Changes of the insulin-like growth factor I system during acute myocardialinfarction: Implications on left ventricular remodeling

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 (IGF BPs) during acute myocardial infarction (AMI) and to explore the relationsh ip between IGF-I levels and myocardial remodeling and function after AMI. T hirty-four patients with acute Q-wave AMI and 17 matched controls were inve stigated in this study. Compared to normal subjects, free IGF-I and IGFBP-3 were significantly elevated, and IGFBP-1 was decreased upon AMI. Myocardia l remodeling occurred after AMI in these patients. The day 2, 3, and 7 tota l IGF-I levels were inversely related to day 7 left ventricular (LV) end-di astolic, 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, tho se patients with poor outcomes had lower total IGF-I levels immediately aft er AMI. Most healthy survivors had total IGF-I levels greater than 137 ng/m L, 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 sy stem. A higher total IGF-I level immediately after the onset of AMI is asso ciated with better myocardial remodeling and ventricular function.