Abstract 1729: PPARγ Regulates ABCG1 Expression in Macrophages via LXR-Driven Dual Promoters

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Makoto Ayaori ◽  
Masatsune Ogura ◽  
Kazuhiro Nakaya ◽  
Tetsuya Hisada ◽  
Shun-ichi Takiguchi ◽  
...  

ATP binding cassette transporter G1 (ABCG1), which is expressed in macrophages, has been implicated in the efflux of cholesterol to high density lipoprotein. Peroxisome proliferator-activated receptor γ (PPARγ) has been reported to be involved in cholesterol efflux from macrophages, and increased expression of ABCG1 via liver receptor X (LXR)-dependent and independent pathways. However, the mechanisms by which ABCG1 expression is increased by PPARγ have not been fully characterized. We observed that pioglitazone, a PPARγ ligand, increases cholesterol efflux from THP-1 macrophages, as well as ABCG1 mRNA and protein levels. Treatment with actinomycin D abolished the inducible effect of pioglitazone on ABCG1, indicating that pioglitazone transcriptionally activated ABCG1 expression. To clarify how pioglitazone regulates ABCG1 expression, we investigated promoter activity using reporter constructs containing human ABCG1 promoter A and B (located upstream of exon 1 and 5, respectively), with or without mutated LXR-binding sites. The results indicated that pioglitazone activated both promoters in an LXR-dependent manner. We also observed that pioglitazone increased two major transcripts driven by promoter A and B using specific primers for each transcript. To determine whether PPARγ and LXRα were involved in these effects of pioglitazone, we performed siRNA-knockdown of PPARγ and LXRα in macrophages, which resulted in 75% and 91% decreases in PPARγ and LXRα mRNA levels, respectively. PPARγ and LXRα-knockdown, respectively, completely or partially abolished pioglitazone-induced ABCG1 expression. In conclusion, these results suggest that pioglitazone transcriptionally increased ABCG1 expression in macrophages by activating dual promoters in an LXR-dependent manner. Further studies are needed to assess LXR-independent mechanisms for the stimulatory effect of pioglitazone on ABCG1.

2006 ◽  
Vol 290 (5) ◽  
pp. E916-E924 ◽  
Author(s):  
Juan Kong ◽  
Yan Chun Li

We have investigated the molecular mechanism whereby 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] inhibits adipogenesis in vitro. 1,25(OH)2D3 blocks 3T3-L1 cell differentiation into adipocytes in a dose-dependent manner; however, the inhibition is ineffective 24–48 h after the differentiation is initiated, suggesting that 1,25(OH)2D3 inhibits only the early events of the adipogenic program. Treatment of 3T3-L1 cells with 1,25(OH)2D3 does not block the mitotic clonal expansion or C/EBPβ induction; rather, 1,25(OH)2D3 blocks the expression of C/EBPα, peroxisome proliferator-activated receptor-γ (PPARγ), sterol regulatory element-binding protein-1, and other downstream adipocyte markers. The inhibition by 1,25(OH)2D3 is reversible, since removal of 1,25(OH)2D3 from the medium restores the adipogenic process with only a temporal delay. Interestingly, although the vitamin D receptor (VDR) protein is barely detectable in 3T3-L1 preadipocytes, its levels are dramatically increased during the early phase of adipogenesis, peaking at 4–8 h and subsiding afterward throughout the rest of the differentiation program; 1,25(OH)2D3 treatment appears to stabilize the VDR protein levels. Consistently, adenovirus-mediated overexpression of human (h) VDR in 3T3-L1 cells completely blocks the adipogenic program, confirming that VDR is inhibitory. Inhibition of adipocyte differentiation by 1,25(OH)2D3 is ameliorated by troglitazone, a specific PPARγ antagonist; conversely, hVDR partially suppresses the transacting activity of PPARγ but not of C/EBPβ or C/EBPα. Moreover, 1,25(OH)2D3 markedly suppresses C/EBPα and PPARγ mRNA levels in mouse epididymal fat tissue culture. Taken together, these data indicate that the blockade of 3T3-L1 cell differentiation by 1,25(OH)2D3 occurs at the postclonal expansion stages and involves direct suppression of C/EBPα and PPARγ upregulation, antagonization of PPARγ activity, and stabilization of the inhibitory VDR protein.


2021 ◽  
Vol 49 (11) ◽  
pp. 030006052110550
Author(s):  
Xing Wang ◽  
Shuchun Chen ◽  
Dan Lv ◽  
Zelin Li ◽  
Luping Ren ◽  
...  

Objective To investigate the effect of liraglutide on the browning of white fat and the suppression of obesity via regulating microRNA (miR)-27b in vivo and in vitro. Methods Sprague-Dawley rats were fed a high-fat (HF) diet and 3T3-L1 pre-adipocytes were differentiated into mature white adipocytes. Rats and mature adipocytes were then treated with different doses of liraglutide. The mRNA and protein levels of browning-associated proteins, including uncoupling protein 1 (UCP1), PR domain containing 16 (PRDM16), CCAAT enhancer binding protein β (CEBPβ), cell death-inducing DFFA-like effector A (CIDEA) and peroxisome proliferator-activated receptor-γ-coactivator 1α (PGC-1α), were detected using quantitative real-time polymerase chain reaction and Western blotting. Results Liraglutide decreased body weight and reduced the levels of blood glucose, triglyceride and low-density lipoprotein cholesterol in HF diet-fed rats. Liraglutide increased the levels of UCP1, PRDM16, CEBPβ, CIDEA and PGC-1α in vivo and vitro. The levels of miR-27b were upregulated in HF diet-fed rats, whereas liraglutide reduced the levels of miR-27b. In vitro, overexpression of miR-27b decreased the mRNA and protein levels of UCP1, PRDM16, CEBPβ, CIDEA and PGC-1α. Transfection with the miR-27b mimics attenuated the effect of liraglutide on the browning of white adipocytes. Conclusion Liraglutide induced browning of white adipose through regulation of miR-27b.


2002 ◽  
Vol 22 (8) ◽  
pp. 2607-2619 ◽  
Author(s):  
Taro E. Akiyama ◽  
Shuichi Sakai ◽  
Gilles Lambert ◽  
Christopher J. Nicol ◽  
Kimihiko Matsusue ◽  
...  

ABSTRACT Disruption of the peroxisome proliferator-activated receptor γ (PPARγ) gene causes embryonic lethality due to placental dysfunction. To circumvent this, a PPARγ conditional gene knockout mouse was produced by using the Cre-loxP system. The targeted allele, containing loxP sites flanking exon 2 of the PPARγ gene, was crossed into a transgenic mouse line expressing Cre recombinase under the control of the alpha/beta interferon-inducible (MX) promoter. Induction of the MX promoter by pIpC resulted in nearly complete deletion of the targeted exon, a corresponding loss of full-length PPARγ mRNA transcript and protein, and marked reductions in basal and troglitazone-stimulated expression of the genes encoding lipoprotein lipase, CD36, LXRα, and ABCG1 in thioglycolate-elicited peritoneal macrophages. Reductions in the basal levels of apolipoprotein E (apoE) mRNA in macrophages and apoE protein in total plasma and high-density lipoprotein (HDL) were also observed in pIpC-treated PPARγ-MXCre+ mice. Basal cholesterol efflux from cholesterol-loaded macrophages to HDL was significantly reduced after disruption of the PPARγ gene. Troglitazone selectively inhibited ABCA1 expression (while rosiglitazone, ciglitazone, and pioglitazone had little effect) and cholesterol efflux in both PPARγ-deficient and control macrophages, indicating that this drug can exert paradoxical effects on cholesterol homeostasis that are independent of PPARγ. Together, these data indicate that PPARγ plays a critical role in the regulation of cholesterol homeostasis by controlling the expression of a network of genes that mediate cholesterol efflux from cells and its transport in plasma.


Nutrients ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 652 ◽  
Author(s):  
Ju-Sik Park ◽  
John O. Holloszy ◽  
Kijin Kim ◽  
Jin-Ho Koh

This study aimed to investigate the long-term effects of training intervention and resting on protein expression and stability of peroxisome proliferator-activated receptor β/δ (PPARβ), peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1α), glucose transporter type 4 (GLUT4), and mitochondrial proteins, and determine whether glucose homeostasis can be regulated through stable expression of these proteins after training. Rats swam daily for 3, 6, 9, 14, or 28 days, and then allowed to rest for 5 days post-training. Protein and mRNA levels were measured in the skeletal muscles of these rats. PPARβ was overexpressed and knocked down in myotubes in the skeletal muscle to investigate the effects of swimming training on various signaling cascades of PGC-1α transcription, insulin signaling, and glucose uptake. Exercise training (Ext) upregulated PPARβ, PGC-1α, GLUT4, and mitochondrial enzymes, including NADH-ubiquinone oxidoreductase (NUO), cytochrome c oxidase subunit I (COX1), citrate synthase (CS), and cytochrome c (Cyto C) in a time-dependent manner and promoted the protein stability of PPARβ, PGC-1α, GLUT4, NUO, CS, and Cyto C, such that they were significantly upregulated 5 days after training cessation. PPARβ overexpression increased the PGC-1α protein levels post-translation and improved insulin-induced signaling responsiveness and glucose uptake. The present results indicate that Ext promotes the protein stability of key mitochondria enzymes GLUT4, PGC-1α, and PPARβ even after Ext cessation.


2007 ◽  
Vol 194 (1) ◽  
pp. 87-99 ◽  
Author(s):  
Masaya Takeda ◽  
Fumio Otsuka ◽  
Hiroyuki Otani ◽  
Kenichi Inagaki ◽  
Tomoko Miyoshi ◽  
...  

Involvement of peroxisome proliferator-activated receptor-γ (PPAR-γ ) activation and bone morphogenetic protein (BMP) signaling in regulating cell proliferation and hormonal production of pituitary tumors has been reported, although the underlying mechanism remains poorly understood. Here, we investigated regulatory roles of PPARα and PPARγ in gonadotropin transcription and cell mitosis modulated by pituitary activin/BMP systems using a mouse gonadotropinoma cell line Lβ T2, which expresses activin/BMP receptors, transcription factor Smads, PPARα , and PPARγ . In Lβ T2 cells, BMP signaling shown by Smad1/5/8 phosphorylation and Id-1 transcription was readily activated by BMPs. A PPARγ agonist, pioglitazone significantly reduced BMP-induced DNA synthesis by Lβ T2; whereas the PPARα agonist, fenofibric acid, did not. In accordance with the effects on cell mitosis, pioglitazone but not fenofibric acid significantly decreased BMP-induced Id-1-Luc activation. Neither fenofibric acid nor pioglitazone affected activin signaling detected by (CAGA)9-Luc activity. Both PPARα and PPARγ ligands directly suppressed transcriptional activities of FSHβ , LHβ , and GnRHR. Activation of PPARα and PPARγ increased mRNA levels of follistatin, but did not affect the expression of follistatin-related gene. Thus, PPAR agonists not only directly suppress gonadotropin transcription and BMP signaling, but also inhibit the biological actions of activins which facilitate gonadotropin transcription through upregulating follistatin expression. In addition, pioglitazone increased BMP ligands mRNA, but decreased activin-β B mRNA in Lβ T2 cells. Collectively, PPAR activation differentially regulates gonadotrope cell proliferation and gonadotropin transcription in a ligand-dependent manner.


2015 ◽  
Vol 35 (1) ◽  
pp. 92-103 ◽  
Author(s):  
Yuriy Nozhenko ◽  
Ana M. Rodríguez ◽  
Andreu Palou

Background: Skeletal muscle can experience pronounced metabolic adaptations in response to extrinsic stimuli, and expresses leptin receptor (OB-Rb). We aimed to further the understanding of leptin effects on muscle cells, by studying the expression of key energy metabolism genes in C2C12 myotubes. Methods: We performed a dose-time-dependent study with physiological concentrations of leptin: 5, 10 and 50ng/ml, for 0, 30', 3h, 6h, 12h and 24h, also monitoring time-course changes in non-treated cells. mRNA levels were analyzed by RT-qPCR and peroxisome proliferator activated receptor γ coactivator 1α (PGC1α) protein levels by western blot. Results: The most significant effects were observed with 50ng/ml leptin. In the short-term (30' and/or 3h), leptin significantly induced the expression of PGC1α, muscle carnitine palmitoyl transferase 1 (mCPT1), uncoupling protein 3 (UCP3), OB-Rb, Insulin receptor (InsR) and interleukins 6 and 15 (IL6, IL15). There was a decrease in mRNA levels of pyruvate dehydrogenase kinase 4 (PDK4) and mCPT1 in the long-term (24h). PGC1α protein levels were increased (24h). Conclusion: Leptin rapidly induces the expression of genes important for its own response and the control of metabolic fuels, with the rapid responses of the genes encoding the master regulator PGC1α, mCPT1, UCP3, PDK4 and the signaling secretory molecule IL6 particularly interesting.


2021 ◽  
Author(s):  
Jennifer J. Schlezinger ◽  
Tuulia Hyotylainen ◽  
Tim Sinioja ◽  
Catherine Boston ◽  
Hannah Puckett ◽  
...  

Per- and polyfluoroalkyl substances (PFAS) are pervasive in the environment resulting in nearly universal detection in people. Human serum PFAS concentrations are strongly associated with increased serum low-density lipoprotein cholesterol (LDL-C), and growing evidence suggests an association with serum triacylglycerides (TG). Here, we tested the hypothesis that perfluorooctanoic acid (PFOA) dysregulates liver and serum triacylglycerides in human peroxisome proliferator activated receptor α (hPPAR α)-expressing mice fed an American diet. Mice were exposed to PFOA (3.3 mg/l) in drinking water for 6 weeks resulting in a serum concentration of 48 ± 9 μg/ml. In male and female hPPAR α mice, PFOA increased total liver TG and TG substituted with saturated and monounsaturated fatty acids. Lack of expression of hPPARα alone also increased total liver TG, and PFOA treatment had little effect on liver TG in null mice. In hPPARα mice, PFOA neither significantly increased nor decreased serum TG; however, there was a modest increase in TG associated with very low-density cholesterol particles in both sexes. Across studies, a non-monotonic effect of PFOA on serum TG is evident, with the serum PFOA concentration in this study falling near the null point between increasing and decreasing serum TG. Intriguingly, in female PPARα null mice, PFOA significantly increased serum TG, with a similar trend in males. PFOA also modified fatty acid and TG homeostasis-related gene expression in liver, in a hPPARα-dependent manner, but not in adipose. The results reveal the importance of context (serum concentration and genotype) in determining the effect of PFOA on lipid homeostasis.


1998 ◽  
Vol 158 (2) ◽  
pp. 237-246 ◽  
Author(s):  
LQ Fan ◽  
RC Cattley ◽  
JC Corton

The 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) family of proteins regulates the levels of the active 17 beta-hydroxy forms of sex steroids. The expression of 17 beta-HSD type IV is induced by peroxisome proliferator chemicals (PPC) in rat liver. In order to characterize more generally the impact of PPC on 17 beta-HSD expression, we determined (1) if expression of other members of the 17 beta-HSD family was coordinately induced by PPC exposure, (2) the tissues in which 17 beta-HSD was induced by PPC, and (3) whether the induction of 17 beta-HSD by PPC was dependent on the peroxisome proliferator-activated receptor alpha (PPAR alpha), the central mediator of PPC effects in the mouse liver. The mRNA levels of 17 beta-HSD I, II, and III were not altered in the liver, kidney, and testis or uterus of rats treated with PPC. The mRNA or 80 kDa a full-length protein levels of 17 beta-HSD IV were strongly induced in liver and kidney, but not induced in adrenals, brown fat, heart, testis, and uterus of rats treated with diverse PPC. In liver and kidneys from treated rats, additional proteins of 66 kDa, 56 kDa, and 32 kDa were also induced which reacted with the anti-17 beta-HSD IV antibodies and were most likely proteolytic fragments of 17 bega-HSD IV. Treatment of mice which lack a functional form of PPAR alpha with PPC, demonstrated that PPC-inducibility of 17 beta-HSD IV mRNA or the 80 kDa protein was dependent on PPAR alpha expression in liver and kidney. Our results demonstrate that 17 beta-HSD IV is induced by PPC through a PPAR alpha-dependent mechanism and support the hypothesis that exposure to PPC leads to alterations in sex steroid metabolism.


Endocrinology ◽  
2003 ◽  
Vol 144 (1) ◽  
pp. 101-109 ◽  
Author(s):  
Masoumeh Jalouli ◽  
Linda Carlsson ◽  
Caroline Améen ◽  
Daniel Lindén ◽  
Anna Ljungberg ◽  
...  

Abstract Peroxisome proliferator-activated receptor (PPAR) α is a nuclear receptor that is mainly expressed in tissues with a high degree of fatty acid oxidation such as liver, heart, and skeletal muscle. Unsaturated fatty acids, their derivatives, and fibrates activate PPARα. Male rats are more responsive to fibrates than female rats. We therefore wanted to investigate if there is a sex difference in PPARα expression. Male rats had higher levels of hepatic PPARα mRNA and protein than female rats. Fasting increased hepatic PPARα mRNA levels to a similar degree in both sexes. Gonadectomy of male rats decreased PPARα mRNA expression to similar levels as in intact and gonadectomized female rats. Hypophysectomy increased hepatic PPARα mRNA and protein levels. The increase in PPARα mRNA after hypophysectomy was more pronounced in females than in males. GH treatment decreased PPARα mRNA and protein levels, but the sex-differentiated secretory pattern of GH does not determine the sex-differentiated expression of PPARα. The expression of PPARα mRNA in heart or soleus muscle was not influenced by gender, gonadectomy, hypophysectomy, or GH treatment. In summary, pituitary-dependent hormones specifically regulate hepatic PPARα expression. Sex hormones regulate the sex difference in hepatic PPARα levels, but not via the sexually dimorphic GH secretory pattern.


2014 ◽  
Vol 306 (6) ◽  
pp. E615-E626 ◽  
Author(s):  
A. H. V. Remels ◽  
N. A. Pansters ◽  
H. R. Gosker ◽  
A. M. W. J. Schols ◽  
R. C. J. Langen

Physical inactivity-induced loss of skeletal muscle oxidative phenotype (OXPHEN), often observed in chronic disease, adversely affects physical functioning and quality of life. Potential therapeutic targets remain to be identified, since the molecular mechanisms involved in reloading-induced recovery of muscle OXPHEN remain incompletely understood. We hypothesized a role for alternative NF-κB, as a recently identified positive regulator of muscle OXPHEN, in reloading-induced alterations in muscle OXPHEN. Markers and regulators (including alternative NF-κB signaling) of muscle OXPHEN were investigated in gastrocnemius muscle of mice subjected to a hindlimb suspension/reloading (HLS/RL) protocol. Expression levels of oxidative phosphorylation subunits and slow myosin heavy chain isoforms I and IIA increased rapidly upon RL. After an initial decrease upon HLS, mRNA levels of peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC) molecules PGC-1α and PGC-1β and mRNA levels of mitochondrial transcription factor A (Tfam) and estrogen-related receptor α increased upon RL. PPAR-δ, nuclear respiratory factor 1 (NRF-1), NRF-2α, and sirtuin 1 mRNA levels increased during RL although expression levels were unaltered upon HLS. In addition, both Tfam and NRF-1 protein levels increased significantly during the RL period. Moreover, upon RL, IKK-α mRNA and protein levels increased, and phosphorylation of P100 and subsequent processing to P52 were elevated, reflecting alternative NF-κB activation. We conclude that RL-induced recovery of muscle OXPHEN is associated with activation of alternative NF-κB signaling.


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