Introduction

The interdisciplinary Bergen BrainGut study was designed to stratify the complex interaction between the brain, gut and microbiota in patients with irritable bowel syndrome (IBS) (1). Some bacterial species have a critical function in the gut and a functional bacterial profile is useful to identify potential dysfunction when there are observations of deviation from expected normal abundance (Table 1).

Aims & Methods

In this in-depth sub-study we aimed to assess the functional bacterial profile and dysbiosis in patients with IBS compared to healthy controls (HCs), and investigate changes in the patients after a dietitian-led strict 12-week low FODMAP diet (LFD). Sixty patients with Rome IV-confirmed IBS (mean age 38 years, 46 (77%) females) with moderate to severe symptoms (IBS-SSS > 175), and 42 HCs (mean age 35 years, 27 (64%) females) were included. Participants answered IBS Symptom Severity Scale (IBS-SSS) and delivered fecal samples at baseline (IBS and HC) and 12 weeks post LFD (IBS only). Functional bacterial profiles were assessed by GA-map^TM Dysbiosis Test Lx® based on 16s rRNA sequence of bacterial species or groups (Table 1). Patients were classified as LFD responders if they had a ≥ 50-point reduction in IBS-SSS from pre to post LFD. Dysbiosis was classified as dysbiosis index (DI) > 2 (range 0-5).

Results

Twenty-one patients were classified as IBS-D (diarrhea), 31 IBS-M (mixed diarrhea and constipation) and eight IBS-C (constipation). Thirty-six patients with IBS-M and IBS-D completed the 12-week LFD. At baseline, the relative frequency of dysbiosis was higher in IBS (24.6%) compared to HCs (5.6%, p = .023), but no significant difference in functional bacterial profile was observed between the groups. In week 12, patients showed a significant reduction in symptom severity (IBS-SSS, p < .005) and a significant increase in dysbiosis (BL: 17.6% vs week 12: 58.8%, p < .001). Eighty percent (n = 28) were classified as responders, but no significant change in functional bacterial profile from pre to post LFD was observed for this group, nor between responders and non-responders post LFD.

Table 1. Description of functional bacterial profiles. Modified table from ga-map.com.

Conclusion

Although the literature suggests a different bacterial profile in IBS compared to healthy controls, our results provide no evidence for a difference in functional bacterial profile between IBS and healthy controls, nor associations with changes in symptom severity score. However, the relative frequency of dysbiosis in patients with IBS increased after a 12-week strict low FODMAP diet as avoiding some of the high FODMAP food items in a long period might lead to missing their prebiotic effects in gut.

References

1. Berentsen B, Bharath HN, Lied GA et al. Study protocol of the Bergen brain-gut-microbiota-axis study: a prospective case-report characterization and dietary intervention study to evaluate the effects of dietary-induced microbiota signature-alterations on cognition and anatomical and functional brain connectivity in patients with irritable bowel syndrome. Medicine 2020;Vol;No(e21950).

Introduction

Functional diseases of the gastrointestinal tract are a common diagnosis, with the most common manifestations being functional dyspepsia and IBS. The pathophysiological mechanisms and etiology of this group of diseases are not fully understood, but stress is believed to play a key role.

Aims & Methods

This study aims to evaluate the effectiveness of a low-histamine diet in patients with irritable bowel syndrome. Patients who meet the ROME IV criteria were included in the study. The study included 120 patients, divided into three groups: low- histamine diet, FODMAP diet and mediterranian diet.Questionnaires were used to assess stress levels PSS-4, anxiety GAD-7, severity of IBS - IBS Severity Score, and quality of life. The questionnaires were completed three times: both at the beginning of the study, immediately after the end of the 4-week diet, and one month after the end of the diet therapy.

Results

The low-histamine diet led to a statistically significant improvement in IBS symptoms compared to baseline. These findings suggest that the dietary intervention had a positive therapeutic effect ( low- histamine diet : t = 9.6181, p-value < 0.001, low FODMAP diet Z = 22, p-value < 0.001, mediterannian diet Z =119, p-value < 0.001).

Conclusion

Dietary therapy plays a key role in the management of IBS. The low-histamine diet shows promising results and may serve as a viable alternative to the FODMAP diet.

Disclosure

The study was launched after receiving approval from the Research Ethics Committee (REC) at the Medical University "Prof. Dr. Paraskev Stoyanov" – Varna, protocol 111/ 20.01.2022y.Data were processed and analyzed using appropriate statistical methods chosen according to the nature of the variables and research questions. The analysis includes:

• Evaluation of the statistical significance of the main and interactions between the factors (Repeated Measures with Wicolxon and Paired t-test).
• Regression analysis to assess relationships between dependent and independent variables. As well as using heteroskedasticity-robust standard error estimates (HC3) to ensure accuracy of regression analysis results.

Introduction

The interdisciplinary Bergen BrainGut study was designed to stratify the complex interaction between the brain, gut and microbiota in patients with irritable bowel syndrome (IBS) (1). IBS has been associated with increased gut permeability and impaired gut barrier integrity and function.

Aims & Methods

In this in-depth substudy, we aimed to assess relevant biomarkers by analysing plasma levels of gut integrity and permeability markers in patients with IBS with moderate to severe symptoms (n = 36, IBS-SSS > 175), compared to healthy controls (HCs, n = 20), and investigate changes after a dietitian-led strict 12-week low FODMAP diet (LFD) and changes in IBS symptom severity score (IBS-SSS; only patients). Responders were classified as having ≥ 50 p reduction in IBS-SSS from baseline to week 12. Blood samples were collected at baseline and after 12 weeks. ELISA was used to analyse the gut integrity markers intestinal fatty acid-binding protein (i-FABP), lipopolysaccharide-binding protein (LBP) and zonulin, and tight junction proteins Zonula Occludens 1 (ZO1) and Claudin-1 in plasma.

Results

Fifteen patients were classified as IBS-D (diarrhea), 21 as IBS-M (mix of diarrhea and constipation), mean age 38 years, 46 (77%) females and 20 HCs with a mean age 30 years, 13 (65%) females. At baseline, trends indicated higher levels of ZO1, LBP and Claudin-1, lower levels of i-FABP, and similar levels of zonulin in IBS compared to HCs. However, there was no statistically significant difference observed. Overall, there was a significant reduction in IBS-SSS after the 12-week strict LFD (p < 0.005), and 80% (n = 28) were classified as responders. Analysis of blood samples collected at 12 weeks revealed a trend of reduced levels of ZO1, i-FABP, LBP and Claudin-1. However, these were not statistically significantly different from baseline concentrations. No change was seen in zonulin following LFD. At baseline, higher IBS-SSS was associated with higher levels of i-FABP (r = 0.394, p = 0.031), but no associations between gut integrity or tight junction protein markers was observed at week 12. No difference in plasma levels was observed between responders and non-responders post LFD.

Conclusion

Higher symptom severity was associated with higher levels of i-FABP at baseline, but no associations with gut integrity markers or tight junction proteins were observed following a 12-week LFD despite the significant reduction in symptom severity. Hence, our results provide no clear evidence of differences in plasma levels of gut integrity markers and tight junction proteins in IBS patients compared to HCs, nor between LFD responders and non-responders.

References

1. Berentsen B, Bharath HN, Lied GA et al. Study protocol of the Bergen brain-gut-microbiota-axis study: a prospective case-report characterization and dietary intervention study to evaluate the effects of dietary-induced microbiota signature-alterations on cognition and anatomical and functional brain connectivity in patients with irritable bowel syndrome. Medicine 2020;Vol;No(e21950).

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

Food is often reported as a trigger for symptoms in patients with irritable bowel syndrome (IBS). One of the proposed pathophysiological mechanisms is a local immune response to food antigens, triggered by a preceding infection¹.

Aims & Methods

This study aimed to investigate rectal mucosal reactions to food in patients with IBS. Therefore, patients with IBS and food-related symptoms were included. Allergies to the food items that were tested during the colonoscopic antigen provocation (COLAP) were excluded by an allergologist. The COLAP was started in the absence of macroscopic abnormalities during sigmoidoscopy. A 200 μL solution of each food antigen (wheat, gluten, soy, and milk; administered in a randomized order and blinded), a negative control (NaCl 0.9%), and a positive control (histamine) were injected in the rectal mucosa, with a positive reaction defined as mucosal edema 12 minutes after injection and judged based on a previously used semiquantitative scale ². The reaction was independently judged by two endoscopists, resulting in a positive or negative reaction when they agreed and doubtful when they did not.

Results

Data from ten patients were available for this interim analysis. Nine were female, with a median age of 45 [range 24-58] years, and a median IBS symptom severity score of 356 [range 197-416], i.e. in the moderate to severe range. Six patients had predominant constipation, one predominant diarrhea, and three mixed bowel habits. COLAP was positive in seven patients, with a positive reaction for one food antigen in three patients and for two food antigens in four patients. In the other three patients, the test was only doubtful for one of the food antigens (n=2), or negative for all (n=1). A positive reaction to gluten was observed in five patients, to soy in three, to wheat in two, and to milk in one (Table). The reaction to histamine was positive in eight patients, with no positive reaction after injection of the negative control in all.

Conclusion

A local intestinal reaction to food antigens was seen in a subset of patients with IBS. Further research will focus on underlying pathophysiological mechanisms and clinical relevance of these findings.

References

1. Aguilera-Lizarraga J, Florens MV, Viola MF, Jain P, Decraecker L, Appeltans I, et al. Local immune response to food antigens drives meal-induced abdominal pain. Nature. 2021;590(7844):151-6.
2. Bischoff SC, Mayer J, Wedemeyer J, Meier PN, Zeck-Kapp G, Wedi B, et al. Colonoscopic allergen provocation (COLAP): a new diagnostic approach for gastrointestinal food allergy. Gut. 1997;40(6):745-53.

Introduction

Gut-brain dysregulation and microbiome dysfunction are central to the pathogenesis of irritable bowel syndrome (IBS). Depressive and anxiety symptoms are highly prevalent and contribute to disease burden but are not commonly addressed in practice. The low FODMAP diet is efficacious for managing gastrointestinal symptoms but may not be appropriate in those with psychological comorbidity due to its complexity. A Mediterranean diet (MD), rich in vegetables, pulses, wholegrains and olive oil, has potential benefit in IBS as it leads to positive shifts in microbiome composition and function, and RCTs have demonstrated antidepressant effects.

Aims & Methods

The TANDIM trial aimed to assess the feasibility of a MD in patients with IBS and psychological comorbidity. Adults aged 18-65 years with Rome IV IBS and mild or moderate anxiety and/or depressive symptoms were recruited to a 6-week RCT. Significant medical or mental health conditions (e.g. inflammatory bowel disease, bipolar disorder) and recent change in IBS or psychotropic treatment were excluded. Patients were randomised to MD advice from a dietitian or advice to continue habitual diet. MD advice was individualised and incorporated advice regarding gradual reintroduction of high fibre or high FODMAP foods in individuals in which these components were restricted. Habitual diet controls undertook identical research activities to MD but were not provided dietary advice. Diet adherence was measured using a Mediterranean diet adherence screener (MEDAS) and 3-day diet records were collected at baseline and follow up. Gastrointestinal symptoms (IBS-SSS), psychological symptoms (HADS) and quality of life (IBS-QOL) data were collected at baseline and follow up. Stool samples were collected for metagenomic sequencing. Data were analysed on an intention-to-treat basis. For continuous variables, analysis of covariance with adjustment for baseline was used; for categorical data, Fisher's exact tests were used. Between group differences in diversity and differential abundance of taxa and potential functions of the microbiome were analysed using linear mixed effects models and FDR correction.

Results

In total, 59 individuals were randomised (29 MD, 30 control) and 48 completed the trial. Seven of 11 withdrawals were due to antibiotic commencement. The MEDAS score was higher, indicating better adherence to MD, at week 6 in MD vs controls (7.5 [95% CI: 6.9, 8.0] vs 5.7 [5.2, 6.3], p<0.001) and there was no difference in total FODMAP intake (p=0.51).There was a lower IBS-SSS at week 6 in MD vs controls (168 [95% CI: 146, 191] vs 260 [95% CI: 238, 282], p<0.001) and a greater proportion of IBS-SSS responders in MD vs controls (≥50-point reduction; 83% vs 37%, p<0.001). There was also a greater proportion of HADS-D responders (52% vs 20%, p=0.015) and IBS-QOL responders (≥14-point reduction 62% vs 23%, p=0.004). Gastrointestinal adverse events were similar between groups (p=0.588). There were no differences between groups in change in microbiome alpha diversity (richness, Shannon Index), beta diversity, relative abundance of taxa, or functional potential.

Conclusion

The MD is a feasible and potentially therapeutic dietary intervention for reducing gut and psychological symptom burden in IBS. The broader health benefits with a MD style eating pattern provide further impetus for studying its effects in IBS. Larger blinded RCTs, in which influence of expectation bias is minimised, are required.