Evidence of decreased fibrinolytic activity in hypertensive premenopausal women

Estrogen receptor-alpha mediates estrogen facilitation of baroreflex heart rate responses in conscious mice

Estrogen facilitates baroreflex heart rate responses evoked by intravenous infusion of ANG II and phenylephrine (PE) in ovariectomized female mice. The present study aims to identify the estrogen receptor subtype involved in mediating these effects of estrogen. Baroreflex responses to PE, ANG II, and sodium nitroprusside (SNP) were tested in intact and ovariectomized estrogen receptor-alpha knockout (ERalphaKO) with (OvxE+) or without (OvxE-) estrogen replacement. Wild-type (WT) females homozygous for the ERalpha(+/+) were used as controls. Basal mean arterial pressures (MAP) and heart rates were comparable in all the groups except the ERalphaKO-OvxE+ mice. This group had significantly smaller resting MAP, suggesting an effect of estrogen on resting vascular tone possibly mediated by the ERbeta subtype. Unlike the WT females, estrogen did not facilitate baroreflex heart rate responses to either PE or ANG II in the ERalphaKO-OvxE+ mice. The slope of the line relating baroreflex heart rate decreases with increases in MAP evoked by PE was comparable in ERalphaKO-OvxE- (-6.97 +/- 1.4 beats.min(-1).mmHg(-1)) and ERalphaKO-OvxE+ (-6.18 +/- 1.3) mice. Likewise, the slope of the baroreflex bradycardic responses to ANG II was similar in ERalphaKO-OvxE- (-3.87 +/- 0.5) and ERalphaKO-OvxE+(-2.60 +/- 0.5) females. Data suggest that estrogen facilitation of baroreflex responses to PE and ANG II is predominantly mediated by ERalpha subtype. A second important observation in the present study is that the slope of ANG II-induced baroreflex bradycardia is significantly blunted compared with PE in the intact as well as the ERalphaKO-OvxE+ females. We have previously reported that this ANG II-mediated blunting of cardiac baroreflexes is observed only in WT males and not in ovariectomized WT females independent of their estrogen replacement status. The present data suggest that in females lacking ERalpha, ANG II causes blunting of cardiac baroreflexes similar to males and may be indicative of a direct modulatory effect of the ERalpha on those central mechanisms involved in ANG II-induced resetting of cardiac baroreflexes. These observations suggest an important role for ERalpha subtype in the central modulation of baroreflex responses. Lastly, estrogen did not significantly affect reflex tachycardic responses to SNP in both WT and ERalphaKO mice.

Angiotensin-converting enzyme inhibitor prevents plasminogen activator inhibitor-1 expression in a rat model with cardiovascular remodeling induced by chronic inhibition of nitric oxide synthesis

Plasminogen activator inhibitor-1 (PAI-1) may participate in the development of cardiovascular remodeling by inhibiting extracellular matrix turnover and fibrinolysis. However, little is known about physiological regulators of PAI-1 in vivo. Angiotensin II has been shown to stimulate PAI-1 in vitro. We previously reported that long-term inhibition of nitric oxide (NO) synthesis with Nomega-nitro-L-arginine methyl ester (L-NAME) causes cardiovascular remodeling (vascular medial thickening and fibrosis) associated with increased tissue angiotensin-converting enzyme (ACE) activity. In the present study, we examined whether treatment with an ACE inhibitor modulates the cardiovascular PAI-1 expression in this model in vivo. Wistar-Kyoto rats were treated with either no drugs, L-NAME (100 mg/kg x day), or L-NAME plus the ACE inhibitor imidapril (20 mg/kg day). Marked increases in PAI-1 mRNA and protein levels in the aorta and left ventricle were observed after the first and fourth weeks of PAI-1 treatment. PAI-1 immunoreactivity was increased in the endothelium and the media of the aorta and coronary arteries after treatment of L-NAME. This increase in PAI-1 levels was associated with an increase in ACE activity of the aorta and left ventricle. ACE inhibition with imidapril significantly prevented both the increases in PAI-1 levels and the development of cardiovascular remodeling. These findings suggest that the local renin-angiotensin system regulates PAI-1 expression, and that the increased PAI-1 levels may contribute to the cardiovascular remodeling in this model.

Hypertension in women: current understanding of gender differences

High blood pressure is a major individual and public-health issue because of its wide prevalence and associated complications. More women than men have hypertension, but until recently, women have been relatively underrepresented in clinical trials. Gender differences in the physiology, genetics, and treatment benefit of hypertension have been noted in several studies that have included women. These findings have raised concerns about the generalizability of the results of previous investigations to women. The currently available information regarding gender differences and similarities and the results of hypertension treatment trials in women are reviewed herein. These studies suggest that, although gender differences exist, women benefit significantly when they receive therapy to normalize blood pressure.

Soluble vascular cell adhesion molecule-1 as a biohumoral correlate of atherosclerosis

Vascular cell adhesion molecule-1 (VCAM-1) is a protein expressed on the surface of activated endothelial cells and expressed in early atherosclerosis. Because part of the protein is shed in the circulation and can be detected in peripheral plasma [soluble (s) VCAM-1], we hypothesized that sVCAM-1 may be a circulating marker of the presence and severity of atherosclerosis in humans. We selected 11 patients with essential hypertension plus peripheral vascular disease (PVD) and matched them for age, gender, body mass index, and smoking habits with 11 patients with uncomplicated essential hypertension (UH) and 11 healthy controls. We evaluated plasma concentrations of sVCAM-1 along with those of the soluble form of two other endothelial leukocyte adhesion molecules [sE-selectin and s-intercellular adhesion molecule-1 (sICAM-1)] and other markers of endothelial dysfunction/ damage [s-thrombomodulin, plasminogen activator inhibitor type I, and von Willebrand factor (vWF)]. We also measured insulin, glucose, fibrinogen, total and HDL cholesterol, and the urinary albumin excretion (UAE), which may also be related to atherosclerosis. Results of these assays were related to the echographic assessment of the maximum intima-media thickness (IMTmax) at the carotid bifurcation, as an index of atherosclerosis in the carotids. PVD patients had a clearly elevated IMTmax [2.7 (1.1-3.1) mm, median (range)] compared with both UH patients [1.2 (0.8-2.4) mm] and controls [1 (0.6-2) mm]. sVCAM-1 was clearly higher in PVD patients [990 (273-1808) ng/mL, median (range)] versus 340 (236-975) ng/mL in UH and 386 (204-835) ng/mL in controls, and it separated clinical categories better than sICAM-1, vWF, glucose, insulin, UAE, triglycerides, or total, LDL or HDL cholesterol, sVCAM-1 was also the best biohumoral correlate of IMTmax (R = .59; P < .001) in univariate analysis. Because many of the biohumoral variables assessed were mutually intercorrelated, they were entered in a multivariate analysis to assess their contribution in explaining IMTmax variability. sVCAM-1 remained the only independent predictor of IMTmax and totally abolished the contribution of other variables to IMTmax variability. Thus, sVCAM-1 is a good biohumoral correlate of overt atherosclerosis, independent of underlying hypertension, and may be an in vivo marker of endothelial activation. Its potential value as a surrogate for global risk assessment and its behavior in intervention studies remain to be determined.

Haemostasis balance disorders in patients with essential hypertension

This study was aimed at investigating haemostasis parameters in patients (pts) with arterial hypertension (AH) before any medical treatment and to correlate these findings with those in healthy normal Greek population 83 pts (48 m, 35 w) mean age 49.8 +/- 10.1 yrs, body mass index 23.4 +/- 1.5 with mild to moderate AH and 42 healthy volunteers matched for sex (24 m, 18 w), age 51.2 +/- 10.5 yrs and body mass index 22.8 +/- 1.46 were studied. Fibrinogen, vWF, plasminogen, ECLT, a2 antiplasmin, tPA-Ag, PAI-1 in all pts and in the control group were measured. Mean age and BMI did not significantly differ between the two groups. The hypertensive patients had significantly higher levels of fibrinogen (327.75 +/- 51.36 vs. 272.84 +/- 46.8 mg/dl), tPA-Ag (8.81 +/- 3.32 vs. 5.76 +/- 2.54 ng/ml) and PAI-1 (11.8 +/- 10.9 vs. 7.91 +/- 5.5 IU/ml), whereas a2 antiplasmin level was significantly lower (98.71 +/- 15.40 vs. 107.84 +/- 17.52%). No differences were found between hypertensives and normal subjects in vWF, plasminogen and ECLT. These preliminary data suggest that in pts with mild to moderate AH, before any medical treatment, there are significantly higher levels of fibrinogen, tPA-Ag and PAI-1 compared with normal volunteers, whereas there are significantly lower a antiplasmin levels. These findings indicate a disturbance in the haemostasis balance with hypercoagulability and fibrinolytic deficiency.

Fibrinolytic function after dietary supplementation with omega3 polyunsaturated fatty acids

Hypertension is associated with derangements in glucose and lipid metabolism. Increased levels of plasminogen activator inhibitor type 1 (PAI-1) are thought to potentiate the development of coronary events in this condition. Fish oil (omega3 polyunsaturated fatty acids [PUFAs]) have lipid-lowering effects, but the cardioprotective potential has been questioned because fish oil has been found to increase PAI-1 activity. This study was performed to determine the effects of omega3 PUFAs on the fibrinolytic function in hypertension. Seventy-eight persons with untreated hypertension were included in a 16-week, double-blind, randomized, controlled intervention study with 4 g/d of eicosapentaenoic and docosahexaenoic acids or corn oil placebo. Plasma PAI-1 activity, tissue plasminogen activator (tPA) activity, levels of fibrinogen and factor VII(c), and platelet count were measured before and after intervention (mean+/-SE). PAI-1 activity changed similarly in the fish oil and corn oil groups (1.8+/-1.0 U/mL versus 3.5+/-1.2 U/mL, P=.25), as did tPA (-0.02+/-0.02 IU/mL versus -0.13+/-0.03 IU/mL, P=.28), levels of factor VII(c) (6+/-5% versus 5+/-4%, P>.3), and platelet count (2+/-7x10(9)/L versus 3+/-5x10(9)/L, P>.3). None of these variables changed from pretreatment levels during fish oil intake. Fibrinogen levels increased significantly both during fish oil (0.6+/-0.1 g/L, P=.0001) and corn oil (0.4+/-0.1 g/L, P=.002) intake. There was no between-group difference (P>.3). In conclusion, a daily intake of 4 g omega3 PUFAs does not affect PAI-1 and tPA activity in persons with hypertension. A modest increase in fibrinogen levels was observed after both fish oil and corn oil intake.

Cardiovascular risk factors and the prediabetic syndrome

Cardiovascular disease is increased 2- to 4-fold in non-insulin-dependent diabetes mellitus (NIDDM); yet in most studies, there is a relatively weak relationship between the frequency of coronary heart disease (CHD) and the duration of diabetes and severity of hyperglycaemia. A number of authors have suggested that the prediabetic stage may contribute to the risk of CHD in NIDDM. Hyperinsulinaemia and insulin resistance have been strongly associated with the development of NIDDM. Data are less conclusive about the relationship of hyperinsulinaemia to the development of CHD in nondiabetic subjects. Relatively little data are available on hyperinsulinaemia and/or insulin resistance to CHD in NIDDM subjects. Tight control of glycaemia with exogenous insulin improves cardiovascular risk factors in NIDDM subjects and therefore is unlikely to increase the risk of CHD. Although the relation of insulin to CHD in the general population is somewhat controversial, insulin is clearly related to multiple cardiovascular risk factors (especially elevated triglyceride, decreased high-density lipoprotein, small dense low-density lipoprotein, impaired glucose tolerance and increased plasminogen activator inhibitor 1 (PAI-1)). However, the relation of insulin resistance to hypertension remains controversial.

Characteristics and treatment of hypertension in women: a review of the literature

Although there are documented differences between women and men in frequency and severity of hypertension and in the relation between hypertension and cardiovascular risk, few studies have been designed to evaluate efficacy and safety of antihypertensive therapy in women. Efficacy of nonpharmacologic interventions to lower blood pressure may differ between the sexes; women have greater difficulty losing weight than men but may respond better than men to dietary sodium reduction. In general, women and men do not respond differently to antihypertensive therapy; however, there may be differences in response to certain classes of antihypertensives. There are limited data on safety of specific antihypertensive agents in women. In some studies, researchers found a greater incidence of adverse effects in women. Effects on sexual functioning and pharmacokinetic and pharmacodynamic characteristics of antihypertensive drugs in women have been studies inadequately. More data are needed to guide the management of hypertension in women.

Insulin sensitivity is not an independent determinant of plasma plasminogen activator inhibitor-1 activity

It recently has been hypothesized that increased plasma plasminogen activator inhibitor-1 (PAI-1) activity could be a possible link between insulin resistance and coronary heart disease. However, it is not known whether insulin sensitivity per se is a determinant of plasma PAI-1 activity or whether other intermediates could explain this association. We investigated the relationship between plasma PAI-1 activity and insulin sensitivity, obesity, distribution of body fat, blood pressure, plasma insulin concentration, and serum lipid levels in normoglycemic men (n = 61) and women (n = 77) 53 to 61 years old who participated in a previous population-based study. Insulin sensitivity was estimated by the minimal model from a frequently sampled intravenous glucose tolerance test. In univariate analyses, PAI-1 correlated positively with body mass index, waist-to-hip ratio (WHR), fasting and 2-hour insulin levels, and triglyceride level in both men and women. Furthermore, in women PAI-1 correlated inversely with high-density lipoprotein (HDL) cholesterol level. There was an inverse relationship between PAI-1 and insulin sensitivity (r = -.39, P < .01 in men; r = -.38, P < .001 in women). In multivariate analyses in men, insulin sensitivity failed to show any significant association with PAI-1. In contrast, triglyceride level and body mass index were independently associated with PAI-1. Also in women, insulin sensitivity was not independently associated with PAI-1. In women, WHR and HDL cholesterol concentration or WHR and 2-hour insulin concentration were independently related to PAI-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta blockers, Lp(a), hypertension, and reduced basal fibrinolytic activity

To assess the hypothesis that beta blocker use and hypertension are associated with high lipoprotein(a) [Lp(a)] or with reduced basal fibrinolytic activity, the authors studied relationships of hypertension and beta blockers to Lp(a), lipids, lipoproteins, apolipoproteins, and basal fibrinolytic activity in 385 patients consecutively referred for diagnosis and therapy of hyperlipidemia. A second aim was to determine possible gender differences in fibrinolytic activity among patients with hypertension. Ninety-nine patients (58 women [88% post-menopausal] and 41 men) had drug-treated hypertension. In women, hypertension was a positive, independent predictor of the major inhibitors of fibrinolysis, plasminogen activator inhibitor antigen (p = 0.017), and plasminogen activator inhibitor activity (p = 0.004). In men and women, major risk factors for atherosclerosis were significant, independent predictors of reduced basal fibrinolysis. Median Lp(a) in the 99 patients with hypertension (16 mg/dL) did not differ from Lp(a) (18 mg/dL) in normotensive patients (p > 0.1). Of the 385 patients, the 39 beta blocker users had higher plasminogen activator inhibitor activity (p = 0.01), higher triglyceride (p = 0.02) levels, and higher Quetelet Indices (p = 0.01) than non-users (n = 346). After covariance adjusting for age, Quetelet Indices, sex, and triglycerides, plasminogen activator inhibitor activity was not higher in beta blocker users than in non-users (p > 0.1). Median Lp(a) did not differ in beta blocker users (16 mg/dL) and in non-users (17 mg/dL), p greater than 0.1. Hypertensive, predominantly post-menopausal women are likely to have high plasminogen activator inhibitor activity and plasminogen activator inhibitor antigen with concurrent reduced fibrinolytic activity, as well as high fibrinogen levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between hemorrheologic factors and insulin sensitivity in healthy young men

The present study aimed at testing a possible relationship between hemorrheologic factors, such as hematocrit, fibrinogen, and whole-blood viscosity, and insulin sensitivity in healthy humans. Twenty-one 21-year-old men were studied with the hyperinsulinemic euglycemic glucose clamp technique. We found statistically significant negative correlations between the glucose disposal rate (GDR) and calculated whole-blood viscosity at both high (r = -.55, P = .01) and low (r = -.51, P = .01) shear rates. We observed negative associations between GDR and fibrinogen (r = -.66, P = .002), GDR and hematocrit (r = -.63, P = .002), GDR and body mass index (r = -.51, P = .007), and GDR and resting heart rate (r = -.46, P = .04). Using stepwise multiple regression considering whole-blood viscosity, body mass index, mean arterial blood pressure, and heart rate as independent variables, we found that only whole-blood viscosity and body mass index were independent explanatory variables of the GDR. Together they accounted for 63% of the variability in the GDR in our subjects. These results suggest hemorrheologic, and therefore indirectly hemodynamic, factors as correlates to insulin sensitivity.