| Objective: Insulin resistance is thought to play an important role in the pathogenesis of obesity and associated metabolic diseases and regarded as the centre step and physiopathologic base of the onset of the above mentioned diseases. In addition, elevated plasma free fatty acid level which is thought to be associated with insulin resistance are often seen in those individuals who are obese and (or) diagnosed as"metabolic syndrome". Moreover concordant occurrence of high plasma free fatty acids level and low plasma adiponectin level is often seen in the same individual. In view of those above reasons, we speculate that whether insulin resistance which is induced and (or) aggravated by elevated plasma free fatty acids level is achieved by regulation of adiponectin and(or) adiponectin receptor expression level, and subsequent the signaling path of adiponectin .so here we observed the effects of exogenous palmitic acid which is a kind of saturated fatty acid on the expression of adiponectin,adiponectin receptor1 in the model of 3T3-L1 mature adipocyte. And in addition, whether palmitic acid is a natural ligand of PPARγwhich was thought to bind with PPRE in the promoter of adiponectin so as to activate the transcription of the target gene was also testified.Method: 3T3-L1 preadipocyte was induced to mature adipocyte using the"traditional cocktail wine"method. After more than 70% of preadipocytes became mature, various concentrations of palmitic acids (100,200,400,600μM )were added into the basal culture medium and 6 hours later, the cells were harvested and mRNA was extracted. The mRNA levels of adiponectin,adiponectin receptor1 and PPARγwas quantified using RT-PCR. In addition, the time course of expression of three above mentioned genes were observed at 6h and 12h after adding 100μM palmitic acid. The same method was using to quantify the mRNA level.Results:①adiponectin mRNA levels were declining with the increase of palmitic acid concentration, reaching a significance(P<0.01); The adiponectin mRNA level of 400μM and 600μM palmitic acid groups declined to 60% and 28% of that observed in control group, respectively. The corresponding adiponetin mRNA levels of 6h and 12h at the concentration of 100μM palmitic acid were reduced to 84% and 29% of that of control group. So palmitic acid regulated the expression of adiponectin in 3T3-L1 mature adipocyte in a concentration-dependent and time- dependent fashion.②adiponectin receptor1 mRNA levels slightly went up when palmitic acid varied between 100-400μM, but with no significances compared to control group, while when the concentration reached 600μM, the mRNA level of adiponectin receptor 1 were declined and reached a significance(p<0.01) compared to control group. In addition, the corresponding adiponetin mRNA levels of 6h and 12h at the concentration of 100μM palmitic acid were 102%(P>0.05) and 135%(p<0.01) of that observed in control group.③The mRNA level of PPARγat concentration of 100μM palmitic acid were slightly elevated, but with no significance,compared to control group. And When the concentration of palmitic was 200μM,400μM and 600μM, the mRNA level went down by 33%,34%,54% ,respectively. As for the effects of 6h and 12h at 100μM palmitic acid, the level of PPARγmRNA slightly went up and then sharply went down to 40% of that observed in control group.Conclusion:①adiponectin,adiponectin receptor and the adiponectin signaling path were likely to play an important role the pathgenesis of insulin resistance induced and (or) aggravated by high level of plasma free fatty acid which were often seen in obesity and obesity related metabolic diseases.②The approximately parallel relationship between the mRNA levels of adiponectin and PPARγindicated that free fatty acids were likely to act as natural ligands for PPARγand then regulate the expression of adiponectin through activating the transcription of adiponectin by PPARγ, binding to PPRE in the promoter of adiponectin gene. |
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