Insulin-like growth factor-1 overexpression in cardiomyocytes diminishes ex vivo heart functional recovery after acute ischemia

Background: Acute insulin-like growth factor-1 administration has been shown to have beneficial effects in cardiac pathological conditions. The aim of the present study was to assess the structural and ex vivo functional impacts of long-term cardiomyocyte-specific insulin-like growth factor-1 overexpression in hearts of transgenic alpha MHC-IGF-1 Ea mice. Methods: Performance of isolated transgenic alpha MHC-IGF-1 Ea and littermate wild-type control hearts was compared under baseline conditions and in response to 20-min ischemic insult. Cardiac desmin and laminin expression patterns were determined histologically, and myocardial hydroxyproline was measured to assess collagen content. Results: Overexpression of insulin-like growth factor-1 did not modify expression patterns of desmin or laminin but was associated with a pronounced increase (similar to 30%) in cardiac collagen content (from similar to 3.7 to 4.8 mu g/mg). Baseline myocardial contractile function and coronary flow were unaltered by insulin-like growth factor-1 overexpression. In contrast to prior evidence of acute cardiac protection, insulin-like growth factor-1 overexpression was associated with significant impairment of acute functional response to ischemia reperfusion. Insulin-like growth factor-1 overexpression did not modify ischemic contracture development, but postisehemic diastolic dysfunction was aggravated (51 +/- 5 vs. 22 +/- 6 mmHg in nontransgenic littertnates). Compared with wild-type control, recovery of pressure development and relaxation indices relative to baseline performance were significantly reduced in transgenic alpha MHC-IGF-1 Ea after 60-min reperfusion (34 +/- 7% vs. 62 +/- 7% recovery of +dP/dt; 35 +/- 11% vs. 57 +/- 8% recovery of -dP/dt). Conclusions: Chronic insulin-like growth factor-1 overexpression is associated with reduced functional recovery after acute ischemic insult. Collagen deposition is elevated in transgenic alpha MHC-IGF-1 Ea hearts, but there is no change in expression of the myocardial structural proteins desmin and laminin. These findings suggest that sustained cardiac elevation of insulin-like growth factor-1 may not be beneficial in the setting of an acute ischemic insult. (C) 2012 Elsevier Inc. All rights reserved.