| First Author | Yang KC | Year | 2012 |
| Journal | J Mol Cell Cardiol | Volume | 53 |
| Issue | 4 | Pages | 532-41 |
| PubMed ID | 22824041 | Mgi Jnum | J:188789 |
| Mgi Id | MGI:5442234 | Doi | 10.1016/j.yjmcc.2012.07.004 |
| Citation | Yang KC, et al. (2012) Exercise training and PI3Kalpha-induced electrical remodeling is independent of cellular hypertrophy and Akt signaling. J Mol Cell Cardiol 53(4):532-41 |
| abstractText | In contrast with pathological hypertrophy, exercise-induced physiological hypertrophy is not associated with electrical abnormalities or increased arrhythmia risk. Recent studies have shown that increased cardiac-specific expression of phosphoinositide-3-kinase-alpha (PI3Kalpha), the key mediator of physiological hypertrophy, results in transcriptional upregulation of ion channel subunits in parallel with the increase in myocyte size (cellular hypertrophy) and the maintenance of myocardial excitability. The experiments here were undertaken to test the hypothesis that Akt1, which underlies PI3Kalpha-induced cellular hypertrophy, mediates the effects of augmented PI3Kalpha signaling on the transcriptional regulation of cardiac ion channels. In contrast to wild-type animals, chronic exercise (swim) training of mice (Akt1(-/-)) lacking Akt1 did not result in ventricular myocyte hypertrophy. Ventricular K(+) current amplitudes and the expression of K(+) channel subunits, however, were increased markedly in Akt1(-/-) animals with exercise training. Expression of the transcripts encoding inward (Na(+) and Ca(2+)) channel subunits were also increased in Akt1(-/-) ventricles following swim training. Additional experiments in a transgenic mouse model of inducible cardiac-specific expression of constitutively active PI3Kalpha (icaPI3Kalpha) revealed that short-term activation of PI3Kalpha signaling in the myocardium also led to the transcriptional upregulation of ion channel subunits. Inhibition of cardiac Akt activation with triciribine in this (inducible caPI3Kalpha expression) model did not prevent the upregulation of myocardial ion channel subunits. These combined observations demonstrate that chronic exercise training and enhanced PI3Kalpha expression/activity result in transcriptional upregulation of myocardial ion channel subunits independent of cellular hypertrophy and Akt signaling. |
