Arg972 Insulin receptor substrate-1 is associated with decreased serum angiotensin-converting enzyme 2 levels in acute myocardial infarction patients: in vivo and in vitro evidence

Wei Liu,Wen Hu,Jianguo Hu,Fenglei Yu,Xinmin Zhou

doi:10.1186/1475-2840-12-151

Abstract

BackgroundActivation of the renin-angiotensin system (RAS) plays a critical role in the pathophysiology of myocardial infarction (MI) and the development of heart failure. Both angiotensin-converting enzyme 2 (ACE2) and insulin/insulin receptor substrate-1 (IRS-1) show cardioprotective effects after acute MI. The Arg972 IRS-1 polymorphism is associated with diminished activity of insulin. In the present study, we explored the association among Arg972 IRS-1, acute MI, and serum levels of ACE2.MethodsA total of 711 subjects, including 351 subjects with first-time acute MI and 360 subjects without a history of MI were genotyped for Arg972 IRS-1 polymorphism. Serum levels of ACE2 and MI severity scores were determined. Primary human cardiomyocytes with overexpression of wild type IRS-1 or Arg972 IRS-1 or knockdown of endogenous IRS-1 were exposed to normoxia and hypoxia, and the expression levels of ACE2 were determined.ResultsThe serum ACE2 level was significantly increased in acute MI patients compared with that of non-MI controls. Compared with wild type IRS-1 carriers, Arg972 IRS-1 carriers exhibited decreased serum ACE2 levels and increased MI severity scores after MI. Our in vitro data demonstrate that impairment of insulin/IRS-1/PI3K signaling by overexpression of Arg972-IRS-1, knockdown of endogenous IRS-1, or PI3K inhibitor can abolish hypoxia-induced IRS-1-associated PI3K activity and ACE2 expression in human cardiomyocytes, which suggests a causal relationship between Arg972-IRS-1 and decreased serum ACE2 levels in acute MI patients. Our in vitro data also indicate that insulin/IRS-1/PI3K signaling is required for ACE2 expression in cardiomyocytes, and that hypoxia can enhance the induction effect of insulin/IRS-1/PI3K signaling on ACE2 expression in cardiomyocytes.ConclusionsThis study provides the first evidence of crosstalk between insulin/IRS-1/PI3K signaling and RAS after acute MI, thereby adding fresh insights into the pathophysiology and treatment of acute MI.

Highlights

Activation of the renin-angiotensin system (RAS) plays a critical role in the pathophysiology of myocardial infarction (MI) and the development of heart failure
We explored the association among Arg972 insulin receptor substrate-1 (IRS-1), acute MI, and serum levels of angiotensin-converting enzyme 2 (ACE2) in a relatively large sample of acute MI patients, with an aim to identify potential interaction between insulin/IRS-1 signaling and RAS in the pathophysiology of acute MI
The findings indicate that insulin/IRS-1/phosphoinositide-3 kinase (PI3K) signaling is required for ACE2 expression in cardiomyocytes, and that hypoxia can markedly enhance the induction effect of insulin/IRS-1/PI3K signaling on ACE2 expression in cardiomyocytes

Summary

Introduction

Activation of the renin-angiotensin system (RAS) plays a critical role in the pathophysiology of myocardial infarction (MI) and the development of heart failure Both angiotensin-converting enzyme 2 (ACE2) and insulin/insulin receptor substrate-1 (IRS-1) show cardioprotective effects after acute MI. We explored the association among Arg972 IRS-1, acute MI, and serum levels of ACE2. Activation of the renin-angiotensin system (RAS) plays a critical role in the pathophysiology of myocardial infarction (MI) and the development of heart failure [1]. RAS blockade with angiotensin-converting enzyme (ACE) inhibitors improves cardiac remodeling and outcomes in both experimental models of MI as well as in humans [1]. It has been reported that ACE2 serum activity rises during the first week following acute MI and that ACE2 activation may be a compensatory mechanism in advanced heart failure [8]

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