β-Hydroxybutyrate enhances malate dehydrogenase 2 β-hydroxybutyrylation to alleviate hepatic steatosis in MASLD

Over the past three decades, the global prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) has rapidly increased, leading to significant economic and clinical burdens. However, aside from resmetirom (Rezdiffra™), an oral thyroid hormone receptor-β agonist, there remains a lack of approved targeted pharmacological treatments for MASLD, emphasizing the need for more optimized therapeutic strategies. Given the limitations in the safety and efficacy of the ketogenic diet, β-hydroxybutyrate (β-OHB) has emerged as a crucial regulator in MASLD treatment, but the precise mechanisms underlying its therapeutic effects remain unclear. This study aims to investigate the therapeutic effects of β-OHB on MASLD mice and elucidate the underlying mechanisms. In this study, we demonstrate that β-OHB ameliorates lipid deposition and increases pan-β-hydroxybutyrylation (Kbhb) levels in both MASLD mice and in vitro. Additionally, β-OHB also improves excessive ROS accumulation and enhances mitochondrial respiratory capacity. Furthermore, β-OHB protects against impaired fatty acid oxidation (FAO) activity in MASLD. Proteomic analysis of β-OHB-treated mice identified a significant Kbhb modification at K239 on malate dehydrogenase 2 (MDH2), which was associated with increased MDH2 enzymatic activity. Overall, this study demonstrates β-OHB exhibits therapeutic effects on hepatic steatosis and mitochondrial dysfunction in MASLD mice. We uncover a novel mechanism where β-OHB enhances MDH2 enzymatic activity through Kbhb modification at K239, thereby maintaining mitochondrial homeostasis and alleviating lipid deposition.