High-fat diet induces protein kinase A and G-protein receptor kinase phosphorylation of β2 -adrenergic receptor and impairs cardiac adrenergic reserve in animal hearts.

Key pointsPatients with diabetes show a blunted cardiac inotropic response to β-adrenergic stimulation despite normal cardiac contractile reserve. Acute insulin stimulation impairs β-adrenergically induced contractile function in isolated cardiomyocytes and Langendorff-perfused hearts. In this study, we aimed to examine the potential effects of hyperinsulinaemia associated with high-fat diet (HFD) feeding on the cardiac β2 -adrenergic receptor signalling and the impacts on cardiac contractile function. We showed that 8 weeks of HFD feeding leads to reductions in cardiac functional reserve in response to β-adrenergic stimulation without significant alteration of cardiac structure and function, which is associated with significant changes in β2 -adrenergic receptor phosphorylation at protein kinase A and G-protein receptor kinase sites in the myocardium. The results suggest that clinical intervention might be applied to subjects in early diabetes without cardiac symptoms to prevent further cardiac complications.AbstractPatients with diabetes display reduced exercise capability and impaired cardiac contractile reserve in response to adrenergic stimulation. We have recently uncovered an insulin receptor and adrenergic receptor signal network in the heart. The aim of this study was to understand the impacts of high-fat diet (HFD) on the insulin-adrenergic receptor signal network in hearts. After 8 weeks of HFD feeding, mice exhibited diabetes, with elevated insulin and glucose concentrations associated with body weight gain. Mice fed an HFD had normal cardiac structure and function. However, the HFD-fed mice displayed a significant elevation of phosphorylation of the β2 -adrenergic receptor (β2 AR) at both the protein kinase A site serine 261/262 and the G-protein-coupled receptor kinase site serine 355/356 and impaired adrenergic reserve when compared with mice fed on normal chow. Isolated myocytes from HFD-fed mice also displayed a reduced contractile response to adrenergic stimulation when compared with those of control mice fed normal chow. Genetic deletion of the β2 AR led to a normalized adrenergic response and preserved cardiac contractile reserve in HFD-fed mice. Together, these data indicate that HFD promotes phosphorylation of the β2 AR, contributing to impairment of cardiac contractile reserve before cardiac structural and functional remodelling, suggesting that early intervention in the insulin-adrenergic signalling network might be effective in prevention of cardiac complications in diabetes

Cardiac Macrophages and Their Effects on Arrhythmogenesis

Cardiac electrophysiology is a complex system established by a plethora of inward and outward ion currents in cardiomyocytes generating and conducting electrical signals in the heart. However, not only cardiomyocytes but also other cell types can modulate the heart rhythm. Recently, cardiac macrophages were demonstrated as important players in both electrophysiology and arrhythmogenesis. Cardiac macrophages are a heterogeneous group of immune cells including resident macrophages derived from embryonic and fetal precursors and recruited macrophages derived from circulating monocytes from the bone marrow. Recent studies suggest antiarrhythmic as well as proarrhythmic effects of cardiac macrophages. The proposed mechanisms of how cardiac macrophages affect electrophysiology vary and include both direct and indirect interactions with other cardiac cells. In this review, we provide an overview of the different subsets of macrophages in the heart and their possible interactions with cardiomyocytes under both physiologic conditions and heart disease. Furthermore, we elucidate similarities and differences between human, murine and porcine cardiac macrophages, thus providing detailed information for researchers investigating cardiac macrophages in important animal species for electrophysiologic research. Finally, we discuss the pros and cons of mice and pigs to investigate the role of cardiac macrophages in arrhythmogenesis from a translational perspective

The Implications of Altered Cholinergic Signaling in Cardiac Health and Disease

­Cardiac remodeling and dysfunction occur prior to the onset of heart failure. Altered regulation of cardiac function by the autonomic nervous system has been implicated in the progression of heart disease. Both altered sympathetic and parasympathetic tone contribute to cardiac disease; however, the role of the parasympathetic nervous system, and specifically acetylcholine (ACh), in cardiac dysfunction has not been fully elucidated. In these studies, we sought to determine whether changes in neuronal and/or non-neuronal ACh release regulate cardiac activity and alter the progression of cardiac remodeling and dysfunction. A systemic decrease in the expression of the vesicular acetylcholine transporter (VAChT), the protein responsible for packaging ACh, led to the development of significant ventricular dysfunction coupled with significant transcriptional changes in cardiac tissue. Furthermore, we identified that murine cardiomyocytes possess an intrinsic cholinergic system, which prevents hypertrophy and molecular remodeling in cardiomyocytes in response to hyperadrenergic stimulation, in vitro. In addition, this cardiac non-neuronal cholinergic system (NNCS) is also critical in regulating heart activity and remodeling, in vivo. Inhibition of cardiomyocyte-specific ACh secretion led to delayed heart rate recovery following physiological stress, including exercise, as well as significant ventricular remodeling. Cardiomyocytes lacking the intrinsic cholinergic system displayed hypertrophy and molecular remodeling. This NNCS also plays a significant role under pathological conditions as chronic treatment with angiotensin II led to enhanced cardiac remodeling and ventricular dysfunction in mice lacking the NNCS. Additionally, this intrinsic cholinergic system in the heart is also present in human cardiomyocytes, suggesting the conserved expression of prototypic markers of the cholinergic system in man. This system might be of functional significance in cardiac disease as failing human cardiomyocytes exhibit increased VAChT expression, which likely leads to an increase in ACh secretion directly from cardiomyocytes. The increase in VAChT expression may play a protective role in heart failure, as overexpression of VAChT in mice did not reveal adverse phenotypes under physiological conditions. Our data suggest that both neuronal and non-neuronal ACh are critical in maintaining cardiac homeostasis and deficient cholinergic signaling contributes to ventricular remodeling and cardiac dysfunction

Phosphoinositide 3kinase γ controls LPSinduced myocardial depression via sequential cAMP and iNOS signaling

Ziel der vorliegenden Untersuchung ist die Aufklärung der spezifischen Rolle der lipidkinase-abhängigen und –unabhängigen Funktionen von PI3Kγ bei SIRS-induzierter SIMD. Bei PI3Kγ-Wildtyp (wt), Knockout (PI3Kγ-/-), und Kinase-dead (PI3KγKD/KD) Mäuse wurde eine LPS- induzierte SIRS induziert und deren Überleben, die Auswirkungen auf das kardiale autonome Nervensystem (ANS) und die linksventrikuläre (LV) kontraktile Funktion ermittelt. Darüber hinaus wurden an primären adulten Kardiomyozyten mechanistische Untersuchungen zu PI3Kγ-abhängigen Auswirkungen auf die myokardiale Kontraktilität und die inflammatorische Antwort durchgeführt

Catecholamines for inflammatory shock: a Jekyll-and-Hyde conundrum

Catecholamines are endogenous neurosignalling mediators and hormones. They are integral in maintaining homeostasis by promptly responding to any stressor. Their synthetic equivalents are the current mainstay of treatment in shock states to counteract myocardial depression and/or vasoplegia. These phenomena are related in large part to decreased adrenoreceptor sensitivity and altered adrenergic signalling, with resultant vascular and cardiomyocyte hyporeactivity. Catecholamines are predominantly used in supraphysiological doses to overcome these pathological consequences. However, these adrenergic agents cause direct organ damage and have multiple ‘off-target’ biological effects on immune, metabolic and coagulation pathways, most of which are not monitored or recognised at the bedside. Such detrimental consequences may contribute negatively to patient outcomes. This review explores the schizophrenic ‘Jekyll-and-Hyde’ characteristics of catecholamines in critical illness, as they are both necessary for survival yet detrimental in excess. This article covers catecholamine physiology, the pleiotropic effects of catecholamines on various body systems and pathways, and potential alternatives for haemodynamic support and adrenergic modulation in the critically ill

Neural crest lineage analysis: from past to future trajectory

Since its discovery 150 years ago, the neural crest has intrigued investigators owing to its remarkable developmental potential and extensive migratory ability. Cell lineage analysis has been an essential tool for exploring neural crest cell fate and migration routes. By marking progenitor cells, one can observe their subsequent locations and the cell types into which they differentiate. Here, we review major discoveries in neural crest lineage tracing from a historical perspective. We discuss how advancing technologies have refined lineage-tracing studies, and how clonal analysis can be applied to questions regarding multipotency. We also highlight how effective progenitor cell tracing, when combined with recently developed molecular and imaging tools, such as single-cell transcriptomics, single-molecule fluorescence in situ hybridization and high-resolution imaging, can extend the scope of neural crest lineage studies beyond development to regeneration and cancer initiation

Benefits in cardiac function by CD38 suppression: Improvement in NAD+ levels, exercise capacity, heart rate variability and protection against catecholamine-induced ventricular arrhythmias

CD38 enzymatic activity regulates NAD+ and cADPR levels in mammalian tissues, and therefore has a prominent role in cellular metabolism and calcium homeostasis. Consequently, it is reasonable to hypothesize about its involvement in cardiovascular physiology as well as in heart related pathological conditions. Aim: To investigate the role of CD38 in cardiovascular performance, and its involvement in cardiac electrophysiology and calcium-handling. Methods and results: When submitted to a treadmill exhaustion test, a way of evaluating cardiovascular performance, adult male CD38KO mice showed better exercise capacity. This benefit was also obtained in genetically modified mice with catalytically inactive (CI) CD38 and in WT mice treated with antibody 68 (Ab68) which blocks CD38 activity. Hearts from these 3 groups (CD38KO, CD38CI and Ab68) showed increased NAD+ levels. When CD38KO mice were treated with FK866 which inhibits NAD+ biosynthesis, exercise capacity as well as NAD+ in heart tissue decreased to WT levels. Electrocardiograms of conscious unrestrained CD38KO and CD38CI mice showed lower basal heart rates and higher heart rate variability than WT mice. Although inactivation of CD38 in mice resulted in increased SERCA2a expression in the heart, the frequency of spontaneous calcium release from the sarcoplasmic reticulum under stressful conditions (high extracellular calcium concentration) was lower in CD38KO ventricular myocytes. When mice were challenged with caffeine-epinephrine, CD38KO mice had a lower incidence of bidirectional ventricular tachycardia when compared to WT ones. Conclusion: CD38 inhibition improves exercise performance by regulating NAD+ homeostasis. CD38 is involved in cardiovascular function since its genetic ablation decreases basal heart rate, increases heart rate variability and alters calcium handling in a way that protects mice from developing catecholamine induced ventricular arrhythmias.Fil: Agorrody, Guillermo. Universidad de la Republica. Facultad de Medicina; UruguayFil: Peclat, Thais R.. Mayo Clinic College Of Medicine; Estados UnidosFil: Peluso, Gonzalo. Universidad de la Republica. Facultad de Medicina; UruguayFil: Gonano, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Santos, Leonardo. Instituto Pasteur de Montevideo; UruguayFil: van Schooten, Wim. Teneobio; Estados UnidosFil: Chini, Claudia C. S.. Mayo Clinic College Of Medicine; Estados UnidosFil: Escande, Carlos. Instituto Pasteur de Montevideo; UruguayFil: Chini, Eduardo N.. Mayo Clinic College Of Medicine; Estados UnidosFil: Contreras, Paola. Universidad de la Republica. Facultad de Medicina; Urugua

Insight Into Autonomic Dysfunctions With Novel Interventions: Focusing On Vascular Tone And Breathing Regulations

The autonomic nervous system (ANS) controls most involuntary functions of the body. Dysfunctions of the ANS can be life-threatening. However, several critical questions related to cardiovascular and breathing regulations remain unclear. One of the open questions is how the system lose control of the vascular tones under certain circumstances. Using the septic shock model induced by lipopolysaccharide (LPS) in isolated and perfused mesenteric arterial rings, we found the vascular hyporeactivity is attributed to the decreased vasoconstriction to α-adrenoceptor agonists. The endotoxin-induced vasodilation can be intervened with endothelin-1 (ET-1), serotonin (5-HT) or vasopressin, which have never been used in clinical treatment. It is unclear how the excitability of endothelium affects vascular tones. Using optogenetics and transgenic mice with channelrhodopsin expression in endothelial cells (ECs), we found selective activation of the ECs induces a fast, robust, reproducible and long-lasting vasoconstriction in isolated and perfused hearts and kidneys. Breathing control by the ANS within the brain becomes abnormal in certain genetic diseases, such as Rett syndrome with defected norepinephrine (NE) system in locus coeruleus (LC). The LC neurons are hyperexcitable while NE release is deficient. Using optogenetics and double transgenic mice with Mecp2 null and channelrhodopsin expression in LC neurons, we found the NE-ergic modulation of hypoglossal neurons was impaired in transgenic mice, which cannot be improved with optostimulation, suggesting that LC neuronal hyperexcitability may not benefit the NE modulation in Rett syndrome. Collectively, our results provide insight into the autonomic dysfunctions using experimental interventions that have barely been used before