Testosterone deficiency reduces cardiac hypertrophy in a rat model of severe volume overload

Differences in cardiac adaptation to exercise in male and female athletes assessed by noninvasive techniques: a state-of-the-art review

Athlete's heart is generally regarded as a physiological adaptation to regular training, with specific morphological and functional alterations in the cardiovascular system. Development of the noninvasive imaging techniques over the past several years enabled better assessment of cardiac remodeling in athletes, which may eventually mimic certain pathological conditions with the potential for sudden cardiac death, or disease progression. The current literature provides a compelling overview of the available methods that target the interrelation of prolonged exercise with cardiac structure and function. However, this data stems from scientific studies that included mostly male athletes. Despite the growing participation of females in competitive sport meetings, little is known about the long-term cardiac effects of repetitive training in this population. There are several factors-biochemical, physiological and psychological, that determine sex-dependent cardiac response. Herein, the aim of this review was to compare cardiac adaptation to endurance exercise in male and female athletes with the use of electrocardiographic, echocardiographic, and biochemical examination, to determine the sex-specific phenotypes, and to improve the healthcare providers' awareness of cardiac remodeling in athletes. Finally, we discuss the possible exercise-induced alternations that should arouse suspicion of pathology and be further evaluated.

Understanding One Half of the Sex Difference Equation: The Modulatory Effects of Testosterone on Diabetic Cardiomyopathy

Diabetes is a prevalent disease, primarily characterized by high blood sugar (hyperglycemia). Significantly higher rates of myocardial dysfunction have been noted in individuals with diabetes, even in those without coronary artery disease or high blood pressure (hypertension). Numerous molecular mechanisms have been identified through which diabetes contributes to the pathology of diabetic cardiomyopathy, which presents as cardiac hypertrophy and fibrosis. At the cellular level, oxidative stress and inflammation in cardiomyocytes are triggered by hyperglycemia. Although males are generally more likely to develop cardiovascular disease than females, diabetic males are less likely to develop diabetic cardiomyopathy than are diabetic females. One reason for these differences may be the higher levels of serum testosterone in males compared with females. Although testosterone appears to protect against cardiomyocyte oxidative stress and exacerbate hypertrophy, its role in inflammation and fibrosis is much less clear. Additional preclinical and clinical studies will be required to delineate testosterone's effect on the diabetic heart.

Sex Differences in Therapies against Myocardial Ischemia-Reperfusion Injury: From Basic Science to Clinical Perspectives

Mortality from myocardial infarction (MI) has declined over recent decades, which could be attributed in large part to improved treatment methods. Early reperfusion is the cornerstone of current MI treatment. However, reoxygenation via restored blood flow induces further damage to the myocardium, leading to ischemia-reperfusion injury (IRI). While experimental studies overwhelmingly demonstrate that females experience greater functional recovery from MI and decreased severity in the underlying pathophysiological mechanisms, the outcomes of MI with subsequent reperfusion therapy, which is the clinical correlate of myocardial IRI, are generally poorer for women compared with men. Distressingly, women are also reported to benefit less from current guideline-based therapies compared with men. These seemingly contradicting outcomes between experimental and clinical studies show a need for further investigation of sex-based differences in disease pathophysiology, treatment response, and a sex-specific approach in the development of novel therapeutic methods against myocardial IRI. In this literature review, we summarize the current knowledge on sex differences in the underlying pathophysiological mechanisms of myocardial IRI, including the roles of sex hormones and sex chromosomes. Furthermore, we address sex differences in pharmacokinetics, pharmacodynamics, and pharmacogenetics of current drugs prescribed to limit myocardial IRI. Lastly, we highlight ongoing clinical trials assessing novel pharmacological treatments against myocardial IRI and sex differences that may underlie the efficacy of these new therapeutic approaches.

Cardiodiagnostic sex-specific differences of the female athlete in sports cardiology

The cardiovascular care of highly active individuals and competitive athletes has developed into an important focus within the field of sports medicine. An evolving understanding of exercise-induced cardiovascular remodeling in athletes has led to a more robust characterization of physiologic adaptation versus pathological dysfunction, but this distinction is often challenging due to diagnostic commonalities. Current data reflects sporting-focused analyses of mainly male athletes, which may not be easily applicable to the female athletic heart. Increasingly female-specific cardiac dimensional and physiologic data are starting to emerge from comparative studies that may be utilized to address this growing need, and further guide individualized care. Here, we review current literature evaluating female-specific cardiovascular adaptations of the athletic heart, and formulate a discussion on cardiac remodeling, cardiodiagnostic findings, etiologic mechanisms, limitations of currently available data, and direction for future research in the cardiovascular care of female athletes.

Cholecystokinin Expression in the Development of Myocardial Hypertrophy

BACKGROUND

Expression of cholecystokinin is found in myocardial tissues as a gastrointestinal hormone and may be involved in cardiovascular regulation. However, it is unclear whether there is an increase in cholecystokinin expression in myocardial hypertrophy progression induced by abdominal aortic constriction. The study is aimed at exploring the relationship between cholecystokinin expression and myocardial hypertrophy.

METHODS

We randomly divided the 70 Sprague-Dawley rats into two groups: the sham operation group and the abdominal aortic constriction group. The hearts of rats were measured by echocardiography, and myocardial tissues and blood were collected at 4 weeks, 8 weeks, and 12 weeks after surgery. Morphological changes were assessed by microscopy. The cholecystokinin expression was evaluated by immunochemistry, Western blotting, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assay.

RESULTS

The relative protein levels of cholecystokinin were significantly increased in the abdominal aortic constriction groups compared with the corresponding sham operation groups at 8 weeks and 12 weeks. The cholecystokinin mRNA in the abdominal aortic constriction groups was significantly higher than the time-matched sham operation groups. Changes in the left ventricular wall thickness were positively correlated with the relative protein levels of cholecystokinin and the mRNA of cholecystokinin.

CONCLUSIONS

The development of myocardial hypertrophy can affect the cholecystokinin expression of myocardial tissues.

Testosterone, cardiomyopathies, and heart failure: a narrative review

Testosterone exerts an important regulation of cardiovascular function through genomic and nongenomic pathways. It produces several changes in cardiomyocytes, the main actor of cardiomyopathies, which are characterized by pathological remodeling, eventually leading to heart failure. Testosterone is involved in contractility, in the energy metabolism of myocardial cells, apoptosis, and the remodeling process. In myocarditis, testosterone directly promotes the type of inflammation that leads to fibrosis, and influences viremia with virus localization. At the same time, testosterone exerts cardioprotective effects that have been observed in different studies. There is increasing evidence that low endogenous levels of testosterone have a negative impact in some cardiomyopathies and a protective impact in others. This review focuses on the interrelationships between testosterone and cardiomyopathies and heart failure.

Aortic Root Dilation and Testosterone Use: Are They Associated?

Aortic root dilation and thoracic aortic aneurysms are relatively rare in young and healthy patient populations. However, a number of observed incidental cases regarding young males and testosterone use raises suspicion of a potential risk factor for aortic root dilation. The authors' patient, a healthy 40-year-old man with a significant history of testosterone use who developed a massively dilated aortic root, is sufficiently alarming to report. Notwithstanding anecdotal cases, there exists a well-known association between elite strength athletes and aortic root dilation. Nevertheless, very little clinical research exists on the relationship between testosterone use and aortic root dilation and/or thoracic aortic aneurysms. Furthermore, a small number of animal studies showed a relationship between testosterone and vascular dilation, particularly the aorta. Although testosterone may play a role in the development of aortic pathologies, further research is necessary to clarify the possible relationship if cases such as these are to be prevented.

Sex differences in the evolution of left ventricle remodeling in rats with severe volume overload

Background

Aortic valve regurgitation (AR) results in left ventricle (LV) volume overload (VO) leading to its dilation and hypertrophy (H). We study a rat model of severe AR induced by puncturing one or two leaflets using a catheter. Most of our studies were conducted in male animals. Recently, we started investigating if sex dimorphism existed in the AR rat model. We observed that AR females developed as much LVH as males but morphological remodeling differences were present. A head-to-head comparison of LV morphological and functional changes had never been performed in AR males (M) and females (F) using the latest modalities in cardiac imaging by echocardiography.

Methods

We performed a longitudinal study to evaluate the development of LV hypertrophy caused by chronic AR in male and female rats over 6 months. Sham-operated (sham) animals were used as controls.

Results

LV diastolic volumes (EDV) increased more over 6 months in sham males than in females (38% vs. 23% for EDV, both p < 0.01). AR resulted in significant LV dilation for both sexes (54% vs. 51% increase in EDV) vs. baseline values. Since normal cardiac growth was less in females, dilation from AR was relatively more important for them (88% (M) vs. 157% (F) increase in EDV over sham). AR caused LV wall thickening in both males and females. It happened sooner for AR females and was more important than in males (25% (M) vs. 56% (F) increase in septum thickness at 2 months and 10% (M) vs. 30% (F) at 6 months). We then evaluated if AR was associated with changes in LV strain using speckle-tracking 2D echocardiography. Global longitudinal strain remained similar between AR and sham animals. Circumferential strain was negatively modulated by AR but only in females and early after VO induction (13% (M) vs. 26% (F)).

Conclusion

AR resulted in more LV dilation and quicker wall thickening in female AR rats compared to males. Global circumferential strain was negatively modulated in AR females but not in males. AR also seemed to lead to a more spherical LV shape in females whereas; it kept mostly an ellipsoid shape in males. This can influence validity of mass estimation of the dilated LV in females by echocardiography.

Effects of the loss of estrogen on the heart's hypertrophic response to chronic left ventricle volume overload in rats

Aortic valve regurgitation (AR) can result in heart failure from chronic overloading of the left ventricle (LV). Little is known of the role of estrogens in the LV responses to this condition. The aim of the study was to compare LV remodeling in female rats with severe AR in absence of estrogens by ovariectomy (Ovx). In a first study, we investigated over 6 months the development of hypertrophy in four groups of female Wistar rats: AR or sham-operated (sham) and Ovx or not. Ovx reduced normal heart growth. As expected, volume overload (VO) from AR resulted in significant LV dilation (42% and 32% increase LV end-diastolic diameter in intact and Ovx groups vs. their respective sham group; p < 0.0001). LV weight was also significantly and similarly increased in both AR groups (non-Ovx and Ovx). Increase in stroke volume or cardiac output and loss of systolic function were similar between AR intact and AR Ovx groups compared to sham. We then investigated what were the effects of 17beta-estradiol (E2; 0.03 mg/kg/day) treatment on the parameters studied in Ovx rats. Ovx reduced uterus weight by 85% and E2 treatment restored up to 65% of the normal weight. E2 also helped normalize heart size to normal values. On the other hand, it did not influence the extent of the hypertrophic response to AR. In fact, E2 treatment further reduced LV hypertrophy in AR Ovx rats (41% over Sham Ovx + E2). Systolic and diastolic functions parameters in AR Ovx + E2 were similar to intact AR animals. Ovx in sham rats had a significant effect on the LV gene expression of several hypertrophy markers. Atrial natriuretic peptide (Nppa) gene expression was reduced by Ovx in sham-operated females whereas brain natriuretic peptide (Nppb) expression was increased. Alpha (Myh6) and beta (Myh7) myosin heavy chain genes were also significantly modulated by Ovx in sham females. In AR rats, LV expression of both Nppa and Nppb genes were increased as expected. Ovx further increased it of AR rats for Nppa and did the opposite for Nppb. Interestingly, AR in Ovx rats had only minimal effects on Myh6 and Myh7 genes whereas they were modulated as expected for intact AR animals. In summary, loss of estrogens by Ovx in AR rats was not accompanied by a worsening of hypertrophy or cardiac function. Normal cardiac growth was reduced by Ovx in sham females but not the hypertrophic response to AR. On the other hand, Ovx had important effects on LV gene expression both in sham and AR female rats.

Sex differences in the response to angiotensin II receptor blockade in a rat model of eccentric cardiac hypertrophy

Background. Men and women differ in their susceptibility to cardiovascular disease, though the underlying mechanism has remained elusive. Heart disease symptoms, evolution and response to treatment are often sex-specific. This has been studied in animal models of hypertension or myocardial infarction in the past but has received less attention in the context of heart valve regurgitation. The aim of the study was to evaluate the development of cardiac hypertrophy (CH) in response to left ventricle (LV) volume overload (VO) caused by chronic aortic valve regurgitation (AR) in male and female rats treated or not with angiotensin II receptor blocker (ARB), valsartan. We studied eight groups of Wistar rats: male or female, AR or sham-operated (sham) and treated or not with valsartan (30 mg/kg/day) for 9 weeks starting one week before AR surgical induction.

Results. As expected, VO from AR resulted for both male and female rats in significant LV dilation (39% vs. 40% end-diastolic LV diameter increase, respectively; p < 0.0001) and CH (53% vs. 64% heart weight increase, respectively; p < 0.0001) compared to sham. Sex differences were observed in LV wall thickening in response to VO. In untreated AR males, relative LV wall thickness (a ratio of wall thickness to end-diastolic diameter) was reduced compared to sham, whereas this ratio in females remained unchanged. ARB treatment did not prevent LV dilation in both male and female animals but reversed LV wall thickening in females. Systolic and diastolic functions in AR animals were altered similarly for both sexes. ARB treatment did not improve systolic function but helped normalizing diastolic parameters such as left atrial mass and E wave slope in female AR rats. Increased LV gene expression of Anp and Bnp was normalized by ARB treatment in AR females but not in males. Other hypertrophy gene markers (Fos, Trpc6, Klf15, Myh6 and Myh7) were not modulated by ARB treatment. The same was true for genes related to LV extracellular matrix remodeling (Col1a1, Col3a1, Fn1, Mmp2, Timp1 and Lox). In summary, ARB treatment of rats with severe AR blocked the female-specific hypertrophic response characterized by LV chamber wall thickening. LV dilation, on the other hand, was not significantly decreased by ARB treatment. This also indicates that activation of the angiotensin II receptor is probably more involved in the early steps of LV remodeling caused by AR in females than in males.