AMPK and substrate availability regulate creatine transport in cultured cardiomyocytes

Area of Science:

• Biochemistry
• Cell Biology
• Cardiology

Background:

• Heart failure is associated with altered cellular energy metabolism, including changes in creatine and phosphocreatine levels.
• Cardiomyocytes rely on a cell membrane creatine transporter to maintain intracellular creatine stores, crucial for energy homeostasis.
• Creatine transport is reduced in failing hearts, potentially exacerbating energy imbalance.

Purpose of the Study:

• To investigate the impact of substrate availability and AMPK activation on creatine transport in cardiomyocytes.
• To elucidate the regulatory mechanisms of the creatine transporter in cardiac cells.

Main Methods:

• Cultured rat neonatal cardiomyocytes and HL-1 cardiac cells expressing the human creatine transporter.
• Manipulation of extracellular creatine concentrations to alter substrate availability.
• Activation of AMP-activated protein kinase (AMPK) using 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR).
• Measurement of creatine transport kinetics and quantification of creatine transporter protein levels.

Main Results:

• Creatine transport was enhanced in cardiomyocytes cultured in creatine-depleted medium.
• Activation of AMPK with AICAR significantly increased creatine transport.
• These transport enhancements were attributed to increased V(max), correlating with elevated total and cell surface creatine transporter protein expression.

Conclusions:

• Creatine transport in cardiomyocytes is modulated by both substrate availability and AMPK signaling.
• AMPK activation plays a positive role in regulating creatine transporter activity in cultured cardiomyocytes.
• These findings suggest potential therapeutic targets for managing energy deficits in heart failure.