Image analysis was performed as previously described [21, 22]. Image analysis and the quantification of gel spots were performed with Prodigy SameSpots software (Nonlinear Dynamics, Newcastle upon Tyne, UK). From the menu of SameSpots normalization options, we chose to normalize the intensity of each spot to the total intensity of all matched spots within each gel and to identify differentially expressed spots by comparing spot intensity differences between samples from STZ-treated mice and control mice using ANOVA.