Transcriptional factors in calcium mishandling and atrial fibrillation development

Assessment of the relative cardiotoxicity and behavioral effects of butylated hydroxytoluene and its metabolites in developing zebrafish (Danio rerio)

Butylated hydroxytoluene (BHT) and its transformation products are ubiquitously detected in aquatic environments. Despite studies reporting on the adverse effects of BHT exposure in early-staged zebrafish, the comparative toxicity of its metabolites is not known. To address this, zebrafish embryos were exposed continuously to 0.01-1 μM BHTs (BHT, BHT-Q, BHT-OH, BHT-CHO, and BHT-COOH) for up to 6 days. Each chemical altered the heart rates of developing zebrafish at 72 hpf. When assessing cardiac morphology at 48 and 72 hpf, BHT-COOH showed stronger effects compared to BHT in inducing pericardial edema and myocardial hypertrophy. This effect is hypothesized to be attributed to differences in transcriptional regulation of key genes during cardiac development. BHT predominantly affected transcript expression in the early (15 hpf) or late stages (48-72 hpf) of heart development, but did not impact the transcription during the middle stage (24-36 hpf). Conversely, BHT-COOH altered the expression of early transcription factors (i.e. tbx5, nkx2.5, gata4, hand2) and functional genes (i.e. myh6, nppa, cacna1ab, and atp2a2) at all stages of cardiac development. The effects on the heart may also be related to behavioral changes observed in larval fish. Behavior was most sensitive with low chemical exposures (0.01 μM), while at higher concentrations, heart rate was a more sensitive indicator of BHT-induced toxicity. Taken together, our results indicate that BHTs induce adverse effects on cardiovascular function and BHT metabolites may pose higher risk than the parent compound.

Iron and atrial fibrillation: A review

Atrial fibrillation (AF), one of the most common arrhythmias in clinical practice, is classified into paroxysmal, persistent, and permanent AF according to its duration. The development of AF is associated with increased cardiovascular morbidity and mortality. However, the exact etiology of this disease remains poorly understood. Recent studies found disorders of iron metabolism might be involved in the progression of AF. Abnormal iron metabolism in cardiomyocytes provides arrhythmogenic substrates through a variety of mechanisms, including calcium mishandling, ion channel remodeling, and oxidative stress overaction. Interestingly, in AF patients with iron overload, interventions on iron metabolism, such as iron chelators and ferroptosis inhibitors, has been shown to prevent AF via reducing ferroptosis. Herein, we review the possible mechanisms, consequences, and therapeutic implications of altered atrial iron handling for AF pathophysiology.

Comparison of Serum Selenium Levels Between Patients with Newly Diagnosed Atrial Fibrillation and Normal Controls

Atrial fibrillation (AF) is the most common sustained dysrhythmia in the elderly population. It is estimated to affect more than 30 million people worldwide. AF occurs when abnormal electrical impulses start to activate in the atria and override the heart's natural pacemaker, which can no longer control the heart's rhythm. Since atrial contractility is impaired in AF, blood flow in the atria becomes stasis over time and causes thrombus formation. This thrombus causes the risk of embolism and causes complications such as stroke. Therefore, it is a fundamental cause of cardiovascular mortality and morbidity. The diagnosis of AF is usually made with the help of electrocardiography (ECG). The absence of P waves in ECG and irregular R-R interval is sufficient for diagnosis. AF is most commonly associated with advanced age, hypertension, diabetes mellitus, thyroid dysfunction, obesity, alcohol use, physical inactivity, and underlying ischemic heart diseases. As well as to all these usual risk factors, electrolyte disorders and mineral deficiencies also play an essential role in the etiology of AF. Previous studies have clearly demonstrated that serum electrolyte changes have a role in the etiology of AF. These include electrolytes such as serum magnesium, calcium, potassium, and chloride. However, there is not enough information in the literature about the effects of trace elements on AF. Selenium is a trace element that plays an important role in many systems in the human body. It has a vital role in inflammation, regulation of antioxidant reactions, and fibrosis of tissues in both animals and humans. It is known that selenium deficiency causes many cardiovascular diseases such as heart failure, coronary artery disease, and arrhythmia. Our study aimed to compare serum selenium levels in newly diagnosed AF patients with the healthy control group.