Abstract 13202: IGF-1 Prevents High Glucose Induced Cell Cycle Arrest in Cardiomyocyte via Catenin Pathway

Abstract

Background: High glucose(HG)-induced cell cycle arrest of cardiomyocytes is considered to be the main cause of the development of cardiomyopathy in patients with diabetes. Insulin-like growth factor (IGF-1) stimulates cell cycle-reentry. β-catenin is a positive regulator of cardiac growth. This study investigated whether IGF-1 prevents HG-induced myocyte cell cycle arrest via β-catenin pathway.

Methods and Results: p21 is a negative cell cycle regulator and its expression was used as an indicator of cell cycle arrest. Our data showed that H9C2 myocyte cells incubated in high glucose (25 mM) resulted in increased p21 mRNA levels (2.7 ± 0.4 fold at 24 h, p<0.02, assessed by real-time PCR) when compared with H9C2 incubated in normal glucose (NG) (5 mM), whereas mannitol (25 mM, osmotic control) has no effect. HG-induced cell cycle arrest was determined by DNA synthesis (BrdU assay) and cytokinesis (Calcein-AM fluorescence intensity and Aurora expression). HG-induced cell cycle arrest was indicated by the incidence of BrdU incorporation, Calcein-AM fluorescence intensity and Aurora expression remained constant during a 72-h incubation period. Co-incubation of H9C2 cells with HG and IGF-1, IGF-1 (30 ng/ml) dose-dependently blocked the HG -induced cell cycle arrest, which were attenuated by IGF-1 receptor neutralizing antibody and by PI3 kinase inhibitor (LY294002, 15 μ M), but not by MAP kinase inhibitor (PD98059, 0-30 μ M). IGF-1 treatment increased the amount of active β-catenin (positive regulator of cardiac growth) assessed by ELISA. Furthermore, the effects of IGF-1 on cell-cycle and proliferation were blocked by silencing β-catenin with small interference RNA (siRNA-β-catenin) compared to non-targeting scrambled siRNA. The effects of IGF-1 on cell-cycle reentry and proliferation were also blocked by specific β-catenin inhibitor (PNU74654).

Conclusion: Our data demonstrate that IGF-1 inhibits HG-induced cell cycle and proliferation arrest via PI3 kinase/β-catenin pathway. These findings provide a new paradigm for the biological effects of IGF-1 on cardiomyocyte cell cycle reentry under diabetic condition, and suggest that activation of IGF-1 signaling pathway may be a useful strategy to prevent diabetic cardiomyopathy.