Akt induces enhanced myocardial contractility and cell size in vivo in transgenic mice

Gianluigi Condorelli, Alessandra Drusco, Giorgio Stassi, Alfonso Bellacosa, Roberta Roncarati, Guido Iaccarino, Matteo A. Russo, Yusu Gu, Nancy Dalton, Clarence Chung, Michael V G Latronico, Claudio Napoli, Junichi Sadoshima, Carlo M. Croce, John Ross

Research output: Contribution to journalArticlepeer-review

Abstract

The serine-threonine kinase Akt seems to be central in mediating stimuli from different classes of receptors. In fact, both IGF-1 and IL6-like cytokines induce hypertrophic and antiapoptotic signals in cardiomyocytes through PI3K-dependent Akt activation. More recently, it was shown that Akt is involved also in the hypertrophic and antiapoptotic effects of β-adrenergic stimulation. Thus, to determine the effects of Akt on cardiac function in vivo, we generated a model of cardiac-specific Akt overexpression in mice. Transgenic mice were generated by using the E40K, constitutively active mutant of Akt linked to the rat α-myosin heavy chain promoter. The effects of cardiac-selective Akt overexpression were studied by echocardiography, cardiac catheterization, histological and biochemical techniques. We found that Akt overexpression produced cardiac hypertrophy at the molecular and histological levels, with a significant increase in cardiomyocyte cell size and concentric LV hypertrophy. Akt-transgenic mice also showed a remarkable increase in cardiac contractility compared with wild-type controls as demonstrated by the analysis of left ventricular (dP/dtmax) in an invasive hemodynamic study, although with graded dobutamine infusion, the maximum response was not different from that in controls. Diastolic function, evaluated by left ventricular dP/dtmin, was not affected at rest but was impaired during graded dobutamine infusion. Isoproterenol-induced cAMP levels, β-adrenergic receptor (β-AR) density, and β-AR affinity were not altered compared with control mice. Moreover, studies on signaling pathway activation from myocardial extracts demonstrated that glycogen synthase kinase3-β is phosphorylated, whereas p42/44 mitogen-activated protein kinases is not, indicating that Akt induces hypertrophy in vivo by activating the glycogen synthase kinase3-β/GATA 4 pathway. In summary, our results not only demonstrate that Akt regulates cardiomyocyte cell size in vivo, but, importantly, show that Akt modulates cardiac contractility in vivo without directly affecting β-AR signaling capacity.

Original languageEnglish
Pages (from-to)12333-12338
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume99
Issue number19
DOIs
Publication statusPublished - Sep 17 2002

ASJC Scopus subject areas

  • Genetics
  • General

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