Effect of synbiotic and probiotic supplementation on serum brain-derived neurotrophic factor level, depression and anxiety symptoms in hemodialysis patients: a randomized, double-blinded, clinical trial

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.

The influence of the gut-brain axis on anxiety and depression: A review of the literature on the use of probiotics

This review aims to argue how using probiotics can improve anxiety and depressive behaviour without adverse effects, also exploring the impact of postbiotics on it. Specifically, probiotics have drawn more attention as effective alternative treatments, considering the rising cost of antidepressant and anti-anxiety drugs and the high risk of side effects. Depression and anxiety disorders are among the most common mental illnesses in the world's population, characterised by low mood, poor general interest, and cognitive or motor dysfunction. Thus, this study analysed published literature on anxiety, depression, and probiotic supplementation from PubMed and Scopus, focusing on the last twenty years. This study focused on the effect of probiotics on mental health as they have drawn more attention because of their extensive clinical applications and positive impact on various diseases. Numerous studies have demonstrated how the gut microbiota might be critical for mood regulation and how probiotics can affect host health by regulating the gut-brain axis. By comparing the different works analysed, it was possible to identify a strategy by which they are selected and employed and, at the same time, to assess how the effect of probiotics can be optimised using postbiotics, an innovation to improve mental well-being in humans.

Effectiveness of Psychobiotics in the Treatment of Psychiatric and Cognitive Disorders: A Systematic Review of Randomized Clinical Trials

In this study, a systematic review of randomized clinical trials conducted from January 2000 to December 2023 was performed to examine the efficacy of psychobiotics-probiotics beneficial to mental health via the gut-brain axis-in adults with psychiatric and cognitive disorders. Out of the 51 studies involving 3353 patients where half received psychobiotics, there was a notably high measurement of effectiveness specifically in the treatment of depression symptoms. Most participants were older and female, with treatments commonly utilizing strains of Lactobacillus and Bifidobacteria over periods ranging from 4 to 24 weeks. Although there was a general agreement on the effectiveness of psychobiotics, the variability in treatment approaches and clinical presentations limits the comparability and generalization of the findings. This underscores the need for more personalized treatment optimization and a deeper investigation into the mechanisms through which psychobiotics act. The research corroborates the therapeutic potential of psychobiotics and represents progress in the management of psychiatric and cognitive disorders.

Effects of xylo-oligosaccharide on gut microbiota, brain protein expression, and lipid profile induced by high-fat diet

Midlife overweight and obesity are risk factors of cognitive decline and Alzheimer' s disease (AD) in late life. In addition to increasing risk of obesity and cognitive dysfunction, diets rich in fats also contributes to an imbalance of gut microbiota. Xylo-oligosaccharides (XOS) are a kind of prebiotic with several biological advantages, and can selectively promote the growth of beneficial microorganisms in the gut. To explore whether XOS can alleviate cognitive decline induced by high-fat diet (HFD) through improving gut microbiota composition, mice were fed with normal control or 60% HFD for 9 weeks to induce obesity. After that, mice were supplemented with XOS (30 g or 60 g/kg-diet) or without, respectively, for 12 weeks. The results showed that XOS inhibited weight gain, decreased epidydimal fat weight, and improved fasting blood sugar and blood lipids in mice. Additionally, XOS elevated spatial learning and memory function, decreased amyloid plaques accumulation, increased brain-derived neurotrophic factor levels, and improved neuroinflammation status in hippocampus. Changes in glycerolipids metabolism-associated lipid compounds caused by HFD in hippocampus were reversed after XOS intervention. On the other hand, after XOS intervention, increase in immune-mediated bacteria, Faecalibacterium was observed. In conclusion, XOS improved gut dysbiosis and ameliorated spatial learning and memory dysfunction caused by HFD by decreasing cognitive decline-associated biomarkers and changing lipid composition in hippocampus.

Stress-induced changes in cognitive function and intestinal barrier integrity can be ameliorated by venlafaxine and synbiotic supplementations

Stress profoundly impacts various aspects of both physical and psychological well-being. Our previous study demonstrated that venlafaxine (Vlx) and synbiotic (Syn) treatment attenuated learned fear-like behavior and recognition memory impairment in immobilized-stressed rats. In this study, we further investigated the physical, behavior, and cellular mechanisms underlying the effects of Syn and/or Vlx treatment on brain and intestinal functions in stressed rats. Adult male Wistar rats, aged 8 weeks old were subjected to 14 days of immobilization stress showed a decrease in body weight gain and food intake as well as an increase in water consumption, urinary corticosterone levels, and adrenal gland weight. Supplementation of Syn and/or Vlx in stressed rats resulted in mitigation of weight loss, restoration of normal food and fluid intake, and normalization of corticosterone levels. Behavioral analysis showed that treatment with Syn and/or Vlx enhanced depressive-like behaviors and improved spatial learning-memory impairment in stressed rats. Hippocampal dentate gyrus showed stress-induced neuronal cell death, which was attenuated by Syn and/or Vlx treatment. Stress-induced ileum inflammation and increased intestinal permeability were both effectively reduced by the supplementation of Syn. In addition, Syn and Vlx partly contributed to affecting the expression of the glial cell-derived neurotrophic factor in the hippocampus and intestines of stressed rats, suggesting particularly protective effects on both the gut barrier and the brain. This study highlights the intricate interplay between stress physiological responses in the brain and gut. Syn intervention alleviate stress-induced neuronal cell death and modulate depression- and memory impairment-like behaviors, and improve stress-induced gut barrier dysfunction which were similar to those of Vlx. These findings enhance our understanding of stress-related health conditions and suggest the synbiotic intervention may be a promising approach to ameliorate deleterious effects of stress on the gut-brain axis.

Probiotics' Effects in the Treatment of Anxiety and Depression: A Comprehensive Review of 2014-2023 Clinical Trials

Changes in the gut microbiome can affect cognitive and psychological functions via the microbiota-gut-brain (MGB) axis. Probiotic supplements are thought to have largely positive effects on mental health when taken in sufficient amounts; however, despite extensive research having been conducted, there is a lack of consistent findings on the effects of probiotics on anxiety and depression and the associated microbiome alterations. The aim of our study is to systematically review the most recent literature of the last 10 years in order to clarify whether probiotics could actually improve depression and anxiety symptoms. Our results indicate that the majority of the most recent literature suggests a beneficial role of probiotics in the treatment of depression and anxiety, despite the existence of a substantial number of less positive findings. Given probiotics' potential to offer novel, personalized treatment options for mood disorders, further, better targeted research in psychiatric populations is needed to address concerns about the exact mechanisms of probiotics, dosing, timing of treatment, and possible differences in outcomes depending on the severity of anxiety and depression.

The Anti-Inflammatory and Curative Exponent of Probiotics: A Comprehensive and Authentic Ingredient for the Sustained Functioning of Major Human Organs

Several billion microorganisms reside in the gastrointestinal lumen, including viruses, bacteria, fungi, and yeast. Among them, probiotics were primarily used to cure digestive disorders such as intestinal infections and diarrhea; however, with a paradigm shift towards alleviating health through food, their importance is large. Moreover, recent studies have changed the perspective that probiotics prevent numerous ailments in the major organs. Probiotics primarily produce biologically active compounds targeting discommodious pathogens. This review demonstrates the implications of using probiotics from different genres to prevent and alleviate ailments in the primary human organs. The findings reveal that probiotics immediately activate anti-inflammatory mechanisms by producing anti-inflammatory cytokines such as interleukin (IL)-4, IL-10, IL-11, and IL-13, and hindering pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α by involving regulatory T cells (Tregs) and T helper cells (Th cells). Several strains of Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus reuteri, Bifidobacterium longum, and Bifidobacterium breve have been listed among the probiotics that are excellent in alleviating various simple to complex ailments. Therefore, the importance of probiotics necessitates robust research to unveil the implications of probiotics, including the potency of strains, the optimal dosages, the combination of probiotics, their habitat in the host, the host response, and other pertinent factors.

Mood and microbes: a comprehensive review of intestinal microbiota's impact on depression

Depression is considered a multifaceted and intricate mental disorder of growing concern due to its significant impact on global health issues. The human gut microbiota, also known as the "second brain," has an important role in the CNS by regulating it through chemical, immunological, hormonal, and neurological processes. Various studies have found a significant bidirectional link between the brain and the gut, emphasizing the onset of depression therapies. The biological and molecular processes underlying depression and microbiota are required, as the bidirectional association may represent a novel study. However, profound insights into the stratification and diversity of the gut microbiota are still uncommon. This article investigates the emerging evidence of a bacterial relationship between the gut and the brain's neurological system and its potential pathogenicity and relevance. The interplay of microbiota, immune system, nervous system neurotransmitter synthesis, and neuroplasticity transitions is also widely studied. The consequences of stress, dietary fibers, probiotics, prebiotics, and antibiotics on the GB axis are being studied. Multiple studies revealed the processes underlying this axis and led to the development of effective microbiota-based drugs for both prevention and treatment. Therefore, the results support the hypothesis that gut microbiota influences depression and provide a promising area of research for an improved knowledge of the etiology of the disease and future therapies.

The Role of Spirituality in Anxiety and Psychological Resilience of Hemodialysis Patients in Turkey

Chronic kidney disease (CKD) is a significant health problem that affects millions of people worldwide and its end-stage manifestation requires hemodialysis treatment, which can have a considerable impact on patients' mental health and quality of life. This study aims to examine the relationship between spirituality and anxiety, as well as spirituality and psychological resilience among hemodialysis patients using the iterative weighted least squares method. Participants included 91 hemodialysis patients, consisting of 49 females and 42 males, whose ages ranged from 20 to 82 years, with a mean age of 48 (SD = 14). The data were collected using the Beck Anxiety Inventory, Spirituality Scale, and Brief Psychological Resilience Scale. Results indicated a weak positive relationship between spirituality and psychological resilience (t = 1.35, P = .183) and a moderate negative relationship between spirituality and anxiety (t = -2.84, P = .006). Furthermore, spirituality accounted for a 1% variance in psychological resilience and a 5% of the variance in anxiety. Additionally, patients' education level, gender, and whom they live with were relatively stronger correlates of psychological resilience, while the patient's education level, gender, marital status, whom they live with, presence of another patient at home receiving hemodialysis treatment were strong correlates of anxiety. This study emphasizes the need for comprehensive care that addresses both physical and psychological aspects of CKD management to improve patient outcomes and quality of life.

Microbiota-Gut-Brain Axis and Antidepressant Treatment

In the treatment of depressive disorders, conventional antidepressant therapy has been the mainstay of clinical management, along with well-established nonpharmacological interventions such as various kinds of psychotherapy. Over the last 2 decades, there has been considerable interest in the role of the gastrointestinal system and its microbiota on brain function, behavior, and mental health. Components of what is referred to as the microbiota-gut-brain axis have been uncovered, and further research has elicited functional capabilities such as "gut-brain modules." Some studies have found associations with compositional alterations of gut microbiota in patients with depressive disorders and individuals experiencing symptoms of depression. Regarding the pathogenesis and neurobiology of depression itself, there appears to be a multifactorial contribution, in addition to the theories involving deficits in catecholaminergic and monoamine neurotransmission. Interestingly, there is evidence to suggest that antidepressants may play a role in modulating the gut microbiota, thereby possibly having an impact on the microbiota-gut-brain axis in this manner. The development of prebiotics, probiotics, and synbiotics has led to studies investigating not only their impact on the microbiota but also their therapeutic value in mental health. These psychobiotics have the potential to be used as therapeutic adjuncts in the treatment of depression. Regarding future directions, and in an attempt to further understand the role of the microbiota-gut-brain axis in depression, more studies such as those involving fecal microbiota transplantation will be required. In addition to recent findings, it is also suggested that more research will have to be undertaken to elicit whether specific strains of gut organisms are linked to depression. In terms of further investigation of the therapeutic potential of prebiotics, probiotics, and synbiotics as adjuncts to antidepressant treatment, we also expect there to be more research targeting specific microorganisms, as well as a strong focus on the effects of specific prebiotic fibers from an individualized (personalized) point of view.

Unraveling the Interplay: Exploring the Links Between Gut Microbiota, Obesity, and Psychological Outcomes

This narrative review delves into the complex and intricate mechanisms of the gut-brain axis. Gut microbiota has gained immense importance in the treatment of various diseases. The therapeutic potential of gut-microbial modulation is slowly coming to light. With good preclinical evidence, some human studies shed light on the translation potential of gut-microbial modulation. The concept of gut-microbial modulation has been studied for over a few decades. The relationship between gut microbiota and various homeostatic mechanisms is fascinating. Over the years, we have started understanding the immense role of gut microbiota in various homeostatic mechanisms. There are a good number of clinical studies that have shown the therapeutic potential of gut-microbial modulation in obesity and psychological diseases, especially depression and anxiety. The gut-microbial modulation can be achieved by dietary factors or supplementation. In this review, we explore the mechanisms by which prebiotics, probiotics, and synbiotics alter the gut-brain axis. The review limits its discussion to the most recent clinical studies that have shown promise as therapeutic strategies.

Synbiotics, prebiotics and probiotics for people with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a major public health problem affecting 13% of the global population. Prior research has indicated that CKD is associated with gut dysbiosis. Gut dysbiosis may lead to the development and/or progression of CKD, which in turn may in turn lead to gut dysbiosis as a result of uraemic toxins, intestinal wall oedema, metabolic acidosis, prolonged intestinal transit times, polypharmacy (frequent antibiotic exposures) and dietary restrictions used to treat CKD. Interventions such as synbiotics, prebiotics, and probiotics may improve the balance of the gut flora by altering intestinal pH, improving gut microbiota balance and enhancing gut barrier function (i.e. reducing gut permeability).

OBJECTIVES

This review aimed to evaluate the benefits and harms of synbiotics, prebiotics, and probiotics for people with CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 9 October 2023 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) measuring and reporting the effects of synbiotics, prebiotics, or probiotics in any combination and any formulation given to people with CKD (CKD stages 1 to 5, including dialysis and kidney transplant). Two authors independently assessed the retrieved titles and abstracts and, where necessary, the full text to determine which satisfied the inclusion criteria.

DATA COLLECTION AND ANALYSIS

Data extraction was independently carried out by two authors using a standard data extraction form. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous outcomes. The methodological quality of the included studies was assessed using the Cochrane risk of bias tool. Data entry was carried out by one author and cross-checked by another. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Forty-five studies (2266 randomised participants) were included in this review. Study participants were adults (two studies in children) with CKD ranging from stages 1 to 5, with patients receiving and not receiving dialysis, of whom half also had diabetes and hypertension. No studies investigated the same synbiotic, prebiotic or probiotic of similar strains, doses, or frequencies. Most studies were judged to be low risk for selection bias, performance bias and reporting bias, unclear risk for detection bias and for control of confounding factors, and high risk for attrition and other biases. Compared to prebiotics, it is uncertain whether synbiotics improve estimated glomerular filtration rate (eGFR) at four weeks (1 study, 34 participants: MD -3.80 mL/min/1.73 m², 95% CI -17.98 to 10.38), indoxyl sulfate at four weeks (1 study, 42 participants: MD 128.30 ng/mL, 95% CI -242.77 to 499.37), change in gastrointestinal (GI) upset (borborymgi) at four weeks (1 study, 34 participants: RR 15.26, 95% CI 0.99 to 236.23), or change in GI upset (Gastrointestinal Symptom Rating Scale) at 12 months (1 study, 56 participants: MD 0.00, 95% CI -0.27 to 0.27), because the certainty of the evidence was very low. Compared to certain strains of prebiotics, it is uncertain whether a different strain of prebiotics improves eGFR at 12 weeks (1 study, 50 participants: MD 0.00 mL/min, 95% CI -1.73 to 1.73), indoxyl sulfate at six weeks (2 studies, 64 participants: MD -0.20 μg/mL, 95% CI -1.01 to 0.61; I² = 0%) or change in any GI upset, intolerance or microbiota composition, because the certainty of the evidence was very low. Compared to certain strains of probiotics, it is uncertain whether a different strain of probiotic improves eGFR at eight weeks (1 study, 30 participants: MD -0.64 mL/min, 95% CI -9.51 to 8.23; very low certainty evidence). Compared to placebo or no treatment, it is uncertain whether synbiotics improve eGFR at six or 12 weeks (2 studies, 98 participants: MD 1.42 mL/min, 95% CI 0.65 to 2.2) or change in any GI upset or intolerance at 12 weeks because the certainty of the evidence was very low. Compared to placebo or no treatment, it is uncertain whether prebiotics improves indoxyl sulfate at eight weeks (2 studies, 75 participants: SMD -0.14 mg/L, 95% CI -0.60 to 0.31; very low certainty evidence) or microbiota composition because the certainty of the evidence is very low. Compared to placebo or no treatment, it is uncertain whether probiotics improve eGFR at eight, 12 or 15 weeks (3 studies, 128 participants: MD 2.73 mL/min, 95% CI -2.28 to 7.75; I² = 78%), proteinuria at 12 or 24 weeks (1 study, 60 participants: MD -15.60 mg/dL, 95% CI -34.30 to 3.10), indoxyl sulfate at 12 or 24 weeks (2 studies, 83 participants: MD -4.42 mg/dL, 95% CI -9.83 to 1.35; I² = 0%), or any change in GI upset or intolerance because the certainty of the evidence was very low. Probiotics may have little or no effect on albuminuria at 12 or 24 weeks compared to placebo or no treatment (4 studies, 193 participants: MD 0.02 g/dL, 95% CI -0.08 to 0.13; I² = 0%; low certainty evidence). For all comparisons, adverse events were poorly reported and were minimal (flatulence, nausea, diarrhoea, abdominal pain) and non-serious, and withdrawals were not related to the study treatment.

AUTHORS' CONCLUSIONS

We found very few studies that adequately test biotic supplementation as alternative treatments for improving kidney function, GI symptoms, dialysis outcomes, allograft function, patient-reported outcomes, CVD, cancer, reducing uraemic toxins, and adverse effects. We are not certain whether synbiotics, prebiotics, or probiotics are more or less effective compared to one another, antibiotics, or standard care for improving patient outcomes in people with CKD. Adverse events were uncommon and mild.

Probiotics supplementation and brain-derived neurotrophic factor (BDNF): a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

An emerging body of evidence has demonstrated the beneficial effects of probiotics on various mental health conditions. In this systematic review and meta-analysis, we sought to examine the effects of probiotics supplementation on brain-derived neurotrophic factor (BDNF) in adults.

METHODS

PubMed, Scopus, ISI Web of Science, and the Cochrane Library were searched, from database inception to April 2021, for eligible randomized controlled trials (RCTs). We pooled mean differences and standard deviations from RCTs using random-effect models.

RESULTS

Overall, meta-analysis of 11 trials (n = 648 participants) showed no significant changes in serum level of BDNF following probiotics. However, subgroup analysis revealed that probiotics increased BDNF levels in individuals suffering from neurological disorders (n = 214 participants; WMD = 3.08 ng/mL, 95% CI: 1.83, 4.34; P = 0.001; I2 = 7.5%; P-heterogeneity 0.34), or depression (n = 268 participants; WMD = 0.77 ng/mL, 95% CI: 0.07, 1.47; P = 0.032; I2 = 88.4%; P-heterogeneity < 0.001). Furthermore, a significant increase in BDNF levels was found in studies that administered the mixture of Lactobacillus and Bifidobacterium genera, and were conducted in Asia .

CONCLUSION

Our main findings suggest that probiotics may be effective in elevating BDNF levels in patients with depression and neurological disorders, and a mixed of Lactobacillus and Bifidobacterium appear to show greater efficacy than the single genus supplement. The low quality of evidence reduces clinical advocacy, and indicates that more large-scale, high-quality, RCTs are needed to facilitate reliable conclusions.

Unveiling the role of gut-brain axis in regulating neurodegenerative diseases: A comprehensive review

Emerging evidence have shown the importance of gut microbiota in regulating brain functions. The diverse molecular mechanisms involved in cross-talk between gut and brain provide insight into importance of this communication in maintenance of brain homeostasis. It has also been observed that disturbed gut microbiota contributes to neurological diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis and aging. Recently, gut microbiome-derived exosomes have also been reported to play an essential role in the development and progression of neurodegenerative diseases and could thereby act as a therapeutic target. Further, pharmacological interventions including antibiotics, prebiotics and probiotics can influence gut microbiome-mediated management of neurological diseases. However, extensive research is warranted to better comprehend this interconnection in maintenance of brain homeostasis and its implication in neurological diseases. Thus, the present review is aimed to provide a detailed understanding of gut-brain axis followed by possibilities to target the gut microbiome for improving neurological health.

The Brain-Gut-Microbiota Interplay in Depression: a key to design innovative therapeutic approaches

Depression is the most prevalent mental disorder in the world associated with huge socio-economic consequences. While depressive-related symptoms are well known, the molecular mechanisms underlying disease pathophysiology and progression remain largely unknown. The gut microbiota (GM) is emerging as a key regulator of the central nervous system homeostasis by exerting fundamental immune and metabolic functions. In turn, the brain influences the intestinal microbial composition through neuroendocrine signals, within the so-called gut microbiota-brain axis. The balance of this bidirectional crosstalk is important to ensure neurogenesis, preserve the integrity of the blood-brain barrier and avoid neuroinflammation. Conversely, dysbiosis and gut permeability negatively affect brain development, behavior, and cognition. Furthermore, although not fully defined yet, changes in the GM composition in depressed patients are reported to influence the pharmacokinetics of common antidepressants by affecting their absorption, metabolism, and activity. Similarly, neuropsychiatric drugs may shape in turn the GM with an impact on the efficacy and toxicity of the pharmacological intervention itself. Consequently, strategies aimed at re-establishing the correct homeostatic gut balance (i.e., prebiotics, probiotics, fecal microbiota transplantation, and dietary interventions) represent an innovative approach to improve the pharmacotherapy of depression. Among these, probiotics and the Mediterranean diet, alone or in combination with the standard of care, hold promise for clinical application. Therefore, the disclosure of the intricate network between GM and depression will give precious insights for innovative diagnostic and therapeutic approaches towards depression, with profound implications for drug development and clinical practice.

Gut Microbiota in Anxiety and Depression: Unveiling the Relationships and Management Options

The gut microbiota is critical for maintaining human health and the immunological system. Several neuroscientific studies have shown the significance of microbiota in developing brain systems. The gut microbiota and the brain are interconnected in a bidirectional relationship, as research on the microbiome-gut-brain axis shows. Significant evidence links anxiety and depression disorders to the community of microbes that live in the gastrointestinal system. Modified diet, fish and omega-3 fatty acid intake, macro- and micro-nutrient intake, prebiotics, probiotics, synbiotics, postbiotics, fecal microbiota transplantation, and 5-HTP regulation may all be utilized to alter the gut microbiota as a treatment approach. There are few preclinical and clinical research studies on the effectiveness and reliability of various therapeutic approaches for depression and anxiety. This article highlights relevant research on the association of gut microbiota with depression and anxiety and the different therapeutic possibilities of gut microbiota modification.

Gut microbiota and its metabolites in depression: from pathogenesis to treatment

Major depressive disorder is one of the most disabling mental disorders worldwide. Increasing preclinical and clinical studies have highlighted that compositional and functional (e.g., metabolite) changes in gut microbiota, known as dysbiosis, are associated with the onset and progression of depression via regulating the gut-brain axis. However, the gut microbiota and their metabolites present a double-edged sword in depression. Dysbiosis is involved in the pathogenesis of depression while, at the same time, offering a novel therapeutic target. In this review, we describe the association between dysbiosis and depression, drug-microbiota interactions in antidepressant treatment, and the potential health benefits of microbial-targeted therapeutics in depression, including dietary interventions, fecal microbiota transplantation, probiotics, prebiotics, synbiotics, and postbiotics. With the emergence of microbial research, we describe a new direction for future research and clinical treatment of depression.

Synergistic antidepressant-like effect of n-3 polyunsaturated fatty acids and probiotics through the brain-gut axis in rats exposed to chronic mild stress

N-3 polyunsaturated fatty acids (PUFA) and probiotics have antidepressant-like effects, but the underlying mechanisms are unclear. We hypothesized that n-3 PUFA combined with live and dead probiotics synergistically improves depression by modulating the hypothalamic-pituitary-adrenal (HPA) axis and serotonergic pathways through the brain-gut axis. Rats were randomly divided into seven groups (n = 8/group): non-chronic mild stress (CMS) with n-6 PUFA, CMS with n-3 PUFA, n-6 PUFA, live probiotics, dead probiotics, n-3 PUFA and live probiotics, and n-3 PUFA and dead probiotics. Diets of n-6 and n-3 PUFA and oral supplementation of live and dead probiotics were provided for 12 weeks, and CMS was performed for the last 5 weeks. N-3 PUFA and probiotics improved depressive behaviors and modulated the brain and gut HPA axis by synergistically increasing glucocorticoid receptor expression and decreasing corticotropin-releasing factor expression and blood levels of adrenocorticotropic hormone and corticosterone. N-3 PUFA and probiotics upregulated the brain serotonergic pathway through serotonin levels and expression of brain-derived neurotrophic factor, phosphorylated cAMP response binding protein, and 5-hydroxytryptamine 1A receptor while downregulating the gut serotonergic pathway. Furthermore, n-3 PUFA and probiotics increased the abundance of Ruminococcaceae, brain and gut short chain fatty acid levels, and occludin expression while decreasing the expression of tumor necrosis factor-α, interleukin-1β, and prostaglandin E₂ and blood lipopolysaccharides levels. There was no significant difference between the live and dead probiotics. In conclusion, n-3 PUFA and probiotics had synergistic antidepressant-like effects on the HPA axis and serotonergic pathways of the brain and gut through the brain-gut axis.

Gut microbiota: A new target for traditional Chinese medicine in the treatment of depression

ETHNIC PHARMACOLOGICAL RELEVANCE

The causes of depression are complex. Many factors are involved in its pathogenesis, including the individual's biological and social environment. Although numerous studies have reported that the gut microbiota plays a significant role in depression, drugs that regulate the gut microbiota to treat depression have not yet been comprehensively reviewed. At the same time, more and more attention has been paid to the characteristics of traditional Chinese medicine (TCM) in improving depression by regulating gut microbiota. In ancient times, fecal microbiota transplantation was recorded in TCM for the treatment of severe diseases. There are also records in Chinese ancient books about the use of TCM to adjust gut microbiota to treat diseases, which has opened up a unique research field in TCM. Therefore, this article focuses on the pharmacological effects, targets, and mechanisms of TCM in improving depression by mediating the influence of gut microbiota.

AIM OF THIS REVIEW

To summarize the role the gut microbiota plays in depression, highlight potential regulatory targets, and elucidate the anti-depression mechanisms of TCMs through regulation of the gut microbiota.

METHODS

A systematic review of 256 clinical trials and pharmaceutical studies published until June 2022 was conducted in eight electronic databases (Web of Science, PubMed, SciFinder, Research Gate, ScienceDirect, Google Scholar, Scopus, and China Knowledge Infrastructure), according to the implemented PRISMA criteria, using the search terms "traditional Chinese medicine," "depression," and "gut microbiota."

RESULTS

Numerous studies reported the effects of different gut bacteria on depression and that antidepressants work through the gut microbiota. TCM preparations based on compound Chinese medicine, the Chinese Materia Medica, and major bioactive components exerted antidepressant-like effects by improving levels of neurotransmitters, short-chain fatty acids, brain-derived neurotrophic factor, kynurenine, and cytokines via regulation of the gut microbiota.

CONCLUSION

This review summarized the anti-depression effects of TCM on the gut microbiota, providing evidence that TCMs are safe and effective in the treatment of depression and may provide a new therapeutic approach.

Lifestyle risk factors for obsessive-compulsive symptoms and related phenomena: What should lifestyle interventions target?

OBJECTIVE

Understanding the impact of lifestyle on mental illness symptoms is important for informing psycho-education and developing interventions which target mental and physical comorbidities. Obsessive-compulsive and related disorders can have a significant impact on health-related quality of life and physical health. However, our understanding of the impact of lifestyle on obsessive-compulsive symptoms and broader compulsive and impulsive problematic repetitive behaviours is limited.

AIMS

We investigated whether lifestyle factors predicted change in obsessive-compulsive symptoms and problematic repetitive behaviours in a general population sample over a 3-month period.

METHODS

Eight hundred thirty-five participants completed an online questionnaire battery assessing lifestyle and mental health. Of these, 538 participants completed the same battery 3 months later. We conducted negative binomial regressions to analyse the association of lifestyle factors at baseline with future (1) obsessive-compulsive symptoms, (2) compulsive problematic repetitive behaviours and (3) impulsive problematic repetitive behaviours, adjusting for baseline obsessive-compulsive symptoms and problematic repetitive behaviours.

RESULTS

Lower vegetable (p = 0.020) and oily fish (p = 0.040) intake and lower moderate intensity physical activity (p = 0.008) predicted higher obsessive-compulsive symptoms at follow-up. Higher intake of high-fat foods (p < 0.001) predicted higher compulsive problematic repetitive behaviours at follow-up. No lifestyle factors significantly predicted impulsive problematic repetitive behaviours at follow-up.

CONCLUSION

Our results speak to the potential importance of lifestyle quality screening, education and lifestyle interventions (e.g. an anti-inflammatory diet) for individuals experiencing compulsivity-related behaviours and/or symptoms. Further research into potential mechanisms of action will allow for more targeted approaches to lifestyle interventions for transdiagnostic compulsive behaviours.

Effects of a high-prebiotic diet versus probiotic supplements versus synbiotics on adult mental health: The "Gut Feelings" randomised controlled trial

Background

Preliminary evidence supports the use of dietary interventions and gut microbiota-targeted interventions such as probiotic or prebiotic supplementation for improving mental health. We report on the first randomised controlled trial (RCT) to examine the effects of a high-prebiotic dietary intervention and probiotic supplements on mental health.

Methods

"Gut Feelings" was an 8-week, 2 × 2 factorial RCT of 119 adults with moderate psychological distress and low prebiotic food intake. Treatment arms: (1) probiotic supplement and diet-as-usual (probiotic group); (2) high-prebiotic diet and placebo supplement (prebiotic diet group); (3) probiotic supplement and high-prebiotic diet (synbiotic group); and (4) placebo supplement and diet-as-usual (placebo group). The primary outcome was assessment of total mood disturbance (TMD; Profile of Mood States Short Form) from baseline to 8 weeks. Secondary outcomes included anxiety, depression, stress, sleep, and wellbeing measures.

Results

A modified intention-to-treat analysis using linear mixed effects models revealed that the prebiotic diet reduced TMD relative to placebo at 8 weeks [Cohen's d = -0.60, 95% confidence interval (CI) = -1.18, -0.03; p = 0.039]. There was no evidence of symptom improvement from the probiotic (d = -0.19, 95% CI = -0.75, 0.38; p = 0.51) or synbiotic treatments (d = -0.03, 95% CI = -0.59, 0.53; p = 0.92). Improved anxiety, stress, and sleep were noted in response to the prebiotic diet while the probiotic tentatively improved wellbeing, relative to placebo. No benefit was found in response to the synbiotic intervention. All treatments were well tolerated with few adverse events.

Conclusion

A high-prebiotic dietary intervention may improve mood, anxiety, stress, and sleep in adults with moderate psychological distress and low prebiotic intake. A synbiotic combination of high-prebiotic diet and probiotic supplement does not appear to have a beneficial effect on mental health outcomes, though further evidence is required. Results are limited by the relatively small sample size.

Clinical trial registration

https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=372753, identifier ACTRN12617000795392.

The effect of synbiotic supplementation on hypothyroidism: A randomized double-blind placebo controlled clinical trial

OBJECTIVE

We hypothesize that synbiotic supplementation could modulate the intestinal microbiota and subsequently, improve the condition of hypothyroid patients.

METHODS

Fifty-six adult hypothyroid patients were recruited to this double-blind, placebo-controlled, randomized clinical trial. The intervention was 10 weeks of synbiotic (500 mg of 109 CFU/g probiotics plus fructo-oligosaccharide, n = 28) compared to placebo (lactose, magnesium stearate, talc, and silicon dioxide, n = 28). Randomization and allocation to trial groups were carried out using random number sequences drawn from https://sealedenvelope.com/. Primary outcomes were serum thyroid stimulating hormone (TSH) and free thyroxine (FT4), and secondary outcomes were depression, quality of life, and blood pressure (BP). P-values< 0.05 were considered statistically significant.

RESULTS

Analysis on 51 patients who completed the trial showed that TSH and depression (p> 0.05) did not change significantly, while serum FT4 significantly increased in both groups (p = 0.03 and p = 0.02 in symbiotic and placebo respectively). A significant decrease in systolic BP occurred only in the synbiotic group (p = 0.05). Significant improvements occurred regarding different domains and areas of quality of life in the crude and adjusted analysis, including perceived mental health (p = 0.02), bodily pain (p = 0.02), general health perception (p = 0.002), and wellbeing (p = 0.002), which were significantly higher in the synbiotic group.

CONCLUSIONS

Ten-week supplementation with synbiotic had no favorable effect on depression and TSH, but it improved blood pressure and quality of life in patients with hypothyroidism. More trials are needed to support or reject these findings.

TRIAL REGISTRATION

IRCT20210926052583N1, Iranian Registry of Clinical Trials (IRCT), registered October 1st, 2021.

Probiotics as a Tool for Regulating Molecular Mechanisms in Depression: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Depression is one of the main mental disorders. Pharmacological treatment of depression is often associated with delayed effects or insufficient efficacy. Consequently, there is a need to discover new therapeutic methods to cope with depression faster and more effectively. Several lines of evidence indicate that the use of probiotic therapy reduces depressive symptoms. Nonetheless, the exact mechanisms linking the gut microbiota and the central nervous system, as well as the potential mechanisms of action for probiotics, are still not entirely clarified. The aim of this review was to systematically summarize the available knowledge according to PRISMA guidelines on the molecular mechanisms linking probiotics and healthy populations with subclinical depression or anxiety symptoms, as well as depressed patients with or without comorbid somatic illnesses. The standardized mean difference (SMD) with 95% confidence intervals (CI) was calculated. Twenty records were included. It has been found that probiotic administration is linked to a significant increase in BDNF levels during probiotic treatment compared to the placebo (SMD = 0.37, 95% CI [0.07, 0.68], p = 0.02) when considering the resolution of depressive symptoms in depressed patients with or without comorbid somatic illnesses. CRP levels were significantly lower (SMD = -0.47, 95% CI [0.75, -0.19], p = 0.001), and nitric oxide levels were significantly higher (SMD = 0.97, 95% CI [0.58, 1.36], p < 0.0001) in probiotic-treated patients compared to the placebo, however, only among depressed patients with somatic co-morbidities. There were no significant differences in IL-1β, IL-6, IL-10, TNF-α, and cortisol levels after probiotic administration between the intervention and control groups (all p > 0.05). Firm conclusions on the effectiveness of probiotics and their possible association with inflammatory markers in the healthy population (only with subclinical depressive or anxiety symptoms) cannot be drawn. The advent of clinical trials examining the long-term administration of probiotics could evaluate the long-term effectiveness of probiotics in treating depression and preventing its recurrence.

The current state of research for psychobiotics use in the management of psychiatric disorders-A systematic literature review

The need to find new therapeutic interventions in patients diagnosed with psychiatric disorders is supported by the data suggesting high rates of relapse, chronic evolution, therapeutic resistance, or lack of adherence and disability. The use of pre-, pro-, or synbiotics as add-ons in the therapeutic management of psychiatric disorders has been explored as a new way to augment the efficacy of psychotropics and to improve the chances for these patients to reach response or remission. This systematic literature review focused on the efficacy and tolerability of psychobiotics in the main categories of psychiatric disorders and it has been conducted through the most important electronic databases and clinical trial registers, using the PRISMA 2020 guidelines. The quality of primary and secondary reports was assessed using the criteria identified by the Academy of Nutrition and Diabetics. Forty-three sources, mostly of moderate and high quality, were reviewed in detail, and data regarding the efficacy and tolerability of psychobiotics was assessed. Studies exploring the effects of psychobiotics in mood disorders, anxiety disorders, schizophrenia spectrum disorders, substance use disorders, eating disorders, attention deficit hyperactivity disorder (ADHD), neurocognitive disorders, and autism spectrum disorders (ASD) were included. The overall tolerability of the interventions assessed was good, but the evidence to support their efficacy in specific psychiatric disorders was mixed. There have been identified data in favor of probiotics for patients with mood disorders, ADHD, and ASD, and also for the association of probiotics and selenium or synbiotics in patients with neurocognitive disorders. In several domains, the research is still in an early phase of development, e.g., in substance use disorders (only three preclinical studies being found) or eating disorders (one review was identified). Although no well-defined clinical recommendation could yet be formulated for a specific product in patients with psychiatric disorders, there is encouraging evidence to support further research, especially if focused on the identification of specific sub-populations that may benefit from this intervention. Several limitations regarding the research in this field should be addressed, i.e., the majority of the finalized trials are of short duration, there is an inherent heterogeneity of the psychiatric disorders, and the diversity of the explored Philae prevents the generalizability of the results from clinical studies.

Advances in the gut microbiome and mood disorders

PURPOSE OF REVIEW

The gut microbiome is in constant bidirectional communication with the brain through the microbiota-gut-brain-axis. Mood disorders are among the most common psychiatric disorders and include major depressive disorder and bipolar disorder. The gut microbiome is altered in individuals with mood disorders and has a role in its inflammatory pathophysiology. In this article, we performed a narrative review of clinical studies, randomized controlled trials and meta-analyses addressing advances in gut microbiome research in mood disorders and included articles that were published between 2021 and 2022.

RECENT FINDINGS

Studies highlight transdiagnostic alterations of microbiota in mood disorders, with reductions of butyrate-producing bacteria. Participants with major depressive disorder showed altered beta-diversity, while participants with bipolar disorder showed reduced alpha-diversity. Both disorders exhibit alterations in the metabolome. Early pilot studies addressed the possibility of using the gut microbiome for the prediction of treatment response and the blood microbiome for the diagnosis of psychiatric disorders. Findings from clinical trials support the use of probiotics as an add-on therapy for major depressive disorder. The second published case report in the literature reported a favourable outcome of a patient with bipolar disorder after faecal microbiota transplantation.

SUMMARY

Gut microbiome modulations allow new treatment strategies including the use of psychobiotics for the treatment and prevention of mood disorders. Well designed clinical trials aiming for personalized medicine are needed to investigate the efficacy and safety of psychobiotic interventions.

The Role of Gut Dysbiosis in the Pathophysiology of Neuropsychiatric Disorders

Mounting evidence shows that the complex gut microbial ecosystem in the human gastrointestinal (GI) tract regulates the physiology of the central nervous system (CNS) via microbiota and the gut-brain (MGB) axis. The GI microbial ecosystem communicates with the brain through the neuroendocrine, immune, and autonomic nervous systems. Recent studies have bolstered the involvement of dysfunctional MGB axis signaling in the pathophysiology of several neurodegenerative, neurodevelopmental, and neuropsychiatric disorders (NPDs). Several investigations on the dynamic microbial system and genetic-environmental interactions with the gut microbiota (GM) have shown that changes in the composition, diversity and/or functions of gut microbes (termed "gut dysbiosis" (GD)) affect neuropsychiatric health by inducing alterations in the signaling pathways of the MGB axis. Interestingly, both preclinical and clinical evidence shows a positive correlation between GD and the pathogenesis and progression of NPDs. Long-term GD leads to overstimulation of hypothalamic-pituitary-adrenal (HPA) axis and the neuroimmune system, along with altered neurotransmitter levels, resulting in dysfunctional signal transduction, inflammation, increased oxidative stress (OS), mitochondrial dysfunction, and neuronal death. Further studies on the MGB axis have highlighted the significance of GM in the development of brain regions specific to stress-related behaviors, including depression and anxiety, and the immune system in the early life. GD-mediated deregulation of the MGB axis imbalances host homeostasis significantly by disrupting the integrity of the intestinal and blood-brain barrier (BBB), mucus secretion, and gut immune and brain immune functions. This review collates evidence on the potential interaction between GD and NPDs from preclinical and clinical data. Additionally, we summarize the use of non-therapeutic modulators such as pro-, pre-, syn- and post-biotics, and specific diets or fecal microbiota transplantation (FMT), which are promising targets for the management of NPDs.

Involvement of Intestinal Microbiota in Adult Neurogenesis and the Expression of Brain-Derived Neurotrophic Factor

Growing evidence suggests a possible involvement of the intestinal microbiota in generating new neurons, but a detailed breakdown of the microbiota composition is lacking. In this report, we systematically reviewed preclinical rodent reports addressing the connection between the composition of the intestinal microbiota and neurogenesis and neurogenesis-affecting neurotrophins in the hippocampus. Various changes in bacterial composition from low taxonomic resolution at the phylum level to high taxonomic resolution at the species level were identified. As for neurogenesis, studies predominantly used doublecortin (DCX) as a marker of newly formed neurons or bromodeoxyuridine (BrdU) as a marker of proliferation. Brain-derived neurotrophic factor (BDNF) was the only neurotrophin found researched in relation to the intestinal microbiota. Phylum Actinobacteria, genus Bifidobacterium and genus Lactobacillus found the strongest positive. In contrast, phylum Firmicutes, phylum Bacteroidetes, and family Enterobacteriaceae, as well as germ-free status, showed the strongest negative correlation towards neurogenesis or BDNF mRNA expression. Age, short-chain fatty acids (SCFA), obesity, and chronic stress were recurring topics in all studies identified. Overall, these findings add to the existing evidence of a connection between microbiota and processes in the brain. To better understand this interaction, further investigation based on analyses of higher taxonomic resolution and clinical studies would be a gain to the matter.

Mapping trends and hotspot regarding gastrointestinal microbiome and neuroscience: A bibliometric analysis of global research (2002-2022)

BACKGROUND

Scholars have long understood that gastrointestinal microorganisms are intimately related to human disorders. The literature on research involving the gut microbiome and neuroscience is emerging. This study exposed the connections between gut microbiota and neuroscience methodically and intuitively using bibliometrics and visualization. This study's objectives were to summarize the knowledge structure and identify emerging trends and potential hotspots in this field.

MATERIALS AND METHODS

On October 18, 2022, a literature search was conducted utilizing the Web of Science Core Collection (WoSCC) database for studies on gut microbiota and neuroscience studies from 2002 to 2022 (August 20, 2022). VOSviewer and CiteSpace V software was used to conduct the bibliometrics and visualization analysis.

RESULTS

From 2002 to 2022 (August 20, 2022), 2,275 publications in the WoSCC database satisfied the criteria. The annual volume of publications has rapidly emerged in recent years (2016-2022). The most productive nation (n = 732, 32.18%) and the hub of inter-country cooperation (links: 38) were the United States. University College Cork had the most research papers published in this area, followed by McMaster University and Harvard Medical School. Cryan JF, Dinan TG, and Clarke G were key researchers with considerable academic influence. The journals with the most publications are "Neurogastroenterology and Motility" and "Brain Behavior and Immunity." The most cited article and co-cited reference was Cryan JF's 2012 article on the impact of gut microbiota on the brain and behavior. The current research hotspot includes gastrointestinal microbiome, inflammation, gut-brain axis, Parkinson's disease (PD), and Alzheimer's disease (AD). The research focus would be on the "gastrointestinal microbiome, inflammation: a link between obesity, insulin resistance, and cognition" and "the role of two important theories of the gut-brain axis and microbial-gut-brain axis in diseases." Burst detection analysis showed that schizophrenia, pathology, and psychiatric disorder may continue to be the research frontiers.

CONCLUSION

Research on "gastrointestinal microbiome, inflammation: a link between obesity, insulin resistance, and cognition" and "the role of two important theories of the gut-brain axis and microbial-gut-brain axis in diseases" will continue to be the hotspot. Schizophrenia and psychiatric disorder will be the key research diseases in the field of gut microbiota and neuroscience, and pathology is the key research content, which is worthy of scholars' attention.

Correlation Between Sleep Electroencephalogram, Brain-Derived Neurotrophic Factor, AVPR1B Gene Polymorphism, and Suicidal Behavior in Patients with Depression

The purpose of this article was to investigate the level of serum brain-derived neurotrophic factor and its relationship with suicidal symptoms and severity in mentally ill suicide attempt patients, and to explore the possible role of serum brain-derived neurotrophic factor (BDNF) in the occurrence of psychotic suicidal behavior. A retrospective analysis was performed on patients with depression in the neurology department of a hospital. General physical examination, neurological specialist examination, and cranial magnetic resonance imaging (MRI) examination were performed on any selected group. We applied the 24-item Hamilton Depression Scale, Hamilton Anxiety Scale, and Mini-Intelligence Mental State Scale, and performed polysomnography and electroencephalography (EEG) monitoring to conduct statistical analysis on sleep indicators. The amplitude of low-frequency fluctuation (ALFF) values of the right frontal gyrus, left posterior cerebellar lobe, right anterior cerebellar lobe, and right occipital lingual gyrus of the patient group were significantly lower than those of the control group. The ReHo values of the right superior parietal lobule, the left precuneus, and the right occipital lingual gyrus were significantly higher than those of the control group. The genotype and allele frequency distribution of FKBP5, AVPR1B, and CRHR2 gene SNPs had no significant difference between the case group and the control group (P > 0.05). The ReHo value of the precuneus is significantly correlated with the proportion of N3 sleep, and the dysfunction of the precuneus or default network may be related to the altered sleep structure in patients with depression. The GT and TT genotypes at rs9324924 of the NR3C1 gene are associated with suicide attempts.

ROLE OF GUT MICROBIOTA IN DEPRESSION: UNDERSTANDING MOLECULAR PATHWAYS, RECENT RESEARCH, AND FUTURE DIRECTION

Gut microbiota, also known as the "second brain" in humans because of the regulatory role it has on the central nervous system via neuronal, chemical and immune pathways. It has been proven that there exists a bidirectional communication between the gut and the brain. Increasing evidence supports that this crosstalk is linked to the etiology and treatment of depression. Reports suggest that the gut microbiota control the host epigenetic machinery in depression and gut dysbiosis causes negative epigenetic modifications via mechanisms like histone acetylation, DNA methylation and non-coding RNA mediated gene inhibition. The gut microbiome can be a promising approach for the management of depression. The diet and dietary metabolites like kynurenine, tryptophan, and propionic acid also greatly influence the microbiome composition and thereby, the physiological activities. This review gives a bird-eye view on the pathological updates and currently used treatment approaches targeting the gut microbiota in depression.

Impact of Environmental Pollutants on Gut Microbiome and Mental Health via the Gut–Brain Axis

Over the last few years, the microbiome has emerged as a high-priority research area to discover missing links between brain health and gut dysbiosis. Emerging evidence suggests that the commensal gut microbiome is an important regulator of the gut–brain axis and plays a critical role in brain physiology. Engaging microbiome-generated metabolites such as short-chain fatty acids, the immune system, the enteric nervous system, the endocrine system (including the HPA axis), tryptophan metabolism or the vagus nerve plays a crucial role in communication between the gut microbes and the brain. Humans are exposed to a wide range of pollutants in everyday life that impact our intestinal microbiota and manipulate the bidirectional communication between the gut and the brain, resulting in predisposition to psychiatric or neurological disorders. However, the interaction between xenobiotics, microbiota and neurotoxicity has yet to be completely investigated. Although research into the precise processes of the microbiota–gut–brain axis is growing rapidly, comprehending the implications of environmental contaminants remains challenging. In these milieus, we herein discuss how various environmental pollutants such as phthalates, heavy metals, Bisphenol A and particulate matter may alter the intricate microbiota–gut–brain axis thereby impacting our neurological and overall mental health.

Clinical, gut microbial and neural effects of a probiotic add-on therapy in depressed patients: a randomized controlled trial

A promising new treatment approach for major depressive disorder (MDD) targets the microbiota-gut-brain (MGB) axis, which is linked to physiological and behavioral functions affected in MDD. This is the first randomized controlled trial to determine whether short-term, high-dose probiotic supplementation reduces depressive symptoms along with gut microbial and neural changes in depressed patients. Patients with current depressive episodes took either a multi-strain probiotic supplement or placebo over 31 days additionally to treatment-as-usual. Assessments took place before, immediately after and again four weeks after the intervention. The Hamilton Depression Rating Sale (HAM-D) was assessed as primary outcome. Quantitative microbiome profiling and neuroimaging was used to detect changes along the MGB axis. In the sample that completed the intervention (probiotics N = 21, placebo N = 26), HAM-D scores decreased over time and interactions between time and group indicated a stronger decrease in the probiotics relative to the placebo group. Probiotics maintained microbial diversity and increased the abundance of the genus Lactobacillus, indicating the effectivity of the probiotics to increase specific taxa. The increase of the Lactobacillus was associated with decreased depressive symptoms in the probiotics group. Finally, putamen activation in response to neutral faces was significantly decreased after the probiotic intervention. Our data imply that an add-on probiotic treatment ameliorates depressive symptoms (HAM-D) along with changes in the gut microbiota and brain, which highlights the role of the MGB axis in MDD and emphasizes the potential of microbiota-related treatment approaches as accessible, pragmatic, and non-stigmatizing therapies in MDD. Trial Registration: www.clinicaltrials.gov , identifier: NCT02957591.

Post-Weaning Treatment with Probiotic Inhibited Stress-Induced Amnesia in Adulthood Rats: The Mediation of GABAergic System and BDNF/c-Fos Signaling Pathways

The current study aimed to examine the effect of post-weaning treatment with probiotics on memory formation under stress during the adult period in male Wistar rats. Considering GABA is a potential mediator between probiotics and the host, the present study also investigated the involvement of the GABAergic system in the probiotic response. The hippocampal and prefrontal cortical (PFC) expression levels of BDNF and c-Fos were also assessed to show whether the treatments affect the memory-related signaling pathway. Three weeks after birth, the post-weaning rats were fed with probiotic water (PW) or tap water (TW) for 2, 3, 4, or 5 weeks. Exposure to acute stress impaired memory formation in a passive avoidance learning task. Feeding the post-weaning animals with probiotic strains (3, 4, or 5 weeks) inhibited stress-induced amnesia of the adult period. Post-training intracerebroventricular (ICV) microinjection of muscimol improved stress-induced amnesia in the animals fed with TW. ICV microinjection of muscimol inhibited probiotic treatment's significant effect on the stress response in the memory task. The expression levels of BDNF and c-Fos in the PFC and the hippocampus were significantly decreased in the stress animal group. The levels of BDNF and c-Fos were increased in the PW/stress animal group. The muscimol response was compounded with the decreased levels of BDNF and c-Fos in the PFC and the hippocampus. Thus, the GABA-A receptor mechanism may mediate the inhibitory effect of this probiotic mixture on stress-induced amnesia, which may be associated with the PFC and hippocampal BDNF/c-Fos signaling changes.

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

Depression is a highly common mental disorder, which is often multifactorial with sex, genetic, environmental, and/or psychological causes. Recent advancements in biomedical research have demonstrated a clear correlation between gut dysbiosis (GD) or gut microbial dysbiosis and the development of anxiety or depressive behaviors. The gut microbiome communicates with the brain through the neural, immune, and metabolic pathways, either directly (via vagal nerves) or indirectly (via gut- and microbial-derived metabolites as well as gut hormones and endocrine peptides, including peptide YY, pancreatic polypeptide, neuropeptide Y, cholecystokinin, corticotropin-releasing factor, glucagon-like peptide, oxytocin, and ghrelin). Maintaining healthy gut microbiota (GM) is now being recognized as important for brain health through the use of probiotics, prebiotics, synbiotics, fecal microbial transplantation (FMT), etc. A few approaches exert antidepressant effects via restoring GM and hypothalamus–pituitary–adrenal (HPA) axis functions. In this review, we have summarized the etiopathogenic link between gut dysbiosis and depression with preclinical and clinical evidence. In addition, we have collated information on the recent therapies and supplements, such as probiotics, prebiotics, short-chain fatty acids, and vitamin B12, omega-3 fatty acids, etc., which target the gut–brain axis (GBA) for the effective management of depressive behavior and anxiety.

A Comprehensive Review on the Role of the Gut Microbiome in Human Neurological Disorders

The human body is full of an extensive number of commensal microbes, consisting of bacteria, viruses, and fungi, collectively termed the human microbiome. The initial acquisition of microbiota occurs from both the external and maternal environments, and the vast majority of them colonize the gastrointestinal tract (GIT). These microbial communities play a central role in the maturation and development of the immune system, the central nervous system, and the GIT system and are also responsible for essential metabolic pathways. Various factors, including host genetic predisposition, environmental factors, lifestyle, diet, antibiotic or nonantibiotic drug use, etc., affect the composition of the gut microbiota. Recent publications have highlighted that an imbalance in the gut microflora, known as dysbiosis, is associated with the onset and progression of neurological disorders. Moreover, characterization of the microbiome-host cross talk pathways provides insight into novel therapeutic strategies. Novel preclinical and clinical research on interventions related to the gut microbiome for treating neurological conditions, including autism spectrum disorders, Parkinson's disease, schizophrenia, multiple sclerosis, Alzheimer's disease, epilepsy, and stroke, hold significant promise. This review aims to present a comprehensive overview of the potential involvement of the human gut microbiome in the pathogenesis of neurological disorders, with a particular emphasis on the potential of microbe-based therapies and/or diagnostic microbial biomarkers. This review also discusses the potential health benefits of the administration of probiotics, prebiotics, postbiotics, and synbiotics and fecal microbiota transplantation in neurological disorders.

The Effect of Pro-/Synbiotic Supplementation on Brain-Derived Neurotrophic Factor: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

There is a growing interest in supplementation with pro-/synbiotics for brain and mental health. Animal studies have reported that pro-/synbiotic administration can increase brain-derived neurotrophic factor (BDNF), a key regulator...

Microbiota-targeted interventions for mental health

PURPOSE OF REVIEW

The gut microbiota has emerged as a key conduit in mental health and is a promising target for interventions. This review provides an update on recent advances in using microbiota-targeted approaches for the management of mental health.

RECENT FINDINGS

Approaches that have emerged as microbiota-targeted interventions in the management of mental health include probiotics, prebiotics, synbiotics, fecal microbiota transplant as well as diet. Among these approaches, probiotic supplementation has been investigated most prominently, providing promising evidence for its use in improving mood and anxiety. There is also growing interest in the use of multistrain probiotics, whole dietary interventions or combined approaches, with encouraging results emerging from recent studies.

SUMMARY

Although the current literature preliminarily supports targeting the microbiota to manage mental health and use as adjuvant therapies for certain brain disorders, large gaps remain and especially data including clinical cohorts remains scarce. Research studies including larger cohorts, well-characterized clinical populations and defined duration and dosage of the intervention are required to develop evidence-based guidelines for microbiota-targeted strategies.

The Role of the Gut Microbiota in the Development and Progression of Major Depressive and Bipolar Disorder

A growing number of studies in rodents indicate a connection between the intestinal microbiota and the brain, but comprehensive human data is scarce. Here, we systematically reviewed human studies examining the connection between the intestinal microbiota and major depressive and bipolar disorder. In this review we discuss various changes in bacterial abundance, particularly on low taxonomic levels, in terms of a connection with the pathophysiology of major depressive and bipolar disorder, their use as a diagnostic and treatment response parameter, their health-promoting potential, as well as novel adjunctive treatment options. The diversity of the intestinal microbiota is mostly decreased in depressed subjects. A consistent elevation of phylum Actinobacteria, family Bifidobacteriaceae, and genus Bacteroides, and a reduction of family Ruminococcaceae, genus Faecalibacterium, and genus Roseburia was reported. Probiotics containing Bifidobacterium and/or Lactobacillus spp. seemed to improve depressive symptoms, and novel approaches with different probiotics and synbiotics showed promising results. Comparing twin studies, we report here that already with an elevated risk of developing depression, microbial changes towards a “depression-like” microbiota were found. Overall, these findings highlight the importance of the microbiota and the necessity for a better understanding of its changes contributing to depressive symptoms, potentially leading to new approaches to alleviate depressive symptoms via alterations of the gut microbiota.

Different Types and Functional Effects of Probiotics on Human Health through Regulating Glucose Homeostasis

With the increasing improvement of people's living standards, hyperglycemia has become one of the most frequent diseases in the world. The current drug therapy may have some negative effects and even cause some complications. As one of the most popular functional ingredients, probiotic bacteria have been proven to play important roles in balancing the glucose homeostasis level in animal and human clinic trials. In this perspective, we sorted three types of probiotics, discussed probiotic safety evaluation, and listed the known probiotic functional foods that assist to control glucose homeostasis. Then, the further summarization of the mechanisms on how probiotic bacteria could regulate glucose homeostasis and the developing trend of probiotic functional foods were discussed.

Role of Phytoconstituents as PPAR Agonists: Implications for Neurodegenerative Disorders

Peroxisome proliferator-activated receptors (PPAR-γ, PPAR-α, and PPAR-β/δ) are ligand-dependent nuclear receptors that play a critical role in the regulation of hundreds of genes through their activation. Their expression and targeted activation play an important role in the treatment of a variety of diseases, including neurodegenerative, cardiovascular, diabetes, and cancer. In recent years, several reviews have been published describing the therapeutic potential of PPAR agonists (natural or synthetic) in the disorders listed above; however, no comprehensive report defining the role of naturally derived phytoconstituents as PPAR agonists targeting neurodegenerative diseases has been published. This review will focus on the role of phytoconstituents as PPAR agonists and the relevant preclinical studies and mechanistic insights into their neuroprotective effects. Exemplary research includes flavonoids, fatty acids, cannabinoids, curcumin, genistein, capsaicin, and piperine, all of which have been shown to be PPAR agonists either directly or indirectly. Additionally, a few studies have demonstrated the use of clinical samples in in vitro investigations. The role of the fruit fly Drosophila melanogaster as a potential model for studying neurodegenerative diseases has also been highlighted.

The role of psychological distress in the relationship between lifestyle and compulsivity: An analysis of independent, bi-national samples

BACKGROUND

Poor mental health is a state of psychological distress that is influenced by lifestyle factors such as sleep, diet, and physical activity. Compulsivity is a transdiagnostic phenotype cutting across a range of mental illnesses including obsessive-compulsive disorder, substance-related and addictive disorders, and is also influenced by lifestyle. Yet, how lifestyle relates to compulsivity is presently unknown, but important to understand to gain insights into individual differences in mental health. We assessed (a) the relationships between compulsivity and diet quality, sleep quality, and physical activity, and (b) whether psychological distress statistically contributes to these relationships.

METHODS

We collected harmonized data on compulsivity, psychological distress, and lifestyle from two independent samples (Australian n = 880 and US n = 829). We used mediation analyses to investigate bidirectional relationships between compulsivity and lifestyle factors, and the role of psychological distress.

RESULTS

Higher compulsivity was significantly related to poorer diet and sleep. Psychological distress statistically mediated the relationship between poorer sleep quality and higher compulsivity, and partially statistically mediated the relationship between poorer diet and higher compulsivity.

CONCLUSIONS

Lifestyle interventions in compulsivity may target psychological distress in the first instance, followed by sleep and diet quality. As psychological distress links aspects of lifestyle and compulsivity, focusing on mitigating and managing distress may offer a useful therapeutic approach to improve physical and mental health. Future research may focus on the specific sleep and diet patterns which may alter compulsivity over time to inform lifestyle targets for prevention and treatment of functionally impairing compulsive behaviors.

The effect of interventions targeting gut microbiota on depressive symptoms: a systematic review and meta-analysis

BACKGROUND

Despite their popularity, the efficacy of interventions targeting gut microbiota to improve depressive symptoms is unknown. Our objective is to summarize the effect of microbiome-targeting interventions on depressive symptoms.

METHODS

We conducted a systematic review and meta-analysis. We searched MEDLINE, Embase, PsycINFO, Database of Abstracts of Reviews of Effects, Cochrane Database of Systematic Reviews and the Cochrane Controlled Register of Trials from inception to Mar. 5, 2021. We included studies that evaluated probiotic, prebiotic, synbiotic, paraprobiotic or fecal microbiota transplant interventions in an adult population (age ≥ 18 yr) with an inactive or placebo comparator (defined by the absence of active intervention). Studies must have measured depressive symptoms with a validated scale, and used a randomized controlled trial study design. We conducted a random effects meta-analysis of change scores, using standardized mean difference as the measure of effect.

RESULTS

Sixty-two studies formed the final data set, with 50 included in the meta-analysis. Probiotic, prebiotic, and synbiotic interventions on depressive symptoms showed statistically significant benefits. In the single studies evaluating each of fecal microbiota transplant and paraprobiotic interventions, neither showed a statistically significant benefit.

INTERPRETATION

Despite promising findings of benefit of probiotic, prebiotic and synbiotic interventions for depressive symptoms in study populations, there is not yet strong enough evidence to favour inclusion of these interventions in treatment guidelines for depression. Critical questions about species administered, dosage and timing relative to other antidepressant medications remain to be answered.

STUDY REGISTRATION

PROSPERO no. 143178.

Lifestyle Interventions in the Treatment of Obsessive-Compulsive and Related Disorders: A Systematic Review

OBJECTIVE

Lifestyle medicine is increasingly important in psychiatry for its efficacy as a transdiagnostic treatment, its preventative potential, and its increased tolerability compared with first-line strategies. Although the impact of lifestyle medicine is strong across many psychiatric illnesses, our understanding of the effectiveness of lifestyle interventions in treating obsessive-compulsive and related disorders (OCRDs) is minimal. We aimed to conduct a systematic review examining the effect of lifestyle interventions (targeting diet, exercise, sleep, stress management, and tobacco/alcohol use) on OCRD symptoms.

METHODS

We systematically searched four electronic databases for published randomized controlled trials reporting on lifestyle interventions for OCRDs. We qualitatively synthesized results of eligible studies and calculated mean changes in symptom severity from baseline to end point and standardized between-group effect sizes.

RESULTS

We identified 33 eligible studies. Poor efficacy was noted across a number of rigorous dietary supplement interventions with some promising data in four (of six) studies regarding N-acetylcysteine for trichotillomania, skin picking, and obsessive-compulsive disorder. Stress management interventions, generally characterized by high risk of bias, reported mild effectiveness with greater effects noted for mind-body exercises (yoga) for obsessive-compulsive disorder. Greater improvements may be achieved when lifestyle intervention is adjunct to first-line treatments and delivered by facilitators.

CONCLUSIONS

Diet (particularly N-acetylcysteine) and stress management interventions seem promising avenues for OCRDs treatment. We present an action plan to move the lifestyle interventions for OCRDs field forward. Further high-quality lifestyle interventions are required to improve the certainty of findings and to inform clinical treatment guidelines.Review Registration Number: CRD42020151407.

Neuroprotective Potential of Non-Digestible Oligosaccharides: An Overview of Experimental Evidence

Non-digestible oligosaccharides (NDOs) from dietary sources have the potential as prebiotics for neuroprotection. Globally, diverse populations suffering from one or the other forms of neurodegenerative disorders are on the rise, and NDOs have the potential as supportive complementary therapeutic options against these oxidative-linked disorders. Elevated levels of free radicals cause oxidative damage to biological molecules like proteins, lipids, and nucleic acids associated with various neurological disorders. Therefore, investigating the therapeutic or prophylactic potential of prebiotic bioactive molecules such as NDOs as supplements for brain and cognitive health has merits. Few prebiotic NDOs have shown promise as persuasive therapeutic solutions to counter oxidative stress by neutralizing free radicals directly or indirectly. Furthermore, they are also known to modulate through brain-derived neurotrophic factors through direct and indirect mechanisms conferring neuroprotective and neuromodulating benefits. Specifically, NDOs such as fructo-oligosaccharides, xylo-oligosaccharides, isomalto-oligosaccharides, manno-oligosaccharides, pectic-oligosaccharides, and similar oligosaccharides positively influence the overall health via various mechanisms. Increasing evidence has suggested that the beneficial role of such prebiotic NDOs is not only directed towards the colon but also distal organs including the brain. Despite the wide applications of these classes of NDOs as health supplements, there is limited understanding of the possible role of these NDOs as neuroprotective therapeutics. This review provides important insights into prebiotic NDOs, their source, and production with special emphasis on existing direct and indirect evidence of their therapeutic potential in neuroprotection.

Effects of Probiotic NVP-1704 on Mental Health and Sleep in Healthy Adults: An 8-Week Randomized, Double-Blind, Placebo-Controlled Trial

The human gut microbiome is closely linked to mental health and sleep. We aimed to verify the efficacy and safety of probiotic NVP-1704, a mixture of Lactobacillus reuteri NK33 and Bifidobacterium adolescentis NK98, in improving stress, depression, anxiety, and sleep disturbances, along with the measurement of some blood biomarkers. A total of 156 healthy adults with subclinical symptoms of depression, anxiety, and insomnia were retrospectively registered and randomly assigned to receive either NVP-1704 (n = 78) or a placebo (n = 78) for eight weeks. Participants completed the Stress Response Inventory, Beck’s Depression and Anxiety Inventory, Pittsburg Sleep Quality Index, and Insomnia Severity Index at baseline, at four and eight weeks of treatment. Pre- and post-treatment blood tests for biomarkers were conducted. After intervention, gut microbiota composition was quantified by pyrosequencing the bacterial 16S rRNA gene. The NVP-1704 group had a more significant reduction in depressive symptoms at four and eight weeks of treatment, and anxiety symptoms at four weeks compared to the placebo group. Those receiving NVP-1704 also experienced an improvement in sleep quality. NVP-1704 treatment led to a decrease in serum interleukin-6 levels. Furthermore, NVP-1704 increased Bifidobacteriaceae and Lactobacillacea, whereas it decreased Enterobacteriaceae in the gut microbiota composition. Our findings suggest that probiotic NVP-1704 could be beneficial for mental health and sleep.

The Putative Antidepressant Mechanisms of Probiotic Bacteria: Relevant Genes and Proteins

Probiotic bacteria are widely accepted as therapeutic agents against inflammatory bowel diseases for their immunostimulating effects. In the last decade, more evidence has emerged supporting the positive effects of probiotics on the course of neurodegenerative and psychiatric diseases. This brief review summarizes the data from clinical studies of probiotics possessing antidepressant properties and focuses on the potential genes and proteins underlying these mechanisms. Data from small-sample placebo-controlled pilot studies indicate that certain strains of bacteria can significantly reduce the symptoms of depression, especially in depressed patients. Despite the disparity between studies attempting to pinpoint the bacterial putative genes and proteins accounting for these mechanisms, they ultimately show that bacteria are a potential source of metabiotics—microbial metabolites or structural components. Since the constituents of cells—namely, secreted proteins, peptides and cell wall components—are most likely to be entangled in the gut–brain axis, they can serve as starting point in the search for probiotics with concrete properties.

Gut microbiota in mental health and depression: role of pre/pro/synbiotics in their modulation

The microbiome residing in the human gut performs a wide range of biological functions. Recently, it has been elucidated that a change in dietary habits is associated with alteration in the gut microflora which results in increased health risks and vulnerability towards various diseases. Falling in line with the same concept, depression has also been shown to increase its prevalence around the globe, especially in the western world. Various research studies have suggested that changes in the gut microbiome profile further result in decreased tolerance of stress. Although currently available medications help in relieving the symptoms of depressive disorders briefly, these drugs are not able to completely reverse the multifactorial pathology of depression. The discovery of the communication pathway between gut microbes and the brain, i.e. the Gut-Brain Axis, has led to new areas of research to find more effective and safer alternatives to current antidepressants. The use of probiotics and prebiotics has been suggested as being effective in various preclinical studies and clinical trials for depression. Therefore, in the present review, we address the new antidepressant mechanisms via gut microbe alterations and provide insight into how these can provide an alternative to antidepressant therapy without the side effects and risk of adverse drug reactions.