Gut microbial changes of patients with psychotic and affective disorders: A systematic review

Gut microbiome in Schizophrenia: Altered functional pathways related to immune modulation and atherosclerotic risk

“…On the other hand, Lachnospiraceae has also been found to be depleted in schizophrenia and positively correlated with psychosis symptom severity (Zheng et al, 2019). A recent systematic review (Vindegaard et al, 2020) noted that the most consistent finding when pooling results from affective and psychotic disorders is lower levels of Lachnospiraceae. It is possible that this taxon may be a transdiagnostic marker of psychiatric disease, perhaps related to common mood symptoms or medications across disorders.…”

Human gastrointestinal (GI) tract microbiome-derived pro-inflammatory neurotoxins from Bacteroides fragilis: Effects of low fiber diets and environmental and lifestyle factors

“…Neurotoxins detrimental to the normal structure, function and signaling properties of brain cells: (i) may be acquired directly via naturally-occurring, plant growth-and plant yield-promoting factors or processed components of ingested foodstuffs; (ii) from the environment; (iii) from the individual lifestyles that we live; and also (iv) from the neurotoxic exudates derived from thousands of species of stressed GI-tract resident microbes. Diet, environment and lifestyle are inextricably linked when considering 'hologenome' aspects of a highly networked 'metaorganism' and metagenomics factors with the most recent findings that microbiome-derived neurotoxins can strongly contribute to human diseases from intestinal and systemic inflammation, to obesity to schizophrenia and to Alzheimer's disease (AD) [21,[27][28][29][30][31][32][33][37][38][39][40]. For example, in fiber-deprived diets which can be strongly impacted by environmental and lifestyle choices certain GI-tract abundant Gram negative bacilli such as B. fragilis appear to strongly proliferate, increasing both their potential and abundance for the synthesis and release of neurotoxins by mass action alone.…”

“…About ~99.5% of all of the microbes in the human GI-tract microbiome consist of facultative and/or obligate anaerobic bacteria depending mostly on their position along the human digestive/intestinal systems that measures about ~3.5 cm in diameter and approximately ~7 m in length [1][2][3][4][5][6]21,[36][37][38][39]. Perhaps not too surprisingly the microbes in the deeper, more anaerobic parts of the small intestine are the most enriched in anaerobic microbial subtypes suggesting a robust adaptation to the pH and the biophysical and microbial composition of that segment of the GI-tract environment [14,15,[21][22][23][24][25][26][27][28][29][30][31].…”

“…When the highly toxic exudates of enterotoxigenic strains of B. fragilis escape the microbial-dense environment of the human GI-tract they can produce substantial systemic inflammatory pathology with significant mortality and morbidity. B. fragilis proliferation and excess is associated with the development of multiple pro-inflammatory bowel cancers, bacteremia, brain and intra-abdominal abscess, cellulitis, colitis, diabetic ulcer, diarrhea, necrotizing fasciitis, peritonitis, sepsis, septicemia, systemic infection and systemic inflammation, the development of neurological diseases involving progressive, age-related inflammatory neurodegeneration (such as AD), and those neurological disorders that display a significantly elevated incidence of atypical developmental programming against a background of aging (such as schizophrenia) [37,[70][71][72][73][74][75][76]. Very recently LPS-induced systemic inflammation has been associated with synaptic loss and cognitive decline in multiple human neurological disorders and in transgenic murine models for AD, and a role for LPS-mediated microglial release of pro-inflammatory cytokines, such as interleukin IL-1β, is currently based on both in vivo and primary culture studies in vitro [53,73].…”

“…In a more recent study in Homo sapiens the consumption of almonds, a rich source of both soluble and insoluble fiber, unsaturated fats, and polyphenols, all nutrients that can favorably alter the composition of the gut microbiome, were found to decrease the abundance of the pathogenic bacterium Bacteroides fragilis by 48% (overall relative abundance, p<0.05) [50]. It appears from multiple studies and from the evidence available that an adequate intake of dietary fiber is associated with digestive health and reduced risk for heart disease, stroke, hypertension, certain gastrointestinal disorders, obesity, type 2 diabetes, certain cancers such as colorectal cancer as well as neurological diseases ranging from schizophrenia to AD [13,34,37,42,43,50,57,74].…”