Influence of gut microbiota on the development of most prevalent neurodegenerative dementias and the potential effect of probiotics in elderly: A scoping review

Abstract

Dementia is one of today's greatest public health challenges. Its high socio‐economic impact and difficulties in diagnosis and treatment are of increasing concern to an aging world population. In recent years, the study of the relationship between gut microbiota and different neurocognitive disorders has gained a considerable interest. Several studies have reported associations between gut microbiota dysbiosis and some types of dementia. Probiotics have been suggested to restore dysbiosis and to improve neurocognitive symptomatology in these dementias. Based on these previous findings, the available scientific evidence on the gut microbiota in humans affected by the most prevalent dementias, as well as the probiotic trials conducted in these patients in recent years, have been here reviewed. Decreased concentrations of short‐chain fatty acids (SCFA) and other bacterial metabolites appear to play a major role in the onset of neurocognitive symptoms in Alzheimer disease (AD) and Parkinson disease dementia (PDD). Increased abundance of proinflammatory taxa could be closely related to the more severe clinical symptoms in both, as well as in Lewy Bodies dementia. Important lack of information was noted in Frontotemporal dementia behavioral variant. Moreover, geographical differences in the composition of the gut microbiota have been reported in AD. Some potential beneficial effects of probiotics in AD and PDD have been reported. However, due to the controversial results further investigations are clearly necessary.

Subconcussive head impacts sustained during American football alter gut microbiome diversity and composition

“…Depletion of Prevotellaceae has been associated with increased production of pro-inflammatory cytokines TNF-α and IL-1β in serum and decreased butyrate production in the gut, which has been shown to provide a neuroprotective effect by restoring the blood-brain barrier (BBB) following TBI. 93,94 Additionally, the Prevotella genus has been demonstrated to increase the concentration of short-chain fatty acids (SCFAs) in pigs; SFCAs inhibit inflammation and are potentially protective against dementia risk 95,96 . Yet, certain species of Prevotella (a genus within Prevotellaceae) have been shown to decrease SCFA production and perpetuate intestinal inflammation 97 .…”

Oral and gut microbiome profiles in early Parkinson’s disease

“…In early Parkinson's disease (PD), the microbial community of the gut is altered before motor symptoms fully manifest [4][5][6] , and may play a role in disease susceptibility 7,8 . At autopsy, -synuclein-containing Lewy bodies, which are the pathological hallmark of PD 5 , are found at all levels throughout the gut-brain axis, including the central, autonomic, and enteric neurons 9 .…”

“…The gut may then become a source of seeding -synuclein 12 which is tra cked to the brain. The microbiome also appears to be important in the later stages of PD, as microbial shifts delay the absorption of dopaminergic drugs 13 and correlate with more severe clinical symptoms including PD dementia 4,14,15 .…”

Lactiplantibacillus (Lactobacillus) plantarum as a Complementary Treatment to Improve Symptomatology in Neurodegenerative Disease: A Systematic Review of Open Access Literature

“…Of these, Lactiplantibacillus (Lactobacillus) plantarum appears to have the most promising results in the intervention of symptoms associated with neurodegeneration [ 78 , 79 , 80 ]. Several authors have suggested that the use of Lactiplantibacillus plantarum , alone or in combination, improves specific symptoms such as motor, cognitive and psychiatric signs in neurodegenerative processes [ 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 ]. Research regarding these effects has increased in the last decades, making it necessary to compare with the results obtained.…”