Loss of Sec-1 Family Domain-Containing 1 (scfd1) Causes Severe Cardiac Defects and Endoplasmic Reticulum Stress in Zebrafish.

Dilated cardiomyopathy (DCM) is a common heart muscle disorder that frequently leads to heart failure, arrhythmias, and death. While DCM is often heritable, disease-causing mutations are identified in only ~30% of cases. In a forward genetic mutagenesis screen, we identified a novel zebrafish mutant, heart and head (hahvcc43), characterized by early-onset cardiomyopathy and craniofacial defects. Linkage analysis and next-generation sequencing identified a nonsense variant in the highly conserved scfd1 gene, also known as sly1, that encodes sec1 family domain-containing 1. Sec1/Munc18 proteins, such as Scfd1, are involved in membrane fusion regulating endoplasmic reticulum (ER)/Golgi transport. CRISPR/Cas9-engineered scfd1vcc44 null mutants showed severe cardiac and craniofacial defects and embryonic lethality that recapitulated the phenotype of hahvcc43 mutants. Electron micrographs of scfd1-depleted cardiomyocytes showed reduced myofibril width and sarcomere density, as well as reticular network disorganization and fragmentation of Golgi stacks. Furthermore, quantitative PCR analysis showed upregulation of ER stress response and apoptosis markers. Both heterozygous hahvcc43 mutants and scfd1vcc44 mutants survived to adulthood, showing chamber dilation and reduced ventricular contraction. Collectively, our data implicate scfd1 loss-of-function as the genetic defect at the hahvcc43 locus and provide new insights into the role of scfd1 in cardiac development and function.

Humming (Simple Bhramari Pranayama) as a Stress Buster: A Holter-Based Study to Analyze Heart Rate Variability (HRV) Parameters During Bhramari, Physical Activity, Emotional Stress, and Sleep.

Objective In this study, our goal was to understand the comparative impact of humming, physical activity, emotional stress, and sleep on several heart rate variability (HRV) parameters, including the stress index (SI), and to assess the effectiveness of humming (simple Bhramari) as a stress buster based on the HRV parameters. Methods This pilot study assessed the long-term HRV parameters of 23 participants in terms of four activities: humming (simple Bhramari), physical activity, emotional stress, and sleep. The single-channel Holter device measured the readings, and data was analyzed using Kubios HRV Premium software for time and frequency-domain HRV parameters, including the stress index. Regarding statistical analysis, single-factor ANOVA followed by paired t-test was used to compare the results of HRV parameters "during" the four activities to understand if humming generates the outcome to enhance the autonomic nervous system. Results Our findings revealed that humming generates the lowest stress index compared to all three other activities (physical activity, emotional stress, and sleep). Several additional HRV parameters also supported the positive impact on the autonomic nervous, equivalent to stress reduction. Conclusions Humming (simple Bhramari) can be an effective stress-buster based on the assessment of several HRV parameters during its practice and in comparison with other activities. A regular daily humming routine can help enhance the parasympathetic nervous system and slow down sympathetic activation.

Effect of Various Lengths of Respiration on Heart Rate Variability during Simple Bhramari (Humming).

Background: Heart rate varies during breathing and the heart rate variability (HRV) facilitates the autonomic homeostatic capacity. The maximum HRV was observed at around 10 s of prolonged respiration as per HRV biofeedback literature. However, there is a gap in understanding the variations in HRV by different respiration lengths during simple Bhramari practice. Objective: To assess the effect of various respiration lengths (8, 10, 12, and 14 s) on HRV during the simple Bhramari (humming) practice. Methodology: A total of 118 individuals (67 males, 51 females) signed up for the study based on convenience sampling at a wellness center. A randomized (simple permutation) within-subject crossover design with repeated measures was used to measure their HRV during the simple Bhramari practice. The results were analyzed with one-way ANOVA and paired samples t-test. Results: The results indicate that, unlike the 10 s of respiration during HRV biofeedback breathing, maximum HRV during humming happens between 12 and 14 s of long breathing. Conclusions: The unique findings of the study demonstrate the maximization of HRV between the respiration lengths of 12 and 14 s. Future work should explore expanding the research to a broader group of participants, including individuals with chronic conditions and other demographic variables and mantra chanting.

Adverse Childhood Experiences & mental health - the urgent need for public health intervention in India.

Global evidence has demonstrated that Adverse Childhood Experiences (ACEs) up to age 18 significantly increases the risk of mental and physical health for an adult. The research linking ACE with health and well-being has confirmed a dose-response relationship between the number of ACEs experienced and the extent of the impact on wellbeing. The source of ACE is the family, community, and the immediate environment, and it causes long-term risk for mental health with the potential to carry it over beyond the present generation. The findings are consistent across the developed and developing countries, and the evidence highlights the need for new elements beyond the 10 ACE elements in the pathbreaking original study. India needs urgent intervention on ACE prevention and management with 0.4 billion children and adolescents, with one out of seven Indians with mental health issues. Firstly, this commentary reviews global research and summarizes the limited evidence available in India on ACE elements' impact on mental health. And, secondly, it proposes a multi-pronged approach to identify, manage and prevent the mental health implications of ACE in India to preempt a significant public health challenge.

Bhramari Pranayama - A simple lifestyle intervention to reduce heart rate, enhance the lung function and immunity.

Individuals with chronic diseases have a higher risk of infection and show lung function impairment. Poor lifestyle choices such as physical inactivity, poor diet, stress, excess tobacco, and alcohol, and sleep disruption increase the risk of chronic inflammation and immune impairment but the evidence does not quantify the specific risk factor(s) and their correlation with the immune system impairment. COVID-19 related uncertainty has created a more urgent need to understand the need to identify interventions that could help in managing the risk factors, especially for healthy individuals who are at a higher risk of infection and/or immune system impairment. The role of three parameters, the Resting Heart Rate (HR), increased Heart Rate Variability (HRV), and lung function is considered as risk factors for systemic inflammation and chronic diseases. The evidence on Bhramari Pranayama is presented for possible lifestyle interventions to reduce the risk of infection, increase lung function, enhance autonomic function, and improve sleep quality in healthy individuals.

Conserved Role of the Large Conductance Calcium-Activated Potassium Channel, KCa1.1, in Sinus Node Function and Arrhythmia Risk.

BACKGROUND: KCNMA1 encodes the α-subunit of the large-conductance Ca2+-activated K+ channel, KCa1.1, and lies within a linkage interval for atrial fibrillation (AF). Insights into the cardiac functions of KCa1.1 are limited, and KCNMA1 has not been investigated as an AF candidate gene. METHODS: The KCNMA1 gene was sequenced in 118 patients with familial AF. The role of KCa1.1 in normal cardiac structure and function was evaluated in humans, mice, zebrafish, and fly. A novel KCNMA1 variant was functionally characterized. RESULTS: A complex KCNMA1 variant was identified in 1 kindred with AF. To evaluate potential disease mechanisms, we first evaluated the distribution of KCa1.1 in normal hearts using immunostaining and immunogold electron microscopy. KCa1.1 was seen throughout the atria and ventricles in humans and mice, with strong expression in the sinus node. In an ex vivo murine sinoatrial node preparation, addition of the KCa1.1 antagonist, paxilline, blunted the increase in beating rate induced by adrenergic receptor stimulation. Knockdown of the KCa1.1 ortholog, kcnma1b, in zebrafish embryos resulted in sinus bradycardia with dilatation and reduced contraction of the atrium and ventricle. Genetic inactivation of the Drosophila KCa1.1 ortholog, slo, systemically or in adult stages, also slowed the heartbeat and produced fibrillatory cardiac contractions. Electrophysiological characterization of slo-deficient flies revealed bursts of action potentials, reflecting increased events of fibrillatory arrhythmias. Flies with cardiac-specific overexpression of the human KCNMA1 mutant also showed increased heart period and bursts of action potentials, similar to the KCa1.1 loss-of-function models. CONCLUSIONS: Our data point to a highly conserved role of KCa1.1 in sinus node function in humans, mice, zebrafish, and fly and suggest that KCa1.1 loss of function may predispose to AF.

Comparative Study of the Impact of Active Meditation Protocol and Silence Meditation on Heart Rate Variability and Mood in Women.

AIM: The aim of this study was to understand the impact of an active meditation protocol on heart rate variability (HRV) and mood in women as compared to breath-focused silence meditation. MATERIALS AND METHODS: Women experienced two different practices of 20 min each: (a) control group: silence meditation focusing on breath and (b) experiment group: active meditation that included four activities, each lasting for 5 minutes - (1) simple humming, (2) coherent heart-focused breathing with 5s of inhalation and 5s of exhalation, (3) coherent heart-focused breathing while invoking positive emotions, and (4) guided imagery about a preidentified goal. The silence meditation encouraged women to only focus on the breath. The Positive and Negative Affect Scale measured mood before/after the practice (n = 24), and emWavePro device measured HRV parameters for 5 min before/after the practices (n = 18). Statistical data analysis was done using a paired t-test. RESULTS: HRV (specifically, parasympathetic nervous system [PNS]) parameters showed a statistically significant improvement in the experiment group as compared to the control group. There was a statistically significant reduction in negative affect after both the practices, and the increase in positive affect was observed only for the experiment group. CONCLUSIONS: The active meditation provides a significant enhancement in mood and HRV parameters related to PNS as compared to silence meditation where the changes in HRV were not consistent and the positive mood did not increase significantly. Future research in this area could explore the impact of such practice for a longer duration and understand the impact of each component of the meditative practices.

A-Band Titin Truncation in Zebrafish Causes Dilated Cardiomyopathy and Hemodynamic Stress Intolerance.

Background Truncating variants in the TTN gene ( TTNtv) are common in patients with dilated cardiomyopathy (DCM) but also occur in the general population. Whether TTNtv are sufficient to cause DCM or require a second hit for DCM manifestation is an important clinical issue. Methods We generated a zebrafish model of an A-band TTNtv identified in 2 human DCM families in which early-onset disease appeared to be precipitated by ventricular volume overload. Cardiac phenotypes were serially assessed from 0 to 12 months using video microscopy, high-frequency echocardiography, and histopathologic analysis. The effects of sustained hemodynamic stress resulting from an anemia-induced hyperdynamic state were also evaluated. Results Homozygous ttna mutants had severe cardiac dysmorphogenesis and premature death, whereas heterozygous mutants ( ttnatv/+) survived into adulthood and spontaneously developed DCM. Six-month-old ttnatv/+ fish had reduced baseline ventricular systolic function and failed to mount a hypercontractile response when challenged by hemodynamic stress. Pulsed wave and tissue Doppler analysis also revealed unsuspected ventricular diastolic dysfunction in ttnatv/+ fish with prolonged isovolumic relaxation and increased diastolic passive stiffness in the absence of myocardial fibrosis. These defects reduced diastolic reserve under stress conditions and resulted in disproportionately greater atrial dilation than observed in wild-type fish. Conclusions Heterozygosity for A-band titin truncation is sufficient to cause DCM in adult zebrafish. Abnormalities of systolic and diastolic reserve in titin-truncated fish reduce stress tolerance and may contribute to a substrate for atrial arrhythmogenesis. These data suggest that hemodynamic stress may be an important modifiable risk factor in human TTNtv-related DCM.

A transgenic zebrafish model of a human cardiac sodium channel mutation exhibits bradycardia, conduction-system abnormalities and early death.

The recent exponential increase in human genetic studies due to the advances of next generation sequencing has generated unprecedented numbers of new gene variants. Determining which of these are causative of human disease is a major challenge. In-vitro studies and murine models have been used to study inherited cardiac arrhythmias but have several limitations. Zebrafish models provide an attractive alternative for modeling human heart disease due to similarities in cardiac electrophysiology and contraction, together with ease of genetic manipulation, external development and optical transparency. Although zebrafish cardiac mutants and morphants have been widely used to study loss and knockdown of zebrafish gene function, the phenotypic effects of human dominant-negative gene mutations expressed in transgenic zebrafish have not been evaluated. The aim of this study was to generate and characterize a transgenic zebrafish arrhythmia model harboring the pathogenic human cardiac sodium channel mutation SCN5A-D1275N, that has been robustly associated with a range of cardiac phenotypes, including conduction disease, sinus node dysfunction, atrial and ventricular arrhythmias, and dilated cardiomyopathy in humans and in mice. Stable transgenic fish with cardiac expression of human SCN5A were generated using Tol2-mediated transgenesis and cardiac phenotypes were analyzed using video microscopy and ECG. Here we show that transgenic zebrafish expressing the SCN5A-D1275N mutation, but not wild-type SCN5A, exhibit bradycardia, conduction-system abnormalities and premature death. We furthermore show that SCN5A-WT, and to a lesser degree SCN5A-D1275N, are able to compensate the loss of endogenous zebrafish cardiac sodium channels, indicating that the basic pathways, through which SCN5A acts, are conserved in teleosts. This proof-of-principle study suggests that zebrafish may be highly useful in vivo models to differentiate functional from benign human genetic variants in cardiac ion channel genes in a time- and cost-efficient manner. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".

Epistatic effects of potassium channel variation on cardiac repolarization and atrial fibrillation risk.

OBJECTIVES: The aim of this study was to evaluate the role of cardiac K(+) channel gene variants in families with atrial fibrillation (AF). BACKGROUND: The K(+) channels play a major role in atrial repolarization but single mutations in cardiac K(+) channel genes are infrequently present in AF families. The collective effect of background K(+) channel variants of varying prevalence and effect size on the atrial substrate for AF is largely unexplored. METHODS: Genes encoding the major cardiac K(+) channels were resequenced in 80 AF probands. Nonsynonymous coding sequence variants identified in AF probands were evaluated in 240 control subjects. Novel variants were characterized using patch-clamp techniques and in silico modeling was performed using the Courtemanche atrial cell model. RESULTS: Nineteen nonsynonymous variants in 9 genes were found, including 11 rare variants. Rare variants were more frequent in AF probands (18.8% vs. 4.2%, p < 0.001), and the mean number of variants was greater (0.21 vs. 0.04, p < 0.001). The majority of K(+) channel variants individually had modest functional effects. Modeling simulations to evaluate combinations of K(+) channel variants of varying population frequency indicated that simultaneous small perturbations of multiple current densities had nonlinear interactions and could result in substantial (>30 ms) shortening or lengthening of action potential duration as well as increased dispersion of repolarization. CONCLUSIONS: Families with AF show an excess of rare functional K(+) channel gene variants of varying phenotypic effect size that may contribute to an atrial arrhythmogenic substrate. Atrial cell modeling is a useful tool to assess epistatic interactions between multiple variants.