Psychological stress and corticotropin-releasing hormone increase intestinal permeability in humans by a mast cell-dependent mechanism

Immune Activation in Functional Dyspepsia: Bystander Becoming the Suspect

Disorders of gut-brain interaction (DGBI), formerly termed functional gastrointestinal disorders (FGID), are highly prevalent although exact pathophysiological mechanisms remain unclear. Intestinal immune activation has been recognized, but increasing evidence supports a pivotal role for an active inflammatory state in these disorders. In functional dyspepsia (FD), marked eosinophil and mast cell infiltration has been repeatedly demonstrated and associations with symptoms emphasize the relevance of an eosinophil-mast cell axis in FD pathophysiology. In this Review, we highlight the importance of immune activation in DGBI with a focus on FD. We summarize eosinophil biology in both homeostasis and inflammatory processes. The evidence for immune activation in FD is outlined with attention to alterations on both cellular and molecular level, and how these may contribute to FD symptomatology. As DGBI are complex and multifactorial conditions, we shed light on factors associated to, and potentially influencing immune activation, including bidirectional gut-brain interaction, allergy and the microbiota. Crucial studies reveal a therapeutic benefit of treatments targeting immune activation, suggesting that specific anti-inflammatory therapies could offer renewed hope for at least a subset of DGBI patients. Lastly, we explore the future directions for DGBI research that could advance the field. Taken together, emerging evidence supports the recognition of FD as an immune-mediated organic-based disorder, challenging the paradigm of a strictly functional nature.

Increased fermentable carbohydrate intake alters colonic mucus barrier function through glycation processes and increased mast cell counts

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder for which dietary interventions can be a useful treatment. In recent years, the low-FODMAP approach is gaining traction in this regard. The fermentation of these non-absorbed carbohydrates by the gut microbiota can generate toxic glycating metabolites, such as methylglyoxal. These metabolites can have harmful effects by their role in the generation of advanced glycation end products (AGEs), which activates Receptor for AGEs (AGER). Mast cells can be stimulated by AGEs and play a role in IBS. We have treated mice with lactose or fructo-oligosaccharides (FOS), with or without co-administration of pyridoxamine and investigated the colonic mucus barrier. We have found that an increased intake of lactose and fructo-oligosaccharides induces a dysregulation of the colonic mucus barrier, increasing mucus discharge in empty colon, while increasing variability and decreasing average thickness mucus layer covering the fecal pellet. Changes were correlated with increased mast cell counts, pointing to a role for the crosstalk between these and goblet cells. Additionally, AGE levels in colonic epithelium were increased by treatment with the selected fermentable carbohydrates. Observed effects were prevented by co-treatment with anti-glycation agent pyridoxamine, implicating glycation processes in the negative impact of fermentable carbohydrate ingestion. This study shows that excessive intake of fermentable carbohydrates can cause colonic mucus barrier dysregulation in mice, by a process that involves glycating agents and increased mucosal mast cell counts.

Effect of chronic restraint stress and western-diet feeding on colonic regulatory gene expression in mice

BACKGROUND

Diet-induced obesity (DIO) and psychological stress are significant independent regulators of gastrointestinal physiology; however, our understanding of how these two disorders influence the host-microbe interface is still poorly characterized. The aim of this study was to assess the combined influences of diet-induced obesity and psychological stress on microbiome composition and colonic gene expression.

METHODS

C57BL/6J mice (n = 48) were subject to a combination of 22 weeks of Western diet (WD) feeding and a chronic restraint stressor (CRS) for the last 4 weeks of feeding. At the end of the combined intervention, microbiome composition was determined from cecal contents, and colonic tissue gene expression was assessed by multiplex analysis using NanoString nCounter System and real-time qPCR.

RESULTS

WD feeding induced a DIO phenotype with increased body weight, worsened metabolic markers, and alterations to microbiome composition. CRS reduced body weight in both dietary groups while having differential effects on glucose metabolism. CRS improved the Firmicutes/Bacteroidetes ratio in WD-fed animals while expanding the Proteobacteria phyla. Significantly lower expression of colonic Tlr4 (p = 0.008), Ocln (p = 0.004), and Cldn3 (p = 0.004) were noted in WD-fed animals compared to controls with no synergistic effects observed when combined with CRS. No changes to colonic expression of downstream inflammatory mediators were observed. Interestingly, higher levels of expression of Cldn2 (p = 0.04) and bile acid receptor Nr1h4 (p = 0.02) were seen in mice exposed to CRS.

CONCLUSION

Differential but not synergistic effects of WD and CRS were noted at the host-microbe interface suggesting multifactorial responses that require further investigation.

Belgian consensus on irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is characterised by recurrent abdominal pain related to defaecation or associated with altered stool frequency or consistency. Despite its prevalence, major uncertainties in the diagnostic and therapeutic management persist in clinical practice.

METHODS

A Delphi consensus was conducted by 20 experts from Belgium, and consisted of literature review and voting process on 78 statements. Grading of recommendations, assessment, development and evaluation criteria were applied to evaluate the quality of evidence. Consensus was defined as > 80 % agreement.

RESULTS

Consensus was reached for 50 statements. The Belgian consensus agreed as to the multifactorial aetiology of IBS. According to the consensus abdominal discomfort also represents a cardinal symptom, while bloating and abdominal distension often coexist. IBS needs subtyping based on stool pattern. The importance of a positive diagnosis, relying on history and clinical examination is underlined, while additional testing should remain limited, except when alarm features are present. Explanation of IBS represents a crucial part of patient management. Lifestyle modification, spasmolytics and water-solube fibres are considered first-line agents. The low FODMAP diet, selected probiotics, cognitive behavioural therapy and specific treatments targeting diarrhoea and constipation are considered appropriate. There is a consensus to restrict faecal microbiota transplantation and gluten-free diet, while other treatments are strongly discouraged.

CONCLUSIONS

A panel of Belgian gastroenterologists summarised the current evidence on the aetiology, symptoms, diagnosis and treatment of IBS with attention for the specificities of the Belgian healthcare system.

Gut barrier disruption and chronic disease

The intestinal barrier protects the host against gut microbes, food antigens, and toxins present in the gastrointestinal tract. However, gut barrier integrity can be affected by intrinsic and extrinsic factors, including genetic predisposition, the Western diet, antibiotics, alcohol, circadian rhythm disruption, psychological stress, and aging. Chronic disruption of the gut barrier can lead to translocation of microbial components into the body, producing systemic, low-grade inflammation. While the association between gut barrier integrity and inflammation in intestinal diseases is well established, we review here recent studies indicating that the gut barrier and microbiota dysbiosis may contribute to the development of metabolic, autoimmune, and aging-related disorders. Emerging interventions to improve gut barrier integrity and microbiota composition are also described.

The Role of Leaky Gut in Functional Dyspepsia

Patients with functional dyspepsia (FD) complain of epigastric symptoms with no identifiable cause. Increased intestinal permeability has been described in these patients, especially in the proximal small bowel or duodenum, and was associated with mucosal immune activation and symptoms. In this review, we discuss duodenal barrier function, including techniques currently applied in FD research. We summarize the available data on duodenal permeability in FD and factors associated to increased permeability, including mucosal eosinophils, mast cells, luminal and systemic factors. While the increased influx of antigens into the duodenal mucosa could result in local immune activation, clinical evidence for a causal role of permeability is lacking in the absence of specific barrier-protective treatments. As both existing and novel treatments, including proton pump inhibitors (PPI) and pre- or probiotics may impact duodenal barrier function, it is important to recognize and study these alterations to improve the knowledge and management of FD.

[Duodenal Microbiome and Its Clinical Implications in Functional Dyspepsia]

Functional dyspepsia is one of the most common functional gastrointestinal disorders with chronic bothersome epigastric pain or postprandial fullness without a definite organic cause. Despite its high clinical burden, the treatment modalities for modulating impaired motor dysfunction and visceral hypersensitivity have been unsatisfactory. Recently, studies demonstrating low-grade inflammation and dysbiosis of the duodenal mucosa as potential triggers of the disease have attracted attention. Observations, such as an increase in the proportion of oral commensal bacteria in the duodenal mucosa, such as Streptococcus species, highlight the importance of bacterial ecology in developing symptoms of functional dyspepsia. In the near future, anti-inflammatory drugs and probiotics that modulate the host-microbiome interaction are expected to emerge to treat functional dyspepsia.

Probiotic Mixture Containing Lactobacillus helveticus, Bifidobacterium longum and Lactiplantibacillus plantarum Affects Brain Responses to an Arithmetic Stress Task in Healthy Subjects: A Randomised Clinical Trial and Proof-of-Concept Study

Probiotics are suggested to impact physiological and psychological stress responses by acting on the gut-brain axis. We investigated if a probiotic product containing Bifidobacterium longum R0175, Lactobacillus helveticus R0052 and Lactiplantibacillus plantarum R1012 affected stress processing in a double-blinded, randomised, placebo-controlled, crossover proof-of-concept study (NCT03615651). Twenty-two healthy subjects (24.2 ± 3.4 years, 6 men/16 women) underwent a probiotic and placebo intervention for 4 weeks each, separated by a 4-week washout period. Subjects were examined by functional magnetic resonance imaging while performing the Montreal Imaging Stress Task (MIST) as well as an autonomic nervous system function assessment during the Stroop task. Reduced activation in regions of the lateral orbital and ventral cingulate gyri was observed after probiotic intervention compared to placebo. Significantly increased functional connectivity was found between the upper limbic region and medioventral area. Interestingly, probiotic intervention seemed to predominantly affect the initial stress response. Salivary cortisol secretion during the task was not altered. Probiotic intervention did not affect cognitive performance and autonomic nervous system function during Stroop. The probiotic intervention was able to subtly alter brain activity and functional connectivity in regions known to regulate emotion and stress responses. These findings support the potential of probiotics as a non-pharmaceutical treatment modality for stress-related disorders.

NSAID-Associated Small Intestinal Injury: An Overview From Animal Model Development to Pathogenesis, Treatment, and Prevention

With the wide application of non-steroidal anti-inflammatory drugs (NSAIDs), their gastrointestinal side effects are an urgent health burden. There are currently sound preventive measures for upper gastrointestinal injury, however, there is a lack of effective defense against lower gastrointestinal damage. According to a large number of previous animal experiments, a variety of NSAIDs have been demonstrated to induce small intestinal mucosal injury in vivo. This article reviews the descriptive data on the administration dose, administration method, mucosal injury site, and morphological characteristics of inflammatory sites of various NSAIDs. The cells, cytokines, receptors and ligands, pathways, enzyme inhibition, bacteria, enterohepatic circulation, oxidative stress, and other potential pathogenic factors involved in NSAID-associated enteropathy are also reviewed. We point out the limitations of drug modeling at this stage and are also pleased to discover the application prospects of chemically modified NSAIDs, dietary therapy, and many natural products against intestinal mucosal injury.

Glutamate attenuates lipopolysaccharide induced intestinal barrier injury by regulating corticotropin-releasing factor pathway in weaned pigs

Objective

The purpose of this study was to evaluate the protection of glutamate (GLU) against the impairment in intestinal barrier function induced by lipopolysaccharide (LPS) stress in weaned pigs.

Methods

Twenty-four weaned pigs were divided into four treatments containing: i) non-challenged control, ii) LPS-challenged control, iii) LPS+1.0% GLU, and iv) LPS+2.0% GLU. On day 28, pigs were treated with LPS or saline. Blood samples were collected at 0, 2, and 4 h post-injection. After blood samples collection at 4 h, all pigs were slaughtered, and spleen, mesenteric lymph nodes, liver and intestinal samples were obtained.

Results

Dietary GLU supplementation inhibited the LPS-induced oxidative stress in pigs, as demonstrated by reduced malondialdehyde level and increased glutathione level in jejunum. Diets supplemented with GLU enhanced villus height, villus height/crypt depth and claudin-1 expression, attenuated intestinal histology and ultrastructure impairment induced by LPS. Moreover, GLU supplementation reversed intestinal intraepithelial lymphocyte number decrease and mast cell number increase induced by LPS stress. GLU reduced serum cortisol concentration at 4 h after LPS stress and downregulated the mRNA expression of intestinal corticotropin-releasing factor signal (corticotrophin-releasing factor [CRF], CRF receptor 1 [CRFR1], glucocorticoid receptor, tryptase, nerve growth factor, tyrosine kinase receptor A), and prevented mast cell activation. GLU upregulated the mRNA expression of intestinal transforming growth factor β.

Conclusion

These findings indicate that GLU attenuates LPS-induced intestinal mucosal barrier injury, which is associated with modulating CRF signaling pathway.

Exploring the relationship between the gut microbiome and mental health outcomes in a posttraumatic stress disorder cohort relative to trauma-exposed controls

Posttraumatic stress disorder (PTSD) imposes a significant burden on patients and communities. Although the microbiome-gut-brain axis has been proposed as a mediator or moderator of PTSD risk and persistence of symptoms, clinical data directly delineating the gut microbiome's relationship to PTSD are sparse. This study investigated associations between the gut microbiome and mental health outcomes in participants with PTSD (n = 79) and trauma-exposed controls (TECs) (n = 58). Diagnoses of PTSD, major depressive disorder (MDD), and childhood trauma were made using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5), MINI International Neuropsychiatric Interview (MINI), and Childhood Trauma Questionnaire (CTQ), respectively. Microbial communities from stool samples were profiled using 16S ribosomal RNA gene V4 amplicon sequencing and tested for associations with PTSD-related variables of interest. Random forest models identified a consortium of four genera, i.e.,  a combination of Mitsuokella, Odoribacter, Catenibacterium, and Olsenella, previously associated with periodontal disease, that could distinguish PTSD status with 66.4% accuracy. The relative abundance of this consortium was higher in the PTSD group and correlated positively with CAPS-5 and CTQ scores. MDD diagnosis was also associated with increased relative abundance of the Bacteroidetes phylum. Current use of psychotropics significantly impacted community composition and the relative abundances of several taxa. Early life trauma may prime the microbiome for changes in composition that facilitate a pro-inflammatory cascade and increase the risk of development of PTSD. Future studies should rigorously stratify participants into healthy controls, TECs, and PTSD (stratified by psychotropic drug use) to explore the role of the oral-gut-microbiome-brain axis in trauma-related disorders.

Psychobiotic Therapy: Method to Reinforce the Immune System

Psychobiotics are probiotic microorganisms that beneficially affect the central nervous system functions mediated by the gut-brain axis, improving the host’s immune system. Psychobiotic microorganisms can regulate brain pathways and serotonin production (mood controller). The main microbial genera with psychobiotic characteristics are Lactobacillus, Lactococcus and Bifidobacterium. The daily consumption of psychobiotics is called “Psychobiotic Therapy”. Psychobio-tic therapy has proven antidepressant/anxiolytic properties. Psychobiotic therapy can be used to boost the host’s immune balance against pathogens, for example: virus, bacteria and fungus. Thus, psychobiotic therapy can be a promising strategy to improve and/or maintain the quality of life of people who are healthy or who suffer from anxiety/stress disorders, intestinal dysbiosis and even immunosuppressed people. This is such a hot theme it can surely only be a matter of time for psychobiotic therapy offers an “alternative treatment”, but scientific, for people diagnosed with a variety of mental/immunological disorders. Instead of targeting the mind (brain), we could go for the gut. “This new way of looking at mental health linked to gut health is literally looking at health upside down”.

Gut Barrier Dysfunction and Type 2 Immunity: Implications for Compulsive Behavior

To date, much of the focus of gut-brain axis research has been on gut microbiota regulation of anxiety and stress-related behaviors. Much less attention has been directed to potential connections between gut microbiota and compulsive behavior. Here, we discuss a potential link between gut barrier dysfunction and compulsive behavior that is mediated through "type 2" rather than "type 1" inflammation. We examine connections between compulsive behavior and type 2 inflammation in Tourette syndrome, obsessive-compulsive disorder, autism, addiction, and post-traumatic stress disorder. Next, we discuss potential connections between gut barrier dysfunction, type 2 inflammation, and compulsive behavior. We posit a potential mechanism whereby gut barrier dysfunction-associated type 2 inflammation may drive compulsive behavior through histamine regulation of dopamine neurotransmission. Finally, we discuss the possibility of exploiting the greater accessibility of the gut relative to the brain in identifying targets to treat compulsive behavior disorders.

Increased prevalence of gastrointestinal symptoms and disorders of gut-brain interaction during the COVID-19 pandemic: An internet-based survey

BACKGROUND

Quarantine with social distancing has reduced transmission of COVID-19; however, fear of the disease and these remedial measures cause anxiety and stress. It is not known whether these events have impacted the prevalence of gastrointestinal (GI) symptoms and disorders of brain-gut interaction (DGBI).

METHODS

An online platform evaluated the prevalence of GI symptoms during the COVID-19 pandemic. Data collection utilized validated questionnaires and was fully anonymized. Findings were compared with identical data acquired in 2019. The association of results with stress and anxiety was analyzed.

RESULTS

Data were collected from 1896 subjects May - August 2019 to 980 non-identical subjects May - June 2020. GI symptoms were reported by 68.9% during the COVID-19 lockdown compared with 56.0% the previous year (p < 0.001). The prevalence of irritable bowel syndrome (26.3% vs. 20.0%; p < 0.001), functional dyspepsia (18.3% vs. 12.7%; p < 0.001), heartburn (31.7% vs. 26.2%, p = 0.002), and self-reported milk intolerance (43.5% vs. 37.8% p = 0.004) was higher during the pandemic. Many individuals reported multiple symptoms. Anxiety was associated with presence of all GI symptoms. High levels of stress impacted functional dyspepsia (p = 0.045) and abdominal pain (p = 0.013). The presence of DGBI (p < 0.001; OR 22.99), self-reported milk intolerance (p < 0.001; OR 2.50), and anxiety (p < 0.001; OR 2.18) was independently associated with increased GI symptoms during COVID-19 pandemic.

CONCLUSIONS

The prevalence of GI symptoms was significantly higher during the COVID-19 lockdown than under normal circumstances the previous year. This increase was attributable to increased numbers of patients with DGBI, an effect that was associated with anxiety.

Sex and Gender Differences in Overlap Syndrome of Functional Gastrointestinal Disorder and Effect of Genetic Polymorphisms in South Korea: A Long-term Follow-up Study

BACKGROUND/AIMS

Overlap functional gastrointestinal disorder (FGID) is associated with more severe gastrointestinal symptoms and lower quality of life. The aim of this study is to evaluate clinical features of non-erosive reflux disease (NERD), functional dyspepsia, irritable bowel syndrome, their overlap in terms of sex and gender, and to assess the risk factors, including genetic polymorphisms.

METHODS

A total of 494 FGIDs and 239 controls were prospectively enrolled between 2004 and 2020. FGIDs were diagnosed based on the Rome III criteria and symptoms were evaluated using a questionnaire. Follow-up questionnaires were conducted to determine the change of symptoms during the 75.8-month mean observation period. Risk factors including genetic polymorphisms in neurotransmitter receptor (SLC6A4 5-HTTLPR, GNB3, ADRA2A, CCKAR, and TRPV1) and cytokine (TNFA and IL10) genes.

RESULTS

NERD was more prevalent in men, and functional dyspepsia in women. Overlap FGIDs (n = 239) were more prevalent than nonoverlap FGIDs (n = 255) in women (P = 0.019). Anxiety and depression scores were higher in the overlaps (P = 0.012 and P < 0.001, respectively). Symptoms were more frequent and severe in the overlap FGIDs than in the non-overlaps (P < 0.001). During followup, symptoms progressed more frequently in the overlap FGIDs, especially in patients with the L/S genotype of SLC6A4 5-HTTLPR and anxiety/depression.

CONCLUSIONS

Overlap FGID patients need attention given their association with anxiety/depression and more severe symptoms, especially in women. Genetic polymorphisms also may be associated with certain symptoms of overlap FGIDs.

Sex and Gender Differences in Overlap Syndrome of Functional Gastrointestinal Disorder and Effect of Genetic Polymorphisms in South Korea: A Long-term Follow-up Study

Background/Aims

Overlap functional gastrointestinal disorder (FGID) is associated with more severe gastrointestinal symptoms and lower quality of life. The aim of this study is to evaluate clinical features of non-erosive reflux disease (NERD), functional dyspepsia, irritable bowel syndrome, their overlap in terms of sex and gender, and to assess the risk factors, including genetic polymorphisms.

Methods

A total of 494 FGIDs and 239 controls were prospectively enrolled between 2004 and 2020. FGIDs were diagnosed based on the Rome III criteria and symptoms were evaluated using a questionnaire. Follow-up questionnaires were conducted to determine the change of symptoms during the 75.8-month mean observation period. Risk factors including genetic polymorphisms in neurotransmitter receptor (SLC6A4 5-HTTLPR, GNB3, ADRA2A, CCKAR, and TRPV1) and cytokine (TNFA and IL10) genes.

Results

NERD was more prevalent in men, and functional dyspepsia in women. Overlap FGIDs (n = 239) were more prevalent than non-overlap FGIDs (n = 255) in women (P = 0.019). Anxiety and depression scores were higher in the overlaps (P = 0.012 and P < 0.001, respectively). Symptoms were more frequent and severe in the overlap FGIDs than in the non-overlaps (P < 0.001). During follow-up, symptoms progressed more frequently in the overlap FGIDs, especially in patients with the L/S genotype of SLC6A4 5-HTTLPR and anxiety/depression.

Conclusions

Overlap FGID patients need attention given their association with anxiety/depression and more severe symptoms, especially in women. Genetic polymorphisms also may be associated with certain symptoms of overlap FGIDs.

[Functional Gastrointestinal Disorders in Patients with Inflammatory Bowel Disease]

With emerging more effective drugs, the therapeutic goal of inflammatory bowel disease (IBD) has progressed from clinical remission to mucosal healing. Although the inflammation could be controlled more effectively than before, symptoms such as abdominal pain and bowel habit change is still bothersome to some IBD patients. Recently, these "refractory functional gastrointestinal symptoms" in quiescent IBD patients has been paid more attention. The pathophysiology could be multifactorial with genetics, change in gut motility associated with post inflammatory condition, increased permeability, impaired colorectal function, visceral hypersensitivity and gut microbiota. Because both IBD and functional gastrointestinal disease (FGID) could share similar symptoms and some pathophysiology, it is sometimes challenging to distinguish them exactly. However, to reduce the risk of overtreatment or insufficient control of inflammation, exact diagnosis of functional disease or symptoms in quiescent IBD patients is important. Because there is limited randomized controlled trials or prospective study currently, most of the therapeutic approach in IBD patients are empirical or referred to those of functional gastrointestinal disorders. However, approaches based on pathophysiological mechanisms could give appropriate therapies for both IBD and FGIDs.

Postoperative Ileus: a Pharmacological Perspective

Post-operative ileus (POI) is a frequent complication after abdominal surgery. The consequences of POI can be potentially serious such as bronchial inhalation or acute functional renal failure. Numerous advances in peri-operative management, particularly early rehabilitation, have made it possible to decrease POI. Despite this, the rate of prolonged POI ileus remains high and can be as high as 25% of patients in colorectal surgery. From a pathophysiological point of view, POI has two phases, an early neurological phase and a later inflammatory phase, to which we could add a "pharmacological" phase during which analgesic drugs, particularly opiates, play a central role. The aim of this review article is to describe the phases of the pathophysiology of POI, to analyse the pharmacological treatments currently available through published clinical trials and finally to discuss the different research areas for potential pharmacological targets.

Gut-Brain Axis: Possible Role of Gut Microbiota in Perioperative Neurocognitive Disorders

Aging is becoming a severe social phenomenon globally, and the improvements in health care and increased health awareness among the elderly have led to a dramatic increase in the number of surgical procedures. Because of the degenerative changes in the brain structure and function in the elderly, the incidence of perioperative neurocognitive disorders (PND) is much higher in elderly patients than in young people following anesthesia/surgery. PND is attracting more and more attention, though the exact mechanisms remain unknown. A growing body of evidence has shown that the gut microbiota is likely involved. Recent studies have indicated that the gut microbiota may affect postoperative cognitive function via the gut-brain axis. Nonetheless, understanding of the mechanistic associations between the gut microbiota and the brain during PND progression remains very limited. In this review, we begin by providing an overview of the latest progress concerning the gut-brain axis and PND, and then we summarize the influence of perioperative factors on the gut microbiota. Next, we review the literature on the relationship between gut microbiota and PND and discuss how gut microbiota affects cognitive function during the perioperative period. Finally, we explore effective early interventions for PND to provide new ideas for related clinical research.

MODULATION OF INTESTINAL BARRIER FUNCTION BY GLUCOCORTICOIDS: LESSONS FROM PRECLINICAL MODELS

Glucocorticoids (GCs) are widely used drugs for their anti-inflammatory and immunosuppressant effects, but they are associated with multiple adverse effects. Despite their frequent oral administration, relatively little attention has been paid to the effects of GCs on intestinal barrier function. In this review, we present a summary of the published studies on this matter carried out in animal models and cultured cells. In cultured intestinal epithelial cells, GCs have variable effects in basal conditions and generally enhance barrier function in the presence of inflammatory cytokines such as tumor necrosis factor (TNF). In turn, in rodents and other animals, GCs have been shown to weaken barrier function, with increased permeability and lower production of IgA, which may account for some features observed in stress models. When given to animals with experimental colitis, barrier function may be debilitated or strengthened, despite a positive anti-inflammatory activity. In sepsis models, GCs have a barrier-enhancing effect. These effects are probably related to the inhibition of epithelial cell proliferation and wound healing, modulation of the microbiota and mucus production, and interference with the mucosal immune system. The available information on underlying mechanisms is described and discussed.

Mucosal Mast Cell Distribution in the Gastrointestinal Tract of Children: A Preliminary Study for Establishing Reference Values

OBJECTIVES

The physiological number and distribution of mast cells (MCs) in the pediatric gastrointestinal (GI) tract is not well defined and reference values of normality are missing. To define a physiological and disease defining cut-off, a systematic histological exploration of MC distribution from the esophagus to the rectum in healthy as well as in patients with gastrointestinal food allergies (GFA) was performed.

METHODS

Nine pediatric subjects that exhibited unremarkable histopathological evaluations or underwent endoscopy for surveillance reasons after a previous polypectomy of single colonic juvenile polyps served as reference cohort. In all of these subjects, a chronic inflammatory disease (eg, inflammatory bowel disease, celiac disease) or allergy was excluded. In addition, a group of 15 patients with gastrointestinal complaints suspected to be caused by a GFA were investigated. Immunohistochemistry was performed from all biopsies using CD117 (c-Kit) as a reliable marker to identify MCs in the lamina propria.

RESULTS

There were distinct differences of MC counts in all parts of the pediatric GI tract. The highest counts of MCs in both symptomatic patients and control cohort, were found in the duodenum, terminal ileum, cecum and ascending colon. The lowest counts were found in the esophagus. Significant disparities between GFA and healthy subjects were found in the gastric corpus (22.1 ± 4.0/ high power field [HPF] vs 32.0 ± 10.1/HPF; P = 0.034) and ascending colon (44.8 ± 10.4/HPF vs 60.4 ± 24.3/HPF; P = 0.047).

CONCLUSIONS

Mucosal MC counts in the pediatric GI tract are higher than previously reported, with a considerable overlap between healthy and GFA patients. These results provide detailed information on distribution and numbers of MCs in pediatric allergic patients while allowing estimates of physiological values in childhood for the first time. With regard to diagnostic procedures in GFA further laboratory parameters have to be integrated.

Protective effects of nanocurcumin against stress-induced deterioration in the intestine

The therapeutic activities of curcumin have long been investigated in some chronic and inflammatory diseases. This study was designed to investigate the protective effects of nanocurcumin on intestinal barrier function, apoptosis, and oxidative stress in rats exposed to traffic noise. Forty rats were divided into four groups: two traffic noise-exposed groups of animals that received either vehicle (NOISE) or nanocurcumin (NCUR + NOISE) and two control groups that either remained intact (CON) or received nanocurcumin (NCUR). Nanocurcumin injection (15 mg/Kg/ip) and traffic noise exposure were administered daily for two weeks. The relative protein expression of intestinal tight junctions, occludin, and ZO-1 and Bax/Bcl-2 ratio was measured to evaluate barrier integrity and apoptosis in intestinal samples, respectively. Plasma D-lactate concentration was examined as a criterion of intestinal permeability. Corticosterone, superoxide dismutase (SOD) activity, glutathione (GSH), total antioxidant capacity (TAC), and nitrite were measured in serum. The noise exposure increased Bax/Bcl-2 ratio, corticosterone, and oxidative stress in the NOISE animals. Nanocurcumin treatment improved the Bax/Bcl-2 ratio and reduced corticosterone and oxidative stress in the NCUR + NOISE animals. The expression of tight junction proteins was decreased while the concentration of D-lactate was increased in the NOISE animals. Nanocurcumin did not efficiently impact the expression of tight junction proteins and the D-lactate level in the NCUR + NOISE group. Nanocurcumin administration displayed antioxidant and anti-apoptotic roles in the noise-exposed rats, however, it did not affect the intestinal barrier integrity. We concluded that reduced apoptosis in the intestine might be related to the antioxidant activity of nanocurcumin and its modulatory effects on the HPA axis in the nanocurcumin-treated animals.

Traumatic Brain Injury and Gut Brain Axis: The Disruption of an Alliance

BACKGROUND

Traumatic brain injury (TBI) can be considered a "silent epidemic", causing morbidity, disability, and mortality in all age cohorts. Therefore, a greater understanding of the underlying pathophysiological intricate mechanisms and interactions with other organs and systems is necessary to intervene not only in the treatment but also in the prevention of complications. In this complex of reciprocal interactions, the complex brain-gut axis has captured a growing interest.

SCOPE

The purpose of this manuscript is to examine and systematize existing evidence regarding the pathophysiological processes that occur following TBI and the influences exerted on these by the brain-gut axis.

LITERATURE REVIEW

A systematic review of the literature was conducted according to the PRISMA methodology. On the 8th of October 2021, two independent databases were searched: PubMed and Scopus. Following the inclusion and exclusion criteria selected, 24 (12 from PubMed and 12 from Scopus) eligible manuscripts were included in the present review. Moreover, references from the selected articles were also updated following the criteria mentioned above, yielding 91 included manuscripts.

DISCUSSION

Published evidence suggests that the brain and gut are mutually influenced through four main pathways: microbiota, inflammatory, nervous, and endocrine.

CONCLUSION

These pathways are bidirectional and interact with each other. However, the studies conducted so far mainly involve animals. An autopsy methodological approach to corpses affected by traumatic brain injury or intestinal pathology could represent the keystone for future studies to clarify the complex pathophysiological processes underlying the interaction between these two main systems.

Lactobacillus rhamnosus CNCM I-3690 decreases subjective academic stress in healthy adults: a randomized placebo-controlled trial

Psychological stress negatively affects the intestinal barrier function in animals and humans. We aimed to study the effect of Lactobacillus rhamnosus CNCM I-3690 on intestinal permeability and stress-markers during public speech. Healthy students were randomized to L. rhamnosus-containing (test) or acidified (placebo) milk consumed twice daily for 4 weeks, with 46 subjects per treatment group. Small intestinal permeability was quantified by a 2 h urinary lactulose-mannitol ratio (LMR, primary outcome), fractional excretion of lactulose (FEL) and mannitol (FEM). Salivary cortisol, State-Trait Anxiety Inventory (STAI) and Perceived Stress scores (PSS) were collected. No between-treatment differences were found for LMR (p = .71), FEL or FEM. Within-treatment analyses showed similar LMR and FEL but a stress-induced increase of FEM with the placebo (p < .05) but not test product. Despite a similar increase in salivary cortisol, the stress-induced increase in STAI was significantly lower with the test product vs. placebo (p = .01). Moreover, a stress-preventative effect of the probiotic was found for PSS and more pronounced in subjects with high stress-induced cortisol (p = .01). While increased FEM was mediated by salivary cortisol levels, the effect of the test product on subjective stress was not mediated by changes in FEM. No serious adverse events occurred. In conclusion, we demonstrated that L. rhamnosus CNCM I-3690 prevented stress-induced hyperpermeability to mannitol. Subjective but not objective stress-markers were reduced with L. rhamnosus vs. placebo, suggesting anxiolytic effects, which were independent of barrier stabilization and attractive for the reduction of stress in both health and disease. Clinicaltrials.gov, number NCT03408691.

Endurance Training in Humans Modulates the Bacterial DNA Signature of Skeletal Muscle

Accumulating evidence supports the existence of a tissue microbiota, which may regulate the physiological function of tissues in normal and pathological states. To gain insight into the regulation of tissue-borne bacteria in physiological conditions, we quantified and sequenced the 16S rRNA gene in aseptically collected skeletal muscle and blood samples from eight healthy male individuals subjected to six weeks of endurance training. Potential contamination bias was evaluated and the taxa profiles of each tissue were established. We detected bacterial DNA in skeletal muscle and blood, with background noise levels of detected bacterial DNA considerably lower in control versus tissue samples. In both muscle and blood, Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes were the most prominent phyla. Endurance training changed the content of resident bacterial DNA in skeletal muscle but not in blood, with Pseudomonas being less abundant, and both Staphylococcus and Acinetobacter being more abundant in muscle after exercise. Our results provide evidence that endurance training specifically remodels the bacterial DNA profile of skeletal muscle in healthy young men. Future investigations may shed light on the physiological impact, if any, of training-induced changes in bacterial DNA in skeletal muscle.

[Gut microbiome as a therapeutic target in the treatment of depression and anxiety]

There is a bi-directional connection between the gut microbiome and the brain. Changes in the composition of the microbiome affect emotions, behavior, and the stress response involved in the pathogenesis of depression. Depression and anxiety are often associated with dysbiosis and inflammatory bowel disease. Dysbiosis enhances stress response and low-grade systemic inflammation, and vice versa. This vicious circle may be responsible for the formation of depression. Antidepressants therapy should be accompanied by the elimination of dysbiosis. For these purposes diet, prebiotics, probiotics and faecal microbiota transplantation can be used. The advantages and disadvantages of each method are considered. The manipulation of microbiome composition has been shown to have great therapeutic potential in the treatment of depression and anxiety.

Corticotropin releasing hormone promotes inflammatory bowel disease via inducing intestinal macrophage autophagy

Psychosocial stress is a vital factor contributing to the pathogenesis and progression of inflammatory bowel disease (IBD). The contribution of intestinal macrophage autophagy to the onset and development of IBD has been widely studied. Herein, we investigated the underlying mechanism of psychosocial stress in an IBD mouse model pertaining to macrophage autophagy. Corticotropin releasing hormone (CRH) was peripherally administrated to induce psychosocial stress. For in vivo studies, dextran sulfate sodium (DSS) was used for the creation of our IBD mouse model. For in vitro studies, lipopolysaccharide (LPS) was applied on murine bone marrow-derived macrophages (BMDMs) as a cellular IBD-related challenge. Chloroquine was applied to inhibit autophagy. We found that CRH aggravated the severity of DSS-induced IBD, increasing overall and local inflammatory reactions and infiltration. The levels of autophagy in intestinal macrophages and murine BMDMs were increased under these IBD-related inflammatory challenges and CRH further enhanced these effects. Subsequent administration of chloroquine markedly attenuated the detrimental effects of CRH on IBD severity and inflammatory reactions via inhibition of autophagy. These findings illustrate the effects of peripheral administration of CRH on DSS-induced IBD via the enhancement of intestinal macrophage autophagy, thus providing a novel understanding as well as therapeutic target for the treatment of IBD.

Synchronizing Our Clocks as We Age: The Influence of the Brain-Gut-Immune Axis on the Sleep-Wake Cycle Across the Lifespan

The microbes that colonize the small and large intestines, known as the gut microbiome, play an integral role in optimal brain development and function. The gut microbiome is a vital component of the bi-directional communication pathway between the brain, immune system, and gut, also known as the brain-gut-immune axis. To date there has been minimal investigation into the implications of improper development of the gut microbiome and the brain-gut-immune axis on the sleep-wake cycle, particularly during sensitive periods of physical and neurological development, such as childhood, adolescence, and senescence. Therefore, this review will explore the current literature surrounding the overlapping developmental periods of the gut microbiome, brain, and immune system from birth through to senescence, while highlighting how the brain-gut-immune axis affects maturation and organisation of the sleep-wake cycle. We also examine how dysfunction to either the microbiome or the sleep-wake cycle negatively affects the bidirectional relationship between the brain and gut, and subsequently the overall health and functionality of this complex system. Additionally, this review integrates therapeutic studies to demonstrate when dietary manipulations, such as supplementation with probiotics and prebiotics, can modulate the gut microbiome to enhance health of the brain-gut-immune axis and optimize our sleep-wake cycle.

Sex differences in zonulin in affective disorders and associations with current mood symptoms

INTRODUCTION

The bidirectional connection between the brain and the gut within psychiatric entities has gained increasing scientific attention over the last years. As a regulator of intestinal permeability, zonulin acts as a key player on the interface of this interplay. Like several psychiatric disorders, intestinal permeability was associated with inflammation in previous findings.

METHODS

In this study we explored differences in zonulin serum levels in currently depressed (n = 55) versus currently euthymic (n = 37) individuals with an affective disorder. Further, we explored sex differences and possible influences on zonulin and affective symptoms like medication, age, body mass index, and smoking status.

RESULTS

Serum zonulin was significantly higher in females than in men independent from affective status (z = -2.412, p = .016). More specifically, females in the euthymic subgroup had higher zonulin levels than euthymic men (z = -2.114, p = .035). There was no difference in zonulin serum levels in individuals taking or not taking a specific psychopharmacotherapy. We found no correlation between zonulin serum levels and depression severity.

DISCUSSION

Increased serum zonulin levels as a proxy for increased intestinal permeability in women may indicate a state of elevated susceptibility for depression-inducing stimuli.

Present and Future Therapeutic Approaches to Barrier Dysfunction

There is converging and increasing evidence, but also uncertainty, for the role of abnormal intestinal epithelial barrier function in the origin and development of a growing number of human gastrointestinal and extraintestinal inflammatory disorders, and their related complaints. Despite a vast literature addressing factors and mechanisms underlying changes in intestinal permeability in humans, and its connection to the appearance and severity of clinical symptoms, the ultimate link remains to be established in many cases. Accordingly, there are no directives or clinical guidelines related to the therapeutic management of intestinal permeability disorders that allow health professionals involved in the management of these patients to carry out a consensus treatment based on clinical evidence. Instead, there are multiple pseudoscientific approaches and commercial propaganda scattered on the internet that confuse those affected and health professionals and that often lack scientific rigor. Therefore, in this review we aim to shed light on the different therapeutic options, which include, among others, dietary management, nutraceuticals and medical devices, microbiota and drugs, and epigenetic and exosomes-manipulation, through an objective evaluation of the scientific publications in this field. Advances in the knowledge and management of intestinal permeability will sure enable better options of dealing with this group of common disorders to enhance quality of life of those affected.

[The Gut Microbiome and Its Clinical Implications in Anorexia Nervosa]

The Gut Microbiome and Its Clinical Implications in Anorexia Nervosa Abstract. The diverse interactions of the gut microbiome with the metabolism, the immune system, and the brain of the host are increasingly becoming to the forefront of relevant research. Studies suggest a connection between an altered intestinal microbiome and somatic diseases, such as colitis ulcerosa, Crohn's disease, and diabetes, as well as mental illnesses such as anxiety and depression. Patients with anorexia nervosa (AN) also show significant changes in their gut microbiome which seem to be associated, among other things, with a different energy uptake from food, immunological and inflammatory processes, genetic predisposition, hormonal changes, and possibly increased intestinal permeability. In rats, stool transplantation from patients with AN resulted in decreased appetite and weight as well as anxious and compulsive behavior. In this review, we summarize the possible mechanisms of interaction between the microbiome and the host, and present initial findings on the microbiome in AN. Research on nutritional interventions, for example, with prebiotics and probiotics or nutritional supplements such as omega-3 fatty acids, which aim to positively influence the intestinal microbiome, could lead to additional treatment options in the therapy of patients with AN.

The Preventive Role of Exercise on the Physiological, Psychological, and Psychophysiological Parameters of Coronavirus 2 (SARS-CoV-2): A Mini Review

The world has been severely challenged by the Coronavirus Disease (COVID-19) outbreak since the early 2020s. Worldwide, there have been more than 66 million cases of infection and over 3,880,450 deaths caused by this highly contagious disease. All sections of the population including those who are affected, those who are not affected and those who have recovered from this disease, are suffering physiologically, psychologically or psychophysiologically. In this paper we briefly discuss the consequences of COVID-19 on physiological, psychological and psychophysiological vulnerability. We also attempt to provide evidence in support of exercise management as a prevention strategy for improving and minimizing the physiological, psychological and psychophysiological effects of COVID-19. Moderate exercise including walking, yoga and tai-chi to name but a few exercise regimes are critical in preventing COVID-19 and its complications. Governments, public health authorities and the general population should maintain physical activity during the COVID-19 pandemic to prevent additional physical and mental distress.

Microbiota-gut-brain axis: A novel potential target of ketogenic diet for epilepsy

Ketogenic diet (KD) has been used to the control of seizure for 100 years because it was developed for the treatment of epilepsy in 1921. Based on current research on the microbiota-gut-brain axis to explore the new communication tool between gut bacteria and the brain and the progress of microbiota-gut-brain axis and KD for the treatment of epilepsy, the role of neurotransmitters adenosine and γ-aminobutyric acid in the epileptic brain, we propose that the balance between beneficial and harmful bacteria in the gut microbiota would be a promising target in the future to underlying the working mechanism of KD for epilepsy.

Microbial metabolites and immune regulation: New targets for major depressive disorder

Treatments for depression and mood disorders have been singularly targeted at the brain without consideration for the context of the rest of the body. As evidence mounts for a role of autoimmunity and inflammation as risk factors and contributors to mood disorders, attention has shifted to one of the primary immunoregulatory organs in the body--the gut. Gut-brain interactions have been established and correlative links between the microbiome and mood have been examined, but with novel tools and a base of understanding, focus shifts to the mechanisms of these communications. In this review, we examine how the small molecules produced by metabolic processes of bacteria in the gut influence the host immune system. The gaps in knowledge discussed here include the under characterized diversity of small molecules crossing the gut walls, as well as the need to close the logical loop connecting the microbiome to the immune system, and the immune system to behavior and mood. As we move past the dawn of this field, more precise understanding using novel tools and techniques will help move toward a more informed and systematic process for clinically evaluating the efficacy of probiotics and bacterially derived compounds as antidepressants and mood regulators.

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Metabolism of the gut microbiota results in diverse molecules available to the host.

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Small molecules influence inflammation which modulates behavior and mood.

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Novel targets for mood stabilizers may be produced by the gut microbiota.

Duodenum at a crossroads: Key integrator of overlapping and psychological symptoms in functional dyspepsia?

The study of the interaction between gastrointestinal (GI) function and psychological features is a complex and developing field. The bidirectional communication between the gut and the brain or gut-brain axis is considered as a pivotal player in the pathogenesis of the highly prevalent functional GI disorders, including irritable bowel syndrome and functional dyspepsia (FD), which have been redefined as disorders of gut-brain interaction. However, the mechanisms through which changes in the gut alter brain functioning, feelings, and behavior remain unclear. Based on the presence of duodenal pathology in adult FD patients, Ronkainen et al. provide the first prospective evidence for duodenal eosinophils potentially driving anxiety. Also in this edition, associations between gastroduodenal pathology and rumination syndrome, which may coexist with FD, have now been confirmed in children by Friesen et al. Together these findings confirm not only the potential role of duodenal alterations in determining overlapping upper GI but also psychological symptoms, which result from bidirectional and complex interactions. In this review, we provide an overview of the recent advances in this field and highlight the novel contributions of the original studies of Ronkainen et al. and Friesen et al. to this topic.

Human milk oligosaccharides alleviate stress-induced visceral hypersensitivity and associated microbiota dysbiosis

Pain-related functional gastrointestinal disorders (FGIDs) are characterized by visceral hypersensitivity (VHS) associated with alterations in the microbiota-gut-brain axis. Since human milk oligosaccharides (HMOs) modulate microbiota, gut and brain, we investigated whether HMOs impact VHS, and explored the role of gut microbiota. To induce VHS, C57BL/6JRj mice received hourly water avoidance stress (WAS) sessions for 10 d, or antibiotics (ATB) for 12 d. Challenged and unchallenged (Sham) animals were fed AIN93M diet (Cont) or AIN93M containing 1% of a 6-HMO mix (HMO6). VHS was assessed by monitoring the visceromotor response to colorectal distension. Fecal microbiome was analyzed by shotgun metagenomics. The effect of HMO6 sub-blends on VHS and nociceptive pathways was further tested using the WAS model. In mice fed Cont, WAS and ATB increased the visceromotor response to distension. HMO6 decreased WAS-mediated electromyographic rise at most distension volumes and overall Area Under Curve (AUC=6.12±0.50 in WAS/HMO6 vs. 9.46±0.50 in WAS/Cont; P<.0001). In contrast, VHS in ATB animals was not improved by HMO6. In WAS, HMO6 promoted most microbiota taxa and several functional pathways associated with low VHS and decreased those associated with high VHS. Among the sub-blends, 2'FL+DFL and LNT+6'SL reduced visceromotor response close to Sham/Cont values and modulated serotoninergic and CGRPα-related pathways. This research further substantiates the capacity of HMOs to modulate the microbiota-gut-brain communication and identifies mitigation of abdominal pain as a new HMO benefit. Ultimately, our findings suggest the value of specific HMO blends to alleviate pain associated FGIDs such as infantile colic or Irritable Bowel Syndrome.

The Role of Intestinal Permeability in Gastrointestinal Disorders and Current Methods of Evaluation

An increased intestinal permeability has been described in various gastrointestinal and non-gastrointestinal disorders. Nevertheless, the concept and definition of intestinal permeability is relatively broad and includes not only an altered paracellular route, regulated by tight junction proteins, but also the transcellular route involving membrane transporters and channels, and endocytic mechanisms. Paracellular intestinal permeability can be assessed in vivo by using different molecules (e.g., sugars, polyethylene glycols, ⁵¹Cr-EDTA) and ex vivo in Ussing chambers combining electrophysiology and probes of different molecular sizes. The latter is still the gold standard technique for assessing the epithelial barrier function, whereas in vivo techniques, including putative blood biomarkers such as intestinal fatty acid-binding protein and zonulin, are broadly used despite limitations. In the second part of the review, the current evidence of the role of impaired barrier function in the pathophysiology of selected gastrointestinal and liver diseases is discussed. Celiac disease is one of the conditions with the best evidence for impaired barrier function playing a crucial role with zonulin as its proposed regulator. Increased permeability is clearly present in inflammatory bowel disease, but the question of whether this is a primary event or a consequence of inflammation remains unsolved. The gut-liver axis with a crucial role in impaired intestinal barrier function is increasingly recognized in chronic alcoholic and metabolic liver disease. Finally, the current evidence does not support an important role for increased permeability in bile acid diarrhea.

Altered gut microbial metabolites could mediate the effects of risk factors in Covid-19

Coronavirus disease 2019 (Covid-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, is now pandemic. While most Covid-19 patients will experience mild symptoms, a small proportion will develop severe disease, which could be fatal. Clinically, Covid-19 patients manifest fever with dry cough, fatigue and dyspnoea, and in severe cases develop into acute respiratory distress syndrome (ARDS), sepsis and multi-organ failure. These severe patients are characterized by hyperinflammation with highly increased pro-inflammatory cytokines including IL-6, IL-17 and TNF-alpha as well as C-reactive protein, which are accompanied by decreased lymphocyte counts. Clinical evidence supports that gut microbiota dysregulation is common in Covid-19 and plays a key role in the pathogenesis of Covid-19. In this narrative review, we summarize the roles of intestinal dysbiosis in Covid-19 pathogenesis and posit that the associated mechanisms are being mediated by gut bacterial metabolites. Based on this premise, we propose possible clinical implications. Various risk factors could be causal for severe Covid-19, and these include advanced age, concomitant chronic disease, SARS-CoV-2 infection of enterocytes, use of antibiotics and psychological distress. Gut dysbiosis is associated with risk factors and severe Covid-19 due to decreased commensal microbial metabolites, which cause reduced anti-inflammatory mechanisms and chronic low-grade inflammation. The preconditioned immune dysregulation enables SARS-CoV-2 infection to progress to an uncontrolled hyperinflammatory response. Thus, a pre-existing gut microbiota that is diverse and abundant could be beneficial for the prevention of severe Covid-19, and supplementation with commensal microbial metabolites may facilitate and augment the treatment of severe Covid-19.

Common contributing factors to COVID-19 and inflammatory bowel disease

The devastating complications of coronavirus disease 2019 (COVID-19) result from an individual's dysfunctional immune response following the initial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Multiple toxic stressors and behaviors contribute to underlying immune system dysfunction. SARS-CoV-2 exploits the dysfunctional immune system to trigger a chain of events ultimately leading to COVID-19. We have previously identified many contributing factors (CFs) (representing toxic exposure, lifestyle factors and psychosocial stressors) common to myriad chronic diseases. We hypothesized significant overlap between CFs associated with COVID-19 and inflammatory bowel disease (IBD), because of the strong role immune dysfunction plays in each disease. A streamlined dot-product approach was used to identify potential CFs to COVID-19 and IBD. Of the fifty CFs to COVID-19 that were validated for demonstration purposes, approximately half had direct impact on COVID-19 (the CF and COVID-19 were mentioned in the same record; i.e., CF---→COVID-19), and the other half had indirect impact. The nascent character of the COVID-19 core literature (∼ one year old) did not allow sufficient time for the direct impacts of many CFs on COVID-19 to be identified. Therefore, an immune system dysfunction (ID) literature directly related to the COVID-19 core literature was used to augment the COVID-19 core literature and provide the remaining CFs that impacted COVID-19 indirectly (i.e., CF---→immune system dysfunction---→COVID-19). Approximately 13000 potential CFs for myriad diseases (obtained from government and university toxic substance lists) served as the starting point for the dot-product identification process. These phrases were intersected (dot-product) with phrases extracted from a PubMed-derived IBD core literature, a nascent COVID-19 core literature, and the COVID-19-related immune system dysfunction (ID) core literature to identify common ID/COVID-19 and IBD CFs. Approximately 3000 potential CFs common to both ID and IBD, almost 2300 potential CFs common to ID and COVID-19, and over 1900 potential CFs common to IBD and COVID-19 were identified. As proof of concept, we validated fifty of these ∼3000 overlapping ID/IBD candidate CFs with biologic plausibility. We further validated 24 of the fifty as common CFs in the IBD and nascent COVID-19 core literatures. This significant finding demonstrated that the CFs indirectly related to COVID-19 -- identified with use of the immune system dysfunction literature -- are strong candidates to emerge eventually as CFs directly related to COVID-19. As discussed in the main text, many more CFs common to all these core literatures could be identified and validated. ID and IBD share many common risk/contributing factors, including behaviors and toxic exposures that impair immune function. A key component to immune system health is removal of those factors that contribute to immune system dysfunction in the first place. This requires a paradigm shift from traditional Western medicine, which often focuses on treatment, rather than prevention.

Food allergies and food-induced anaphylaxis: role of cofactors

Food allergies and food-induced anaphylaxis are important health problems. Several cofactors modulating the onset of anaphylaxis have been identified. In the presence of cofactors, allergic reactions may be induced at lower doses of food allergens and/or become severe. Exercise and concomitant infections are well-documented cofactors of anaphylaxis in children. Other factors such as consumption of nonsteroidal anti-inflammatory drugs, alcohol ingestion, and stress have been reported. Cofactors reportedly play a role in approximately 30% of anaphylactic reactions in adults and 14%-18.3% in children. Food-dependent exercise-induced anaphylaxis (FDEIA) is the best-studied model of cofactor-induced anaphylaxis. Wheat-dependent exercise-induced anaphylaxis, the most common FDEIA condition, has been studied the most. The mechanisms of action of cofactors have not yet been fully identified. This review aims to educate clinicians on recent developments in the role of cofactors and highlight the importance of recognizing cofactors in food allergies and food-induced anaphylaxis.

Sauna dehydration as a new physiological challenge model for intestinal barrier function

The intestinal barrier plays a crucial role in maintaining gut health, and an increased permeability has been linked to several intestinal and extra-intestinal disorders. There is an increasing demand for interventions aimed at strengthening this barrier and for in vivo challenge models to assess their efficiency. This study investigated the effect of sauna-induced dehydration on intestinal barrier function (clinicaltrials.gov: NCT03620825). Twenty healthy subjects underwent three conditions in random order: (1) Sauna dehydration (loss of 3% body weight), (2) non-steroidal anti-inflammatory drug (NSAID) intake, (3) negative control. Intestinal permeability was assessed by a multi-sugar urinary recovery test, while intestinal damage, bacterial translocation and cytokines were assessed by plasma markers. The sauna dehydration protocol resulted in an increase in gastroduodenal and small intestinal permeability. Presumably, this increase occurred without substantial damage to the enterocytes as plasma intestinal fatty acid-binding protein (I-FABP) and liver fatty acid-binding protein (L-FABP) were not affected. In addition, we observed significant increases in levels of lipopolysaccharide-binding protein (LBP), IL-6 and IL-8, while sCD14, IL-10, IFN-ɣ and TNF-α were not affected. These results suggest that sauna dehydration increased intestinal permeability and could be applied as a new physiological in vivo challenge model for intestinal barrier function.

Gut Microbiota and Pathophysiology of Depressive Disorder

BACKGROUND

Accumulating evidence has suggested that the bi-directional communication pathway, the microbiota-gut-brain axis, plays an important role in the pathophysiology of many neuropsychiatric diseases including major depressive disorder (MDD). This review outlines current evidence and promising findings related to the pathophysiology and treatment of MDD.

SUMMARY

There are at least 4 key biological molecules/systems underlying the pathophysiology of MDD: central dopamine, stress responses by the hypothalamic-pituitary-adrenal axis and autonomic nervous system, inflammation, and brain-derived neurotrophic factor. Animal experiments in several depression models have clearly indicated that gut microbiota is closely related to these molecules/systems and administration of probiotics and prebitotics may have beneficial effects on them. Although the results of microbiota profile of MDD patients varied from a study to another, multiple studies reported that bacteria which produce short-chain fatty acids such as butyrate and those protective against metabolic diseases (e.g., Bacteroidetes) were reduced. Clinical trials of probiotics have emerged, and the majority of the studies have reported beneficial effects on depression symptoms and related biological markers. Key Messages: The accumulating evidence suggests that research on the microbiota-gut-brain axis in major depressive disorder (MDD) is promising to elucidate the pathophysiology and to develop novel treatment of MDD, although there is still a long distance yet to reach the goals.

Short intense psychological stress induced by skydiving does not impair intestinal barrier function

Background and aim

Psychological stress has been shown to increase intestinal permeability and is associated with the development of gastrointestinal disorders. This study aimed to investigate skydiving as an alternative model to analyse the effect of acute psychological stress on intestinal barrier function.

Materials and methods

Twenty healthy subjects participated in a tandem skydive followed by a negative control visit, of which 19 (9 females and 10 males, 25.9 ± 3.7 years) were included in the study. Intestinal permeability was assessed by a multi-sugar urinary recovery test. Sucrose recovery and lactulose/rhamnose ratio in 0-5h urine indicated gastroduodenal and small intestinal permeability, respectively, and sucralose/erythritol ratio in 5-24h urine indicated colonic permeability. Blood samples were taken to assess markers associated with barrier function. This study has been registered at ClinicalTrials.gov (NCT03644979) on August 23, 2018.

Results

Skydiving resulted in a significant increase in salivary cortisol levels directly after skydiving compared to the control visit. Cortisol levels were still increased two hours after landing, while cortisol levels before skydiving were not significantly different from the baseline at the control visit. Skydiving did not induce a significant increase in gastroduodenal, small intestinal or colonic permeability. There was also no significant increase in plasma intestinal and liver fatty acid-binding proteins, suggesting no damage to the enterocytes.

Discussion

These results show that the acute intense psychological stress induced by skydiving does not affect intestinal permeability in healthy subjects. Future models aiming to investigate the effect of stress on human intestinal barrier function should consider a more sustained exposure to the psychological stressor.

Does chronic inflammation cause acute inflammation to spiral into hyper-inflammation in a manner modulated by diet and the gut microbiome, in severe Covid-19?

We propose that hyper-inflammation (HYPi) is a ''runaway'' consequence of acute inflammation (ACUi) that arises more easily (and also abates less easily) in those who host a pre-existing chronic inflammation (CHRi), because (i) most factors involved in generating an ACUi to limit viral proliferation are already present when there is an underlying CHRi, and also because (ii) anti-inflammatory (AI) mechanisms for the abatement of ACUi (following containment of viral proliferation) are suppressed and desensitized where there is an underlying CHRi, with this causing the ACUi to spiral into a HYPi. Stress, pollution, diet, and gut microbiomes (alterable in weeks through dietary changes) have an intimate and bidirectional cause-effect relationship with CHRi. We propose that avoidance of CHRi-promoting foods and adoption of CHRi-suppressing foods could reduce susceptibility to HYPi, in Covid-19 and in other viral diseases, such as influenza, which are characterized by episodic and unpredictable HYPi.

Association of stress management skills and stressful life events with allergy risk: a case-control study in southern China

BACKGROUND

Psychosocial stress and stressful life events are known to aggravate allergic diseases. Less is known about the impact of stress management skills on allergies. Here we sought to determine whether stress management skills are associated with the allergies and to assess the combined effects of stress management skills and stressful events on allergy risk.

METHODS

A survey on risk factors for self-reported allergic diseases was carried out among 28,144 southern Chinese people; 14 stressful life events and 8 stress management skills were retrospectively recorded in a case-control setting with multivariate logistic regression analysis. Multiplicative and additive interactions between stressful events and stress management skills were evaluated.

RESULTS

Stressful events significantly increased allergy risk. The odds ratio (OR) for allergies was 1.65 (95% confidence interval CI, 1.41-1.93) for those reporting one or two stressful events and 3.10 (95% CI, 2.55-3.79) for those reporting more than three stressful events compared to participants without stressful events. Stress management skills were adversely associated with allergic risk for people experiencing stressful events (OR, 0.71; 95% CI, 0.53-0.97) when adjusted demographically, particularly "concentrate on pleasant thoughts at bedtime" (OR, 0.67; 95% CI, 0.51-0.89), "pace myself to prevent tiredness" (OR, 0.67; 95% CI, 0.54-0.83), "get enough sleep" (OR, 0.48; 95% CI, 0.32-0.72) and "take some time for relaxation each day" (OR, 0.55; 95% CI, 0.37-0.80). But in people without stressful events, no association was observed. There was a significant linear trend for allergy risk from good stress management skills with no stressful events to poor stress management skills with stressful events (P < 0.001), with significant interaction in additive models (P = 0.006).

CONCLUSIONS

There are independent and antagonistic combined associations of stressful life events and stress management skills with allergy risk. The data supports the use of stress management skills in managing allergic disease among people with stressful life events.

Dietary Fibre Intervention for Gut Microbiota, Sleep, and Mental Health in Adults with Irritable Bowel Syndrome: A Scoping Review

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder affecting 4-5% of the global population. This disorder is associated with gut microbiota, diet, sleep, and mental health. This scoping review therefore aims to map existing research that has administrated fibre-related dietary intervention to IBS individuals and reported outcomes on at least two of the three following themes: gut microbiota, sleep, and mental health. Five digital databases were searched to identify and select papers as per the inclusion and exclusion criteria. Five articles were included in the assessment, where none reported on all three themes or the combination of gut microbiota and sleep. Two studies identified alterations in gut microbiota and mental health with fibre supplementation. The other three studies reported on mental health and sleep outcomes using subjective questionnaires. IBS-related research lacks system biology-type studies targeting gut microbiota, sleep, and mental health in patients undergoing diet intervention. Further IBS research is required to explore how human gut microbiota functions (such as short-chain fatty acids) in sleep and mental health, following the implementation of dietary pattern alteration or component supplementation. Additionally, the application of objective sleep assessments is required in order to detect sleep change with more accuracy and less bias.