Metabolic syndrome remodels electrical activity of the sinoatrial node and produces arrhythmias in rats

• Published in: PloS one Vol. 8; no. 11; p. e76534
• Main Authors: Albarado-Ibañez, Alondra, Avelino-Cruz, José Everardo, Velasco, Myrian, Torres-Jácome, Julián, Hiriart, Marcia
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 08.11.2013; Public Library of Science (PLoS)
• Subjects: Adipocytes; Animals; Arrhythmia; Arrhythmias, Cardiac - etiology; Arrhythmias, Cardiac - physiopathology; Atrial Remodeling - physiology; Bioengineering; Cardiac arrhythmia; Cardiomyocytes; Cardiovascular disease; Depolarization; Diabetes; Drinking water; EKG; Electrocardiography; Gene expression; Glucose tolerance; Heart rate; Humans; Hypertension; Hypertriglyceridemia; Innervation; Insulin; Insulin resistance; International organizations; Intolerance; Male; Medical research; Metabolic syndrome; Metabolic Syndrome - complications; Metabolic Syndrome - physiopathology; Microelectrodes; Obesity; Patch-Clamp Techniques; Personal computers; Physiology; Rats; Rodents; Sinoatrial Node - physiology; Sinus; Sucrose; Sugar
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0076534

In the last ten years, the incidences of metabolic syndrome and supraventricular arrhythmias have greatly increased. The metabolic syndrome is a cluster of alterations, which include obesity, hypertension, hypertriglyceridemia, glucose intolerance and insulin resistance, that increase the risk of developing, among others, atrial and nodal arrhythmias. The aim of this study is to demonstrate that metabolic syndrome induces electrical remodeling of the sinus node and produces arrhythmias. We induced metabolic syndrome in 2-month-old male Wistar rats by administering 20% sucrose in the drinking water. Eight weeks later, the rats were anesthetized and the electrocardiogram was recorded, revealing the presence of arrhythmias only in treated rats. Using conventional microelectrode and voltage clamp techniques, we analyzed the electrical activity of the sinoatrial node. We observed that in the sinoatrial node of "metabolic syndrome rats", compared to controls, the spontaneous firing of all cells decreased, while the slope of the diastolic depolarization increased only in latent pacemaker cells. Accordingly, the pacemaker currents If and Ist increased. Furthermore, histological analysis showed a large amount of fat surrounding nodal cardiomyocytes and a rise in the sympathetic innervation. Finally, Poincaré plot denoted irregularity in the R-R and P-P ECG intervals, in agreement with the variability of nodal firing potential recorded in metabolic syndrome rats. We conclude that metabolic syndrome produces a dysfunction SA node by disrupting normal architecture and the electrical activity, which could explain the onset of arrhythmias in rats.