Introduction

Emerging evidence suggests a possible role for γ-aminobutyric acid (GABA) in the development of irritable bowel syndrome with diarrhea (IBS-D), as well as its possible therapeutic use.

Aims & Methods

This study primary aimed to assess the efficacy of a GABA-based supplement in patients with IBS-D in terms of improvement in quality of life. Secondary aims included assessing its impact on psychological wellbeing and gastrointestinal symptoms.
In this double-blind, placebo-controlled, single center, crossover pilot study, 20 IBS-D patients were randomized to receive a food supplement containing GABA and Melissa officinalis or a placebo, at the dosage of one tablet three times daily for two treatment periods of 4 weeks each, separated by a 2-week washout period. Before and after each treatment, patients were assessed through:

• IBS Symptom Severity Scale (IBS-SSS). Responders were those with a ≥50-point reduction in IBS-SSS.
• Short Form Health Survey 36 (SF-36) multidimensional questionnaire.
• Hospital Anxiety and Depression Scale (HADS).

Pre- and post-treatment values were compared using a paired t-test; treatment comparisons used mixed models analysis.

Results

Eighteen patients completed the study (10 females, age 30.3±10.3 years).
A significant reduction of IBSS-SSS total score, as well as in all individual items, was observed in the GABA group (Table 1). A reduction of at least 50 points was achieved in 66.7% of patients treated with GABA and in 33.3% of those treated with placebo. Mixed models analysis showed a significant improvement with GABA compared to placebo in the IBS-SSS total score (p=0.01) and in the «Bowel satisfaction» item (p=0.005).
A significant improvement on the «Mental health» (p=0.007) and «Bodily pain» (p=0.09) items and in the mental composite score (MCS) of the SF-36 (0.037, Table 1) was observed with GABA. Mixed models analysis showed a significant improvement with GABA compared to placebo in the «Physical limitations» (p=0.033) and «Emotional limitation» (p=0.028) domains of SF-36.
GABA supplementation significantly improved the «HAD-Anxiety» score compared to baseline (6.7±3.0 Vs 5.1 ±2.7, p=0.02, Table 1) even though at mixed model analysis there was no significant effect.

Table 1. Comparison between pre- and post-treatment in placebo and GABA arms of the study.

Conclusion

In this pilot study, GABA and Melissa officinalis supplementation showed a higher overall improvement in IBS-D symptoms (IBS-SSS total) and particularly in bowel habits satisfaction compared to placebo. GABA supplementation was superior to placebo in improving daily functioning, especially regarding physical and emotional limitations in IBS-D patients. GABA may be a valuable therapeutic option deserving further investigation in larger trials.

Disclosure

No conflicts of interest to declare

Introduction

Inflammatory bowel disease (IBD) is a growing global health problem with increasing prevalence. Current therapeutic strategies for IBD are mainly aimed at modulating the dysregulated immune activity in the intestinal mucosa. Targeting the JAK/STAT signalling pathway has been shown to be highly effective in ulcerative colitis, but not in Crohn's disease (CD), where efficacy was found to be insufficient in the initiation phase of a clinical trial [1]. Failure of the therapeutic response in Crohn’s disease may be influenced by the unique immune microenvironments in the small and large intestine and their characteristic cytokine profiles and immune cell compositions.

Aims & Methods

To gain deeper insight into region-specific efficacy in the inflamed ileum versus colon, this study investigates the immunomodulatory effects of filgotinib, a Jak1 inhibitor, using precision-cut intestinal slices (PCIS) from patients with Crohn's diseases. PCIS are viable, ultra-thin human tissue slices that retain the original intestinal architecture ex vivo and contain important cell types, including resident immune cells.
PCIS were prepared from resected ileal and colonic tissue of CD patients. The slices were cultured ex vivo and stimulated with concanavalin A or anti-CD3/CD28 antibodies to induce T cell-driven inflammatory responses. Filgotinib (1-100 µM) was applied to assess the immunomodulatory effects of JAK1 inhibition following Concanavalin A preactivation. To exclude treatment-related toxicity, cellular integrity was evaluated using an LDH release assay. Tissue morphology was examined by H&E staining and immunofluorescence. The immune response was assessed by multiplex ELISA of 20 cytokines.

Results

After filgotinib treatment, primary tissue slices from the ileum and colon of CD patients remained viable. Regional morphological characteristics of ileum and colon tissue were preserved after ex vivo cultivation, with prominent villi and smaller crypts in the ileum, and larger, more frequent crypts and flattened villi in the colon. Compared to non-CD tissue slices, Crohn’s disease-related changes, such as immune cell accumulation, were also observed in CD tissue slices ex vivo. Upon T cell-specific stimulation with anti-CD3/CD28 antibodies, region-specific immune reactivity was observed. Colonic PCIS showed an increased release of IL-2 (~3-fold), IL-10 (~2‑fold) and TRAIL (~4-fold) compared to ileal PCIS, indicating a stronger involvement of Th and regulatory T cells in the colon. In contrast, ileal PCIS showed higher levels of MIP-3α (2-fold) and granzyme A (~8-fold) after stimulation, suggesting increased cytotoxic T cell activity in this region. Filgotinib treatment showed region-specific differences in its ability to modulate cytokine release in PCIS of CD patients. In colonic PCIS, filgotinib reduced the induced secretion of Th17-associated cytokines such as IL-17F and IL-22 by up to 95%, whereas in ileal PCIS it showed no effect on the same cytokines.

Conclusion

In conclusion, filgotinib exhibited more potent anti‑inflammatory effect on Th17 cells in the colon, and a markedly reduced efficacy in the ileum. This study demonstrates for the first time that precision-cut intestinal slices can be used to predict region-specific drug response in inflamed intestinal tissue ex vivo, underscoring the critical importance of region-specific immune profiling in IBD and highlight the limited efficacy of JAK1 inhibition in ileum. This ex vivo, patient-derived model represents a valuable platform for evaluating localised treatment efficacy and advancing personalised therapeutic strategies in IBD.

References

[1] Rogler G. Efficacy of JAK inhibitors in Crohn's Disease. J Crohns Colitis. 2020 Aug 1;14(Supplement_2):S746-S754. doi: 10.1093/ecco-jcc/jjz186