Influence of estrogen on aortic stiffness and endothelial function in female rats

Effects of dietary soy content on cerebral artery function and behavior in ovariectomized female mice

As females age, they transition through menopause, experiencing a decrease in estrogen and an increase in cardiovascular and neurodegenerative disease risk. Most standard rodent chows contain phytoestrogen-rich soybean meal, which can mimic the effects of estrogen. Understanding the impact of this soybean meal on vascular outcomes is crucial to proper experimental design. Thus, this study aimed to compare the effects of standard and soy-free chows on cerebral artery endothelial function and cognitive function in ovariectomized mice. Young female C57Bl/6J mice (n = 43; ∼6 mo) were randomly assigned to three groups: sham, ovariectomy (OVX), or ovariectomy on a diet containing soy (OVX + Soy). In posterior cerebral arteries, the OVX mice had a 27% lower maximal response to insulin compared with the sham mice. The OVX + Soy mice had a 27% greater maximal vasodilation to insulin compared with the OVX mice and there were no differences in vasodilation between the OVX + Soy and sham groups. The group differences in vasodilation were mediated by differences in nitric oxide bioavailability. The OVX + Soy mice also had greater insulin receptor gene expression in cerebral arteries compared with the OVX mice. However, no differences in aortic or cerebral artery stiffness were observed between groups. Interestingly, the OVX + Soy group scored better on nesting behavior compared with both sham and OVX groups. In summary, we found that ovariectomy impairs insulin-mediated vasodilation in cerebral arteries, but a diet containing soy mitigates these effects. These findings highlight the importance of considering dietary soy when performing vascular and behavioral tests in mice, particularly in females.NEW & NOTEWORTHY To properly design experiments, we must consider how variables like diet impact our outcomes, particularly the effects of soy on females. We found that cerebral artery vasodilation in response to insulin was impaired in ovariectomized female mice compared with intact shams. However, ovariectomized mice fed a soy diet had a preserved cerebral artery insulin-mediated vasodilation. These results highlight that the effects of diet on vascular function may explain inconsistencies found between studies.

Long-term cardiovascular consequences of adolescent anorexia nervosa

BACKGROUND

Anorexia nervosa (AN) is associated with maladaptive cardiovascular changes. This study investigated whether individuals who recovered from AN during adolescence experience long-term cardiovascular risk in early adulthood.

METHODS

Former AN patients discharged from the Royal Children's and Monash Children's Hospital Eating Disorder Services in Melbourne, Australia underwent cardiovascular testing. Measurements were performed using an oscillometric device for blood pressure and pulse wave velocity, ultrasound for carotid wall structure/function, resting electrocardiogram for heart-rate variability, and the EndoPat 2000 (Itamar) system for endothelial function. Patient measures were compared to healthy controls and/or normal thresholds.

RESULTS

Ninety-one percent of the former AN patients (N = 22) and controls (N = 66) were female, aged approximately 25 years, with a healthy body mass index. The mean time interval from AN recovery to participation was 7.4 years. Pulse wave velocity was lower in the former AN patients than controls. Carotid intima-media thickness was not different; however, carotid distensibility and compliance were lower, and the elastic modulus higher in the former AN patients. Greater vagal tone was observed and endothelial dysfunction was evident in 46% of the former patients.

CONCLUSIONS

Young adults who recovered from adolescent AN exhibit persistent cardiovascular adaptations. Routine cardiovascular monitoring could manage potential disease risk.

IMPACT

Cardiovascular complications are common in patients with anorexia nervosa (AN) and population studies have revealed that developmental adaptations in response to undernutrition have long-term consequences for cardiovascular health. In this study of young adults treated for AN during adolescence, there was evidence of increased carotid artery stiffness, reduced aortic stiffness, vagal hyperactivity, and endothelial dysfunction in early adulthood when compared to healthy controls. It is important to consider the cardiovascular health of patients with AN beyond achieving medical stability. Interventions that monitor cardiovascular health could minimise the burden of future cardiovascular disease.

Evidence for Menopause as a Sex-Specific Risk Factor for Glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide and is characterized by progressive loss of visual function and retinal ganglion cells (RGC). Current epidemiological, clinical, and basic science evidence suggest that estrogen plays a role in the aging of the optic nerve. Menopause, a major biological life event affecting all women, coincides with a decrease in circulating sex hormones, such as estrogen. While 59% of the glaucomatous population are females, sex is not considered a risk factor for developing glaucoma. In this review, we explore whether menopause is a sex-specific risk factor for glaucoma. First, we investigate how menopause is defined as a sex-specific risk factor for other pathologies, including cardiovascular disease, osteoarthritis, and bone health. Next, we discuss clinical evidence that highlights the potential role of menopause in glaucoma. We also highlight preclinical studies that demonstrate larger vision and RGC loss following surgical menopause and how estrogen is protective in models of RGC injury. Lastly, we explore how surgical menopause and estrogen signaling are related to risk factors associated with developing glaucoma (e.g., intraocular pressure, aqueous outflow resistance, and ocular biomechanics). We hypothesize that menopause potentially sets the stage to develop glaucoma and therefore is a sex-specific risk factor for this disease.

The direct effect of fibroblast growth factor 23 on vascular smooth muscle cell phenotype and function

BACKGROUND

In chronic kidney disease (CKD) patients, increased levels of fibroblast growth factor 23 (FGF23) are associated with cardiovascular mortality. The relationship between FGF23 and heart hypertrophy has been documented, however, it is not known whether FGF23 has an effect on vasculature. Vascular smooth muscle cells VSMCs may exhibit different phenotypes; our hypothesis is that FGF23 favours a switch from a contractile to synthetic phenotype that may cause vascular dysfunction. Our objective was to determine whether FGF23 may directly control a change in VSMC phenotype.

METHODS

This study includes in vitro, in vivo and ex vivo experiments and evaluation of patients with CKD stages 2-3 studying a relationship between FGF23 and vascular dysfunction.

RESULTS

In vitro studies show that high levels of FGF23, by acting on its specific receptor FGFR1 and Erk1/2, causes a change in the phenotype of VSMCs from contractile to synthetic. This change is mediated by a downregulation of miR-221/222, which augments the expression of MAP3K2 and PAK1. miR-221/222 transfections recovered the contractile phenotype of VSMCs. Infusion of recombinant FGF23 to rats increased vascular wall thickness, with VSMCs showing a synthetic phenotype with a reduction of miR-221 expression. Ex-vivo studies on aortic rings demonstrate also that high FGF23 increases arterial stiffening. In CKD 2-3 patients, elevation of FGF23 was associated with increased pulse wave velocity and reduced plasma levels of miR-221/222.

CONCLUSION

In VSMCs, high levels of FGF23, through the downregulation of miR-221/222, causes a change to a synthetic phenotype. This change in VSMCs increases arterial stiffening and impairs vascular function, which might ultimately worsen cardiovascular disease.

Multiple Tumor-Associated Intracranial Aneurysms Adjacent to a Suprasellar Germ Cell Tumor: Case Report and Review of Literature

INTRODUCTION

Tumor-associated intracranial aneurysms are rare and not well understood.

CASE PRESENTATION

We describe a 4-year-old female with multiple intracranial aneurysms intimately associated with a suprasellar germ cell tumor (GCT). We provide the clinical history, medical, and surgical treatment course, as well as a comprehensive and concise synthesis of the literature on tumor-associated aneurysms.

DISCUSSION

We discuss mechanisms for aneurysm formation with relevance to the current case, including cellular and paracrine signaling pertinent to suprasellar GCTs and possible molecular pathways involved. We review the complex multidisciplinary treatment required for complex tumor and cerebrovascular interactions.

Effect of supraphysiological estrogen levels on arterial stiffness and hemodynamic parameters

OBJECTIVE

The present study evaluates the arterial stiffness and hemodynamic parameters in patients with a supraphysiological estrogen level due to in vitro fertilization (IVF) with controlled ovarian hyperstimulation (COH).

METHODS

A total of 82 female patients aged 24-45 years were included. Their arterial stiffness parameters were analyzed before and after the appropriate COH protocol involving arteriography using Mobil-O-Graph NG (IEM GmbH, Stolberg, Germany) 24-hour ambulatory blood pressure monitor.

RESULTS

Systolic, diastolic, mean, central systolic, and diastolic blood pressures, as well as peripheral vascular resistance, were significantly lower after COH therapy (p=0.001, 0.002, <0.001, <0.001, 0.040, and <0.001, respectively). In contrast, there was no statistically significant difference observed in heart rate, pulse pressure, or cardiac output. The pulse wave velocity measurement was significantly lower after COH than the baseline levels [5.3 m/s (4.5-6.9 m/s) versus 5.4 m/s (4.7-7.3 m/s,); p<0.001], but the augmentation index was not significantly different [28% (4%-41%) versus 29% (5%-43%); p=0.090]. When the patients were grouped according to the occurrence of a pregnancy after IVF therapy, all parameters were not different between the pregnancy (+) and pregnancy (-) patients (p>0.05).

CONCLUSION

Arterial stiffness and hemodynamic parameters significantly decreased in IVF patients who underwent COH therapy. The long-term clinical significance of this short-term effect should be investigated with prospective studies. There was no significant difference in all parameters before and after COH when the pregnancy (+) and pregnancy (-) patients were compared.

Resistance training and caloric restriction prevent systolic blood pressure rise by improving the nitric oxide effect on smooth muscle and morphological changes in the aorta of ovariectomized rats

In this study, we investigated the effects of resistance training (RT), caloric restriction (CR), and the association of both interventions in aortic vascular reactivity and morphological alterations, matrix metalloproteinase-2 (MMP-2) activity, insulin resistance and systolic blood pressure (SBP) in ovariectomized rats. Fifty female Holtzman rats were subjected to ovariectomy and Sham surgery and distributed into the following groups: Sham-sedentary, ovariectomized-sedentary, ovariectomized-resistance training, ovariectomized-caloric restriction, and ovariectomized-resistance training and caloric restriction groups. RT and 30% CR protocols were performed for 13 weeks. Analyses were conducted to evaluate the following: acetylcholine and sodium nitroprusside-induced relaxation of aortic rings, MMP-2 activity, insulin tolerance test, highlighting of the aorta wall cross-sectional area by hematoxylin-eosin stain, aorta vessel remodeling and SBP. We observed that ovariectomy decreased the potency of dependent and independent endothelium relaxation and MMP-2 activity, prevented insulin resistance, promoted aorta vessel remodeling in the cross-sectional area, and promoted the media-to-lumen ratio, the collagen content, and the alteration of the structure and elastic fibers of the vessel. The effects of the ovariectomy could contribute to SBP increases. However, the association of exercise and diet improved the relaxation potency in dependent and independent endothelium relaxation, elevated MMP-2 activity, ameliorate insulin sensitivity, increased the aorta cross-sectional area and media-to-lumen ratio, decreased collagen content and promoted histological parameters of the aorta vessel wall, preventing the increase of SBP.

CONCLUSION

Our study revealed that the RT and CR separately, and even associatively, improved vascular function, activated MMP-2, and produced a beneficial hypertrophic remodeling, preventing the elevation of SBP in ovariectomized rats.

New insights into arterial stiffening: does sex matter?

This review discusses sexual dimorphism in arterial stiffening, disease pathology interactions, and the influence of sex on mechanisms and pathways. Arterial stiffness predicts cardiovascular mortality independent of blood pressure. Patients with increased arterial stiffness have a 48% higher risk for developing cardiovascular disease. Like other cardiovascular pathologies, arterial stiffness is sexually dimorphic. Young women have lower stiffness than aged-matched men, but this sex difference reverses during normal aging. Estrogen therapy does not attenuate progressive stiffening in postmenopausal women, indicating that currently prescribed drugs do not confer protection. Although remodeling of large arteries is a protective adaptation to higher wall stress, arterial stiffening increases afterload to the left ventricle and transmits higher pulsatile pressure to smaller arteries and target organs. Moreover, an increase in aortic stiffness may precede or exacerbate hypertension, particularly during aging. Additional studies are needed to elucidate the mechanisms by which females are protected from arterial stiffness to provide insight into its mechanisms and, ultimately, therapeutic targets for treating this pathology.

Greater Progression of Age-Related Aortic Stiffening in Adults with Poor Trunk Flexibility: A 5-Year Longitudinal Study

Purpose: Having a low level of physical fitness, especially cardiorespiratory fitness, appears to accelerate age-related aortic stiffening. Whereas, some studies have reported that trunk flexibility is a component of physical fitness, it is also negatively associated with arterial stiffening independent of cardiorespiratory fitness in cross-sectional studies. However, no long-term longitudinal study has determined whether poor trunk flexibility accelerates the progression of age-related aortic stiffening. We examined trunk flexibility and aortic stiffness progression in a 5-year longitudinal study.

Methods and Results: A total of 305 apparently healthy men and women participated in this study (49.6 ± 9.5 years of age). Trunk flexibility was measured using a sit-and-reach test. Aortic stiffness was assessed using carotid-femoral pulse wave velocity (cfPWV) at baseline and after 5 years. Analysis of covariance (ANCOVA) was used to assess the association of the annual rate of cfPWV across flexibility levels (low, middle, high). There were no significant differences in baseline cfPWV among the three groups (835 ± 164, 853 ± 140, 855 ± 2.68 cm/s; P = 0.577). Annual ΔcfPWV was significantly higher in the low-flexibility group than in the high-flexibility group (P = 0.009). ANCOVA revealed an inverse relationship between flexibility level and annual ΔcfPWV (14.41 ± 2.73, 9.79 ± 2.59, 2.62 ± 2.68 cm/s/year; P for trend = 0.011). Multiple regression analysis revealed that baseline sit and reach (β = −0.12, −0.70 to −0.01) was independently correlated with ΔcfPWV following adjustment for baseline peak oxygen uptake, age, sex, body fat, heart rate, and cfPWV. The 5-year change in cfPWV was not significantly correlated with 5-year change in sit-and-reach performance (P = 0.859).

Conclusion: Poor trunk flexibility is associated with greater progression of age-related aortic stiffening in healthy adults. However, we failed to confirm a significant association between 5-year change in aortic stiffness and 5-year change in trunk flexibility. The association between increased age-related increase in aortic stiffness and deterioration in flexibility due to age may require observation for more than 5 years.

Xanthine oxidase inhibition protects against Western diet-induced aortic stiffness and impaired vasorelaxation in female mice

Consumption of a high-fat, high-fructose diet [Western diet (WD)] promotes vascular stiffness, a critical factor in the development of cardiovascular disease (CVD). Obese and diabetic women exhibit greater arterial stiffness than men, which contributes to the increased incidence of CVD in these women. Furthermore, high-fructose diets result in elevated plasma concentrations of uric acid via xanthine oxidase (XO) activation, and uric acid elevation is also associated with increased vascular stiffness. However, the mechanisms by which increased xanthine oxidase activity and uric acid contribute to vascular stiffness in obese females remain to be fully uncovered. Accordingly, we examined the impact of XO inhibition on endothelial function and vascular stiffness in female C57BL/6J mice fed a WD or regular chow for 16 wk. WD feeding resulted in increased arterial stiffness, measured by atomic force microscopy in aortic explants (16.19 ± 1.72 vs. 5.21 ± 0.54 kPa, P < 0.05), as well as abnormal aortic endothelium-dependent and -independent vasorelaxation. XO inhibition with allopurinol (widely utilized in the clinical setting) substantially improved vascular relaxation and attenuated stiffness (16.9 ± 0.50 vs. 3.44 ± 0.50 kPa, P < 0.05) while simultaneously lowering serum uric acid levels (0.55 ± 0.98 vs. 0.21 ± 0.04 mg/dL, P < 0.05). In addition, allopurinol improved WD-induced markers of fibrosis and oxidative stress in aortic tissue, as analyzed by immunohistochemistry and transmission electronic microscopy. Collectively, these results demonstrate that XO inhibition protects against WD-induced vascular oxidative stress, fibrosis, impaired vasorelaxation, and aortic stiffness in females. Furthermore, excessive oxidative stress resulting from XO activation appears to play a key role in mediating vascular dysfunction induced by chronic exposure to WD consumption in females.

Effect of ovariectomy and Sideritis euboea extract administration on large artery mechanics, morphology, and structure in middle-aged rats

BACKGROUND

Arterial function is regulated by estrogen, but no consistent pattern of arterial mechanical remodeling in response to depleted estrogen levels is available.

OBJECTIVE

To examine long-term effects of ovariectomy (OVX) on the mechanical properties, morphology, and histological structure of the carotid artery in middle-aged rats and a potentially protective effect of Sideritis euboea extract (SID), commonly consumed as "mountain tea".

METHODS

10-month-old female Wistar rats were allocated into control (sham-operated), OVX, OVX+SID, and OVX+MALT (maltodextrin; excipient used for dilution of SID) groups. They were sacrificed after 6 months and their carotid arteries were submitted to inflation/extension tests and to dimensional and histological evaluation.

RESULTS

Remodeling in OVX rats was characterized by a decreased in situ axial extension ratio, along with increased opening angle, thickness, and area of the vessel wall and of its medial layer, but unchanged lumen diameter. Compositional changes involved increased elastin/collagen densities. Characterization by the "four-fiber" microstructure-motivated model revealed similar in situ biaxial response of carotid arteries in OVX and control rats.

CONCLUSIONS

Carotid artery remodeling in OVX rats was largely consistent with hypertensive remodeling, despite the minor arterial pressure changes found, and was not altered by administration of SID, despite previous evidence of its osteo-protective effect.

17β-Estradiol Attenuates Conduit Pulmonary Artery Mechanical Property Changes With Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH), a rapidly fatal vascular disease, strikes women more often than men. Paradoxically, female PAH patients have better prognosis and survival rates than males. The female sex hormone 17β-estradiol has been linked to the better outcome of PAH in females; however, the mechanisms by which 17β-estradiol alters PAH progression and outcomes remain unclear. Because proximal pulmonary arterial (PA) stiffness, one hallmark of PAH, is a powerful predictor of mortality and morbidity, we hypothesized that 17β-estradiol attenuates PAH-induced changes in mechanical properties in conduit proximal PAs, which imparts hemodynamic and energetic benefits to right ventricular function. To test this hypothesis, female mice were ovariectomized and treated with 17β-estradiol or placebo. PAH was induced in mice using SU5416 and chronic hypoxia. Extra-lobar left PAs were isolated and mechanically tested ex vivo to study both static and frequency-dependent mechanical behaviors in the presence or absence of smooth muscle cell activation. Our static mechanical test showed significant stiffening of large PAs with PAH (P<0.05). 17β-Estradiol restored PA compliance to control levels. The dynamic mechanical test demonstrated that 17β-estradiol protected the arterial wall from the PAH-induced frequency-dependent decline in dynamic stiffness and loss of viscosity with PAH (P<0.05). As demonstrated by the in vivo measurement of PA hemodynamics via right ventricular catheterization, modulation by 17β-estradiol of mechanical proximal PAs reduced pulsatile loading, which contributed to improved ventricular-vascular coupling. This study provides a mechanical mechanism for delayed disease progression and better outcome in female PAH patients and underscores the therapeutic potential of 17β-estradiol in PAH.

The effect of hormone therapy on mean blood pressure and visit-to-visit blood pressure variability in postmenopausal women: results from the Women's Health Initiative randomized controlled trials

OBJECTIVES

Mean and visit-to-visit variability (VVV) of blood pressure (BP) are associated with an increased cardiovascular disease risk. We examined the effect of hormone therapy on mean and VVV of BP in postmenopausal women from the Women's Health Initiative (WHI) randomized controlled trials.

METHODS

BP was measured at baseline and annually in the two WHI hormone therapy trials, in which 10 739 and 16 608 postmenopausal women were randomized to conjugated equine estrogens (CEEs, 0.625 mg/day) or placebo, and CEEs and medroxyprogesterone acetate (MPA, 2.5 mg/day) or placebo, respectively.

RESULTS

At the first annual visit (year 1), mean SBP was 1.04 mmHg [95% confidence interval (CI) 0.58, 1.50] and 1.35 mmHg (95% CI 0.99, 1.72) higher in the CEEs and CEEs and MPA arms, respectively, compared with the corresponding placebos. These effects remained stable after year 1. CEEs also increased the VVV of SBP (ratio of VVV in CEEs vs. placebo, 1.03; P < 0.001), whereas CEEs and MPA did not (ratio of VVV in CEEs and MPA vs. placebo, 1.01; P = 0.20). After accounting for study drug adherence, the effects of CEEs and CEEs and MPA on mean SBP increased at year 1, and the differences in the CEEs and CEEs and MPA arms vs. placebos also continued to increase after year 1. Further, both CEEs and CEEs and MPA significantly increased the VVV of SBP (ratio of VVV in CEEs vs. placebo, 1.04; P < 0.001; ratio of VVV in CEEs and MPA vs. placebo, 1.05; P < 0.001).

CONCLUSION

Among postmenopausal women, CEEs and CEEs and MPA at conventional doses increased mean and VVV of SBP.

Sex differences in postischemic cardiac dysfunction and norepinephrine overflow in rat heart: the role of estrogen against myocardial ischemia-reperfusion damage via an NO-mediated mechanism

The purpose of this study is to elucidate the relationship between sex difference and norepinephrine (NE) release in the pathogenesis of myocardial ischemia/reperfusion (I/R) injury. Isolated male and female rat hearts were subjected to 40-minute global ischemia followed by 30-minute reperfusion. Compared with male hearts, I/R-induced cardiac dysfunction, such as decreased left ventricular developed pressure and dP/dtmax and increased left ventricular end diastolic pressure, was significantly attenuated in female hearts. An excessive NE overflow in the coronary effluent from the postischemic heart in females was much less than that in males. These sex differences were abolished by ovariectomy, but in vivo treatment with 17β-estradiol recovered it. This ameliorating effect of 17β-estradiol was not observed in the presence of nitric oxide (NO) synthase inhibitor N-nitro-L-arginine. When NOx (NO2/NO3) levels in the coronary effluent after onset of reperfusion were measured, reversed correlated relationships between NOx production and I/R-induced cardiac dysfunction, and NE overflow, were observed. These findings suggest that sex differences in the postischemic cardiac dysfunction are closely related to the NE overflow from the postischemic heart and that estrogen plays a key role in the cardioprotective effect against I/R injury in female rats, by suppressing NE release via the enhancement of NO production.

HZE ⁵⁶Fe-ion irradiation induces endothelial dysfunction in rat aorta: role of xanthine oxidase

Ionizing radiation has been implicated in the development of significant cardiovascular complications. Since radiation exposure is associated with space exploration, astronauts are potentially at increased risk of accelerated cardiovascular disease. This study investigated the effect of high atomic number, high-energy (HZE) iron-ion radiation on vascular and endothelial function as a model of space radiation. Rats were exposed to a single whole-body dose of iron-ion radiation at doses of 0, 0.5 or 1 Gy. In vivo aortic stiffness and ex vivo aortic tension responses were measured 6 and 8 months after exposure as indicators of chronic vascular injury. Rats exposed to 1 Gy iron ions demonstrated significantly increased aortic stiffness, as measured by pulse wave velocity. Aortic rings from irradiated rats exhibited impaired endothelial-dependent relaxation consistent with endothelial dysfunction. Acute xanthine oxidase (XO) inhibition or reactive oxygen species (ROS) scavenging restored endothelial-dependent responses to normal. In addition, XO activity was significantly elevated in rat aorta 4 months after whole-body irradiation. Furthermore, XO inhibition, initiated immediately after radiation exposure and continued until euthanasia, completely inhibited radiation-dependent XO activation. ROS production was elevated after 1 Gy irradiation while production of nitric oxide (NO) was significantly impaired. XO inhibition restored NO and ROS production. Finally, dietary XO inhibition preserved normal endothelial function and vascular stiffness after radiation exposure. These results demonstrate that radiation induced XO-dependent ROS production and nitroso-redox imbalance, leading to chronic vascular dysfunction. As a result, XO is a potential target for radioprotection. Enhancing the understanding of vascular radiation injury could lead to the development of effective methods to ameliorate radiation-induced vascular damage.

Relationship between arterial calcification and bone loss in a new combined model rat by ovariectomy and vitamin D(3) plus nicotine

Epidemiological studies have reported an association between arterial calcification and bone loss after menopause. However, the underlying mechanism of the association remains unclear. Therefore, to explore the possible mechanisms of the association, we tried to develop a new combined model rat of ovariectomy (OVX, an animal model of osteoporosis) and vitamin D(3) plus nicotine (VDN rat, an animal model of arterial calcification). We tested them by using sham-operated control rats (SC), OVX control rats (OC), and OVX plus VDN-treated rats (OVN). Dissections were performed twice at 4 (4SC, 4OC, and 4OVN) and 8 (8SC, 8OC, and 8OVN) weeks after treatment. 8OVN showed bone loss and arterial calcification, although 8OC showed only bone loss. Moreover, arterial calcium content was associated with indexes of bone loss at 8 weeks. Thus, the OVN rat is considered a good model to examine the relationship of the two disorders after menopause. Additionally, the arterial endothelin-1 (ET-1, a potent regulator of arterial calcification) levels increased in both 4OVN and 8OVN, and the level was associated with arterial calcium content at 8 weeks. Furthermore, the arterial endothelial nitric oxide synthase (eNOS) protein, which is an enzyme that produces nitric oxide (an antiatherosclerotic substance), was significantly reduced in only 8OVN. Estrogens affect the alterations of the eNOS and ET-1 proteins. Therefore, we suggest that impairment of the ET-1- and NO-producing system in arterial tissue during periods of rapid bone loss by estrogen deficiency might be a mechanism of the relationship between the two disorders seen in postmenopausal women.

Voluntary running exercise attenuates the progression of endothelial dysfunction and arterial calcification in ovariectomized rats

AIM

Loss of oestrogen synthesis capacity after menopause contributes to increases in arterial stiffness and calcification. Exercise training improves arterial stiffness and calcification. However, the mechanism of exercise training-induced improvement of arterial stiffness and calcification remains unclear.

METHOD

We examined the mechanism by using aortas of sham-operated rats (sham control; SC), ovariectomized rats (OVX control; OC), OVX plus treatment with vitamin D(3) plus nicotine (VDN) rats (OV sedentary; OVSe), which is an animal model of endothelial dysfunction and arterial calcification, and voluntary running wheel exercise for 8 weeks plus OVX plus VDN rats (OV exercise; OVEx).

RESULTS

The arterial tissue calcium and endothelin-1 (ET-1: a vasoconstrictor peptide and a potent regulator of arterial calcification) levels were significantly higher in OVSe rats compared with the SC and OC rats, whereas these levels in the OVEx rats were significantly lower than in the OVSe rats. Additionally, arterial expression of endothelial nitric oxide synthase (eNOS), which is an enzyme that produces nitric oxide (NO: a vasodilator substance), was reduced in OVSe rats. However, exercise training prevented the decrease in eNOS expression. Moreover, there was a significant positive correlation between arterial calcium level and arterial ET-1 level.

CONCLUSION

These findings suggest that exercise training-induced improvement of ET-1 and NO prevents the impairment of endothelial function after menopause in females, and this improvement may result in less arterial calcification.

Estrogen deficiency and low-calcium diet increased bone loss and urinary calcium excretion but did not alter arterial stiffness in young female rats

Many epidemiological studies have reported that the severity of arterial diseases such as arterial calcification and stiffness is inversely related to bone loss, i.e., osteoporosis. However, the nature of this relationship is unclear. The purpose of the present study was to examine the influences of estrogen deficiency and/or low-calcium diet (0.1% Ca) on bone metabolism and calcium balance, as well as aortic wall composition and stiffness in young female rats. Twenty-eight 6-week-old female rats were randomized into four groups: OVX-Low calcium (OL) and OVX-Normal calcium groups (ON) were ovariectomized, and Sham-Low calcium (SL) and Sham-Normal calcium groups (SN) were sham-operated. After 12 weeks, the bone mineral density of the lumbar spine and tibial proximal metaphysis were significantly lower in ON than in SN, and also significantly lower in OL than in ON. Additionally, OL rats had significant higher (vs. SN and SL) urinary deoxypyridinoline, but not urinary calcium, excretion at 4 weeks after ovariectomy. However, at 12 weeks after ovariectomy, urinary calcium excretion was significantly higher in OL than in SL, with corresponding increases in two bone turnover markers, bone-type alkaline phosphatase and tartrate-resistant acid phosphatase. Neither estrogen deficiency nor low-calcium diet affected aortic stiffness or elastin degeneration and calcium deposition over the course of the present study, although changes of bone metabolism occurred rapidly. Taken together, these results show that bone loss and arterial stiffness did not progress simultaneously in the present experimental protocol.

Sex dimorphism in cardiac pathophysiology: experimental findings, hormonal mechanisms, and molecular mechanisms

The higher cardiovascular risk in men and post-menopausal women implies a protective action of estrogen. A large number of experimental studies have provided strong support to this concept. However, the recent clinical trials with negative outcomes regarding hormone replacement therapy call for "post hoc" reassessment of existing information, models, and research strategies as well as a summary of recent findings. Sex steroid hormones, in particular estrogen, regulate numerous processes that are related to the development and progression of cardiovascular disease through a variety of signaling pathways. Use of genetically modified models has resulted in interesting information on diverse actions mediated by steroid receptors. By focusing on experimental findings, we have reviewed hormonal, cellular, and signaling mechanisms responsible for sex dimorphism and actions of hormone replacement therapy and addressed current limitations and future directions of experimental research.

Role of estrogen deficiency in the formation and progression of cerebral aneurysms. Part I: experimental study of the effect of oophorectomy in rats

Object. Estrogen has been shown to play a central role in vascular biology. Although it may exert beneficial vascular effects, its role in the pathogenesis of cerebral aneurysms remains to be determined. To elucidate the role of hormones further, the authors examined the effects of bilateral oophorectomy on the formation and progression of cerebral aneurysms in rats.

Methods. Forty-five female, 7-week-old Sprague—Dawley rats were divided into three equal groups. Group I consisted of intact rats (controls). To induce cerebral aneurysms, the animals in Groups II and III were subjected to ligation of the right common carotid and bilateral posterior renal arteries. One month later, the rats in Group II underwent bilateral oophorectomy. Three months after the experiment began all animals were killed and cerebral vascular corrosion casts were prepared and screened for cerebral aneurysms by using a scanning electron microscope. Plasma was used to determine the level of estradiol and the gelatinase activity.

Hypertension developed in all rats except those in the control group. The estradiol level was significantly lower in Group II than in the other groups (p < 0.01). The incidence of cerebral aneurysm formation in Group II (60%) was three times higher than that in Group III (20%), and the mean size of aneurysms in Group II (76 ± 27 µm, mean ± standard deviation) was larger than that in Group III (28 ± 4.6 µm) (p < 0.05). No aneurysm developed in control animals (Group I), and there was no significant difference in plasma gelatinase activity among the three groups.

Conclusions. The cerebral aneurysm model was highly reproducible in rats. Bilateral oophorectomy increased the susceptibility of rats to aneurysm formation, indicating that hormones play a role in the pathogenesis of cerebral aneurysms.

Effects of estrogens on cardiovascular structure in uninephrectomized SHRsp rats

BACKGROUND

The risk of cardiovascular disease in uremic patients is greater in male than in female patients. Estrogens seem to play a cardioprotective role until menopause. Experimental data on the effect of estrogens on cardiovascular damage are controversial and potential underlying mechanisms especially in renal failure have not been fully clarified.

METHODS

Three-month-old female uninephrectomized stroke-prone spontaneously hypertensive (SHRsp) rats were sham-operated or ovariectomized. Subsequently, they received either vehicle (sesame oil) or 17-beta-3 benzoate estradiol (E2) (25 microg/day) or estriol (E3) (0.02 mg/day), respectively. After 3 months the animals were sacrified and the organs were harvested using pressure-controlled perfusion fixation. Stereologic parameters such as capillary length density (L(V)), mean intercapillary distance (MID), and volume density of the interstitial tissue (Vv) were quantitated. Additionally, expression of transforming growth factor-beta (TGF-beta), vascular endothelial growth factor (VEGF), flt-1, endothelial nitric oxide synthase (eNOS), endothelin-1 (ET-1), endothelin A receptor (ETA) receptor, and alpha estrogen receptor was assessed using immunohistochemistry. Intramyocardial capillaries and the aorta were investigated by morphometric methods.

RESULTS

L(V) (mm/mm(3)) was significantly lower (2421 +/- 500) and MID (microm) significantly higher (22.2 +/- 2.33) in vehicle-treated uninephrectomized/ovariectomized compared to uninephrectomized/sham-ovariectomized controls (L(V) 3629 +/- 960, MID 12.7 +/- 2.7) as well as estradiol (L(V) 3340 +/- 739, MID 12.1 +/- 4.96) and estriol (L(V) 4655 +/- 618, MID 14.2 +/- 2.89) treated uninephrectomized/ovariectomized animals. The volume density of the cardiac interstitium was higher in vehicle-treated uninephrectomized/ovariectomized animals compared to uninephrectomized/sham-ovariectomized, estradiol and estriol treated uninephrectomized/ovariectomized rats. The protein level expression of TGF-beta was higher in vehicle treated uninephrectomized/ovariectomized compared to uninephrectomized/sham and all treatment groups.

CONCLUSION

In ovariectomized SHRsp rats with moderate renal failure cardiac lesions were strikingly less after estradiol or estriol treatment. The results document a beneficial role of estrogens on cardiac abnormalities in a model of moderate renal dysfunction.

Effect of hormone therapy on the elastic properties of the arteries in healthy postmenopausal women

The aim of the study was to assess the effect of continuous hormone therapy (HT) for 1 yr on pulse wave analysis and central aortic pressure in healthy postmenopausal women. Sixty-five healthy postmenopausal women were randomly allocated to receive either conjugated equine estrogens 0.625 mg plus medroxyprogesterone acetate 5 mg (CEE/MPA, Premelle 5, Wyeth-Ayerst Lab, Philadelphia, PA, no.=32) or no therapy (no.=33). Treatment was continuous, and the study period lasted 12 months. Central aortic pressure, augmentation and augmentation index (AI) were determined non-invasively using applanation tonometry. All measurements were performed at baseline and at the end of the study by the same person. Ns differences were found between baseline values and values at the end of the study in either the control or the CEE/MPA group in central systolic aortic pressure (107.0 +/- 13.1 vs 107.6 +/- 11.3 mmHg, p=0.80, and 110.8 +/- 10.8 vs 112.3 +/- 11.4 mmHg, p=0.23, respectively), augmentation (12.6 +/- 4.2 vs 11.9 +/- 4.8 mmHg, p=0.45 and 11.7 +/- 3.7 vs 12.6 +/- 4.2 mmHg, p=0.34, respectively), and percentage of AI (36.8 +/- 9.3 vs 36.3 +/- 10.3, p=0.81 and 34.1 +/- 8.9 vs 34.9 +/- 9.8, p=0.72, respectively). The results of this preliminary report suggest that HT for 1 yr does not have any significant effect on central aortic pressure and wave reflection in healthy postmenopausal women.

Augmentation of Pulse Wave Velocity Precedes Vascular Structural Changes of the Aorta in Rats Treated with N.OMEGA.-Nitro-L-Arginine Methyl Ester

We examined the relationship between structural changes of the aorta and pulse wave velocity (PWV), and the effects of antihypertensive treatments on PWV in N(omega)-nitro-L-arginine methyl ester (L-NAME)-treated rats. Twelve-week-old Wistar-Kyoto (WKY) rats were divided into the following groups, all of which received drug treatment in their drinking water: an untreated control group (n = 36), an L-NAME-treated group (0.7 mg/ml) (n = 32), an L-NAME and angiotensin converting enzyme (ACE) inhibitor (ACEI)-treated group (imidapril: 0.4 mg/ml) (n = 8), and an L-NAME and hydralazine-treated group (0.2 mg/ml) (n = 10). PWV was measured at the same blood pressure (BP) level as in the control group and the wall-to-lumen ratio of the thoracic aorta was evaluated in all groups. In the L-NAME group, PWV increased compared with the value in the control group, at the same time that BP was increasing. After the third day of treatment, PWV was higher in the L-NAME group than in the control group after adjusting BP to the control level, while the wall-to-lumen ratios were equal between the two groups. After the first week of treatment, not only the adjusted PWV, but also the wall-to-lumen ratios were greater in the L-NAME group than in the control group. With administration of antihypertensive agents, both PWV and the thickening of the aortic wall were reduced, but there was no significant difference between the ACEI and hydralazine-treated groups. In conclusion, in a rat model of nitric oxide (NO) synthesis inhibition, the increase in PWV preceded the vascular structural changes, while antihypertensive treatment reduced both changes. There was no significant difference between treatments with ACEI and hydralazine in this model.