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Mechanisms of Hemorrhage-Induced Hepatic Insulin Resistance: Role of Tumor Necrosis Factor-

Department of Pathology (Y.M., A.B.K., L.T.H., J.L.M.), Division of Molecular and Cellular Pathology, and Center for Surgical Research and Department of Surgery (B.T., I.H.C.), The University of Alabama at Birmingham, Birmingham Alabama 35294

Address all correspondence and requests for reprints to: Joseph L. Messina, Ph.D., Department of Pathology, Division of Molecular and Cellular Pathology, Volker Hall, G019, 1670 University Boulevard, University of Alabama at Birmingham, Birmingham, Alabama 35294-0019. E-mail: messina{at}path.uab.edu.

Hemorrhage, sepsis, burn injury, surgical trauma and critical illness all induce insulin resistance. Recently we found that trauma and hemorrhage acutely induced hepatic insulin resistance in the rat. However, the mechanisms of this hemorrhage-induced acute hepatic insulin resistance are unknown. Here we report on the mechanisms of this hepatic insulin resistance. Protein levels and phosphorylation of the insulin receptor and insulin receptor substrate-1/2 (IRS-1/2) were measured, as was the association between IRS-1/2 and phosphatidylinositol 3-kinase (PI3K). Also examined were the hepatic expression of TNF and TNF-induced serine phosphorylation of IRS-1. Insulin receptor and IRS-1/2 protein levels and insulin-induced tyrosine phosphorylation of the insulin receptor were unaltered. In contrast, insulin-induced tyrosine phosphorylation of IRS-1/2 and association between IRS-1/2 and PI3K were dramatically reduced after hemorrhage. Hepatic levels of TNF mRNA and protein were increased as was phosphorylation of IRS-1 serine 307 after hemorrhage. Our data provide the first evidence that compromised IRS-1/2 tyrosine phosphorylation and their association with PI3K contribute to hemorrhage-induced acute hepatic insulin resistance. Increased local TNF may play a role in inducing this hepatic insulin resistance after trauma and hemorrhage.