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PubMed2002

Combination therapy with nateglinide and a thiazolidinedione improves glycemic control in type 2 diabetes.

OBJECTIVE: To compare the effects of monotherapy using nateglinide and the thiazolidinedione troglitazone with initial combination of the two agents on glycated hemoglobin (HbA(1c)) in patients with type 2 diabetes inadequately controlled by diet alone. RESEARCH DESIGN AND METHODS: This study consisted of a 28-week, double-blind, randomized, multicenter study that included a 4-week, single-blind, placebo, run-in period and a 24-week (shortened to 16 weeks), double-blind, active treatment period. RESULTS: At the 16-week end point, nateglinide 120 mg, troglitazone 600 mg, and the combination of the agents achieved statistically significant decreases in HbA(1c) in comparison with placebo and a baseline HbA(1c) of 8.1-8.4% (P < 0.001). The reductions in HbA(1c) were similar in the nateglinide (0.6%) and troglitazone (0.8%) monotherapy groups. The reduction in HbA(1c) (1.7%) was greatest in the combination group; 79% of patients in the combination group achieved HbA(1c) levels of <7%. The combination group had a higher number of adverse events, primarily due to an increased incidence of mild hypoglycemia in this treatment group. CONCLUSIONS: Nateglinide and troglitazone are equally effective in decreasing HbA(1c) levels. However, these reductions from baseline HbA(1c) values of >8% are not adequate to achieve HbA(1c) levels of <7%. In contrast, the combination of nateglinide and of a thiazolidinedione shows an additive effect that is highly effective in reducing HbA(1c) levels to the target of <7% in 66% of patients, from a baseline HbA(1c) that is just above 8%.

Adult↗
PubMed2005

The effect of PPARgamma ligands on UV- or chemically-induced carcinogenesis in mouse skin.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand activated transcription factor. There have been suggestions that PPARgamma ligands may have utility in preventing tumor development in rodent mammary glands and colon. The recent finding that mice lacking one allele of the PPARgamma gene were significantly more susceptible to 7,12-dimethylbenz[a]anthracene (DMBA)-induced skin carcinogenesis compared to wild-type mice highlights mouse skin as another potential organ in which PPARgamma ligands may be effective as chemopreventive agents. In this study, we assessed the effect of two PPARgamma ligands (rosiglitazone and troglitazone) on UV and DMBA/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse skin carcinogenesis, two of the most commonly used mouse skin carcinogenesis models. Unexpectedly, neither rosiglitazone (dietary 200 ppm) nor troglitazone (topical 100 microg) significantly inhibited UV-induced skin tumor development in SKH-1 hairless mice. Likewise, dietary rosiglitazone did not statistically significantly inhibit DMBA/TPA-induced skin tumor development. Interestingly, dietary troglitazone significantly inhibited basal level keratinocyte proliferation as shown by 5-bromo-2'-deoxyuridine (BrdU) labeling, but it had no effect on TPA-induced epidermal cell proliferation. Northern blot analysis showed that PPARgamma expression was extremely low in normal mouse epidermis and was virtually undetectable in skin tumors. Collectively, our data suggest that PPARgamma ligands may not be useful in the prevention of chemically or UV-induced skin tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2002

Biochemical correlates of thiazolidinedione-induced adipocyte differentiation by high-resolution magic angle spinning NMR spectroscopy.

Thiazolidinediones, a class of synthetic ligands to the peroxisome proliferator-activated receptor-gamma, induce terminal adipocyte differentiation of 3T3 F442A cells, and have already been used as alternative therapeutic agents for the treatment of liposarcoma in clinical trials. The biochemical changes occurring in the 3T3 F442A cell line and well-differentiated liposarcoma following induction of adipocyte differentiation with the thiazolidinedione troglitazone were measured using high-resolution magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. 3T3 F442A cell differentiation was characterized by a large accumulation of intracellular triglyceride and withdrawal from the cell cycle. Phosphatidylcholine (PTC), phosphocholine (PC), myo-inositol, and glycerol were found to be possible biochemical markers for adipocyte differentiation induced by thiazolidenediones. The molar ratio of PTC to PC increased fourfold in differentiated 3T3 F442A cells compared to undifferentiated cells, suggesting a substantial increase in CTP:phosphocholine cytidylyltransferase activity with differentiation. A 2.8-fold increase in the PTC:PC ratio was observed in the lipoma-like well-differentiated liposarcoma of three patients who were treated with troglitazone when compared to liposarcoma from patients not treated with this drug. Thus, this ratio may be an NMR-detectable marker of troglitazone efficacy and response to differentiation therapy for liposarcoma.

3T3 Cells↗
PubMed2003

Suppression of experimental crescentic glomerulonephritis by peroxisome proliferator-activated receptor (PPAR)gamma activators.

BACKGROUND: It has been recently reported that peroxisome proliferator-activated receptors (PPARs)gamma exist in various tissues and that they exibit anti-inflammatory effects. METHODS: We investigated the effects of PPARgamma activators on the development of crescentic glomerulonephritis. Crescentic glomerulonephritis was induced by the injection of rabbit anti-rat glomerular basement membrane antibody in WKY rats. RESULTS: Administration of troglitazone suppressed urinary protein excretion and crescent formation as indicated by crescent scores. Pioglitazone, a PPARgamma activator, mimicked the effect of troglitazone, but bezafibrate, a PPARalpha-activator, did not. Immunohistology revealed that troglitazone and pioglitazone inhibited the infiltration of ED-1-positive monocyte/macrophages and CD8-positive cells into glomeruli. CONCLUSIONS: In the present study, we demonstrated that PPARgamma activators exert antinephritic effects by suppressing the recruitment of inflammatory cells via a PPARgamma-dependent mechanism.

Animals↗
PubMed2006

A Ligand for peroxisome proliferator-activated receptor gamma inhibits human cholangiocarcinoma cell growth: potential molecular targeting strategy for cholangioma.

Peroxisome proliferator-activated receptor gamma (PPARgamma) ligands have an antitumor effect. The aim of this study was to clarify whether PPARgamma ligands could inhibit the growth of human cholangiocarcinoma cells. PPAR( expression in HuH-28 and HuCCT1 cells (intrahepatic bile duct carcinoma) was determined using the reverse transcription-polymerase chain reaction (RT-PCR). Expression of PPARgamma mRNA was detected in both cell lines. Activation of PPARgamma by troglitazone caused marked growth inhibition in a time- and dose-dependent manner. Troglitazone inhibited the growth of human cholangiocarcinoma cell lines by inducing apoptosis and by cell cycle regulation (G1 arrest), and this was associated with caspase 3 and caspase 9 activation. Thus, molecular targeting with troglitazone, a nuclear receptor ligand, may be a promising strategy for treating cholangiocarcinoma, although a delivery system needs to be established.

Antineoplastic Agents↗
PubMed2006

Differences in hepatotoxicity and gene expression profiles by anti-diabetic PPAR gamma agonists on rat primary hepatocytes and human HepG2 cells.

Agonists of peroxisome proliferator-activated receptor gamma (PPARgamma) are a new class of oral drugs designed to treat insulin-resistant diabetes (i.e., type 2 diabetes). However, troglitazone, the first compound in the class approved by the US Food and Drug Administration (FDA) in 1997 was found to be hepatotoxic and was withdrawn from the market after reports of severe liver failure. The mechanism of PPAR gamma agonist-induced hepatotoxicity remains unknown. In this study, we examined the hepatotoxic effects of five PPAR gamma agonists (ciglitazone, pioglitazone, rosiglitazone, troglitazone, and JTT-501) on rat primary hepatocytes and human HepG2 cells. We also compared the gene expression profiles of rat primary hepatocytes after exposure to PPAR gamma agonists by using the Rat Genome Survey Microarray system from Applied Biosystems in order to understand the mechanisms of hepatotoxicities induced by PPARgamma agonists. Consistent with the hepatotoxicity data, our results demonstrate that the gene expression profiles affected by troglitazone and ciglitazone can be clearly distinguished from those by pioglitazone and rosiglitazone. Genes that are differentially expressed between the more toxic troglitazone/ciglitazone group and the less toxic rosiglitazone/pioglitazone group are involved in necrotic, apoptotic, and cell proliferative pathways. The five compounds were also clustered based on a set of molecular descriptors. The clustering based on chemical structural information is in good agreement with the clustering of compounds based on cytotoxicity or gene expression data, indicating a strong relationship between chemical structure and biological endpoints. Our work suggests that microarray analysis together with toxicological observations can be used to rank drugs for hepatotoxicity and to evaluate the safety of new compounds.

Animals↗
PubMed2004

Health-related quality of life in women with polycystic ovary syndrome, a self-administered questionnaire, was validated.

OBJECTIVE: We examined the measurement properties of a questionnaire (PCOSQ) measuring health-related quality of life (HRQOL) in women with the polycystic ovary syndrome (PCOS). STUDY DESIGN: This multicenter prospective randomized placebo-controlled blinded study enrolled 393 patients with PCOS at tertiary care sites. Participants were randomized to placebo or troglitazone (150 mg/d, 300 mg/d, or 600 mg/d). At baseline (n=393) and after 44 weeks of treatment (n=284) the proportion of normal menstrual cycles, the free testosterone (T) level, four objective measures of facial hair growth (hair density and hair growth rate by photography, and hair diameter and hair growth rate using plucked hairs), and a subjective assessment of the degree of hirsutism, the modified Ferriman-Gallwey (F-G) score, were determined. At both visits, patients also completed the PCOSQ. Since the trial was conducted, troglitazone has been removed from the market because of toxic effects. The PCOSQ includes 26 questions (items) that address five areas of concern (domains), including emotions, body hair, body weight, fertility, and menstruation rated on a seven-point scales in which lower scores denote higher degrees of patient concern and a lower HRQOL. RESULTS: Cronbach's alpha was >0.7 for four of five domains. Factor analysis provided moderate to strong support for the five-domain structure of the PCOSQ. Cross-sectional correlations were weak with all measures but the F-G score and hair growth (r=-.46, P < .01). The change in the F-G score showed a statistically significant (P < .01) correlation with changes in PCOSQ hair growth (r=-.22), weight (r=-.17), infertility (r=-.20), and menstruation (r=-.20). Changes in the proportion of normal menstrual cycles correlated with change in the infertility domain (r=.14, P < .03) and with the change in the menstruation domain (r=.31, P < .001). The PCOSQ proved as responsive as the F-G, and more responsive than the objective measures of hair growth, to effects of troglitazone. CONCLUSIONS: Our data provides some support for the discriminative and longitudinal validity, and appreciable support for the responsiveness, of the PCOSQ.

Adult↗
PubMed2005

Effect of ecdysterone on glucose metabolism in vitro.

The aims of this study was to investigate whether ecdysterone is able to exert glucose-lowering effect on hepatocytes or stimulate the secretion of insulin. HepG2 cell line was used for glucose consumption (GC) studies. At moderate high glucose concentration (11.1 mmol/L), GC of HepG2 cells was increased by 44% to 77% with ecdysterone 1 x 10(-6) to 1 x 10(-4) mol/L, which was comparable to that with 1 x 10(-3) mol/L metformin. The glucose-lowering effect of ecdysterone decreased as the glucose concentration of medium increased. The maximal potency was reached in the presence of 5.5 mmol/L glucose, and the effect was disappeared as the glucose consumption was increased to 22.2 mmol/L. This effect was independent on insulin concentration, which was similar to that of metformin and was different from that of troglitazone, whose glucose-lowering effect was insulin-dependent. Troglitazone had a better antihyperglycemic potency than metformin when insulin was added. Simultaneously, a significant toxicity of troglitazone to HepG2 cells was observed. betaTC3 cells were not stimulated by ecdysterone, that is, no secretogogue effect of ecdysterone was observed. The results indicate that ecdysterone is able to exert the glucose-lowering effect in hepatocytes which is insulin-independent, but has no effect on insulin release.

Animals↗
PubMed2000

Dissociation between the Ca(2+) signal and tube formation induced by vascular endothelial growth factor in bovine aortic endothelial cells.

The correlation between the intracellular Ca(2+) signal and the tube formation in collagen gels induced by vascular endothelial cell growth factor (VEGF) was investigated using cultured bovine aortic endothelial cells. The VEGF-induced sustained elevation of cytosolic Ca(2+) concentration ([Ca(2+)](i)) was similarly inhibited by 10 microM 1-¿beta-[3-(4-methoxyphenyl)propyl]-4-methoxyphenethyl¿-1H-imidazole hydrochloride (SKF 96365) and 10 microM troglitazone. However, 10 microM diltiazem had no effect. The basal tube formation obtained with 1% serum was augmented twofold by 100 ng/ml VEGF. SKF 96365 (0. 1-10 microM) inhibited the VEGF-induced and basal tube formation, while 10 microM troglitazone or 10 microM diltiazem had no effect. The proliferation of endothelial cells was markedly inhibited by SKF 96365 but only slightly by troglitazone and diltiazem. The inhibition of tube formation by three Ca(2+) entry blockers thus correlated with the inhibition of cell proliferation. The [Ca(2+)](i) elevation is thus not a prerequisite for VEGF to induce tube formation.

Animals↗
PubMed1999

PPARgamma activators down-regulate the expression of PPARgamma in 3T3-L1 adipocytes.

Transcriptional activation of PPARgamma by the anti-diabetic compound troglitazone enhances the rate of 3T3-L1 adipocyte differentiation. In this study, we examined the effects of troglitazone, a specific PPARgamma ligand, on the expression of PPARgamma during and after 3T3-L1 adipocyte differentiation. Troglitazone treatment caused a significant decrease in PPARgamma proteins and DNA binding activity. This reduction was associated with a similar decrease in transcription of PPARgamma mRNA. These data suggest that in 3T3-L1 cells, the expression of PPARgamma is auto-regulated.

3T3 Cells↗
PubMed2001

Bezafibrate attenuates the overexpression of plasminogen activator inhibitor-1 messenger RNA by a combination of mono-unsaturated fatty acid and insulin in hepG2 cells.

The effects of bezafibrate (PPAR alpha activator) and troglitazone (PPAR gamma activator) on the expression of plasminogen activator inhibitor type-1 (PAI-1) in HepG2 cells were investigated. Exposure of the cells for 24 hours to either oleic acid or insulin showed no obvious effects on PAI-1 synthesis, whereas the combination of the two agents induced a 2.3-fold increase in PAI-1 synthesis, which was accompanied by a 3-fold increase in both the 2.2 kb and 3.2 kb forms of PAI-1 mRNA. This up-regulation of PAI-1 synthesis was attenuated by bezafibrate in a dose-dependent manner (1-100 microM) with 30% reversal at 100 microM. In contrast, troglitazone further stimulated PAI-1 synthesis to 140% of the level obtained in the presence of both oleic acid and insulin. This attenuation by bezafibrate and enhancement by troglitazone required the presence of both oleic acid and insulin. It is interesting that PAI-1 expression was affected so differently by these two PPAR activators.

Bezafibrate↗
PubMed2000

Peroxisome proliferator-activated receptor gamma1 (PPARgamma1) expresses in rat mesangial cells and PPARgamma agonists modulate its differentiation.

Thiazolidinediones, synthetic ligands of peroxisome proliferator-activated receptor gamma (PPARgamma), are reported to have direct beneficial effects on diabetic nephropathy without lowering blood glucose levels in human and rat. We hypothesized these effects of thiazolidinediones might be derived from PPARgamma activation of kidney cells, and we examined the expression of PPARgamma and the effect of PPARgamma agonists, troglitazone and 15-deoxy-delta-prostaglandin J2 (15d-PGJ2), on the proliferation and differentiation in rat mesangial cells. A single band of mRNA of PPARgamma with a predicted size was detected in reverse transcription-polymerase chain reaction products (RT-PCR) using established PCR probes of PPARgamma. PPARgamma protein in rat mesangial cells was identified as PPARgamma1 by a Western blot. In a gel mobility shift assay to determine a binding activity of PPARgamma, the nuclear protein from rat mesangial cells bound to a (32)P-labeled oligonucleotide probe, including PPAR response elements. A synthetic and a natural ligand of PPARgamma, troglitazone and 15d-PGJ2, decreased thymidine incorporation in a dose dependent manner. After 7 days incubation with troglitazone and 15d-PGJ2, alpha-smooth muscle actin expression, a marker of mesangial cell de-differentiation, was decreased significantly compared to that of control. These results indicate that PPARgamma1 is expressing in rat mesangial cells, and PPARgamma1 activation with its agonists modulates the proliferation and differentiation of cultured rat mesangial cells.

Animals↗
PubMed2003

Hepatotoxicity of the thiazolidinediones.

Troglitazone, the first of the thiazolidinediones, caused severe hepatotoxicity including liver failure in several patients. It appears, however, that the thiazolidinediones as a class are not as hepatotoxic as troglitazone. Comparative data at comparable dates of usage indicate that pioglitazone and rosiglitazone are not significant hepatotoxins. This is further supported by experimental data that demonstrate that troglitazone, alone among the thiazolidinediones, is toxic in hepatocyte cell culture. All of the thiazolidinediones cause ALT elevations; however, ALT monitoring for hepatotoxicity does not appear to prevent serious liver disease nor reduce patient risk.

Chemical and Drug Induced Liver Injury↗
PubMed2000

Effects of peroxisome proliferator-activated receptor-alpha and -gamma agonist, JTT-501, on diabetic complications in Zucker diabetic fatty rats.

This study has investigated the effects of JTT-501, a peroxisome proliferator-activated receptor (PPAR)-alpha and PPAR-gamma agonist, on the pathogenesis of diabetic complications in the Zucker diabetic fatty (ZDF) rats, a model of type 2 diabetes. Comparison is made with troglitazone, a PPAR-gamma agonist. The ZDF rats exhibited hyperglycaemia and hyperlipidaemia, and developed diabetic complications such as cataract, nephropathy, and neuropathy. Treatment with JTT-501 from the prediabetic stage controlled glycaemia and lipidaemia, and prevented the development of diabetic complications. Troglitazone was less effective in controlling serum cholesterol and neuropathy. ZDF rats developed diabetic osteopenia with reduced bone turnover, and this was prevented by JTT-501 and troglitazone, possibly mediated by increased bone turnover and bone formation. Since JTT-501 controlled glycaemia and lipidaemia in ZDF rats and prevented several diabetic complications, it is suggested that treatment with JTT-501, which activates both PPAR-alpha and PPAR-gamma, could provide a valuable therapeutic approach against diabetic complications in type 2 diabetes.

Absorptiometry, Photon↗
PubMed2000

Effects of ligand activation of peroxisome proliferator-activated receptor gamma in human prostate cancer.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear hormone receptor that plays a key role in the differentiation of adipocytes. Activation of this receptor in liposarcomas and breast and colon cancer cells also induces cell growth inhibition and differentiation. In the present study, we show that PPARgamma is expressed in human prostate adenocarcinomas and cell lines derived from these tumors. Activation of this receptor with specific ligands exerts an inhibitory effect on the growth of prostate cancer cell lines. Further, we show that prostate cancer and cell lines do not have intragenic mutations in the PPARgamma gene, although 40% of the informative tumors have hemizygous deletions of this gene. Based on our preclinical data, we conducted a phase II clinical study in patients with advanced prostate cancer using troglitazone, a PPARgamma ligand used for the treatment of type 2 diabetes. Forty-one men with histologically confirmed prostate cancer and no symptomatic metastatic disease were treated orally with troglitazone. An unexpectedly high incidence of prolonged stabilization of prostate-specific antigen was seen in patients treated with troglitazone. In addition, one patient had a dramatic decrease in serum prostate-specific antigen to nearly undetectable levels. These data suggest that PPARgamma may serve as a biological modifier in human prostate cancer and its therapeutic potential in this disease should be further investigated.

Aged↗
PubMed2000

Effects of a low-energy diet and an insulin-sensitizing agent on ambulatory blood pressure in overweight hypertensive patients.

OBJECTIVE: To clarify the role of insulin resistance and hyperinsulinaemia in the pathogenesis of obesity-related hypertension. DESIGN: An open study comparing the effects of weight reduction by low-energy diet and treatment with troglitazone, an insulin-sensitizing agent. SETTING: A tertiary teaching hospital. PATIENTS: Thirty overweight hypertensive patients (15 men and 15 women, mean age 61 years, mean body mass index 29.1 kg/m2). INTERVENTIONS: Fifteen patients were assigned to a weight-reduction programme by low-energy diet (3360 kJ/day) for 3 weeks; the remaining 15 patients were treated with troglitazone (400 mg/day) for 8 weeks. MAIN OUTCOME MEASURES: Casual and ambulatory blood pressures, glucose and lipid metabolism, and insulin sensitivity. RESULTS: The baseline values of body mass index, fasting and post-glucose plasma insulin, and casual and ambulatory blood pressures were comparable between the two groups. Weight reduction (4.1 +/- 0.3 kg, mean +/- SEM) was associated with significant decreases in plasma insulin, blood glucose, homeostasis model assessment (HOMA) insulin resistance index, serum triglyceride, casual blood pressure (7.7 +/- 2.3/ 3.9 +/- 1.4 mmHg) and 24 h blood pressure (8.3 +/- 1.9/ 4.3 +/- 1.1 mmHg). Treatment with troglitazone caused comparable decreases in the metabolic parameters and HOMA index, but did not change casual or 24 h blood pressure (0.8 +/- 3.4/0.8 +/- 2.1 and 1.5 +/- 2.4/ 1.0 +/- 1.9 mmHg, respectively). CONCLUSIONS: Insulin resistance/hyperinsulinaemia may not have an important role in the pathogenesis of obesity-related hypertension. The antihypertensive effect of weight reduction seems to be mediated mainly by other mechanisms.

Adult↗
PubMed1999

Peroxisome proliferator-activated receptor gamma induces growth arrest and differentiation markers of human colon cancer cells.

Peroxisome proliferator-activated receptor gamma (PPAR gamma), one of the nuclear receptors expressed in adipose tissue, plays an important role in adipocyte differentiation. In this study, we investigated the expression of PPAR gamma and its role in cellular growth and differentiation in six colon cancer cell lines: HT-29, CaCo-2, SW-480, DLD-1, LoVo, and T-84. All six expressed PPAR gamma mRNA and protein, shown respectively on northern and western blot analyses. Luciferase assay in HT-29 cells, which strongly express PPAR gamma, showed that troglitazone, a selective ligand for PPAR gamma, transactivated the transcription of a peroxisome proliferator response element (PPRE)-driven promoter. Furthermore, troglitazone caused a marked decrease in [3H]thymidine incorporation and G1 cell-cycle arrest determined by flow cytometry. Finally, troglitazone induced expression of mRNAs for villin and intestinal alkaline phosphatase, markers for enterocyte differentiation. In conclusion, human colon cancer cells express PPAR gamma, the ligands of which inhibit cell growth and induce differentiation markers.

Calcium-Binding Proteins↗
PubMed2003

Peroxisome proliferator-activated receptor ligands affect growth-related gene expression in human leukemic cells.

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors. Three subtypes of PPARs (alpha, beta, and gamma) have been identified in different tissues. PPAR alpha and PPAR gamma ligands inhibit cell proliferation and induce differentiation in several human cell models. We demonstrated that both PPAR alpha (clofibrate and ciprofibrate) and PPAR gamma ligands (troglitazone and 15 deoxy-prostaglandin J2, 15d-PGJ2) inhibited growth, induced the onset of monocytic-like differentiation, and increased the proportion of G0/G1 cells in the HL-60 leukemic cell line. Moreover, 3 days after the treatment with 2.5 microM 15d-PGJ2, an increase in sub-G0/G1 population occurred, compatible with an induction of programmed cell death. To clarify the mechanisms involved in HL-60 growth inhibition due to the effects of PPAR ligands, we investigated their action on the expression of some genes involved in the control of cell proliferation, differentiation, and cell cycle progression such as c-myc, c-myb, and cyclin D1 and D2. Clofibrate (50 microM), ciprofibrate (50 microM), and 15d-PGJ2 (2.5 microM) inhibited c-myb and cyclin D2 expression, whereas they did not affect c-myc and cyclin D1 expression. Only troglitazone (5 microM) decreased c-myc mRNA and protein levels, besides decreasing c-myb and cyclin D2. The down-regulations of c-myb and cyclin D2 expression represent the first evidence of the inhibitory effect exerted by PPAR ligands on these genes. Moreover, the inhibition of c-myc expression by troglitazone may depend on a PPAR-independent mechanism.

Antineoplastic Agents↗