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

Background: 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. The Arg(972) IRS-1 polymorphism is associated with diminished activity of insulin. In the present study, we explored the association among Arg(972) IRS-1, acute MI, and serum levels of ACE2. Methods: A total of 711 subjects, including 351 subjects with first-time acute MI and 360 subjects without a history of MI were genotyped for Arg(972) IRS-1 polymorphism. Serum levels of ACE2 and MI severity scores were determined. Primary human cardiomyocytes with overexpression of wild type IRS-1 or Arg(972) IRS-1 or knockdown of endogenous IRS-1 were exposed to normoxia and hypoxia, and the expression levels of ACE2 were determined. Results: The serum ACE2 level was significantly increased in acute MI patients compared with that of non-MI controls. Compared with wild type IRS-1 carriers, Arg(972) 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 Arg(972)-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 Arg(972)-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. Conclusions: This 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.