The Effects of Supplementing Tyrosine on Blood Pressure in Parkinson's Disease

Study Overview
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Brief Summary
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The objective of this experiment is: Primary: To determine the effects of tyrosine supplementation on orthostatic hypotension in people with PD. Secondary: To determine the effects of tyrosine supplementation in people with PD with autonomic insufficiency on HR, BP, and norepinephrine responses during acute exercise stress. Orthostatic hypotension and autonomic abnormalities are a common problem for individuals who suffer from PD, especially as it leads to lightheadedness and falling. For those affected, it can drastically reduce quality of life. It has been hypothesized that tyrosine may impact upon individuals suffering from PD. There is ample evidence in animal models that supports our theory; however there is no clinical evidence of the impact tyrosine supplementation may have in PD patients who suffer from orthostatic hypotension and blunted BP and HR responses. Positive findings that supplemental tyrosine increases BP and HR in people with PD during daily activities such as standing up from a chair and walking can lead to new therapies to improve Parkinsonian orthostatic hypotension. Hypothesis We will test the hypothesis that symptomatic individuals with PD on dopamine therapy who suffer from orthostatic hypotension and blunted HR and BP responses will improve after tyrosine supplementation.

Official Title
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The Effects of Supplementing Tyrosine on Blood Pressure in Parkinson's Disease

Conditions
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Parkinson's Disease

Intervention / Treatment
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* Dietary Supplement: Tyrosine
* Other: Placebo Comparator:Sugar Pill


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Diagnosis of PD according to the UK Brain Bank Diagnostic criteria Diagnosis of orthostatic hypotension according to EFNS guidelines Able to walk on a treadmill comfortably for 6-10 minutes Currently taking levodopa Subjects between the age of 50-80 years old Exclusion Criteria: Currently taking an amino acid supplement Currently taking medication that affects BP Normal BP response to testing

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Tyrosine<br>Tyrosine supplementation (500 mg 2x daily) for 7 days | Dietary Supplement: Tyrosine<br>* Tyrosine supplementation (500 mg 2 x daily) for 7 days<br>|
| Placebo Comparator: Sugar pill<br>Placebo sugar pills (2x daily) for 7 days | Other: Placebo Comparator:Sugar Pill<br>* Placebo sugar pills (2x daily<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Determine the effects of tyrosine supplementation on orthostatic hypotension in people with PD | Orthostatic Blood Pressure Testing: Subjects will sit and rest for 10 minutes. Blood pressure will be taken in this resting position after the 10 minutes. Subjects will then stand upright for 3 minutes. Blood pressure will be taken every minute for those 3 minutes. A drop in systolic BP of 20 mmHg and a 10 mmHg in diastolic drop within these 3 minutes indicates orthostatic hypotension according to the American Academy of Neurology. Blood Samples: Norepinephrine and tyrosine will all be examined via blood samples drawn by a medical assistant or physician from the forearm vein in vacutainer tubes. Two vacutainers of three cc's of blood will be collected and frozen until analyzed. | 7 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| To determine the effects of tyrosine supplementation in people with PD with autonomic insufficiency on heart rate, blood pressure, and norepinephrine responses during acute exercise stress. | An exercise stress test using a Modified Bruce Protocol, which consists of five 3-minute stages on a treadmill, will be used to implement acute stress. During the test, heart rate, oxygen consumption (VO2), Respiratory Exchange Ratio (RER), and 12 lead EKG tracings will be recorded at 1-minute intervals and BP and a rate of perceived exertion (RPE) will be recorded. The treadmill test will conclude when subjects attain peak exercise. Peak exercise will be determined when a subject attains any one of the following: 1) 85% of target heart rate; 2) an RPE of 8; 3) inability to maintain the pace of the treadmill; 4) an RER of over 1.3. Additionally, the American College of Sports Medicine (ACSM) guidelines for terminating exercise testing will be followed. Subjects will be tested on the first visit and then receive supplementation or placebo for 2x daily for 7 days. Subjects will then repeat all the tests they performed on the first visit. | 7 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Parkinson's Disease (PD), Orthostatic hypotension (OH)