HealthyNCT06551545
Tryptophan Metabolism in Healthy Young Adults
A study testing Tryptophan intake in people with Healthy, run by The Hospital for Sick Children at 1 site in Canada.
Trial summary
Tryptophan is an essential amino acid needed for growth and bodily functions. It is used to make serotonin which is needed for the brain to develop and function properly. However, when the body is stressed, tryptophan is broken down into compounds that can cause harm to the brain. Read more about this study
- Who is it for?
- Ages 18 to 45 yearsHealthy volunteers can take part
- Conditions the study is for
- Healthy
- What is being tested?
- Tryptophan intake
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 10 participants
- Where
- 1 siteCanada
- Study dates
- 1 Jan 2025to 31 Jul 2025
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 45 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Consent provided
- Aged 18 to 45 years old (inclusive)
- In good general health as evidenced by medical history, physical health and biochemistry
- Fasting blood glucose, hemoglobin A1c (HbA1c), urea, creatinine and CRP levels within normal ranges for age.
Who cannot join
- Presence of chronic disease and/or acute illness known to affect protein/amino acid metabolism (e.g. HIV, diabetes, cancer, liver or kidney disease, neurological conditions including depression and anxiety, hypo- / hyperthyroidism, inflammatory conditions,, anemia, acute cold or flu)
- Taking medications known to affect protein/AA metabolism (e.g. steroids, anti-inflammatory medications, acetaminophen, selective serotonin reuptake inhibitors (SSRI))
- Inability to tolerate the diet (i.e. allergy)
- Significant weight loss during the past month or consumption of weight reducing diets.
- Significant caffeine consumption (>2 cups per day)
- Significant consumption of alcohol (>1 drink per day i.e. 1 beer or ½ glass of wine).
- Unwilling to have blood drawn from a venous access or using a ventilated hood indirect calorimeter for the purposes of the study.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Tryptophan Metabolism in Healthy Young Adults in Response to Graded Tryptophan Intakes: a Pilot Study
Tryptophan is an essential amino acid needed for growth and bodily functions. It is used to make serotonin which is needed for the brain to develop and function properly. However, when the body is stressed, tryptophan is broken down into compounds that can cause harm to the brain. Premature babies who get nutrition through their vein [i.e. total parenteral nutrition (TPN)] can experience this type of stress. The amount of tryptophan in TPN solutions is much higher than what premature babies need and can produce too much harmful compounds. So, it is important to study the amount of these compounds made from tryptophan. But there are no methods available to study this. Therefore, the goal of this study is to develop a method to measure the compounds made from tryptophan breakdown in adults so that it can be used for preterm babies on TPN later.
Read the detailed description
Tryptophan is an essential amino acid and must be obtained from the diet. In addition to its essential role in protein synthesis, tryptophan has diverse and complex physiological functions via various metabolic pathways. Two primary metabolic pathways include the kynurenine and serotonin pathways. Tryptophan is the only precursor for both the kynurenine and serotonin pathways. Since these two pathways share tryptophan as the common nitrogenous substrate, a competition between these pathways is demonstrated. This can result in serotonin deficiency when kynurenine pathway is activated and may contribute to the pathophysiology of developing neurological disease. Furthermore, metabolites of the kynurenine pathway can exert neurotoxic effects because they can cross the blood brain barrier to reach the central nervous system (CNS). Evidence thus far indicates that the contribution of the different pathways of tryptophan metabolism can differ based on the physiological and pathological status. However, there is no clear evidence of whether the kynurenine pathway takes precedence over synthesis of protein (for growth) or serotonin during immune activation. There are also no investigations examining the impact of tryptophan intake during immune activation, for the purposes of this study meaning any activity by the immune system, on the production of neurotoxic metabolites of the kynurenine pathway.
Tryptophan uptake from parenteral nutrition fed to preterm neonates with current amino acid solutions may be about 2-2.5 times the estimated requirement based on data from neonatal piglets. Long-term effects of this excess intake in this vulnerable population are unknown. The potential adverse effects of increased catabolism via the kynurenine pathway during stress on growth and neurodevelopment of hospitalized preterm infants has not been explored. A method to quantify the partitioning of tryptophan between the different pathways will be highly beneficial but has not been established in humans. This will enable studies in parenterally fed neonates to assess whether tryptophan concentrations in current commercial amino acid solutions produce toxic metabolites or serotonin deficiency, which can contribute to neurocognitive deficits seen in this population.
- Conditions
- Healthy
- Being tested
- Tryptophan intake
- Keywords
- adults, healthy, tryptophan, tryptophan breakdown, indicator amino acid oxidation, stable isotope
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Tryptophan intakeDietary supplement
There are 5 different tryptophan test intake levels ranging from 2, 3, 4.5, 6, 8 mg.kg-1.day.1. Levels of tryptophan intake will depend on [15N2]tryptophan dose.
| Study group | Role | What they receive |
|---|---|---|
| Experimental: Tryptophan in healthy young adults (18-45 years) | Experimental | Tryptophan intake levels, up to 5 levels, will be tested in a random order in all subjects Receives: Dietary Supplement: Tryptophan intake |
What is being measured
The primary outcome is the main question the study is designed to answer.
Steady state
Time at which plasma and urine enrichment of L-[15N2]tryptophan reaches steady-state.
Measured: 10 hours
Fractional Synthesis Rate (FSR) of tryptophan metabolites
Enrichment of L-[15N2]tryptophan and its metabolites (15N2-L-kynurenine, 15N-kynurenic acid, 15N-quinolinic acid, 15N2-serotonin and 15N-5-hydroxyindole acetic acid) in plasma and urine following orally administered tracer, L-[15N2]tryptophan.
Measured: 10 hours
Secondary outcomes (2)
Partitioning of tryptophan metabolism
Partitioning of tryptophan between kynurenine and serotonin pathway at tryptophan intake below and above requirements
Measured: 10 hours
Fractional synthesis rate (FSR)
Fractional synthesis rate (FSR) of metabolites of tryptophan (15N2-L-kynurenine, 15N-kynurenic acid, 15N-quinolinic acid, 15N2-serotonin and 15N-5-hydroxyindole acetic acid) at isotopic steady state
Measured: 10 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 Aug 2024
- Study start1 Jan 2025
- Primary completion31 Jul 2025
- Study completion31 Jul 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HealthyStudies of the same condition, open and under way.
- More trials run by The Hospital for Sick ChildrenThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 10 participants (actual)
Sponsor and investigators
- Lead sponsor
- The Hospital for Sick Children
- Sponsor type
- University, hospital or other
- Collaborators
- Canadian Institutes of Health Research (CIHR)
- Responsible party
- Principal investigator, Glenda Courtney-Martin, The Hospital for Sick Children
- Investigators
- Glenda Courtney-Martin, PhD, RD, Principal investigator, The Hospital for Sick Children
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06551545
- Sponsor's protocol ID
- 1000081438
- Status last verified
- Sep 2026
- First submitted
- 8 Aug 2024
- Last updated
- 2 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 2 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Tryptophan Metabolism in Healthy Young Adults in Response to Graded Tryptophan Intakes: a Pilot Study
- ClinicalTrials.gov ID
- NCT06551545
- Acronym / sponsor ID
- 1000081438
- Conditions
- Healthy
- Keywords
- adults, healthy, tryptophan, tryptophan breakdown, indicator amino acid oxidation, stable isotope
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 10 participants (actual)
- Lead sponsor
- The Hospital for Sick ChildrenUniversity, hospital or other
- Collaborators
- Canadian Institutes of Health Research (CIHR)
- Study start
- 1 Jan 2025 (actual)
- Primary completion
- 31 Jul 2025 (actual)
- Study completion
- 31 Jul 2025 (actual)
- First posted
- 13 Aug 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Tryptophan is an essential amino acid needed for growth and bodily functions. It is used to make serotonin which is needed for the brain to develop and function properly. However, when the body is stressed, tryptophan is broken down into compounds that can cause harm to the brain. Premature babies who get nutrition through their vein [i.e. total parenteral nutrition (TPN)] can experience this type of stress. The amount of tryptophan in TPN solutions is much higher than what premature babies need and can produce too much harmful compounds. So, it is important to study the amount of these compounds made from tryptophan. But there are no methods available to study this. Therefore, the goal of this study is to develop a method to measure the compounds made from tryptophan breakdown in adults so that it can be used for preterm babies on TPN later.
Detailed description
Tryptophan is an essential amino acid and must be obtained from the diet. In addition to its essential role in protein synthesis, tryptophan has diverse and complex physiological functions via various metabolic pathways. Two primary metabolic pathways include the kynurenine and serotonin pathways. Tryptophan is the only precursor for both the kynurenine and serotonin pathways. Since these two pathways share tryptophan as the common nitrogenous substrate, a competition between these pathways is demonstrated. This can result in serotonin deficiency when kynurenine pathway is activated and may contribute to the pathophysiology of developing neurological disease. Furthermore, metabolites of the kynurenine pathway can exert neurotoxic effects because they can cross the blood brain barrier to reach the central nervous system (CNS). Evidence thus far indicates that the contribution of the different pathways of tryptophan metabolism can differ based on the physiological and pathological status. However, there is no clear evidence of whether the kynurenine pathway takes precedence over synthesis of protein (for growth) or serotonin during immune activation. There are also no investigations examining the impact of tryptophan intake during immune activation, for the purposes of this study meaning any activity by the immune system, on the production of neurotoxic metabolites of the kynurenine pathway.
Tryptophan uptake from parenteral nutrition fed to preterm neonates with current amino acid solutions may be about 2-2.5 times the estimated requirement based on data from neonatal piglets. Long-term effects of this excess intake in this vulnerable population are unknown. The potential adverse effects of increased catabolism via the kynurenine pathway during stress on growth and neurodevelopment of hospitalized preterm infants has not been explored. A method to quantify the partitioning of tryptophan between the different pathways will be highly beneficial but has not been established in humans. This will enable studies in parenterally fed neonates to assess whether tryptophan concentrations in current commercial amino acid solutions produce toxic metabolites or serotonin deficiency, which can contribute to neurocognitive deficits seen in this population.
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Experimental: Tryptophan in healthy young adults (18-45 years) | Experimental | Dietary Supplement: Tryptophan intakeTryptophan intake levels, up to 5 levels, will be tested in a random order in all subjects |
Who may qualify
- Ages
- 18 to 45 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Consent provided
- Aged 18 to 45 years old (inclusive)
- In good general health as evidenced by medical history, physical health and biochemistry
- Fasting blood glucose, hemoglobin A1c (HbA1c), urea, creatinine and CRP levels within normal ranges for age.
Key exclusion criteria (7 listed)
- Presence of chronic disease and/or acute illness known to affect protein/amino acid metabolism (e.g. HIV, diabetes, cancer, liver or kidney disease, neurological conditions including depression and anxiety, hypo- / hyperthyroidism, inflammatory conditions,, anemia, acute cold or flu)
- Taking medications known to affect protein/AA metabolism (e.g. steroids, anti-inflammatory medications, acetaminophen, selective serotonin reuptake inhibitors (SSRI))
- Inability to tolerate the diet (i.e. allergy)
- Significant weight loss during the past month or consumption of weight reducing diets.
- Significant caffeine consumption (>2 cups per day)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Tryptophan intakeThere are 5 different tryptophan test intake levels ranging from 2, 3, 4.5, 6, 8 mg.kg-1.day.1. Levels of tryptophan intake will depend on [15N2]tryptophan dose. | Dietary supplement | Experimental: Tryptophan in healthy young adults (18-45 years) |
Primary outcome
Steady state
Time frame: 10 hours
Time at which plasma and urine enrichment of L-[15N2]tryptophan reaches steady-state.
Fractional Synthesis Rate (FSR) of tryptophan metabolites
Time frame: 10 hours
Enrichment of L-[15N2]tryptophan and its metabolites (15N2-L-kynurenine, 15N-kynurenic acid, 15N-quinolinic acid, 15N2-serotonin and 15N-5-hydroxyindole acetic acid) in plasma and urine following orally administered tracer, L-[15N2]tryptophan.
2 secondary outcomes
Partitioning of tryptophan metabolism
Time frame: 10 hours
Fractional synthesis rate (FSR)
Time frame: 10 hours
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Oct 2026.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Glenda Courtney-Martin, PhD, RD principal investigator
The Hospital for Sick Children
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Tryptophan intake in people with Healthy, run by The Hospital for Sick Children at 1 site in Canada.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 2 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Steady state (time frame: 10 hours). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Oct 2026.