What This Means
This research suggests that the gut bacteria of people with schizophrenia may play a role in producing some of the behavioral characteristics associated with the condition. When researchers transplanted gut bacteria from schizophrenia patients into healthy mice, the mice showed behavioral changes similar to schizophrenia symptoms, including problems with short-term memory, reduced interest in social novelty, and impaired sensory filtering (prepulse inhibition). These changes were accompanied by reduced activity of a gene called Prodh in the colon, which is responsible for breaking down an amino acid called proline, and higher-than-normal levels of proline in the blood.
To investigate which specific bacteria might be responsible, the researchers identified five bacterial species that were more prevalent in the schizophrenia patient microbiome: Escherichia fergusonii, Shigella sonnei, Morganella morganii, Citrobacter freundii, and Enterococcus faecalis. When mice were given a mixture of just these five species orally, they showed the same behavioral problems, the same reduction in colonic PRODH expression, and the same elevated blood proline levels as mice that received the full microbiome transplant from schizophrenia patients.
This research suggests there may be a biological pathway connecting specific gut bacteria, reduced ability to break down proline in the intestine, elevated proline levels in the blood, and behavioral changes relevant to schizophrenia. While this work was conducted in mice and cannot be directly applied to human patients, it points to gut microbiota and proline metabolism as potentially important areas for understanding the biological basis of schizophrenia, and may inform future research into microbiome-based approaches in neuropsychiatric conditions.