The Study Of Exendin-4-antagonizing Palmitic Acid-induced Lipotoxicity In β Cells Through The TLR4/JNK/Bax Signaling Pathway

Objective: To explore the effect of lipotoxicity in βTC6 cells on the signaling pathway of TLR4/JNK/Bax and the change of cell apoptosis and Insulin release and to investigate the intervene effect of Exendin-4 on the aforesaid mechanism.Methods: 1. βTc6 cells were cultured in vitro, βTC6 cells were divided into three groups: control, BSA(treated with 0.5% BSA for 24h), PA(0.5mmol/L of PA for 24h). Cell apoptosis was quantified by flow cytometry. Insulin release was assessed with an insulin ELISA. The Protein expression of TLR4、p-JNK、JNK、Bax and Bcl-2 were measured by Western blotting. 2. TLR4 inhibitor(CLI-095)or JNK inhibitor(SP600125) was added to culture medium, respectively. βTC6 cells were divided into six groups: control, PA(treated with 0.5mmol/L of PA for 24 h), CLI-095(treated with 3umol/L of CLI-095 for 24 h),SP600125(treated with 25umol/L of SP600125 for 24h), PA+CLI-095( pretreated with 3umol/L of CLI-095 for 4h, and then treated with the combination of PA and CLI-095 for 24h), PA+SP600125( pretreated with 25umol/L of SP600125 for 4h, and then treated with the combination of PA and SP600125 for 24h). The Protein expression of Bax and Bcl-2 were measured by Western blotting. 3. βTC6 cells were divided into four groups: control, PA(treated with 0.5mmol/L of PA for 24h), Exendin-4(treated with 50nmol/L of Exendin-4 for 24h), and Exendin-4+PA(pretreated with 50nmol/L of Exendin-4 for 24 h, and then treated with the combination of PA and Exendin-4 for 24h). Cell apoptosis was quantified by flow cytometry. Insulin release was assessed with an insulin ELISA. The Protein expression of TLR4、p-JNK、Bax and Bcl-2 were measured by Western blotting.Results: 1. After intervening with PA for 24 h, the apoptosis of βTc6 cells increased, insulin secretion impairment,the protein expression of TLR4、p-JNK、Bax were increased, Bcl-2 was decreased. After adding with TLR4 inhibitor or JNK inhibitor, the protein expression of Bax was decreased, Bcl-2 was increased. 2. After treating with Exendin-4 for 24 h, the apoptosis of βTc6 cells decreased, insulin secretion improvement, the protein expression of TLR4、p-JNK、Bax were decreased, Bcl-2 was increased.Conclusions: 1. PA induce the apoptosis of β cell through TLR4/JNK/Bax signal pathway. 2. The protective role of Exendin-4 on lipapoptosis of β cell and the improvement of insulin secretion maybe partly related with interfering TLR4/JNK/Bax signal pathway.