Insulin signaling cascade in the hearts of long-lived growth hormone receptor knockout mice: effects of calorie restriction.
Calorie restriction (CR) improves insulin sensitivity and increases life span in normal but not in long-lived growth hormone-resistant knockout (GHRKO) mice. In this study, we examined interactive effects of GH resistance and long-term CR on cardiac insulin action. GHRKO mice exhibited marked increases in the insulin-induced phosphorylation of the insulin receptor (IR), insulin receptor substrate-1 (IRS-1), Akt, and ERK1/2 along with elevated insulin-stimulated IRS-1-associated regulatory subunit of phosphatidylinositol 3-kinase in the heart. These changes were associated with elevated protein levels of IR, IRS-1, and Akt and with a down-regulation of cardiac glucose transporter 4 (GLUT4). In normal mice, CR induced an important increase in the phosphorylation of cardiac Akt without elevation of Akt protein, reaching activation levels similar to those seen in GHRKO mice. This change may be cardioprotective and thus contribute to increased longevity in response to CR. Interestingly, the insulin signaling cascade in the heart of GHRKO mice was unaffected by CR.
Giani
Jorge F
JF
Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas (IQUIFIB), Buenos Aires, Buenos Aires 1113, Argentina.
Bonkowski
Michael S
MS
Muñoz
Marina C
MC
Masternak
Michal M
MM
Turyn
Daniel
D
Bartke
Andrzej
A
Dominici
Fernando P
FP
D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology; D000263:Adenylate Kinase / Q000378:metabolism; D000818:Animals; D031204:Caloric Restriction; D015536:Down-Regulation / Q000502:physiology; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006321:Heart / Q000502:physiology*; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008136:Longevity; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D011972:Receptor, Insulin / Q000502:physiology; D011986:Receptors, Somatotropin / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D011986:Receptors, Somatotropin; C495678:Slc2a1 protein, mouse; C495693:Slc2a4 protein, mouse; D007334:Insulin-Like Growth Factor I; D011972:Receptor, Insulin; D000263:Adenylate Kinase