Introduction

Irritable bowel syndrome (IBS) is one of the most frequent gastrointestinal disorders with high impact on quality of life and national health systems. Diarrhea predominant IBS (IBS-D) is characterized by abdominal pain and chronic diarrhea. Elevated intestinal permeability is a pathophysiological element of the disease pathogenesis. Mucus layer is a novel target of IBS research.

Aims & Methods

Our aims were to examine the permeability and mucus alterations in IBS-D patients’ different colonic segments and the effect of formulation of xyloglucan (XG), pea protein (PP), grape seed extract (GS) and xylo-oligosaccharides (XOS) on pain and intestinal permeability in IBS-D subjects.
Methods:14 subjects (IBS-D patients and control) were involved. After initial colonoscopy with biopsy sampling XG+PP+GS+XOS was administered to IBS-D patients for 12 weeks. Stool count and pain scores were documented. After treatment, colonoscopy was repeated. Permeability of biopsy samples was measured in Ussing-chambers. Adherent mucus layer thickness and Muc-2 expression were evaluated by histology/immunohistochemistry.

Results

XG+PP+GS+XOS treatment significantly reduced diarrhea and abdominal pain. Intestinal permeability in IBS-D patients was elevated compared to controls, XG+PP+GS+XOS restored permeability in ascendent colon. PAS-stained mucus layer was significantly thinner in IBS-D compared to controls. XG+PP+GS+XOS therapy caused a further reduction in mucus thickness. After XG+PP+GS+XOS treatment, proportion of Muc-2 positive cells was reduced compared to controls.

Conclusion

The study shows the physiological variance regarding to the adherent mucus thickness and mucus secreting cell count in the different colon segments. Our study verifies the segmental difference in permeability alteration and shows adherent mucus thickness reduction in IBS-D. These results show the segmentally different pathophysiology in IBS-D. Mucus thickness alteration can be a new therapeutic target for the treatment. In fact, treatment with XG PP+GS+XOS significantly improved abdominal pain, and diarrhea. Moreover, it was able to restore the permeability in IBS-D patients to a physiological state. Based on this study, XG+PP+GS+XOS can be considered as an effective therapy for IBS-D symptoms.
Funded: by Hungarian National Research, Development and Innovation Office under grant agreement No.116370.

Introduction

Irritable bowel syndrome (IBS) is a complex multifactorial disorder characterized by recurrent abdominal pain associated with defecation or a change in bowel habits. Patients with IBS often complain of extra-intestinal symptoms resulting in impaired related quality of life. Growing evidence support the hypothesis that intestinal barrier dysfunction has a central role in the pathophysiology of IBS being the interface between the gut lumen and the deeper intestinal layers as well as the brain.

Aims & Methods

The aims of this study were: to characterize the epithelial and vascular barriers; to correlate molecular, morphological and functional aspects of epithelial and vascular barriers with IBS symptoms. 66 healthy subjects (AC) and 223 patients with IBS (112 IBS-D, 58 IBS-C and 53 IBS-M) were enrolled in the study. Rome IV criteria, Bowel disease questionnaire, Short Form 36, Hospital Anxiety Depression Scale were used to phenotype patients. Sugar test was used to evaluate in vivo permeability. The vascular barrier was characterized by using immunohistochemistry, western blot and electron microscopy. Vascular permeability was evaluated by assessing two markers: plasmalemma vesicle–associated protein-1 (PV1) and vascular endothelial cadherin (VEC). A translational model based on Caco-2 cells or HUVEC was used to evaluate permeability changes induced by mediators spontaneously released by mucosal biopsies and to highlight the underlying molecular mechanisms. Correlation analyses have been performed among experimental and clinical data.

Results

Compared to AC, lactulose (P<0.05), sucralose (P<0.01), sucrose (P<0.01) excretion and the L/M ratio (P<0.01) were significantly increased in IBS patients. Soluble mediators released by mucosal biopsies of IBS patients increased Caco-2 permeability compared to AC mediators (P<0.05) via a down-regulation of tight junction gene expression. Blood vessels were significantly increased by 1.5 fold in the colonic mucosa of IBS patients compared to AC (P<0.01). PV1 expression was increased (P<0.01) while VEC expression was decreased in the colonic mucosa of IBS group compared to AC (P<0.05). IBS mucosal mediators increased HUVEC permeability compared to AC mediators. The HUVEC changes associated with IBS samples were mediated by a protease-activated receptor (PAR)2 dependent mechanism resulting in VEC down-regulation. Significant correlations emerged among permeability changes and intestinal, extra-intestinal symptoms and health-related quality of life reported by IBS patients.

Conclusion

Epithelial and vascular barriers are compromised in IBS and are likely involved in symptom development.

Disclosure

Nothing to disclose

Introduction

Irritable bowel syndrome (IBS) is a disorder of brain-gut interaction often accompanied by psychiatric and/or somatic comorbidities. Intestinal barrier dysfunction has long been hypothesised to be a key player in IBS pathophysiology. However, it is unknown how psychiatric and somatic comorbidities affect intestinal barrier dysfunction. This study aims to assess intestinal barrier function in a large multicentric cohort of adult IBS patients with and without psychiatric/somatic comorbidities.

Aims & Methods

IBS patients (Rome IV) with (N=197) and without (N=171) comorbidities, and healthy volunteers (N=23), were included in six European hospitals. Intestinal permeability (IP) was assessed in vivo with the lactulose-mannitol-sucralose test (LMS) and ex vivo in colonic biopsies using Ussing chambers. Sugar concentrations in the urine were assessed through HPLC-ELSD and GC-MS. The L/M ratio after 2 hours was used as an estimation of the small intestinal permeability, and the %S excreted and the S/M ratio from 2 to 24 hours, for colonic permeability. Colonic biopsies were collected from 17 controls and 18 IBS patients and mounted in Ussing chambers to measure the paracellular permeability to FITC-dextran (4 kDa).

Results

When compared with healthy controls, L/M ratio did not differ in IBS patients with (p=0.33) or without comorbidities (p=0.44). Moreover, the %S excreted and S/M were not altered in IBS patients with (respectively p=0.3 and p=0.09) and without (p=0.14, p=0.1) comorbidities. Interestingly, when comparing results from IBS patients among recruiting hospitals in different parts of Europe, significant differences were found in L/M ratio (p<0.0001), %S (p<0.0001), and S/M ratio (p<0.0001). Lastly, paracellular permeability assessed ex vivo in colonic biopsies was not different between IBS patients and controls (p=0.46).

Conclusion

These results suggest that psychiatric and somatic comorbidities do not alter small intestinal and colonic permeability in IBS patients. Interestingly, our results highlight a strong variability between IBS patients from different countries, which may be explained by lifestyle, environmental, and genetic factors. Further investigations are needed to better understand these findings.

Disclosure

no conflicts of interest

Introduction

Gut metabolites are suggested to be potential etiological factors of irritable bowel syndrome (IBS). However, the potential mechanisms remain unclear.

Aims & Methods

This study aimed to elucidated the effect and mechanism of gut metabolite homocysteine(Hcy) in IBS development. A stress-induced IBS model was established using neonatal maternal separation (NMS), while a post-inflammatory IBS (PI-IBS) model was constructed by intracolonic administration of trinitrobenzene sulfonic acid (TNBS). A high-methionine diet was applied to elevate homocysteine levels in both blood and feces of mice or rats. Visceral hypersensitivity was assessed by measuring abdominal withdrawal reflex (AWR) and visceral motor responses (VMR). Carmine red was used to determine whole intestinal transit time. The composition of the gut microbiota in rats fecal samples was analyzed by using 16S rRNA sequencing. A series of cell and molecular experiments, including immunostaining, western blot and ELISA was conducted to illustrate the mechanism.

Results

We found that fecal Hcy levels were significantly elevated in both patients with IBS and rats with IBS induced by water avoidance stress (WAS). Moreover, fecal Hcy levels were positively correlated with the severity of IBS symptoms in patients. Next, we investigated the effects of Hcy on the gut-brain axis in NMS rat model and TNBS mice model. Our study showed that elevated Hcy in stool exacerbated visceral hypersensitivity, increased intestinal permeability and disrupted the mucus barrier of IBS rats/mice. Interestingly, folic acid supplementation lowered the Hcy levels and alleviated the effect of Hcy in exacerbating IBS phenotype. Mechanistically, treatment of Hcy inhibited the expression of NLR family pyrin domain containing 6 (NLRP6) and downregulated mucin MUC2 expression in LS174T and intestinal organoids, and impaired the expression of tight junction proteins ZO1 and Occludin in Caco2. Genetic overexpression of NLRP6 and PPARγ agonist Rosiglitazone rescued the inhibitory effect of Hcy on MUC2 expression. In addition, by using 16S rRNA sequencing, we found that Hcy reduced gut bacterial diversity and lowered the abundances of Coprococcus, Roseburia and Acetitomaculum in NMS rats.

Conclusion

Our study showed that gut metabolite Hcy was involved in the pathogenesis of IBS by disrupting mucus barrier and disturbing gut microbiota, indicating Hcy as a therapeutic target and folic acid administration as a potential strategy for IBS management.

Introduction

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder characterized by abdominal pain and changes in bowel habits. Small intestinal bacterial overgrowth (SIBO) refers to a group of gastrointestinal syndromes caused by an excessive number of bacteria in the small intestine. Up to now, the relationship between IBS and SIBO remains contentious. So we set out to investigate the differences between these two conditions.

Aims & Methods

Participants who met the Rome III diagnostic criteria for IBS and had a negative lactulose hydrogen and methane breath test (LHMBT) were diagnosed with IBS. Those who presented with gastrointestinal symptoms and had a positive LHMBT were diagnosed with SIBO. Overlapping cases were excluded. Participants who had a negative LHMBT and no significant abdominal symptoms were classified as healthy controls (HC). All participants were instructed to provide fecal samples for 16S rRNA sequencing.

Results

Our results showed that a history of enteritis was more common in IBS patients, and the severity of gastrointestinal symptoms was significantly higher in IBS and SIBO groups compared to healthy controls. IBS patients also reported more severe symptoms than SIBO. Additionally, IBS patients were more affected by their symptoms, while the SIBO group reported more dissatisfaction with bowel habits. We observed differences in dietary intake between the groups, with IBS patients having the highest total energy and protein intake, and the lowest dietary fiber intake. SIBO patients had higher fat intake and significantly lower carbohydrate intake compared to the other two groups. Regarding the fecal microbiome, both IBS and SIBO patients had higher structural diversity and lower functional diversity than the HC group. The abundance of Firmicutes/Bacteroidetes in the IBS group was significantly higher than in the other two groups. Our analyses indicated that the fecal microbiome could significantly distinguish the three groups, and specific bacterial species were associated with different symptoms in each group. In SIBO, Thalassospira and Christensenellaceae_group were associated with intestinal motility abnormalities, while Ruminococcaceae_group, Butyricimonas, and Oscillospira were associated with gas production. In the IBS group, Klebsiella and Mitsuokella were associated with abdominal pain, and other bacteria such as Escherichia_Shigella and Enterobacter were generally associated with enteritis infection, abdominal pain, and diarrhea. We also found that the predicted KEGG pathways were enriched in various nutrient metabolism pathways, with potential implications for elevated blood folate levels and vitamin B12 deficiency in SIBO patients.Protein bacterial motility and biofilm formation_ Escherichia coli, were mainly enhanced in IBS, and these functions were related to the mucosal barrier damage.

Conclusion

Our study shows that although IBS and SIBO share similar symptom spectra, they may be two distinct diseases. Despite the potential differences in the fecal flora of small intestinal flora in SIBO group, significant differences were found between IBS and SIBO in terms of clinical phenotype and fecal microbiome. Further exclusion of SIBO using lactulose hydrogen and methane breath testing in patients who meet the diagnostic criteria for IBS is warranted, as the differences suggest that different treatment strategies may be needed for these two populations. Future studies are needed to explore the underlying mechanisms and potential therapies for these conditions, which may ultimately benefit patients with IBS and SIBO.

References

1. Quigley EMM, Murray JA, Pimentel M. AGA Clinical Practice Update on Small Intestinal Bacterial Overgrowth: Expert Review. Gastroenterology. 2020; 159(4):1526-1532. DOI: 10.1053/j.gastro.2020.06.090
2. Bushyhead D, Quigley EMM. Small Intestinal Bacterial Overgrowth-Pathophysiology and Its Implications for Definition and Management. Gastroenterology. 2022; 163(3):593-607. DOI: 10.1053/j.gastro.2022.04.002
3. Ghoshal UC, Nehra A, Mathur A, Rai S. A meta-analysis on small intestinal bacterial overgrowth in patients with different subtypes of irritable bowel syndrome. J Gastroenterol Hepatol. 2020; 35(6):922-931. DOI: 10.1111/jgh.14938
4. Mearin F,Lacy BE,Chang L, et al. BowelDisorders[J].Gastroenterology,2016;150;1393-1407.
5. Zhu L, Huang D, Shi L, et al.Intestinal symptoms and psychological factors jointly affect quality of life of patients with irritable bowel syndrome with diarrhea.Health
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6. Sperber AD,Dumitrascu D, Fukudo S, et al.Gut 2017;66:1075–1082
7. Jindong Zhang, Jiao Liu, Shiwei Zhu, Ben Wang, Qiong Jia, Qihua He, Lijin Song, Yuan Fang, Baoli Zhu, Liping Duan. Berberine alleviates visceral hypersensitivity in rats by altering gut microbiome and suppressing spinal microglial activation. Acta Pharmacologica Sinica，Accepted 2020

Introduction

Irritable Bowel Syndrome (IBS) is a complex gastrointestinal functional disorder characterized by abdominal pain or discomfort and altered bowel habits. Despite its prevalence, and often chronic relapsing nature, the underlying pathophysiology of IBS remains incompletely understood. The etiology is likely multifactorial. Chronic low-grade subclinical inflammation has been implicated in the disease process and thought to perpetuate the symptoms of IBS.
Through previous studies on the serum proteomic profiles of IBS patients, it was seen that some inflammatory proteins are overexpressed in IBS, giving rise to a different serum proteome signature in IBS compared to healthy controls. [1,2] Systemic inflammatory protein profiles have also been used to distinguish patients with ulcerative colitis from IBS patients. [3] This suggests that proteomic profiling can potentially give us more insight into understanding the inflammatory mechanisms driving IBS.

Aims & Methods

This study aims to determine if systemic inflammatory protein profiles differ between patients with IBS and healthy controls.
Serum inflammatory proteins from 42 asymptomatic healthy controls undergoing screening colonoscopy with no colonic pathology, and 41 IBS patients fulfilling ROME IV criteria were analyzed using the Olink Target 96 Inflammation Panel. A partial-least square discriminant analysis was undertaken to identify additional discriminative inflammatory proteins. Univariate t-test analyses, with false discovery rate correction, were also performed to identify proteins unique to varying subtypes of IBS.

Results

Among IBS patients, the mean age was 48.6 years (SD +/- 15.5), while 31.7% were male. Among the controls, the mean age was 61.6 years (SD +/- 7) and 50% were male. There were 18 (43.9%), 14 (34.1%), 8 (19.5%) and 1 (2.4%) IBS patients with IBS-D, IBS-M, IBS-C and IBS-U respectively. 73.2% of IBS patients and 90.5% of controls were Chinese, with the rest being Indians, Malays or others.
Majority of the proteins (n=88, 96%) were prevalent in >40% of the study participants. Of which, 6 proteins (AXIN1, CCL19, CCL28, CD8A, EN-RAGE, MMP10) were differentially abundant (p<0.05) in IBS patients. Participants with IBS-C displayed higher levels of CD8A, while participants with IBS-D showed higher levels of AXIN1 and EN-RAGE (Table 1).
Interestingly, a recent study showed that CCL28 is elevated in IBS patients, which is consistent with our findings. [4] EN-RAGE has also been studied to be elevated in several digestive diseases including IBS, inflammatory bowel disease, digestive tract cancers, necrotizing enterocolitis and gastroenteritis. [5]

Table 1: Differentially abundant immunoproteins in IBS

Conclusion

We conclude that the serum cytokine profiles of IBS patients differ from that of healthy controls. We identified 6 immunoproteins that distinguish IBS from controls, and found that the levels of these immunoproteins also differ amongst the IBS subtypes. As this was a pilot study, the data collected was preliminary and limited by a small sample size. Future larger scale studies on proteomic profiling can potentially help with understanding the immune dysregulatory mechanisms driving IBS, and guide the diagnosis of and differentiation between subtypes.

References

[1] Tsigaridas A, Anagnostopoulos AK, Papadopoulou A, Ioakeim S, Vaiopoulou A, Papanikolaou IS, Viazis N, Karamanolis G, Mantzaris GJ, Tsangaris GT, Gazouli M. Identification of serum proteome signature of irritable bowel syndrome: Potential utility of the tool for early diagnosis and patient's stratification. J Proteomics. 2018 Sep 30;188:167-172.
[2] Darkoh C, Comer L, Zewdie G, Harold S, Snyder N, Dupont HL. Chemotactic chemokines are important in the pathogenesis of irritable bowel syndrome. PLoS One. 2014 Mar 25;9(3):e93144.
[3] Moraes L, Magnusson MK, Mavroudis G, Polster A, Jonefjäll B, Törnblom H, Sundin J, Simrén M, Strid H, Öhman L. Systemic Inflammatory Protein Profiles Distinguish Irritable Bowel Syndrome (IBS) and Ulcerative Colitis, Irrespective of Inflammation or IBS-Like Symptoms. Inflamm Bowel Dis. 2020 May 12;26(6):874-884.
[4] Sheikhesmaili F, Jalili A, Taghizadeh E, Fakhari S, Jalili K, Ghaderi E, Rahimi E. The CCL28 levels are elevated in the serum of patients with irritable bowel syndrome and associated with the clinical symptoms. Am J Clin Exp Immunol. 2021 Feb15;10(1):23-29.
[5] Carvalho A, Lu J, Francis JD, Moore RE, Haley KP, Doster RS, Townsend SD, Johnson JG, Damo SM, Gaddy JA. S100A12 in Digestive Diseases and Health: A Scoping Review. Gastroenterol Res Pract. 2020 Feb 26;2020:2868373

Introduction

The pathophysiological mechanisms of irritable bowel syndrome (IBS) are complex and incompletely known. Studies investigating the role of colonic volumes and their relation with symptoms and measurements of gut physiology in IBS are sparse.

Aims & Methods

The aim of this study was to explore the associations between colonic volume and symptoms and measurements of gut physiology in IBS and healthy individuals. We included 18 IBS patients (4 IBS-diarrhea, 5 IBS-constipation, 9 IBS-mixed or IBS-unspecified) and 19 healthy individuals. Total and segmental colonic volumes were determined by magnetic resonance imaging (MRI). The GSRS-IBS was used to measure gastrointestinal symptoms and a stool diary (Bristol Stool Form Scale) was completed 14 days before the MRI. Oro-anal transit time (radiopaque markers) and rectal sensitivity (rectal barostat, including pressure thresholds for first perception, defecation, and discomfort) were measured.

Results

The total colonic volume did not differ between IBS patients and healthy individuals (736 ml [528-903] vs 597 [498-939] (median [IQR]); p=0.44). In the IBS group, there were trends towards inverse associations between total colonic volume and the perceived severity of diarrhea (r_s= -0.43; p=0.08), as well as the volume of the descending colon and stool frequency (r_s= -0.48; p=0.07). Other GI symptoms and stool consistency were not associated with colonic volumes. When investigating the physiological parameters in IBS, the total colonic volume was positively associated with oro-anal transit time (r_s=0.54; p=0.02) and negatively associated with rectal pressure thresholds for sensations (first perception: r_s= -0.51; p=0.04, defecation: r_s= -0.44; p=0.09), Table 1. A similar pattern was seen when investigating individual colonic segments, with tendencies towards positive associations between segmental colonic volumes and oro-anal transit time, and negative associations with rectal sensory thresholds. The associations in healthy individuals between colonic volumes and oro-anal transit time and rectal sensitivity, respectively, were overall weaker (all p>0.05).

Conclusion

In this pilot study, we have shown that larger colonic volumes, measured with MRI, seem to be associated with slower oro-anal transit and rectal hypersensitivity in IBS. This suggests a potential role for measuring colonic volumes in IBS pathophysiology studies, but larger studies are needed to better appreciate subtype differences and their relevance for symptoms.