Role of adrenal androgens in the development of arteriosclerosis as judged by pulse wave velocity and calcification of the aorta

Beneficial Effects of Adrenal Androgen Supplement in Bleeding Cirrhotic Rats

Critical illness is accompanied by hypothalamic-pituitary-adrenal axis activation, but adrenal insufficiency characterized by inadequate glucocorticoid synthesis is common in critically ill cirrhotic patients, the "hepato-adrenal syndrome." Adrenal cortex also synthesizes androgen (dehydroepiandrosterone, DHEA). DHEA maintains microcirculation by enhancing vascular endothelial nitric oxide synthase (eNOS) activity. In critical patients of other disease entities, a shift of adrenal steroidogenesis away from androgens toward glucocorticoid has been noted, arousing interests in androgen replacement in critical settings. Nevertheless, this has not been surveyed in cirrhosis with hemorrhage. In this study, liver cirrhosis was induced with common bile duct ligation (BDL) in Spraque-Dawley rats. Sham rats were controls. DHEA or vehicle was injected at the beginning of hemorrhage-transfused procedure, followed by terlipressin injection. Hemodynamic parameters were measured. Then abdominal aorta, superior mesenteric arteries (SMA) and splenorenal shunt (prominent portosystemic collateral vessel in rodents) eNOS and inducible NOS protein expressions were evaluated. In bleeding BDL groups without terlipressin injection, adrenocorticotropic hormone (ACTH) stimulation test was performed to evaluate the DHEA response. The results showed that DHEA significantly elevated mean arterial pressure, cardiac output, and stroke volume of bleeding cirrhotic rats treated with terlipressin and reduced systemic vascular resistance without affecting SMA flow, resistance, and portal pressure. DHEA upregulated abdominal aorta and SMA eNOS expressions. ACTH did not stimulate DHEA synthesis in bleeding BDL rats. In conclusion, androgen deficiency exists in bleeding cirrhotic rats. DHEA augments terlipressin-induced amelioration of shock without influencing splanchnic hemodynamics, possibly rendering it a feasible adjunct to vasoconstrictors in variceal hemorrhage.

Molecular docking simulations provide insights in the substrate binding sites and possible substrates of the ABCC6 transporter

The human ATP-binding cassette family C member 6 (ABCC6) gene encodes an ABC transporter protein (ABCC6), primarily expressed in liver and kidney. Mutations in the ABCC6 gene cause pseudoxanthoma elasticum (PXE), an autosomal recessive connective tissue disease characterized by ectopic mineralization of the elastic fibers. The pathophysiology underlying PXE is incompletely understood, which can at least partly be explained by the undetermined nature of the ABCC6 substrates as well as the unknown substrate recognition and binding sites. Several compounds, including anionic glutathione conjugates (N-ethylmaleimide; NEM-GS) and leukotriene C4 (LTC4) were shown to be modestly transported in vitro; conversely, vitamin K3 (VK3) was demonstrated not to be transported by ABCC6. To predict the possible substrate binding pockets of the ABCC6 transporter, we generated a 3D homology model of ABCC6 in both open and closed conformation, qualified for molecular docking and virtual screening approaches. By docking 10 reported in vitro substrates in our ABCC6 3D homology models, we were able to predict the substrate binding residues of ABCC6. Further, virtual screening of 4651 metabolites from the Human Serum Metabolome Database against our open conformation model disclosed possible substrates for ABCC6, which are mostly lipid and biliary secretion compounds, some of which are found to be involved in mineralization. Docking of these possible substrates in the closed conformation model also showed high affinity. Virtual screening expands this possibility to explore more compounds that can interact with ABCC6, and may aid in understanding the mechanisms leading to PXE.

Role of DHEA in cardiovascular diseases

Dehydroepiandrosterone (DHEA) is a steroid hormone derived from cholesterol synthesized by the adrenal glands. DHEA and its 3β-sulphate ester (DHEA-S) are the most abundant circulating steroid hormones. In human, there is a clear age-related decline in serum DHEA and DHEA-S and this has suggested that a relative deficiency in these steroids may be causally related to the development of a series of diseases associated with aging including cardiovascular diseases (CVD). This commentary aims to highlight the action of DHEA in CVD and its beneficial effect in therapy. We thus discuss the possible impact of serum DHEA decline and DHEA supplementation in diseases such as hypertension, coronary artery disease and atherosclerosis. More specifically, we provide evidence for a beneficial action of DHEA in the main disease of the pulmonary circulation: pulmonary hypertension. We also examine the potential cellular mechanism of action of DHEA in terms of receptors (membrane/nuclear) and associated signaling pathways (ion channels, calcium signaling, PI3K/AKT/eNos pathway, cGMP, RhoA/RhoK pathway). We show that DHEA acts as an anti-remodeling and vasorelaxant drug. Since it is a well-tolerated and inexpensive drug, DHEA may prove to be a valuable molecule in CVD but it deserves further studies both at the molecular level and in large clinical trials.

Relationship between low serum endogenous androgen concentrations and arterial stiffness in men with type 2 diabetes mellitus

The aim of this study was to evaluate the relationship between arterial stiffness determined by pulse wave velocity (PWV) and serum endogenous androgen concentrations as well as major cardiovascular risk factors in men with type 2 diabetes mellitus. Serum free testosterone and dehydroepiandrosterone sulfate (DHEA-S) concentrations were measured in 268 men with type 2 diabetes mellitus. Relationships between PWV and serum endogenous androgen concentrations as well as major cardiovascular risk factors, including age, blood pressure, serum lipid concentration, glycemic control (hemoglobin A(1c)), body mass index, and degree of albuminuria, were evaluated. Positive correlations were found between PWV and age (r = 0.491, P < .0001), duration of diabetes (r = 0.320, P < .0001), systolic blood pressure (r = 0.292, P < .0001), and log (urinary albumin excretion) (r = 0.269, P < .0001). Inverse correlations were found between serum free testosterone concentration and PWV (r = -0.228, P = .0003) and between serum DHEA-S concentration and PWV (r = -0.252, P = .0002) in men with type 2 diabetes mellitus. Pulse wave velocity was significantly greater in patients with lower concentrations of free testosterone (<10 pg/mL) than in patients with higher concentrations of free testosterone (1864 +/- 359 vs 1736 +/- 327 cm/s; P = .0053). Pulse wave velocity also was significantly greater in patients with lower concentrations of DHEA-S (<1000 ng/mL) than in patients with higher concentrations of DHEA-S (1843 +/- 371 vs 1686 +/- 298 cm/s; P = .0008). Multiple regression analysis identified both serum free testosterone concentration (beta = -.151, P = .0150) and serum DHEA-S concentration (beta = -.200, P = .0017) as independent determinants of PWV. In conclusion, serum endogenous androgen concentrations are inversely associated with arterial stiffness determined by PWV in men with type 2 diabetes mellitus, which is true for men in general based on other works.

The skin as a mirror of the aging process in the human organism--state of the art and results of the aging research in the German National Genome Research Network 2 (NGFN-2)

As our society is growing older, the consequences of aging have begun to gain particular attention. Improvement of quality of life at old age and prevention of age-associated diseases have become the main focus of the aging research. The process of aging in humans is complex and underlies multiple influences, with the probable involvement of heritable and various environmental factors. In particular, hormones are decisively involved in the generation of aging. Over time, important circulating hormones decline due to a reduced secretion of the pituitary, the adrenal glands and the gonads or due to an intercurrent disease. Among them, serum levels of growth factors and sexual steroids show significant aging-associated changes. Within the scope of the Explorative Project 'Genetic aetiology of human longevity' supported by the German National Genome Research Network 2 (NGFN-2) an in vitro model of human hormonal aging has been developed. Human SZ95 sebocytes were maintained under a hormone-substituted environment consisting of growth factors and sexual steroids in concentrations corresponding to those circulating in 20- and in 60-year-old women. Eight hundred and ninety-nine genes showed a differential expression in SZ95 sebocytes maintained under the 20- and 60-year-old hormone mixture, respectively. Among them genes were regulated which are involved in biological processes which are all hallmarks of aging. The most significantly altered signaling pathway identified was that of the transforming growth factor-beta (TGF-beta). A disturbed function of this cascade has been associated with tumorigenesis, i.e. in pancreatic, prostate, intestine, breast, and uterine cancer. Interestingly, genes expressed in signaling pathways operative in age-associated diseases such as Huntington's disease (HD), dentatorubral-pallidoluysian atrophy (DRPLA), and amyotrophic lateral sclerosis (ALS) were also identified. These data demonstrate that skin and its appendages may represent an adequate model for aging research. Hormones interact in a complex fashion, and aging may be partly attributed to the changes in their circulating blood levels. Furthermore, a disturbed hormone status may partially act towards the manifestation of neurodegenerative diseases. Thus, these results could be a basis for an integrated and interdisciplinary approach to the analysis of the aging process.

Low testosterone levels are associated with carotid atherosclerosis in men

OBJECTIVE

To study the relationship between endogenous sex hormone levels and intima-media thickness (IMT) of the carotid artery measured by ultrasonography.

DESIGN

Population-based cross-sectional study.

METHODS

Sex hormone levels measured by immunoassay, anthropometric measurements and IMT was studied in 1482 men aged 25-84 years participating in the 1994-1995 Tromsø study. The data were analysed with partial correlation, multiple linear regression and logistic regression analysis.

RESULTS

Linear regression models showed that total testosterone and sex hormone-binding globulin levels, but not calculated free testosterone, serum oestradiol or dehydroepiandrosterone sulphate levels were inversely associated with the age-adjusted IMT (P = 0.008 and P < 0.001 respectively). These associations were independent of smoking, physical activity, blood pressure and lipid levels, but were not independent of body mass index (BMI). Excluding men with cardiovascular disease (CVD) did not materially change these results. In a logistic regression model adjusted for the confounding effect of CVD risk factors, men with testosterone levels in the lowest quintile (<9.0 nmol L(-1)) had an independent OR = 1.51 (P = 0.015) of being in the highest IMT quintile.

CONCLUSIONS

We found an inverse association between total testosterone levels and IMT of the carotid artery in men that was present also after excluding men with CVD, but was not independent of BMI. The clinical relevance of this, however, is uncertain and needs to be investigated in a clinical setting.

Dehydroepiandrosterone Sulfate Induces Acute Vasodilation of Porcine Coronary Arteries In Vitro and In Vivo

Although an inverse relationship between dehydroepiandrosterone sulfate (DHEAS) and coronary artery disease has been demonstrated in men, the vascular effects of DHEAS are not well defined. The vasoactive effects of intracoronary DHEAS and testosterone (0.1 nM to 1 microM) were examined in vivo in 24 pigs. Epicardial cross-sectional area was measured by intravascular ultrasound, and coronary flow velocity by intravascular Doppler velocimetry. We also examined the effects of antagonism of the androgen receptor, nitric oxide synthase, and potassium channels on DHEAS-induced vasodilation in vitro in coronary rings from male and female pig hearts. DHEAS and testosterone induced increases in cross-sectional area, average peak velocity, and coronary blood flow. The maximal increase in coronary blood flow in response to testosterone was 1.26-fold (P=0.02), and in average peak velocity 1.43-fold (P=0.05), greater than that to DHEAS, whereas increases in cross-sectional area were similar. Vasodilation to both hormones was rapid, with maximal responses occurring <10 minutes after administration. In vitro, DHEAS and testosterone induced vasodilation in coronary rings, greater with testosterone. At doses of 0.1 and 1 microM, the vasodilator effects of DHEAS and testosterone were inhibited by the androgen receptor antagonist flutamide but not the estrogen receptor antagonist ICI 182,780. At 10 microM, neither DHEAS- nor testosterone-induced vasorelaxation was inhibited by flutamide, ICI 182,780, L-NAME, or deendothelialization, but both were attenuated by pretreatment with glibenclamide. No gender differences were observed in any of the responses examined. In conclusion, DHEAS is an acute coronary artery vasodilator, but less potent than testosterone. Its effect might be mediated via androgen receptors and may involve ATP-sensitive potassium channels.

Effect of moderate alcohol consumption on plasma dehydroepiandrosterone sulfate, testosterone, and estradiol levels in middle-aged men and postmenopausal women: a diet-controlled intervention study

BACKGROUND

Moderate alcohol consumption is inversely associated with cardiovascular diseases. Changes in hormone levels might in part help explain the positive health effect. This study was performed to examine the effect of moderate alcohol consumption on plasma dehydroepiandrosterone sulfate (DHEAS), testosterone, and estradiol levels.

METHODS

In a randomized, diet-controlled, crossover study, 10 middle-aged men and 9 postmenopausal women, all apparently healthy, nonsmoking, and moderate alcohol drinkers, consumed beer or no-alcohol beer with dinner during two successive periods of 3 weeks. During the beer period, alcohol intake equaled 40 and 30 g per day for men and women, respectively. The total diet was supplied and had essentially the same composition during these 6 weeks. Before each treatment there was a 1 week washout period, in which the subjects were not allowed to drink alcoholic beverages. At the end of each of the two experimental periods, fasting blood samples were collected in the morning.

RESULTS

Moderate alcohol consumption increased plasma DHEAS level by 16.5% (95% confidence interval, 8.0-24.9), with similar changes for men and women. Plasma testosterone level decreased in men by 6.8% (95% confidence interval, -1.0- -12.5), but no effect was found in women. Plasma estradiol level was not affected. Serum high-density lipoprotein cholesterol level increased by 11.7% (95% confidence interval, 7.3-16.0), with similar changes for men and women. The overall alcohol-induced relative changes in DHEAS, testosterone, and estradiol correlated positively with the relative increase in high-density lipoprotein cholesterol (adjusted for the relative change in body weight); however, findings were only borderline significant for DHEAS and estradiol (r = 0.44, p = 0.08; r = 0.32, p = 0.21; and r = 0.46, p = 0.06, respectively).

CONCLUSIONS

A protective effect of moderate alcohol consumption for cardiovascular disease risk may in part be explained by increased plasma DHEAS level.

The Relationship Between Androgens and Arterial Stiffness in Older Men

OBJECTIVES

To assess the relationship between endogenous androgen levels and arterial stiffness in older men.

DESIGN

A retrospective, cross-sectional study.

SETTING

A London hospital-based, clinical research unit for the elderly.

PARTICIPANTS

Fifty-five men (mean age+/-standard deviation=71.1+/-8.0).

INTERVENTION

Sex hormone-binding globulin (SHBG), testosterone, and dehydroepiandrosterone sulfate (DHEAS) were measured in all subjects who had a stored serum sample drawn the same day as arterial stiffness measures were performed. Free testosterone index (FTI) was calculated ((total testosterone/SHBG) x 100 (%)). The measures of arterial stiffness used were pulse wave velocity (PWV) using the Complior system and systemic arterial compliance (SAC) using the area method.

MEASUREMENTS

Relationship between arterial stiffness and serum androgens.

RESULTS

: FTI showed a strong positive relationship with SAC (r=0.507, P<.001) and, correspondingly, an inverse relationship with carotid-femoral (C-F) and carotid-radial (C-R) PWV (r=-0.427 and -0.402, respectively, P<or=.002). With multiple regression, including age, blood pressure, cholesterol, body mass index, and waist/hip ratio, FTI remained a significant determinant of SAC and C-R PWV but not C-F PWV. In the subgroup of men without cardiovascular disease or vasoactive medication use (n=37), all three relationships remained significant. DHEAS was inversely related to C-F PWV only (r=-0.304, P=.041).

CONCLUSION

The known association between lower androgenicity and increased cardiovascular risk in men might be explained by altered vascular stiffness.

Endogenous sex hormones and cardiovascular disease in men

Unlike women, men do not experience an abrupt reduction in endogenous sex hormone production. It has, however, become clear that an age-associated decrease in the levels of (bioactive) sex hormones does occur. Whether endogenous sex hormones have an impact on cardiovascular disease has for many years remained largely unknown, but during the last decade more attention has been drawn to the importance of testosterone, estrogens, and adrenal androgens in etiology, prevention, and treatment of male cardiovascular disease. The purpose of this article is to summarize the evidence currently available on the association between endogenous sex hormones and cardiovascular disease in males. Published studies dealing with the relationship between circulating levels of sex hormones and cardiovascular disease in males were reviewed. The studies reviewed in this article suggest that circulating endogenous sex hormones and estrogens have a neutral or beneficial effect on cardiovascular disease in men.

Androgens and coronary artery disease

A significant and independent association between endogenous testosterone (T) levels and coronary events in men and women has not been confirmed in large prospective studies, although cross-sectional data have suggested coronary heart disease can be associated with low T in men. Hypoandrogenemia in men and hyperandrogenemia in women are associated with visceral obesity; insulin resistance; low high-density lipoprotein (HDL) cholesterol (HDL-C); and elevated triglycerides, low-density lipoprotein cholesterol, and plasminogen activator type 1. These gender differences and confounders render the precise role of endogenous T in atherosclerosis unclear. Observational studies do not support the hypothesis that dehydroepiandrosterone sulfate deficiency is a risk factor for coronary artery disease. The effects of exogenous T on cardiovascular mortality or morbidity have not been extensively investigated in prospective controlled studies; preliminary data suggest there may be short-term improvements in electrocardiographic changes in men with coronary artery disease. In the majority of animal experiments, exogenous T exerts either neutral or beneficial effects on the development of atherosclerosis. Exogenous androgens induce both apparently beneficial and deleterious effects on cardiovascular risk factors by decreasing serum levels of HDL-C, plasminogen activator type 1 (apparently deleterious), lipoprotein (a), fibrinogen, insulin, leptin, and visceral fat mass (apparently beneficial) in men as well as women. However, androgen-induced declines in circulating HDL-C should not automatically be assumed to be proatherogenic, because these declines may instead reflect accelerated reverse cholesterol transport. Supraphysiological concentrations of T stimulate vasorelaxation; but at physiological concentrations, beneficial, neutral, and detrimental effects on vascular reactivity have been observed. T exerts proatherogenic effects on macrophage function by facilitating the uptake of modified lipoproteins and an antiatherogenic effect by stimulating efflux of cellular cholesterol to HDL. In conclusion, the inconsistent data, which can only be partly explained by differences in dose and source of androgens, militate against a meaningful assessment of the net effect of T on atherosclerosis. Based on current evidence, the therapeutic use of T in men need not be restricted by concerns regarding cardiovascular side effects. Available data also do not justify the uncontrolled use of T or dehydroepiandrosterone for the prevention or treatment of coronary heart disease.

Effect of estrogen replacement therapy on distribution of myocardial blood flow in female anesthetized rabbits

Estrogen replacement therapy reduces risk of cardiovascular events by altering coronary vasoregulation and distribution of blood flow. Vessel reactivity and blood flow distribution were assessed in anesthetized female rabbits in the following groups: 1) sham, 2) ovariectomy, 3) ovariectomy + 17beta-estradiol, and 4) ovariectomy + dehydroepiandrosterone. After a 2-wk treatment, cardiac hemodynamics, vascular reserve, and blood flow were evaluated during the following infusions: 1) NaCl, or vehicle (0.5 ml/min), 2) acetylcholine (2 mg/kg), 3) isoproterenol (2 mg. kg(-1). min(-1)), and 4) chromonar (8 mg/kg). In hearts from ovariectomized rabbits, autoregulatory blood flow was preserved despite lower diastolic perfusion pressures (55 +/- 8 vs. 64 +/- 8 mmHg in sham) and rate-pressure product (14.4 +/- 0.8 vs. 19.3 +/- 0.8 beats/min. mmHg x 10(-3)). Estrogen replacement therapy restored coronary pressure and reserve, and all drugs increased vascular conductance. In conclusion, in hearts from ovariectomized rabbits, vascular reserve declined because coronary pressure was lower; however, blood flow was preserved at a higher level than expected for oxygen demand. Estrogen replacement therapy restores myocardial oxygen supply-demand indices and returns coronary pressure-flow data to levels observed in animals with intact ovaries.

Sex-specific action of insulin to acutely increase the metabolic clearance rate of dehydroepiandrosterone in humans

To test the hypothesis that insulin acutely enhances the metabolic clearance rate (MCR) of dehydroepiandrosterone in humans, the effect of a short-term insulin infusion on the MCR of dehydroepiandrosterone was assessed in 10 men and 7 women. After an overnight fast, dehydroepiandrosterone was infused at 3.47 mumol/h for 6.5 h. At 240 min, a hyperinsulinemic-euglycemic clamp was begun by infusing insulin at 21.5 pmol/kg per min for 2.5 h. MCR of dehydroepiandrosterone was calculated at baseline (210-240 min) and during the insulin infusion (360-390 min). A control study was conducted at least 1 wk later, in which 0.45% saline was substituted for the hyperinsulinemic-euglycemic clamp. During the insulin clamp study, serum insulin rose from 34 +/- 2 to 1084 +/- 136 pmol/liter (P = 0.0001) in men and from 40 +/- 5 to 1357 +/- 175 pmol/liter (P = 0.0003) in women, while serum glucose remained constant in both groups. MCR of dehydroepiandrosterone rose in men during the insulin infusion from 2443 +/- 409 to 3599 +/- 500 liters/24 h (P = 0.003), but did not change during the control saline infusion. In contrast, MCR of dehydroepiandrosterone in women did not change in the insulin clamp study during insulin infusion (2526 +/- 495 liters/24 h at baseline vs. 2442 +/- 491 liters/24 h during insulin infusion; P = 0.78). These findings suggest that insulin acutely increases the MCR of dehydroepiandrosterone in men but not in women.