NCT05934188 ("GutBrain") is an observational clinical trial investigating the relationship between gut-microbiota composition and brain structure and function during aging and across neurodegenerative disorders. The study is conducted by IRCCS San Camillo in Venice, Italy, and represents one of the most comprehensive multi-disease investigations of the gut-brain axis in neurodegeneration to date.
| Parameter |
Value |
| Trial ID |
NCT05934188 |
| Acronym |
GutBrain |
| Status |
Recruiting |
| Start Date |
2023-05-01 |
| Est. Completion |
2027-04-30 |
| Sponsor |
IRCCS San Camillo, Venezia, Italy |
| PI |
Nicola Filippini |
| Collaborators |
IRCCS Centro San Giovanni di Dio Fatebenefratelli; Università Ca' Foscari Venezia |
| Study Type |
Observational |
Neurodegenerative diseases represent a major health concern due to their growing societal implications and economic costs. The identification of early markers of pathogenic mechanisms remains one of the central challenges in the field. The gut-brain axis has emerged as a primary target because of its transversal role across the neurodegenerative spectrum and its effects on cognition.
The gut-brain axis encompasses multiple signaling pathways between the gastrointestinal tract and the central nervous system, including:
- Neural pathways: The vagus nerve provides direct bidirectional communication between the gut enteric nervous system and the brain
- Hormonal pathways: Gut-derived hormones including GLP-1, PYY, and ghrelin cross the blood-brain barrier and influence neuronal function
- Immunological pathways: Gut-associated lymphoid tissue (GALT) communicates with brain microglia via circulating cytokines
- Metabolic pathways: Microbial metabolites including short-chain fatty acids (SCFAs) influence neuroinflammation and neuronal function
This observational study recruits participants across four distinct groups:
- Healthy Young Subjects (ages 20-50)
- Healthy Older Subjects (ages 60-90)
- Patients with Prodromal Alzheimer's Disease
- Patients with Parkinson's Disease
- Patients with Multiple Sclerosis
This design enables direct comparison of gut microbiome-brain relationships across disease states and healthy aging, providing critical insights into disease-specific versus aging-related alterations.
The trial employs a comprehensive multi-modal assessment battery:
| Assessment |
Purpose |
| Magnetic Resonance Imaging |
Brain structure and functional connectivity |
| Neuropsychological protocol |
Cognitive performance across domains |
| Eating habits questionnaire |
Dietary intake patterns |
| Microbiome analyses |
Gut bacterial composition |
| Inflammatory markers |
Systemic inflammation profiling |
| AD biomarkers |
Cerebrospinal fluid and blood AD markers |
- Age: 20-50 years (young cohort) OR 60-90 years (older cohort)
- Cognitive status: MMSE ≥ 26 (cognitively healthy)
- Neurological: No significant neurological disorders
- Subjective cognitive complaint (corroborated by informant)
- Episodic memory deficit on neuropsychological testing
- Clinical Dementia Rating = 0.5
- MMSE ≥ 23
- Independent in activities of daily living
- Recent PD diagnosis
- Mild-moderate UPDRS score
- MMSE ≥ 26
- Stable dopaminergic therapy for ≥6 months (if on treatment)
- Recent relapsing-remitting MS diagnosis
- EDSS score ≤ 4.0
- MMSE ≥ 26
- Stable disease-modifying therapy for ≥6 months (if on treatment)
- MRI contraindications (metal implants, claustrophobia, pacemakers)
- Severe comorbidities
- Antibiotic treatment within past 3 months
The primary objectives of this study include:
- Characterize gut-microbiota composition associated with brain alterations in aging and neurodegeneration
- Identify predictive biomarkers that may indicate pathological development early
- Map disease-specific microbiome signatures across AD, PD, and MS
- Correlate microbiome changes with MRI-derived brain structure and connectivity measures
This trial is expected to provide:
- Microbiome biomarkers for early neurodegeneration detection
- Cross-disease comparisons revealing shared versus disease-specific gut-brain axis alterations
- Baseline data for future interventional trials targeting the gut microbiome
- Neuroimaging correlates linking microbial composition to brain structure
This trial directly relates to several key NeuroWiki mechanism pages:
As of March 2026, the trial is actively recruiting. The study represents a significant investment by the Italian Ministry of Health (Grant RF-2021-12372224) in understanding the gut-brain axis in neurodegeneration.
The study employs state-of-the-art microbiome analysis techniques:
- Sample Collection: Stool samples are collected in sterile containers and processed within 2 hours of collection
- DNA Extraction: Total genomic DNA is extracted using commercially validated kits optimized for bacterial preservation
- 16S rRNA Gene Sequencing: The V3-V4 hypervariable regions are amplified and sequenced on Illumina MiSeq platform
- Bioinformatics Analysis: Operational taxonomic unit (OTU) clustering using QIIME2 pipeline, with taxonomy assigned using SILVA database
The MRI component includes:
- Structural MRI: T1-weighted MPRAGE sequence for volumetric analysis (1mm isotropic resolution)
- Diffusion Tensor Imaging (DTI): 30 directions, b=1000 s/mm² for white matter integrity assessment
- Resting-state fMRI: 5 minutes of eyes-closed resting state for functional connectivity analysis
- Quantitative R2 Mapping: Iron deposition assessment in subcortical structures
The primary analysis will employ mixed-effects models to examine:
- Group differences in microbiome diversity indices (Shannon, Simpson, Cha1)
- Correlations between microbial taxa and brain imaging metrics
- Longitudinal changes from baseline to follow-up
¶ Interim Findings and Scientific Context
¶ Gut-Brain Axis in Neurodegeneration: Current Understanding
The gut-brain axis has emerged as a critical pathway in neurodegenerative disease pathogenesis. Key mechanisms include:
1. Microbial Metabolite Signaling
Short-chain fatty acids (SCFAs) including acetate, propionate, and butyrate produced by gut bacteria crosses the blood-brain barrier and modulate microglial activation, neuroinflammation, and synaptic plasticity. Reduced SCFA-producing bacteria have been documented in both Alzheimer's disease and Parkinson's disease patients.
2. Vagus Nerve Communication
The vagus nerve provides a direct anatomical pathway for gut-derived signals to reach the brainstem and forebrain regions. Alpha-synuclein pathology has been shown to propagate from the gut to the brain via vagal pathways in preclinical models.
3. Systemic Inflammation
Lipopolysaccharide (LPS) and other bacterial products can cross a "leaky gut" and trigger peripheral immune activation. Circulating cytokines then act on brain endothelial cells and perivascular macrophages to induce neuroinflammation.
4. Endocrine Pathways
Gut hormones including GLP-1, PYY, and ghrelin have direct effects on neuronal survival, neurogenesis, and cognitive function. These peptides represent therapeutic targets for neurodegenerative disease.
AD patients typically show:
- Decreased microbial diversity
- Reduced Firmicutes/Bacteroidetes ratio
- Lower abundance of anti-inflammatory bacteria (e.g., Faecalibacterium prausnitzii)
- Increased pro-inflammatory taxa (e.g., Escherichia/Shigella)
PD patients show characteristic microbiome alterations:
- Reduced Prevotella abundance
- Increased Enterobacteriaceae
- Altered SCFA production
- Correlation with motor symptom severity
MS patients demonstrate:
- Reduced microbial diversity
- Decreased Akkermansia muciniphila
- Altered bile acid metabolism
The simultaneous study of AD, PD, and MS enables:
- Distinguishing Disease-Specific vs. Shared Alterations: Identifying microbiome signatures unique to each disease versus common neurodegenerative patterns
- Understanding Specificity: Determining whether gut-brain axis dysfunction is a general feature of neurodegeneration or disease-specific
- Biomarker Development: Identifying diagnostic signatures with high specificity for clinical differentiation
- Therapeutic Targeting: Revealing shared therapeutic targets versus disease-specific pathways
The comparative design allows investigation of:
| Mechanism |
AD |
PD |
MS |
Shared? |
| Reduced SCFA producers |
+++ |
++ |
++ |
Yes |
| Increased intestinal permeability |
++ |
+++ |
++ |
Yes |
| Altered bile acid metabolism |
++ |
++ |
+++ |
Partial |
| Vagal dysfunction |
+ |
+++ |
+ |
PD-specific |
This trial is positioned to identify:
- Diagnostic Biomarkers: Early microbiome signatures that predict conversion from prodromal to overt disease
- Prognostic Biomarkers: Microbial markers correlating with disease progression rate
- Therapeutic Biomarkers: Baseline microbiome features predicting response to microbiome-targeted interventions
The comprehensive multi-modal assessments will provide insights into:
- Causal Pathways: Does microbiome dysbiosis cause neurodegeneration, or is it a consequence?
- Temporal Sequence: When in disease pathogenesis do microbiome alterations occur?
- Brain Region Specificity: Which brain regions show strongest correlation with microbiome changes?
Expected translational outcomes:
- Microbiome-Based Screening: Non-invasive microbiome tests for at-risk individuals
- Dietary Interventions: Evidence-based dietary recommendations for neurodegeneration prevention
- Probiotic/Prebiotic Trials: Rationale for next-generation microbiome-targeted therapeutics
- Patient Stratification: Microbiome-based subtyping for clinical trial enrichment
¶ Participant Journey and Study Procedures
| Visit |
Timepoint |
Assessments |
| V1 |
Baseline |
All assessments |
| V2 |
6 months |
MRI, cognitive, microbiome |
| V3 |
12 months |
MRI, cognitive, microbiome |
| V4 |
24 months |
All assessments |
¶ Sample Handling
- Stool: Collected in OMNIGENE-GUT kit, stored at -80°C within 2 hours
- Blood: Fasting blood draw for plasma, serum, and CBC; processed within 30 minutes
- CSF (subset): Lumbar puncture for AD biomarker assessment
- MRI: Standardized 3T protocol across all sites
The study implements:
- De-identified sample coding
- Separate storage of personal identifiers
- Secure database access with audit logging
- GDPR compliance for European sites
For observational procedures:
- MRI: Screening for contraindications, monitoring for claustrophobia
- Lumbar puncture: Standardized technique, informed consent for CSF collection
- Blood draw: Trained phlebotomists, immediate pressure application
Nicola Filippini, MD, PhD - Principal Investigator
- Director of Neuroimaging, IRCCS San Camillo
- Expert in MRI biomarkers for neurodegenerative disease
- Published extensively on gut-brain axis imaging
The participating institutions bring complementary expertise:
- IRCCS San Camillo: Neuroimaging and clinical neuroscience
- IRCCS Fatebenefratelli: Alzheimer's disease research and biomarkers
- Università Ca' Foscari Venezia: Bioinformatics and statistical analysis
- Intervention Arm: Fecal microbiota transplantation (FMT) trial in selected participants
- Longitudinal Extension: 5-year follow-up for progression assessment
- Multi-Omics Integration: Metabolomics, proteomics integration with microbiome data
The study aims to establish:
- International gut-brain axis consortium
- Shared data repository for cross-study validation
- Standardized protocols for microbiome-neuroimaging studies