Visceral and somatic hypersensitivity, autonomic cardiovascular dysfunction and low-grade inflammation in a subset of irritable bowel syndrome patients

Somatization Mediates the Relationship Between Childhood Trauma and Pain Ratings in Patients with Irritable Bowel Syndrome

GOALS

To identify potential mechanisms by which childhood trauma may lead to the adult development of abdominal symptoms in patients with irritable bowel syndrome (IBS).

BACKGROUND

Patients with IBS frequently report a history of childhood trauma. The pathophysiology by which abdominal pain arises in patients with IBS is multidimensional, consisting of both peripheral factors, such as altered motility, inflammation, and bacterial overgrowth, as well as central factors, such as psychological distress and neuro-hormonal dysregulation.

STUDY

Adult psychological factors (anxiety, depression, and somatization) were examined to determine if they mediate the relationship between retrospective reports of childhood trauma and current adult IBS abdominal symptoms in a study of 436 patients (M age=41.6, 79% F) meeting Rome III diagnosis criteria. Childhood trauma was measured using retrospective questions assessing physical and sexual abuse. Psychological factors in adulthood were measured with the subscales of the Brief Symptom Inventory-18. Outcome variables included adult IBS symptoms of abdominal pain, bloating, and satisfaction with bowel habits from the IBS Symptoms Severity Scale.

RESULTS

Results indicated that somatization mediated the relationship between childhood abuse and abdominal pain and bloating but not bowel satisfaction.

CONCLUSIONS

This study provides insight into the multifactorial nature of IBS-associated abdominal pain in patients with a history of childhood trauma, elucidating the need for a trauma-informed treatment approach for patients with histories of abuse.

The influence of Nav1.9 channels on intestinal hyperpathia and dysmotility

The Nav1.9 channel is a voltage-gated sodium channel. It plays a vital role in the generation of pain and the formation of neuronal hyperexcitability after inflammation. It is highly expressed in small diameter neurons of dorsal root ganglions and Dogiel II neurons in enteric nervous system. The small diameter neurons in dorsal root ganglions are the primary sensory neurons of pain conduction. Nav1.9 channels also participate in regulating intestinal motility. Functional enhancements of Nav1.9 channels to a certain extent lead to hyperexcitability of small diameter dorsal root ganglion neurons. The hyperexcitability of the neurons can cause visceral hyperalgesia. Intestinofugal afferent neurons and intrinsic primary afferent neurons in enteric nervous system belong to Dogiel type II neurons. Their excitability can also be regulated by Nav1.9 channels. The hyperexcitability of intestinofugal afferent neurons abnormally activate entero-enteric inhibitory reflexes. The hyperexcitability of intrinsic primary afferent neurons disturb peristaltic waves by abnormally activating peristaltic reflexes. This review discusses the role of Nav1.9 channels in intestinal hyperpathia and dysmotility.

A systematic review and meta-analysis of the associations between endometriosis and irritable bowel syndrome

Endometriosis and Irritable Bowel Syndrome (IBS) are common conditions among young women of reproductive age. The etiologies to the diseases are uncertain, but multifactorial pathophysiology has been proposed for each of them. Many studies have examined the two conditions separately, but the literature on the associations between endometriosis and IBS is sparse. However, there is an increasing amount of research on how endometriosis patients are likely to also have a diagnosis of IBS. Furthermore, endometriosis shares several features with IBS, such as low-grade inflammation and visceral hypersensitivity. This systematic review summarized published original articles in English that have compared associations between endometriosis and IBS. The inclusion criteria for articles in the review were: i) endometriosis was diagnosed by surgical methods, ii) gastrointestinal symptoms were examined in a structured manner and iii) IBS was diagnosed by Rome criteria. From the initial 254 publications identified on PubMed, Web of Science and EMBASE, 13 fulfilled the criteria and could finally be included in the summary. The findings from the review showed that women diagnosed with endometriosis seem to have a twofold or threefold risk to also fulfill the criteria for IBS. The summary risk estimate of the four studies included in the meta-analysis was 2.39 (95 % confidence interval: 1.83-3.11). In women initially diagnosed with IBS, some studies reported a threefold risk of having an endometriosis diagnosis. Despite the strong associations reported between the two conditions, this review also revealed a gap in adjusting for factors that may have affected the expression of gastrointestinal symptoms, e.g., phases of the menstrual cycle, medication and psychological aspects, which may have interpretation of the reviewed articles' results. The conclusion of this review is that there is a coexistence of gastrointestinal symptoms fulfilling the Rome criteria in patients with endometriosis, but it is uncertain whether there is a true comorbidity between endometriosis and IBS, or whether the gastrointestinal symptomatology in endometriosis depends on medication. Additionally, the adequacy of the Rome criteria to differentiate IBS from the shared symptomatology of other diseases with visceral hypersensitivity must be further evaluated.

Susceptibility to diarrhea is related to hemodynamic markers of sympathetic activation in the general population

Objectives: Functional gastrointestinal (GI) symptoms, such as IBS (irritable bowel syndrome), have been suggested to be associated with autonomic neuropathy. We therefore examined associations between hemodynamic indices of autonomic control, functional GI symptoms and stress in a population-based cohort.Methods and materials: The study included 2094 participants of the Malmö Offspring Study (mean age 40.6 ± 13.8 years, 53.9% women). 509 (24.3%) reported having GI symptoms the last 2 weeks, without having organic GI disease, and 347 subjects (16.6%) reported IBS. Office and ambulatory 24-h systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were measured. Associations between hemodynamic parameters and abdominal pain, diarrhea, constipation, bloating and flatulence, vomiting and nausea and psychological well-being according to the visual analog scale for IBS (VAS-IBS), and stress, were performed by Spearman's correlation test and linear regression models.Results: Subjects who reported GI symptoms had lower office supine and standing DBP and lower 24 h SBP and DBP compared with those without GI symptoms. Regarding specific symptoms, diarrhea was correlated with 24-h measurements of SBP (rs = 0.197), DBP (rs = 0.173) and heart rate (rs = 0.134). Subjects with the most severe diarrhea had higher 24-h SBP (125.2 vs. 119.0 mmHg; p = .038), DBP (74.0 vs. 69.0 mmHg; p = .033) and heart rate (74.5 vs 71.1 beats/minute; p = .048), after adjustments for confounders, compared to the other. There were no associations between other GI symptoms, IBS, stress and hemodynamic alterations.Conclusion: Functional diarrhea was associated with hemodynamic indices of sympathetic activation, supporting a possible role of the autonomic nervous system in diarrhea.

Increased expression of brain-derived neurotrophic factor is correlated with visceral hypersensitivity in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Visceral hypersensitivity is considered to play a vital role in the pathogenesis of irritable bowel syndrome (IBS). Neurotrophins have drawn much attention in IBS recently. Brain-derived neurotrophic factor (BDNF) was found to mediate visceral hypersensitivity via facilitating sensory nerve growth in pre-clinical studies. We hypothesized that BDNF might play a role in the pathogenesis of diarrhea-predominant IBS (IBS-D).

AIM

To investigate BDNF levels in IBS-D patients and its role in IBS-D pathophysiology.

METHODS

Thirty-one IBS-D patients meeting the Rome IV diagnostic criteria and 20 age- and sex-matched healthy controls were recruited. Clinical and psychological assessments were first conducted using standardized questionnaires. Visceral sensitivity to rectal distension was tested using a high-resolution manometry system. Colonoscopic examination was performed and four mucosal pinch biopsies were taken from the rectosigmoid junction. Mucosal BDNF expression and nerve fiber density were analyzed using immunohistochemistry. Mucosal BDNF mRNA levels were quantified by quantitative real-time polymerase chain reaction. Correlations between these parameters were examined.

RESULTS

The patients had a higher anxiety score [median (interquartile range), 6.0 (2.0-10.0) vs 3.0 (1.0-4.0), P = 0.003] and visceral sensitivity index score [54.0 (44.0-61.0) vs 21.0 (17.3-30.0), P < 0.001] than controls. The defecating sensation threshold [60.0 (44.0-80.0) vs 80.0 (61.0-100.0), P = 0.009], maximum tolerable threshold [103.0 (90.0-128.0) vs 182.0 (142.5-209.3), P < 0.001] and rectoanal inhibitory reflex threshold [30.0 (20.0-30.0) vs 30.0 (30.0-47.5), P = 0.032] were significantly lower in IBS-D patients. Intestinal mucosal BDNF protein [3.46E-2 (3.06E-2-4.44E-2) vs 3.07E-2 (2.91E-2-3.48E-2), P = 0.031] and mRNA [1.57 (1.31-2.61) vs 1.09 (0.74-1.42), P = 0.001] expression and nerve fiber density [4.12E-2 (3.07E-2-7.46E-2) vs 1.98E-2 (1.21E-2-4.25E-2), P = 0.002] were significantly elevated in the patients. Increased BDNF expression was positively correlated with abdominal pain and disease severity and negatively correlated with visceral sensitivity parameters.

CONCLUSION

Elevated mucosal BDNF may participate in the pathogenesis of IBS-D via facilitating mucosal nerve growth and increasing visceral sensitivity.

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.

Increased intestinal mucosal leptin levels in patients with diarrhea-predominant irritable bowel syndrome

AIM

To measure the leptin levels in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) and analyze the relationship of leptin with clinical features, visceral sensitivity, mast cells, and nerve fibers.

METHODS

Forty-two patients with IBS-D fulfilling the Rome III criteria and 20 age- and sex-matched healthy controls underwent clinical and psychological evaluations using validated questionnaires (including IBS Symptom Severity Scale, IBS-specific Quality of Life, Hamilton Anxiety Scale, and Hamilton Depression Scale), along with colonoscopy, colonic mucosal biopsy, and visceral sensitivity testing. Serum leptin levels were assayed using enzyme-linked immunosorbent assay. Mucosal leptin expression and localization were evaluated using immunohistochemistry and immunofluorescence. Mucosal leptin mRNA levels were quantified using quantitative real-time reverse transcription polymerase chain reaction. Mast cell counts and activation rates were investigated by toluidine blue staining. Correlation analyses between these parameters were performed.

RESULTS

There were no statistically significant differences in age, gender, or body mass index between the IBS-D group and the control group. The median IBS Symptom Severity Scale score in the IBS-D group was 225.0 (range, 100-475). IBS-D patients had significantly increased anxiety [IBS-D: median, 6.5; interquartile range (IQR), 3.3; control: median, 2.0; IQR, 2.0; P < 0.001] and depression (IBS-D: median, 7.0; IQR, 3.0; control: median, 3.0; IQR, 2.0; P < 0.001) scores. IBS-D patients had significantly lower first sensation threshold (IBS-D: median, 50.6; IQR, 25.9; control: median, 80.5; IQR, 18.6; P < 0.001), defecation sensation threshold (IBS-D: median, 91.5; IQR, 29.3; control: median, 155.0; IQR, 21.1; P < 0.001) and maximum tolerable threshold (IBS-D: median, 163.2; IQR, 71.2; control: median, 226.2; IQR, 39.3; P < 0.001). Mucosal leptin expression, as reflected by integrated optical density (IBS-D: median, 4424.71; IQR, 4533.63; control: median, 933.65; IQR, 888.10; P < 0.001), leptin mRNA expression (IBS-D: median, 1.1226; IQR, 1.6351; control: median, 0.8947; IQR, 0.4595; P = 0.009), and mast cell activation rate (IBS-D: median, 71.2%; IQR, 12.9%; control group: median, 59.4%; IQR, 18.88%; P < 0.001) were significantly increased in IBS-D patients. The colocalization of leptin and leptin receptors was observed on mast cells and PGP9.5-positive nerve fibers in the intestinal mucosa. Also, leptin expression was positively correlated with anxiety, depression, and the mast cell activation rate, but negatively correlated with the defecation sensation threshold and the maximum tolerance threshold during visceral sensitivity testing (adjusted P < 0.0038).

CONCLUSION

Increased levels of mucosal leptin may interact with mast cells and the nervous system to contribute to the pathogenesis of IBS-D.

Effect of combined consumption of Lactobacillus brevis KB290 and β-carotene on minor diarrhoea-predominant irritable bowel syndrome-like symptoms in healthy subjects: a randomised, double-blind, placebo-controlled, parallel-group trial

People with non-pathological diarrhoea-predominant irritable bowel syndrome (IBS-D)-like symptoms are present at a significant level even in healthy populations, but established prophylaxis is lacking. Previously, we have found that co-administration of Lactobacillus brevis KB290 (KB290) and β-carotene (βC) attenuated murine colitis (potential cause of IBS-D-like symptoms) significantly. Here, we investigated the effect of KB290 and βC on minor IBS-D-like symptoms in healthy volunteers. After a 4-week run-in period, subjects received a KB290 + βC or placebo capsule for 12 weeks, followed by a 4-week washout period. The KB290 + βC group showed a significant improvement in intensity of abdominal pain and stool frequency compared with the placebo group. The KB290 + βC group showed a significantly higher serum concentration of anti-inflammatory cytokine, interleukin-10, compared with the placebo group. In conclusion, we demonstrated that consumption of KB290 + βC improves minor IBS-D-like symptoms and inflammatory status in healthy volunteers. (UMIN000018002).

Increased expression of nerve growth factor correlates with visceral hypersensitivity and impaired gut barrier function in diarrhoea-predominant irritable bowel syndrome: a preliminary explorative study

BACKGROUND

Neural-immune-endocrine network mechanism has attracted increased attention in diarrhoea-predominant irritable bowel syndrome (IBS-D). Pre-clinical evidence indicates that nerve growth factor (NGF) mediates visceral hypersensitivity and gut barrier dysfunction, via interactions with mast cells and sensory nerve fibres.

AIM

To explore the role of nerve growth factor, as well as mast cell-nerve growth factor-nerve interaction in IBS-D pathophysiology.

METHODS

In this cross-sectional study, IBS-D patients and healthy controls first underwent clinical and psychological assessments. Visceral sensitivity to rectal distension was tested. As gut barrier function markers, serum diamine oxidase and d-lactate were detected. Rectosigmoid biopsies were taken for the analyses of nerve growth factor expression, mast cell count and activation, and sensory nerve fibres expressing transient receptor potential vanilloid 1 and calcitonin gene-related peptide. Correlations between these parameters were examined in patients.

RESULTS

Thirty-eight IBS-D patients (28 males, 10 females; average age 30.2 years) and 20 healthy controls (12 males, 8 females; average age 26.8 years) participated in the study. The patients presented increased psychological symptoms, visceral hypersensitivity and impaired gut barrier function. NGF gene expression, mast cell count and sensory nerve fibres were significantly increased in the patients (P < 0.05). In correlation analysis, NGF expression was positively correlated with the disease severity, anxiety and serum diamine oxidase; visceral sensitivity thresholds were negatively associated with NGF expression (Bonferroni corrected P < 0.0029).

CONCLUSIONS

Elevated mucosal NGF may interact with mast cells and sensory nerve fibres, contributing to visceral hypersensitivity and impaired gut barrier function in IBS-D.

Nerve growth factor and diarrhea-predominant irritable bowel syndrome (IBS-D): a potential therapeutic target?

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder characterized by recurrent abdominal pain or discomfort associated with abnormal bowel habits. Diarrhea-predominant IBS (IBS-D) is a major subtype of IBS, the predominant manifestations of which are abdominal pain and diarrhea. The pathogenesis of IBS-D remained unknown until recently. The effects of psychosocial stress, central hypervigilance, neuroendocrine abnormality, disturbed gastrointestinal motility, mucosal immune activation, intestinal barrier dysfunction, visceral hypersensitivity (VH), altered gut flora, and genetic susceptibility may be involved in its development. Recently, increased attention has been placed on the neural-immune-endocrine network mechanism in IBS-D, especially the role of various neuroendocrine mediators. As a member of the neurotrophin family, nerve growth factor (NGF) has diverse biological effects, and participates in the pathogenesis of many diseases. Basic studies have demonstrated that NGF is associated with inflammatory- and stress-related VH, as well as stress-related intestinal barrier dysfunction. The aim of this study is to summarize recent literature and discuss the role of NGF in the pathophysiology of IBS-D, especially in VH and intestinal barrier dysfunction, as well as its potential as a therapeutic target in IBS-D.

Fecal calprotectin for diagnosis of digestive system diseases

Calprotectin is a 36 kDa calcium- and zinc-binding protein that belongs to the S100 family. Calprotectin shows an excellent stability in feces and appears to be superior to conventional fecal markers. Fecal calprotectin concentrations closely correlate with the fecal excretion of in-labelled leukocytes. In addition, fecal calprotectin has an overall high specificity. Therefore, it could be a useful marker for diagnosis of intestinal diseases. In this review we summarize the structure, physical and chemical characteristics of fecal calprotectin and analyze the relationship between calprotectin and intestinal diseases.