Tauroursodeoxycholic Acid Reduces Tumor Necrosis Factor-a-omdiced Lipolysis In3T3-L1Adipocytes And The Underlying Molecularregulation Mechanism

OBJECTIVE:To explore the effects of Tauroursodeoxycholic acid on the lpolytic action of TNF-alpha in3T3-L1adipocytes and the underlying molecularregulation mechanism.METHODS:3T3-L1preadipocytes were differentiated into adipocytes. After treatment with TNF-a at different concentrations and various time, cell viability was determined by MTT to choose the best concentration and time of TNF-a on3T3-L1adipocytes. The intrcelluar lipid droplets were stained by nile red, Glyserol released in the media was determined and served as an index of lipolysis.Western Blotting was performed to determine the protiens levels of the signaling transduction pathways participating in ERs,such as Bip、IRE、JNK and the expression of perilipin A protein which is previously proposed to contribute to the mechanism of lipolysis.RESULTS:After treatment with TNF-alpha (50ng/ml) for24h,it is showed that glyserol accumulation was increased(3.89±0.24) and lipid droplets were dispersed. On the contrary, TUDCA (1mmol/L) significantly prevented TNF-a-induced lipolysis, it reduced glyserol accumulation(2.41±0.17) and the dispersion of lipid droplets. Meanwhile,as determined by Western analysis, the expression of perilipin A is diminished in response to TNF-a treatment while cotreatment with TUDCA restored perilipin A expression. Furthermore,TNF-a up-regulated the expression of Bip and phosphorylation of IRE and JNK in protein levels, which took place at an early phase of TNF-a stimulation and develpoed in a time-dependent manner(it began at2h, peaked at4h, and decreased gradually after6h), while3hours pretreatment of TUDCA (1mmol/L) significantly blocked the protein level of TNF-a-induced p-IRE、p-JNK、Bip(p<0.01). There were statistical differences between them in the content of released glycerol(p<0.01). CONCLUSION:In the present study,we have demonstrated that TNF-a Induces the endoplasmic reticulum stress in3T3-L1adipocyte,and TUDCA protects against TNF-a-indured lipolysis associated with improving ER stress and the lipolysis-related signaling.