Tim Vanuytsel

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.

Long-term Outcome of Pneumatic Dilation in the Treatment of Achalasia

BACKGROUND & AIMS Achalasia is treated with pneumatic dilation or Heller myotomy, but studies suggest poor long-term outcomes. We analyzed long-term outcomes after initial pneumatic dilation and studied factors associated with failure. METHODS A total of 209 patients (111 men; mean age, 51.2 +/- 1.4 years) with achalasia who were treated with pneumatic dilation between 1992 and 2002 were followed. Outcomes were correlated with demographics, presenting symptoms, manometric features, and treatment variables by using chi(2) and Student t tests. RESULTS All patients were initially treated with consecutive esophageal dilations up to balloon diameters of 3.0 (26%), 3.5 (41%), or 4.0 cm (33%). After dilations, mean lower esophageal sphincter (LES) pressure had decreased from 31.3 +/- 1.3 to 14.0 +/- 0.7 mm Hg (P < .0001); dysphagia decreased from 96% to 26%; and 49% had gained an average of 4.6 +/- 0.5 kg (weight loss at presentation was 10.6 +/- 0.7 kg in 39%). During follow-up, 66% required no additional treatment, whereas 23% underwent repeat dilations after 79 +/- 8 months. Patients without recurrence were older (41.2 +/- 2.1 vs 56.6 +/- 1.6 years; P < .0001) and had lower post-treatment LES pressure (17.8 +/- 1.2 vs 12.9 +/- 0.6 mm Hg; P < .005). After 70-month follow-up, balloon dilation yielded good or excellent outcomes in 72% of patients. In nonresponders, rescue surgery yielded higher success rates than botulinum toxin therapy (84% vs 44%). Patient satisfaction ranged from good to excellent in 81% of patients. CONCLUSIONS Treating achalasia with initial dilation and then surgery for short-term failures yielded good long-term results in more than 70% and treatment satisfaction in more than 80% of patients. Management of dilation failures is more problematic.

Obeticholic acid, a farnesoid X receptor agonist, improves portal hypertension by two distinct pathways in cirrhotic rats.

The farnesoid X receptor (FXR) is a nuclear bile acid receptor involved in bile acid homeostasis, hepatic and intestinal inflammation, liver fibrosis, and cardiovascular disease. We studied the effect of short‐term treatment with obeticholic acid (INT‐747), a potent selective FXR agonist, on intrahepatic hemodynamic dysfunction and signaling pathways in different rat models of cirrhotic portal hypertension (PHT). For this, thioacetamide (TAA)‐intoxicated and bile‐duct–ligated (BDL) rats were used as models. After gavage of two doses of 30 mg/kg of INT‐747 or vehicle within 24 hours, in vivo hemodynamics were assessed. Additionally, we evaluated the direct effect of INT‐747 on total intrahepatic vascular resistance (IHVR) and intrahepatic vascular tone (endothelial dysfunction and hyperresponsiveness to methoxamine) by means of an in situ liver perfusion system and on hepatic stellate cell contraction in vitro. FXR expression and involved intrahepatic vasoactive pathways (e.g., endothelial nitric oxide synthase [eNOS], Rho‐kinase, and dimethylarginine dimethylaminohydrolase [DDAH]) were analyzed by immunohistochemistry, reverse‐transcriptase polymerase chain reaction, or western blotting. In both cirrhotic models, FXR expression was decreased. Treatment with INT‐747 in TAA and BDL reactivated the FXR downstream signaling pathway and decreased portal pressure by lowering total IHVR without deleterious systemic hypotension. In the perfused TAA and BDL cirrhotic liver, INT‐747 improved endothelial vasorelaxation capacity, but not hyperresponsiveness. In both groups, this was associated with an increased eNOS activity, which, in TAA, related to down‐regulation of Rho‐kinase and in BDL to up‐regulation of DDAH‐2. Conclusion: FXR agonist INT‐747 improves PHT in two different rat models of cirrhosis by decreasing IHVR. This hemodynamic effect relates to increased intrahepatic eNOS activity by pathways that differ depending on the etiology of cirrhosis. (Hepatology 2014;59:2286–2298)

Botulinum toxin reduces Dysphagia in patients with nonachalasia primary esophageal motility disorders.

BACKGROUND & AIMS Endoscopic injection of botulinum toxin (BTX) has shown benefits for patients with diffuse esophageal spasm (DES) and nutcracker esophagus (NE) in small uncontrolled trials. We investigated the effect of BTX on symptoms of patients with DES or NE and assessed manometry findings in a prospective, double-blind, randomized, controlled study. METHODS We assessed 22 patients with dysphagia-predominant, manometry-confirmed DES or NE (6 men; age, 63 ± 2 y) at a tertiary care medical center. Patients were given injections of BTX (8 × 12.5 U) or saline (8 × 0.5 mL) in 4 quadrants, at 2 and 7 cm above the esophagogastric junction. After 1 month, patients crossed over between groups and received endoscopic injections of BTX or saline. When the study began and 4 weeks after each injection, the patients were assessed by esophageal manometry and completed a symptom questionnaire (to determine solid and liquid dysphagia, chest pain, and regurgitation and heartburn; all scored 0-4). Responders were defined based on modified Vantrappen criteria for achalasia. RESULTS After BTX injections, patients had significant decreases in total symptom scores (sum of solid and liquid dysphagia and chest pain; from 7.6 ± 0.7 to 4.8 ± 0.8; P = .01); this decrease was not observed in patients who received saline injections. Moreover, BTX injection stabilized unintentional weight loss (weight gain of 0.3 ± 0.3 after BTX injection vs further weight loss of 1.6 ± 0.5 kg after saline injection; P = .01). Fifty percent of patients had a response 1 month after BTX injection, compared with 10% after saline injection (P = .04); 30% still had a response 1 year after BTX injection. BTX injection also caused a significant decrease in the mean esophagogastric junction pressure, compared with baseline (15.8 ± 1.7 vs 24.0 ± 2.8 mm Hg; P = .02). CONCLUSIONS In a prospective controlled study of patients with DES and NE, injections of BTX reduced symptoms and stabilized unintentional weight loss. TRIAL REGISTRY http://www.targid.eu, ML2669, ML6294.

The FXR Agonist Obeticholic Acid Prevents Gut Barrier Dysfunction and Bacterial Translocation in Cholestatic Rats

Bacterial translocation (BTL) drives pathogenesis and complications of cirrhosis. Farnesoid X-activated receptor (FXR) is a key transcription regulator in hepatic and intestinal bile metabolism. We studied potential intestinal FXR dysfunction in a rat model of cholestatic liver injury and evaluated effects of obeticholic acid (INT-747), an FXR agonist, on gut permeability, inflammation, and BTL. Rats were gavaged with INT-747 or vehicle during 10 days after bile-duct ligation and then were assessed for changes in gut permeability, BTL, and tight-junction protein expression, immune cell recruitment, and cytokine expression in ileum, mesenteric lymph nodes, and spleen. Auxiliary in vitro BTL-mimicking experiments were performed with Transwell supports. Vehicle-treated bile duct-ligated rats exhibited decreased FXR pathway expression in both jejunum and ileum, in association with increased gut permeability through increased claudin-2 expression and related to local and systemic recruitment of natural killer cells resulting in increased interferon-γ expression and BTL. After INT-747 treatment, natural killer cells and interferon-γ expression markedly decreased, in association with normalized permeability selectively in ileum (up-regulated claudin-1 and occludin) and a significant reduction in BTL. In vitro, interferon-γ induced increased Escherichia coli translocation, which remained unaffected by INT-747. In experimental cholestasis, FXR agonism improved ileal barrier function by attenuating intestinal inflammation, leading to reduced BTL and thus demonstrating a crucial protective role for FXR in the gut-liver axis.

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.

Dual Inhibition of Endocannabinoid Catabolic Enzymes Produces Enhanced Antiwithdrawal Effects in Morphine-Dependent Mice:

Inhibition of the endocannabinoid catabolic enzymes, monoacylglycerol lipase (MAGL) or fatty acid amide hydrolase (FAAH) attenuates naloxone-precipitated opioid withdrawal signs in mice via activation of CB1 receptors. Complete FAAH inhibition blocks only a subset of withdrawal signs, whereas complete MAGL inhibition elicits enhanced antiwithdrawal efficacy, but is accompanied with some cannabimimetic side effects. Thus, the primary objective of the present study was to determine whether combined, full FAAH inhibition and partial MAGL represents an optimal strategy to reduce opioid withdrawal. To test this hypothesis, we examined whether combined administration of high-dose of the FAAH inhibitor PF-3845 and low-dose of the MAGL inhibitor JZL184, as well as the novel dual FAAH-MAGL inhibitor SA-57, which is 100-fold more potent in inhibiting FAAH than MAGL, would prevent spontaneous withdrawal in morphine-dependent mice, a model with greater face validity than precipitating withdrawal with μ-opioid receptor antagonists. Strikingly, a combination of low-dose JZL184 and high-dose PF-3845 as well as the dual inhibitor SA-57 reduced all abrupt withdrawal signs (ie, platform jumping, paw flutters, head shakes, diarrhea, and total body weight loss), but did not elicit any cannabimimetic side effects. In addition, JZL184 or PF-3845 blocked naloxone-precipitated hypersecretion in morphine-dependent small intestinal tissue. Collectively, these results are the first to show that endocannabinoid catabolic enzyme inhibitors reduce abrupt withdrawal in morpine-dependent mice and are effective in a novel in vitro model of opioid withdrawal. More generally, these findings support the idea that joint MAGL and FAAH inhibition represents a promising approach for the treatment of opioid dependence.

Conservative management of esophageal perforations during pneumatic dilation for idiopathic esophageal achalasia.

BACKGROUND & AIMS Esophageal perforation is the most serious adverse event of pneumatic dilation (PD) for achalasia; it is usually managed by surgical repair. We investigated risk factors for esophageal perforation after PD and evaluated safety and long-term outcome of nonsurgical management strategies. METHODS We analyzed medical records of patients with achalasia who were treated with PD from 1992-2010 at the University Hospital Gasthuisberg in Leuven, Belgium; all patients with esophageal perforation were contacted to determine long-term outcomes. Achalasia outcomes were assessed by using the Vantrappen criteria. RESULTS Of 830 PD procedures performed on 372 patients with manometry-confirmed achalasia (57 ± 1 years, 51% male), 16 were complicated by transmural esophageal perforation (4.3% of patients, 1.9% of dilations). Age >65 years was the only significant risk factor for complications (odds ratio, 3.5; 95% confidence interval, 1.2-10.2). All patients were treated conservatively with broad-spectrum antibiotics and nothing by mouth. In 6 patients (38%) the clinical course was further complicated by a pleural effusion, which required a drain in 4 patients. One patient (6%) died of mediastinal hemorrhage within 12 hours after PD. Patients with complications were discharged after 19 ± 2.3 days, compared with 4 ± 0.2 days for those without complications (P < .0001). Long-term outcomes (mean follow-up, 84 ± 14 months) were determined for 12 patients (75%); 11 had excellent or good outcomes (69%), and 1 had a moderate outcome (6%). CONCLUSIONS Age >65 years is a significant risk factor for esophageal perforation after PD. Nonsurgical management of transmural esophageal tears is feasible, with favorable short-term and long-term outcomes, but is not devoid of complications.

The role of Haptoglobin and its related protein, Zonulin, in inflammatory bowel disease

Crohn’s disease (CD) and ulcerative colitis (UC), collectively called inflammatory bowel disease (IBD), are immune-mediated conditions characterized by a chronic inflammation of the gut. Their precise etiology is unknown, although an increased intestinal permeability has been shown to play a central role in the pathogenesis of IBD. The intestinal epithelium provides the largest interface between the external environment and the host, and is thus a crucial regulation site of innate and adaptive immunity. Zonulin is one of the few known physiological mediators of paracellular intestinal permeability. It was found upregulated in different immune diseases like Celiac disease and Type 1 Diabetes (T1D). Recently, human zonulin was identified as prehaptoglobin-2 (pre-HP2) which before only had been regarded as the inactive precursor for HP2. Haptoglobin (HP) is a hemoglobin-binding protein with immunomodulatory properties. Its gene harbors a common polymorphism with 2 different alleles: HP1 and HP2. Allele HP2 and genotype HP22 has been shown to be overrepresented in different immune diseases like Rheumatoid Arthritis (RA), Systemic Lupus Erythematosus (SLE) and T1D, and has also been found to be more frequent in patients with IBD (UC and CD) than in healthy controls. In order to get some clues about the mechanism of action of HP(2) in IBD pathogenesis, we here review the current state of knowledge about zonulin and haptoglobin structure and function, and their plausible role in immune mediated diseases with an emphasis on IBD.