Figure 5.

Verbascoside improves human islets of Langerhans function. Islets were incubated with or without 16 µM verbascoside for 5 days. (A) Mitochondrial membrane potential. Human islets were loaded with 100 nM MitoSpy™ Orange CMTMRos and 100 μM MitoSpy™ Green FM and the mitochondrial membrane potential and mass were measured by fluorimetry (551/576 nm Ex/Em and 490/516 nm Ex/Em, respectively). The bar graph illustrates the average responses ± SD, data were normalized to the mitochondrial mass (Two-way ANOVA, post-hoc Tukey’s test, °° p = 0.0013 H₂O₂ vs. Basal). (B) The insulin content was evaluated by ELISA assay. Data (mean ± SD) are expressed as mU insulin/g protein (n = 5 independent experiments; Student’s t-test, * p < 0.05 VB vs. Ctr). (C) The insulin release in basal (3.3 mM glucose) and stimulated (16.7 mM glucose) conditions were measured by ELISA assay and data (mean ± SD; n = 3 independent experiments) are expressed as stimulation index (stimulated/basal insulin release). (D) Western blot analysis of ER stress markers in islets treated with 16 μM verbascoside (VB) for 5 days (15 μg protein/sample). On the right, the molecular-weight size markers in kDa are reported. (E) The quantitative analysis shows a trend toward decrease of P-eIF2α expression and P-eIF2α/eIF2α ratio. Data (mean values ± SD) are expressed as fold change over control (dashed line). (n = 2 different islets isolation, performed in duplicate).