Metformin Ameliorates Renal Fibrosis in Mice with Unilateral Ureteral Obstruction and Inhibits TGF-ß1-Induced Upregulation of Cadherin-6 in Renal Proximal Tubule Epithelial Cells

Abstract

Background: Metformin has been reported of nephroprotective effects by suppressing TGF-β1-induced renal tubulointerstitial fibrosis. The mechanisms have not been fully clarified. Cadherin-6(CDH6) is a TGF-β1 target gene related to epithelial-to-mesenchymal transition(EMT). This study aimed to examine the effects of metformin on TGF-β1-induced expression of CDH6 and renal fibrosis in a mouse model of unilateral ureteral obstruction (UUO) and HK-2 human renal proximal tubule epithelial cells. Methods: Six-week-old male Kunming mice(n=18) were randomly divided into three groups: 1. Sham: sham-operated mice; 2. UUO: mice underwent UUO; 3. MET+UUO: UUO mice received metformin by gavage for 21 days after UUO. Kidneys were harvested for histopathologic examination and urine was collected for creatinine evaluation. HK-2 cells were stimulated with either TGF-β1 and/or metformin. RT-qPCR and Western Blot were used to evaluate mRNA and protein level respectively. Results: Masson’s Trichrome staining showed significant tubulointerstitial accumulation of extracellular matrix in obstructed kidneys, which could be reduced by metformin. Meanwhile, urinary creatinine was increased with metformin treatment. Upregulation of CDH6, COL1A1, PAI-1 mRNA level was observed in obstructed kidneys, which was reduced in MET+UUO group. Immunohistochemistry showed increased expression of CDH6, α-SMA in obstructed kidneys, which was alleviated in metformin treated group. In HK-2 cells, TGF-β1 upregulated mRNA level of CDH6, vimentin, PAI-1 and protein level of CDH6. Pretreatment with metformin attenuated TGF-β1-induced upregulation of CDH6, vimentin, PAI-1 mRNA level. Conclusion: Metformin prevents renal fibrosis partly through inhibition of TGF-β1-induced increase of CDH6 expression and EMT in renal proximal tubule epithelial cells. Disclosure D. Liang: None. S. Liu: None. Z. Song: None. W. Liang: None. R. Chang: None. Y. Li: None.