Changes of the Insulin-Like Growth Factor I System during Acute Myocardial Infarction: Implications on Left Ventricular Remodeling¹

In vitro and in vivo experiments have shown important biological actions of insulin-like growth factor I (IGF-I) in heart. The aims of this study were to determine the changes in circulating IGF-I and IGF-binding proteins (IGFBPs) during acute myocardial infarction (AMI) and to explore the relationship between IGF-I levels and myocardial remodeling and function after AMI. Thirty-four patients with acute Q-wave AMI and 17 matched controls were investigated in this study. Compared to normal subjects, free IGF-I and IGFBP-3 were significantly elevated, and IGFBP-1 was decreased upon AMI. Myocardial remodeling occurred after AMI in these patients. The day 2, 3, and 7 total IGF-I levels were inversely related to day 7 left ventricular (LV) end-diastolic, end-systolic diameters (r = -0.395 to -0.516) and LV mass (r = -0.487 to -0.661). Moreover, total IGF-I levels were positively related to LV ejection fraction (r = 0.402-0.453). Compared to the healthy survivors, those patients with poor outcomes had lower total IGF-I levels immediately after AMI. Most healthy survivors had total IGF-I levels greater than 137 ng/mL, but all patients with poor outcome had total IGF-I levels less than 137 ng/mL. Thus, AMI is associated with significant alterations in the IGF-I system. A higher total IGF-I level immediately after the onset of AMI is associated with better myocardial remodeling and ventricular function.