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

Role of sex hormones in modulating myocardial perfusion and coronary flow reserve

Background

A growing body of evidence highlights sex differences in the diagnostic accuracy of cardiovascular imaging modalities. Nonetheless, the role of sex hormones in modulating myocardial perfusion and coronary flow reserve (CFR) is currently unclear. The aim of our study was to assess the impact of female and male sex hormones on myocardial perfusion and CFR.

Methods

Rest and stress myocardial perfusion imaging (MPI) was conducted by small animal positron emission tomography (PET) with [¹⁸F]flurpiridaz in a total of 56 mice (7–8 months old) including gonadectomized (Gx) and sham-operated males and females, respectively. Myocardial [¹⁸F]flurpiridaz uptake (% injected dose per mL, % ID/mL) was used as a surrogate for myocardial perfusion at rest and following intravenous regadenoson injection, as previously reported. Apparent coronary flow reserve (CFR_App) was calculated as the ratio of stress and rest myocardial perfusion. Left ventricular (LV) morphology and function were assessed by cardiac magnetic resonance (CMR) imaging.

Results

Orchiectomy resulted in a significant decrease of resting myocardial perfusion (Gx vs. sham, 19.4 ± 1.0 vs. 22.2 ± 0.7 % ID/mL, p = 0.034), while myocardial perfusion at stress remained unchanged (Gx vs. sham, 27.5 ± 1.2 vs. 27.3 ± 1.2 % ID/mL, p = 0.896). Accordingly, CFR_App was substantially higher in orchiectomized males (Gx vs. sham, 1.43 ± 0.04 vs. 1.23 ± 0.05, p = 0.004), and low serum testosterone levels were linked to a blunted resting myocardial perfusion (r = 0.438, p = 0.020) as well as an enhanced CFR_App (r = −0.500, p = 0.007). In contrast, oophorectomy did not affect myocardial perfusion in females. Of note, orchiectomized males showed a reduced LV mass, stroke volume, and left ventricular ejection fraction (LVEF) on CMR, while no such effects were observed in oophorectomized females.

Conclusion

Our experimental data in mice indicate that sex differences in myocardial perfusion are primarily driven by testosterone. Given the diagnostic importance of PET-MPI in clinical routine, further studies are warranted to determine whether testosterone levels affect the interpretation of myocardial perfusion findings in patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-022-05675-2.

Low free testosterone level as a predictor of cardiovascular events in Japanese men with coronary risk factors

Aim: We investigated whether low plasma free testosterone (FT) levels could predict cardiovascular events (CVE) in Japanese men with coronary risk factors.Methods: Male patients with classical coronary risk factors who had undergone serum FT testing were enrolled. New incidences of CVE were retrospectively investigated among all eligible participants based on their medical records.Results: Overall, 466 male outpatients with coronary risk factors without a previous history of CVE were identified. Throughout the follow-up period (median = 92 months), 126 CVE occurred. The Kaplan-Meier survival analysis according to the tertiles of plasma FT levels revealed that patients with the lowest FT tertile (<6.5 pg/mL) had a higher likelihood of developing CVE than those with the highest tertile (>9.3 pg/mL) (p<.01). Multivariate analysis showed that increased frequency of CVE was observed with lower FT tertiles, independent of other coronary risk factors, with hazard ratios of 0.617 (95% CI, 0.389-0.976; p=.030) and 0.524 (95% CI, 0.309-0.887; p=.016) for the second and highest tertile relative to the lowest FT tertile, respectively.Conclusion: Among Japanese men with coronary risk factors, a lower FT level was a predictor for the development of cardiovascular diseases independent of other coronary risk factors and age.

Microvessel Density: Integrating Sex-Based Differences and Elevated Cardiovascular Risks in Metabolic Syndrome

Metabolic syndrome (MetS) is a complex pathological state consisting of metabolic risk factors such as hypertension, insulin resistance, and obesity. The interconnectivity of cellular pathways within various biological systems suggests that each individual component of MetS may share common pathological sources. Additionally, MetS is closely associated with vasculopathy, including a reduction in microvessel density (MVD) (rarefaction) and elevated risk for various cardiovascular diseases. Microvascular impairments may contribute to perfusion-demand mismatch, where local metabolic needs are insufficiently met due to the lack of nutrient and oxygen supply, thus creating pathological positive-feedback loops and furthering the progression of disease. Sexual dimorphism is evident in these underlying cellular mechanisms, which places males and females at different levels of risk for cardiovascular disease and acute ischemic events. Estrogen exhibits protective effects on the endothelium of pre-menopausal women, while androgens may be antagonistic to cardiovascular health. This review examines MetS and its influences on MVD, as well as sex differences relating to the components of MetS and cardiovascular risk profiles. Finally, translational relevance and interventions are discussed in the context of these sex-based differences.

Sex steroids and markers of micro- and macrovascular damage among women and men from the general population

AIMS

The contribution of sex hormones to micro- and macrovascular damage might differ among women and men. In particular, little is known about the association between sex hormones and small vessel disease. Therefore, we examined the association of total oestradiol, total testosterone, free-androgen index (FAI), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), and androstenedione levels with micro- and macrovascular diseases.

METHODS AND RESULTS

This cross-sectional study included 2950 women and 2495 men from the population-based Rotterdam Study. As proxy of microvascular damage, we measured diameters of retinal arterioles and venules. Markers of macrovascular damage included carotid intima-media thickness and carotid plaque, coronary artery calcification (CAC), and peripheral artery disease. Linear and logistic regression models were used and adjusted for age, cardiovascular risk factors, and years since menopause. Associations with microvasculature: In women, total testosterone [mean difference per 1-unit increase in natural-log transformed total testosterone (95% confidence interval, CI): 2.59 (0.08-5.09)] and androstenedione [4.88 (1.82-7.95)] and in men DHEAS [2.80 (0.23-5.37)] and androstenedione [5.83 (2.19-9.46)] were associated with larger venular caliber. Associations with markers of large vessel disease: In women, higher total testosterone [-0.29 (-0.56 to -0.03)], FAI [-0.33 (-0.56 to -0.10)], and androstenedione levels [-0.33 (-0.64 to -0.02)] were associated with lower CAC burden and FAI [odds ratio (95% CI): 0.82 (0.71-0.94)] was associated with lower prevalence of plaque.

CONCLUSION

A more androgenic profile was associated with more microvascular damage in both women and men. Among women, however, higher androgen levels were also associated with less macrovascular damage. Our findings suggest that androgens might have distinct effects on the vasculature, depending on the vascular bed and stages of the atherosclerosis process.

Effects of Testosterone Deficiency and Angiotensin II-Induced Hypertension on the Biomechanics of Intramural Coronary Arteries

BACKGROUND

Andropause and hypertension also increase the risk of coronary artery damage.

AIM

To investigate the effect of testosterone deficiency and hypertension on intramural coronary vessels.

METHODS

4 groups of 8-week-old Sprague-Dawley rats were studied: control male (Co, n=10), orchidectomized male (OCT, n=13), angiotensin (AII) hypertensive male (AII, n=10), and AII hypertensive and OCT (AII + OCT, n=8). Surgical orchidectomy was performed, and an osmotic minipump was inserted for chronic angiotensin II infusion (100 ng/min/kg). After 4 weeks, spontaneous tone and biomechanical properties of the intramural coronary resistance artery were investigated in vitro, by pressure microarteriography.

OUTCOMES

Morphology and biomechanics of the intramural coronaries were evaluated: the outer diameter, wall thickness-to-lumen diameter ratio, and tangential wall stress in the contracted and relaxed states.

RESULTS

The outer diameter was reduced in OCT and AII + OCT groups (on 50 mmHg 315 ± 20 Co; 237 ± 21 OCT; 291 ± 16 AII, and 166 ± 12 μm AII + OCT). The increased wall thickness-to-lumen diameter ratio resulted in lower tangential wall stress in AII + OCT rats (on 50 mmHg 19 ± 2 Co; 24 ± OCT; 26 ± 5 AII, and 9 ± 1 kPa AII + OCT). Spontaneous tone was increased in the hypertensive rats (AII and AII + OCT groups) (on 50 mmHg 7.7 ± 1.8 Co; 6.1 ± 1.4 OCT; 14.5 ± 3.0 AII, and 17.4 ± 4.1 % AII + OCT).

CLINICAL IMPLICATIONS

Andropause alone can be considered as a cardiovascular risk factor that will further exacerbate vascular damage in hypertension.

STRENGTHS & LIMITATIONS

A limitation of our study is that it was performed on relatively young rats, and the conclusions might not apply to coronary remodelling in older animals with slower adaptation processes.

CONCLUSIONS

Testosterone deficiency and hypertension damage the mechanical adaptation of the vessel wall additively: double noxa caused inward eutrophic remodeling and increased tone. Jósvai A, Török M, Mátrai M, et al. Effects of Testosterone Deficiency and Angiotensin II-Induced Hypertension on the Biomechanics of Intramural Coronary Arteries. J Sex Med 2020;17:2322-2330.

Late-onset hypogonadism: Reductio ad absurdum of the cardiovascular risk-benefit of testosterone replacement therapy

BACKGROUND

Low testosterone (T) level is considered a marker of poor cardiovascular health. Ten years ago, the Testosterone in Older Men with Mobility Limitations (TOM) trial was discontinued due to a higher number of adverse events in men receiving T compared with placebo. Since then, several studies have investigated the risks of T replacement therapy (TRT) in late-onset hypogonadism (LOH).

OBJECTIVE

To review the mechanism by which TRT could damage the cardiovascular system.

MATERIALS AND METHODS

Comprehensive literature search of recent clinical and experimental studies.

RESULTS

The mechanisms of T-mediated coronary vasodilation were reviewed with emphasis on calcium-activated and ATP-sensitive potassium ion channels. We showed how T regulates endothelial nitric oxide synthase (eNOS) and phosphoinositide 3-kinase/protein kinase B/eNOS signaling pathways in vessel walls and its direct effects on cardiomyocytes via β1-adrenergic and ryanodine receptors and provided data on myocardial infarction and heart failure. Vascular smooth muscle senescence could be explained by the modulation of growth factors, matrix metalloproteinase-2, and angiotensin II by T. Furthermore, leukocyte trafficking, facilitated by changes in TNF-α, could explain some of the effects of T on atheromatous plaques. Conflicting data on prothrombotic risk linked to platelet aggregation inhibition via NO-triggered arachidonate synthesis or increased aggregability due to enhanced thromboxane A in human platelets provide evidence regarding the hypotheses on plaque maturation and rupture risk. The effects of T on cardiac electrophysiology and oxygen delivery were also reviewed.

DISCUSSION

The effects of TRT on the cardiovascular system are complex. Although molecular studies suggest a potential benefit, several clinical observations reveal neutral or occasionally detrimental effects, mostly due to confounding factors.

CONCLUSIONS

Attempts to demonstrate that TRT damages the cardiovascular system via systematic analysis of the putative mechanisms led to the contradiction of the initial hypothesis. Current evidence indicates that TRT is safe once other comorbidities are addressed.

Ischemia and reperfusion injury following cardioplegic arrest is attenuated by age and testosterone deficiency in male but not female mice

BACKGROUND

Cardiovascular disease increases with age in both sexes. Treatment can require cardiac surgery, where the hearts are pre-treated with protective cardioplegic solution before ischemia and reperfusion (I/R). While endogenous estrogen is beneficial in I/R, whether testosterone is involved is uncertain and whether age modifies responses to I/R is unclear. We investigated sex- and age-specific differences in I/R injury in the hearts pre-treated with clinically relevant cardioplegic solution.

METHODS

The hearts were isolated from young (6-9 months) and old (20-28 months) mice of both sexes and perfused (Langendorff) with Krebs-Henseleit buffer (15 min, 37 °C), followed by St. Thomas' two cardioplegia (6 min, 6-7 °C), global ischemia (90 min, 23-24 °C), and reperfusion (30 min, 37 °C). The hearts were perfused with triphenyltetrazolium chloride to quantify infarct area. Testosterone's role was investigated in gonadectomized (GDX, 6-9 months) male mice; serum testosterone and estradiol were measured with ELISA assays.

RESULTS

Left ventricular developed pressure (LVDP) recovered to 67.3 ± 7.4% in the old compared to 21.8 ± 9.2% in the young male hearts (p < 0.05). Similar results were seen for rates of pressure development (+dP/dt) and decay (-dP/dt). Infarct areas were smaller in the old male hearts (16.6 ± 1.6%) than in the younger hearts (55.8 ± 1.2%, p < 0.05). By contrast, the hearts from young and old females exhibited a similar post-ischemic functional recovery and no age-dependent difference in infarcts. There was a sex difference in the young group, where ventricular function (LVDP, +dP/dt, -dP/dt) recovered better and infarcts were smaller in females than males. Estradiol levels were highest in young females. Testosterone was high in young males but low in females and old males, which suggested beneficial effects of low testosterone. Indeed, the hearts from GDX males exhibited much better recovery of LVDP in reperfusion than that from intact males (values were 64.4 ± 7.5 % vs. 21.8 ± 9.2%; p < 0.05). The GDX hearts also had smaller infarcts than the hearts from intact males (p < 0.05).

CONCLUSIONS

Although age had no effect on susceptibility to I/R injury after cardioplegic arrest in females, it actually protected against injury in older males. Our findings indicate that low testosterone may be protective against I/R injury following cardioplegic arrest in older males.

Diminished androgen and estrogen receptors and aromatase levels in hypogonadal diabetic men: reversal with testosterone

AIMS

One-third of males with type 2 diabetes (T2DM) have hypogonadism, characterized by low total and free testosterone concentrations. We hypothesized that this condition is associated with a compensatory increase in the expression of androgen receptors (AR) and that testosterone replacement reverses these changes. We also measured estrogen receptor and aromatase expression.

MATERIALS AND METHODS

This is a randomized double-blind placebo-controlled trial. Thirty-two hypogonadal and 32 eugonadal men with T2DM were recruited. Hypogonadal men were randomized to receive intramuscular testosterone or saline every 2 weeks for 22 weeks. We measured AR, ERα and aromatase expression in peripheral blood mononuclear cells (MNC), adipose tissue and skeletal muscle in hypogonadal and eugonadal males with T2DM at baseline and after 22 weeks of treatment in those with hypogonadism.

RESULTS

The mRNA expression of AR, ERα (ESR1) and aromatase in adipose tissue from hypogonadal men was significantly lower as compared to eugonadal men, and it increased significantly to levels comparable to those in eugonadal patients with T2DM following testosterone treatment. AR mRNA expression was also significantly lower in MNC from hypogonadal patients compared to eugonadal T2DM patients. Testosterone administration in hypogonadal patients also restored AR mRNA and nuclear extract protein levels from MNC to that in eugonadal patients. In the skeletal muscle, AR mRNA and protein expression are lower in men with hypogonadism. Testosterone treatment restored AR expression levels to that comparable to levels in eugonadal men.

CONCLUSIONS

We conclude that, contrary to our hypothesis, the expression of AR, ERα and aromatase is significantly diminished in hypogonadal men as compared to eugonadal men with type 2 diabetes. Following testosterone replacement, there is a reversal of these deficits.

Erectile dysfunction, metabolic syndrome, and cardiovascular risks: facts and controversies

Erectile dysfunction (ED) is the most common male sexual dysfunction, and shares many risk factors with systemic conditions including cardiovascular disease (CVD) and the metabolic syndrome (MetS). ED is considered to be an independent risk factor for CVD and can be a harbinger of future cardiovascular events. Given this relationship, each encounter for ED should be viewed by healthcare providers as an opportunity to screen for CVD and other comorbid conditions, including the MetS, that can significantly affect a man's overall health. While universally accepted screening guidelines are lacking, expert panels do recommend an approach to risk stratification in men with ED. In this review, we discuss the current state of understanding of the relationship between ED, the MetS, and CV risk, and how this impacts the approach to the patient presenting with ED.

Roles of Testosterone Replacement in Cardiac Ischemia-Reperfusion Injury

Testosterone is an anabolic steroid hormone, which is the major circulating androgen hormone in males. Testosterone levels decreasing below the normal physiological levels lead to a status known as androgen deficiency. Androgen deficiency has been shown to be a major risk factor in the development of several disorders, including obesity, metabolic syndrome, and ischemic heart disease. In the past decades, although several studies from animal models as well as clinical studies demonstrated that testosterone exerted cardioprotection, particularly during ischemia-reperfusion (I/R) injury, other preclinical and clinical studies have shown an inverse relationship between testosterone levels and cardioprotective effects. As a result, the effects of testosterone replacement on the heart remain controversial. In this review, reports regarding the roles of testosterone replacement in the heart following I/R injury are comprehensively summarized and discussed. At present, it may be concluded that chronic testosterone replacement at a physiological dose demonstrated cardioprotective effects, whereas acute testosterone replacement can cause adverse effects in the I/R heart.

Testosterone therapy and cardiovascular risk: advances and controversies

Two recent studies raised new concerns regarding cardiovascular (CV) risks with testosterone (T) therapy. This article reviews those studies as well as the extensive literature on T and CV risks. A MEDLINE search was performed for the years 1940 to August 2014 using the following key words: testosterone, androgens, human, male, cardiovascular, stroke, cerebrovascular accident, myocardial infarction, heart attack, death, and mortality. The weight and direction of evidence was evaluated and level of evidence (LOE) assigned. Only 4 articles were identified that suggested increased CV risks with T prescriptions: 2 retrospective analyses with serious methodological limitations, 1 placebo-controlled trial with few major adverse cardiac events, and 1 meta-analysis that included questionable studies and events. In contrast, several dozen studies have reported a beneficial effect of normal T levels on CV risks and mortality. Mortality and incident coronary artery disease are inversely associated with serum T concentrations (LOE IIa), as is severity of coronary artery disease (LOE IIa). Testosterone therapy is associated with reduced obesity, fat mass, and waist circumference (LOE Ib) and also improves glycemic control (LOE IIa). Mortality was reduced with T therapy in 2 retrospective studies. Several RCTs in men with coronary artery disease or heart failure reported improved function in men who received T compared with placebo. The largest meta-analysis to date revealed no increase in CV risks in men who received T and reduced CV risk among those with metabolic disease. In summary, there is no convincing evidence of increased CV risks with T therapy. On the contrary, there appears to be a strong beneficial relationship between normal T and CV health that has not yet been widely appreciated.

Serum testosterone levels and mortality in men with CKD stages 3-4

BACKGROUND

Hypogonadism in men (total testosterone <350 ng/dL) is associated with higher risk of cardiovascular disease and mortality in men on dialysis therapy. We evaluated the association of hypogonadism with all-cause mortality in men with non-dialysis-dependent chronic kidney disease (CKD).

STUDY DESIGN

Retrospective, cohort study.

SETTING & PARTICIPANTS

2,419 men with CKD stages 3-4 (estimated glomerular filtration rate, 15-59 mL/min/1.73 m2) who had total testosterone measured for cause between January 1, 2005, and October 31, 2011, at a tertiary-care center in Cleveland, OH.

PREDICTORS

Total testosterone measured using an immunoassay measurement in 3 forms: (1) categorized as low or testosterone replacement therapy versus normal, (2) continuous log testosterone, and (3) quintiles (100-226, 227-305, 306-392, 393-511, and 512-3,153 ng/dL).

OUTCOMES

Factors associated with low total testosterone level and the association between low total testosterone level and all-cause mortality were evaluated using logistic regression, Cox proportional hazard models, and Kaplan-Meier survival curves.

RESULTS

Hypogonadism was found in 1,288 of 2,419 (53%) men. In a multivariable logistic regression analysis, African American ethnicity and higher estimated glomerular filtration rate were associated with lower odds of having hypogonadism. Diabetes and higher body mass index were associated with higher odds of having hypogonadism. 357 of 2,419 (15%) patients died during a median follow-up of 2.3 years. In the multivariate Cox model, testosterone level <350 ng/dL or testosterone replacement therapy was not associated with mortality. In a multivariable model also adjusted for testosterone supplementation, higher log testosterone was associated with significantly lower mortality (HR per 1 log unit, 0.70; 95% CI, 0.55-0.89). When compared to the highest quintile, the second lowest quintile of testosterone was associated with higher mortality (HR, 1.53; 95% CI, 1.09-2.16).

LIMITATIONS

Single-center study, timing of testosterone testing, lack of adjustment for proteinuria, and sampling bias.

CONCLUSIONS

Low total testosterone level may be associated with higher mortality in men with CKD stages 3-4, but more studies are needed.