Role Of Peroxisome Proliferator-activated Receptor Gamma Research Articles

Vinpocetine attenuates fluoxetine-induced liver damage in rats; Role of Nrf2 and PPAR-γ.

Fluoxetine (FLX) has been widely used as first-line treatment in cases of depression and other neuropsychiatric disorders. Although its safety has been approved, the use of FLX was associated with liver injury and chronic liver disease. Vinpocetine (Vinpo), a nootropic drug, possesses antioxidant and anti-inflammatory effects. This study aimed to evaluate the protective effects of Vinpo on FLX-induced liver damage pointing to the role of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and nuclear factor erythroid 2-related factor 2 (Nrf2). Rats were randomized to four groups: control group, Vinpo group (20mg/kg/day; orally), FLX group (10mg/kg/day; orally), and Vinpo + FLX group. FLX-induced liver damage was evidenced through elevated liver function biomarkers and induced hepatic histopathological changes. Concurrent Vinpo treatment resulted in a significant decrease in hepatotoxicity biomarkers and histopathological alterations. FLX-induced oxidative stress and inflammation were attenuated by Vinpo. In addition, Vinpo attenuated the hepatic NRF2 and HO-1 levels and up-regulated PPAR-γ expression. Moreover, FLX elevated Bcl-2-associated X protein (Bax) mRNA expression and decreased B-cell lymphoma 2 (Bcl2) mRNA expression were markedly reversed by Vinpo. Vinpo possesses ameliorative effects against FLX-induced liver injury in rats. This effect may be due to attenuation of oxidative stress and inflammation, in addition to upregulation of PPAR-γ expression.

Chronic Low-Dose Alcohol Consumption Attenuates Post-Ischemic Inflammation via PPARγ in Mice.

Ischemic stroke is one of the leading causes of death and permanent disability in adults. Recently, we found that light alcohol consumption (LAC) suppresses post-ischemic inflammatory response, which plays an important role in ischemic brain damage. Our goal was to determine the role of peroxisome proliferator-activated receptor-gamma (PPARγ) in the anti-inflammatory effect of LAC against transient focal cerebral ischemia. In in vivo study, male C57BL/6J wild type (WT) and endothelial-specific conditional PPARγ knockout mice were gavage fed with 0.7 g/kg/day ethanol or volume-matched water daily for 8 weeks. From the 7th week, 3 mg/kg/day GW9662 (a selective PPARγ antagonist) was intraperitoneally given for two weeks. Cerebral ischemia/reperfusion (I/R) injury and expression of manganese superoxide dismutase (MnSOD) and adhesion molecules, neutrophil infiltration, and microglial activation in the cerebral cortex before and following a 90 min unilateral middle cerebral artery occlusion (MCAO)/24 h reperfusion were evaluated. In in vitro study, the impact of chronic alcohol exposure on expression of PPARγ and MnSOD in C57BL/6J mouse brain microvascular endothelial cells (MBMVECs) was measured. PPARγ and MnSOD were significantly upregulated in the cerebral cortex of ethanol-fed WT mice and low-concentration ethanol-exposed C57BL/6J MBMVECs. GW9662 significantly inhibited alcohol-induced upregulation of MnSOD. Eight-week ethanol feeding significantly reduced cerebral I/R injury and alleviated the post-ischemic inflammatory response (upregulation of intercellular adhesion molecule-1 (ICAM-1) and E-selectin, microglial activation, and neutrophil infiltration). Treatment with GW9662 and endothelial-specific conditional knockout of PPARγ did not alter cerebral I/R injury and the inflammatory response in the control mice but abolish the neuroprotective effect in ethanol-fed mice. In addition, GW9662 and endothelial-specific conditional knockout of PPARγ diminished the inhibitory effect of LAC on the post-ischemic expression of adhesion molecules and neutrophil infiltration. Our findings suggest that LAC may protect against cerebral I/R injury by suppressing the post-ischemic inflammation via activation of PPARγ.

The PPAR-γ/SFRP5/Wnt/β-catenin signal axis regulates the dexamethasone-induced osteoporosis

BackgroundThe inhibition of glucocorticoid (GC) on osteoblastic differentiation of bone marrow stromal stem cells (BMSC) is an important pathway for GC to reduce bone formation. Recent studies implicated an important role of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in GC-mediated cell proliferation and differentiation. Thus, our purpose is to investigate the role of PPAR-γ in regulating rat BMSC (rBMSC) osteoblastic differentiation. MethodsThe rBMSC treated with dexamethasone (Dex) was used to construct an in vitro cell model of GC-induced osteoporosis. The expressions of PPAR-γ, RUNX2, ALP, OPN and SFRP5 in cells were detected by RT-qPCR and western blot assays. Osteogenic differentiation of rBMSC was measured by Alizarin Red S (ARS) staining analysis. Lentivirus-delivered shRNA was used to knock down PPAR-γ or SFRP5, and lentivirus-delivered constructs were used to overexpress SFRP5 in rBMSC to verify the effect of PPAR-γ or SFRP5 on cell osteogenic differentiation. ResultsDex significantly reduced rBMSC osteoblastic differentiation. The expression of PPAR-γ was enhanced in Dex treated rBMSC. PPAR-γ down-regulation improved Dex inhibition of rBMSC osteogenic differentiation. Moreover, PPAR-γ knockdown promoted protein levels of RUNX2, ALP, OPN and Dex-decreased rBMSC osteogenic differentiation. The expression of SFRP5 was reduced while Wnt and β-catenin were increased in PPAR-γ knockdown and Dex treated rBMSC. Moreover, the up-regulation of SFRP5 reversed the osteogenic differentiation of rBMSC induced by PPAR-γ knockdown. ConclusionThese data indicated that in GC-induced osteoporosis, PPAR-γ/SFRP5 affects osteogenic differentiation by regulating the Wnt/β-catenin signaling pathway.

Celecoxib inhibits acute edema and inflammatory biomarkers through peroxisome proliferator-activated receptor-γ in rats.

Objective(s):Celecoxib (CLX), a selective cyclooxygenase-II (COX-2) inhibitor, has been used for management of several inflammatory disorders. The present study aimed to explore the role of peroxisome proliferator-activated receptor-gamma (PPARγ) in CLX induced anti-inflammatory response in rats.Materials and Methods:Carrageenan-induced paw edema was used as an acute inflammation model. Rats were treated with various intra-peritoneal (IP) doses of CLX (0.3–30 mg/kg) and pioglitazone (PGL; PPARγ agonist, 1–20 mg/kg) alone or in combination. Amounts of PPARγ, COX-2, and prostaglandin E2 (PGE2) in paw tissue, and extents of TNF-α and IL-10 in serum were measured. Moreover, levels of oxidative stress parameters as malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx) activity in the cortex, hippocampus, and paw tissues were also determined. Results:CLX and PGL dose-dependent administration (IP), alone or in combination reduced carrageenan-induced paw edema. Further, both agents, alone or in combination, reduced either the amounts of COX-2, PGE2, and MDA in the inflamed paw, and the levels of TNF-α in serum which were elevated by carrageenan. Both drugs also increased both levels of PPARγ, GSH, GPx activity in paws, and serum levels of IL-10 that were decreased by carrageenan. Intraplantar injection of GW-9662 (IPL), a selective PPARγ antagonist, inhibited all biochemical modifications caused by both single and combined drug treatments. Conclusion:CLX produced its anti-inflammatory effects probably through PPARγ receptor activation. Besides, increased anti-inflammatory effects of CLX with PGL suggest that their combination might be applied for the clinical management of inflammation especially in patients suffering from diabetes.

Role of peroxisome proliferators-activated receptor-gamma in advanced glycation end product-mediated functional loss of voltage-gated potassium channel in rat coronary arteries

Abstract Background Voltage-gated K+ (Kv) channels in coronary artery smooth muscle cells (CSMCs), especially the major specific Kv1 subfamily, contribute to coronary artery vasodilation. Advanced glycation end products (AGEs) have been strongly implicated in diabetes-related cardiovascular complications. Our previous study showed AGEs can impair Kv channel-mediated coronary vasodilation by reducing Kv channel activity. However, its underlying mechanism remains unclear. Purpose Here, we used isolated rat small coronary arteries (RSCAs) and primary CSMCs to investigate the effect of AGEs on Kv channel-mediated coronary vasodilation and the possible involvement of peroxisome proliferators-activated receptor (PPAR)-γ pathway. Methods RSCAs and primary CSMCs were isolated, cultured and treated with bovine serum albumin (BSA), AGE-BSA, alagrebrium (ALA, AGE cross-linking breaker), pioglitazone (PIO) and/or GW9662, and then divided into the following groups: DMEM, BSA, AGE, AGE+ALA, AGE+PIO, and AGE+PIO+GW9662. Kv channel-mediated coronary vasodilation was analyzed using wire myograph. Histology and immunohistochemistry of RSCAs were performed. Western blot was used to detect the protein expression of RAGE, the major Kv1 channel subunits expressed in CSMCs (Kv1.2/1.5), PPAR-γ, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2 (NOX-2). Results AGEs markedly reduced forskolin-induced Kv channel-mediated vasodilation of RSCAs by interacting with the receptor for AGEs (RAGE), and ALA or PIO significantly reversed this effect. In both RSCAs and primary CSMCs, AGEs decreased Kv1.2 and Kv1.5 channel protein expression, inhibited PPAR-γ expression, increased RAGE and NOX-2 expression. Treatment with ALA or PIO partially reversed the effects of AGEs on Kv1.2/Kv1.5 expression, accompanied by elevation of PPAR-γ level and diminished oxidative stress. Conclusion AGE/RAGE axis-induced inhibition of PPAR-γ pathway and enhancement of oxidative stress may contribute to AGEs-mediated Kv channel dysfunction and coronary vasodilation in RSCAs. Our results may provide new insights into developing therapeutic strategies to manage diabetic vasculature. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): National Natural Science Foundation of China; Natural Science Foundation of Beijing (7172059)

Role of peroxisome proliferators-activated receptor-gamma in advanced glycation end product-mediated functional loss of voltage-gated potassium channel in rat coronary arteries

BackgroundHigh blood glucose impairs voltage-gated K+ (Kv) channel-mediated vasodilation in rat coronary artery smooth muscle cells (CSMCs) via oxidative stress. Advanced glycation end product (AGE) and receptor for AGE (RAGE) axis has been found to impair coronary dilation by reducing Kv channel activity in diabetic rat small coronary arteries (RSCAs). However, its underlying mechanism remain unclear. Here, we used isolated arteries and primary CSMCs to investigate the effect of AGE incubation on Kv channel-mediated coronary dilation and the possible involvement of peroxisome proliferators-activated receptor (PPAR) -γ pathway.MethodsThe RSCAs and primary CSMCs were isolated, cultured, and treated with bovine serum albumin (BSA), AGE-BSA, alagrebrium (ALA, AGE cross-linking breaker), pioglitazone (PIO, PPAR-γ activator) and/or GW9662 (PPAR-γ inhibitor). The groups were accordingly divided as control, BSA, AGE, AGE + ALA, AGE + PIO, or AGE + PIO + GW9662. Kv channel-mediated dilation was analyzed using wire myograph. Histology and immunohistochemistry of RSCAs were performed. Western blot was used to detect the protein expression of RAGE, major Kv channel subunits expressed in CSMCs (Kv1.2 and Kv1.5), PPAR-γ, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2 (NOX-2).ResultsAGE markedly reduced Forskolin-induced Kv channel-mediated dilation of RSCAs by engaging with RAGE, and ALA or PIO significantly reversed the functional loss of Kv channel. In both RSCAs and CSMCs, AGE reduced Kv1.2/1.5 expression, increased RAGE and NOX-2 expression, and inhibited PPAR-γ expression, while ALA or PIO treatment partially reversed the inhibiting effects of AGE on Kv1.2/1.5 expression, accompanied by the downregulation of RAGE and decreased oxidative stress. Meanwhile, silencing of RAGE with siRNA remarkably alleviated the AGE-induced downregulation of Kv1.2/1.5 expression in CSMCs.ConclusionAGE reduces the Kv channel expression in CSMCs and further impairs the Kv channel-mediated dilation in RSCAs. The AGE/RAGE axis may enhance oxidative stress by inhibiting the downstream PPAR-γ pathway, thus playing a critical role in the dysfunction of Kv channels.

PGC1α protects against hepatic steatosis and insulin resistance via enhancing IL10-mediated anti-inflammatory response.

Inflammatory responses are pivotal incidences in hepatic metabolic derangements. However, the underlying mechanism remains elusive. The present study aimed to evaluate the role of peroxisome proliferator-activated receptor-gamma, coactivator 1 alpha (PGC1α) in IL10-mediated anti-inflammatory response, and its role in hepatic steatosis and insulin resistance. Hepatocyte-specific PGC1α knock-in (LivPGC1α) mice and the control mice were fed high-fat diet (HFD) for 8weeks. IL-10 neutralizing antibody was injected into the liver of PGC1α mice. A variety of biological and histological approaches were applied to assess hepatic function. We demonstrated that hepatic PGC1α expression was significantly reduced in mice fed HFD. LivPGC1α livers exhibited enhanced gene expressions involving mitochondrial function, and favored an accelerated lipid metabolism upon HFD. Meanwhile, LivPGC1α mice revealed improved hepatic steatosis and insulin resistance. Mechanistically, PGC1α bound and activated the promotor region of IL-10, thereby attenuating inflammatory response in the liver. Administration of IL10 neutralizing antibody to LivPGC1α mice abolished PGC1α-mediated anti-inflammatory effects in mice. Further, IL-10 neutralizing antibody intervention aggravated hepatic steatosis and insulin resistance in LivPGC1α mice. Taken together, our data indicated that hepatic-specific overexpression of PGC1α exerts a beneficial role in the regulation of hepatic steatosis and insulin resistance via enhancing IL10-mediated anti-inflammatory response. Pharmacological activation of PGC1α-IL10 axis may be promising for the treatment of fatty liver diseases.

Role of Peroxisome Proliferator‐activated Receptor‐gamma in Type 2 Diabetes‐induced Testicular DNA Damage and Repair in Leptin Receptor‐deficient Obese Mice

The DNA damage repair mechanisms under hyperglycemic conditions are a subject of intense research as unrepaired DNA damage may enhance the possibility of carcinogenicity in diabetic patients. In this study, we investigated the role of peroxisome proliferator‐activated receptor‐gamma (PPARγ) in diabetes‐induced alterations in testicular functions and DNA damage and repair. Leptin signaling intact lean (heterozygous; db+/db−) and leptin receptor‐mutant (db−/db−) obese male mice (7‐week‐old; n=10/group) received either pioglitazone (a PPARγ agonist) or 2‐chloro‐5‐nitro‐N‐phenylbenzamide (a PPARγ antagonist) for 84 days (12 weeks) to modulate the receptor activities. Semi‐quantification of 4‐hydroxynonenal and 8‐oxo‐dG levels meassured the oxidative stress, and the TUNEL assay measured apoptotic testicular cells. Western blotting technique quantified the levels of base‐excision repair (BER) pathway proteins‐8‐oxoguanine glycosylases 1&2, apurinic/apyrimidinic endonuclease, DNA polymerase δ, poly (ADP‐ribose) polymerase 1 and X‐ray repair cross‐complementing protein‐1. PPARγ activation increased the body weights and reduced the blood glucose levels, but inhibition of PPARγ activities did not significantly affect these parameters in obese diabetic mice. Inhibition of PPARγ activities improved testis and epididymis weights and sperm counts in obese diabetic mice. The obese diabetic mice showed seminiferous tubular degeneration, epithelial sloughing and tubular atrophy and, modulation of PPARγ activities did not significantly protect testicular structure and function. The lack of leptin signaling in obese diabetic mice increased oxidative stress and oxidative DNA damage, and stimulation of PPARγ activities reduced only lipid peroxidation, and inhibition of PPARγ activities inhibited both lipid peroxidation and oxidative DNA damage. The obese diabetic mice showed upregulated base excision repair proteins to repair the increased oxidative DNA damage. PPARγ stimulation inhibited the DNA damage repair indicating its detrimental effects, and the inhibition of PPARγ activities led to inhibition of DNA damage repair in conjunction with reduced oxidative DNA damage. However, regardless of these modulatory effects of PPARγ, the obese diabetic mice showed comparable levels of apoptosis in their testes. In conclusion, PPARγ activation although reduces blood glucose levels, in the absence of leptin signaling upregulates DNA damage and inhibits base excision repair mechanisms in the testis. The inhibited PPARγ activities in the absence of leptin signaling are beneficial to protect the testicular functions in obese diabetic mice.Support or Funding InformationSupported by Kuwait University grant # YM05/17 and CGS.

PPARG Negatively Modulates Six2 in Tumor Formation of Clear Cell Renal Cell Carcinoma.

Substantial research has revealed that peroxisome proliferator-activated receptor-gamma (PPARG) plays a critical role in glucose homeostasis and lipid metabolism, and recent studies have shown different effects in the progression of different tumors. However, the role of PPARG and its target gene in clear cell renal cell carcinoma (ccRCC) are incompletely understood. Clinical data revealed abnormal glucolipid metabolism in primary ccRCC samples. In addition, transcriptional profiling indicated that PPARG expression was positively correlated, whereas Six2 expression was negatively correlated with the overall survival of ccRCC patients. Staining showed that PPARG was mainly expressed in tumor cell cytoplasm, and Six2 was localized to the nuclei. In a ccRCC cell line, PPARG activation promoted cell apoptosis, inhibited cell migration and proliferation, and reduced Six2 expression. Mechanistically, overexpressing Six2 downregulated E-cadherin expression and cell apoptosis, but PPARG activation reversed those effects. Taken together, PPARG promotes apoptosis and suppresses the migration and proliferation of ccRCC cells by inhibiting Six2. These findings reveal that the PPARG/Six2 axis acts as a central pathobiological mediator of ccRCC formation and as a potential therapeutic target for the treatment of patients with ccRCC.

Role of PPARG (Pro12Ala) in Malaysian type 2 diabetes mellitus patients

Diabetes is one of the major lifestyle disorders in the world. Asian countries, including Malaysia, contribute with more than 60 % of the world’s diabetic population. The single nucleotide polymorphisms (SNPs) of the peroxisome proliferator-activated receptor gamma (PPARG) have been identified as one of the key regulators of glucose and lipid metabolism that controls the protein synthesis in multiple metabolic, biochemical, and molecular pathways. The aim of this study was to investigate the possible role of PPARG (Pro12Ala) gene polymorphism as a genetic risk factor for type 2 diabetes mellitus (T2DM) patients in Malaysian population. A total of 241 subjects between the age of 35 and 85 years were recruited in this study. Out of the total 241 subjects, 120 were T2DM patients and 121 were healthy individuals. SNP of PPARG (Pro12Ala) was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphisms (RFLPs). The frequencies of wild homozygote (WH), heterozygote (H), and mutant homozygote (MH) among the T2DM patients were (n = 73) 60.8 %, (n = 39) 32.5 %, and (n = 3) 2.5 % compared to (n = 57) 47 %, (n = 46) 38 %, and (n = 16) 13.2 % among the healthy subjects. The mean of Hba1C (%) among normal and diabetic patients with genotypes were different (5.36 ± 0.54 vs 7.58 ± 1.76), p < 0.005. SNP of PPARG (Pro12Ala) gene could be a genetic risk factor for insulin resistance and T2DM among Malaysian population.

Peroxisome proliferator-activated receptor-gamma expression in dendritic cells determines immune tolerance versus immune activation (HYP6P.256)

Abstract Dendritic cells (DCs) play a central role in regulating immune tolerance and activation but the molecular axis within DCs that dictates immune outcome is unknown. We investigated the role of Peroxisome proliferator-activated receptor-gamma (PPARγ) in DCs in establishment of immune tolerance in the airways using an experimental model. Using mice with selective deletion of PPARγ in CD11c+ cells (PPARγΔ) to ablate PPARγ expression in DCs, we show that DC-specific PPARγ expression exerts a dual role whose collective goal in response to inhaled antigen is to not only promote de novo Foxp3 expression in T cells but to actively dampen T effector cell development. We demonstrate that PPARγ plays a crucial role in enhancing aldh1a2 expression in lung CD103+ DCs under tolerogenic conditions and when tolerized PPARγΔ mice were antigen-challenged, a complete loss of immune tolerance with increased neutrophil-dominated airway inflammation was observed. Absence of PPARγ promoted the expression of multiple pro-inflammatory cytokines such as IL-6 and IL-23 in DCs, limited Foxp3 induction but augmented IL-17 production in T cells with significant increase in the frequency of dual Foxp3+RORγt+ CD4+ T cells in PPARγΔ mice. In summary, our study identifies PPARγ as a central regulator in DC-mediated programming of the Foxp3/RORγt balance in CD4+ T cells dictating tolerance versus inflammation upon antigen provocation.

Hyperbaric oxygen preconditioning protects cortical neurons against oxygen-glucose deprivation injury: Role of peroxisome proliferator-activated receptor-gamma

Ischemic stroke is one of the leading causes of mortality and disability worldwide. Our previous studies have shown that hyperbaric oxygen (HBO) preconditioning can afford significant neuroprotection against cerebral ischemia–reperfusion (I/R) injury in rats. However, it is still unknown whether HBO preconditioning can directly protect primary cultured cortical neurons against oxygen-glucose deprivation (OGD). Peroxisome proliferator-activated receptor-gamma (PPAR γ) plays a central role in the regulation of apoptosis, oxidative stress and inflammation as well as affords significant neuroprotection against cerebral I/R injury. 15-deoxy-∆12,14-prostaglandin J2 (15d-PGJ2) is an endogenous ligand with a high affinity for PPAR γ. Recently, some studies demonstrate that activation of PPAR γ mediates lipopolysaccharide and anesthetic preconditioning. In the present study, we firstly found that OGD exposure caused the significant damage of cultured cortical neurons evaluated by cell viability, lactate dehydrogenase (LDH) release and caspase-3 activity, which were significantly ameliorated by HBO preconditioning. Furthermore, HBO preconditioning significantly increased the levels of PPAR γ mRNA and protein, PPAR γ DNA binding activity, 15d-PGJ2 and antioxidant enzymatic activities in primary cultured cortical neurons with OGD exposure. Moreover, PPAR γ antagonist GW9662 dose-dependently abolished the protection of HBO preconditioning in OGD-exposed neurons. GW9662 blocked the increase of PPAR γ DNA binding activity and antioxidant enzymatic activities, but did not influence the 15d-PGJ2 level in OGD-exposed neurons with HBO preconditioning. However, the cyclooxygenase (COX)-2 inhibitor NS-398 blocked the production of 15d-PGJ2 in OGD-exposed neurons with HBO preconditioning. In addition, 15d-PGJ2 preconditioning could also protect cultured neurons against OGD injury. These results demonstrate that HBO preconditioning has directly beneficial effects on ODG-exposed cortical neurons by the activation of PPAR γ subsequent to the production of 15d-PGJ2, which in turn increases the downstream antioxidant enzymatic activities.

NUCLEAR RECEPTORS

NUCLEAR RECEPTORS

Synergism in hyperhomocysteinemia and diabetes: role of PPAR gamma and tempol

BackgroundHyperhomocysteinemia (HHcy) and hyperglycemia cause diabetic cardiomyopathy by inducing oxidative stress and attenuating peroxisome proliferator- activated receptor (PPAR) gamma. However, their synergistic contribution is not clear.MethodsDiabetic Akita (Ins2+/-) and hyperhomocysteinemic cystathionine beta synthase mutant (CBS+/-) were used for M-mode echocardiography at the age of four and twenty four weeks. The cardiac rings from WT, Akita and hybrid (Ins2+/-/CBS+/-) of Akita and CBS+/- were treated with different doses of acetylcholine (an endothelial dependent vasodilator). High performance liquid chromatography (HPLC) was performed for determining plasma homocysteine (Hcy) level in the above groups. Akita was treated with ciglitazone (CZ) - a PPAR gamma agonist and tempol-an anti-oxidant, separately and their effects on cardiac remodeling were assessed.ResultsAt twenty four week, Akita mice were hyperglycemic and HHcy. They have increased end diastolic diameter (EDD). In their heart PPAR gamma, tissue inhibitor of metalloproteinase-4 (TIMP-4) and anti-oxidant thioredoxin were attenuated whereas matrix metalloproteinase (MMP)-9, TIMP-3 and NADPH oxidase 4 (NOX4) were induced. Interestingly, they showed synergism between HHcy and hyperglycemia for endothelial-myocyte (E-M) uncoupling. Additionally, treatment with CZ alleviated MMP-9 activity and fibrosis, and improved EDD. On the other hand, treatment with tempol reversed cardiac remodeling in part by restoring the expressions of TIMP-3,-4, thioredoxin and MMP-9.ConclusionsEndogenous homocysteine exacerbates diabetic cardiomyopathy by attenuating PPAR gamma and inducing E-M uncoupling leading to diastolic dysfunction. PPAR gamma agonist and tempol mitigates oxidative stress and ameliorates diastolic dysfunction in diabetes.

17β-Estradiol inhibits oleic acid-induced rat VSMC Proliferation and migration by restoring PGC-1α expression

Estrogen shows a vasoprotective role through inhibiting the proliferation and migration of vascular smooth muscle cells (VSMCs). The mechanism underlying the effect of estrogen, however, is not completely understood. Here, we explored the role of peroxisome proliferator-activated receptor-gamma (PPARgamma) coactivator-1alpha (PGC-1alpha) in estrogen-mediated vasoprotection. Firstly, we showed that oleic acid (OA) decreased PGC-1alpha expression while stimulating VSMC proliferation and migration. In contrast, administration of VSMCs with 17beta-estradiol (E(2), 1 or 10nM) significantly restored OA-decreased PGC-1alpha expression, treatment with 10nM E(2) almost completely abolished OA-induced VSMC proliferation and migration. Secondly, by using PGC-1alpha siRNA, the inhibitory effect of E(2) on VSMC growth is strongly reduced via suppressing PGC-1alpha expression, indicating that E(2) may exert its role through restoring PGC-1alpha. Finally, E(2) (10nM) treatment inhibits OA-induced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, however, suppression of PGC-1alpha expression abolishes this inhibitory effect of E(2). Our findings demonstrate for the first time that in OA-stimulated rat VSMCs, treatment with E(2) (1 or 10nM) diminishes VSMC proliferation and migration via restoring OA-decreased PGC-1alpha expression. This observation offers a novel molecular basis of the vasoprotective effect of estrogen.

Glycine regulates the production of pro-inflammatory cytokines in lean and monosodium glutamate-obese mice

Fat tissue plays an important role in the regulation of inflammatory processes. Increased visceral fat has been associated with a higher production of cytokines that triggers a low-grade inflammatory response, which eventually may contribute to the development of insulin resistance. In the present study, we investigated whether glycine, an amino acid that represses the expression in vitro of pro-inflammatory cytokines in Kupffer and 3T3-L1 cells, can affect in vivo cytokine production in lean and monosodium glutamate-induced obese mice (MSG/Ob mice). Our data demonstrate that glycine treatment in lean mice suppressed TNF-α transcriptional expression in fat tissue, and serum protein levels of IL-6 were suppressed, while adiponectin levels were increased. In MSG/Ob mice, glycine suppressed TNF-α and IL-6 gene expression in fat tissue and significantly reduced protein levels of IL-6, resistin and leptin. To determine the role of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in the modulation of this inflammatory response evoked by glycine, we examined its expression levels in fat tissue. Glycine clearly increased PPAR-γ expression in lean mice but not in MSG/Ob mice. Finally, to identify alterations in glucose metabolism by glycine, we also examined insulin levels and other biochemical parameters during an oral glucose tolerance test. Glycine significantly reduced glucose tolerance and raised insulin levels in lean but not in obese mice. In conclusion, our findings suggest that glycine suppresses the pro-inflammatory cytokines production and increases adiponectin secretion in vivo through the activation of PPAR-γ. Glycine might prevent insulin resistance and associated inflammatory diseases.

Peroxisome Proliferator-Activated Receptor Gamma Promotes Lymphocyte Survival Via a Mitochondrial Pathway Mediated by GSK-3 Beta.

Peroxisome proliferator-activated receptor (PPAR) gamma is a nuclear hormone receptor involved in maintaining glucose and fatty acid homeostasis. Besides its metabolic functions, the receptor has also been implicated in tumorigenesis. Ligands of PPAR gamma induce apoptosis in several types of tumor cells including lymphomas, leading to the proposal that these ligands may be used as anti-cancer agents. However, apoptosis induction requires high doses of ligands, suggesting the effect may not be receptor-dependent. Previously, we reported that PPAR gamma is expressed in human primary T cell lymphoma tissues and activation of PPAR gamma with low doses of ligands protects lymphoma cells from serum starvation-induced apoptosis. The prosurvival effect of PPAR gamma is linked to its actions on mitochondria. In serum-deprived cells, PPAR gamma attenuates the decline in ATP, reduces mitochondrial hyperpolarization and limits the amount of reactive oxygen species (ROS) in favor of cell survival (Yang et al, Am J Pathol , 170, 722–32, 2007). In the current study, we investigated the molecular mechanisms by which PPAR gamma maintains mitochondria homeostasis. We demonstrated that PPAR gamma modulates the activities of two key components of Wnt signaling pathway, Fzd4 and GSK-3 beta. The receptor up-regulates the mRNA expression of Fzd4, a cell surface receptor of Wnt, through a conserved PPAR-response element (PPRE) in the promoter region of the Fzd4 gene. Moreover, PPAR gamma suppresses the activation of GSK-3 beta, a downstream inhibitory serine/threonine kinase, by maintaining its phosphorylation at serine 9 and decreasing its association with mitochondria. Downregulation of GSK-3 beta activity results in maintenance of mitochondrial membrance potential and suppression of ROS production in growth factor-deprived cells. Our studies revealed a novel interaction between PPAR gamma and Wnt signaling in lymphocyte survival. Since Wnt signaling plays an important role in tumorigenesis, our studies highlight the need for further investigation into the role of PPAR gamma in cancer prior to widespread use of its agonists as anticancer therapeutics.

P4-087: Amyloid precursor protein processing: Role of peroxisome proliferator-activated receptor-gamma

P4-087: Amyloid precursor protein processing: Role of peroxisome proliferator-activated receptor-gamma

Role of peroxisome proliferator-activated receptor-gamma in maintenance of the characteristics of mature 3T3-L1 adipocytes.

Peroxisome proliferator-activated receptor (PPAR)-gamma plays an important role in adipogenesis. However, the functions of PPAR-gamma in differentiated adipocytes have remained unclear. The role of PPAR-gamma in mature 3T3-L1 adipocytes was therefore investigated by overexpression of a dominant negative mutant of this protein (PPAR-gamma-DeltaC) that lacks the 16 COOH-terminal amino acids and that has been shown to prevent the thiazolidinedione-induced differentiation of 3T3-L1 cells into adipocytes. Overexpression of PPAR-gamma-DeltaC in mature 3T3-L1 adipocytes by adenovirus gene transfer resulted in a decrease in both cell size and intracellular triglyceride content, an increase in the extent of lipolysis, and a reduction in the rate of free fatty acid uptake. Furthermore, overexpression of this mutant reduced the abundance of mRNAs for several key enzymes that contribute to triglyceride and free fatty acid metabolism as well as the amounts of GLUT4, insulin receptor, insulin receptor substrate (IRS), and C/EBPalpha mRNAs. It also reduced both the concentration of IRS2 and the insulin-stimulated glucose uptake. These results suggest that PPAR-gamma plays an important role in mature 3T3-L1 adipocytes at least in part by maintaining the expression of genes that confer the characteristics of mature adipocytes.

Transcriptional Regulation of the Mouse Uncoupling Protein-2 Gene: DOUBLE E-BOX MOTIF IS REQUIRED FOR PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-γ-DEPENDENT ACTIVATION

Uncoupling protein-2 (UCP2) is present in many tissues with relevance to fuel metabolism, and its expression is increased in fat and muscle in response to elevated circulating free fatty acids resulting from fasting and high fat feeding. We proposed a role for peroxisome proliferator-activated receptor-gamma (PPARgamma) as a mediator of these physiological changes in UCP2, because thiazolidinediones also increase expression of UCP2 in these cell types (). To determine the molecular basis for this regulation, we isolated the 7.3-kilobase promoter region of the mouse UCP2 gene. The -7.3-kilobase/+12-base pair fragment activates transcription of a reporter gene by 50-100-fold. Deletion and point mutation analysis, coupled with gel shift assays, indicate the presence of a 43-base pair enhancer (-86/-44) that is responsible for the majority of both basal and PPARgamma-dependent transcriptional activity. The distal (-86/-76) part of the enhancer specifically binds Sp1, Sp2, and Sp3 and is indistinguishable from a consensus Sp1 element in competition experiments. Point mutation in this sequence reduces basal activity by 75%. A second region (-74/-66) is identical to the sterol response element consensus and specifically binds ADD1/SREBP1. However, deletion of this sequence does not affect basal transcriptional activity or the response to PPARgamma. The proximal portion of the enhancer contains a direct repeat of two E-Box motifs, which contributes most strongly to basal and PPARgamma-dependent transcription of the UCP2 promoter. Deletion of this region results in a 10-20-fold reduction of transcriptional activity and complete loss of PPARgamma responsiveness. Point mutations in either E-Box, but not in the spacer region between them, eliminate the stimulatory response to PPARgamma. However, gel shift assays show that PPARgamma does not bind to this region. Taken together, these data indicate that PPARgamma activates the UCP2 gene indirectly by altering the activity or expression of other transcription factors that bind to the UCP2 promoter.