Arrhythmogenic effect of androgens on the rat heart

Harnessing the power of nutritional antioxidants against adrenal hormone imbalance-associated oxidative stress

Oxidative stress, resulting from dysregulation in the secretion of adrenal hormones, represents a major concern in human health. The present review comprehensively examines various categories of endocrine dysregulation within the adrenal glands, encompassing glucocorticoids, mineralocorticoids, and androgens. Additionally, a comprehensive account of adrenal hormone disorders, including adrenal insufficiency, Cushing's syndrome, and adrenal tumors, is presented, with particular emphasis on their intricate association with oxidative stress. The review also delves into an examination of various nutritional antioxidants, namely vitamin C, vitamin E, carotenoids, selenium, zinc, polyphenols, coenzyme Q10, and probiotics, and elucidates their role in mitigating the adverse effects of oxidative stress arising from imbalances in adrenal hormone levels. In conclusion, harnessing the power of nutritional antioxidants has the potential to help with oxidative stress caused by an imbalance in adrenal hormones. This could lead to new research and therapeutic interventions.

Brugada Syndrome: More than a Monogenic Channelopathy

Brugada syndrome (BrS) is an inherited cardiac channelopathy first diagnosed in 1992 but still considered a challenging disease in terms of diagnosis, arrhythmia risk prediction, pathophysiology and management. Despite about 20% of individuals carrying pathogenic variants in the SCN5A gene, the identification of a polygenic origin for BrS and the potential role of common genetic variants provide the basis for applying polygenic risk scores for individual risk prediction. The pathophysiological mechanisms are still unclear, and the initial thinking of this syndrome as a primary electrical disease is evolving towards a partly structural disease. This review focuses on the main scientific advancements in the identification of biomarkers for diagnosis, risk stratification, pathophysiology and therapy of BrS. A comprehensive model that integrates clinical and genetic factors, comorbidities, age and gender, and perhaps environmental influences may provide the opportunity to enhance patients' quality of life and improve the therapeutic approach.

The Impact of Testosterone on the QT Interval: A Systematic Review

Humans and mammals have sex-specific differences in cardiac electrophysiology, linked to the action of sex hormones in the cardiac muscle. These hormones can upregulate or downregulate the expression of ionic channels modulating the cardiac cycle through genomic and non-genomic interactions. Systematic search in PubMed, Medline and EMBASE including keywords pertaining to testosterone and QT interval. Included experimental studies and observation studies and case reports presenting the results of testosterone administration, excess or deficiency in humans and animals. Testosterone has been shown to shorten the action potential duration, by enhancing the expression of K⁺ channels and downregulating I_CaL increasing the repolarization reserve of the cardiac muscle. This effect has been observed in both genders and animals. Testosterone deficient states can promote arrhythmogenesis. The evidence in this paper may be used to guide clinical considerations, such as increased clinical surveillance of patients in testosterone deficient states using ECG.

Cardiac arrhythmia considerations of hormone cancer therapies

Breast and prostate cancers are among the most prevalent cancers worldwide. Oestradiol and progesterone are major drivers for breast cancer proliferation, and androgens for prostate cancer. Endocrine therapies are drugs that interfere with hormone-activated pathways to slow cancer progression. Multiple new breakthrough drugs improving overall survival have recently been developed within this class. As the use of these latter drugs grows, incidence of cardiac arrhythmias has emerged as an unappreciated complication. These changes are not surprising given that sex hormones alter ventricular repolarization. Testosterone shortens action potential duration and QT interval duration, while oestradiol has an opposite effect. In patients with breast cancer, selective oestrogen receptor modulators are associated with more reports for long QT and torsade de pointes (TdP) than aromatase inhibitors, likely through an oestradiol-like effect on the heart. Cyclin-dependent kinase 4/6 inhibitors, a new class of anticancer drugs used in combination with endocrine therapies in hormone receptor positive breast cancer, are also variably associated with drug-induced long QT, particularly with ribociclib. In prostate cancer, androgen deprivation therapy is associated with long QT and TdP, and possibly atrial fibrillation for abiraterone. In this review, we have summarized the clinical and preclinical data focusing on cardiac arrhythmia considerations of hormone cancer therapies.

Asparagine-linked glycosylation modifies voltage-dependent gating properties of CaV3.1-T-type Ca2+ channel

T-type channels are low-voltage-activated channels that play a role in the cardiovascular system particularly for pacemaker activity. Glycosylation is one of the most prevalent post-translational modifications in protein. Among various glycosylation types, the most common one is asparagine-linked (N-linked) glycosylation. The aim of this study was to elucidate the roles of N-linked glycosylation for the gating properties of the CaV3.1-T-type Ca2+ channel. N-linked glycosylation synthesis inhibitor tunicamycin causes a reduction of CaV3.1-T-type Ca2+ channel current (CaV3.1-ICa.T) when applied for 12 h or longer. Tunicamycin (24 h) significantly shifted the activation curve to the depolarization potentials, whereas the steady-state inactivation curve was unaffected. Use-dependent inactivation of CaV3.1-ICa.T was accelerated, and recovery from inactivation was prolonged by tunicamycin (24 h). CaV3.1-ICa.T was insensitive to a glycosidase PNGase F when the channels were expressed on the plasma membrane. These findings suggest that N-glycosylation contributes not only to the cell surface expression of the CaV3.1-T-type Ca2+ channel but to the regulation of the gating properties of the channel when the channel proteins were processed during the folding and trafficking steps in the cell.

Testosterone-mediated upregulation of delayed rectifier potassium channel in cardiomyocytes causes abbreviation of QT intervals in rats

Men have shorter rate-corrected QT intervals (QTc) than women, especially at the period of adolescence or later. The aim of this study was to elucidate the long-term effects of testosterone on cardiac excitability parameters including electrocardiogram (ECG) and potassium channel current. Testosterone shortened QT intervals in ECG in castrated male rats, not immediately after, but on day 2 or later. Expression of Kv7.1 (KCNQ1) mRNA was significantly upregulated by testosterone in cardiomyocytes of male and female rats. Short-term application of testosterone was without effect on delayed rectifier potassium channel current (IKs), whereas IKs was significantly increased in cardiomyocytes treated with dihydrotestosterone for 24 h, which was mimicked by isoproterenol (24 h). Gene-selective inhibitors of a transcription factor SP1, mithramycin, abolished the effects of testosterone on Kv7.1. Testosterone increases Kv7.1-IKs possibly through a pathway related to a transcription factor SP1, suggesting a genomic effect of testosterone as an active factor for cardiac excitability.