Protective mechanism of demethylase fat mass and obesity-associated protein in energy metabolism disorder of hypoxia-reoxygenation-induced cardiomyocytes

Abstract

New findings: What is the central question of this study? What is the effect of fat mass and obesity-associated protein (FTO) on energy metabolism in hypoxia-reoxygenation (H/R)-induced cardiomyocytes? What is the main finding and its importance? FTO modification of N⁶ -methyladenosine (m⁶ A) is associated with myocardial cell energy metabolism disorder. FTO reduced the m⁶ A level of sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a) mRNA through demethylation, thus promoting SERCA2a expression, maintaining calcium homeostasis, and improving energy metabolism of H/R cardiomyocytes.

Abstract: Energy metabolism disorder is the initial physiological link of myocardial ischaemia-reperfusion injury. Fat mass and obesity-associated protein (FTO) is an N⁶ -methyladenosine (m⁶ A) demethylase implicated in several cardiac defects. This study sought to investigate the effect of FTO on energy metabolism in hypoxia-reoxygenation (H/R)-induced cardiomyocytes. FTO and sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a) expression in H/R-induced cardiomyocytes were determined. Cardiomyocyte viability, cytotoxicity and apoptosis were measured. The total RNA and polyA⁺ RNA contents were isolated from cells. The m⁶ A level of RNA and the enrichment of m⁶ A of SERCA2a mRNA were calculated. Several indices such as the glycolytic potential, reactive oxygen species (ROS), mitochondrial activity and ATP content were evaluated. The concentration of calcium in cardiomyocytes was determined. FTO and SERCA2a were poorly expressed in H/R-induced cardiomyocytes. There was an elevated m⁶ A level in total RNA and enrichment of m⁶ A in SERCA2a mRNA. H/R treatment reduced the cell viability, mitochondrial membrane potential and ATP content in cardiomyocytes, but increased the cytotoxicity, apoptosis, ROS content and calcium concentration. Upregulation of FTO reversed the preceding findings with downregulation of the m⁶ A level of SERCA2a mRNA. Downregulation of SERCA2a annulled the promoting effect of FTO on calcium homeostasis and energy metabolism in H/R-induced cardiomyocytes. Collectively, the current study demonstrated that FTO reduced the m⁶ A level on SERCA2a mRNA through demethylation, thus promoting SERCA2a expression, maintaining calcium homeostasis and improving the energy metabolism of H/R cardiomyocytes.

Keywords: FTO; SERCA2a; calcium overload; cardiomyocytes; demethylase; energy metabolism disorder; hypoxia-reoxygenation; m6A.