Human Cerebral Blood Flow Regulation: Sex, Mechanism, and Stress Differences
试验速览
- 阶段
- 1 期
- 状态
- 已完成
- 入组人数
- 42
- 试验地点
- 2
- 主要终点
- Cerebrovascular Conductance (CVC) in response to Hypoxia
研究概览
简要总结
To determine cerebrovascular control mechanisms in humans and provide mechanistic knowledge to offer new sex-specific therapeutic options for cerebrovascular diseases. The current objective is to determine how sex and sex hormones influence CBF control in healthy young adults without confounds of age or disease. The central hypothesis is men exhibit reduced cerebral vasodilator function due in part to differences in COX signaling compared to women. Comprehensive CBF data from multi-modal MRI indicate the magnitude of sex differences-as well as the vasodilator mechanisms-are regionally distinct. Research confounding variables like aging and disease will be mitigated by comparing younger adults (18-40 years old).
详细描述
Cerebrovascular disease is the third leading killer in the U.S. and contributes to decreased quality of life and increased long-term care spending. The risk of cerebrovascular disease is inversely associated with resting cerebral blood flow (CBF). Men exhibit a lower resting CBF and have twice the risk of cerebrovascular disease when compared to premenopausal women. The ability of cerebral vessels to respond to challenges is also inversely related to disease risk, and may be useful in identifying at-risk patients pre-clinically. However, these studies are often confounded by aging and/or comorbidities, and the associations provide little insight into physiologic mechanisms responsible for sexually dimorphic cerebrovascular disease risk. Conversely, animal studies use supraphysiologic levels of hormone treatment in primarily young animals, which limits the translational relevance of animal CBF mechanisms. While there is general agreement that estrogen is protective in healthy adults, the basic impact of sex, and physiologic fluctuations in sex hormones, on mechanisms of CBF control remains unclear.
The overall goal of this research program is to investigate the mechanisms which actively control cerebral blood flow (CBF) in humans, particularly how men and women differ in control mechanisms on a regional basis throughout the brain circulation. The investigators propose to study CBF control mechanisms in healthy younger (18-40 yrs) adult men and women. The overall hypothesis is that female sex and sex hormones contribute to larger stress-induced increases in CBF, due to greater prostanoid (COX) and nitric oxide (NOS) dilation.
A key technological innovation of this proposal derives from multi-mode, high-resolution, flow sensitive MRI to quantify CBF at macrovascular and microvascular levels, at rest, and in response to environmental challenges (stress test for the brain). Additionally, the research design allows for quantification of sex differences in two vascular control mechanisms across all brain regions. Preliminary data demonstrate: hypoxic cerebral vasodilation is 60-100% higher in women compared to men, COX inhibition reduces dilation in women but not men, NOS inhibition reduces vasodilation more in women. Those concepts will be tested in Aims 1-2 of the grant in this current proposal, covered in Phase 1 using technical innovative MRI and pharmacologic tools to test potential sex specific mechanisms of CBF control. The conceptual innovation is planned in Aim 3 of the grant (or Phase 2). Participants must complete Phase 1 studies to continue to Phase 2. Study procedures in Phase 1 and 2 are identical, but the investigators conduct them twice: once in the context of sex hormone suppression, and a second time during a single hormone replacement (during suppression), to study the independent impact of testosterone (men) and estrogen (women) on CBF control mechanisms.
Substantial preliminary findings support these hypotheses, and integrated physiologic, pharmacologic, and MRI approaches are available to test them. This state-of-the-art approach will yield previously unattainable insight into not only maintaining basal CBF, but actively controlling it during physiologic demands for increased flow. These novel, high resolution, regionally-specific, sex-specific, and mechanism-specific findings will serve as a knowledge platform, for designing sex-specific CBF studies in high risk disease populations (e.g. diabetes, hypertension, Alzheimer's) which exhibit strong sex-specific etiology and important vascular contributions.
Three Specific Aims will be addressed in this study:
研究设计
- 研究类型
- Interventional
- 分配方式
- Non Randomized
- 干预模型
- Parallel
- 主要目的
- Basic Science
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 40 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •All participants will be healthy adults between 18-40 years old, matched for age and aerobic fitness
- •Participants will be non-hypertensive (<125/80mm Hg)
- •Participants will be non-obese (BMI 19-25 kg/m2)
- •Participants will have normal blood glucose (<100 g/dl)
- •Participants will have normal lipids (LDL cholesterol <130 mg/dl, triglycerides <150 mg/dl)
- •Women must have a natural regular menstrual cycle
排除标准
- •Participants with a history of:
- •peripheral vascular disease
- •hepatic disease
- •renal disease
- •hematologic disease
- •prediabetes
- •sleep apnea
- •Participants with current BP>130/85 mmHg
- •Regular smokers
- •Taking cardiovascular medications
- •Women who take hormonal birth control
- •Women who are pregnant or have polycystic ovarian syndrome [Hormonal birth control will not be allowed in women]
- •Contradictions to MRI
- •Lactose intolerance
研究组 & 干预措施
Male NOS
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Indomethacin 25 MG/50 MG (Drug)
Male NOS
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Ganirelix Acetate (Drug)
Male NOS
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Testosterone Transdermal Product (Drug)
Male NOS
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Antacid (Drug)
Male COX
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Placebo - Lactose (Drug)
Male COX
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Ganirelix Acetate (Drug)
Male COX
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Testosterone Transdermal Product (Drug)
Male COX
Males visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Antacid (Drug)
Female NOS
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Indomethacin 25 MG/50 MG (Drug)
Female NOS
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Ganirelix Acetate (Drug)
Female NOS
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Estradiol Topical (Drug)
Female NOS
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Antacid (Drug)
Female COX
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Placebo - Lactose (Drug)
Female COX
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Ganirelix Acetate (Drug)
Female COX
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Estradiol Topical (Drug)
Female COX
Females visit MRI twice. Once for indomethacin visit (hypoxia + hypercapnia), and once for placebo visit (hypoxia + hypercapnia). These 2 MRI visits are conducted in a double-blind placebo controlled design. CBF measured via MRI sequences, and hemodynamics monitored for safety/research.
干预措施: Antacid (Drug)
结局指标
主要结局
Cerebrovascular Conductance (CVC) in response to Hypoxia
时间窗: up to 75 minutes for entire visit, but hypoxia lasts about 20 minutes
CVC is the ratio between Cerebral Blood Flow (CBF) and blood pressure (BP). Change in CVC in response to hypoxia between male and female groups, where baseline CVC is subtracted from hypoxia CVC. Hypoxia typically lasts about 20 minutes. The hypothesis is that women will exhibit 50-60% more vasodilation in response to hypoxia \[Aim 1\].
CVC in response to Hypercapnia
时间窗: up to 75 minutes for entire visit, but hypercapnia lasts about 10-15 minutes
CVC is the ratio between Cerebral Blood Flow (CBF) and blood pressure (BP). Change in CVC in response to hypercapnia between male and female groups, where CBF is normalized for BP. Baseline CVC will be subtracted from hypercapnia CVC. Hypercapnia typically lasts about 10-15 minutes.The hypothesis is that hypercapnic vasodilation will be similar between groups \[Aim 1B\].
CVC change in response to Drug Infusion
时间窗: approximately 10 minutes in the middle of 75 minute study visit
CVC is the ratio between Cerebral Blood Flow (CBF) and blood pressure (BP). Change in CVC in response to drug infusion between male \[NOS or COX\] and female \[NOS or COX\] groups. The hypothesis is that acute inhibition of COX or NOS will reduce sex differences in hypoxia-mediated cerebral vasodilation \[Aim 2\].
Change in hypoxia CVC in response to Ganirelix compared to no ganirelix Baseline (Aim 3a)
时间窗: baseline and up to 7 days during ganirelix treatment
Change in hypoxia CVC response to ganirelix compared to baseline within male and female groups, where CVC is CBF is normalized for BP. The hypothesis is that GnRH suppression will abolish hypoxic CBF differences, indicating sex steroids play a vital role in CBF control \[Aim 3\].
Change in hypoxia CVC response to sex hormone suppression with single sex hormone add-back
时间窗: baseline and up to 14 days
Change in hypoxia CVC response to ganirelix+testosterone (in males Aim 3B) or ganirelix+estradiol (in females, Aim 3C) compared to baseline within male and female groups, where CVC is CBF is normalized for BP. The hypothesis is that adding a sex steroid will magnify hypoxic CVC differences, indicating sex steroids play a vital role in CBF control \[Aim 3\].
Change in hypoxia CVC response to NOS or COX inhibition during ganirelix+single sex hormone add-back
时间窗: baseline and up to 14 days
Change in hypoxia CVC drug response to NOS or COX inhibition during ganirelix+testosterone (in males Aim 3B) or ganirelix+estradiol (in females, Aim 3C) compared to baseline hypoxia studies from Aim 2. The hypothesis is that adding a sex steroid will magnify hypoxic CVC differences in drug effects, indicating sex steroids play a vital role in CBF control \[Aim 3\].
次要结局
未报告次要终点