Transplantation of Schizophrenia via Gut Microbiome

The gut microbiome contributes to psychiatric symptoms via changes in serotonin.

Posted Oct 27, 2020

Genetic and environmental factors contribute to schizophrenia.  Science has not yet determined how these two factors interact to produce the diverse array of behavioral and neurochemical changes in the brains of these patients.  During the past few years, scientists have focused on the role of the gut microbiome as an underlying cause of some aspects of schizophrenia.

This concept is no longer considered science fiction. The bugs in your gut are known to communicate indirectly with your brain via the release of a large variety of chemicals. Your brain function, as well as your general health, is profoundly dependent upon these chemicals. Many studies have shown that a shift in the mixture of these bugs, or the chemicals they release, can make you vulnerable to certain mental and physical disorders. What’s the connection to schizophrenia?

Let’s imagine that you have inherited genes from your parents that predispose you to developing schizophrenia. A recent study suggests that those same genes influence the balance of bugs in your gut and, together, they determine some of the symptoms of your schizophrenia. I realize that this seems like a really big leap of logic—however, a few microbial bug species have already been shown to be associated with both schizophrenia and its genetically-related condition, bipolar disorder.

Your intestinal microbiome, or gut bugs, modulates many critical body systems, such as the hypothalamus-pituitary-adrenal axis, as well as the release of adrenocorticotrophic hormone and corticosterone; these systems function abnormally in schizophrenic patients. Your gut microbiome also indirectly modulates the metabolism of serotonin in the brain via their control of tryptophan in your blood. Previous studies have shown that the microbes in the feces of patients with schizophrenia actively disturb tryptophan metabolism in both the peripheral and central nervous systems. Some of these tryptophan metabolites are now thought to contribute to the learning and cognitive deficits associated with schizophrenia.

A recent study investigated whether the microbes in your gut play a role in the symptoms of schizophrenia. What they did may sound a little crazy. These scientists transplanted the fecal matter, i.e. poop, from humans diagnosed with schizophrenia into mice. The human fecal microbes quickly made themselves at home in the mouse intestines and survived for at least two weeks and then disappeared gradually. Take note, it is not easy to change your microbiome. Whatever you have read about probiotic supplements that claim to “correct” your gut microbiome is total nonsense designed to sell you a useless, and rather expensive, placebo.

The mice in this study developed many schizophrenia-like behavioral abnormalities. The authors were able to correlate many of these behavioral changes to altered tryptophan metabolism. The fecal transplant did not reproduce all of the symptoms of schizophrenia and alterations in the gut microbiome are not the sole cause of schizophrenia; however, this study provided further evidence for a functional role of the gut microbiota in the pathophysiology of schizophrenia. Similar studies may lead to effective, and safer, therapies for schizophrenia in the future.

© Gary L. Wenk, Ph.D.

References

Zhu F, et al (2020) Transplantation of microbiota from drug-free patients with schizophrenia causes schizophrenia-like abnormal behaviors and dysregulated kynurenine metabolism in mice. Molecular Psychiatry Vol 25:2905–2918, https://doi.org/10.1038/s41380-019-0475-4