Fig. 7. ER stress and SREBP-1 activation are implicated in ß-cell glucolipotoxicity. (A) The gene expression patterns in INS-1E cells cultured in either standard (11.2 mM; -) or 30 mM (+) glucose medium for 48 hours were quantified by northern blotting. Total RNA samples (20 µg/lane) were analysed by hybridizing with the indicated cDNA probes. Four independent experiments are shown side by side to demonstrate the consistency of the results. (B) Gel-shift assay of nuclear extracts from isolated rat islets using the SRE sequence of the IRS2 promoter. SREBP-1 protein binding activity was assessed in rat islets treated with 30 mM glucose for 0 (freshly isolated), 1, 2, 3, 4, and 5 days or alternatively with two ER stress inducers, thapsigargin (1 µM) and tunicamycin (10 µg/ml) for 1 day. The mouse monoconal antibody against SREBP-1 was used for supershift experiments.