Probiotics and Subclinical Psychological Symptoms in Healthy Participants: A Systematic Review and Meta-Analysis

Improved gastrointestinal health for irritable bowel syndrome with metagenome-guided interventions

Irritable bowel syndrome (IBS) is the most prevalent functional gastrointestinal disorder worldwide, and the most common reason for referral to gastroenterology clinics. However, the pathophysiology is still not fully understood and consequently current management guidelines are very symptom-specific, leading to mixed results. Here we present a study of 88 individuals with IBS who had baseline sequencing of their gut microbiome (stool samples), received targeted interventions that included dietary, supplement, prebiotic/probiotic, and lifestyle recommendations for a 30-day period, and a follow-up sequencing of their gut microbiome. The study's objectives were to demonstrate unique metagenomic signatures across the IBS phenotypes and to validate whether metagenomic-guided interventions could lead to improvement of symptom scores in individuals with IBS. Enrolled subjects also completed a baseline and post-intervention questionnaire that assessed their symptom scores. The average symptom score of an individual with IBS at baseline was 160 and at the endpoint of the study the average symptom score of the cohort was 100.9. The mixed IBS subtype showed the most significant reduction in symptom scores across the different subtypes (average decrease by 102 points, P = 0.005). The metagenomics analysis reveals shifts in the microbiome post-intervention that have been cross-validated with the literature as being associated with improvement of IBS symptoms. Given the complex nature of IBS, further studies with larger sample sizes, more targeted analyses, and a broader population cohort are needed to explore these results further.

Gut microbiome composition and diversity are related to human personality traits

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Investigation of gut microbiome composition and diversity with respect to human personality.

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Analyses targeted bacterial genera linked to behaviour in animal and human psychiatric studies.

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Bacterial genera were modelled (using negative binomial regression) with respect to personality.

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Genera linked to autism are also related to social behaviour in the general population.

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Sociability is associated with higher diversity, and anxiety and stress with reduced diversity.

The gut microbiome has a measurable impact on the brain, influencing stress, anxiety, depressive symptoms and social behaviour. This microbiome–gut–brain axis may be mediated by various mechanisms including neural, immune and endocrine signalling. To date, the majority of research has been conducted in animal models, while the limited number of human studies has focused on psychiatric conditions. Here the composition and diversity of the gut microbiome is investigated with respect to human personality. Using regression models to control for possible confounding factors, the abundances of specific bacterial genera are shown to be significantly predicted by personality traits. Diversity analyses of the gut microbiome reveal that people with larger social networks tend to have a more diverse microbiome, suggesting that social interactions may shape the microbial community of the human gut. In contrast, anxiety and stress are linked to reduced diversity and an altered microbiome composition. Together, these results add a new dimension to our understanding of personality and reveal that the microbiome–gut–brain axis may also be relevant to behavioural variation in the general population as well as to cases of psychiatric disorders.

Recent Advancements in the Development of Modern Probiotics for Restoring Human Gut Microbiome Dysbiosis

A healthy gut is predominantly occupied by bacteria which play a vital role in nutrition and health. Any change in normal gut homeostasis imposes gut dysbiosis. So far, efforts have been made to mitigate the gastrointestinal symptoms using modern day probiotics. The majority of the probiotics strains used currently belong to the genera Lactobacillus, Clostridium, Bifidobacterium and Streptococcus. Recent advancements in culturomics by implementing newer techniques coupled with the use of gnotobiotic animal models provide a subtle ground to develop novel host specific probiotics therapies. In this review article, the recent advances in the development of microbe-based therapies which can now be implemented to treat a wide spectrum of diseases have been discussed. However, these probiotics are not classified as drugs and there is a lack of stringent law enforcement to protect the end users against the pseudo-probiotic products. While modern probiotics hold strong promise for the future, more rigorous regulations are needed to develop genuine probiotic products and characterize novel probiotics using the latest research and technology. This article also highlights the possibility of reducing antibiotic usage by utilizing probiotics developed using the latest concepts of syn and ecobiotics.

Technical and Theoretic Limitations of the Experimental Evidence Supporting a Gut Bacterial Etiology in Mental Illness

The impact of gut bacteria on the brain and behavior has become the subject of intense research. The brain is sensitive to biochemical and physiologic changes in the body, for example, changes in blood oxygenation or nutritional status. The collection of microorganisms residing within the digestive tract (the gut microbiome) is increasingly considered a major contributor to human physiology. These 2 considerations have led to the hypothesis that human psychology, including complex constructs like emotion and mental illness, could be influenced by the composition or function of gut bacteria. Five lines of evidence have been used to support the concept, including human correlational research, probiotic supplementation, antibiotic use, germ-free animal research, and fecal transplantation. Results from these experiments do not provide substantial support for the theory that complex human psychology is under the influence of gut bacteria. Placebo-controlled interventional research in humans, in particular fecal microbiota transplantation, will be required before a stronger conclusion can be reached.

The effects of probiotic supplementation on mental health, biomarkers of inflammation and oxidative stress in patients with psychiatric disorders: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

In the current meta-analysis of randomized controlled trials (RCTs), the effects of probiotic supplementation on mental health, biomarkers of inflammation and oxidative stress in patients with psychiatric disorders were assessed.

METHODS

The following databases were search up to February 2019: PubMed, Scopus, Web of Science, Google scholar and Cochrane Central Register of Controlled Trials.

RESULTS

Twelve studies were included in the current meta-analysis. The findings demonstrated that probiotic supplementation resulted in a significant reduction in Hamilton Depression Rating Scale (HAMD) [Weighted Mean Difference (WMD): -9.60; 95 % CI: -10.08, -9.11]. In addition, a significant reduction in C-reactive protein (CRP) (WMD: -1.59; 95 % CI: -2.22, -0.97), interleukin 10 (IL-10) (WMD: -0.29; 95 % CI: -0.48, -0.11) and malondialdehyde (MDA) levels (WMD: -0.38; 95 % CI: -0.63, -0.13) was found after probiotics supplementation. No significant change was seen in Beck Depression Inventory (BDI) score (WMD: -11.17; 95 % CI: -24.99, 2.65), tumor necrosis factor-α (TNF-α) (WMD: -0.12; 95 % CI: -0.20, -0.05), IL-1B (WMD: -0.34; 95 % CI: -1.43, 0.74), IL-6 (WMD: 0.03; 95 % CI: -0.32, 0.38), nitric oxide (NO) (WMD: -0.54; 95 % CI: -2.16, 1.08), glutathione (GSH) (WMD: 46.79; 95 % CI: -17.25, 110.83) and total antioxidant capacity (TAC) levels (WMD: 15.21; 95 % CI: -59.96, 90.37) after probiotics supplementation.

CONCLUSION

Overall, the current meta-analysis demonstrated that taking probiotic by patients with psychiatric disorders had beneficial effects on HAMD, CRP, IL-10 and MDA levels, but it did not affect BDI score, other markers of inflammation and oxidative stress.

Antidepressive Mechanisms of Probiotics and Their Therapeutic Potential

The accumulating knowledge of the host-microbiota interplay gives rise to the microbiota-gut-brain (MGB) axis. The MGB axis depicts the interkingdom communication between the gut microbiota and the brain. This communication process involves the endocrine, immune and neurotransmitters systems. Dysfunction of these systems, along with the presence of gut dysbiosis, have been detected among clinically depressed patients. This implicates the involvement of a maladaptive MGB axis in the pathophysiology of depression. Depression refers to symptoms that characterize major depressive disorder (MDD), a mood disorder with a disease burden that rivals that of heart diseases. The use of probiotics to treat depression has gained attention in recent years, as evidenced by increasing numbers of animal and human studies that have supported the antidepressive efficacy of probiotics. Physiological changes observed in these studies allow for the elucidation of probiotics antidepressive mechanisms, which ultimately aim to restore proper functioning of the MGB axis. However, the understanding of mechanisms does not yet complete the endeavor in applying probiotics to treat MDD. Other challenges remain which include the heterogeneous nature of both the gut microbiota composition and depressive symptoms in the clinical setting. Nevertheless, probiotics offer some advantages over standard pharmaceutical antidepressants, in terms of residual symptoms, side effects and stigma involved. This review outlines antidepressive mechanisms of probiotics based on the currently available literature and discusses therapeutic potentials of probiotics for depression.

Gut Microbiome and Modulation of CNS Function

Preclinical evidence strongly suggests a role for the gut microbiome in modulating the host central nervous system function and behavior. Several communication channels have been identified that enable microbial signals to reach the brain and that enable the brain to influence gut microbial composition and function. In rodent models, endocrine, neural, and inflammatory signals generated by gut microbes can alter brain structure and function, while autonomic nervous system activity can affect the microbiome by modulating the intestinal environment and by directly regulating microbial behavior. The amount of information that reaches the brain is dynamically regulated by the blood-brain barrier and the intestinal barrier. In humans, associations between gut microbial composition and function and several brain disorders have been reported, and fecal microbial transplants from patient populations into gnotobiotic mice have resulted in the reproduction of homologous features in the recipient mice. However, in contrast to preclinical findings, there is little information about a causal role of the gut microbiome in modulating human central nervous system function and behavior. Longitudinal studies in large patient populations with therapeutic interventions are required to demonstrate such causality, which will provide the basis for future clinical trials. © 2020 American Physiological Society. Compr Physiol 10:57-72, 2020.

Targeting the gut microbiota for the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder that affects an estimated 11% of people across the world. IBS patients are one of the largest subgroups seen in gastroenterology clinics, exhibit a lesser quality of life, and take greater use of the healthcare system. The exact etiology of IBS remains uncertain. Alterations in the gut microbiome may characterize apotential mechanism in the pathogenesis of IBS. This hypothesis is paralleled by rodent models in which manipulation of the gut microbiota leads to disturbed physiological functions along the brain-gut axis. Recent research in IBS treatments has redirected its focus towards gu microbiome based therapeutics. In this review, we discuss potential roles of enteric bacteria in the pathogenesis of IBS and its comorbidities. We then explore the manipulation of the enteric microbiota by prebiotics, probiotics, antibiotics, dietary changes, and fecal microbiota transfer. We also discuss the positive and negative effects of these therapeutics on IBS symptoms.

Clinical and psychological responses to synbiotic supplementation in obese or overweight adults: A randomized clinical trial

BACKGROUND

Obesity is highly prevalent worldwide. Emerging clinical studies suggest that pre- and pro- biotic formulations may be effective interventions for the management of obesity and associated metabolic complications. The current trial was conducted to assess the effect of synbiotic supplementation on anthropometric indices, glycemic and lipid profile, blood pressure, and psychological status of adults with overweight or obesity.

METHODS

This randomized double-blind, placebo-controlled trial was conducted on 60 adults with overweight or obesity. Participants were randomly assigned into two groups to receive either synbiotics (n = 30) in form of a 500 mg capsule (containing Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium bifidum plus inulin) or placebo (n = 30) for 8 weeks. The level of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), fasting blood glucose (FPG), insulin, body weight, body mass index (BMI), waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure (DBP), stress, anxiety, and depression were measured at the baseline and end of the study.

RESULTS

In total, 59 subjects (39 men and 20 women) completed the present study. A significant between-group decrease in body weight (P = 0.03), TC (P = 0.01), TG (P = 0.02), LDL-C (P = 0.01), stress (P < 0.001), anxiety (P = 0.03), and depression (P = 0.03) was found in the synbiotic group compared to the placebo. However, synbiotics had no significant effect on HDL-C, SBP, DBP, FPG and fasting insulin concentrations, as well the BMI and WC (P < 0.05).

CONCLUSION

The present study showed that synbiotic supplementation can confer a number of health benefits including improvements in TG, TC, LDL-C, body weight, stress, anxiety, and depression to subjects that are overweight or obesity.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials IRCT20180201038585N3.

Efficacy of a multispecies probiotic as adjunctive therapy in generalized anxiety disorder: a double blind, randomized, placebo-controlled trial

ABSTRACT Objectives: Studies have shown that probiotics may decrease anxiety symptoms, but to our knowledge so far no trial has investigated the effects of probiotics in generalized anxiety disorder (GAD). The aim of the present study was to determine the effects of probiotics as adjunctive therapy on anxiety severity and quality of life (QOL) in patients with GAD. Methods: Forty-eight drug-free patients with a diagnosis of GAD based on DSM-V criteria were randomly assigned to two groups to receive daily either one capsule of probiotics or placebo in addition to 25 mg sertraline for 8 weeks. Probiotic capsules contained 18*10⁹ CFU Bifidobacterium longom, Bifidobacterium bifidum, Bifidobacterium lactis and Lactobacillus acidophilus bacteria. Results: Intention to treat analysis was performed in 39 Patients who completed at least 4 weeks of the intervention. After 8 weeks, the score of Hamilton Rating Scale for anxiety (HAM-A) decreased more in the probiotics + sertraline (PS) group (p = 0.003). Although the reduction of Beck Anxiety Inventory (BAI) was also more in the PS group, it was not significantly different from that of the sertraline alone(S) group. Moreover, despite the greater reduction of State-Anxiety Inventory score in the PS group, the score of Trait-Anxiety Inventory was not statistically different between the two groups at week 8. With regard to QOL, there was no significant difference between the two groups in the change of the score of QOL domains. Conclusions: Probiotics + sertraline combination was superior to sertraline alone in decreasing anxiety symptoms after 8 weeks in patients with GAD, although it did not affect QOL.

Gut microbiome patterns depending on children's psychosocial stress: Reports versus biomarkers

AIM

Chronic stress increases disease vulnerability factors including inflammation, a pathological characteristic potentially regulated by the gut microbiota. We checked the association between the gut microbiome and psychosocial stress in children/adolescents and investigated which stress parameter (negative versus positive emotion, self-report versus parental report, events versus emotions, biomarker cortisol versus parasympathetic activity) is the most relevant indicator herein.

METHODS

Gut microbiome sequencing was completed in fecal samples from 93 Belgian 8-16y olds. Stress measures included negative events, negative emotions, emotional problems reported by parents, happiness, hair cortisol and heart rate variability (pnn50 parameter reflecting parasympathetic activity). Alpha diversity, beta diversity and linear discriminant analysis were the unadjusted analyses. Age, sex, socio-economic status, diet, physical activity, sleep and weight status were adjusted for via a redundancy analysis and differential abundance via zero-inflated negative binomial regression.

RESULTS

High stress as reflected by low pnn50 and more negative events were associated with a lower alpha diversity as indicated by the Simpson index. Happiness and pnn50 showed significant differences between high and low stress groups based on weighted UniFrac distance, and this remained significant after confounder adjustment. Adjusted and unadjusted taxonomic differences were also most pronounced for happiness and pnn50 being associated respectively with 24 OTU (=11.8% of bacterial counts) and 31 OTU (=13.0%). As a general pattern, high stress was associated with lower Firmicutes at the phylum level and higher Bacteroides, Parabacteroides, Rhodococcus, Methanobrevibacter and Roseburia but lower Phascolarctobacterium at genus level. Several genera gave conflicting results between different stress measures e.g. Ruminococcaceae UCG014, Tenericutes, Eubacterium coprostanoligenes, Prevotella 9 and Christensenellaceae R7. Differential results in preadolescents versus adolescents were also evident.

CONCLUSION

Even in this young healthy population, stress parameters were cross-sectionally associated with gut microbial composition but this relationship was instrument specific. Positive emotions and parasympathetic activity appeared the strongest parameters and should be integrated in future microbiota projects amongst other stress measures.

Probiotics in pregnancy: protocol of a double-blind randomized controlled pilot trial for pregnant women with depression and anxiety (PIP pilot trial)

Background

Maternal prenatal depressive or anxiety symptoms are associated with adverse maternal and infant health outcomes. With prevalence rates of maternal prenatal depression and anxiety ranging between 10 and 20%, attempts to identify effective interventions to reduce symptoms are priority. There are indications that probiotics can reduce symptoms of maternal depression or anxiety. Probiotics ingested by the mother may thus offer a promising and accessible intervention to complement existing treatments.

Methods

The Probiotics in Pregnancy (PIP) pilot trial is a double-blind, placebo-controlled, randomized pilot trial. While one group orally consumes a probiotic mixture (Ecologic® Barrier; 2,5 × 109 colony forming units/g; 2 g; daily), the other group consumes a placebo, from between 26 and 30 weeks gestation until delivery. Subjects are randomly allocated (1:1) to the intervention or placebo group. Forty healthy pregnant women with symptoms of depression or anxiety and uncomplicated pregnancies at randomization will be included. The primary aim is to determine the feasibility and acceptability of a probiotic trial to reduce symptoms of maternal depression or anxiety in pregnancy. The secondary aim is to exploratorily compare the potential effect of probiotics, compared to placebo, on depressive and/or anxiety symptoms, maternal stress (i.e. reported/hair cortisol), maternal vaginal and intestinal microbiota, and by possibly affecting maternal mood and microbiota, maternal bonding to offspring, infant microbiota and infant crying.

Discussion

Results of this pilot trial will help determine whether or not to proceed with a full trial after the pilot trial, and if so, whether revisions should be made to the study protocol and procedures before conducting a full randomized controlled trial. Additionally, they are expected to provide insights into whether changes in psychological, behavioral and biological parameters can be attributed to the probiotic intervention.

Trial registration

Netherlands Trial Register, NTR6219. Registered on 28 February 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3389-1) contains supplementary material, which is available to authorized users.

Biological underpinnings from psychosocial stress towards appetite and obesity during youth: research implications towards metagenomics, epigenomics and metabolomics

Psychosocial stress, uncontrolled eating and obesity are three interrelated epidemiological phenomena already present during youth. This broad narrative conceptual review summarises main biological underpinnings of the stress-diet-obesity pathway and how new techniques can further knowledge. Cortisol seems the main biological factor from stress towards central adiposity; and diet, physical activity and sleep are the main behavioural pathways. Within stress-diet, the concepts of comfort food and emotional eating are highlighted, as cortisol affects reward pathways and appetite brain centres with a role for insulin, leptin, neuropeptide Y (NPY), endocannabinoids, orexin and gastrointestinal hormones. More recently researched biological underpinnings are microbiota, epigenetic modifications and metabolites. First, the gut microbiota reaches the stress-regulating and appetite-regulating brain centres via the gut-brain axis. Second, epigenetic analyses are recommended as diet, obesity, stress and gut microbiota can change gene expression which then affects appetite, energy homeostasis and stress reactivity. Finally, metabolomics would be a good technique to disentangle stress-diet-obesity interactions as multiple biological pathways are involved. Saliva might be an ideal biological matrix as it allows metagenomic (oral microbiota), epigenomic and metabolomic analyses. In conclusion, stress and diet/obesity research should be combined in interdisciplinary collaborations with implementation of several -omics analyses.

Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials

With growing interest in the gut microbiome, prebiotics and probiotics have received considerable attention as potential treatments for depression and anxiety. We conducted a random-effects meta-analysis of 34 controlled clinical trials evaluating the effects of prebiotics and probiotics on depression and anxiety. Prebiotics did not differ from placebo for depression (d = -.08, p = .51) or anxiety (d = .12, p = .11). Probiotics yielded small but significant effects for depression (d = -.24, p < .01) and anxiety (d = -.10, p = .03). Sample type was a moderator for probiotics and depression, with a larger effect observed for clinical/medical samples (d = -.45, p < .001) than community ones. This effect increased to medium-to-large in a preliminary analysis restricted to psychiatric samples (d = -.73, p < .001). There is general support for antidepressant and anxiolytic effects of probiotics, but the pooled effects were reduced by the paucity of trials with clinical samples. Additional randomized clinical trials with psychiatric samples are necessary fully to evaluate their therapeutic potential.

Effect of probiotic interventions on depressive symptoms: A narrative review evaluating systematic reviews

Depression is one of the most prevalent mental illnesses and is often associated with various other medical disorders. Since the 1980s, the primary pharmacological treatment has been antidepressants, but due to the recent discovery of the association between the gut microbiome and mental health, probiotics have been proposed as an adjunctive or alternate treatment. In this narrative review, we aim to provide a holistic perspective by synthesizing and evaluating existing evidence, discussing key biological mechanisms, exploring the history of probiotic use, and appreciating the influence of modern diet on mental health. Five online databases were searched for relevant studies up to December 2017. Systematic reviews that included randomized controlled trials assessing the efficacy of probiotics in the treatment of depressive symptoms were included. Seven systematic reviews met the inclusion criteria. Three of these reviews conducted meta-analyses, out of which, two concluded that probiotics improved depressive symptoms in the sample population. Out of the four reviews that conducted qualitative analysis, three reviews concluded that probiotics have the potential to be used as a treatment. Due to the differences in clinical trials, a definitive effect of probiotics on depressive symptoms cannot be concluded. Nonetheless, probiotics seem to potentially produce a significant therapeutic effect for subjects with pre-existing depressive symptoms. Further studies are warranted for definitive conclusions.

Probiotic food consumption is associated with lower severity and prevalence of depression: A nationwide cross-sectional study

OBJECTIVE

It has been suggested that probiotics have beneficial effects on a variety of health problems including immunologic diseases and metabolic disorders, however, the effects on brain function are yet to be fully studied. The aim of this study was to evaluate the association between probiotic food consumption and depression status through a cross-sectional analysis of a nationwide, large population-based data.

METHODS

The study population included 26 118 individuals 19 to 64 y of age who participated in the Korean National Health and Nutrition Examination Survey (KNHANES, 2012-2016). A food frequency questionnaire was used to assess probiotic food consumption. Depression status was determined by two different methods including a Patient Health Questionnaire (PHQ-9) and self-reported clinical diagnosis.

RESULTS

Compared with the lowest tertile of probiotic food consumption, the highest tertile had significantly lower odds in PHQ-9 depression severity (odds ratio [OR], 0.48; 95% confidence interval [CI], 0.28-0.81; P = 0.0065) and self-reported clinical depression (OR, 0.59; 95% CI, 0.35-0.96; P = 0.0129). Although there was no significant association between probiotic food consumption and clinical depression in women (OR, 0.85; 95% CI, 0.47-1.54; P = 0.3081), men showed a significantly lower prevalence of clinical depression (OR, 0.24; 95% CI, 0.06-0.92; P = 0.0256) in the highest tertile.

CONCLUSIONS

These results suggest that probiotic food consumption might have beneficial effects on depression, particularly in men. Further studies are required to identify the mechanistic relations between probiotics and depression.

The antidepressant-like effect of probiotics and their faecal abundance may be modulated by the cohabiting gut microbiota in rats

Numerous studies have been published describing the effect of various probiotics (PRO) on behaviours related to psychiatric disease. We have previously shown a robust antidepressant-like effect of PRO in rats, but over time, the treatment effect seems to vary significantly between different sets of rats from the same commercial vendor. Therefore, we hypothesised that the antidepressant-like response may be modulated by the cohabiting gut microbiota. The aims of the present study were (1) to investigate any differences in the gut microbiota composition between responders (Resp) and non-responders (Non-resp) to PRO with regards to depressive-like behaviour, and (2) to evaluate the effects of PRO on the microbiota composition. Two sets of 20 male Sprague-Dawley rats each were treated with multi-species PRO (nine Bifidobacterium, Lactococcus and Lactobacillus species) for eight weeks and subjected to a behavioural assessment. Faecal samples were collected for 16 s rRNA (VR4) gene amplicon sequencing (Illumina MiSeq). As previously reported, PRO-treated Resp animals showed a marked decrease in depressive-like behaviour, whereas no such response was seen in Non-resp. We observed profound differences in the gut microbiota composition between the two sets of rats, and the relative faecal abundance of the genera that comprised PRO was higher in Resp than in Non-resp although treated with the same dose of PRO. Particularly, the relative abundance of the Lactobacillus genus was not increased in PRO-treated Non-resp animals. In conclusion, the cohabiting microbiota and the faecal abundance of PRO may modulate the antidepressant-like effect of PRO in rats.

The Gut-Brain Axis and the Microbiome: Mechanisms and Clinical Implications

BACKGROUND & AIMS

Based largely on results from preclinical studies, the concept of a brain gut microbiome axis has been established, mediating bidirectional communication between the gut, its microbiome, and the nervous system. Limited data obtained in human beings suggest that alterations in these interactions may play a role in several brain gut disorders.

METHODS

We reviewed the preclinical and clinical literature related to the topic of brain gut microbiome interactions.

RESULTS

Well-characterized bidirectional communication channels, involving neural, endocrine, and inflammatory mechanisms, exist between the gut and the brain. Communication through these channels may be modulated by variations in the permeability of the intestinal wall and the blood-brain barrier. Brain gut microbiome interactions are programmed during the first 3 years of life, including the prenatal period, but can be modulated by diet, medications, and stress throughout life. Based on correlational studies, alterations in these interactions have been implicated in the regulation of food intake, obesity, and in irritable bowel syndrome, even though causality remains to be established.

CONCLUSIONS

Targets within the brain gut microbiome axis have the potential to become targets for novel drug development for brain gut disorders.

Criteria for standartization of probiotic components in functional food products

The increasing volume of consumption of probiotics and functional food products requires determination of standardized criteria for cultures and their exometabolites used in functional products manufacturing. The study was aimed at developing criteria for the estimation and standardization of exometabolites and the colony-forming ability of probiotic strains for functional food production. The work included such microbiological and physicochemical methods as GC-MS, GPC, UV, and FT-IR-spectroscopy. Based on the results of the study, the comparative analysis of the microbiological properties of probiotic Bifidobacterium strains was provided, the fatty acid composition of the cell wall was described, and the physical and chemical study of the exopolymers produced by them was carried out. According to the data of FT-IR- spectroscopy, the characteristic features of the components of the cell wall of Bifidobacterium strains were established. Bifidobacteria form the unique composition of organophosphorus structures of lipoteichoic acids, which determines the adhesive ability of strains. The authors studied the molecular weight distribution of the samples of exometabolites isolated from the nutrient medium after the cultivation of bifidobacteria, under conditions of gel-permeation chromatography. The spectral (UV, FT-IR) characteristics of the produced metabolites and their chromatographic fractions were compared. The fatty acids of the Bifidobacterium cell membrane were analyzed using the GC/MS method. The fatty acids were extracted from bacterial cells with different hydrophobicity with a mixture of chloroform and hexane. It has been established that the hydrophobicity is determined by different contents of unsaturated and branched fatty acids in the bacterial membrane. Hydrophobic bifidobacteria are the only that contain the isopentadecane (isoC15:0) and methyl-tetradecanoic (13Me-C14:0) acids. With the mean hydrophobicity, a high content of the isopalmitic (isoC16:0) and stearic (C18:0) acids was established. Low-hydrophobic strains are characterized by a low content of monounsaturated fatty acids.

Microbiome-The Missing Link in the Gut-Brain Axis: Focus on Its Role in Gastrointestinal and Mental Health

The central nervous system (CNS) and the human gastrointestinal (GI) tract communicate through the gut-brain axis (GBA). Such communication is bi-directional and involves neuronal, endocrine, and immunological mechanisms. There is mounting data that gut microbiota is the source of a number of neuroactive and immunocompetent substances, which shape the structure and function of brain regions involved in the control of emotions, cognition, and physical activity. Most GI diseases are associated with altered transmission within the GBA that are influenced by both genetic and environmental factors. Current treatment protocols for GI and non-GI disorders may positively or adversely affect the composition of intestinal microbiota with a diverse impact on therapeutic outcome(s). Alterations of gut microbiota have been associated with mood and depressive disorders. Moreover, mental health is frequently affected in GI and non-GI diseases. Deregulation of the GBA may constitute a grip point for the development of diagnostic tools and personalized microbiota-based therapy. For example, next generation sequencing (NGS) offers detailed analysis of microbiome footprints in patients with mental and GI disorders. Elucidating the role of stem cell⁻host microbiome cross talks in tissues in GBA disorders might lead to the development of next generation diagnostics and therapeutics. Psychobiotics are a new class of beneficial bacteria with documented efficacy for the treatment of GBA disorders. Novel therapies interfering with small molecules involved in adult stem cell trafficking are on the horizon.

Efficacy of probiotics on anxiety-A meta-analysis of randomized controlled trials

BACKGROUND

The concept "psychobiotics" claims potential beneficial effect of probiotics on anxiety, whereas findings from clinical trials are inconsistent. Thus, a meta-analysis is needed to clarify the effect of probiotics on anxiety.

METHODS

Randomized controlled trials (RCTs) assessing the effect of probiotics on anxiety were systematically retrieved from online databases and manually screened for references of relevant published literature through September 1, 2017. Standardized mean difference in change from baseline of anxiety rating scales between probiotics groups and placebo groups was selected as the main effect index. Subgroup analyses were conducted with respect to overall health status of the sample, existence of gastrointestinal symptoms, strains of flora, trial duration, and risk of bias assessment. Publication bias was evaluated by funnel plot and Egger's test. The reliability of the result was assessed by leave-one-out sensitivity analysis.

RESULTS

Twelve studies with 1,551 subjects (871 in probiotics group and 680 in control group) were included. All the studies were rated as low or moderate risk of bias. The meta-analysis and subgroup analyses all showed no significant difference between probiotics and placebo in alleviating anxiety symptoms. The Egger's test revealed no evidence of significant publication bias. Sensitivity analysis showed that leaving out one study would result in marginal significance.

CONCLUSIONS

The evidence for the efficacy of probiotics in alleviating anxiety, as presented in currently published RCTs, is insufficient. More reliable evidence from clinical trials is needed before a case can be made for promoting the use of probiotics for alleviating anxiety.

Gut-Brain Psychology: Rethinking Psychology From the Microbiota-Gut-Brain Axis

Mental disorders and neurological diseases are becoming a rapidly increasing medical burden. Although extensive studies have been conducted, the progress in developing effective therapies for these diseases has still been slow. The current dilemma reminds us that the human being is a superorganism. Only when we take the human self and its partner microbiota into consideration at the same time, can we better understand these diseases. Over the last few centuries, the partner microbiota has experienced tremendous change, much more than human genes, because of the modern transformations in diet, lifestyle, medical care, and so on, parallel to the modern epidemiological transition. Existing research indicates that gut microbiota plays an important role in this transition. According to gut-brain psychology, the gut microbiota is a crucial part of the gut-brain network, and it communicates with the brain via the microbiota-gut-brain axis. The gut microbiota almost develops synchronously with the gut-brain, brain, and mind. The gut microbiota influences various normal mental processes and mental phenomena, and is involved in the pathophysiology of numerous mental and neurological diseases. Targeting the microbiota in therapy for these diseases is a promising approach that is supported by three theories: the gut microbiota hypothesis, the "old friend" hypothesis, and the leaky gut theory. The effects of gut microbiota on the brain and behavior are fulfilled by the microbiota-gut-brain axis, which is mainly composed of the nervous pathway, endocrine pathway, and immune pathway. Undoubtedly, gut-brain psychology will bring great enhancement to psychology, neuroscience, and psychiatry. Various microbiota-improving methods including fecal microbiota transplantation, probiotics, prebiotics, a healthy diet, and healthy lifestyle have shown the capability to promote the function of the gut-brain, microbiota-gut-brain axis, and brain. It will be possible to harness the gut microbiota to improve brain and mental health and prevent and treat related diseases in the future.

Can prebiotics assist in the management of cognition and weight gain in schizophrenia?

Schizophrenia is among the top half of the 25 leading causes of disabilities worldwide with a 10-20 year decrease in life expectancy. Ineffective pharmacotherapy in the management of cognitive deficits and weight gain are known to be significant contributors; therefore interventions that may mitigate one, or both, of these parameters would be highly beneficial. Manipulation of the gut microbiome using dietary supplements such as prebiotics may be one such intervention. Preclinical studies have shown that a 2-4 week dietary supplementation with a prebiotic has beneficial effects on learning and memory, and prevents pro-inflammatory signals that are detrimental to cognitive processes. Furthermore, prebiotics influence metabolism, and in obesity they increase the expression of anorexigenic gut hormones such as peptide tyrosine tyrosine, glucagon-like peptide 1 and leptin, as well as decrease levels of orexigenic hormones such as ghrelin. Despite compelling evidence for the pro-cognitive and neuroprotective effects of prebiotics in rodents, their ability to alleviate cognitive deficits or enhance cognition needs to be evaluated in humans. Here we suggest that important symptoms associated with schizophrenia, such as cognitive impairment and weight gain, may benefit from concurrent prebiotic therapy.

The gut microbiome and irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders encountered in clinical practice. It is a heterogeneous disorder with a multifactorial pathogenesis. Recent studies have demonstrated that an imbalance in gut bacterial communities, or "dysbiosis", may be a contributor to the pathophysiology of IBS. There is evidence to suggest that gut dysbiosis may lead to activation of the gut immune system with downstream effects on a variety of other factors of potential relevance to the pathophysiology of IBS. This review will highlight the data addressing the emerging role of the gut microbiome in the pathogenesis of IBS and review the evidence for current and future microbiome based treatments.

Gut microbiota-immune-brain interactions in chemotherapy-associated behavioral comorbidities

Increasing scientific attention is focused on the gut-brain axis, including the ability of the gastrointestinal (GI) tract to modulate central nervous system function. Changes in the intestinal microbiome can influence affective-like behavior, cognitive performance, fatigue, and sleep in rodents and humans. Patients with cancer who are receiving chemotherapy experience similar negative behavioral changes and concurrent GI symptoms. These chemotherapy comorbidities can be long-lasting and may reduce patients' quality of life and motivation to comply with treatment. This review summarizes the clinical and preclinical evidence supporting a role for the intestinal microbiome in mediating behavioral comorbidities through peripheral immune activation in patients with cancer who are receiving chemotherapy. In addition, evidence suggesting that targeted modification of the intestinal microbiome during cancer treatment could ameliorate associated behavioral comorbidities is reviewed.

"Immune Gate" of Psychopathology-The Role of Gut Derived Immune Activation in Major Psychiatric Disorders

Interaction between the gastrointestinal tract (GI) and brain functions has recently become a topic of growing interest in psychiatric research. These multidirectional interactions take place in the so-called gut-brain axis or more precisely, the microbiota-gut-brain axis. The GI tract is the largest immune organ in the human body and is also the largest surface of contact with the external environment. Its functions and permeability are highly influenced by psychological stress, which are often a precipitating factor in the first episode, reoccurrence and/or deterioration of symptoms of psychiatric disorders. In recent literature there is growing evidence that increased intestinal permeability with subsequent immune activation has a major role in the pathophysiology of various psychiatric disorders. Numerous parameters measured in this context seem to be aftermaths of those mechanisms, yet at the same time they may be contributing factors for immune mediated psychopathology. For example, immune activation related to gut-derived bacterial lipopolysaccharides (LPS) or various food antigens and exorphins were reported in major depression, schizophrenia, bipolar disorder, alcoholism and autism. In this review the authors will summarize the evidence and roles of such parameters and their assessment in major psychiatric disorders.

A review of probiotic supplementation in healthy adults: helpful or hype?

Probiotic supplements have a positive impact on several health outcomes. However, the majority of published studies have focused on populations with specific health pathologies. Therefore, this study reviewed the current literature on the health effects of probiotic consumption in "healthy adults." The findings from this review may help guide consumers, researchers, and manufacturers regarding probiotic supplementation. Relevant literature published between 1990 and August 2017 was reviewed. Studies were included if they were experimental trials, included healthy adults, used live bacteria, and had accessible full-text articles published in English. Included studies were classified according to common foci that emerged. Forty-five studies were included in this review. Five foci emerged: gut microbiota changes (n = 15); immune system response (n = 16); lipid profile and cardiovascular disease risk (n = 14); gastrointestinal discomfort (n = 11); and female reproductive health (n = 4). Results suggest that probiotic supplementation in healthy adults can lead to transient improvement in gut microbiota concentration of supplement-specific bacteria. Evidence also supports the role of probiotics in improving immune system responses, stool consistency, bowel movement, and vaginal lactobacilli concentration. There is insufficient evidence to support the role of probiotics to improve blood lipid profile. Probiotic consumption can improve in the immune, gastrointestinal, and female reproductive health systems in healthy adults. However, this review failed to support the ability of probiotics to cause persistent changes in gut microbiota, or improve lipid profile in healthy adults. The feasibility of probiotics consumption to provide benefits in healthy adults requires further investigation.

Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders

The vagus nerve represents the main component of the parasympathetic nervous system, which oversees a vast array of crucial bodily functions, including control of mood, immune response, digestion, and heart rate. It establishes one of the connections between the brain and the gastrointestinal tract and sends information about the state of the inner organs to the brain via afferent fibers. In this review article, we discuss various functions of the vagus nerve which make it an attractive target in treating psychiatric and gastrointestinal disorders. There is preliminary evidence that vagus nerve stimulation is a promising add-on treatment for treatment-refractory depression, posttraumatic stress disorder, and inflammatory bowel disease. Treatments that target the vagus nerve increase the vagal tone and inhibit cytokine production. Both are important mechanism of resiliency. The stimulation of vagal afferent fibers in the gut influences monoaminergic brain systems in the brain stem that play crucial roles in major psychiatric conditions, such as mood and anxiety disorders. In line, there is preliminary evidence for gut bacteria to have beneficial effect on mood and anxiety, partly by affecting the activity of the vagus nerve. Since, the vagal tone is correlated with capacity to regulate stress responses and can be influenced by breathing, its increase through meditation and yoga likely contribute to resilience and the mitigation of mood and anxiety symptoms.

Microbiome, inflammation, epigenetic alterations, and mental diseases

Major mental diseases such as autism, bipolar disorder, schizophrenia, and major depressive disorder are debilitating illnesses with complex etiologies. Recent findings show that the onset and development of these illnesses cannot be well described by the one-gene; one-disease approach. Instead, their clinical presentation is thought to result from the regulative interplay of a large number of genes. Even though the involvement of many genes are likely, up regulating and activation or down regulation and silencing of these genes by the environmental factors play a crucial role in contributing to their pathogenesis. Much of this interplay may be moderated by epigenetic changes. Similar to genetic mutations, epigenetic modifications such as DNA methylation, histone modifications, and RNA interference can influence gene expression and therefore may cause behavioral and neuronal changes observed in mental disorders. Environmental factors such as diet, gut microbiota, and infections have significant role in these epigenetic modifications. Studies show that bioactive nutrients and gut microbiota can alter either DNA methylation and histone signatures through a variety of mechanisms. Indeed, microbes within the human gut may play a significant role in the regulation of various elements of "gut-brain axis," via their influence on inflammatory cytokines and production of antimicrobial peptides that affect the epigenome through their involvement in generating short chain fatty acids, vitamin synthesis, and nutrient absorption. In addition, they may participate in-gut production of many common neurotransmitters. In this review we will consider the potential interactions of diet, gastrointestinal microbiome, inflammation, and epigenetic alterations in psychiatric disorders.

Oral spore-based probiotic supplementation was associated with reduced incidence of post-prandial dietary endotoxin, triglycerides, and disease risk biomarkers

AIM

To determine if 30-d of oral spore-based probiotic supplementation could reduce dietary endotoxemia.

METHODS

Apparently healthy men and women (n = 75) were screened for post-prandial dietary endotoxemia. Subjects whose serum endotoxin concentration increased by at least 5-fold from pre-meal levels at 5-h post-prandial were considered “responders” and were randomized to receive either placebo (rice flour) or a commercial spore-based probiotic supplement [Bacillus indicus (HU36), Bacillus subtilis (HU58), Bacillus coagulans, and Bacillus licheniformis, and Bacillus clausii] for 30-d. The dietary endotoxemia test was repeated at the conclusion of the supplementation period. Dietary endotoxin (LAL) and triglycerides (enzymatic) were measured using an automated chemistry analyzer. Serum disease risk biomarkers were measured using bead-based multiplex assays (Luminex and Milliplex) as secondary, exploratory measures.

RESULTS

Data were statistically analyzed using repeated measures ANOVA and a P < 0.05. We found that spore-based probiotic supplementation was associated with a 42% reduction in endotoxin (12.9 ± 3.5 vs 6.1 ± 2.6, P = 0.011) and 24% reduction in triglyceride (212 ± 28 vs 138 ± 12, P = 0.004) in the post-prandial period Placebo subjects presented with a 36% increase in endotoxin (10.3 ± 3.4 vs 15.4 ± 4.1, P = 0.011) and 5% decrease in triglycerides (191 ± 24 vs 186 ± 28, P = 0.004) over the same post-prandial period. We also found that spore-based probiotic supplementation was associated with significant post-prandial reductions in IL-12p70 (24.3 ± 2.2 vs 21.5 ± 1.7, P = 0.017) and IL-1β (1.9 ± 0.2 vs 1.6 ± 0.1, P = 0.020). Compared to placebo post supplementation, probiotic subject had less ghrelin (6.8 ± 0.4 vs 8.3 ± 1.1, P = 0.017) compared to placebo subjects.

CONCLUSION

The key findings of the present study is that oral spore-based probiotic supplementation reduced symptoms indicative of “leaky gut syndrome”.

Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: A Pilot Study in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Probiotics can reduce symptoms of irritable bowel syndrome (IBS), but little is known about their effects on psychiatric comorbidities. We performed a prospective study to evaluate the effects of Bifidobacterium longum NCC3001 (BL) on anxiety and depression in patients with IBS.

METHODS

We performed a randomized, double-blind, placebo-controlled study of 44 adults with IBS and diarrhea or a mixed-stool pattern (based on Rome III criteria) and mild to moderate anxiety and/or depression (based on the Hospital Anxiety and Depression scale) at McMaster University in Canada, from March 2011 to May 2014. At the screening visit, clinical history and symptoms were assessed and blood samples were collected. Patients were then randomly assigned to groups and given daily BL (n = 22) or placebo (n = 22) for 6 weeks. At weeks 0, 6, and 10, we determined patients' levels of anxiety and depression, IBS symptoms, quality of life, and somatization using validated questionnaires. At weeks 0 and 6, stool, urine and blood samples were collected, and functional magnetic resonance imaging (fMRI) test was performed. We assessed brain activation patterns, fecal microbiota, urine metabolome profiles, serum markers of inflammation, neurotransmitters, and neurotrophin levels.

RESULTS

At week 6, 14 of 22 patients in the BL group had reduction in depression scores of 2 points or more on the Hospital Anxiety and Depression scale, vs 7 of 22 patients in the placebo group (P = .04). BL had no significant effect on anxiety or IBS symptoms. Patients in the BL group had a mean increase in quality of life score compared with the placebo group. The fMRI analysis showed that BL reduced responses to negative emotional stimuli in multiple brain areas, including amygdala and fronto-limbic regions, compared with placebo. The groups had similar fecal microbiota profiles, serum markers of inflammation, and levels of neurotrophins and neurotransmitters, but the BL group had reduced urine levels of methylamines and aromatic amino acids metabolites. At week 10, depression scores were reduced in patients given BL vs placebo.

CONCLUSION

In a placebo-controlled trial, we found that the probiotic BL reduces depression but not anxiety scores and increases quality of life in patients with IBS. These improvements were associated with changes in brain activation patterns that indicate that this probiotic reduces limbic reactivity. ClinicalTrials.gov no. NCT01276626.