Introduction

Gastric visceral hypersensitivity (VH) is a key pathophysiological feature of functional dyspepsia (FD), characterized by enhanced perception of gastric distension and postprandial pain. Recent studies suggest that dietary gluten may act as a pro-nociceptive factor in FD, particularly in individuals without celiac disease but with dyspeptic symptoms. However, mechanisms linking gluten to VH remain elusive.

Aims & Methods

In the clinical arm, multiple linear regression assessed associations between gluten intake and symptom frequency/severity (postprandial fullness, epigastric pain, early satiety), adjusting for age, sex, and BMI. In the experimental arm, Sprague-Dawley rats received either a 20% gluten diet or gluten-free diet for 8 weeks; an iodoacetamide-induced FD model served as a positive control. Gastric sensitivity was evaluated by abdominal withdrawal reflex (AWR) and electromyography (EMG) following surgical placement of a gastric balloon and electrodes. Duodenal and fecal samples were collected for 16S rRNA microbiota profiling and RNA-seq. Histological and molecular analyses included H&E staining, intraepithelial lymphocyte (IEL) counts, RT-qPCR of cytokines, and quantification of GFAP, Substance P, and MAPK components by RT-qPCR, Western blot, or immunofluorescence. Aprepitant (10 mg/kg/day) was administered during the final 2 weeks to assess its therapeutic effect.

Results

A total of 74 patients diagnosed with FD based on Rome IV criteria (EPS (epigastric pain syndrome)+PDS (postprandial distress syndrome): 29, EPS: 12, PDS: 33) and 29 healthy controls were included. FD patients, particularly EPS subtypes, exhibited significantly higher gluten intake than healthy controls (P＜0.001). Multiple linear regression revealed that gluten intake was a significant positive predictor of symptom frequency and severity in FD patients (frequency: β = 0.0407, 95% CI: 0.0197–0.0617, P ＜0.001; severity: β = 0.0230, 95% CI: 0.0091–0.0368, P＜0.01).
In rats, gastric sensitivity in the 20% gluten group was comparable to the iodoacetamide-induced FD model and significantly greater than the gluten-free control group, exhibited by slower weight gain, increased AWR score, higher area under the curve (AUC) of electromyograph and reduced 24-hour food intake. Compared to controls, gluten-fed rats showed reduced fecal abundance of Lactobacillus and Lactococcus, increased Lachnoclostridium, and decreased Lactococcus in duodenal mucosa. Duodenal tissues also exhibited elevated intraepithelial lymphocyte (IEL) counts, increased expression of IL-1β, IL-4, and IL-5, and upregulation of inflammation-related genes Reg1α and Reg3β, indicating low-grade mucosal inflammation. In addition, gluten exposure significantly increased duodenal expression of Substance P (SP), GFAP, and phosphorylated MAPK pathway proteins.
At week 8, rats in the gluten group were treated with either the NK1R antagonist aprepitant or saline. Aprepitant administration significantly attenuated VH, as shown by reduced AWR scores and EMG AUC compared with the gluten+saline group. Aprepitant also suppressed the expression of IL-1β, IL-4, Reg1α, Reg3β, and MAPK-related genes, suggesting a key role of SP-mediated neuroimmune activation in gluten-induced VH.

Conclusion

Long-term high gluten intake induces gastric hypersensitivity, accompanied by gut dysbiosis, mucosal inflammation, and SP-mediated MAPK signaling. Targeting neuroimmune pathways may offer novel therapeutic strategies for gluten-induced epigastric symptom management.

References

POMENTI S, DEVINSKY J, JODORKOVSKY D. Diet for Functional Gastrointestinal Disorders/Disorders of Gut-Brain Interaction [J]. The Medical clinics of North America, 2022, 106(5): 899-912.
SHAH A, KANG S, TALLEY N J, et al. The duodenal mucosa associated microbiome, visceral sensory function, immune activation and psychological comorbidities in functional gastrointestinal disorders with and without self-reported non-celiac wheat sensitivity [J]. Gut microbes, 2022, 14(1): 2132078.

Introduction

Biomarkers, like stool short-chain fatty acids (SCFA), metabolites by fermented nondigestible carbohydrates and branched-chain fatty acids (BCFA) derived from the metabolism of essential amino acids may allow for objective measurements of IBS biological changes without self-reporting bias. Diets low in FODMAP significantly reduce the abnormal fecal total SCFA in IBS patients, indicating that the diet normalizes the IBS patients’ abnormal fecal SCFA output.

Aims & Methods

By conducting an exploratory analysis, we aimed to measure stool SCFAs/BCFAs level changes in a subgroup of subjects enrolled in an RCT evaluating the efficacy of a Mediterranean version of the Low-FODMAPS diet (MED-LFD) compared to the nutritional recommendations of the British National Institute for Health and Care Excellence (NICE) for managing non-constipation IBS. A subset of 40 (23 MED-LFD & 17 NICE) patients provided stool samples at 3 time points: Before dietary intervention, at the 1st (4 weeks after initiation of intervention for NICE and at the end of phase 2 for MED-LFD), and the 2nd folow-up (FU), 6 months after intervention initiation. We measured symptoms severity using IBS-SSS. Table 1 shows the detailed measurement of the consumed FODMAPs per day assessed using a triple-pass 24-hour dietary recall twice at the two FUs.

Table 1.

Results

We detected a significant reduction in the concentrations of total SCFAs and BCFAs in the MED-LFD (-21.4±20 and -0.429±0.882) and the NICE (-9.9±17.7 and -0.819±0.933) groups, respectively, at the 1st FU. At the 2nd FU, similar reductions from the baseline concentration levels were detected in both intervention groups (total SCFAs: -20.2±18.7 in MED-LFD vs. -10.9±7.4 in NICE; total BCFAs: -0.494±0.806 in MED-LFD vs. -0.76±0.83 in NICE). A polynomial association was observed between the changes in IBS-SSS scores and the changes in stool concentrations of BCFAs and SCFAs from baseline to the 1st FU. Specifically, there was a slight upward trend in the difference of BCFA levels, indicating that a decrease in IBS-SSS scores is associated with a reduction in BCFA levels during the 1st follow-up. This trend peaked around an IBS-SSS change of minus 50 points, the cut-off value for clinical response. Beyond this point, this association slightly declines. A similar trend was noted for SCFA level changes, with the peak occurring around an IBS-SSS change of minus 100 points, after which the association diminishes.

Conclusion

SCFA/BCFA stool levels changes from baseline might be an objective measure of successful dietary intervention for IBS

References

1. Ju X, Jiang Z, Ma J, Yang D. Changes in Fecal Short-Chain Fatty Acids in IBS Patients and Effects of Different Interventions: A Systematic Review and Meta-Analysis. Nutrients. 2024;16(11):1727
2. Rossi M, Aggio R, Staudacher HM, et al. Volatile Organic Compounds in Feces Associate With Response to Dietary Intervention in Patients With Irritable Bowel Syndrome. Clin Gastroenterol Hepatol. 2018;16(3):385-391.e1.

Introduction

Low mucosal impedance has been associated with reduced mucosal integrity and is measured during ambulatory pH/impedance monitoring, defined as mean nocturnal baseline impedance (MNBI)¹. More recently, techniques to measure impedance during endoscopy are emerging². In a prospective cohort of patients with EoE (SWALLeOeW Study, ISRCTN17786884, recruitment ongoing) we assessed the technicality of comparing mucosal impedance using MNBI with impedance measured during high-resolution impedance manometry (HRIM).

Aims & Methods

Here we aim to assess the practicability of obtaining mucosal impedance measurements during HRIM and to compare this with impedance measured using MNBI in a group of patients with EoE.
Prospective participants with EoE were assessed with HRIM and MNBI and this was repeated following a treatment period (Oro-dispersible Budesonide). The pooling of repeat measures from an individual participant was deemed to be appropriate in this evaluation as the purpose was to technically validate the process of comparing MNBI with HRIM, rather than to compare individual data points.
MNBI was calculated during a quiescent nocturnal period (Laborie, Ohmega) using the average of distal impedance channels 3 and 5 cm above the proximal border of the LOS¹. Impedance data was obtained during the supine resting period during HRIM and manually exported from the software (Medtronic). Extracted frames were at least 3 respiratory cycles and up to 30 seconds, and impedance was calculated based on the sensors 2.5 and 4.5, or 3.5 and 5.5 cm above the proximal border of the LOS, depending on catheter position.

Results

22 paired HRIM and MNBI measurements were obtained to date, from 15 participants. Reasons for unsuccessful MNBI measurements were not attempting test (n=2), non-tolerance (n=10), Nickel allergy (n=1), drop-out (n=2), or unable to intubate (n=1). Reasons for unsuccessful impedance measurement during HRIM were reflux during resting pressure measurement (n=1), catheter failure (n=3), drop-out (n=2), non-tolerance (n=8) or measurement not attempted (n=2).
The mean impedance values as measured by the two methods were not significantly different: mean MNBI (95% CI): 1570 (1210-1930) ohms, HRIM (95% CI) = 1330 (920-1740) ohms, p = 0.18. The mean difference between MNBI and HRIM was 245 ohms (1380-1870) (5-95^th percentiles).
Using a normality threshold of <1500 ohms³ being suggestive of impaired mucosal integrity, the majority (19/22) of the readings showed agreement between the two methods. Of the three that did not agree, MNBI suggested impaired mucosal integrity in one, and HRIM in the other two.

Conclusion

Measuring impedance during HRIM appears to be comparably practicable to MNBI measurement in patients with EoE, with the same numbers of successful measurements achieved by the two methods. Comparison of this preliminary data also indicates good agreement between methods. Impedance measurement during HRIM could provide a faster method of assessing mucosal integrity in EoE, whilst simultaneously assessing oesophageal motility. Further work in the SWALLeOeW study will correlate mucosal impedance findings with the Eosinophilic Oesophagitis Histology Scoring System⁴ and assess impedance change in response to treatment.

References

1. Hoshikawa, Y. et al. Measurement of Esophageal Nocturnal Baseline Impedance: A Simplified Method. J Neurogastroenterol Motil 26, 241–247 (2020).
2. Lei, W.-Y., Vaezi, M. F., Naik, R. D. & Chen, C.-L. Mucosal impedance testing: A new diagnostic testing in gastroesophageal reflux disease. Journal of the Formosan Medical Association 119, 1575–1580 (2020).
3. Sifrim, D. et al. Normal values and regional differences in oesophageal impedance-pH metrics: a consensus analysis of impedance-pH studies from around the world. Gut gutjnl-2020-322627 (2020).
4. Collins, M. H. et al. Newly developed and validated eosinophilic esophagitis histology scoring system and evidence that it outperforms peak eosinophil count for disease diagnosis and monitoring. Diseases of the Esophagus 30, (2016).

Introduction

The Atmo Capsule is a wireless motility capsule that senses and telemetrically transmits measurements of hydrogen (H₂) and carbon dioxide (CO₂) along the gut. In the colon, luminal concentrations of H₂ and CO₂ represent the metabolic activity of the microbial community. We hypothesized that delayed colonic transit would lead to altered gas profiles due to earlier depletion of fermentable substrates relative to transit time and/or facilitation of contact between methanogens and hydrogen (Levitt et al. CGH 2006).

Aims & Methods

The Atmo Capsule was administered to subjects with suspected upper and/or lower gut dysmotility. Colonic transit times (CTT) ≥ 59 h were considered delayed. Luminal H₂ and CO₂ concentrations (as time-normalized, area-under-the-curve [TN-AUC], [%.h]/h) were evaluated across the entire colon. Regional colonic profiles were evaluated per quartile of relative colonic transit, with quartiles 1 and 4 indicative of the proximal and distal colon, respectively. Gas measures were included if ≥ 50% of data were available for the corresponding segment. Fermentation profiles were estimated by the ratio of quartile 1:4 values, and time to peak concentrations were evaluated relative to CTT. Data were analyzed via Mann-Whitney test.

Results

The Atmo Capsule was administered to 209 subjects (median age 41; 188 female) with 170 yielding valid data on both colonic transit and colonic gas concentrations. Delayed colonic transit was identified in 60/170 (35%) subjects. In subjects with delayed CTT, H₂ concentrations tended to be higher in the proximal colon and lower in the distal colon with no overall difference across the region compared with those with normal transit (Table 1). CO₂ concentrations were higher throughout the colon except in the distal colon in subjects with delayed CTT. Peak concentrations of colonic H₂ and CO₂ were higher (H2, 8.7 h vs 5.9 %.h/h, p<0.01; CO2, 37.4 vs 29.9 %.h/h, p<0.01) and tended to occur earlier (H₂, 35.9 vs 47.0 % of colonic transit p=0.14; CO₂, 49.1 vs 86.8 % colonic transit, p<0.01) in patients with delayed compared with normal CTT.

Table 1. Gas profiles in patients with delayed colonic transit and correlation with symptom profiles. Data shown as median (interquartile range) and analyzed via Mann-Whitney test.

Conclusion

Colonic gas profiles, as measured via the Atmo Capsule, differed in patients with delayed compared with normal CTT, with patterns suggesting progressive depletion of fermentable substrates and/or conversion of H2 to methane during transit in those with delayed transit.

References

Levitt MD, Furne JK, Kuskowski M, Ruddy J. Stability of human methanogenic flora over 35 years and a review of insights obtained from breath methane measurements. Clin Gastroenterol Hepatol. 2006 Feb;4(2):123-9. doi: 10.1016/j.cgh.2005.11.006. PMID: 16469670.

Disclosure

These authors disclose the following: Braden Kuo, Anthony J. Lembo, Eammon M.M. Quigley, Satish S.C. Rao, and William D. Chey serve on the Medical Advisory Board of Atmo Biosciences. Michael Cline and Baharak Moshiree served on the Medical Advisory Board of Atmo Biosciences. Braden Kuo has received funding from NIH, Vanda, Atmo Biosciences, and Takeda and has consulted for Evoke, Takeda, Ironwood, Novo Nordisk, Cindome, and Neurogastrx. Thomas Abell has received funding from Gastric Dysrhythmias, Neurogastrx, NIH GpCRC, and Vanda and has consulted for Enterra Medical, Novo Nordisk, Nuvaira, and Vanda. Anthony J. Lembo has received funding from Ardelyx, Biomerica, GSK, Ironwood, Takeda, and Vibrant and holds stock with Allurion, Bristol Myer Squibb, and J&J. Abigail Stocker has received funding from Cindome, Enterra Medical, and Vanda. William D. Chey has received funding from Atmo Biosciences, Commonwealth Diagnostics Intl, QOL Medical, and Salix; has consulted for AbbVie, Ardelyx, Biomerica, Comvita, Gemelli, Ironwood, Nestle, QOL Medical, Phathom, Redhill, Salix, Vibrant, and Takeda; has filed patents with My Nutrition Health, Digital Manometry, and Rectal Expulsion Device; and holds stock options with Coprata, Evinature, Food Marble, Kiwi Bioscience, and Modify Health. The remaining authors disclose no conflicts.