Influence of postbiotics on the microbiota-gut-brain axis in cognitive impairment and dementia

Mild cognitive impairment (MCI) and dementias, such as Alzheimer’s disease (AD)-induced dementia and vascular dementia, are major public health burdens. The blood-brain barrier (BBB) disruption, systemic inflammation, neuroinflammation, and abnormal activation of the hypothalamic-pituitary-adrenal (HPA) axis are primary pathological mechanisms. Recent findings have highlighted the importance of the interplay between the gut-brain axis and cognitive function. In the gut-brain axis, gut microbiota composition plays a pivotal role in cognitive functioning. Therefore, dysbiosis of the gut microbiota may contribute to MCI and dementia. Probiotics have been administered to improve gut health; however, several adverse effects such as abdominal bloating and allergic reactions have driven the development of alternative therapies. Postbiotics containing inanimate microorganisms and/or their components derived from probiotics exert beneficial effects, such as anti-inflammatory, anti-bacterial, and anti-oxidant properties, on the host. Postbiotics exhibit protective effects against gut dysbiosis, gut barrier disruption, systemic and central inflammation, BBB breakdown, and abnormal HPA activity in patients with cognitive disorders. The intake of postbiotics may be a promising adjuvant alternative to probiotics for improving cognitive function in clinical settings if conducting human clinical trials in cognitive disorders to explore the mechanism of action of specific postbiotics components, or studying their differential effects on various types of cognitive impairment.