Considering the Microbiome in Stress-Related and Neurodevelopmental Trajectories to Schizophrenia

Stress, Environment and Early Psychosis

Existing literature provides extended evidence of the close relationship between stress dysregulation, environmental insults, and psychosis onset. Early stress can sensitize genetically vulnerable individuals to future stress, modifying their risk for developing psychotic phenomena. Neurobiological substrate of the aberrant stress response to hypothalamic-pituitary-adrenal axis dysregulation, disrupted inflammation processes, oxidative stress increase, gut dysbiosis, and altered brain signaling, provides mechanistic links between environmental risk factors and the development of psychotic symptoms. Early-life and later-life exposures may act directly, accumulatively, and repeatedly during critical neurodevelopmental time windows. Environmental hazards, such as pre- and perinatal complications, traumatic experiences, psychosocial stressors, and cannabis use might negatively intervene with brain developmental trajectories and disturb the balance of important stress systems, which act together with recent life events to push the individual over the threshold for the manifestation of psychosis. The current review presents the dynamic and complex relationship between stress, environment, and psychosis onset, attempting to provide an insight into potentially modifiable factors, enhancing resilience and possibly influencing individual psychosis liability.

More than a small adult brain: Lessons from chemotherapy-induced cognitive impairment for modelling paediatric brain disorders

Childhood is recognised as a period of immense physical and emotional development, and this, in part, is driven by underlying neurophysiological transformations. These neurodevelopmental processes are unique to the paediatric brain and are facilitated by augmented rates of neuroplasticity and expanded neural stem cell populations within neurogenic niches. However, given the immaturity of the developing central nervous system, innate protective mechanisms such as neuroimmune and antioxidant responses are functionally naïve which results in periods of heightened sensitivity to neurotoxic insult. This is highly relevant in the context of paediatric cancer, and in particular, the neurocognitive symptoms associated with treatment, such as surgery, radio- and chemotherapy. The vulnerability of the developing brain may increase susceptibility to damage and persistent symptomology, aligning with reports of more severe neurocognitive dysfunction in children compared to adults. It is therefore surprising, given this intensified neurocognitive burden, that most of the pre-clinical, mechanistic research focuses exclusively on adult populations and extrapolates findings to paediatric cohorts. Given this dearth of age-specific research, throughout this review we will draw comparisons with neurodevelopmental disorders which share comparable pathways to cancer treatment related side-effects. Furthermore, we will examine the unique nuances of the paediatric brain along with the somatic systems which influence neurological function. In doing so, we will highlight the importance of developing in vitro and in vivo paediatric disease models to produce age-specific discovery and clinically translatable research.

Evaluation of Human Performance Aiding Live Synthetically Engineered Bacteria in a Gut-on-a-Chip

Synbiotics are a new class of live therapeutics employing engineered genetic circuits. The rapid adoption of genetic editing tools has catalyzed the expansion of possible synbiotics, exceeding traditional testing paradigms in terms of both throughput and model complexity. Herein, we present a simplistic gut-chip model using common Caco2 and HT-29 cell lines to establish a dynamic human screening platform for a cortisol sensing tryptamine producing synbiotic for cognitive performance sustainment. The synbiotic, SYN, was engineered from the common probiotic E. coli Nissle 1917 strain. It had the ability to sense cortisol at physiological concentrations, resulting in the activation of a genetic circuit that produces tryptophan decarboxylase and converts bioavailable tryptophan to tryptamine. SYN was successfully cultivated within the gut-chip showing log-phase growth comparable to the wild-type strain. Tryptophan metabolism occurred quickly in the gut compartment when exposed to 5 μM cortisol, resulting in the complete conversion of bioavailable tryptophan into tryptamine. The flux of tryptophan and tryptamine from the gut to the vascular compartment of the chip was delayed by 12 h, as indicated by the detectable tryptamine in the vascular compartment. The gut-chip provided a stable environment to characterize the sensitivity of the cortisol sensor and dynamic range by altering cortisol and tryptophan dosimetry. Collectively, the human gut-chip provided human relevant apparent permeability to assess tryptophan and tryptamine metabolism, production, and transport, enabled host analyses of cellular viability and pro-inflammatory cytokine secretion, and succeeded in providing an efficacy test of a novel synbiotic. Organ-on-a-chip technology holds promise in aiding traditional therapeutic pipelines to more rapidly down select high potential compounds that reduce the failure rate and accelerate the opportunity for clinical intervention.

Gut and oral microbiome modulate molecular and clinical markers of schizophrenia-related symptoms: A transdiagnostic, multilevel pilot study

Although increasing evidence links microbial dysbiosis with the risk for psychiatric symptoms through the microbiome-gut-brain axis (MGBA), the specific mechanisms remain poorly characterized. In a diagnostically heterogeneous group of treated psychiatric cases and nonpsychiatric controls, we characterized the gut and oral microbiome, plasma cytokines, and hippocampal inflammatory processes via proton magnetic resonance spectroscopic imaging (1H-MRSI). Using a transdiagnostic approach, these data were examined in association with schizophrenia-related symptoms measured by the Positive and Negative Syndrome Scale (PANSS). Psychiatric cases had significantly greater heterogeneity of gut alpha diversity and an enrichment of pathogenic taxa, like Veillonella and Prevotella, in the oral microbiome, which was an accurate classifier of phenotype. Cases exhibited significantly greater positive, negative, and general PANSS scores that uniquely correlated with bacterial taxa. Strong, positive correlations of bacterial taxa were also found with cytokines and hippocampal gliosis, dysmyelination, and excitatory neurotransmission. This pilot study supports the hypothesis that the MGBA influences psychiatric symptomatology in a transdiagnostic manner. The relative importance of the oral microbiome in peripheral and hippocampal inflammatory pathways was highlighted, suggesting opportunities for probiotics and oral health to diagnose and treat psychiatric conditions.

The Molecular Gut-Brain Axis in Early Brain Development

Millions of nerves, immune factors, and hormones in the circulatory system connect the gut and the brain. In bidirectional communication, the gut microbiota play a crucial role in the gut-brain axis (GBA), wherein microbial metabolites of the gut microbiota regulate intestinal homeostasis, thereby influencing brain activity. Dynamic changes are observed in gut microbiota as well as during brain development. Altering the gut microbiota could serve as a therapeutic target for treating abnormalities associated with brain development. Neurophysiological development and immune regulatory disorders are affected by changes that occur in gut microbiota composition and function. The molecular aspects relevant to the GBA could help develop targeted therapies for neurodevelopmental diseases. Herein, we review the findings of recent studies on the role of the GBA in its underlying molecular mechanisms in the early stages of brain development. Furthermore, we discuss the bidirectional regulation of gut microbiota from mother to infant and the potential signaling pathways and roles of posttranscriptional modifications in brain functions. Our review summarizes the role of molecular GBA in early brain development and related disorders, providing cues for novel therapeutic targets.

A sister's search for the seeds of psychosis

Dr. Dolores Malaspina sought a better way to understand the origins of psychosis than a schizophrenogenic mother, as her family had been informed upon her sisters illness. She moved her attention from environmental biology and zoology, to medical science and assembled knowledge on the multilevel components purported to underpin severe mental illness. Her studies cross levels to consider connections among exposures and genetic etiologies, intrinsic homeostatic mechanisms, stimuli perception and clinical illness features. Original contributions include associating later paternal age with increasing risk for schizophrenia in offspring and proposing that de novo mutations with shorter cell cycles explained the association, showing increased resting hippocampal blood flow in psychosis and that it was associated with inflammation, and that autonomic nervous system dysfunction was related to hippocampal inflammation, plausibly reflecting vascular abnormalities. She has been a professor of psychiatry in medical schools at Columbia University, New York University and at Mount Sinai in New York, USA.

Recent progress of Lycium barbarum polysaccharides on intestinal microbiota, microbial metabolites and health: a review

Intestinal microbiota is symbiotically associated with host health, learning about the characteristics of microbiota and the factors that modulate it could assist in developing strategies to promote human health and prevent diseases. Polysaccharides from Lycium barbarum (LBPs) are found beneficial for enhancing the activity of gut microbiota, as a potential prebiotic, which not only participates in improving body immunity, obesity, hyperlipidemia and systemic inflammation induced by oxidative stress, but also plays a magnificent role in regulating intestinal microenvironment and improving host health and target intestinal effects via its biological activities, as well as gut microbiota and metabolites. To highlight the internal relationship between intestinal microbiota and LBPs, this review focuses on the latest advances in LBPs on the intestinal microbiota, metabolites, immune regulation, intestinal barrier protection, microbiota-gut-brain axis and host health. Moreover, the preparation, structure, bioactivity and modification of LBPs were also discussed. This review may offer new perspective on LBPs improving health of gut and host via intestinal microbiota, and provide useful guidelines for the application of LBPs in the food industry.

Childhood adversity and psychotic disorders: Epidemiological evidence, theoretical models and clinical considerations

While genetic factors play a critical role in the risk for schizophrenia and other psychotic disorders, increasing evidence points to the role of childhood adversity as one of several environmental factors that can significantly impact the development, manifestations and outcome of these disorders. This paper reviews the epidemiological evidence linking childhood adversity and psychotic disorders and explores various theoretical models that seek to explain the connection. We discuss neurobiological parallels between the impact of childhood trauma and psychosis on the brain and then explore the impact of childhood adversity on different domains of clinical presentation. Finally, implications for prevention and treatment are considered, both on individual and structural levels.

Prenatal ambient temperature and risk for schizophrenia

OBJECTIVE

We conducted a systematic review of the published literature to test the hypothesis that maternal exposure to extremes of ambient temperatures during pregnancy is associated with the risk for psychiatric disorders or congenital malformations in offspring, both of which are indicative of perturbations of fetal neurodevelopment.

METHOD

This study was conducted in accordance with the recommendations outlined in the Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting proposal. Electronic databases (Ovid MEDLINE, Ovid Embase, Ovid PsycINFO, Ovid Global Health, Web of Science, and Cochrane Library) were searched. Four independent reviewers selected studies with the following criteria: (1) prenatal maternal ambient temperature exposure; (2) outcome of offspring psychiatric disorder or congenital defects; (3) empirical study; (4) full-length article, no conference presentations or abstracts.

RESULTS

Twenty-two studies met criteria and one was added from a reference list (n = 23). Of these, schizophrenia (n = 5), anorexia nervosa (n = 3) and congenital cardiovascular malformations (n = 6) studies were the most common. Each of these categories showed some evidence of association with an early pregnancy maternal ambient heat exposure effect, with other evidence for a late pregnancy cold effect.

CONCLUSION

Some evidence supports a role for early pregnancy maternal exposure to extreme ambient heat in the development of psychiatric disorders, but large-scale, prospective cohort data on individual births is essential. Optimal studies will be conducted in seasonally variable climates, accounting for actual maternal residence over the pregnancy and at parturition, local environmental temperature records, and appropriate covariates, similar to studies identified by this systematic review for congenital malformations.

Low income and schizophrenia risk: a narrative review

Despite decades of research, the precise etiology of schizophrenia is not fully understood. Ample evidence indicates that the disorder derives from a complex interplay of genetic and environmental factors during vulnerable stages of brain maturation. Among the plethora of risk factors investigated, stress, pre- and perinatal insults, and cannabis use have been repeatedly highlighted as crucial environmental risk factors for schizophrenia. Compelling findings from population-based longitudinal studies suggest low income as an additional risk factor for future schizophrenia diagnosis, but underlying mechanisms remain unclear. In this narrative review, we 1) summarize the literature in support of a relationship between low (parental) income and schizophrenia risk, and 2) explore the mediating role of chronic stress, pre- and perinatal factors, and cannabis use as established risk factors for schizophrenia. Our review describes how low income facilitates the occurrence and severity of these established risk factors and thus contributes to schizophrenia liability. The broadest influence of low income was identified for stress, as low income was found to be associated with exposure to a multitude of severe psychological and physiological stressors. This narrative review adds to the growing literature reporting a close relationship between income and mental health.

Patient-reported exposures and outcomes link the gut-brain axis and inflammatory pathways to specific symptoms of severe mental illness

We developed a "gut-brain-axis questionnaire" (GBAQ) to obtain standardized person-specific "review of systems" data for microbiome-gut-brain-axis studies. Individual items were compared to PANSS symptom measures using dimensional, transdiagnostic and traditional categorical approaches.

METHOD

Forty psychotic participants, independent of diagnoses, and 42 without psychosis (18 nonpsychotic affective disorders, 24 healthy controls) completed the GBAQ and underwent research diagnostic and symptom assessments. The PANSS scales and its dysphoric mood, autistic preoccupation and activation factors were computed.

RESULTS

Transdiagnostic analyses robustly linked psychosis severity to constipation (p<.001), and Negative (p=.045) and General Psychopathology scores (p=.016) with bowel hypomotility. Activation factor scores predicted numbers of psychiatric (p=.009) and medical conditions (p=.003), BMI (p=.003), skin (p<.001) and other conditions. Categorical analyses comparing psychotic, nonpsychotic and control groups revealed behavioral differences: cigarette smoking (p=.013), alcohol use (p=.007), diet (p's <.05), exercise (p<.001). All subjects accurately self-reported their diagnosis.

CONCLUSIONS

The GBAQ is a promising tool. Transdiagnostic analyses associated psychotic symptoms to gut hypomotility, indicative of low gut vagal tone, consistent with reduced cardiovagal activity in psychosis. Activation, similar to delirium symptoms, predicted medical comorbidity and systemic inflammatory conditions. Group level comparisons only showed behavioral differences. Underpinnings of psychiatric disorders may include reduced gut vagal function, producing psychosis, and systemic inflammation, impacting risks for psychotic and nonpsychotic conditions.

Gallic Acid Alleviates Gut Dysfunction and Boosts Immune and Antioxidant Activities in Puppies Under Environmental Stress Based on Microbiome-Metabolomics Analysis

Early-life exposure to environmental stress disrupts the gut barrier and leads to inflammatory responses and changes in gut microbiota composition. Gallic acid (GA), a natural plant polyphenol, has received significant interest for its antioxidant, anti-inflammatory, and antimicrobial properties that support the maintenance of intestinal health. To assess whether dietary supplementation of GA alleviates environmental stress, a total of 19 puppies were randomly allocated to the following three dietary treatments for 2 weeks: 1) basal diet (control (CON)); 2) basal diet + transportation (TS); and 3) basal diet with the addition of 500 mg/kg of GA + transportation (TS+GA). After a 1-week supplementation period, puppies in the TS and TS+GA groups were transported from a stressful environment to another livable location, and puppies in the CON group were then left in the stressful environment. Results indicated that GA markedly reduced the diarrhea rate in puppies throughout the trial period and caused a moderate decline of serum cortisol and HSP-70 levels after transportation. Also, GA alleviated the oxidative stress and inflammatory response caused by multiple environmental stressors. Meanwhile, puppies fed GA had a higher abundance of fecal Firmicutes and Lactobacillus and lower Proteobacteria, Escherichia–Shigella, and Clostridium_sensu_stricto_1 after transportation. As a result, the TS+GA group had the highest total short-chain fatty acids and acetic acid. Also, the fecal and serum metabolomics analyses revealed that GA markedly reversed the abnormalities of amino acid metabolism, lipid metabolism, carbohydrate metabolism, and nucleotide metabolism caused by stresses. Finally, Spearman’s correlation analysis was carried out to explore the comprehensive microbiota and metabolite relationships. Overall, dietary supplementation of GA alleviates oxidative stress and inflammatory response in stressed puppies by causing beneficial shifts on gut microbiota and metabolites that may support gut and host health.

Stress and the Role of the Gut-Brain Axis in the Pathogenesis of Schizophrenia: A Literature Review

Schizophrenia is a severe neuropsychiatric disorder, and its etiology remains largely unknown. Environmental factors have been reported to play roles in the pathogenesis of schizophrenia, and one of the major environmental factors identified for this disorder is psychosocial stress. Several studies have suggested that stressful life events, as well as the chronic social stress associated with city life, may lead to the development of schizophrenia. The other factor is the gut–brain axis. The composition of the gut microbiome and alterations thereof may affect the brain and may lead to schizophrenia. The main interest of this review article is in overviewing the major recent findings on the effects of stress and the gut–brain axis, as well as their possible bidirectional effects, in the pathogenesis of schizophrenia.

How do established developmental risk-factors for schizophrenia change the way the brain develops?

The recognition that schizophrenia is a disorder of neurodevelopment is widely accepted. The original hypothesis was coined more than 30 years ago and the wealth of supportive epidemiologically data continues to grow. A number of proposals have been put forward to suggest how adverse early exposures in utero alter the way the adult brain functions, eventually producing the symptoms of schizophrenia. This of course is extremely difficult to study in developing human brains, so the bulk of what we know comes from animal models of such exposures. In this review, I will summarise the more salient features of how the major epidemiologically validated exposures change the way the brain is formed leading to abnormal function in ways that are informative for schizophrenia symptomology. Surprisingly few studies have examined brain ontogeny from embryo to adult in such models. However, where there is longitudinal data, various convergent mechanisms are beginning to emerge involving stress and immune pathways. There is also a surprisingly consistent alteration in how very early dopamine neurons develop in these models. Understanding how disparate epidemiologically-validated exposures may produce similar developmental brain abnormalities may unlock convergent early disease-related pathways/processes.