Ruifei Chen1, Yenan Feng1, Jimin Wu1, Yao Song1, Hao Li1, Qiang Shen1, Dan Li1, Jianshu Zhang1, Zhizhen Lu1, Han Xiao1, Youyi Zhang1. 1. Institute of Vascular Medicine, Peking University Third Hospital and Academy for Advanced Interdisciplinary Studies, Peking University, Key Laboratory of Cardiovascular Molecular Biology and Regulatory Peptides, Ministry of Health, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing, China.
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. TGFβ1 is a key cytokine mediating cardiac fibrosis. Here, we investigated the effects of metformin on TGFβ1 production induced by angiotensin II (AngII) and the underlying mechanisms. EXPERIMENTAL APPROACH: Wild-type and AMPKα2-/- 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 TGFβ1 expression via AMPK activation. Analysis using bioinformatics predicted a potential hepatocyte nuclear factor 4α (HNF4α)-binding site in the promoter region of the Tgfb1 gene. Overexpressing HNF4α increased TGFβ1 expression in CFs. HNF4α siRNA attenuated AngII-induced TGFβ1 production and cardiac fibrosis in vitro and in vivo. Metformin inhibited the AngII-induced increases in HNF4α protein expression and binding to the Tgfb1 promoter in CFs. In vivo, metformin blocked the AngII-induced increase in cardiac HNF4α protein levels in wild-type mice but not in AMPKα2-/- mice. Consequently, metformin inhibited AngII-induced TGFβ1 production and cardiac fibrosis in wild-type mice but not in AMPKα2-/- mice. CONCLUSIONS AND IMPLICATIONS: HNF4α mediates AngII-induced TGFβ1 transcription and cardiac fibrosis. Metformin inhibits AngII-induced HNF4α expression via AMPK activation, thus decreasing TGFβ1 transcription and cardiac fibrosis. These findings reveal a novel antifibrotic mechanism of action of metformin and identify HNF4α 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.
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. TGFβ1 is a key cytokine mediating cardiac fibrosis. Here, we investigated the effects of metformin on TGFβ1 production induced by angiotensin II (AngII) and the underlying mechanisms. EXPERIMENTAL APPROACH: Wild-type and AMPKα2-/- 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 TGFβ1 expression via AMPK activation. Analysis using bioinformatics predicted a potential hepatocyte nuclear factor 4α (HNF4α)-binding site in the promoter region of the Tgfb1 gene. Overexpressing HNF4α increased TGFβ1 expression in CFs. HNF4α siRNA attenuated AngII-induced TGFβ1 production and cardiac fibrosis in vitro and in vivo. Metformin inhibited the AngII-induced increases in HNF4α protein expression and binding to the Tgfb1 promoter in CFs. In vivo, metformin blocked the AngII-induced increase in cardiac HNF4α protein levels in wild-type mice but not in AMPKα2-/- mice. Consequently, metformin inhibited AngII-induced TGFβ1 production and cardiac fibrosis in wild-type mice but not in AMPKα2-/- mice. CONCLUSIONS AND IMPLICATIONS: HNF4α mediates AngII-induced TGFβ1 transcription and cardiac fibrosis. Metformin inhibits AngII-induced HNF4α expression via AMPK activation, thus decreasing TGFβ1 transcription and cardiac fibrosis. These findings reveal a novel antifibrotic mechanism of action of metformin and identify HNF4α 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.
Authors: Jürgen Soutschek; Akin Akinc; Birgit Bramlage; Klaus Charisse; Rainer Constien; Mary Donoghue; Sayda Elbashir; Anke Geick; Philipp Hadwiger; Jens Harborth; Matthias John; Venkitasamy Kesavan; Gary Lavine; Rajendra K Pandey; Timothy Racie; Kallanthottathil G Rajeev; Ingo Röhl; Ivanka Toudjarska; Gang Wang; Silvio Wuschko; David Bumcrot; Victor Koteliansky; Stefan Limmer; Muthiah Manoharan; Hans-Peter Vornlocher Journal: Nature Date: 2004-11-11 Impact factor: 49.962
Authors: Stephen Ph Alexander; John A Cidlowski; Eamonn Kelly; Neil Marrion; John A Peters; Helen E Benson; Elena Faccenda; Adam J Pawson; Joanna L Sharman; Christopher Southan; Jamie A Davies Journal: Br J Pharmacol Date: 2015-12 Impact factor: 8.739