An interventional study of Indole-3-propionic acid and Placebo in Healthy, sponsored by Glostrup University Hospital, Copenhagen. Completed at 1 site in Denmark. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-03-05.
Sponsored by Glostrup University Hospital, Copenhagen · Not applicable, Interventional, and Basic science
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:
Participants will:
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.
Glostrup University Hospital, Copenhagen is the lead sponsor of 106 studies on the registry; 5 are open to participants now.
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Placebo
Dietary Supplement: Placebo
50 mg indole-3-propionic acid
Dietary Supplement: Indole-3-propionic acid
120 mg indole-3-propionic acid
Dietary Supplement: Indole-3-propionic acid
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.
Two capsules of placebo will be taken orally, once daily in the morning after an overnight fast for 14 consecutive days.
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.
Time frame: 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.
Time frame: Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
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.
Time frame: 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.
Time frame: 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).
Triglycerides
Plasma triglycerides (mmol/l).
Time frame: Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
non-HDL cholesterol
Non-HDL cholesterol calculated as total cholesterol minus HDL cholesterol (mmol/l)
Time frame: 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.
Time frame: Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
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.
Time frame: Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Isoprostane-F2-alpha
Isoprostane-F2-alpha measured in blood or morningurine samples as a marker of lipid oxidation.
Time frame: 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.
Time frame: Results from samples taken on day 15 and adjusted for results from day 1.
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.
Time frame: 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.
Total cholesterol
Plasma cholesterol (mmol/l).
Time frame: 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).
Time frame: 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).
Time frame: 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).
Time frame: Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Malondialdehyde
Malondialdehyde measured in blood or morningurine samples as a marker of oxidative stress.
Time frame: 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.
Time frame: Results from samples taken on day 15 and adjusted for results from day 1.
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.
Time frame: Results from fasting blood samples taken on day 15 and adjusted for results from day 1 (fasting just before first supplement/placebo dosis).
Changes in the gut microbiome
Characterization of the gut microbiome using molecular biology methods such as 16s rRNA sequencing.
Time frame: 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.
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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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
Time frame: Results from samples taken on day 15 and adjusted for results from day 1.
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.
Time frame: 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.
Time frame: 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.
Time frame: 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
Time frame: 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.
Time frame: 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)
Time frame: 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)
Time frame: 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).
Time frame: 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).
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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).
Time frame: 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.
Time frame: 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.
Time frame: 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).
Time frame: 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)
Time frame: 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.
Time frame: Measured on day 1 and then again on day 15
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: Yes — Individual participant data that underlie the results reported in published articles, after deidentification (text, tables, figures, and appendices).
Supporting information: Study protocol, Statistical analysis plan, Analytic code
Time frame: Beginning 3 months and ending 5 years following publication of the article they are presented in.
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.
Ran from Nov 2024 to primary completion in Feb 2025, 3 months.
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This study is completed, as verified in Mar 2025. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: 3-(indol-3-yl)propionic acid
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