Intestinal permeability in children/adolescents with functional dyspepsia

Breaking Barriers in Functional Dyspepsia: A Systematic Review and Meta-analysis on Duodenal Tight Junction Protein Expression

BACKGROUND/AIMS

Disruptions in tight junction (TJ) protein expression leading to duodenal epithelial barrier impairment may contribute to increased intestinal permeability, potentially playing a role in functional dyspepsia (FD) pathophysiology. Currently published studies evaluated the role of several TJ proteins in FD patients with inconsistent results. Therefore, we conducted this systematic review and metaanalysis to evaluate the duodenal mucosal expression of several TJ proteins in FD.

METHODS

We performed a systematic electronic search on PubMed, EMBASE, and Scopus using predefined keywords. Diagnosis of FD by Rome III or Rome IV criteria was considered acceptable. Full articles satisfying our inclusion and exclusion criteria were included. The principal summary outcome was the mean difference of several TJ proteins in FD patients and control subjects.

RESULTS

A total of 8 and 5 studies were included in our qualitative and quantitative synthesis, respectively, with a total population of 666 participants, out of which 420 were FD patients. No significant differences were observed between FD patients and controls in the expression of claudin-1 (-0.102 [95% CI, -0.303, 0.099]), claudin-2 (0.161 [95% CI, -0.134, 0.456)], claudin-3 (0.278 [95% CI, -0.280, 0.837]), claudin-4 (0.045 [95% CI, -0.264, 0.354]), ZO-1 (-0.221 [95% CI, -0.683, 0.241]), ZO-2 (-0.070 [95% CI, -0.147, 0.007]), ZO-3 (-0.129 [95% CI, -0.376, 0.118]), β-catenin (-0.135 [95% CI, -0.484, 0.214]), E-cadherin (-0.083 [95% CI, -0.229, 0.063]), and occludin (-0.158 [95% CI, -0.409, 0.093]).

CONCLUSIONS

The expressions of all evaluated proteins including claudin-1, claudin-2, claudin-3, claudin-4, ZO-1, ZO-2, ZO-3, β-catenin, E-cadherin, and occludin did not significantly differ between FD patients and controls. However, due to the limited number of included studies, results should be interpreted with caution.

Duodenal Eosinophils and Mast Cells in Functional Dyspepsia: A Systematic Review and Meta-Analysis of Case-Control Studies

BACKGROUND & AIMS

This study explored the link between duodenal eosinophils and mast cells in patients with functional dyspepsia (FD).

METHODS

MEDLINE (PubMed) and Embase electronic databases were searched until June 2021 for case-control studies reporting duodenal eosinophils and mast cells in FD. Pooled standardized mean difference (SMD), odds ratio, and 95% CIs of duodenal eosinophils and mast cells in FD patients and controls were calculated, using a random-effects model.

RESULTS

Twenty-two case-control studies with 1108 FD patients and 893 controls were identified. Duodenal eosinophils (SMD, 1.29; 95% CI, 0.85-1.73; P = .0001) and mast cells (SMD, 2.11; 95% CI, 1.14-3.07; P = .0001) were increased in FD patients compared with controls. Substantial heterogeneity was found (I2 = 93.61, P = .0001; and I2 = 96.69, P = .0001, respectively) and visual inspection of funnel plots confirmed publication bias. Degranulation of duodenal eosinophils was significantly higher in FD patients compared with controls (odds ratio, 3.78; 95% CI, 6.76-4.48; P = .0001), without statistically significant heterogeneity. We conducted a sensitivity analysis for duodenal eosinophils, by including only high-quality studies, and the results remained unchanged (SMD, 1.73; 95% CI, 1.06-2.40; P = .0001), with substantial heterogeneity. Postinfectious FD patients had increased duodenal eosinophils compared with controls (SMD, 3.91; 95% CI, 1.32-6.51; P = .001) and FD patients without any history of infection (SMD, 1.42; 95% CI, 0.88-1.96; P = .001). Helicobacter pylori-negative FD patients had significantly higher duodenal eosinophils compared with controls (SMD, 3.98; 95% CI, 2.13-5.84; P = .0001), with substantial heterogeneity. No significant difference in duodenal eosinophils was seen according to FD subtypes.

CONCLUSIONS

This meta-analysis suggests a link between duodenal microinflammation and FD. However, the quality of evidence is very low, largely owing to the unexplained heterogeneity and serious risk of publication bias in all comparative analyses. Thus, causality remains uncertain and further studies are required.

The Role of Leaky Gut in Functional Dyspepsia

Patients with functional dyspepsia (FD) complain of epigastric symptoms with no identifiable cause. Increased intestinal permeability has been described in these patients, especially in the proximal small bowel or duodenum, and was associated with mucosal immune activation and symptoms. In this review, we discuss duodenal barrier function, including techniques currently applied in FD research. We summarize the available data on duodenal permeability in FD and factors associated to increased permeability, including mucosal eosinophils, mast cells, luminal and systemic factors. While the increased influx of antigens into the duodenal mucosa could result in local immune activation, clinical evidence for a causal role of permeability is lacking in the absence of specific barrier-protective treatments. As both existing and novel treatments, including proton pump inhibitors (PPI) and pre- or probiotics may impact duodenal barrier function, it is important to recognize and study these alterations to improve the knowledge and management of FD.

Brain to Belly: Abdominal Variants of Migraine and Functional Abdominal Pain Disorders Associated With Migraine

Migraine is one of the most frequent causes of primary headache and 9% of children suffer from migraines. Most children will continue to experience migraine attacks as adults, therefore it is imperative that we have a thorough understanding of this major health issue. This article considers the so-called abdominal variants of migraine, which are more commonly seen in children rather than adults: abdominal migraine, cyclic vomiting syndrome, and infantile colic. Other functional abdominal pain disorders such as irritable bowel syndrome and functional dyspepsia have also been linked to migraine in clinical studies. The common pathophysiological root of these diseases seems to be the gut-brain axis mechanism. Abdominal variants of migraine are considered pediatric precursors of migraine whereas the functional abdominal pain disorders related to migraine seem to share a pathophysiological root with no temporarily link as for today. In this review we aim to describe the epidemiological background, the current pathophysiological theories and the relationship of each disease to migraine. This review is the first to compile abdominal variants of migraine and functional abdominal pain disorders associated with migraine and we endeavor to elucidate the broad spectrum of migraine-related episodes in children.

Sini San ameliorates duodenal mucosal barrier injury and low‑grade inflammation via the CRF pathway in a rat model of functional dyspepsia

The gut-brain interaction is associated with impaired duodenal mucosal integrity and low-grade inflammation, which have been proven to be important pathological mechanisms of functional dyspepsia (FD). Sini San (SNS) is a classical Chinese medicine used to treat FD, but its underlying mechanisms are poorly understood. The aim of the present study was to evaluate the effects of SNS on duodenal mucosal barrier injury and low-grade inflammation with FD, and to assess its potential molecular mechanisms on the brain-gut axis. FD rats were established using the iodoacetamide and tail-squeezed methods. The expression of corticotropin-releasing factor (CRF), CRF receptor 1 (CRF-R1) and CRF-R2, were determined by western blot analysis and/or immunohistochemistry (IHC). In addition, mast cell (MC) migration was assessed by IHC with an anti-tryptase antibody, and histamine concentration was quantified using ELISA. The mRNA expression levels of tryptase and protease-activated receptor 2 (PAR-2) were quantified using reverse transcription-quantitative PCR, and the protein expression levels of zona occludens protein 1 (ZO-1), junctional adhesion molecule 1 (JAM-1), β-catenin and E-cadherin were determined via western blot analysis. It was demonstrated that the expression level of CRF was downregulated in the central nervous system and duodenum following SNS treatment, and that SNS modulated the expression of both CRF-R1 and CRF-R2. In addition, SNS suppressed MC infiltration and the activity of the tryptase/PAR-2 pathway in the duodenum. Furthermore, treatment with SNS restored the normal expression levels of ZO-1, JAM-1 and β-catenin in FD rats. These findings suggested that the therapeutic effects of SNS on FD were achieved by restoring mucosal barrier integrity and suppressing low-grade inflammation in the duodenum, which was at least partially mediated via the CRF signaling pathway.

The role of mast cells in pediatric gastrointestinal disease

Mast cells are granulocytes derived from CD34+ pluripotent progenitor cells that demonstrate plasticity in their development, leaving the bone marrow and differentiating in the tissue where they ultimately reside. They are best known for their role in the allergic response, but also play a prominent immunoregulatory role in other processes, including immune tolerance, the innate immune response, angiogenesis, wound healing and tissue remodeling. Mast cells are found throughout the gastrointestinal tract; their metabolic products influence and regulate intestinal epithelial and endothelial function, gastrointestinal secretion, intestinal motility and absorption, and contribute to host defense. They also play an important role in the development of visceral hypersensitivity through bidirectional interaction with the enteric nervous system. Mast cells have been found to have an increasingly important role in the pathophysiology of a number of pediatric gastrointestinal diseases. This review summarizes the current understanding of the role that mast cells play in the development of pediatric gastrointestinal disorders, including eosinophilic esophagitis, functional dyspepsia, irritable bowel syndrome, celiac disease, inflammatory bowel disease, histologically negative appendicitis, Hirschsprung’s disease, intestinal neuronal dysplasia, and food protein-induced enterocolitis syndrome.

Functional dyspepsia is associated with duodenal eosinophilia in an Australian paediatric cohort

BACKGROUND

The pathophysiology of functional dyspepsia (FD) remains unknown. Duodenal eosinophil infiltration has been reported.

AIM

To assess the association between dyspeptic symptoms and duodenal eosinophilia in children undergoing upper gastrointestinal endoscopy.

METHODS

In this retrospective cohort study, children with normal upper endoscopy and routine histology at a single tertiary paediatric centre between 2010 and 2014 were included. FD was defined as epigastric pain or discomfort >2 months without response to acid suppression. Controls presented with nonerosive reflux disease, dysphagia or rumination syndrome. Intramucosal eosinophil counts were compared between the groups using uni- and multivariate regression analyses.

RESULTS

Thirty-six cases and 36 nonmatched controls were identified. Atopic history (39% vs. 25%) and psychological comorbidity (53% vs. 39%; both P = 0.2) were frequent in cases and controls. Self-reported nausea (64% vs. 17%; P < 0.0001), lethargy (19% vs. 0%; P = 0.005) and family functional gastrointestinal disorder(FGID) (28% vs. 3%; P = 0.003) were more common in cases than controls. Duodenal eosinophil counts [median (IQR): 151 (118-207) vs. 76 (60-106) per mm² ; P < 0.001] were significantly higher in cases than controls with >112 eosinophils per mm² predictive for FD (OR: 33.6, 95% CI: 7.1-159.0; P < 0.001). Duodenal eosinophilia was associated with weight loss (OR: 7.1, 95% CI: 1.1-45.5; P = 0.04).

CONCLUSIONS

Functional dyspepsia in children is strongly associated with duodenal eosinophilia, in the absence of endoscopic or routine histological findings. Frequent atopic and psychological comorbidity illustrate likely multifactorial mechanisms.

[Current Status of Translational Research on Functional Dyspepsia]

Functional dyspepsia (FD) has a diverse pathophysiology and treatment is difficult. Translational research to understand its pathophysiology is underway. Hormonal factors, including ghrelin, seem promising, offering an understanding of appetite and eating. Functional MRI brain study can expand our knowledge of the brain-gut axis. Finally, immune systems research, including mast cells, can help with comprehensive understanding of FD. The clinical approaches based on these translational research projects are necessary to improve understanding of FD, leading to more effective treatment.

The role of mast cells in functional GI disorders

Functional gastrointestinal disorders (FGIDs) are characterized by chronic complaints arising from disorganized brain-gut interactions leading to dysmotility and hypersensitivity. The two most prevalent FGIDs, affecting up to 16-26% of worldwide population, are functional dyspepsia and irritable bowel syndrome. Their etiopathogenic mechanisms remain unclear, however, recent observations reveal low-grade mucosal inflammation and immune activation, in association with impaired epithelial barrier function and aberrant neuronal sensitivity. These findings come to challenge the traditional view of FGIDs as pure functional disorders, and relate the origin to a tangible organic substrate. The mucosal inflammatory infiltrate is dominated by mast cells, eosinophils and intraepithelial lymphocytes in the intestine of FGIDs. It is well established that mast cell activation can generate epithelial and neuro-muscular dysfunction and promote visceral hypersensitivity and altered motility patterns in FGIDs, postoperative ileus, food allergy and inflammatory bowel disease. This review will discuss the role of mucosal mast cells in the gastrointestinal tract with a specific focus on recent advances in disease mechanisms and clinical management in irritable bowel syndrome and functional dyspepsia.

Intestinal permeability in children with recurrent respiratory and gastrointestinal symptoms

AIM

Increased intestinal permeability has been reported in asthmatic subjects as well as in patients with gastrointestinal disease, thus suggesting the involvement of all the mucosal immune system. We aimed to assess intestinal permeability according to recurrent respiratory and gastrointestinal symptoms in children with asthma and children with functional gastrointestinal disorders (FGIDs).

METHODS

In 108 outpatients aged 3-14 years (45 asthmatic, 63 with FGIDs), we measured the urinary lactulose/mannitol (L/M) ratio, performed allergy skin prick tests and administered questionnaires for recurrent respiratory and gastrointestinal symptoms starting from at least 2 months which persisted over the previous 4 weeks. L/M ratios were compared with previously reported normal values yielded by our chromatographic method (liquid chromatography-mass spectrometry).

RESULTS

High L/M ratios (>0.030) were less frequent in asthmatic children than in children with FGIDs (9/45: 20% vs. 41/63: 65%, P < 0.001). High L/M ratios were associated with gastrointestinal symptoms in 8/9 asthmatic (P < 0.05) and 39/41 subjects with FGIDs (P < 0.005). L/M ratios were not associated with respiratory symptoms or atopy. In a regression model, a high L/M was predicted by low height, absence of asthma and presence of gastrointestinal symptoms (r = 0.72, P < 0.001).

CONCLUSIONS

Increased intestinal permeability is associated with recurrent gastrointestinal symptoms rather than with recurrent respiratory symptoms in both asthmatic children and those with FGIDs. Our findings do not support the hypothesis of mucosal intestinal damage following an inflammatory stimulus in the respiratory mucosa.