Regulation of IRS-2 signaling by IGF-1 receptor in the diabetic rat heart

Can J Physiol Pharmacol. 2010 May;88(5):553-61. doi: 10.1139/y10-006.

Abstract

Cardiovascular disease involves changes in inflammatory markers. Since insulin/insulin-like growth factor 1 receptor (IGF-1R) can activate vascular endothelial growth factor to promote vascular growth, reduced IGF-1R signaling in the type I diabetic heart could be detrimental, leading to reduced, collateral blood vessel growth. This study assessed whether diabetes can induce an inflammatory phenotype to regulate molecules in the IGF-1 signaling cascade, thus mediating apoptosis. Rats were made diabetic using streptozotocin (to render them type I diabetic) for 2 months with no insulin treatment. At 2 months, rats were sacrificed under anesthesia, and the left ventricle was immediately removed and placed into cold lysis buffer for protein analyses. Western blotting, immunoprecipitation, and enzyme-linked immunosorbent assay analyses were completed to evaluate protein levels. Diabetes increased TNF-alpha, interleukin-6 (IL-6), and IL-1alpha levels in the heart. JNK and p42/p44 activity was significantly increased in the diabetic heart, while IGF-1R phosphorylation, IRS-2 tyrosine phosphorylation, and Akt activities were reduced. A significant increase in Bad protein levels and the cleavage of caspase 3 was observed in the diabetic heart. These results suggest that diabetes activates multiple inflammatory markers in the heart, which then signal a decrease in the activities of key players in the insulin-signaling cascade, namely IGF-1R, IRS-2, and Akt, to regulate apoptosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Biomarkers / analysis
  • Caspase 3 / metabolism
  • Diabetes Mellitus, Experimental / enzymology
  • Diabetes Mellitus, Experimental / metabolism*
  • Diabetes Mellitus, Experimental / pathology
  • Enzyme-Linked Immunosorbent Assay
  • Immunoprecipitation
  • In Situ Nick-End Labeling
  • Insulin / metabolism
  • Insulin Receptor Substrate Proteins / metabolism*
  • Interleukin-1alpha / metabolism
  • Interleukin-6 / metabolism
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Myocardium / enzymology
  • Myocardium / metabolism*
  • Myocardium / pathology
  • Phosphorylation
  • Rats
  • Rats, Inbred Lew
  • Receptor, IGF Type 1 / metabolism
  • Receptor, IGF Type 1 / physiology*
  • Signal Transduction*
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Biomarkers
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Interleukin-1alpha
  • Interleukin-6
  • Irs2 protein, rat
  • Tumor Necrosis Factor-alpha
  • Receptor, IGF Type 1
  • JNK Mitogen-Activated Protein Kinases
  • Caspase 3