Recruiting

Observational Study

Sponsor:

UCLA

Code:

NCT06668922

Conditions

Irritable Bowel Syndrome (IBS)

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Accepted

Interventions

Inulin

Study Details

Brief summary:

The study will investigate the relationship between fecal bile acids, short-chain fatty acids (SCFAs), and the gut microbiota in irritable bowel syndrome (IBS). The central hypothesis of this study is that specific shifts in the GI microbiome composition correlate with altered colonic SCFAs and BAs and contribute to IBS symptoms. Primary aims include: (a) identifying GI microbiome signatures in IBS subtypes (IBS-C and IBS-D) and matched controls, and test if microbiome signatures in these groups correlate with fecal SCFAs and bacterial fermentation of an indigestible carbohydrate (inulin) after a dietary challenge (fecal inulin), and (b) determining if GI microbiome signatures in IBS subtypes and controls correlate with fecal BAs or markers of SCFA production (fecal SCFAs or inulin) and test if BAs correlate with fecal SCFAs or inulin.

The target population is adults ages 18-65 years meeting Rome IV criteria for IBS (both diarrhea- and constipation-predominant, IBS-D and IBS-C) and asymptomatic controls. Primary outcomes will be fecal bile acid excretion and profile, short-chain fatty acid excretion and profile, colonic transit, and fecal microbiota. Secondary outcomes will be stool characteristics based on responses to validated bowel diaries. Stool samples will be collected from participants during the last 2 days of a 4-day 100 g fat diet and split into 3 samples for fecal microbiota, SCFA, and bile acid analysis.

Conditions

Irritable Bowel Syndrome (IBS)

Study ID

NCT06668922

Start date

Nov 28, 2024

Status verified date

Aug, 2026

Completion date

Dec 31, 2030

Anticipated

Primary completion date

Dec 31, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 70+

Healthy Volunteers: Accepted

Inclusion Criteria:

  • Age 18-75
  • Individuals with irritable bowel syndrome (IBS)
  • Healthy volunteers (healthy controls) with no prior history of gastrointestinal (GI) disease or symptoms
  • No dietary restrictions other than vegetarian

Exclusion Criteria:

  • Inflammatory bowel disease, celiac disease, or certain types of abdominal cancer, as well as those with thyroid or liver issues
  • Abdominal surgery or abdominal radiation within 6 months of study participation, with an exception for C-section or gallbladder removal
  • Use of any prescription, over the counter, or herbal medications known to affect gastrointestinal function or study interpretation, such as opioids, inflammatory drugs or certain antidepressants, within 6 months prior to study participation for healthy volunteers, or within 2 days of study participation for participants with IBS.
  • An exception will be permitted for limited use of stable low doses of antidepressants for individuals who have been taking them for a period greater than one month.
  • Rescue medication such as Bisacodyl (dulcolax) to relieve severe constipation and allow for stool collection will be permitted when needed.
  • Use of Ozempic and Ozempic-type medications
  • Pregnant or breastfeeding women
  • Antibiotic use within 3 months of study participation
  • Use of prebiotics or probiotics within the 2 weeks before the study initiation
  • Regular tobacco use within the past 6 months

Study Design

Enrollment

72 participants

Anticipated

Allocation

Non randomized

Intervention Model

Single group

Primary purpose

Diagnostic

Interventions and Outcome Measures

Arms

experimental: Healthy volunteers

Adults ages 18-65 years with no prior history of gastrointestinal diseases or symptoms.

experimental: Irritable Bowel Syndrome Patients with Diarrhea (IBS-D)

Patients with irritable bowel syndrome (IBS) with diarrhea, ages 18-65 years fulfilling Rome IV criteria for IBS.

experimental: Irritable Bowel Syndrome Patients with Constipation (IBS-C)

Patients with irritable bowel syndrome (IBS) with constipation, ages 18-65 years fulfilling Rome IV criteria for IBS.

Interventions

Inulin

Inulin ingestion is not being used to diagnose, treat, or prevent IBS. Inulin is being used to study an individual's ability to ferment dietary fiber.

Primary outcome measure

  • Total fecal bile acids [ Time Frame: 48 hours ]
  • Total fecal short chain fatty acids [ Time Frame: 48 hours ]
  • Individual fecal short chain fatty acids [ Time Frame: 48 hours ]
  • Fecal microbial population [ Time Frame: 48 hours ]
  • Fecal inulin [ Time Frame: 48 hours ]

Central Contacts and Locations

Locations

University of California, Los Angeles

Recruiting

Los Angeles, California, United States, 90095

Contacts

Ren Cutrer

(310) 794-9507rcutrer@mednet.ucla.edu

Principal Investigator:

Andrea S Shin

More Information

Sponsor

University of California, Los Angeles

Last update posted

Aug 12, 2026

Last verified

Aug, 2026

Keywords

  • irritable bowel syndrome
  • IBS
  • short-chain fatty acids
  • SCFAs
  • bile acids
  • fecal inulin
  • microbiota

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by University of California, Los Angeles on 2026-08-12.