Betulinic Acid Counteracts Statin‐Induced PCSK9 Upregulation Through FXR / SHP ‐Associated Signaling

BACKGROUND AND AIM: Statins increase hepatic low-density lipoprotein receptor (LDLR) expression but also induce proprotein convertase subtilisin/kexin type 9 (PCSK9), which promotes LDLR degradation and may limit the lipid-lowering response. Although betulinic acid (BA) has been reported to reduce basal PCSK9 expression, whether it counteracts the compensatory increase in PCSK9 during statin treatment remains unclear. We investigated the effect of BA on atorvastatin-induced PCSK9 upregulation and the contribution of farnesoid X receptor (FXR)/small heterodimer partner (SHP) signaling. EXPERIMENTAL PROCEDURE: The effects of BA were examined in HepG2 and Huh7 cells using ELISA, RT-qPCR, and immunoblotting. RNA sequencing, pharmacological modulation of FXR, siRNA-mediated knockdown of FXR or SHP, time-course analysis, and co-immunoprecipitation were used to investigate the underlying mechanism. The effects of BA alone or combined with atorvastatin were also evaluated in high-fat diet-fed mice. KEY RESULTS: BA reduced basal and atorvastatin-induced PCSK9 expression and secretion while maintaining or increasing LDLR expression in both cell lines. BA increased SHP and SLC51B expression and reduced CYP7A1 and CYP8B1 expression. Pharmacological modulation and siRNA-mediated knockdown showed that reduced FXR or SHP expression weakened BA-mediated regulation of PCSK9 and LDLR. BA also increased the SHP signal detected in SREBP2 immunoprecipitates without a marked reduction in SREBP2 abundance. In high-fat diet-fed mice, BA reduced circulating and hepatic PCSK9 and further lowered serum LDL-c during atorvastatin treatment. CONCLUSIONS AND IMPLICATIONS: This study extends the known PCSK9-lowering activity of BA by showing that BA counteracts statin-induced PCSK9 upregulation through an FXR/SHP-associated mechanism. These findings support BA as a potential modulator of the PCSK9-LDLR axis during statin treatment.