Dynamic Response to Probiotics in Context of Alzheimer Disease: a Proof-of-concept Study

BACKGROUND: A growing body of evidence suggests an effect of gut bacteria and their metabolites on brain health, including the development of neurodegenerative conditions and Alzheimer's disease (AD). Probiotic supplementation is commonplace in medicine but targeting the gut microbiome to prevent AD is poorly understood and little is known on the dynamic effects of probiotics on physiology.

AIM: This is a proof-of-concept study to adequately design a larger trial to investigate the effect of supplementation of a probiotic (SLAB51) on AD biomarker. The study will use a high frequency sampling to closely monitor the physiological dynamics as the result of low and high dose consumption of the probiotic.

METHODS: Study subjects will be three patients with prodromal AD between 60 and 80 years old and carrying the apolipoprotein E (APOE) e4 allele. Participants will sequentially receive no supplement (run-in), low and high doses of probiotics for five consecutive days with a washout period in-between. Blood and stools will be collected every day or every second days. The main readout will be the established plasma markers of AD, and more exploratory analysis will be performed on putative mediators of the gut-brain axis.

EXPECTED OUTCOME: Curves of dynamic change of the readouts will be built for each subject, and a model of the response will be estimated. The results of this project will help design a larger trial to identify the most promising analytes showing a dynamic response to probiotic consumption and better understand the link to the pathology.

Inclusion criteria

• Diagnosis of mild cognitive impairment (MCI) due to AD, obtained from the clinical path of the participant in the memory clinic according to the criteria of Petersen et al. 1999 (46)
• Previous evidence of brain amyloidosis (assessed by positron emission tomographie (PET) or cerebrospinal fluid (CSF))
• Carrier of APOEe4 gene allele
• Defecates at least once a day

Exclusion criteria

• Antibiotic consumption 1 month prior the intervention
• Prebiotic consumption 1 month prior the intervention
• Recent change in diet habit (eg: vegetarian, vegan, high protein diet)
• Current alcohol addiction
• Current smoking habit
• Clinical diagnosis of dementia.
• Contraindications to probiotic consumption
• Inability to undergo the procedures of the study, e.g., severe behavioural disturbances.
• severe diseases:

• Life threatening diseases,
• Severe systemic diseases (e.g., kidney insufficiency, cardiac insufficiency, decompensated diabetes, decompensated metabolic diseases, decompensated hypothyroidism, uncontrolled autoimmune diseases);
• Chronic digestive diseases (e.g.: Crohn's disease, Ulcerative colitis, C. difficile infection)
• Chronic immune diseases
• The participation to a clinical trial involving potential Alzheimer's disease modifying therapies.