Richard D. Jones

The Effect of Testosterone Replacement on Endogenous Inflammatory Cytokines and Lipid Profiles in Hypogonadal Men

Testosterone has immune-modulating properties, and current in vitro evidence suggests that testosterone may suppress the expression of the proinflammatory cytokines TNFalpha, IL-1beta, and IL-6 and potentiate the expression of the antiinflammatory cytokine IL-10. We report a randomized, single-blind, placebo-controlled, crossover study of testosterone replacement (Sustanon 100) vs. placebo in 27 men (age, 62 +/- 9 yr) with symptomatic androgen deficiency (total testosterone, 4.4 +/- 1.2 nmol/liter; bioavailable testosterone, 2.4 +/- 1.1 nmol/liter). Compared with placebo, testosterone induced reductions in TNFalpha (-3.1 +/- 8.3 vs. 1.3 +/- 5.2 pg/ml; P = 0.01) and IL-1beta (-0.14 +/- 0.32 vs. 0.18 +/- 0.55 pg/ml; P = 0.08) and an increase in IL-10 (0.33 +/- 1.8 vs. -1.1 +/- 3.0 pg/ml; P = 0.01); the reductions of TNFalpha and IL-1beta were positively correlated (r(S) = 0.588; P = 0.003). In addition, a significant reduction in total cholesterol was recorded with testosterone therapy (-0.25 +/- 0.4 vs. -0.004 +/- 0.4 mmol/liter; P = 0.04). In conclusion, testosterone replacement shifts the cytokine balance to a state of reduced inflammation and lowers total cholesterol. Twenty of these men had established coronary disease, and because total cholesterol is a cardiovascular risk factor, and proinflammatory cytokines mediate the development and complications associated with atheromatous plaque, these properties may have particular relevance in men with overt vascular disease.

Testosterone replacement in hypogonadal men with angina improves ischaemic threshold and quality of life

Background: Low serum testosterone is associated with several cardiovascular risk factors including dyslipidaemia, adverse clotting profiles, obesity, and insulin resistance. Testosterone has been reported to improve symptoms of angina and delay time to ischaemic threshold in unselected men with coronary disease. Objective: This randomised single blind placebo controlled crossover study compared testosterone replacement therapy (Sustanon 100) with placebo in 10 men with ischaemic heart disease and hypogonadism. Results: Baseline total testosterone and bioavailable testosterone were respectively 4.2 (0.5) nmol/l and 1.7 (0.4) nmol/l. After a month of testosterone, delta value analysis between testosterone and placebo phase showed that mean (SD) trough testosterone concentrations increased significantly by 4.8 (6.6) nmol/l (total testosterone) (p  =  0.05) and 3.8 (4.5) nmol/l (bioavailable testosterone) (p  =  0.025), time to 1 mm ST segment depression assessed by Bruce protocol exercise treadmill testing increased by 74 (54) seconds (p  =  0.002), and mood scores assessed with validated questionnaires all improved. Compared with placebo, testosterone therapy was also associated with a significant reduction of total cholesterol and serum tumour necrosis factor α with delta values of −0.41 (0.54) mmol/l (p  =  0.04) and −1.8 (2.4) pg/ml (p  =  0.05) respectively. Conclusion: Testosterone replacement therapy in hypogonadal men delays time to ischaemia, improves mood, and is associated with potentially beneficial reductions of total cholesterol and serum tumour necrosis factor α.

The vasodilatory action of testosterone: a potassium-channel opening or a calcium antagonistic action?

British Journal of Pharmacology (2003) 138, 733–744. doi:10.1038/sj.bjp.0705141

TESTOSTERONE ACTS AS A CORONARY VASODILATOR BY A CALCIUM ANTAGONISTIC ACTION

T acts as a vasodilator in vitro and in vivo. Supplemental T therapy in humans with angina improves symptoms and reduces objective measures of ischemia. In left anterior descending coronary arteries taken from adult male Wistar rats, T abolishes 100±4.2% of calcium-dependent contraction induced by potassium chloride, 82.3±6.1% of the mostly calcium-dependent contraction induced by prostaglandin-F-2-α, but only 45.3+_3.4% of the contraction induced by phorbol-12,13-dibutyrate (PDBu) in the presence of extracellular calcium, and 54.5±4.5% of the contraction induced by PDBu in the absence of extracellular calcium. These findings suggest that T is primarily inhibiting the calcium-dependent elements of vascular contraction.

Pulmonary vasodilatory action of testosterone: Evidence of a calcium antagonistic action

Recent evidence supports a beneficial effect of testosterone on the cardiovascular system. Testosterone acts as a coronary vasodilator and reduces myocardial ischemia in men with coronary heart disease. The aim of the current study was to determine whether testosterone has a similar vasodilatory action in the pulmonary circulation and to characterize the underlying mechanism of action. The vasodilatory action of testosterone was studied in pulmonary arteries (n = 132, mean internal diameter = 344 ± 8 &mgr;m) isolated from male rats (n = 48, mass = 396 ± 7 g) mounted in a small vessel wire myograph and loaded to a tension equivalent to 17.5 mm Hg. Micromolar concentrations of testosterone induced dilatation in pulmonary arteries preconstricted with prostaglandin F2&agr; (100 &mgr;M) within seconds of application. Dilatation to testosterone was similar in vessels treated with N-&ggr;-nitro-l-arginine methyl ester (l-NAME) (10 &mgr;M) or vehicle (5 &mgr;l distilled water), −38.2 ± 2.9%, and −38.1 ± 3.4%, respectively, and in vessels treated with indomethacin (10 &mgr;M), flutamide (10 &mgr;M), or vehicle (5 &mgr;l ethanol), −35.5 ± 2.8%, −43.2 ± 3.6%, and −35.7 ± 4.6%, respectively (all p > 0.05). Maximal dilatation to testosterone occurred following preconstriction with agents that activated voltage-gated calcium channels such as prostaglandin F2&agr; (−34.6 ± 5.0%), BAY K8644 (−32.9 ± 8.7), or potassium chloride (−26.7 ± 1.5%), compared with calcium-independent protein kinase C activation by phorbol dibutyrate (−14.7 ± 1.6%) or capacitative calcium entry via thapsigargin (−5.1 ± 0.9%). This study demonstrates that testosterone induces pulmonary dilatation via a mechanism that is independent of the classic androgen receptor and also of the release of nitric oxide or dilator prostaglandins. The data support a calcium antagonistic action for testosterone in the pulmonary circulation, primarily against voltage-gated calcium channels.

Physiological Testosterone Replacement Therapy Attenuates Fatty Streak Formation and Improves High-Density Lipoprotein Cholesterol in the Tfm Mouse. An Effect That Is Independent of the Classic Androgen Receptor

Background— Research supports a beneficial effect of physiological testosterone on cardiovascular disease. The mechanisms by which testosterone produces these effects have yet to be elucidated. The testicular feminized (Tfm) mouse exhibits a nonfunctional androgen receptor and low circulating testosterone concentrations. We used the Tfm mouse to determine whether testosterone modulates atheroma formation via its classic signaling pathway involving the nuclear androgen receptor, conversion to 17&bgr;-estradiol, or an alternative signaling pathway. Methods and Results— Tfm mice (n=31) and XY littermates (n=8) were separated into 5 experimental groups. Each group received saline (Tfm, n=8; XY littermates, n=8), physiological testosterone alone (Tfm, n=8), physiological testosterone in conjunction with the estrogen receptor &agr; antagonist fulvestrant (Tfm, n=8), or physiological testosterone in conjunction with the aromatase inhibitor anastrazole (Tfm, n=7). All groups were fed a cholesterol-enriched diet for 28 weeks. Serial sections from the aortic root were examined for fatty streak formation. Blood was collected for measurement of total cholesterol, high-density lipoprotein cholesterol (HDLC), non-HDLC, testosterone, and 17&bgr;-estradiol. Physiological testosterone replacement significantly reduced fatty streak formation in Tfm mice compared with placebo-treated controls (0.37±0.07% versus 2.86±0.39%, respectively; P≤0.0001). HDLC concentrations also were significantly raised in Tfm mice receiving physiological testosterone replacement compared with those receiving placebo (2.81±0.30 versus 2.08±0.09 mmol/L, respectively; P=0.05). Cotreatment with either fulvestrant or anastrazole completely abolished the improvement in HDLC. Conclusion— Physiological testosterone replacement inhibited fatty streak formation in the Tfm mouse, an effect that was independent of the androgen receptor. The observed increase in HDLC is consistent with conversion to 17&bgr;-estradiol.

Testosterone and atherosclerosis in aging men: purported association and clinical implications.

Two of the strongest independent risk factors for coronary heart disease (CHD) are increasing age and male sex. Despite a wide variance in CHD mortality between countries, men are consistently twice as likely to die from CHD than their female counterparts. This sex difference has been attributed to a protective effect of female sex hormones, and a deleterious effect of male sex hormones, upon the cardiovascular system. However, little evidence suggests that testosterone exerts cardiovascular harm. In fact, serum levels of testosterone decline with age, and low testosterone is positively associated with other cardiovascular risk factors. Furthermore, testosterone exhibits a number of potential cardioprotective actions. For example, testosterone treatment is reported to reduce serum levels of the pro-inflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α, and to increase levels of the anti-inflammatory cytokine IL-10; to reduce vascular cell adhesion molecule (VCAM)-1 expression in aortic endothelial cells; to promote vascular smooth muscle and endothelial cell proliferation; to induce vasodilatation and to improve vascular reactivity, to reduce serum levels of the pro-thrombotic factors plasminogen activator inhibitor (PAI)-1 and fibrinogen; to reduce low-density lipoprotein-cholesterol (LDL-C); to improve insulin sensitivity; and to reduce body mass index and visceral fat mass. These actions of testosterone may confer cardiovascular benefit since testosterone therapy reduces atheroma formation in cholesterol-fed animal models, and reduces myocardial ischemia in men with CHD. Consequently, an alternative hypothesis is that an age-related decline in testosterone contributes to the atherosclerotic process. This is supported by recent findings, which suggest that as many as one in four men with CHD have serum levels of testosterone within the clinically hypogonadal range. Consequently, restoration of serum levels of testosterone via testosterone replacement therapy could offer cardiovascular, as well as other, clinical advantages to these individuals.

Effect of testosterone on ex vivo vascular reactivity in man

Testosterone is reported to have an acute vasodilating action in vitro, an effect that may impart a favourable haemodynamic response in patients with chronic heart failure. However, the effect of chronic testosterone exposure on general vascular reactivity is poorly described. In the present study, fresh subcutaneous resistance arteries were obtained from patients with heart failure (n=10), healthy controls (n=9) and men with androgen-deficiency (n=17). All arteries were studied using a wire myograph to examine the effect of cumulative additions of testosterone (1 nmol/l-100 micromol/l) compared with vehicle control following maximal pre-constriction with KCl (1-100 micromol/l). The vascular reactivity of arteries from androgen-deficient patients was examined further by recording tension concentration curves to cumulative additions of noradrenaline (1 nmol/l-100 micromol/l) and U46619 (1-300 nmol/l), followed by relaxation concentration curves to additions of ACh (acetylcholine; 10 nmol/l-30 micromol/l) and SNP (sodium nitroprusside; 10 nmol-30 micromol/l) respectively. In all cases, statistical analysis was performed by ANOVA. Patients with proven androgen-deficiency were treated according to clinical recommendations for a minimum of 3 months and further arteries (n=19) were taken for experimentation using the same protocol. In all groups, testosterone was confirmed to be an acute concentration-dependent vasodilator at concentrations > or =1 micromol/l (P=0.0001). The dilating effect of testosterone was augmented in patients with androgen-deficiency prior to treatment, and this effect was abrogated following appropriate testosterone replacement. Testosterone therapy significantly reduced the normal vascular dilating response to ACh and SNP (P<0.01) and significantly increased the contractile response to noradrenaline (P<0.01), but not U46619. Testosterone is an acute dose-dependent vasodilator of resistance arteries. Physiological testosterone replacement attenuates general vascular reactivity in androgen-deficient subjects. The numerous perceived benefits of testosterone replacement may be offset by a decline in vascular reactivity and, therefore, further studies and careful monitoring of patients is recommended.

Testosterone-induced coronary vasodilatation occurs via a non-genomic mechanism: evidence of a direct calcium antagonism action

Testosterone decreases myocardial ischaemia in men with coronary artery disease via a coronary vasodilatory action. However, long-term therapy may increase the risk of prostatic carcinoma via activation of the nuclear AR (androgen receptor). In the present study, we have investigated the mechanism of testosterone-induced vasodilatation using isolated rat coronary arteries and thoracic aortae from control and AR-deficient testicular-feminized mice. Vasodilatation induced by testosterone, T-3-OCMO [testosterone 3-(O-carboxymethyl)oxime] or T-3-OCMO conjugated to BSA was initially measured in preconstricted vessels that had undergone endothelial denudation or incubation with flutamide (10 microM). Cellular fluorescence was also measured in primary aortic SMCs (smooth muscle cells) following exposure to the above fluorescent-labelled agents. Subsequently, vessels were incubated with testosterone (100 microM) or vehicle prior to constriction with KCl (1-100 mM). Testosterone-induced vasodilatation was unaffected by endothelial denudation, flutamide treatment, AR deficiency or conjugation to BSA. Cells exposed to T-3-OCMO-BSA (10 microM) had a higher fluorescence than control cells (32.8+/-4.5 compared with 14.5+/-1.8 arbitrary units respectively; P<0.01). Incubation with testosterone (100 microM) reversibly attenuated coronary vasoconstriction to KCl (1-100 mM; 0.08+/-0.09 compared with 0.79+/-0.08 mN/mm respectively; P<0.0001). Testosterone-induced vasodilatation is independent of the vascular endothelium and nuclear AR, and is initiated at the SMC membrane, which contains testosterone binding sites. A direct calcium antagonistic action is implicated.

Testosterone and Coronary Artery Disease

The strongest independent risk factors for coronary artery disease (CAD) are increasing age and male gender. Whilst a wide variation in CAD mortality exists between countries, a male to female ratio of approximately 2:1 is consistently observed. These observations have led to the assumption that testosterone may exert a detrimental influence on the cardiovascular system. Despite this, coronary atherosclerosis increases with age, whilst a marked fall in serum bioavailable testosterone levels is observed. Similarly, low testosterone levels are also associated with other cardiovascular risk factors and increased expression of mediators of the atherosclerotic process. This in itself suggests that testosterone does not promote atheroma formation. Moreover, epidemiological studies show an inverse relationship between testosterone levels and surrogate markers of atherosclerosis, which suggests that it may be a testosterone deficient state, rather than male sex which is associated with CAD. In cholesterol-fed animal models, atherosclerosis is accelerated by castration and reduced after testosterone replacement therapy. Testosterone has also been shown to improve myocardial ischemia in men with angina pectoris. Consequently, increasing evidence suggests that the process of atherosclerosis is beneficially modulated by testosterone. These studies are the focus of this chapter.