Hyodeoxycholic acid attenuates atherosclerosis by antagonizing FXR and modulating the PD-1/mTORC1 signaling axis.

Accumulating evidence suggested that bile acids play a significant role in modulating metabolic and inflammatory diseases. In this study, we investigated the roles of the farnesoid X receptor (FXR) and its endogenous antagonist hyodeoxycholic acid (HDCA) in the development of atherosclerosis (AS). We found that serum HDCA was significantly reduced in patients with AS, and systemic HDCA therapy attenuated plaque burden in vivo. Adoptive transfer of HDCA-treated Foxp3+ Tregs into ApoE-deficient recipients reduced lesion growth, whereas FXR-deficient Tregs failed to confer benefit. HDCA enhanced Treg migration and accumulation within plaques and reprogrammed Treg metabolism by antagonizing FXR and modulating PD-1/mTORC1 signaling. This shift relieved CPT1a-driven fatty acid oxidation bias, increased glycolysis and ATP production, and improved migratory capacity and effector function. We further identify ZNF671 as a transcriptional inhibitor of Treg migration that is mitigated by HDCA-dependent metabolic switching. Collectively, HDCA reduced FXR-mediated metabolic constraints while activating glycolytic and migratory programs in Tregs, thereby improving lipid handling and immune regulation within the plaque microenvironment. These findings position the HDCA-FXR-PD-1/mTORC1 axis as a novel immunometabolic target for AS.