Effect of testosterone on ex vivo vascular reactivity in man

Blood pressure responses to testosterone therapy are amplified by hematocrit levels in opioid-induced androgen deficiency: a double-blind, randomized, placebo-controlled trial

Our study aimed to examine the effect of testosterone replacement therapy (TRT) on blood pressure in opioid-treated men with relative hypogonadism, and whether the effect of TRT on blood pressure was modified by body composition, red blood cell levels, or carotid intima media thickness. Men (over 18 years old) receiving opioid treatment and total testosterone less than 12 nmol were randomly assigned to receive either TRT or placebo. Baseline and 6-month measurements included anthropometric measurements, office blood pressure (OBPM), 24-h ambulatory blood pressure, blood samples, and carotid ultrasound. The mean systolic OBPM increased by 6.2 mmHg (0.2-12.1) in the TRT group and decreased by 7.0 mmHg (1.0-15.1) in the placebo group, with a mean difference of 13.2 mmHg (3.4-23.1), P  = 0.01. In the TRT group, a 10 mmHg increase in systolic OBPM was associated with an increase in hematocrit of 0.3% points (0.1-0.5) ( P  = 0.01), whereas no association was observed in the placebo group ( P  = 0.266). Daytime SBP showed a nonsignificant increase of 5.2 mmHg (-1.7, 12.1) ( P  = 0.134) in the TRT group compared to that in the placebo group. However, the impact of TRT on the increase in daytime ambulatory blood pressure was significantly accentuated by baseline values of BMI, hematocrit, and hemoglobin. In conclusion, TRT was associated with higher OBPM compared to placebo, and the increase in blood pressure was linked to higher hematocrit during TRT. Our data suggest that men with opioid-induced androgen deficiency, particularly those with obesity or red blood cell levels in the upper normal range, are more susceptible to increased daytime SBP during TRT.

Effects of Sex Hormones on Vascular Reactivity in Boys With Hypospadias

BACKGROUND

Arteries from boys with hypospadias demonstrate hypercontractility and impaired vasorelaxation. The role of sex hormones in these responses in unclear.

AIMS

We compared effects of sex steroids on vascular reactivity in healthy boys and boys with hypospadias.

METHODS

Excess foreskin tissue was obtained from 11 boys undergoing hypospadias repair (cases) and 12 undergoing routine circumcision (controls) (median age [range], 1.5 [1.2-2.7] years) and small resistance arteries were isolated. Vessels were mounted on wire myographs and vascular reactivity was assessed in the absence/presence of 17β-estradiol, dihydrotestosterone (DHT), and testosterone.

RESULTS

In controls, testosterone and 17β-estradiol increased contraction (percent of maximum contraction [Emax]: 83.74 basal vs 125.4 after testosterone, P < .0002; and 83.74 vs 110.2 after estradiol, P = .02). 17β-estradiol reduced vasorelaxation in arteries from controls (Emax: 10.6 vs 15.6 to acetylcholine, P < .0001; and Emax: 14.6 vs 20.5 to sodium nitroprusside, P < .0001). In hypospadias, testosterone (Emax: 137.9 vs 107.2, P = .01) and 17β-estradiol (Emax: 156.9 vs 23.6, P < .0001) reduced contraction. Androgens, but not 17β-estradiol, increased endothelium-dependent and endothelium-independent vasorelaxation in cases (Emax: 77.3 vs 51.7 with testosterone, P = .02; and vs 48.2 with DHT to acetylcholine, P = .0001; Emax: 43.0 vs 39.5 with testosterone, P = .02; and 39.6 vs 37.5 with DHT to sodium nitroprusside, P = .04).

CONCLUSION

In healthy boys, testosterone and 17β-estradiol promote a vasoconstrictor phenotype, whereas in boys with hypospadias, these sex hormones reduce vasoconstriction, with androgens promoting vasorelaxation. Differences in baseline artery function may therefore be sex hormone-independent and the impact of early-life variations in androgen exposure on vascular function needs further study.

Additive damage in the thromboxane related vasoconstriction and bradykinin relaxation of intramural coronary resistance arterioles in a rodent model of andropausal hypertension

Hypertension and andropause both accelerate age–related vascular deterioration. We aimed to evaluate the effects of angiotensin-II induced hypertension and deficiency of testosterone combined regarding the resistance coronaries found intramurally.

Four male groups were formed from the animals: control group (Co, n = 10); the group that underwenr orchidectomy (ORC, n = 13), those that received an infusion of angiotensin-II (AII, n = 10) and a grous that received AII infusion and were also surgically orchidectomized (AII + ORC, n = 8). AII and AII + ORC animals were infused with infusing angiotensin-II (100 ng/min/kg) using osmotic minipumps. Orchidectomy was perfomed in the ORC and the AII + ORC groupsto establish deficiency regarding testosterone. Following four weeks of treatment, pressure-arteriography was performed in vitro, and the tone induced by administration of thromboxane-agonist (U46619) and bradykinin during analysis of the intramural coronaries (well-known to be resistance arterioles) was studied.

U46619-induced vasoconstriction poved to be significantly decreased in the ORC and AII + ORC groups when compared with Co and AII animals. In ORC and AII + ORC groups, the bradykinin-induced relaxation was also significantly reduced to a greater extent compared to Co and AII rats. Following orchidectomy, the vasocontraction and vasodilatation capacity of blood vessels is reduced. The effect of testosterone deficiency on constrictor tone and relaxation remains pronounced even in AII hypertension: testosterone deficiency further narrows adaptation range in the double noxa (AII + ORC) group. Our studies suggest that vascular changes caused by high blood pressure and testosterone deficiency together may significantly increase age-related cardiovascular risk.

Androgens and Non-Genomic vascular responses in hypertension

Arterial hypertension is a global public health concern. In the last few years, the interest in androgen deficiency has been growing, and the association between androgens and high blood pressure (BP) is still controversial. One purpose of this review was to summarize the available findings in order to clarify whether male sex steroid hormones have beneficial or harmful effect on BP. The second purpose was to enhance the recognition of the acute non-genomic sex-independent vasorelaxing effect of androgens. Remarkably, BP variation is expected to be a consequence of the androgen-induced vasorelaxation which reduces systemic BP; hence the in vivo vasodepressor, hypotensive, and antihypertensive responses of androgens were also analyzed. This article reviews the current understanding of the physiological regulation of vascular smooth muscle contractility by androgens. Additionally, it summarizes older and more recent data on androgens, and some of the possible underlying mechanisms of relaxation, structural-functional differences in the androgen molecules, and their designing ability to induce vasorelaxation. The clinical relevance of these findings in terms of designing future therapeutics mainly the 5-reduced metabolite of testosterone, 5β-dihydrotestosterone, is also highlighted. Literature collected through a PubMed database search, as well as our experimental work, was used for the present review.

Vascular mechanisms of testosterone: The non-genomic point of view

Testosterone (T) is the predominant endogenous androgen in the bloodstream. At the vascular level, T presents genomic and non-genomic effects, and both effects may overlap. The genomic actions assume that androgens can freely cross the plasma membrane of target cells and bind to nuclear androgen receptors, inducing gene transcription and protein synthesis. The non-genomic effects have a more rapid onset and may be related to the interaction with protein/receptor/ion channels of the plasma membrane. The key T effect at the vascular level is vasorelaxation, which is primarily due to its rapid effect. Thus, the main purpose of this review is to discuss the T non-genomic effects at the vascular level and the molecular pathways involved in its vasodilator effect observed in in vivo and in vitro studies. In this sense, the nuclear receptor activation, the influence of vascular endothelium and the activation or inhibition of ion channels (potassium and calcium channels, respectively) will be reviewed regarding all the data that corroborated or not. Moreover, this review also provides a brief update on the association of T with the risk factors for cardiovascular diseases, namely metabolic syndrome, type 2 diabetes mellitus, obesity, atherosclerosis, dyslipidaemia, and hypertension. In summary, in this paper we consider the non-genomic vascular mode of action of androgen in physiological conditions and the main risk factors for cardiovascular diseases.

Androgens are effective bronchodilators with anti-inflammatory properties: A potential alternative for asthma therapy

Changes in plasma androgen levels in asthmatic men may be linked to asthma severity, seemingly acting through nongenomic and genomic effects. Nongenomic effects include rapid relaxation of carbachol or antigenic challenge pre-contracted guinea pig airway smooth muscle (ASM) in vitro: testosterone (TES) blocks l-type voltage dependent Ca²⁺ channels, stored operated Ca²⁺ channels, inositol 1,4,5-trisphosphate receptors and promotes prostaglandin E₂ biosynthesis. In ASM at rest, TES lowers basal intracellular Ca²⁺ concentration and tension, maintaining a proper airway patency keeping steady smooth muscle tension and basal intracellular Ca²⁺ concentration at rest. Moreover, the bronchospasm in sensitized guinea-pigs was ablated by dehydroepiandrosterone (DHEA), a precursor of steroids, TES and its metabolites 5α- and 5β-dihydrotestosterone (DHT). On the other hand, genomic effects related to androgens' anti-inflammatory properties in asthma have been recently studied. Briefly, TES negatively regulates type 2 immune response sustained by CD4+ Th2 and group 2 innate lymphoid cells, diminishing allergic airway inflammation in males. Also, novel findings establish that TES decreases interleukin (IL)-17A protein expression produced by CD4+ Th17 cells and therefore neutrophilic airway inflammation. Clearly, DHEA, TES or its 5β-reduced metabolite that possesses minimal androgenic effect, might have potential therapeutic capacities in the treatment of severe asthma via mechanisms distinct from corticosteroid treatment.

Androgen-Regulated Cardiac Metabolism in Aging Men

The prevalence of cardiovascular mortality is higher in men than in age-matched premenopausal women. Gender differences are linked to circulating sex-related steroid hormone levels and their cardio-specific actions, which are critical factors involved in the prevalence and features of age-associated cardiovascular disease. In women, estrogens have been described as cardioprotective agents, while in men, testosterone is the main sex steroid hormone. The effects of testosterone as a metabolic regulator and cardioprotective agent in aging men are poorly understood. With advancing age, testosterone levels gradually decrease in men, an effect associated with increasing fat mass, decrease in lean body mass, dyslipidemia, insulin resistance and adjustment in energy substrate metabolism. Aging is associated with a decline in metabolism, characterized by modifications in cardiac function, excitation-contraction coupling, and lower efficacy to generate energy. Testosterone deficiency -as found in elderly men- rapidly becomes an epidemic condition, associated with prominent cardiometabolic disorders. Therefore, it is highly probable that senior men showing low testosterone levels will display symptoms of androgen deficiency, presenting an unfavorable metabolic profile and increased cardiovascular risk. Moreover, recent reports establish that testosterone replacement improves cardiomyocyte bioenergetics, increases glucose metabolism and reduces insulin resistance in elderly men. Thus, testosterone-related metabolic signaling and gene expression may constitute relevant therapeutic target for preventing, or treating, age- and gender-related cardiometabolic diseases in men. Here, we will discuss the impact of current evidence showing how cardiac metabolism is regulated by androgen levels in aging men.

Randomized controlled trials - mechanistic studies of testosterone and the cardiovascular system

Testosterone deficiency is common in men with cardiovascular disease (CVD), and randomized placebo-controlled trials (RCTs) have reported beneficial effects of testosterone therapy on exercise-induced cardiac ischemia in chronic stable angina, functional exercise capacity, maximum oxygen consumption during exercise (VO_2max) and muscle strength in chronic heart failure (CHF), shortening of the Q-T interval, and improvement of some cardiovascular risk factors. Testosterone deficiency is associated with an adverse CV risk profile and mortality. Clinical and scientific studies have provided mechanistic evidence to support and explain the findings of the RCTs. Testosterone is a rapid-onset arterial vasodilator within the coronary circulation and other vascular beds including the pulmonary vasculature and can reduce the overall peripheral systemic vascular resistance. Evidence has demonstrated that testosterone mediates this effect on vascular reactivity through calcium channel blockade (L-calcium channel) and stimulates potassium channel opening by direct nongenomic mechanisms. Testosterone also stimulates repolarization of cardiac myocytes by stimulating the ultra-rapid potassium channel-operated current. Testosterone improves cardiac output, functional exercise capacity, VO_2max and vagally mediated arterial baroreceptor cardiac reflex sensitivity in CHF, and other mechanisms. Independent of the benefit of testosterone on cardiac function, testosterone substitution may also increase skeletal muscle glucose metabolism and enhance muscular strength, both factors that could contribute to the improvement in functional exercise capacity may include improved glucose metabolism and muscle strength. Testosterone improves metabolic CV risk factors including body composition, insulin resistance, and hypercholesterolemia by improving both glucose utilization and lipid metabolism by a combination of genomic and nongenomic actions of glucose uptake and utilization expression of the insulin receptor, glucose transporters, and expression on regulatory enzymes of key metabolic pathways. The effect on high-density lipoprotein-cholesterol (HDL-C) differs between studies in that it has been found to fall, rise, or have no change in levels. Testosterone replacement can suppress the levels of circulating pro-inflammatory cytokines and stimulate the production of interleukin-10 (IL-10) which has anti-inflammatory and anti-atherogenic actions in men with CVD. No effect on C-reactive protein has been detected. No adverse effects on clotting factors have been detected. RCTs have not clearly demonstrated any significant evidence that testosterone improves or adversely affects the surrogate markers of atherosclerosis such as reduction in carotid intima thickness or coronary calcium deposition. Any effect of testosterone on prevention or amelioration of atherosclerosis is likely to occur over years as shown in statin therapy trials and not months as used in testosterone RCTs. The weight of evidence from long-term epidemiological studies supports a protective effect as evidenced by a reduction in major adverse CV events (MACEs) and mortality in studies which have treated men with testosterone deficiency. No RCT where testosterone has been replaced to the normal healthy range has reported a significant benefit or adverse effect on MACE nor has any recent meta-analysis.

Vasoactive androgens: Vasorelaxing effects and their potential regulation of blood pressure

BACKGROUND

Testosterone, 5α- and 5β-dihydrotestosterone (-DHT) induce an acute in vitro vasorelaxation and in vivo vasodepressor, hypotensive and antihypertensive responses. Our aim was to study whether androgen-induced blood pressure (BP) reduction is involved with a blockade of Ca²⁺ influx through L-type voltage-operated calcium channels (L-VOCCs) and/or the signaling pathways of α₁-adrenoceptors to induce vasoconstriction, which are one of the major mechanisms of BP maintenance.

MATERIALS AND METHODS

The relaxing potency and efficacy of each androgen in large conduit (thoracic aorta) and resistance (mesenteric) arteries from male hypertensive (SHR) and normotensive (WKY) rats were established. Blood vessels were isometrically recorded and precontracted with KCl or phenylephrine (Phe).

RESULTS

Androgens induced concentration-dependent vasorelaxation in precontracted arteries from SHR and WKY rats. 5β-DHT was always the most potent vasorelaxant in arteries from SHR. The KCl-induced contraction resulted significantly more sensitive to androgen-induced vasorelaxation than the Phe-induced contraction. On Phe-induced contraction, 5β-DHT was more potent in the mesenteric artery than in the thoracic aorta.

CONCLUSIONS

The vasorelaxation induced by androgens is mainly mediated by blocking L-VOCCs and in lesser extent by the blockade of multiple signaling pathways operative during α-adrenoceptor-induced vasoconstriction. 5β-DHT regulates vascular resistance and BP by mainly acting in the mesenteric arterial bed, which may explain its outstanding antihypertensive response previously reported.

A 3-year observation of testosterone deficiency in Chinese patients with chronic heart failure

Testosterone deficiency is present in a certain proportion men with chronic heart failure (CHF). Low testosterone levels in American and European patients with CHF lead to the high mortality and readmission rates. Interestingly, this relationship has not been studied in Chinese patients. To this end, 167 Chinese men with CHF underwent clinical and laboratory evaluations associated with determinations of testosterone levels. Total testosterone (TT) levels and sex hormone-binding globulin were measured by chemiluminescence or immunoassays assays and free testosterone (FT) levels were calculated, Based upon results from these assays, patients were divided into either a low testosterone (LT; n = 93) or normal testosterone (NT; n = 74) group. Subsequently, records from each patient were reviewed over a follow-up duration of at least 3 years. Patients in the LT group experienced worse cardiac function and a higher prevalence of etiology (ischemic vs. no ischemic) and comorbidity (both P < 0.05). In addition, readmission rates of patients in the LT group were higher than that of patients in the NT group (3.32 ± 1.66 VS 1.57 ± 0.89). Overall, deficiencies in FT levels were accompanied with increased mortalities (HR = 6.301, 95% CI 3.187–12.459, P < .0001).

Sex steroids effects on guinea pig airway smooth muscle tone and intracellular Ca2+ basal levels

Testosterone (TES), other androgens and female sex steroids induce non-genomic rapid relaxing effects in airway smooth muscle (ASM). In guinea pig ASM, basal tension was relaxed by dehydroepiandrosterone (DHEA) and TES; 17β-estradiol (E2) had a small effect. Blockers of L-type voltage dependent Ca²⁺ channel (L-VDCC, D-600) and store operated Ca²⁺ channel (SOC, 2-APB) also relaxed the basal tone. In tracheal myocytes, DHEA and TES diminished intracellular basal Ca²⁺ concentrations (_b[Ca²⁺]_i) as D-600+2-APB but to a higher extend. TES after D-600+2APB or Pyr3, a blocker of canonical transient receptor potential 3 (TRPC3), further decreased _b[Ca²⁺]_i rendering this response equal to TES alone. With indomethacin, the _b[Ca²⁺]_i decrease induced by the blockade of L-VDCC and TRPC3 was not changed by the addition of TES. PGE₂ or forskolin addition after D600+2-APB, decreased _b[Ca²⁺]_i resembling TES response. An adenylate cyclase inhibitor followed by D-600+2-APB lowered _b[Ca²⁺]_i, TES showed no further effect. Carbachol-induced [Ca²⁺]i increment was reduced by TES or DHEA. 17β-estradiol diminished KCl-induced contraction and, in tracheal myocytes, the voltage-dependent inward Ca²⁺ current.

CONCLUSION

DHEA and TES diminish ASM tone and _b[Ca²⁺]i by blocking L-VDCC and probably a constitutively active TRPC3, and by PGE₂ synthesis. E2 lowers ASM basal tone by blocking only L-VDCC.

Effects of two-year testosterone replacement therapy on cognition, emotions and quality of life in young and middle-aged hypogonadal men

The aim of the study was to examine the effects of two-year testosterone replacement therapy on cognitive functioning, emotional state and quality of life in young and middle-aged men with hypogonadotropic hypogonadism. Nineteen males diagnosed with hypogonadotropic hypogonadism participated in the study. Cognitive functions were assessed by Trail Making Test and Digit Span Test of Wechsler Adult Intelligence Scale. Emotional state was evaluated by Profile of Mood States. Quality of life was evaluated by WHO Brief Quality of Life Questionnaire. Changes after two-year testosterone replacement therapy were detected in Trail Making A (42.9 ± 22.3 vs. 36.2 ± 22.5, p = .050) and B (90.6 ± 55.3 vs. 65.6 ± 21.4, p = .025) tests, showing improvement in attention and visual scanning abilities, executive function and psychomotor speed, as well as in Digit Span Test forward score (5.4 ± 2.0 vs. 6.1 ± 2.6, p = .046), showing improvement in attention capacity and psychomotor speed. No significant differences were observed in emotional state and quality of life. In conclusion, beneficial effect in cognitive functioning (improved attention and visual scanning ability, executive function and psychomotor speed), but not in emotional state and quality of life, was observed in young and middle-aged hypogonadal men after two-year testosterone replacement therapy.

Androgen receptor (AR) in cardiovascular diseases

Cardiovascular diseases (CVDs) are still the highest leading cause of death worldwide. Several risk factors have been linked to CVDs, including smoking, diabetes, hyperlipidemia, and gender among others. Sex hormones, especially the androgen and its receptor, androgen receptor (AR), have been linked to many diseases with a clear gender difference. Here, we summarize the effects of androgen/AR on CVDs, including hypertension, stroke, atherosclerosis, abdominal aortic aneurysm (AAA), myocardial hypertrophy, and heart failure, as well as the metabolic syndrome/diabetes and their impacts on CVDs. Androgen/AR signaling exacerbates hypertension, and anti-androgens may suppress hypertension. Androgen/AR signaling plays dual roles in strokes, depending on different kinds of factors; however, generally males have a higher incidence of strokes than females. Androgen and AR differentially modulate atherosclerosis. Androgen deficiency causes elevated lipid accumulation to enhance atherosclerosis; however, targeting AR in selective cells without altering serum androgen levels would suppress atherosclerosis progression. Androgen/AR signaling is crucial in AAA development and progression, and targeting androgen/AR profoundly restricts AAA progression. Men have increased cardiac hypertrophy compared with age-matched women that may be due to androgens. Finally, androgen/AR plays important roles in contributing to obesity and insulin/leptin resistance to increase the metabolic syndrome.

Basic Science Evidence for the Link Between Erectile Dysfunction and Cardiometabolic Dysfunction

INTRODUCTION

Although clinical evidence supports an association between cardiovascular/metabolic diseases (CVMD) and erectile dysfunction (ED), scientific evidence for this link is incompletely elucidated.

AIM

This study aims to provide scientific evidence for the link between CVMD and ED.

METHODS

In this White Paper, the Basic Science Committee of the Sexual Medicine Society of North America assessed the current literature on basic scientific support for a mechanistic link between ED and CVMD, and deficiencies in this regard with a critical assessment of current preclinical models of disease.

RESULTS

A link exists between ED and CVMD on several grounds: the endothelium (endothelium-derived nitric oxide and oxidative stress imbalance); smooth muscle (SM) (SM abundance and altered molecular regulation of SM contractility); autonomic innervation (autonomic neuropathy and decreased neuronal-derived nitric oxide); hormones (impaired testosterone release and actions); and metabolics (hyperlipidemia, advanced glycation end product formation).

CONCLUSION

Basic science evidence supports the link between ED and CVMD. The Committee also highlighted gaps in knowledge and provided recommendations for guiding further scientific study defining this risk relationship. This endeavor serves to develop novel strategic directions for therapeutic interventions.

Androgen deprivation therapy reversibly increases endothelium-dependent vasodilation in men with prostate cancer

Background

Androgen deprivation therapy (ADT) is a standard treatment for patients with aggressive prostate cancer. Although ADT improves survival, it increases the risk of diabetes. Emerging evidence suggests that ADT increases adverse cardiovascular events as early as 3 months after initiation in patients with cardiovascular disease, but the mechanism is unknown. We hypothesized that ADT may impair endothelium‐dependent vasodilation due to increases in lipids and insulin resistance and may provide a link for heightened cardiovascular risk in this population.

Methods and Results

We prospectively evaluated conduit artery endothelium‐dependent and ‐independent vasodilation, lipids, and insulin resistance in 16 consecutively treated men (mean age 66±7 years; 25% with diabetes) with prostate cancer before and after 3 months of ADT. High‐resolution B‐mode ultrasound was used to assess flow‐mediated (endothelium‐dependent) and nitroglycerine‐mediated (endothelium‐independent) brachial artery vasodilation. ADT significantly increased insulin resistance, total cholesterol, HDL, and LDL. Endothelium‐dependent vasodilation was greater at 3 months than at baseline (10.8% [interquartile range: 7.7% to 14.6%] versus 8.9% [interquartile range: 4.0% to 12.6%], respectively; P=0.046, allometric P=0.037). Nitroglycerine‐mediated vasodilation did not change from baseline (P>0.2). The subset of participants on ADT for 6 months returned for reevaluation at 1 year. In this group, endothelium‐dependent vasodilation increased from baseline to 3 months and returned to baseline 6 months after ADT withdrawal (9.4% [interquartile range: 6.9% to 10.9%], 11.6% [interquartile range: 7.9% to 15.2%], and 9.0% [interquartile range: 5.1% to 12.5%], respectively; P=0.05).

Conclusions

In contrast to our expectation, ADT improved endothelium‐dependent vasodilation and its cessation returned endothelium‐dependent vasodilation to baseline. Determining the mechanism of this change requires further investigation.

Crucial role of androgen receptor in vascular H2S biosynthesis induced by testosterone

BACKGROUND AND PURPOSE

Hydrogen sulphide (H2S) is a gaseous mediator strongly involved in cardiovascular homeostasis, where it provokes vasodilatation. Having previously shown that H2 S contributes to testosterone-induced vasorelaxation, here we aim to uncover the mechanisms underlying this effect.

EXPERIMENTAL APPROACH

H2 S biosynthesis was evaluated in rat isolated aortic rings following androgen receptor (NR3C4) stimulation. Co-immunoprecipitation and surface plasmon resonance analysis were performed to investigate mechanisms involved in NR3C4 activation.

KEY RESULTS

Pretreatment with NR3C4 antagonist nilutamide prevented testosterone-induced increase in H2S and reduced its vasodilator effect. Androgen agonist mesterolone also increased H2S and induced vasodilatation; effects attenuated by the selective cystathionine-γ lyase (CSE) inhibitor propargylglycine. The NR3C4-multicomplex-derived heat shock protein 90 (hsp90) was also involved in this effect; its specific inhibitor geldanamycin strongly reduced testosterone-induced H2S production. Neither progesterone nor 17-β-oestradiol induced H2S release. Furthermore, we demonstrated that CSE, the main vascular H2S-synthesizing enzyme, is physically associated with the NR3C4/hsp90 complex and the generation of such a ternary system represents a key event leading to CSE activation. Finally, H2S levels in human blood collected from male healthy volunteers were higher than those in female samples.

CONCLUSIONS AND IMPLICATIONS

We demonstrated that selective activation of the NR3C4 is essential for H2S biosynthesis within vascular tissue, and this event is based on the formation of a ternary complex between cystathionine-γ lyase, NR3C4and hsp90. This novel molecular mechanism operating in the vasculature, corroborated by higher H2S levels in males, suggests that the L-cysteine/CSE/H2S pathway may be preferentially activated in males leading to gender-specific H2S biosynthesis.

Testosterone and cardiovascular disease

PURPOSE OF REVIEW

Use of testosterone among men is increasing rapidly. Low serum testosterone is positively associated with cardiovascular disease and its risk factors. No large randomized controlled trial (RCT) has assessed the effects of testosterone on cardiovascular outcomes. Here recent evidence accumulating from other sources - pharmacoepidemiology, Mendelian randomization studies and meta-analysis of small RCTs - is reviewed to inform current testosterone usage.

RECENT FINDINGS

In a large, well conducted pharmacoepidemiology study specifically testosterone prescription was associated with myocardial infarction. Two Mendelian randomization studies did not corroborate beneficial effects of higher endogenous testosterone on cardiovascular risk factors, but suggested higher endogenous testosterone raised LDL cholesterol and lowered HDL cholesterol. A comprehensive meta-analysis of RCTs summarizing 27 trials including 2994 men found increased risk of cardiovascular-related events on testosterone (odds ratio 1.54, 95% confidence interval 1.09-2.18).

SUMMARY

Contrary to expectations from observational studies, current indications suggest testosterone causes ischemic cardiovascular disease with corresponding implications for practice. A large RCT would undoubtedly settle the issue definitively. Given mounting evidence of harm and the urgency of the situation assembling all the evidence from completed RCTs of testosterone or androgen deprivation therapy and use of Mendelian randomization might generate a definitive answer most quickly.

Testosterone-induced relaxation involves L-type and store-operated Ca2+ channels blockade, and PGE 2 in guinea pig airway smooth muscle

In vascular smooth muscle, it has been described that testosterone (TES) produces relaxation by blocking L-type Ca(2+) channels. Recently, we found that L-type Ca(2+) and store-operated Ca(2+) (SOC) channels are the main membranal structures that provide extracellular Ca(2+) for carbachol (CCh)-induced contraction in airway smooth muscle (ASM). We studied the possible interactions between L-type and SOC channels in TES-induced relaxation in guinea pig ASM. TES (10, 32, 100, and 178 μM) induced a complete relaxation of CCh-precontracted tracheal smooth muscle, and indomethacin partially inhibited this response. In single myocytes, the KCl-induced intracellular Ca(2+) increase ([Ca(2+)]i) was decreased by 32 and completely blocked by 100 nM TES. This androgen (32 and 100 μM) significantly diminished (~25 and 49 %, respectively) the capacitative Ca(2+) entry. Myocytes stimulated with CCh produced a transient Ca(2+) peak followed by a sustained plateau. D-600 was added during the plateau phase, and a partial diminution (~35 %) was observed. A greater decrease (~78 %) was seen when 2-aminoethyl diphenylborinate (2-APB, SOC antagonist) was used. The combination of both drugs completely abolished the Ca(2+) plateau induced by CCh. TES (100 μM) also completely abolished the CCh-induced Ca(2+) plateau. Indomethacin significantly diminished this effect of TES. PGE2 and butaprost proportionally decreased the Ca(2+) plateau as indomethacin blocked it. Sarcoplasmic reticulum refilling was partially, dependently, and significantly diminished by TES. We concluded that TES-induced relaxation involves blockade of L-type Ca(2+) channels at nanomolar and SOC channels at micromolar concentration and PGE2 seems to be also involved in this phenomenon.

Androgen activity, ischaemic heart disease and risk factors among men in NHANES III

AIM

Observationally, low serum testosterone among men is associated with cardiovascular diseases and its risk factors, but it is unclear whether raising endogenous androgens would be protective. To clarify the role of androgens, the association of two different androgen biomarkers (serum testosterone and androstanediol glucuronide) with cardiovascular disease risk factors and mortality was examined in a nationally representative sample of US men.

RESEARCH DESIGN AND METHODS

Multivariable linear and proportion hazards regression were used to examine the adjusted associations of serum testosterone and androstanediol glucuronide with cardiovascular disease risk factors and death from major cardiovascular diseases in 1460 men from NHANES III phase 1 (1988-1991) followed-up through 2006.

RESULTS

Serum testosterone and androstanediol glucuronide were weakly correlated (0·13). Serum testosterone was associated with healthier values of most cardiovascular disease risk factors but not with death from ischaemic heart disease or stroke, adjusted for age, education, race/ethnicity, smoking and alcohol use. Similarly adjusted, androstanediol glucuronide was associated with unhealthier values of some cardiovascular risk factors and death from ischaemic heart disease (hazard ratio 1·16, 95% confidence interval 1·003-1·33 per standard deviation).

CONCLUSIONS

Androgen biomarkers had inconsistent associations with cardiovascular disease risk factors and ischaemic heart disease. Androstanediol glucuronide, rather than serum testosterone, had associations with cardiovascular disease risk factors more similar to those seen in randomized controlled trials of testosterone therapy, with corresponding implications for raising androgens.

Beneficial and adverse effects of testosterone on the cardiovascular system in men

CONTEXT

The widespread use of T therapy, particularly in aging males, necessitates knowledge of the relationship between T and the cardiovascular system.

EVIDENCE ACQUISITION

The review is based on a 1970 to 2013 PubMed search with terms related to androgens in combination with cardiovascular disease, including T, dihydrotestosterone, trial, mortality, cardiovascular disease, myocardial infarction, blood pressure, endothelial function, dyslipidemia, thrombosis, ventricular function, and arrhythmia. Original articles, systematic reviews and meta-analyses, and relevant citations were screened.

EVIDENCE SYNTHESIS

Low T has been linked to increased blood pressure, dyslipidemia, atherosclerosis, arrhythmia, thrombosis, endothelial dysfunction, as well as to impaired left ventricular function. On the one hand, a modest association is suggested between low endogenous T and incident cardiovascular disease or cardiovascular mortality, implying unrecognized beneficial T effects, residual confounding, or a relationship with health status. On the other hand, treatments with T to restore "normal concentrations" have so far not been proven to be beneficial with respect to cardiovascular disease; neither have they definitely shown specific adverse cardiovascular effects. The cardiovascular risk-benefit profile of T therapy remains largely evasive in view of a lack of well-designed and adequately powered randomized clinical trials.

CONCLUSIONS

The important knowledge gap as to the exact relationship between T and cardiovascular disease would support a cautious, restrained approach to T therapy in aging men, pending clarification of benefits and risks by adequately powered clinical trials of sufficient duration.

Testosterone: a vascular hormone in health and disease

Coronary heart disease is a leading cause of premature death in men. Epidemiological studies have shown a high prevalence of low serum testosterone levels in men with cardiovascular disease (CVD). Furthermore, a low testosterone level is associated in some but not in all observational studies with an increase in cardiovascular events and mortality. Testosterone has beneficial effects on several cardiovascular risk factors, which include cholesterol, endothelial dysfunction and inflammation: key mediators of atherosclerosis. A bidirectional relationship between low endogenous testosterone levels and concurrent illness complicates attempts to validate causality in this association and potential mechanistic actions are complex. Testosterone is a vasoactive hormone that predominantly has vasodilatory actions on several vascular beds, although some studies have reported conflicting effects. In clinical studies, acute and chronic testosterone administration increases coronary artery diameter and flow, improves cardiac ischaemia and symptoms in men with chronic stable angina and reduces peripheral vascular resistance in chronic heart failure. Although the mechanism of the action of testosterone on vascular tone in vivo is not understood, laboratory research has found that testosterone is an L-calcium channel blocker and induces potassium channel activation in vascular smooth muscle cells. Animal studies have consistently demonstrated that testosterone is atheroprotective, whereas testosterone deficiency promotes the early stages of atherogenesis. The translational effects of testosterone between in vitro animal and human studies, some of which have conflicting effects, will be discussed in this review. We review the evidence for a role of testosterone in vascular health, its therapeutic potential and safety in hypogonadal men with CVD, and some of the possible underlying mechanisms.

Early life stress induces renal dysfunction in adult male rats but not female rats

Maternal separation (MatSep) is a model of behavioral stress during early life. We reported that MatSep exacerbates ANG II-induced hypertension in adult male rats. The aims of this study were to determine whether exposure to MatSep in female rats sensitizes blood pressure to ANG II infusion similar to male MatSep rats and to elucidate renal mechanisms involved in the response in MatSep rats. Wistar Kyoto (WKY) pups were exposed to MatSep 3 h/day from days 2 to 14, while control rats remained with their mothers. ANG II-induced mean arterial pressure (MAP; telemetry) was enhanced in female MatSep rats compared with control female rats but delayed compared with male MatSep rats. Creatinine clearance (Ccr) was reduced in male MatSep rats compared with control rats at baseline and after ANG II infusion. ANG II infusion significantly increased T cells in the renal cortex and greater histological damage in the interstitial arteries of male MatSep rats compared with control male rats. Plasma testosterone was greater and estradiol was lower in male MatSep rats compared with control rats with ANG II infusion. ANG II infusion failed to increase blood pressure in orchidectomized male MatSep and control rats. Female MatSep and control rats had similar Ccr, histological renal analysis, and sex hormones at baseline and after ANG II infusion. These data indicate that during ANG II-induced hypertension, MatSep sensitizes the renal phenotype in male but not female rats.

Altered insulin-induced relaxation of aortic rings in a dihydrotestosterone-induced rodent model of polycystic ovary syndrome

OBJECTIVE

To clarify the effects of dihydrotestosterone (DHT)-induced polycystic ovary syndrome (PCOS) on the insulin-dependent vasodilatation of the thoracic aorta and the role of vitamin D in a rat model.

DESIGN

Controlled experimental animal study.

SETTING

Laboratory.

ANIMAL(S)

Thirty adolescent female Wistar rats.

INTERVENTION(S)

The PCOS model was induced by 10 weeks of DHT treatment (83 μg/d). One-half of the DHT-treated animals also received vitamin D (120 ng/kg/wk).

MAIN OUTCOME MEASURE(S)

The aortic rings of the control, DHT, and DHT plus vitamin D-treated animals were isolated. The insulin-dependent vasodilation of the isolated aortic rings was compared in Krebs-Ringer solution and under blockade of nitric oxide (NO) synthase or cyclooxygenase.

RESULT(S)

The insulin-dependent vasorelaxation decreased in both DHT-treated groups independently from the vitamin D treatment; NO-dependent and -independent relaxations were both impaired. In response to prostanoid, vasoconstriction was increased after DHT treatment. The NO-independent relaxation was partially improved by vitamin D treatment, which was neutralized by increased prostanoid-dependent vasoconstriction.

CONCLUSION(S)

Previously, we found that vitamin D treatment prevented systemic insulin resistance; however, in this study, we did not detect any influence on the vascular insulin resistance of the aorta that was induced by DHT treatment. Consequently, controlling insulin resistance with vitamin D alone did not resolve the aortic endothelial dysfunction caused by the hyperandrogenic state.

The vulnerable man: impact of testosterone deficiency on the uraemic phenotype

Testosterone deficiency or hypogonadism is a common finding in men undergoing dialysis, to a great extent a consequence of the failing kidney per se. Testosterone restoration in hypogonadism is common practice among endocrinologists. However, there is currently little awareness of this condition among both uremic patients and nephrologists, and in many cases, testosterone deficiency remains unscreened and untreated. This review article summarizes our current understanding of the role of testosterone deficiency at the crossroad of cardiometabolic complications of patients with chronic kidney disease. Pathways discussed include, among others, the plausible role of testosterone deficiency in the development of anaemia and ESA hyporesponsiveness, muscle catabolism, endothelial dysfunction, cognitive dysfunction, decreased libido, cardiovascular disease and mortality. As there are limited sources to guide decision-making, we also review existing testosterone replacement therapy studies in the context of CKD as well as considerations for side and adverse effects. This review makes a case for consideration of screening and better management of hypogonadism in men undergoing dialysis.

Effect of the single or combined administration of cocaine and testosterone on cardiovascular function and baroreflex activity in unanesthetized rats

Abuse of cocaine and androgenic-anabolic steroids has become a serious public health problem. Despite reports of an increase in the incidence of simultaneous illicit use of these substances, potential toxic interactions between cocaine and androgenic-anabolic steroids in the cardiovascular system are unknown. In the present study, we investigated the effect of single or combined administration of testosterone and cocaine for 1 or 10 consecutive days on basal cardiovascular parameters, baroreflex activity, and hemodynamic responses to vasoactive agents in unanesthetized rats. Ten-day combined administration of testosterone and cocaine increased baseline arterial pressure. Changes in arterial pressure were associated with altered baroreflex activity and impairment of both hypotensive response to intravenous sodium nitroprusside and pressor effect of intravenous phenylephrine. Chronic single administration of either testosterone or cocaine did not affect baseline arterial pressure. However, testosterone-treated animals presented rest bradycardia, cardiac hypertrophy, alterations in baroreflex activity, and enhanced response to sodium nitroprusside. Repeated administration of cocaine affected baroreflex activity and impaired vascular responsiveness to both sodium nitroprusside and phenylephrine. One-day single or combined administration of the drugs did not affect any parameter investigated. In conclusion, the present results suggest a potential interaction between toxic effects of cocaine and testosterone on the cardiovascular activity. Changes in baseline arterial pressure after combined administration of these 2 drugs may result from alterations in baroreflex activity and impairment of vascular responsiveness to vasoactive agents.

Differential effects of androgens on coronary blood flow regulation and arteriolar diameter in intact and castrated swine

Background

Low endogenous testosterone levels have been shown to be a risk factor for the development of cardiovascular disease and cardiovascular benefits associated with testosterone replacement therapy are being advocated; however, the effects of endogenous testosterone levels on acute coronary vasomotor responses to androgen administration are not clear. The objective of this study was to compare the effects of acute androgen administration on in vivo coronary conductance and in vitro coronary microvascular diameter in intact and castrated male swine.

Methods

Pigs received intracoronary infusions of physiologic levels (1–100 nM) of testosterone, the metabolite 5α-dihydrotestosterone, and the epimer epitestosterone while left anterior descending coronary blood flow and mean arterial pressure were continuously monitored. Following sacrifice, coronary arterioles were isolated, cannulated, and exposed to physiologic concentrations (1–100 nM) of testosterone, 5α-dihydrotestosterone, and epitestosterone. To evaluate effects of the androgen receptor on acute androgen dilation responses, real-time PCR and immunohistochemistry for androgen receptor were performed on conduit and resistance coronary vessels.

Results

In vivo, testosterone and 5α-dihydrotestosterone produced greater increases in coronary conductance in the intact compared to the castrated males. In vitro, percent maximal dilation of microvessels was similar between intact and castrated males for testosterone and 5α-dihydrotestosterone. In both studies epitestosterone produced significant increases in conductance and microvessel diameter from baseline in the intact males. Androgen receptor mRNA expression and immunohistochemical staining were similar in intact and castrated males.

Conclusions

Acute coronary vascular responses to exogenous androgen administration are increased by endogenous testosterone, an effect unrelated to changes in androgen receptor expression.

The vasodilatory effect of testosterone on renal afferent arterioles

BACKGROUND

Sex differences exist in a variety of cardiovascular and renal diseases, and testosterone may contribute to the discrepancy. Afferent arterioles (Af-Arts) are the major resistance vessels in the kidney, and they play an important role in the development of renal injury and hypertension.

OBJECTIVE

We sought to determine the acute effect and underlying mechanism(s) of action of testosterone on Af-Arts.

METHODS

The mRNA expression of androgen receptors (ARs) in microdissected Af-Arts was measured by reverse transcription-polymerase chain reaction (RT-PCR). An in vitro microperfusion model was used to measure the diameter of Af-Arts in mice. Nitric oxide (NO) was evaluated by an NO-sensitive fluorescent dye, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate.

RESULTS

Testosterone had no effect on microperfused Af-Arts when added to the bath. Therefore, we preconstricted the Af-Arts to approximately 30% with norepinephrine (10(-6) M); administration of testosterone (10(-9)-10(-7) M) subsequently dilated the Af-Arts in a dose-dependent manner (P < 0.001; n = 7). The AR mRNA was expressed in microdissected Af-Arts measured by RT-PCR. An AR antagonist, flutamide (10(-5) M), totally blocked the testosterone (10(-8) M)-induced vasodilator effect. Mean (SEM) NO production of the Af-Art wall was increased when testosterone was added to the bath solution after norepinephrine treatment, from 278.4 (12.1) U/min to 351.2 (33.1) U/min (P < 0.05; n = 3). In the presence of NO inhibition with N(G)-nitro-L-arginine methyl ester (3 × 10(-4) M), the testosterone-induced dilatation was blunted compared with norepinephrine (P < 0.05).

CONCLUSIONS

Testosterone dilated preconstricted mouse Af-Arts in a dose-dependent manner by activation of ARs and partially mediated by NO.

Regional differences in the vasorelaxing effects of testosterone and its 5-reduced metabolites in the canine vasculature

Although the vasorelaxing effects of testosterone (T) and various androgen metabolites have been observed in a variety of blood vessels and species, previous studies have not systematically compared the vasorelaxing effects of androgen metabolites in different vascular beds within the same species. Therefore, we studied the vasorelaxing effects of T and its 5-reduced metabolites (5α- and 5β-DHT) on KCl-induced contractions of the canine left coronary artery, femoral artery and saphenous vein, using standard isometric recordings. KCl contractions were inhibited by each androgen in a concentration-dependent manner from 1.8 to 310μM. Vascular sensitivity and efficacy were expressed as inhibitory concentration 50 (IC₅₀) and maximal relaxation (R(max)), respectively. The coronary artery was significantly more sensitive to androgen-induced vasorelaxation than the saphenous vein or femoral artery. These vasorelaxing responses were unaffected by an antiandrogen (Flutamide) or the sulfhydryl reagent, N-ethylmaleimide, suggesting a nongenomic mechanism independent of signaling mediated by the androgen receptor or G proteins. Concentration-response curves were unchanged in endothelium-denuded preparations; thus, the endothelium appears to have no role in androgen-induced vasorelaxation. 5β-DHT was the most potent androgen in both coronary and femoral artery, but all three androgens were equipotent in the saphenous vein. It is concluded that: 1) significant regional differences exist in vasorelaxing effects of androgen metabolites in the canine vasculature; 2) structural differences in these androgens determine their vasorelaxing efficacy; and 3) regional differences in androgen-induced vasorelaxation may account for some of the conflicting findings reported on the vasorelaxing effects of the androgens.

Alterations in vasomotor systems and mechanics of resistance-sized mesenteric arteries from SHR and WKY male rats following in vivo testosterone manipulation

Background

Testosterone (T) and the sympathetic nervous system each contribute to the pathology of hypertension. Altered blood vessel reactivity is also associated with the pathology of high blood pressure. The purpose of this study was to examine the effects of T manipulation in the regulation of resistance-sized blood vessel reactivity.

Methods

Adult spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) male rats at 8 weeks of age were used. The rats were divided into groups consisting of gonadally intact controls (CONT), castrate with sham implant (CAST) and castrate with T implant (CAST + T) (n = 6 to 12 per group). Following a short-term period of T treatment (approximately 4 weeks), plasma norepinephrine (NE) and plasma T were assessed by performing high-performance liquid chromatography and RIA, respectively. Resistance-sized mesenteric artery reactivity was assessed on a pressurized arteriograph for myogenic reactivity (MYO), phenylephrine (PE) responsiveness and passive structural mechanics.

Results

SHR and WKY males exhibited similar physiological trends in T manipulation, with castration significantly lowering plasma T and NE and T replacement significantly increasing plasma T and NE. T manipulation in general resulted in significant alterations in MYO of second-order mesenteric arteries, with T replacement decreasing MYO in SHR (P < 0.05) compared to CONT, T replacement increasing MYO, and CAST decreasing MYO in WKY rats (P < 0.001) compared to CONT rats. Additionally, PE-induced constriction was significantly altered in both strains following T treatment, with the effective concentration of PE to constrict the vessel to 50% of the total diameter significantly increased in the CAST + T SHR compared to CONT (P < 0.05). Comparisons of passive structural mechanics between SHR and WKY treatment groups indicated in SHR a significantly increased wall-to-lumen ratio and decreased circumferential wall stress compared to WKY treatment groups.

Conclusions

These data suggest that T and NE are involved in a complex interaction with both myogenic reactivity and structural alterations of resistance-sized blood vessels and that these factors likely contribute to the development and maintenance of hypertension.

Onset of effects of testosterone treatment and time span until maximum effects are achieved

OBJECTIVE

Testosterone has a spectrum of effects on the male organism. This review attempts to determine, from published studies, the time-course of the effects induced by testosterone replacement therapy from their first manifestation until maximum effects are attained.

DESIGN

Literature data on testosterone replacement.

RESULTS

Effects on sexual interest appear after 3 weeks plateauing at 6 weeks, with no further increments expected beyond. Changes in erections/ejaculations may require up to 6 months. Effects on quality of life manifest within 3-4 weeks, but maximum benefits take longer. Effects on depressive mood become detectable after 3-6 weeks with a maximum after 18-30 weeks. Effects on erythropoiesis are evident at 3 months, peaking at 9-12 months. Prostate-specific antigen and volume rise, marginally, plateauing at 12 months; further increase should be related to aging rather than therapy. Effects on lipids appear after 4 weeks, maximal after 6-12 months. Insulin sensitivity may improve within few days, but effects on glycemic control become evident only after 3-12 months. Changes in fat mass, lean body mass, and muscle strength occur within 12-16 weeks, stabilize at 6-12 months, but can marginally continue over years. Effects on inflammation occur within 3-12 weeks. Effects on bone are detectable already after 6 months while continuing at least for 3 years.

CONCLUSION

The time-course of the spectrum of effects of testosterone shows considerable variation, probably related to pharmacodynamics of the testosterone preparation. Genomic and non-genomic effects, androgen receptor polymorphism and intracellular steroid metabolism further contribute to such diversity.

Testosterone deficiency is a cause of anaemia and reduced responsiveness to erythropoiesis-stimulating agents in men with chronic kidney disease

BACKGROUND

Hypogonadism or testosterone deficiency is a prevalent condition in men with chronic kidney disease (CKD). Testosterone stimulates erythropoiesis via production of haematopoietic growth factors and possible improvement of iron bioavailability. We hypothesized that testosterone deficiency predisposes to anaemia and reduced responsiveness to erythropoiesis-stimulating agents (ESAs) in CKD men. Materials and methods. We studied associations between endogenous testosterone and haemoglobin in 239 ESA-naïve nondialysed CKD Stages 1-5 male patients. Additionally, we studied associations between endogenous testosterone levels and ESA dose (U/kg/week) in 126 ESA-treated men undergoing haemodialysis (HD).

RESULTS

Among ESA-naïve males, patients with anaemia presented lower testosterone values. Endogenous testosterone was negatively associated with haemoglobin levels in uni- and multivariate models. Testosterone-deficient patients (total testosterone <10 nmol/L) were 5.3 (95% confidence interval 2.2-12.5) times more likely to be anaemic (Hb < 13.0 g/dL) than testosterone-sufficient patients. In ESA-treated men undergoing HD, higher ESA doses (above the median value of 121 IU/kg body weight/week) are associated with lower testosterone levels and higher percentage of hypochromic red blood cells (RBC). The inverse association between testosterone levels and ESA doses persisted after multivariate adjustment for age, sex hormone-binding globulin, comorbidities, C-reactive protein and s-albumin but was lost after further adjustment for iron medication and hypochromic RBC.

CONCLUSIONS

Hypogonadism may be an additional cause of anaemia and reduced ESA responsiveness in men with CKD. Our results raise the possibility that restoration of testosterone levels in hypogonadal CKD males may translate into lower prevalence of anaemia and better ESA responsiveness.

Testosterone therapy: treatment of metabolic disturbances in heart failure

Heart failure (HF) is a complex progressive multisystem disease state with significant morbidity and mortality, which is not solely defined by pathology of the cardiovascular system but also is influenced by neurohormonal regulatory adjustments, peripheral cytokines, as well as hormonal and musculoskeletal dysfunction. Recent attention to the catabolic state found in patients with chronic heart failure has sparked interest in new potential targets for medical therapy. In particular, as many as 26% to 37% of men affected with HF have been found to be testosterone deficient. The severity of androgen deficiency has been shown to correlate with symptoms, functional class, and prognosis in patients with heart failure. Testosterone supplementation has been an accepted therapy in hypogonadal men with fatigue, muscle wasting, and sexual dysfunction for some time. Patients with severe HF show a similar constellation of symptoms and hypothetically would benefit from androgen replacement. Recent clinical studies have confirmed that functional, biochemical, and cardiopulmonary status in patients with HF have significant improvements when treated with testosterone supplementation. Symptomatic improvements may be obtainable in hypogonadal patients with HF who receive supplemental testosterone. This review seeks to outline the cardiovascular and peripheral effects of testosterone supplementation in patients with chronic HF.

Growth hormone and testosterone in heart failure therapy

IMPORTANCE OF THE FIELD

Heart failure is a progressive disease affecting millions of people worldwide. The disease carries a significantly high morbidity and mortality risk. There are multiple pharmaceutical options to decrease this risk and prolong survival; however, despite optimization of medical management, several patients still await heart transplant, the only definitive cure for heart failure. To slow the progression of disease preventing need for transplantation, improve clinical symptoms, and improve heart failure outcomes, there is a persistent need to discover new therapeutic strategies. Of interest, low growth hormone and testosterone levels have been associated with a worsening degree of heart failure. Many studies have begun to show a clinical improvement in heart failure symptoms when these levels are corrected with hormonal therapy. These findings, although mixed, are promising and indicate that both testosterone and growth hormone therapy should be considered as adjunctive therapy in advanced heart failure patients.

AREAS COVERED IN THIS REVIEW

This review discusses the physiology of both of these natural hormones, their therapeutic effects in heart failure and data from the published literature on studies using growth hormone or testosterone in patients with chronic heart failure. An extensive search of PubMed was conducted for topics on heart failure, growth hormone, insulin-like growth factor, testosterone, their physiology and pathophysiology, and trials in which they have been used as therapeutic interventions between 1989 and 2009.

WHAT THE READER WILL GAIN

The reader will gain an understanding of the intricate balance of both of these hormones in the disease state of heart failure. In addition, the trials conducted using these hormones in pharmacotherapy for heart failure are discussed along with proposed theories for interstudy variability.

TAKE HOME MESSAGE

Testosterone deficiency and growth hormone resistance are positively associated with a poor state of heart failure. Treatment of deficiency improves outcomes in heart failure; however, there is a significant paucity of data with regard to testosterone and heart failure as well as a significant amount of study variability with growth hormone and heart failure.

PKG is involved in testosterone-induced vasorelaxation of human umbilical artery

The cyclic nucleotides involvement in the vasorelaxation induced by testosterone in human umbilical artery was investigated. The effect of this hormone on denuded human umbilical arteries contracted by serotonin (5-HT), histamine or KCl was analysed. Testosterone effect on potassium current (IK) was also studied in human umbilical artery vascular smooth muscle cells (HUASMC). In general, the relaxant effects of testosterone, sodium nitroprusside (SNP) and atrial natriuretic peptide (ANP) are similar. The testosterone relaxant effect is not different to the induced by the conjoint application of ANP and testosterone. However, the effects of SNP and testosterone seem additive. The inhibition of protein kinase A (PKA) did not modify the testosterone relaxant effect, but protein kinase G (PKG) inhibition significantly reduced the testosterone effect independently of the contractile stimuli. In HUASMC, the IK is mainly constituted by potassium exit through voltage sensitive (KV) and large-conductance Ca2+ activated (BKCa) potassium channels. Testosterone significantly activates the basal IK. SNP does not induce a significant modification in basal or testosterone stimulated IK. In contrast, ANP stimulates the basal IK, but does not increase the testosterone stimulation on IK. The IK increases induced by testosterone or by ANP are not significantly affected by the PKA inhibition, but are completely inhibited by the PKG inhibition. Our results show that testosterone and ANP stimulate the activity of BKCa and KV channels due to PKG activation and suggest that this hormone relaxes by activating particulate guanylate cyclase which increases the cGMP intracellular level.

Role of polyamines and cAMP-dependent mechanisms on 5alpha-dihydrotestosterone-elicited functional effects in isolated right atria of rat

Androgens produce acute vasodilation of systemic, pulmonary, and coronary arteries in several mammal preparations and increase cardiomyocyte contractility. A decrease of the spontaneous beating of sinoatrial cells has also been described. The aim of this study was to characterize the direct effect of 5alpha-dihydrotestosterone on the spontaneous chronotropism and inotropism in the same preparation as an approach to establish the effect on cardiac output and their mechanism of action. The effects were studied on isolated right atria of Wistar rats placed in an organ bath in Tyrode solution at 37 degrees C and bubbled with carbogen. In male rats, the acute administration of 5alpha-dihydrotestosterone, a nonaromatizable derivate of testosterone, elicited a positive inotropism, which was associated with a negative chronotropism. As reported in the left atria, polyamines and beta-adrenoceptors played a role in 5alpha-dihydrotestosterone-elicited positive inotropism because the effect was antagonized by alpha-difluoromethylornithine, an inhibitor of polyamine synthesis, and atenolol, a beta1-adrenoceptor blocker, but not on the negative effect on chronotropism. The androgen increased the sinoatrial node recovery time, suggesting an effect on the mechanisms of spontaneous diastolic depolarization involved in atria pacemaking. These effects of 5alpha-dihydrotestosterone are not hormonally regulated because they are similarly produced in estrogenized females and gonadectomized male and female rats. These results suggest that the androgen could acutely improve cardiac performance.

Do androgens play a beneficial role in the regulation of vascular tone? Nongenomic vascular effects of testosterone metabolites

The marked sexual dimorphism that exists in human cardiovascular diseases has led to the dogmatic concept that testosterone (Tes) has deleterious effects and exacerbates the development of cardiovascular disease in males. While some animal studies suggest that Tes does exert deleterious effects by enhancing vascular tone through acute or chronic mechanisms, accumulating evidence suggests that Tes and other androgens exert beneficial effects by inducing rapid vasorelaxation of vascular smooth muscle through nongenomic mechanisms. While this effect frequently has been observed in large arteries at micromolar concentrations, more recent studies have reported vasorelaxation of smaller resistance arteries at nanomolar (physiological) concentrations. The key mechanism underlying Tes-induced vasorelaxation appears to be the modulation of vascular smooth muscle ion channel function, particularly the inactivation of L-type voltage-operated Ca(2+) channels and/or the activation of voltage-operated and Ca(2+)-activated K(+) channels. Studies employing Tes analogs and metabolites reveal that androgen-induced vasodilation is a structurally specific nongenomic effect that is fundamentally different than the genomic effects on reproductive targets. For example, 5alpha-dihydrotestosterone exhibits potent genomic-androgenic effects but only moderate vasorelaxing activity, whereas its isomer 5beta-dihydrotestosterone is devoid of androgenic effects but is a highly efficacious vasodilator. These findings suggest that the dihydro-metabolites of Tes or other androgen analogs devoid of androgenic or estrogenic effects could have useful therapeutic roles in hypertension, erectile dysfunction, prostatic ischemia, or other vascular dysfunctions.

Testosterone acts as an efficacious vasodilator in isolated human pulmonary arteries and veins: evidence for a biphasic effect at physiological and supra-physiological concentrations

BACKGROUND

Testosterone is recognized to elicit vasodilatation in numerous vascular beds, however to date no study has investigated whether testosterone has this effect in the human pulmonary vasculature.

AIM

To determine whether isolated human pulmonary arteries and veins dilate in response to testosterone and whether the response differs in relation to gender, endothelial function or location with the pulmonary vasculature.

METHODS

Intralobar pulmonary arteries [no.=44, diameter =581 (349) microm] and veins [no.=27, diameter =573 (302) microm] were dissected from lobectomy samples obtained from male and female patients [no.=40, age =69 (8) yr]. Vessels were mounted in an automated wire myograph, bathed in physiological saline at 37 C and pH 7.4, and loaded to their in vivo pressure. Vessels were preconstricted with noradrenaline (10 microM) and exposed to acetylcholine (1 microM) to assess endothelial function, washed and then preconstricted with potassium chloride (1-100 mM) followed by either cumulative concentrations of testosterone (1 nM-100 microM) or ethanol vehicle (<0.1%).

RESULTS

Significant marked vasodilatation was seen in all vessels, irrespective of size, gender and endothelial function at micromolar concentrations. Testosterone triggered significant vasodilatation at concentrations > or = 10 nM in pulmonary arteries obtained from males, a response which was not observed in vessels from females. The maximal response at 100 microM was also significantly greater in male pulmonary arteries. Significant vasodilatation was only observed at physiological (nM) concentrations in pulmonary resistance arteries and pulmonary arteries with good endothelial function.

CONCLUSION

Testosterone acts as an efficacious vasodilator in the human pulmonary vasculature, with dilatation observed at physiological concentrations in the male arterial resistance bed, dependent on the presence of an intact endothelium.

Involvement of protein kinase C-CPI-17 in androgen modulation of angiotensin II-renal vasoconstriction

AIMS

Previous studies suggested that androgens augmented renal vascular responses to angiotensin II (Ang II). The protein kinase C (PKC)-CPI-17 pathway is involved in vascular constriction. We tested the hypothesis that this pathway may contribute to androgenic amplification of Ang II-renal vasoconstriction in the New Zealand genetically hypertensive (NZGH) rat.

METHODS AND RESULTS

NZGH underwent sham operation, castration, or castration with testosterone replacement at 5 weeks of age. When the rats were 16-17 weeks of age, mean arterial pressure (MAP) and renal vascular resistance (RVR) responses to intravenous Ang II infusion (20, 40, and 80 ng/kg/min) were recorded before and after treatment with a PKC inhibitor, chelerythrine. mRNA expression of PKC isoforms and CPI-17 protein expression were analysed in renal cortex. MAP and RVR responses to Ang II were enhanced in androgen-replete NZGH. The Ang II-induced increase in RVR was significantly lower in castrated NZGH (ranged from 100 +/- 8% to 161 +/- 9% of baseline) than in sham-operated NZGH (ranged between 123 +/- 3% and 237 +/- 19% of baseline). Testosterone treatment restored RVR responses to Ang II in castrated rats. Chelerythrine treatment markedly reduced the MAP and RVR responses to Ang II in each group and attenuated the differential MAP and RVR responses to Ang II amongst the three groups. PKCdelta and PKCepsilon mRNA levels were significantly reduced by castration and increased by testosterone treatment. In contrast, no significant differences in protein expression were detected for these PKC isoforms. Castration decreased while testosterone treatment increased CPI-17 and phospho-CPI-17 expression.

CONCLUSION

Collectively, these results suggest that androgens modulate renal vascular responses to Ang II in part via an effect on the PKC-CPI-17 signalling pathway.

Long-term benefits of testosterone replacement therapy on angina threshold and atheroma in men

INTRODUCTION

In short-term studies, testosterone replacement therapy has been shown to protect male subjects from exercise-induced ischaemia and modify cardiovascular risk factors such as insulin resistance, fat mass and lipid profiles.

METHODS

This randomised parallel group controlled trial was designed to assess the treatment effect of testosterone therapy (Nebido) compared with placebo in terms of exercise-induced ischaemia, lipid profiles, carotid intima-media thickness (CIMT) and body composition during 12 months treatment in men with low testosterone levels and angina.

RESULTS

A total of 15 men were recruited but 13 (n=13) reached adequate duration of follow-up; seven were treated with testosterone and six with placebo. Testosterone increased time to ischaemia (129+/-48 s versus 12+/-18, P=0.02) and haemoglobin (0.4+/-0.6 g/dl versus -0.03+/-0.5, P=0.04), and reduced body mass index (-0.3 kg/m(2) versus 1.3+/-1, P=0.04) and triglycerides (-0.36+/-0.4 mmol/l versus 0.3+/-1.2, P=0.05). The CIMT decreased in the testosterone group more than placebo, but full between group analyses suggested this was only a statistical trend (-0.5+/-0.1 vs -0.09+/-0.06, P=0.16). There were no significant effects on serum prostate specific antigen, total or high-density lipoprotein cholesterol; or on mood and symptom scores as assessed by Seattle Angina Score and EuroQol.

CONCLUSION

The protective effect of testosterone on myocardial ischaemia is maintained throughout treatment without decrement. Previously noted potentially beneficial effects of testosterone on body composition were confirmed and there were no adverse effects.

Sexual dimorphism in the aging kidney: differences in the nitric oxide system

Females-both rats and women-are substantially protected against the age-dependent decrease in renal function that occurs in males of the species. In part, this finding reflects the cardioprotective and renoprotective effects of estrogens, but estrogen has multiple actions, not all of which are beneficial. In addition, the low androgen level in women might be protective against a decline in renal function, but animal and clinical data on possible adverse effects of androgens are controversial. Androgens also have multiple actions, one of which-aromatization to estrogen-is likely to be protective. Sex steroids clearly have many complex actions, which explains the conflicting information on their relative benefits and dangers. Endothelial nitric oxide (NO) deficiency contributes importantly to cardiovascular risk and intrarenal NO deficiency is clearly linked to chronic kidney disease progression in animal models. Endothelial dysfunction develops with increasing age but is delayed in females, correlating with a delayed rise in asymmetric dimethylarginine level. There is no clear link between aging and arginine (the NO synthase substrate) deficiency. Animal data suggest that the aging kidney develops NO deficiency as a result of changes in neuronal NO synthase. The increased oxidative stress that occurs with aging affects multiple stages of the NO biosynthetic pathway and results in decreased production and/or action of NO. NO production is better preserved in females than in males, partly as a result of the actions of estrogens.

Effect of orchiectomy on renal function in control and diabetic rats with chronic inhibition of nitric oxide

1. Male gender is associated with higher blood pressure (BP) and more rapid loss of renal function in a spectrum of clinical and experimental renal diseases, including diabetic nephropathy. Consequently, modulation of testosterone levels could exert beneficial effects in the diabetic kidney. 2. The aim of the present study was to determine whether testosterone deficiency (orchiectomy) could influence BP and renal function in streptozotocin-diabetic rats, with or without accelerated endothelial dysfunction achieved by chronic inhibition of nitric oxide (NO) synthesis using N(G)-nitro-L-arginine methyl ester (l-NAME; 40-100 mg/L in the drinking water for 2 weeks), as well as in age-matched non-diabetic rats subjected to the same interventions. 3. Orchiectomy did not affect L-NAME-induced increases in BP in non-diabetic or diabetic rats. In non-diabetic rats, orchiectomy prevented L-NAME-induced increases in proteinuria. These effects on proteinuria were not observed in diabetic rats. In non-diabetic rats, orchiectomy had no effect on renal haemodynamics in animals receiving vehicle and did not affect L-NAME-induced changes in renal haemodynamics, characterized by reductions in renal plasma flow (RPF) and higher filtration fractions (FF). In intact diabetic rats, L-NAME treatment resulted in lower RPF. This difference was not observed in diabetic rats subjected to orchiectomy, although L-NAME-treated diabetic orchiectomized rats had lower RPF and higher FF compared with vehicle-treated intact diabetic rats. 4. In conclusion, we report modest beneficial effects of orchiectomy on proteinuria in normal, but not in diabetic, rats with inhibition of NO production. This suggests that testosterone reduction does not attenuate the deleterious impact of the diabetic metabolic milieu in the kidney.

Effect of testosterone replacement therapy on arterial stiffness in older hypogonadal men

OBJECTIVE

To assess arterial stiffness in a cohort of hypogonadal males and to investigate the effect of testosterone replacement therapy on arterial properties in this specific group.

DESIGN

Eighteen male patients with untreated acquired hypogonadism due to either adult-onset idiopathic hypogonadotropic hypogonadism (n=9) or pituitary tumor (n=9) and 12 age-, sex, and weight-matched eugonadal healthy controls were recruited for the study. Arterial properties, plasma glucose, lipid profile, total, and bioavailable testosterone (BT) levels were measured in fasting state. In the hypogonadal subjects, the effect of transdermal testosterone replacement therapy on arterial properties was studied by repeat noninvasive measurements at baseline, as well as 48 h and 90 days following the initiation of treatment.

METHODS

Arterial stiffness was evaluated using applanation tonometry and pulse wave analysis by three different standard devices that assess various measures of arterial stiffness: pulse wave velocity (PWV), augmentation index (AIx), and large/small artery compliance (C1 and C2).

RESULTS

Age- and blood pressure-adjusted PWV was significantly higher in hypogonadal men (8.90+/-2.29 vs 6.78+/-1.16 m/s in the control group; P=0.025). Testosterone therapy increased BT level from 2.01+/-1.04 to 4.68+/-2.43 and 7.83+/-6.2 nmol/l after 48 h and 3 months respectively (P=0.001). PWV decreased from 8.9+/-2.29 to 8.24+/-1.39 and 8.25+/-1.82 m/s after 48 h and 3 months of treatment respectively (P=0.03).

CONCLUSIONS

Male hypogonadism is associated with increased PWV, which is rapidly but incompletely ameliorated by normalization of circulating testosterone levels.

Castration modifies aortic vasoreactivity and serum fatty acids in a sucrose-fed rat model of metabolic syndrome

Levels of testosterone and estradiol influence the incidence of cardiovascular diseases: generally, estrogens in females are protective before menopause; coronaropathies, hypertension, and dyslipidemias in normal men are more frequent at comparable ages. We investigated the modulation by castration of in vitro vasoreactivity, serum lipid content, and systolic blood pressure (SBP) in rats with sucrose-induced metabolic syndrome. The main characteristics of the rat model are: hypertriglyceridemia, moderately high blood pressure, intra-abdominal accumulation of adipose tissue, hyperinsulinemia, nephropathy, increased oxidative stress, and altered vasoreactivity. Male weanling rats received 30% sucrose solution for 16 weeks (metabolic syndrome; MS), controls (C) had plain water; both had commercial rodent chow. They were subdivided into five groups with two subgroups each: Group 1, intact C and MS rats, Groups 2-5, C and MS rats castrated for periods of 16, 12, 8, and 4 weeks. At the end of the study period, systolic blood pressure was measured, and blood and aortas were obtained for fatty acid determination and vasoreactivity assays, respectively. After 16 weeks' sucrose treatment MS aortas showed hypercontractility and decreased vasodilation. Palmitic and palmitoleic acids were increased in MS versus C. Arachidonic acid levels in MS were lower than in intact or castrated C. Long-term castration of 16 weeks normalized the levels of palmitic and oleic acids. With the shorter periods of castration, contractility increased and relaxation decreased in C and MS, but it was more significant in C. Regarding fatty acid composition, long-term castration increased polyunsaturated (arachidonic and eicosapentaenoic) fatty acids. The shorter periods did not modify the fatty acid profile in either C or MS. Metabolic syndrome altered SBP, aortic reactivity, and levels of fatty acids; castration of long duration normalized them in some cases.

Influence of gender and sex hormones on 5alpha-dihydrotestosterone elicited effect in isolated left atria of rats: Role of beta-adrenoceptors and ornithine decarboxylase activity

Androgens elicit an acute cardiotonic effect in cardiac preparations of rats. This effect is produced via an extracellular interaction that may be coupled to pertussis-sensitive G-proteins and is associated with an increase in cAMP, polyamine synthesis and intracellular calcium. The nature of the targets and the existence of a dimorphic effect in this nongenomic effect of androgens are unknown. The purpose of this study was to characterize a possible gender and sex hormone influence on the 5alpha-dihydrotestosterone-elicited cardiotonic effect, taking into account the possible role of the beta-adrenoceptors and ornithine decarboxylase activity on this response. [Float1]Regarding this, the effect of 5alpha-dihydrotestosterone on isolated left atria from male, estrogenized female and gonadectomized male and female rats was studied. The results showed that 5alpha-dihydrotestosterone-elicited cardiotonic effect was preserved independent of gender and sex hormones, being higher in control males than in the rest of the groups. This correlated with the testosterone plasma levels, except in estrogenized females, suggesting that the androgens positively and the estrogens negatively regulated the response. In all groups, 5alpha-dihydrotestosterone produced an increase in cAMP levels, but only in control males did it produce an increase in ornithine decarboxylase activity. In the other groups, the absence of an effect on ornithine decarboxylase might limit the capability of the response to the androgen. Altogether, androgens may help to control cardiac performance by a direct interaction on the heart in both sexes. Gender and sex differences in the magnitude of inotropism being due mainly to changes in beta-adrenoceptors and cAMP production and in intracellular polyamine synthesis.

Role of putrescine on androgen-elicited positive inotropism in the left atrium of rats

Functional and biochemical studies were performed in isolated left atria of male Wistar rats to study whether endogenous polyamines may mediate androgen-elicited positive inotropism and their relationship with a rise in cAMP during the cardiotonic effect. 5 alpha-Dihydrotestosterone (100 microM) exposure increased intracellular putrescine as determined by HPLC, but it did not increase spermidine and spermine. This effect was antagonized by an inhibitor of ornithine decarboxylase, alpha-difluoromethylornithine (10 mM), suggesting enzyme activation. alpha-Difluoromethylornithine also antagonized androgens-elicited inotropism and the increase in intracellular cAMP. Putrescine (1 to 10 mM) elicited a concentration-dependent positive inotropism associated with the cAMP increase. The prior incubation with putrescine antagonized 5 alpha-dihydrotestosterone-elicited inotropism and did not produce sinergism on intracellular cAMP. Short-term incubation with 5 alpha-dihydrotestosterone or forskolin shifted to the left the cardiotonic effect of isoproterenol, an agonist of beta-adrenoceptors, without any increase in Emax, suggesting that a common mechanism was involved. Therefore, polyamines might modulate the cAMP production associated with the cardiotonic effect of androgens.

Modulatory role of endogenous androgens on airway smooth muscle tone in isolated guinea-pig and bovine trachea; involvement of beta2-adrenoceptors, the polyamine system and external calcium

Androgens relax several smooth muscles, including the airways. They also contract ileum and myocardium via nongenomic mechanisms. To find out whether androgens modulate airway smooth muscles in different species and further assess their mechanism of action, regarding the role of beta-adrenoceptors, polyamines and extracellular Ca(2+), and the modulation of contraction, 5 alpha-dihydrotestosterone, testosterone and 5 beta-dihydrotestosterone were used. A preliminary study was performed to evaluate the effect of 5 alpha-dihydrotestosterone, a non-aromatisable derivate of testosterone, in isolated guinea-pig trachea and a more exhaustive characterisation was followed in bovine trachea, to also characterise the effect of testosterone and 5 beta-dihydrotestosterone. The androgens elicited a nongenomic epithelium-independent relaxation of the trachea which had been precontracted. In the bovine trachea, the order of potency was: testosterone>5 alpha-dihydrotestosterone=5 beta-dihydrotestosterone. This effect was inversely proportional to the magnitude of carbachol-raised tone and was independent of beta(2)-adrenoceptors, since the beta-blockers, propranolol and ICI-118,551, and beta(2)-adrenoceptor desensitisation did not modify 5 alpha-dihydrotestosterone-elicited relaxation. 5 alpha-Dihydrotestosterone was unable to displace the radiolabel, [(3)H]dihydroalprenolol, from these receptors in the binding assay. Polyamine synthesis was not involved in this androgen effect, since an ornithine decarboxylase inhibitor, alpha-difluoromethylornithine, was ineffective. The androgens were more effective relaxing bovine trachea precontracted by KCl (80 mM), suggesting a calcium entry blockade, as reported for several smooth muscles. This mechanism might be involved in the observed 5 alpha-dihydrotestosterone facilitation of salbutamol-relaxation. Androgens facilitated carbachol-elicited contraction independently of polyamine synthesis, contrary to what has been reported in the ileum. Therefore, androgens modulate tracheal smooth muscle tone which might be of importance in the regulation of airway reactivity.