Indole-3-PROpionic Acid Clinical Trials - a Pilot Study (iPROACT-pilot)

Indole-3-PROpionic Acid Clinical Trials - a Pilot Study (iPROACT-pilot)

The goal of this pilot intervention trial is to investigate the biological effects of daily supplementation with different doses of indole-3-propionic acid (IPA) in healthy adults. The main scientific questions are:

• Does supplementation with IPA increase the abundance regulatory T cells in the blood? Regulatory T cells are believed to play an important role in preventing autoimmune diseases.
• Does supplementation with IPA increase the concentration of brain-derived neurotrophic factor (BDNF) in the blood? BDNF is believed to play an important role in maintaining brain health.
• Does supplementation with IPA affect blood analyses commonly performed to assess the risk of metabolic disorders like type 2 diabetes and cardiovascular diseases?
• How big a dose of IPA is necessary to achieve the above benefits?

Participants will:

• Take 50 mg IPA or 120 mg IPA or 500 mg IPA or placebo every morning for 14 days.
• Visit the clinic at the beginning (day 1) and at the end (day 15) of IPA supplementation to deliver blood, urine and fecal samples, have simple measurements performed, fulfil questionnaires and report any side effects.

Study Overview

• Status: Completed
• Conditions: Healthy
• Intervention / Treatment: Dietary supplement: Placebo; Dietary supplement: Indole-3-propionic acid

Detailed Description

Indole-3-propionic acid (IPA) is a gut bacterial metabolite with the amino acid tryptophan as substrate. In vitro and animal studies, suggest that IPA could contribute to regulating inflammation and metabolic function, preventing oxidative damage and upregulating expression of brain-derived neurotrophic factor. With this study we aim to investigate the biochemical effects of IPA at supraphysiological levels in humans.

• Study Type: Interventional
• Enrollment (Actual): 79
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Denmark
  • Glostrup, Denmark, 2600
    • Optic Neuritis Clinic, Danish Multiple Sclerosis Center, Department of Neurology, Copenhagen University Hospital, Rigshospitalet-Glostrup

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy women and men ≥18 and ≤65 years of age
• Deemed mentally and physically able to participate

Exclusion Criteria:

• Diagnosis of gut-, heart-, liver-, kidney or immune-related disorders
• Use of antibiotics within the last month
• Pregnant or lactating women or birth within the last five months
• Use of medicine that requires prescription

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo	Dietary supplement: Placebo; Two capsules of placebo will be taken orally, once daily in the morning after an overnight fast for 14 consecutive days.
Experimental: 50 mg IPA; 50 mg indole-3-propionic acid	Dietary supplement: Indole-3-propionic acid; A dosis of either 50 mg IPA, 120 mg IPA or 500 mg IPA (two capsules) will be taken orally, once daily in the morning after an overnight fast for 14 consecutive days.
Experimental: 120 mg IPA; 120 mg indole-3-propionic acid	Dietary supplement: Indole-3-propionic acid; A dosis of either 50 mg IPA, 120 mg IPA or 500 mg IPA (two capsules) will be taken orally, once daily in the morning after an overnight fast for 14 consecutive days.
Experimental: 500 mg IPA; 500 mg indole-3-propionic acid	Dietary supplement: Indole-3-propionic acid; A dosis of either 50 mg IPA, 120 mg IPA or 500 mg IPA (two capsules) will be taken orally, once daily in the morning after an overnight fast for 14 consecutive days.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Regulatory T cells (first primary outcome)	FoxP3+CD25+CD127- regulatory T cells expressed as a percentage of single, live CD3+CD4+CD8- lymphocytes. Analysed in freshly isolated peripheral blood mononuclear cells using a Symphony A3 flowcytometer.	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Brain-derived neurotrophic factor (second primary outcome)	Brain-derived neurotrophic factor measured in plasma samples using ELISA or mesoscale.	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Flowcytometric profiling of T cells	T cell profiling of freshly isolated peripheral blood mononuclear cells using a Symphony A3 flowcytometer. Panel antigens: CD3, CD4, CD8, CD45RA, CCR7, CXCR3, CCR6, CCR4, CCR10, CD25, CD127, FoxP3. Target populations Th1: CXCR3+CCR4-CCR6-CCR10- Th2: CXCR3-CCR4+CCR6-CCR10- Th17: CXCR3-CCR4+CCR6+CCR10- Th17.1: CXCR3+CCR4-CCR6+CCR10- Th22: CXCR3-CCR4+CCR6+CCR10+ all of the above expressed as a percentage of single, live CD3+CD4+CD8-CD45RA- lymphocytes. Furthermore, Th1/Th2 and Th17/Treg ratios will be calculated and the expression of CCR7 will be analysed within the target populations. In addition, the expression of the above chemokine receptors will be explored within the population of FoxP3+CD25+C1D127- T regulatory cells. This will allow for monitoring of newly identified T cells subsets such as Th1-like Tregs. Lastly, an untargetted approach may be employed to allow for unbiased identification of changes in novel, yet uncharacterized populations.	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Serum metabolomics	Targetted and untargetted liquid-chromatography mass-spectrometry-based metabolomics of serum samples. Targetted analyses aim to quantify indole-3-propionic acid and its metabolites (biomarker of compliance as well as absorptive and metabolic capacity), other bacterial- and host metabolites of tryptophan as well as short-chain fatty acids.	Four samples in total. Day 1 prior to and again 1.5 hour after intake of first capsule of IPA/ placeblo. Day 15 prior to and again 1.5 hour after intake of last capsule of IPA/ placebo.
Changes in the gut microbiome	Characterization of the gut microbiome using molecular biology methods such as 16s rRNA sequencing.	Fecal samples are collected at three time points: prior to supplementation (earliest 48 hours prior to first visit (day 1)), short after initiation of supplementation (day 3 or soonest thereafter) and again earliest 48 hours prior to last visit.
Fasting glucose	Plasma glucose (mmol/l). Participants abstain from eating and drinking after 22.00 the day before. Only water is allowed. Fasting blood samples are taken between 8.00-10.00 in the morning.	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Glycated hemoglobin (HbA1c)	HbA1c (IFCC, mmol/mol) measured in whole blood. Estimated average glucose values (mmol/l) are also calculated automatically from HbA1c by our laboratory.	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
C-peptide	Proinsulin C-peptide (pmol/l) measured in plasma.	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Total cholesterol	Plasma cholesterol (mmol/l).	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
HDL cholesterol	Plasma high-density lipoprotein (HDL) (mmol/l).	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
LDL cholesterol	Plasma low-density lipoprotein (LDL) (mmol/l).	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
VLDL cholesterol	Plasma very low-density lipoproteins (mmol/l).	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Triglycerides	Plasma triglycerides (mmol/l).	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
CRP	C-reactive protein (CRP) measured in plasma (mg/L) as a biomarker of infection and systemic inflammation. Lower-limit of quantification: 0,4 mg/L. Values below 0,4 mg/L are imputed as 0,2 mg/L.	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Malondialdehyde	Malondialdehyde measured in blood or morningurine samples as a marker of oxidative stress.	Results from samples taken on day 15 and adjusted for results from day 1.
Isoprostane-F2-alpha	Isoprostane-F2-alpha measured in blood or morningurine samples as a marker of lipid oxidation.	Results from samples taken on day 15 and adjusted for results from day 1.
8-oxo-dG	8-oxo-dG (8-Oxo-2'-deoxyguanosine) measured in blood or morningurine samples as a marker of DNA-related stress damage.	Results from samples taken on day 15 and adjusted for results from day 1.
Protein carbonyls	Protein carbonyls measured in blood or morningurine samples as a marker of protein oxidation.	Results from samples taken on day 15 and adjusted for results from day 1.
Characterization of the metabolic activity of the gut microbiota	Targetted and untargetted liquid-chromatography mass-spectrometry-based metabolomics. Targetted analyses aim to quantify indole-3-propionic acid, other bacterial- and host metabolites of tryptophan as well as short-chain fatty acids.	Fecal samples are collected at three time points: prior to supplementation (earliest 48 hours prior to first visit (day 1)), short after initiation of supplementation (day 3 or soonest thereafter) and again earliest 48 hours prior to last visit.
Bacterial polysaccharides	Endotoxin, capsular polysaccharides or other bacterial polysaccharides measured in blood samples as biomarker of bacterial translocation across the intestinal epithelium.	Results from samples taken on day 15 and adjusted for results from day 1.
Pre-haptoglobin 2	Measurement of pre-haptoglobin 2 in blood samples as a biomarker of intestinal permeability.	Results from samples taken on day 15 and adjusted for results from day 1.
Intestinal fatty acid binding protein	Measurements of intestinal fatty acid binding protein in blood samples as a biomarker of enterocyte damage.	Results from samples taken on day 15 and adjusted for results from day 1.
Citrulline	Measurement of citrulline in blood samples as a biomarker of intestinal function.	Results from samples taken on day 15 and adjusted for results from day 1.
Calprotectin	Calprotectin measured in fecal samples as a biomarker of intestinal inflammation.	Results from samples taken on day 15 and adjusted for results from day 1.
Neopterin	Neopterin measured in morningurine samples as a biomarker of systemic inflammation.	Results from samples taken on day 15 and adjusted for results from day 1.
suPAR	Soluble urokinase plasminogen activator receptor (suPAR) measured in blood samples.	Results from samples taken on day 15 and adjusted for results from day 1.
Microvesicles	Flow cytometric analyses of microvesicles/ microparticles in platelet-free plasma as biomarker of systemic inflammation.	Results from samples taken on day 15 and adjusted for results from day 1.
Endothelial progenitor cells	Flow cytometric analyses of endothelial progenitor cells measured in platelet-free plasma as biomarker of systemic inflammation	Results from samples taken on day 15 and adjusted for results from day 1.
non-HDL cholesterol	Non-HDL cholesterol calculated as total cholesterol minus HDL cholesterol (mmol/l)	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Gastrointestinal comfort	Self-reported (questionnaire) gastrointestinal symptoms of bloating, pain, rumbling, flatulence, constipation, hard stools and diarrhea evaluated using a visual analogue scale as well as a question on the frequency of defecation.	Gastrointestinal symptoms are assessed on day 1 and day 15.
Gastrointestinal transit time	Measurement of transit time through the digestive system using a so-called maize test. Participants consume 100 grams of sweet maize in the morning between 5.30-10.00 while still in a fasting state. The exact date and time of consumption is registered and so is the exact date and time when maize is observed for the first time in feces. Transit time is expressed as the difference between the ingestion and fecal excretion timepoints in hours.	Maize is ingested five days before visit 1 and again five days before visit 2.
Stool consistency	Classification of stool consistency using the Bristol Stool Chart. Numerical scale ranging from 1 (separate hard lumps) to 7 (liquid consistency with no solid pieces) with one-unit increments.	Bristol stool chart is used in association with each maize test and collection of fecal samples (earliest 48 hours prior to first visit and day 3 or soonest thereafter and again earliest 48 hours prior to last visit (day 15)).
Fecal pH	pH of collected fecal samples	Fecal samples are collected at three time points: prior to supplementation (earliest 48 hours prior to first visit (day 1)), short after initiation of supplementation (day 3 or soonest thereafter) and again earliest 48 hours prior to last visit (day 15).
Antibody-coating of bacteria	Characterization of IgA, IgG and IgM-coating of bacteria from fecal samples using bacterial flow cytometry.	Fecal samples are collected at three time points: prior to supplementation (earliest 48 hours prior to first visit (day 1)), short after initiation of supplementation (day 3 or soonest thereafter) and again earliest 48 hours prior to last visit (day 15).
Immunoglobulin G	Plasma immunoglobulin G (g/l)	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (just before first supplement/placebo dosis).
Immunoglobulin A	Plasma immunoglobulin A (g/l)	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Leucocyte counts	Total leucocytes as well as basophils, eosinophils, lymphocytes, monocytes, neutrophils as well as the joint group of metamyelo-, myelo- and promyelocytes. All counted in whole blood samples (10^9/l).	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (just before first supplement/placebo dosis).
Hemoglobin	Hemoglobin measured in whole blood (mmol/l).	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Alanine transaminase	Plasma alanine transaminase (ALT, U/l) as a biomarker of liver function.	Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Alkaline phosphatase	Alkaline phosphatase (U/l) as a biomarker of liver function.	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Aspartate aminotransferase	Aspartate aminotransferase also known as aspartate transaminase measured in plasma (U/l) as a biomarker of liver damage.	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Bilirubin	Bilirubins measured in plasma (µmol/L) as a biomarker of liver function.	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Coagulation factors II + VII + X	Coagulation factors II + VII + X (INR: International Normalized Ratio) measured in plasma as a biomarker of liver function.	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Lactate dehydrogenase (LDH)	Lactate dehydrogenase measured in plasma (U/l).	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Creatinine	Plasma creatinine (µmol/L) as a biomarker of kidney function.	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis)
eGFR	Estimated glomerular filtration rate (eGFR/ 1,73m² (ml/min)) as a biomarker of kidney function.	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Albumin	Albumin measured in plasma (g/l).	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
25-OH-vitamin D	Plasma 25-OH-vitamin D (D3+D2) (nmol/L)	Results from blood samples taken on day 15 (just before last supplement/placebo dosis) and adjusted for results from day 1 (just before first supplement/placebo dosis).
Blood pressure	Blood pressure (mm Hg) defined as the lowest value obtained across three measurements.	Measured on day 1 and then again on day 15

Collaborators and Investigators

• Sponsor: Glostrup University Hospital, Copenhagen
• Collaborators: University of Copenhagen; University of Southampton
• Investigators: Principal Investigator: Jette Lautrup Frederiksen, Prof, DMSc, MD, Jette Lautrup Frederiksen

Study record dates

Study Major Dates

• Study Start (Actual): November 14, 2024
• Primary Completion (Actual): February 25, 2025
• Study Completion (Actual): February 25, 2025

Study Registration Dates

• First Submitted: November 2, 2024
• First Submitted That Met QC Criteria: November 2, 2024
• First Posted (Actual): November 5, 2024

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: March 1, 2025
• Last Verified: March 1, 2025

More Information

Terms related to this study

• Keywords: dietary supplement; regulatory T cells; brain-derived neurotrophic factor; Indole-3-propionic acid; gut bacterial metabolite
• Other Study ID Numbers: H-24008127

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Individual participant data that underlie the results reported in published articles, after deidentification (text, tables, figures, and appendices).
• IPD Sharing Time Frame: Beginning 3 months and ending 5 years following publication of the article they are presented in.
• IPD Sharing Access Criteria: Researchers who provide a methodologically sound proposal can access the IPD to achieve the aims of the approved proposal. Proposals should be directed to jette.lautrup.battistini@regionh.dk. To gain access, data requestors will need to sign a data access agreement. Data and explanatory files will be made available at a third party website.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No