Testosterone-associated blood pressure dysregulation in women with androgen excess polycystic ovary syndrome.

We tested the hypothesis that hyperandrogenemia in androgen excess polycystic ovary syndrome (AE-PCOS) is a primary driver in blood pressure (BP) dysregulation via altered sympathetic nervous system activity (SNSA), reduced integrated baroreflex gain and increased renin-angiotensin system (RAS) activation. We measured resting SNSA (microneurography), integrated baroreflex gain, and RAS with lower body negative pressure in obese insulin-resistant (IR) women with AE-PCOS [n = 8, 23 ± 4 yr; body mass index (BMI) = 36.3 ± 6.4 kg/m2] and obese IR controls (n = 7, control, 29 ± 7 yr; BMI = 34.9 ± 6.8 kg/m2), at baseline (BSL), after 4 days of gonadotropin-releasing hormone antagonist (ANT, 250 µg/day) and 4 days of ANT + testosterone (ANT + T, 5 mg/day) administration. Resting BP was similar between groups for systolic blood pressure (SBP; 137 ± 14 vs. 135 ± 14 mmHg, AE-PCOS, control) and diastolic BP (89 ± 21 vs. 76 ± 10 mmHg, AE-PCOS, control). BSL integrated baroreflex gain was similar between groups [1.4 ± 0.9 vs. 1.0 ± 1.3 forearm vascular resistance (FVR) U/mmHg], but AE-PCOS had lower SNSA (10.3 ± 2.0 vs. 14.4 ± 4.4 burst/100 heartbeats, P = 0.04). In AE-PCOS, T suppression increased integrated baroreflex gain, which was restored to BSL with ANT + T (4.3 ± 6.5 vs. 1.5 ± 0.8 FVR U/mmHg, ANT, and ANT + T, P = 0.04), with no effect in control. ANT increased SNSA in AE-PCOS (11.2 ± 2.4, P = 0.04). Serum aldosterone was greater in AE-PCOS versus control (136.5 ± 60.2 vs. 75.7 ± 41.4 pg/mL, AE-PCOS, control, P = 0.04) at BSL but was unaffected by intervention. Serum angiotensin-converting enzyme was greater in AE-PCOS versus control (101.9 ± 93.4 vs. 38.2 ± 14.7 pg/mL, P = 0.04) and reduced by ANT in AE-PCOS (77.7 ± 76.5 vs. 43.4 ± 27.3 µg/L, ANT, and ANT + T, P = 0.04) with no impact on control. Obese, IR women with AE-PCOS showed decreased integrated baroreflex gain and increased RAS activation compared with control.NEW & NOTEWORTHY Here we present evidence for an important role of testosterone in baroreflex control of blood pressure and renal responses to baroreceptor unloading in women with a common, high-risk androgen excess polycystic ovary syndrome (AE-PCOS) phenotype. These data indicate a direct effect of testosterone on the vascular system of women with AE-PCOS independent of body mass index (BMI) and insulin-resistant (IR). Our study indicates that hyperandrogenemia is a central underlining mechanism of heightened cardiovascular risk in women with PCOS.

Sex, Oxidative Stress, and Hypertension: Insights From Animal Models.

One of the mechanisms responsible for blood pressure (BP) regulation is thought to be oxidative stress. In this review, we highlight preclinical studies that strongly support a role for oxidative stress in development and maintenance of hypertension in male animals, based on depressor responses to antioxidants, particularly tempol and apocynin. In females, oxidative stress seems to be important in the initial development of hypertension. However, whether maintenance of hypertension in females is mediated by oxidative stress is not clear. In clinical studies, pharmacological intervention to reduce BP with antioxidants has conflicting results, mostly negative. This review will discuss the uncertainties regarding blood pressure control and oxidative stress and potential reasons for these outcomes.

Cardiometabolic Features of Polycystic Ovary Syndrome: Role of Androgens.

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder that affects reproductive-age women. Hyperandrogenemia is present in a significant fraction (~80%) of women with PCOS. Increased prevalence of cardiometabolic risk factors is frequently observed in PCOS women. The present review aims to highlight the key role of androgens in mediating the negative cardiometabolic profile observed in PCOS women.

Gender differences in hypertension.

PURPOSE OF REVIEW: The review is a short discussion of sex/gender differences in blood pressure control with a focus on gender differences in hypertension awareness, prevalence, and treatment, the new American College of Cardiology/American Heart Association Guidelines, and recent discoveries in animal models and humans on mechanisms responsible for sex/gender differences in hypertension. RECENT FINDINGS: Hypertension awareness is greater in women than men, the prevalence of hypertension is higher in men than women until after menopause, and although the American College of Cardiology/American Heart Association Guidelines recommend similar treatment for men and women, this is not currently the case in practice. New studies into mechanisms responsible for sex/gender differences in hypertension include the role of the kidneys, the renin-angiotensin system, relaxin, and developmental programming. SUMMARY: Specific guidelines for hypertension treatment in women and men have yet to be developed. However, numerous animal and human studies have shown differences in the mechanisms responsible for blood pressure control between the sexes. Thus more research into the sex/gender differences in mechanisms responsible for hypertension are needed to determine the best treatment options that will reduce the risk of hypertension and subsequent cardiovascular diseases in both genders.

Rodent vertical sleeve gastrectomy alters maternal immune health and fetoplacental development.

Bariatric surgery is increasingly employed to improve fertility and reduce obesity-related co-morbidities in obese women. Surgical weight loss not only improves the chance of conception but reduces the risk of pregnancy complications including pre-eclampsia, gestational diabetes, and macrosomia. However, bariatric procedures increase the incidence of intrauterine growth restriction (IUGR), fetal demise, thromboembolism, and other gestational disorders. Using our rodent model of vertical sleeve gastrectomy (VSG), we tested the hypothesis that VSG in diet-induced, obese dams would cause immune and placental structural abnormalities that may be responsible for fetal demise during pregnancy. VSG dams studied on gestational day (G) 19 had reduced circulating T-cell (CD3+ and CD8+) populations compared with lean or obese controls. Further, local interleukin (IL) 1ß and IL 1 receptor antagonist (il1rn) cmRNA were increased in placenta of VSG dams. Placental barrier function was also affected, with increased transplacental permeability to small molecules, increased matrix metalloproteinase 9 expression, and increased apoptosis in VSG. Furthermore, we identified increased placental mTOR signaling that may contribute to preserving the body weight of the fetuses during gestation. These changes occurred in the absence of a macronutrient deficit or gestational hypertension in the VSG dams. In summary, previous VSG in dams may contribute to fetal demise by affecting maternal immune system activity and compromise placental integrity.

The Importance of Biological Sex and Estrogen in Rodent Models of Cardiovascular Health and Disease.

Nearly one-third of deaths in the United States are caused by cardiovascular disease (CVD) each year. In the past, CVD was thought to mainly affect men, leading to the exclusion of women and female animals from clinical studies and preclinical research. In light of sexual dimorphisms in CVD, a need exists to examine baseline cardiac differences in humans and the animals used to model CVD. In humans, sex differences are apparent at every level of cardiovascular physiology from action potential duration and mitochondrial energetics to cardiac myocyte and whole-heart contractile function. Biological sex is an important modifier of the development of CVD with younger women generally being protected, but this cardioprotection is lost later in life, suggesting a role for estrogen. Although endogenous estrogen is most likely a mediator of the observed functional differences in both health and disease, the signaling mechanisms involved are complex and are not yet fully understood. To investigate how sex modulates CVD development, animal models are essential tools and should be useful in the development of therapeutics. This review will focus on describing the cardiovascular sexual dimorphisms that exist both physiologically and in common animal models of CVD.

Sex Differences in Regulation of Blood Pressure.

Hypertension is one of the leading risk factors for cardiovascular disease, myocardial infarction, and stroke. There are gender differences in the prevalence of hypertension and in the mechanisms responsible for hypertension in humans. This review will discuss the mechanisms for regulation of blood pressure, sex differences that have been identified in animal studies, and the gender differences that have been identified in humans.

20-HETE and CYP4A2 ω-hydroxylase contribute to the elevated blood pressure in hyperandrogenemic female rats.

In male rats, androgen supplements increase 20-hydroxyeicosatetraenoic acid (20-HETE) via cytochrome P-450 (CYP)4A ω-hydroxylase and cause an increase in blood pressure (BP). In the present study, we determined the roles of 20-HETE and CYP4A2 on the elevated BP in hyperandrogenemic female rats. Chronic dihydrotestosterone (DHT) increased mean arterial pressure (MAP) in female Sprague-Dawley rats (96 ± 2 vs. 108 ± 2 mmHg, P < 0.05) and was associated with increased renal microvascular CYP4A2 mRNA expression (15-fold), endogenous renal 20-HETE (5-fold), and ω-hydroxylase activity (3-fold). Chronic DHT also increased MAP in low salt-fed Dahl salt-resistant female rats (81 ± 4 vs. 95 ± 1 mmHg, P < 0.05) but had no effect on MAP in Dahl salt-sensitive female rats (154 ± 3 vs. 153 ± 3 mmHg), which are known to be 20-HETE deficient. To test the role of CYP4A2, female CYP4A2(-/-) and SS.5(Bn) (wild type) rats were treated with DHT. DHT increased MAP in SS.5(Bn) female rats (104 ± 1 vs. 128 ± 1 mmHg, P < 0.05) but had no effect in CYP4A2(-/-) female rats (118 ± 1 vs. 120 ± 1 mmHg). Renal microvascular 20-HETE was reduced in control CYP4A2(-/-) female rats and was increased with DHT in SS.5(Bn) female rats (6-fold) but not CYP4A2(-/-) female rats. ω-Hydroxylase activity was 40% lower in control CYP4A2(-/-) female rats than in SS.5(Bn) female rats, and DHT decreased ω-hydroxylase activity in SS.5(Bn) female rats (by 50%) but significantly increased ω-hydroxylase activity in CYP4A2(-/-) female rats (3-fold). These data suggest that 20-HETE via CYP4A2 contributes to the elevation in BP in hyperandrogenemic female rats. The data also suggest that 20-HETE synthesis inhibition may be effective in treating the elevated BP in women with hyperandrogenemia, such as women with polycystic ovary syndrome.

Low-dose testosterone protects against renal ischemia-reperfusion injury by increasing renal IL-10-to-TNF-α ratio and attenuating T-cell infiltration.

Renal ischemia-reperfusion (I/R) in male rats causes reductions in plasma testosterone, and infusion of testosterone 3 h postreperfusion is protective. We tested the hypotheses that acute high doses of testosterone promote renal injury after I/R, and that acute low-dose testosterone is protective by the following: 1) increasing renal IL-10 and reducing TNF-α; 2) its effects on nitric oxide; and 3) reducing intrarenal T-cell infiltration. Rats were subjected to renal I/R, followed by intravenous infusion of vehicle or testosterone (20, 50, or 100 µg/kg) 3 h postreperfusion. Low-dose testosterone (20 µg/kg) reduced plasma creatinine, increased nitrate/nitrite excretion, increased intrarenal IL-10, and reduced intrarenal TNF-α, whereas 50 µg/kg testosterone failed to reduce plasma creatinine, increased IL-10, but failed to reduce TNF-α. A higher dose of testosterone (100 mg/kg) not only failed to reduce plasma creatinine, but significantly increased both IL-10 and TNF-α compared with other groups. Low-dose nitro-l-arginine methyl ester (1 mg·kg(-1)·day(-1)), given 2 days before I/R, prevented low-dose testosterone (20 µg/kg) from protecting against I/R injury, and was associated with lack of increase in intrarenal IL-10. Intrarenal CD4(+) and CD8(+) T cells were significantly increased with I/R, but were attenuated with low-dose testosterone, as were effector T helper 17 cells. The present studies suggest that acute, low-dose testosterone is protective against I/R AKI in males due to its effects on inflammation by reducing renal T-cell infiltration and by shifting the balance to favor anti-inflammatory cytokine production rather than proinflammatory cytokines.

Reactive oxygen species: players in the cardiovascular effects of testosterone.

Androgens are essential for the development and maintenance of male reproductive tissues and sexual function and for overall health and well being. Testosterone, the predominant and most important androgen, not only affects the male reproductive system, but also influences the activity of many other organs. In the cardiovascular system, the actions of testosterone are still controversial, its effects ranging from protective to deleterious. While early studies showed that testosterone replacement therapy exerted beneficial effects on cardiovascular disease, some recent safety studies point to a positive association between endogenous and supraphysiological levels of androgens/testosterone and cardiovascular disease risk. Among the possible mechanisms involved in the actions of testosterone on the cardiovascular system, indirect actions (changes in the lipid profile, insulin sensitivity, and hemostatic mechanisms, modulation of the sympathetic nervous system and renin-angiotensin-aldosterone system), as well as direct actions (modulatory effects on proinflammatory enzymes, on the generation of reactive oxygen species, nitric oxide bioavailability, and on vasoconstrictor signaling pathways) have been reported. This mini-review focuses on evidence indicating that testosterone has prooxidative actions that may contribute to its deleterious actions in the cardiovascular system. The controversial effects of testosterone on ROS generation and oxidant status, both prooxidant and antioxidant, in the cardiovascular system and in cells and tissues of other systems are reviewed.

Roles for the sympathetic nervous system, renal nerves, and CNS melanocortin-4 receptor in the elevated blood pressure in hyperandrogenemic female rats.

Women with polycystic ovary syndrome (PCOS) have hyperandrogenemia and increased prevalence of risk factors for cardiovascular disease, including elevated blood pressure. We recently characterized a hyperandrogenemic female rat (HAF) model of PCOS [chronic dihydrotestosterone (DHT) beginning at 4 wk of age] that exhibits similar characteristics as women with PCOS. In the present studies we tested the hypotheses that the elevated blood pressure in HAF rats is mediated in part by sympathetic activation, renal nerves, and melanocortin-4 receptor (MC4R) activation. Adrenergic blockade with terazosin and propranolol or renal denervation reduced mean arterial pressure (MAP by telemetry) in HAF rats but not controls. Hypothalamic MC4R expression was higher in HAF rats than controls, and central nervous system MC4R antagonism with SHU-9119 (1 nmol/h icv) reduced MAP in HAF rats. Taking a genetic approach, MC4R null and wild-type (WT) female rats were treated with DHT or placebo from 5 to 16 wk of age. MC4R null rats were obese and had higher MAP than WT control rats, and while DHT increased MAP in WT controls, DHT failed to further increase MAP in MC4R null rats. These data suggest that increases in MAP with chronic hyperandrogenemia in female rats are due, in part, to activation of the sympathetic nervous system, renal nerves, and MC4R and may provide novel insights into the mechanisms responsible for hypertension in women with hyperandrogenemia such as PCOS.

Postmenopausal hypertension: role of the sympathetic nervous system in an animal model.

In postmenopausal women the mechanisms responsible for hypertension have not been completely elucidated, and there are no gender-specific guidelines for women despite studies showing that blood pressure is not as well controlled to goal in women as in men. In the present study we tested the hypotheses that the sympathetic nervous system and the renal sympathetic nerves contribute to hypertension in aging female rats, that sympathetic activation may be mediated by the melanocortin 3/4 receptor (MC3/4R), and that MC3/4R activation may be due to increases in leptin. α-1, ß-1,2-Adrenergic blockade reduced blood pressure in both young (3-4 mo) and old (18-19 mo) female spontaneously hypertensive rats (SHR). Renal denervation attenuated the hypertension more in old females than young females. MC3/4R antagonism with SHU-9119 given intracerebroventricularly had no effect on blood pressure in either young or old females but significantly reduced blood pressure in old males. Plasma leptin levels were similar in old male and female SHR and in old versus young females. These data suggest that the hypertension in old female SHR is in part due to activation of the sympathetic nervous system, that the renal nerves contribute to the hypertension, and that the mechanism responsible for sympathetic activation in old females is independent of the MC3/4R.

Roles played by 20-HETE, angiotensin II and endothelin in mediating the hypertension in aging female spontaneously hypertensive rats.

Prevalence of hypertension (HT) increases in women after menopause, and there is evidence that HT is not as well controlled in postmenopausal women as men. The reasons for this are not clear but may be related to the lack of adequate blockade of the systems contributing to HT in women. This study aimed to determine the roles of three of the systems known to contribute to HT in animal studies: angiotensin II (ANG II; enalapril inhibitor), eicosanoids [1-aminobenzotriazole (1-ABT) inhibitor], and endothelin (ET(A) receptor antagonist), on blood pressure (BP) in three groups of female spontaneously hypertensive rats (SHR), aged 18 mos (postmenopausal rat, PMR). After baseline telemetry BP, three drug periods were performed for 5 days each: single blockade (ABT or enalapril), double blockade (ABT+enalapril or enalapril+ABT), and triple blockade (all 3 drugs). Controls received no treatment until the third period when they received ET(A) receptor antagonist alone. Single drug blockade reduced BP in PMR to similar levels. Double blockade reduced mean arterial pressure more in ABT+enalapril rats than in the other group (enalapril+ABT). Triple drug blockade reduced BP to similar levels in both groups, but the BP remained ∼110 mmHg. The data suggest that these three systems, ANG II, eicosanoids, and endothelin, contribute together and independently to BP control in old female SHR. However, other systems also contribute to the HT since the BP was not normalized, supporting the notion that HT in postmenopausal women may require complex multidrug therapy to be better controlled and that may require the development of additional drugs.

Protective role of testosterone in ischemia-reperfusion-induced acute kidney injury.

Men are at greater risk for renal injury and dysfunction after acute ischemia-reperfusion (I/R) than are women. Studies in animals suggest that the reason for the sex difference in renal injury and dysfunction after I/R is the protective effect of estrogens in females. However, a reduction in testosterone in men is thought to play an important role in mediating cardiovascular and renal disease, in general. In the present study, we tested the hypothesis that I/R of the kidney reduces serum testosterone, and that contributes to renal dysfunction and injury. Male rats that were subjected to renal ischemia of 40 min followed by reperfusion had a 90% reduction in serum testosterone by 3 h after reperfusion that remained at 24 h. Acute infusion of testosterone 3 h after reperfusion attenuated the increase in plasma creatinine and urinary kidney injury molecule-1 (KIM-1) at 24 h, prevented the reduction in outer medullary blood flow, and attenuated the increase in intrarenal TNF-α and the decrease in intrarenal VEGF at 48 h. Castration of males caused greater increases in plasma creatinine and KIM-1 at 24 h than in intact males with renal I/R, and treatment with anastrozole, an aromatase inhibitor, plus testosterone almost normalized plasma creatinine and KIM-1 in rats with renal I/R. These data show that renal I/R is associated with sustained reductions in testosterone, that testosterone repletion protects the kidney, whereas castration promotes renal dysfunction and injury, and that the testosterone-mediated protection is not conferred by conversion to estradiol.

Sex and gender differences in control of blood pressure.

In recent years, the interest in studying the impact of sex steroids and gender on the regulation of blood pressure and cardiovascular disease has been growing. Women are protected from most cardiovascular events compared with men until after menopause, and postmenopausal women are at increased risk of cardiovascular complications compared with premenopausal women. The pathophysiological mechanisms have not been elucidated, but are not likely to be as simple as the presence or absence of oestrogens, since hormone replacement therapy in elderly women in the Women's Health Initiative or HERS (Heart and Estrogen/progestin Replacement Study) did not provide primary or secondary prevention against cardiovascular events. Men are also thought to be at risk of cardiovascular disease at earlier ages than women, and these mechanisms too are not likely to be as simple as the presence of testosterone, since androgen levels fall in men with cardiovascular and other chronic diseases. In fact, many investigators now believe that it is the reduction in androgen levels that frequently accompanies chronic disease and may exacerbate cardiovascular disease in men. In the present review, the roles of sex steroids and gender in mediating or protecting against hypertension and cardiovascular disease will be discussed.

Mechanisms of sex and gender differences in hypertension.

The mechanisms that control blood pressure are multifaceted including the sympathetic nervous system and the renin-angiotensin system leading to vasoconstriction and sodium reabsorption that causes a shift in the pressure-natriuesis relationship to higher blood pressures. Sex steroids can affect these mechanisms either directly or indirectly, and the effects may be different depending on the sex of the individual. This review will discuss some of the major blood pressure-controlling mechanisms and how sex steroids may affect them and the need for future studies to better clarify the mechanisms responsible for sex and gender differences in blood pressure control. New mechanisms that are identified, along with what is already known, will provide better tools for treatment of hypertension in men and women of all ethnicities and decrease the risk of cardiovascular disease in the future.

Insights Into the Cardiomodulatory Effects of Sex Hormones: Implications in Transgender Care.

Transgender individuals that undergo gender-affirming hormone therapy may experience discrimination in the health care setting with a lack of access to medical personnel competent in transgender medicine. Recent evidence suggests that gender-affirming hormone therapy is associated with an increased risk of cardiovascular diseases and cardiovascular risk factors. A recent statement from the American Heart Association reinforces the importance of cardiovascular-focused clinical management and the necessity for more research into the impact of gender-affirming hormone therapy. With this in mind, this review will highlight the known cardiovascular risk factors associated with gender-affirming hormone therapy and identify potential molecular mechanisms determined from the limited animal studies that explore the role of cross-sex steroids on cardiovascular risk. The lack of data in this understudied population requires future clinical and basic research studies to inform and educate clinicians and their transgender patient population to promote precision medicine for their care to improve their quality of life.