Mechanistic Insights into the Link between Gut Dysbiosis and Major Depression: An Extensive Review

Psychedelic-assisted Therapy as a Promising Treatment for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is prevalent and can be disabling. Many patients remain symptomatic despite behavioral and medical therapies. Psychedelic-assisted therapy (PAT), in which serotonergic agents like psilocybin are administered in a psychotherapeutic context, has shown promise for refractory psychiatric disorders, including major depressive disorder and post-traumatic stress disorder. Emerging evidence suggests PAT may also be beneficial for chronic pain conditions, including fibromyalgia, low back pain, and migraines. IBS is highly comorbid with depression, anxiety, and other chronic pain disorders, suggesting shared cognitive and neurological roots and potentially shared therapeutic targets. In this editorial, we discuss 3 lines of evidence for PAT as a treatment for IBS, under the overarching themes of (1) psychological mechanisms (the findings from historic studies of psychedelics for chronic pain and the elements of psychobiological dysfunction targeted by PAT), (2) central nervous system mechanisms (default mode network modulation and induction of neuroplasticity), and (3) the neurointestinal pathophysiology of IBS that may be modified by PAT. We argue that this evidence suggests PAT is worthy of study as a new therapy for IBS, and potentially for other disorders of gut-brain interaction (DGBI). Successful application of PAT to gastrointestinal disease would represent a major step beyond mind-body dualism, with potential implications for other functional somatic disorders.

Depression in Diarrhea-Predominant IBS Patients: Exploring the Link Between Gut Barrier Dysfunction and Erythrocyte Polyunsaturated Fatty Acid Levels

Background: Patients with irritable bowel syndrome (IBS) often experience comorbid psychological conditions, notably depression and anxiety. Evidence suggests that these conditions are linked to gut barrier dysfunction, dysbiosis, and chronic inflammation. All these factors are central to IBS pathophysiology and mood disturbances. Polyunsaturated fatty acids (PUFAs) play crucial roles in modulating inflammation and depression. This study examined the associations among intestinal permeability, PUFA profiles, low-grade inflammation, and depression severity in IBS patients with diarrhea (IBS-D). Methods: Forty-three IBS-D patients (7 men, 36 women; 44.56 ± 1.52 years) were categorized into depressed (IBS-D(d+)) and non-depressed (IBS-D(d-)) groups according to scores on the depression subscale of the Symptom Checklist-90-Revised (SCL-90-R). Biomarkers of small intestinal permeability (s-IP) were assessed in urine and blood, alongside erythrocyte membrane PUFA composition, dysbiosis, and inflammation indices. Results: IBS-D (d+) patients exhibited elevated s-IP and altered PUFA metabolism compared to their IBS-D (d-) counterparts. Additionally, in the first group, omega-3 PUFA concentrations inversely correlated with s-IP biomarkers, while the omega-6/omega-3 ratio showed a positive correlation. Moreover, depression severity is significantly associated with s-IP markers and omega-3 PUFA levels. Lastly, IBS-D (d+) patients exhibited higher levels of dysbiosis and pro-inflammatory cytokines than IBS-D (d-) patients. Conclusions: These findings highlight the interplay between intestinal barrier integrity and PUFA metabolism in IBS-D patients with depression, suggesting that s-IP markers and erythrocyte PUFA profiles could represent novel therapeutic targets for managing depression in this population. This study was registered on ClinicalTrials.gov (NCT03423069), with a date of registration of 30 January 2018.

Early-life gut microbiome is associated with behavioral disorders in the Rio birth cohort

Emerging evidence has been linking changes in the early-life gut microbiome and neurodevelopmental outcomes. The founder bacteria that first colonize the infant's gut determine the microbial succession that signals host tissues and impact development including the brain. Here we investigated the association between the meconium microbiome and neurobehavior. To this end, we surveyed the 16S rRNA gene on meconium samples and assessed behavioral outcomes at six-months of age by the Denver Developmental Screening Test II (DDST-II). Among the four behavioral domains investigated, the personal-social domain was associated with significant differences in meconium bacterial beta diversity (unweighted UniFrac; R2 0.078, p = 0.021) and reduced alpha diversity (β = -2.290, 95% CI = -4.212; CI = -0.368), after adjustment for gestational antibiotics, preterm delivery, and delivery mode. Besides, this altered neurobehavior (failing to meet the milestone) was associated with overrepresented Ruminococcaceae, Christensenellaceae, and Eubacterium, Treponema, Senegalimassilia, Ruminiclostridium, Roseburia, Romboutsia, Prevotella, and Veillonella seminalis. Predicted functional genes showed reduced abundance in association with altered neurobehavior (all q < 0.15). Fine and gross motor skills presented no associations with the microbiome. This pilot study shows associations between the first gut microbiome and behavioral outcomes that deserve further studies in different neonate populations.

Advances in molecular mechanisms and therapeutic strategies for central nervous system diseases based on gut microbiota imbalance

BACKGROUD

Central nervous system (CNS) diseases pose a serious threat to human health, but the regulatory mechanisms and therapeutic strategies of CNS diseases need to be further explored. It has been demonstrated that the gut microbiota (GM) is closely related to CNS disease. GM structure disorders, abnormal microbial metabolites, intestinal barrier destruction and elevated inflammation exist in patients with CNS diseases and promote the development of CNS diseases. More importantly, GM remodeling alleviates CNS pathology to some extent.

AIM OF REVIEW

Here, we have summarized the regulatory mechanism of the GM in CNS diseases and the potential treatment strategies for CNS repair based on GM regulation, aiming to provide safer and more effective strategies for CNS repair from the perspective of GM regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The abundance and composition of GM is closely associated with the CNS diseases. On the basis of in-depth analysis of GM changes in mice with CNS disease, as well as the changes in its metabolites, therapeutic strategies, such as probiotics, prebiotics, and FMT, may be used to regulate GM balance and affect its microbial metabolites, thereby promoting the recovery of CNS diseases.

The influence of seminal microbiota on human testicular steroidogenesis: a prospective study

OBJECTIVE

Preclinical evidence has demonstrated that gut microbiota composition can influence steroid hormone biosynthesis and spermatogenesis. This study aims to investigate the association of seminal microbiota and testicular steroidogenesis.

PATIENTS AND METHODS

One hundred adult eugonadal men were consecutively enrolled. The seminal concentration of Lactobacilli, anaerobic and facultative bacteria, as well as serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and total testosterone (TT) were evaluated. Unadjusted and adjusted multi-regression models were built to evaluate the relationship between seminal Lactobacilli, anaerobic and facultative bacteria, and Lactobacilli/total bacteria ratio, and serum LH, FSH, and TT. The concentrations of seminal Lactobacilli, anaerobic, and facultative bacteria predictive of serum TT values in the lowest quartile (< 3.8 ng/mL) were calculated.

RESULTS

TT levels were weakly and positively correlated with seminal Lactobacillus concentration (r = 0.33; p = 0.001), with seminal Lactobacilli/total bacteria ratio (r = 0.89; p < 0.001), and negatively with anaerobic and facultative bacteria (r = - 0.69; p < 0.001). Opposite correlations were found for gonadotropin concentrations. These data persisted after adjustment for confounding factors. Seminal concentration of Lactobacilli ≤ 0.1 × 106/mL (AUC 0.917, 95% CI: 0.845 to 0.963), of anaerobic and facultative bacteria > 2 × 104/mL (AUC 0.924, 95% CI: 0.853 to 0.967), or a Lactobacilli/total bacteria ratio ≤ 90% (AUC 0.910, 95% CI: 0.837 to 0.958) were found to predict serum TT level < 3.8 ng/mL with a sensitivity of 92.0% and a specificity of 88.0%.

CONCLUSION

A relationship between the composition of the seminal microbiota and testicular steroidogenesis seems to exist. The mechanisms underlying this association are still unknown.

The role of the gut microbiome in disorders of gut-brain interaction

Disorders of Gut-Brain Interaction (DGBI) are widely prevalent and commonly encountered in gastroenterology practice. While several peripheral and central mechanisms have been implicated in the pathogenesis of DGBI, a recent body of work suggests an important role for the gut microbiome. In this review, we highlight how gut microbiota and their metabolites affect physiologic changes underlying symptoms in DGBI, with a particular focus on their mechanistic influence on GI transit, visceral sensitivity, intestinal barrier function and secretion, and CNS processing. This review emphasizes the complexity of local and distant effects of microbial metabolites on physiological function, influenced by factors such as metabolite concentration, duration of metabolite exposure, receptor location, host genetics, and underlying disease state. Large-scale in vitro work has elucidated interactions between host receptors and the microbial metabolome but there is a need for future research to integrate such preclinical findings with clinical studies. The development of novel, targeted therapeutic strategies for DGBI hinges on a deeper understanding of these metabolite-host interactions, offering exciting possibilities for the future of treatment of DGBI.

Repeated exposure to antibiotics exhibits anxiety-like behaviors with a reduction in neurogenesis in the ventral hippocampus of dentate gyrus

Disruption of gut microbiota balance is known to contribute to the development of anxiety; however, it remains unclear whether dysbiosis-induced anxiety involves the glycogen synthase kinase-3β (GSK-3β)/cAMP response element binding protein (CREB)/brain-derived neurotrophic factor (BDNF) pathway and neurogenesis in the ventral hippocampal dentate gyrus (DG). In this study, Male ddY mice were administered an antibacterial cocktail to induce dysbiosis. The dysbiosis model displayed anxiety-like behaviors in the hole-board and elevated plus-maze tests, decreased the phosphorylation levels of GSK-3β (Ser9) and CREB, decreased the expression level of BDNF in the ventral hippocampus, and reduced neurogenesis in the ventral hippocampal DG. This suggests that dysbiosis-induced anxiety-like behaviors are associated with reduced neurogenesis in the ventral hippocampal DG via the GSK-3β/CREB/BDNF pathway.

Psychobiotic Protection of Nutritional Supplements and Probiotics in Patients Undergoing Hemodialysis: A Randomized Trial

BACKGROUND/OBJECTIVES

The prevalence of depression and anxiety symptoms is remarkably high in malnourished individuals undergoing hemodialysis. The goal of this project was to evaluate the impact of administering an oral nutritional supplement combined with a probiotic blend on the microbiota, intestinal permeability, and depression symptoms in malnourished hemodialysis patients.

METHODS

With this aim, a randomized trial was conducted with three parallel groups: a control group with individualized diet, a supplement-placebo (SU-PL) group with oral nutritional supplementation (ONS), and a supplement-probiotic (SU-PR) group with ONS in conjunction with a probiotic blend. Blood and fecal samples were collected at basal time, and at 3 and 6 months. Several blood biomarkers, like zonulin, lipopolysaccharide-binding protein (LBP), lipopolysaccharide (LPS), and brain-derived neurotrophic factor (BDNF), were measured, and the fecal microbiome was sequenced with the Illumina platform. The Hospital Anxiety and Depression Scale (HADS) was used for the estimation of depression (HADS-D) and anxiety (HADS-A) symptoms, along with the standardized mental health index SF12-MH from the general health questionnaire SF-12.

RESULTS

The results showed that patients who consumed the probiotic blend maintained the LPS levels from their baseline readings and decreased their BDNF levels compared to the SU-PL or control groups. Moreover, a significant decrease in HADS-D scores (less depressive symptoms) and an increase in SF12-MH scores (higher quality of life) were found in that group in comparison to the other groups. The intervention produced an impact on the microbiome population, where the SU-PR group had reduced Akkermansia abundance with respect to the other groups, while their Acidaminococcus abundance decreased and their Barnesiella abundance increased with respect to the SU-PL group.

CONCLUSIONS

Overall, the results indicate that the probiotic with the nutritional supplement could reduce the intestinal permeability biomarkers and improve depressive symptoms and quality of life in malnourished hemodialysis patients.

Unpredictable chronic mild stress induced anxio-depressive disorders and enterobacteria dysbiosis: Potential protective effects of Detariummicrocarpum

ETHNOPHARMACOLOGICAL RELEVANCE

Detarium microcarpum Guill. & Perr. is used traditionally in Far North Cameroun to treat stomach aches, anxiety, epilepsy, and other mental disorders.

AIM OF THE STUDY

Evaluate the anxiolytic and antidepressant-like effects of D. microcarpum (DM) in unpredictable chronic mild stress (UCMS) model of depression in male rats and its impact on fecal enterobacteria of stressed rats.

MATERIALS AND METHODS

Rats were handled daily (control) or subjected to the UCMS procedure for 42 days. Anxiety-like behaviors were assessed using the light and dark box test (LBD) and the open field test (OFT). Depressive-like behaviors were assessed using the forced swimming test (FST), the sucrose preference test (SPT), and the novelty suppressed feeding test (NSFT). Feces were then collected, followed by blood, brain, and duodenum sections after sacrifice. Monoamine levels, pro-inflammatory cytokines, oxidative stress factors, and nitrosative stress were assessed. Feces were introduced into Hectoen enteric agar for the identification of enterobacteria. An in vitro growth test was performed.

RESULTS

The DM ethanolic extract has significantly increased the time spent in the light box, in the LBD, and in the center area of the OFT. Moreover, the extract has significantly reduced the preference for sucrose in the SPT, the time of immobility in the FST, and the latency period to consume the pet in the NSFT. DM extract has significantly reduced serum cortisol levels. It also significantly decreased the pro-inflammatory cytokines TNF-α and Il-1β in both brain and duodenum homogenate. DM has increased the brain's serotonin, GABA, and dopamine levels. The DM extract also decreased the MDA and nitrite levels. It also increased the SOD and CAT activities in both brain and duodenal homogenate. Histologically, the DM extract restored the cell's density in hippocampi sections and prevented gut inflammation and peroxidation characterizing leaky gut syndrome. DM extract has no effect on the growth of enterobacteria species isolated in vitro.

CONCLUSION

The ethanolic extract of DM would have anxiolytic and antidepressant effects via the modulation of the HPA axis, brain antioxidant enzyme activities, inflammation, and nitrosative stress. Moreover, it could act by preventing leaky gut syndrome.

Sleep deprivation-induced shifts in gut microbiota: Implications for neurological disorders

Sleep deprivation is a prevalent issue in contemporary society, with significant ramifications for both physical and mental well-being. Emerging scientific evidence illuminates its intricate interplay with the gut-brain axis, a vital determinant of neurological function. Disruptions in sleep patterns disturb the delicate equilibrium of the gut microbiota, resulting in dysbiosis characterized by alterations in microbial composition and function. This dysbiosis contributes to the exacerbation of neurological disorders such as depression, anxiety, and cognitive decline through multifaceted mechanisms, including heightened neuroinflammation, disturbances in neurotransmitter signalling, and compromised integrity of the gut barrier. In response to these challenges, there is a burgeoning interest in therapeutic interventions aimed at restoring gut microbial balance and alleviating neurological symptoms precipitated by sleep deprivation. Probiotics, dietary modifications, and behavioural strategies represent promising avenues for modulating the gut microbiota and mitigating the adverse effects of sleep disturbances on neurological health. Moreover, the advent of personalized interventions guided by advanced omics technologies holds considerable potential for tailoring treatments to individualized needs and optimizing therapeutic outcomes. Interdisciplinary collaboration and concerted research efforts are imperative for elucidating the underlying mechanisms linking sleep, gut microbiota, and neurological function. Longitudinal studies, translational research endeavours, and advancements in technology are pivotal for unravelling the complex interplay between these intricate systems.

The Role of Gut Microbiota Dysbiosis in Erectile Dysfunction: From Pathophysiology to Treatment Strategies

Erectile dysfunction (ED) is a prevalent male sexual disorder characterized by the persistent inability to achieve or maintain an erection sufficient for satisfactory sexual performance. While its etiology is multifactorial, encompassing vascular, neurological, hormonal, and psychological components, emerging evidence suggests a significant role for gut microbiota dysbiosis in its development. The gut microbiota influences various metabolic, inflammatory, and neuropsychological processes critical to erectile function. Dysbiosis can lead to systemic inflammation, endothelial dysfunction, hormonal imbalances, and altered neurotransmitter production, all of which are key factors in ED pathogenesis. This narrative review synthesizes current research on the association between gut microbiota alterations and ED, highlighting specific bacterial taxa implicated in ED through mechanisms involving inflammation, metabolic disturbances, and hormonal regulation. This review explores potential mechanisms linking gut microbiota and ED, including pro-inflammatory cytokines, gut barrier integrity disruption, metabolic disorders, psychological factors via the gut-brain axis, and hormonal regulation. Furthermore, the gut microbiota offers promising avenues for developing non-invasive biomarkers and therapeutic interventions such as probiotics, prebiotics, dietary modifications, and fecal microbiota transplantation. Future research should focus on longitudinal studies, mechanistic explorations, and clinical trials to validate these findings and translate them into clinical practice. Understanding the interplay between the gut microbiota and erectile function could unveil novel diagnostic biomarkers and pave the way for innovative treatments targeting the microbiota, ultimately improving men's sexual and overall health.

Critical Review of the Cross-Links Between Dietary Components, the Gut Microbiome, and Depression

The complex relationship between diet, the gut microbiota, and mental health, particularly depression, has become a focal point of contemporary research. This critical review examines how specific dietary components, such as fiber, proteins, fats, vitamins, minerals, and bioactive compounds, shape the gut microbiome and influence microbial metabolism in order to regulate depressive outcomes. These dietary-induced changes in the gut microbiota can modulate the production of microbial metabolites, which play vital roles in gut-brain communication. The gut-brain axis facilitates this communication through neural, immune, and endocrine pathways. Alterations in microbial metabolites can influence central nervous system (CNS) functions by impacting neuroplasticity, inflammatory responses, and neurotransmitter levels-all of which are linked to the onset and course of depression. This review highlights recent findings linking dietary components with beneficial changes in gut microbiota composition and reduced depressive symptoms. We also explore the challenges of individual variability in responses to dietary interventions and the long-term sustainability of these strategies. The review underscores the necessity for further longitudinal and mechanistic studies to elucidate the precise mechanisms through which diet and gut microbiota interactions can be leveraged to mitigate depression, paving the way for personalized nutritional therapies.

Limited Changes in Red Blood Cell Parameters After Probiotic Supplementation in Depressive Individuals: Insights from a Secondary Analysis of the PRO-DEMET Randomized Controlled Trial

Background: Depression often coexists with anemia, potentially sharing common pathways, highlighting the need for treatments addressing both conditions simultaneously. This study evaluated the effect of probiotics on red blood cell (RBC) parameters in adults with depressive disorder. We hypothesized that probiotics would positively influence RBC parameters, potentially modulated by baseline inflammation or dietary intake, with improved RBC function correlating with better antidepressant outcomes. Methods: This secondary analysis of a two-arm, randomized, double-blind, controlled trial involved 116 adults with depressive disorder. Participants received a probiotic formulation containing Lactobacillus helveticus Rosell®-52 and Bifidobacterium longum Rosell®-175 or a placebo for 60 days. Data from 97 subjects were analyzed for RBC parameters, including hemoglobin (HGB), RBC count, hematocrit (HCT), mean corpuscular volume (MCV), mean hemoglobin concentration (MCH), mean corpuscular hemoglobin concentration (MCHC), and RBC distribution width (RDW). Results: Probiotic supplementation did not result in significant changes in RBC parameters compared to the placebo. However, probiotics may help stabilize HGB, HCT, MCH, and MCHC levels, potentially preventing fluctuations observed in the placebo group. Conclusions: While probiotics showed potential benefits for depressive symptoms, significant changes in RBC parameters were not observed. Larger studies are needed to clarify the mechanisms and clinical implications.

Gut microbiome-gut brain axis-depression: interconnection

OBJECTIVES

The relationship between the gut microbiome and mental health, particularly depression, has gained significant attention. This review explores the connection between microbial metabolites, dysbiosis, and depression. The gut microbiome, comprising diverse microorganisms, maintains physiological balance and influences health through the gut-brain axis, a communication pathway between the gut and the central nervous system.

METHODS

Dysbiosis, an imbalance in the gut microbiome, disrupts this axis and worsens depressive symptoms. Factors like diet, antibiotics, and lifestyle can cause this imbalance, leading to changes in microbial composition, metabolism, and immune responses. This imbalance can induce inflammation, disrupt neurotransmitter regulation, and affect hormonal and epigenetic processes, all linked to depression.

RESULTS

Microbial metabolites, such as short-chain fatty acids and neurotransmitters, are key to gut-brain communication, influencing immune regulation and mood. The altered production of these metabolites is associated with depression. While progress has been made in understanding the gut-brain axis, more research is needed to clarify causative relationships and develop new treatments. The emerging field of psychobiotics and microbiome-targeted therapies shows promise for innovative depression treatments by harnessing the gut microbiome's potential.

CONCLUSIONS

Epigenetic mechanisms, including DNA methylation and histone modifications, are crucial in how the gut microbiota impacts mental health. Understanding these mechanisms offers new prospects for preventing and treating depression through the gut-brain axis.

Phenome-wide investigation of bidirectional causal relationships between major depressive disorder and common human diseases

The high comorbidity of major depressive disorder (MDD) with other diseases has been well-documented. However, the pairwise causal connections for MDD comorbid networks are poorly characterized. We performed Phenome-wide Mendelian randomization (MR) analyses to explore bidirectional causal associations between MDD (N = 807,553) and 877 common diseases from FinnGen datasets (N = 377,277). The inverse variance weighting method was the primary technique, and other methods (weighted median and MR-Egger) were used for sensitivity analyses. Our MR analyses showed that the genetic liability to MDD is causally associated with the risks of 324 disease phenotypes (average b: 0.339), including 46 psychiatric and behavioral disorders (average b: 0.618), 18 neurological diseases (average b: 0.348), 44 respiratory diseases (average b: 0.345), 40 digestive diseases (average b: 0.281), 18 circulatory diseases (average b: 0.237), 37 genitourinary diseases (average b: 0.271), 66 musculoskeletal and connective diseases (average b: 0.326), 22 endocrine diseases (average b: 0.302), and others. In a reverse analysis, a total of 51 genetic components predisposing to various diseases were causally associated with MDD risk (average b: 0.086), including 5 infectious diseases (average b: 0.056), 11 neurological diseases (average b: 0.106), 14 oncological diseases (average b: 0.108), and 5 psychiatric and behavioral disorders (average b: 0.114). Bidirectional causal associations were identified between MDD and 15 diseases. For most MR analyses, little evidence of heterogeneity and pleiotropy was detected. Our findings confirmed the extensive and significant causal role of genetic predisposition to MDD in contributing to human disease phenotypes, which were more pronounced than those seen in the reverse analysis of the causal influences of other diseases on MDD.

Unraveling the Role of the Blood-Brain Barrier in the Pathophysiology of Depression: Recent Advances and Future Perspectives

Depression is a highly prevalent psychological disorder characterized by persistent dysphoria, psychomotor retardation, insomnia, anhedonia, suicidal ideation, and a remarkable decrease in overall well-being. Despite the prevalence of accessible antidepressant therapies, many individuals do not achieve substantial improvement. Understanding the multifactorial pathophysiology and the heterogeneous nature of the disorder could lead the way toward better outcomes. Recent findings have elucidated the substantial impact of compromised blood-brain barrier (BBB) integrity on the manifestation of depression. BBB functions as an indispensable defense mechanism, tightly overseeing the transport of molecules from the periphery to preserve the integrity of the brain parenchyma. The dysfunction of the BBB has been implicated in a multitude of neurological disorders, and its disruption and consequent brain alterations could potentially serve as important factors in the pathogenesis and progression of depression. In this review, we extensively examine the pathophysiological relevance of the BBB and delve into the specific modifications of its components that underlie the complexities of depression. A particular focus has been placed on examining the effects of peripheral inflammation on the BBB in depression and elucidating the intricate interactions between the gut, BBB, and brain. Furthermore, this review encompasses significant updates on the assessment of BBB integrity and permeability, providing a comprehensive overview of the topic. Finally, we outline the therapeutic relevance and strategies based on BBB in depression, including COVID-19-associated BBB disruption and neuropsychiatric implications. Understanding the comprehensive pathogenic cascade of depression is crucial for shaping the trajectory of future research endeavors.

Exploring the Potential of Probiotics and Prebiotics in Major Depression: From Molecular Function to Clinical Therapy

Major depressive disorder (MDD) represents a complex and challenging mental health condition with multifaceted etiology. Recent research exploring the gut-brain axis has shed light on the potential influence of gut microbiota on mental health, offering novel avenues for therapeutic intervention. This paper reviews current evidence on the role of prebiotics and probiotics in the context of MDD treatment. Clinical studies assessing the effects of prebiotic and probiotic interventions have demonstrated promising results, showcasing improvements in depression symptoms and metabolic parameters in certain populations. Notably, prebiotics and probiotics have shown the capacity to modulate inflammatory markers, cortisol levels, and neurotransmitter pathways linked to MDD. However, existing research presents varied outcomes, underscoring the need for further investigation into specific microbial strains, dosage optimization, and long-term effects. Future research should aim at refining personalized interventions, elucidating mechanisms of action, and establishing standardized protocols to integrate these interventions into clinical practice. While prebiotics and probiotics offer potential adjunctive therapies for MDD, continued interdisciplinary efforts are vital to harnessing their full therapeutic potential and reshaping the landscape of depression treatment paradigms.

The gut microbiota-brain connection: insights into major depressive disorder and bipolar disorder

Major depressive disorder (MDD) and bipolar disorder (BD) are two of the most prevalent mood disorders that seriously jeopardize both physical and mental health. The current diagnosis of MDD and BD relies primarily on clinical symptoms. However, correctly differentiating between MDD and BD during depressive episode states remains a substantial clinical challenge. The human gut hosts a large and diverse microbiota, which plays a pivotal role in various physiological processes. Emerging evidence suggests that the gut microbiota (GM) exerts beneficial effects on mental health disorders, including MDD, BD, and schizophrenia, through the microbe-gut-brain axis (MGBA). In recent years, the relationship between GM and mood disorders has garnered considerable attention, leading to intensive research in this area. The MGBA is a bidirectional communication system between the gut and the brain. Growing evidence indicates that the brain can influence the GM, which in turn may modulate the brain through this axis. This review aims to explore the changes in the GM of patients with MDD and BD and evaluate the effects of different treatments on their GM, including medication, probiotic, prebiotic and synbiotic interventions, and fecal microbiota transplantation (FMT). By doing so, we seek to identify potential disease-specific biomarkers, improve differential diagnosis, and offer novel therapeutic avenues for these disorders.

Dysbiosis and fecal microbiota transplant: Contemplating progress in health, neurodegeneration and longevity

The gut-brain axis plays an important role in mental health. The intestinal epithelial surface is colonized by billions of commensal and transitory bacteria, known as the Gut Microbiota (GM). However, potential pathogens continuously stimulate intestinal immunity when they find the place. The last two decades have witnessed several studies revealing intestinal bacteria as a key factor in the health-disease balance of the gut, as well as disease-emergent in other parts of the body. Various neurological processes, such as cognition, learning, and memory, could be affected by dysbiosis in GM. Additionally, the aging process and longevity are related to systemic inflammation caused by dysbiosis. Commensal GM affects brain development, behavior, and healthy aging suggesting that building changes in GM might be a potential therapeutic method. The innovation in GM dysbiosis is intervention by Fecal Microbiota Transplantation (FMT), which has been confirmed as a therapy for recurrent Clostridium difficile infections and is promising for other clinical disorders, such as Parkinson's disease, Multiple Sclerosis (MS), Alzheimer's disease, and depression. Additionally, FMT may be possible to promote healthy aging, and extend longevity. This review aims to connect dysbiosis, neurological disorders, and aging and the potential of FMT as a therapeutic strategy to treat these disorders, and to enhance the quality of life in the elderly.

Regulation of gut microbiota and serum neurotransmitters in mice by Streptococcus thermophilus GA8- and Lacticaseibacillus rhamnosus HAO9-fermented milk containing high levels of gamma-aminobutyric acid

BACKGROUND

Gamma-aminobutyric acid (GABA) is an important neurotransmitter in the human body, with several negative emotions reported as being associated with GABA dysregulation. This study investigates the safety and modulatory effects of GABA-enriched milk, fermented by Streptococcus thermophilus GA8 and Lacticasebacillus rhamnosus HAO9, on the gut microbiota and neurotransmitter profiles in mice.

RESULTS

Through rigorous culturing and fermentation processes, we achieved consistent GABA production in milk, with concentrations reaching 4.6 and 8.5 g L-1 for GA8-fermented and co-fermented milk, respectively, after 48 h. Using SPF male C57BL/6J mice, we administered either mono-culture or combined-culture milk treatments and monitored physiological impacts. The treatments did not affect mouse body weight but induced significant changes in gut microbiota composition. Beta diversity analysis revealed distinct microbial profiles between treatment groups, highlighting fermentation-specific microbial shifts, such as an increase in Verrucomicrobia for the GA8 group and a modulation in Saccharibacteria_genera_incertae_sedis for the GA8 + HAO9 group. Serum neurotransmitter levels were elevated in both treatment groups, with significant increases in l-glutamine, l-tryptophan and, notably, serotonin hydrochloride in the GA8 + HAO9 group. Correlation analysis identified a positive association between specific bacterial genera and neurotransmitter levels, suggesting a probiotic effect on neuroactive substances.

CONCLUSION

These findings suggest that fermented milk has potential as a probiotic supplement for mood improvement and stress relief, highlighting its role in modulating the gut-brain axis. © 2024 Society of Chemical Industry.

Effect of dietary fibre on cognitive function and mental health in children and adolescents: a systematic review and meta-analysis

Objective: The purpose of this study is to investigate the impact of dietary fibre on the mental health and cognitive function of children and adolescents. Methods: All interventional and observational studies that contained information on the relevant population (children and adolescents), intervention/exposures (high dietary fibre consumption) and outcomes (mental and cognitive parameters) were eligible. Eight electronic databases (Embase, Medline, Pubmed, Web of Science, Scopus, PsycINFO, Cochrane Library and ClinicalTrials.gov) were searched up to December 11, 2023. Results: A total of 15 studies (n = 4628) met inclusion criteria, consisting of 9 intervention trials and 6 observational studies. According to observational studies, higher dietary fibre consumption was associated with a 49% reduction in the odds of depression compared to lower intake (P < 0.0001; OR = 0.51; 95% CI: 0.38, 0.69; I2 = 0%). Furthermore, no significant correlations were found between dietary fibre consumption and intelligence or anxiety. Among intervention studies, no significant difference was observed between fibre supplementation and placebo in terms of anxiety (standardized mean difference (SMD): -0.23; 95% CI: -0.72, 0.27), stress (SMD: 0.03; 95% CI: -0.21, 0.28), memory (SMD: 0.46; 95% CI: -0.79, 1.71), or attention (SMD: -2.72; 95% CI: -6.30, 0.86). Conclusion: Evidence from observation studies demonstrated that higher dietary fibre consumption is associated with a decreased odds of depression symptoms, both in childhood and adolescence. However, the causal relationship between dietary fibre intake and mental and cognitive function in children and adolescents still requires further clarification through high-quality intervention studies in the future.

Effects of Dietary Fiber, Phenolic Compounds, and Fatty Acids on Mental Health: Possible Interactions with Genetic and Epigenetic Aspects

Scientific evidence shows that dietary patterns are a key environmental determinant of mental health. Dietary constituents can modify epigenetic patterns and thus the gene expression of relevant genetic variants in various mental health conditions. In the present work, we describe some nutrigenomic effects of dietary fiber, phenolic compounds (plant secondary metabolites), and fatty acids on mental health outcomes, with emphasis on their possible interactions with genetic and epigenetic aspects. Prebiotics, through their effects on the gut microbiota, have been associated with modulation in the neuroendocrine response to stress and the facilitation of the processing of positive emotions. Some of the genetic and epigenetic mechanisms include the serotonin neurotransmitter system (TPH1 gene) and the brain-derived neurotrophic factor (inhibition of histone deacetylases). The consumption of phenolic compounds exerts a positive role in neurocognitive domains. The evidence showing the involvement of genetic and epigenetic factors comes mainly from animal models, highlighting the role of epigenetic mechanisms through miRNAs and methyltransferases as well as the effect on the expression of apoptotic-related genes. Long-chain n-3 fatty acids (EPA and DHA) have been mainly related to psychotic and mood disorders, but the genetic and epigenetic evidence is scarce. Studies on the genetic and epigenetic basis of these interactions need to be promoted to move towards a precision and personalized approach to medicine.

Role of Semaphorin 3A in common psychiatric illnesses such as schizophrenia, depression, and anxiety

With societal development and an ageing population, psychiatric disorders have become a common cause of severe and long-term disability and socioeconomic burdens worldwide. Semaphorin 3A (Sema-3A) is a secreted glycoprotein belonging to the semaphorin family. Sema-3A is well known as an axon guidance factor in the neuronal system and a potent immunoregulator at all stages of the immune response. It is reported to have various biological functions and is involved in many human diseases, including autoimmune diseases, angiocardiopathy, osteoporosis, and tumorigenesis. The signals of sema-3A involved in the pathogenesis of these conditions, are transduced through its cognate receptors and diverse downstream signalling pathways. An increasing number of studies show that sema-3A plays important roles in synaptic and dendritic development, which are closely associated with the pathophysiological mechanisms of psychiatric disorders, including schizophrenia, depression, and autism, suggesting the involvement of sema-3A in the pathogenesis of mental diseases. This indicates that mutations in sema-3A and alterations in its receptors and signalling may compromise neurodevelopment and predispose patients to these disorders. However, the role of sema-3A in psychiatric disorders, particularly in regulating neurodevelopment, remains elusive. In this review, we summarise the recent progress in understanding sema-3A in the pathogenesis of mental diseases and highlight sema-3A as a potential target for the prevention and treatment of these diseases.

Fecal microbiota transplantation alleviates mild-moderate COVID-19 associated diarrhoea and depression symptoms: A prospective study of a randomized, double-blind clinical trial

Currently, the emergence of the endemic Coronavirus disease (COVID-19) situation still poses a serious threat to public health. However, it remains elusive about the role of fecal microbiota transplantation in treating COVID-19. We performed a randomized, double-blind, placebo-controlled clinical trial enrolling a cohort of 40 COVID-19 patients with mild-moderate symptoms. Our results showed that fecal microbiota transplantation provided an amelioration in diarrhoea (p = 0.026) of digestive system and depression (p = 0.006) of neuropsychiatric-related symptom in COVID-19 patients, respectively. Meanwhile, we found that the number of patients with diarrhoea decreased from 19 to 0 on day 7 after fecal microbiota transplantation treatment, and it was statistically changed compared to the placebo group (p = 0.047). Of note, the serum concentration of aspartate aminotransferase-to-alanine aminotransferase ratio (AST/ALT, fecal microbiota transplantation, pre vs. post: 0.966 vs. 0.817), a biomarker for predicting long COVID-19, was significantly reduced by fecal microbiota transplantation. In all, our study supports that fecal microbiota transplantation could be a novel therapeutic strategy for COVID-19 patients with diarrhoea and depressive symptoms, which is potentially valuable in ameliorating long COVID-19 symptoms.

The Role of Intestinal Microbiota and Probiotics Supplementation in Multiple Sclerosis Management

Multiple sclerosis (MS) is a neurological autoimmune disorder predominantly afflicting young adults. The etiology of MS is intricate, involving a variety of environmental and genetic factors. Current research increasingly focuses on the substantial contribution of gut microbiota in MS pathogenesis. The commensal microbiota resident within the intestinal milieu assumes a central role within the intricate network recognized as the gut-brain axis (GBA), wielding beneficial impact in neurological and psychological facets. As a result, the modulation of gut microbiota is considered a pivotal aspect in the management of neural disorders, including MS. Recent investigations have unveiled the possibility of using probiotic supplements as a promising strategy for exerting a positive impact on the course of MS. This therapeutic approach operates through several mechanisms, including the reinforcement of gut epithelial integrity, augmentation of the host's resistance against pathogenic microorganisms, and facilitation of mucosal immunomodulatory processes. The present study comprehensively explains the gut microbiome's profound influence on the central nervous system (CNS). It underscores the pivotal role played by probiotics in forming the immune system and modulating neurotransmitter function. Furthermore, the investigation elucidates various instances of probiotic utilization in MS patients, shedding light on the potential therapeutic advantages afforded by this intervention.

Anxiolytic, Antidepression, and Memory-Enhancing Effects of the Novel Instant Soup RJ6601 in the Middle-Aged of Female Rats

Due to the health benefits of polyphenols and dietary fiber in combating mental disorders, we hypothesized that a polyphenol- and dietary fiber-enriched soup (RJ6601) would improve mental wellness in a rat model of middle-aged women. To test this hypothesis, female Wistar rats aged 18 months (350-450 g) were orally administered RJ6601 at doses of 200 and 400 mg/kg BW for 28 days. The anxiolytic, antidepression, and memory-enhancing effects were assessed every 7 days throughout the study period. The neuron density and levels of activities of AChE, total MAO, MAO-A, MAO-B, MDA, SOD, CAT, GSH-Px, IL-1β, IL-6, and BDNF in the prefrontal cortex at the end of study were also investigated. Furthermore, the amounts of Lactobacillus spp. and Bifidobacterium spp. in their feces were also determined. The results revealed that the developed soup shows anxiolytic, antidepression, and memory-enhancing effects. An increased neuron density; reductions in AChE, total MAO, MAO-A, MAO-B, and MDA; and an elevation of serum BDNF, together with increased amounts of both bacterial species in feces, were also observed. Our results suggest that RJ6601 is a potential mental wellness promotion supplement that enhances BDNF levels, brain plasticity, neurotransmitter balance, and oxidative stress and inflammation status, along with improving microbiota.

Current landscape of fecal microbiota transplantation in treating depression

Depression, projected to be the predominant contributor to the global disease burden, is a complex condition with diverse symptoms including mood disturbances and cognitive impairments. Traditional treatments such as medication and psychotherapy often fall short, prompting the pursuit of alternative interventions. Recent research has highlighted the significant role of gut microbiota in mental health, influencing emotional and neural regulation. Fecal microbiota transplantation (FMT), the infusion of fecal matter from a healthy donor into the gut of a patient, emerges as a promising strategy to ameliorate depressive symptoms by restoring gut microbial balance. The microbial-gut-brain (MGB) axis represents a critical pathway through which to potentially rectify dysbiosis and modulate neuropsychiatric outcomes. Preclinical studies reveal that FMT can enhance neurochemicals and reduce inflammatory markers, thereby alleviating depressive behaviors. Moreover, FMT has shown promise in clinical settings, improving gastrointestinal symptoms and overall quality of life in patients with depression. The review highlights the role of the gut-brain axis in depression and the need for further research to validate the long-term safety and efficacy of FMT, identify specific therapeutic microbial strains, and develop targeted microbial modulation strategies. Advancing our understanding of FMT could revolutionize depression treatment, shifting the paradigm toward microbiome-targeting therapies.

Sleep apnoea, gut dysbiosis and cognitive dysfunction

Sleep disorders are becoming increasingly common, and their distinct effects on physical and mental health require elaborate investigation. Gut dysbiosis (GD) has been reported in sleep-related disorders, but sleep apnoea is of particular significance because of its higher prevalence and chronicity. Cumulative evidence has suggested a link between sleep apnoea and GD. This review highlights the gut-brain communication axis that is mediated via commensal microbes and various microbiota-derived metabolites (e.g. short-chain fatty acids, lipopolysaccharide and trimethyl amine N-oxide), neurotransmitters (e.g. γ-aminobutyric acid, serotonin, glutamate and dopamine), immune cells and inflammatory mediators, as well as the vagus nerve and hypothalamic-pituitary-adrenal axis. This review also discusses the pathological role underpinning GD and altered gut bacterial populations in sleep apnoea and its related comorbid conditions, particularly cognitive dysfunction. In addition, the review examines the preclinical and clinical evidence, which suggests that prebiotics and probiotics may potentially be beneficial in sleep apnoea and its comorbidities through restoration of eubiosis or gut microbial homeostasis that regulates neural, metabolic and immune responses, as well as physiological barrier integrity via the gut-brain axis.

Therapeutic benefit of probiotic in alcohol dependence syndrome: Evidence from a tertiary care centre of India

Probiotic adjuvant has promising effects in treating alcohol induced hepatitis, depression, and anxiety. This study aimed to assess the effectiveness of adjuvant probiotic use in improving the liver functions, anxiety, and depression among patients with alcohol dependence syndrome (ADS) in a tertiary care hospital in Andhra Pradesh, India. In this prospective observational design, ADS patients with or without probiotics were followed-up at one and three months after initiation of treatment. They were assessed for liver function test (LFT), anxiety by HAM-A and depression by HAM-D scale. A total of 120 patients complied with the treatment, 60 in each group, mean age being 35.0 years (SD 9.5 years). The baseline socio-demographic and clinical characteristics were similar in both the groups. Significant reduction was noted in the probiotic group for total bilirubin (Mean difference (MD) 0.18; 95 % CI: 0.04, 0.31), AST (MD 5.0; 95 % CI: 0.5, 9.5), and ALT (MD 8.6; 95 % CI: 1.4, 15.7) at one month after treatment. Both the groups showed a considerable change in anxiety and depression scores (HAM-A and HAM-D) till three months. At three months of treatment initiation, proportional improvement of severity grade to mild form in anxiety was more in the probiotic group (35 %) than the non-probiotic group (13.3 %) (p < 0.05). Hence, probiotic supplementation can significantly reduce the hepatic enzymes and depression severity in patients with alcohol dependence syndrome but demands additional robust evidence on the causal inference.

Human Gut Microbiota for Diagnosis and Treatment of Depression

Nowadays, depressive disorder is spreading rapidly all over the world. Therefore, attention to the studies of the pathogenesis of the disease in order to find novel ways of early diagnosis and treatment is increasing among the scientific and medical communities. Special attention is drawn to a biomarker and therapeutic strategy through the microbiota-gut-brain axis. It is known that the symbiotic interactions between the gut microbes and the host can affect mental health. The review analyzes the mechanisms and ways of action of the gut microbiota on the pathophysiology of depression. The possibility of using knowledge about the taxonomic composition and metabolic profile of the microbiota of patients with depression to select gene compositions (metagenomic signature) as biomarkers of the disease is evaluated. The use of in silico technologies (machine learning) for the diagnosis of depression based on the biomarkers of the gut microbiota is given. Alternative approaches to the treatment of depression are being considered by balancing the microbial composition through dietary modifications and the use of additives, namely probiotics, postbiotics (including vesicles) and prebiotics as psychobiotics, and fecal transplantation. The bacterium Faecalibacterium prausnitzii is under consideration as a promising new-generation probiotic and auxiliary diagnostic biomarker of depression. The analysis conducted in this review may be useful for clinical practice and pharmacology.

Importance of good hosting: reviewing the bi-directionality of the microbiome-gut-brain-axis

Gut microorganisms have been shown to significantly impact on central function and studies that have associated brain disorders with specific bacterial genera have advocated an anomalous gut microbiome as the pathophysiological basis of several psychiatric and neurological conditions. Thus, our knowledge of brain-to-gut-to microbiome communication in this bidirectional axis seems to have been overlooked. This review examines the known mechanisms of the microbiome-to-gut-to-brain axis, highlighting how brain-to-gut-to-microbiome signaling may be key to understanding the cause of disrupted gut microbial communities. We show that brain disorders can alter the function of the brain-to-gut-to-microbiome axis, which will in turn contribute to disease progression, while the microbiome-to gut-to brain direction presents as a more versatile therapeutic axis, since current psychotropic/neurosurgical interventions may have unwanted side effects that further cause disruption to the gut microbiome. A consideration of the brain-to-gut-to-microbiome axis is imperative to better understand how the microbiome-gut-brain axis overall is involved in brain illnesses, and how it may be utilized as a preventive and therapeutic tool.

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.

Microbial composition, functionality, and stress resilience or susceptibility: unraveling sex-specific patterns

BACKGROUND

Following exposure to traumatic stress, women are twice as likely as men to develop mood disorders. Yet, individual responses to such stress vary, with some people developing stress-induced psychopathologies while others exhibit resilience. The factors influencing sex-related disparities in affective disorders as well as variations in resilience remain unclear; however, emerging evidence suggests differences in the gut microbiota play a role. In this study, using the single prolonged stress (SPS) model of post-traumatic stress disorder, we investigated pre- and post-existing differences in microbial composition, functionality, and metabolites that affect stress susceptibility or resilience in each sex.

METHODS

Male and female Sprague-Dawley rats were randomly assigned to control or SPS groups. Two weeks following SPS, the animals were exposed to a battery of behavioral tests and decapitated a day later. Based on their anxiety index, they were further categorized as SPS-resilient (SPS-R) or SPS-susceptible (SPS-S). On the day of dissection, cecum, and selected brain tissues were isolated. Stool samples were collected before and after SPS, whereas urine samples were taken before and 30 min into the SPS.

RESULTS

Before SPS exposure, the sympathoadrenal axis exhibited alterations within male subgroups only. Expression of tight junction protein claudin-5 was lower in brain of SPS-S males, but higher in SPS-R females following SPS. Across the study, alpha diversity remained consistently lower in males compared to females. Beta diversity revealed distinct separations between male and female susceptible groups before SPS, with this separation becoming evident in the resilient groups following SPS. At the genus level, Lactobacillus, Lachnospiraceae_Incertae_Sedis, and Barnesiella exhibited sex-specific alterations, displaying opposing abundances in each sex. Additionally, sex-specific changes were observed in microbial predictive functionality and targeted functional modules both before and after SPS. Alterations in the microbial short-chain fatty acids (SCFAs), were also observed, with major and minor SCFAs being lower in SPS-susceptible males whereas branched-chain SCFAs being higher in SPS-susceptible females.

CONCLUSION

This study highlights distinct pre- and post-trauma differences in microbial composition, functionality, and metabolites, associated with stress resilience in male and female rats. The findings underscore the importance of developing sex-specific therapeutic strategies to effectively address stress-related disorders. Highlights SPS model induces divergent anxiety and social behavioral responses to traumatic stress in both male and female rodents. SPS-resilient females displayed less anxiety-like behavior and initiated more interactions towards a juvenile rat than SPS-resilient males. Sex-specific pre-existing and SPS-induced differences in the gut microbial composition and predictive functionality were observed in susceptible and resilient rats. SPS-resilient males displayed elevated cecal acetate levels, whereas SPS-susceptible females exhibited heightened branched-chain SCFAs.

Exploring gender differences in the relationship between gut microbiome and depression - a scoping review

Background

Major depressive disorder (MDD) exhibits gender disparities, and emerging evidence suggests the involvement of the gut microbiome, necessitating exploration of sex-specific differences.

Methods

A review was conducted, encompassing a thorough examination of relevant studies available in Medline via Ovid, Embase via OvidSP, CINAHL, and PsycINFO databases from their inception to June 2023. The search strategy employed specific keywords and Medical Subject Headings (MeSH) terms tailored to major depressive disorder in women, encompassing unipolar depression, depressive symptoms, and dysbiosis.

Results

Five studies were included. Among the four studies, alterations in alpha (n=1) and beta diversity (n=3) in the gut microbiome of individuals with MDD were revealed compared to controls. Gender-specific differences were observed in four studies, demonstrating the abundance of specific bacterial taxa and highlighting potential sex-specific implications in MDD pathophysiology. Correlation analyses (n=4) indicated associations between certain bacterial taxa and the severity of depressive symptoms, with varying patterns between males and females. Studies (n=3) also highlighted promising findings regarding the potential utility of microbial markers in diagnosing MDD, emphasizing the crucial role of sex stratification in understanding the disease pathophysiology.

Conclusions

The findings underscore the importance of recognizing gender-specific differences in the composition of the gut microbiome and its relationship with MDD. Further comprehensive robust studies are required to unravel the intricate mechanisms underlying these disparities.

Systematic identification of the role of gut microbiota in mental disorders: a TwinsUK cohort study

Mental disorders are complex disorders influenced by multiple genetic, environmental, and biological factors. Specific microbiota imbalances seem to affect mental health status. However, the mechanisms by which microbiota disturbances impact the presence of depression, stress, anxiety, and eating disorders remain poorly understood. Currently, there are no robust biomarkers identified. We proposed a novel pyramid-layer design to accurately identify microbial/metabolomic signatures underlying mental disorders in the TwinsUK registry. Monozygotic and dizygotic twins discordant for mental disorders were screened, in a pairwise manner, for differentially abundant bacterial genera and circulating metabolites. In addition, multivariate analyses were performed, accounting for individual-level confounders. Our pyramid-layer study design allowed us to overcome the limitations of cross-sectional study designs with significant confounder effects and resulted in an association of the abundance of genus Parabacteroides with the diagnosis of mental disorders. Future research should explore the potential role of Parabacteroides as a mediator of mental health status. Our results indicate the potential role of the microbiome as a modifier in mental disorders that might contribute to the development of novel methodologies to assess personal risk and intervention strategies.

A Study of the Relationship between Inflammatory Immune Function and Intestinal Flora in Adolescent Patients with First-Episode Depression

BACKGROUND

Depression has become one of the most common mood disorders in adolescents, with an increasing incidence each year. Abnormal activation of peripheral immunity causes an increase in pro-inflammatory factors, which in turn affects neuroendocrine dysfunction and alters neurobiochemistry, leading to depression. In this study, we aimed to explore the relationship between inflammatory immune function and intestinal flora in adolescents with first-episode depression.

METHODS

A total of 170 cases of adolescent patients with first-episode depression who attended our hospital from January 2020 to March 2023 were retrospectively selected as the observation group. Simultaneously, 170 individuals who underwent a healthy physical examination during the same period were chosen as the control group. The enzyme-linked immunosorbent assay (ELISA) was employed to quantify the levels of monoamine neurotransmitters 5-hydroxytryptamine (5-HT), substance P (SP), neuropeptide Y (NPY), serum tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 in the patients. Flow cytometry was utilized to assess the levels of T-lymphocytes CD3+, CD4+, and CD8+ cells. The levels of 16S ribosomal RNA (16SrRNA) method were used to determine the intestinal flora of the subjects in both groups. Inflammatory factor levels, immune function, and intestinal flora expression were observed, and correlation analysis was performed.

RESULTS

The levels of 5-HT and NPY in the observation group were lower than those in the control group. The SP level was significantly higher in the observation group compared to the control group (p < 0.05). The observation group demonstrated significantly higher TNF-α, IL-1β, and IL-6 levels than the control group (p < 0.05). The values of CD3+, CD4+, CD4+/CD8+ in the observation group were lower than those in the control group (p < 0.05), whereas the CD8+ values were notably higher (p < 0.05). Bifidobacterium, Escherichia coli, Lactobacillus, and Bacteroides in the observation group were less than those in the control group (p < 0.05). The content of Bifidobacterium was negatively correlated with the level of TNF-α (r = -0.358, p < 0.001), positively correlated with the level of CD3+, CD4+, CD4+/CD8+ (r = 0.490, 0.169, 0.165, p < 0.05), and negatively correlated with the level of CD8+ (r = -0.154, p < 0.05). The level of Escherichia coli content was negatively correlated with the levels of IL-6, CD3+, CD4+, CD4+/CD8+ (r = -0.483, -0.548, -0.317, -0.328, p < 0.001), and positively correlated with the levels of CD8+ (r = 0.325, p < 0.001). The content of Lactobacillus was positively correlated with the levels of CD3+, CD4+, CD4+/CD8+ (r = 0.552, 0.188, 0.194, p < 0.05), and negatively correlated with the level of CD8+ (r = -0.186, p < 0.05). The content of Bacteroides was positively correlated with the level of CD3+, CD4+, CD4+/CD8+ (r = -0.570, -0.183, -0.193, p < 0.05), and negatively correlated with the level of CD8+ levels were positively correlated (r = 0.187, p < 0.05).

CONCLUSIONS

The intestinal flora is related to the level of inflammatory factors and immune function. Further study on the relationship between intestinal flora, inflammatory immune function, and depression could offer novel insights for the prevention and treatment of depressive disorders.

Contributing roles of mitochondrial dysfunction and hepatocyte apoptosis in liver diseases through oxidative stress, post-translational modifications, inflammation, and intestinal barrier dysfunction

This review provides an update on recent findings from basic, translational, and clinical studies on the molecular mechanisms of mitochondrial dysfunction and apoptosis of hepatocytes in multiple liver diseases, including but not limited to alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and drug-induced liver injury (DILI). While the ethanol-inducible cytochrome P450-2E1 (CYP2E1) is mainly responsible for oxidizing binge alcohol via the microsomal ethanol oxidizing system, it is also responsible for metabolizing many xenobiotics, including pollutants, chemicals, drugs, and specific diets abundant in n-6 fatty acids, into toxic metabolites in many organs, including the liver, causing pathological insults through organelles such as mitochondria and endoplasmic reticula. Oxidative imbalances (oxidative stress) in mitochondria promote the covalent modifications of lipids, proteins, and nucleic acids through enzymatic and non-enzymatic mechanisms. Excessive changes stimulate various post-translational modifications (PTMs) of mitochondrial proteins, transcription factors, and histones. Increased PTMs of mitochondrial proteins inactivate many enzymes involved in the reduction of oxidative species, fatty acid metabolism, and mitophagy pathways, leading to mitochondrial dysfunction, energy depletion, and apoptosis. Unique from other organelles, mitochondria control many signaling cascades involved in bioenergetics (fat metabolism), inflammation, and apoptosis/necrosis of hepatocytes. When mitochondrial homeostasis is shifted, these pathways become altered or shut down, likely contributing to the death of hepatocytes with activation of inflammation and hepatic stellate cells, causing liver fibrosis and cirrhosis. This review will encapsulate how mitochondrial dysfunction contributes to hepatocyte apoptosis in several types of liver diseases in order to provide recommendations for targeted therapeutics.

The role of nutrition in mild traumatic brain injury rehabilitation for service members and veterans

BACKGROUND

Veterans Affairs and the Department of Defense (DOD) acknowledge that nutrition may be a modifier of mild traumatic brain injury (TBI) sequelae. Military clinicians are considering nutritional supplements and dietary interventions when managing patients with mild TBI. Therefore, clinicians should be familiar with the current evidence for nutritional interventions in mild TBI and special considerations related to the military lifestyle.

OBJECTIVE

This narrative review aims to summarize the existing evidence surrounding the role of special diets and select nutrients in mild TBI outcomes, gut microbiota changes, and special considerations for Service members and Veterans recovering from mild TBI.

METHODS

We conducted a literature review in PubMed and Google Scholar limited to nutritional interventions and nine topics with primary focus on mild TBI, although we included some articles related to moderate-to-severe TBI where relevant: 1) ketogenic diet, 2) Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, 3) omega-3 fatty acids, 4) creatine, 5) vitamin D, 6) weight management, 7) gut microbiota, 8) caffeine, and 9) alcohol. We summarized key findings and safety factors where appropriate for each intervention. We also identified nutritional supplement safety and operational rations considerations and areas in need of further research.

RESULTS

Preclinical studies and early human trials suggest that the specific nutrients and diets discussed in the current article may offer neuroprotection or benefit during mild TBI rehabilitation. Omega-3 fatty acids, creatine, and vitamin D are generally safe when taken within recommended guidelines.

CONCLUSION

More evidence is needed to support nutritional recommendations for enhancing neuroprotection and mitigating mild TBI symptoms in humans. The DOD's Warfighter Nutrition Guide recommends a whole food diet rich in antioxidants, phytonutrients, omega-3 fatty acids, micronutrients, probiotics, and fiber to optimize long-term health and performance.

Regulation of colonic neuropeptide Y expression by the gut microbiome in patients with ulcerative colitis and its association with anxiety- and depression-like behavior in mice

Patients with inflammatory bowel disease (IBD), including ulcerative colitis (UC), show an increased incidence of anxiety and depression; however, the association between UC-associated psychiatric disorders and the gut microbiota is unclear. This study aimed to examine whether gut microbiota from patients with UC can alter colonic gene expression, leading to anxiety- and depression-like behavior in mice receiving fecal microbiota transplantation (FMT). RNA sequencing transcriptome analyses revealed a difference in colonic gene expression between mice receiving FMT from patients with UC (UC-FMT mice) and those receiving FMT from healthy controls (HC-FMT mice). Gene ontology analysis revealed the downregulation of neuropeptide signaling pathways, including neuropeptide Y (NPY) expression, in the colons of UC-FMT mice. The protein levels of NPY also decreased in the colon and plasma of UC-FMT mice compared to those in HC-FMT mice. The oral administration of Enterococcus mundtii (EM), a bacterium isolated from the feces of patients with UC, reduced NPY expression in the colons of mice and induced intestinal inflammation, anxiety, and depression-like behavior. Reduced NPY protein levels were also observed in the plasma and hippocampus of EM-treated mice. Intraperitoneal administration of NPY significantly alleviated anxiety- and depressive-like behaviors induced by EM in mice. Capsular polysaccharide in EM was associated with EM-induced NPY downregulation in the colon. Analysis of Gene Expression Omnibus datasets showed markedly reduced NPY expression in the inflamed colons of patients with UC compared with that in the colons of healthy controls. In summary, EM-induced reduction in the colonic expression of NPY may be associated with a decrease in hippocampal NPY and anxiety- and depression-like behavior in mice.

Gut microbiota composition may be an indicator of erectile dysfunction

Erectile Dysfunction (ED) is considered a physical and mental illness. A variety of potential associations between gut microbiota and health or disease have been found. By comparing the gut microbiota of healthy controls and ED patients, our study investigated the relationship between ED and gut microbiota. The results revealed that the ED group exhibited a significantly higher relative abundance of Bacteroides, Fusobacterium, Lachnoclostridium, Escherichia-Shigella and Megamonas, while showing a significantly lower relative abundance of Bifidobacterium compared to the control group. The dysbiosis of gut microbiota played a role in the onset and progression of ED by influencing the gut barrier, cardiovascular system and mental health, which provided a novel perspective on understanding the pathophysiology of ED. What is more, we had identified several key gut microbiota. By combining 16S rRNA sequencing with machine learning techniques, we were able to uncover the significant value and impact of gut microbiota in the early detection of ED.

Gut liver brain axis in diseases: the implications for therapeutic interventions

Gut-liver-brain axis is a three-way highway of information interaction system among the gastrointestinal tract, liver, and nervous systems. In the past few decades, breakthrough progress has been made in the gut liver brain axis, mainly through understanding its formation mechanism and increasing treatment strategies. In this review, we discuss various complex networks including barrier permeability, gut hormones, gut microbial metabolites, vagus nerve, neurotransmitters, immunity, brain toxic metabolites, β-amyloid (Aβ) metabolism, and epigenetic regulation in the gut-liver-brain axis. Some therapies containing antibiotics, probiotics, prebiotics, synbiotics, fecal microbiota transplantation (FMT), polyphenols, low FODMAP diet and nanotechnology application regulate the gut liver brain axis. Besides, some special treatments targeting gut-liver axis include farnesoid X receptor (FXR) agonists, takeda G protein-coupled receptor 5 (TGR5) agonists, glucagon-like peptide-1 (GLP-1) receptor antagonists and fibroblast growth factor 19 (FGF19) analogs. Targeting gut-brain axis embraces cognitive behavioral therapy (CBT), antidepressants and tryptophan metabolism-related therapies. Targeting liver-brain axis contains epigenetic regulation and Aβ metabolism-related therapies. In the future, a better understanding of gut-liver-brain axis interactions will promote the development of novel preventative strategies and the discovery of precise therapeutic targets in multiple diseases.

Post-translational modifications of histone and non-histone proteins in epigenetic regulation and translational applications in alcohol-associated liver disease: Challenges and research opportunities

Epigenetic regulation is a process that takes place through adaptive cellular pathways influenced by environmental factors and metabolic changes to modulate gene activity with heritable phenotypic variations without altering the DNA sequences of many target genes. Epigenetic regulation can be facilitated by diverse mechanisms: many different types of post-translational modifications (PTMs) of histone and non-histone nuclear proteins, DNA methylation, altered levels of noncoding RNAs, incorporation of histone variants, nucleosomal positioning, chromatin remodeling, etc. These factors modulate chromatin structure and stability with or without the involvement of metabolic products, depending on the cellular context of target cells or environmental stimuli, such as intake of alcohol (ethanol) or Western-style high-fat diets. Alterations of epigenetics have been actively studied, since they are frequently associated with multiple disease states. Consequently, explorations of epigenetic regulation have recently shed light on the pathogenesis and progression of alcohol-associated disorders. In this review, we highlight the roles of various types of PTMs, including less-characterized modifications of nuclear histone and non-histone proteins, in the epigenetic regulation of alcohol-associated liver disease (ALD) and other disorders. We also describe challenges in characterizing specific PTMs and suggest future opportunities for basic and translational research to prevent or treat ALD and many other disease states.

The Intertwining Roads between Psychological Distress and Gut Microbiota in Inflammatory Bowel Disease

Inflammatory bowel disease represents one of the most life-altering gastrointestinal pathologies, with its multifactorial nature and unclear physiopathology. The most relevant clinical forms, ulcerative colitis and Crohn's disease, clinically manifest with mild to severe flares and remission periods that alter the patient's social, familial and professional integration. The chronic inflammatory activity of the intestinal wall determines severe modifications of the local environment, such as dysbiosis, enteric endocrine, nervous and immune system disruptions and intestinal wall permeability changes. These features are part of the gastrointestinal ecosystem that modulates the bottom-to-top signaling to the central nervous system, leading to a neurobiologic imbalance and clinical affective and/or behavioral symptoms. The gut-brain link is a bidirectional pathway and psychological distress can also affect the central nervous system, which will alter the top-to-bottom regulation, leading to possible functional digestive symptoms and local inflammatory responses. In the middle of this neuro-gastrointestinal system, the microbiome is a key player, as its activities offer basic functional support for both relays. The present article presents current scientific information that links the pathophysiology and clinical aspects of inflammatory bowel disease and psychiatric symptomatology through the complex mechanism of the gut-brain axis and the modulatory effects of the gut microbiota.

The synergistic mechanism of action of Dajianzhong decoction in conjunction with ketamine in the treatment of depression

Depression is a multifactorial syndrome with a variety of underlying pathological mechanisms. While ketamine, an N-methyl-D-aspartate receptor (NMDAR) antagonist, exhibits a rapid antidepressant action in the central never system (CNS), the potential addiction and psychotomimetic adverse effects of ketamine limit its chronic use in clinical practice. Therefore, it is necessary to discover an additional agent that shows a synergistic antidepressant activity with ketamine to sustain its therapeutic action so as to reduce its use frequency in depression treatment. The present study indicated that Dajianzhong decoction (DJZT), an empirical herbal formula used for the clinical treatment of several inflammation-related intestinal disorders, sustains behavioral and synaptic action of ketamine in depressive mouse models. Additionally, ketamine was also demonstrated to exert a synergistic action with DJZT to alleviate the chronic unpredictable mild stress (CUMS)-induced abnormalities in gut barrier proteins and colonic histology, and subsequently to normalize the diversity and composition of gut microbiota. Furthermore, DJZT was shown to possess an anti-inflammatory activity to prevent activation of NF-κB from releasing proinflammatory cytokines, specifically through inhibiting Th17 cells/IL-17A pathway. Our results uncovered the mechanism of action of DJZT in conjunction with ketamine in depression treatment by which these agents target different pathological factors across biological systems and exert a synergistic activity through a bidirectional communication in the gut-brain axis, and also provided new insights into the systematic treatment of depression.

Gut brain regulation using psychobiotics for improved neuropsychological illness

"Psychobiotics" are a novel class of probiotics that are beneficial to the health and functional efficiency of our brain and psychology. The main hold on command in ill conditions of the brain and psychology is overtaken by these psychobiotic bacteria (a dietary supplement) via the action/determined role of bacterial neurochemicals or neuroactive substances that are released by them in the intestinal epithelium after their ingestion. Although these psychobiotics flourish in the gut of the host consuming them, the effect is widely spread to the brain due to the communication between the gut and the brain via the bidirectional gut-brain axis. The nervous system involved in this directional process includes both the enteric nervous system and the central nervous system. With time, several corroborations have proved the effectiveness of psychobiotics in terms of mental illnesses and brain disorders. In the prevailing situation of the coronavirus pandemic, psychobiotics may serve as an aid because a majority of the population worldwide is already suffering from psychological issues due to changes in lifestyle and dietary habits, and in need of an immediate solution to cope with it. Moreover, the in silico approach is also vital for the development of biological relevance to neurosubstances.

The extract based on the Kampo formula daikenchuto (Da Jian Zhong Tang) induces Bdnf expression and has neurotrophic effects in cultured cortical neurons

Reductions in brain-derived neurotrophic factor (BDNF) expression levels have been reported in the brains of patients with neurological disorders such as Alzheimer's disease. Therefore, upregulating BDNF and preventing its decline in the diseased brain could help ameliorate neurological dysfunctions. Accordingly, we sought to discover agents that increase Bdnf expression in neurons. Here, we screened a library of 42 Kampo extracts to identify those with the ability to induce Bdnf expression in cultured cortical neurons. Among the active extracts identified in the screen, we focused on the extract based on the Kampo formula daikenchuto. The extract of daikenchuto in the library used in this study was prepared using the mixture of Zingiberis Rhizoma Processum (ZIN), Zanthoxyli Piperiti Pericarpium (ZAN), and Ginseng Radix (GIN) without Koi. In this study, we defined DKT as the mixture of ZIN, ZAN, and GIN without Koi (DKT extract means the extract prepared from the mixture of ZIN, ZAN, and GIN without Koi). DKT extract significantly increased endogenous Bdnf expression by mediated, at least in part, via Ca²⁺ signaling involving L-type voltage-dependent Ca²⁺ channels in cultured cortical neurons. Furthermore, DKT extract significantly improved the survival of cultured cortical neurons and increased neurite complexity in immature neurons. Taken together, our findings suggest that DKT extract induces Bdnf expression and has a neurotrophic effect in neurons. Because BDNF inducers are expected to have therapeutic potential for neurological disorders, re-positioning of Kampo formulations such as daikenchuto may lead to clinical application in diseases associated with reduced BDNF in the brain.

Exploration of the Gut Microbiome in Thai Patients with Major Depressive Disorder Shows a Specific Bacterial Profile with Depletion of the Ruminococcus Genus as a Putative Biomarker

Maes et al. (2008) published the first paper demonstrating that major depressive disorder (MDD) is accompanied by abnormalities in the microbiota-gut-brain axis, as evidenced by elevated serum IgM/IgA to lipopolysaccharides (LPS) of Gram-negative bacteria, such as Morganella morganii and Klebsiella Pneumoniae. The latter aberrations, which point to increased gut permeability (leaky gut), are linked to activated neuro-immune and oxidative pathways in MDD. To delineate the profile and composition of the gut microbiome in Thai patients with MDD, we examined fecal samples of 32 MDD patients and 37 controls using 16S rDNA sequencing, analyzed α- (Chao1 and Shannon indices) and β-diversity (Bray-Curtis dissimilarity), and conducted linear discriminant analysis (LDA) effect size (LEfSe) analysis. Neither α- nor β-diversity differed significantly between MDD and controls. Rhodospirillaceae, Hungatella, Clostridium bolteae, Hungatella hathewayi, and Clostridium propionicum were significantly enriched in MDD, while Gracillibacteraceae family, Lutispora, and Ruminococcus genus, Ruminococcus callidus, Desulfovibrio piger, Coprococcus comes, and Gemmiger were enriched in controls. Contradictory results have been reported for all these taxa, with the exception of Ruminococcus, which is depleted in six different MDD studies (one study showed increased abundance), many medical disorders that show comorbidities with MDD, and animal MDD models. Our results may suggest a specific profile of compositional gut dysbiosis in Thai MDD patients, with increases in some pathobionts and depletion of some beneficial microbiota. The results suggest that depletion of Ruminococcus may be a more universal biomarker of MDD that may contribute to increased enteral LPS load, LPS translocation, and gut-brain axis abnormalities.

Probiotics for the treatment of depression and its comorbidities: A systemic review

Depression is one of the most common psychiatric conditions, characterized by significant and persistent depressed mood and diminished interest, and often coexists with various comorbidities. The underlying mechanism of depression remain elusive, evidenced by the lack of an appreciate therapy. Recent abundant clinical trials and animal studies support the new notion that the gut microbiota has emerged as a novel actor in the pathophysiology of depression, which partakes in bidirectional communication between the gut and the brain through the neuroendocrine, nervous, and immune signaling pathways, collectively known as the microbiota-gut-brain (MGB) axis. Alterations in the gut microbiota can trigger the changes in neurotransmitters, neuroinflammation, and behaviors. With the transition of human microbiome research from studying associations to investigating mechanistic causality, the MGB axis has emerged as a novel therapeutic target in depression and its comorbidities. These novel insights have fueled idea that targeting on the gut microbiota may open new windows for efficient treatment of depression and its comorbidities. Probiotics, live beneficial microorganisms, can be used to modulate gut dysbiosis into a new eubiosis and modify the occurrence and development of depression and its comorbidities. In present review, we summarize recent findings regarding the MGB axis in depression and discuss the potential therapeutic effects of probiotics on depression and its comorbidities.

Role of the Microbiome in Gut-Heart-Kidney Cross Talk

Homeostasis is a prerequisite for health. When homeostasis becomes disrupted, dysfunction occurs. This is especially the case for the gut microbiota, which under normal conditions lives in symbiosis with the host. As there are as many microbial cells in and on our body as human cells, it is unlikely they would not contribute to health or disease. The gut bacterial metabolism generates numerous beneficial metabolites but also uremic toxins and their precursors, which are transported into the circulation. Barrier function in the intestine, the heart, and the kidneys regulates metabolite transport and concentration and plays a role in inter-organ and inter-organism communication via small molecules. This communication is analyzed from the perspective of the remote sensing and signaling theory, which emphasizes the role of a large network of multispecific, oligospecific, and monospecific transporters and enzymes in regulating small-molecule homeostasis. The theory provides a systems biology framework for understanding organ cross talk and microbe-host communication involving metabolites, signaling molecules, nutrients, antioxidants, and uremic toxins. This remote small-molecule communication is critical for maintenance of homeostasis along the gut-heart-kidney axis and for responding to homeostatic perturbations. Chronic kidney disease is characterized by gut dysbiosis and accumulation of toxic metabolites. This slowly impacts the body, affecting the cardiovascular system and contributing to the progression of kidney dysfunction, which in its turn influences the gut microbiota. Preserving gut homeostasis and barrier functions or restoring gut dysbiosis and dysfunction could be a minimally invasive way to improve patient outcomes and quality of life in many diseases, including cardiovascular and kidney disease.