Activation of AMPK by metformin inhibits TGF-β-induced collagen production in mouse renal fibroblasts

Aims: To clarify whether activation of adenosine monophosphate-activated protein kinase (AMPK) by metformin inhibits transforming growth factor beta (TGF-beta)-induced collagen production in primary cultured mouse renal fibroblasts and further to address the molecular mechanisms. Main methods: Primary cultured mouse renal fibroblasts were stimulated with TGF-beta 1 and the sequence specific siRNA of Smad3 or connective tissue growth factor (CTGF) was applied to investigate the involvement of these molecular mediators in TGF-beta 1-induced collagen type I production. Cells were pre-incubated with AMPK agonist metformin or co-incubated with AMPK agonist metformin and AMPK inhibitor Compound C before TGF-beta 1 stimulation to clarify whether activation of AMPK inhibition of TGF-beta 1-induced renal fibroblast collagen type I expression. Key findings: Our results demonstrate that TGF-beta 1 time- and dose-dependently induced renal fibroblast collagen type I production; TGF-beta 1 also stimulated Smad3-dependent CfGF expression and caused collagen type I generation; this effect was blocked by knockdown of Smad3 or CFGF. Activation of AMPK by metformin reduced TGF-beta 1-induced collagen type I production by suppression of Smad3-driven CTGF expression. Significance: This study suggests that activation of AMPK might be a novel strategy for the treatment of chronic kidney disease (CKD) partially by inhibition of renal interstitial fibrosis (RIF). (C) 2015 Elsevier Inc. All rights reserved.