Do interactions between stress and immune responses lead to symptom exacerbations in irritable bowel syndrome?

Managing gastrointestinal challenges: Diarrhea in sickle cell anemia

Sickle cell anemia (SCA), a hereditary hemoglobinopathy, is characterized by the presence of abnormal hemoglobin and has long been associated with a wide range of complications. While much attention has been given to the condition hematological aspects, gastrointestinal complications, particularly diarrhea, have been relatively understudied and often overlooked. This publication delves into the management of gastrointestinal challenges, with a focus on diarrhea, in individuals living with SCA. The pathophysiology of SCA is intrinsically linked to gastrointestinal complications, and diarrhea is a common manifestation of this condition. This abstract publication outlines the key elements discussed in the full-length work, which includes the clinical presentation of diarrhea in these patients, the diagnostic tools used to evaluate the condition, and various management strategies to alleviate symptoms and enhance the overall quality of life for affected individuals. The paper emphasizes the importance of patient education, offering healthcare professionals valuable insights into how to inform and support patients in managing their conditions effectively. It also highlights the need for continued research to further our understanding of gastrointestinal challenges in SCA and to identify potential areas for future therapeutic interventions. Ultimately, the comprehensive management of diarrhea in individuals with SCA is vital for their overall well-being. This publication serves as a valuable resource for healthcare providers, researchers, and caregivers in addressing the gastrointestinal challenges that accompany SCA, ultimately working toward a better quality of life for those affected by this condition.

Irritable bowel syndrome (IBS): could we decide what is behind?

Functional visceral problems are frequently present nowadays in the medical practice probably due to the significant mental and emotional load on people. Although physicians and psychophysiologists are active on the field, still we are far from a complete knowledge, despite the fact that scientists like the Hungarian Professor György Ádám already had initiated a new approach called visceral psychophysiology already a long time ago. In this article, we commemorate Professor Ádám by analyzing one of the most frequent functional disorders, irritable bowel syndrome (IBS), calling psychophysiology for help. First, we try to give a definition, then show the general descriptions and characteristics of IBS. Factors like stress, gender, and gastrointestinal pain are followed by the potential role of the immune system and the neuronal factors as well as the supposed brain mechanisms. We hope that this overview of the IBS-history would show how significant scientists can be decisive in certain fields of the science and practice.

Major depressive disorder and the risk of irritable bowel syndrome: A Mendelian randomization study

BACKGROUND

The association between major depressive disorder (MDD) and irritable bowel syndrome (IBS) has been found in observational research; however, the causative relationship between MDD and IBS remains uncertain. Using the two-sample Mendelian randomization (MR) approach, we attempted to examine the causal effect of MDD on IBS.

METHODS

Independent genetic variants for MDD identified by Howard et al. based on a genome-wide meta-analysis were selected for this study. Gene-Outcome associations for IBS were gathered from UK Biobank and FinnGen databases. The MR analysis included inverse variance weighted (IVW), MR-Egger regression, weighted median, weighted mode, and MR-PRESSO sensitivity analyses.

RESULTS

FinnGen database subjected to inverse variance weighted (IVW) analysis revealed that MDD may be a risk factor for the development of IBS (OR = 1.356, 95% CI: 1.125-1.632, p = 0.0013). The same finding was reached in UK Biobank for IVW (OR = 1.011, 95% CI: 1.006-1.015, p = 3.18 × 10-7 ), MR-Egger progression (OR = 1.030, 95% CI: 1.008-1.051, p = 0.007), and weighted median (OR = 1.011, 95% CI: 1.005-1.016, p = 0.0001).

CONCLUSION

Our findings supported a causal relationship between MDD and IBS, which may have implications for the clinical management of IBS in individuals with MDD.

Constipation preceding depression: a population-based cohort study

Background

Constipation is generally considered a common physical symptom of depression or a side effect of antidepressant treatments. However, according to the gut-brain axis hypothesis, the association between depression and constipation might be bi-directional. This study investigated the association between premorbid constipation and depression.

Methods

We conducted a retrospective cohort study using data from UK Biobank. Individuals free of depression between 2006 and 2010 were included. Constipation status was determined using diagnostic codes from electronic health records or a baseline questionnaire. Data on covariates, including socio-demographic characteristics, lifestyle factors, health conditions, and regular medication use, were also collected through a baseline questionnaire. The primary outcome is incident depression, which was extracted from hospital inpatient admissions, primary care, self-report, and death data from baseline to 2022. The secondary outcome is depressive symptoms, which was assessed by Patient Health Questionnaire-9 (PHQ-9) from an online survey in 2016. Cox proportional hazard regression models were employed to assess the prospective association between constipation and incident depression. Logistic regression models were used to assess its association with depressive symptoms.

Findings

Among the 449,459 participants included in the study, 18,596 (4.1%) experienced constipation at baseline, and 18,576 (4.1%) developed depression over a median follow-up period of 12.3 years. Premorbid constipation is associated with a 2.28-fold higher risk of depression. After adjusting the covariates, we found those with constipation still had a 48% higher risk of developing depression (adjusted hazard ratio [aHR] 1.48; 95% CI, 1.41-1.56) than those without constipation. Self-reported and diagnosed constipation were both associated with a higher risk of depression, with the aHR being 1.42 (95% CI: 1.34-1.51) and 1.66 (95% CI: 1.51-1.82), respectively. Participants with constipation were more likely to report depressive symptoms than people without (adjusted odds ratio 2.18; 95% CI, 1.97-2.43). These findings remained consistent in sensitivity analyses.

Interpretation

Diagnosed and self-reported constipation are both prospectively associated with an elevated risk of depression. These explorative findings suggest that constipation may be an independent risk factor or a prodromal symptom of depression. Gastroenterologists and primary care physicians should pay more attention to the depressive symptoms of their constipation patients.

Funding

The Shenzhen Science and Technology Program and the Strategic Priority Research Program of Chinese Academy of Sciences.

Preventive effect of peptides derived from fermented milk on chronic stress-induced brain damage and intestinal dysfunction in mice

This study investigated the preventive effects of peptides derived from milk fermented with the probiotic strain Lactobacillus gasseri 505 (505) against stress-related brain damage and anxiety-like behavior. The peptides MKPWIQPKTKVIPYVRYL (Pep14) and VYQHQKAMKPWIQPKTKVIPYVRYL (Pep21), which exhibit high antioxidant and anti-inflammatory activities, were administered to stressed mice. The results showed that the stress mechanism in the gut-brain axis was regulated by pretreatment with both peptides, leading to inhibition of neurodevelopment and neuroinflammation through the hypothalamic-pituitary-adrenal (HPA) axis, based on the expression of related mRNA and proteins. The expression of colonic inflammation-related mRNA and proteins was also reduced. Moreover, anxiety-like behavior was significantly reduced in mice treated with Pep14 and Pep21. These results indicate that the bioactive peptides Pep14 and Pep21, derived from milk fermented with 505, may prevent stress-induced brain damage and anxiety-like behavior via regulation of the HPA axis.

Inflammation and emotion regulation: a narrative review of evidence and mechanisms in emotion dysregulation disorders

Emotion dysregulation (ED) describes a difficulty with the modulation of which emotions are felt, as well as when and how these emotions are experienced or expressed. It is a focal overarching symptom in many severe and prevalent neuropsychiatric diseases, including bipolar disorders (BD), attention deficit/hyperactivity disorder (ADHD), and borderline personality disorder (BPD). In all these disorders, ED can manifest through symptoms of depression, anxiety, or affective lability. Considering the many symptomatic similarities between BD, ADHD, and BPD, a transdiagnostic approach is a promising lens of investigation. Mounting evidence supports the role of peripheral inflammatory markers and stress in the multifactorial aetiology and physiopathology of BD, ADHD, and BPD. Of note, neural circuits that regulate emotions appear particularly vulnerable to inflammatory insults and peripheral inflammation, which can impact the neuroimmune milieu of the central nervous system. Thus far, few studies have examined the link between ED and inflammation in BD, ADHD, and BPD. To our knowledge, no specific work has provided a critical comparison of the results from these disorders. To fill this gap in the literature, we review the known associations and mechanisms linking ED and inflammation in general, and clinically, in BD, ADHD, and BD. Our narrative review begins with an examination of the routes linking ED and inflammation, followed by a discussion of disorder-specific results accounting for methodological limitations and relevant confounding factors. Finally, we critically discuss both correspondences and discrepancies in the results and comment on potential vulnerability markers and promising therapeutic interventions.

Distinct Alterations in Central Pain Processing of Visceral and Somatic Pain in Quiescent Ulcerative Colitis Compared to Irritable Bowel Syndrome and Health

BACKGROUND AND AIMS

Despite relevance to pain chronicity, disease burden, and treatment, mechanisms of pain perception for different types of acute pain remain incompletely understood in patients with inflammatory bowel disease [IBD]. Building on experimental research across pain modalities, we herein addressed behavioural and neural correlates of visceral versus somatic pain processing in women with quiescent ulcerative colitis [UC] compared to irritable bowel syndrome [IBS] as a patient control group and healthy women [HC].

METHODS

Thresholds for visceral and somatic pain were assessed with rectal distensions and cutaneous thermal pain, respectively. Using functional magnetic resonance imaging, neural and behavioural responses to individually calibrated and intensity-matched painful stimuli from both modalities were compared.

RESULTS

Pain thresholds were comparable across groups, but visceral thresholds correlated with gastrointestinal symptom severity and chronic stress burden exclusively within UC. Upon experience of visceral and somatic pain, both control groups demonstrated enhanced visceral pain-induced neural activation and greater perceived pain intensity, whereas UC patients failed to differentiate between pain modalities at both behavioural and neural levels.

CONCLUSIONS

When confronted with acute pain from multiple bodily sites, UC patients' responses are distinctly altered. Their failure to prioritise pain arising from the viscera may reflect a lack of adaptive behavioural flexibility, possibly resulting from long-lasting central effects of repeated intestinal inflammatory insults persisting during remission. The role of psychological factors, particularly chronic stress, in visceral sensitivity and disease-specific alterations in the response to acute pain call for dedicated mechanistic research as a basis for tailoring interventions for intestinal and extraintestinal pain symptoms in IBD.

Usefulness of Self-Assessment of Gastrointestinal Symptoms: Web-Based Study in Anhui, China

BACKGROUND

Gastrointestinal symptoms (GISs) are caused by a combination of biopsychosocial factors and are highly prevalent worldwide. Given their complex nature, coupled with ineffective communication of diagnoses by physicians, patients with intimate GISs often feel stigmatized. This, in turn, can inhibit their ability to express their thoughts and feelings adequately, leading them to over- or underreport their symptoms. Moreover, selective service-seeking for and reporting of GISs have a direct bearing on the stage of disease at presentation and, consequently, on the overall prognosis.

OBJECTIVE

This study aimed to investigate the usefulness of a web-based self-assessment of GISs as a supplementary means to cope with potential over- or underreporting during routine consultations.

METHODS

GIS data were collected using a novel web-based self-assessment tool (n=475) and from nonparticipative observation of doctor-patient consultations (n=447) and household surveys (n=10,552) in Anhui, China. Data analysis focused primarily on the description of the composition of respondents and the occurrence rates of GISs by sociodemographics, and by symptom solicitation methods and settings. Chi-square power tests were used when necessary to compare differences in the occurrence rates between relevant groups. The level of significance for the 2-sided test was set at α<.05.

RESULTS

The average occurrence rates of both upper and lower GISs derived from the web-based self-assessment were higher than those from the observation (upper GISs: n=661, 20.9% vs n=382, 14.2%; P<.001; lower GISs: n=342, 12.9% vs n=250, 10.8%; P=.02). The differences in 6 of the 9 upper GISs and 3 of the 11 lower GISs studied were tested with statistical significance (P<.05); moreover, a higher frequency rate was recorded for symptoms with statistical significance via self-assessment than via observation. For upper GISs, the self-assessed versus observed differences ranged from 17.1% for bloating to 100% for bad mood after a meal, while for lower GISs, the differences ranged from -50.5% for hematochezia or melena to 100% for uncontrollable stool. Stomachache, regurgitation, and dysphagia had higher occurrence rates among participants of the self-assessment group than those of the household survey group (20% vs 12.7%, 14% vs 11%, and 3% vs 2.3%, respectively), while the opposite was observed for constipation (5% vs 10.9%), hematochezia or melena (4% vs 5%), and anorexia (4% vs 5.2%). All differences noted in the self-assessed occurrence rates of specific, persistent GISs between sociodemographic groups were tested for nonsignificance (P>.05), while the occurrence rates of any of the 6 persistent GISs among respondents aged 51-60 years was statistically higher than that among other age groups (P=.03).

CONCLUSIONS

The web-based self-assessment tool piloted in this study is useful and acceptable for soliciting more comprehensive GISs, especially symptoms with concerns about stigmatization, privacy, and shame. Further studies are needed to integrate the web-based self-assessment with routine consultations and to evaluate its efficacy.

Causal association between psycho-psychological factors, such as stress, anxiety, depression, and irritable bowel syndrome: Mendelian randomization

BACKGROUND

Pathogenesis, diagnosis, and treatment of irritable bowel syndrome (IBS) have been reported to be challenging hotspots in clinical practice. Previous observational studies have found that stress, anxiety, depression, and other mental and psychological diseases are closely associated with IBS. This study aimed to further explore the causal relationships of these associations through Mendelian randomization (MR).

METHODS

The data needed for MR were obtained from publicly published genome-wide association databases. We performed a bidirectional, 2-sample MR analysis using instrumental variables (IV) associated with stress, anxiety, and depression, and other mental and psychological factors as exposures and IBS as the outcome. A reverse MR analysis with IBS as exposure and stress, anxiety, depression, and other mental and psychological factors as the outcomes was also performed. The inverse variance weighting (IVW) method was adopted as the main method of MR, and the causal effect between stress, anxiety, depression, and other mental and psychological factors and IBS was evaluated as the main result of the study. In addition, a series of sensitivity analyses was conducted to comprehensively evaluate the causal relationship between them.

RESULTS

Stress, anxiety, depression, and other mental and psychological factors were the underlying etiologies for IBS (odds ratio [OR] = 1.06, 95% confidence interval [CI]: 1.03-1.08), and they were positively correlated. Univariate analysis further supported the above conclusions (Depression, [OR = 1.31, 95% CI: 1.05-1.63, P = .016], Anxiety, [OR = 1.53, 95% CI: 1.16-2.03, P = .003]). However, in reverse MR analysis, we found that IBS did not affect stress, anxiety, depression, or other mental and psychological factors and that there was no causal relationship between IBS and stress, anxiety, depression, or other mental and psychological factors (P > .05).

CONCLUSION

This study demonstrates that mental and psychological factors are the underlying etiologies for IBS. These findings may provide important information for physicians regarding the clinical treatment of IBS.

Physical Activity as an Adjunct Treatment for People Living with HIV?

This review evaluates physical activity as a candidate for an adjunct treatment, in conjunction with antiretroviral therapy (ART), for people living with HIV (PLWH). Evidence is summarized that chronic, non-resolving inflammation (a principal feature of immune system dysfunction) and a dysfunctional state of the gut environment are key factors in HIV infection that persist despite treatment with ART. In addition, evidence is summarized that regular physical activity may restore normal function of both the immune system and the gut environment and may thereby ameliorate symptoms and non-resolving inflammation-associated comorbidities that burden PLWH. Physicians who care for PLWH could thus consider incorporating physical activity into treatment plans to complement ART. It is also discussed that different types of physical activity can have different effects on the gut environment and immune function, and that future research should establish more specific criteria for the design of exercise regimens tailored to PLWH.

The Microbiota-Gut-Brain Axis: Psychoneuroimmunological Insights

There is growing interest in the role that the intestinal microbiota and the related autoimmune processes may have in the genesis and presentation of some psychiatric diseases. An alteration in the communication of the microbiota-gut-brain axis, which constitutes a communicative model between the central nervous system (CNS) and the gastro-enteric tract, has been identified as one of the possible causes of some psychiatric diseases. The purpose of this narrative review is to describe evidence supporting a role of the gut microbiota in psychiatric diseases and the impact of diet on microbiota and mental health. Change in the composition of the gut microbiota could determine an increase in the permeability of the intestinal barrier, leading to a cytokine storm. This could trigger a systemic inflammatory activation and immune response: this series of events could have repercussions on the release of some neurotransmitters, altering the activity of the hypothalamic-pituitary-adrenal axis, and reducing the presence of trophic brain factors. Although gut microbiota and psychiatric disorders seem to be connected, more effort is needed to understand the potential causative mechanisms underlying the interactions between these systems.

Interactions between symptoms and psychological status in irritable bowel syndrome: An exploratory study of the impact of a probiotic combination

BACKGROUND

Stress is an exacerbator of irritable bowel syndrome (IBS) symptoms, and anxiety and depression are co-morbidities. Bifidobacterium longum strains 1714® and 35642® attenuate stress responses in healthy people and reduce symptoms in IBS, respectively. Here, we explore relationships between the psychological and visceral effects of the two strains (COMBO) in IBS subjects and biomarkers of stress and inflammation.

METHODS

We recruited 40 patients with IBS (Rome III) and mild to moderate anxiety (HADS-A) and/or depression (HADS-D) and 57 asymptomatic female controls with low or moderate stress. IBS patients were fed COMBO (1 × 10⁹ cfu/day) for 8 weeks with an 8-week washout. IBS symptoms, psychometric measures, salivary cortisol awakening response (CAR), and plasma inflammatory biomarkers were assessed every 4 weeks.

KEY RESULTS

Compared to healthy controls, IBS subjects had a blunted CAR. Treatment with COMBO restored CAR and improved IBS symptoms compared to baseline during the treatment phase. The COMBO reduced HADS-D, HADS-A score, and TNF-α, while sleep quality improved significantly from baseline to the end of the intervention. Surprisingly, these parameters improved further once treatment ended and maintained this improvement by Week 16.

CONCLUSIONS AND INFERENCES

These findings suggest that the stress response is a major driver of IBS symptoms. The time course of the beneficial effect of COMBO on IBS symptoms suggests that this is achieved through a restoration of the stress response. In contrast, the time course of the effects of COMBO on anxiety and depression in IBS paralleled an anti-inflammatory effect as indicated by a reduction in circulating levels of TNF-α.

Circulating Pro-inflammatory Cytokines Do Not Explain Interindividual Variability in Visceral Sensitivity in Healthy Individuals

A role of the immune system in the pathophysiology of pain and hyperalgesia has received growing attention, especially in the context of visceral pain and the gut-brain axis. While acute experimental inflammation can induce visceral hyperalgesia as part of sickness behavior in healthy individuals, it remains unclear if normal plasma levels of circulating pro-inflammatory cytokines contribute to interindividual variability in visceral sensitivity. We herein compiled data from a tightly screened and well-characterized sample of healthy volunteers (N = 98) allowing us to assess associations between visceral sensitivity and gastrointestinal symptoms, and plasma concentrations of three selected pro-inflammatory cytokines (i.e., TNF-α, IL-6, and IL-8), along with cortisol and stress-related psychological variables. For analyses, we compared subgroups created to have distinct pro-inflammatory cytokine profiles, modelling healthy individuals at putative risk or resilience, respectively, for symptoms of the gut-brain axis, and compared them with respect to rectal sensory and pain thresholds and subclinical GI symptoms. Secondly, we computed multiple regression analyses to test if circulating pro-inflammatory markers predict visceral sensitivity in the whole sample. Despite pronounced subgroup differences in pro-inflammatory cytokine and cortisol concentrations, we observed no differences in measures of visceroception. In regression analyses, cytokines did not emerge as predictors. The pain threshold was predicted by emotional state and trait variables, especially state anxiety, together explaining 10.9% of the variance. These negative results do not support the hypothesis that systemic cytokine levels contribute to normal interindividual variability in visceroception in healthy individuals. Trajectories to visceral hyperalgesia as key marker in disorders of gut-brain interactions likely involve complex interactions of biological and psychological factors in keeping with a psychosocial model. Normal variations in systemic cytokines do not appear to constitute a vulnerability factor in otherwise healthy individuals, calling for prospective studies in at risk populations.

STW 5 Herbal Preparation Modulates Wnt3a and Claudin 1 Gene Expression in Zebrafish IBS-like Model

Aim: Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by chronic abdominal pain and stool irregularities. STW 5 has proven clinical efficacy in functional gastrointestinal disorders, including IBS, targeting pathways that suppress inflammation and protect the mucosa. Wnt signaling is known to modulate NF-kβ-dependent inflammatory cytokine production. This sparked the idea of evaluating the impact of STW 5 on the expression of inflammatory-response and Wnt/β catenin-target genes in an IBS-like model. Main methods: We used zebrafish and dextran sodium sulfate (DSS) treatment to model IBS-like conditions in vivo and in vitro and examined the effects of subsequent STW 5 treatment on the intestines of DSS-treated fish and primary cultured intestinal and neuronal cells. Gross gut anatomy, histology, and the expression of Wnt-signaling and cytokine genes were analyzed in treated animals and/or cells, and in controls. Key findings: DSS treatment up-regulated the expression of interleukin-8, tumor necrosis factor-α, wnt3a, and claudin-1 in explanted zebrafish gut. Subsequent STW 5 treatment abolished both the macroscopic signs of gut inflammation, DSS-induced mucosecretory phenotype, and normalized the DSS-induced upregulated expression of il10 and Wnt signaling genes, such as wnt3a and cldn1 in explanted zebrafish gut. Under inflammatory conditions, STW 5 downregulated the expression of the pro-inflammatory cytokine genes il1β, il6, il8, and tnfα while it upregulated the expression of the anti-inflammatory genes il10 and wnt3a in enteric neuronal cells in vitro. Significance: Wnt signaling could be a novel target for the anti-inflammatory and intestinal permeability-restoring effects of STW 5, possibly explaining its clinical efficacy in IBS.

Altered Brain Structure in Chronic Visceral Pain: Specific Differences in Gray Matter Volume and Associations With Visceral Symptoms and Chronic Stress

Structural brain alterations in chronic pain conditions remain incompletely understood, especially in chronic visceral pain. Patients with chronic-inflammatory or functional bowel disorders experience recurring abdominal pain in concert with other gastrointestinal symptoms, such as altered bowel habits, which are often exacerbated by stress. Despite growing interest in the gut-brain axis and its underlying neural mechanisms in health and disease, abnormal brain morphology and possible associations with visceral symptom severity and chronic stress remain unclear. We accomplished parallelized whole-brain voxel-based morphometry analyses in two patient cohorts with chronic visceral pain, i.e., ulcerative colitis in remission and irritable bowel syndrome, and healthy individuals. In addition to analyzing changes in gray matter volume (GMV) in each patient cohort vs. age-matched healthy controls using analysis of covariance (ANCOVA), multiple regression analyses were conducted to assess correlations between GMV and symptom severity and chronic stress, respectively. ANCOVA revealed reduced GMV in frontal cortex and anterior insula in ulcerative colitis compared to healthy controls, suggesting alterations in the central autonomic and salience networks, which could however not be confirmed in supplemental analyses which rigorously accounted for group differences in the distribution of sex. In irritable bowel syndrome, more widespread differences from healthy controls were observed, comprising both decreased and increased GMV within the sensorimotor, central executive and default mode networks. Associations between visceral symptoms and GMV within frontal regions were altered in both patient groups, supporting a role of the central executive network across visceral pain conditions. Correlations with chronic stress, on the other hand, were only found for irritable bowel syndrome, encompassing numerous brain regions and networks. Together, these findings complement and expand existing brain imaging evidence in chronic visceral pain, supporting partly distinct alterations in brain morphology in patients with chronic-inflammatory and functional bowel disorders despite considerable overlap in symptoms and comorbidities. First evidence pointing to correlations with chronic stress in irritable bowel syndrome inspires future translational studies to elucidate the mechanisms underlying the interconnections of stress, visceral pain and neural mechanisms of the gut-brain axis.

Divergent effects of exendin-4 and interleukin-6 on rat colonic secretory and contractile activity are associated with changes in regional vagal afferent signaling

BACKGROUND

The pro-inflammatory cytokine, interleukin (IL)-6 is elevated in individuals with the functional bowel disorder, irritable bowel syndrome (IBS). IL-6 can independently modify intestinal secreto-motor function, thereby contributing to IBS pathophysiology. Additionally, hormonal changes may underlie symptom flares. Post-prandial exacerbation of IBS symptoms has been linked to secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1), which can also influence colonic secreto-motor activity. This study aimed to ascertain if the effects of GLP-1 on colonic secretory and contractile activity was impacted by elevated IL-6 levels and if sensory signals regarding such changes were reflected in altered vagal afferent activity.

METHODS

Colonic secretory currents and circular muscle contractile activity was investigated in Sprague Dawley rats using Ussing chamber and organ bath electrophysiology. Regional afferent signaling was assessed using extracellular electrophysiological recordings from colonic vagal afferents.

KEY RESULTS

Application of the GLP-1 receptor agonist, exendin-4 (Ex-4) in the presence of IL-6 potentiated colonic secretory currents and transepithelial resistance. Vagal afferent fibers originating in the submucosal layer exhibited larger responses to Ex-4 when IL-6 was also present. In contrast, co-application of Ex-4 and IL-6 to gut-bath chambers suppressed circular muscle contractile activity. The activity in extrinsic afferents originating in the colonic myenteric layer was similarly suppressed.

CONCLUSIONS & INFERENCES

Application of Ex-4 in the presence of IL-6 had divergent modulatory effects on colonic secretion and contractile activity. Similar patterns were observed in vagal afferent signaling originating in the submucosal and myenteric neuronal layers, indicating regional afferent activity reflected immune- and endocrine-mediated changes in colonic function.

Association of stress and functional gastrointestinal disorders in high school graduates

BACKGROUND

Psychosocial factors are seemed as important causes of functional gastrointestinal disorders (FGIDs). However, the role of stress in FGIDs in high school students under the pressure of college entrance examination is largely unknown. The aim of this study is to investigate the association between the stress and FGIDs in high school graduates.

METHODS

A cross-sectional survey was conducted in randomly selected high school fresh graduates. Questionnaires concerned health condition, living habits, gastrointestinal symptoms and life stress were given out and be finished voluntarily. Participants were diagnosed as FGIDs based on the Rome IV criteria.

RESULTS

Stress level of FGIDs population was higher than control group and stress was independent predicted factor of high risk of FGIDs. The stressor "changes" was significantly correlated with functional gastroduodenal disorders (OR1.118(1.011-1.238)). Stressor "frustration" was significantly correlated with functional bowel disorders (OR1.038(1.006-1.071)). "Physiological reaction" was correlated with functional bowel disease and functional gastroduodenal disorders + functional bowel disorders (OR1.027(1.007-1.046) and OR1.055(1.000-1.113)). Students with more than one gastrointestinal symptom exhibited higher stress level. Moreover, there was mediation effect of stress in the association between gender, sleep quality, allergies and FGIDs.

LIMITATIONS

This was a cross-section study and the sample included in the study were only from Wuhan, China.

CONCLUSIONS

Our findings illustrated the predicted and mediated role of stress in FGIDs in high school fresh graduates. Different stressors and reactions to stressors contributed to different FGIDs. Intervening measures aimed at stress coping strategies were warranted for students in daily school life.

Development and validation of the Health Promoting Behaviour for Bloating (HPB-Bloat) scale

Background

Health management strategies may help patients with abdominal bloating (AB), but there are currently no tools that measure behaviour and awareness. This study aimed to validate and verify the dimensionality of the newly-developed Health Promoting Behaviour for Bloating (HPB-Bloat) scale.

Methods

Based on previous literature, expert input, and in-depth interviews, we generated new items for the HPB-Bloat. Its content validity was assessed by experts and pre-tested across 30 individuals with AB. Construct validity and dimensionality were first determined using exploratory factor analysis (EFA) and Promax rotation analysis, and then using confirmatory factor analysis (CFA).

Results

During the development stage, 35 items were generated for the HPB-Bloat, and were maintained following content validity assessment and pre-testing. One hundred and fifty-two participants (mean age of 31.27 years, 68.3% female) and 323 participants (mean age of 27.69 years, 59.4% male) completed the scale for EFA and CFA, respectively. Using EFA, we identified 20 items that we divided into five factors: diet (five items), health awareness (four items), physical activity (three items), stress management (four items), and treatment (four items). The total variance explained by the EFA model was 56.7%. The Cronbach alpha values of the five factors ranged between 0.52 and 0.81. In the CFA model, one problematic latent variable (treatment) was identified and three items were removed. In the final measurement model, four factors and 17 items fit the data well based on several fit indices (root mean square error of approximation (RMSEA) = 0.044 and standardized root mean squared residual (SRMR) = 0.052). The composite reliability of all factors in the final measurement model was above 0.60, indicating acceptable construct reliability.

Conclusion

The newly developed HPB-Bloat scale is valid and reliable when assessing the awareness of health-promoting behaviours across patients with AB. Further validation is needed across different languages and populations.

Inflammation and Overlap of Irritable Bowel Syndrome and Functional Dyspepsia

Irritable bowel syndrome (IBS) and functional dyspepsia (FD) are common functional gastrointestinal disorders (FGIDs) and account for a large proportion of consulting patients. These 2 disorders overlap with each other frequently. The pathogenesis of IBS or FD is complicated and multi-factors related, in which infectious or non-infectious inflammation and local or systemic immune response play significant roles. There are few studies focusing on the mechanism of inflammation in patients with overlap syndrome of irritable bowel syndrome and functional dyspepsia (IBS-FD). This review focuses on current advances about the role of inflammation in the pathogenesis of IBS and FD and the possible mechanism of inflammation in IBS-FD.

Comorbid anxiety-like behavior in a rat model of colitis is mediated by an upregulation of corticolimbic fatty acid amide hydrolase

Peripheral inflammatory conditions, including those localized to the gastrointestinal tract, are highly comorbid with psychiatric disorders such as anxiety and depression. These behavioral symptoms are poorly managed by conventional treatments for inflammatory diseases and contribute to quality of life impairments. Peripheral inflammation is associated with sustained elevations in circulating glucocorticoid hormones, which can modulate central processes, including those involved in the regulation of emotional behavior. The endocannabinoid (eCB) system is exquisitely sensitive to these hormonal changes and is a significant regulator of emotional behavior. The impact of peripheral inflammation on central eCB function, and whether this is related to the development of these behavioral comorbidities remains to be determined. To examine this, we employed the trinitrobenzene sulfonic acid-induced model of colonic inflammation (colitis) in adult, male, Sprague Dawley rats to produce sustained peripheral inflammation. Colitis produced increases in behavioral measures of anxiety and elevations in circulating corticosterone. These alterations were accompanied by elevated hydrolytic activity of the enzyme fatty acid amide hydrolase (FAAH), which hydrolyzes the eCB anandamide (AEA), throughout multiple corticolimbic brain regions. This elevation of FAAH activity was associated with broad reductions in the content of AEA, whose decline was driven by central corticotropin releasing factor type 1 receptor signaling. Colitis-induced anxiety was reversed following acute central inhibition of FAAH, suggesting that the reductions in AEA produced by colitis contributed to the generation of anxiety. These data provide a novel perspective for the pharmacological management of psychiatric comorbidities of chronic inflammatory conditions through modulation of eCB signaling.

Fatigue in irritable bowel syndrome is associated with plasma levels of TNF-α and mesocorticolimbic connectivity

Irritable bowel syndrome (IBS) is a symptom-based disorder of gut-brain interactions generating abdominal pain. It is also associated with a vulnerability to develop extraintestinal symptoms, with fatigue often reported as one of the most disturbing. Fatigue is related to brain function and inflammation in several disorders, however, the mechanisms of such relations in IBS remain elusive. This study aimed to elucidate fatigue and its association with a resting state network of mesocorticolimbic regions of known importance in fatigue, and to explore the possible role of circulating TNF-α levels in IBS and healthy controls (HC). Resting state functional magnetic resonance imaging (fMRI) was conducted in 88 IBS patients and 47 HC of similar age and gender to investigate functional connectivity between mesocorticolimbic regions. Further, fatigue impact on daily life and plasma levels of the proinflammatory cytokine tumor necrosis factor-α (TNF-α), of known relevance to immune activation in IBS, were also measured. The selected mesocorticolimbic regions indeed formed a functionally connected network in all participants. The nucleus accumbens (NAc), in particular, exhibited functional connectivity to all other regions of interest. In IBS, fatigue impact on daily life was negatively correlated with the connectivity between NAc and dorsolateral prefrontal cortex bilaterally (left p = 0.019; right p = 0.038, corrected for multiple comparisons), while in HC, fatigue impact on daily life was positively correlated to the connectivity between the right NAc and anterior middle insula in both hemispheres (left p = 0.009; right p = 0.011). We found significantly higher levels of TNF-α in IBS patients compared to HC (p = 0.001) as well as a positive correlation between TNF-α and fatigue impact on daily life in IBS patients (rho = 0.25, p = 0.02) but not in HC (rho = -0.13, p = 0.37). There was no association between functional connectivity in the mesocorticolimbic network and plasma levels of TNF-α in either group In summary, this novel multimodal study provides the first evidence that the vulnerability to fatigue in IBS is associated with connectivity within a mesocorticolimbic network as well as immune activation. These findings warrant further investigation, both peripherally and potentially with measurements of central immune activation as well.

Aberrant Gut-To-Brain Signaling in Irritable Bowel Syndrome - The Role of Bile Acids

Functional bowel disorders such as irritable bowel syndrome (IBS) are common, multifactorial and have a major impact on the quality of life of individuals diagnosed with the condition. Heterogeneity in symptom manifestation, which includes changes in bowel habit and visceral pain sensitivity, are an indication of the complexity of the underlying pathophysiology. It is accepted that dysfunctional gut-brain communication, which incorporates efferent and afferent branches of the peripheral nervous system, circulating endocrine hormones and local paracrine and neurocrine factors, such as host and microbially-derived signaling molecules, underpins symptom manifestation. This review will focus on the potential role of hepatic bile acids in modulating gut-to-brain signaling in IBS patients. Bile acids are amphipathic molecules synthesized in the liver, which facilitate digestion and absorption of dietary lipids. They are also important bioactive signaling molecules however, binding to bile acid receptors which are expressed on many different cell types. Bile acids have potent anti-microbial actions and thereby shape intestinal bacterial profiles. In turn, bacteria with bile salt hydrolase activity initiate the critical first step in transforming primary bile acids into secondary bile acids. Individuals with IBS are reported to have altered microbial profiles and modified bile acid pools. We have assessed the evidence to support a role for bile acids in the pathophysiology underlying the manifestation of IBS symptoms.

Camelina sativa Methanolic and Ethanolic Extract Potential in Alleviating Oxidative Stress, Memory Deficits, and Affective Impairments in Stress Exposure-Based Irritable Bowel Syndrome Mouse Models

Camelina sativa is mainly used as an oilseed crop; its edible oil is being also used as a traditional home remedy for the treatment of ulcers, wounds, and eye inflammations, due to the antioxidant activities. In the present study, the chemically characterized alcoholic extracts of Camelina sativa var. Madalina defatted seeds (5 g/kg body weight p.o., suspended in CMC-Na 0.1%) were administered to stress-induced animal models of irritable bowel syndrome (based on combinations of contention stress and multifactorial stress and maternal stress) and evaluated for the behavioural (short-term memory by the Y maze test, the anxious behaviour using the elevated plus maze test, and the antidepressant effect using the forced swimming test) and brain and bowel tissue oxidative status (superoxide dismutase and glutathione peroxidase enzymes activities and malondialdehyde and total soluble protein levels) improving effects. According to the chemical characterization, the extracts were rich in sinapine, glucosinolates, and flavonol glycosides. Moreover, this study showed the beneficial effects of Camelina sativa seed methanolic and ethanolic extracts on the behaviour and brain and bowel tissues oxidative stress status of stress exposure-based IBS mouse models. Despite the slight differences in the chemical composition of the methanolic and ethanolic extracts, the results suggested that the Camelina sativa extracts could reverse the short-term memory impairments caused by stress exposure and also could decrease the intensity and frequency of the anxiety and depressive-like behaviours observed in the stress-exposed animal models of IBS. Furthermore, the Camelina sativa extracts showed a significant effect on the oxidative stress markers in the brain and bowel tissues of the studied animal model by decreasing the superoxide dismutase activity and increasing the glutathione peroxidase activity. However, the results suggested that the extracts could also increase lipid peroxidation in bowel tissues. In this way, this study provides additional evidence that the administration of Camelina sativa seed alcoholic extracts could improve cognitive performances and mood and exhibit the antioxidant capacity in both the brain and bowel tissues.

Network Pharmacology Identifies the Mechanisms of Action of Tongxie Anchang Decoction in the Treatment of Irritable Bowel Syndrome with Diarrhea Predominant

AIM

This study aims to uncover the pharmacological mechanism of Tongxie Anchang Decoction (TXACD), a new and effective traditional Chinese medicine (TCM) prescription, for treating irritable bowel syndrome with diarrhea predominant (IBS-D) using network pharmacology.

METHODS

The active compounds and putative targets of TXACD were retrieved from TCMSP database and published literature; related target genes of IBS-D were retrieved from GeneCards; PPI network of the common target hub gene was constructed by STRING. Furthermore, these hub genes were analyzed using gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis.

RESULTS

A total of 54 active compounds and 639 targets were identified through a database search. The compound-target network was constructed, and the key compounds were screened out according to the degree. By using the PPI and GO and KEGG enrichment analyses, the pharmacological mechanism network of TXACD in the treatment of IBS-D was constructed.

CONCLUSIONS

This study revealed the possible mechanisms by which TXACD treatment alleviated IBS-D involvement in the modulation of multiple targets and multiple pathways, including the immune regulation, inflammatory response, and oxidative stress. These findings provide novel insights into the regulatory role of TXACD in the prevention and treatment of IBS-D and hold promise for herb-based complementary and alternative therapy.

Assessment of causal link between psychological factors and symptom exacerbation in inflammatory bowel disease: a systematic review utilising Bradford Hill criteria and meta-analysis of prospective cohort studies

BACKGROUND

Psychological stress is a prevalent factor in inflammatory bowel disease (IBD) with detrimental effects on patients' quality of life and possibly disease course. Although the aetiology of symptom exacerbation in IBD has been explored, determining any causation between psychological stress and symptom worsening remains challenging and requires a methodologically rigorous approach.

AIM

The aim of this systematic review with meta-analysis was to determine a causal relationship between psychological stress and symptom exacerbation in IBD, subsequently utilising Bradford Hill's criteria (approach never used in this topic area before) to evaluate the likelihood of causal associations.

METHODS

Medline, EMBASE, CINAHL and PsycInfo were searched for relevant studies up to July 20, 2019. Data extraction and quality appraisal were performed by two independent reviewers. Results of all retained papers were presented as a narrative synthesis. A random-effect meta-analysis was conducted on studies meeting the criteria for meta-analysis. Bradford Hill criteria were applied to assess the causality of the relationship between all psychological factors and symptom exacerbation.

RESULTS

The searches yielded 2472 potential articles. Nineteen clinical prospective cohort studies were eligible for the narrative review with five suitable for the meta-analysis. Meta-analysis showed depression, anxiety and perceived stress did not have a statistically significant association with an increased risk of symptom exacerbation. Four of the Bradford Hill criteria were met which indicates that there is weak to moderate evidence of a causal association between all the psychological factors and disease activity. Inconsistent results and a dearth of studies using the same tools for measuring psychological factors suggest the need for more research to be done to facilitate more conclusive findings.

CONCLUSIONS

This original review utilising Bradford Hill criteria in addition to meta-analysis to evaluate the causality of relationship between psychological factors and symptom exacerbation in IBD provides evidence that psychological factors have a weak to moderate causal involvement in IBD symptom exacerbation. However, when combining this finding with the outcomes of the meta-analysis, we can say that the results were inconclusive. Interventions to reduce the associated psychological impact should be part of the treatment plan for patients with IBD.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42012003143.

Gut-organ axis: a microbial outreach and networking

Human gut microbiota (GM) includes a complex and dynamic population of microorganisms that are crucial for well-being and survival of the organism. It has been reported as diverse and relatively stable with shared core microbiota, including Bacteroidetes and Firmicutes as the major dominants. They are the key regulators of body homeostasis, involving both intestinal and extra-intestinal effects by influencing many physiological functions such as metabolism, maintenance of barrier homeostasis, inflammation and hematopoiesis. Any alteration in GM community structures not only trigger gut disorders but also influence other organs and cause associated diseases. In recent past, the GM has been defined as a 'vital organ' with its involvement with other organs; thus, establishing a link or a bi- or multidirectional communication axis between the organs via neural, endocrine, immune, humoral and metabolic pathways. Alterations in GM have been linked to several diseases known to humans; although the exact interaction mechanism between the gut and the organs is yet to be defined. In this review, the bidirectional relationship between the gut and the vital human organs was envisaged and discussed under several headings. Furthermore, several disease symptoms were also revisited to redefine the communication network between the gut microbes and the associated organs.

Validity and Reliability of the Newly Developed Malay-Language Health Belief of Bloating (HB-Bloat) Scale

Abdominal bloating (AB), a common complaint that affects quality of life and disturbs psychological well-being, is largely a behavioral-driven disorder. We aimed to develop and validate a new health belief of bloating (HB-Bloat) scale in the Malay language. The initial item pool was developed based on the theory of planned behavior, empirical literatures, expert review and in-depth interviews. Using the population with bloating (diagnosed based on the Rome IV criteria and pictogram), exploratory and confirmatory factor analytical approaches (EFA and CFA, respectively) were utilized to explore and confirm the domains in the new scale. There were 150 and 323 respondents in the EFA and CFA, respectively. There were 45 items in the initial scale, but it was reduced to 32 items after content validity and pre-testing. In EFA, 17 items with three (3) structure factors (attitude 4 items, subjective norm 7 items, and perceived behavior control 6 items) were identified. Total variance explained by the EFA model was 40.92%. The Cronbach alpha of the three (3) factors ranged from 0.61 to 0.79. With CFA, the three factors model was further tested. Five problematic items were identified and removed. The final measurement model fit the data well (root mean square error of approximation (RMSEA (90% CI) = 0.054 (0.038, 0.070), Comparative Fit Index (CFI) = 0.941, Tucker–Lewis Fit Index (TLI) = 0.924, and standardized root mean squared residual (SRMR) = 0.044). The construct reliability of the final measurement model ranged from 0.76 to 0.84. As a conclusion, the new HB-Bloat scale is a valid and reliable tool for assessment of health beliefs in bloating.

Vitamin D3 Supplementation in Diarrhea-Predominant Irritable Bowel Syndrome Patients: The Effects on Symptoms Improvement, Serum Corticotropin-Releasing Hormone, and Interleukin-6 - A Randomized Clinical Trial

OBJECTIVES

This study aimed to evaluate whether vitamin D deficiency is associated with the severity of symptoms of irritable bowel syndrome (IBS) patients. Stress and gut inflammation can increase the serum level of corticotropin-releasing hormone (CRH) and interleukin-6 (IL-6), leading to a change in bowel movements. The aim of this study was to evaluate the anti-inflammatory and psychological effects of vitamin D3 supplementation on the symptom improvement of patients with a diarrhea-predominant form of IBS (IBS-D).

METHODS

Eighty-eight IBS-D patients (age: 18-65 years) based on Rome IV criteria who suffered from vitamin D deficiency and/or insufficiency were enrolled in this randomized, placebo-controlled trial from February 2017 to May 2018 at Rasoul-e-Akram Hospital, Tehran, Iran. Participants were randomly divided into two groups. The intervention group received 50,000 IU vitamin D3 weekly and the control group received a placebo for 9 weeks. All patients received Mebeverine 135 mg twice a day besides supplementation. The IBS Severity Score System (IBS-SSS), serum 25(OH) vitamin D3, CRH, and IL-6 were measured before and after interventions.

RESULTS

Seventy-four patients completed the study. The severity of IBS symptoms (p < 0.01) and IL-6 (p = 0.02) decreased significantly in the intervention group as compared to the control group, but there was no significant difference in the serum level of CRH. Also, in the treatment group, IBS-SSS and IL-6 were significantly reduced at the end of the study from baseline (p < 0.01 and p < 0.03, respectively).

CONCLUSION

Our findings indicate that vitamin D3 supplementation can modulate the serum level of CRH and IL-6 and can improve symptoms in IBS-D patients. Vitamin D3 supplementation should be considered in IBS-D patients who suffer from vitamin D deficiency and/or insufficiency.

Activation of Peripheral Blood CD4+ T-Cells in IBS is not Associated with Gastrointestinal or Psychological Symptoms

Immune activation may underlie the pathogenesis of irritable bowel syndrome (IBS), but the evidence is conflicting. We examined whether peripheral CD4+ T-cells from IBS patients demonstrated immune activation and changes in cytokine production. To gain mechanistic insight, we examined whether immune activation correlated with psychological stress and changing symptoms over time. IBS patients (n = 29) and healthy volunteers (HV; n = 29) completed symptom and psychological questionnaires. IBS patients had a significant increase in CD4+ T-cells expressing the gut homing marker integrin β7 (p = 0.023) and lymphoid marker CD62L (p = 0.026) compared to HV. Furthermore, phytohaemagglutinin stimulated CD4+ T-cells from IBS-D patients demonstrated increased TNFα secretion when compared to HV (p = 0.044). Increased psychological scores in IBS did not correlate with TNFα production, while stress hormones inhibited cytokine secretion from CD4+ T-cells of HV in vitro. IBS symptoms, but not markers of immune activation, decreased over time. CD4+ T-cells from IBS-D patients exhibit immune activation, but this did not appear to correlate with psychological stress measurements or changing symptoms over time. This could suggest that immune activation is a surrogate of an initial trigger and/or ongoing parallel peripheral mechanisms.

Antioxidant Capacity and Behavioral Relevance of a Polyphenolic Extract of Chrysanthellum americanum in a Rat Model of Irritable Bowel Syndrome

Chrysanthellum americanum L. (Vatke) is a medicinal plant from the Compositae family used in west-African traditional medicine, known for its flavonoid and saponin richness and for its strong antioxidant potential. In the present study, we assessed the effects of Chrysanthellum americanum polyphenolic extract in the psychological stress-induced rat model of irritable bowel syndrome (IBS), a chronic functional digestive tract disorder marked by immune and inflammatory-related disturbances of central nervous and peripheral intestinal systems, which is often associated with mood disorders including depression and anxiety. Consequently, memory impairment, anxiety and depression behavioral indicators, and cerebral oxidative stress biomarker dynamics were evaluated in a multifactorial heterotypic stress-exposed IBS rats after 6-day gavage with polyphenolic C. americanum extract (100 mg/kg body weight). Y-maze, elevated plus maze, and forced swimming tests were used for assessing behavioral responses. Administration of the extract exhibited significant anxiolytic and antidepressant-like effects coupled with significantly increased temporal lobe antioxidant enzyme specific activity (superoxide dismutase and glutathione peroxidase) and decreased malondialdehyde levels, a well-known lipid peroxidation marker. Furthermore, linear regression statistical analyses showed significant correlations between the oxidative stress parameters and behavioral tests. In conclusion, our results suggest that the administration of Chrysanthellum americanum polyphenolic extract could ameliorate mood and cognitive disturbances related to stress-induced in an IBS rat model. This could be also related to cerebral oxidative stress status attenuation.

Endocrine regulation of gut function - a role for glucagon-like peptide-1 in the pathophysiology of irritable bowel syndrome

NEW FINDINGS

What is the topic of this review? Pathophysiological changes linked to irritable bowel syndrome (IBS) include stress and immune activation, changes in gastrointestinal microbial and bile acid profiles and sensitization of extrinsic and intrinsic gut neurons. This review explores the potential role for L-cells in these pathophysiological changes. What advances does it highlight? L-cells, which secrete glucagon-like peptide-1 in response to nutrients, microbial factors, bile acids and short-chain fatty acids, may sense IBS-related changes in the luminal environment. Glucagon-like peptide-1 can act as a hormone, a paracrine factor or a neuromodulatory factor and, through its actions on central or peripheral neurons, may play a role in gastrointestinal dysfunction.

ABSTRACT

The prevalent and debilitating functional bowel disorder, irritable bowel syndrome (IBS), is characterized by symptoms that include abdominal pain, bloating, diarrhoea and/or constipation. The heterogeneity of IBS underscores a complex multifactorial pathophysiology, which is not completely understood but involves dysfunction of the bi-directional signalling axis between the brain and the gut. This axis incorporates efferent and afferent branches of the autonomic nervous system, circulating endocrine hormones and immune factors, local paracrine and neurocrine factors and microbial metabolites. L-cells, which are electrically excitable biosensors embedded in the gastrointestinal epithelium, secrete glucagon-like peptide-1 (GLP-1) in response to nutrients in the small intestine. However, they appear to function in a different manner more distally in the gastrointestinal tract, where they are activated by luminal factors including short-chain fatty acids, bile acids and microbial metabolic products, all of which are altered in IBS patients. Glucagon-like peptide-1 can also interact with the hypothalamic-pituitary-adrenal stress axis and the immune system, both of which are activated in IBS. Given that a GLP-1 mimetic has been found to alleviate acute pain symptoms in IBS patients, GLP-1 might be important in the manifestation of IBS symptoms. This review assesses the current knowledge about the role of GLP-1 in IBS pathophysiology and its potential role as a signal transducer in the microbiome-gut-brain signalling axis.

Intestinal Dysmotility Syndromes following Systemic Infection by Flaviviruses

Although chronic gastrointestinal dysmotility syndromes are a common worldwide health problem, underlying causes for these disorders are poorly understood. We show that flavivirus infection of enteric neurons leads to acute neuronal injury and cell death, inflammation, bowel dilation, and slowing of intestinal transit in mice. Flavivirus-primed CD8⁺ T cells promote these phenotypes, as their absence diminished enteric neuron injury and intestinal transit delays, and their adoptive transfer reestablished dysmotility after flavivirus infection. Remarkably, mice surviving acute flavivirus infection developed chronic gastrointestinal dysmotility that was exacerbated by immunization with an unrelated alphavirus vaccine or exposure to a non-infectious inflammatory stimulus. This model of chronic post-infectious gastrointestinal dysmotility in mice suggests that viral infections with tropism for enteric neurons and the ensuing immune response might contribute to the development of bowel motility disorders in humans. These results suggest an opportunity for unique approaches to diagnosis and therapy of gastrointestinal dysmotility syndromes.

The Microbiota-Gut-Brain Axis in Neuropsychiatric Disorders: Pathophysiological Mechanisms and Novel Treatments

Background

The human gut microbiome comprise a huge number of microorganisms with co-evolutionary associations with humans. It has been repeatedly revealed that bidirectional communication exists between the brain and the gut and involves neural, hormonal, and immunological pathways. Evidences from neuroscience researches over the past few years suggest that microbiota is essential for the development and maturation of brain systems that are associated to stress responses.

Method

This review provides that the summarization of the communication among microbiota, gut and brain and the results of preclinical and clinical studies on gut microbiota used in treatments for neuropsychiatric disorders.

Result

Recent studies have reported that diverse forms of neuropsychiatric disorders (such as autism, depression, anxiety, and schizophrenia) are associated with or modulated by variations in the microbiome, by microbial substrates, and by exogenous prebiotics, antibiotics, and probiotics.

Conclusion

The microbiota–gut–brain axis might provide novel targets for prevention and treatment of neuropsychiatric disorders. However, further studies are required to substantiate the clinical use of probiotics, prebiotics and FMT.

Harnessing the Power of Microbiome Assessment Tools as Part of Neuroprotective Nutrition and Lifestyle Medicine Interventions

An extensive body of evidence documents the importance of the gut microbiome both in health and in a variety of human diseases. Cell and animal studies describing this relationship abound, whilst clinical studies exploring the associations between changes in gut microbiota and the corresponding metabolites with neurodegeneration in the human brain have only begun to emerge more recently. Further, the findings of such studies are often difficult to translate into simple clinical applications that result in measurable health outcomes. The purpose of this paper is to appraise the literature on a select set of faecal biomarkers from a clinician’s perspective. This practical review aims to examine key physiological processes that influence both gastrointestinal, as well as brain health, and to discuss how tools such as the characterisation of commensal bacteria, the identification of potential opportunistic, pathogenic and parasitic organisms and the quantification of gut microbiome biomarkers and metabolites can help inform clinical decisions of nutrition and lifestyle medicine practitioners.

Visceral hypersensitivity induced by optogenetic activation of the amygdala in conscious rats

In vivo optogenetics identifies brain circuits controlling behaviors in conscious animals by using light to alter neuronal function and offers a novel tool to study the brain-gut axis. Using adenoviral-mediated expression, we aimed to investigate whether photoactivation with channelrhodopsin (ChR2) or photoinhibition with halorhodopsin (HR3.0) of fibers originating from the central nucleus of the amygdala (CeA) at the bed nucleus of the stria terminalis (BNST) had any effect on colonic sensitivity. We also investigated whether there was any deleterious effect of the adenovirus on the neuronal population or the neuronal phenotype within the CeA-BNST circuitry activated during the optogenetic stimulation. In male rats, the CeA was infected with vectors expressing ChR2 or HR3.0 and fiber optic cannulae were implanted on the BNST. After 8-10 wk, the response to graded, isobaric colonic distension was measured with and without laser stimulation of CeA fibers at the BNST. Immunohistochemistry and histology were used to evaluate vector expression, neuronal integrity, and neurochemical phenotype. Photoactivation of CeA fibers at the BNST with ChR2 induced colonic hypersensitivity, whereas photoinhibition of CeA fibers at the BNST with HR3.0 had no effect on colonic sensitivity. Control groups treated with virus expressing reporter proteins showed no abnormalities in neuronal morphology, neuronal number, or neurochemical phenotype following laser stimulation. Our experimental findings reveal that optogenetic activation of discrete brain nuclei can be used to advance our understanding of complex visceral nociceptive circuitry in a freely moving rat model. NEW & NOTEWORTHY Our findings reveal that optogenetic technology can be employed as a tool to advance understanding of the brain-gut axis. Using adenoviral-mediated expression of opsins, which were activated by laser light and targeted by fiber optic cannulae, we examined central nociceptive circuits mediating visceral pain in a freely moving rat. Photoactivation of amygdala fibers in the stria terminalis with channelrhodopsin induced colonic hypersensitivity, whereas inhibition of the same fibers with halorhodopsin did not alter colonic sensitivity.

The Role of Diet in the Treatment of Irritable Bowel Syndrome: A Systematic Review

Irritable bowel syndrome (IBS) is a multifaceted illness involving maladaptive shifts in the gut microbiota that affect the enteric nervous and immune systems, mucosal barrier function, the balance of neurotransmitters and hormones, and emotional well-being. There is abundant evidence indicating that certain foods elicit symptoms in IBS. Numerous elimination-type diets have been shown to alleviate symptoms. However, among these, the most controversial is a group of foods called fructo, oligo-, di-, and monosaccharides and polyols (FODMAPs). This paper reviews the role of diet and systematically analyze the literature for the role of FODMAPs in IBS.

Mechanisms of Stress-induced Visceral Pain

Evidence suggests that long-term stress facilitates visceral pain through sensitization of pain pathways and promotes chronic visceral pain disorders such as the irritable bowel syndrome (IBS). This review will describe the importance of stress in exacerbating IBS-induced abdominal pain. Additionally, we will briefly review our understanding of the activation of the hypothalamic-pituitary-adrenal axis by both chronic adult stress and following early life stress in the pathogenesis of IBS. The review will focus on the glucocorticoid receptor and corticotropin-releasing hormone-mediated mechanisms in the amygdala involved in stress-induced visceral hypersensitivity. One potential mechanism underlying persistent effects of stress on visceral sensitivity could be epigenetic modulation of gene expression. While there are relatively few studies examining epigenetically mediated mechanisms involved in stress-induced visceral nociception, alterations in DNA methylation and histone acetylation patterns within the brain, have been linked to alterations in nociceptive signaling via increased expression of pro-nociceptive neurotransmitters. This review will discuss the latest studies investigating the long-term effects of stress on visceral sensitivity. Additionally, we will critically review the importance of experimental models of adult stress and early life stress in enhancing our understanding of the basic molecular mechanisms of nociceptive processing.

Panic Disorder Comorbidity with Medical Conditions and Treatment Implications

Panic disorder (PD) is unique among the anxiety disorders in that panic symptoms are primarily of a physical nature. Consequently, comorbidity with medical illness is significant. This review examines the association between PD and medical illness. We identify shared pathophysiological and psychological correlates and illustrate how physiological activation in panic sufferers underlies their symptom experience in the context of the fight-or-flight response and beyond a situation-specific response pattern. We then review evidence for bodily symptom perception accuracy in PD. Prevalence of comorbidity for PD and medical illness is presented, with a focus on respiratory and cardiovascular illness, irritable bowel syndrome, and diabetes, followed by an outline for potential pathways of a bidirectional association. We conclude by illustrating commonalities in mediating mechanistic pathways and moderating risk factors across medical illnesses, and we discuss implications for diagnosis and treatment of both types of conditions.

Systematic assessment of environmental risk factors for bipolar disorder: an umbrella review of systematic reviews and meta-analyses

OBJECTIVES

The pathophysiology of bipolar disorder is likely to involve both genetic and environmental risk factors. In our study, we aimed to perform a systematic search of environmental risk factors for BD. In addition, we assessed possible hints of bias in this literature, and identified risk factors supported by high epidemiological credibility.

METHODS

We searched the Pubmed/MEDLINE, EMBASE and PsycInfo databases up to 7 October 2016 to identify systematic reviews and meta-analyses of observational studies that assessed associations between putative environmental risk factors and BD. For each meta-analysis, we estimated its summary effect size by means of both random- and fixed-effects models, 95% confidence intervals (CIs), the 95% prediction interval, and heterogeneity. Evidence of small-study effects and excess of significance bias was also assessed.

RESULTS

Sixteen publications met the inclusion criteria (seven meta-analyses and nine qualitative systematic reviews). Fifty-one unique environmental risk factors for BD were evaluated. Six meta-analyses investigated associations with a risk factor for BD. Only irritable bowel syndrome (IBS) emerged as a risk factor for BD supported by convincing evidence (k=6; odds ratio [OR]=2.48; 95% CI=2.35-2.61; P<.001), and childhood adversity was supported by highly suggestive evidence. Asthma and obesity were risk factors for BD supported by suggestive evidence, and seropositivity to Toxoplasma gondii and a history of head injury were supported by weak evidence.

CONCLUSIONS

Notwithstanding that several environmental risk factors for BD were identified, few meta-analyses of observational studies were available. Therefore, further well-designed and adequately powered studies are necessary to map the environmental risk factors for BD.

Early adverse life events are associated with altered brain network architecture in a sex- dependent manner

INTRODUCTION

Early adverse life events (EALs) increase the risk for chronic medical and psychiatric disorders by altering early neurodevelopment. The aim of this study was to examine associations between EALs and network properties of core brain regions in the emotion regulation and salience networks, and to test the influence of sex on these associations.

METHODS

Resting-state functional and diffusion tensor magnetic resonance imaging were obtained in healthy individuals (61 men, 63 women). Functional and anatomical network properties of centrality and segregation were calculated for the core regions of the two networks using graph theory. Moderator analyses were applied to test hypotheses.

RESULTS

The type of adversity experienced influences brain wiring differently, as higher general EALs were associated with decreased functional and anatomical centrality in salience and emotion regulation regions, while physical and emotional EALs were associated with increased anatomical centrality and segregation in emotion regulation regions. Sex moderated the associations between EALs and measures of centrality; with decreased centrality of salience and emotion regulation regions with increased general EALs in females, and increased centrality in salience regions with higher physical and emotional EALs in males. Increased segregation of salience regions was associated with increased general EALs in males. Centrality of the amygdala was associated with physical symptoms, and segregation of salience regions was correlated with higher somatization in men only.

CONCLUSIONS

Emotion regulation and salience regions are susceptible to topological brain restructuring associated with EALs. The male and female brains appear to be differently affected by specific types of EALs.

Is-it possible to distinguish irritable bowel syndrome with constipation from functional constipation?

BACKGROUND

The Rome III criteria classify patients complaining of constipation into two main groups: patients with functional constipation (FC) and patients with constipation predominant irritable bowel syndrome (IBS-C). The purpose of this study was to identify differences in the intensity of symptoms and total and segmental colonic transit time in these two types of patients.

METHODS

We performed a prospective evaluation of 337 outpatients consecutively referred for chronic constipation and classified according to the Rome III criteria as FC or IBS-C. They were asked to report symptom intensity, on a 10-point Likert scale, for diarrhea, constipation, bloating and abdominal pain. Stool form was reported using the Bristol scale, and colonic transit time was measured by using multiple-ingestion single-marker single-film technique. Statistical analysis was completed by a discriminant analysis.

RESULTS

Female gender and obstructed defecation was more frequent in IBS-C patients than in FC patients. IBS-C patients reported greater symptom intensity than FC patients, but stool form, and total and segmental colonic transit time were not different between the two groups. Multivariate logistic regression showed that only two parameters, bloating and abdominal pain, were related to the IBS-C or to the FC phenotype, and discriminant analysis showed that these two parameters were sufficient to give a correct classification of 71% of the patients.

CONCLUSIONS

Our study suggests that self-evaluation of abdominal pain and bloating is more helpful than colonic transit time in classifying patient as IBS-C or FC.

Functional urological disorders: a sensitized defence response in the bladder-gut-brain axis

Functional urological and gastrointestinal disorders are interrelated and characterized by a chronic course and considerable treatment resistance. Urological disorders associated with a sizeable functional effect include overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS), and chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). Poor treatment outcomes might be attributable to untreated underlying psychological and psychiatric disorders, as the co-occurrence of functional urological and gastrointestinal disorders with mood and anxiety disorders is common. The hypothetical bladder-gut-brain axis (BGBA) is a useful framework under which this interaction can be studied, suggesting that functional disorders represent a sensitized response to earlier threats such as childhood adversity or previous traumatic events, resulting in perceived emotional and bodily distress - the symptoms of functional disorders. Psychological and physical stress pathways might contribute to such alarm falsification, and neuroticism could be a risk factor for the co-occurrence of functional disorders and affective conditions. Additionally, physical threat - either from external sources or internal sources such as infection - might contribute to alarm falsification by influencing body-brain crosstalk on homeostasis and, therefore, affecting mood, cognition, and behaviour. Multidisciplinary research and an integrated care approach is, therefore, required to further elucidate and remediate functional urological and gastrointestinal polymorphic phenotypes.

Risk of psychiatric disorders following pelvic inflammatory disease: a nationwide population-based retrospective cohort study

Pelvic inflammatory disease (PID) a common infection in women that is associated with significant morbidity and is a major cause of infertility. A clear temporal causal relationship between PID and psychiatric disorders has not been well established. We used a nationwide population-based retrospective cohort study to explore the relationship between PID and the subsequent development of psychiatric disorders. We identified subjects who were newly diagnosed with PID between 1 January 2000 and 31 December 2002 in the Taiwan National Health Insurance Research Database. A comparison cohort was constructed for patients without PID. A total of 21 930 PID and 21 930 matched control patients were observed until diagnosed with psychiatric disorders, or until death, withdrawal from the NHI system, or until 31 December 2009. Adjusted hazard ratio (HR) of bipolar disorder, depressive disorder, anxiety disorder and sleep disorder in subjects with PID were significantly higher (HR: 2.671, 2.173, 2.006 and 2.251, respectively) than that of the controls during the follow-up. PID may increase the risk of subsequent newly diagnosed bipolar disorder, depressive disorder, anxiety disorder and sleep disorder, which will impair life quality. Our findings highlight that clinicians should pay particular attention to psychiatric comorbidities in PID patients.

In vivo neutralization of IL-6 receptors ameliorates gastrointestinal dysfunction in dystrophin-deficient mdx mice

BACKGROUND

Duchenne muscular dystrophy (DMD) is a fatal disease characterized by progressive deterioration and degeneration of striated muscle. A mutation resulting in the loss of dystrophin, a structural protein which protects cells from contraction-induced damage, underlies DMD pathophysiology. Damage to muscle fibers results in chronic inflammation and elevated levels of proinflammatory cytokines such as interleukin-6 (IL-6). However, loss of cellular dystrophin also affects neurons and smooth muscle in the gastrointestinal (GI) tract with complaints such as hypomotility, pseudo-obstruction, and constipation reported in DMD patients.

METHODS

Using dystrophin-deficient mdx mice, studies were carried out to examine colonic morphology and function compared with wild-type mice. Treatment with neutralizing IL-6 receptor antibodies (xIL-6R) and/or the corticotropin-releasing factor (CRF) 2 receptor agonist, urocortin 2 (uro2) was tested to determine if they ameliorated GI dysfunction in mdx mice.

KEY RESULTS

Mdx mice exhibited thickening of colonic smooth muscle layers and delayed stress-induced defecation. In organ bath studies, neurally mediated IL-6-evoked contractions were larger in mdx colons. In vivo treatment of mdx mice with xIL-6R normalized defecation rates and colon lengths. Uro2 treatment did not affect motility or morphology. The potentiated colonic contractile response to IL-6 was attenuated by treatment with xIL-6R.

CONCLUSIONS & INFERENCES

These findings confirm the importance of dystrophin in normal GI function and implicate IL-6 as an important regulator of GI motility in the mdx mouse. Inhibition of IL-6 signaling may offer a potential new therapeutic strategy for treating DMD-associated GI symptoms.