Ox-LDL Induces ER Stress and Promotes the adipokines Secretion in 3T3-L1 Adipocytes

Adipocytes behave as a rich source of adipokines, which may be the link between obesity and its complications. Endoplasmic reticulum (ER) stress in adipocytes can modulate adipokines secretion. The aim of this study is to evaluate the effect of oxidized low density lipoprotein square ox-LDL square treatment on ER stress and adipokines secretion in differentiated adipocytes. 3T3-L1 pre-adipocytes were cultured and differentiated into mature adipocytes in vitro. Differentiated adipocytes were incubated with various concentrations of ox-LDL (0-100 mu g/ml) for 48 hours; 50 mu g/ml ox-LDL for various times (0-48 hours) with or without tauroursodeoxycholic acid (TUDCA) (0-400 mu M) pre-treatment. The protein expressions of ER stress markers, glucose regulated protein 78(GRP78) and CCAAT/enhancer binding protein [C/EBP] homologous protein (CHOP) in adipocytes were detected by Western blot. The mRNA expressions of visfatin and resistin were measured by real-time PCR and the protein release of visfatin and resistin in supernatant were determined by ELISA. Treatment with ox-LDL could increase the cholesterol concentration in adipocytes. Ox-LDL induced the expressions of GRP78 and CHOP protein in adipocytes and promoted visfatin and resistin secretion in culture medium in dose and time-dependent manner. TUDCA could attenuate the effect of ox-LDL on GRP78 and CHOP expressions and reduce visfatin and resistin at mRNA and protein level in dose-dependent manner. In conclusion, ox-LDL promoted the expression and secretion of visfatin and resistin through its activation of ER stress, which may be related to the increase of cholesterol load in adipocytes.