Peroxisome proliferator-activated receptors as targets to treat metabolic diseases:Focus on the adipose tissue,liver,and pancreas

The world is experiencing reflections of the intersection of two pandemics:Obesity and coronavirus disease 2019.The prevalence of obesity has tripled since 1975 worldwide,representing substantial public health costs due to its comorbidities.The adipose tissue is the initial site of obesity impairments.During excessive energy intake,it undergoes hyperplasia and hypertrophy until overt inflammation and insulin resistance turn adipocytes into dysfunctional cells that send lipotoxic signals to other organs.The pancreas is one of the organs most affected by obesity.Once lipotoxicity becomes chronic,there is an increase in insulin secretion by pancreatic beta cells,a surrogate for type 2 diabetes mellitus(T2DM).These alterations threaten the survival of the pancreatic islets,which tend to become dysfunctional,reaching exhaustion in the long term.As for the liver,lipotoxicity favors lipogenesis and impairs beta-oxidation,resulting in hepatic steatosis.This silent disease affects around 30%of the worldwide population and can evolve into end-stage liver disease.Although therapy for hepatic steatosis remains to be defined,peroxisome proliferator-activated receptors(PPARs)activation copes with T2DM management.Peroxisome PPARs are transcription factors found at the intersection of several metabolic pathways,leading to insulin resistance relief,improved thermogenesis,and expressive hepatic steatosis mitigation by increasing mitochondrial beta-oxidation.This review aimed to update the potential of PPAR agonists as targets to treat metabolic diseases,focusing on adipose tissue plasticity and hepatic and pancreatic remodeling.

Peroxisome proliferator-activated receptors as targets to treat non-alcoholic fatty liver disease

Lately, the world has faced tremendous progress in the understanding of non-alcoholic fatty liver disease(NAFLD) pathogenesis due to rising obesity rates. Peroxisome proliferator-activated receptors(PPARs) are transcription factors that modulate the expression of genes involved in lipid metabolism, energy homeostasis and inflammation, being altered in diet-induced obesity. Experimental evidences show that PPAR-alpha is the master regulator of hepatic beta-oxidation(mitochondrial and peroxisomal)and microsomal omega-oxidation, being markedly decreased by high-fat(HF) intake. PPAR-beta/delta is crucial to the regulation of forkhead box-containing protein O subfamily-1 expression and, hence, the modulation of enzymes that trigger hepatic gluconeogenesis. In addition, PPAR-beta/delta can activate hepatic stellate cells aiming to the hepatic recovery from chronic insult. On the contrary, PPAR-gamma upregulation by HF diets maximizes NAFLD through the induction of lipogenic factors, which are implicated in the fatty acid synthesis. Excessive dietary sugars also upregulate PPAR-gamma, triggering de novo lipogenesis and the consequent lipid droplets deposition within hepatocytes. Targeting PPARs to treat NAFLD seems a fruitful approach as PPAR-alpha agonist elicits expressive decrease in hepatic steatosis by increasing mitochondrial beta-oxidation, besides reduced lipogenesis. PPAR-beta/delta ameliorates hepatic insulin resistance by decreasing hepatic gluconeogenesis at postprandial stage. Total PPAR-gamma activation can exert noxious effects by stimulating hepatic lipogenesis. However, partial PPAR-gamma activation leads to benefits, mainly mediated by increased adiponectin expression and decreased insulin resistance. Further studies are necessary aiming at translational approaches useful to treat NAFLD in humans worldwide by targeting PPARs.

Pro12Ala polymorphism of the peroxisome proliferator-activated receptor γ2 in patients with fatty liver diseases

AIM:To test the occurrence of the Pro12Ala mutation of the peroxisome proliferator-activated receptor-γ (PPARγ)2-gene in patients with non-alcoholic fatty liver disease (NAFLD) or alcoholic fatty liver disease (AFLD).METHODS:DNA from a total of 622 specimens including 259 blood samples of healthy blood donors and 363 histologically categorized liver biopsies of patients with NAFLD (n=263) and AFLD (n=100) were analyzed by Real-time polymerase chain reaction using allele-specific probes.RESULTS:In the NAFLD and the AFLD collective,3% of the patients showed homozygous occurrence of the Ala12 PPARγ2-allele,differing from only 1.5% cases in the healthy population.In NAFLD patients,a high incidence of the Ala12 mutant was not associated with the progression of fatty liver disease.However,we observed a significantly higher risk (odds ratio=2.50,CI:1.05-5.90,P=0.028) in AFLD patients carrying the mutated Ala12 allele to develop inflammatory alterations.The linkage of the malfunctioning Ala12-positive PPARγ2 isoform to an increased risk in patients with AFLD to develop severe steatohepatitis and fibrosis indicates a more prominent anti-inflammatory impact of PPARγ2 in progression of AFLD than of NAFLD.CONCLUSION:In AFLD patients,the Pro12Ala single nuclear polymorphism should be studied more extensively in order to serve as a novel candidate in biomarker screening for improved prognosis.

Effect of insulin and metformin on methylation and glycolipid metabolism of peroxisome proliferator-activated receptor γcoactivator-1A of rat offspring with gestational diabetes mellitus

Objective:To discuss the effect of insulin and metformin on amethylation and glycolipid metabolism of peroxisome proliferator-activated receptor γ coactivator-1A(PPARGC1A) of rat offspring with gestational diabetes mellitus(GDM).Methods:A total of 45 pregnant rats received the intraperitoneal injection of streptozotocin to establish the pregnant rat model of GDM.A total of 21 pregnant rats with GDM were randomly divided into three groups,with 7ruts in each group,namely the insulin group,metformin group and control group.Rats in the insulin group received the abdominal subcutaneous injection of 1 mL/kg recombinant insulin glargine at 18:00 every day.Rats in the metformin group received the intragastric infusion of metformin hydrochloride at 18:00 every day,with the first dose of 300 mg/kg.The doses of two groups were adjusted every 3 d to maintain the blood glucose level at 2.65-7.62 mmol/L.Rats in the control group received the intragastric infusion of 1 mL normal saline at 18:00 every day.After the natural delivery of pregnant rats.10 offspring rats were randomly selected from each group.At birth,4 wk and 8 wk after the birth of offspring rats,the weight of offspring rats was measured.The blood glucose level of offspring rats was measured at 4wk and 8 wk,while the level of serum insulin,triglyceride and leptin was measured at 8 wk.Results:The weight of offspring rats at birth in the insulin group and metformin group was significantly lower than the one in the control group(P<0.05),and there was no significant difference at 4 wk and 8 wk among three groups(P>0.05).The fasting blood glucose and random blood glucose in the insulin group and metformin group at 4 wk and 8 wk were all significantly lower than ones in the control group(P<0.05);there was no significant difference between the insulin group and metformin group(P>0.05).The expression of PPARGC1 A mRNA in the insulin group and metformin group was significantly higher and the methylation level of PPARGC1 A was significantly lower than the one in the control group(P<0.05),but there was no significant difference between the insulin group and metformin group(P>0.05).Insulin and leptin at 8 wk in the insulin group and metformin group were significantly higher,while triglyceride was significantly lower than the one in the control group(P<0.05);triglyceride level of rats in the insulin group was significantly higher than the one in the metformin group(P<0.05).There was no significant difference in insulin and leptin level of offspring rats between the insulin group and metformin group(P>0.05).Conclusions:GDM can induce the methylation of PPARGC1 A of offspring rats to reduce the expression of PPARGC1 A mRNA and then cause the disorder of glycolipid metabolism when the offspring rats grow up;the insulin or metformin in the treatment of pregnant rats with GDM can reduce the methylation level of PPARGC1 A and thus improve the abnormal glycolipid metabolism of offspring rats.

Troglitazone, a peroxisome proliferator-activated receptor γ ligand, induces growth inhibition and apoptosis of HepG2 human liver cancer cells

AIM: To examine the effect of troglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) ligand, on the proliferation and apoptosis of human liver cancer cells. METHODS: Liver cancer cell line HepG2 was cultured and treated with troglitazone. Cell proliferation was detected by 3-(4-,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay; apoptosis was detected by flow cytometry and terminal deoxynucleotidyl transferase- mediated nick end labeling of DNA fragmentation sites (TUNEL) assay; and apoptosis-related protein was detected by immunocytochemistry and Western blotting. RESULTS: Troglitazone inhibited growth and induced apoptosis of HepG2 cells in a dose-dependent manner, and induced activation of caspase-3 expression. Troglitazone not only drove apoptosis-inhibiting factor survivin to translocate incompletely from the nucleus to the cytoplasm, but also inhibited expression of survivin, while it did not affect expression of apoptosis-promoting factor Bax. CONCLUSION: PPARγ ligands inhibit growth and induce apoptosis of liver cancer cells, and may have applications for the prevention and treatment of liver cancer.

Peroxisome proliferator-activated receptor-γ is essential in the pathogenesis of gastric carcinoma

AIM： To investigate whether peroxisome proliferatoractivated receptor γ （PPAR-γ） is expressed in human gastric carcinoma and whether PPAR-γ, is a potential target for gastric carcinoma therapy. METHODS： PPAR-γ protein in gastric carcinoma was examined by immunohistochemistry. In the gastric carcinoma cell line MGCS03, PPAR-7, survivin, Skp2 and p27 protein and mRNA were examined by Western blotting and real-time reverse transcription-polymerase chain reaction, respectively; proliferation was examined by MTT; apoptosis was examined by chromatin staining with Hoechst 33342 and fluorescence activated cell sorting （FACS）. and cell cycle was examined by FACS; the knockdown of PPAR-γ was done by RNA interference. RESULTS： A high level of expression of PPAR-γ was observed in human gastric carcinoma and in a human gastric carcinoma cell line MGCS03. The PPAR-γ agonist 15-deoxy-△12,14-prostaglandin J2 （15d-PGJ2）inhibited growth, and induced apoptosis and G1/G0 cell cycle arrest in MGC803 cells in a concentration-dependent and time-dependent manner. The effect of 15d-PGJ2 on MGC803 cells was not reversed by the selective and irreversible antagonist GW9662 for PPAR-γ. Furthermore, survivin and Skp2 expression were decreased, whereas p27 expression was enhanced following 15d-PGJ2 treatment in a dose-dependent manner in MGC803 cells. Interestingly, we also found that small interfering RNA for PPAR-γ inhibited growth and induced apoptosis in MGC803 cells. The inhibition of PPAR-γ function may be a potentially important and novel modality for treatment and prevention of gastric carcinoma. CONCLUSION： A PPAR-γ agonist inhibited growth of human gastric carcinoma MGC803 cells by inducing apoptosis and G1/G0 cell cycle arrest with the involvement of survivin, Skp2 and p27 and not via PPAR-γ.

Peroxisome proliferator-activated receptor gamma inhibits hepatic fibrosis in rats

BACKGROUND:Hepatic fibrosis is a necessary step in the development of hepatic cirrhosis.In this study we used lentiviral vector-mediated transfection technology to evaluate the effect of peroxisome proliferator-activated receptor gamma(PPAR-γ) on rat hepatic fibrosis. METHODS:Hepatic fibrosis in rats was induced by CCl4 for 2 weeks(early fibrosis)and 8 weeks(sustained fibrosis).The rats were randomly divided into four groups:normal control, fibrosis,blank vector,and PPAR-γ.They were infected with the recombinant lentiviral expression vector carrying the rat PPAR-γgene by portal vein injection.The liver of the rats was examined histologically and hydroxyproline was assessed.In vitro primary hepatic stellate cells(HSCs)were infected with the recombinant lentiviral expression vector carrying the rat PPAR-γgene.The status of HSC proliferation was measured by the MTT assay.The protein levels of PPAR-γ,α-smooth muscle actin(α-SMA)and type I collagen expression were evaluated by the Western blotting method. RESULTS:In vitro studies revealed that expression of PPAR-γ inhibited expression ofα-SMA and type I collagen in activated HSCs(P<0.01)as well as HSC proliferation(P<0.01).In vivo experiments indicated that in the early hepatic fibrosis group,the hydroxyproline content and the level of collagen I protein in the liver in the PPAR-γtransfected group were not significantly different compared to the hepatic fibrosis group and the blank vector group;whereas the expressions of PPAR-γ andα-SMA were different compared to the hepatic fibrosis group(P<0.01).In the sustained hepatic fibrosis group,there were significant differences in the hydroxyproline content and the expression of PPAR-γ,α-SMA,and type I collagen between each group.CONCLUSION:PPAR-γcan inhibit HSC proliferation and hepatic fibrosis,and suppressα-SMA and type I collagen expression.

Peroxisome proliferator-activated receptors for hypertension

Peroxisome proliferator-activated receptors(PPARs) are ligand-activated transcription factors belonging to the nuclear receptor superfamily, which is composed of four members encoded by distinct genes(α, β, γ, and δ). The genes undergo transactivation or transrepression under specific mechanisms that lead to the induction or repression of target gene expression. As is the case with other nuclear receptors, all four PPAR isoforms contain five or six structural regions in four functional domains; namely, A/B, C, D, and E/F. PPARs have many functions, particularly functions involving control of vascular tone, inflammation, and energy homeostasis, and are, therefore, important targets for hypertension, obesity, obesity-induced inflammation, and metabolic syndrome in general. Hence, PPARs also represent drug targets, and PPARα and PPARγ agonists are used clinically in the treatment of dyslipidemia and type 2 diabetes mellitus, respectively. Because of their pleiotropic effects, they have been identified as active in a number of diseases and are targets for the development of a broad range of therapies for a variety of diseases. It is likely that the range of PPARγ agonist therapeutic actions will result in novel approaches to lifestyle and other diseases. The combination of PPARs with reagents or with other cardiovascular drugs, such as diuretics and angiotensin Ⅱ receptor blockers, should be studied.This article provides a review of PPAR isoform characteristics, a discussion of progress in our understanding of the biological actions of PPARs, and a summary of PPAR agonist development for patient management. We also include a summary of the experimental and clinical evidence obtained from animal studies and clinical trials conducted to evaluate the usefulness and effectiveness of PPAR agonists in the treatment of lifestyle-related diseases.

Peroxisome proliferator-activated receptor α,a potential therapeutic target for alcoholic liver disease

Alcoholic liver injury represents a progressive process with a range of consequences including hepatic steatosis, steatohepatitis, liver fibrosis, cirrhosis, and hepatocellular carcinoma. Targeting key molecular regulators involved in the development of alcoholic liver injury may be of great value in the prevention of liver injury. Peroxisome proliferator-activated receptor &#x003b1; (PPAR&#x003b1;) plays a pivotal role in modulation of hepatic lipid metabolism, oxidative stress, inflammatory response and fibrogenesis. As such, PPAR&#x003b1; may be a potential therapeutic target for the treatment of alcoholic liver disease.

Decreased hepatic peroxisome proliferator-activated receptor-γ contributes to increased sensitivity to endotoxin in obstructive jaundice

AIM: To investigate the role of hepatic peroxisome proliferator-activated receptor-γ (PPAR-γ) in increased susceptibility to endotoxin-induced toxicity in rats with bile duct ligation during endotoxemia.METHODS: Male Sprague-Dawley rats were subjected to bile duct ligation (BDL). Sham-operated animals served as controls. DNA binding were determined by polymerase chain reaction, Western blotting analysis,and electrophoretic mobility shift assay, respectively.BDL and sham-operated rats received a non-lethal dose of intraperitoneal lipopolysaccharide (LPS) injection (3 mg/kg, i.p.). Additionally, the potential beneficial effects of the PPAR-γ agonist rosiglitazone were determined in BDL and sham-operated rats treated with a non-lethal dose of LPS. Survival was assessed in BDL rats treated with a non-lethal dose of LPS and in sham-operatedrats treated at a lethal dose of LPS (6 mg/kg, i.p.).RESULTS: PPAR-γ activity in rats undergoing BDL wassignificantly lower than in the sham-controls. Hepatic PPAR-γ gene expression was downregulated at both them RNA and protein levels. In a parallel group, serumlevels of pro-inflammatory cytokines were nearly unde-tectable in the sham-operated rats. When challenged with a non-lethal dose of LPS (3 mg/kg), the BDL ratshad approximately a 2.4-fold increase in serum IL-6,a 2.7 fold increase in serum TNF-α, 2.2-fold increasein serum IL-1 and 4.2-fold increase in serum ALT. Thesurvival rate was significantly lower as compared with that in sham-operated group. Additionally, rosiglitazone significantly reduced the concentration of TNF-α, IL-1β, IL-6 and ALT in sham-operated rats, but not in BDL rats, in response to LPS (3 mg/kg). Also, the survival was improved by rosiglita zone in sham-operated rats challenged with a lethal dose of LPS, but not in BDL rats, even with a non-lethal dose of LPS (3 mg/kg).CONCLUSION: Obstructive jaundice downregulates hepatic PPAR-γ expression, which in turn may contributeto hypersensitivity towards endotoxin.

Peroxisome proliferator-activated receptor γ and colorectal cancer

Peroxisome proliferator-activated receptors(PPARs) are members of the nuclear hormone receptor superfamily and ligand-activated transcription factors.PPARγ plays an important role in adipocyte differentiation,lipid storage and energy dissipation in adipose tissue,and is involved in the control of inflammatory reactions as well as in glucose metabolism through the improvement of insulin sensitivity.Growing evidence has demonstrated that activation of PPARγ has an antineoplastic effect in tumors,including colorectal cancer.High expression of PPARγ is detected in human colon cancer cell lines and adenocarcinoma.This review describes the molecular mechanisms by which PPARγ regulates tumorigenesis in colorectal cancer,and examines current clinical trials evaluating PPARγ agonists as therapeutic agents for colorectal cancer.

EFFECT OF PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR ACTIVATORS ON TUMOR NECROSIS FACTOR-αEXPRESSION IN NEONATAL RAT CARDIAC MYOCYTES

Objective To investigate the effect of peroxisome proliferator-activated receptor-α(PPARα) and PPARγactivators on tumor necrosis factor-α(TNFα) expression in neonatal rat cardiac myocytes. Methods Primary cultures of cardiac myocytes from 1- to 3-day-old Wistar rats were prepared, and myocytes were ex-posed to lipopolysaccharide (LPS) and varying concentrations of PPARαor PPARγactivator (fenofibrate or pioglitazone).RT-PCR and ELISA were used to measure TNFα, PPARα, and PPARγexpression in cultured cardiac myocytes. Transient tr-ansfection of TNFαpromoter with or without nuclear factor-kappaB (NF-κB) binding site to cardiac myocytes was performed. Results Pretreatment of cardiac myocytes with fenofibrate or pioglitazone inhibited LPS-induced TNFαmRNA and protein expression in a dose-dependent manner. However, no significant changes were observed on PPARαor PPARγmRNA expression when cardiac myocytes were pretreated with fenofibrate or pioglitazone. Proportional suppression of TNFαpromoter activity was observed when myocytes was transiently transfected with whole length of TNFαpromoter (-721/+17) after being stimulated with LPS and fenofibrate or pioglitazone, whereas no change of promoter activity was observed with transfection of TNFαreporter construct in deletion of NF-κB binding site (-182/+17). Conclusions PPARαand PPARγactivators may inhibit cardiac TNFαexpression but not accompanied by change of PPARαor PPARγmRNA expression. Therefore PPARαand PPARγactivators appear to play a role in anti-inflammation. The mechanism may partly be involved in suppression of the NF-κB pathway.

Peroxisome proliferator-activated receptor γ agonist reduces the severity of post-ERCP pancreatitis in rats

AIM： To determine the effects of prophylactic peroxisome proliferator-activated receptor （PPARy） agonist administration in an experimental model of post-endoscopic retrograde cholangiopancreatography （post-ERCP） acute pancreatitis. METHODS： Post-ERCP pancreatitis was induced in male Wistar rats by infusion of contrast medium into the pancreatic duct. In additional group, rosiglitazone, a PPARγ agonist, was administered 1 h before infusion of contrast medium. Plasma and pancreas samples were obtained 6 h after the infusion. RESULTS： Infusion of contrast medium into the pancreatic duct resulted in an inflammatory process characterized by increased lipase levels in plasma, and edema and myeloperoxidase activity （MPO） in pancreas. This result correlated with the activation of nuclear factor κB （NFκB） and the inducible NO synthase （iNOS） expression in pancreatic cells. Rosiglitazone reduced the increase in lipase and the level of edema and the increase in myeloperoxidase as well as the activation of NFκB and iNOS expression. CONCLUSION： A single oral dose of rosiglitazone, given 1 h before post-ERCP pancreatitis induction is effective in reducing the severity of the subsequent inflammatory process. The protective effect of rosiglitazone was associated with NFκB inhibition and the blockage of leukocyte infiltration in pancreas.

Effect of ligand of peroxisome proliferator-activated receptor γ on the biological characters of hepatic stellate cells

AIM： To study the effect of rosiglitazone, which is a ligand of peroxisome proliferator-activated receptor gamma （PPARy）, on the expression of PPARy in hepatic stellate cells （HSCs） and on the biological characteristics of HSCs. METHODS： The activated HSCs were divided into three groups： control group, 3 μmol/L rosiglitazone group, and 10 μmol/L rosiglitazone group. The expression of PPARγ, α-smooth muscle actin （α-SMA）, and type Ⅰ and Ⅲ collagen was detected by RT-PCR, Western blot and immunocytochemical staining, respectively. Cell proliferation was determined with methylthiazolyltetrazolium （MTT） colodmetric assay. Cell apoptosis was demonstrated with flow cytometry. RESULTS： The expression of PPARγ at mRNA and protein level markedly increased in HSCs of 10 μmol/L rosiglitazone group （tvalue was 10.870 and 4.627 respectively, P〈0.01 in both）. The proliferation of HSCs in 10 μmol/L rosiglitazone group decreased significantly （t = 5.542, P〈0.01）, α-SMA expression level and type Ⅰ collagen synthesis ability were also reduced VS controls （tvalue = 10.256 and 14.627 respectively, P〈0.01 in both）. The apoptotic rate of HSCs significantly increased in 10 μmol/L rosiglitazone group vs control （X^2= 16.682, P〈0.01）. CONCLUSION： By increasing expression of PPARγ in activated HSCs, rosiglitazone, an agonist of PPARγ, decreases α-SNA expression and type Ⅰ collagen synthesis, inhibits cell proliferation, and induces cell apoptosis.

THE INCREASE IN PLASMINOGEN ACTIVATOR INHIBITOR TYPE-1 EXPRESSION BY STIMULATION OF ACTIVATORS FOR PEROXISOME PROLIFERATOR-ACTIVATED RECEPTORS IN HUMAN ENDOTHELIAL CELLS

Objective.To investigate the effect of peroxis ome proliferator-activated recept ors(PPARs )activators on plasminogen activator inhibitor ty pe-1(PAI-1)expression in human umbilical vein e ndothelial cells and the possi-ble mechanism.Methods.Human umbilical vein endothelial ce lls(HUVECs )were obtained from normal fetus,and cul-tured conventionally.Then the HUVECs were exposed to test agents(linolenic acid,linoleic acid,oleic acid,stearic acid and prostaglandin J 2 respectively)in varying concentrations with fresh media.RT -PCR and ELISA were applied to determine the expression of PPARs and PAI-1in HUVECs.Results.PPARα,PPARδand PPARγmRNA were detected by using RT-PCR in HUVECs.Treatment of HUVECs with PPARαand PPARγactivators---linolenic acid,linoleic acid,oleic acid and prostaglandin J 2 respectively,but not with stearic a cid could augment PAI-I mRNA expression and protein secretion in a concentration-dependent manner.However,the mRNA expressions of 3subclasses of PPAR with their activators in HUVECs were not changed compared w ith controls.Conclusion.HUVECs express PPARs.PPARs activators may increase PAI-1expression in ECs,but the underlying mechanism remains uncle ar.Although PPARs expression was not enhanced after stimulated by their activators in ECs,the role of functionally active PPARs in regulating PA I-1expression in ECs needs to be further investigated by using transient gen e transfection assay.

Peroxisome proliferator-activated receptor gamma as a therapeutic target for hepatocellular carcinoma:Experimental and clinical scenarios

Hepatocellular carcinoma(HCC)is the most common type of liver cancer worldwide.Viral hepatitis is a significant risk factor for HCC,although metabolic syndrome and diabetes are more frequently associated with the HCC.With increasing prevalence,there is expected to be>1 million cases annually by 2025.Therefore,there is an urgent need to establish potential therapeutic targets to cure this disease.Peroxisome-proliferator-activated receptor gamma(PPARγ)is a ligand-activated transcription factor that plays a crucial role in the pathophysiology of HCC.Many synthetic agonists of PPARγsuppress HCC in experimental studies and clinical trials.These synthetic agonists have shown promising results by inducing cell cycle arrest and apoptosis in HCC cells and preventing the invasion and metastasis of HCC.However,some synthetic agonists also pose severe side effects in addition to their therapeutic efficacy.Thus natural PPARγagonists can be an alternative to exploit this potential target for HCC treatment.In this review,the regulatory role of PPARγin the pathogenesis of HCC is elucidated.Furthermore,the experimental and clinical scenario of both synthetic and natural PPARγagonists against HCC is discussed.Most of the available literature advocates PPARγas a potential therapeutic target for the treatment of HCC.

Effect of ligand troglitazone on peroxisome proliferator-activated receptor γ expression and cellular growth in human colon cancer cells

AIM： To investigate the effect of troglitazone on peroxisome proliferator-activated receptor γ （PPARγ） expression and cellular growth in human colon cancer HCT-116 and HCT-15 cells and to explore the related molecular mechanism.METHODS： Human colon cancer HCT-116 and HCT-15 cells cultured in vitro were treated with troglitazone. Reverse transcription-polymerase chain reaction （RT-PCR） and Western blot were employed to detect the effect of troglitazone on PPARy expression. The proliferative activity was determined by MTT assay, cell cycle and apoptosis were detected by flow cytometry. Apoptosisrelated genes, cell cycle regulatory genes and p53 were examined by RT-PCR and Western blot respectively. RESULTS： The expression of PPARy in colon cancer HCT-116 and HCT-15 cells was up-regulated by troglitazone. Troglitazone inhibited proliferation, induced apoptosis and cell cycle G1 arrest in colon cancer cells. Troglitazone induced p53 expression in HCT-116 cells, but not in HCT-15 cells. The down-regulation of survivin and bcl-2 was found in both cell lines and up-regulation of bax was found only in HCT-116 cells, being consistent with growth inhibition in HCT-116 cells but not in HCT-15 cells. Troglitazone increased expression of p21^WAF1/CIP1 （p21）, p27^KIP1 （p27） and reduced cyclin D1 in HCT-116 cells while only a minor decrease of cyclin D1 was found in HCT-15 cells. CONCLUSION： Troglitazone is an inductor of PPARγ in colon cancer cells and inhibits PPARγ-dependently proliferation, which may attribute to cell cycle G1 arrest and apoptosis in colon cancer cells. Troglitazone may induce p53-independent apoptosis and p53- dependent expression of p21 and p27. Depending on cell background, different activation pathways may exist in colon cancer cells.

An innovative approach for the treatment of Alzheimer's disease: the role of peroxisome proliferator-activated receptors and their ligands in development of alternative therapeutic interventions

Alzheimer＇s disease is a multifactorial pathology, for which no cure is currently available. Nowadays, researchers are moving towards a new hypothesis of the onset of the illness, linking it to a metabolic impairment, q-his innovative approach will lead to the identification of new targets for the preparation of new effective drugs. Peroxisome proliferator-activated receptors and their ligands are the ideal candidates to reach the necessary breakthrough to defeat this complicate disease.

Leptin and peroxisome proliferator-activated receptor γ expression in colorectal adenoma

AIM： To investigate the expressions of leptin and per- oxisome proliferator-activated receptor y （PPARG） in relation to body mass index （BMI）. METHODS： We evaluated leptin and PPARG expres- sion in 30 adenomas over 1 cm in size by immunohisto- chemical staining. In addition, clinicopathologic features including BMI were assessed. RESULTS： PPARG and leptin expression showed a strong positive correlation （P = 0.035）. The average BMI of the leptin-positive group was higher than that of the leptin-negative group （25.4 ＋ 3.4 kg/m2 vs 22.6 ＋ 2.4 kg/m2, P = 0.018）, and leptin expression was sig- nificantly correlated with high BMI （P = 0.024）. Leptinexpression was more frequently observed in intermedi- ate/high grade dysplasia than in low grade dysplasia （P = 0.030）. However, PPARG expression was not cor- related with BMI and grade of dysplasia. CONCLUSION： BMI has influenced on the leptin ex- pression of colorectal adenoma. The exact mechanism underlies the strong correlation between leptin and PPARG expression needs further study.

Expression for peroxisome proliferator-activated receptor gamma in pituitary adenomas 38 cases for semi-quantitative immunohistochemical analysis

BACKGROUND： It has been reported that peroxisome proliferator-activated receptor γ （PPAR γ ） is highly expressed in lung cancer, colon cancer, and gastric cancer, as well as other tumors.OBJECTIVE： To study expression of PPAR γ in pituitary adenomas and analyze the role of PPAR γ in hormonal typing of pituitary adenomas. DESIGN, TIME AND SETTING： Semi-quantitative immunohistochemistry of pathological specimens. The experiment was conducted at the Department of Neurosurgery, Wuxi Second Hospital Affiliated to Nanjing Medical University between January 2002 and May 2005. MATERIALS： Surgical resection samples of pituitary adenomas from 38 cases （18 male and 20 female） were analyzed. Eight cases were determined to be invasive pituitary adenomas and 30 cases were non-invasive pituitary adenomas. Hormonal classification of the types of pituitary adenomas revealed somatotrophic adenomas in six cases, corticotrophic adenoma in five cases, prolactinomas in 13 cases, multi-hormone secreting adenomas in six cases, and eight cases of adenoma without altered endocrine function. Five autopsy specimens were collected during the same period from patients of matching age that died from unrelated diseases and were included as normal anterior pituitar3, controls. METHODS： Cell counts for positive immunohistochemical signals were recorded from histopathological sections. The percentage of positive cells was reported as a semi-quantitative analysis. MAIN OUTCOME MEASURES： The rate of PPAR γ positive cells in different types of adenoma was based on hormonal levels and invasiveness of pituitary tumor cells. RESULTS： All tumor biopsies were determined to express PPAR γ. The rate of PPAR γ -positive cells ranged between 8%-65% in the pituitary adenomas. According to hormonal type, PPAR γ expression did not vary between the groups. In addition, there was no significant difference in PPAR γ expression between the non-invasive and invasive pituitary adenomas. CONCLUSIONS： Human pituitary adenomas express PPAR γ, and this expression is unrelated to hormonal type and invasiveness.