Modulating Glucose Tolerance With Dietary Tyrosine
![]() |
The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. |
ClinicalTrials.gov Identifier: NCT03872557 |
Recruitment Status :
Completed
First Posted : March 13, 2019
Last Update Posted : May 5, 2021
|
- Study Details
- Tabular View
- No Results Posted
- Disclaimer
- How to Read a Study Record
Condition or disease | Intervention/treatment | Phase |
---|---|---|
Glucose Tolerance | Dietary Supplement: Tyrosine (TYR) Supplementation | Not Applicable |
Study Type : | Interventional (Clinical Trial) |
Actual Enrollment : | 10 participants |
Allocation: | Non-Randomized |
Intervention Model: | Crossover Assignment |
Masking: | None (Open Label) |
Primary Purpose: | Basic Science |
Official Title: | Modulating Glucose Tolerance With Dietary Tyrosine |
Actual Study Start Date : | August 7, 2019 |
Actual Primary Completion Date : | January 24, 2020 |
Actual Study Completion Date : | January 24, 2020 |

Arm | Intervention/treatment |
---|---|
Active Comparator: Tyrosine (TYR) depletion, then oral TYR
TYR supplementation: Subjects will be directed to avoid consumption of L-DOPA and TYR enriched foods for 48 hours before oral glucose tolerance test (OGTT). On the evening prior to OGTT, subjects will substitute normal meal and snack for three prepackaged tyrosine-phenylalanine-free liquid meals. Visit 2. Placement of intravenous catheter for the collection of serial blood samples and an OGTT with supplementation with oral tyrosine supplement. To supplement the OGTT with Tyrosine, the contents of four (4) L-Tyrosine 500 mg capsule are given 45 minutes before the oral glucose solution is administered. The capsules are to be administered with less than eight ounces of water to minimize dilution of gastric acidity. |
Dietary Supplement: Tyrosine (TYR) Supplementation
L-Tyrosine dietary supplement will be provided as 500 mg capsules and 4 (four) 500 mg capsules are to be given before OGTT. The capsules are formed from animal gelatin, and the contents are formulated with magnesium stearate as a flow agent, but without binders, coatings or colorings and also have no added flavorings, sugars, salt, artificial sweeteners, preservatives or salicylates. The capsules are to be administered with less than eight ounces of water to minimize dilution of gastric acidity. |
No Intervention: TYR depletion, then no oral TYR
Subjects will be directed to avoid consumption of L-DOPA and TYR enriched foods for 48 hours before OGTT. On the evening prior to OGTT, subjects will substitute normal meal and snack for three prepackaged tyrosine-phenylalanine-free liquid meals. Subsequent Visit 3. This visit will consist of placement of intravenous catheter for the collection of serial blood samples and an OGTT without supplementation with oral tyrosine supplement. |
- Whole blood glucose level [ Time Frame: Up to 120 minutes from baseline ]Glucose concentration versus time profile following glucose challenge define glucose tolerance
- Plasma insulin concentration [ Time Frame: Up to 120 minutes from baseline ]Plasma insulin concentration versus time profile following glucose challenge define glucose tolerance
- Plasma dopamine concentration [ Time Frame: Up to 120 minutes from baseline ]Plasma dopamine concentration versus time profile following glucose challenge may affect glucose tolerance
- Plasma L-DOPA concentration [ Time Frame: Up to 120 minutes from baseline ]Plasma L-DOPA concentration versus time profile following glucose challenge may affect glucose tolerance
- L-tyrosine concentration [ Time Frame: Up to 120 minutes from baseline ]Plasma L-tyrosine concentration versus time profile following glucose challenge may affect glucose tolerance
- Plasma glucagon concentration [ Time Frame: Up to 120 minutes from baseline ]Plasma glucagon concentration versus time profile following glucose challenge impacts glucose tolerance
- Plasma GLP-1 concentration [ Time Frame: Up to 120 minutes from baseline ]Plasma GLP-1 concentration versus time profile following glucose challenge impacts glucose tolerance

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.
Ages Eligible for Study: | 18 Years to 65 Years (Adult, Older Adult) |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | Yes |
i. Inclusion Criteria
- Capable of giving written as well as oral informed consent.
- A fasting plasma glucose level (FPG) < 126 mg/dL (< 7.0 mmol/L) and an Hb1ac in the 5.7-6.4 % range.
- BMI in the range of 18-45 kg/m2.
- Normal Complete blood count (CBC), renal and liver function tests.
ii. Exclusion Criteria:
- Any diabetes medication within previous three (3) months.
- Fasting plasma Glucose (FPG) >126 mg/dl or HbA1c > 6.4%
- Current use (or within 6 months) of antipsychotic, anti-anxiety, or antidepressant medications (e.g. monoamine oxidase (MAO) inhibitors, 5-Hydroxytryptophan (5HT) inhibitors, tricyclic antidepressants, L-DOPA), reserpine, β-2-receptor agonists (e.g., terbutaline), steroids, weight loss medication, anticoagulant medication, over-the-counter nutritional supplements other than standard vitamin and mineral supplements
- History of Phenylketonuria or other inherited disorders of amino acid metabolism.
- History of movement disorder such as Parkinson's disease or Huntington's disease
- Cardiovascular, renal, pulmonary, gastrointestinal, migraines or other medical conditions deemed significant by investigators
- History of/ or psychiatric illness such as major depression, bipolar disease, anxiety or schizophrenia.
- History of bariatric surgery with the exception of gastric band if the band has been removed
- Female of child-bearing age, currently pregnant, breastfeeding or not using a form of birth control.
- Previous or current use of cocaine, methamphetamine, ecstasy (3-4 methylenedioxymethamphetamine (MDMA))
- Current daily intake of caffeine >500 mg/day (>4-5 cups of coffee; >10 12-oz cans of soda)
- Consumption of more than 1 alcoholic drink per day or smoking more than 5 cigarettes/day.
- Systolic Blood Pressure (SBP) > 150 mmHg; Diastolic Blood Pressure (DBP) > 100 mmHg.
- Recent history (in the past three months) of more than a 3% gain or loss in body wt.
- Difficulty in swallowing capsules.
- Concurrent use of antacids or proton pump inhibitors (e.g.,Prilosec Prevacid, dexilant, Aciphex, Protonix, Nexium, Vimovo, Zegerid)

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT03872557
United States, New York | |
Columbia University Irving Medical Center | |
New York, New York, United States, 10032 |
Principal Investigator: | Judith Korner, MD | Columbia University |
Documents provided by Judith Korner, Columbia University:
Responsible Party: | Judith Korner, Professor of Medicine, Columbia University |
ClinicalTrials.gov Identifier: | NCT03872557 |
Other Study ID Numbers: |
AAAS2124 R01DK104740 ( U.S. NIH Grant/Contract ) |
First Posted: | March 13, 2019 Key Record Dates |
Last Update Posted: | May 5, 2021 |
Last Verified: | April 2021 |
Individual Participant Data (IPD) Sharing Statement: | |
Plan to Share IPD: | No |
Studies a U.S. FDA-regulated Drug Product: | No |
Studies a U.S. FDA-regulated Device Product: | No |
Glucose tolerance Tyrosine |