Abstract: Objective To investigate the effects of 1-deoxynojirimycin (DNJ) on the proliferation and the synthesis of extracellular matrix (ECM)in mouse mesangial cells cultured in high glucose. Methods The mouse mesangial cell line was cultured.The proliferation of the cells was detected by MTT assay.The concentration of type IV collagen (ColIV) and fibronectin(FN) was examined with ELISA in cultured medium of mouse mesangial cells.The expression of the mRNA of TGF-β₁ and PPARγwas detected by RT-PCR.The expression of the protein of TGF-β1 was detected by Western Blot. Results(1)High glucose significantly stimulated the proliferation of the cells treated for 48 h as compared to normal glucose group (NG) and mannitol group (MG) (P<0.05).Compared with NG and MG,the remarkable inhibition effect was observed by high glucose for 72 h and 96 h(P<0.05).There was no significant difference between mannitol group (MG) and NG(P>0.05).(2)DNJ significantly inhibited the proliferation of mouse mesangial cells cultured in high glucose.The effect of DNJ was time and dose-dependent. The further research was made in the cells treated with high glucose +5 mmol/L DNJ for 48 h.(3)High glucose increased the expression level of TGF-β1mRNA and PPARγ mRNA and the synthesis of ColIV and FN (P<0.05或P<0.01).There was no significant difference between MG and NG(P>0.05).(4)DNJ could decrease the expression level of TGF-β₁ mRNA and the synthesis of ColIV and FNof cells cultured in high glucose(P<0.05),while DNJ had no effect on increased expression level of PPARγ mRNA of cells cultured in high glucose. Conclusion DNJ inhibits proliferation and ECM synthesis of mesangial cells cultured in high glucose,which may be mediated by downregulating the expression of TGF-β₁ mRNA.