SUN-651 Murine Cecal Ligation and Puncture (CLP) Perturbs Phosphorylation of Insulin Receptor Substrate 2 (IRS-2)

Abstract

Hyperglycemia is a characteristic finding in sepsis, and its presence worsens outcome (1). Patients with sepsis need larger doses of insulin to reduce glucose levels. This abnormality has been termed “insulin resistance” but the molecular mechanism by which sepsis attenuates the insulin signaling pathway is unknown. Previous work has shown impairment of phosphorylation in several intracellular signaling pathways following CLP, a well-validated murine model of sepsis (2). Phosphorylation of tyrosine in IRS-2 is essential for functional insulin signaling in hepatocytes (3). Therefore the aim of this study was to investigate the effects of CLP on IRS-2 phosphorylation. Hypothesis: CLP attenuates phosphorylation of IRS-2. Methods: All studies were approved by the Feinstein IACUC and conformed to ARRIVE guidelines. CLP was performed on C57Bl6 mice. Before CLP, animals were identified for sacrifice at specific post-procedure time points. To stimulate phosphorylation of IRS-2, insulin was injected in control and CLP mice at 24 and 48 hours post CLP. Following sacrifice, protein was isolated from liver tissue. Protein abundance was determined using immunoblotting. The detection of the phosphorylated form of these proteins was determined by enzyme-linked immunosorbent assay (ELISA) with a phospho-insulin receptor antibody. Statistical significance was determined using ANOVA for repeated measures with a Sidak post-hoc correction. Results: Relative to the control, tyrosine phosphorylation of IRS-2 was significantly (p<0.05) reduced at 24 and 48 hours following CLP. Conclusions: Tyrosine phosphorylation of hepatic IRS2 is attenuated at early time points following CLP. These results are consistent with other studies examining the effects of CLP on intra-cellular signal transduction pathways (1). Further, these results provide evidence that changes in the insulin signaling transduction underlie CLP-induced “insulin resistance”.