Arrhythmia causes lipid accumulation and reduced glucose uptake

Area of Science:

• Cardiology
• Molecular Biology
• Metabolic Research

Background:

• Atrial fibrillation (AF) involves irregular atrial cardiomyocyte contractions, leading to increased cellular energy demands.
• Understanding metabolic alterations during AF is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the impact of arrhythmia on glucose and fatty acid (FA) metabolism in cardiomyocytes, mouse models, and human atrial tissue.
• To elucidate the molecular mechanisms linking AF-induced metabolic changes to cardiomyocyte dysfunction and apoptosis.

Main Methods:

• Neonatal rat cardiomyocytes were subjected to irregular pacing to mimic AF conditions.
• Metabolic assessments included substrate uptake (glucose, FA) and protein expression analysis (FAT/CD36, GLUT-4).
• Studies utilized a transgenic mouse model of AF and human atrial myocardial samples from AF patients versus controls.

Main Results:

• Irregular pacing increased intracellular calcium, activated CaMKII and AMPK, enhanced FA uptake (via FAT/CD36), and reduced glucose uptake (via GLUT-4).
• These metabolic changes, including lipid accumulation and increased glycogen, were observed in AF mice and human atrial tissue.
• Inhibition of AMPK and CaMKII reversed these metabolic alterations in cardiomyocytes.

Conclusions:

• AF induces significant metabolic reprogramming in cardiomyocytes, favoring lipid metabolism and impairing glucose utilization.
• Activation of CaMKII and AMPK pathways are key mediators of AF-associated metabolic changes.
• These metabolic shifts contribute to lipid accumulation, altered energy homeostasis, and activation of pro-apoptotic pathways in AF.