Variations in endothelial function and arterial compliance during the menstrual cycle

Evaluation of gender differences in endothelium-independent dilation using peripheral arterial tonometry

BACKGROUND

A change in peripheral arterial tonometry (PAT) in response to reactive hyperaemia is often used to provide a non-invasive measure of endothelium-dependent dilation (EDD). Reactive hyperaemia does not allow one to quantify endothelium-independent dilation (EID), which is part of overall vascular function. Although most research examining vascular function and cardiovascular disease has focused on EDD, there is evidence that cardiovascular risk factors may impair EID.

PURPOSE

To examine the microvascular vasodilation response to nitroglycerin (NTG) in healthy adults using PAT.

METHODS

Microvascular responses to reactive hyperaemia and NTG were evaluated in 86 (41 female and 45 male) healthy subjects (age 37 ± 5 years). Beat-to-beat plethysmographic measurements of finger arterial pulse waves were recorded for 5 min following reactive hyperaemia. After a 10-min rest period, sublingual NTG (0.4 mg) was administered and PAT signal changes were measured for 10 min. Peak reactive hyperaemic index (RHI) and peak NTG-mediated index (NMI) were determined in all subjects.

RESULTS

There were no significant gender differences in peak RHI (females: 2.07 ± 0.56 versus males: 1.91 ± 0.58, P = 0.20). Mean peak NMI for all subjects was 2.78 (± 1.49). Peak NMI was significantly greater in females than in males (3.11 ± 1.59 versus 2.50 ± 1.34, P = 0.05). Time to peak NMI was not significantly different between genders (7 min, 28 s [± 1 min, 47 s], versus 7 min, 14 s [± 1 min, 49 s], P = 0.58).

CONCLUSION

In this population of healthy adults, peak NMI was significantly greater in females than in males. These findings suggest that gender differences exist in the microvascular vasodilation responses to NTG using PAT.

Gender differences in artery wall biomechanical properties throughout life

Elevated large artery stiffness and pulse pressure have emerged as important risk factors for cardiovascular disease. The genders differ in large artery biomechanical properties throughout the lifespan with females displaying higher stiffness than males during the prepubertal years and a dramatic increase after menopause. Males on the other hand experience an increase in arterial stiffness postpuberty and a linear increase thereafter, suggesting that females have intrinsically stiffer large arteries than males, but that such effects are mitigated by sex steroids during the reproductive years. This review discusses anthropometric and sex steroid influences on gender differences in large artery stiffness and pressure dynamics from childhood to senescence. In particular, the sex-specific effects of estrogen, progesterone and testosterone on vascular structure and function and how these influence arterial stiffness are explored. These factors may contribute in part to the observed gender differences in the pathophysiology and clinical manifestations of cardiovascular disease.

Plasma norepinephrine is an independent predictor of vascular endothelial function with aging in healthy women

We tested the hypothesis that reductions in vascular endothelial function (endothelium-dependent dilation, EDD) with age are related to increases in sympathetic activity. Among 314 healthy men and women, age was inversely related to brachial artery flow-mediated dilation (FMD) (r = -0.30, P < 0.001), a measure of EDD, and positively related to plasma norepinephrine concentrations (PNE), a marker of sympathetic activity (r = 0.49, P < 0.001). Brachial FMD was inversely related to PNE in all subjects (r = -0.25, P < 0.001) and in men (n = 187, r = -0.17, P = 0.02) and women (n = 127, r = -0.37, P < 0.001) separately. After controlling for PNE (multiple regression analysis), brachial FMD remained significantly related to age in all subjects (r = -0.20, P < 0.001) and in men (r = -0.23, P < 0.01), but not women (r = -0.16, P = 0.06). Consistent with this, brachial FMD remained significantly related to PNE when controlling for age (r = -0.24, P < 0.01) and menopause status (r = -0.24, P < 0.01) in women. Indeed, PNE was the strongest independent correlate of brachial FMD in women after controlling for conventional cardiovascular disease risk factors (r = -0.22, P = 0.01). This relation persisted in a subset of women (n = 113) after further accounting for the effects of plasma oxidized low-density lipoprotein (P < 0.05), a circulating marker of oxidative stress. Endothelium-independent dilation was not related to age in either men or women (P > 0.05). These results provide the first evidence that EDD is inversely related to sympathetic activity, as assessed by PNE, among healthy adults varying in age. In particular, our findings suggest that sympathetic nervous system activity may be a key factor involved in the modulation of vascular endothelial function with aging in women.

Short-term oral progesterone administration antagonizes the effect of transdermal estradiol on endothelium-dependent vasodilation in young healthy women

Very few studies have explored the cardiovascular effects of progesterone in premenopausal women. This study aimed to examine the short-term effects of oral progesterone alone, transdermal estrogen alone, and progesterone and estrogen combined on flow-mediated dilation (FMD) in healthy reproductive-aged women. We suppressed endogenous estrogens and progesterone in 17 premenopausal women for 10-12 days using a gonadotropin-releasing hormone antagonist. On day 4 (hormone suppression condition), subjects were tested (n = 17) and were then supplemented with either 200 mg micronized progesterone (n = 8) orally or 0.1 mg estradiol (n = 9) transdermally per day. On day 7 (progesterone-first or estradiol-first condition), subjects were tested and began supplementation with both hormones (n = 17) and were tested again on day 10 (combined hormone condition). FMD of the brachial artery was assessed using B-mode arterial ultrasound, combined with synchronized Doppler analysis. As a result, significant differences in FMD were observed between hormone suppression (7.85 ± 1.06%) and estrogen-first conditions (10.14 ± 1.40%; P < 0.05). The estradiol-induced increase was abolished when oral progesterone was also supplemented (6.27 ± 0.96%). In contrast, we observed a trend toward a decrease in FMD with unopposed progesterone administration, but no statistically significant differences were found between the progesterone-first (6.66 ± 1.23%), hormone suppression (7.80 ± 1.23%), and combined hormone conditions (7.40 ± 1.29%). In conclusion, these data suggest that short-term oral micronized progesterone administration antagonizes the beneficial effect of transdermal estradiol on FMD.

The research on endothelial function in women and men at risk for cardiovascular disease (REWARD) study: methodology

Background

Endothelial function has been shown to be a highly sensitive marker for the overall cardiovascular risk of an individual. Furthermore, there is evidence of important sex differences in endothelial function that may underlie the differential presentation of cardiovascular disease (CVD) in women relative to men. As such, measuring endothelial function may have sex-specific prognostic value for the prediction of CVD events, thus improving risk stratification for the overall prediction of CVD in both men and women. The primary objective of this study is to assess the clinical utility of the forearm hyperaemic reactivity (FHR) test (a proxy measure of endothelial function) for the prediction of CVD events in men vs. women using a novel, noninvasive nuclear medicine -based approach. It is hypothesised that: 1) endothelial dysfunction will be a significant predictor of 5-year CVD events independent of baseline stress test results, clinical, demographic, and psychological variables in both men and women; and 2) endothelial dysfunction will be a better predictor of 5-year CVD events in women compared to men.

Methods/Design

A total of 1972 patients (812 men and 1160 women) undergoing a dipyridamole stress testing were recruited. Medical history, CVD risk factors, health behaviours, psychological status, and gender identity were assessed via structured interview or self-report questionnaires at baseline. In addition, FHR was assessed, as well as levels of sex hormones via blood draw. Patients will be followed for 5 years to assess major CVD events (cardiac mortality, non-fatal MI, revascularization procedures, and cerebrovascular events).

Discussion

This is the first study to determine the extent and nature of any sex differences in the ability of endothelial function to predict CVD events. We believe the results of this study will provide data that will better inform the choice of diagnostic tests in men and women and bring the quality of risk stratification in women on par with that of men.

Folic acid supplementation improves vascular function in professional dancers with endothelial dysfunction

OBJECTIVE

To determine if folic acid supplementation improves vascular function (brachial artery flow-mediated dilation [FMD]) in professional dancers with known endothelial dysfunction.

DESIGN

Prospective cross-sectional study.

SETTING

Academic institution in the Midwestern United States.

SUBJECTS

Twenty-two professional ballet dancers volunteered for this study.

MAIN OUTCOME MEASURES

Subjects completed a 3-day food record to determine caloric and micronutrient intake. Menstrual status was determined by interview and questionnaire. Endothelial function was determined as flow-induced vasodilation measured by high-frequency ultrasound of the brachial artery. A change in brachial diameter of <5% to hyperemic flow stimulus was defined a priori as endothelial dysfunction. Subjects with abnormal FMD took 10 mg of folic acid daily for 4 weeks, and FMD testing was then repeated. Serum whole blood was measured for folic acid levels before and after supplementation.

RESULTS

Sixty-four percent of dancers (n = 14) had abnormal brachial artery FMD (<5%) (mean ± standard deviation, 2.9% ± 1.5%). After 4 weeks of folic acid supplementation (10 mg/day), FMD improved in all the subjects (7.1% ± 2.3%; P < .0001).

CONCLUSIONS

This study reveals that vascular endothelial function improves in dancers after supplementation with folic acid (10 mg/day) for at least 4 weeks. This finding may have clinically important implications for future cardiovascular disease risk prevention.

Acute change in vascular tone alters intima-media thickness

Atherosclerosis is a lifelong process involving artery wall thickening. Increased wall thickness has been widely adopted as a preclinical surrogate marker of atherosclerosis. A prerequisite for such a surrogate marker is that it is a structural characteristic of the vessel wall that is not subject to acute changes. The purpose of this study was to examine the acute effects of vasodilator drug administration on wall thickness of the carotid and superficial femoral arteries. High-resolution ultrasound was used to examine carotid and femoral artery diameters and wall thickness in 15 young (25±4 years of age) and 15 older (70±6 years of age) healthy men who were administered sublingual glyceryl trinitrate. Diameter and wall thickness were collected before and across a 10-minute period after glyceryl trinitrate administration. Glyceryl trinitrate induced a significant increase in carotid and femoral artery diameter and a decrease in wall thickness in both young and older men (both P<0.001). The latter was significantly larger than in young men (both P<0.01). The changes in carotid artery wall thickness in both young (35±23 μm) and older men (71±46 μm) approximate those considered prognostically relevant. Collectively, our data suggest that vasodilator drug administration induces a rapid and marked decrease in wall thickness, which mirrors conduit artery vasodilation in both young and older men. This finding confirms the presence of acute changes in wall thickness and has important implications for future studies that assess artery wall characteristics as a surrogate measure of atherosclerosis.

Effect of obesity and metabolic syndrome on hypoxic vasodilation

This study was designed to test whether obese adults and adults with metabolic syndrome (MetSyn) exhibit altered hyperemic responses to hypoxia at rest and during forearm exercise when compared with lean controls. We hypothesized blood flow responses due to hypoxia would be lower in young obese subjects (n = 11, 24 ± 2 years, BMI 36 ± 2 kg m(-2)) and subjects with MetSyn (n = 8, 29 ± 3 years BMI 39 ± 2 kg m(-2)) when compared with lean adults (n = 13, 29 ± 2 years, BMI 24 ± 1 kg m(-2)). We measured forearm blood flow (FBF, Doppler Ultrasound) and arterial oxygen saturation (pulse oximetry) during rest and steady-state dynamic forearm exercise (20 contractions/min at 8 and 12 kg) under two conditions: normoxia (0.21 F(i)O(2), ~98% S(a)O(2)) and hypoxia (~0.10 F(i)O(2), 80% S(a)O(2)). Forearm vascular conductance (FVC) was calculated as FBF/mean arterial blood pressure. At rest, the percent change in FVC with hypoxia was greater in adults with MetSyn when compared with lean controls (p = 0.02); obese and lean adult responses were not statistically different. Exercise increased FVC from resting levels in all groups (p < 0.05). Hypoxia caused an additional increase in FVC (p < 0.05) that was not different between groups; responses to hypoxia were heterogeneous within and between groups. Reporting FVC responses as absolute or percent changes led to similar conclusions. These results suggest adults with MetSyn exhibit enhanced hypoxic vasodilation at rest. However, hypoxic responses during exercise in obese adults and adults with MetSyn were not statistically different when compared with lean adults. Individual hypoxic vasodilatory responses were variable, suggesting diversity in vascular control.

Different effects of isoflavones on vascular function in premenopausal and postmenopausal smokers and nonsmokers: NYMPH study

Isoflavone intake has been associated with a reduction in the risk of cardiovascular disease in postmenopausal women. The aim of the present study was to determine if the effects of isoflavones on vascular function differ between premenopausal and postmenopausal women and between women who smoke and those who do not. Women smokers and nonsmokers who consumed 50 mg of isoflavone/day as black soybean tea for a period of 2 months (n = 55, mean age 39) were enrolled in the present study. We examined endothelial function, which was assessed by the percent change in flow-mediated dilation (%FMD) and arterial wall stiffness using the cardio-ankle vascular index (CAVI), as well as by biochemical parameters of the blood. Neither premenopausal (p = 0.697) nor postmenopausal (p = 0.389) smokers experienced an increase in %FMD after daily consumption of isoflavones. However, both premenopausal (p = 0.004) and postmenopausal (p = 0.019) nonsmokers exhibited a marked elevation in %FMD. By contrast, isoflavone intake effectively reduced CAVI among both premenopausal smokers (p = 0.027) and nonsmokers (p = 0.013), but had no effect on CAVI among postmenopausal smokers (p = 0.169) or nonsmokers (p = 0.128). The women smokers and nonsmokers did not differ in age or %FMD at the time of enrollment in the study. Thus, isoflavones have different effects on vascular endothelial function and arterial wall stiffness in premenopausal and postmenopausal smokers and nonsmokers.

Progressive handgrip exercise: evidence of nitric oxide-dependent vasodilation and blood flow regulation in humans

In the peripheral circulation, nitric oxide (NO) is released in response to shear stress across vascular endothelial cells. We sought to assess the degree to which NO contributes to exercise-induced vasodilation in the brachial artery (BA) and to determine the potential of this approach to noninvasively evaluate NO bioavailability. In eight young (25 ± 1 yr) healthy volunteers, we used ultrasound Doppler to examine BA vasodilation in response to handgrip exercise (4, 8, 12, 16, 20, and 24 kg) with and without endothelial NO synthase blockade [intra-arterial N(G)-monomethyl-L-arginine (L-NMMA), 0.48 mg · dl(-1) · min(-1)]. Higher exercise intensities evoked significant BA vasodilation (4-12%) that was positively correlated with the hyperemic stimulus (r = 0.98 ± 0.003, slope = 0.005 ± 0.001). During NO blockade, BA vasodilation at the highest exercise intensity was reduced by ∼70% despite similar exercise-induced increases in shear rate (control, +224 ± 30 s(-1); L-NMMA, +259 ± 46 s(-1)). The relationship and slope of BA vasodilation with increasing shear rate was likewise reduced (r = 0.48 ± 0.1, slope = 0.0007 ± 0.0005). We conclude that endothelial NO synthase inhibition with L-NMMA abolishes the relationship between shear stress and BA vasodilation during handgrip exercise, providing clear evidence of NO-dependent vasodilation in this experimental model. These results support this paradigm as a novel and valid approach for a noninvasive assessment of NO-dependent vasodilation in humans.

Gender differences in vascular function and insulin sensitivity in young adults

To examine influence of insulin resistance and other clinical risk factors for the MetS (metabolic syndrome) on vascular structure and function in young adults. This cross-sectional study was conducted in a cohort of young adults (mean age 22 years) and their siblings participating in a longitudinal study of cardiovascular risk (n=370). Insulin sensitivity was determined by euglycaemic insulin clamp. EDD (endothelium-dependent dilation) was determined by flow-mediated dilation using high-resolution ultrasound imaging of the brachial artery. EID (endothelium-independent dilation) was determined by NTG (nitroglycerine)-mediated dilation. The diameter and cIMT (intima-media thickness) of the carotid artery were also measured. There was no significant difference between males and females for age or body mass index. However, males had significantly higher glucose and triacylglycerol (triglyceride) levels, while the females had significantly higher HDL-C (high-density lipoprotein-cholesterol) and insulin sensitivity (13.00 ± 0.33 compared with 10.71 ± 0.31 mg·kg-1 of lean body mass·min-1, P<0.0001). Although peak EDD was significantly lower (6.28 ± 0.26 compared with 8.50 ± 0.28%, P<0.0001) in males than females, this difference was largely explained by adjustment for brachial artery diameter (P=0.15). Peak EID also was significantly lower in males than females (20.26 ± 0.44 compared with 28.64 ± 0.47%, P<0.0001), a difference that remained significantly lower after adjustment for brachial artery diameter. Males had a significantly greater cIMT compared with females (females 0.420 ± 0.004 compared with males 0.444 ± 0.004 mm, P=0.01), but when adjusted for carotid diameter, there was no significant difference (P=0.163). Although there were gender differences in vascular function and structure in the young adult population examined in this study, many of the differences were eliminated simply by adjusting for artery diameter. However, the lower EID observed in males could not be explained by artery diameter. Future studies need to continue to examine influence of gender on EID and other measures of vascular function.

The endothelium and its role in regulating vascular tone

The endothelium forms an important part of the vasculature and is involved in promoting an atheroprotective environment via the complementary actions of endothelial cell-derived vasoactive factors. Disruption of vascular homeostasis can lead to the development of endothelial dysfunction which in turn contributes to the early and late stages of atherosclerosis. In recent years an increasing number of non-invasive vascular tests have been developed to assess vascular structure and function in different clinical populations. The present review aims to provide an insight into the anatomy of the vasculature as well as the underlying endothelial cell physiology. In addition, an in-depth overview of the current methods used to assess vascular function and structure is provided as well as their link to certain clinical populations.

Effect of brief secondhand smoke exposure on endothelial function and circulating markers of inflammation

OBJECTIVE

In contrast to the well defined detrimental consequences of long-term secondhand smoke (SHS) exposure, little is known about the acute effects of passive smoking on endothelial function and inflammation. The aim of the present study was to assess the acute effects of short-term SHS exposure on endothelial function and circulating markers of inflammation.

METHODS

Peripheral microvascular endothelial function assessed by reactive hyperemia peripheral arterial tonometry (RH-PAT) index, circulating markers of endothelial function (von Willebrand factor antigen, Thrombomodulin, E-selectin) and circulating inflammatory markers (high sensitivity C-reactive protein (hsCRP), Interleukin-6 (IL-6)) were measured in eighteen male, non-smoking volunteers before and 12h after a 1-h SHS exposure.

RESULTS

Twelve hours after passive smoking, average RH-PAT index was significantly lower than before SHS exposure (1.54±0.49 vs 2.01±0.55 (mean±SD), p=0.01) indicating deterioration of peripheral microvascular endothelial function. von Willebrand factor antigen as a marker of endothelial activation was significantly increased after SHS exposure (93.0±25.5% vs 78.4±17.9%, p=0.03). Levels of Thrombomodulin, E-selectin, hsCRP, and IL-6 were unaffected by SHS exposure.

CONCLUSION

Short-term SHS exposure leads to a measurable disturbance of endothelial function. However, 1h of passive smoking appears to be too short to elicit a significant inflammatory response.

Assessment of flow-mediated dilation in humans: a methodological and physiological guideline

Endothelial dysfunction is now considered an important early event in the development of atherosclerosis, which precedes gross morphological signs and clinical symptoms. The assessment of flow-mediated dilation (FMD) was introduced almost 20 years ago as a noninvasive approach to examine vasodilator function in vivo. FMD is widely believed to reflect endothelium-dependent and largely nitric oxide-mediated arterial function and has been used as a surrogate marker of vascular health. This noninvasive technique has been used to compare groups of subjects and to evaluate the impact of interventions within individuals. Despite its widespread adoption, there is considerable variability between studies with respect to the protocols applied, methods of analysis, and interpretation of results. Moreover, differences in methodological approaches have important impacts on the response magnitude, can result in spurious data interpretation, and limit the comparability of outcomes between studies. This review results from a collegial discussion between physiologists with the purpose of developing considered guidelines. The contributors represent several distinct research groups that have independently worked to advance the evidence base for improvement of the technical approaches to FMD measurement and analysis. The outcome is a series of recommendations on the basis of review and critical appraisal of recent physiological studies, pertaining to the most appropriate methods to assess FMD in humans.

Regulation of subcutaneous adipose tissue blood flow is related to measures of vascular and autonomic function

Appropriate blood vessel function is important to cardiovascular health. Adipose tissue plays an important role in metabolic homoeostasis, and subcutaneous abdominal ATBF (adipose tissue blood flow) is responsive to nutritional stimuli. This response is impaired in obesity, suggesting parallels with endothelial function. In the present study, we assessed whether regulation of ATBF is related to the regulation of endothelial function, assessed by FMD (flow-mediated vasodilatation) of the brachial artery. Impaired FMD is a marker of atherosclerotic risk, so we also assessed relationships between ATBF and a marker of atherosclerosis, common carotid artery IMT (intima-media thickness). As ATBF is responsive to sympatho-adrenal stimuli, we also investigated relationships with HRV (heart rate variability). A total of 79 healthy volunteers (44 female) were studied after fasting and after ingestion of 75 g of glucose. FMD, fasting ATBF and the responsiveness of ATBF to glucose were all negatively related to BMI (body mass index), confirming the adverse cardiovascular effects of adiposity. FMD was related to fasting ATBF (rs=0.32, P=0.008) and, at least in males, this relationship was independent of BMI (P=0.02). Common carotid artery IMT, measured in a subset of participants, was negatively related to fasting ATBF [rs=-0.51, P=0.02 (n=20)]. On the other hand, ATBF responsiveness to glucose had no relationship with either FMD or IMT. In multiple regression models, both fasting and stimulated ATBF had relationships with HRV. In conclusion, our results show that the regulation of ATBF has features in common with endothelial function, but also relationships with autonomic cardiovascular control as reflected in HRV.

Central, peripheral and resistance arterial reactivity: fluctuates during the phases of the menstrual cycle

The purpose of this study was to document the temporal changes in vascular reactivity occurring simultaneously in central, peripheral and microvascular resistance arteries in the same cohort of women during the normal menstrual cycle. Twenty-three (n = 23) women (mean age (+/-SD) = 19 +/- 1 y) were tested during four phases of a normal menstrual cycle. Delineation of the four phases occurred as follows: (1) the early follicular phase; (2) the late follicular (LF) phase; (3) the early luteal (EL) phase; and (4) the late luteal phase. Non-invasive measurement of central hemodynamics and peripheral artery pulse wave velocity (PWV) were performed using applanation tonometry. Measurement of peripheral endothelial function was determined by flow-mediated dilation (FMD) testing in the brachial artery and venous occlusion plethysmography in the forearm and calf resistance arteries. Additionally, plasma NOx and 17beta-estradiol (E) concentrations were measured. Both central (aortic) and peripheral blood pressure (BP) were lowest (P < 0.05) during the LF phase and BP reduction was sustained (P < 0.05) into the EL phase. The timing and amplitude of the reflected pressure wave were attenuated only during the LF phase (P < 0.05). No temporal changes were observed in either central (carotid-femoral) or peripheral PWV (femoral-dorsalis pedis, carotid-radial). Peak forearm and calf blood flow during reactive hyperemia were greatest in LF. Brachial FMD was greatest during the LF phase (P < 0.05). Plasma E and NOx concentrations were highest during the LF phase (P < 0.05). Young premenopausal women experienced an overwhelming pattern of reduced BP and increased systemic vascular reactivity during the LF phase prior to ovulation.

Folic acid supplementation improves vascular function in amenorrheic runners

OBJECTIVE

The purpose of this study was to determine if folic acid supplementation improves endothelial vascular function (brachial artery flow-mediated dilation; FMD) in amenorrheic runners.

DESIGN

Prospective cross-sectional study.

SETTING

Academic medical center in the Midwest.

PARTICIPANTS

Ten amenorrheic and 10 eumenorrheic women runners from the community volunteered for this study.

INTERVENTIONS

Each participant was treated with folic acid (10 mg/d) for 4 weeks.

MAIN OUTCOME MEASURES

Brachial artery FMD was measured before and after folic acid supplementation with standard techniques.

RESULTS

The brachial artery FMD response to reactive hyperemia improved after folic acid supplementation in amenorrheic women (3.0% +/- 2.3% vs. 7.7% +/- 4.5%; P = 0.02). In the eumenorrheic control group, there was no change in brachial artery FMD (6.7% +/- 2.0% vs. 5.9% +/- 2.6%; P = 0.52).

CONCLUSIONS

This study demonstrates that brachial artery FMD, an indicator of vascular endothelial function, improves in amenorrheic female runners after short-term supplementation with folic acid.

Metformin reduces arterial stiffness and improves endothelial function in young women with polycystic ovary syndrome: a randomized, placebo-controlled, crossover trial

CONTEXT

Patients with polycystic ovary syndrome (PCOS) have an increased prevalence of insulin resistance and display subclinical evidence of early cardiovascular disease. Metformin improves insulin sensitivity and circulating markers of cardiovascular risk in patients with PCOS, but it is unclear whether this translates into improvements in vascular function.

OBJECTIVE

Our objective was to evaluate the effects of metformin on arterial stiffness and endothelial function in women with PCOS.

DESIGN AND INTERVENTION

Thirty women with PCOS were assigned to consecutive 12-wk treatment periods of metformin or placebo in a randomized, double-blind, crossover design separated by an 8-wk washout.

MAIN OUTCOME MEASURES

The primary outcome measures were assessments of arterial stiffness [augmentation index (AIx), central blood pressure, and brachial and aortic pulse wave velocity (PWV)] and endothelial function. Anthropometry, testosterone, and metabolic biochemistry (lipids, homeostasis model of assessment for insulin resistance, high-sensitivity C-reactive protein, adiponectin, and plasminogen activator inhibitor-1) were also assessed.

RESULTS

Metformin improved AIx [-6.1%; 95% confidence interval (CI) for the difference -8.5 to -3.5%; P < 0.001], aortic PWV (-0.76 m/sec; 95% CI for the difference -1.12 to -0.4 m/sec; P < 0.001), brachial PWV (-0.73 m/sec; 95% CI for the difference -1.09 to -0.38; P < 0.001), central blood pressure (P < 0.001), and endothelium-dependent (AIx after albuterol; P = 0.003) and endothelium-independent (AIx after nitroglycerin; P < 0.001) vascular responses. Metformin also reduced weight (P < 0.001), waist circumference (P < 0.001), and triglycerides (P = 0.004) and increased adiponectin (P = 0.001) but did not affect testosterone or other metabolic measures.

CONCLUSIONS

Short-term metformin therapy improves arterial stiffness and endothelial function in young women with PCOS.

Ethinylestradiol and estradiol have different effects on oxidative stress and nitric oxide synthesis in human endothelial cell cultures

STUDY OBJECTIVE

To compare the effects of ethinylestradiol (EE) and 17β-estradiol (E(2)) on nitric oxide (NO) production and protection against oxidative stress in human endothelial cell cultures.

DESIGN

Experimental study.

SETTINGS

Research laboratory.

MATERIAL

Human ECV304 endothelial cell cultures.

INTERVENTION(S)

The NO synthesis was determined by flow cytometry, and oxidative stress was determined by a cell viability assay, after exposure to hydrogen peroxide (H(2)O(2)) and stimulation of endothelial cells with EE at concentrations similar to those of a contraceptive containing 30 μg EE.

MAIN OUTCOME MEASURE(S)

The effects of EE were compared with those of E(2) at concentrations similar to those occurring during the follicular phase.

RESULT(S)

Ethinylestradiol did not increase NO synthesis and did not protect cells against oxidative stress. The viability of the cells incubated with E(2) in combination with H(2)O(2) was greater than the viability obtained with H(2)O(2) only or with H(2)O(2) in combination with EE. The cells stimulated with E(2) presented a significant increase in NO production compared with control.

CONCLUSION(S)

In contrast to the effects of E(2), EE did not protect human ECV304 endothelial cells against oxidative stress and did not increase their production of NO.

Arterial Wave Reflections During the Menstrual Cycle of Healthy Women

Increased wave reflection is an independent factor associated with cardiovascular diseases, risk, and mortality. The influence of the menstrual cycle on wave reflections and particularly on the reproducibility of their measurement has never been examined. The aim of the present study was to examine the reproducibility and variability of wave reflection indices in premenopausal healthy women during their menstrual cycle. Thirty-two women were examined at 3 phases of their menstrual cycle: days 1 to 2 (menstrual phase), days 6 to 14 (late follicular), and days 4 to 7 after ovulation (early luteal phase). Applanation tonometry of the radial artery and aortic pulse wave analysis were performed for the calculation of augmentation pressure, augmentation index, and timing of reflected waves. Reproducibility of these measures was evaluated by intraclass correlation coefficient and Bland-Altman analysis, whereas ANOVA was performed to assess their variability during the menstrual cycle. The SD of augmentation index differences between repeated measurements within the menstrual cycle ranged from 7.6% to 9.9%. Bland-Altman analysis indicated no evidence of systemic bias and no trend for the reproducibility of measurements to vary with their underlying mean value. Intraclass correlation coefficient indicated a moderate reproducibility of augmentation index and augmentation pressure (>0.80) and a rather low reproducibility for timing of reflected waves (0.43). Mean augmentation pressure, augmentation index, and timing of reflected waves did not vary significantly during the menstrual cycle (ANOVA). Measurement of wave reflections at the same phase of the menstrual cycle or statistical adjustment could be suggested for optimal study design and data interpretation.

Vascular endothelial estrogen receptor alpha is modulated by estrogen status and related to endothelial function and endothelial nitric oxide synthase in healthy women

CONTEXT AND OBJECTIVE

Estrogen receptor alpha (ER alpha), a potent transcription factor expressed in vascular endothelial cells, plays a key role in regulating vascular function and health. We determined whether vascular endothelial cell expression of ER alpha is influenced by estrogen status and is related to vascular endothelial function in healthy women.

METHODS

ER alpha protein expression was measured (quantitative immunofluorescence) in endothelial cells from peripheral veins of 16 healthy, premenopausal women during the early follicular (EF) and late follicular (LF) phases of the menstrual cycle and 17 estrogen-deficient postmenopausal women. Endothelial-dependent dilation (EDD; brachial artery flow-mediated dilation) and endothelial nitric oxide synthase (eNOS) expression and activation were also measured in a subgroup of women.

RESULTS

In premenopausal women (n = 10), ER alpha expression was 30% lower (P < 0.001) during the EF (low estrogen) compared with the LF (high estrogen) phase of the menstrual cycle. In postmenopausal women, ER alpha expression was 33% lower (P < 0.001) compared with the LF phase of the menstrual cycle in premenopausal women. ER alpha expression was strongly related (r = 0.67; P < 0.001) to EDD, which was reduced in postmenopausal women. ER alpha abundance was positively related to expression of eNOS (r = 0.54; P = 0.009; n = 21) and ser1177 phosphorylated eNOS (r = 0.59; P = 0.006; n = 20).

CONCLUSIONS

These results provide the first evidence that expression of ER alpha in vascular endothelial cells is modulated by estrogen status and may be a key determinant of vascular endothelial function in healthy pre- and postmenopausal women. ER alpha expression may influence vascular endothelial function in women by affecting protein levels and activation of eNOS.

Flow-mediated dilation and intima-media thickness of the brachial and axillary arteries in individuals with and without inducible axillary artery compression

The presence of axillary artery aneurysm and/or thrombus in overhead throwing athletes has been linked, theoretically, with the finding of compression by the humeral head induced by a diagnostic arm maneuver. However, whether this intermittent compression is incidental or of pathological significance has yet to be determined. Flow-mediated vasodilation (FMD), intima-media thickness (IMT) and maximum vasodilatory capacity were measured locally (3rd portion of the axillary artery) and downstream (brachial artery) in individuals previously tested for inducible axillary artery compression (compressor group [COMP]: n=8, mean (SD) age: 23 (4) y; "noncompressor" control group [NONCOMP]: n=8, 26 (4) y). A high-resolution ultrasound machine recorded arterial diameter and blood flow velocity. A rapid inflation/deflation pneumatic cuff placed distal to the site of measurement induced reactive hyperemia. Custom-designed wall tracking software with synchronized Doppler waveform analysis detected changes in arterial diameter, blood flow velocity and shear rate from baseline to 3min after cuff deflation. Glyceryl trinitrate and/or ischemic hand grip exercises were administered to induce maximum vasodilation. No significant differences in FMD, IMT or maximum vasodilator capacity were observed between groups at the axillary artery. However, the downstream brachial FMD response was significantly diminished in the COMP group (6.38 [3.28]%) compared with the NONCOMP group (10.38 [2.74]%; p=0.006) despite a comparable shear rate between groups (COMP: 81.92 (44.55) s(-1); NONCOMP: 83.18 (40.02) s(-1); p=0.961). Pooled data revealed a significant negative relationship (r=-0.52, p=0.038) between the FMD response and degree of arterial compression. These results suggest a chronic change in downstream vascular function in individuals demonstrating clinically significant inducible axillary artery compression.

Home-based resistance training improves arterial stiffness in healthy premenopausal women

The present study investigates the effect of home-based resistance training on arterial stiffness in healthy premenopausal women. Twelve healthy non-smoking and normotensive women who were not actively involved in regular physical exercise (aged 42-55 years) performed home-based resistance training twice weekly for 10 weeks using body weight and light dumbbells. Each training session required approximately 40 min to complete. Arterial stiffness was measured using brachial-ankle pulse wave velocity (baPWV). We also determined serum total cholesterol, HDL cholesterol, glucose, triglyceride, insulin, and adiponectin and calculated the homeostasis model assessment of insulin resistance (HOMA-IR), an index of insulin resistance. After home-based resistance training, baPWV, total cholesterol, LDL cholesterol, insulin, and the HOMA-IR decreased, whereas adiponectin increased (P < 0.05) and levels of HDL cholesterol, glucose, triglyceride, blood pressure, and heart rate remained unaffected. These results suggest that home-based resistance training benefits vascular function in healthy premenopausal women.

Influence of the Menstrual Cycle, Pregnancy, and Preeclampsia on Arterial Stiffness

Arterial stiffness and compliance are major predictors of adverse cardiovascular events and are influenced by female sex hormones, including estrogen and progesterone. The aim of this longitudinal study was to evaluate the effect of the menstrual cycle, normal pregnancy, and preeclampsia on central and systemic arterial stiffness. Ten healthy nulliparous women with regular menses were studied in the early and midfollicular, periovulatory, and luteal phases of a single menstrual cycle. Twenty-two primigravida pregnant women were studied throughout pregnancy at 16, 24, 32, and 37 weeks gestation and at 7 weeks postpartum. Fifteen primigravida women with preeclampsia were studied at diagnosis and 7 weeks postpartum. Augmentation index and carotid-radial and carotid-femoral pulse wave velocities were measured using applanation tonometry. Augmentation index fell during the luteal phase of the menstrual cycle (luteal phase versus periovulatory phase; P <0.05). In normal pregnancy, pulse wave velocity and augmentation index increased from 24 weeks over the third trimester ( P ≤0.01 for both). All of the measures were increased in women with preeclampsia ( P ≤0.01), with augmentation index and carotid-femoral pulse wave velocity remaining elevated 7 weeks postpartum ( P ≤0.02). We conclude that systemic arterial stiffness undergoes major changes during the menstrual cycle and pregnancy and that preeclampsia is associated with greater and more prolonged increases in arterial stiffness. These effects may contribute to adverse cardiovascular outcomes of pregnancy and preeclampsia.

A comprehensive assessment of endothelial function in overweight women with and without polycystic ovary syndrome

PCOS (polycystic ovary syndrome) is associated with reproductive abnormalities, IR (insulin resistance) and elevated risk factors for CVD (cardiovascular disease) and Type 2 diabetes, including endothelial dysfunction. The present study aimed to assess a range of circulating markers of endothelial function in overweight women with and without PCOS. Overweight and obese age- and BMI (body mass index)-matched women with (n=80) and without (n=27) PCOS were assessed in a cross-sectional study. End-point measures were HOMA (homoeostasis model assessment)-IR, androgens, lipids, inflammatory markers [hsCRP (high-sensitivity C-reactive protein)] and endothelial function [FMD (flow-mediated dilation), ADMA (asymmetric dimethylarginine), PAI-1 (plasminogen activator inhibitor-1) and vWF (von Willebrand factor)]. Women with PCOS had elevated HOMA-IR (4.1±3.4 compared with 1.9±1.4), free androgen index (9.3±5.6 compared with 4.6±3.8), total cholesterol (5.2±1.0 compared with 4.7±0.9 mmol/l) and triacylglycerols (triglycerides; 1.4±0.7 compared with 0.9±0.3 mmol/l) (P<0.05 for all), but similar hsCRP compared with women without PCOS. With regard to endothelial function, women with PCOS had elevated ADMA (1.0±0.4 compared 0.3±0.1 μmol/l, P<0.001) and PAI-1 (5.6±1.8 compared with 4.6±1.1 units/ml, P=0.006), a trend towards worsened FMD (11.8±5.0 compared with 13.5±4.0%, P=0.075) and no difference in vWF compared with controls. For all subjects, ADMA (P=0.002) and PAI-1 (P<0.001) were increased with higher tertiles of HOMA-IR. Women with PCOS are hyperandrogenic, dyslipidaemic and have IR, and have risk factors for CVD and diabetes including increased circulating markers of endothelial function (ADMA and PAI-1) and a trend towards worse FMD as a global marker of endothelial function. In PCOS, deterioration in endothelial function is related to IR, hyperandrogenism and other factors.

Comparative effects of three popular diets on lipids, endothelial function, and C-reactive protein during weight maintenance

Although popular diets focus on weight loss and their favorable biochemical and physiological effects, fewer investigations have evaluated the biological impact of these diets during weight maintenance. To study this issue, three popular diets-Atkins, South Beach, and Ornish-were tested in a randomized and counterbalanced crossover study between January and December 2006. Participants completed each of the three 4-week isocaloric dietary intervention phases followed by a 4-week washout period. They were weighed weekly and caloric adjustments made if weight change exceeded 1 kg. At the completion of each dietary phase, 3-day food records were analyzed, fasting blood sampled, and brachial artery reactivity testing performed. Eighteen adults completed all three isocaloric dietary phases. During the South Beach and Ornish maintenance phase, there were significant reductions in low-density lipoprotein cholesterol (11.8%; P=0.01, 16.6%; P=0.0006, respectively) compared to prediet baseline. In addition, in contrast to the Atkins maintenance phase, significant reductions in low-density lipoprotein cholesterol and apolipoprotein B levels were observed after the South Beach (P=0.003, P=0.05; repeated measures analyses of variance) and Ornish maintenance phases (P=0.0004, P=0.006, repeated measures analyses of variance). Brachial artery testing revealed an inverse correlation between flow-mediated vasodilatation and intake of saturated fat (r=-0.33; P=0.016). These data suggest that during weight maintenance, less favorable biological effects are observed during a simulated, high-fat Atkins diet when compared to the South Beach and Ornish diet. The findings support additional study in subjects with visceral obesity and the metabolic syndrome, in whom an increased risk of coronary disease at baseline may be accentuated with chronic consumption of a diet that exhibits unfavorable effects on lipids and endothelial function.

Resistance Training Effects on Arterial Compliance in Premenopausal Women

Endurance training has been shown to increase arterial compliance; however, the effect of resistance training is unclear. Purpose: The purpose of this study was to examine the effect lower body resistance training on arterial compliance in healthy premenopausal women. Methods: Thirty-two women were assigned to a resistance training group (n = 21) or a control group (n = 11). Large (C1) and small (C2) arterial compliance (Pulse Contour Analysis) were measured at baseline and after twelve weeks of training. Results: Two-way (group × time) repeated measured ANOVA did not detect significant group, time effects or group × time interactions for small arterial compliance (P > 0.05). There was a significant time effect for large arterial compliance (P < 0.05), which increased in both groups. Conclusions: In contrast to previous studies in men, which found decrease in arterial compliance with resistance training, no decrease in arterial compliance was observed.

Chronic smoking prevents amelioration of endothelial function in the course of the menstrual cycle

BACKGROUND

Smoking is the most important modifiable cardiovascular risk factor in young women. The aim of this study was to investigate whether tobacco use influences physiological changes in endothelial function during the menstrual cycle.

METHODS AND RESULTS

Flow-mediated dilation (FMD) and nitro-mediated dilation (NMD) were assessed in healthy smoking and non-smoking women, by high-resolution ultrasound at 3 time points during the menstrual cycle: at menstruation, in the mid-follicular phase, and in the mid-luteal phase. A total of 25 women (12 non-smokers, 13 smokers) completed the study protocol. FMD did not show differences between smoking and non-smoking women at menstruation and the mid-follicular phase. At the mid-luteal phase, however, FMD was significantly reduced in smoking when compared with non-smoking women. NMD did not differ between smoking and non-smoking women, nor between the different cycle phases.

CONCLUSIONS

In healthy women, smoking eliminates the physiological amelioration of endothelial function during the menstrual cycle. This study underlines the importance of an exact description of menstrual cycle phase and smoking status in studies investigating endothelial function in premenopausal women.

Influence of systolic blood pressure and cigarette smoking on endothelial function in young healthy people

BACKGROUND

Flow-mediated dilatation (FMD) of the brachial artery represents systemic endothelial function, so the relationship between FMD and blood pressure (BP) profile, in relation to the effects of cigarette smoking, was investigated in young healthy subjects.

METHODS AND RESULTS

The 62 healthy subjects (14 females, 48 males; mean 29.7+/-5.5 years old), were divided into a smoking group (n=30) and non-smoking group (n=32). FMD was induced by reactive hyperemia. It was lower in the smoking group than in the non-smoking group (P<0.05). In the non-smoking group, there was an inverse correlation (r=-0.59, P<0.0005) between FMD and systolic BP (SBP), which was not recognized in the smoking group. Multiple stepwise regression analysis revealed that FMD was predicted by either the SBP or the brachial artery diameter in the non-smoking group, whereas it was predicted by the brachial artery diameter in the smoking group. Subdivision by cut-off value of SBP =120 mmHg demonstrated that although FMD with SBP <120 mmHg was preserved in subjects in the non-smoking group, it was depressed to a level comparable with SBP >or=120 mmHg in the smoking group.

CONCLUSIONS

Highly-preserved FMD in subjects with SBP <120 mmHg appears to be impaired by cigarette smoking, resulting in a loss of association between FMD and SBP.

Sex differences in limb vasoconstriction responses to increases in transmural pressures

Women compared with men are more likely to have orthostatic intolerance. The purpose of this study was to examine whether sex affects limb vasoconstrictor response to increases in transmural pressure. Brachial and femoral mean blood velocity (MBV) and diameter (Doppler Ultrasound) were measured in 10 women and 10 men as transmural pressure was altered by applying local suction (-25, -50, -75, and -100 mmHg) via pressurized-limb tanks for 1 min to a single arm and leg. With the abrupt application of forearm suction (-75 and -100 mmHg), women compared with men had a greater initial rise in MBV (peak), followed by a quicker dynamic rate of velocity reduction. In the leg, women had a tendency for higher peak MBV but had similar dynamic velocity reductions compared with men. After 60 s of suction, women compared with men had attenuated reductions in brachial flow and conductance (-8.05 +/- 1.71 vs. -16.25 +/- 1.71 ml/min; -0.12 +/- 0.03 vs. -0.20 +/- 0.03 ml x min(-1) x mmHg(-1); main effect, P < 0.05), as well as attenuated femoral flow and conductance to sustained leg negative pressure at -100 mmHg (P < 0.05). When the data were expressed as percent change, women compared with men continued to have attenuated brachial flow responses (-24 +/- 2 vs. -36 +/- 2%, main effect, P < 0.05), with a trend toward attenuation at the highest leg pressure (-25 +/- 11 vs. -46 +/- 4%; P = 0.08). These sex differences remained after normalizing the flow responses by limb volume (percent change). Our findings suggest that young women compared with men have attenuated brachial and femoral vasoconstrictor responses to increases in transmural pressure, which may have implications for the greater incidence of orthostatic intolerance in women.

Vascular endothelial function and leisure-time physical activity in adolescents

BACKGROUND

Exercise training improves endothelial function in high-risk adolescents, but the influence of habitual leisure-time physical activity on endothelial function in healthy adolescents is unknown.

METHODS AND RESULTS

Brachial artery flow-mediated endothelial function and physical activity habits were assessed in 483 adolescents (13 years of age) participating in an atherosclerosis prevention study (Special Turku Coronary Risk Factor Intervention Project for Children [STRIP]). Endothelial function was examined with ultrasound; physical activity was assessed with self-administered questionnaires. A leisure-time physical activity index was calculated by multiplying mean weekly leisure-time exercise intensity, duration, and frequency [boys, 31.2 +/- 23.0 MET h/wk (mean +/- SD); girls, 24.0 +/- 20.9 MET h/wk; P for gender difference=0.0003]. Maximum flow-mediated dilatation (FMD) and total FMD response (the area under the dilatation curve 40 to 180 seconds after hyperemia) were calculated. In boys, maximum FMD and area under the dilatation curve 40 to 180 seconds after hyperemia were directly associated with leisure-time physical activity index in regression analyses adjusted for brachial artery diameter (maximum FMD, P=0.020; area under the dilatation curve 40 to 180 seconds after hyperemia, P=0.0055). These associations remained significant after further adjustments for body mass index, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, high-sensitivity C-reactive protein, and systolic blood pressure. A difference of approximately 50 MET h/wk corresponding to approximately 10 hours of moderate intensity activity weekly between sedentary and active boys was associated with an approximately 1% unit difference in maximum FMD.

CONCLUSIONS

Leisure-time physical activity is directly associated with brachial artery FMD responses in 13-year-old boys, providing evidence that physical activity beneficially influences endothelial function in healthy male adolescents. Lack of association in girls may reflect their overall lower physical activity level.

Examining the time course of endothelium-independent dilation by nitroglycerin

Arterial smooth muscle function is commonly assessed by measuring the dilation response to sublingual nitroglycerin (NTG), and is referred to as endothelium-independent dilation (EID). The time point at which the brachial artery dilates maximally after NTG administration is generally believed to occur somewhere between three and five minutes. The aim of this study was to examine the time course of brachial artery dilation response to a single dose of sublingual NTG to identify the time point at which maximal dilation occurs and to assess factors effecting EID. Endothelial independent dilation was measured in 125 normal, healthy subjects (male = 67, female = 58) via high-resolution ultrasound on the brachial artery. Mean time to maximal EID was 279.0 +/- 26.9 s. There was a significant (p < 0.0001) difference between brachial EID at three minutes vs. five minutes post NTG. There was also a significant gender difference in EID response (p < 0.0001). The results of this study indicate that maximal EID occurs approximately five minutes after NTG administration. Measuring EID at three minutes after NTG administration likely underestimates the true dilation capacity of the artery.

Physical inactivity rapidly induces insulin resistance and microvascular dysfunction in healthy volunteers

OBJECTIVE

Sedentary lifestyle increases the risk of cardiovascular disease and diabetes. Vascular dysfunction contributes to atherogenesis and has been linked to insulin resistance.

METHODS AND RESULTS

We measured insulin sensitivity by glucose tolerance test and vascular function by ultrasound and venous occlusion plethysmography in 20 healthy subjects (14 men, 6 women) at baseline and during 5 days of bed rest. Bed rest led to a 67% increase in the insulin response to glucose loading (P<0.001) suggesting increased insulin resistance and produced increases in total cholesterol and triglycerides. Bed rest led to decreased reactive hyperemia in the forearm (1317+/-404 to 1112+/-260 mL/min, P=0.01) and the calf (28.5+/-7.0 to 22.2+/-8.7 mL/min/dL, P=0.003) indicating impaired microvascular function. Bed rest decreased brachial artery diameter and increased systolic blood pressure suggesting increased basal arterial tone. There were no changes in circulating inflammatory markers arguing against systemic inflammation as a mechanism for vascular dysfunction in this setting.

CONCLUSIONS

Physical inactivity was associated with the development of insulin resistance, dyslipidemia, increased blood pressure, and impaired microvascular function in healthy volunteers. Our findings may provide insight into the pathogenesis of vascular disease in sedentary individuals and emphasize that even short-term physical inactivity may have adverse metabolic and vascular consequences.

External mechanical compression reduces regional arterial stiffness

Acute aerobic and resistance exercise has been shown to reduce local muscular artery stiffness in the exercised limb while having no effect on the non-exercised limb. The stimulus for these modulations may be related to local muscular compression of underlying vasculature. The purpose of this study was to examine arterial stiffness before and after a series of locally applied external mechanical compressions designed to be similar to the resistance exercise concentric/eccentric duty cycle. One rapidly inflatable cuff was placed around the upper thigh and another around the calf of the left leg in 18 healthy, young (24 +/- 1 years) participants (female n = 10). Cuffs were inflated to a supra-systolic pressure of 200 mmHg for 4 s followed by a 2-s rapid deflation period. One "set" consisted of 12 inflation/deflation cycles. Six sets of 12 compression cycles were performed. Pulse wave velocity (PWV) was used to measure central stiffness (carotid to femoral) and peripheral stiffness (femoral to dorsalis pedis of both legs) before and 10 min after mechanical compressions. No change was found in central PWV (6.2 +/- 0.3 m/s to 6.3 +/- 0.3 m/s, P > 0.05). Peripheral PWV in the non-compressed leg did not change (8.5 +/- 0.4 m/s to 8.3 +/- 0.4 m/s, P > 0.05) while peripheral PWV in the compressed leg significantly decreased from pre to 10 min post (8.6 +/- 0.3 m/s to 7.6 +/- 0.3 m/s, P < 0.05). External compression reduced local artery stiffness of the compressed limb while having no effect on arterial stiffness of the non-compressed limb or central artery stiffness.

Raloxifene improves the ovariectomy-induced impairment in endothelium-dependent vasodilation

OBJECTIVE

To examine the effect of raloxifene on the endothelial dysfunction caused by surgical menopause.

DESIGN

Ten premenopausal women who underwent gynecological surgery with ovariectomy were divided into two groups. Five participants used raloxifene (60 mg/d) for 7 days staring 1 week after the surgery, and the other five participants did not use raloxifene. We examined the changes in flow-mediated dilatation (FMD) of the brachial artery using ultrasonography. Vasodilation in response to nitroglycerin was also studied. We also measured the brachial-ankle pulse wave velocity to examine the change in arterial stiffness in these participants before and after surgical menopause.

RESULTS

In both the raloxifene and control groups, a significant decrease in FMD was observed 1 week after the surgery. Although no further changes in FMD were observed in the control group at 2 weeks after surgery, FMD was significantly increased in the raloxifene group. No remarkable changes in nitroglycerin or brachial-ankle pulse wave velocity were observed after surgery in either group.

CONCLUSIONS

Raloxifene rapidly restored FMD that was impaired after surgical menopause. Therefore, raloxifene may be effective for ameliorating and maintaining endothelial function in premenopausal women who undergo ovariectomy.

Endothelial function across an oral contraceptive cycle in women using levonorgestrel and ethinyl estradiol

Oral contraceptive pills (OCPs) are a popular contraception method. Currently, lower-dose ethinyl estradiol formulations are most commonly prescribed, although they have been linked to increased arterial vascular risk. The aim of this study was to investigate endothelial function in healthy young women using lower-dose ethinyl estradiol OCPs. We examined flow-mediated, endothelium-dependent and nitroglycerin-mediated, endothelium-independent vasodilation of the brachial artery, comparing two doses of ethinyl estradiol/levonorgestrel OCPs in 15 healthy young women on two study days: once during the active phase and once during the placebo phase of an OCP cycle. Group low dose (LD) ( n = 7) active pills contained 150 μg levonorgestrel/30 μg ethinyl estradiol versus Group very low dose (VLD) ( n = 8) with 100 μg levonorgestrel/20 μg ethinyl estradiol. Endothelium-dependent vasodilation was lower during the active phase in Group VLD (5.33 ± 1.77% vs. 7.23 ± 2.60%; P = 0.024). This phase difference was not observed in Group LD (8.00 ± 0.970% vs. 7.61 ± 1.07%; P = 0.647). Endothelium-independent vasodilation did not differ between phases in either group. Finally, we measured endothelium-dependent vasodilation in two additional women who received 10 μg of unopposed ethinyl estradiol. Endothelium-dependent vasodilation was increased by unopposed ethinyl estradiol compared with the placebo phase (10.88 ± 2.34% vs. 6.97 ± 1.83%). These results suggest that levonorgestrel may antagonize the activity of ethinyl estradiol. Thus both the progestin type and estradiol dose need to be considered when assessing arterial vascular risk of OCP use in women.

Pregnancy as the prodrome to vascular dysfunction and cardiovascular risk

In previously apparently healthy women, glucose intolerance and high blood pressure during pregnancy are common and frequently occur together. This article reviews the role of these gestational disorders as markers of vascular dysfunction and its pathophysiology. Mechanisms include alterations to function of large arteries and resistance vessels and to capillary blood flow. Much of the vessel pathology is seen in both gestational diabetes and hypertension. In women who have had transient diabetes during pregnancy and later redeveloped overt diabetes, cardiovascular risk is already elevated nearly fourfold before diagnosis, which is almost as high as the average risk after a clinical diagnosis of diabetes is made. This key finding suggests that vascular risk in such women is at least partly independent of overt hyperglycemia.

Effects of eccentric and concentric resistance training on arterial stiffness

It has been suggested that resistance training (RT) increases arterial stiffness. The purpose of the present study was to clarify the effect of eccentric RT (ERT) and concentric RT (CRT) on arterial stiffness in female adults by an interventional study. In total, 29 healthy female subjects were randomly assigned to either the ERT group (n=10), CRT group (n=10) or sedentary (SED) group (n=9). The ERT and CRT groups performed resistance training three times a week for 8 weeks. We determined brachial blood pressure, brachial-ankle pulse wave velocity (baPWV), carotid artery intimamedial thickness (IMT) and carotid arterial lumen diameter before and after training and after detraining. The before-training baPWV did not differ significantly among the three groups. After 8 weeks of RT, arterial stiffness in the CRT group was increased compared with the ERT and SED group (P<0.05). However, brachial blood pressure, baPWV, carotid IMT and carotid lumen diameter in the ERT and CRT groups were unchanged by RT for 8 weeks. Consequently, it was clarified that arterial stiffness was not changed by ERT for 8 weeks. This suggests that ERT may be effective as an exercise prescription for middle-aged and elderly adults.

Changes in Central Arterial Pressure Waveforms during the Normal Menstrual Cycle

BACKGROUND

Changes in estradiol and progesterone during the human menstrual cycle may impact vascular and cardiac function. Renin-angiotensin-aldosterone system (RAAS) hormones increase during the luteal phase of the menstrual cycle and may antagonize the vascular effects of estradiol. This study was designed to investigate central arterial changes, cardiac function, and RAAS activity in response to gonadal steroid variations during the menstrual cycle.

METHODS

We studied 15 women during the follicular and midluteal phases with determination of estradiol, progesterone, hormones of the RAAS, and spot urine sodium and creatinine levels. Central pulsatile hemodynamics was evaluated using calibrated carotid tonometry and central aortic Doppler flow. Systolic ejection period (SEP) and systolic pressure time integral (SPTI) were computed from carotid pressure waveforms.

RESULTS

Levels of estradiol, progesterone, and RAAS hormones were higher in the luteal phase. SEP and SPTI were lower during the luteal phase, whereas central and peripheral blood pressures and measures of arterial stiffness were unchanged between the two phases. The urine sodium-to-creatinine ratio was similar at both phases.

CONCLUSION

Central arterial stiffness does not differ between the follicular and midluteal phases of the menstrual cycle in healthy women, despite significant changes in estradiol and progesterone levels. Systole was shortened during the midluteal phase. RAAS activation during the luteal phase may be responsible for a lack of the expected estradiol-mediated reduction in arterial stiffness between the two phases of the menstrual cycle. Because load was unchanged, the decrease in SEP and SPTI may represent a direct effect of estrogen, progesterone, or RAAS activation on ventricular function.

Variations in carotid arterial compliance during the menstrual cycle in young women

The effect of menstrual cycle phase on arterial elasticity is controversial. In 10 healthy women (20.6+/-1.5 years old, mean+/-s.d.), we investigated the variations in central and peripheral arterial elasticity, blood pressure (carotid and brachial), carotid intima-media thickness (IMT), and serum oestradiol and progesterone concentrations at five points in the menstrual cycle (menstrual, M; follicular, F; ovulatory, O; early luteal, EL; and late luteal, LL). Carotid arterial compliance (simultaneous ultrasound and applanation tonometry) varied cyclically, with significant increases from the values seen in M (0.164+/-0.036 mm2 mmHg-1) and F (0.171+/-0.029 mm2 mmHg-1) to that seen in the O phase (0.184+/-0.029 mm2 mmHg-1). Sharp declines were observed in the EL (0.150+/-0.033 mm2 mmHg-1) and LL phases (0.147+/-0.026 mm2 mmHg-1; F=8.51, P<0.05). Pulse wave velocity in the leg (i.e. peripheral arterial stiffness) did not exhibit any significant changes. Fluctuations in carotid arterial elasticity correlated with the balance between oestradiol and progesterone concentrations. No significant changes were found in carotid and brachial blood pressures, carotid artery lumen diameter, or IMT throughout the menstrual cycle. These data provide evidence that the elastic properties of central, but not peripheral, arteries fluctuate significantly with the phases of the menstrual cycle.