Functionally Enhanced Limosilactobacillus Reuteri Probiotic Preparation in Elderly Patients With Functional Bowel Disorders

This single-center, open-label, single-arm interventional study is designed to evaluate the effects of a functionally enhanced Limosilactobacillus reuteri probiotic preparation on intestinal immunity, gut microbiota balance, and intestinal function in elderly patients with functional bowel disorders. Participants will be middle-aged and older adults, aged 50-65 years, diagnosed with functional constipation, irritable bowel syndrome, or functional abdominal pain syndrome according to Rome IV criteria. Patients with organic gastrointestinal diseases or severe systemic illnesses will be excluded.

Eligible participants will receive the functionally enhanced Limosilactobacillus reuteri probiotic preparation orally, in addition to continuing conventional symptomatic treatment as needed. The probiotic will be administered over a period of 8 consecutive weeks.

Participants will be instructed to maintain their usual diet and lifestyle and avoid additional probiotic supplements or antibiotics during the intervention period. Adherence will be monitored through capsule counts at each visit and participant diaries recording intake and any adverse events. Regular assessments will include in-person visits at baseline, Week 4, and Week 8, as well as telephone follow-ups at Weeks 1, 2, and 6 to ensure compliance and capture any tolerability issues. Safety monitoring will include routine laboratory tests (blood count, liver and renal function, and serum biochemical markers) and recording of all adverse events throughout the study period.

Primary outcome measures include changes in senescence-associated secretory phenotype (SASP) expression levels, which will be assessed to determine the extent of aging improvement and thereby evaluate intestinal immune aging.Clinical symptoms, including abdominal pain, abdominal distension, bowel movement frequency, and stool form assessed using the Bristol Stool Form Scale, will also be recorded. In addition, gut microbiota composition and key functional bacterial abundance will be analyzed through fecal metagenomic sequencing, along with metabolomic profiling of tryptophan-related metabolites. Safety outcomes include monitoring adverse events and routine laboratory parameters, such as complete blood count, liver and renal function, and serum biochemical indicators.

Assessments will be performed at baseline, Week 4, and Week 8, including in-person visits and telephone follow-up to ensure participant compliance and timely collection of samples. Fecal samples will be collected for metagenomic and metabolomic analyses to explore the relationship between probiotic intervention, gut microbiota metabolic function, and intestinal immune aging. This study aims to provide comprehensive evidence for the potential mechanism by which this functionally enhanced probiotic preparation may regulate the gut immune-microbiota network, maintain mucosal barrier integrity, and improve intestinal aging-related microenvironment in elderly patients with functional bowel disorders, thereby informing future clinical application and larger-scale trials.

Inclusion criteria

1.Diagnosis and Symptom Presentation: Participants must be diagnosed with functional gastrointestinal disorders (FGID) according to Rome IV criteria, including but not limited to:

• Functional constipation;
• Irritable bowel syndrome (IBS);
• Functional abdominal pain syndrome;
• Participants must have clear intestinal dysfunction-related symptoms such as abdominal pain, abdominal distension, difficulty in defecation, or changes in bowel habits, with organic gastrointestinal diseases excluded by clinical evaluation.

2.Age and Disease Duration: Participants aged 50-65 years, with relevant symptoms persisting for at least 6 months, and having inadequate response to prior conventional treatment. Conventional treatments include but are not limited to: antidiarrheal agents (e.g., loperamide), gastrointestinal motility regulators (e.g., pinaverium bromide, trimebutine), intestinal microbiota products, or other commonly used drugs to improve diarrhea or regulate bowel function.

3.Symptom Severity Assessment: Participants must have a total score of 10-20 on the functional bowel symptom scoring scale as specified in the study protocol (see Appendix).

4.General Condition and Compliance: Participants must be able to understand the study purpose, provide written informed consent, and comply with the study procedures, including scheduled visits and collection of blood and fecal samples.

Exclusion criteria

• History or current presence of organic gastrointestinal diseases, such as gastrointestinal malignancy, inflammatory bowel disease (IBD), intestinal obstruction, or intestinal polyps.
• Presence of serious systemic diseases, including severe cardiovascular or cerebrovascular diseases (e.g., myocardial infarction within the past 6 months, New York Heart Association (NYHA) class III-IV heart failure, uncontrolled hypertension), significant liver or kidney dysfunction (alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >2× upper limit of normal, estimated glomerular filtration rate (eGFR) <45 mL/min/1.73m²), or uncontrolled diabetes (HbA1c ≥9%).
• Use of antibiotics, probiotics, or other drugs significantly affecting gut microbiota within 4 weeks prior to enrollment, or anticipated need to continue these drugs during the study.
• Pregnant or breastfeeding women, or those planning pregnancy during the study period.
• Participation in other clinical trials within 3 months prior to enrollment.
• Any other health conditions deemed unsuitable for participation by the investigator.