Vascular Dysfunction in Hypertensive Postmenopausal Women

University of Delaware

Status and phase: Terminated; Phase 4

Conditions: Hypertension; Cardiovascular Diseases

Treatments: Other: Normotensive; Drug: Hypertensives

Study type: Interventional

Funder types: Other; NIH

Identifiers

NCT03371823

1009297

Details and patient eligibility

About

The purpose of this study is to investigate the role of ET-1 in mediating vasoconstrictor tone in hypertensive postmenopausal women (PMW) alone and in combination with a commonly prescribed Angiotensin II (ANG II) antagonist. The long term goal is to understand the mechanisms contributing to hypertension (HTN) in PMW. This study is the first step in reaching our goal.

Full description

Cardiovascular disease (CVD) is the leading cause of death in women, and mortality from CVD is higher in PMW compared to age-matched men. PMW are at a greater risk for developing HTN, a major risk factor for CVD. They are also more likely to have uncontrolled or resistant HTN despite medication.

ANG II is a common therapeutic target for the treatment HTN. ANG II blockade is highly effective in normalizing blood pressure (BP) in hypertensive male rats, but does not reduce BP to the same degree in hypertensive post menopausal female rats. Endothelin-1 (ET-1) receptor antagonists reduce BP in hypertensive postmenopausal female rats, but have no effect on males. Thus the mechanisms contributing to HTN in female rats and likely women, particularly after menopause, are complex, multifactorial and not completely understood.

After menopause, the vasoconstrictor effects of both ANG II and ET-1 are amplified in animal models. As such, these two predominant pathways may contribute to the high incidence of HTN in PMW. ET-1 is a potent vasoconstrictor produced and released by endothelial cells that binds to two receptor subtypes, ET-A and ET-B. While both receptors are located on vascular smooth muscle (VSM) and mediate vasoconstriction, ET-B receptors are also located on the endothelium and mediate vasodilation via nitric oxide.

Importantly, the production of ET-1 and expression of ET-A and B receptors can be modulated by hormones such as estradiol and ANG II. Estradiol attenuates ET-1 production, and reduces ET-1 mediated vasoconstriction via an ET-B receptor mechanism in vitro. Thus, decline in estradiol after menopause may enhance vasoconstrictor tone via ET-1 and lead to HTN. ET-1 also potentiates the vasoconstrictor effects of ANG II since the vasoconstrictor and hypertensive effects of ANG II are ameliorated by ET-1 receptor blockade. Additionally, ANG II stimulates the synthesis of ET-1 and upregulates ET-A and ET-B receptor expression on VSM. The ANG II receptor antagonist Losartan reduces ET-A and ET-B receptor expression and attenuates the constrictor effects of ET-1 in a diabetic rat model. Therefore, ET-1 is an important independent factor contributing to HTN in PMW, but therapeutic agents targeting both ANG II and ET-1 may have greater efficacy given their interactions.

The investigators propose a comprehensive assessment of vascular function by measuring blood flow responses in the cutaneous circulation during perfusion of ET-1 receptor antagonists via microdialysis, combined with measures of intracellular protein and receptor expression of endothelial cells and skin punch biopsies collected from normotensive and hypertensive PMW. Investigators central hypothesis is that hypertensive PMW have greater ET-1 mediated vasoconstrictor tone due to increased ET-1 expression, down-regulation of ET-B receptors on endothelial cells and up-regulation of both ET-A and ET-B receptors on VSM leading to increased vasoconstriction and HTN. Investigators further hypothesize that ANG II exacerbates the increase in ET-1, and ET-A and ET-B receptor expression contributing to exaggerated constriction with HTN in PMW.

Enrollment: 8 patients

Sex: Female

Ages: 50 to 70 years old

Volunteers: Accepts Healthy Volunteers

Inclusion and exclusion criteria

Inclusion Criteria: - Women.

• > 1year post menopausal.
• Age range 50-70 years
• Resting ECG in normal limits
• Standard blood chemistry within normal limits
• Systolic blood pressure: <130mm Hg for normotensives; >130mm Hg for hypertensives.
• Diastolic blood pressure: < 80mm Hg for normotensives; > 80mm Hg for hypertensives.

Exclusion Criteria:

• History of cardiovascular disease
• Blood clots or stroke
• Cancer
• Diabetes
• Kidney or Liver disease
• Obesity (BMI>35kg/m2)
• Pregnant/Breast feeding
• Current use of hormone therapy
• Current use of tobacco products
• High cholesterol
• Current use of anti-hypertensive meds

Trial design

Primary purpose: Other

Allocation: Non-Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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8 participants in 2 patient groups

Normotensive

Other group

Description:

Normotensive PMW will complete an experimental visit to assess vascular function. All women will wear an ambulatory BP monitor during the 24 hours preceding the experimental visit to confirm BP classification. Large blood vessel function will be assessed using two non-invasive techniques: 1. Flow Mediated Dilation (FMD) 2. Pulse Wave Analysis and Pulse Wave Velocity. ET-1 mediated vasoconstrictor tone is assessed by measuring the cutaneous blood flow during microdialysis perfusions of ET-A and ET-B receptor antagonist. ET-1 production, ET-A and ET-B receptor expression is assessed from antecubital vein endothelial cells and skin punch biopsy samples.

Treatment:

Other: Normotensive

Hypertensives

Experimental group

Description:

Hypertensive women will be tested at baseline and then administered Losartan 50 mg once a day at night for 14 days. Vascular function is measured at baseline and again after 2 weeks of losartan. All women will wear an ambulatory BP monitor during the 24 hours preceding the experimental visits to confirm BP classification. Large blood vessel function will be assessed using two non-invasive techniques: 1. Flow Mediated Dilation (FMD) 2. Pulse Wave Analysis and Pulse Wave Velocity. ET-1 mediated vasoconstrictor tone is assessed by measuring the cutaneous blood flow during microdialysis perfusions of ET-A and ET-B receptor antagonist. ET-1 production, ET-A and ET-B receptor expression is assessed from antecubital vein endothelial cells and skin punch biopsy samples.

Treatment:

Drug: Hypertensives