Effect of selected bisphenol derivatives on nuclear receptor expression in ovarian cell line COV434.

Objectives. Bisphenol A (BPA), as an indispensable plastic additive, has also been proven as an endocrine disruptor associated with adverse health effects including impaired ovarian function and cancer. Due to the restrictions of its usage, several analogs have been employed to replace BPA. Although many studies revealed a harmfulness in the biological effects of BPA analogs, their specific targets remain largely unknown. Nuclear receptors (NRs) may be one of the most important targets of bisphenols. Therefore, in this study, our attention was directed to explore the effect of BPA and its analogs, AF and S, on the mRNA expression of selected NRs involved in the steroidogenic and carcinogenic pathways in the human granulosa cell line COV434. The NRs investigated included: thyroid hormone receptor α (THRA), peroxisome proliferator activating receptor ß/δ (PPARD), retinoid X receptor α (RXRA), chicken ovalbumin upstream promoter-transcription factor II (COUPTFII), nuclear receptor-related protein 1 (NURR1), and liver receptor homolog-1 (LRH1).Methods. COV434 cells were treated with the bisphenols at the concentrations of 10-9 M, 10-7 M, and 10-5 M, and after 24 and 48 h, cell viability was monitored by the MTS assay and gene expressions were analyzed using RT-qPCR.Results. Bisphenol treatment did not alter the COV434 cell viability. After 24 h, the expression of neither of the NRs was changed. Likewise, after 48 h, the expression of the selected genes was not altered. However, both BPAF and BPS increased, at the highest concentration (10-5 M) used, the mRNA levels of both PPARD and NURR1 NRs after 48 h of the treatment. In the BPA-treated groups, no significant upregulation was observed.Conclusions. In the present study, the effect of bisphenols on COUP-TFII, Nurr1, and LRH-1 NRs was investigated for the first time. Although generally we did not observe that BPs provoked any alterations in the expression of the selected NRs in COV434 cells, at specific concentrations and time points they might alter mRNA expression of certain NRs (NURR1, PPARD).

Nutritional strategies to modulate inflammation pathways via regulation of peroxisome proliferator-activated receptor ß/δ.

The peroxisome proliferator-activated receptor (PPAR) ß/δ has an important role in multiple inflammatory conditions, including obesity, hypertension, cancer, cardiovascular disease, diabetes mellitus, and autoimmune diseases. PPARß/δ forms a heterodimer with the retinoic acid receptor and binds to peroxisome proliferator response elements to initiate transcription of its target genes. PPARß/δ is also able to suppress the activities of several transcription factors, including nuclear factor κB, and activator protein 1, thus regulating anti-inflammatory cellular responses and playing a protective role in several diseases. Recent studies have shown that nutritional compounds, including nutrients and bioactive compounds, can regulate PPARß/δ expression. This review discusses key nutritional compounds that are known to modulate PPARß/δ and are likely to affect human health.

Estrogen and voluntary exercise attenuate cardiometabolic syndrome and hepatic steatosis in ovariectomized rats fed a high-fat high-fructose diet.

The prevalence of cardiometabolic syndrome (CMS) is increased in women after menopause. While hormone replacement therapy has been prescribed to relieve several components of CMS in postmenopausal women, some aspects of cardiometabolic dysfunction cannot be completely restored. The present study examined the effectiveness of estrogen replacement alone and in combination with exercise by voluntary wheel running (VWR) for alleviating the risks of CMS, insulin-mediated skeletal muscle glucose transport, and hepatic fat accumulation in ovariectomized Sprague-Dawley rats fed a high-fat high-fructose diet (OHFFD). We compared a sham-operated group with OHFFD rats that were subdivided into a sedentary, estradiol replacement (E2), and E2 plus VWR for 12 wk. E2 prevented the development of insulin resistance in skeletal muscle glucose transport and decreased hepatic fat accumulation in OHFFD rats. Furthermore, E2 treatment decreased visceral fat mass and low-density lipoprotein (LDL)-cholesterol in OHFFD rats, while VWR further decreased LDL-cholesterol and increased the ratio of high-density lipoprotein-cholesterol to total cholesterol to a greater extent. Although E2 treatment alone did not reduce serum triglyceride levels in OHFFD rats, the combined intervention of E2 and VWR lowered serum triglycerides in E2-treated OHFFD rats. The addition of VWR to E2-treated OHFFD rats led to AMPK activation and upregulation of peroxisome proliferator-activated receptor-γ (PPARγ) coactivator-1α and PPARδ in skeletal muscle along with increased fatty acid oxidation and suppressed fatty acid synthesis in the liver. Collectively, our findings indicate that, to achieve greater health benefits, physical exercise is required for E2-treated individuals under ovarian hormone deprivation with high-energy consumption.

All-trans retinoic acid increases the expression of oxidative myosin heavy chain through the PPARδ pathway in bovine muscle cells derived from satellite cells.

All-trans retinoic acid (ATRA) has been associated with various physiological phenomenon in mammalian adipose tissue and skeletal muscle. We hypothesized that ATRA may affect skeletal muscle fiber type in bovine satellite cell culture through various transcriptional processes. Bovine primary satellite cell (BSC) culture experiments were conducted to determine dose effects of ATRA on expression of genes and protein levels related to skeletal muscle fiber type and metabolism. The semimembranosus from crossbred steers (n = 2 steers), aged approximately 24 mo, were used to isolate BSC for 3 separate assays. Myogenic differentiation was induced using 3% horse serum upon cultured BSC with increasing doses (0, 1, 10, 100, and 1,000 nM) of ATRA. After 96 h of incubation, cells were harvested and used to measure the gene expression of protein kinase B (Akt), AMP-activated protein kinase alpha (AMPK), glucose transporter 4 (GLUT4), myogenin, lipoprotein lipase (LPL), myosin heavy chain (MHC) I, MHC IIA, MHC IIX, insulin like growth factor-1 (IGF-1), Peroxisome proliferator activated receptor gamma (PPARγ), PPARδ, and Smad transcription factor 3 (SMAD3) mRNA relative to ribosomal protein subunit 9 (RPS9). The mRNA expression of LPL was increased (P < 0.05) with 100 and 1,000 nM of ATRA. Expression of GLUT4 was altered (P < 0.05) by ATRA. The treatment of ATRA (1,000 nM) also increased (P < 0.05) mRNA gene expression of SMAD3. The gene expression of both PPARδ and PPARγ were increased (P < 0.05) with 1,000 nM of ATRA. Protein level of PPARδ was also affected (P < 0.05) by 1,000 nM of ATRA and resulted in a greater (P < 0.05) protein level of PPARδ compared to CON. All-trans retinoic acid (10 nM) increased gene expression of MHC I (P < 0.05) compared to CON. Expression of MHC IIA was also influenced (P < 0.05) by ATRA. The mRNA expression of MHC IIX was decreased (P < 0.05) with 100 and 1,000 nM of ATRA. In muscle cells, ATRA may cause muscle fibers to transition towards the MHC isoform that prefers oxidative metabolism, as evidenced by increased expression of genes associated with the MHC I isoform. These changes in MHC isoforms appeared to be brought about by changing PPARδ gene expression and protein levels.

Telmisartan Activates PPARδ to Improve Symptoms of Unpredictable Chronic Mild Stress-Induced Depression in Mice.

Major depression is a common mental disorder that has been established to be associated with a decrease in serotonin and/or serotonin transporters in the brain. Peroxisome proliferator-activated receptor δ (PPARδ) has been introduced as a potential target for depression treatment. Telmisartan was recently shown to activate PPARδ expression; therefore, the effectiveness of telmisartan in treating depression was investigated. In unpredictable chronic mild stress (UCMS) model, treatment with telmisartan for five weeks notably decrease in the time spent in the central and the reduced frequency of grooming and rearing in open filed test (OFT) and the decreased sucrose consumption in sucrose preference test (SPT) compared with the paradigms. Telmisartan also reversed the decrease in PPARδ and 5-HTT levels in the hippocampus of depression-like mice. Administration of PPARδ antagonist GSK0660 and direct infusion of sh-PPARδ into the brain blocked the effects of telmisartan on the improvement of depression-like behavior in these mice. Moreover, telmisartan enhanced the expression of PPARδ and 5HTT in H19-7 cells. In conclusion, the obtained results suggest that telmisartan improves symptoms of stress-induced depression in animals under chronic stress through activation of PPARδ. Therefore, telmisartan may be developed as a potential anti-depressant in the future.

Activation of Peroxisome Proliferator Activator Receptor ß/δ Improves Endothelial Dysfunction and Protects Kidney in Murine Lupus.

Women with systemic lupus erythematosus exhibit a high prevalence of hypertension, endothelial dysfunction, and renal injury. We tested whether GW0742, a peroxisome proliferator activator receptor ß/δ (PPARß/δ) agonist, ameliorates disease activity and cardiovascular complications in a female mouse model of lupus. Thirty-week-old NZBWF1 (lupus) and NZW/LacJ (control) mice were treated with GW0742 or with the PPARß/δ antagonist GSK0660 plus GW0742 for 5 weeks. Blood pressure, plasma double-stranded DNA autoantibodies and cytokines, nephritis, hepatic opsonins, spleen lymphocyte populations, endothelial function, and vascular oxidative stress were compared in treated and untreated mice. GW0742 treatment reduced lupus disease activity, blood pressure, cardiac and renal hypertrophy, splenomegaly, albuminuria, and renal injury in lupus mice, but not in control. GW0742 increased hepatic opsonins mRNA levels in lupus mice and reduced the elevated T, B, Treg, and Th1 cells in spleens from lupus mice. GW0742 lowered the higher plasma concentration of proinflammatory cytokines observed in lupus mice. Aortae from lupus mice showed reduced endothelium-dependent vasodilator responses to acetylcholine and increased nicotinamide adenine dinucleotide phosphate oxidase-driven vascular reactive oxygen species production, which were normalized by GW0742 treatment. All these effects of GW0742 were inhibited by PPARß/δ blockade with GSK0660. Pharmacological activation of PPARß/δ reduced hypertension, endothelial dysfunction, and organ damage in severe lupus mice, which was associated with reduced plasma antidouble-stranded DNA autoantibodies and anti-inflammatory and antioxidant effects in target tissues. Our findings identify PPARß/δ as a promising target for an alternative approach in the treatment of systemic lupus erythematosus and its associated vascular damage.

Oxygenized low density lipoprotein down-regulates the TRPV4 protein expression of macrophage through activation of peroxisome proliferator-activated receptor γ.

BACKGROUND: TRPV4, a non-selective cation channel, is involved in lipometabolism and atherosclerosis. However, whether TRPV4 participates in oxygenized low density lipoprotein (oxLDL)-induced foam cell formation remains unknown. The present study investigates the effect of oxLDL on the expression of TRPV4 in macrophages and its underlying mechanisms. METHODS: The expression of TRPV4 in RAW264.7 and phorbol-12-myristate-13-acetate (PMA) induced U937, THP-1 cells was detected by immunofluorescence, and western blot was used to detect the TRPV4 expression before and after PMA induction. Each cell line was divided into three groups, including control group, native low-density lipoprotein (nLDL) (100 µg/mL) group and oxLDL (100µg/mL) group; the expression of TRPV4 in each group was measured using immunohistochemistry and western blot. TRPV4 protein expression was detected by western blot after RAW 264.7 cells were treated with 0, 0.01 µM, 0.1 µM and 1 µM T0070907 or preincubated with 0.1 µM T0070709 for 1 h before incubation with oxLDL for 24 h. RESULTS: In all macrophage cell lines, TRPV4 was widely expressed. PMA increased TRPV4 expression in U937 and THP-1 cells. There was no significant difference in TRPV4 expression in the nLDL group compared to that in the control group; however a significant reduction in TRPV4 expression was detected in the oxLDL group compared to that in the control and nLDL groups using measurements obtained from both immunohistochemistry and western blot. The PPARγ inhibitor T0070907 enhanced the basal expression of TRPV4 and protected RAW264.7 cells from oxLDL-induced TRPV4 down-regulation. CONCLUSIONS: This study revealed that TRPV4 was widely expressed in macrophages and that oxLDL could induce the down-regulation of TRPV4 expression through its actions on PPARγ. This study may serve as an important first step for further investigation into the roles of TRPV4 in macrophage-derived foam cell formation in atherosclerosis.

Non-classical Transcriptional Activity of Retinoic Acid.

It has long been established that the transcriptional activity of retinoic acid (RA) is mediated by members of the nuclear receptor family of ligand-activated transcription factors termed RA receptors (RARs). More recent observations have established that RA also activates an additional nuclear receptor, PPARß/δ. Partitioning RA between RARs and PPARß/δ is governed by different intracellular lipid-binding proteins: cellular RA binding protein 2 (CRABP2) delivers RA to nuclear RARs and a fatty acid binding protein (FABP5) delivers the hormone from the cytosol to nuclear PPARß/δ. Consequently, RA signals through RARs in CRABP2-expressing cells, but activates PPARß/δ in cells that express a high level of FABP5. RA elicits different and sometimes opposing responses in cells that express different FABP5/CRABP2 ratios because PPARß/δ and RARs regulate the expression of distinct sets of genes. An overview of the observations that led to the discovery of this non-classical activity of RA are presented here, along with a discussion of evidence demonstrating the involvement of the dual transcriptional activities of RA in regulating energy homeostasis, insulin responses, and adipocyte and neuron differentiation.

Ligand activation of peroxisome proliferator-activated receptor-ß/δ suppresses liver tumorigenesis in hepatitis B transgenic mice.

Peroxisome proliferator-activated receptor-ß/δ (PPARß/δ) inhibits steatosis and inflammation, known risk factors for liver cancer. In this study, the effect of ligand activation of PPARß/δ in modulating liver tumorigenesis in transgenic hepatitis B virus (HBV) mice was examined. Activation of PPARß/δ in HBV mice reduced steatosis, the average number of liver foci, and tumor multiplicity. Reduced expression of hepatic CYCLIN D1 and c-MYC, tumor necrosis factor alpha (Tnfa) mRNA, serum levels of alanine aminotransaminase, and an increase in apoptotic signaling was also observed following ligand activation of PPARß/δ in HBV mice compared to controls. Inhibition of Tnfa mRNA expression was not observed in wild-type hepatocytes. Ligand activation of PPARß/δ inhibited lipopolysaccharide (LPS)-induced mRNA expression of Tnfa in wild-type, but not in Pparß/δ-null Kupffer cells. Interestingly, LPS-induced expression of Tnfa mRNA was also inhibited in Kupffer cells from a transgenic mouse line that expressed a DNA binding mutant form of PPARß/δ compared to controls. Combined, these results suggest that ligand activation of PPARß/δ attenuates hepatic tumorigenesis in HBV transgenic mice by inhibiting steatosis and cell proliferation, enhancing hepatocyte apoptosis, and modulating anti-inflammatory activity in Kupffer cells.

Ligand-activated PPARδ upregulates α-smooth muscle actin expression in human dermal fibroblasts: A potential role for PPARδ in wound healing.

BACKGROUND: The phenotypic changes that accompany differentiation of resident fibroblasts into myofibroblasts are important aspects of the wound healing process. Recent studies showed that peroxisome proliferator-activated receptor (PPAR) δ plays a critical role in wound healing. OBJECTIVE: To determine whether the nuclear receptor PPARδ can modulate the differentiation of human dermal fibroblasts (HDFs) into myofibroblasts. METHODS: These studies were undertaken in primary HDFs using Western blot analyses, small interfering (si)RNA-mediated gene silencing, reporter gene assays, chromatin immunoprecipitation (ChIP), migration assays, collagen gel contraction assays, and real-time PCR. RESULTS: Activation of PPARδ by GW501516, a specific ligand of PPARδ, specifically upregulated the myofibroblast marker α-smooth muscle actin (α-SMA) in a time- and concentration-dependent manner. This induction was significantly inhibited by the presence of siRNA against PPARδ, indicating that PPARδ is involved in myofibroblast transdifferentiation of HDFs. Ligand-activated PPARδ increased α-SMA promoter activity in a dual mode by directly binding a direct repeat-1 (DR1) site in the α-SMA promoter, and by inducing expression of transforming growth factor (TGF)-ß, whose downstream effector Smad3 interacts with a Smad-binding element (SBE) in another region of the promoter. Mutations in these cis-elements totally abrogated transcriptional activation of the α-SMA gene by the PPARδ ligand; thus both sites represent novel types of PPARδ response elements. GW501516-activated PPARδ also increased the migration and contractile properties of HDFs, as demonstrated by Transwell and collagen lattice contraction assays, respectively. In addition, PPARδ-mediated upregulation of α-SMA was correlated with elevated expression of myofibroblast markers such as collagen I and fibronectin, with a concomitant reduction in expression of the epithelial marker E-cadherin. CONCLUSION: PPARδ plays pivotal roles in wound healing by promoting fibroblast-to-myofibroblast differentiation via TGF-ß/Smad3 signaling.

Ginger extract prevents high-fat diet-induced obesity in mice via activation of the peroxisome proliferator-activated receptor δ pathway.

The initiation of obesity entails an imbalance wherein energy intake exceeds expenditure. Obesity is increasing in prevalence and is now a worldwide health problem. Food-derived peroxisome proliferator-activated receptor δ (PPARδ) stimulators represent potential treatment options for obesity. Ginger (Zingiber officinale Roscoe) was previously shown to regulate the PPARγ signaling pathway in adipocytes. In this study, we investigated the antiobesity effects of ginger in vivo and the mechanism of action in vitro. Energy expenditure was increased, and diet-induced obesity was attenuated in C57BL/6J mice treated with dietary ginger extract (GE). GE also increased the number of Type I muscle fibers, improved running endurance capacity and upregulated PPARδ-targeted gene expression in skeletal muscle and the liver. 6-Shogaol and 6-gingerol acted as specific PPARδ ligands and stimulated PPARδ-dependent gene expression in cultured human skeletal muscle myotubes. An analysis of cellular respiration revealed that pretreating cultured skeletal muscle myotubes with GE increased palmitate-induced oxygen consumption rate, which suggested an increase in cellular fatty acid catabolism. These results demonstrated that sustained activation of the PPARδ pathway with GE attenuated diet-induced obesity and improved exercise endurance capacity by increasing skeletal muscle fat catabolism. 6-Shogaol and 6-gingerol may be responsible for the regulatory effects of dietary ginger on PPARδ signaling.

PPARδ signaling regulates colorectal cancer.

Peroxisome proliferator-activated receptorδ (PPARδ) belongs to the PPARs receptor family including PPARα, PPARδ, and PPARγ. PPARδ is a ligand-activated transcription factor that plays a critical role in regulating cancer progression. PPARδ-linked tumorigenesis was first identified in colorectal cancer, which is demonstrated by the following evidences, so PPARε is a potential drug target for colorectal cancer. In contrast, some observations show that PPARδ negatively regulates colorectal cancer event. In the present review, the recent progress of PPARδ signaling-mediated colorectal cancer is covered.

Regulation of peroxisome proliferator-activated receptor ß/δ expression and activity levels by toll-like receptor agonists and MAP kinase inhibitors in rat astrocytes.

Peroxisome proliferator-activated receptor ß/δ (PPARß/δ) is a potential regulator of neuroinflammation. Toll-like receptors (TLR) are innate immunity-related receptors of inflammatory stimuli. In the present report, we evaluate the molecular mechanisms of regulation of mRNA, protein, and transcriptional activity levels of PPARß/δ by agonists of TLR4, TLR1/2, and TLR5, using lipopolysaccharide (LPS), peptidoglycan, and flagellin, respectively. We found that these stimuli increase the PPARß/δ levels in astrocytes. Expression and activity of PPARß/δ are separately regulated by inhibitors of p38, MEK1/2, extracellular signal-regulated kinases 1/2, and c-Jun N-terminal Kinase mitogen-activated protein kinases. The LPS-induced kinetics of PPARß/δ expression is similar to that of the proinflammatory gene cyclooxygenase 2. Moreover, for both genes the expression depends on nuclear factor kappa-light-chain-enhancer of activated B cells and p38, and is induced after inhibition of protein synthesis. The up-regulation of the expression after inhibition of protein synthesis signifies the participation of a labile protein in regulation of PPARß/δ expression. In contrast to cyclooxygenase 2, the cycloheximide-sensitive PPARß/δ expression was not responsive to nuclear factor kappa-light-chain-enhancer of activated B cells inhibition. Measurements of PPARß/δ mRNA stability showed that the PPARß/δ mRNA levels are regulated post-transcriptionally. We found that in LPS-stimulated astrocytes, the half-life of PPARß/δ mRNA was 50 min. Thus, we demonstrate that PPARß/δ expression and activity are regulated in TLR agonist-stimulated astrocytes by mechanisms that are widely used for regulation of proinflammatory genes. Protein expression level of nuclear receptor PPARß/δ is important for functions of this transcription factor. We investigate the regulatory mechanisms of PPARß/δ in rat primary astrocytes stimulated by agonists of toll-like receptors (TLR): TLR4, TLR1/2, and TLR5. Expression, activity, mRNA stability, and superinduction of PPARß/δ were up-regulated after TLR stimulation. These processes are sensitive to MAPKs and NF-kB inhibitors. Superinduction is up-regulation of mRNA expression after inhibition of protein synthesis.

Therapeutic modulators of peroxisome proliferator-activated receptors (PPAR): a patent review (2008-present).

INTRODUCTION: Peroxisome proliferator-activated receptors (PPAR) are ligand-activated transcription factors belonging to the nuclear receptor superfamily. The three known subtypes PPARα, PPARγ and PPARδ have different tissue distribution and play a key role as regulators of glucose and lipid homeostasis as well as in cell proliferation, differentiation and inflammatory responses. They have gained a lot of interest as pharmaceutical targets over the last years and with the antidiabetic thiazolidindiones (TZDs) and the hypolipidemic fibrates, two classes of drugs had entered the market. Early observations of severe adverse events changed the situation in the recent past. AREAS COVERED: Herein the authors summarize recent (2008-present) patent applications concerning PPAR ligands claimed for the use in metabolic disorders as well as patents indicating new applications for modulators of the PPAR subtypes. EXPERT OPINION: Looking at the recent patent activity regarding novel compounds, there have not been real innovations. As major applications for therapeutic PPAR ligands cancer therapy, skin-related disorders and systemic anti-inflammatory therapies might arise in the mid-term future. The known PPAR targeting drugs might see a repurposing for novel indications.

The loss of muscle mass and sarcopenia: non hormonal intervention.

Muscle aging is a key component of the increase in frailty in human populations. The generation of critical levels of power is a prerequisite to perform simple tasks of daily living, such as rising from a chair or climbing stairs. There is great scientific and social interest to determine which behaviors can lead to the maintenance of the muscle mass in young immobilized subjects and in the elderly. Several hormonal treatments have been proposed for the treatment of sarcopenia. However, the side effects associated to these treatments emphasize the need of finding non-toxic and non-hormonal treatments that help increase muscle strength, improve muscle function, and decrease the degree of dependency in the old population. Recently, several studies have shed new light on this topic. Any medical efforts to develop treatments to prevent muscle dysfunction leading to sarcopenia, and eventually frailty, will be a major breakthrough in the public health in advances countries. Moreover, any significant improvement in the loss of muscle function will be a major breakthrough in the health and welfare of the population.

The natural protective mechanism against hyperglycemia in vascular endothelial cells: roles of the lipid peroxidation product 4-hydroxydodecadienal and peroxisome proliferator-activated receptor delta.

OBJECTIVE: Vascular endothelial cells (VECs) downregulate their rate of glucose uptake in response to hyperglycemia by decreasing the expression of their typical glucose transporter GLUT-1. Hitherto, we discovered critical roles for the protein calreticulin and the arachidonic acid-metabolizing enzyme 12-lipoxygenase in this autoregulatory process. The hypothesis that 4-hydroxydodeca-(2E,6Z)-dienal (4-HDDE), the peroxidation product of 12-lipoxygenase, mediates this downregulatory mechanism by activating peroxisome proliferator-activated receptor (PPAR) delta was investigated. RESEARCH DESIGN AND METHODS: Effects of 4-HDDE and PPARdelta on the glucose transport system and calreticulin expression in primary bovine aortic endothelial cells were evaluated by pharmacological and molecular interventions. RESULTS: Using GW501516 (PPARdelta agonist) and GSK0660 (PPARdelta antagonist), we discovered that high-glucose-induced downregulation of the glucose transport system in VECs is mediated by PPARdelta. A PPAR-sensitive luciferase reporter assay in VECs revealed that high glucose markedly increased luciferase activity, while GSK0660 abolished it. High-performance liquid chromatography analysis showed that high-glucose incubation substantially elevated the generation of 4-HDDE in VECs. Treatment of VECs, exposed to normal glucose, with 4-HDDE mimicked high glucose and downregulated the glucose transport system and increased calreticulin expression. Like high glucose, 4-HDDE significantly activated PPARdelta in cells overexpressing human PPAR (hPPAR)delta but not hPPARalpha, -gamma1, or -gamma2. Moreover, silencing of PPARdelta prevented high-glucose-dependent alterations in GLUT-1 and calreticulin expression. Finally, specific binding of PPARdelta to a PPAR response element in the promoter region of the calreticulin gene was identified by utilizing a specific chromatin immunoprecipitation assay. CONCLUSIONS: Collectively, our data show that 4-HDDE plays a central role in the downregulation of glucose uptake in VECs by activating PPARdelta.

Curcumin suppresses PPARdelta expression and related genes in HT-29 cells.

AIM: To investigate the effects of curcumin on the expression of peroxisome proliferator-activated receptordelta (PPARdelta) and related genes in HT-29 cells. METHODS: HT-29 cells were treated with curcumin (0-80 micromol/L) for 24 h. The effects of curcumin on the morphology of HT-29 cells were studied by Hoechst 33342 staining. The activity of caspase-3 was determined using DEVD-pNA as substrate. The levels of peroxisome PPARdelta, 14-3-3epsilon and vascular endothelial growth factor (VEGF) in HT-29 cells were determined by Western blotting analysis and their mRNA expression was determined by real-time quantitative RT-PCR. RESULTS: Treatment with 10-80 micromol/L curcumin induced typical features of apoptosis and activated the caspase-3 in HT-29 cells. The expression of PPARdelta, 14-3-3epsilon and VEGF was reduced and the activity of beta-catenin/Tcf-4 signaling was inhibited by curcumin treatment. CONCLUSION: Curcumin can induce apoptosis of HT-29 cells and down-regulate the expression of PPARdelta, 14-3-3epsilon and VEGF in HT-29.

Structure-based design and synthesis of fluorescent PPARalpha/delta co-agonist and its application as a probe for fluorescent polarization assay of PPARdelta ligands.

Based on the result of X-ray crystallographic analysis of our peroxisome proliferator-activated receptor alpha and delta (PPARalpha/delta) co-agonist complexed with human PPAR ligand binding domain (LBD), we designed and synthesized an optically active fluorescent PPARalpha/delta co-agonist, which has a pyrene unit incorporated directly at the hydrophobic tail part of the structure as a fluorophore. This fluorescent co-agonist was applied in a homogeneous fluorescent polarization assay format for the identification of PPARdelta ligands.

A novel selective peroxisome proliferator-activator receptor-gamma modulator-SPPARgammaM5 improves insulin sensitivity with diminished adverse cardiovascular effects.

The use of the thiazolidinedione insulin sensitizers rosiglitazone and pioglitazone for the treatment of type 2 diabetes mellitus in recent years has proven to be effective in helping patients resume normal glycemic control. However, their use is often associated with undesirable side effects including peripheral edema, congestive heart failure and weight gain. Here, we report the identification and characterization of a novel selective PPARgamma modulator, SPPARgammaM5 ((2S)-2-(2-chloro-5-{[3-(4-chlorophenoxy)-2-methyl-6-(trifluoromethoxy)-1H-indol-1-yl]methyl} phenoxy)propionic acid), which has notable insulin sensitizing properties and a superior tolerability profile to that of rosiglitazone. SPPARgammaM5 is a potent ligand of human PPARgamma with high selectivity versus PPARalpha or PPARdelta in receptor competitive binding assays. In cell-based transcriptional activation assays, SPPARgammaM5 was a potent partial agonist of human PPARgamma in comparison to the PPARgamma full agonist rosiglitazone. Compared to rosiglitazone or the PPARgamma full agonist COOH (2-(2-(4-phenoxy-2-propylphenoxy)ethyl)indole-5-acetic acid), SPPARgammaM5 induced an attenuated PPARgamma-regulated gene expression profile in fully differentiated 3T3-L1 adipocytes and white adipose tissue of chronically treated db/db mice. SPPARgammaM5 treatment also reduced the insulin resistance index by homeostasis model assessment (HOMA), suggesting an improvement in insulin resistance in these db/db mice. Treatment of obese Zucker rats with either rosiglitazone or SPPARgammaM5 resulted in an improvement in selected parameters that serve as surrogate indicators of insulin resistance and hyperlipidemia. However, unlike rosiglitazone, SPPARgammaM5 did not cause significant fluid retention or cardiac hypertrophy in these rats. Thus, compounds such as SPPARgammaM5 may offer beneficial effects on glycemic control with significantly attenuated adverse effects.

Nuclear receptors as drug targets in obesity, dyslipidemia and atherosclerosis.

Nuclear hormone receptors, including peroxisome proliferator-activated receptors (PPARs), liver X receptors (LXRs), and the farnesoid X receptor (FXR), are transcription factors involved in the regulation of essential metabolic functions, including glucose and lipid metabolism, reverse cholesterol transport, and the regulation of bile acids. This review summarizes new developments in the use of PPAR, LXR and FXR agonists for the treatment of obesity and cardiovascular diseases, including dyslipidemia and atherosclerosis. Currently available drugs and future areas of research for new therapies are also discussed.