PPARgamma Activation Research Articles

Activation and dephosphorylation of PPARgamma induce PCSK9 production

PCSK9 plays an important role in cholesterol homeostasis by enhancing the degradation of LDLR protein. PPARγ, a ligand activated transcriptional factor, has been shown to be atheroprotective. PPARγ can be phosphorylated by ERK1/2 and the phosphorylated status of PPARγ greatly impacts its biological activity. However, the interplay between PCSK9 and PPARγ/phosph‐PPARγ remains unknown. We observed that PPARγ ligands induced PCSK9 mRNA and protein expression in HepG2 cells. Inhibition of ERK1/2 induced while activation of ERK1/2 inhibited PCSK9 expression. Co‐treatment of PPARγ ligand and ERK1/2 inhibitor had no additive effect on the induction of PCSK9 expression. The induction of PCSK9 expression by ERK1/2 inhibitor was tightly linked to the dephosphorylation of PPARγ. In vivo, the administration of PPARγ ligand or ERK1/2 inhibitor alone increased PCSK9 expression in mouse liver but had no effect on PCSK9 secretion. However, the co‐administration of PPARγ ligand and ERK1/2 inhibitor enhanced both PCSK9 expression and secretion. Interestingly, the up‐regulation of PCSK9 expression by PPARγ ligand and/or ERK1/2 inhibitor was associated with the increased LDLR expression in the liver and the decreased LDL‐cholesterol levels in serum. Our study discloses a new mechanism involving in regulation of PCSG9 expression and may have implication in the development of strategies for PCSK9 expression and function.

근육세포 배양 계 에서 Biochanin A의 항 당뇨 효능평가

In this study, we evaluated the effects of Biochanin A on glucose uptake in C2C12 myotube. We found that Biochanin A significantly stimulated 2-[N-(7-nitrobenz-2- oxa-1,3-diazol-4-yl)amino]-2-deoxy-d-glucose (2-NBDG) uptake in a dose-dependent manner. In addition, AMPK and PPAR-gamma activities were markedly increased by Biochanin A in a dose-dependent manner. However, Akt, an insulin dependent signaling molecule, did not change by Biochanin A. These results suggest that Biochanin A stimulates glucose uptake via AMPK and PPAR-gamma pathways.

Structural basis for telmisartan-mediated partial activation of PPAR gamma

Telmisartan, a selective angiotensin II type 1 receptor blocker, has recently been shown to act as a partial agonist for peroxisome proliferator-activated receptor gamma (PPARγ). To understand how telmisartan partially activates PPARγ, we determined the ternary complex structure of PPARγ, telmisartan, and a coactivator peptide from steroid receptor coactivator-1 at a resolution of 2.18 Å. Crystallographic analysis revealed that telmisartan exhibits an unexpected binding mode in which the central benzimidazole ring is engaged in a non-canonical--and suboptimal--hydrogen-bonding network around helix 12 (H12). This network differs greatly from that observed when full-agonists bind with PPARγ and prompt high-coactivator recruitment through H12 stabilized by multiple hydrogen bonds. Binding with telmisartan results in a less stable H12 that in turn leads to attenuated coactivator binding, thus explaining the mechanism of partial activation.

Levels of adiponectin, a marker for PPAR-gamma activity, correlate with skin fibrosis in systemic sclerosis: potential utility as biomarker?

IntroductionProgressive fibrosis in systemic sclerosis (SSc) is linked to aberrant transforming growth factor beta (TGF-beta) signaling. Peroxisome proliferator-activated receptor gamma (PPAR-gamma) blocks fibrogenic TGF-beta responses in vitro and in vivo. Reduced expression and function of PPAR-gamma in patients with SSc may contribute to progression of fibrosis. Here we evaluated the levels of adiponectin, a sensitive and specific index of PPAR-gamma activity, as a potential fibrogenic biomarker in SSc.MethodsAdiponectin levels were determined in the sera of 129 patients with SSc and 86 healthy controls, and serial determinations were performed in 27 patients. Levels of adiponectin mRNA in skin biopsies from SSc patients were assessed in an expression profiling microarray dataset. Regulation of adiponectin gene expression in explanted human subcutaneous preadipocytes and fibroblasts was examined by real-time quantitative PCR.ResultsPatients with diffuse cutaneous SSc had reduced serum adiponectin levels. A significant inverse correlation between adiponectin levels and the modified Rodnan skin score was observed. In longitudinal studies changes in serum adiponectin levels were inversely correlated with changes in skin fibrosis. Skin biopsies from a subset of SSc patients showed reduced adiponectin mRNA expression which was inversely correlated with the skin score. An agonist ligand of PPAR-gamma potently induced adiponectin expression in explanted mesenchymal cells in vitro.ConclusionsLevels of adiponectin, reflecting PPAR-gamma activity, are correlated with skin fibrosis and might have potential utility as a biomarker in SSc.

PPAR gamma, bioactive lipids, and cancer progression.

In this article we review the evolution of cancer research involving PPARgamma, including mechanisms, target genes, and clinical applications. For the last thirteen years, the effects of PPARgamma activity on tumor biology have been studied intensely. Most of this research has focused upon the potential for employing agonists of this nuclear receptor in cancer treatment. As a monotherapy such agonists have shown little success in clinical trials, while they have shown promise as components of combination treatments both in culture and in animal models. Other investigations have explored a possible role for PPARgamma as a tumor suppressor, and as an inducer of differentiation of cancer stem cells. Whereas early studies have yielded variable conclusions regarding the prevalence of PPARgamma mutations in cancer, the protein level of this receptor has been more recently identified as a significant prognostic marker. We predict that indicators of PPARgamma activity may also serve as predictive markers for tailoring treatments.

Aldosterone inhibits endothelial morphogenesis and angiogenesis through the downregulation of vascular endothelial growth factor receptor-2 expression subsequent to peroxisome proliferator-activated receptor gamma

Angiogenesis plays a pivotal role in cardiovascular diseases such as ischemic heart disease, limb ischemia and heart failure, and has recently been shown to mediate various biological activities related to the pathogenesis of these diseases. In the present study, we evaluated the role of aldosterone in angiogenesis. Tube formation assay on Matrigel using human umbilical vein endothelial cells (HUVEC) revealed that aldosterone inhibited endothelial morphogenesis in a manner sensitive to eplerenone, a selective mineralocorticoid receptor antagonist. The anti-angiogenic effect of aldosterone was further confirmed by an in vivo angiogenesis assay using a Matrigel plug model in mice. Reverse transcription-mediated polymerase chain reaction and immunoblotting demonstrated that aldosterone downregulated the expression levels of vascular endothelial growth factor receptor-2 (VEGFR-2) and peroxisome proliferators-activated receptor gamma (PPAR gamma). VEGFR-2 expression was found to be enhanced in response to PPAR gamma activation by troglitazone, and attenuated by GW9662, a specific antagonist of PPAR gamma. In the tube formation assay, endothelial morphogenesis was stimulated by troglitazone, and inhibited by GW9662, indicating that PPAR gamma activation mediates positive regulation of angiogenesis through enhancement of VEGFR-2 expression. These data suggest that aldosterone inhibits angiogenesis through VEGFR-2 downregulation, subsequent to, at least in part, attenuation of PPAR gamma expression. The present findings provide a new insight into the possible therapeutic application of mineralocorticoid receptor blockade to various cardiovascular diseases.

P2-05-02: PGC1, Peroxisome Proliferator Activated Receptor-gamma (PPAR-gamma) Coactivator-1, Is Necessary in PPAR-gamma Modulated Angiogenesis.

Abstract Background. Peroxisome proliferator activated receptor- gamma (PPAR-gamma), a nuclear hormone receptor, has been shown to be an important regulator of gene expression. PPAR-gamma agonists have been shown to have anti-cancer properties by ways of inducing expression of tumour suppressor genes. It has been indicated that this action of PPAR-gamma is manifested by forming a complex with the PPAR-gamma coactivators (PGC1 &2) and in association with other transcription factors such as SRC-1 and CREB binding proteins. Both PPAR-gamma and PGC-1 have been shown to be aberrantly expressed in human cancer including human breast cancer (1). PPAR-gamma also plays a role in regulating angiogenesis and that PPAR-gamma agonists have been shown to have anti-angiogenic functions. In the present study, we investigated the role of PGC-1 in PPAR-gamma mediated actions on vascular endothelial cells. Materials and methods. Mammalian expression systems for human full length PGC-1 ereonstructed. Anti-PGC-1 transgenes were constructed again using human mammalian expression vector in order to knock down PGC-1 transcript from the cells. Human vascular endothelial cell, HECV, was used in the study. Cell functions linked to angiogenesis including cell adhesion and cellular migration was evaluated using the electric cell impedance sensing method. PPAR-gamma agonists and antagonists were used in the cell models during the analyses. Results. HECV cells weakly expressed PGC-1 and PPAR-gamma. Using the transgenes created, sublines over-expressing PGC1 (HECVPGC1exp) or with PGC-1 expression knockdown (HECVPGC1KD) were established. Loss of PGC1 showed marked increase in both adhesion and cellular migration, opposite was true forHECVPGC1exp cells. PPAR-gamma agonist, pioglitizone and ciglitizone, reduced the adhesion of control cells. In contrast, PPAR-gamma antagonist SR202 exhibited a concentration dependent stimulation of both adhesion and migration of the control cells. Knocking down PGC1 in endothelial cells rendered cells lost response to SR202. Conclusions. PGC-1 is essential in during the modulation of endothelial cells by PPAR-gamma. Together with the aberrant expression of both PPAR-gamma and PGC-1 in breast cancer, it is concluded that PGC-1 is a central player in PPAR-gamma mediated action in both cancer cells and angiogenesis. 1. Jiang WG, Douglas-Jones A, Mansel RE. Expression of peroxisome-proliferator activated receptor-gamma (PPARgamma) and the PPARgamma co-activator, PGC-1, in human breast cancer correlates with clinical outcomes. Int J Cancer. 2003, 106(5):752–757. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-05-02.

Molecular Signature of Human Brown Adipocyte-Like PAZ6 Cells

Background: Prevalence of metabolic syndrome is directly correlated with increasing occurrence of obesity characterized by accumulation of fat in visceral, lower body, and upper body subcutaneous depots. In a number of species, brown adipose tissue (BAT) converts triglycerides into heat by non-shivering thermogenesis, thus controlling the amount of white adipose tissue. Until recently, BAT was thought to be mostly absent in adult humans but now sizeable BAT depots have been visualized by Positron Emission Tomography (PET) and Computed Tomography (CT) scanning. Relatively little is known about the signaling pathways differentially regulated in brown adipocytes compared to white adipocytes. However, our progress of understanding is hindered by the paucity of well-characterized reliable in vitro model systems. Objectives: The aim of this study is to characterize the only in vitro model of human BAT cell line, and to identify signature genes for BAT, and compounds implicated in the enhancement of brown phenotype. Methods: A human BAT cell line, PAZ6, was previously created by immortalizing somatic cells using the large T antigen of Simian Virus 40. The expression of BAT associated markers has been verified by real time RT-PCR done on RNA and immunoblot using specific antibodies performed on cell lysates and supernatants, before and after differentiation and treatment with various compounds such as adrenergic receptor agonist (isoproterenol) and PPAR agonist (rosiglitazone). Results: We have identified several BAT associated markers, including PDRM16 and the 3 adrenergic receptor. This marker is highly expressed in PAZ6 cells compared to the white adipocyte. In addition, we demonstrate that these cells share a common precursor with myocytes but not with white adipocytes. Our results show that several genes are up-regulated after PPAR gamma activation. Moreover, we confirm that these cells respond to Beta adrenergic agonist treatment. Finally, we identify that the transcription factor farnesoid X Receptor (FXR) induces the expression of BAT associated marker following treatment by its agonist : CDCA. Conclusions: The PAZ6 cells constitute a readily available surrogate for human brown adipocytes to develop pharmacologic strategies to promote BAT expansion and activation.

1048 POSTER Ligand Activation of PPAR Gamma Enhances Cytotoxicity of Chemotherapeutic Drugs in Breast Cancer Cells: the Mechanism Involving Tumour-specific Suppression of Mitochondrial MnSOD in Vitro and in Vivo

1048 POSTER Ligand Activation of PPAR Gamma Enhances Cytotoxicity of Chemotherapeutic Drugs in Breast Cancer Cells: the Mechanism Involving Tumour-specific Suppression of Mitochondrial MnSOD in Vitro and in Vivo

15‐lipoxygenase‐1 exerts its tumor suppressive role by inhibiting nuclear factor‐kappa B via activation of PPAR gamma

15-Lipoxygenase-1 (15-LOX-1) is an enzyme of the inflammatory eicosanoid pathway whose expression is known to be lost in colorectal cancer (CRC). We have previously shown that reintroduction of the gene in CRC cell lines slows proliferation and induces apoptosis (Cimen et al. [2009] Cancer Sci 100: 2283-2291). We have hypothesized that 15-LOX-1 may be anti-tumorigenic by the inhibition of the anti-apoptotic inflammatory transcription factor nuclear factor kappa B. We show here that ectopic expression of 15-LOX-1 gene in HCT-116 and HT-29 CRC cell lines inhibited the degradation of inhibitor of kappa B (IκBα), decreased nuclear translocation of p65 and p50, decreased DNA binding in the nucleus and decreased transcriptional activity of Nuclear factor kappa B (NF-κB). As the 15-LOX-1 enzymatic product 13(S)-HODE is known to be a peroxisome proliferator-activated receptor gamma (PPARγ) agonist, and NF-κB can be inhibited by PPARγ, we examined whether activation of PPARγ was necessary for the abrogation of NF-κB activity. Our data show that the inhibition of both early and late stages of NF-κB activation could rescued by the PPARγ antagonist GW9662 indicating that the inhibition was most likely mediated via PPARγ.

Polyacetylenes from Notopterygium incisum as a novel class of specific PPARgamma activators

In the course of our search for PPARγ active anti-inflammatory natural products we have investigated the dichloromethane extract of the dried rhizome and root of Notopterygium incisum Ting ex H. T. Chang (Umbelliferae). PPARγ is one of the three Peroxisome Proliferator Activated Receptor (PPAR) subtypes and is involved in the regulation of glucose and lipid metabolism and therefore an important target for metabolic diseases. Additionally, PPARγ plays a role in other chronic diseases such as inflammation, cancer and atherosclerosis.1 We have isolated six polyacetylenes, which were structurally characterized by means of multidimensional NMR and mass spectroscopy, and which were shown to inhibit NO production in RAW 264.7 macrophages.2 Now, the potency of these polyacetylenes as PPARγ agonists has been evaluated. The EC50s of 8-acetoxyfalcarinol, falcarindiol, 9-epoxy-falcarindiol, crithmumdiol, 9-heptadecene-4,6-diyn-1-ol and 2Z,9Z)-2,9-heptadecadiene-4,6-diyn-1-ol were determined as 2.36-fold activation (EC50 of 3.59µM), 2.29-fold activation (EC50 of 4.25µM), 1.88-fold activation (EC50 of 2.03µM) and 2.29-fold activation (EC50 of 4.58µM), 1.921 fold activation (EC50 of 11.31µM) and 1.73-fold activation (EC50 of 4.18µM), respectively, whereas the positive control pioglitazone exhibited 7.96-fold activation (EC50 of 0.31µM). Therefore, these polyacetylene derivatives contribute to the anti-inflammatory activity of Notopterygium incisum by selectively activating PPARγ without affecting the other two PPAR subtypes.3

Telmisartan, a unique ARB, improves left ventricular remodeling of infarcted heart by activating PPAR gamma

Unfavorable left ventricular (LV) remodeling after myocardial infarction (MI) leads to cardiac dysfunction. We examined whether Telmisartan, an angiotensin (Ang) II type I receptor blocker (ARB), could improve the recovery of LV function in a rat model of MI. The effect of Telmisartan as a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist was also investigated. After 28 days of MI, a significant improvement of survival was observed in the Telmisartan-treated rat group compared with the vehicle control rat group, non-PPAR-γ agonistic ARB (Losartan)-treated rat group, and Telmisartan plus specific PPAR-γ antagonist (GW9662)-treated rat group. Although no significant differences of blood pressure or infarct size were observed among these four groups, the Telmisartan group had better systolic and diastolic LV function. There was a significant reduction of the plasma brain natriuretic peptide level, cardiac fibrosis area, infiltration of macrophages, size of cardiomyocytes, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive myocytes, activation of matrix metalloproteinases-2 and -9 (MMPs-2/9), and expression of transforming growth factor β-1 (TGF-β1), connective tissue growth factor (CTGF), and osteopontin (OPN), while expression of PPAR-γ and activation of tissue inhibitor of metalloproteinase-1 (TIMP-1) was enhanced, in the noninfarcted myocardium of rats from the Telmisartan group compared with the other three groups. To mimic ischemic conditions in vitro, neonatal rat cardiomyocytes and cardiac fibroblasts were incubated in hypoxic condition for 24 h. Increased transcriptional activation of PPAR-γ and TIMP-1, and inhibition of TGF-β1 expression were observed in cardiomyocytes, while decreased activation of MMPs-2/9 and decrease in CTGF and OPN expression was seen in cardiac fibroblasts cultured with Telmisartan. In conclusion, Telmisartan prevented unfavorable cardiac remodeling through a reduction of cardiac hypertrophy and fibrosis. An anti-inflammatory effect and PPAR-γ activation were suggested to be important in addition to suppression of Ang II activity.

PPARgamma activators stimulate aquaporin 3 expression in keratinocytes/epidermis

Aquaporin 3 (AQP3), a member of the aquaglyceroporin family, which transports water and glycerol, is robustly expressed in epidermis and plays an important role in stratum corneum hydration, permeability barrier function and wound healing. PPAR and LXR activation regulates the expression of many proteins in the epidermis and thereby can affect epidermal function. Here, we report that PPARgamma activators markedly stimulate AQP3 mRNA expression in both undifferentiated and differentiated cultured human keratinocytes (CHKs). The increase in AQP3 mRNA by PPARgamma activator occurs in a dose- and time-dependent fashion. Increased AQP3 mRNA levels are accompanied by an increase in AQP3 protein in undifferentiated keratinocytes and a significant increase in glycerol uptake. Activation of LXR, RAR and RXR also increases AQP3 mRNA levels in undifferentiated and differentiated CHKs, but to a lesser extent. PPARdelta activation stimulates AQP3 expression in undifferentiated CHKs but decreases expression in differentiated CHKs. In contrast, PPARalpha activators do not alter AQP3 expression. AQP9 and AQP10, other members of aquaglyceroporin family, are less abundantly expressed in CHKs, and their expression levels are not significantly altered by treatment with LXR, PPAR, RAR or RXR activators. Finally, when topically applied, the PPARgamma activator, ciglitazone, induces AQP3 but not AQP9 gene expression in mouse epidermis. Our data demonstrate that PPAR and LXR activators stimulate AQP3 expression, providing an additional mechanism by which PPAR and LXR activators regulate epidermal function.

The Activation of GLUT1, AMPK alpha and PPAR gamma by Tinospora crispa in L6 Myotubes

ABSTRACT AIM: Tinospora crispa (T. crispa, TC) has long been used in traditional medicine in South East Asia for the treatment of Type 2 diabetes mellitus. In the present study, it was aim to investigate the effect of water-ethanol extract of T. crispa (WETC) on glucose transporter (GLUT1 and GLUT4), 5\\\\\\\\\\\\\\\'AMP-activated protein kinase (AMPK alpha1) and peroxisome proliferator-activated receptors (PPAR gamma) expression. METHODS: The activation of GLUT1, GLUT4, AMPK alpha1 and PPAR gamma by T. crispa were assessed in vitro by the treatment of WETC to L6 myotubes followed by determined these genes expression using reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: WETC at 400 µg/ml significantly increased glucose uptake at 24 hours (214.49 +/- 9.00%, p

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.

Pioglitazone Attenuates Allergic Inflammation and Induces Production of Regulatory T Lymphocytes

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonists have been shown to be involved in the regulation of allergic inflammatory responses. The molecular mechanisms by which PPAR-gamma activation inhibits the inflammatory process have not been well understood. BALB/c mice received ovalbumin (OVA) sensitization followed by OVA intranasal challenge. Mice in the treatment group received intragastric administration with pioglitazone (PIO; 30 mg/kg) before each OVA challenge. Various allergic responses were then assessed. The frequencies of sneezing and nose-scratching and eosinophil infiltration decreased significantly in the PIO treatment group compared with the OVA group (p < 0.05). The PIO treatment also showed that the levels of nasal cavity lavage fluid interleukin (IL)-5 and sera OVA-specific immunoglobulin E (IgE) were markedly reduced (p < 0.05). PIO significantly increased the expression of Foxp3 mRNA (p < 0.05) and induced production of regulatory T lymphocyte (p < 0.01) compared with the OVA group. Given the potent effectiveness shown by PIO, we conclude that PPAR-gamma agonists deserve investigation as potential therapies for human allergic upper airway inflammation.

PPARgamma activation attenuates T-lymphocyte-dependent inflammation of adipose tissue and development of insulin resistance in obese mice

BackgroundInflammation of adipose tissue (AT) has been recently accepted as a first step towards obesity-mediated insulin resistance. We could previously show that mice fed with high fat diet (HFD) develop systemic insulin resistance (IR) and glucose intolerance (GI) associated with CD4-positive T-lymphocyte infiltration into visceral AT. These T-lymphocytes, when enriched in AT, participate in the development of fat tissue inflammation and subsequent recruitment of proinflammatory macrophages. The aim of this work was to elucidate the action of the insulin sensitizing PPARgamma on T-lymphocyte infiltration during development of IR, and comparison of the PPARgamma-mediated anti-inflammatory effects of rosiglitazone and telmisartan in diet-induced obesity model (DIO-model) in mice.MethodsIn order to investigate the molecular mechanisms underlying early development of systemic insulin resistance and glucose intolerance male C57BL/6J mice were fed with high fat diet (HFD) for 10-weeks in parallel to the pharmacological intervention with rosiglitazone, telmisartan, or vehicle.ResultsBoth rosiglitazone and telmisartan were able to reduce T-lymphocyte infiltration into AT analyzed by quantitative analysis of the T-cell marker CD3gamma and the chemokine SDF1alpha. Subsequently, both PPARgamma agonists were able to attenuate macrophage infiltration into AT, measured by the reduction of MCP1 and F4/80 expression. In parallel to the reduction of AT-inflammation, ligand-activated PPARgamma improved diet-induced IR and GI.ConclusionTogether the present study demonstrates a close connection between PPARgamma-mediated anti-inflammation in AT and systemic improvement of glucose metabolism identifying T-lymphocytes as one cellular mediator of PPARgamma´s action.

PPAR-gamma activation inhibits proliferation of endometriotic epithelial and stromal cells and is pro-apoptotic in endometriotic stromal cells in vitro

OBJECTIVE: The PPAR-gamma ligand, ciglitazone (CIG), has been shown to decrease aromatase levels in endometriotic epithelial and stromal cell lines. Dose-response experiments showed CIG 20 μM to be ideal; endometriotic cell number decreased in a dose-dependent manner. We sought to determine if the decrease in endometriotic cell number was due to antiproliferative (CDK2, CDK4) and/or apoptotic (caspase-3) effects. DESIGN: In vitro study using the immortalized human endometriotic stromal cell line 22B and epithelial cell line 12Z. MATERIALS AND METHODS: Endometriotic cells were cultured and subsequently treated with CIG x 24 hours. Treatment groups (n=3 for each experiment) consisted of control (no CIG) compared to CIG at 20 μM. Western blot was performed to assess effects of CIG on CDK2, CDK4, and caspase-3. Comparisons between treatment groups were made using a one-way ANOVA followed by post-hoc comparison of means. RESULTS: Activation of PPAR-gamma using CIG 20 μM decreased expression of CDK2 and CDK4 proteins in the endometriotic stromal cells 22B 4-fold (P < 0.05) and in the endometriotic epithelial cells 12Z 1-fold; CIG 20 μM cleaved caspase-3 protein in 22B (P < 0.05) but not in 12Z cells. CONCLUSION: In the endometriotic epithelial cell type, CIG did not induce apoptosis but did dysregulate cell cycle machinery. In contrast, in the endometriotic stromal cell type, CIG induced both apoptosis and cell cycle deregulation.

Transcriptional Regulation of Human and Rat Hepatic Lipid Metabolism by the Grapefruit Flavonoid Naringenin: Role of PPARα, PPARγ and LXRα

Disruption of lipid and carbohydrate homeostasis is an important factor in the development of prevalent metabolic diseases such as diabetes, obesity, and atherosclerosis. Therefore, small molecules that could reduce insulin dependence and regulate dyslipidemia could have a dramatic effect on public health. The grapefruit flavonoid naringenin has been shown to normalize lipids in diabetes and hypercholesterolemia, as well as inhibit the production of HCV. Here, we demonstrate that naringenin regulates the activity of nuclear receptors PPARα, PPARγ, and LXRα. We show it activates the ligand-binding domain of both PPARα and PPARγ, while inhibiting LXRα in GAL4-fusion reporters. Using TR-FRET, we show that naringenin is a partial agonist of LXRα, inhibiting its association with Trap220 co-activator in the presence of TO901317. In addition, naringenin induces the expression of PPARα co-activator, PGC1α. The flavonoid activates PPAR response element (PPRE) while suppressing LXRα response element (LXRE) in human hepatocytes, translating into the induction of PPAR-regulated fatty acid oxidation genes such as CYP4A11, ACOX, UCP1 and ApoAI, and inhibition of LXRα-regulated lipogenesis genes, such as FAS, ABCA1, ABCG1, and HMGR. This effect results in the induction of a fasted-like state in primary rat hepatocytes in which fatty acid oxidation increases, while cholesterol and bile acid production decreases. Our findings explain the myriad effects of naringenin and support its continued clinical development. Of note, this is the first description of a non-toxic, naturally occurring LXRα inhibitor.

Low dose of telmisartan prevents ischemic brain damage with peroxisome proliferator-activated receptor-γ activation in diabetic mice

Telmisartan is a unique AT1 receptor blocker with a peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonistic action. Activation of PPAR-gamma could prevent inflammation and brain damage. We investigated the beneficial effect of telmisartan on ischemic brain damage via PPAR-gamma activation as well as AT1 receptor blockade. Eight-week-old male KK-Ay mice were subjected to middle cerebral artery occlusion. Before middle cerebral artery occlusion, they were administered telmisartan or losartan, with or without GW9662, a PPAR-gamma antagonist, for 2 weeks. Ischemic area, neurological score, oxidative stress, inflammation and cerebral blood flow were assessed 24 h after middle cerebral artery occlusion. Administration of telmisartan, losartan, GW9662 and these AT1 receptor blockers with GW9662 had no significant effect on blood pressure. KK-Ay mice exhibited a significant increase in the ischemic area compared with C57BL6 mice. Treatment with telmisartan decreased the ischemic area and improved the neurological score compared with the no-treatment group, with an increase in cerebral blood flow and a reduction in superoxide production and expression of inflammatory cytokines. These protective effects of telmisartan were partially attenuated by coadministration of GW9662, although GW9662 treatment alone had no significant effect on ischemic area. Losartan treatment showed a reduction in ischemic area compared with nontreated KK-Ay mice. However, coadministration of GW9662 had no effect on the losartan-mediated reduction in ischemic area. These results suggest that telmisartan has a beneficial effect on stroke partly due to activation of PPAR-gamma as well as AT1 receptor blockade.