Islet Brain 1 Protects Insulin Producing Cells against Lipotoxicity

Figure 1

Effect of palmitate on the Ib1 mRNA level. (a) Quantification of Ib1 mRNA level by RT-qPCR from MIN6 cells (open bar) and isolated rat islets (grey bar) cultured with 0.5 mM palmitate or BSA (−) at different indicated times. (b) Assessment of Ib1 transcriptional activity in MIN6 cells cultured with palmitate. Cells were transiently transfected with a luciferase reporter construct driven by the 731 bp fragment of the human MAPK8IP1 promoter (IB1luc). Palmitate was added to the medium 24 hrs after transfection and luciferase activity was measured 48 hrs later. To test the role of ICER, IB1luc was cotransfected together with duplexes of control small interfering RNA (siGFP, open bar) or siRNA directed specifically against ICER (siICER, filled bar). The data are expressed as fold increase over the control vector pGL3basic and are the mean ± SEM of three independent experiments. (c) Role of ICER in the drop of Ib1 mRNA induced by palmitate. The Ib1 mRNA was measured by RT-qPCR in MIN6 cells that were transfected with duplexes of either siGFP (open bar) or siICER (filled bar). After transfection, (24 hrs) the cells were cultured with BSA (ctrl) or 0.5 mM palmitate for additional 48 hrs. The results were normalized against Rplp0 and the expression levels from cells cultured with BSA were set to 100%. Data are the mean ± SEM of 3 independent experiments (; ).

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