Effect of Rosiglitazone on the Differential Expression of Diabetes-associated Proteins in Pancreatic Islets of C57Bl/6 lep/lep Mice

Abstract

The insulin sensitizer drug, rosiglitazone, has been shown to have a protective effect on pancreatic islet cell structure and function in animal models of type 2 diabetes. The identification of new molecular targets associated both with islet cell dysfunction and protection is a crucial research goal. In the present study, a proteomics approach has been used to identify such targets. Obese C57Bl/6J lep/lep mice and lean littermates were given the insulin sensitizer drug BRL49653, rosiglitazone. It normalized the impaired glucose tolerance in lep/lep mice but had no significant effect on glucose tolerance in the lean mice. Pancreatic islet polypeptides were arrayed by a two-dimensional gel electrophoresis system that separated more than 2500 individual spots. Three overexpressed and six underexpressed proteins were significant (p < 0.05) between lep/lep and lean mice, and four were modulated significantly (p < 0.05) by the rosiglitazone treatment of the obese mice. The identity of these differentially expressed proteins was made using mass spectrometric analysis and provided evidence that differential expression of actin-binding proteins may be an important aspect of defective islet function. Rosiglitazone increased carboxypeptidase B expression in both lep/lep and normal mice suggesting that this might be an independent effect of rosiglitazone that contributes to improved insulin processing.

Glucose-induced changes of multiple mouse islet proteins analysed by two-dimensional gel electrophoresis and mass spectrometry

“…The excised spots were selected among the differentially expressed proteins but also among other proteins. The latter spots were selected to ensure range in pI and molecular weight, of which some coincided with already identified proteins demonstrating concordance of the present map with previously published maps [15][16][17]. A representative MALDI-TOF PMF spectrum of the heat shock protein 60 (HSP60) is presented in Fig.…”

Proteomics in diabetes research

“…To compensate the insulin resistance with enhanced secretion the C57BL/6J lep/lep mouse develops β-cell hypertrophy (Baetens, et al 1978). Comparison between 2DGE islet maps from C57BL/6J lep/lep and lean litter mates revealed different expression levels of nine proteins of which several were involved in actin cytoskeleton organisation (Sanchez et al 2002).…”

“…Since the preparation was made from whole pancreas and islets only constitute about 2 % of organ mass it cannot be taken for granted that these changes can be attributed to changes in β-cells or islets. In an attempt to elucidate mechanisms of obesityinduced changes in the islet proteome, islet maps from C57BL/6J and C57BL/6J lep/lep mice were compared (Sanchez, et al 2002). A mutation in the gene encoding the hormone leptin in C57BL/6J mice produces the obese C57BL/6J lep/lep or ob/ob mouse strain (Zhang, et al 1994).…”

The application of proteomics to diabetes

“…Treatment with thiazolidinediones in Lep/Lep mice leads to increased expression of carboxypeptidase B, a protein involved in insulin processing, which suggests that PPARγ agonists may normalise glucose homoeostasis in part through improved insulin processing. 27 …”