a limited role for pi(3,4,5)p3 regulation in controlling skeletal muscle mass in response to resistance exercise作用有限π(3、4、5)p3监管控制骨骼肌质量以应对抵抗运动.pdfVIP

A Limited Role for PI(3,4,5)P3 Regulation in Controlling Skeletal Muscle Mass in Response to Resistance Exercise D. Lee Hamilton, Andrew Philp¤a, Matthew G. MacKenzie, Keith Baar*¤b Division of Molecular Physiology, University of Dundee, Dundee, Scotland, United Kingdom Abstract Background: Since activation of the PI3K/(protein kinase B; PKB/akt) pathway has been shown to alter muscle mass and growth, the aim of this study was to determine whether resistance exercise increased insulin like growth factor (IGF) I/ phosphoinositide 3-kinase (PI3K) signalling and whether altering PI(3,4,5)P3 metabolism genetically would increase load induced muscle growth. Methodology/Principal Findings: Acute and chronic resistance exercise in wild type and muscle specific PTEN knockout mice were used to address the role of PI(3,4,5)P3 regulation in the development of skeletal muscle hypertrophy. Acute resistance exercise did not increase either IGF-1 receptor phosphorylation or IRS1/2 associated p85. Since insulin/IGF signalling to PI3K was unchanged, we next sought to determine whether inactivation of PTEN played a role in load-induced muscle growth. Muscle specific knockout of PTEN resulted in small but significant increases in heart (PTEN+/+ = 5.0060.02 mg/g, PTEN2/ 2 = 5.5060.09 mg/g), and TA (PTEN+/+ = 1.7460.04 mg/g, PTEN2/ 2 = 1.89 60.03) muscle mass, while the GTN, SOL, EDL and PLN remain unchanged. Following ablation, hypertrophy of the PLN, SOL or EDL muscles was similar between PTEN2/ 2 and PTEN+/+ animals. Even though there were some changes in overload-induced PKB and S6K1 phosphorylation, 1 hr following acute resistance exercise there was no difference in the phosphorylation state of S6K1 Thr389 between genot