The effect of FFAR1 on pioglitazone-mediated attenuation of palmitic acid-induced oxidative stress and apoptosis in βTC6 cells

Objective. We sought to determine whether free fatty acid receptor 1 (FFAR1), a receptor for free fatty acids on the beta-cell membrane, can mediate the pioglitazone (PIO)-attenuating effect on lipoapoptosis in beta cells and its relationship to oxidative stress. Methods. The glucose-sensitive mouse beta pancreatic cell line beta TC6 was used to investigate the effect of FFAR1 on PIO-attenuating palmitic acid (PA)-induced oxidative stress and apoptosis. Results. (1) PIO reduced PA-induced lipoapoptosis in beta cells and upregulated the expression of FFAR1 at the mRNA and protein levels in a dose- and time-dependent manner. Silencing of FFAR1 expression was shown to weaken the protective effect of PIO on PA-induced lipoapoptosis in beta TC6 cells; while lentiviral-mediated overexpression of FFAR1 was shown to enhance the protective effect of PIO against lipoapoptosis in beta cells. (2) Downregulation of FFAR1 expression reduced the attenuating effect of PIO on the expression of NAPDH oxidase subunit p47(phox), Bax, cleaved caspase 3, and the production of reactive oxygen specific (ROS) induced by lipotoxicity, thereby preventing the upregulation of the expression of bcl-2. Inducing the overexpression of FFAR1 enhanced the anti-oxidative stress effect of PIO. Similarly, these effects of FFAR1 on PIO were reproduced under conditions of oxidative stress and apoptosis in beta TC6 cells that were induced by H2O2. (3) PIO was found to increase the expression of PLC-gamma, ERK1/2, and PPAR-gamma in lipotoxic beta cells. Silencing FFAR1 expression reduced the PIO-mediated increases in the expression of above proteins; while inducing FFAR1 overexpression showed the opposite effect. Use of an inhibitor of PLC-gamma, ERK1/2, PPAR gamma was shown to restrict the protective effect of PIO on oxidative stress and lipoapoptosis of p cells. Conclusions. FFAR1 can mediate PIO suppression of beta-cell lipoapoptosis through antioxidative stress, which may be related to the activation of the PLC gamma-ERK1/2-PPAR-gamma pathway. (C) 2014 Elsevier Inc. All rights reserved.