Inhibitory roles of protein kinase B and peroxisome proliferator-activated receptor gamma coactivator on hepatic HMG-CoA reductase promoter activity

Since we had previously demonstrated that siRNAs to tristetraprolin (TTP) markedly inhibited insulin stimulation of hepatic HMG-CoA reductase (HMGR) transcription, we investigated the effects of transfecting rat liver with TTP constructs. We found that transfecting diabetic rats with TTP did not increase HMGR transcription but rather led to modest inhibition. We then investigated whether co-transfection with protein kinase B, hepatic form (AKT2), might lead to phosphorylation and result in activation of HMGR transcription. We found that this treatment resulted in near complete inhibition of transcription. Transfection with peroxisome proliferator-activated receptor g coactivator (PGC-1a) also inhibited HMGR transcription. These results show that although TTP is needed for activation of HMGR transcription, it cannot by itself activate this process. AKT2 and PGC-1a, which mediate the activation of gluconeogenic genes by insulin, exert the opposite effect on HMGR.

Blockage of PPARδ increases the expression of inflammatory factors in 3T3-L1 cells stimulated with TNFα

Objective： To investigate the role of peroxisome proliferator-activated receptors δ （PPARδ） in inflammatory reaction and its possible mechanism in adipocyte. Methods：Lentivirus-mediated RNA interference （RNAi） was used to block the expression of PPARδ in 3T3-L1 cells. In order to induce inflammation in 3T3-L1, cells were stimulated with tumor necrosis factor-α（TNFα, 20 ng/ml） for 4 h. The expression of PPARδ, nuclear factor κB （NFκB） and C reactive protein （CRP） were determined by Western blot analysis. Results：The expression of PPARδ was reduced by 80% after RNAi. Blockage of PPARδ promoted the expression of CRP and NFκB in cells stimulated with TNFα but had no effect on normal cells. Conclusion： PPARδ is involved in inflammatory reaction in adipocyte. Blockage of PPARδ can promote the inflammation mediated by inflammatory factors and increase the expression of NFκB and CRP in 3T3-L1 cells stimulated with TNFα.

PPARα activator irbesartan suppresses the proliferation of endometrial carcinoma cells via SREBP1 and ARID1A

Endometrial carcinoma(EMC)is associated with obesity;however,the underlying mechanisms have not yet been elucidated.Peroxisome proliferator-activated receptor alpha(PPARα)is a nuclear receptor that is involved in lipid,glucose,and energy metabolism.PPARαreportedly functions as a tumor suppressor through its effects on lipid metabolism;however,the involvement of PPARαin the development of EMC remains unclear.The present study demonstrated that the immunohistochemical expression of nuclear PPARαwas lower in EMC than in normal endometrial tissues,suggesting the tumor suppressive nature of PPARα.A treatment with the PPARαactivator,irbesartan,inhibited the EMC cell lines,Ishikawa and HEC1A,by down-regulating sterol regulatory element-binding protein 1(SREBP1)and fatty acid synthase(FAS)and up-regulating the tumor suppressor genes p21 and p27,antioxidant enzymes,and AT-rich interaction domain 1A(ARID1A).These results indicate the potential of the activation of PPARαas a novel therapeutic approach against EMC.

辅激活因子SRC/p160家族与炎症相关转录因子的关系

SRC/p160(steroid receptor coactivator/p160)家族作为一类辅激活因子,可以辅助多种转录因子,包括炎症相关转录因子,如核转录因子κB,激活蛋白-1,过氧化物酶体增殖物激活受体-γ,糖皮质类固醇激素受体,进而在转录水平上调节多种基因的表达。SRC/p160家族的作用决定于上游的配体、信号通路和转录因子类型,并在不同的组织细胞中表现出一定的特异性及复杂性。而对SRC/p160家族与炎症相关转录因子关系的研究有利于更深入地了解机体对炎症相关基因转录的精细调节和炎症相关性疾病的可能机制,并为抗炎治疗提供新靶点。

尿毒症患者上肢静脉血管组织中PPAR-γ、TLR4、NF-κB的蛋白表达及意义

目的探讨尿毒症患者上肢静脉血管组织中过氧化物酶体增殖物激活受体γ(PPAR-γ)、Toll样受体4(TLR4)、核因子-κB(NF-κB)的蛋白表达水平及其临床意义。方法选取南昌大学第一附属医院10例上肢外伤患者作为对照组(A组)、15例尿毒症未透析患者作为慢性肾衰组(B组)、15例尿毒症透析非糖尿病内瘘闭塞患者作为非糖尿病内瘘闭塞组(C组)和15例尿毒症透析糖尿病内瘘闭塞患者作为糖尿病内瘘闭塞组(D组)。采用Western blot法检测各组上肢静脉血管组织中PPAR-γ、TLR4、NF-κB的蛋白表达水平。结果 B组上肢静脉血管组织中NF-κB蛋白表达水平与A组比较差异无统计学意义(P>0.05)。与A组比较,B、C、D 3组上肢静脉血管组织中PPAR-γ、TLR4蛋白表达水平均明显升高(均P<0.05)。与A、B 2组比较,C、D 2组上肢静脉血管组织中NF-κB蛋白表达水平均明显升高(均P<0.05)。结论 PPAR-γ、TLR4参与了尿毒症患者的内瘘闭塞,而NF-κB可能未参与尿毒症患者血管壁的炎症反应,但参与了动静脉内瘘的失功。

Study on the relationship between relieving energy crisis in myofascial trigger points with An-Pressing manipulation and AMPK/PGC-1α pathway activation

Objective To explore the mechanism of An-Pressing manipulation in relieving energy crisis in chronic myofascial trigger points(MTrPs)by observing the effects of An-Pressing manipulation on adenosine triphosphate(ATP),adenosine 5′-monophosphate(AMP)-activated protein kinase(AMPK)/peroxisome proliferator-activated receptorγcoactivator 1α(PGC-1α)pathway and mitochondrial ultrastructure of skeletal muscle cells in MTrPs rats.Methods Forty-eight male Sprague-Dawley rats were randomly divided into a blank group,a model group,a lidocaine group,and an An-Pressing manipulation group,with 12 rats in each group.The model group,lidocaine group and An-Pressing manipulation group were used to replicate the MTrPs rat model by blunt shock and centrifugal motion method.After modeling,the An-Pressing manipulation group was subjected to 7 times An-Pressing manipulation,once every other day;the lidocaine group was treated with 3 times of injection of lidocaine at the MTrPs,once every 6 d.The blank group and the model group were fed normally without intervention.After the intervention,local muscle tissue was taken to detect the content of ATP and the expression of AMPK,phosphorylated AMPK(phospho-AMPK),PGC-1α,and glucose transporter 4(GluT4),and the ultrastructure of mitochondria was observed under an electron microscope.Results Compared with the blank group,the ATP content in the model group was decreased(P<0.05),the protein expression levels of phospho-AMPK,PGC-1α,and GluT4 and the ratio of phospho-AMPK to AMPK were decreased(P<0.05);under the electron microscope,the number of mitochondria decreased,and they were deformed,small in volume,and had deformed cristae.Compared with the model group,the ATP contents in the An-Pressing manipulation group and the lidocaine group were increased(P<0.05),and the protein expression levels of phospho-AMPK,PGC-1α,and GluT4 and the ratio of phospho-AMPK to AMPK were increased(P<0.05);under the electron microscope,the number of mitochondria increased,the shape and size of the mitochondria were basically normal,and the cristae could be seen.Compared with the lidocaine group,phospho-AMPK and the ratio of phospho-AMPK to AMPK in the An-Pressing manipulation group were increased(P<0.05);under the electron microscope,the numbers of mitochondria were similar,and the shape and size of the mitochondria were basically normal without swelling,and the cristae could be observed.Conclusion An-Pressing manipulation can increase the ATP content in MTrPs tissue,improve the expression levels of PGC-1α and GluT4 proteins and the ratio of phospho-AMPK to AMPK;its mechanism may relate to the activation of AMPK/PGC-1α signaling pathway to promote the repair of mitochondrial damages.

Antifibrotic Effect of Total Flavonoids of Astmgali Radix on Dimethylnitrosamine-lnduced Liver Cirrhosis in Rats

Objective：To study the effect of total flavonoids of Astmgali Radix（TFA）on liver cirrhosis induced with dimethylnitrosamine（DMN）in rats,and the effect on peroxisome proliferator-activated receptorγ（PPARγ）,uncoupling protein 2（UCP2）and farnesoid X receptor（FXR）.Methods：Fifty-three Sprague-Dawley rats were randomly divided into a control group（10 rats）and a DMN group（43 rats）.Rats in the DMN group were given DMN for 4 weeks and divided randomly into a model group（14 rats）,a low-dosage TFA group（14 rats）and a high-dosage TFA group（15 rats）in the 3rd week.Rats were given TFA for 4 weeks at the dosage of 15 and 30 mg/kg in the low-and high-TFA groups,respectively.At the end of the experiment blood and liver samples were collected.Serum liver function and liver tissue hydroxyproline content were determined.hematoxylin-eosin（HE）,Sirus red and immunohistochemical stainings of collagenⅠ,smooth muscle actin（α-SMA）was conducted in paraffinembedded liver tissue slices.Real time polymerase chain reaction（PCR）was adopted to determine PPARγ,UCP2 and FXR m RNA levels.Western blot was adopted to determine protein levels of collagenⅠ,α-SMA,PPARγ,UCP2 and FXR.Results：Compared with the model group,TFA increased the ratio of liver/body weight（low-TFA group P〈0.05,high-TFA group P〈0.01）,improved liver biochemical indices（P〈0.01 for ALT,AST,GGT in both groups,P〈0.05 for albumin and TBil in the high-TFA group）and reduced liver tissue hydroxproline content（P〈0.01 in both groups）in treatment groups significantly.HE staining showed that TFA alleviated liver pathological changes markedly and Sirus red staining showed that TFA reduced collagen deposition,alleviated formation and extent of liver pseudolobule.CollagenⅠandα-SMA immunohistochemical staining showed that staining area and extent markedly decreased in TFA groups compared with the model group.TFA could increase PPARγ,it regulated target UCP2,and FXR levels significantly compared with the model group（in the low-TFA group all P〈0.05,in the high group all P〈0.01）.Conclusions：TFA could improve liver function,alleviate liver pathological changes,and reduce collagen deposition and formation of liver pseudolobule in rats with liver cirrhosis.The antifibrotic effect of TFA was through regulating PPARγsignal pathway and the interaction with FXR.

Anti-Hypertensive Action of Fenofibrate via UCP2 Upregulation Mediated by PPAR Activation in Baroreflex Afferent Pathway

Fenofibrate, an agonist for peroxisome proliferator-activated receptor alpha(PPAR-a), lowers blood pressure, but whether this action is mediated via baroreflex afferents has not been elucidated. In this study, the distribution of PPAR-a and PPAR-c was assessed in the nodose ganglion(NG) and the nucleus of the solitary tract(NTS). Hypertension induced by drinking high fructose(HFD) was reduced, along with complete restoration of impaired baroreceptor sensitivity, by chronic treatment with fenofibrate. The molecular data also showed that both PPAR-a and PPAR-c were dramatically up-regulated in the NG and NTS of the HFD group. Expression of the downstream signaling molecule of PPAR-a, the mitochondrial uncoupling protein 2(UCP2), was up-regulated in the baroreflex afferent pathway under similar experimental conditions, along with amelioration of reduced superoxide dismutase activity and increased superoxide in HFD rats.These results suggest that chronic treatment with fenofibrate plays a crucial role in the neural control of blood pressure by improving baroreflex afferent function due at least partially to PPAR-mediated up-regulation of UCP2 expression and reduction of oxidative stress.

Silencing of DsbA-L gene impairs the PPARγagonist function of improving insulin resistance in a high-glucose cell model

Disulfide-bond A oxidoreductase-like protein(DsbA-L)is a molecular chaperone involved in the multimeri-zation of adiponectin.Recent studies have found that DsbA-L is related to metabolic diseases including gestational diabetes mellitus(GDM),and can be regulated by peroxisome proliferator-activated receptorγ(PPARγ)agonists;the specific mechanism,however,is uncertain.Furthermore,the relationship between DsbA-L and the novel adipokine chemerin is also unclear.This article aims to investigate the role of DsbA-L in the improvement of insulin resistance by PPARγagonists in trophoblast cells cultured by the high-glucose simulation of GDM placenta.Immunohistochemistry and western blot were used to detect differences between GDM patients and normal pregnant women in DsbA-L expression in the adipose tissue.The western blot technique was performed to verify the relationship between PPARγagonists and DsbA-L,and to explore changes in key molecules of the insulin signaling pathway,as well as the effect of chemerin on DsbA-L.Results showed that DsbA-L was significantly downregulated in the adipose tissue of GDM patients.Both PPARγagonists and chemerin could upregulate the level of DsbA-L.Silencing DsbA-L affected the function of rosiglitazone to promote the phosphatidylinositol 3-kinase(PI3K)-protein kinase B(PKB)/AKT pathway.Therefore,it is plausible to speculate that DsbA-L is essential in the environment of PPARγagonists for raising insulin sensitivity.Overall,we further clarified the mechanism by which PPARγagonists improve insulin resistance.