β-hydroxybutyrate exerts protective effects against sepsis-associated acute kidney injury by promoting HMGB1 β-hydroxybutyrylation

Sepsis-associated acute kidney injury (SA-AKI) is a leading cause of mortality in critically ill patients, involving complex interactions between metabolic reprogramming and excessive inflammation. β-hydroxybutyrate (BHB), an endogenous ketone body, has emerged as a regulator of post-translational modifications through inducing β-hydroxybutyrylation (Kbhb). However, the role of BHB in SA-AKI remains unclear. A multi-system research strategy integrating clinical samples, animal models, and cellular experiments was employed. The clinical correlation between BHB and renal function was assessed in SA-AKI patients. SA-AKI mouse model was established using CLP, followed by intervention with either a ketogenic diet or exogenous BHB administration. Renal function, inflammatory factors, and global Kbhb modifications in kidney tissues were assessed. The effects of BHB were further validated in LPS-stimulated HK-2 cells and mouse primary renal tubular epithelial cells. Proteomics combined with Kbhb modification profiling was employed to screen key target proteins. Techniques including Co-IP, site-directed mutagenesis, and customized antibodies were utilized to identify Kbhb modification on the target protein high mobility group box 1 (HMGB1) and to determine its critical modification sites. Co-IP coupled with mass spectrometry was applied to screen for HMGB1-interacting proteins. Clinical analysis demonstrated that elevated serum BHB levels in SA-AKI patients correlated with improved renal function recovery and showed prognostic value for renal recovery (AUC = 0.819). In vivo and in vitro experiments demonstrated that BHB intervention significantly improved renal function in CLP mice and attenuated LPS-induced cell injury. Mechanistic investigations revealed that BHB enhanced HMGB1-Kbhb modification through a p300/CBP-dependent mechanism, with lysine 90 (K90) identified as a functionally important modification site. This modification inhibited HMGB1 nuclear-cytoplasmic translocation, thereby reducing cytoplasmic HMGB1 availability and attenuating its interaction with GSDME, resulting in suppression of downstream inflammatory mediators including IL-1β and IL-18. This study demonstrates that BHB may serve as a potential prognostic biomarker in SA-AKI. Mechanistically, BHB protects against renal injury partially through p300/CBP-mediated HMGB1-K90bhb modification, which inhibits HMGB1 nuclear-cytoplasmic translocation and its interaction with GSDME, thereby suppressing inflammatory pyroptotic responses. These findings reveal a novel mechanism by which BHB regulates SA-AKI and provide potential therapeutic targets for its treatment.