Introduction

Functional dyspepsia (FD) is associated with duodenal eosinophilia and gut microbiota dysbiosis. Proton pump inhibitors (PPIs), as a first-line therapy, can suppress duodenal eosinophilic inflammation to ameliorate symptoms, yet the symptom relief rate is low. Rifaximin (RIF), an antibiotic known to modulate the gut microbiota, may offer an alternative therapeutic avenue. It is hypothesized that combining RIF with PPIs could more effectively alleviate FD symptoms and duodenal inflammation by targeting the gut microbiota.

Aims & Methods

A single-center, open-label, randomized controlled clinical trial was conducted on subjects who met the inclusion and exclusion criteria (Trial registration: ChiCTR2300069313). Ninety-six patients were randomly assigned in a 1:1 ratio to either the PPI+RIF group or the PPI group. The follow-up period extended to 4 weeks post-treatment cessation. The primary endpoint was the symptom relief rate, while secondary endpoints included symptom response rate, duodenal eosinophil counts, and changes in the microbiota. The study hypothesis was that the clinical efficacy of PPI+RIF would be superior to that of PPI monotherapy.

Results

	PPI+RIF	PPI	Z value	P value	PPI+RIF	PPI	Z value	P value
Abbreviations: PPI+RIF: Proton Pump Inhibitor plus Rifaximin; PPI: Proton Pump Inhibitor; ITT: the intention-to-treat analysis;PP: the per-protocol analysis.
Symptom relief rate	ITT				PP
Week 2	54.2%（26/48）	54.2%（26/48）	0.000	0.500	53.7%（22/41）	53.3%（24/45）	0.030	0.488
Week 4	72.9%（35/48）	58.3%（28/48）	1.522	0.064	76.7%（33/43）	56.8%（25/44）	2.020	0.022
4 weeks post-treatment	77.1%（37/48）	47.9%（23/48）	3.095	0.001	78.6%（33/42）	48.9%（22/45）	3.036	0.001
Symptom response rate	ITT				PP
Week 2	70.8%（34/48）	72.9%（35/48）	-0.227	0.590	68.3%（28/41）	73.3%（33/45）	-0.514	0.696
Week 4	81.3%（39/48）	77.1%（37/48）	-0.503	0.307	83.7%（36/43）	75.0%（33/44）	1.012	0.156
4 weeks post-treatment	85.4%（41/48）	68.8%（33/48）	1.982	0.024	85.7%（36/42）	71.1%（32/45）	1.688	0.046

A total of 96 patients were enrolled in the randomized controlled study. There were no statistically significant differences in baseline demographic data and clinical characteristics between the two groups. According to the intention-to-treat (ITT) analysis, the PPI+RIF group showed significantly higher rates of symptom relief (P = 0.001) and symptom response (P = 0.024) at 4 weeks post-treatment. These findings were supported by the per-protocol (PP) analysis, which revealed a superior symptom relief rate for the combination group at both 4 weeks of treatment (P = 0.022) and 4 weeks post-treatment (P = 0.001), as well as a superior symptom response rate at 4 weeks post-treatment (P = 0.046). Combination therapy also led to a greater reduction in duodenal eosinophil infiltration (P = 0.036) and significantly decreased peak hydrogen sulfide (H₂S) levels (P < 0.001), indicating a reduction in small intestinal bacterial load. Oral microbiota analysis revealed that β-diversity of the oral flora increased following the PPI+RIF intervention, with an increased relative abundance of Enterococcus (P = 0.004). Conversely, the PPI intervention led to the enrichment of the potentially pathogenic bacterium Catonella (P = 0.006). Notably, treatment responders in the PPI+RIF group showed a specific enrichment of the Eubacterium_yurii_group (P = 0.037), an alteration associated with the amelioration of duodenal eosinophilic inflammation and the enhancement of pathways related to preventing bacterial invasion of the epithelium.

Conclusion

In patients with FD, combining a PPI with Rifaximin is superior to PPI monotherapy, improving both symptoms and duodenal eosinophil infiltration. This effect is linked to a reduction in H₂S-producing bacteria and a beneficial shift in the oral microbiota. The oral abundance of Eubacterium_yurii_group may serve as a biomarker for treatment response.

Disclosure

The authors declare that they have no conflicts of interest.

Introduction

Hypergastrinemia, caused by chronic atrophic gastritis or Helicobacter pylori (H. pylori) associated pangastritis, is associated with an increased risk of non-cardia gastric cancer. Recent studies have also found an increased risk of gastric cancer in long-term proton pump inhibitor (PPI) users. Patients with chronic atrophic gastritis also have an increased risk of neuroendocrine neoplasms (NEN) due to hypergastrinemia. However, whether long-term PPI use increases the risk of gastric NEN has not been assessed in the general population.

Aims & Methods

The aim of the present study was to assess the risk of gastric NEN among long-term PPI users in a multinational population-based study from the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden). The study was based on the Nordic Gastric and Esophageal Tumor Study (NordGETS), which is a population-based multinational sex, age, calendar year, and country matched case-control study including all adults (≥18 years of age) with a diagnosis of gastric or esophageal tumor in the Nordic countries. In the present study, the cases were incident gastric NEN identified in the cancer registries and the exposure was long-term use of PPI categorised into three equal-sized groups (tertiles) of defined daily doses (DDDs) from the medication registries of the Nordic countries between 1996 and 2020. Multivariable logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for chronic atrophic gastritis, NEN in the duodenum or pancreas, and H. pylori infection identified in the patient registries and medication registries.

Results

In total, 1,790 gastric NEN case patients were compared to 17,897 control participants. After a one-year run-in period, the median follow-up was 11.8 years. The risk of incident gastric NEN increased in PPI users compared to non-users in a dose-dependent manner. The adjusted OR for incident gastric NEN was 1.83 (95% CI 1.56 to 2.15) in the highest tertile of PPI use (>385 DDDs, entire drug history) compared to no PPI use (Table). The risk was higher in the younger age group (<65 years) than the older age group (≥65 years) and the estimates were consistent when excluding individuals with chronic atrophic gastritis, other NENs, and H. pylori.

Table Risk of gastric neuroendocrine neoplasms (NEN) by proton pump inhibitor (PPI) exposure defined by tertiles of defined daily doses (DDD) for the entire drug history between 1996 and 2020.
PPI (DDD)*	Crude odds ratio (95% confidence interval)**	Adjusted odds ratio (95% confidence interval)***
None	1.00 (reference)	1.00 (reference)
Tertile 1	1.46 (1.25-1.70)	1.34 (1.14-1.58)
Tertile 2	1.54 (1.30-1.81)	1.37 (1.15-1.64)
Tertile ​3	1.92 (1.65-2.24)	1.83 (1.56-2.15)
* Tertiles: 1 ≤56 DDDs; 2 >56-385 DDDs; 3 >385 DDDs. ** Matched for sex, age, calendar year, and country. *** Matched for sex, age, calendar year, and country, and adjusted for chronic atrophic gastritis, NEN in duodenum or pancreas, and H. pylori.

Conclusion

In this population-based study from the five Nordic countries the risk of gastric NEN was increased in PPI users compared to non-users of PPI in a seemingly dose-dependent manner. The risk was higher in younger age groups of PPI users compared to older age groups.

Disclosure

No conflicts of interest