Influence Of Inflammation On Adipocyte Function And Underneath Mechanism

ObjectiveThe pro-inflammatory cytokine TNF-αhas multiple effects on adipocyte function, including differentiation, lipolyis and the production of adipokines. In this paper, we have evaluated the effects of TNF-αon cholesterol efflux in passaged rabbit subcutaneous adipocyte, which had been elucidated in macrophages, and the possible mechanism involved.MethodsPassaged rabbit inguina subcutaneous adipocytes were incubated with 5, 10, 20 ng/ml different doses of TNF-αfor 24 hrs. The cholesterol effiux onto apolipoprotein AⅠ(apoAⅠ) was assessed, and the related peroxisome proliferator activated receptorγ(PPARγ), liver X receptorα(LXRα) and ATP-binding cassette transporter A1 (ABCA1) mRNA expression in adipocytes were quantitated by reverse transcription polymerase chain reaction (RT-PCR).Results1. Treatment of normal passaged adipocytes with TNF-α(5 or 10 ng/ml) for 24 hrs increased the level of cholesterol effiux onto apoAⅠ, and the effct of 10 ng/ml TNF-αwas significant (7.03±1.17% vs 3.92± 0.46%, P＜0.01). In contrast, 20 ng/ml TNF-αdecreased cholesterol effulux by 16.2% compared with 10 ng/ml TNF-α( P<0.05).2. The expression of ABCA1 was elevated under treatment of 5 or 10 ng/ml TNF-α(0.444±0.17 vs 0.204±0.06, 0.914±0.26 vs 0.20±0.06, respectively, P＜0.05), and inhibited by 20 ng/ml TNF-α(0.694±0.13). In consistence with the change of ABCA1, the PPARγand LXRαmRNA were significantly induced by 10 ng/ml TNF-α(1.36±0.25 vs 0.48±0.12, 0.844±0.18 vs 0.324±0.08) and downregulated by higher TNF-α.3. After pre-treated by PPARγspecial inbhibitor GW9662 for half an hour, the introduction of PPARγby 10 ng/ml TNF-αwas partially prevented, subsequent to the downregulation of LXRαand ABCA1.ConclusionTNF-αaffects cholesterol effiux and ABCA1 expression of adipocytes, and the pathway of PPARγ-LXRα-ABCA1 is probably involved. ObjectiveObesity is caused by increased adipose mass, which is characterized with enlarged adipocytes. The energy homeostasis management and endocrinal function of enlarged fat cell under certain state, e.g lipid-laden, will be different with that of normal cells. Here we have investigated the effect of pro-inflammatory cytokine TNF-αon cholesterol effulux in the cholesterol laden adipocytes, which was induced by oxidized low density lipoprotein (oxLDL), and the possible mediators in its action.MethodsAdipocyte isolated from the New Zealand White Rabbit inguina subcutaneous adipose were incubated with 50/zg/ml oxLDL for 24 hrs, then were treated with different doses of TNF-α(5, 10, 20 ng/ml) for another 24 hrs. The cholesterol efflux onto apoAⅠwas assessed. The related gene of PPARγ, LXRαand ABCA1 expression in adipocytes were evaluated by RT-PCR.Results1. Cholesterol efflux was induced by uptake of oxLDL in adipocyte (7.46±2.34% vs 3.92±0.46%, P＜0.05). TNF-αsignificantly inhibited the effects of oxLDL under 5 or 10 ng/ml (6.02±0.31%, 4.56±1.62%). 20 ng/ml TNF-αreversed the downregulation to some extent (6.12±0.53%).2. ABCA1 mRNA was increased in lipid-laden adipocyte induced by oxLDL (1.19±0.32 vs 0.20±0.06), and decreased under addition of 5 ng/ml TNF-α(1.02±0.29) or 10 ng/ml TNF-α(0.78±0.24). In contast, 20 ng/ml TNF-αprevented the downregulation (0.98±0.17).3. The induction of PPARγand LXRαmRNA in lipid-laden adipocyte were decreased by TNF-αin a dose dependent pattern. From the low to the high dose of TNF-α, PPARγexpression was 0.93±0.21, 0.77±0.15, 0.60±0.16 compared with oxLDL control group 1.07±0.26. LXRαexpression was 0.72±0.19, 0.61±0.17, 0.49±0.09 compared with oxLDL control group 0.83±0.16.ConclusionTNF-αdownregulated the augmentation of PPARγand LXRαresulted from lipid burden in rabbit subcutaneous adipocyte induced by oxLDL, and subsequently influenced the expression of ABCA1 and cholesterol effiux. ObjectiveTo investigate the potential benefits of curcumin, an extract from traditional medical plants, on adipocyte function.MethodsRabbit subcutaneous adipocytes were treated with 5, 10, 20μg/ml curcumin for 24 hrs. One of the major adipokines, adiponectin secretion in supernatant was examined by special ELISA kit. The expression of adiponectin and PPARγ, its upstream regulator, were quantitated by RT-PCR.Results1. Curcumin increased the adiponectin secretion examined in supernatant in a dose dependent pattern. From 5μg/ml to 20μg/ml, the secretion of adiponectin were 3.93±0.26, 4.49±0.34, 5.21±0.39 vs 3.13±0.21μmol/1 (control group).2. Curcumin induced the expression of PPARγin cultured adipocyte, and reached its peak value on 20μg/ml (1.01±0.15 vs 0.48±0.12). The adiponectin mRNA was also increased under treatment of all the doses of curcumin (0.55±0.09, 0.66±0.11, 0.80±0.13 vs 0.40±0.10).ConclusionCurcumin is able to induce the expression and secretion of adiponectin in adipocyte, which related to its upregulation of expression of PPARγ.