Modulating Glucose Tolerance With Dietary Tyrosine

Metabolic or Bariatric surgery is an effective treatment for type 2 diabetes mellitus (T2DM) diabetes associated with obesity. There remain some questions about the biochemical mechanism that drive how these surgeries work to reverse hyperglycemia. In the proposed human studies, the investigators will test the hypothesis that the amino acid tyrosine is a key metabolite in regulating blood sugar levels and that manipulation of the amount tyrosine supplied by nutrition is able to achieve some of the metabolic benefits seen in the early post-surgical period following bariatric surgery. The central hypothesis is that that the tyrosine content of the meal challenge affects post-prandial intestinal and plasma dopamine and levodopa and L-3,4-dihydroxyphenylalanine (L-DOPA) levels, which, in turn, impact β-cell insulin secretion and glucose excursions. The investigators now propose to characterize the possible effects of manipulating dopamine and L-DOPA levels in the gut and plasma on glucose tolerance, insulin secretion, and insulin sensitivity in healthy volunteers with a range of body mass indexes (BMIs).

Study Overview

• Status: Completed
• Conditions: Glucose Tolerance
• Intervention / Treatment: Dietary supplement: Tyrosine (TYR) Supplementation

Detailed Description

Several biochemical mechanisms explaining how Roux-en-Y Gastric Bypass (RYGB) provides an effective treatment for obesity associated type 2 diabetes mellitus (T2DM) and improves hyperglycemia independently of weight loss have been proposed. Two are of particular interest; a) the hindgut hypothesis suggesting that nutrient delivery to the distal intestine drives the production of "incretins" which enhance insulin secretion (e.g. glucagon-like peptide-1 (GLP-1)), and b) the foregut hypothesis, positing that foregut bypass reduces the secretion of factors (i.e. anti-incretins) that normally defend against hypoglycemia. The investigators have been actively investigating this topic and have developed a hypothesis based on past studies that they wish to test in a limited human clinical study. In addition, preclinical data suggest that there exists a gut-to-beta cell pathway, responsive to nutritional tyrosine, regulating insulin secretion, and this pathway provides a mechanism for the early postoperative improvements in hyperglycemia observed in RYGB.

• Study Type: Interventional
• Enrollment (Actual): 10
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • New York
    • New York, New York, United States, 10032
      • Columbia University Irving Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

i. Inclusion Criteria

1. Capable of giving written as well as oral informed consent.
2. A fasting plasma glucose level (FPG) < 126 mg/dL (< 7.0 mmol/L) and an Hb1ac in the 5.7-6.4 % range.
3. BMI in the range of 18-45 kg/m2.
4. Normal Complete blood count (CBC), renal and liver function tests.

ii. Exclusion Criteria:

1. Any diabetes medication within previous three (3) months.
2. Fasting plasma Glucose (FPG) >126 mg/dl or HbA1c > 6.4%
3. 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
4. History of Phenylketonuria or other inherited disorders of amino acid metabolism.
5. History of movement disorder such as Parkinson's disease or Huntington's disease
6. Cardiovascular, renal, pulmonary, gastrointestinal, migraines or other medical conditions deemed significant by investigators
7. History of/ or psychiatric illness such as major depression, bipolar disease, anxiety or schizophrenia.
8. History of bariatric surgery with the exception of gastric band if the band has been removed
9. Female of child-bearing age, currently pregnant, breastfeeding or not using a form of birth control.
10. Previous or current use of cocaine, methamphetamine, ecstasy (3-4 methylenedioxymethamphetamine (MDMA))
11. Current daily intake of caffeine >500 mg/day (>4-5 cups of coffee; >10 12-oz cans of soda)
12. Consumption of more than 1 alcoholic drink per day or smoking more than 5 cigarettes/day.
13. Systolic Blood Pressure (SBP) > 150 mmHg; Diastolic Blood Pressure (DBP) > 100 mmHg.
14. Recent history (in the past three months) of more than a 3% gain or loss in body wt.
15. Difficulty in swallowing capsules.
16. Concurrent use of antacids or proton pump inhibitors (e.g.,Prilosec Prevacid, dexilant, Aciphex, Protonix, Nexium, Vimovo, Zegerid)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Whole blood glucose level	Glucose concentration versus time profile following glucose challenge define glucose tolerance	Up to 120 minutes from baseline
Plasma insulin concentration	Plasma insulin concentration versus time profile following glucose challenge define glucose tolerance	Up to 120 minutes from baseline
Plasma dopamine concentration	Plasma dopamine concentration versus time profile following glucose challenge may affect glucose tolerance	Up to 120 minutes from baseline
Plasma L-DOPA concentration	Plasma L-DOPA concentration versus time profile following glucose challenge may affect glucose tolerance	Up to 120 minutes from baseline
L-tyrosine concentration	Plasma L-tyrosine concentration versus time profile following glucose challenge may affect glucose tolerance	Up to 120 minutes from baseline
Plasma glucagon concentration	Plasma glucagon concentration versus time profile following glucose challenge impacts glucose tolerance	Up to 120 minutes from baseline
Plasma GLP-1 concentration	Plasma GLP-1 concentration versus time profile following glucose challenge impacts glucose tolerance	Up to 120 minutes from baseline

Collaborators and Investigators

• Sponsor: Columbia University
• Collaborators: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• Investigators: Principal Investigator: Judith Korner, MD, Columbia University

Publications and helpful links

General Publications

• Korner J, Cline GW, Slifstein M, Barba P, Rayat GR, Febres G, Leibel RL, Maffei A, Harris PE. A role for foregut tyrosine metabolism in glucose tolerance. Mol Metab. 2019 May;23:37-50. doi: 10.1016/j.molmet.2019.02.008. Epub 2019 Feb 27.

Study record dates

Study Major Dates

• Study Start (Actual): August 7, 2019
• Primary Completion (Actual): January 24, 2020
• Study Completion (Actual): January 24, 2020

Study Registration Dates

• First Submitted: March 11, 2019
• First Submitted That Met QC Criteria: March 11, 2019
• First Posted (Actual): March 13, 2019

Study Record Updates

• Last Update Posted (Actual): May 5, 2021
• Last Update Submitted That Met QC Criteria: April 30, 2021
• Last Verified: April 1, 2021

More Information

Terms related to this study

• Keywords: Glucose tolerance; Tyrosine
• Other Study ID Numbers: AAAS2124; R01DK104740 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No