Effect of Beetroot Juice on Coronary Blood Flow and Walking Performance in PAD

Study Overview
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Brief Summary
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In this study the investigators will test the hypothesis that short-term consumption of inorganic nitrate (supplied in concentrated beetroot juice) enhances coronary blood flow responses, large artery hemodynamics, and leg oxygenation/exercise tolerance in patients with peripheral arterial disease (PAD). Understanding and improving blood flow regulation in the heart and skeletal muscles of patients with PAD is important because exercise triggers symptoms of leg pain and substantially raises blood pressure and myocardial demand in these patients.

Detailed Description
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Peripheral arterial disease (PAD) is a strong predictor of cardiovascular mortality and negatively affects functional capacity and quality of life for as many as 14 million patients in the U.S. alone. One open-label study showed that acute consumption of beetroot juice improved 6 min walk performance, reduced blood pressure, and enhanced leg muscle oxygenation in PAD patients. However, no studies have rigorously confirmed these findings in a double-blind manner, nor have the effects of this supplement been investigated (acutely or short-term) in the coronary circulation of PAD patients. In addition to studying its effects on graded treadmill walking performance and consequent large artery vasodilation, the present study will examine the effects of short-term beetroot juice consumption (twice/day) on both coronary and leg vasodilator (graded calf flexion) and vasoconstrictor (isometric handgrip, voluntary apnea) responses in patients with PAD. Participants will randomly consume either nitrate-rich or nitrate-depleted beetroot juice with a 7 to 14 day wash-out period between. Effects of beetroot juice consumption on plasma nitrate, nitrite and methemoglobin will also be assessed.

Official Title
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Effects of Dietary Nitrate Supplementation on Coronary Blood Flow and Walking Performance in Peripheral Arterial Disease

Conditions
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Peripheral Arterial Disease

Intervention / Treatment
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* Drug: Beetroot juice
* Drug: Beetroot juice placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients with peripheral arterial disease (PAD) Capable of giving informed consent Men and women age 21- 85 years Diagnosed with PAD (i.e., ankle-brachial index below 0.9) Fontaine stage II or less - no pain while resting Satisfactory history and physical exam Exclusion Criteria: Children Pregnant or nursing women Patients taking nitroglycerine or nitrate preparations Patients taking phosphodiesterase inhibitors such as sildenafil or tadalafil Patients taking proton pump inhibitors Ejection fraction < 40% Uncontrolled hypertension Uncontrolled diabetes Myocardial infarction within past 6 months or unstable angina Severe lung disease (i.e., on supplemental oxygen or frequently use rescue inhalers) Abnormality in hemoglobin or hematocrit or methemoglobin Impaired renal function Impaired liver function History or diagnosis of Barrett's esophagus Known allergy to beetroot juice or lemon juice Inability to walk on a treadmill at a moderate pace (2.0 miles/hour)

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 85 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: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Beetroot juice (Beet-It Organic Shot)<br>Subjects will consume 70 ml of beetroot juice (Beet-It Organic Shot) twice per day (morning, afternoon) for 5 to 7 days to assess the short term effects of this nitrate supplement on graded treadmill walking responses (day 4) and vasodilator/vasoconstrictor responses in the coronary and lower leg circulations (day 5 or 6 or 7). On both study visits, subjects will consume their morning dose 1 hour 45 min before experiments begin. | Drug: Beetroot juice<br>* This beverage contains 0.3 g of inorganic nitrate per 70 ml container, and is bottled and supplied by James White Drinks (UK).<br>* Other names: Beet-It Organic Shot;|
| Placebo Comparator: Beetroot juice placebo (Beet-It Organic Placebo)<br>Subjects will consume 70 ml of beetroot juice placebo (Beet-It Organic Placebo) twice per day (morning, afternoon) for 5 to 7 days to assess the short term effects of this nitrate supplement on graded treadmill walking responses (day 4) and vasodilator/vasoconstrictor responses in the coronary and lower leg circulations (day 5 or 6 or 7). On both study visits, subjects will consume their morning dose 1 hour 45 min before experiments begin. | Drug: Beetroot juice placebo<br>* This beverage is identical in look and taste to the Beet-It organic shot, but has the nitrate removed. It is also bottled and supplied by James White Drinks (UK).<br>* Other names: Beet-It organic placebo;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Exercise performance | Exercise capacity will be assessed using a graded treadmill walking test to peak exertion with expired gas analysis and determination of peak oxygen uptake, calf muscle oxygenation, blood pressure, claudication onset time, and peak walking time. | 5 to 7 days after initiating daily ingestion of beetroot juice | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Coronary vascular function | Coronary artery (transthoracic ultrasound) blood flow responses to plantar flexion and handgrip exercise. | 4 days after initiating daily ingestion of beetroot juice | 
| Leg vascular function | Popliteal artery and near infrared spectroscopy (NIRS) responses to plantar flexion and handgrip exercise. | 4 days after initiating daily ingestion of beetroot juice | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Dietary nitrate supplementation, Beetroot juice