The Microbiome and Alzheimer’s Disease: Potential and Limitations of Prebiotic, Synbiotic, and Probiotic Formulations

Abstract

The Microbiome has generated significant attention for its impacts not only on gastrointestinal health, but also on signaling pathways of the enteric and central nervous system via the microbiome gut–brain axis. In light of this, microbiome modulation may be an effective therapeutic strategy for treating or mitigating many somatic and neural pathologies, including neurodegenerative disorders. Alzheimer’s disease (AD) is a chronic neurodegenerative disease that interferes with cerebral function by progressively impairing memory, thinking and learning through the continuous depletion of neurons. Although its etiopathogenesis remains uncertain, recent literature endorses the hypothesis that probiotic, prebiotic and synbiotic supplementation alters AD-like symptoms and improves many of its associated disease biomarkers. Alternatively, a dysfunctional microbiota impairs the gut epithelial barrier by inducing chronic gastric inflammation, culminating in neuroinflammation and accelerating AD progression. The findings in this review suggest that probiotics, prebiotics or synbiotics have potential as novel biological prophylactics in treatment of AD, due to their anti-inflammatory and antioxidant properties, their ability to improve cognition and metabolic activity, as well as their capacity of producing essential metabolites for gut and brain barrier permeability.

Gut Microbiota, Probiotic Interventions, and Cognitive Function in the Elderly: A Review of Current Knowledge

“…Recent studies also indicate that prebiotic and synbiotic supplementation may also have significant ability to improve metabolic activity and improve cognition in AD patients. Synbiotics showed to increase bioavailability of microbially produced antioxidant metabolites, enhancing activity of antioxidant systems and improving cognitive function among AD patients [ 155 , 156 ]. Within possible mechanisms behind AD, there is also one related to the secretory function of gut microbiota, which may modulate brain plasticity, affect cognitive function and develop AD via other than previously mentioned neurotransmitters and neuromodulators (e.g., serotonin, GABA, and histamine), or neurotoxic metabolites (e.g., D-lactic acid and ammonia) [ 38 , 113 , 131 ].…”

Nutrition, Gut Microbiota, and Alzheimer's Disease

“…The modulation of systemic inflammatory response with prebiotics and probiotics can be part of a comprehensive approach to slow down the cognitive decline through an impact on gut-brain axis ( 122 , 123 ). A positive effect on cognitive performance for diets rich in fiber and polyphenols can partially be attributed to the prebiotic properties of the mentioned nutrients.…”

Novel Insights into the Role of Probiotics in Respiratory Infections, Allergies, Cancer, and Neurological Abnormalities

“…Afflicted lipid metabolism could trigger neurodegenerative processes, and reversely Labarre et al have shown that dietary treatment with L. rhamnosus HA-114 restored lipid homeostasis, including energy balance via mitochondrial b-oxidation [105]. According to previously documented studies, probiotics have shown impressive ability to decelerate AD advancement due to clinically proved anti-inflammatory and antioxidant effects, including their ability to normalize cognitive deterioration that appreciably highlights their therapeutic applicability and effectiveness [106][107][108][109].…”

“…Of late, studies have suggested that probiotics could shape and induce balance in the microbiome and ameliorate AD symptoms via miscellaneous mechanisms [ 106 ]. Most of these mechanisms are generally assigned due to the production of antioxidants and their potential to neutralize ROS and inhibit the cytokine production of pro-inflammatory cascades [ 106 ].…”