Bifidobacterium longum and Lactobacillus helveticus Synergistically Suppress Stress-related Visceral Hypersensitivity Through Hypothalamic-Pituitary-Adrenal Axis Modulation

Exploring the interaction between the gut microbiota and cyclic adenosine monophosphate-protein kinase A signaling pathway: a potential therapeutic approach for neurodegenerative diseases

The interaction between the gut microbiota and cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling pathway in the host's central nervous system plays a crucial role in neurological diseases and enhances communication along the gut-brain axis. The gut microbiota influences the cAMP-PKA signaling pathway through its metabolites, which activates the vagus nerve and modulates the immune and neuroendocrine systems. Conversely, alterations in the cAMP-PKA signaling pathway can affect the composition of the gut microbiota, creating a dynamic network of microbial-host interactions. This reciprocal regulation affects neurodevelopment, neurotransmitter control, and behavioral traits, thus playing a role in the modulation of neurological diseases. The coordinated activity of the gut microbiota and the cAMP-PKA signaling pathway regulates processes such as amyloid-β protein aggregation, mitochondrial dysfunction, abnormal energy metabolism, microglial activation, oxidative stress, and neurotransmitter release, which collectively influence the onset and progression of neurological diseases. This study explores the complex interplay between the gut microbiota and cAMP-PKA signaling pathway, along with its implications for potential therapeutic interventions in neurological diseases. Recent pharmacological research has shown that restoring the balance between gut flora and cAMP-PKA signaling pathway may improve outcomes in neurodegenerative diseases and emotional disorders. This can be achieved through various methods such as dietary modifications, probiotic supplements, Chinese herbal extracts, combinations of Chinese herbs, and innovative dosage forms. These findings suggest that regulating the gut microbiota and cAMP-PKA signaling pathway may provide valuable evidence for developing novel therapeutic approaches for neurodegenerative diseases.

Microbiome contributions to pain: a review of the preclinical literature

ABSTRACT

Over the past 2 decades, the microbiome has received increasing attention for the role that it plays in health and disease. Historically, the gut microbiome was of particular interest to pain scientists studying nociplastic visceral pain conditions given the anatomical juxtaposition of these microorganisms and the neuroimmune networks that drive pain in such diseases. More recently, microbiomes both inside and across the surface of the body have been recognized for driving sensory symptoms in a broader set of diseases. Microbiomes have never been a more popular topic in pain research, but to date, there has not been a systematic review of the preclinical microbiome pain literature. In this article, we identified all animal studies in which both the microbiome was manipulated and pain behaviors were measured. Our analysis included 303 unique experiments across 97 articles. Microbiome manipulation methods and behavioral outcomes were recorded for each experiment so that field-wide trends could be quantified and reported. This review specifically details the animal species, injury models, behavior measures, and microbiome manipulations used in preclinical pain research. From this analysis, we were also able to conclude how manipulations of the microbiome alter pain thresholds in naïve animals and persistent pain intensity and duration in cutaneous and visceral pain models. This review summarizes by identifying existing gaps in the literature and providing recommendations for how to best plan, implement, and interpret data collected in preclinical microbiome pain experiments.

The gut microbiome and the brain

PURPOSE OF REVIEW

The importance of the gut microbiome for human health and well-being is generally accepted, and elucidating the signaling pathways between the gut microbiome and the host offers novel mechanistic insight into the (patho)physiology and multifaceted aspects of healthy aging and human brain functions.

RECENT FINDINGS

The gut microbiome is tightly linked with the nervous system, and gut microbiota are increasingly emerging as important regulators of emotional and cognitive performance. They send and receive signals for the bidirectional communication between gut and brain via immunological, neuroanatomical, and humoral pathways. The composition of the gut microbiota and the spectrum of metabolites and neurotransmitters that they release changes with increasing age, nutrition, hypoxia, and other pathological conditions. Changes in gut microbiota (dysbiosis) are associated with critical illnesses such as cancer, cardiovascular, and chronic kidney disease but also neurological, mental, and pain disorders, as well as chemotherapies and antibiotics affecting brain development and function.

SUMMARY

Dysbiosis and a concomitant imbalance of mediators are increasingly emerging both as causes and consequences of diseases affecting the brain. Understanding the microbiota's role in the pathogenesis of these disorders will have major clinical implications and offer new opportunities for therapeutic interventions.

Microbiome Shifts and Their Impact on Gut Physiology in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most prevalent functional gastrointestinal disorders characterized by recurrent abdominal pain and altered bowel habits. The exact pathophysiological mechanisms for IBS development are not completely understood. Several factors, including genetic predisposition, environmental and psychological influences, low-grade inflammation, alterations in gastrointestinal motility, and dietary habits, have been implicated in the pathophysiology of the disorder. Additionally, emerging evidence highlights the role of gut microbiota in the pathophysiology of IBS. This review aims to thoroughly investigate how alterations in the gut microbiota impact physiological functions such as the brain-gut axis, immune system activation, mucosal inflammation, gut permeability, and intestinal motility. Our research focuses on the dynamic "microbiome shifts", emphasizing the enrichment or depletion of specific bacterial taxa in IBS and their profound impact on disease progression and pathology. The data indicated that specific bacterial populations are implicated in IBS, including reductions in beneficial species such as Lactobacillus and Bifidobacterium, along with increases in potentially harmful bacteria like Firmicutes and Proteobacteria. Emphasis is placed on the imperative need for further research to delineate the role of specific microbiome alterations and their potential as therapeutic targets, providing new insights into personalized treatments for IBS.

The Role of Probiotics in Modulating Myocardial Infarction and Depression-like Symptoms: A Study on Sex-Specific Responses

BACKGROUND/OBJECTIVES

This study explores the effects of two probiotics, Lactobacillus helveticus R0052 and Bifidobacterium longum R0175, on myocardial infarction (MI) and associated depression-like behaviours, with a focus on sex differences.

METHODS

MI was induced in adult male and female rats by occluding the left anterior coronary artery for 30 min, followed by 24 h of reperfusion. Probiotics were administered via drinking water for at least two weeks before ischemia. Infarct size, plasma C-reactive protein (CRP), estradiol levels, and intestinal permeability were then measured. Two weeks after, MI subgroups of rats were tested for depression-like behaviours.

RESULTS

We found a significant interaction between sex and probiotics in relation to infarct size. Probiotics significantly reduced the infarct size compared to the vehicle group in female rats but not in males. Probiotics increased the plasma estradiol levels and reduced the CRP concentrations in females, suggesting anti-inflammatory and cardioprotective properties. Probiotics significantly increased intestinal resistance following MI in males only, suggesting sex-specific physiological responses to treatment. Probiotics enhanced social interaction in males with MI but not in females. Similarly, in the forced swim test, probiotics reduced immobility in males with MI but increased it in females, further underscoring the sex-dependent effects of probiotics.

CONCLUSIONS

This study reports cardioprotective effects of probiotics upon MI in female rats, while benefits in male rats were rather at the behavioural level. These results highlight distinct physiological and behavioural responses between sexes, emphasizing the need to account for sex differences in future tests of probiotics as a prophylactic treatment for MI.

Contributions of Gamma-Aminobutyric Acid (GABA) Produced by Lactic Acid Bacteria on Food Quality and Human Health: Current Applications and Future Prospects

The need to increase food safety and improve human health has led to a worldwide increase in interest in gamma-aminobutyric acid (GABA), produced by lactic acid bacteria (LABs). GABA, produced from glutamic acid in a reaction catalyzed by glutamate decarboxylase (GAD), is a four-carbon, non-protein amino acid that is increasingly used in the food industry to improve the safety/quality of foods. In addition to the possible positive effects of GABA, called a postbiotic, on neuroprotection, improving sleep quality, alleviating depression and relieving pain, the various health benefits of GABA-enriched foods such as antidiabetic, antihypertension, and anti-inflammatory effects are also being investigated. For all these reasons, it is not surprising that efforts to identify LAB strains with a high GABA productivity and to increase GABA production from LABs through genetic engineering to increase GABA yield are accelerating. However, GABA's contributions to food safety/quality and human health have not yet been fully discussed in the literature. Therefore, this current review highlights the synthesis and food applications of GABA produced from LABs, discusses its health benefits such as, for example, alleviating drug withdrawal syndromes and regulating obesity and overeating. Still, other potential food and drug interactions (among others) remain unanswered questions to be elucidated in the future. Hence, this review paves the way toward further studies.

Opioid Use and Gut Dysbiosis in Cancer Pain Patients

Opioids are commonly used for the management of severe chronic cancer pain. Their well-known pharmacological effects on the gastrointestinal system, particularly opioid-induced constipation (OIC), are the most common limiting factors in the optimization of analgesia, and have led to the wide use of laxatives and/or peripherally acting mu-opioid receptor antagonists (PAMORAs). A growing interest has been recently recorded in the possible effects of opioid treatment on the gut microbiota. Preclinical and clinical data, as presented in this review, showed that alterations of the gut microbiota play a role in modulating opioid-mediated analgesia and tolerability, including constipation. Moreover, due to the bidirectional crosstalk between gut bacteria and the central nervous system, gut dysbiosis may be crucial in modulating opioid reward and addictive behavior. The microbiota may also modulate pain regulation and tolerance, by activating microglial cells and inducing the release of inflammatory cytokines and chemokines, which sustain neuroinflammation. In the subset of cancer patients, the clinical meaning of opioid-induced gut dysbiosis, particularly its possible interference with the efficacy of chemotherapy and immunotherapy, is still unclear. Gut dysbiosis could be a new target for treatment in cancer patients. Restoring the physiological amount of specific gut bacteria may represent a promising therapeutic option for managing gastrointestinal symptoms and optimizing analgesia for cancer patients using opioids.

Acupuncture influences multiple diseases by regulating gut microbiota

Acupuncture, an important green and side effect-free therapy in traditional Chinese medicine, is widely use both domestically and internationally. Acupuncture can interact with the gut microbiota and influence various diseases, including metabolic diseases, gastrointestinal diseases, mental disorders, nervous system diseases, and other diseases. This review presents a thorough analysis of these interactions and their impacts and examines the alterations in the gut microbiota and the potential clinical outcomes following acupuncture intervention to establish a basis for the future utilization of acupuncture in clinical treatments.

The Underlying Neurobiological Mechanisms of Psychosis: Focus on Neurotransmission Dysregulation, Neuroinflammation, Oxidative Stress, and Mitochondrial Dysfunction

Psychosis, defined as a set of symptoms that results in a distorted sense of reality, is observed in several psychiatric disorders in addition to schizophrenia. This paper reviews the literature relevant to the underlying neurobiology of psychosis. The dopamine hypothesis has been a major influence in the study of the neurochemistry of psychosis and in development of antipsychotic drugs. However, it became clear early on that other factors must be involved in the dysfunction involved in psychosis. In the current review, it is reported how several of these factors, namely dysregulation of neurotransmitters [dopamine, serotonin, glutamate, and γ-aminobutyric acid (GABA)], neuroinflammation, glia (microglia, astrocytes, and oligodendrocytes), the hypothalamic-pituitary-adrenal axis, the gut microbiome, oxidative stress, and mitochondrial dysfunction contribute to psychosis and interact with one another. Research on psychosis has increased knowledge of the complexity of psychotic disorders. Potential new pharmacotherapies, including combinations of drugs (with pre- and probiotics in some cases) affecting several of the factors mentioned above, have been suggested. Similarly, several putative biomarkers, particularly those related to the immune system, have been proposed. Future research on both pharmacotherapy and biomarkers will require better-designed studies conducted on an all stages of psychotic disorders and must consider confounders such as sex differences and comorbidity.

The Effects of Bacillus amyloliquefaciens SC06 on Behavior and Brain Function in Broilers Infected by Clostridium perfringens

Poultry studies conducted on Clostridium perfringens (CP) mainly focus on the effects of intestinal health and productive performance. Notably, the probiotic Bacillus amyloliquefaciens SC06 (BaSC06) is known to play a role in preventing bacterial infection. However, whether CP could induce the changes in brain function and behaviors and whether BaSC06 could play roles in these parameters is yet to be reported. The aim of this study was to evaluate the effects of BaSC06 on stress-related behaviors and gene expression, as well as the brain morphology and mRNA sequence of the hypothalamus in broiler chickens. A total of 288 one-day-old chicks were randomly divided into four groups: (1) a control group with no treatment administered or infection; (2) birds treated with the BaSC06 group; (3) a CP group; and (4) a BaSC06 plus CP (Ba_CP) group. The results showed that stress and fear-related behaviors were significantly induced by a CP infection and decreased due to the treatment of BaSC06. CP infection caused pathological damage to the pia and cortex of the brain, while BaSC06 showed a protective effect. CP significantly inhibited hypothalamic GABA and promoted HTR1A gene expression, while BaSC06 promoted GABA and decreased HTR1A gene expression. The different genes were nearly found between the comparisons of control vs. Ba group and Ba vs. CP group, while there were a great number of different genes between the comparisons of control vs. Ba_CP as well as CP vs. Ba_CP. Several different gene expression pathways were found that were related to disease, energy metabolism, and nervous system development. Our results will help to promote poultry welfare and health, as well as provide insights into probiotics to replace antibiotics and reduce resistance in the chicken industry.

Probiotic Yeast from Miso Ameliorates Stress-Induced Visceral Hypersensitivity by Modulating the Gut Microbiota in a Rat Model of Irritable Bowel Syndrome

Background/Aims

Recent studies indicate that probiotics, which have attracted attention as a treatment for irritable bowel syndrome, affect intestinal homeostasis. In this study, we investigated whether Zygosaccharomyces sapae (strain I-6), a probiotic yeast isolated from miso (a traditional Japanese fermented food), could improve irritable bowel syndrome symptoms.

Methods

Male Wistar rats were exposed to water avoidance stress (WAS). The number of defecations during WAS and the visceral hypersensitivity before and after WAS were evaluated using colorectal distension. Tight junction changes were assessed by Western blotting. Some rats were fed with strain I-6 or β-glucan from strain I-6. Changes in the intestinal microbiota were analyzed. The effect of fecal microbiota transplantation after WAS was evaluated similarly. Caco-2 cells were stimulated with interleukin-1β and tight junction changes were investigated after coculture with strain I-6.

Results

The increased number of stool pellets and visceral hypersensitivity induced by WAS were suppressed by administering strain I-6. The decrease in tight junction protein occludin by WAS was reversed by the administration of strain I-6. β-Glucan from strain I-6 also suppressed those changes induced by WAS. In the rat intestinal microbiota, treatment with strain I-6 altered the β-diversity and induced changes in bacterial occupancy. Upon fecal microbiota transplantation, some symptoms caused by WAS were ameliorated.

Conclusions

These results suggest that traditional fermented foods such as miso in Japan are valuable sources of probiotic yeast candidates, which may be useful for preventing and treating stress-induced visceral hypersensitivity.

Dietary Galacto-oligosaccharides Ameliorate Atopic Dermatitis-like Skin Inflammation and Behavioral Deficits by Modulating Gut Microbiota-Brain-Skin Axis

Atopic dermatitis (AD), a chronic, highly pruritic, and inflammatory skin disorder, often coexists with psychiatric comorbidities including anxiety and depression, posing considerable challenges for treatment. The current research aims at evaluating the efficacy and potential therapeutic mechanism of galacto-oligosaccharides (GOS) on AD-like skin lesions and comorbid anxiety/depressive disorders. Macroscopical and histopathological examination showed that GOS could markedly relieve skin inflammation by decreasing the production of IgE, IL-4, IL-13, IFN-γ, and TNF-α and regulating the PPAR-γ/NF-κB signaling in DNFB-induced AD mice. Moreover, GOS significantly improved the anxiety- and depressive-like symptoms as mirrored by the behavior tests including FST, TST, OFT, and EZM through normalizing the neurotransmitter levels of 5-HT, DA, NE, and CORT in the brain. Mechanistically, by virtue of the high-throughput 16S rRNA gene sequencing and GC-MS techniques, GOS restructured the gut microbiota and specifically induced the proliferation of Lactobacillus and Alloprevotella, leading to an increase in the total content of fecal SCFAs, in particular acetate and butyrate. Pearson correlation analysis found a marked correlation among the altered gut microbiota/SCFAs, AD-associated skin manifestations, and comorbid behavioral phenotypes. Collectively, this work highlights that GOS is a promising strategy against both AD and associated depressive symptoms by modulating the gut microbiota-brain-skin axis.

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

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

The cancer-immune dialogue in the context of stress

Although there is little direct evidence supporting that stress affects cancer incidence, it does influence the evolution, dissemination and therapeutic outcomes of neoplasia, as shown in human epidemiological analyses and mouse models. The experience of and response to physiological and psychological stressors can trigger neurological and endocrine alterations, which subsequently influence malignant (stem) cells, stromal cells and immune cells in the tumour microenvironment, as well as systemic factors in the tumour macroenvironment. Importantly, stress-induced neuroendocrine changes that can regulate immune responses have been gradually uncovered. Numerous stress-associated immunomodulatory molecules (SAIMs) can reshape natural or therapy-induced antitumour responses by engaging their corresponding receptors on immune cells. Moreover, stress can cause systemic or local metabolic reprogramming and change the composition of the gastrointestinal microbiota which can indirectly modulate antitumour immunity. Here, we explore the complex circuitries that link stress to perturbations in the cancer-immune dialogue and their implications for therapeutic approaches to cancer.

Paraventricular thalamus-insular cortex circuit mediates colorectal visceral pain induced by neonatal colonic inflammation in mice

AIMS

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder, but its pathogenesis remains incompletely understood, particularly the involvements of central nervous system sensitization in colorectal visceral pain. Our study was to investigate whether the paraventricular thalamus (PVT) projected to the insular cortex (IC) to regulate colorectal visceral pain in neonatal colonic inflammation (NCI) mice and underlying mechanisms.

METHODS

We applied optogenetic, chemogenetic, or pharmacological approaches to manipulate the glutamatergicPVT-IC pathway. Fiber photometry was used to assess neuronal activity. Electromyography activities in response to colorectal distension (CRD) were measured to evaluate the colorectal visceral pain.

RESULTS

NCI enhanced c-Fos expression and calcium activity upon CRD in the ICGlu, and optogenetic manipulation of them altered colorectal visceral pain responses accordingly. Viral tracing indicated that the PVTGlu projected to the ICGlu. Optogenetic manipulation of PVTGlu changed colorectal visceral pain responses. Furthermore, selective optogenetic modulation of PVT projections in the IC influenced colorectal visceral pain, which was reversed by chemogenetic manipulation of downstream ICGlu.

CONCLUSIONS

This study identified a novel PVT-IC neural circuit playing a critical role in colorectal visceral pain in a mouse model of IBS.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Effect of dietary supplementation with Lactobacillus helveticus R0052 on seizure thresholds and antiseizure potency of sodium valproate in mice

OBJECTIVE

Both animal and human studies, though limited, showed that multi-strain probiotic supplementation may reduce the number of seizures and/or seizure severity. Here, we evaluated the effect of a single strain probiotic supplementation on seizure susceptibility, antiseizure efficacy of sodium valproate, and several behavioral parameters in mice.

METHODS

Lactobacillus helveticus R0052 was given orally for 28 days. Its influence on seizure thresholds was evaluated in the ivPTZ- and electrically-induced seizure tests. The effect on the antiseizure potency of valproate was assessed in the scPTZ test. We also investigated the effects of probiotic supplementation on anxiety-related behavior (in the elevated plus maze and light/dark box tests), motor coordination (in the accelerating rotarod test), neuromuscular strength (in the grip-strength test), and spontaneous locomotor activity. Serum and brain concentrations of valproate as well as cecal contents of SCFAs and lactate were determined using HPLC method.

RESULTS

L. helveticus R0052 significantly increased the threshold for the 6 Hz-induced psychomotor seizure. There was also a slight increase in the threshold for myoclonic and clonic seizure in the ivPTZ test. L. helveticus R0052 did not affect the threshold for tonic seizures both in the maximal electroshock- and ivPTZ-induced seizure tests. No changes in the antiseizure potency of valproate against the PTZ-induced seizures were reported. Interestingly, L. helveticus R0052 increased valproate concentration in serum, but not in the brain. Moreover, L. helveticus R0052 did not produce any significant effects on anxiety-related behavior, motor coordination, neuromuscular strength, and locomotor activity. L. helveticus R0052 supplementation resulted in increased concentrations of total SCFAs, acetate, and butyrate.

CONCLUSIONS

Altogether, this study shows that a single-strain probiotic - L. helveticus R0052 may decrease seizure susceptibility and this effect can be mediated, at least in part, by increased production of SCFAs. In addition, L. helveticus R0052 may affect bioavailability of valproate, which warrants further investigations.

An updated overview on the relationship between human gut microbiome dysbiosis and psychiatric and psychological disorders

There is a lot of evidence establishing that nervous system development is related to the composition and functions of the gut microbiome. In addition, the central nervous system (CNS) controls the imbalance of the intestinal microbiota, constituting a bidirectional communication system. At present, various gut-brain crosstalk routes have been described, including immune, endocrine and neural circuits via the vagal pathway. Several empirical data have associated gut microbiota alterations (dysbiosis) with neuropsychiatric diseases, such as Alzheimer's disease, autism and Parkinson's disease, and with other psychological disorders, like anxiety and depression. Fecal microbiota transplantation (FMT) therapy has shown that the gut microbiota can transfer behavioral features to recipient animals, which provides strong evidence to establish a causal-effect relationship. Interventions, based on prebiotics, probiotics or synbiotics, have demonstrated an important influence of microbiota on neurological disorders by the synthesis of neuroactive compounds that interact with the nervous system and by the regulation of inflammatory and endocrine processes. Further research is needed to demonstrate the influence of gut microbiota dysbiosis on psychiatric and psychological disorders, and how microbiota-based interventions may be used as potential therapeutic tools.

The importance of the gut microbiome and its signals for a healthy nervous system and the multifaceted mechanisms of neuropsychiatric disorders

Increasing evidence links the gut microbiome and the nervous system in health and disease. This narrative review discusses current views on the interaction between the gut microbiota, the intestinal epithelium, and the brain, and provides an overview of the communication routes and signals of the bidirectional interactions between gut microbiota and the brain, including circulatory, immunological, neuroanatomical, and neuroendocrine pathways. Similarities and differences in healthy gut microbiota in humans and mice exist that are relevant for the translational gap between non-human model systems and patients. There is an increasing spectrum of metabolites and neurotransmitters that are released and/or modulated by the gut microbiota in both homeostatic and pathological conditions. Dysbiotic disruptions occur as consequences of critical illnesses such as cancer, cardiovascular and chronic kidney disease but also neurological, mental, and pain disorders, as well as ischemic and traumatic brain injury. Changes in the gut microbiota (dysbiosis) and a concomitant imbalance in the release of mediators may be cause or consequence of diseases of the central nervous system and are increasingly emerging as critical links to the disruption of healthy physiological function, alterations in nutrition intake, exposure to hypoxic conditions and others, observed in brain disorders. Despite the generally accepted importance of the gut microbiome, the bidirectional communication routes between brain and gut are not fully understood. Elucidating these routes and signaling pathways in more detail offers novel mechanistic insight into the pathophysiology and multifaceted aspects of brain disorders.

Elucidating the role of diet in maintaining gut health to reduce the risk of obesity, cardiovascular and other age-related inflammatory diseases: recent challenges and future recommendations

A healthy balanced diet is crucial in protecting the immune system against infections and diseases. Poor diets, such as the Western diet, contribute to the development of metabolic diseases, hypertension, and obesity. Microbiota, primarily composed of different microorganisms and residing in the gastrointestinal tract (GIT), also play a significant role in maintaining gut health. Polyphenols and probiotics found in fruits, vegetables, whole grains, legumes, nuts, and seeds promote gut health and support the growth of beneficial bacteria. Different types of diets, their categories, and their impact on health are also mentioned. The relationship between diet, gut health, and the risk of developing obesity, cardiovascular diseases, and inflammatory diseases is discussed in this review article. The rationale behind the review concludes future recommendations for maintaining gut health and reducing the occurrence of obesity, cardiometabolic diseases, and other inflammatory diseases. There is also the need for standardized research methods, long-term studies, and translating scientific knowledge into practical dietary recommendations.

Probiotics in Postoperative Pain Management

Postoperative pain is the unpleasant sensory and emotional experience after surgery, its origin being both the inflammatory reaction induced by the surgical trauma on the abdominal wall and the splanchnic pain induced by the activation of nociceptors of the viscera, which are highly sensitive to distension, ischemia, and inflammation. Nowadays, it is well recognized that there is a close relationship between the gut microbiome and pain perception, and that microbiome is highly affected by both anesthesia and surgical manipulation. Thus, efforts to restore the disturbed microbiome via supplementation with beneficial bacteria, namely probiotics, seem to be effective. In this article, the knowledge gained mainly from experimental research on this topic is analyzed, the concluding message being that each probiotic strain works in its own way towards pain relief.

Modulation of microbiota as a target in the management of patients with irritable bowel syndrome

Irritable  bowel syndrome  (IBS) is one of the  most common  diseases  of the  digestive  tract. IBS negatively  affects  the  quality of life and work ability of patients. It is generally  accepted that  IBS is an important medical  and social problem  associated with high financial  costs  both  on the  part of the  patient  and the  public health  system. The pathophysiology of the  disease involves the participation of many factors (genetic, dietary, psychosocial, infectious) and the mechanisms of their implementation, including  disruption  of interaction along  the  functional  “gut-brain axis”, visceral  hypersensitivity,  changes  in motility, low-grade  inflammation, increased permeability of the epithelial intestinal barrier, modulation of microbiota, changes  in neurohumoral  regulation and  processes of central  processing  of peripheral stimuli. Research  shows  an important role  for gut microbiota  in the development of IBS. Modulation of the intestinal microbiota  through  diet, the use of pre- and probiotics  or fecal microbiota transplantation is considered as a promising target  for disease  therapy. A reduction  in the number of bacteria of the genus  Bifidobacterium is described  as a universal  change  in the microbiota  in IBS, regardless of the clinical course and severity of the disease  and the possibility of using different  strains of Bifidobacterium in treatment regimens  for the disease  is of particular  interest. This article  provides  a review of the literature on modern  approaches to prescribing  probiotics  for IBS. Using our own clinical observations as an example, we demonstrated the effectiveness and safety of prolonged administration of the probiotic strain Bifidobacterium longum 35624®  for up to 12 weeks.

Lactococcus lactis CNCM I-5388 versus NCDO2118 by its GABA hyperproduction ability, counteracts faster stress-induced intestinal hypersensitivity in rats

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by its main symptom, visceral hypersensitivity (VH), which is aggravated by stress. Gut-brain interactions and gut bacteria may alleviate IBS symptoms, including VH. γ-amino butyric acid (GABA), produced notably by lactic acid bacteria (LAB), shows promising result in IBS symptoms treatment. In bacteria, GABA is generated through glutamate decarboxylase (GAD) metabolism of L-glutamic acid, maintaining intracellular pH. In mammals, GABA acts as an inhibitory neurotransmitter, modulating pain, stress, and anxiety. Therefore, utilizing GABA-producing LAB as a therapeutic approach might be beneficial. Our previous work showed that a GABA-producing Lactococcus lactis strain, NCDO2118, reduced VH induced by acute stress in rats after a 10-day oral treatment. Here, we identified the strain CNCM I-5388, with a four-fold higher GABA production rate under the same conditions as NCDO2118. Both strains shared 99.1% identical GAD amino acid sequences and in vitro analyses revealed the same optimal pH for GAD activity; however, CNCM I-5388 exhibited 17 times higher intracellular GAD activity and increased resistance to acidic pH. Additionally, in vivo experiments have demonstrated that CNCM I-5388 has faster anti-VH properties in rats compared with NCDO2118, starting from the fifth day of treatment. Finally, CNCM I-5388 anti-VH effects partially persisted after 5-day treatment interruption and after a single oral treatment. These findings highlight CNCM I-5388 as a potential therapeutic agent for managing VH in IBS patients.

Effect of acetate supplementation on traumatic stress-induced behavioral impairments in male rats

Gut microbiota and their metabolites have emerged as key players in the pathogenesis of neuropsychiatric disorders. Recently, we demonstrated that animals susceptible to Single Prolonged Stress (SPS) have an overall pro-inflammatory gut microbiota and significantly lower cecal acetate levels than SPS-resilient rats, which correlated inversely with the anxiety index. Here, we investigated whether the microbial metabolite, acetate, could ameliorate SPS-triggered impairments. Male rats were randomly divided into unstressed controls or groups exposed to SPS. The groups received continued oral supplementation of either 150 mM of sodium acetate or 150 mM of sodium chloride-matched water. Two weeks after SPS, a battery of behavioral tests was performed, and the animals were euthanized the following day. While not affecting the unstressed controls, acetate supplementation reduced the impact of SPS on body weight gain and ameliorated SPS-induced anxiety-like behavior and the impairments in social interaction, but not depressive-like behavior. These changes were accompanied by several beneficial effects of acetate supplementation. Acetate alleviated the stress response by reducing urinary epinephrine levels, induced epigenetic modification by decreasing histone deacetylase (HDAC2) gene expression, inhibited neuroinflammation by reducing the density of Iba1+ cells and the gene expression of IL-1ß in the hippocampus, and increased serum β-hydroxybutyrate levels. The findings reveal a causal relationship between oral acetate treatment and mitigation of several SPS-induced behavioral impairments. Mechanistically, it impacted neuronal and metabolic pathways including changes in stress response, epigenetic modifications, neuroinflammation and showed novel link to ketone body production. The study demonstrates the preventive-therapeutic potential of acetate supplementation to alleviate adverse responses to traumatic stress.

Fibromyalgia and Irritable Bowel Syndrome Interaction: A Possible Role for Gut Microbiota and Gut-Brain Axis

Fibromyalgia (FM) is a serious chronic pain syndrome, characterised by muscle and joint stiffness, insomnia, fatigue, mood disorders, cognitive dysfunction, anxiety, depression and intestinal irritability. Irritable Bowel Syndrome (IBS) shares many of these symptoms, and FM and IBS frequently co-exist, which suggests a common aetiology for the two diseases. The exact physiopathological mechanisms underlying both FM and IBS onset are unknown. Researchers have investigated many possible causes, including alterations in gut microbiota, which contain billions of microorganisms in the human digestive tract. The gut-brain axis has been proven to be the link between the gut microbiota and the central nervous system, which can then control the gut microbiota composition. In this review, we will discuss the similarities between FM and IBS. Particularly, we will focus our attention on symptomatology overlap between FM and IBS as well as the similarities in microbiota composition between FM and IBS patients. We will also briefly discuss the potential therapeutic approaches based on microbiota manipulations that are successfully used in IBS and could be employed also in FM patients to relieve pain, ameliorate the rehabilitation outcome, psychological distress and intestinal symptoms.

Effects of Glutamine, Curcumin and Fish Bioactive Peptides Alone or in Combination on Intestinal Permeability in a Chronic-Restraint Stress Model

Irritable bowel syndrome (IBS), a multifactorial intestinal disorder, is often associated with a disruption in intestinal permeability as well as an increased expression of pro-inflammatory markers. The aim of this study was to first test the impact of treatment with glutamine (Gln), a food supplement containing natural curcumin extracts and polyunsaturated n-3 fatty acids (Cur); bioactive peptides from a fish protein hydrolysate (Ga); and a probiotic mixture containing Bacillus coagulans, Lactobacillus acidophilus, Lactobacillus gasseri and Lactobacillus helveticus. These compounds were tested alone on a stress-based IBS model, the chronic-restraint stress model (CRS). The combination of Gln, Cur and Ga (GCG) was also tested. Eight-week-old C57Bl/6 male mice were exposed to restraint stress for two hours every day for four days and received different compounds every day one week before and during the CRS procedure. Plasma corticosterone levels were measured as a marker of stress, and colonic permeability was evaluated ex vivo in Ussing chambers. Changes in the gene expression of tight junction proteins (occludin, claudin-1 and ZO 1) and inflammatory cytokines (IL1β, TNFα, CXCL1 and IL10) were assessed using RT-qPCR. The CRS model led to an increase in plasma corticosterone and an increase in colonic permeability compared with unstressed animals. No change in plasma corticosterone concentrations was observed in response to CRS with the different treatments (Gln, Cur, Ga or GCG). Stressed animals treated with Gln, Cur and Ga alone and in combination showed a decrease in colonic permeability when compared to the CRS group, while the probiotic mixture resulted in an opposite response. The Ga treatment induced an increase in the expression of the anti-inflammatory cytokine IL-10, and the GCG treatment was able to decrease the expression of CXCL1, suggesting the synergistic effect of the combined mixture. In conclusion, this study demonstrated that a combined administration of glutamine, a food supplement containing curcumin and polyunsaturated n-3 fatty acids, and bioactive peptides from a fish hydrolysate was able to reduce colonic hyperpermeability and reduce the inflammatory marker CXCL1 in a stress-based model of IBS and could be of interest to patients suffering from IBS.

A Microbial-Based Approach to Mental Health: The Potential of Probiotics in the Treatment of Depression

Probiotics are currently the subject of intensive research pursuits and also represent a multi-billion-dollar global industry given their vast potential to improve human health. In addition, mental health represents a key domain of healthcare, which currently has limited, adverse-effect prone treatment options, and probiotics may hold the potential to be a novel, customizable treatment for depression. Clinical depression is a common, potentially debilitating condition that may be amenable to a precision psychiatry-based approach utilizing probiotics. Although our understanding has not yet reached a sufficient level, this could be a therapeutic approach that can be tailored for specific individuals with their own unique set of characteristics and health issues. Scientifically, the use of probiotics as a treatment for depression has a valid basis rooted in the microbiota-gut-brain axis (MGBA) mechanisms, which play a role in the pathophysiology of depression. In theory, probiotics appear to be ideal as adjunct therapeutics for major depressive disorder (MDD) and as stand-alone therapeutics for mild MDD and may potentially revolutionize the treatment of depressive disorders. Although there is a wide range of probiotics and an almost limitless range of therapeutic combinations, this review aims to narrow the focus to the most widely commercialized and studied strains, namely Lactobacillus and Bifidobacterium, and to bring together the arguments for their usage in patients with major depressive disorder (MDD). Clinicians, scientists, and industrialists are critical stakeholders in exploring this groundbreaking concept.

Differences in gut microbiota associated with stress resilience and susceptibility to single prolonged stress in female rodents

Exposure to traumatic stress is a major risk factor for the development of neuropsychiatric disorders in a subpopulation of individuals, whereas others remain resilient. The determinants of resilience and susceptibility remain unclear. Here, we aimed to characterize the microbial, immunological, and molecular differences between stress-susceptible and stress-resilient female rats before and after exposure to a traumatic experience. Animals were randomly divided into unstressed controls (n = 10) and experimental groups (n = 16) exposed to Single Prolonged Stress (SPS), an animal model of PTSD. Fourteen days later, all rats underwent a battery of behavioral tests and were sacrificed the following day to collect different organs. Stool samples were collected before and after SPS. Behavioral analyses revealed divergent responses to SPS. The SPS treated animals were further subdivided into SPS-resilient (SPS-R) and SPS-susceptible (SPS-S) subgroups. Comparative analysis of fecal 16S sequencing before and after SPS exposure indicated significant differences in the gut microbial composition, functionality, and metabolites of the SPS-R and SPS-S subgroups. In line with the observed distinct behavioral phenotypes, the SPS-S subgroup displayed higher blood-brain barrier permeability and neuroinflammation relative to the SPS-R and/or controls. These results indicate, for the first time, pre-existing and trauma-induced differences in the gut microbial composition and functionality of female rats that relate to their ability to cope with traumatic stress. Further characterization of these factors will be crucial for understanding susceptibility and fostering resilience, especially in females, who are more likely than males to develop mood disorders.

Theaflavins in Black Tea Mitigate Aging-Associated Cognitive Dysfunction via the Microbiota-Gut-Brain Axis

Aging-associated cognitive dysfunction has a great influence on the lifespan and healthspan of the elderly. Theaflavins (TFs), a mixture of ingredients formed from enzymatic oxidation of catechins during the manufacture of tea, have a positive contribution to the qualities and antiaging activities of black tea. However, the role of TFs in mitigating aging-induced cognitive dysfunction and the underlying mechanism remains largely unknown. Here, we find that TFs effectively improve behavioral impairment via the microbiota-gut-brain axis: TFs maintain gut homeostasis by improving antioxidant ability, strengthening the immune response, increasing the expression of tight junction proteins, restructuring the gut microbiota, and altering core microbiota metabolites, i.e., short-chain fatty acids and essential amino acids (SCFAs and AAs), and upregulating brain neurotrophic factors. Removing the gut microbiota with antibiotics partly abolishes the neuroprotective effects of TFs. Besides, correlation analysis indicates that the decrease in gut microbiota, such as Bacteroidetes and Lachnospiraceae, and the increase in microbiota metabolites' levels are positively correlated with behavioral improvements. Taken together, our findings reveal a potential role of TFs in mitigating aging-driven cognitive dysfunction via the microbiota-gut-brain axis. The intake of TFs can be translated into a novel dietary intervention approach against aging-induced cognitive decline.

Understanding the Connection between Gut Homeostasis and Psychological Stress

Long-term exposure to adverse life events that provoke acute or chronic psychological stress (hereinafter "stress") can negatively affect physical health and even increase susceptibility to psychological illnesses, such as anxiety and depression. As a part of the hypothalamic-pituitary-adrenal axis, corticotropin-releasing factor (CRF) released from the hypothalamus is primarily responsible for the stress response. Typically, CRF disrupts the gastrointestinal system and leads to gut microbiota dysbiosis, thereby increasing risk of functional gastrointestinal diseases, such as irritable bowel syndrome. Furthermore, CRF increases oxidative damage to the colon and triggers immune responses involving mast cells, neutrophils, and monocytes. CRF even affects the differentiation of intestinal stem cells (ISCs), causing enterochromaffin cells to secrete excessive amounts of 5-hydroxytryptamine (5-HT). Therefore, stress is often accompanied by damage to the intestinal epithelial barrier function, followed by increased intestinal permeability and bacterial translocation. There are multi-network interactions between the gut microbiota and stress, and gut microbiota may relieve the effects of stress on the body. Dietary intake of probiotics can provide energy for ISCs through glycolysis, thereby alleviating the disruption to homeostasis caused by stress, and it significantly bolsters the intestinal barrier, alleviates intestinal inflammation, and maintains endocrine homeostasis. Gut microbiota also directly affect the synthesis of hormones and neurotransmitters, such as CRF, 5-HT, dopamine, and norepinephrine. Moreover, the Mediterranean diet enhances the stress resistance to some extent by regulating the intestinal flora. This article reviews recent research on how stress damages the gut and microbiota, how the gut microbiota can improve gut health by modulating injury due to stress, and how the diet relieves stress injury by interfering with intestinal microflora. This review gives insight into the potential role of the gut and its microbiota in relieving the effects of stress via the gut-brain axis.

Evaluation of two laboratory model methods for diarrheal irritable bowel syndrome

BACKGROUND

Diarrheal irritable bowel syndrome (IBS-D) is a common chronic functional gastrointestinal disorder, and the underlying pathogenic mechanism is still unclear. Animal models that mimic the pathological state of IBS-D patients were constructed to provide a reference for later drug research and model development.

METHODS

The IBS-D model was induced using restraint stress and chemical stimulation (rhubarb), and rats were divided into normal control group (NC), chemically stimulated group (CS), and restraint stress group (RS). Visceral motility responses to Colorectal Balloon Dilation (CRD) were measured by Abdominal Withdrawal Reflex (AWR); evaluation of faecal properties and water content; determination of colonic tissue tight junction (TJ) mRNA expression by RT-PCR; measurement of inflammatory cytokines by ELISA; and intestinal flora and short chain fatty acids.

RESULTS

Compared to NC group, CS and RS group rats showed increased intestinal sensitivity and Bristol stool score, significant diarrheal symptoms and weight loss. Mucin 2, ZO-1, OCLN, CLDN4 mRNA expression was reduced and the intestinal mucosal barrier function was diminished. In addition, the levels of inflammatory factors IL-1β, IL-6, IL-8, IL-10 and TNF-α increased, the abundance and diversity of intestinal flora decreased, the content of beneficial bacteria such as Bifidobacteria decreased, and SCFAs such as acetic acid, propionic acid and butyric acid decreased to different degrees. Although, no significant difference was observed for any molecular and inflammatory marker, but compared to CS group, RS group had less water in the stool, higher visceral sensitivity, and higher relative abundance of beneficial intestinal bacteria such as Actinobacteria.

CONCLUSION

In conclusion, restraint stress combined with chemical stimulation can mimic the pathological state of diarrhoea symptoms, visceral hypersensitivity, reduced intestinal mucosal barrier permeability, immune regulatory dysfunction and dysbiosis in IBS-D patients. However, herbs with antibacterial effects such as rhubarb and senna, for example, are not suitable as the first choice for chemical stimulation, as they may lead to a decrease in harmful bacteria and an increase in beneficial bacteria in the intestinal fraction and do not perfectly mimic the imbalanced state of intestinal flora in IBS-D patients, while restraint stress may be a key factor in modelling.

Global research progress of visceral hypersensitivity and irritable bowel syndrome: bibliometrics and visualized analysis

Background: Irritable bowel syndrome (IBS) is a group of functional intestinal disorders characterized by abdominal pain, bloating, and changes in bowel habits, and/or stool characteristics. Recent studies have shown that there has been a significant advancement in the study of visceral hypersensitivity in IBS. Through the use of bibliometrics, this study aims to provide a comprehensive overview of the knowledge structure and research hotpots of visceral hypersensitivity in IBS. Methods: Publications related to visceral hypersensitivity in IBS from 2012 to 2022 were searched on the web of science core collection (WoSCC) database. CiteSpace.6.1. R2 and Vosviewer 1.6.17 were used to perform bibliometric analysis. Results: A total of 974 articles led by China and the United States from 52 countries were included. Over the past decade, the number of articles on visceral hypersensitivity and IBS has steadily increased year by year. China, the United States, and Belgium are the main countries in this field. Univ Oklahoma, Univ Gothenburg, and Zhejiang University are the main research institutions. Simren, Magnus, Greenwood-van meerveld, Beverley, and Tack, Jan are the most published authors in this research field. The research on the causes, genes, and pathways involved in visceral hypersensitivity in IBS and the mechanism of IBS are the main topics and hotspots in this field. This study also found that gut microbiota may be related to the occurrence of visceral hypersensitivity, and probiotics may be a new method for the treatment of visceral hypersensitivity and pain, which may become a new direction for research in this field. Conclusion: This is the first bibliometric study to comprehensively summarize the research trends and developments of visceral hypersensitivity in IBS. This information provides the research frontier and hot topics in this field in recent years, which will provide a reference for scholars studying this field.

Beneficial Effects of Limosilactobacillus fermentum in the DCA Experimental Model of Irritable Bowel Syndrome in Rats

Limosilactobacillus fermentum CECT5716, a probiotic strain isolated from human milk, has reported beneficial effects on different gastrointestinal disorders. Moreover, it has shown its ability to restore altered immune responses, in association with microbiome modulation in different pathological conditions. Therefore, our aim was to assess the effects of a Limosilacbacillus fermentum CECT5716 in a rat experimental model of irritable bowel syndrome (IBS) that resembles human IBS. The experimental IBS was induced by deoxycholic acid (DCA) in rats and then, Limosilactobacillus fermentum CECT5716 (109 CFU/day/rat) was administered. Behavioral studies, hyperalgesia and intestinal hypersensitivity determinations were performed and the impact of the probiotic on the inflammatory and intestinal barrier integrity was evaluated. Additionally, the gut microbiota composition was analyzed. Limosilactobacillus fermentum CECT5716 attenuated the anxiety-like behavior as well as the visceral hypersensitivity and referred pain. Moreover, this probiotic ameliorated the gut inflammatory status, re-establishing the altered intestinal permeability, reducing the mast cell degranulation and re-establishing the gut dysbiosis in experimental IBS. Therefore, our results suggest a potential use of Limosilactobacillus fermentum CECT5716 in clinical practice for the management of IBS patients.

Gut-Brain Axis, Neurodegeneration and Mental Health: A Personalized Medicine Perspective

Neurological conditions such as neurodegenerative diseases and mental health disorders are a result of multifactorial underpinnings, leading to individual-based complex phenotypes. Demystification of these multifactorial connections will promote disease diagnosis and treatment. Personalized treatment rather than a one-size-fits-all approach would enable us to cater to the unmet healthcare needs based on protein-protein and gene-environment interactions. Gut-brain axis, as the name suggests, is a two-way biochemical communication pathway between the central nervous system (CNS) and enteric nervous system (ENS), enabling a mutual influence between brain and peripheral intestinal functions. The gut microbiota is a major component of this bidirectional communication, the composition of which is varied depending on the age, and disease conditions, among other factors. Gut microbiota profile is typically unique and personalized therapeutic intervention can aid in treating or delaying neurodegeneration and mental health conditions. Besides, research on the gut microbial influence on these conditions is gaining attention, and a better understanding of this concept can lead to identification of novel targeted therapies.

Graphical Abstract

The gut microbiota, HPA axis, and brain in adolescent-onset depression: Probiotics as a novel treatment

Stress-associated disruptions in the development of frontolimbic regions may play a critical role in the emergence of adolescent-onset depression. These regions are particularly sensitive to Hypothalamic-Pituitary-Adrenal (HPA) axis signaling. The HPA axis is hyperactive in adolescent depression, and interventions that attenuate such hyperactivity hold promise as potential treatments. The Microbiome-Gut-Brain (MGB) axis is an important pathway through which stress dysregulates HPA-axis activity and thus exerts deleterious effects on the adolescent brain. Probiotic agents, which alter the gut microbiota composition by introducing bacterial strains with beneficial physiological effects, normalize aberrant HPA-axis activity and reduce depressive symptoms in both animal studies and adult clinical trials. While the potential utility of such agents in treating or preventing adolescent depression remains largely unexplored, recent data suggest the existence of an adolescent sensitive window during which probiotics may be especially efficacious in reducing depressive symptoms compared to effects observed in adult populations. In this review, we outline evidence that probiotic use may attenuate stress effects on frontolimbic development, providing a novel means of improving depressive symptoms among adolescent populations.

Serpin-positive Bifidobacterium breve CNCM I-5644 improves intestinal permeability in two models of irritable bowel syndrome

Probiotic supplementation can help to mitigate the pathogenesis of irritable bowel syndrome (IBS) by reinforcing the intestinal barrier, and reducing both inflammation and proteolytic activity. Here, a combination of in vitro tests was performed on 33 Bifidobacterium strains as probiotic candidates for IBS. In addition to the classical tests performed, the detection of the serine protease inhibitor (serpin) enzyme capable of decreasing the high proteolytic activity found in IBS patients was included. Three serpin-positive strains were selected: Bifidobacterium breve CNCM I-5644, Bifidobacterium longum subsp. infantis CNCM I-5645 and B. longum CNCM I-5646 for their immunomodulation properties and protection of intestinal epithelial integrity in vitro. Furthermore, we found that B. breve CNCM I-5644 strain prevented intestinal hyperpermeability by upregulating Cingulin and Tight Junction Protein 1 mRNA levels and reducing pro-inflammatory markers. The ability of CNCM I-5644 strain to restore intestinal hyperpermeability (FITC-dextran) was shown in the murine model of low-grade inflammation induced by dinitrobenzene sulfonic acid (DNBS). This effect of this strain was corroborated in a second model of IBS, the neonatal maternal separation model in mice. Altogether, these data suggest that serpin-positive B. breve CNCM I-5644 may partially prevent disorders associated with increased barrier permeability such as IBS.

Functional Gastrointestinal Disorders with Psychiatric Symptoms: Involvement of the Microbiome-Gut-Brain Axis in the Pathophysiology and Case Management

Functional Gastrointestinal Disorders have been an important cause of poor life quality in affected populations. The unclear etiology and pathophysiological mechanism alter the clinical evolution of the patient. Although a strong connection with psychological stress has been observed, it was not until recently that the gut-brain axis involvement has been revealed. Furthermore, the current literature not only promotes the gut-brain axis modulation as a therapeutical target for functional digestive disorders but also states that the gut microbiome has a main role in this bi-directional mechanism. Psychiatric symptoms are currently recognized as an equally important aspect of the clinical manifestation and modulation of both the digestive and central nervous systems and could be the best approach in restoring the balance. As such, this article proposes a detailed description of the physiology of the microbiome-gut-brain axis, the pathophysiology of the functional gastrointestinal disorders with psychiatric symptoms and current perspectives for therapeutical management, as revealed by the latest studies in the scientific literature.

The clinical evidence for postbiotics as microbial therapeutics

An optimally operating microbiome supports protective, metabolic, and immune functions, but disruptions produce metabolites and toxins which can be involved in many conditions. Probiotics have the potential to manage these. However, their use in vulnerable people is linked to possible safety concerns and maintaining their viability is difficult. Interest in postbiotics is therefore increasing. Postbiotics contain inactivated microbial cells or cell components, thus are more stable and exert similar health benefits to probiotics. To review the evidence for the clinical benefits of postbiotics in highly prevalent conditions and consider future potential areas of benefit. There is growing evidence revealing the diverse clinical benefits of postbiotics in many prevalent conditions. Postbiotics could offer a novel therapeutic approach and may be a safer alternative to probiotics. Establishing interaction mechanisms between postbiotics and commensal microorganisms will improve the understanding of potential clinical benefits and may lead to targeted postbiotic therapy.

Electroacupuncture at Tianshu (ST25) and Zusanli (ST36) alleviates stress-induced irritable bowel syndrome in mice by modulating gut microbiota and corticotropin-releasing factor

OBJECTIVE

To investigate whether electroacupuncture (EA) at bilateral Tianshu (ST25) and Zusanli (ST36) acupoints could alleviate stress-induced irritable bowel syndrome (IBS) and evaluate its effect on gut microbiota and corticotropin-releasing factor (CRF).

METHODS

Thirty C57BL/6 mice were randomly divided into the normal, water avoidance stress (WAS), and WAS+EA groups (10 mice per group). An experimental model of IBS was established by exposing the animals to WAS. The mice were treated with EA at the bilateral Tianshu (ST25) and Zusanli (ST36) acupoints. The abdominal withdrawal reflex test was conducted to evaluate visceral sensitivity in IBS. Gut microbiota was analyzed using 16S rRNA sequencing and analysis. The expression of CRF was determined using immune-ofluorescence and quantitative real-time polymerase chain reaction.

RESULTS

EA alleviated visceral hypersensitivity in a mouse model of WAS-induced IBS. It modulated the dysbiosis of gut microbiota induced by WAS. Moreover, it suppressed the WAS-induced overexpression of CRF in colon tissues.

CONCLUSION

The findings of this study suggest that EA alleviated WAS-induced IBS mechanisms possibly involving the modulation of the dysbiosis of gut microbiota and suppression of CRF expression.

The effects of antimicrobials and lipopolysaccharide on acute immune responsivity in pubertal male and female CD1 mice

Exposure to stress during critical periods of development—such as puberty—is associated with long-term disruptions in brain function and neuro-immune responsivity. However, the mechanisms underlying the effect of stress on the pubertal neuro-immune response has yet to be elucidated. Therefore, the objective of the current study was to investigate the effect antimicrobial and lipopolysaccharide (LPS) treatments on acute immune responsivity in pubertal male and female mice. Moreover, the potential for probiotic supplementation to mitigate these effects was also examined. 240 male and female CD1 mice were treated with one week of antimicrobial treatment (mixed antimicrobials or water) and probiotic treatment (L. rhamnosis R0011 and L. helveticus R0052 or L. helveticus R0052 and B. longum R0175) or placebo at five weeks of age. At six weeks of age (pubertal stress-sensitive period), the mice received a single injection of LPS or saline. Sickness behaviours were assessed, and mice were euthanized 8 h post-injection. Brain, blood, and intestinal samples were collected. The results indicated that the antimicrobial treatment reduced sickness behaviours, and potentiated LPS-induced plasma cytokine concentrations and pro-inflammatory markers in the pre-frontal cortex (PFC) and hippocampus, in a sex-dependent manner. However, probiotics reduced LPS-induced plasma cytokine concentrations along with hippocampal and PFC pro-inflammatory markers in a sex-dependent manner. L. rhamnosis R0011 and L. helveticus R0052 treatment also mitigated antimicrobial-induced plasma cytokine concentrations and sickness behaviours. These findings suggest that the microbiome is an important modulator of the pro-inflammatory immune response during puberty.

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Pubertal dysbiosis increases LPS-induced neuroinflammation.

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Pubertal dysbiosis increases LPS-induced plasma cytokine concentrations.

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Pubertal probiotic treatment reduces LPS-induced neuroinflammation.

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Pubertal probiotic treatment reduces LPS-induced plasma cytokine concentrations.

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Pubertal probiotic treatment reduces LPS-induced sickness.

Effect of Oral Administration of Lactiplantibacillus plantarum SNK12 on Temporary Stress in Adults: A Randomized, Placebo-Controlled, Double-Blind, Parallel-Group Study

Mouse studies have reported anti-stress effects of Lactiplantibacillus plantarum SNK12 (SNK). Specifically, oral SNK administration increased mRNA levels of hippocampal neurotrophic factor and gamma-aminobutyric acid receptor in mice with sub-chronic mild stress-induced social defeat; moreover, it improved depressive behavior. We aimed to evaluate the efficacy of SNK ingestion against stress in healthy adults. We used the Uchida–Kraepelin test for the stress load, with a low-dose (50 mg/day), high-dose (150 mg/day), and placebo groups (dextrin). The primary outcome was the psychological evaluation as measured by the Profile of Mood States 2nd Edition (POMS2) using total mood disturbance (TMD) scores. The secondary outcomes were the score of each POMS2 item, salivary cortisol as a stress marker, and autonomic balance with the low frequency (LF)/ high frequency (HF) ratio. Compared with the placebo group, the SNK ingestion group showed significantly lower TMD scores. Additionally, compared with the placebo group, the high-dose group showed significantly lower scores for Tension-Anxiety and Confusion-Bewilderment, while the low-dose group showed significantly lower Anger-Hostility scores, salivary cortisol levels, and LF/HF scores. Our findings suggest that SNK ingestion could relieve stress (negative feelings, anxiety, tension, embarrassment, confusion, anger, and hostility) resulting from the temporary load caused by work and study.

The Intervention of Prebiotics on Depression via the Gut-Brain Axis

The imbalance of intestinal microbiota can cause the accumulation of endotoxin in the main circulation system of the human body, which has a great impact on human health. Increased work and life pressure have led to a rise in the number of people falling into depression, which has also reduced their quality of life. The gut–brain axis (GBA) is closely related to the pathological basis of depression, and intestinal microbiota can improve depressive symptoms through GBA. Previous studies have proven that prebiotics can modulate intestinal microbiota and thus participate in human health regulation. We reviewed the regulatory mechanism of intestinal microbiota on depression through GBA, and discussed the effects of prebiotics, including plant polysaccharides and polyphenols on the regulation of intestinal microbiota, providing new clues for the prevention and treatment of depression.

Clostridium butyricum RH2 Alleviates Chronic Foot Shock Stress-Induced Behavioral Deficits in Rats via PAI-1

Recent investigations have demonstrated that the chronic stress-induced behavioral disorders can be ameliorated by probiotics including Clostridium butyricum (C. butyricum) via the gut-brain-axis. However, the molecular mechanisms underlying the beneficial effects of C. butyricum on brain remain largely unknown. Here, we investigated whether chronic foot shock stress (CFSS) paradigm used for a hypertensive animal model could induce mood disorders such as anxiety, depression and cognitive impairments. Then, we assessed the impact of C. butyricum RH2 on the behavior disorders and neurobiological alterations in the hippocampus. Male Sprague-Dawley (SD) rats received intermittent electric shocks for consecutive 14 days and were treated with C. butyricum RH2 for 17 days. Anxiety- or depression-like behaviors were evaluated by open field test (OFT), and elevated plus maze (EPM). The Morris water maze test (MWM) was used to evaluate the cognitive functions. CFSS intervention led to mild anxiety- or depression-like behavior or cognitive impairment and C. butyricum RH2 treatment reversed the CFSS-induced symptoms. The serum ACTH or CORT was increased following CFSS but was completely reversed by C. butyricum RH2 treatment. In the hippocampus of CFSS rats, the expressions of BDNF and TrkB were downregulated but proBDNF and P75^NTR were upregulated. These expression changes were partially reversed by C. butyricum RH2, suggesting a mode of action on BDNF and proBDNF balance. CFSS exposure resulted in downregulation of tissue-type plasminogen activator (tPA) but upregulation of plasminogen activator inhibitor 1(PAI-1), which could contribute to the decrease in BDNF by reduced conversion from proBDNF to BDNF in the hippocampus. C. butyricum RH2 treatment reversed the upregulated PAI-1 but not the downregulated tPA, which was in parallel with the amelioration of behavioral abnormalities, suggesting a novel tPA independent mechanism for PAI-1 action. Our results demonstrate for the first time that C. butyricum RH2 attenuates stress-induced behavior disorders via inhibiting the expression of brain PAI-1.

Antibiotics, gut microbiota, and irritable bowel syndrome: What are the relations?

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder in which recurrent abdominal pain is associated with defecation or a change in bowel habits (constipation, diarrhea, or both), and it is often accompanied by symptoms of abdominal bloating and distension. IBS is an important health care issue because it negatively affects the quality of life of patients and places a considerable financial burden on health care systems. Despite extensive research, the etiology and underlying pathophysiology of IBS remain incompletely understood. Proposed mechanisms involved in its pathogenesis include increased intestinal permeability, changes in the immune system, visceral hypersensitivity, impaired gut motility, and emotional disorders. Recently, accumulating evidence has highlighted the important role of the gut microbiota in the development of IBS. Microbial dysbiosis within the gut is thought to contribute to all aspects of its multifactorial pathogenesis. The last few decades have also seen an increasing interest in the impact of antibiotics on the gut microbiota. Moreover, antibiotics have been suggested to play a role in the development of IBS. Extensive research has established that antibacterial therapy induces remarkable shifts in the bacterial community composition that are quite similar to those observed in IBS. This suggestion is further supported by data from cohort and case-control studies, indicating that antibiotic treatment is associated with an increased risk of IBS. This paper summarizes the main findings on this issue and contributes to a deeper understanding of the link between antibiotic use and the development of IBS.

Microbiota and Pain: Save Your Gut Feeling

Recently, a growing body of evidence has emerged regarding the interplay between microbiota and the nervous system. This relationship has been associated with several pathological conditions and also with the onset and regulation of pain. Dysregulation of the axis leads to a huge variety of diseases such as visceral hypersensitivity, stress-induced hyperalgesia, allodynia, inflammatory pain and functional disorders. In pain management, probiotics have shown promising results. This narrative review describes the peripheral and central mechanisms underlying pain processing and regulation, highlighting the role of the gut-brain axis in the modulation of pain. We summarized the main findings in regard to the stress impact on microbiota’s composition and its influence on pain perception. We also focused on the relationship between gut microbiota and both visceral and inflammatory pain and we provided a summary of the main evidence regarding the mechanistic effects and probiotics use.

Integrated 16S rRNA Gene Sequencing and Metabolomics Analysis to Investigate the Important Role of Osthole on Gut Microbiota and Serum Metabolites in Neuropathic Pain Mice

Accumulating evidence suggests that neuropathic pain (NP) is closely connected to the metabolic disorder of gut microbiota, and natural products could relieve NP by regulating gut microbiota. The purpose of this study is to investigate the important regulatory effects of osthole on gut microbiota and serum metabolites in mice with chronic constriction injury (CCI). Mice's intestinal contents and serum metabolites were collected from the sham group, CCI group, and osthole treatment CCI group. The 16S rRNA gene sequencing was analyzed, based on Illumina NovaSeq platform, and ANOVA analysis were used to analyze the composition variety and screen differential expression of intestinal bacteria in the three groups. Ultra-high-performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry (UHPLC-Q-TOF-MS) was used for analyzing the data obtained from serum specimens, and KEGG enrichment analysis was used to identify pathways of differential metabolites in the treatment of neuralgia mice. Furthermore, the Pearson method and Cytoscape soft were used to analyze the correlation network of differential metabolites, gut microbiota, and disease genes. The analysis results of 16S rRNA gene sequencing displayed that Bacteroidetes, Firmicutes, and Verrucomicrobia were highly correlated with NP after osthole treatment at the phylum level. Akkermansia, Lachnospiraceae_unclassified, Lachnospiraceae_NK4A136_group, Bacteroides, Lactobacillus, and Clostridiales_unclassified exhibited higher relative abundance and were considered important microbial members at genus level in neuralgia mice. Serum metabolomics results showed that 131 metabolites were considered to be significantly different in the CCI group compared to the sham group, and 44 metabolites were significantly expressed between the osthole treatment group and the CCI group. At the same time, we found that 29 differential metabolites in the two comparison groups were overlapping. Integrated analysis results showed that many intestinal microorganisms and metabolites have a strong positive correlation. The correlation network diagram displays that 10 genes were involved in the process of osthole alleviating NP through a metabolic pathway and gut microbiota, including IGF2, GDAP1, MYLK, IL18, CD55, MIR331, FHIT, F3, ERBB4, and ITGB3. Our findings have preliminarily confirmed that NP is closely related to metabolism and intestinal microbial imbalance, and osthole can improve the metabolic disorder of NP by acting on gut microbiota.

One Giant Leap from Mouse to Man: The Microbiota-Gut-Brain Axis in Mood Disorders and Translational Challenges Moving towards Human Clinical Trials

The microbiota–gut–brain axis is a bidirectional communication pathway that enables the gut microbiota to communicate with the brain through direct and indirect signaling pathways to influence brain physiology, function, and even behavior. Research has shown that probiotics can improve several aspects of health by changing the environment within the gut, and several lines of evidence now indicate a beneficial effect of probiotics on mental and brain health. Such evidence has prompted the arrival of a new term to the world of biotics research: psychobiotics, defined as any exogenous influence whose effect on mental health is bacterially mediated. Several taxonomic changes in the gut microbiota have been reported in neurodevelopmental disorders, mood disorders such as anxiety and depression, and neurodegenerative disorders such as Alzheimer’s disease. While clinical evidence supporting the role of the gut microbiota in mental and brain health, and indeed demonstrating the beneficial effects of probiotics is rapidly accumulating, most of the evidence to date has emerged from preclinical studies employing different animal models. The purpose of this review is to focus on the role of probiotics and the microbiota–gut–brain axis in relation to mood disorders and to review the current translational challenges from preclinical to clinical research.