Exploring the Effect of Inorganic Nitrates on the Human Microvascular Physiology - a Pilot Study.

NCT ID: NCT04276766

Last Updated: 2020-02-19

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 25 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2015-06-01
• Study Completion Date: 2018-01-01

Brief Summary

We conducted a randomised, placebo-controlled, double blind, cross-over, trial to examine the short-term effect of concentrated beetroot juice on vascular outcomes in a young (18-35 years) and older group (55-75 years). The study included a run-in period of one day preceding the test day. A wash-out period of at least 7 days was implemented to ensure to avoid a carry-over effect of the interventions.

Detailed Description

Cardiovascular disease (CVD) is the largest cause of global mortality accounting for over twenty-nine percent of all deaths with coronary heart disease and stroke projected to become the global leading causes of mortality by 2020. Increased mortality represents only one side of the problem since the clinical care of CVD is costly and prolonged and potentially diverts family and societal resources towards life-saving intensive medical treatments. Therefore, it is crucial to develop preventative and therapeutic strategies that will reduce the financial and social burden of CVD.

Ageing is a major risk factor for chronic diseases such as cancer, diabetes neurodegeneration and CVD. For example, the prevalence and incidence of Chronic Venous Insufficiency (CVI) is closely linked to an age-related dysfunction of micro-circulation control. Similarly, ageing is associated with increased risk of atherosclerosis and formation of macroscopic lesions in large arteries leading to obstruction of blood flow and onset of ischaemic events . The rapid changes in worldwide trends of age-demographics are therefore closely correlated with the rising burden of CVD.

Hypertension is an important risk factor for CVD. Raised blood pressure (BP) is primarily caused by increased vascular resistance, mainly due to arterial wall thickening, autonomic dysregulation and endothelial dysfunction . Endothelium-derived nitric oxide (NO) is a potent vasodilator that plays a pivotal role in the moment-to-moment control of vascular tone . Therefore, it is no surprise that a key aspect of endothelial dysfunction is a reduced NO production via the L-arginine-dependent enzymatic pathway. NO also decreases platelet aggregation, improves mitochondrial function, and diminishes cellular vascular adhesion . Hence a reduction in NO bioavailability is causally related to an increase in BP and atherosclerotic risk.

Until recently it was believed that dietary nitrate (NO3-) and nitrite (NO2-) offered limited physiological benefits, despite them being produced endogenously as part of the NO metabolic pathway . The discovery of the entero-salivary circulation and non-enzymatic reduction of NO3- into NO2- and NO provides an important alternative source of NO, particularly in environment with reduced pH and oxygen tension . The major sources of dietary NO3- are green leafy vegetables such as rocket or spinach or tuberous product such as beetroot. The typical nitrate intake of a western diet provides between 50-100mg/NO3-/day whereas diets rich in fruit- and vegetables such as the Mediterranean or Japanese diets could provide up to 1000mg/NO3-/day. Increasing evidence seems to support the association between the high NO3- content of these dietary patterns with protective cardiovascular effects.

The cardiovascular benefits of NO3- are thought to be derived by an improvement of endothelial function achieved by improved NO bioavailability. Other mechanisms may include a direct effect of NO2- on calcium-channels in vascular smooth muscle cells (SMVCs) in resistance vessels . The conversion of NO3- into NO2- by the oral micro-environment is a key mechanism of the entero-salivary NO3- circulation and non-enzymatic synthesis of NO. The oral microbiota is critically involved in the first reducing step (NO3- into NO2-) and an alteration of the reducing capacity of the oral microbiota (i.e., spitting, antiseptic mouthwash) interrupts the beneficial effects of inorganic NO3- on vascular function. Siervo et al has recently demonstrated a reduced efficacy of concentrated beetroot juice supplementation in older overweight and obese subjects. Ageing appears to be linked to changes in the oral micro-environment as well as a reduced responsiveness of the endothelium and SMVCs to NO.

However, there is limited knowledge on the influence of the ageing process on factors that affect NO3- conversion starting from the NO3- -reducing potential in the oral environment. Therefore, a better understanding of the age-related mechanisms linked to endothelial dysfunction could lead to the development of effective and targeted dietary strategies for the early prevention of hypertension, arterial stiffness and CVD across the life-course.

Conditions

Aging

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: PREVENTION
• Blinding Strategy: TRIPLE

Study Groups

Beetroot

Following baseline microcirculatory and blood pressure measurements, as well as the collection of urine and saliva samples, participants on the "beetroot" group were asked to consume 140ml beetroot juice (James White Drinks Company, Suffolk, UK). The 140 ml of beetroot juice equate to approximately 8.4 mmol of NO3- .

Group Type: EXPERIMENTAL

Crossover intervention

Intervention Type: OTHER

Drink consumption was followed by regular BP measurements and collection of saliva samples every 30 minutes for four hours. Microcirculatory measurements were then repeated and saliva and urine samples were collected again.

After the last measurement subjects were provided with a standardized meal with a very low nitrate intake to eat within 30minutes. Participant then left the research centre and they were asked to collect a saliva sample after two hours from the completion of the meal. This was immediately followed a dose of labelled nitrate (4mg in 100ml of distilled water) to drink within one minute. Subjects were then asked to collect six additional saliva samples until the next morning (four before going to bed and two in the morning), accompanied by measurements of resting BP.

Cross-over assessments were then repeated in the same order at Visit 3, followed a wash-out period of at least one week before entering the second arm of the study.

Placebo

Following baseline microcirculatory and blood pressure measurements, as well as the collection of urine and saliva samples, participants on the "placebo" group were asked to consume 140 ml nitrate-depleted beetroot juice (James White Drinks Company, Suffolk, UK).

Group Type: PLACEBO_COMPARATOR

Crossover intervention

Intervention Type: OTHER

Drink consumption was followed by regular BP measurements and collection of saliva samples every 30 minutes for four hours. Microcirculatory measurements were then repeated and saliva and urine samples were collected again.

After the last measurement subjects were provided with a standardized meal with a very low nitrate intake to eat within 30minutes. Participant then left the research centre and they were asked to collect a saliva sample after two hours from the completion of the meal. This was immediately followed a dose of labelled nitrate (4mg in 100ml of distilled water) to drink within one minute. Subjects were then asked to collect six additional saliva samples until the next morning (four before going to bed and two in the morning), accompanied by measurements of resting BP.

Cross-over assessments were then repeated in the same order at Visit 3, followed a wash-out period of at least one week before entering the second arm of the study.

Interventions

Crossover intervention

Drink consumption was followed by regular BP measurements and collection of saliva samples every 30 minutes for four hours. Microcirculatory measurements were then repeated and saliva and urine samples were collected again.

After the last measurement subjects were provided with a standardized meal with a very low nitrate intake to eat within 30minutes. Participant then left the research centre and they were asked to collect a saliva sample after two hours from the completion of the meal. This was immediately followed a dose of labelled nitrate (4mg in 100ml of distilled water) to drink within one minute. Subjects were then asked to collect six additional saliva samples until the next morning (four before going to bed and two in the morning), accompanied by measurements of resting BP.

Cross-over assessments were then repeated in the same order at Visit 3, followed a wash-out period of at least one week before entering the second arm of the study.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• non-smoking,
• healthy (defined by the absence of overt chronic diseases that could affect their micro- and macro- vascular function - e.g. chronic venous insufficiency, systemic sclerosis, hypercholesterolemia, diabetes, cardiovascular disease - as determined by a medical history questionnaire),
• male or female adults aged between 18 and 35 years (Group A) and 55 and 75 years (Group B).
• normotensive (systolic blood pressure (SBP) between 115 and 140 mmHg and diastolic blood pressure (DBP) between 75 and 90 mmHg) with body mass index (BMI) 18-30 kg/m2.

Exclusion Criteria

• taking medications interfering with the study outcomes,
• have lost more than 3kg in the month before the study,
• wearing complete dentures and diagnosis of inflammatory oral diseases.

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 75 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

University of Sheffield

OTHER

Sponsor Role: collaborator

University of Nottingham

OTHER

Sponsor Role: collaborator

Sheffield Hallam University

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Other Identifiers

HWB-S&E-23

Identifier Type: -

Identifier Source: org_study_id