Fecal Short-Chain Fatty Acid Ratios as Related to Gastrointestinal and Depressive Symptoms in Young Adults

Tiger nut/coconut dietary intervention as antidotal nutritional remediation strategy against neurobehavioural deficits following organophosphate-induced gut-brain axis dysregulation in mice

Organophosphate poisoning remains a global health crisis without efficacious treatments to prevent neurotoxicity. We examined whether antidotal tiger nut and coconut dietary intervention could ameliorate neurobehavioral deficits from organophosphate dichlorvos-induced gut-brain axis dysregulation in a mouse model. Mice were divided into groups given control diet, dichlorvos-contaminated diets, or dichlorvos plus nut-enriched diets. They were exposed to a DDVP-contaminated diet for 4 weeks before exposure to the treatment diets for another 8 weeks. This was followed by behavioural assessments for cognitive, motor, anxiety-, and depressive-like behaviours. Faecal samples (pre- and post-treatment), as well as blood, brain, and gut tissues, were collected for biochemical assessments following euthanasia. Dichlorvos-exposed mice displayed impairments in cognition, motor function, and mood along with disrupted inflammatory and antioxidant responses, neurotrophic factor levels, and acetylcholinesterase activity in brain and intestinal tissues. Weight loss and altered short-chain fatty acid levels additionally indicated gut dysfunction. However, intervention with tiger nut and/or coconut- enriched diet after dichlorvos exposure attenuated these neurobehavioral, and biochemical alterations. Our findings demonstrate organophosphate-induced communication disruptions between the gut and brain pathways that manifest in neuropsychiatric disturbances. Overall, incorporating fibre-rich nuts may represent an antidotal dietary strategy to reduce neurotoxicity and prevent brain disorders associated with organophosphate poisoning.

Gut-Brain Axis: Focus on Sex Differences in Neuroinflammation

In recent years, there has been a growing interest in the concept of the "gut-brain axis". In addition to well-studied diseases associated with an imbalance in gut microbiota, such as cancer, chronic inflammation, and cardiovascular diseases, research is now exploring the potential role of gut microbial dysbiosis in the onset and development of brain-related diseases. When the function of the intestinal barrier is altered by dysbiosis, the aberrant immune system response interacts with the nervous system, leading to a state of "neuroinflammation". The gut microbiota-brain axis is mediated by inflammatory and immunological mechanisms, neurotransmitters, and neuroendocrine pathways. This narrative review aims to illustrate the molecular basis of neuroinflammation and elaborate on the concept of the gut-brain axis by virtue of analyzing the various metabolites produced by the gut microbiome and how they might impact the nervous system. Additionally, the current review will highlight how sex influences these molecular mechanisms. In fact, sex hormones impact the brain-gut microbiota axis at different levels, such as the central nervous system, the enteric nervous one, and enteroendocrine cells. A deeper understanding of the gut-brain axis in human health and disease is crucial to guide diagnoses, treatments, and preventive interventions.

Short-Chain Fatty Acids and Human Health: From Metabolic Pathways to Current Therapeutic Implications

The gastrointestinal tract is home to trillions of diverse microorganisms collectively known as the gut microbiota, which play a pivotal role in breaking down undigested foods, such as dietary fibers. Through the fermentation of these food components, short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate are produced, offering numerous health benefits to the host. The production and absorption of these SCFAs occur through various mechanisms within the human intestine, contingent upon the types of dietary fibers reaching the gut and the specific microorganisms engaged in fermentation. Medical literature extensively documents the supplementation of SCFAs, particularly butyrate, in the treatment of gastrointestinal, metabolic, cardiovascular, and gut-brain-related disorders. This review seeks to provide an overview of the dynamics involved in the production and absorption of acetate, propionate, and butyrate within the human gut. Additionally, it will focus on the pivotal roles these SCFAs play in promoting gastrointestinal and metabolic health, as well as their current therapeutic implications.

The Power of Psychobiotics in Depression: A Modern Approach through the Microbiota-Gut-Brain Axis: A Literature Review

The microbiota-gut-brain (MGB) axis is a complex communication network linking the gut, microbiota, and brain, influencing various aspects of health and disease. Dysbiosis, a disturbance in the gut microbiome equilibrium, can significantly impact the MGB axis, leading to alterations in microbial composition and function. Emerging evidence highlights the connection between microbiota alterations and neurological and psychiatric disorders, including depression. This review explores the potential of psychobiotics in managing depressive disorders, emphasizing their role in restoring microbial balance and influencing the MGB axis. Psychobiotics exhibit positive effects on the intestinal barrier, immune response, cortisol levels, and the hypothalamic-pituitary-adrenal (HPA) axis. Studies suggest that probiotics may serve as an adjunct therapy for depression, especially in treatment-resistant cases. This review discusses key findings from studies on psychobiotics interventions, emphasizing their impact on the gut-brain axis and mental health. The increasing acceptance of the expanded concept of the MGB axis underscores the importance of microorganisms in mental well-being. As our understanding of the microbiome's role in health and disease grows, probiotics emerge as promising agents for addressing mental health issues, providing new avenues for therapeutic interventions in depressive disorders.

SCFAs Supplementation Rescues Anxiety- and Depression-like Phenotypes Generated by Fecal Engraftment of Treatment-Resistant Depression Rats

Alteration of gut microbiota and microbial metabolites such as short-chain fatty acids (SCFAs) coexisted with stress-generated brain disorders, including depression. Herein, we investigated the effect of SCFAs in a treatment-resistant depression (TRD) model of rat. Rats were exposed to chronic-unpredictable mild stress (CUMS) and repeated adrenocorticotropic hormone (ACTH) injections to generate a TRD-like phenotype. The cecal contents of these animals were engrafted into healthy-recipient rats and allowed to colonize for 4 weeks (TRD-FMT group). Blood, brain, colon, fecal, and cecal samples were collected for molecular studies. Rats exposed to CUMS + ACTH showed TRD-like phenotypes in sucrose-preference (SPT), forced swim (FST), and elevated plus maze (EPM) tests. The TRD-FMT group also exhibited anxiety- and depression-like behaviors. Administration of SCFAs (acetate, propionate, and butyrate at 67.5, 25, and 40 mM, respectively) for 7 days exerted robust antidepressant and antianxiety effects by restoring the levels of SCFAs in plasma and fecal samples, and proinflammatory cytokines (TNF-α and IL-6), serotonin, GABA, norepinephrine, and dopamine in the hippocampus and/or frontal cortex of TRD and TRD-FMT animals. SCFAs treatment elevated the expression of free-fatty acid receptors 2/3, BDNF, doublecortin, and zonula-occludens, and reduced the elevated plasma levels of kynurenine and quinolinic acid and increased mucus-producing goblet cells in TRD and TRD-FMT animals. In 16S sequencing results, decreased microbial diversity in TRD rats corresponds with differences in the genus of Faecalibacterium, Anaerostipes, Allobaculum, Blautia, Peptococcus, Rombustia, Ruminococcaceae_UCG-014, Ruminococcaceae_UCG-002, Solobacterium, Subdolibacterium, and Eubacterium ventriosum. SCFAs may impart beneficial effects via modulation of tryptophan metabolism, inflammation, neurotransmitters, and microbiota-gut-brain axis in TRD rats.

The Landscape of Gut Microbiota and Its Metabolites: A Key to Understanding the Pathophysiology of Pattern in Chinese Medicine

Liver Stagnation and Spleen Deficiency (LSSD) is a Chinese Medicine (CM) pattern commonly observed in gastrointestinal (GI) diseases, yet its biological nature remains unknown. This limits the global use of CM medications for treating GI diseases. Recent studies emphasize the role of gut microbiota and their metabolites in the pathogenesis and treatment of LSSD-associated GI diseases. There is increasing evidence supporting that an altered gut microbiome in LSSD patients or animals contributes to GI and extra-intestinal symptoms and affects the effectiveness of CM therapies. The gut microbiota is considered to be an essential component of the biological basis of LSSD. This study aims to provide an overview of existing research findings and gaps for the pathophysiological study of LSSD from the gut microbiota perspective in order to understand the relationship between the CM pattern and disease progression and to optimize CM-based diagnosis, prevention, and therapy.

Clostridium butyricum Prazmowski can degrade and utilize resistant starch via a set of synergistically acting enzymes

Resistant starch is a prebiotic fiber that is best known for its ability to increase butyrate production by the gut microbiota. This butyrate then plays an important role in modulating the immune system and inflammation. However, the ability to use this resistant starch appears to be a rare trait within the gut microbiota, with only a few species such as Ruminococcus bromii and Bifidobacterium adolescentis having been demonstrated to possess this ability. Furthermore, these bacteria do not directly produce butyrate themselves, rather they rely on cross-feeding interactions with other gut bacteria for its production. Here, we demonstrate that the often-used probiotic organism Clostridium butyricum also possesses the ability to utilize resistant starch from a number of sources, with direct production of butyrate. We further explore the enzymes responsible for this trait, demonstrating that they exhibit significant synergy, though with different enzymes exhibiting more or less importance depending on the source of the resistant starch. Thus, the co-administration of Clostridium butyricum may have the ability to improve the beneficial effects of resistant starch.IMPORTANCEClostridium butyricum is seeing increased use as a probiotic, due to potential health benefits tied to its ability to produce butyrate. Here, we demonstrate that this organism can use a variety of resistant starch sources and characterize the enzymes it uses to accomplish this. Given the relative rarity of resistant starch utilizing ability within the gut and the health benefits tied to resistant starch, the combined use of this organism with resistant starch in synbiotic formulations may prove beneficial.

Molecular Mechanisms of Reelin in the Enteric Nervous System and the Microbiota-Gut-Brain Axis: Implications for Depression and Antidepressant Therapy

Current pharmacological treatments for depression fail to produce adequate remission in a significant proportion of patients. Increasingly, other systems, such as the microbiome-gut-brain axis, are being looked at as putative novel avenues for depression treatment. Dysbiosis and dysregulation along this axis are highly comorbid with the severity of depression symptoms. The endogenous extracellular matrix protein reelin is present in all intestinal layers as well as in myenteric and submucosal ganglia, and its receptors are also present in the gut. Reelin secretion from subepithelial myofibroblasts regulates cellular migration along the crypt-villus axis in the small intestine and colon. Reelin brain expression is downregulated in mood and psychotic disorders, and reelin injections have fast antidepressant-like effects in animal models of depression. This review seeks to discuss the roles of reelin in the gastrointestinal system and propose a putative role for reelin actions in the microbiota-gut-brain axis in the pathogenesis and treatment of depression, primarily reflecting on alterations in gut epithelial cell renewal and in the clustering of serotonin transporters.

Fibre-rich diet attenuates chemotherapy-related neuroinflammation in mice

The gastrointestinal microbiota has received increasing recognition as a key mediator of neurological conditions with neuroinflammatory features, through its production of the bioactive metabolites, short-chain fatty acids (SCFAs). Although neuroinflammation is a hallmark shared by the neuropsychological complications of chemotherapy (including cognitive impairment, fatigue and depression), the use of microbial-based therapeutics has not previously been studied in this setting. Therefore, we aimed to investigate the effect of a high fibre diet known to modulate the microbiota, and its associated metabolome, on neuroinflammation caused by the common chemotherapeutic agent 5-fluorouracil (5-FU). Twenty-four female C57Bl/6 mice were treated with 5-FU (400 mg/kg, intraperitoneal, i.p.) or vehicle control, with or without a high fibre diet (constituting amylose starch; 4.7 % crude fibre content), given one week prior to 5-FU and until study completion (16 days after 5-FU). Faecal pellets were collected longitudinally for 16S rRNA gene sequencing and terminal SCFA concentrations of the caecal contents were quantified using gas chromatography-mass spectrometry (GC-MS). Neuroinflammation was determined by immunofluorescent analysis of astrocyte density (GFAP). The high fibre diet significantly altered gut microbiota composition, increasing the abundance of Bacteroidaceae and Akkermansiaceae (p < 0.0001 and p = 0.0179) whilst increasing the production of propionate (p = 0.0097). In the context of 5-FU, the diet reduced GFAP expression in the CA1 region of the hippocampus (p < 0.0001) as well as the midbrain (p = 0.0216). Astrocyte density negatively correlated with propionate concentrations and the abundance of Bacteroidaceae and Akkermansiaceae, suggesting a relationship between neuroinflammatory and gastrointestinal markers in this model. This study provides the first evidence of the neuroprotective effects of fibre via dietary intake in alleviating the neuroimmune changes seen in response to systemically administered 5-FU, indicating that the microbiota-gut-brain axis is a targetable mediator to reduce the neurotoxic effects of chemotherapy treatment.

Landscape of gut microbiota and metabolites and their interaction in comorbid heart failure and depressive symptoms: a random forest analysis study

IMPORTANCE

There is increasing evidence that alterations in gut microbial composition and function are associated with cardiovascular or psychiatric disease. Therefore, it is meaningful to investigate the taxonomic and functional characterization of the microbiota in HF patients who also have depressive symptoms. In this cross-sectional study, Cloacibacillus and alpha-tocopherol were determined as new diagnostic markers. Furthermore, intestinal microecosystem disorders are closely linked to depressive symptoms in HF patients, providing a new reference viewpoint for understanding the gut-heart/brain axis.

Promising new pharmacological targets for depression: The search for efficacy

Pharmacological treatment of major depressive disorder (MDD) still relies on the use of serotonergic drugs, despite their limited efficacy. A few mechanistically new drugs have been developed in recent years, but many fail in clinical trials. Several hypotheses have been proposed to explain MDD pathophysiology, indicating that physiological processes such as neuroplasticity, circadian rhythms, and metabolism are potential targets. Here, we review the current state of pharmacological treatments for MDD, as well as the preclinical and clinical evidence for an antidepressant effect of molecules that target non-serotonergic systems. We offer some insights into the challenges facing the development of new antidepressant drugs, and the prospect of finding more effectiveness for each target discussed.

Associations between short-chain fatty acid levels and mood disorder symptoms: a systematic review

Background: Available evidence points to a possible role of Short Chain Fatty Acids (SCFAs) in mood disorders. This is the first systematic review to map the associations between SCFA levels and mood disorder symptoms.Methods: Following the PRISMA guidelines, the databases PubMed, Embase, and PsycINFO were searched for studies that assessed SCFA levels in human populations with mood disorder symptoms, or animal models of mood disorder. Risk of bias was assessed by the Strengthening of Reporting of Observational Studies in Epidemiology (STROBE) checklist.Results: 19 studies were included and could be divided into animal (n=8) and human studies (n=11), with the animal studies including 166 animals and 100 controls, and the human studies including 662 participants and 330 controls. The studies were characterized by heterogeneity and methodological challenges on multiple parameters, limiting the validity and transferability of findings. Notably, only two of the clinical studies assessed the presence of mood disorder with diagnostic criteria, and no studies of mania or bipolar disorder met the inclusion criteria.Discussion: Despite significant methodological limitations, associations between SCFA levels and depressive symptoms were reported in most of the studies. However, the direction of these associations and the specific SCFAs identified varied. The quantification of SCFA levels in mood disorders is an emerging yet sparsely studied research field. Although there is some evidence suggesting a link between SCFAs and depressive symptoms, the directionality of effects and mechanisms are unclear and the relation to manic symptoms is uninvestigated.

Post-stroke depression: epigenetic and epitranscriptomic modifications and their interplay with gut microbiota

Epigenetic and epitranscriptomic modifications that regulate physiological processes of an organism at the DNA and RNA levels, respectively, are novel therapeutic candidates for various neurological diseases. Gut microbiota and its metabolites are known to modulate DNA methylation and histone modifications (epigenetics), as well as RNA methylation especially N6-methyladenosine (epitranscriptomics). As gut microbiota as well as these modifications are highly dynamic across the lifespan of an organism, they are implicated in the pathogenesis of stroke and depression. The lack of specific therapeutic interventions for managing post-stroke depression emphasizes the need to identify novel molecular targets. This review highlights the interaction between the gut microbiota and epigenetic/epitranscriptomic pathways and their interplay in modulating candidate genes that are involved in post-stroke depression. This review further focuses on the three candidates, including brain-derived neurotrophic factor, ten-eleven translocation family proteins, and fat mass and obesity-associated protein based on their prevalence and pathoetiologic role in post-stroke depression.

Characterization of gut microbiota profile in Iranian patients with bipolar disorder compared to healthy controls

Introduction

The human gut microbiota plays a crucial role in mental health through the gut-brain axis, impacting central nervous system functions, behavior, mood, and anxiety. Consequently, it is implicated in the development of neuropsychiatric disorders. This study aimed to assess and compare the gut microbiota profiles and populations of individuals with bipolar disorder and healthy individuals in Iran.

Methods

Fecal samples were collected from 60 participants, including 30 bipolar patients (BPs) and 30 healthy controls (HCs), following rigorous entry criteria. Real-time quantitative PCR was utilized to evaluate the abundance of 10 bacterial genera/species and five bacterial phyla.

Results

Notably, Actinobacteria and Lactobacillus exhibited the greatest fold change in BPs compared to HCs at the phylum and genus level, respectively, among the bacteria with significant population differences. Ruminococcus emerged as the most abundant genus in both groups, while Proteobacteria and Bacteroidetes showed the highest abundance in BPs and HCs, respectively, at the phylum level. Importantly, our investigation revealed a lower Firmicutes/Bacteroidetes ratio, potentially serving as a health indicator, in HCs compared to BPs.

Conclusion

This study marks the first examination of an Iranian population and provides compelling evidence of significant differences in gut microbiota composition between BPs and HCs, suggesting a potential link between brain functions and the gut microbial profile and population.

The gut-brain vascular axis in neuroinflammation

The multifaceted microbiota characterizing our gut plays a crucial role in maintaining immune, metabolic and tissue homeostasis of the intestine as well as of distal organs, including the central nervous system. Microbial dysbiosis is reported in several inflammatory intestinal diseases characterized by the impairment of the gut epithelial and vascular barriers, defined as leaky gut, and it is reported as a potential danger condition associated with the development of metabolic, inflammatory and neurodegenerative diseases. Recently, we pointed out the strict connection between the gut and the brain via a novel vascular axis. Here we want to deepen our knowledge on the gut-brain axis, with particular emphasis on the connection between microbial dysbiosis, leaky gut, cerebral and gut vascular barriers, and neurodegenerative diseases. The firm association between microbial dysbiosis and impairment of the vascular gut-brain axis will be summarized in the context of protection, amelioration or boosting of Alzheimer, Parkinson, Major depressive and Anxiety disorders. Understanding the relationship between disease pathophysiology, mucosal barrier function and host-microbe interaction will foster the use of the microbiome as biomarker for health and disease as well as a target for therapeutic and nutritional advances.

Tezacaftor/Ivacaftor therapy has negligible effects on the cystic fibrosis gut microbiome

People with cystic fibrosis (pwCF) experience a range of persistent gastrointestinal symptoms throughout life. There is evidence indicating interaction between the microbiota and gut pathophysiology in CF. However, there is a paucity of knowledge on the potential effects of CF transmembrane conductance regulator (CFTR) modulator therapies on the gut microbiome. In a pilot study, we investigated the impact of Tezacaftor/Ivacaftor dual combination CFTR modulator therapy on the gut microbiota and metabolomic functioning in pwCF. Fecal samples from 12 pwCF taken at baseline and following placebo or Tezacaftor/Ivacaftor administration were subjected to microbiota sequencing and to targeted metabolomics to assess the short-chain fatty acid (SCFA) composition. Ten healthy matched controls were included as a comparison. Inflammatory calprotectin levels and patient symptoms were also investigated. No significant differences were observed in overall gut microbiota characteristics between any of the study stages, extended also across intestinal inflammation, gut symptoms, and SCFA-targeted metabolomics. However, microbiota and SCFA metabolomic compositions, in pwCF, were significantly different from controls in all study treatment stages. CFTR modulator therapy with Tezacaftor/Ivacaftor had negligible effects on both the gut microbiota and SCFA composition across the course of the study and did not alter toward compositions observed in healthy controls. Future longitudinal CFTR modulator studies will investigate more effective CFTR modulators and should use prolonged sampling periods, to determine whether longer-term changes occur in the CF gut microbiome. IMPORTANCE People with cystic fibrosis (pwCF) experience persistent gastrointestinal (GI) symptoms throughout life. The research question "how can we relieve gastrointestinal symptoms, such as stomach pain, bloating, and nausea?" remains a top priority for clinical research in CF. While CF transmembrane conductance regulator (CFTR) modulator therapies are understood to correct underlying issues of CF disease and increasing the numbers of pwCF are now receiving some form of CFTR modulator treatment. It is not known how these therapies affect the gut microbiome or GI system. In this pilot study, we investigated, for the first time, effects of the dual combination CFTR modulator medicine, Tezacaftor/Ivacaftor. We found it had negligible effects on patient GI symptoms, intestinal inflammation, or gut microbiome composition and functioning. Our findings are important as they fill important knowledge gaps on the relative effectiveness of these widely used treatments. We are now investigating triple combination CFTR modulators with prolonged sampling periods.

Prebiotics for depression: how does the gut microbiota play a role?

Depression, a mood disorder characterized by persistent feelings of sadness and aversion to activity that can interfere with daily life, is a condition of great concern. Prebiotics, which are non-digestible substances selectively utilized by host microorganisms for health benefits, have gained attention for their potential to improve overall wellness and alleviate various disorders including depression. This study aims to review clinical trials utilizing carbohydrate-type prebiotics such as inulin-type fructans, galactooligosaccharides (GOS), human milk oligosaccharides, resistant starch, prebiotic phytochemicals including epigallocatechin gallate (EGCG), chlorogenic acids, resveratrol, and prebiotic lipids (n-3 polysaturated fatty acids) to determine their effects on depression. Our findings suggest that GOS at a daily dosage of 5 g and eicosapentaenoic acid at or less than 1 g can effectively mitigate depressive symptoms. While EGCG exhibits potential antidepressant properties, a higher dosage of 3 g/d may be necessary to elicit significant effects. The plausible mechanisms underlying the impact of prebiotics on depression include the synthesis of neurotransmitters, production of short-chain fatty acids, and regulation of inflammation.

Enterogenic metabolomics signatures of depression: what are the possibilities for the future

INTRODUCTION

An increasing number of studies indicate that the microbiota-gut-brain axis is an important pathway involved in the onset and progression of depression. The responses of the organism (or its microorganisms) to external cues cannot be separated from a key intermediate element: their metabolites.

AREAS COVERED

In recent years, with the rapid development of metabolomics, an increasing amount of metabolites has been detected and studied, especially the gut metabolites. Nevertheless, the increasing amount of metabolites described has not been reflected in a better understanding of their functions and metabolic pathways. Moreover, our knowledge of the biological interactions among metabolites is also incomplete, which limits further studies on the connections between the microbial-entero-brain axis and depression.

EXPERT OPINION

This paper summarizes the current knowledge on depression-related metabolites and their involvement in the onset and progression of this disease. More importantly, this paper summarized metabolites from the intestine, and defined them as enterogenic metabolites, to further clarify the function of intestinal metabolites and their biochemical cross-talk, providing theoretical support and new research directions for the prevention and treatment of depression.

Microbiota-gut-brain axis mechanisms in the complex network of bipolar disorders: potential clinical implications and translational opportunities

Bipolar disorders (BD) represent a severe leading disabling mental condition worldwide characterized by episodic and often progressive mood fluctuations with manic and depressive stages. The biological mechanisms underlying the pathophysiology of BD remain incompletely understood, but it seems that there is a complex picture of genetic and environmental factors implicated. Nowadays, gut microbiota is in the spotlight of new research related to this kind of psychiatric disorder, as it can be consistently related to several pathophysiological events observed in BD. In the context of the so-called microbiota-gut-brain (MGB) axis, it is shown to have a strong influence on host neuromodulation and endocrine functions (i.e., controlling the synthesis of neurotransmitters like serotonin or mediating the activation of the hypothalamic-pituitary-adrenal axis), as well as in modulation of host immune responses, critically regulating intestinal, systemic and brain inflammation (neuroinflammation). The present review aims to elucidate pathophysiological mechanisms derived from the MGB axis disruption and possible therapeutic approaches mainly focusing on gut microbiota in the complex network of BD. Understanding the mechanisms of gut microbiota and its bidirectional communication with the immune and other systems can shed light on the discovery of new therapies for improving the clinical management of these patients. Besides, the effect of psychiatric drugs on gut microbiota currently used in BD patients, together with new therapeutical approaches targeting this ecosystem (dietary patterns, probiotics, prebiotics, and other novelties) will also be contemplated.

When the microbiome helps the brain-current evidence

The gut microbiota-brain axis has been recognized as a network of connections that provides communication between the gut microflora and both central and autonomic nervous system. The gut microbiota alteration has been targeted for therapy in various neurodegenerative and psychiatric disbalances. Psychobiotics are probiotics that contribute beneficially to the brain function and the host mental health as a result of an interaction with the commensal gut bacteria, although their mechanism of action has not been completely revealed. In this state-of-art review, the findings about the potential therapeutic effects of the psychobiotics alone or in combination with conventional medicine in the treatment of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, as well as in some psychiatric diseases like depression, schizophrenia, and bipolar disorder, have been summarized. The evidence of the psychobiotics therapeutic outcomes obtained in preclinical and clinical trials have been given respectively for the observed neurodegenerative and psychiatric disorders.

The role of selenium in shaping mice brain metabolome and selenoproteome through the gut-brain axis by combining metabolomics, metallomics, gene expression and amplicon sequencing

Selenium (Se) is a trace element crucial for human health. Recently, the impact of Se supplementation on gut microbiota has been pointed out as well as its influence on the expression of certain selenoproteins and gut metabolites. This study aims to elucidate the link between Se supplementation, brain selenoproteins and brain metabolome as well as the possible connection with the gut-brain axis. To this end, an in vivo study with 40 BALB/c mice was carried out. The study included conventional (n=20) and mice model with microbiota depleted by antibiotics (n=20) under a regular or Se supplemented diet. Brain selenoproteome was determined by a transcriptomic/gene expression profile, while brain metabolome and gut microbiota profiles were accomplished by untargeted metabolomics and amplicon sequencing, respectively. The total content of Se in brain was also determined. The selenoproteins genes Dio and Gpx isoenzymes, SelenoH, SelenoI, SelenoT, SelenoV and SelenoW and 31 metabolites were significantly altered in the brain after Se supplementation in conventional mice, while 11 selenoproteins and 26 metabolites were altered in microbiota depleted mice. The main altered brain metabolites were related to glyoxylate and dicarboxylate metabolism, amino acid metabolism, and gut microbiota that have been previously related with the gut-brain axis (e.g., members of Lachnospiraceae and Ruminococcaceae families). Moreover, specific associations were determined between brain selenoproteome and metabolome, which correlated with the same bacteria, suggesting an intertwined mechanism. Our results demonstrated the effect of Se on brain metabolome through specific selenoproteins gene expression and gut microbiota.

Outrunning a bad diet: interactions between exercise and a Western-style diet for adolescent mental health, metabolism and microbes

Adolescence is a period of biological, psychological and social changes, and the peak time for the emergence of mental health problems. During this life stage, brain plasticity including hippocampal neurogenesis is increased, which is crucial for cognitive functions and regulation of emotional responses. The hippocampus is especially susceptible to environmental and lifestyle influences, mediated by changes in physiological systems, resulting in enhanced brain plasticity but also an elevated risk for developing mental health problems. Indeed, adolescence is accompanied by increased activation of the maturing hypothalamic-pituitary-adrenal axis, sensitivity to metabolic changes due to increased nutritional needs and hormonal changes, and gut microbiota maturation. Importantly, dietary habits and levels of physical activity significantly impact these systems. In this review, the interactions between exercise and Western-style diets, which are high in fat and sugar, on adolescent stress susceptibility, metabolism and the gut microbiota are explored. We provide an overview of current knowledge on implications of these interactions for hippocampal function and adolescent mental health, and speculate on potential mechanisms which require further investigation.

Disorders in the gut and liver are involved in depression contagion between isosexual post-stroke depression mice and the healthy cohabitors

Despite the accumulated evidence that pair housing could attenuate post-stroke depression (PSD), but less attention has been paid to the healthy cohabitors, and the underlying mechanisms remain unclear. This study aimed to determine whether there is depressive contagion between PSD mice and their healthy cohabitors. PSD was induced by middle cerebral artery occlusion (MCAO) plus restraint stress for four weeks. Three days after MCAO, the mice were restrained two hours per day and isosexually pair-housed for four weeks. The results showed that, compared with the partners pair housed with normal control mice (Ctrl group), the partners pair housed with PSD mice (CH group) displayed depressive-like behaviors, including decreased sucrose preference rate, significantly shorter duration in the center arena and reduced total distance in the open-field test, and extended immobile time in forced swimming test and tail-suspension test without sex differences. Regarding the change in the body weight, only the males showed a significant reduction on days 17 and 24 after treatment. Furthermore, the CH group showed significantly increased corticosterone and decreased oxytocin (OXT) levels in serum, while the mRNA levels of OXT, vasopressin and oxytocin receptor were remarkably upregulated in the hypothalamus of the CH group. However, there was no significant change in the vasopressin receptor V1a. Interestingly, compared with the Ctrl group, there was a significant decrease in butyrate in serum of the CH group. Consistently, they had mild liver dysfunction with increased alanine transaminase, extended hepatic sinus surrounded by enhanced SLC22A9, and significantly increased Iba1-positive macrophages. Moreover, the expression of tight junction protein (Occludin and ZO-1) obviously decreased in the colon with increasing Iba1-positive cells. These results suggest that isosexual pair-housing with PSD mice causes the healthy partners to develop depressive-like behaviors with disturbances in the gut and liver.

Anti-depressive-like and cognitive impairment alleviation effects of Gastrodia elata Blume water extract is related to gut microbiome remodeling in ApoE-/- mice exposed to unpredictable chronic mild stress

ETHNOPHARMACOLOGY RELEVANCE

Gastrodia elata Blume (GE) is a traditional Chinese dietary therapy used to treat neurological disorders. Gastrodia elata Blume water extract (WGE) has been shown to ameliorate inflammation and improve social frustration in mice in a chronic social defeat model. However, studies on the anti-depressive-like effects and cognitive impairment alleviation related to the impact of WGE on the gut microbiome of ApoE-/- mice remain elusive.

AIM OF THE STUDY

The present study aimed to investigate the anti-depressive-like effect and cognitive impairment alleviation and mechanisms of WGE in ApoE-/- mice subjected to unpredictable chronic mild stress (UCMS), as well as its impact on the gut microbiome of the mice.

MATERIALS AND METHODS

Sixty ApoE-/- mice (6 months old) were randomly grouped into six groups: control, UCMS, WGE groups [5, 10, 20 mL WGE/kg body weight (bw) + UCMS], and a positive group (fluoxetine 20 mg/kg bw + UCMS). After four weeks of the UCMS paradigm, the sucrose preference, novel object recognition, and open field tests were conducted. The neurotransmitters serotonin (5-HT), dopamine (DA) and their metabolites were measured in the prefrontal cortex. Serum was collected to measure corticosterone and amyloid-42 (Aβ-42) levels. Feces were collected, and the gut microbiome was analyzed.

RESULTS

WGE restored sucrose preference, exploratory behavior, recognition ability, and decreased the levels of serum corticosterone and Aβ-42 in ApoE-/- mice to alleviate depressive-like behavior and cognitive impairment. Furthermore, WGE regulated the monoamine neurotransmitter via reduced the 5-HT and DA turnover rates in the prefrontal cortex. Moreover, WGE elevated the levels of potentially beneficial bacteria such as Bifidobacterium, Akkermansia, Alloprevotella, Defluviitaleaceae_UCG-011, and Bifidobacterium pseudolongum as well as balanced fecal short-chain fatty acids (SCFAs).

CONCLUSION

WGE demonstrates anti-depressive-like effects, cognitive impairment alleviation, and gut microbiome and metabolite regulation in ApoE-/- mice. Our results support the possibility of developing a functional and complementary medicine to prevent or alleviate depression and cognitive decline using WGE in CVDs patients.

The Influence of Probiotic Supplementation on the Severity of Anxiety and Depressive Symptoms; Function and Composition of Gut Microbiota; and Metabolic, Inflammation, and Oxidative Stress Markers in Patients with Depression-A Study Protocol

This article aims to present the theoretical basis, methodology, and design of a clinical trial we will conduct. The study will be prospective, randomized, placebo-controlled, and double-blind. Each intervention period will last 8 weeks and the trial will be conducted on 100 patients in total, who will be randomly divided into two groups consisting of 50 patients each. We plan to investigate the impact of Lactobacillus helveticus Rosell and Bifidobacterium longum Rosell on the depressive, anxiety, and stress levels in patients with depressive disorders with possible comorbid anxiety. In addition to assessing the influence of probiotics on the clinical condition, we also plan to study the clinical and biochemical parameters of metabolic syndrome, which often coexists with depression. Both depressive and metabolic issues may have part of their etiopathology in common, e.g., inflammation, oxidative stress, and dysbiosis. This is why we will additionally investigate the parameters related to gut microbiota, inflammatory, and oxidative statuses. Thus, the primary endpoint of the study will be the change in depression score measured with the Montgomery-Åsberg Depression Rating Scale. The secondary endpoints will include changes in anxiety and stress levels, as well as metabolic, inflammation, and oxidative stress parameters.

Microbiota-Gut-Brain Axis: Pathophysiological Mechanism in Neuropsychiatric Disorders

Gut microbiota influence human behavior. The immunological, metabolic, and endocrine systems are involved in bidirectional communication between the gut and the brain, which is regulated by microbes through the microbiota-derived neurochemicals and metabolites. Gut microbiota have certain effects on neurodevelopment and maturation of immunity. However, gut dysbiosis can lead to neuropsychiatric disorders. Animal research and clinical case-control studies have demonstrated that gut dysbiosis has an adverse effect on human behavior through a variety of mechanisms. Recent meta-analysis on clinical studies confirmed gut dysbiosis in several major neuropsychiatric disorders. Microbiota-targeted intervention has recently been in the spotlight and meta-analyses have confirmed its effectiveness. In this chapter, we summarize the evidence for the interactions between microbiota and brain-gut network, as well as the potential pathophysiological mechanisms involved.

Prophylactic Effect of Bovine Colostrum on Intestinal Microbiota and Behavior in Wild-Type and Zonulin Transgenic Mice

The microbiota-gut-brain axis (MGBA) involves bidirectional communication between intestinal microbiota and the gastrointestinal (GI) tract, central nervous system (CNS), neuroendocrine/neuroimmune systems, hypothalamic-pituitary-adrenal (HPA) axis, and enteric nervous system (ENS). The intestinal microbiota can influence host physiology and pathology. Dysbiosis involves the loss of beneficial microbial input or signal, diversity, and expansion of pathobionts, which can lead to loss of barrier function and increased intestinal permeability (IP). Colostrum, the first milk from mammals after birth, is a natural source of nutrients and is rich in oligosaccharides, immunoglobulins, growth factors, and anti-microbial components. The aim of this study was to investigate if bovine colostrum (BC) administration might modulate intestinal microbiota and, in turn, behavior in two mouse models, wild-type (WT) and Zonulin transgenic (Ztm)-the latter of which is characterized by dysbiotic microbiota, increased intestinal permeability, and mild hyperactivity-and to compare with control mice. Bioinformatics analysis of the microbiome showed that consumption of BC was associated with increased taxonomy abundance (p = 0.001) and diversity (p = 0.004) of potentially beneficial species in WT mice and shifted dysbiotic microbial community towards eubiosis in Ztm mice (p = 0.001). BC induced an anxiolytic effect in WT female mice compared with WT female control mice (p = 0.0003), and it reduced anxiogenic behavior in Ztm female mice compared with WT female control mice (p = 0.001), as well as in Ztm male mice compared with WT BC male mice (p = 0.03). As evidenced in MGBA interactions, BC supplementation may well be applied for prophylactic approaches in the future. Further research is needed to explore human interdependencies between intestinal microbiota, including eubiosis and pathobionts, and neuroinflammation, and the potential value of BC for human use. The MGH Institutional Animal Care and Use Committee authorized the animal study (2013N000013).

Surveying the Genetic Design Space for Transcription Factor-Based Metabolite Biosensors: Synthetic Gamma-Aminobutyric Acid and Propionate Biosensors in E. coli Nissle 1917

Engineered probiotic bacteria have been proposed as a next-generation strategy for noninvasively detecting biomarkers in the gastrointestinal tract and interrogating the gut-brain axis. A major challenge impeding the implementation of this strategy has been the difficulty to engineer the necessary whole-cell biosensors. Creation of transcription factor-based biosensors in a clinically-relevant strain often requires significant tuning of the genetic parts and gene expression to achieve the dynamic range and sensitivity required. Here, we propose an approach to efficiently engineer transcription-factor based metabolite biosensors that uses a design prototyping construct to quickly assay the gene expression design space and identify an optimal genetic design. We demonstrate this approach using the probiotic bacterium Escherichia coli Nissle 1917 (EcN) and two neuroactive gut metabolites: the neurotransmitter gamma-aminobutyric acid (GABA) and the short-chain fatty acid propionate. The EcN propionate sensor, utilizing the PrpR transcriptional activator from E. coli, has a large 59-fold dynamic range and >500-fold increased sensitivity that matches biologically-relevant concentrations. Our EcN GABA biosensor uses the GabR transcriptional repressor from Bacillus subtilis and a synthetic GabR-regulated promoter created in this study. This work reports the first known synthetic microbial whole-cell biosensor for GABA, which has an observed 138-fold activation in EcN at biologically-relevant concentrations. Using this rapid design prototyping approach, we engineer highly functional biosensors for specified in vivo metabolite concentrations that achieve a large dynamic range and high output promoter activity upon activation. This strategy may be broadly useful for accelerating the engineering of metabolite biosensors for living diagnostics and therapeutics.

Role of Short Chain Fatty Acids in Epilepsy and Potential Benefits of Probiotics and Prebiotics: Targeting “Health” of Epileptic Patients

The WHO’s definition of health transcends the mere absence of disease, emphasizing physical, mental, and social well-being. As this perspective is being increasingly applied to the management of chronic diseases, research on gut microbiota (GM) is surging, with a focus on its potential for persistent and noninvasive dietary therapeutics. In patients with epilepsy (PWE), a chronic lack of seizure control along with often neglected psychiatric comorbidities greatly disrupt the quality of life. Evidence shows that GM-derived short chain fatty acids (SCFAs) may impact seizure susceptibility through modulating (1) excitatory/inhibitory neurotransmitters, (2) oxidative stress and neuroinflammation, and (3) psychosocial stress. These functions are also connected to shared pathologies of epilepsy and its two most common psychiatric consequences: depression and anxiety. As the enhancement of SCFA production is enabled through direct administration, as well as probiotics and prebiotics, related dietary treatments may exert antiseizure effects. This paper explores the potential roles of SCFAs in the context of seizure control and its mental comorbidities, while analyzing existing studies on the effects of pro/prebiotics on epilepsy. Based on currently available data, this study aims to interpret the role of SCFAs in epileptic treatment, extending beyond the absence of seizures to target the health of PWE.

Short-Chain Fatty Acids Ameliorate Depressive-Like Behaviors of High Fructose-Fed Mice by Rescuing Hippocampal Neurogenesis Decline and Blood–Brain Barrier Damage

Excessive fructose intake is associated with the increased risk of mental illness, such as depression, but the underlying mechanisms are poorly understood. Our previous study found that high fructose diet (FruD)-fed mice exhibited neuroinflammation, hippocampal neurogenesis decline and blood–brain barrier (BBB) damage, accompanied by the reduction of gut microbiome-derived short-chain fatty acids (SCFAs). Here, we found that chronic stress aggravated these pathological changes and promoted the development of depressive-like behaviors in FruD mice. In detail, the decreased number of newborn neurons, mature neurons and neural stem cells (NSCs) in the hippocampus of FruD mice was worsened by chronic stress. Furthermore, chronic stress exacerbated the damage of BBB integrity with the decreased expression of zonula occludens-1 (ZO-1), claudin-5 and occludin in brain vasculature, overactivated microglia and increased neuroinflammation in FruD mice. These results suggest that high fructose intake combined with chronic stress leads to cumulative negative effects that promote the development of depressive-like behaviors in mice. Of note, SCFAs could rescue hippocampal neurogenesis decline, improve BBB damage and suppress microglia activation and neuroinflammation, thereby ameliorate depressive-like behaviors of FruD mice exposed to chronic stress. These results could be used to develop dietary interventions to prevent depression.

Gut Microbiota Metabolites in Major Depressive Disorder-Deep Insights into Their Pathophysiological Role and Potential Translational Applications

The gut microbiota is a complex and dynamic ecosystem essential for the proper functioning of the organism, affecting the health and disease status of the individuals. There is continuous and bidirectional communication between gut microbiota and the host, conforming to a unique entity known as "holobiont". Among these crosstalk mechanisms, the gut microbiota synthesizes a broad spectrum of bioactive compounds or metabolites which exert pleiotropic effects on the human organism. Many of these microbial metabolites can cross the blood-brain barrier (BBB) or have significant effects on the brain, playing a key role in the so-called microbiota-gut-brain axis. An altered microbiota-gut-brain (MGB) axis is a major characteristic of many neuropsychiatric disorders, including major depressive disorder (MDD). Significative differences between gut eubiosis and dysbiosis in mental disorders like MDD with their different metabolite composition and concentrations are being discussed. In the present review, the main microbial metabolites (short-chain fatty acids -SCFAs-, bile acids, amino acids, tryptophan -trp- derivatives, and more), their signaling pathways and functions will be summarized to explain part of MDD pathophysiology. Conclusions from promising translational approaches related to microbial metabolome will be addressed in more depth to discuss their possible clinical value in the management of MDD patients.

Gut Microbiota and Depressive Symptoms at the End of CRT for Rectal Cancer: A Cross-Sectional Pilot Study

BACKGROUND

The role of alterations in gut microbiota composition (termed dysbiosis) has been implicated in the pathobiology of depressive symptoms; however, evidence remains limited. This cross-sectional pilot study is aimed at exploring whether depressive symptom scores changed during neoadjuvant chemotherapy and radiation therapy to treat rectal cancer, and if gut microbial taxa abundances and predicted functional pathways correlate with depressive symptoms at the end of chemotherapy and radiation therapy.

METHODS

40 newly diagnosed rectal cancer patients (ages 28-81; 23 males) were assessed for depressive symptoms using the Hamilton Rating Scale for Depression (HAM-D) and provided stool samples for 16S rRNA sequencing. Gut microbiome data were analyzed using QIIME2, and correlations and regression analyses were performed in R.

RESULTS

Participants had significantly higher depressive symptoms at the end as compared to before CRT. The relative abundances of Gemella, Bacillales Family XI, Actinomyces, Streptococcus, Lactococcus, Weissella, and Leuconostocaceae were positively correlated (Spearman's rho = 0.42 to 0.32), while Coprobacter, Intestinibacter, Intestimonas, Lachnospiraceae, Phascolarctobacterium, Ruminiclostridium, Ruminococcaceae (UCG-005 and uncultured), Tyzzerella, and Parasutterella (Spearman's rho = -0.43 to - 0.31) were negatively correlated with HAM-D scores. Of the 14 predicted MetaCyc pathways that correlated with depressive symptom scores at the end of CRT, 11 (79%) were associated with biosynthetic pathways.

CONCLUSIONS

Significant bacterial taxa and predicted functional pathways correlated with depressive symptoms at the end of chemotherapy and radiation therapy for rectal cancer which warrants further examination and replication of our findings.