Flow-mediated vasodilation and the risk of developing hypertension in healthy postmenopausal women

The underlying mechanisms for development of hypertension in the metabolic syndrome

High blood pressure is an important constituent of the metabolic syndrome. However, the underlying mechanisms for development of hypertension in the metabolic syndrome are very complicated and remain still obscure. Visceral/central obesity, insulin resistance, sympathetic overactivity, oxidative stress, endothelial dysfunction, activated renin-angiotensin system, increased inflammatory mediators, and obstructive sleep apnea have been suggested to be possible factors to develop hypertension in the metabolic syndrome. Here, we will discuss how these factors influence on development of hypertension in the metabolic syndrome.

A population-based screening for microalbuminuria among relatives of CKD patients: the Kidney Evaluation and Awareness Program in Sheffield (KEAPS)

BACKGROUND

Microalbuminuria has been used to detect subjects at risk of cardiovascular disease and chronic kidney disease (CKD) in patients with diabetes, those with hypertension, and the general population. However, relatives of patients with CKD have not been investigated for microalbuminuria in the United Kingdom.

STUDY DESIGN

A cross-sectional study evaluating the prevalence of microalbuminuria in relatives of patients with CKD compared with the general population of Sheffield, England.

SETTING & PARTICIPANTS

Participants in the Kidney Evaluation and Awareness Program in Sheffield, a population-based screening program for microalbuminuria. 274 relatives of patients with CKD were studied and compared with an age- and sex-matched control group from the general population.

PREDICTOR

Family history of CKD.

MEASUREMENT & OUTCOMES

Screening tools included a questionnaire collating information for demographics, lifestyle, and medical and family history of diabetes, hypertension, and CKD. Urine samples were collected for microalbuminuria estimation. Microalbuminuria measurements were obtained by using immunonephelometry. Microalbuminuria thresholds were defined using albumin-creatinine ratio.

RESULTS

The prevalence of microalbuminuria was 9.5% in those with a family history of CKD. This was significantly greater than the prevalence of 1.4% in the age- and sex-matched control group with no family history of CKD (P = 0.001). Independent determinants of microalbuminuria in the study population in an adjusted logistic regression model were family history of diabetes (odds ratio [OR], 2.88; 95% confidence interval, 1.17 to 7.04), obesity (OR, 3.29; 95% confidence interval, 1.61 to 6.69), and family history of CKD (OR, 6.96; 95% confidence interval, 3.48 to 13.92).

LIMITATIONS

Cross-sectional snapshot analysis, microalbuminuria measured once.

CONCLUSIONS

The prevalence of microalbuminuria in relatives of patients with CKD is greater than in an age- and sex-matched control group from the general population. The prognostic value of microalbuminuria in this category of at-risk population remains to be determined in longitudinal studies.

Raloxifene, soy phytoestrogens and endothelial function in postmenopausal women

OBJECTIVE

To compare the effects of raloxifene and soy phytoestrogens on endothelial function in healthy, postmenopausal women.

DESIGN

Randomized, double-blind, placebo-controlled, cross-over trial. Subjects (n = 22; mean age 58.5 years) underwent endothelial function testing at baseline and following 6 weeks of daily raloxifene 60 mg, soy phytoestrogens 55 mg, and placebo in random sequence with intervening 6-week wash-out periods. Endothelial function was assessed as flow-mediated vasodilatation (FMD) of the brachial artery using high-resolution ultrasound; digital flux was measured with laser Doppler velocimetry.

RESULTS

Baseline (pretreatment) FMD was almost within normal range at 9.6% (+/-6.4). FMD did not change from baseline within any treatment group, and no between-group differences were detected. FMD values following treatment with raloxifene, soy, and placebo were 10.3% (+/-12.3), 8.3% (+/-7.7), and 9.5% (+/-4.4), respectively. Area under curve ratios showed no treatment differences for digital velocimetry.

CONCLUSIONS

In this study, neither raloxifene nor soy enhanced endothelial function in postmenopausal women. However, the cohort had relatively normal endothelial function at baseline. Further study is required to determine if particular subgroups of postmenopausal women derive vascular benefit from the use of selective estrogen receptor modulators or soy phytoestrogens.

Prognostic role of flow-mediated dilation and cardiac risk factors in post-menopausal women

OBJECTIVES

The aim of this study was to examine the association between brachial artery flow-mediated dilation (FMD) and cardiovascular events in a cohort of initially asymptomatic post-menopausal women, with adjustment for the presence of the major cardiovascular risk factors.

BACKGROUND

Conventional major cardiovascular risk factors (cigarette smoking, hypercholesterolemia, hypertension, and diabetes) fail to explain nearly 50% of cardiovascular events. Defining the magnitude of future risk for the development of clinical events is a major focus of effective primary prevention. Evaluation of endothelial function, utilizing the noninvasive measurement of the brachial artery FMD, may serve as a screening tool to individualize high-risk patients.

METHODS

We conducted a prospective study on 2,264 post-menopausal women, age 54 +/- 6 years. The length of the follow-up was 45 +/- 13 months (range 6 to 65 months).

RESULTS

During observation, 90 major events were recorded. Risk-adjusted relative risk values resulted 1.0, 1.33 (95% confidence interval [CI] 1.09 to 4.09), and 4.42 (95% CI 2.97 to 8.01) for women in the higher, intermediate, and lower tertile of FMD, respectively (p < 0.0001 for trend). The event rate for women in the lower tertile (FMD <or=4.5%) was greater than the combined event rate noted in the other 2 tertiles (women in the lower tertile accounted for 51 events [56.6% of total events]). When added to age and other conventional cardiovascular risk factors (smoking habits, presence of hypercholesterolemia, history of diabetes, hypertension), FMD contributed significantly to the model predicting cardiovascular events (likelihood ratio chi-square change: 10.22; p < 0.0001).

CONCLUSIONS

In post-menopausal women, the knowledge of FMD provided incremental prognostic information regarding the risk of developing cardiovascular events.

Randomized, placebo-controlled trial of the effects of drospirenone-estradiol on blood pressure and potassium balance in hypertensive postmenopausal women receiving hydrochlorothiazide

OBJECTIVE

Drospirenone (DRSP), a spironolactone analog with aldosterone antagonist activity, is a novel progestogen developed for use as hormone therapy in postmenopausal women in combination with 17beta-estradiol (E2). DRSP/E2 lowers blood pressure when used alone in hypertensive postmenopausal women or when administered concomitantly with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. DRSP/E2 has not been studied in combination with the widely prescribed hydrochlorothiazide (HCTZ). We investigated the effects of 3 mg DRSP/1 mg E2 versus placebo on blood pressure and potassium balance when added to existing therapy with 25 mg HCTZ in postmenopausal women with established stage I hypertension.

DESIGN

This was a single-center, double-blind, randomized, placebo-controlled, two-treatment, two 4-week treatment period crossover study in 36 postmenopausal women with stage I hypertension maintained on 25 mg HCTZ. The endpoint was a change from baseline in systolic and diastolic blood pressures by 24-hour ambulatory blood pressure monitoring. Safety monitoring included serum potassium (mEq/L) and adverse events.

RESULTS

Mean systolic and diastolic blood pressures by 24-hour ambulatory blood pressure monitoring were reduced significantly, by -7.2 and -4.5 mm Hg, respectively, with DRSP/E2 as compared with placebo. The decrease in potassium with HCTZ was 0.2 mEq/L less with DRSP/E2 than placebo, suggesting a potassium-sparing effect. The most frequently observed adverse events with DRSP/E2 were vaginal bleeding and breast tenderness, which were attributable to the hormone therapy.

CONCLUSIONS

DRSP/E2 substantially lowers systolic and diastolic blood pressure when added to existing antihypertensive therapy with HCTZ in hypertensive postmenopausal women. In addition, DRSP/E2 has a potassium-sparing effect that counteracts HCTZ-induced potassium loss.

Type 2 diabetes mellitus is a risk factor for the development of hypertension in postmenopausal women

OBJECTIVE

Hypertension and type 2 diabetes mellitus are common diseases that are frequently found concomitantly in postmenopausal women. These findings suggest a close and/or synergistic nature in the relationship between the two disease processes; however, no prospective data exist on the incidence rate of hypertension in postmenopausal women with type 2 diabetes mellitus.

METHODS

The present study assessed the risk of developing hypertension in 840 postmenopausal women: 102 women (12.1% of the cohort) with type 2 diabetes mellitus and 738 (87.9%) free of diabetes. The mean +/- SD follow-up was 3.2 +/- 0.9 years (range 0.5-6.0 years).

RESULTS

The incidence rate (cases of hypertension per 100 person-years) was 1.1 for the group of women without diabetes versus 5.6 in women with diabetes (P < 0.0001). Compared with the non-diabetic group, women with type 2 diabetes mellitus had a statistically significant higher risk of developing hypertension. The relative risks for women with diabetes was 5.09 [crude: 95% confidence interval (CI) = 3.52-7.36; P < 0.0001]; 3.43 (adjusted for body mass index and waist circumference: 95% CI = 2.25-5.14; P < 0.001); and 2.95 (adjusted for all potential confounders: 95% CI = 1.86-4.32; P < 0.01).

CONCLUSION

In our prospective study, on the incidence of hypertension, the presence of type 2 diabetes was found to be a potent independent risk determinant. This suggests that postmenopausal women affected by type 2 diabetes mellitus comprise a population at high risk for the subsequent development of hypertension.

Correlation of flow mediated dilation with inflammatory markers in patients with impaired cardiac function. Beneficial effects of inhibition of ACE

Impaired cardiac function is frequently accompanied by peripheral vascular dysfunction and a pro-inflammatory condition, which may be associated with elevated levels of angiotensin II. We hypothesized that the magnitude of flow mediated dilatation (FMD) of the brachial artery of post myocardial infarction patients will correlate with serum levels of tumor necrosis factor alpha (TNFalpha) and C-reactive protein (CRP), and that treatment with angiotensin converting enzyme inhibitors (ACEI) will increase FMD by reducing TNFalpha and CRP. Patients were treated with low dose (10 mg/day) quinapril (Q) or enalapril (E) and their effects on FMD and inflammatory markers were evaluated after 8 and 12 weeks. Before treatment, in both groups FMD showed a low value (Q: 2.95+0.42% and E: 3.3+/-0.33%), whereas TNF-alpha (Q: 31.65+/-8.23 pg/ml and E: 29.5+/-5.9 pg/ml) and CRP (Q: 7.28+/-2.96 mg/ml and E: 7.08+/-3.02 mg/ml) were elevated. In the Q group, but not in the E group FMD increased significantly, (to 5.96+1.10%), whereas TNF-alpha (19.0+/-12.21 pg/ml) and CRP (to 3.91+/-1.82 mg/L) significantly decreased after 8 and 12 weeks of Q treatment. Moreover, the magnitude of FMD showed a strong inverse correlation with serum levels of TNF-alpha and CRP after Q treatment. Thus, in post myocardial infarction patients endothelial dysfunction assessed by FMD correlates with elevated levels of plasma inflammatory markers, and low dose quinapril improves endothelial function, likely by reducing vascular inflammation.

Age-associated impairment in vasorelaxation to fluid shear stress in the female vasculature is improved by TNF-α antagonism

Aging is associated with alterations in vascular homeostasis, including a reduction in flow-mediated vasodilation, which in women is related to the onset of menopause. We previously found that in female animals, aging is associated with an increase in TNF-α. Thus we investigated the role of in vivo TNF-α inhibition on vascular responses to shear stress in aging female rats. Mesenteric arteries (∼150 μm) were isolated from young (3 mo) and ovariectomized Sprague-Dawley female rats approaching reproductive senescence (12 mo) treated with either placebo or a TNF-α inhibitor (etanercept; 0.3 mg/kg) and were mounted on a pressure myograph system. Vessels were equilibrated at an intraluminal pressure of 60 mmHg and then preconstricted with phenylephrine at ∼70% of their initial diameter. Perfusate flow was increased in steps from 0 to 150 μl/min. Compared with young vessels, aged vessels have a decrease in flow-mediated dilation [maximal dilation (means ± SE): 52 ± 4 vs. 24 ± 15%; P < 0.05], which was improved by TNF-α inhibition. Moreover, in aged vessels maximal dilation to flow was achieved at higher levels of shear stress compared with young vessels. In all groups, flow-mediated dilation was abolished by either endothelial removal or nitric oxide synthase inhibition with NG-nitro-l-arginine methyl ester. However, the modulation by NG-nitro-l-arginine methyl ester was reduced in vessels from aged animals compared with young animals but was improved in the etanercept-treated aged animals. In vivo chronic TNF-α inhibition improves flow-mediated arterial dilation in resistance arteries of aged female animals.

Urinary Albumin Excretion as a Predictor of the Development of Hypertension in the General Population

The hypothesis that high urinary albumin excretion (UAE; indicating mild renal damage) may precede development of hypertension was tested, and the relation among UAE, GFR, and development of hypertension was investigated. Data of 4635 patients of a prospective cohort study who participated in an extensive screening in 1997 to 1998 and 2001 to 2003 at our outpatient unit and were normotensive at baseline were used. Hypertension was defined according to the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure criteria, UAE was measured in two consecutive 24-h urine samples, and GFR was calculated with the modified Modification of Diet in Renal Disease formula. Mean follow-up was 4.3 yr. Baseline UAE was significantly associated with the risk for developing hypertension (odds ratio 2.29; 95% confidence interval 1.77 to 2.95 per 10-fold increase of UAE). This association was independent of potential confounders. An interaction between UAE and GFR was found (P = 0.030), indicating that with elevated UAE and lowered GFR, but still within the normal range, the risk for developing hypertension was highest. In conclusion, these findings support the hypothesis that mild renal damage may precede the development of hypertension.

Endothelial dysfunction: its role in hypertensive coronary disease

PURPOSE OF REVIEW

Coronary artery disease is the major cause of death worldwide. Hypertension is a major risk factor for developing coronary disease. It is now recognized that endothelial dysfunction is an early marker of coronary artery disease before structural changes to the vessel wall are apparent on angiography or intravascular ultrasound and that it has a prognostic value in predicting cardiovascular events in hypertensive patients. This review addresses recent developments in hypertension-induced endothelial dysfunction.

RECENT FINDINGS

Hyperaldosteronism causes endothelial dysfunction independent of high blood pressure. Exaggerated exercise blood pressure response has been related to endothelial dysfunction. Cyclosporin-A-induced endothelial dysfunction is related to reduced cholesterol content in caveolae. Chronic kidney disease induces changes in caveoli-1 and thus contributes to the reduced nitric oxide bioavailability, and causes oxidative stress independent of the high blood pressure. Asymmetric dimethylarginine plays a role in endothelial dysfunction in hypertensive patients independent of insulin resistance. 20-Hydroxyeicosatetraenoic acid is an independent predictor of hypertension in postmenopausal women. Endothelial dysfunction precedes and predicts the development of hypertension in postmenopausal women. Oral treatment with L-arginine improves endothelial dysfunction in hypertensives and lowers the blood pressure.

SUMMARY

The pathophysiology of endothelial dysfunction in hypertension is multifactorial. Recent findings have contributed to our understanding of mechanisms of endothelial dysfunction and support a role for early intervention to prevent irreversible vascular and organ damage.