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Completed

NCT Number: NCT03370991

Blueberries for Improving Vascular Endothelial Function in Postmenopausal Women With Elevated Blood Pressure

Postmenopausal women are at an increased risk of developing cardiovascular disease (CVD) largely due to accelerated aging-related modifications to vascular health following menopause. The vascular endothelium is responsible for producing chemicals that are essential for proper vasodilation and blood flow and therefore is involved in maintaining normal blood pressure. A major modification that occurs during aging and is accelerated during menopause is termed vascular endothelial dysfunction which is characterized by impaired endothelium-dependent dilation. This can lead to increased blood pressure, atherosclerosis, and increased risk of CVD and death. Nitric oxide (NO) is a chemical produced by the endothelium and is essential for normal endothelial function and cardiovascular health. Vascular endothelial dysfunction is primarily caused by reduced NO bioavailability secondary to excessive oxidative stress. Approximately 3/4 of postmenopausal women have elevated blood pressure or hypertension which further worsens endothelial function and increases CVD risk through increased oxidative stress and inflammation. Blueberries are rich in phytochemicals including anthocyanins, phenolic acids, and pterostilbene. These phytochemicals and their metabolites are known to attenuate oxidative stress and inflammation. The overall goal of the current study is to assess the efficacy of blueberries to improve vascular endothelial dysfunction in this high-risk population and to gain insight into underlying mechanisms. 58 postmenopausal women with elevated blood pressure and stage 1-HTN will be asked to consume 22 grams freeze-dried blueberry powder or placebo powder per day for 12 weeks. Vascular endothelial function will be assessed at baseline and 12 weeks. Measurements indicative of vascular nitric oxide production, oxidative stress, inflammation, cardiometabolic health, cognitive function, and blueberry phytochemical metabolism will be measured at baseline and 12 weeks. Blood pressure will be assessed at baseline and 4, 8, and 12 weeks.

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Key information

Conditions

Menopause Aneurysm Arterial Occlusive Diseases Arteriosclerosis Atherosclerosis Cardiovascular Diseases Elevated Blood Pressure Endothelial Dysfunction Hypertension Vascular Diseases

Age range

45 year–65 year

Sex eligibility

Female

Study type

Interventional

Phase

Not applicable

Primary location

Department of Food Science and Human Nutrition, Colorado State University

Fort Collins, Colorado, 80523-1571, United States

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Aged 45-65 years
  • Postmenopausal women (≥ 1 years postmenopausal; natural or surgical menopause; confirmed by measurement of estradiol at a level < 30 pg/mL and follicle-stimulating hormone at a level ≥ 30 mIU/mL)
  • Elevated or stage 1-HTN (confirmed as resting seated systolic blood pressure < 120 or ≥ 139 mmHg and/or a diastolic blood pressure ≥ 90 mmHg using an average of 3 measurements, on 2 separate occasions - screening and baseline visits)
  • Ability to provide informed consent

Exclusion criteria

  • Systolic blood pressure < 120 or ≥ 139 mm Hg and/or diastolic blood pressure ≥ 90 mmHg
  • Taking > 1 antihypertensive medication and/or taking the antihypertensive medication for < 3 months
  • Diagnosed cancer, cardiovascular disease, diabetes, or gastrointestinal, kidney, liver, and/or pancreatic disease
  • Triglycerides > 350 mg/dL, low-density lipoprotein cholesterol (LDL-C) ≥ 190 mg/dL, and/or taking a lipid-lowering medication
  • Hormone replacement therapy use 6 months prior to study start
  • Taking phosphodiesterase-5 inhibitors
  • Weight change ≥ 3 kg in the past 3 months, actively trying to lose weight, or unwilling to remain weight stable throughout the study
  • Current smokers or history of smoking in the past 12 months
  • Binge and/or heavy drinker (>3 drinks on any given occasion and/or >7 drinks/week for women, and >4 drinks on any given occasion and/or >14 drinks/week for men)
  • Body mass index < 18.5 or > 40 kg/m2
  • Active infection or antibiotic therapy
  • Allergies or contraindication to study treatments, pharmacological agents, or procedures

Treatment and study plan

Blueberry powder

Dietary Supplement

22 g/day freeze-dried blueberry powder for 12 weeks

Placebo Powder

Dietary Supplement

22 g/day placebo powder for 12 weeks

Primary outcomes

  1. Endothelium-dependent dilation

    Time frame: Baseline to 12 Weeks

    Assessed as brachial artery flow-mediated dilation in a study subset of participants

  2. Blood pressure

    Time frame: Baseline to 12 weeks

    Assessed using an automated blood pressure monitor (SphgmoCor)

Secondary outcomes

  1. Vascular oxidative stress

    Time frame: Baseline and 12 weeks

    Change in brachial artery flow-mediated dilation following acute infusion of ascorbic acid (a dose known to scavenge superoxide) as an index of vascular oxidative stress in a study subset of participants

  2. Endothelial cell nitric oxide production, oxidative stress, and inflammation

    Time frame: Baseline and 12 weeks

    Protein expression markers will be measured by quantitative immunofluorescence in biopsied venous endothelial cells in a study subset of participants

  3. Systemic markers of cardiometabolic health

    Time frame: Baseline and 12 weeks

    Circulating markers of lipid and glucose metabolism, nitric oxide, and inflammation

  4. Plasma blueberry polyphenol metabolites

    Time frame: Baseline and 12 weeks

    Targeted analysis of plasma metabolites by GC-MS and LC-MS

  5. Endothelium-independent dilation

    Time frame: Baseline to 12 weeks

    Assessed as brachial artery diameter responses to sublingual nitroglycerin in a study subset of participants

  6. Augmentation index

    Time frame: Baseline to 12 weeks

    Arterial stiffness assessed as augmentation index using the SphygmoCor XCEL

  7. Pulse wave velocity

    Time frame: Baseline to 12 weeks

    Arterial stiffness assessed as carotid-femoral pulse wave velocity using the SphygmoCor XCEL

  8. Gut microbiota

    Time frame: Baseline to 12 weeks

    Determine the effects on stool sample microbial populations

Other outcomes

  1. Processing speed

    Time frame: Baseline and 12 weeks

    Exploratory measures assessed using the NIH Cognitive Toolbox iPad app

  2. Language

    Time frame: Baseline and 12 weeks

    Exploratory measures assessed using the NIH Cognitive Toolbox iPad app

  3. Working memory

    Time frame: Baseline and 12 weeks

    Exploratory measures assessed using the NIH Cognitive Toolbox iPad app

  4. Executive function and attention

    Time frame: Baseline and 12 weeks

    Exploratory measures assessed using the NIH Cognitive Toolbox iPad app

  5. Episodic memory

    Time frame: Baseline and 12 weeks

    Exploratory measures assessed using the NIH Cognitive Toolbox iPad app

  6. Peripheral blood mononuclear cell inflammation and oxidative stress

    Time frame: Baseline and 12 weeks

    Exploratory measures analyzed by gene expression

Sponsors and collaborators

Lead sponsor

Colorado State University

Other

Collaborators

  • U.S. Highbush Blueberry Council

Registry information

Official study title

Blueberry Consumption for Improving Vascular Endothelial Dysfunction in Postmenopausal Women With Elevated Blood Pressure and Stage 1-Hypertension

Important dates

Study start
2017
Primary completion
2021
Study completion
2021
First posted
Dec 13, 2017
Registry last updated
Sep 14, 2022

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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