Insulin signaling cascade in the heart of growth hormone receptor knockout mice: effects of calorie restriction

JORGE F GIANI; MICHAEL S BONKOWSKI; MARINA C MUÑOZ; MICHAL M MASTERNAK; DANIEL TURYN; ANDRZEJ BARTKE; FERNANDO P DOMINICI

JOURNALS OF GERONTOLOGY SERIES A-BIOLOGICAL SCIENCES AND MEDICAL SCIENCES

The Gerontological Society of America

Lugar: Washington, DC ; Año: 2008 vol. 63A p. 788 - 797

1079-5006

Calorie restriction (CR) improves insulin sensitivity and increases life span in normal but not in long lived growth hormone (GH) resistant 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), 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 downregulation of cardiac 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.