Metformin attenuates angiotensin II-induced TGF?1 expression by targeting hepatocyte nuclear factor-4-?.

ABSTRACT: BACKGROUND AND PURPOSE:Metformin, a small molecule, antihyperglycaemic agent, is a well-known activator of AMP-activated protein kinase (AMPK) and protects against cardiac fibrosis. However, the underlying mechanisms remain elusive. TGF?1 is a key cytokine mediating cardiac fibrosis. Here, we investigated the effects of metformin on TGF?1 production induced by angiotensin II (AngII) and the underlying mechanisms. EXPERIMENTAL APPROACH:Wild-type and AMPK?2-/- C57BL/6 mice were injected s.c. with metformin or saline and infused with AngII (3 mg·kg-1 ·day-1 ) for 7 days. Adult mouse cardiac fibroblasts (CFs) were isolated for in vitro experiments. KEY RESULTS:In CFs, metformin inhibited AngII-induced TGF?1 expression via AMPK activation. Analysis using bioinformatics predicted a potential hepatocyte nuclear factor 4? (HNF4?)-binding site in the promoter region of the Tgfb1 gene. Overexpressing HNF4? increased TGF?1 expression in CFs. HNF4? siRNA attenuated AngII-induced TGF?1 production and cardiac fibrosis in vitro and in vivo. Metformin inhibited the AngII-induced increases in HNF4? protein expression and binding to the Tgfb1 promoter in CFs. In vivo, metformin blocked the AngII-induced increase in cardiac HNF4? protein levels in wild-type mice but not in AMPK?2-/- mice. Consequently, metformin inhibited AngII-induced TGF?1 production and cardiac fibrosis in wild-type mice but not in AMPK?2-/- mice. CONCLUSIONS AND IMPLICATIONS:HNF4? mediates AngII-induced TGF?1 transcription and cardiac fibrosis. Metformin inhibits AngII-induced HNF4? expression via AMPK activation, thus decreasing TGF?1 transcription and cardiac fibrosis. These findings reveal a novel antifibrotic mechanism of action of metformin and identify HNF4? as a new potential therapeutic target for cardiac fibrosis. LINKED ARTICLES:This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

SUBMITTER: Chen R 

PROVIDER: S-EPMC5867023 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature