Proliferator-activated Receptor Gamma Gene Expression Research Articles

MicroRNA-34a and promoter methylation contribute to peroxisome proliferator-activated receptor gamma gene expression in patients with type 2 diabetes

AimsThis study aimed to investigate the roles of DNA methylation and miR-34a in the regulation of peroxisome proliferator-activated receptor gamma (PPARγ) in patients with type 2 diabetes (T2D). MethodsWe investigated the methylation status of four regions of the PPARγ promoter and PPARγ expression in a panel of 84 T2D patients using methylation-specific PCR (MSP) and RT-qPCR, respectively. Moreover, we quantified DNA methyltransferases (DNMTs) expression and global DNA methylation levels by RT-qPCR and ELISA, respectively. We measured the expression levels of miR-34a and protein expression of PPARγ by stem-loop RT-qPCR and ELISA, respectively. ResultsWe found significant DNA hypermethylation in the R2 and R3 regions of the PPARγ promoter in people with diabetes. Functionally, this was associated with a significant reduction in PPARγ expression. In addition, we observed a significant increase in 5-methylcytosine levels in people with diabetes. A marked increase in circulating miR-34a in the early stages of T2D (up to 10 years) and a significant decrease in circulating miR-34a with increasing diabetes duration from 10 years after the onset of diabetes. Interestingly, upregulation of DNA methyltransferases 1 (DNMT1), DNMT3A, and DNMT3B was observed in people with diabetes, and the average expression of DNMTs was negatively correlated with circulating miR-34a levels. In contrast, the serum protein level of PPARγ, a direct target of miR-34a, increased considerably with diabetes duration and showed a negative correlation with circulating miR-34a, cholesterol, triglyceride, and low-density lipoprotein. ConclusionPPARγ promoter hypermethylation and miR-34a upregulation are associated with T2D pathogenesis through PPARγ dysregulation.

Synergistic Effect of Omega-3 Fatty Acids and Oral-Hypoglycemic Drug on Lipid Normalization through Modulation of Hepatic Gene Expression in High Fat Diet with Low Streptozotocin-Induced Diabetic Rats.

Type 2 diabetes mellitus, which an outcome of impaired insulin action and its secretion, is concomitantly associated with lipid abnormalities. The study was designed to evaluate the combinational effect of omega-3 fatty acids (flax and fish oil) and glibenclamide on abnormal lipid profiles, increased blood glucose, and impaired liver and kidney functions in a high fat diet with low streptozotocin (STZ)-induced diabetic rats, including its probable mechanism of action. The male Wistar rats (n = 48) were distributed into eight groups. All animal groups except the healthy received a high fat diet (HFD) for 90 days. Further, diabetes was developed by low dose STZ (35 mg/kg). Diabetic animals received, omega-3 fatty acids (500 mg/kg), along with glibenclamide (0.25 mg/kg). Both flax and fish oil intervention decreased (p ≤ 0.001) serum triglycerides and very low density lipoprotein and elevated (p ≤ 0.001) high density lipoprotein levels in diabetic rats. Total cholesterol and low-density lipoprotein level was decreased (p ≤ 0.001) in fish oil-treated rats. However, it remained unaffected in the flax oil treatment group. Both flax and fish oil intervention downregulate the expression of fatty acid metabolism genes, transcription factors (sterol regulatory element-binding proteins-1c and nuclear factor-κβ), and their regulatory genes i.e., acetyl-coA carboxylase alpha, fatty acid synthase, and tumor necrosis factors-α. The peroxisome proliferator-activated receptor gamma gene expression was upregulated (p ≤ 0.001) in the fish oil treatment group. Whereas, carnitine palmitoyltransferase 1 and fatty acid binding protein gene expression were upregulated (p ≤ 0.001) in both flax and fish oil intervention group.

Curcuma longa polyphenols improve insulin-mediated lipid accumulation and attenuate proinflammatory response of 3T3-L1 adipose cells during oxidative stress through regulation of key adipokines and antioxidant enzymes.

Plant polyphenols may exert beneficial action against obesity-related oxidative stress and inflammation which promote insulin resistance. This study evaluated the effect of polyphenols extracted from French Curcuma longa on 3T3-L1 adipose cells exposed to H2 O2 -mediated oxidative stress. We found that Curcuma longa extract exhibited high amounts of curcuminoids identified as curcumin, demethoxycurcumin, and bisdemethoxycurcumin, which exerted free radical-scavenging activities. Curcuma longa polyphenols improved insulin-mediated lipid accumulation and upregulated peroxisome proliferator-activated receptor-gamma gene expression and adiponectin secretion which decreased in H2 O2 -treated cells. Curcuminoids attenuated H2 O2 -enhanced production of pro-inflammatory molecules such as interleukin-6, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and nuclear factor κappa B. Moreover, they reduced intracellular levels of reactive oxygen species elevated by H2 O2 and modulated the expression of genes encoding superoxide dismutase and catalase antioxidant enzymes. Collectively, these findings highlight that Curcuma longa polyphenols protect adipose cells against oxidative stress and may improve obesity-related metabolic disorders. © 2016 BioFactors, 42(4):418-430, 2016.

Effect of Salusin-ß on Peroxisome Proliferator-Activated Receptor Gamma Gene Expression in Vascular Smooth Muscle Cells and its Possible Mechanism

Background/Aims: salusin-ß is considered to be a potential pro-atherosclerotic factor. Regulation and function of vascular smooth muscle cells (VSMCs) are important in the progression of atherosclerosis. Peroxisome proliferator-activated receptor gamma (PPARγ) exerts a vascular protective role beyond its metabolic effects. Salusin-ß has direct effects on VSMCs. The aim of the present study was to assess the effect of salusin-ß on PPARγ gene expression in primary cultured rat VSMCs. Methods: Western blotting analysis, real-time PCR and transient transfection approach were used to determine expression of target proteins. Specific protein knockdown was performed with siRNA transfection. Cell proliferation was determined by 5-bromo-2'-deoxyuridine incorporation. The levels of inflammation indicators interleukin-6 (IL-6) and tumor necrosis factor-a (TNF-a) were determined using enzyme-linked immunosorbent assay. Results: Salusin-ß negatively regulated PPARγ gene expression at protein, mRNA and gene promoter level in VSMCs. The inhibitory effect of salusin-ß on PPARγ gene expression contributed to salusin-ß-induced VSMCs proliferation and inflammation in vitro. IγBa-NF-γB activation, but not NF-γB p50 or p65, mediated the salusin-ß-induced inhibition of PPARγ gene expression. Salusin-ß induced nuclear translocation of histone deacetylase 3 (HDAC3). HDAC3 siRNA prevented salusin-ß-induced PPARγ reduction. Nuclear translocation of HDAC3 in response to salusin-ß was significantly reversed by an IγBa inhibitor BAY 11-7085. Furthermore, IγBa-HDAC3 complex was present in the cytosol of VSMCs but interrupted after salusin-ß treatment. Conclusion: IγBa-HDAC3 pathway may contribute to salusin-ß-induced inhibition of PPARγ gene expression in VSMCs.

Differential Effect of Telmisartan and Amlodipine on Monocyte Chemoattractant Protein-1 and Peroxisome Proliferator-Activated Receptor-Gamma Gene Expression in Peripheral Monocytes in Patients With Essential Hypertension

Monocyte chemoattractant protein-1 (MCP-1) and peroxisome proliferator-activated receptor-γ (PPAR-γ) play a significant role in monocyte activation, vascular inflammation, and atherogenesis. Angiotensin receptor blockers and calcium channel blockers are antihypertensive drugs with established efficacy and a favorable safety profile. We investigated the effect of telmisartan--an angiotensin receptor blocker with PPAR-γ agonist activity--and amlodipine on the activation state of peripheral blood monocytes with respect to MCP-1 and PPAR-γ gene expression in hypertensives. We recruited 31 previously untreated patients with essential hypertension who were randomly assigned to receive treatment with telmisartan (n = 16) or amlodipine (n = 15). Blood samples were taken before and 3 months after therapy initiation. Mononuclear cells were isolated and mRNAs of MCP-1 and PPAR-γ were estimated by real-time quantitative reverse transcription-polymerase chain reaction each time. The 2 treatments decreased all blood pressure components significantly (p <0.001). In contrast, in the amlodipine group, MCP-1 gene expression was significantly downregulated after treatment with telmisartan (from 21.4 ± 20.5 to 8.1 ± 6.5, p = 0.009), whereas the amlodipine group did not show any significant change (12.5 ± 8.5 vs 17.6 ± 16.4, p = NS). In addition, PPAR-γ mRNA levels showed a significant increase in telmisartan-treated patients (from 20 ± 18.5 to 42.6 ± 36, p = 0.006) and no significant alterations in the amlodipine group (from 29.6 ± 42.5 to 24.2 ± 27.7, p = NS). In conclusion, treatment with telmisartan results in a significant attenuation of MCP-1 gene expression and an increase of PPAR-γ gene expression in peripheral monocytes in patients with essential hypertension. Our findings may provide new insights into the cardiovascular protection of telmisartan in hypertensives.

Malignant blue naevus of the scalp

cancer-cell growth by the peroxisome proliferator-activated receptorgamma agonists through induction of apoptosis. Biochem Biophys Res Commun 2000; 270: 400–05. 74 Sasaki H, Tanahashi M, Yukiue H, et al. Decreased perioxisome proliferator-activated receptor gamma gene expression was correlated with poor prognosis in patients with lung cancer. Lung Cancer 2002; 36: 71–76. 75 Han SW, Greene ME, Pitts J, et al. Novel expression and function of peroxisome proliferator-activated receptor gamma (PPARgamma) in human neuroblastoma cells. Clin Cancer Res 2001; 7: 98–104. 76 Rohn TT, Wong SM, Cotman CW, Cribbs DH. 15-deoxy-delta12,14prostaglandin J2, a specific ligand for peroxisome proliferatoractivated receptor-gamma, induces neuronal apoptosis. Neuroreport 2001; 12: 839–43. 77 Burdge GC, Rodway H, Kohler JA, Lillycrop KA. Effect of fatty-acid supplementation on growth and differentiation of human IMR-32 neuroblastoma cells in vitro. J Cell Biochem 2000; 80: 266–73. 78 Berge K, Tronstad KJ, Flindt EN, et al. Tetradecylthioacetic acid inhibits growth of rat glioma cells ex vivo and in vivo via PPARdependent and PPAR-independent pathways. Carcinogenesis 2001; 22: 1747–55. 79 Kato M, Nagaya T, Fujieda M, et al. Expression of PPARgamma and its ligand-dependent growth inhibition in human brain tumor cell lines. Jpn J Cancer Res 2002; 93: 660–66. 80 Zhou XP, Smith WM, Gimm O, et al. Overrepresentation of PPARgamma sequence variants in sporadic cases of glioblastoma multiforme: preliminary evidence for common low-penetrance modifiers for brain-tumour risk in the general population. J Med Genet 2000; 37: 410–14. Review PPAR in cancer therapy

Decreased peroxisome proliferator-activated receptor gamma gene expression is correlated with poor prognosis in patients with esophageal cancer.

Peroxisome proliferator-activated receptor gamma (PPAR gamma) induces apoptosis by ligand stimulation in various tumor cell lines. In esophageal cancer cell lines, PPAR gamma activation also has suppressed the proliferation. In 55 primary esophageal squamous cell carcinomas (ESCCs) we examined the correlation between the expression of PPAR gamma mRNA with prognosis of esophageal cancer patients. The expression of PPAR gamma mRNA was quantified by real-time reverse transcription polymerase chain reaction using LightCycler. Immunohistochemistry was used to study the expression of PPAR gamma protein. The expression of PPAR gamma mRNA was significantly decreased in esophageal cancer cells compared with normal esophageal mucosa (P = 0.0084). Among the clinical factors, PPAR gamma mRNA expression was lower in the tumors with extensive lymph node metastasis (n4) than those with less extensive lymph node metastasis (n0-3) (P = 0.0059). Patients with low PPAR gamma mRNA expression had significantly shorter postoperative survival time than those with high PPAR gamma mRNA expression (P = 0.0191). In immunohistochemistry, PPAR gamma protein was expressed in the nuclei of cells in some cases and expressed in the nuclei and cytoplasm in others. The expression of PPAR gamma protein is decreased in esophageal cancer tissue compared with normal esophageal squamous epithelium. However, we could not deduce the apparent relation for the expression between PPAR gamma mRNA and PPAR gamma proteins in immunohistochemistry (P = 0.284). In esophageal cancer tissues, the expression of PPAR gamma was decreased compared with normal esophageal epithelium. The mRNA expression level of PPAR gamma may be a marker of prognosis after operation in esophageal cancer patients.

Decreased perioxisome proliferator-activated receptor gamma gene expression was correlated with poor prognosis in patients with lung cancer

Activation of the nuclear hormone receptor perioxisome proliferator-activated receptor gamma (PPARγ) inhibits cell growth and induces apoptosis in several human cancers. We have hypothesized that PPARγ mRNA levels could be predictors of the differentiation and survival of lung cancer. The study included 77 lung cancer cases. The mRNA levels were quantified by real time reverse transcription-polymerase chain reaction (RT-PCR) using LightCycler. The PPARγ mRNA levels were decreased in tumor tissues from lung cancer (0.579±1.255) compared to the normal adjacent lung tissues (4.191±2.868) ( P=0.0001). No significant difference in PPARγ mRNA levels was found among gender, age, and pathological subtype. The PPARγ mRNA levels were higher in tumor tissues from higher differentiated lung cancer. The NSCLC patients with low PPARγ mRNA expression (<0.5) had significantly worse survival than the patients without low PPARγ mRNA levels ( P=0.0438, Breslow–Gehan–Wilcoxon test; P=0.0168, Cox's proportional–Hazards regression model). Thus, PPARγ mRNA levels may serve as a prognostic marker in lung cancer. Using the LightCycler RT-PCR assay, the determination of PPARγ mRNA levels might provide a potential marker for treatment of lung cancer by PPARγ agonist. However, further studies and a longer follow up are needed to confirm the impact of PPARγ in the biological behavior of the tumor.

Negative regulation of peroxisome proliferator-activated receptor-gamma gene expression contributes to the antiadipogenic effects of tumor necrosis factor-alpha

Negative regulation of peroxisome proliferator-activated receptor-gamma gene expression contributes to the antiadipogenic effects of tumor necrosis factor-alpha

Negative regulation of peroxisome proliferator-activated receptor-gamma gene expression contributes to the antiadipogenic effects of tumor necrosis factor-alpha.

Recent studies indicate that a peroxisome proliferator-activated receptor, PPAR gamma, functions as an important adipocyte determination factor. In contrast, tumor necrosis factor-alpha (TNF alpha) inhibits adipogenesis, causes dedifferentiation of mature adipocytes, and reduces the expression of several adipocyte-specific genes. Here, we report that treatment of 3T3-L1 adipocytes with TNF alpha resulted in a time- and concentration-dependent decrease in PPAR gamma mRNA expression to the level detected in preadipocytes. PPAR gamma mRNA levels were reduced by 95% with 3 nM TNF alpha treatment for 24 h. Half-maximal effects were seen after 3 h treatment with 3 nM TNF alpha or with 50 pM TNF alpha (24-h exposure). Parallel reductions in PPAR gamma protein levels were also observed after treatment of 3T3-L1 adipocytes with TNF alpha. Using a ribonuclease protection assay, both alternatively spliced PPAR gamma isoforms (gamma 1 and gamma 2) were shown to be negatively regulated by TNF alpha. The down-regulation of PPAR gamma by TNF-alpha preceded the diminution in expression of other adipocyte-specific genes including CCAAT/enhancer binding protein and adipocyte fatty acid-binding protein (aP2). The effect of TNF alpha was specific for the gamma-isoform of PPARs, since the expression of PPAR delta mRNA was not affected by treatment with TNF alpha. Low level constitutive expression of PPAR gamma in 3T3-L1 adipocytes (at levels approximately 2- to 3-fold higher than in preadipocytes) partially blocked the inhibitory effect of TNF alpha on aP2 and adipsin expression. These findings support the following conclusions: 1) PPAR gamma expression is necessary for the maintenance of the adipocyte phenotype. 2) PPAR gamma, but not PPAR delta, expression is sufficient to attenuate TNF alpha-mediated effects on adipocyte phenotype. 3) Reduced PPAR gamma gene expression is likely to represent an important component of the mechanism by which TNF alpha exerts its antiadipogenic effects.