Short-term treatment with a 2-carba analog of cyclic phosphatidic acid induces lowering of plasma cholesterol levels in ApoE-deficient mice.

Plasma cholesterol levels are associated with an increased risk of developing atherosclerosis. An elevated low-density lipoprotein cholesterol (LDL-C) level is a hallmark of hypercholesterolemia in metabolic syndrome. Our previous study suggested that when acetylated LDL (AC-LDL) was co-applied with a PPARγ agonist, rosiglitazone (ROSI), many oil red O-positive macrophages could be observed. However, addition of cyclic phosphatidic acid (cPA) to ROSI-stimulated macrophages completely abolished oil red O-stained cells, indicating that cPA inhibits PPARγ-regulated AC-LDL uptake. This study aimed to determine whether metabolically stabilized cPA, in the form of a carba-derivative of cPA (2ccPA), could reduce plasma cholesterol levels and affect the expression of genes related to atherosclerosis in apolipoprotein E-knockout (apoE(-/-)) mice. 2ccPA reduced LDL-C levels in these mice (n = 3) from 460 to 330 mg/ml, from 420 to 350 mg/ml, and 420 to 281 mg/ml under a western-type diet. 2ccPA also reduced expression of lipid metabolism-related genes, cytokines, and chemokines in ApoE-deficient mice on a high-fat diet. Taken together, these results suggest that 2ccPA governs anti-atherogenic activities in the carotid arteries of apoE-deficient mice.

Higher expression of peroxisome proliferator-activated receptor γ or its activation by agonist thiazolidinedione-rosiglitazone promotes bladder cancer cell migration and invasion.

OBJECTIVE: To investigate the role of peroxisome proliferator-activated receptor γ (PPARγ) in bladder cancer (BCa) progression. MATERIALS AND METHODS: The gene copy number of PPARγ in human BCa tissue samples was analyzed by fluorescence in situ hybridization. The migration and invasive ability of human BCa cell lines with different PPARγ expression levels or treated with thiazolidinedione-rosiglitazone, a PPARγ agonist and an antidiabetic drug, were investigated. RESULTS: PPARγ amplification was increased dramatically in BCa tissue compared with normal urothelium (38.1% vs 4.3%, P = .0082) and in tumors with lymph node metastasis compared with those without metastasis (75.0% vs 15.4%, P = .0176). The human BCa cell line 5637 with strong PPARγ expression demonstrated a greater ability for cell migration and invasion than the UMUC-3 cell line with weak PPARγ expression. Knocking down PPARγ in BCa 5637 cells led to decreased cell migration, and activation of PPARγ with thiazolidinedione-rosiglitazone promoted their migration and invasive ability. CONCLUSION: PPARγ amplification in BCa could play an important role in BCa cell migration and invasion. Alteration of PPARγ expression by PPARγ-small interfering ribonucleic acid or activation by its agonist rosiglitazone, a diabetic thiazolidinedione drug, could lead to alternation of BCa cell migration and invasion.

Synergistic interactions between heregulin and peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist in breast cancer cells.

Here, we demonstrate that troglitazone (Rezulin), a peroxisome proliferator-activated receptor agonist, acted in synergy with heregulin to induce massive cell death in breast cancer cells. Although the combination of heregulin and troglitazone (HRG/TGZ) induced both apoptosis and necrosis, the main mode of cell death was caspase-independent and occurred via necrosis. This combination increased generation of superoxide in mitochondria, which in turn destabilized mitochondria potential. Pretreatment with N-acetyl-l-cysteine and catalase expression ameliorated cell death induced by the combination treatment, indicating a role of oxidative stress in mediating HRG/TGZ-induced cell death. Notably, pretreatment with pyruvate significantly prevented the cell death, suggesting a potential mechanistic link between metabolic stress and HRG/TGZ-induced cell death. The activation of the HRG signaling axis has been considered as a poor prognostic factor in breast cancer and confers resistance to gefitinib (Iressa) and tamoxifen. However, our data presented here paradoxically suggest that HRG expression can actually be beneficial when it comes to treating breast cancer with peroxisome proliferator-activated receptor-γ ligands. Taken together, the combination of HRG and TGZ may provide a basis for the development of a novel strategy in the treatment of apoptosis-resistant and/or hormone-refractory breast cancer.

Troglitazone is an estrogen-related receptor alpha and gamma inverse agonist.

As a ligand for peroxisome proliferators-activated receptor gamma (PPAR gamma), troglitazone inhibits cell growth by mechanisms besides activating PPAR gamma. In this study, we found that troglitazone interfered with the interactions between estrogen-related receptor alpha and gamma (ERR alpha and ERR gamma) and their coactivator PPAR gamma coactivator-1 alpha (PGC-1 alpha) functioning as an inverse agonist. Additionally, troglitazone suppressed the expressions of PGC-1 alpha and its related member PGC-1 beta which are key regulators of mitochondrial function. Consequently, troglitazone reduced mitochondrial mass and suppressed the expressions of superoxide dismutases to elevate reactive oxygen species (ROS) production. The increase in ROS in turn induced the expression of cell cycle inhibitor p21(WAF1). We therefore propose that ERR alpha and ERR gamma are alternative targets of troglitazone important for mediating its growth suppressive effect.

Effects of peroxisome proliferator-activated receptor gamma agonists on Na+ transport and activity of the kinase SGK1 in epithelial cells from lung and kidney.

BACKGROUND AND PURPOSE: Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists, such as rosiglitazone and pioglitazone, sensitize cells to insulin, and are therefore used to treat type 2 diabetes. However, in some patients, these drugs induce oedema, and the present study tests the hypothesis that this side effect reflects serum and glucocorticoid-inducible kinase 1 (SGK1)-dependent enhancement of epithelia Na(+) absorption. EXPERIMENTAL APPROACH: Na(+) absorbing epithelial cells (H441 cells, mpkCCD cells) on permeable membranes were mounted in Ussing chambers, and the effects of rosiglitazone (2 microM) and pioglitazone (10 microM) on transepithelial Na(+) absorption were quantified electrometrically. Changes in SGK1 activity were assessed by monitoring phosphorylation of residues within an endogenous protein. KEY RESULTS: Both cell types absorbed Na(+) via an electrogenic process that was enhanced by insulin. In mpkCCD cells, this stimulation of Na(+) transport was associated with increased activity of SGK1, whereas insulin regulated Na(+) transport in H441 cells through a mechanism that did not involve activation of this kinase. Rosiglitazone and pioglitazone had no discernible effect on transepithelial Na(+) absorption in unstimulated or insulin-stimulated cells and failed to alter cellular SGK1 activity. CONCLUSIONS AND IMPLICATIONS: Our results do not support the view that PPARgamma agonists stimulate epithelial Na(+) absorption or alter the control of cellular SGK1 activity. It is therefore likely that other mechanisms are involved in PPARgamma-mediated fluid retention, and a better understanding of these mechanisms may help with the identification of patients likely to develop oedema or heart failure when treated with these drugs.

Agonistas PPAR (Rosiglitazona, Bezafibrato e Fenofibrato) e alterações bioquímicas e estruturais em órgãos-alvo de camundongos C57BL/6 alimentados com dieta hiperlipídica rica em sacarose / PPAR agonists (Rosiglitazone, Bezafibrate and Fenofibrate) and biochemical and structural alterations in organs target of C57BL/6 mice fed high-fat high sucrose chow

Este trabalho teve o objetivo de estudar o efeito de medicamentos com diferentes ações agonista PPAR (rosiglitazona, fenofibrato e bezafibrato) sobre o perfil lipídico, glicídico e alterações na massa corporal e morfologia do tecido adiposo e pancreático em modelo de diabetes e sobrepeso induzido por dieta. Camundongos C57BL/6 (2 meses de idade) foram alimentados com dieta padrão (SC, n=10) ou dieta hiperlipídica rica em sacarose (HFHS, n=40) por 6 semanas. Logo após, os animais HFHS foram subdividos em: HFHS não tratado e HFHS tratado com rosiglitazona (HFHS-Ro), fenofibrato (HFHS-Fe) ou bezafibrato (HFHS-BZ) (5 semanas). Os camundongos alimentados com dieta HFHS apresentaram maior glicemia e insulina de jejum (+33% e +138%, respectivamente), intolerância à glicose, resistência à insulina, aumento da massa corporal (MC) (+20%) e adiposidade, hipertrofia de adipócitos e redução da imunocoloração para adiponectina no tecido adiposo. No pâncreas houve aumento da massa (+28%), acúmulo de gordura (+700%), hipertrofia da ilhota (+38%) e redução da imunocoloração para GLUT-2 (-60%). A rosiglitazona diminuiu a glicemia e insulina de jejum, porém induziu o ganho de MC e hipertrofia cardíaca. O fenofibrato estabilizou a MC, enquanto o bezafibrato levou a perda de MC. Apenas o bezafibrato impediu a hipertrofia da ilhota. A imunocoloração para GLUT-2 foi aumentada por todos os medicamentos, e não houve alterações na imunocoloração para o PPARalfa. Sinais morfológicos de pancreatite foram vistos no grupo HFHS-Fe, apesar dos níveis normais de amilase e lipase séricos. A rosiglitazona exacerbou a infiltração intrapancreática de gordura (+75% vs. HFHS), e o bezafibrato aumentou a imunocoloração para o PPARbeta/delta nas ilhotas pancreáticas. Em conclusão, o bezafibrato apresentou um efeito mais amplo sobre as alterações metabólicas, morfológicas e biométricas decorrentes da dieta HFHS, sugerindo que a inibição das três isoformas do PPAR seria melhor do que a inibição...

This work aimed to evaluate the effect of peroxisome proliferator-activated receptor (PPAR) agonists (rosiglitazone, fenofibrate and bezafibrate) on lipid and glucose metabolism, body mass, and adipose and pancreatic tissue morphology in a model of diet-induced type 2 diabetes and overweight in mice. Two-month-old male C57BL/6 mice were fed a standard chow (SC, n=10) or a high-fat high-sucrose chow (HFHS, n=40) for 6 weeks, and then HFHS-fed mice were subdivided by treatment: untreated HFHS and HFHS treated with rosiglitazone (HFHS-Ro), fenofibrate (HFHS-Fe), or bezafibrate (HFHS-Bz) (5 weeks on medication). HFHS-fed mice have altered fasting glucose (+33%) and insulin (+138%), GI, IR, increased body mass (+20%) and fat pad weight, adipocyte hypertrophy, and decreased adiponectin immunostain. They also presented increased pancreatic (+28%) mass, intrapancreatic fat (+700%), islet hypertrophy (+38%), and decreased GLUT-2 immunostain (-60%). Rosiglitazone reduced fasting glucose and insulin but induced weight gain and heart hypertrophy. Fenofibrate impaired body mass gain, while bezafibrate induced weight loss. Only bezafibrate impaired islet hypertrophy. GLUT-2 immunostain was improved by all treatments, and there were no alterations in PPAR-alfa stain. There were morphological signs of pancreatitis in fenofibrate-treated mice, although there was no alteration in serum amylase and lipase. Rosiglitazone exacerbated pancreatic fat infiltration (+75% vs. HFHS group), and bezafibrate increased PPAR-beta expression in pancreatic islets. In conclusion, bezafibrate showed a wider range of action on metabolic, morphologic, and biometric alterations due to HFHS intake, suggesting that inhibiting the three PPAR isoforms is better than inhititing each isoform alone. Rosiglitazone exacerbated body mass gain, pancreatic fat infiltration and induced heart hyperthophy as well, thus, precaution has to be taken in prescribing rosiglitazone to obese patients.

Netoglitazone is a PPAR-gamma ligand with selective effects on bone and fat.

Thiazolidinediones are effective anti-diabetic drugs that improve insulin sensitivity through the activation of the nuclear receptor and adipocyte-specific transcription factor, peroxisome proliferator-activated receptor gamma (PPAR-gamma). Recent evidence suggests that PPAR-gamma also controls bone cell development and bone homeostasis. In mice, PPAR-gamma insufficiency results in increased bone mass, whereas administration of the specific PPAR-gamma agonist rosiglitazone leads to bone loss and increased bone marrow adiposity. Although the pro-adipocytic and anti-osteoblastic activities of PPAR-gamma can be separated in vitro using ligands with distinct chemical structures, little evidence exists supporting this functional separation in vivo. Netoglitazone (MCC-555, RWJ-241947) is a thiazolidinedione, which acts as either a full or partial PPAR-gamma agonist, or antagonist, in a cell type specific manner. In this study, the pro-adipocytic and anti-osteoblastic activities of netoglitazone were evaluated in vitro, using both U-33/gamma2 cells as a model of marrow mesenchymal cell differentiation under the control of PPAR-gamma2 and primary bone marrow cultures, and in vivo in C57BL/6 mice. In vitro, netoglitazone induced adipocyte and inhibited osteoblast formation in a PPAR-gamma2-dependent manner; however, it was 100-fold less effective than rosiglitazone. In vivo, the administration of netoglitazone at an effective hyperglycemic dose (10 microg/g body weight/day) did not result in trabecular bone loss. Bone quality parameters such as bone mineral density and bone microarchitecture were not affected in netoglitazone-treated animals. The observed lack of an in vivo effect of netoglitazone on bone was entirely consistent with its low anti-osteoblastic activity in vitro. In contrast to the observed in vitro effects, netoglitazone in vivo effectively induced marrow adipocyte formation and induced changes in the weights of extramedullary fat depots. Consistent with these cell type-specific effects, expression of the adipocyte-specific gene marker FABP4/aP2 was increased, whereas the expression of osteoblast-specific gene markers, Runx2, Dlx5, osteocalcin, and collagen were not affected by netoglitazone. In conclusion, netoglitazone is a member of a new class of PPAR-gamma ligands with distinct anti-diabetic, anti-osteoblastic, and pro-adipocytic activities in vivo.

What are the effects of peroxisome proliferator-activated receptor agonists on adiponectin, tumor necrosis factor-alpha, and other cytokines in insulin resistance?

Patients with type 2 diabetes are at high risk of cardiovascular disease. In addition to treating hyperglycemia, the thiazolidinedione (TZD) class of antidiabetic agents may also benefit the cardiovascular complications associated with the disease. The two available TZDs, pioglitazone and rosiglitazone, are peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists that influence gene expression of key proteins involved in regulating glucose and lipid metabolism. Tumor necrosis factor-alpha (TNF-alpha) and adiponectin are believed to be important in the development of insulin resistance and atherosclerosis. Understanding the role of these cytokines in the inflammatory processes that trigger plaque development might lead to identification of other potential mechanisms that could be exploited to enhance future treatments for patients with diabetes and atherosclerosis.