Betulin Protects Against Cardiac Hypertrophy by Improving AMPK/Nrf2-Dependent Mitochondrial Function

Pathological cardiac hypertrophy (PCH) drives heart failure and affects global mortality, without specific pharmacotherapy. Betulin is a natural pentacyclic triterpene exhibiting diverse pharmacological properties. We investigated the therapeutic potential and underlying mechanisms of betulin in PCH. PCH was induced in C57BL/6J mice via angiotensin II (Ang II) infusion and transverse aortic constriction, with betulin administered in the last 2 weeks. Cardiac function was evaluated using echocardiography, and myocardial injury and remodeling were assessed using histological staining and molecular analyses. RNA sequencing and biochemical analyses elucidated molecular mechanisms. Molecular docking (MD) and molecular dynamics simulations (MDS) analyses predicted potential binding modes of betulin with AMP-activated protein kinase (AMPK) and nuclear factor erythroid 2-related factor 2 (Nrf2). To confirm AMPK/Nrf2 pathway-dependent mitoprotective and cardioprotective effects of betulin, the AMPKα2^-/- mice, AMPK inhibitor, siNrf2, and AMPK agonist intervention were used. Betulin treatment significantly ameliorated cardiac hypertrophy, fibrosis (reducing fibrotic area by 65%), and dysfunction (increasing EF by 13.8% and FS by 11.6%) in PCH mice. Transcriptomic and biochemical analyses revealed that betulin activated AMPK phosphorylation, promoted Nrf2 nuclear translocation, and upregulated antioxidant genes, restoring mitochondrial function in hypertrophied hearts and Ang II-stimulated cardiomyocytes. MD and MDS analyses indicated that betulin enhanced interactions between AMPK and Nrf2. AMPK inhibition significantly reversed betulin-mediated alleviation of mitochondrial dysfunction by the AMPK/Nrf2 signaling axis. Cardioprotective effects of betulin were abolished in AMPKα2^-/- mice and Nrf2-deficient cardiomyocytes. Betulin ameliorates pressure overload-induced PCH and mitochondrial dysfunction by activating AMPK/Nrf2 signaling pathway, highlighting it as a therapeutic agent for PCH.