Regulation of hepatic insulin receptor activity following injury.
Impaired insulin receptor (IR) activity has been found in various models of insulin resistance, including models of injury or critical illness and Type 2 diabetes. However, mechanisms that modulate IR function remain unclear. With an animal model of critical-illness diabetes, we found insulin-induced IR tyrosine phosphorylation in the liver was impaired as early as 15 min following trauma and hemorrhage. Possible mechanisms for this defect were examined, including IR protein levels and IR posttranslational modifications. The total amounts of hepatic IRα and IRβ subunits and the membrane localization of the IR were not altered by trauma and hemorrhage, and, likewise, no change in IR tyrosine nitration was found in the liver. However, there was a decrease in the level of protein O-linked β-N-acetlyglucosamine (O-GlcNac) modification on Ser/Thr in the liver following trauma and hemorrhage. Inhibition of JNK increased IR O-GlcNac modification, implicating an involvement of JNK. These findings suggest that a balance between O-GlcNac modification and JNK-induced phosphorylation may exist, with decreased Ser/Thr O-GlcNac modification following trauma and hemorrhage, allowing JNK to phosphorylate the IR on neighboring Ser/Thr residues, which subsequently inhibits IR activity. The present studies suggest potential mechanisms of hemorrhage-induced defects in IR activity and a potential role for acutely decreased O-GlcNac and increased serine phosphorylation of the IR.
Department of Pathology, Division of Molecular and Cellular Pathology, University of Alabama at Birmingham, Birmingham, Alabama; and.
Shaoning
S
Jiang
Department of Pathology, Division of Molecular and Cellular Pathology, University of Alabama at Birmingham, Birmingham, Alabama; and.
Tatyana A
TA
Gavrikova
Department of Pathology, Division of Molecular and Cellular Pathology, University of Alabama at Birmingham, Birmingham, Alabama; and Veterans Affairs Medical Center, Birmingham, Alabama messinaj@uab.edu.
Joseph L
JL
Messina
D000818:Animals; D006471:Gastrointestinal Hemorrhage / Q000503:physiopathology*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008099:Liver / Q000293:injuries*; D008297:Male; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*
D055504:Insulin Receptor Substrate Proteins; D017351:N-Acetylglucosaminyltransferases; D011972:Receptor, Insulin; D048031:JNK Mitogen-Activated Protein Kinases
O-linked β-N-acetlyglucosamine; c-Jun NH2-terminal kinase; injury; insulin resistance; liver