Vitamin D Attenuates Hepatic Sinusoidal Capillarization in Type 2 Diabetes Mellitus- Metabolic Dysfunction-Associated Fatty Liver Disease via Dual Autophagy Activation and Pyroptosis Suppression in Liver Sinusoidal Endothelial Cells.

Background/Objectives: Metabolic dysfunction-associated fatty liver disease (MAFLD) is closely associated with type 2 diabetes mellitus (T2DM), where T2DM serves as a crucial driving factor for MAFLD progression. While vitamin D (VD) demonstrates protective effects against MAFLD, the underlying mechanisms through which it influences MAFLD-related liver sinusoidal endothelial cell (LSEC) capillarization remain to be elucidated. This study aimed to explore how vitamin D ameliorates LSEC capillarization in T2DM-associated MAFLD. Methods: Culture human liver sinusoidal endothelial cells (HLSECs) according to the established protocol. After 1,25(OH)₂D₃ intervention in high glucose (HG)-induced HLSECs, determine the changes in liver sinusoidal capillarization-related proteins (LN, PLVAP), autophagy and pyroptosis levels. Observe the changes in cell lipid accumulation and fenestration structures. After adding Bafilomycin A1, MCC950, compound C and rapamycin to HLSECs, explore the therapeutic mechanism of 1,25(OH)₂D₃. After supplementing VD to MAFLD model mice, further verify the therapeutic mechanism of VD on MAFLD. Results: HG can induce the capillarization and lipid accumulation of HLSEC, increase the level of pyroptosis, and simultaneously reduce the autophagy level. Vitamin D alleviated high-glucose-induced pyroptosis (by suppressing GSDMD/NLRP3) and autophagic inhibition by activating the AMPK-mTOR axis (upregulating p-AMPK and downregulating mTOR), and improved lipid accumulation and hepatic sinusoidal capillarization. In the mouse model of MAFLD, VD supplementation can induce autophagy, inhibit pyroptosis and capillarization, and improve MAFLD. Conclusions: These results demonstrate, for the first time, that VD mitigates LSEC dysfunction through dual mechanisms: activating AMPK-dependent autophagy and inhibiting pyroptosis, providing a therapeutic rationale for VD in treating MAFLD-related sinusoidal pathology.