Cardiac overexpression of insulin-like growth factor 1 attenuates chronic alcohol intake-induced myocardial contractile dysfunction but not hypertrophy: Roles of Akt, mTOR, GSK3β, and PTEN

Abstract

Chronic alcohol intake leads to the development of alcoholic cardiomyopathy manifested by cardiac hypertrophy and contractile dysfunction. This study was designed to examine the effects of transgenic overexpression of insulin-like growth factor 1 (IGF-1) on alcohol-induced cardiac contractile dysfunction. Wild-type FVB and cardiac-specific IGF-1 mice were placed on a 4% alcohol or control diet for 16 weeks. Cardiac geometry and mechanical function were evaluated by echocardiography and cardiomyocyte and intracellular Ca 2+ properties. Histological analyses for cardiac fibrosis and apoptosis were evaluated by Masson trichrome staining and TUNEL assay, respectively. Expression and phosphorylation of Cu/Zn superoxide dismutase (SOD1), Ca 2+ handling proteins, and key signaling molecules for survival including Akt, mTOR, GSK3β, Foxo3a, and the negative regulator of Akt, phosphatase and tensin homolog on chromosome 10 (PTEN), as well as mitochondrial proteins UCP-2 and PGC1α, were evaluated by Western blot analysis. Chronic alcohol intake led to cardiac hypertrophy, interstitial fibrosis, reduced mitochondrial number, compromised cardiac contractile function and intracellular Ca 2+ handling, decreased SOD1 expression, elevated superoxide production, and overt apoptosis, all of which, with the exception of cardiac hypertrophy, were abrogated by the IGF-1 transgene. Immunoblotting data showed reduced phosphorylation of Akt, mTOR, GSK3β, and Foxo3a; upregulated Foxo3a and PTEN; and dampened SERCA2a, PGC1α, and UCP-2 after alcohol intake. All these alcohol-induced changes in survival and mitochondrial proteins were alleviated by IGF-1. Taken together, these data favor a beneficial role for IGF-1 in alcohol-induced myocardial contractile dysfunction independent of cardiac hypertrophy.