue!
Mycobiota and neurological disorders
One of the most surprising discoveries that the study of the microbiota has generated was the one that established a possible link between the intestinal microbiota and certain alterations in the nervous system. The existence of an axis between the brain and the microbiota is already a reality.
The gut microbiota is related to the brain through the vagus nerve, cytokines and metabolic products such as tryptophan, GABA and acetylcholine, which have effect on the host’s nervous system.
The axis that connects the microbiota, the intestine and the brain is in the crosshairs of many neurological diseases such as autism, Alzheimer’s or Parkinson’s. Therefore, suspecting that the mycobiota (remember, without ‘r’) may also have an important role in this type of pathology is not unreasonable.
Recent scientific studies found that the mycobiota regulated gene expression in the hippocampus. This is how it was created, again, a possible axis between mycobiota, gut and brain.
For example, the Candida kefyr fungus has been shown to improve the processes involved in autoimmune encephalomyelitis when administered to mice. However, infections with other Candida spp species have also been detected, as well as the presence of antibodies and antigens in the blood and cerebrospinal fluid of patients with multiple sclerosis.
Patients with schizophrenia, autism spectrum syndrome and Rett syndrome presented intestinal dysbiosis and less fungal diversity compared to control individuals.
Likewise, in people with depression, differences have also been found in the diversity of the mycobiota, related to changes in the populations of the genus Candida.
How do fungi get to the brain?
The main hypothesis they have developed is that some fungi, such as Candida, are capable of undergoing bacterial translocation processes, that is, can pass through the intestine into the bloodstream.
Furthermore, antibodies against C. albicans have been detected and quantified in patients with schizophrenia, indicating that this fungus had been present in some way (or still was) in these individuals. However, these were the results of a pilot study carried out with very few patients.
It is still unknown how the fungus, after reaching the bloodstream, produces these effects on the host’s nervous system. But one possibility is that Candida is capable of inducing Th17 lymphocytes, which enter the bloodstream and reach certain cells of the nervous system that are in the brain (hippocampal microglia). A) Yes could induce depressive behaviors.
Other authors suggest that the fungus Candida spp. could release toxins from the gastrointestinal tract into the bloodstream. This would reach some components of the central nervous system, which are essential in maintaining the integrity of the blood-brain barrier (a kind of protective barrier of the brain).
Along the same lines, it has also been suggested that some toxins produced by pathogenic fungi could cross the blood-brain barrier and play an important role in the mechanisms involved in the degradation of myelin, a substance that is covering part of the neurons.
Finally, the hypothesis is also proposed that simply bacterial dysbiosis, the cause or consequence of the alteration of fungal populations, directly or indirectly induces depressive behavior in patients.
Reverse connection: from brain to gut
As if that were not enough, the studies also speak of a bidirectional communication between the brain and the intestine through mediator molecules, or neuromediadores, which can have an impact on the mycobiome.
For example, GABA has been shown to increase the virulence and germ tube formation (an extension of the fungus) of Candida albicans. In contrast, serotonin would attenuate the virulence of this yeast.
This field of study is relatively recent but it already makes scientists suspect that intestinal fungi, or mycobiota, can contribute to the progression of diseases that affect the nervous system.
We are still far from knowing in depth the relevance of this group, its interaction mechanisms, communication pathways or neurotransmitters capable of influencing populations. However, these lines already open a new path that can contribute valuable knowledge for the treatment and diagnosis of this type of disease.
* Silvana Teresa Tapia Paniagua is an interim professor and researcher in the area of Microbiology at the University of Malaga. His article was published in The Conversation, whose original version you can read here.
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Eddie is an Australian news reporter with over 9 years in the industry and has published on Forbes and tech crunch.