The Role of Ketone Body Mediated lncRNA MALAT1 in Regulating Cardiac Mitochondrial Function in Cardiomyocytes

Abstract

Heart failure is increasingly recognized as a disorder of mitochondrial bioenergetics in which the myocardium adapts to energetic stress by increasing its reliance on ketone bodies as alternative fuels. In parallel, long noncoding RNAs (lncRNAs) have emerged as important regulators of mitochondrial homeostasis; however, the mechanisms by which metabolic signals, such as ketone bodies, engage lncRNA-mediated control of cardiomyocyte energetics remain incompletely understood. The gap represents a critical unresolved question given the growing therapeutic interest in ketone supplementation for heart failure. This study investigated whether the ketone body β-hydroxybutyrate (BHB) regulated the lncRNA MALAT1 in human AC16 cardiomyocytes and examined whether MALAT1 was required for BHB-induced mitochondrial adaptation. AC16 cells were exposed to graded concentrations of BHB (0.5–5 mM) for 24-72 hours, and transcriptional responses were quantified by quantitative real-time PCR. MALAT1 was silenced using siRNA, and mitochondrial function was evaluated with Western blot analysis of electron transport chain complexes, Seahorse XF Mito Stress Test, reactive oxygen species (ROS) assays, and JC-1-based mitochondrial membrane potential measurements. Our results indicated that BHB significantly upregulated MALAT1 expression at 1 mM and 5 mM after 48-72 hours and concomitantly increased the expression of genes involved in ketone metabolism, mitochondrial biogenesis, and antioxidant defense, including MCT1, BDH1, SCOT, PDK1, PGC-1α, TFAM, SOD2, and NRF2. Transcriptional changes in MALAT1-intact cells were associated with enhanced respiratory capacity, preserved coupling efficiency, reduced total cellular ROS, and maintenance of normal mitochondrial membrane potential. Conversely, MALAT1 knockdown produced a mitochondrial dysfunction phenotype characterized by reduced levels of Complex I and Complex IV proteins, mitochondrial hyperpolarization, and increased mitochondrial and total cellular ROS. In MALAT1-knockdown cells, BHB partially normalized mitochondrial membrane potential and attenuated oxidative stress, but MALAT1 depletion limited BHB-induced upregulation of SCOT and prevented full restoration of respiratory efficiency. Furthermore, the findings defined a BHB-MALAT1-mitochondria axis in human cardiomyocytes and demonstrated that MALAT1 was necessary for translating elevated ketone availability into sustained mitochondrial and bioenergetic benefits.