Altered Resting Brain Functions in Patients With Irritable Bowel Syndrome: A Systematic Review

Efficacy of Nigella sativa seed oil against psychophysical stress induced irritable bowel syndrome and anxiety-like symptoms in Wistar rats

RATIONALE

Stressors play a critical role in the progression of irritable bowel syndrome (IBS). Heterogenous stress causes alterations in our bowel movements which can further cause anxiety and depression-like symptoms, decreasing the ability of individuals worldwide to function in social, academic, and employment settings.

OBJECTIVES

This study was aimed to investigate the effect of orally administered Nigella sativa (0.2 mL/kg b.wt.) seed oil (NSSO) on stress-induced IBS, anxiety, and depression-like symptoms in Wistar rats.

METHODS

In the present study, modelling IBS induced anxiety and depression-like symptoms in rodents have been employed to correlate the pathophysiological mechanisms behind this disorder. Moreover, evaluation of ameliorative potential of traditionally used NSSO in IBS was also carried out.

RESULTS

Present investigation indicated that acute stress of 1.5 h daily for 20 days induced hyper cortisol, gastrointestinal (GI) hypermotility, diarrhoea, altered levels of short chain fatty acids (SCFAs), and inflammation which are common symptoms of IBS. Furthermore, depression and anxiety-like symptoms were validated in test groups by various behavioral tests and decreased levels of 5-HT-Transporter mRNA gene expression, which are clear indicators of cognitive impairment.

CONCLUSIONS

It is possible that these IBS-like symptoms may have contributed to the pathogenesis of cognitive deficits and depression. However, the anti-oxidative, anti-inflammatory, anti-spasmodic, and possibly the anti-anxiolytic properties of NSSO helped in the mitigation of altered gut-brain axis. Because the concurrent treatment of NSSO alleviated the symptoms of modified GI function and consequently, the anxious & depressive behavior of the animals. Overall, this research explored the protective efficacy of NSSO against stress-induced IBS and depression-like symptoms, shedding light on the potential of this natural compound as a therapeutic option in the field of gastroenterology and psychiatry.

The Latest Data Concerning the Etiology and Pathogenesis of Irritable Bowel Syndrome

Globally, irritable bowel syndrome (IBS) is present in approximately 10% of the population. While this condition does not pose a risk of complications, it has a substantial impact on the patient's quality of life. Moreover, this disease has a significant financial impact on healthcare systems. This includes the direct costs associated with the diagnosis and treatment of these patients, as well as the indirect costs that arise from work absenteeism and reduced productivity. In light of these data, recent research has focused on elucidating the pathophysiological basis of this condition in order to improve the quality of life for affected individuals. Despite extensive research to date, we still do not fully understand the precise mechanisms underlying IBS. Numerous studies have demonstrated the involvement of the gut-brain axis, visceral hypersensitivity, gastrointestinal dysmotility, gut microbiota dysbiosis, food allergies and intolerances, low-grade mucosal inflammation, genetic factors, and psychosocial factors. The acquisition of new data is crucial for the advancement of optimal therapeutic approaches aimed at enhancing the general health of these patients while simultaneously reducing the financial burden associated with this ailment.

Deciphering the brain-gut axis: elucidating the link between cerebral cortex structures and functional gastrointestinal disorders via integrated Mendelian randomization

Background

Observational studies have suggested associations between functional gastrointestinal disorders (FGIDs) and variations in the cerebral cortex. However, the causality of these relationships remains unclear, confounded by anxiety and depression. To clarify these causal relationships and explore the mediating roles of anxiety and depression, we applied univariate, multivariable, and mediation Mendelian randomization (MR) analyses.

Method

We utilized genome-wide association study (GWAS) summary data from the FinnGen database and the ENIGMA consortium, identifying genetic variants associated with irritable bowel syndrome (IBS), functional dyspepsia (FD), and cerebral cortex structures. Data on anxiety and depression came from FinnGen and a large meta-analysis. Utilizing a bidirectional univariate MR approach, we explored correlations between FD, IBS, and cortex variations. Then, independent effects were assessed through multivariable MR. A meta-analysis of these results, incorporating data from two cohorts, aimed to increase precision. We also explored the potential mediating roles of anxiety and depression.

Results

Our findings indicate a negative causal correlation between FD and the thickness of the rostral anterior cingulate cortex (rACC) across both global and regional adjustments (β = -0.142, 95% confidence interval (CI): -0.209 to-0.074, P.FDR = 0.004; β = -0.112, 95%CI: -0.163 to-0.006, P.FDR = 0.003) and a positive causal correlation with the globally adjusted thickness of the superior frontal gyrus (SFG) (β = 0.107, 95%CI: 0.062 to 0.153, P.FDR = 0.001). The causal correlation with the rACC persisted after multiple variable adjustments (β = -0.137, 95% CI: -0.187 to-0.087, P.FDR = 1.81 × 10-5; β = -0.109, 95%CI: -0.158 to-0.06, P.FDR = 0.002). A significant causal association was found between globally adjusted surface area of the caudal anterior cingulate cortex (cACC) and IBS (odds ratio = 1.267, 95%CI: 1.128 to 1.424, P.FDR = 0.02). The analysis showed that neither anxiety nor depression mediated the relationship between FGIDs and cerebral cortex structures.

Conclusion

Our research provides significant MR evidence of a bidirectional causal relationship between FGIDs and the cerebral cortex structures. This evidence not only confirms the two-way communication along the brain-gut axis but also illuminates the underlying pathophysiology, paving the way for identifying potential therapeutic approaches.

Overexpression of EphB2 in the basolateral amygdala is crucial for inducing visceral pain sensitization in rats subjected to water avoidance stress

AIMS

Basolateral amygdala (BLA), as a center for stress responses and emotional regulation, is involved in visceral hypersensitivity of irritable bowel syndrome (IBS) induced by stress. In the present study, we aimed to investigate the role of EphB2 receptor (EphB2) in BLA and explore the underlying mechanisms in this process.

METHODS

Visceral hypersensitivity was induced by water avoidance stress (WAS). Elevated plus maze test, forced swimming test, and sucrose preference test were applied to assess anxiety- and depression-like behaviors. Ibotenic acid or lentivirus was used to inactivate BLA in either the induction or maintenance stage of visceral hypersensitivity. The expression of protein was determined by quantitative PCR, immunofluorescence, and western blot.

RESULTS

EphB2 expression was increased in BLA in WAS rats. Inactivation of BLA or downregulation of EphB2 in BLA failed to induce visceral hypersensitivity as well as anxiety-like behaviors. However, during the maintenance stage of visceral pain, visceral hypersensitivity was only partially relieved but anxiety-like behaviors were abolished by inactivation of BLA or downregulation of EphB2 in BLA. Chronic WAS increased the expression of EphB2, N-methyl-D-aspartate receptors (NMDARs), and postsynaptic density protein (PSD95) in BLA. Downregulation of EphB2 in BLA reduced NMDARs and PSD95 expression in WAS rats. However, activation of NMDARs after the knockdown of EphB2 expression still triggered visceral hypersensitivity and anxiety-like behaviors.

CONCLUSIONS

Taken together, the results suggest that EphB2 in BLA plays an essential role in inducing visceral hypersensitivity. In the maintenance stage, the involvement of EphB2 is crucial but not sufficient. The increase in EphB2 induced by WAS may enhance synaptic plasticity in BLA through upregulating NMDARs, which results in IBS-like symptoms. These findings may give insight into the treatment of IBS and related psychological distress.

Gastrointestinal Symptoms in Pediatric Patients with Anxiety Disorders and Their Relationship to Selective Serotonin Reuptake Inhibitor Treatment or Placebo

Gastrointestinal symptoms are commonly reported as adverse effects of selective serotonin reuptake inhibitors (SSRIs), the first-line pharmacologic treatment for pediatric anxiety disorders; however, the temporal course of these symptoms during treatment, although believed to be transient, has never been prospectively evaluated. Additionally, rates of gastrointestinal symptoms and functional gastrointestinal syndromes in anxious youth are poorly understood. We examined gastrointestinal symptoms in youth with anxiety disorders during a double-blind, placebo-controlled trial of escitalopram (n = 51). Then, in a separate sample of prospectively treated children and adolescents with generalized, social and/or separation anxiety disorders (n = 56), we examined the frequency of gastrointestinal symptoms based on the Questionnaire on Pediatric Gastrointestinal Symptoms (QPGS) and ROME III criteria and the association of these symptoms with clinical and demographic characteristics using logistic regression. The frequency/severity of abdominal pain, diarrhea, bloating constipation or total gastrointestinal symptoms did not differ between patients receiving placebo (n = 25) or escitalopram (n = 26). However, escitalopram-treated youth had transient changes in nausea/vomiting and total upper gastrointestinal symptoms during the first two weeks of treatment. ROME III criteria for functional gastrointestinal syndromes were present in 12/56 patients (21.4%). QPGS-related functional gastrointestinal syndromes and symptoms were unrelated to treatment, treatment type, or clinical or demographic variables. Gastrointestinal symptoms are common in youth with anxiety and SSRIs produce transient-rather than sustained-gastrointestinal symptoms. Assessing gastrointestinal symptoms prior to pharmacotherapy and discussing factors that increase (or decrease) the likelihood of transient SSRI-related symptoms in youth may decrease patient uncertainty related to side effects and decrease medication-related anxiety.