Wenyang Huazhuo formula extract ameliorates diabetic kidney disease in db/db mice and is associated with modulation of MHC class II molecules and gut microbiota

analyses to assess the plausibility of interactions between representative metabolites and H2-Aa/H2-Ab1. Western blotting (WB) was performed to validate H2-Aa and H2-Ab1 regulation and to examine fibrosis-associated proteins TGF-β and α-SMA. Gut microbiota alterations were evaluated by 16S rRNA sequencing. WYHZF extract significantly improved hyperglycemia and dyslipidemia, reduced UACR, serum creatinine, and BUN, alleviated glomerular/tubular injury, and restored Nephrin and NGAL expression. Transcriptomic analysis indicated aberrant activation of MHC class II-related pathways in DKD kidneys, which was modulated after WYHZF treatment. Docking and molecular dynamics simulations suggested compatible binding modes and stable interaction patterns between several representative metabolites and H2-Aa/H2-Ab1 under simulated conditions. WB confirmed that H2-Aa and H2-Ab1 were upregulated in DKD and were reversed by WYHZF; notably, TGF-β and α-SMA were also reduced, consistent with attenuation of renal fibrotic features. In addition, WYHZF partially restored gut microbiota diversity and corrected key taxonomic imbalances. Collectively, WYHZF extract may exert multi-level benefits in DKD, accompanied by modulation of MHC class II-related molecules, reduced fibrosis-associated signals, and gut microbiota remodeling.