Selective PPARα Research Articles

Effects of K-877, a novel selective PPARα modulator, on small intestine contribute to the amelioration of hyperlipidemia in low-density lipoprotein receptor knockout mice

Peroxisome proliferator-activated receptor α (PPARα) is a well-known therapeutic target for treating hyperlipidemia. K-877 is a novel selective PPARα modulator (SPPARMα) that enhances PPARα transcriptional activity with high selectivity and potency, resulting in reduced plasma lipid levels. This study aimed to evaluate the effects of K-877 on hyperlipidemia in low-density lipoprotein receptor knockout (Ldlr−/−) mice, a mouse model of atherosclerosis. We revealed that K-877 administration significantly decreased plasma triglyceride (TG) and total cholesterol (TC) levels and increased plasma high-density lipoprotein cholesterol (HDL-C) levels in Ldlr−/− mice. K-877 administration to Ldlr−/− mice efficiently increased the gene expression of PPARα and its target genes related to fatty acid oxidation in the liver and small intestine. The same treatment significantly increased ATP-binding cassette a1 gene expression in the liver and small intestine and reduced Niemann Pick C1-like 1 gene expression in the small intestine, suggesting that K-877 administration induced HDL-C production in the liver and small intestine and reduced cholesterol absorption in the small intestine. In conclusion, K-877 administration had pronounced effects on the liver and small intestine in Ldlr−/− mice. K-877 is an attractive PPARα-modulating drug for treating hyperlipidemia that works equally well in both the liver and small intestine.

Identification of a novel selective PPAR\u03b3 ligand with a unique binding mode and improved therapeutic profile in vitro

Thiazolidinediones (TZD) function as potent anti-diabetic drugs through their direct action on the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ), but their therapeutic benefits are compromised by severe side effects. To address this concern, here we developed a potent “hit” compound, VSP-51, which is a novel selective PPARγ-modulating ligand with improved therapeutic profiles in vitro compared to the multi-billion dollar TZD drug rosiglitazone (Rosi). Unlike Rosi, VSP-51 is a partial agonist of PPARγ with improved insulin sensitivity due to its ability to bind PPARγ with high affinity without stimulating adipocyte differentiation and the expression of adipogenesis-related genes. We have determined the crystal structure of the PPARγ ligand-binding domain (LBD) in complex with VSP-51, which revealed a unique mode of binding for VSP-51 and provides the molecular basis for the discrimination between VSP-51 from TZDs and other ligands such as telmisartan, SR1663 and SR1664. Taken together, our findings demonstrate that: a) VSP-51 can serve as a promising candidate for anti-diabetic drug discovery; and b) provide a rational basis for the development of future pharmacological agents targeting PPARγ with advantages over current TZD drugs.

Fenofibrate Decreases Insulin Clearance and Insulin Secretion to Maintain Insulin Sensitivity

High fat diet reduces the expression of CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1), a transmembrane glycoprotein that promotes insulin clearance and down-regulates fatty acid synthase activity in the liver upon its phosphorylation by the insulin receptor. Because peroxisome proliferator-activated receptor α (PPARα) transcriptionally suppresses CEACAM1 expression, we herein examined whether high fat down-regulates CEACAM1 expression in a PPARα-dependent mechanism. By activating PPARα, the lipid-lowering drug fenofibrate reverses dyslipidemia and improves insulin sensitivity in type 2 diabetes in part by promoting fatty acid oxidation. Despite reducing glucose-stimulated insulin secretion, fenofibrate treatment does not result in insulin insufficiency. To examine whether this is mediated by a parallel decrease in CEACAM1-dependent hepatic insulin clearance pathways, we fed wild-type and Pparα-/- null mice a high fat diet supplemented with either fenofibrate or Wy14643, a selective PPARα agonist, and examined their effect on insulin metabolism and action. We demonstrated that the decrease in insulin secretion by fenofibrate and Wy14643 is accompanied by reduction in insulin clearance in wild-type but not Pparα-/- mice, thereby maintaining normoinsulinemia and insulin sensitivity despite continuous high fat intake. Intact insulin secretion in L-CC1 mice with protected hepatic insulin clearance and CEACAM1 levels provides in vivo evidence that insulin secretion responds to changes in insulin clearance to maintain physiologic insulin and glucose homeostasis. These results also emphasize the relevant role of hepatic insulin extraction in regulating insulin sensitivity.

Does bilirubin prevent hepatic steatosis through activation of the PPARα nuclear receptor?

Several large population studies have demonstrated a negative correlation between serum bilirubin levels and the development of obesity, hepatic steatosis, and cardiovascular disease. Despite the strong correlative data demonstrating the protective role of bilirubin, the mechanism by which bilirubin can protect against these pathologies remains unknown. Bilirubin has long been known as a powerful antioxidant and also has anti-inflammatory actions, each of which may contribute to the protection afforded by increased levels. We have recently described a novel function of bilirubin as a ligand for the peroxisome proliferator-activated receptor-alpha (PPARα), which we show specifically binds to the nuclear receptor. Bilirubin may function as a selective PPAR modulator (SPPARM) to control lipid accumulation and blood glucose. However, it is not known to what degree bilirubin activation of PPARα is responsible for the protection afforded to reduce hepatic steatosis. We hypothesize that bilirubin, acting as a novel SPPARM, increases hepatic fatty acid metabolism through a PPARα-dependent mechanism which reduces hepatic lipid accumulation and protects against hepatic steatosis and non-alcoholic fatty liver disease (NAFLD).

新規選択的PPARαモジュレーター（SPPARMα）候補の探索

新規選択的PPARαモジュレーター（SPPARMα）候補の探索

Selective PPAR modulators (SPPARs) may fill the need for treatment of the atherogenic dyslipidemia of insulin resistance and type 2 diabetes: Can they reduce the associated cardiac risk?

Selective PPAR modulators (SPPARs) may fill the need for treatment of the atherogenic dyslipidemia of insulin resistance and type 2 diabetes: Can they reduce the associated cardiac risk?

The novel selective PPARα modulator (SPPARMα) pemafibrate improves dyslipidemia, enhances reverse cholesterol transport and decreases inflammation and atherosclerosis

BackgroundAtherosclerosis is characterized by lipid accumulation and chronic inflammation in the arterial wall. Elevated levels of apolipoprotein (apo) B-containing lipoproteins are a risk factor for cardiovascular disease (CVD). By contrast, plasma levels of functional high-density lipoprotein (HDL) and apoA-I are protective against CVD by enhancing reverse cholesterol transport (RCT). Activation of peroxisome proliferator-activated receptor-α (PPARα), a ligand-activated transcription factor, controls lipid metabolism, cellular cholesterol trafficking in macrophages and influences inflammation. ObjectiveTo study whether pharmacological activation of PPARα with a novel highly potent and selective PPARα modulator, pemafibrate, improves lipid metabolism, macrophage cholesterol efflux, inflammation and consequently atherosclerosis development in vitro and in vivo using human apolipoprotein E2 Knock-In (apoE2KI) and human apoA-I transgenic (hapoA-I tg) mice. Approach and resultsPemafibrate treatment decreases apoB secretion in chylomicrons by polarized Caco-2/TC7 intestinal epithelium cells and reduces triglyceride levels in apoE2KI mice. Pemafibrate treatment of hapoA-I tg mice increases plasma HDL cholesterol, apoA-I and stimulates RCT to feces. In primary human macrophages, pemafibrate promotes macrophage cholesterol efflux to HDL and exerts anti-inflammatory activities. Pemafibrate also reduces markers of inflammation and macrophages in the aortic crosses as well as aortic atherosclerotic lesion burden in western diet-fed apoE2KI mice. ConclusionsThese results demonstrate that the novel selective PPARα modulator pemafibrate exerts beneficial effects on lipid metabolism, RCT and inflammation resulting in anti-atherogenic properties.

Effects of K-877, a novel selective PPARα modulator (SPPARMα), in dyslipidaemic patients: A randomized, double blind, active- and placebo-controlled, phase 2 trial

Background and aimsTo assess the efficacy and safety of K-877 (Pemafibrate), a novel selective peroxisome proliferator-activated receptor α modulator (SPPARMα) that possesses unique PPARα activity and selectivity, compared with placebo and fenofibrate in dyslipidaemic patients with high triglyceride (TG) and low high-density lipoprotein cholesterol (HDL-C) levels. Methods and resultsThis study was a double blind, placebo-controlled, parallel-group 12-week clinical trial. The study randomized 224 patients to K-877 0.025, 0.05, 0.1, 0.2 mg BID, fenofibrate 100 mg QD, or placebo (1:1:1:1:1:1) groups. Least squares mean percent changes from the baseline TG levels were −30.9%, −36.4%, −42.6%, −42.7% for the K-877 0.025, 0.05, 0.1, 0.2 mg BID respectively (p < 0.001), which were greater than that of the fenofibrate 100 mg QD (−29.7%, p < 0.001) group. Statistically significant improvements from the baseline HDL-C, very-low-density lipoprotein cholesterol, chylomicron cholesterol, remnant lipoprotein cholesterol, apolipoprotein (apo) B (apoB), and apoC-III were also observed in the K-877 groups. The incidence of adverse events (AEs) in the K-877 groups (32.4–56.8%) was comparable to those in placebo (47.2%) and fenofibrate 100 mg QD (56.8%); adverse drug reactions (ADRs) in the K-877 groups (2.7–5.4%) were less than those in placebo (8.3%) and fenofibrate 100 mg QD (10.8%) groups. ConclusionIn dyslipidaemic patients with high TG and low HDL-C, K-877 improved TG, HDL-C, and other lipid parameters without increasing AEs or ADRs, compared to placebo and fenofibrate. K-877 can be expected to improve atherogenicity and to be a new beneficial treatment for dyslipidaemic patients.

PPAR Agonists: I. Role of Receptor Subunits in Alcohol Consumption in Male and Female Mice.

Several peroxisome proliferator-activated receptor (PPAR) agonists reduce voluntary alcohol consumption in rodent models, and evidence suggests that PPARα and γ subunits play an important role in this effect. To define the subunit dependence of this action, we tested selective PPARα and α/γ agonists and antagonists in addition to null mutant mice lacking PPARα. The effects of fenofibrate (PPARα agonist) and tesaglitazar (PPARα/γ agonist) on continuous and intermittent 2-bottle choice drinking tests were examined in male and female wild-type mice and in male mice lacking PPARα. We compared the ability of MK886 (PPARα antagonist) and GW9662 (PPARγ antagonist) to inhibit the effects of fenofibrate and tesaglitazar in wild-type mice. The estrogen receptor antagonist, tamoxifen, can inhibit PPARγ-dependent transcription and was also studied in male and female mice. Fenofibrate and tesaglitazar reduced ethanol (EtOH) consumption and preference in wild-type mice, but these effects were not observed in mice lacking PPARα. MK886 inhibited the action of fenofibrate, but not tesaglitazer, while GW9662 did not inhibit either agonist. The PPAR agonists were more effective in male mice compared to females, and drinking in the continuous 2-bottle choice test was more sensitive to fenofibrate and tesaglitazar compared to drinking in theintermittent access test. Tamoxifen also reduced EtOH consumption in male mice and thisaction was inhibited by GW9662, but not MK886, suggesting that it acts by activation of PPARγ. Our study using selective PPAR agonists, antagonists, and null mutant mice indicates a key role for PPARα in mediating reduced EtOH consumption by fenofibrate and tesaglitazar.

BML-111 Attenuates Renal Ischemia/Reperfusion Injury Via Peroxisome Proliferator-Activated Receptor-α-Regulated Heme Oxygenase-1.

We examine whether BML-111, a lipoxin receptor agonist, inhibits renal ischemia/reperfusion (I/R) injury, and whether peroxisome proliferator-activated receptor-α (PPARα) or heme oxygenase-1 (HO-1) is involved in protective effects of BML-111 on kidney against I/R injury. Rats subjected to renal I/R injury were treated with or without BML-111. Renal histological and immunohistochemical studies were performed. Expressions of phosphorylated p38 mitogen-activated protein kinase (pp38 MAPK), phosphorylated PPARα (pPPARα), and HO-1 were assessed in NRK-52E cells exposed to BML-111. The binding activity of PPARα to peroxisome proliferator-responsive element (PPRE) on HO-1 promoter in the cells was determined. BML-111 treatment resulted in a marked reduction in the severity of histological features of renal I/R injury, and attenuated the rise in renal myeloperoxidase and malondialdehyde, blood urea nitrogen and creatinine, urinary N-acetyl-β-glucosaminidase, and leucine aminopeptidase levels caused by I/R injury. BML-111 stimulated the renal expressions of pPPARα and HO-1, and cellular messenger RNA (mRNA) and protein expressions of pPPARα and HO-1 which were both blocked by GW6471, a selective PPARα antagonist, and ZnPP-IX, a specific inhibitor of HO-1 pretreatment. The pp38 MAPK inhibitor SB203580 blocked the BML-111-induced expressions of pp38 MAPK, pPPARα, and HO-1 in NRK-52E cells. The binding activity of PPARα to PPRE in nuclear extracts of NRK-52E cells was enhanced by treatment of the cells with BML-111, and was suppressed by GW6471 and SB203580. BML-111 protects the kidney against I/R injury via activation of p38 MAPK/PPARα/HO-1 pathway.

Activation of peroxisome proliferator-activated receptor gamma induces anti-inflammatory properties in the chicken free avian respiratory macrophages.

BackgroundActivation of peroxisome proliferator activated receptor gamma (PPAR γ) in the alveolar macrophages (AM) by selective synthetic PPAR γ ligands, improves the ability of the cells to resolve inflammation. In birds, respiratory macrophages are known as free avian respiratory macrophages (FARM) and show distinct functional differences from AM. The effects of treating FARM with PPAR γ ligands are unclear.MethodsFARM were harvested by lavage of chicken respiratory tract and their morphology assessed at microscopic level. The effects of PPAR γ agonists on the FARM in vitro viability, phagocytic capacity and proinflammatory cytokine (TNF-α) production were assessed.ResultsFARM had eccentric nucleus and plasma membrane ruffled with filopodial extensions. Ultrastructurally, numerous vesicular bodies presumed to be lysosomes were present. FARM treated with troglitazone, a selective PPAR γ agonist, had similar in vitro viability with untreated FARM. However, treated FARM co-cultured with polystyrene particles, internalized more particles with a mean volume density of 41 % compared to that of untreated FARM of 21 %. Further, treated FARM significantly decreased LPS-induced TNF-α production in a dose dependent manner.ConclusionResults from this study show that PPAR γ synthetic ligands enhance phagocytic ability of FARM. Further the ligands attenuate production of proinflammatory cytokines in the FARM, suggesting potential therapeutic application of PPAR γ ligands in the management of respiratory inflammatory disorders in the poultry industry.

Identification of dual PPARα/γ agonists and their effects on lipid metabolism

The three peroxisome proliferator-activated receptor (PPAR) isoforms; PPARα, PPARγ and PPARδ, play central roles in lipid metabolism and glucose homeostasis. Dual PPARα/γ agonists, which stimulate both PPARα and PPARγ isoforms to similar extents, are gaining popularity as it is believed that they are able to ameliorate the unwanted side effects of selective PPARα and PPARγ agonists; and may also be used to treat dyslipidemia and type 2 diabetes mellitus simultaneously. In this study, virtual screening of natural product libraries, using both structure-based and ligand-based drug discovery approaches, identified ten potential dual PPARα/γ agonist lead compounds (9–13 and 16–20). In vitro assays confirmed these compounds to show no statistically significant toxicity to cells, with the exception of compound 12 which inhibited cell growth to 74.5%±3.5 and 54.1%±3.7 at 50μM and 100μM, respectively. In support of their potential as dual PPARα/γ agonists, all ten compounds upregulated the expression of cholesterol transporters ABCA1 and ABCG1 in THP-1 macrophages, with indoline derivative 16 producing the greatest elevation (2.3-fold; 3.3-fold, respectively). Furthermore, comparable to the activity of established PPARα and PPARγ agonists, compound 16 stimulated triacylglycerol accumulation during 3T3-L1 adipocyte differentiation as well as fatty acid β-oxidation in HuH7 hepatocytes.

Abstract 13374: Efficacy and Safety of K-877, a Potent and Selective PPAR-α Modulator (SPPARMα), in Combination With Statins in Japanese Patients With Dyslipidemia

Background: Residual cardiovascular risk remains despite intensive statin treatment. K-877, a Selective PPAR-α Modulator (SPPARMα), has shown significant reductions in atherogenic lipids with fewer adverse effects than existing PPARα agonists. We hypothesized that K-877 in combination with statins may provide further benefit and risk reduction than statins alone in patients with dyslipidemia. Methods: This is a multi-center double-blind parallel-group study. A total of 423 patients with fasting high TG (≥200 mg/dL), treated with any statins (stable dosage at least 4 weeks prior to the first screening visit) were randomized to the following 24-weeks treatment groups; placebo (n=108), twice-daily K-877 0.2 mg/day (n=150) and 0.2/0.4 mg/day [patients took 0.2 mg/day, those with TG &gt;150 mg/dL at week 8 were uptitrated to 0.4 mg/day from week 12] (n=165 [n=58]). The primary endpoint was the percentage change of TG from baseline, and rates of adverse drug reactions (ADRs) and adverse events (AEs) were assessed. Results: Fasting TG reduction was as follows; placebo: -0.8%, K-877 0.2 mg: -46.8% and K-877 0.2/0.4 mg: -50.8%. K-877 groups had significant reductions compared with placebo (P&lt;0.01). By dose titration at week 12, more patients achieved the target (fasting TG≤150 mg/dL) at week 24 (36.2% in 0.4 mg group and 29.7% in 0.2 mg group). The incidence of AEs/ADRs in K-877 groups was similar to placebo [placebo, K-877 0.2 and 0.2/0.4 mg: 57.4%/15.7%, 56.0%/19.3% and 63.6%/19.4%, respectively]. The study discontinuation rate was also similar across all dosing groups. K-877 reduced liver enzymes compared to placebo [ALT; placebo, K-877 0.2 and 0.2/0.4 mg: -0.9, -12.8 and -8.0 IU/L, respectively] and [γ-GT; -1.8, -42.6 and -40.4 IU/L, respectively]. Severe liver failure, severe renal failure or the rhabdomyolysis were not observed. Frequencies of AEs, such as CK increase and musculoskeletal and connective tissue disorders were comparable to those of placebo. Conclusions: K-877 significantly reduced TG concentrations in dyslipidemic patients on stable statin treatment, was well tolerated, and associated with reductions in liver enzymes. Thus K-877 has a favorable profile of efficacy and safety and may be useful to reduce residual risk in dyslipidemic patients.

Abstract 12384: Novel Approach to Residual Risk, K-877, a Potent and Selective PPAR-α Modulator (SPPARMα), Added-on to Pitavastatin in Japanese Patients With Dyslipidemia

Background: Residual cardiovascular risk remains despite intensive treatment with statins. K-877, a Selective PPAR-α Modulator (SPPARMα), has shown significant reductions in atherogenic lipids with fewer adverse effects than existing PPARα agonists. We hypothesized that combination with pitavastatin may provide further reduction in atherosclerotic risk, particularly in dyslipidemic patients with hypertriglyceridemia, than statin alone. Methods: This was a multi-center double-blind parallel-group study. A total of 188 patients with fasting high TG (≥200, &lt;1000 mg/dL) and non-HDL-C (≥150 mg/dL), treated with pitavastatin (once daily, 2 mg/day) were randomized to 12-week treatment groups; placebo (n=46), twice-daily K-877 0.1 (n=45), 0.2 (n=49) and 0.4 mg/day (n=48). The primary endpoint was the percentage change in TG from baseline and incidence of adverse drug reactions (ADRs) and adverse events (AEs). Results: Fasting TG reduction was as follows; placebo: -6.9%, K-877 0.1, 0.2 and 0.4 mg: -46.1%, -53.4% and -52.0%. All K-877 groups had significant reductions compared with placebo (P&lt;0.001). Fasting non-HDL-C reductions were -5.9% with placebo and -11.3, -14.1 and -13.3% with K-877 0.1, 0.2 and 0.4 mg, respectively. Significant increase in HDL-C, and reductions in VLDL-C, remnant lipoprotein cholesterol and apoCIII compared to placebo were found in all K-877 groups (P&lt;0.01). Although K-877 had a neutral effect on total LDL-C, HPLC analysis revealed a significant reduction of very small LDL-C with K-877 compared to the placebo group (P&lt;0.05). Moreover, the highest dose of K-877 (0.4 mg/day) showed significant reduction of fasting blood glucose and HOMA-R compared to placebo (P=0.003 and 0.019, respectively). The incidence of AEs and ADRs in the K-877 groups was similar to that in placebo group. The study discontinuation rates were similar across all groups. Conclusions: K-877 significantly improved plasma lipoprotein profiles in dyslipidemia patients on stable statin treatment without increasing the rates of AEs/ADRs. Thus K-877 may be a useful therapy to reduce residual cardiovascular risk in dyslipidemia.

Identification of Eupatilin from Artemisia argyi as a Selective PPARα Agonist Using Affinity Selection Ultrafiltration LC-MS.

Peroxisome proliferator-activated receptors (PPARs) are key nuclear receptors and therapeutic targets for the treatment of metabolic diseases through the regulation of insulin resistance, diabetes, and dyslipidemia. Although a few drugs that target PPARs have been approved, more diverse and novel PPAR ligands are necessary to improve the safety and efficacy of available drugs. To expedite the search for new natural agonists of PPARs, we developed a screening assay based on ultrafiltration liquid chromatography-mass spectrometry (LC-MS) that is compatible with complex samples such as dietary foods or botanical extracts. The known PPARα and/or PPARγ ligands resveratrol and rosiglitazone were used as positive controls to validate the developed method. When applied to the screening of an Artemisia argyi extract, eupatilin was identified as a selective PPARα ligand. A PPAR competitive binding assay based on FRET detection also confirmed eupatilin as a selective PPARα agonist exhibiting a binding affinity of 1.18 μM (IC50). Furthermore, eupatilin activation of the transcriptional activity of PPARα was confirmed using a cell-based transactivation assay. Thus, ultrafiltration LC-MS is a suitable assay for the identification of PPAR ligands in complex matrixes such as extracts of dietary foods and botanicals.

Selective targeting of PPARγ by the natural product chelerythrine with a unique binding mode and improved antidiabetic potency

Type 2 diabetes mellitus (T2DM) is a pervasive metabolic syndrome that is characterized by insulin resistance, hyperglycemia and dyslipidemia. As full agonists of PPARγ, thiazolidinedione (TZD) drugs elicit antidiabetic effects by targeting PPARγ but is accompanied by weight gain, fluid retention and cardiovascular risk associated with their transcriptional agonism potency. We here identify a natural product chelerythrine as a unique selective PPAR modulator (SPPARM) with a potent PPARγ binding activity but much less classical receptor transcriptional agonism. Structural analysis reveals that chelerythrine exhibits unique binding in parallel with H3 of PPARγ. Unlike TZDs, chelerythrine destabilizes helix 12, especially residue tyrosine 473, resulting in a loose configuration of AF-2 and a selective cofactor profile distinct from TZDs, leading to a differential target gene profile in adipogenesis in db/db diabetic mice. Moreover, chelerythrine improved insulin sensitivity by more potently blocking the phosphorylation of PPARγ by CDK5 compared to TZDs. These data fundamentally elucidate the mechanism by which chelerythrine retains the benefits of improving insulin sensitivity while reducing the adverse effects of TZDs, suggesting that the natural product chelerythrine is a very promising pharmacological agent by selectively targeting PPARγ for further development in the clinical treatment of insulin resistance.

P0180 Effect of pioglitazone on proliferation and apoptosis in human uterine leiomyosarcoma cells

Background SK-UT-1 cells, a human uterine leiomyosarcoma cell line, and human uterine smooth muscle cells (HutSMC) (controls) express the peroxisome proliferator-activated receptor γ (PPAR γ ). We investigated the effects of the PPAR γ agonist pioglitazone on the proliferation and induction of apoptosis in SK-UT-1 cells and HutSMC. Methods Cells were exposed to pioglitazone (10 or 25 μmol/l) in the presence or absence of the selective PPAR γ antagonist, GW 9226 (1 μmol/l). Cell proliferation was evaluated by WST-1 assay and cresyl violet staining. Western blot analysis was used to quantify the cleaved caspase-3, Bax, and Bad proteins. Cellular toxicity of pioglitazone was assessed by lactate dehydrogenase (LDH) release. Findings Pioglitazone increased the expression of the PPAR γ in SK-UT-1 cells and in HutSMC by a PPAR γ -dependent mechanism. Pioglitazone reduced cell proliferation in both quiescent and proliferating SK-UT-1 cells in concentration and time dependent fashion. These effects were partially mediated by PPAR γ . In SK-UT-1 cells, pioglitazone (25 μmol/l) activated caspase-3 and induced Bad, Bax, and p53 proteins. Higher levels of MEK and ERK and p-MEK and p-ERK were detected in quiescent SK-UT-1 cells than in quiescent HutSMC. Pioglitazone reduced p-ERK and p-MEK in SK-UT-1 cells in a time dependent manner, but did not alter p-MEK/MEK and p-ERK/ERK levels in HutSMC. Pioglitazone did not exert any cytotoxic effects in SK-UT-1 or HutSMC. Interpretation We demonstrate that pioglitazone reduces proliferation and promotes apoptosis in quiescent and proliferating leiomyosarcoma cells.

Peroxisome Proliferator-Activated Receptor-α Inhibition Protects Against Doxorubicin-Induced Cardiotoxicity in Mice.

Doxorubicin is an effective chemotherapeutic drug against a considerable number of malignancies. However, its toxic effects on myocardium are confirmed as major limit of utilization. PPAR-α is highly expressed in the heart, and its activation leads to an increased cardiac fatty acid oxidation and cardiomyocyte necrosis. This study was performed to adjust the hypothesis that PPAR-α receptor inhibition protects against doxorubicin-induced cardiac dysfunction in mice. Male Balb/c mice were used in this study. Left atria were isolated, and their contractility was measured in response to electrical field stimulation in a standard organ bath. PPAR-α activity was measured using specific PPAR-α antibody in an ELISA-based system coated with double-strand DNA containing PPAR-α response element sequence. Moreover, cardiac MDA and TNF-α levels were measured by ELISA method. Following incubation with doxorubicin (35µM), a significant reduction in atrial contractility was observed (P<0.001). Pretreatment of animals with a selective PPAR-α antagonist, GW6471, significantly improved doxorubicin-induced atrial dysfunction (P<0.001). Furthermore, pretreatment of the mice with a non-selective cannabinoid agonist, WIN55212-2, significantly decreased PPAR-α activity in cardiac tissue, subsequently leading to significant improvement in doxorubicin-induced atrial dysfunction (P<0.001). Also, GW6471 and WIN significantly reduced cardiac MDA and TNF-α levels compared with animals receiving doxorubicin (P<0.001). The study showed that inhibition of PPAR-α is associated with protection against doxorubicin-induced cardiotoxicity in mice, and cannabinoids can potentiate the protection by PPAR-α blockade. Moreover, PPAR-α may be considered as a target to prevent cardiotoxicity induced by doxorubicin in patients undergoing chemotherapy.

PPAR-α agonist elicits metabolically active brown adipocytes and weight loss in diet-induced obese mice.

Obesity is considered a public health problem worldwide. Fenofibrate, a selective peroxisome proliferator-activated receptor α (PPAR-α) agonist, elicits weight loss in animal models. This study aimed to examine the effects of fenofibrate on energy expenditure, body mass (BM) and gene expression of thermogenic factors in brown adipose tissue of diet-induced obese mice. Male C57BL/6 mice were fed a standard chow (SC; 10% lipids) diet or a high-fat (HF; 50% lipids) diet for 10 weeks. Afterwards, groups were subdivided as SC, SC-F, HF and HF-F (n = 10, each). Treatment with fenofibrate (100 mg kg(-1) BM mixed into the diet) lasted 5 weeks. Treated groups had reduced final BM compared with their counterparts (p < 0·05), explained by the increase in energy expenditure, CO2 production and O2 consumption after treatment with fenofibrate (p < 0·05). Similarly, genes involved in thermogenesis as PPAR-α, PPAR-γ coactivator 1α, nuclear respiratory factor 1, mitochondrial transcription factor A (Tfam), PR domain containing 16 (PRDM16), β-3 adrenergic receptor (β3-AR), bone morphogenetic protein 8B and uncoupling protein 1 were significantly expressed in brown adipocytes after the treatment (p < 0·05). All observations ensure that selective PPAR-α agonist can induce thermogenesis by increasing energy expenditure and enhancing the expression of genes involved in the thermogenic pathway. These results suggest fenofibrate as a coadjutant drug for the treatment of obesity.

Regulation of IGFBP-2 expression during fasting.

Insulin-like growth factor (IGF)-binding protein-2 (IGFBP-2), one of the most abundant circulating IGFBPs, is known to attenuate the biological action of IGF-1. Although the effect of IGFBP-2 in preventing metabolic disorders is well known, its regulatory mechanism remains unclear. In the present study, we demonstrated the transcriptional regulation of the Igfbp-2 gene by peroxisome-proliferator-activated receptor (PPAR) α in the liver. During fasting, both Igfbp-2 and PPARα expression levels were increased. Wy14643, a selective PPARα agonist, significantly induced Igfbp-2 gene expression in primary cultured hepatocytes. However, Igfbp-2 gene expression in Pparα null mice was not affected by fasting or Wy14643. In addition, through transient transfection and chromatin immunoprecipitation assay in fasted livers, we determined that PPARα bound to the putative PPAR-responsive element between −511 bp and −499 bp on the Igfbp-2 gene promoter, indicating that the Igfbp-2 gene transcription is activated directly by PPARα. To explore the role of PPARα in IGF-1 signalling, we treated primary cultured hepatocytes with Wy14643 and observed a decrease in the number of IGF-1 receptors (IGF-1Rs) and in Akt phosphorylation. No inhibition was observed in the hepatocytes isolated from Pparα null mice. These results suggest that PPARα controls IGF-1 signalling through the up-regulation of hepatic Igfbp-2 transcription during fasting and Wy14643 treatment.