| Objective We investigated the regulation of peroxisome proliferator activated receptor gamma(PPARγ)and peroxisome proliferator activated receptor alpha (PPARα)function by telmisartan and irbesartan to clarify the possible molecular mechanism that angiotensin type 1 receptor(AT1R)blockers(ARB)can improve glucose and lipids metabolism.Methods(1)The structural expression vectors,including pCMV-PPARγ/ pCMV-PPARα,pGL3-PPRE and the internal control vector pRL-TK were transiently co-transfected into COS-7 cells using SuperFect,the cells were continous cultured with various concentrations of pioglitazone,fenofibrate,valsartan,losartan, telmisartan,irbesartan and GW9662 for 12,24,36,48 and 60 hours,then the peroxisome proliferators response elements(PPRE)controlled luciferase activity was determined by using a Dual-Luciferase Reporter Gene Assay system.(2)The structural expression vectors,including,pGL3-PPRE and the internal control vector pRL-TK were stably co-transfected into 3T3-L1 cells,and then the cells induced to into fat cells.The cells were.continous cultured with various concentrations of pioglitazone,telmisartan,irbesartan and GW9662 for 6,12,18,25 and 30 hours,then the PPRE controlled luciferase activity was determined by using a Dual-Luciferase Reporter Gene Assay system.(3)3T3-L1 cells were induced to differentiate into fat cells,and the expression levels of PPARγmRNA,PPARαmRNA and protein were detected by RT-PCR and Western blot after the cells treated various concentrations of telmisartan or irbesartan.Results(1)Pioglitazone stimulated PPARγtranscriptional activity in a concentration-and time-dependent manners in cultured COS-7 cells,the PPER controlled luciferase activities were about 7.7-fold(16.85±4.28 vs 2.10±0.18, P＜0.01)of the control at 10-5mol/L,.Valsartan and losartan couldn't stimulate PPARγtranscriptional activity.Both telmisartan and irbesartan stimulated PPARγtranscriptional activity in a concentration-and time-dependent manners in cultured COS-7 cells.The PPER controlled luciferase activities were about 11-fold (47.78±11.76 vs 4.33±0.45,P＜0.01)and 9.9-fold(43.27±13.02 vs 4.33±0.45, P＜0.01),respectively,of the control at 10-4mol/L,and the stimulatory effects reached to the peak at 48 h.(2)Fenofibrate,stimulated PPARαtranscriptional activity in a concentration-and time-dependent manners in cultured COS-7 cells,the PPER controlled luciferase activities were about 4.1-fold(40.50±5.61 vs 9.88±1.67,P＜0.01).Valsartan and losartan couldn't stimulate PPARαtranscriptional activity.Both telmisartan and irbesartan stimulated PPARαtranscriptional activity in a concentration-and time-dependent manners in cultured COS-7 cells.The PPER controlled luciferase activities were about 3.8-fold(37.66±4.45 vs 9.88±1.67, P＜0.01)and 2.6-fold(25.72±3.71 vs 9.88±1.67,P＜0.01),respectively,of the control at 10-4mol/L,and the stimulatory effects reached to the peak at 60 h.(3)The PPARγantagonist GW9662(3×10-5mol/L)couldn't blocked the stimulatory effects of fenofibrate(10-6mol/L),telmisartan(10-5mol/L)and irbesartan(10-5mol/L)on the PPARαtranscriptional activity.(4)Both telmisartan and irbesartan increased expression levels of PPARγmRNA,PPARαmRNA and protein in a dose-dependent manner in differentiated 3T3-L1 adipocyte.Conclusions(1)We successfully established a highly sensitive luciferase screening system for PPARs ligands.(2)Angiotensin type 1 receptor blockers,both telmisartan and irbesartan,can increase PPARγand PPARαtranscriptional activity, and their effects on metabolic improvement may due to the activation of PPARγand PPARα.
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