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

NCT07850960 | Not Yet Recruiting Phase 4

• 2 other identifiers: PPI-MICROBIOME-7-02-09-202622-15-00252-P
• Study Type: interventional
• Target: 26
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Obesity & Overweight; Gastroesophageal Reflux Disease

Keywords

Gut Microbiota; Oral Microbiota; Omeprazole; Proton Pump Inhibitors; GERD; 16S rRNA Sequencing

Outcome Measures

Primary Outcomes (1)

• Change in gut microbiota beta diversity

  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 Outcomes (6)

• Change in Shannon diversity index

  Baseline and Day 14

• Change in Simpson diversity index

  Baseline and Day 14

• Change in Chao1 richness estimator

  Baseline and Day 14

• Change in modified Frequency Scale for the Symptoms of GERD total score

  Baseline and Day 14

• Change in high-sensitivity C-reactive protein concentration

  Baseline and Day 14

Other Outcomes (2)

• Change in oral microbiota composition

  Baseline and Day 14

• Change in serum lipopolysaccharide-binding protein concentration

  Baseline and Day 14

Study Arms (2)

Omeprazole Plus Standard Non-pharmacological Recommendations

EXPERIMENTAL

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; Behavioral: Standard Non-pharmacological Recommendations for GERD

Standard Non-pharmacological Recommendations

ACTIVE COMPARATOR

Participants will receive standard non-pharmacological recommendations for gastroesophageal reflux disease for 14 days.

Behavioral: Standard Non-pharmacological Recommendations for GERD

Interventions

Omeprazole DRUG

Omeprazole 20 mg administered orally once daily for 14 days.

Omeprazole Plus Standard Non-pharmacological Recommendations

Standard Non-pharmacological Recommendations for GERD BEHAVIORAL

Standard non-pharmacological recommendations for gastroesophageal reflux disease management.

Omeprazole Plus Standard Non-pharmacological Recommendations; Standard Non-pharmacological Recommendations

Eligibility Criteria

• Age: 50 Years - 65 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Federal State Budgetary Scientific Institution: lead

Study Sites (1)

Federal Research Centre of Nutrition, Biotechnology and Food Safety

Moscow, 115446, Russia

Location

MeSH Terms

Conditions

Obesity; Overweight; Gastroesophageal Reflux

Interventions

Omeprazole

Condition Hierarchy (Ancestors)

Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Esophageal Motility Disorders; Deglutition Disorders; Esophageal Diseases; Gastrointestinal Diseases; Digestive System Diseases

Intervention Hierarchy (Ancestors)

2-Pyridinylmethylsulfinylbenzimidazoles; Sulfoxides; Sulfur Compounds; Organic Chemicals; Pyridines; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Benzimidazoles; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring

Central Study Contacts

Georgy E. Leonov, MD, PhD

CONTACT

+7 9055687783; golerus@gmail.com

Study Design

• Study Type: interventional
• Phase: phase 4
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER GOV
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: September 24, 2026
• First Posted: October 1, 2026
• Study Start: September 25, 2026
• Primary Completion (Estimated): December 25, 2026
• Study Completion (Estimated): December 25, 2026
• Last Updated: October 1, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

RU (1)