Gut microbiota has a proven role in regulating multiple neuro-chemical pathways through the highly interconnected gut-brain axis. Oral bacteriotherapy thus has potential in the treatment of central nervous system-related pathologies, such as Alzheimer’s disease (AD). Current AD treatments aim to prevent onset, delay progression and ameliorate symptoms. In this work, 3xTg-AD mice in the early stage of AD were treated with SLAB51 probiotic formulation, thereby affecting the composition of gut microbiota and its metabolites. This influenced plasma concentration of inflammatory cytokines and key metabolic hormones considered therapeutic targets in neurodegeneration. Treated mice showed partial restoration of two impaired neuronal proteolytic pathways (the ubiquitin proteasome system and autophagy). Their cognitive decline was decreased compared with controls, due to a reduction in brain damage and reduced accumulation of amyloid beta aggregates. Collectively, our results clearly prove that modulation of the microbiota induces positive effects on neuronal pathways that are able to slow down the progression of Alzheimer’s disease.

The gut-brain axis is a bidirectional communication network functionally linking the gut and the central nervous system (CNS). Based on this, the rational manipulation of intestinal microbiota represents a novel attractive therapeutic strategy for the treatment of CNS-associated disorders. In this study, we explored the properties of a probiotic formulation (namely SLAB51) in counteracting brain oxidative damages associated with Alzheimer’s disease (AD). Specifically, transgenic AD mice (3xTg-AD) were treated with SLAB51 and the effects on protein oxidation, neuronal antioxidant defence and repair systems were monitored, with the particular focus on the role of SIRT1-related pathways. We demonstrated that SLAB51 markedly reduced oxidative stress in AD mice brain by activating SIRT1-dependent mechanisms, thus representing a promising therapeutic adjuvant in AD treatment.Electronic supplementary materialThe online version of this article (10.1007/s12035-018-0973-4) contains supplementary material, which is available to authorized users.

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Alzheimer's disease (AD) is a progressive neurodegeneration characterized by neuron death ending in memory and cognitive decline. A major concern in AD research is the identification of new therapeutics that could prevent or delay the onset of the disorder, with current treatments being effective only in reducing symptoms. In this perspective, the use of engineered probiotics as therapeutic tools for the delivery of molecules to eukaryotic cells is finding application in several disorders. This work introduces a new strategy for AD treatment based on the use of a Lactobacillus lactis strain carrying one plasmid (pExu) that contains a eukaryotic expression cassette encoding the human p62 protein. 3xTg-AD mice orally administered with these bacteria for two months showed an increased expression of endogenous p62 in the brain, with a protein delivery mechanism involving both lymphatic vessels and neural terminations, and positive effects on the major AD hallmarks. Mice showed ameliorated memory, modulation of the ubiquitin-proteasome system and autophagy, reduced levels of amyloid peptides, and diminished neuronal oxidative and inflammatory processes. Globally, we demonstrate that these extremely safe, non-pathogenic and non-invasive bacteria used as delivery vehicles for the p62 protein represent an innovative and realistic therapeutic approach in AD.