Effect of Omeprazole on Gut Microbiota in Adults With Obesity and GERD

September 24, 2026 updated by: Federal State Budgetary Scientific Institution

Effect of Proton Pump Inhibitors on Gut Microbiota Composition in Adults With Obesity and Gastroesophageal Reflux Disease

This randomized, open-label, parallel-group study will evaluate the effect of short-term omeprazole therapy on gut and oral microbiota in adults aged 50-65 years with obesity and symptomatic gastroesophageal reflux disease. Participants will be randomized 1:1 to receive omeprazole 20 mg once daily for 14 days plus standard non-pharmacological recommendations for gastroesophageal reflux disease, or standard non-pharmacological recommendations alone. Clinical and laboratory assessments will be performed at baseline and after 14 days. Stool and saliva samples will be collected to assess gut and oral microbiota, and blood samples will be collected for laboratory biomarkers.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

26

Phase

  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Georgy E. Leonov, MD, PhD
  • Phone Number: +7 9055687783
  • Email: golerus@gmail.com

Study Locations

  • Russia
      • Moscow, Russia, 115446
        • Federal Research Centre of Nutrition, Biotechnology and Food Safety
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

50 years to 65 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Age 50 to 65 years, inclusive.
  • Obesity, defined as body mass index (BMI) ≥30 kg/m².
  • Symptomatic gastroesophageal reflux disease with mild or moderate typical symptoms, including heartburn and/or regurgitation.
  • For female participants, postmenopausal status, defined as absence of menstruation for at least 12 months without another apparent cause of amenorrhea.
  • Written informed consent to participate in the study.

Exclusion Criteria:

  • Severe or exacerbated GERD, or GERD requiring acid-suppressive therapy or additional diagnostic evaluation.
  • Use of proton pump inhibitors or histamine H2-receptor antagonists within 8 weeks prior to enrollment.
  • Use of systemic antibiotics within 3 months prior to enrollment.
  • Use of probiotic or synbiotic supplements within 8 weeks prior to enrollment.
  • Inflammatory bowel disease, celiac disease, or other severe chronic gastrointestinal disorders that may substantially affect the gut microbiota.
  • History of bariatric surgery or other major gastrointestinal surgery.
  • Acute infectious or inflammatory disease at enrollment.
  • History of myocardial infarction or stroke.
  • Type 2 diabetes mellitus.
  • Chronic heart failure, New York Heart Association functional class III-IV.
  • Chronic kidney disease with estimated glomerular filtration rate <30 mL/min/1.73 m².
  • Alcohol dependence or other substance use disorder.
  • Severe psychiatric disorder or cognitive impairment that may interfere with providing informed consent or adherence to the study protocol.
  • Known hypersensitivity or contraindications to omeprazole.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Omeprazole Plus Standard Non-pharmacological Recommendations

Participants will receive omeprazole 20 mg orally once daily for 14 days in addition to standard non-pharmacological recommendations for gastroesophageal reflux disease.
Drug: Omeprazole

Omeprazole 20 mg administered orally once daily for 14 days.

Behavioral: Standard Non-pharmacological Recommendations for GERD

Standard non-pharmacological recommendations for gastroesophageal reflux disease management.
Active Comparator: Standard Non-pharmacological Recommendations

Participants will receive standard non-pharmacological recommendations for gastroesophageal reflux disease for 14 days.
Behavioral: Standard Non-pharmacological Recommendations for GERD

Standard non-pharmacological recommendations for gastroesophageal reflux disease management.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in gut microbiota beta diversity
Time Frame: Baseline and Day 14

Gut microbiota beta diversity will be assessed using distance-based measures derived from 16S rRNA gene sequencing of stool samples, including Bray-Curtis dissimilarity and phylogenetic UniFrac distances.
Baseline and Day 14

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in Shannon diversity index
Time Frame: Baseline and Day 14

Change in gut microbiota alpha diversity assessed using the Shannon diversity index derived from 16S rRNA gene sequencing of stool samples. Higher values indicate greater microbial diversity.
Baseline and Day 14
Change in Simpson diversity index
Time Frame: Baseline and Day 14

Change in gut microbiota alpha diversity assessed using the Simpson diversity index derived from 16S rRNA gene sequencing of stool samples. Values range from 0 to 1, with higher values indicating greater microbial diversity.
Baseline and Day 14
Change in Chao1 richness estimator
Time Frame: Baseline and Day 14

Change in gut microbiota richness assessed using the Chao1 richness estimator derived from 16S rRNA gene sequencing of stool samples. Higher values indicate greater estimated microbial richness.
Baseline and Day 14
Change in modified Frequency Scale for the Symptoms of GERD total score
Time Frame: Baseline and Day 14

Change in the total modified Frequency Scale for the Symptoms of GERD (mFSSG) score from baseline to Day 14. The questionnaire includes 14 items scored from 0 to 4. The total score ranges from 0 to 56, with higher scores indicating more frequent GERD-related symptoms.
Baseline and Day 14
Change in high-sensitivity C-reactive protein concentration
Time Frame: Baseline and Day 14

Change in serum high-sensitivity C-reactive protein (hs-CRP) concentration.
Baseline and Day 14
Change in systemic immune-inflammation index
Time Frame: Baseline and Day 14

Change in the systemic immune-inflammation index (SII), calculated as platelet count × neutrophil count / lymphocyte count.
Baseline and Day 14

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in oral microbiota composition
Time Frame: Baseline and Day 14

Changes in oral microbiota composition will be assessed using microbiome analysis of saliva samples, including measures of microbial diversity and taxonomic composition.
Baseline and Day 14
Change in serum lipopolysaccharide-binding protein concentration
Time Frame: Baseline and Day 14

Change in serum lipopolysaccharide-binding protein (LBP) concentration from baseline to Day 14.
Baseline and Day 14

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Federal State Budgetary Scientific Institution

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

September 25, 2026

Primary Completion (Estimated)

December 25, 2026

Study Completion (Estimated)

December 25, 2026

Study Registration Dates

First Submitted

September 24, 2026

First Submitted That Met QC Criteria

September 24, 2026

First Posted (Actual)

October 1, 2026

Study Record Updates

Last Update Posted (Actual)

October 1, 2026

Last Update Submitted That Met QC Criteria

September 24, 2026

Last Verified

September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • PPI-MICROBIOME-7-02-09-2026
  • 22-15-00252-P (Other Grant/Funding Number: Russian Science Foundation)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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