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Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder
Thesis (PhD)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614076758130688 |
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| access_status_str | Open Access |
| author | Rust, Catharina Magdalena |
| author2 | Hemmings, Sian |
| author_browse | Hemmings, Sian Rust, Catharina Magdalena |
| author_facet | Hemmings, Sian Rust, Catharina Magdalena |
| author_sort | Rust, Catharina Magdalena |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134381 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:46:16.958Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134381 Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder Rust, Catharina Magdalena Hemmings, Sian Pretorius, Etheresia Seedat, Soraya Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Psychiatry. Thesis (PhD)--Stellenbosch University, 2025. Rust, C. M. 2025. Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder. Unpublished doctoral thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/d1e6a353-7f54-438a-8516-23589b88303a Differences in the gut microbiome have been implicated in various neuropsychiatric disorders, including Parkinson’s disease (PD), schizophrenia (SCZ), and posttraumatic stress disorder (PTSD). These differences in gut microbial diversity and composition are associated with, but not limited to, increased intestinal permeability, inflammation, and pro-inflammatory cytokine levels that may contribute to disease aetiology. In recent years, the possibility of a blood microbiome, though controversial, and possible association with disease aetiology have been suggested by microbial signatures found in blood samples. The overarching aim of this study was to investigate the gut and blood microbiomes in PD, SCZ, and PTSD. Additionally, we explored correlations between cytokine concentrations and the relative abundance of gut microbial taxa and examined associations between the gut microbiome and depression severity based on the Hamilton Depression Rating Scale (HAM-D). We observed significant beta-diversity differences in the gut microbiome of individuals with PD, with alterations in several taxa such as butyrate-producing bacteria (e.g. Faecalibacterium, Roseburia) and an increase in mucin-degrading bacteria (e.g. Akkermansia). These findings are consistent with previous research highlighting a reduction in butyrate-producing bacteria and an increase in mucin-degrading bacteria. Conversely, no significant associations with alpha-diversity or beta-diversity were found in the gut microbiomes of SCZ and PTSD cohorts. These results highlight that the role of the gut microbiome in neuropsychiatric disorders is complex and suggest that environmental factors, sample size, and study design may influence outcomes. Cytokine analysis revealed a correlation between the increased relative abundance of Lactobacillus and decreased relative abundance of Coprococcus with IL-6 levels in our PD cohort. Faecalibacterium was further correlated with the concentration levels of IL-6 in PD, SCZ, and PTSD, although this observation did not survive the correction for multiple testing. Further, depression severity, as assessed by the HAM-D total score, was significantly associated with overall gut microbial community shifts (beta-diversity), with preliminary associations involving taxa such as Lachnospiraceae and Rikenellaceae. However, these associations did not withstand correction for multiple testing. In the blood microbiome of individuals with PD, we observed an enriched abundance of Acinetobacter wuhouensis and a depleted abundance of Pseudomonas aeruginosa compared to controls. SCZ was associated with an increased abundance of Salmonella enterica and a decreased abundance of several other taxa, including Staphylococcus aureus and Pseudomonas spp. No significant abundance differences were observed in individuals with PTSD compared to controls. Interestingly, eight taxa were present in both the gut and blood microbiomes, including Clostridium and Lactobacillus. However, the abundance of these taxa was not significantly different between cases and controls in the blood microbiome, nor was the abundance of these taxa correlated between the gut and blood microbiomes. Based on the functions of the taxa with relative abundance differences, our results suggest a possible association between inflammation, SCFA production, and intestinal permeability in PD, SCZ, and PTSD. The lack of clear associations between the gut and blood microbiomes underscores the complexity of these relationships and the need for future investigations including other microbiome niches, intestinal permeability markers, and SCFA concentrations. Limitations of this study include the use of 16S rRNA (V4) gene sequencing, which limits species-level resolution, and the absence of longitudinal data. In conclusion, while this study suggests potential associations between gut microbiome alterations and neuropsychiatric disorders, further investigation is required to draw definitive conclusions and valid current observations. Doctoral 2025-11-18T11:44:31Z 2025-11-18T11:44:31Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/134381 en Stellenbosch University 194 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Rust, Catharina Magdalena Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder |
| title | Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder |
| title_full | Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder |
| title_fullStr | Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder |
| title_full_unstemmed | Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder |
| title_short | Investigating the gut and blood microbiome in Parkinson’s disease, schizophrenia, and posttraumatic stress disorder |
| title_sort | investigating the gut and blood microbiome in parkinson s disease schizophrenia and posttraumatic stress disorder |
| url | https://scholar.sun.ac.za/handle/10019.1/134381 |
| work_keys_str_mv | AT rustcatharinamagdalena investigatingthegutandbloodmicrobiomeinparkinsonsdiseaseschizophreniaandposttraumaticstressdisorder |