Ketone bodies independently of metabolic pathway attenuate cardiac hypertrophy through β-hydroxybutyrylation

Background Cardiac hypertrophy, an adaptive response to pathological stimuli such as hypertension, often progresses to heart failure. Emerging evidence suggests that metabolic dysregulation plays a crucial role in this pathological process. Ketone bodies, particularly β-hydroxybutyrate (β-OHB), represent a non-canonical pathway, β-hydroxybutyrylation (Kbhb), contributing to cardioprotective effects beyond energy supply. Purpose This study aimed to investigate the effects of β-OHB and Kbhb modification on the pathogenesis of cardiac hypertrophy, with an emphasis on identifying the underlying molecular targets. Methods Pressure-overload myocardial hypertrophy model was established by transverse aortic constriction (TAC), following surgery, mice were randomly selected and maintained on a ketogenic diet for one month. Isolated mouse hearts were perfused in Langendorff mode, the perfusion buffer contained 0.4mM isotope-labeled mixed long-chain fatty acids, 50μU/mL insulin, 1mM lactate, and 5.5mM glucose. The H9c2 cells were employed to induce cardiac hypertrophy in vitro by isoproterenol (ISO). Meanwhile, the oxygen consumption rates (OCR) of isolated intact mitochondria or cultured cells were measured with Seahorse analyzer. Results and discussion The TAC mice exhibited upregulation of BDH1, while this phenomenon was abrogated in BDH1 cKO mice (Fig A). Considering the dual-directional metabolic function of BDH1, we next examined cardiac endogenous ketogenesis. As expected, myocardial endogenous ketogenic was significantly enhanced after TAC, whereas this capacity was almost completely lost in BDH1 cKO mice (Fig B, C). To compensate for the loss of endogenous cardiac ketogenesis, BDH1 cKO mice were fed a ketogenic diet (KD), which markedly ameliorated TAC-induced hypertrophic remodeling and prevented the reduction in ejection fraction (Fig D, E). Furthermore, KD alleviated mitochondrial respiratory dysfunction (Fig F). Then we measured the level of Kbhb, BDH1 cKO mice failed to increase myocardial Kbhb in response to TAC, while KD increased modification level (Fig G). To further explore the role of Kbhb in cardiac hypertrophy, we employed C646, an inhibitor of Kbhb modification. We first evaluated the potential cytotoxic effects of C646 on H9c2 (Fig H). Notably, β-OHB increased Kbhb level and protected against ISO-induced hypertrophy, while these effects were blocked by C646 for 24 hours (Fig I). Consistently, C646 abrogated the ameliorative effect on mitochondrial respiratory function (Fig J, K). These data confirm that β-OHB against cardiac hypertrophy via a mechanism not just as a metabolic substrate. Moreover, the loss of cardioprotection upon Kbhb abrogation identifies Kbhb as a critical mediator of ketone body-induced effects. Conclusions Hypertrophied heart possesses endogenous β-OHB synthesis, which may alleviate cardiac hypertrophy through Kbhb modification, independent of its canonical metabolic role.Kbhb and Cardiac hypertrophy