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

Authors: Condorelli, G  Drusco, A  Stassi, G  Bellacosa, A  Roncarati, R  Iaccarino, G  Russo, MA  Gu, Y  Dalton, N  Chung, C  Latronico, MV  Napoli, C  Sadoshima, J  Croce, CM  Ross J, JR 
Citation: Condorelli G, etal., Proc Natl Acad Sci U S A 2002 Sep 17;99(19):12333-8.
Pubmed: (View Article at PubMed) PMID:12237475
DOI: Full-text: DOI:10.1073/pnas.172376399

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 beta-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 alpha-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/dt(max)) 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/dt(min), was not affected at rest but was impaired during graded dobutamine infusion. Isoproterenol-induced cAMP levels, beta-adrenergic receptor (beta-AR) density, and beta-AR affinity were not altered compared with control mice. Moreover, studies on signaling pathway activation from myocardial extracts demonstrated that glycogen synthase kinase3-beta is phosphorylated, whereas p42/44 mitogen-activated protein kinases is not, indicating that Akt induces hypertrophy in vivo by activating the glycogen synthase kinase3-beta/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 beta-AR signaling capacity.

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CRRD Object Information
CRRD ID: 734544
Created: 2004-02-03
Species: All species
Last Modified: 2004-02-03
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.