An inositol 1,4,5-triphosphate (IP3)-IP3 receptor pathway is required for insulin-stimulated glucose transporter 4 translocation and glucose uptake in cardiomyocytes

Endocrinology. 2010 Oct;151(10):4665-77. doi: 10.1210/en.2010-0116. Epub 2010 Aug 4.


Intracellular calcium levels ([Ca2+]i) and glucose uptake are central to cardiomyocyte physiology, yet connections between them have not been studied. We investigated whether insulin regulates [Ca2+]i in cultured cardiomyocytes, the participating mechanisms, and their influence on glucose uptake via SLC2 family of facilitative glucose transporter 4 (GLUT4). Primary neonatal rat cardiomyocytes were preloaded with the Ca2+ fluorescent dye fluo3-acetoxymethyl ester compound (AM) and visualized by confocal microscopy. Ca2+ transport pathways were selectively targeted by chemical and molecular inhibition. Glucose uptake was assessed using [3H]2-deoxyglucose, and surface GLUT4 levels were quantified in nonpermeabilized cardiomyocytes transfected with GLUT4-myc-enhanced green fluorescent protein. Insulin elicited a fast, two-component, transient increase in [Ca2+]i. Nifedipine and ryanodine prevented only the first component. The second one was reduced by inositol-1,4,5-trisphosphate (IP3)-receptor-selective inhibitors (xestospongin C, 2 amino-ethoxydiphenylborate), by type 2 IP3 receptor knockdown via small interfering RNA or by transfected Gβγ peptidic inhibitor βARKct. Insulin-stimulated glucose uptake was prevented by bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid-AM, 2-amino-ethoxydiphenylborate, and βARK-ct but not by nifedipine or ryanodine. Similarly, insulin-dependent exofacial exposure of GLUT4-myc-enhanced green fluorescent protein was inhibited by bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid-AM and xestospongin C but not by nifedipine. Phosphatidylinositol 3-kinase and Akt were also required for the second phase of Ca2+ release and GLUT4 translocation. Transfected dominant-negative phosphatidylinositol 3-kinase γ inhibited the latter. In conclusion, in primary neonatal cardiomyocytes, insulin induces an important component of Ca2+ release via IP3 receptor. This component signals to glucose uptake via GLUT4, revealing a so-far unrealized contribution of IP3-sensitive Ca2+ stores to insulin action. This pathway may influence cardiac metabolism in conditions yet to be explored in adult myocardium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Calcium / metabolism
  • Cells, Cultured
  • Glucose / metabolism
  • Glucose / pharmacokinetics*
  • Glucose Transporter Type 4 / metabolism*
  • Inositol 1,4,5-Trisphosphate / metabolism
  • Inositol 1,4,5-Trisphosphate / pharmacology
  • Inositol 1,4,5-Trisphosphate / physiology*
  • Inositol 1,4,5-Trisphosphate Receptors / metabolism
  • Inositol 1,4,5-Trisphosphate Receptors / physiology*
  • Insulin / pharmacology*
  • Myocytes, Cardiac / drug effects*
  • Myocytes, Cardiac / metabolism
  • Protein Transport / drug effects
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Up-Regulation / drug effects


  • Glucose Transporter Type 4
  • Inositol 1,4,5-Trisphosphate Receptors
  • Insulin
  • Inositol 1,4,5-Trisphosphate
  • Glucose
  • Calcium