Hanne Vanheel

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

Objective Intestinal permeability and psychological stress have been implicated in the pathophysiology of IBD and IBS. Studies in animals suggest that stress increases permeability via corticotropin-releasing hormone (CRH)-mediated mast cell activation. Our aim was to investigate the effect of stress on intestinal permeability in humans and its underlying mechanisms. Design Small intestinal permeability was quantified by a 2 h lactulose–mannitol urinary excretion test. In a first study, 23 healthy volunteers were subjected to four different conditions: control; indomethacin; public speech and anticipation of electroshocks. In a second study, five test conditions were investigated in 13 volunteers: control; after pretreatment with disodium cromoglycate (DSCG); administration of CRH; DSCG+CRH and DSCG+public speech. Results Indomethacin, as a positive comparator (0.071±0.040 vs 0.030±0.022; p<0.0001), and public speech (0.059±0.040; p<0.01), but not the shock protocol increased intestinal permeability. Similarly, salivary cortisol was only increased after public speech. Subgroup analysis demonstrated that the effect of public speech on permeability was only present in subjects with a significant elevation of cortisol. CRH increased the lactulose–mannitol ratio (0.042±0.021 vs 0.028±0.009; p=0.02), which was inhibited by the mast cell stabiliser DSCG. Finally, intestinal permeability was unaltered by public speech with DSCG pretreatment. Conclusions Acute psychological stress increases small intestinal permeability in humans. Peripheral CRH reproduces the effect of stress and DSCG blocks the effect of both stress and CRH, suggesting the involvement of mast cells. These findings provide new insight into the complex interplay between the central nervous system and GI function in man.

Impaired duodenal mucosal integrity and low-grade inflammation in functional dyspepsia

Objective Functional dyspepsia (FD) is an extremely common functional gastrointestinal disorder, the pathophysiology of which is poorly understood. We hypothesised that impaired intestinal barrier function is involved in the onset and persistence of this disorder by inducing low-grade inflammation. Therefore, our aim was to evaluate duodenal mucosal integrity and low-grade inflammation in patients with FD. Design Duodenal biopsy specimens were obtained from 15 patients with FD fulfilling the Rome III criteria and 15 age- and gender-matched healthy volunteers. Transepithelial electrical resistance (TEER) and paracellular permeability were measured in Ussing chambers. Expression of cell-to-cell adhesion proteins was evaluated by real-time PCR, western blot and/or immunofluorescence. Numbers of mast cells, eosinophils and intraepithelial lymphocytes were assessed by immunohistochemistry. Results Patients with FD displayed lower TEER and increased paracellular passage compared with healthy controls, which is indicative of impaired mucosal integrity. In addition, abnormal expression of cell-to-cell adhesion proteins at the level of tight junctions, adherens junctions and desmosomes was shown. Furthermore, patients were characterised by the presence of low-grade inflammation, as demonstrated by increased infiltration of mucosal mast cells and eosinophils. A significant association between the expression level of several cell-to-cell adhesion proteins, the extent of increased permeability and the severity of low-grade inflammation was found. Conclusions These findings challenge the classical paradigm that patients with FD show no structural changes in the gastrointestinal tract. We suggest that impaired intestinal barrier function is a pathophysiological mechanism in FD. Thus, restoration of intestinal barrier integrity may be a potential therapeutic target for treating patients with FD.

Impaired barrier function in patients with house dust mite–induced allergic rhinitis is accompanied by decreased occludin and zonula occludens-1 expression

BACKGROUND Tight junction (TJ) defects have recently been associated with asthma and chronic rhinosinusitis. The expression, function, and regulation of nasal epithelial TJs remain unknown in patients with allergic rhinitis (AR). OBJECTIVE We investigated the expression, function, and regulation of TJs in the nasal epithelium of patients with house dust mite (HDM)-induced AR and in an HDM-induced murine model of allergic airway disease. METHODS Air-liquid interface cultures of primary nasal epithelial cells of control subjects and patients with HDM-induced AR were used for measuring transepithelial resistance and passage to fluorescein isothiocyanate-dextran 4 kDa (FD4). Ex vivo transtissue resistance and FD4 permeability of nasal mucosal explants were measured. TJ expression was evaluated by using real-time quantitative PCR and immunofluorescence. In addition, the effects of IL-4, IFN-γ, and fluticasone propionate (FP) on nasal epithelial cells were investigated in vitro. An HDM murine model was used to study the effects of allergic inflammation and FP treatment on transmucosal passage of FD4 in vivo. RESULTS A decreased resistance in vitro and ex vivo was found in patients with HDM-induced AR, with increased FD4 permeability and reduced occludin and zonula occludens-1 expression. AR symptoms correlated inversely with resistance in patients with HDM-induced AR. In vitro IL-4 decreased transepithelial resistance and increased FD4 permeability, whereas IFN-γ had no effect. FP prevented IL-4-induced barrier dysfunction in vitro. In an HDM murine model FP prevented the allergen-induced increased mucosal permeability. CONCLUSION We found impaired nasal epithelial barrier function in patients with HDM-induced AR, with lower occludin and zonula occludens-1 expression. IL-4 disrupted epithelial integrity in vitro, and FP restored barrier function. Better understanding of nasal barrier regulation might lead to a better understanding and treatment of AR.

Activated intestinal macrophages in patients with cirrhosis release NO and IL- 6 that may disrupt intestinal barrier function

BACKGROUND & AIMS Bacterial infections commonly occur in decompensated cirrhosis resulting from bacterial translocation from the intestine. We studied the role of intestinal macrophages and the epithelial barrier in cirrhosis. METHODS Forty-four patients with NASH/ASH cirrhosis (decompensated n=29, compensated n=15) and nineteen controls undergoing endoscopy were recruited. Serum was obtained and LPS and LBP levels determined. Intestinal macrophages were characterized by flow cytometry, immunohistochemistry, and nitric oxide (NO) production measured in supernatant of cultured duodenal samples. Quantitative RT-PCR was performed on duodenal biopsies assessing 84 inflammatory genes. Protein levels of cytokines/chemokines were assessed in serum and supernatant. The duodenal wall was assessed by electron microscopy, tight junction protein expression determined by RT-PCR, immunohistochemistry, and Western blot and, functional analysis performed by transepithelial resistance measurement and permeability studies. RESULTS Increased plasma LPS, LBP levels and higher numbers of duodenal CD33(+)/CD14(+)/Trem-1(+) macrophages, synthesizing iNOS and secreting NO were present in decompensated cirrhosis. Upregulation of IL-8, CCL2, CCL13 at the transcriptional level, and increased IL-8, and IL-6 were detected in supernatant and serum in cirrhosis. IL-6 and IL-8 co-localised with iNOS(+) and CD68(+), but not with CD11c(+) cells. Electron microscopy demonstrated an intact epithelial barrier. Increased Claudin-2 was detected by Western blot and immunohistochemistry, while decreased transepithelial resistance and increased duodenal permeability were detected in decompensated cirrhosis. CONCLUSIONS Our study shows the presence of activated CD14(+)Trem-1(+)iNOS(+) intestinal macrophages, releasing IL-6, NO, and increased intestinal permeability in patients with cirrhosis, suggesting that these cells may produce factors capable of enhancing permeability to bacterial products.

Changes in gastrointestinal tract function and structure in functional dyspepsia

Functional dyspepsia is an extremely common disorder of gastrointestinal function. The disorder is thought to be heterogeneous, with different pathophysiological mechanisms underlying varied symptom patterns. A diversity of changes in gastrointestinal tract function and structure has been described in functional dyspepsia. These involve alterations in the stomach, such as impaired accommodation, delayed gastric emptying and hypersensitivity, and alterations in the duodenum, such as increased sensitivity to duodenal acid and/or lipids and low-grade inflammation. In this Review, we summarize all these abnormalities in an attempt to provide an integrated overview of the pathophysiological mechanisms in functional dyspepsia.

In Functional Dyspepsia, Hypersensitivity to Postprandial Distention Correlates With Meal-Related Symptom Severity

BACKGROUND & AIMS Hypersensitivity to gastric distention, an important feature of functional dyspepsia, is assessed by stepwise balloon distention of the proximal stomach in fasting patients. However, symptoms of functional dyspepsia are often worse after a meal, so studies of postprandial balloon distentions might be more relevant. We compared the effects of fasting and postprandial stomach distention in patients with functional dyspepsia. METHODS Twenty healthy controls and 62 patients with functional dyspepsia participated in a gastric barostat study at Leuven University Hospital with graded isobaric distentions before and after a liquid meal. On a separate day, all patients underwent a gastric emptying breath test with assessment of postprandial severity of 6 different dyspeptic symptoms scored at 15-minute intervals for 4 hours. For each symptom, a meal-related severity score was obtained by adding all scores; the cumulative symptom score (CSS) was obtained by adding individual symptom severity scores. RESULTS In patients, but not in controls, postprandial sensitivity to balloon distention was significantly greater than fasting sensitivity. The CSS and individual symptom scores did not differ between patients with normal or hypersensitivity to fasting distention, but patients who were hypersensitive to postprandial distention had a significantly higher CSS, along with scores for postprandial fullness, bloating, and nausea (all P < .05). On multivariate analysis, hypersensitivity to postprandial distention was associated with hypersensitivity to fasting distention and with impaired accommodation to a meal. CONCLUSIONS Postprandial, but not fasting, distention thresholds are related to the severity of meal-related symptoms in patients with functional dyspepsia.

Evidence for Neuronal and Structural Changes in Submucous Ganglia of Patients With Functional Dyspepsia

OBJECTIVES:An intact and well-functioning enteric nervous system is necessary to efficiently organize gut function. Functional gastrointestinal disorders are pathological entities in which gut function is impaired without a clearly established pathophysiology. On the basis of the relative ease with which intestinal biopsies can be obtained, and taking advantage of a recently developed optical recording technique, we evaluated whether functional neuronal defects exist in enteric nerves of patients with functional dyspepsia (FD).METHODS:The submucous plexus isolated from duodenal biopsies taken from FD patients and control subjects was used to functionally and morphologically examine nerves and ganglionic architecture (neurons and glial cells). In light of previous studies reporting eosinophil and mast cell infiltration in the gut mucosa of FD patients, we also examined whether these cells infiltrated the submucous plexus and whether this correlated with neuronal activity and specific clinical symptoms.RESULTS:We demonstrate that neuronal functioning is impaired in the submucous plexus of FD patients, as shown by decreased calcium responses to depolarization and electrical stimulation. Glial (S100) and neuronal (HuCD) markers show signs of gliosis, altered ganglionic architecture, and neuronal abnormalities in the submucous plexus of FD patients. We found that eosinophils and mast cells infiltrated the submucous layer of FD patients to a much larger extent than in controls. A significant correlation was found between the number of these cells and the calcium transient amplitudes measured in submucous ganglia.CONCLUSIONS:We provide the first direct evidence that FD is characterized by functional and structural abnormalities within the submucous ganglion plexus, which may be of future predictive and diagnostic value in the treatment of FD patients.

Efficacy of Mirtazapine in Patients With Functional Dyspepsia and Weight Loss

BACKGROUND & AIMS A subset of patients with functional dyspepsia (FD) present with early satiation and weight loss, for which there are no established therapeutic options. We investigated the efficacy of mirtazapine (an antidepressant and antagonist of the histamine receptor H1, the α2 adrenergic receptor, and the serotonin receptors 5-HT2C and 5-HT-3) in patients with FD and weight loss. METHODS We conducted a randomized, placebo-controlled pilot trial that studied 34 patients with FD (29 women; mean age, 35.9 ± 2.3 years) with weight loss >10% of original body weight (mean loss, 12.4 ± 2.3 kg) without depression or anxiety. After a run-in period, patients were randomly assigned to groups given placebo (n = 17) or mirtazapine 15 mg each day for 8 weeks (n = 17) in a double-blind manner. Subjects were evaluated during a 2-week baseline and 8-week treatment for dyspepsia symptom severity, quality of life (on the basis of the Nepean Dyspepsia Index), and gastrointestinal-specific anxiety; they were given a nutrient challenge test and weighed. Data were analyzed by using linear mixed models, followed by planned contrasts with adaptive step-down Bonferroni multiple testing correction. RESULTS Two patients in each group dropped out. At weeks 4 and 8, mirtazapine significantly reduced mean dyspepsia symptom severity scores compared with week 0 (P = .003 and P = .017, respectively); there was no significant reduction in the placebo group (P > .37 for weeks 4 and 8). The difference in change from week 0 between mirtazapine and placebo showed a trend with a large effect size at week 4 (P = .059) that was not significant at week 8 (P = .55). However, improvements from week 0 to weeks 4 and 8 were significantly larger in the mirtazapine group than placebo group for early satiation, quality of life, gastrointestinal-specific anxiety, weight, and nutrient tolerance (mostly with large effect sizes). CONCLUSIONS In a randomized, placebo-controlled trial, mirtazapine significantly improved early satiation, quality of life, gastrointestinal-specific anxiety, nutrient tolerance, and weight loss in patients with FD. ClinicalTrials.gov number: NCT01240096.

Pathophysiological Abnormalities in Functional Dyspepsia Subgroups According to the Rome III Criteria

Objectives:The Rome III criteria proposed to subdivide functional dyspepsia (FD) into a postprandial distress syndrome (PDS) group, characterized by the presence of postprandial fullness and/or early satiety, and an epigastric pain syndrome (EPS) group, characterized by the presence of epigastric pain and/or epigastric burning. It has been suggested that different pathophysiological mechanisms underlie the symptom presentations in these subgroups that might determine treatment choices. The aim of this study was to investigate the prevalence of gastric sensorimotor dysfunction in the PDS, EPS, and overlap groups and to evaluate potential differential associations with dyspeptic symptom scores.Methods:Consecutive FD patients fulfilling Rome III criteria were recruited and they scored frequency of dyspeptic symptoms (postprandial fullness, early satiety, nausea, bloating, epigastric pain, and epigastric burning) over the past 3 months (0–5; 1=once a month or less, 2=two or three times a month, 3=once a week, 4=several times a week, 5=every day). The cumulative symptom score was calculated by adding up the score of these dyspeptic symptoms. Based on these symptom scores, the patients were subdivided into subgroups according to the Rome III consensus: (i) PDS, characterized by postprandial fullness and/or early satiety at least several times a week, (ii) EPS, characterized by epigastric pain and/or epigastric burning at least once a week, and (iii) overlap, fulfilling the criteria for both PDS and EPS. Gastric sensitivity and gastric accommodation were measured using barostat testing, and solid gastric emptying was determined using the [14C]octanoate breath test.Results:A total of 560 FD patients (165 men, age 41.8±0.7 years) were classified into PDS (n=131), EPS (n=50), and overlap (n=379) groups. The prevalence of gastric hypersensitivity, impaired gastric accommodation, and delayed gastric emptying were 37%, 37%, and 23%, respectively, without any differential distribution in Rome III subgroups (P=0.16, P=0.27, and P=0.39 respectively). Comparing the physiological parameters for these gastric sensorimotor functions, there was only a significant difference in the gastric half emptying time between subgroups, with the overlap group having a higher t1/2 (P<0.05) compared with the EPS group. In the overlap group, gastric hypersensitivity was associated with the severity of PDS symptoms (P=0.03), EPS symptoms (P=0.02), and the cumulative symptom score (P=0.02), whereas delayed gastric emptying was associated with nausea (P=0.02) and the cumulative symptom score (P=0.02).Conclusions:Except for gastric emptying in the overlap group, FD subgroups as defined by the Rome III criteria are not differentially associated with putative pathophysiological mechanisms. These observations question the utility of this classification for guiding therapeutic choices in clinical practice.

Postprandial symptoms originating from the stomach in functional dyspepsia.

Functional dyspepsia (FD) is characterized by chronic epigastric symptoms. The stomach has been held responsible for the generation of symptoms, but the latest reports have pointed out that also the duodenum can be implicated in the pathophysiology. The aim of this study was to elucidate which dyspeptic symptoms originate from the stomach and/or from the small intestine after a meal.