PPARgamma Expression Research Articles

Prevalence of the Pro12Ala missense mutation in the PPARG2 gene in Kuwaiti patients with primary knee osteoarthritis

BACKGROUND AND OBJECTIVES:Peroxisome proliferator–activated receptors (PPARs) play an important role in a number of cellular and metabolic functions. This study was carried out to determine the prevalence of a missense mutation (Pro12Ala) in the PPARG2 gene in Kuwaiti Arab patients with primary knee osteoarthritis (OA) and healthy controls with the aim of identifying a possible association.DESIGN AND SETTING:A prospective cross-sectional study carried out at three major teaching hospitals (referral centers) in the country over a one-year period.PATIENTS AND METHODS:The prevalence of PPARG2 gene Pro12Ala missense mutation was determined in 104 Kuwaiti Arab patients with primary knee OA and 111 ethnically matched healthy controls. The prevalence of this Pro12Ala missense mutation was also determined in clinical subgroups of OA patients divided on the basis of age at onset, function and radiologic grading.RESULTSThe Pro-Pro genotype of the PPARG2 gene Pro12Ala missense mutation was detected in 95/104 (91.3%) cases compared to 111/111 (100%) in the control subjects. The heterozygous Pro-Ala genotype was detected in 9/104 (8.7%) of the OA patients, while it was not detected in any of the controls. The Ala-Ala genotype was not detected in any of the OA patients or the controls. No significant differences were detected in the PPARG2 gene Pro12Ala genotypes in the subgroups of patients classified on the basis of age at onset, functional assessment using Lequesne’s functional index, and radiological grading using Kellgren-Lawrence (K-L) grading.CONCLUSIONSThis study found no significant association between the PPARG2 gene Pro12Ala missense mutation and knee OA. However, the presence of the Pro-Pro genotype of the PPARG2 gene mutation has a protective effect against development of OA.

Study on effect of total saponins from Semen Nigellae on inflammatory mediators and ERK/MAPK pathway in stimulated macrophage

To study the anti-inflammatory mechanism of total saponins from Semen Nigellae (TSSN). IFN-gamma plus LPS stimulated RAW 264. 7 macrophage has been used as inflammatory experimental model. Griess reaction for nitric oxide production, FRAP assay for total antioxidant capacity, RT-PCR for mRNA expression and Western blot for protein expression examination were performed. TSSN inhibited NO production in a dose-dependent manner. The gene and protein expression of iNOS were also suppressed by the herb extract. TSSN treatment significantly attenuated mRNA of inflammatory mediators such as COX-2, IL-1beta, IL-6 while increased PPAR-gamma gene and protein expression. Furthermore, phosphorylation of ERK (p-ERK) was markedly inhibited by TSSN. TSSN suppressed pro-inflammatory mediators such as COX-2, IL-1beta, IL-6 and increased anti-inflammatory mediator PPAR-gamma expression. Meanwhile, TSSN inhibited over production of NO and iNOS expression through ERK/MAPK pathway.

Modulation of inflammatory changes in early stages of colon cancer through activation of PPARγ by diclofenac

The role of peroxisome proliferator-activated receptor gamma (PPARgamma) was investigated in 1,2-dimethylhydrazine dihydrochloride (DMH)-induced colon carcinogenesis for 6 weeks (early stage) and its chemoprevention by diclofenac in a rat model. Morphological analysis revealed a marked occurrence of preneoplastic features, that is, multiple plaque lesions in the colonic mucosa. Administration of diclofenac at the anti-inflammatory dose along with DMH resulted a significant weakening of these lesions, thus proving the chemopreventive efficacy of diclofenac, which is a preferentially selective inhibitor for the proinflammatory enzyme, cyclooxygenase-2 (COX-2). The colonic mucosa showed increased protein expression and the enhanced activity of COX-2 in the DMH group, whereas the constitutively expressed COX-1 remained unaltered. Diclofenac treatment resulted in a significant reduction in COX-2 expression and its activity. The inflammatory changes were also demonstrated by nuclear factor-kappaB DNA binding activity, which was found to be increased after DMH treatment, thereby leading to the procarcinogenic effects, which were also adequately corrected by diclofenac. PPARgamma expression was found to be decreased after DMH treatment as seen both by western blot and immunohistochemistry. In addition, the protein expression of the apoptotic protease activating factor-1 was studied in the colonic mucosa to observe the role of apoptosis in this study, which showed a distinct decline in the DMH-treated animals. The expression of the protein was, however, recovered by diclofenac treatment to the level of the controls. It is possible that diclofenac may be exerting its chemopreventive action through PPARgamma, a ligand dependent transcription factor, which in turn activates apoptosis through inhibition of COX-2 and simultaneous activation of apoptotic protease activating factor-1.

β,β-Carotene Decreases Peroxisome Proliferator Receptor γ Activity and Reduces Lipid Storage Capacity of Adipocytes in a β,β-Carotene Oxygenase 1-dependent Manner

Increasing evidence has been provided for a connection between retinoid metabolism and the activity of peroxisome proliferator receptors (Ppars) in the control of body fat reserves. Two different precursors for retinoids exist in the diet as preformed vitamin A (all-trans-retinol) and provitamin A (beta,beta-carotene). For retinoid production, beta,beta-carotene is converted to retinaldehyde by beta,beta-carotene monooxygenase 1 (Bcmo1). Previous analysis showed that Bcmo1 knock-out mice develop dyslipidemia and are more susceptible to diet-induced obesity. However, the role of Bcmo1 for adipocyte retinoid metabolism has yet not been well defined. Here, we showed that Bcmo1 mRNA and protein expression are induced during adipogenesis in NIH 3T3-L1 cells. In mature adipocytes, beta,beta-carotene but not all-trans-retinol was metabolized to retinoic acid (RA). RA decreased the expression of Ppar gamma and CCAAT/enhancer-binding protein alpha, key lipogenic transcription factors, and reduced the lipid content of mature adipocytes. This process was inhibited by the retinoic acid receptor antagonist LE450, showing that it involves canonical retinoid signaling. Accordingly, gavage of beta,beta-carotene but not all-trans-retinol induced retinoid signaling and decreased Ppar gamma expression in white adipose tissue of vitamin A-deficient mice. Our study identifies beta,beta-carotene as a critical physiological precursor for RA production in adipocytes and implicates provitamin A as a dietary regulator of body fat reserves.

PPARγ inhibits inflammatory reaction in oxidative stress induced human diploid fibloblast

The ageing of an inevitable life function is an unavoidable regressive physical process. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor family. PPARgamma plays an important role in regulating several metabolic pathways. Recently, PPARgamma has been implicated in inflammatory responses and age-related diseases. The aim of this study was to determine the anti-inflammatory reaction of PPARgamma in an induced ageing progress. The late passage of human diploid fibroblasts (HDF), an in vitro ageing model, reveals the biological index materials of ageing. Aged cells showed decreased PPARgamma expression and elevated levels of intracellular adhesion molecule-1 (ICAM-1), an inflammatory molecule. To induce the aged cell phenotype, the middle stage of HDF cells (PD31) were induced stress induced premature senescence (SIPS) with 200 microM H(2)O(2) for 2 h. SIPS-HDF cells showed high levels of ICAM-1, extracellular signal regulated kinase (ERK1/2) activity and matrix metallomatrix protease (MMP-2, -9) activity, and low levels of PPARgamma expression. A reconstitution of SIPS HDF cells with Ad/PPARgamma resulted in the downregulation of ICAM-1, ERK1/2, MMP-2 and -9, and normalized growth of SIPS-HDF cells. Moreover, PPARgamma in aged HDF cells reduced pro-inflammatory molecules and eliminated the formation of reactive oxygen species (ROS) through the ERK1/2 pathway. These results strongly suggest that PPARgamma plays a key role in age-related inflammation and may have clinical applications as a molecular target in the treatment of age-related inflammation.

A Subset of Osteoblasts Expressing High Endogenous Levels of PPARγ Switches Fate to Adipocytes in the Rat Calvaria Cell Culture Model

BackgroundUnderstanding fate choice and fate switching between the osteoblast lineage (ObL) and adipocyte lineage (AdL) is important to understand both the developmental inter-relationships between osteoblasts and adipocytes and the impact of changes in fate allocation between the two lineages in normal aging and certain diseases. The goal of this study was to determine when during lineage progression ObL cells are susceptible to an AdL fate switch by activation of endogenous peroxisome proliferator-activated receptor (PPAR)γ.Methodology/Principal FindingsMultiple rat calvaria cells within the ObL developmental hierarchy were isolated by either fractionation on the basis of expression of alkaline phosphatase or retrospective identification of single cell-derived colonies, and treated with BRL-49653 (BRL), a synthetic ligand for PPARγ. About 30% of the total single cell-derived colonies expressed adipogenic potential (defined cytochemically) when BRL was present. Profiling of ObL and AdL markers by qRT-PCR on amplified cRNA from over 160 colonies revealed that BRL-dependent adipogenic potential correlated with endogenous PPARγ mRNA levels. Unexpectedly, a significant subset of relatively mature ObL cells exhibited osteo-adipogenic bipotentiality. Western blotting and immunocytochemistry confirmed that ObL cells co-expressed multiple mesenchymal lineage determinants (runt-related transcription factor 2 (Runx2), PPARγ, Sox9 and MyoD which localized in the cytoplasm initially, and only Runx2 translocated to the nucleus during ObL progression. Notably, however, some cells exhibited both PPARγ and Runx2 nuclear labeling with concomitant upregulation of expression of their target genes with BRL treatment.Conclusions/SignificanceWe conclude that not only immature but a subset of relatively mature ObL cells characterized by relatively high levels of endogenous PPARγ expression can be switched to the AdL. The fact that some ObL cells maintain capacity for adipogenic fate selection even at relatively mature developmental stages implies an unexpected plasticity with important implications in normal and pathological bone development.

Pharmacological concentrations of biotin reduce serum triglycerides and the expression of lipogenic genes

Besides its role as a carboxylase prosthetic group, biotin regulates gene expression and has a wide repertoire of effects on systemic processes. Several studies have shown that pharmacological concentrations of biotin reduce hypertriglyceridemia. The molecular mechanisms by which pharmacological concentrations of biotin affect lipid metabolism are largely unknown. The present study analyzed the effects of pharmacological doses of biotin on triglyceridemia, insulin sensitivity and on mRNA expression of various lipogenic genes. Three-week-old male BALB/cAnN Hsd mice were fed a biotin-control or a biotin-supplemented diet (1.76 or 97.7mg of free biotin/kg diet, respectively) over a period of eight weeks. Serum triglyceride concentrations, insulin and glucose tolerance and mRNA abundance of various lipogenic genes were investigated. The biotin-supplemented group showed 35% less serum triglycerides than control mice. In the liver, we found a significant (P<0.05) reduction of mRNA levels of SREBP1-c, glucose transporter-2, phosphofructokinase-1, pyruvate kinase, acetyl-CoA carboxylase and fatty acid synthase, while glucose-6-phosphate dehydrogenase expression increased. No changes in glucokinase, stearoyl-CoA desaturase-1, FoxO1 or PPAR-gamma expression were observed. In adipose tissue, we found a decreased expression of SREBP1c, glucose-6-phosphate deshydrogenase, acetyl-CoA carboxylase, fatty acid synthase, stearoyl-CoA desaturase-1, phosphofructokinase-1 and PPAR-gamma, but no changes in FoxO1 expression. Moreover, the group fed a biotin-supplemented diet showed a significant decrease in adipose tissue weight. No differences in insulin sensitivity or serum insulin concentrations were observed between groups. Our results indicate that pharmacological concentrations of biotin decrease serum tryglyceride concentrations and lipogenic gene expression in liver and adipose tissues.

Thiazolidinedione treatment and constitutive-PPARgamma activation induces ectopic adipogenesis and promotes age-related thymic involution.

Age-related thymic involution is characterized by reduction in T cell production together with ectopic adipocyte development within the hematopoietic and thymic niches. Peroxisome proliferator-activated receptor gamma (PPARgamma) is required for adipocyte development, glucose homeostasis and is a target for several insulin-sensitizing drugs. Our prior studies showed that age-related elevation of PPARgamma expression in thymic stromal cells is associated with thymic involution. Here, using clinically relevant pharmacological and genetic manipulations in mouse models, we provide evidence that activation of PPARgamma leads to reduction in thymopoiesis. Treatment of aged mice with antihyperglycemic PPARgamma-ligand class of thiazolidinedione drug, rosiglitazone caused robust thymic expression of classical pro-adipogenic transcripts. Rosiglitazone reduced thymic cellularity, lowered the naïve T cell number and T cell receptor excision circles (TRECs) indicative of compromised thymopoiesis. To directly investigate whether PPARgamma activation induces thymic involution, we created transgenic mice with constitutive-active PPARgamma (CA-PPARg) fusion protein in cells of adipogenic lineage. Importantly, CA-PPARgamma transgene was expressed in thymus and in fibroblast-specific protein-1/S100A4 (FSP1(+)) cells, a marker of secondary mesenchymal cells. The CAPPARgamma fusion protein mimicked the liganded PPARgamma receptor and the transgenic mice displayed increased ectopic thymic adipogenesis and reduced thymopoiesis. Furthermore, the reduction in thymopoiesis in CA-PPARgamma mice was associated with higher bone marrow adiposity and lower hematopoietic stem cell progenitor pool. Consistent with lower thymic output, CAPPARgamma transgenic mice had restricted T cell receptor repertoire diversity. Collectively, our data suggest that activation of PPARgamma accelerates thymic aging and thymus-specific PPARgamma antagonist may forestall age-related decline in T cell diversity.

AMPK enhances the expression of pancreatic duodenal homeobox-1 via PPARα, but not PPARγ, in rat insulinoma cell line INS-1

To investigate whether AMP-activated protein kinase (AMPK) regulates the expression of pancreatic duodenal homeobox-1 (PDX-1), a beta-cell-specific transcription factor and whether PPARalpha/gamma is involved in the regulation of pancreatic beta-cell lines after acute stimulation. Rat insulinoma cell line INS-1 was treated with an activator (AICAR) or inhibitor (Compound C) of AMPK as well as inhibitors of PPARs (MK886 to PPARalpha and BADGE to PPARgamma). The mRNA levels of PDX-1, PPARalpha and PPARgamma were measured using real-time RT-PCR, and Western blotting was used to detect the protein expression of these factors. Activation of AMPK by AICAR induced significantly increased the expression of PDX-1, and this increase was abrogated when AMPK was inactivated by Compound C. Similarly, the expression of PPARalpha and PPARgamma was also increased by AICAR or decreased by Compound C. However AMPK activation did not increase nuclear PDX-1 protein levels when PPARalpha was inhibited. In contrast, AMPK activation still up-regulated PDX-1 protein levels during PPARgamma inhibition. Additionally, PPARalpha activation induced by fenofibrate significantly enhanced nuclear PDX-1 protein expression. AMPK regulates the expression of PDX-1 at both the transcriptional and protein levels, and PPARalpha may be acutely involved in the regulation of INS-1 cells.

Id4, a New Candidate Gene for Senile Osteoporosis, Acts as a Molecular Switch Promoting Osteoblast Differentiation

Excessive accumulation of bone marrow adipocytes observed in senile osteoporosis or age-related osteopenia is caused by the unbalanced differentiation of MSCs into bone marrow adipocytes or osteoblasts. Several transcription factors are known to regulate the balance between adipocyte and osteoblast differentiation. However, the molecular mechanisms that regulate the balance between adipocyte and osteoblast differentiation in the bone marrow have yet to be elucidated. To identify candidate genes associated with senile osteoporosis, we performed genome-wide expression analyses of differentiating osteoblasts and adipocytes. Among transcription factors that were enriched in the early phase of differentiation, Id4 was identified as a key molecule affecting the differentiation of both cell types. Experiments using bone marrow-derived stromal cell line ST2 and Id4-deficient mice showed that lack of Id4 drastically reduces osteoblast differentiation and drives differentiation toward adipocytes. On the other hand knockdown of Id4 in adipogenic-induced ST2 cells increased the expression of Pparγ2, a master regulator of adipocyte differentiation. Similar results were observed in bone marrow cells of femur and tibia of Id4-deficient mice. However the effect of Id4 on Pparγ2 and adipocyte differentiation is unlikely to be of direct nature. The mechanism of Id4 promoting osteoblast differentiation is associated with the Id4-mediated release of Hes1 from Hes1-Hey2 complexes. Hes1 increases the stability and transcriptional activity of Runx2, a key molecule of osteoblast differentiation, which results in an enhanced osteoblast-specific gene expression. The new role of Id4 in promoting osteoblast differentiation renders it a target for preventing the onset of senile osteoporosis.

Relationship among superoxide-related enzyme, PPARs, and endothelium-dependent relaxation in murine aortas previously organ-cultured in high-glucose conditions

The aim of the present study was to investigate the relationship among superoxide anion, peroxisome proliferator-activated receptors (PPARs), and endothelium-dependent relaxation in murine aortas organ-cultured in a high-glucose condition. Aortas organ-cultured with a high concentration of glucose (40 mmol/L, 20 h; HG group) exhibited the following characteristics (versus aortas cultured in serum-free medium): (i) significantly weaker relaxation to acetylcholine, but unchanged relaxation to SNP and unchanged contractions to norepinephrine and isotonic K+, (ii) significantly greater superoxide generation (indicated by the amount of nitroblue tetrazolium reduced, (iii) significantly higher protein expression levels of gp91phox, NAD(P)H oxidase subunits, and endothelial NO synthase, (iv) significantly lower protein expression level of Mn-superoxide dismutase (SOD), and (v) markedly greater reduction in the protein expression of PPARgamma than in that of PPARalpha. The HG-induced impairment of endothelium-dependent relaxation was prevented by cotreatment with tempol (a SOD mimetic). These results suggest that in the mouse aorta, exposure to high glucose levels may lead to an excessive generation of superoxide via increased gp91phox and decreased Mn-SOD protein expression and that this may in turn trigger an impairment of endothelium-dependent relaxation. Moreover, such protein changes in gp91phox and Mn-SOD may be secondary to a decreased expression of PPARgamma protein.

Platycodin D inhibits adipogenesis of 3T3‐L1 cells by modulating kruppel‐like factor 2 and peroxisome proliferator‐activated receptor γ

In this study, platycodin D was found to inhibit intracellular triglyceride accumulation in 3T3-L1 cells with an IC(50) of 7.1 microM. The expression levels of genes involved in lipid metabolism such as fatty-acid-binding protein 4 and lipoprotein lipase were significantly downregulated following treatment with platycodin D. Treatment with platycodin D also resulted in a reduction of Peroxisome proliferator-activated receptor(PPAR)gamma expression and its binding to target DNA sequence. Among the various upstream regulators of PPARgamma, the expression of Kruppel-like factor(KLF)2, an anti-adipogenic factor, was significantly upregulated following platycodin D treatment. When the upregulation of KLF2 was inhibited by KLF2 siRNA, the expression and binding of PPARgamma to its target sequence were significantly recovered under these conditions. The results of this study suggested that anti-adipogenic effect of platycodin D involves the upregulation of KLF2 and subsequent downregulation of PPARgamma.

Dietary Trans-11 Vaccenic Acid Increases Intestinal PPAR Alpha and Gamma Expression in the JCR:LA-cp Rat

Dietary Trans-11 Vaccenic Acid Increases Intestinal PPAR Alpha and Gamma Expression in the JCR:LA-cp Rat

Serum‐free medium with osteogenic supplements induces adipogenesis in rat bone marrow stromal cells

Adult BMSCs (bone marrow stromal cells) contain MSCs (mesenchymal stem cells). MSCs can differentiate into osteoblasts, chondrocytes, adipocytes and myoblasts and are thus considered useful in tissue engineering for therapeutic and clinical purposes. FCS (fetal calf serum) is usually included in the differentiation medium, but the clinical application of FCS may pose a problem for some patients. To improve the efficiency and safety of BMSC cultivation, the effect of SF (serum-free) conditions on the osteogenic differentiation of rat BMSCs was examined. In the presence of 10% FCS and osteogenic supplements, the cells formed mineralized von Kossa-positive deposits. Under SF conditions with osteogenic supplementation, however, the cells possessed cytosolic lipid vacuoles that could be stained with Oil Red O. The mRNA expression of PPARgamma (peroxisome proliferator-activated receptor gamma), an adipogenic marker, increased under the SF condition with osteogenic supplements. These data indicate that rat BMSCs differentiate into adipocytes under SF conditions even with osteogenic supplementation and that FCS is needed to induce proper osteogenic differentiation in rat BMSCs.

Toll-like receptor-2 deficiency enhances non-alcoholic steatohepatitis

BackgroundPreviously we reported that mice deficient in toll-like receptor 4 (TLR-4) signalling were protected from diet-induced non-alcoholic steatohepatitis (NASH). Another member of the toll-like receptor family, TLR-2, has been shown to play a role in lipid trafficking via uptake of diacylated lipoproteins. However, a role for TLR-2 in NASH has not been elucidated. The objectives of the current study were to examine the influence of dietary fat quality and TLR-2 on NASH pathogenesis.MethodsSteatohepatitis was induced in male Db, C57BL/6 and TLR-2-/- mice by feeding an L-amino acid-defined diet that was deficient in methionine and choline (MCDD). Mice fed the base diet supplemented with methionine and choline (control diet; CD) were used as controls. To determine the role of fat quality, MCDD was enriched with polyunsaturated corn oil (PUFA) or coconut oil that is comprised mostly of saturated fat (SAFA); the total amount of each fat was 112.9 g/kg of diet. After 8 weeks of feeding CD or MCDD, hepatic steatosis, inflammation and necrosis were evaluated in histological sections. Total RNA was extracted from frozen liver samples and mRNA expression of TNFα, collagen α1, IL-10, peroxisome proliferator-activated receptor-γ (PPAR-γ), TLR-4, and CD14, was analyzed via real-time PCR. Protein levels of TLR-2 were analyzed by western blot.ResultsPanlobular macrovessicular steatosis and diffuse leukocyte infiltration were noted in PUFA-fed Db mice. Histological scores demonstrated significantly less steatosis, inflammation and necrosis in SAFA-fed mice of all mouse strains. However, compared to wild type mice, hepatocellular damage was notably more severe in TLR-2-/- mice. Consistent with histological findings, mRNA expression of TNFα was elevated by approximately 3-fold in TLR-2-/- mice; PPAR-γ expression was blunted in this strain compared to wild type. Expression of the matrix protein collagen αI was also significantly higher in TLR-2-/- mice, indicating a pro-fibrogenic state. Sensitivity to steatohepatitis due to dietary fat or TLR-2 deficiency correlated significantly with alterations in the expression of TLR-4 as well as the co-receptor CD-14.ConclusionsOur findings suggest that dietary saturated fat plays a protective role against MCDD-induced steatohepatitis, whereas TLR-2 deficiency exacerbated NASH. The mechanism underlying the response to dietary fat and TLR-2 likely involves altered signalling via the TLR-4 pathway.

OxHDL decreases the expression of CD36 on human macrophages through PPARγ and p38 MAP kinase dependent mechanisms

CD36, belongs to class B scavenger receptor family, is a macrophage receptor for oxidized low-density lipoprotein (oxLDL) and has been proven to play a critical role in atherosclerotic foam cell formation. In addition, CD36 expression is regulated by many factors including oxLDL and HDL. A recent study suggests that CD36 can also bind with oxidized high-density lipoprotein (oxHDL). However, the direct role of oxHDL in atherosclerosis is still not clear and it is not known whether oxHDL has any influence on the expression of CD36 in macrophages. Here, we performed experiments to investigate the effect of oxHDL on the expression of CD36 on human peripheral blood monocytes-macrophages and the possible mechanisms. Our results suggest that the uptake of oxHDL by CD36 on macrophages accelerates foam cell formation. In addition, oxHDL can down-regulate both the mRNA and surface protein expression of CD36 on human peripheral macrophages in vitro. oxHDL increased the mRNA expression and protein phosphorylation of peroxisome proliferators-activated receptor-gamma (PPARgamma). Using different mitogen-activated protein kinase (MAPK) inhibitors, we demonstrated that oxHDL regulated CD36 and PPARgamma expression in a p38-MAP kinase dependent mechanism.

Rosiglitazone Inhibits Cell Proliferation by Inducing G1 Cell Cycle Arrest and Apoptosis in ADPKD Cyst‐Lining Epithelia Cells

Abnormal proliferation is an important pathological feature of autosomal dominant polycystic kidney disease (ADPKD). Many drugs inhibiting cell proliferation have been proved to be effective in slowing the disease progression in ADPKD. Recent evidence has suggested that peroxisome proliferator-activated receptor gamma (PPARgamma) ligands have anti-neoplasm effects through inhibiting cell growth and inducing cell apoptosis in various cancer cells. In the present study, we examined the expression of PPARgamma in human ADPKD kidney tissues and cyst-lining epithelial cell line, and found that the expression of PPARgamma was greater in ADPKD kidney tissues and cyst-lining epithelial cell line than in normal kidney tissues and human kidney cortex (HKC) cell line. Rosiglitazone inhibited significantly proliferation of cyst-lining epithelial cells in a concentration- and time-dependent manner. These effects were diminished by GW9662, a specific PPARgamma antagonist. Cell cycle analysis showed a G0/G1 arrest in human ADPKD cyst-lining epithelial cells with rosiglitazone treatment. Analysis of cell cycle regulatory proteins revealed that rosiglitazone decreased the protein levels of proliferating cell nuclear antigen, pRb, cyclin D1, cyclin D2 and Cdk4 but increased the levels of p21 and p27 in a dose-dependent manner. Rosiglitazone also induced apoptosis in cyst-lining epithelial cells, which was correlated with increased bax expression and decreased bcl-2 expression. These results suggest PPARgamma agonist might serve as a promising drug for the treatment of ADPKD.

Irbesartan treatment up‐regulates hepatic expression of PPARα and its target genes in obese Koletsky (fak/fak) rats: a link to amelioration of hypertriglyceridaemia

Hypertriglyceridaemia is associated with an increased risk of cardiovascular disease. Irbesartan, a well-established angiotensin II type 1 receptor (AT(1)) blocker, improves hypertriglyceridaemia in rodents and humans but the underlying mechanism of action is unclear. Male obese Koletsky (fa(k)/fa(k)) rats, which exhibit spontaneous hypertension and metabolic abnormalities, received irbesartan (40 mg x kg(-1) x day(-1)) or vehicle by oral gavage over 7 weeks. Adipocyte-derived hormones in plasma were measured by ELISA. Gene expression in liver and other tissues was assessed by real-time PCR and Western immunoblotting. In Koletsky (fa(k)/fa(k)) rats irbesartan lowered plasma concentrations of triglycerides and non-esterified fatty acids, and decreased plasma insulin concentrations and the homeostasis model assessment of insulin resistance index. However, this treatment did not affect food intake, body weight, epididymal white adipose tissue weight, adipocyte size and plasma leptin concentrations, although plasma adiponectin was decreased. Irbesartan up-regulated hepatic expression of mRNAs corresponding to peroxisome proliferator-activated receptor (PPAR)alpha and its target genes (carnitine palmitoyltransferase-1a, acyl-CoA oxidase and fatty acid translocase/CD36) that mediate hepatic fatty acid uptake and oxidation; the increase in hepatic PPARalpha expression was confirmed at the protein level. In contrast, irbesartan did not affect expression of adipose PPARgamma and its downstream genes or hepatic genes that mediate fatty acid synthesis. These findings demonstrate that irbesartan treatment up-regulates PPARalpha and several target genes in liver of obese spontaneously hypertensive Koletsky (fa(k)/fa(k)) rats and offers a novel insight into the lipid-lowering mechanism of irbesartan.

PPARγ Expression After a High‐fat Meal Is Associated With Plasma Superoxide Dismutase Activity in Morbidly Obese Persons

Peroxisome proliferator-activated receptor-gamma (PPARgamma) may play a protective role in the regulation of vascular function, partly mediated by its effects on superoxide dismutase (SOD). The aim of this study was to determine the association between PPARgamma expression in peripheral blood mononuclear cells (PBMCs) and SOD activity in morbidly obese persons with varying degrees of insulin resistance (IR). We studied in 10 morbidly obese persons (five with no IR and five with high IR) the effect of a high-fat meal on the plasma activity of various antioxidant enzymes and the mRNA expression of PPARgamma in PBMC. The high-fat meal resulted in a significant decrease in plasma SOD activity, glutathione reductase (GSH-Rd) activity, and mRNA expression of PPARgamma only in the group of morbidly obese persons with high IR. PPARgamma expression after the high-fat meal correlated with the IR levels (r = -0.803, P = 0.009) and the plasma SOD activity (r = 0.903, P = 0.001). Likewise, the reduction in PPARgamma expression correlated with the increase in free fatty acids (FFA) (r = 0.733, P = 0.016). In conclusion, the decreased expression of PPARgamma in PBMC in morbidly obese persons after a high-fat meal was associated with the state of IR, the plasma SOD activity, and the changes in the concentration of FFA.

Rosiglitazone attenuates hypoxia‐induced pulmonary arterial hypertension in rats

Expression of peroxisome proliferator-activated receptor gamma (PPARgamma) is decreased in the lungs of patients with pulmonary hypertension, and PPARgamma ligands have been associated with the release of vasoactive substances from vascular endothelial cells and prevention of vascular remodelling. We hypothesized that PPARgamma may play a critical role in the development of pulmonary hypertension induced by chronic hypoxia. Male adult Sprague-Dawley rats were exposed to normoxia, normoxia and rosiglitazone (8 mg/kg orally, 5 days/week), hypoxia (12% inspired O(2) fraction), or hypoxia and rosiglitazone for 4 weeks. On the last day of the fourth week, pulmonary arterial pressure was measured and morphological changes in pulmonary vessels were assessed. The expression of PPARgamma, endothelin (ET)-1 and vascular endothelial growth factor (VEGF) was also analysed. Rosiglitazone inhibited the development of pulmonary hypertension, and pulmonary vascular remodelling induced by chronic hypoxia. PPARgamma expression was decreased and expression of ET-1 and VEGF was increased in lung tissues of the hypoxia group. Rosiglitazone treatment prevented the hypoxia-induced reduction in PPARgamma expression, and restored ET-1 and VEGF expression almost to the levels of the normoxia group. Rosiglitazone inhibited the development of pulmonary hypertension induced by chronic hypoxia, perhaps by reversing the changes in PPARgamma, ET-1 and VEGF expression induced by hypoxia. These findings indicate that rosiglitazone may be beneficial in the treatment of chronic hypoxic pulmonary hypertension.