Research Paper Advance Articles

Figure 1. 1,25(OH)₂D₃ upregulates Sirt1 expression in C2C12 cells via VDR-mediated transcription. (A) Western blot showing changes in Sirt1 and 1α(OH)ase protein expression levels in tibialis anterior muscle tissues of 2-month-old WT, 1α(OH)ase^−/− and Sirt1^Tg1α(OH)ase^−/− mice and (B) statistical analysis results of Sirt1 protein expression levels. (C) 1,25(OH)₂D₃ treatment upregulated Sirt1 gene expression in C2C12 cells. (Each experiment was conducted in five replicates). (D) VDR binding sites were predicted in the Sirt1 promoter region (yellow area). (E) ChIP-qPCR results showing enrichment of Sirt1 in VDR immunoprecipitation. (F) Schematic diagram of luciferase reporter gene plasmids containing the Sirt1 promoter region. (G) Luciferase activity results. ^**p < 0.01; ^***p < 0.001.