Influence of Dietary Nitrate on Vascular Dysfunction and Inflammation

Study Overview
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Brief Summary
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The principal research objective is to determine whether inorganic nitrate in the form of beetroot juice compared to placebo control prevents the systemic inflammation that underlies typhoid vaccine-induced endothelial dysfunction

Detailed Description
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We wish to determine in a prospective manner whether inorganic nitrate affects the endothelial dysfunction induced by systemic inflammation. At baseline we will measure flow-mediated dilatation (FMD) and peripheral augmentation index, as well as aortic stiffness, as measured by pulse wave velocity (PWV). Volunteers will then receive  8 mmols of dietary nitrate or nitrate free placebo juice once daily for 6 days. After this, depending on availability, volunteers will receive a typhoid vaccine Typherix®, GlaxoSmithKline UK or Typhim Vi ™, AAH Pharmaceuticals Ltd). This vaccine generates a mild systemic inflammation that is associated with vascular dysfunction. All vascular function measures will be repeated at 8 hours and 32 hours after vaccine administration.

Official Title
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A Double-blind, Randomised, Placebo-controlled Parallel Study to Investigate the Effect of Dietary Nitrate on a Model of Vascular Dysfunction in Healthy Volunteers

Conditions
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Cardiovascular Diseases

Intervention / Treatment
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* Biological: Typhoid vaccine
* Dietary Supplement: Concentrate beetroot Juice
* Dietary Supplement: Concentrate beetroot Juice (Placebo)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy volunteers Aged 18-45 Volunteers who are willing to sign the consent form. Normal resting blood pressure (<140/90 mmHg) Exclusion Criteria: Healthy subjects unwilling to consent Pregnant, or any possibility that a subject may be pregnant unless in the latter case a pregnancy test is performed with a negative result History of any serious illnesses, including recent infections or trauma Subjects taking systemic medication (other than the oral contraceptive pill) Subjects with self-reported use of mouthwash or tongue scrapes Subjects with recent (3 months) or current antibiotic use Subjects with a history, or recent treatment of (within last 3 months) any oral condition (excluding caries), including gingivitis, periodontitis and halitosis Subjects with a history of typhoid vaccination in the last 6 months Subjects with any history of a blood-borne infectious disease such Hepatitis B or C virus, or HIV

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Nitrate-rich beetroot juice<br>Biological: Typhoid vaccine The typhoid vaccine is composed of purified polysaccharide from S. typhi capsule 25 micrograms contained in 0.5 ml solution Other Name: Typhim Vi® Dietary Supplement: Concentrate beetroot Juice 140 ml containing  8 mmol of inorganic nitrate | Biological: Typhoid vaccine<br>* The typhoid vaccine is composed of purified polysaccharide from S. typhi capsule 25 micrograms contained in 0.5 ml solution<br>* Other names: Typhim Vi®;Dietary Supplement: Concentrate beetroot Juice<br>* 140 ml containing  8 mmol of inorganic nitrate<br>|
| Placebo Comparator: Nitrate-deplete beetroot juice<br>Biological: Typhoid vaccine The typhoid vaccine is composed of purified polysaccharide from S. typhi capsule 25 micrograms contained in 0.5 ml solution Other Name: Typhim Vi® Dietary Supplement: Concentrate beetroot Juice 140 ml which is nitrate-depleted | Biological: Typhoid vaccine<br>* The typhoid vaccine is composed of purified polysaccharide from S. typhi capsule 25 micrograms contained in 0.5 ml solution<br>* Other names: Typhim Vi®;Dietary Supplement: Concentrate beetroot Juice (Placebo)<br>* 140 ml which is nitrate-depleted<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Flow mediated dilatation | Comparison of change in FMD from baseline after typhoid vaccination following inorganic nitrate versus placebo supplementation | Day 1, Day 7 (8 hours post typhoid vaccine), Day 8 (32 hours post typhoid vaccine) | 
| Plasma nitrite concentration | Comparison of change in plasma nitrite concentration following inorganic nitrate versus placebo supplementation | Day 1, Day 7 (8 hours post typhoid vaccine), Day 8 (32 hours post typhoid vaccine) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Markers of acute inflammation | Comparison of change in peripheral markers of inflammation and leucocyte count following nitrate versus placebo supplementation | Day 1, Day 7 (8 hours post typhoid vaccine), Day 8 (32 hours post typhoid vaccine) | 
| Pulse wave velocity | Comparison of change in PWV from baseline after typhoid vaccination following nitrate versus placebo supplementation | Day 1, Day 7 (8 hours post typhoid vaccine), Day 8 (32 hours post typhoid vaccine) | 
| Platelet reactivity | Comparison of change in platelet reactivity from baseline after typhoid vaccination following nitrate versus placebo supplementation | Day 1, Day 7 (8 hours post typhoid vaccine), Day 8 (32 hours post typhoid vaccine) | 
| Plasma nitrate concentration | Comparison of change in plasma nitrate concentration following inorganic nitrate versus placebo supplementation | Day 1, Day 7 (8 hours post typhoid vaccine), Day 8 (32 hours post typhoid vaccine) |