Interest in the role of the gut microbiome in health and disease has continued to grow in recent years. Trillions of microorganisms, containing more than 2 million bacterial genes, occupy the gut, and affect many aspects of human health, potentially including brain functions, such as cognition and mood. Altered composition of the gut microbiome has also been implicated in psychiatric disorders, such as schizophrenia.
Svetlina Vasileva, a PhD student in the Eyles lab at the Queensland Brain Institute (QBI), has led a study, in collaboration with Professor Dan Siskind, the Gratten lab at the Mater Research Institute and QCMHR, to explore associations between the composition of the gut microbiome, schizophrenia and its treatment.
Ms Vasileva, you’ve spent the last few years exploring the role of the gut microbiome in individuals diagnosed with schizophrenia. Can you tell us why you decided to embark on this work?
Numerous studies have suggested there are links between the gut and the brain. We know that individuals diagnosed with schizophrenia have a high incidence of physical comorbidities, compared to the general population, including metabolic, gastrointestinal, and cardiovascular problems. Previous studies have failed to account for these comorbidities and associated lifestyle factors, and the role they play in gut microbiome composition.
We set out to address this gap in the research. And, because the gut microbiome plays a role in metabolism and human health, we investigated whether its composition was associated with treatment response and resistance in schizophrenia.
We analysed the relationship between the composition of the microbiome in three groups of people diagnosed with schizophrenia, varying in their response or lack of response to treatment, versus healthy controls, to explore the role that microbiome alterations play in the disorder.
You mention treatment-resistant schizophrenia. Could you explain what this means? Why is this distinction important for the study?
Treatment-resistant schizophrenia (TRS) refers to the persistence of symptoms despite two or more trials of antipsychotic medications. When someone is diagnosed with TRS, a trial of a medication called clozapine is recommended.
In the context of this study, differentiating between treatment-resistant versus treatment-responsive schizophrenia allowed us to account for treatment resistance as a trait that may be associated with a particular microbiome profile.
How did you carry out the study?
We collected data from 97 adults in Brisbane over a year-long period. We collected stool samples and gathered data on physical health, diet, activity, and medication use from four participant groups: individuals with treatment-responsive schizophrenia, individuals with treatment-resistant schizophrenia responding well to clozapine, individuals with treatment-resistant schizophrenia who were clozapine non-responsive, and control individuals with no history of psychiatric diagnosis.
And what did you find?
We do see differences in the gut microbiome between all groups of people with schizophrenia and control individuals, confirming findings from previous studies about a distinct gut microbiome in people with schizophrenia.
Because we gathered data on demographic and lifestyle factors such as diet, physical exercise and metabolic health, we were able to confirm that the differences in the gut microbiome were not due to these factors.
