Figure 6.

Proteasome activity and hormone secretion in human islet cells. Human islets were cultured for 6 days in normal (5 mm Glc) or high-glucose (20 mm Glc) media. Old culturing media were replaced with the fresh media containing an increasing concentration of LC (0–10 μm) during the final 8 h of the experiment. A, Western blot analysis of extracellular hIAPP and insulin accumulation following dose-dependent proteasome inhibition with LC (0–10 μm, 12 h). A re-imaged region (5 mm Glc) with improved signal is presented below the original blot. Samples collected from 5 and 20 mm glucose-containing media are separated by two empty lanes in the Western blotting. B, histograms depict fold change in secreted hIAPP and insulin levels relative to control. Significance was established at *, p < 0.05, **, p < 0.01, n = 3, ANOVA followed by Tukey's post hoc comparison test. C, Western blot analysis of extracellular hIAPP and insulin levels in human islet cells cultured in 5 and 20 mm glucose-containing media up to 6 days. Blots showed a significant release in IAPP and insulin release after 48 and 96 h incubation of islets in 20 mm glucose media, respectively.