Ectopic expression of porcine peroxisome proliferator-activated receptor δ regulates adipogenesis in mouse myoblasts1

2008 ◽  
Vol 86 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Y. H. Yu ◽  
S. C. Wu ◽  
W. T. K. Cheng ◽  
H. J. Mersmann ◽  
S. T. Ding
Keyword(s):  
Ectopic Expression ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor

Agouti regulates adipocyte transcription factors

2001 ◽  
Vol 280 (4) ◽  
pp. C954-C961 ◽  
Author(s):  
Randall L. Mynatt ◽  
Jacqueline M. Stephens
Keyword(s):  
Adipose Tissue ◽  
Transgenic Mice ◽  
Ectopic Expression ◽  
Peroxisome Proliferator ◽  
Paracrine Factor ◽  
Peroxisome Proliferator Activated Receptor ◽  
Protein Levels ◽  
Skeletal Mass ◽  
Ppar Γ ◽  
Obesity And Diabetes

Agouti is a secreted paracrine factor that regulates pigmentation in hair follicle melanocytes. Several dominant mutations cause ectopic expression of agouti, resulting in a phenotype characterized by yellow fur, adult-onset obesity and diabetes, increased linear growth and skeletal mass, and increased susceptibility to tumors. Humans also produce agouti protein, but the highest levels of agouti in humans are found in adipose tissue. To mimic the human agoutiexpression pattern in mice, transgenic mice (aP2-agouti) that express agouti in adipose tissue were generated. The transgenic mice develop a mild form of obesity, and they are sensitized to the action of insulin. We correlated the levels of specific regulators of insulin signaling and adipocyte differentiation with these phenotypic changes in adipose tissue. Signal transducers and activators of transcription (STAT)1, STAT3, and peroxisome proliferator-activated receptor (PPAR)-γ protein levels were elevated in the transgenic mice. Treatment of mature 3T3-L1 adipocytes recapitulated these effects. These data demonstrate that agouti has potent effects on adipose tissue. We hypothesize that agouti increases adiposity and promotes insulin sensitivity by acting directly on adipocytes via PPAR-γ.

scholarly journals DEF-1, a Novel Src SH3 Binding Protein That Promotes Adipogenesis in Fibroblastic Cell Lines

1999 ◽  
Vol 19 (3) ◽  
pp. 2330-2337 ◽  
Author(s):  
Frederick J. King ◽  
Erding Hu ◽  
David F. Harris ◽  
Pasha Sarraf ◽  
Bruce M. Spiegelman ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Ectopic Expression ◽  
Signal Transduction Pathway ◽  
Bovine Brain ◽  
Cellular Growth ◽  
Affinity Column ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Efficient Induction ◽  
Signal Transduction Proteins

ABSTRACT The Src homology 3 (SH3) motif is found in numerous signal transduction proteins involved in cellular growth and differentiation. We have purified and cloned a novel protein, DEF-1 (differentiation-enhancing factor), from bovine brain by using a Src SH3 affinity column. Ectopic expression of DEF-1 in fibroblasts resulted in the differentiation of a significant fraction of the culture into adipocytes. This phenotype appears to be related to the induction of the transcription factor peroxisome proliferator-activated receptor γ (PPARγ), since DEF-1 NIH 3T3 cells demonstrated augmented levels of PPARγ mRNA and, when treated with activating PPARγ ligands, efficient induction of differentiation. Further evidence for a role for DEF-1 in adipogenesis was provided by heightened expression of DEF-1 mRNA in adipose tissue isolated fromobese and diabetes mice compared to that in tissue isolated from wild-type mice. However, DEF-1 mRNA was detected in multiple tissues, suggesting that the signal transduction pathway(s) in which DEF-1 is involved is not limited to adipogenesis. These results suggest that DEF-1 is an important component of a signal transduction process that is involved in the differentiation of fibroblasts and possibly of other types of cells.

Fenofibrate inhibits intestinal Cl− secretion by blocking basolateral KCNQ1 K+ channels

2007 ◽  
Vol 293 (6) ◽  
pp. G1288-G1299 ◽  
Author(s):  
Poonam J. Bajwa ◽  
Abderrahmane Alioua ◽  
Jimmy W. Lee ◽  
Daniel S. Straus ◽  
Ligia Toro ◽  
...  
Keyword(s):  
Short Circuit ◽  
Ectopic Expression ◽  
Short Circuit Current ◽  
Selective Inhibition ◽  
Flux Analysis ◽  
Peroxisome Proliferator ◽  
Channel Activity ◽  
T84 Cells ◽  
Peroxisome Proliferator Activated Receptor ◽  
Heat Stable

Fibrates are peroxisome proliferator-activated receptor-α (PPARα) ligands in widespread clinical use to lower plasma triglyceride levels. We investigated the effect of fenofibrate and clofibrate on ion transport in mouse intestine and in human T84 colonic adenocarcinoma cells through the use of short-circuit current ( Isc) and ion flux analysis. In mice, oral administration of fenofibrate produced a persistent inhibition of cAMP-stimulated electrogenic Cl− secretion by isolated jejunum and colon without affecting electroneutral fluxes of 22Na+ or 86Rb+ (K+) across unstimulated colonic mucosa. When applied acutely to isolated mouse intestinal mucosa, 100 μM fenofibrate inhibited cAMP-stimulated Isc within 5 min. In T84 cells, fenofibrate rapidly inhibited ∼80% the Cl− secretory responses to forskolin (cAMP) and to heat stable enterotoxin STa (cGMP) without affecting the response to carbachol (Ca2+). Both fenofibrate and clofibrate inhibited cAMP-stimulated Isc with an IC50 ∼1 μM, whereas other PPARα activators (gemfibrozil and Wy-14,643) were without effect. Membrane permeabilization experiments on T84 cells indicated that fenofibrate inhibits basolateral cAMP-stimulated K+ channels (putatively KCNQ1/KCNE3) without affecting Ca2+-stimulated K+ channel activity, whereas clofibrate inhibits both K+ pathways. Fenofibrate had no effect on apical cAMP-stimulated Cl− channel activity. Patch-clamp analysis of HEK-293T cells confirmed that 100 μM fenofibrate rapidly inhibits K+ currents associated with ectopic expression of human KCNQ1 with or without the KCNE3 β-subunit. We conclude that fenofibrate inhibits intestinal cAMP-stimulated Cl− secretion through a nongenomic mechanism that involves a selective inhibition of basolateral KCNQ1/KCNE3 channel complexes. Our findings raise the prospect of fenofibrate as a safe and effective antidiarrheal agent.

scholarly journals Retinoic acid blocks adipogenesis by inhibiting C/EBPbeta-mediated transcription.

1997 ◽  
Vol 17 (3) ◽  
pp. 1552-1561 ◽  
Author(s):  
E J Schwarz ◽  
M J Reginato ◽  
D Shao ◽  
S L Krakow ◽  
M A Lazar
Keyword(s):  
Transcription Factors ◽  
Retinoic Acid ◽  
Transcriptional Activation ◽  
Adipocyte Differentiation ◽  
Ectopic Expression ◽  
Transient Transfection ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Necessary And Sufficient ◽  
Sequential Induction

Adipocyte differentiation is thought to involve sequential induction of the transcription factors C/EBPbeta, peroxisome proliferator-activated receptor gamma (PPARgamma), and C/EBPalpha. C/EBPalpha expression is both necessary and sufficient for adipocyte differentiation. Here we report that ectopic expression of either C/EBPalpha or C/EBPbeta induces PPARgamma expression and adipogenesis and that retinoic acid (RA) completely inhibits adipogenesis by either form of C/EBP. In studies of normal preadipocytes, RA does not prevent C/EBPbeta induction but blocks induction of PPARgamma, C/EBPalpha, and adipogenesis. In transient transfection studies, liganded RA receptor (RAR) specifically blocks transcriptional activation by either C/EBPalpha or C/EBPbeta. These results strongly suggest that C/EBPalpha substitutes for C/EBPbeta to induce adipocyte differentiation and that liganded RAR inhibits adipogenesis by blocking C/EBPbeta-mediated induction of downstream genes.

scholarly journals Induction of peroxisome proliferator-activated receptor gamma during the conversion of 3T3 fibroblasts into adipocytes is mediated by C/EBPbeta, C/EBPdelta, and glucocorticoids.

1996 ◽  
Vol 16 (8) ◽  
pp. 4128-4136 ◽  
Author(s):  
Z Wu ◽  
N L Bucher ◽  
S R Farmer
Keyword(s):  
Gene Expression ◽  
Expression System ◽  
Ectopic Expression ◽  
Response To Treatment ◽  
Peroxisome Proliferator ◽  
Differentiation Process ◽  
Peroxisome Proliferator Activated Receptor ◽  
Initial Exposure ◽  
3T3 Fibroblasts ◽  
Nih 3T3

The differentiation of 3T3 preadipocytes into adipocytes is accompanied by a transient induction of C/EBPbeta and C/EBPdelta expression in response to treatment of the cells with methylisobutylxanthine (MIX) and dexamethasone (DEX), respectively. In this report, we demonstrate that peroxisome proliferator-activated receptor gamma (PPARgamma) expression in 3T3-L1 preadipocytes is induced by MIX and DEX, suggesting that C/EBPbeta and C/EBPdelta may be involved in this process. Using a tetracycline-responsive expression system, we have recently shown that the conditional ectopic expression of C/EBPbeta in NIH 3T3 fibroblasts (beta2 cells) in the presence of DEX activates the synthesis of peroxisome PPARgamma mRNA. Subsequent exposure of these cells to PPAR activators stimulates their conversion into adipocytes; however, neither the expression of C/EBPbeta nor exposure to DEX alone is capable of inducing PPARgamma expression in the beta2 cell line. We find that unlike the case for 3T3 preadipocytes, C/EBPdelta is not induced by DEX in these 3T3 fibroblasts and therefore is not relaying the effect of this glucocorticoid to the PPARgamma gene. To define the role of glucocorticoids in regulating PPARgamma expression and the possible involvement of C/EBPdelta, we have established an additional set of NIH 3T3 cell lines expressing either C/EBPdelta alone (delta23 cells) or C/EBPdelta and C/EBPbeta together (beta/delta39 cells), using the tetracycline-responsive system. Culture of these cells in tetracycline-deficient medium containing DEX, MIX, insulin, and fetal bovine serum shows that the beta/delta39 cells express PPARgamma and aP2 mRNAs at levels that are almost equivalent to those observed in fully differentiated 3T3-L1 adipocytes. These levels are approximately threefold higher than their levels of expression in the beta2 cells. Despite the fact that these beta/delta39 cells produce abundant amounts of C/EBPbeta and C/EBPdelta (in the absence of tetracycline), they still require glucocorticoids to attain maximum expression of PPARgamma mRNA. Furthermore, the induction of PPARgamma mRNA by exposure of these cells to DEX occurs in the absence of ongoing protein synthesis. The delta23 cells, on the other hand, are not capable of activating PPARgamma gene expression when exposed to the same adipogenic inducers. Finally, attenuation of ectopic C/EBPbeta production at various stages during the differentiation process results in a concomitant inhibition of PPARgamma and the adipogenic program. These data strongly suggest that the induction of PPARgamma gene expression in multipotential mesenchymal stem cells (NIH 3T3 fibroblasts) is dependent on elevated levels of C/EBPbeta throughout the differentiation process, as well as an initial exposure to glucocorticoids. C/EBPdelta may function by synergizing with C/EBPbeta to enhance the level of PPARgamma expression.

scholarly journals Peroxisome-proliferator-activated receptor γ suppresses Wnt/β-catenin signalling during adipogenesis

2003 ◽  
Vol 376 (3) ◽  
pp. 607-613 ◽  
Author(s):  
Marthe MOLDES ◽  
Ying ZUO ◽  
Ron F. MORRISON ◽  
David SILVA ◽  
Bae-Hang PARK ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Ectopic Expression ◽  
Reciprocal Relationship ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Activation Of Transcription ◽  
Undifferentiated State ◽  
Ectopic Production ◽  
Pparγ Expression

The Wnt/β-catenin signalling pathway appears to operate to maintain the undifferentiated state of preadipocytes by inhibiting adipogenic gene expression. To define the mechanisms regulating suppression of Wnt/β-catenin signalling, we analysed the β-catenin expression in response to activation of transcription factors that regulate adipogenesis. The results show an extensive down-regulation of nuclear β-catenin that occurs during the first few days of differentiation of 3T3-L1 preadipocytes and coincides with the induction of the adipogenic transcription factors, C/EBPβ (CCAAT-enhancer-binding protein) and PPARγ (peroxisome-proliferator-activated receptor). To assess the role of each of these factors in this process, we conditionally overexpressed C/EBPβ in Swiss mouse fibroblasts using the TET-off system. Abundant expression of C/EBPβ alone had minimal effect on β-catenin expression, whereas expression of C/EBPβ, in the presence of dexamethasone, induced PPARγ expression and caused a measurable decrease in β-catenin. In addition, exposure of cells expressing both C/EBPβ and PPARγ to a potent PPARγ ligand resulted in an even greater decrease in β-catenin by mechanisms that involve the proteasome. Our studies also suggest a reciprocal relationship between PPARγ activity and β-catenin expression, since ectopic production of Wnt-1 in preadipocytes blocked the induction of PPARγ gene expression. Moreover, by suppressing β-catenin expression, ectopic expression of PPARγ in Wnt-1-expressing preadipocytes rescued the block in adipogenesis after their exposure to the PPARγ ligand, troglitazone.

scholarly journals Estrogen-related receptor-γ and peroxisome proliferator-activated receptor-γ coactivator-1α regulate estrogen-related receptor-α gene expression via a conserved multi-hormone response element

2005 ◽  
Vol 34 (2) ◽  
pp. 473-487 ◽  
Author(s):  
D Liu ◽  
Z Zhang ◽  
C T Teng
Keyword(s):  
Nuclear Receptors ◽  
Molecular Mechanisms ◽  
Ectopic Expression ◽  
Peroxisome Proliferator ◽  
Hormone Response ◽  
Core Element ◽  
Response Element ◽  
Peroxisome Proliferator Activated Receptor ◽  
Hormone Response Element ◽  
Estrogen Related Receptor

The expression of estrogen-related receptor-α (ERRα) is stimulated by estrogen in selective tissues. Recently, a correlation between ERRα expression and the induction of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in the liver of fasting animals and in cold-stressed brown-fat tissues and skeletal muscle was shown. To explore the molecular mechanisms of ERRα regulation by diverse signals, the promoter of the human ERRα gene was cloned and characterized. Mutation and deletion analyses revealed that a 53 bp region containing repeated core element AGGTCA motifs of the ERRα gene serves as a multi-hormone response element (MHRE) for several nuclear receptors in transient co-transfection studies of human endometrial carcinoma (HEC-1B) cells. Among the nuclear receptors tested, ERRγ bound to and robustly stimulated the transcription of reporters containing at least two AGGTCA motifs. Ectopic expression of PGC-1α in HEC-1B cells strongly activated the reporter containing the MHRE, presumably via the endogenous nuclear receptor binding to the element. Reducing the endogenous level of ERRγ by small interfering RNA, and increasing the ERRγ level by ectopic expression, substantially decreased and increased respectively the transactivation capability of PGC-1α. The activation function 2 domain of the ERRγ and the L2 and L3 motifs of PGC-1α were essential to transactivate the MHRE. Additionally, PGC-1α increases the amount of endogenous ERRγ bound to the MHRE region as determined by a chromatin immunoprecipitation assay. The present study demonstrates that the MHRE of the ERRα gene is a target for ERRγ transactivation, which is enhanced by PGC-1α.

scholarly journals Adiponectin Secretion Is Regulated by SIRT1 and the Endoplasmic Reticulum Oxidoreductase Ero1-Lα

2007 ◽  
Vol 27 (13) ◽  
pp. 4698-4707 ◽  
Author(s):  
Li Qiang ◽  
Hong Wang ◽  
Stephen R. Farmer
Keyword(s):  
Endoplasmic Reticulum ◽  
Molecular Mechanisms ◽  
Ectopic Expression ◽  
Terminal Phase ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
3T3 Fibroblasts ◽  
Metabolic States ◽  
Interfering Rna ◽  
Circulating Levels

ABSTRACT Adiponectin is secreted from adipose tissue in response to metabolic effectors in order to sensitize the liver and muscle to insulin. Reduced circulating levels of adiponectin that usually accompany obesity contribute to the associated insulin resistance. The molecular mechanisms controlling the production of adiponectin are essentially unknown. In this report, we demonstrate that the endoplasmic reticulum (ER) oxidoreductase Ero1-Lα and effectors modulating peroxisome proliferator-activated receptor γ (PPARγ) and SIRT1 activities regulate secretion of adiponectin from 3T3-L1 adipocytes. Specifically, adiponectin secretion and Ero1-Lα expression are induced during the early phase of adipogenesis but are then down-regulated during the terminal phase, coincident with an increased expression of SIRT1. Suppression of SIRT1 or activation of PPARγ enhances Ero1-Lα expression and stimulates secretion of high-molecular-weight complexes of adiponectin in mature adipocytes. Suppression of Ero1-Lα through expression of a corresponding small interfering RNA reduces adiponectin secretion during the differentiation of 3T3-L1 preadipocytes. Moreover, ectopic expression of Ero1-Lα in Ero1-Lα-deficient 3T3 fibroblasts stimulates the secretion of adiponectin following their conversion into adipocytes and prevents the suppression of adiponectin secretion in response to activation of SIRT1 by exposure to resveratrol. These findings provide a framework to understand the mechanisms by which adipocytes regulate secretion of adiponectin in response to various metabolic states.

scholarly journals Serum- and Glucocorticoid-Inducible Kinase 1 (SGK1) Regulates Adipocyte Differentiation via Forkhead Box O1

2010 ◽  
Vol 24 (2) ◽  
pp. 370-380 ◽  
Author(s):  
Natalia Di Pietro ◽  
Valentine Panel ◽  
Schantel Hayes ◽  
Alessia Bagattin ◽  
Sunitha Meruvu ◽  
...  
Keyword(s):  
Cellular Localization ◽  
Adipocyte Differentiation ◽  
Binding Protein ◽  
Ectopic Expression ◽  
Peroxisome Proliferator ◽  
Mrna Levels ◽  
Peroxisome Proliferator Activated Receptor ◽  
Fatty Acid Binding ◽  
Mesenchymal Precursor Cells ◽  
And Function

Abstract The serum and glucocorticoid-inducible kinase 1 (SGK1) is an inducible kinase the physiological function of which has been characterized primarily in the kidney. Here we show that SGK1 is expressed in white adipose tissue and that its levels are induced in the conversion of preadipocytes into fat cells. Adipocyte differentiation is significantly diminished via small interfering RNA inhibition of endogenous SGK1 expression, whereas ectopic expression of SGK1 in mesenchymal precursor cells promotes adipogenesis. The SGK1-mediated phenotypic effects on differentiation parallel changes in the mRNA levels for critical regulators and markers of adipogenesis, such as peroxisome proliferator-activated receptor γ, CCAAT enhancer binding protein α, and fatty acid binding protein aP2. We demonstrate that SGK1 affects differentiation by direct phosphorylation of Foxo1, thereby changing its cellular localization from the nucleus to the cytosol. In addition we show that SGK1−/− cells are unable to relocalize Foxo1 to the cytosol in response to dexamethasone. Together these results show that SGK1 influences adipocyte differentiation by regulating Foxo1 phosphorylation and reveal a potentially important function for this kinase in the control of fat mass and function.

scholarly journals Characterization of the human, mouse and rat PGC1beta (peroxisome-proliferator-activated receptor-gamma co-activator 1beta) gene in vitro and in vivo

2003 ◽  
Vol 373 (1) ◽  
pp. 155-165 ◽  
Author(s):  
Aline MEIRHAEGHE ◽  
Vivion CROWLEY ◽  
Carol LENAGHAN ◽  
Christopher LELLIOTT ◽  
Kath GREEN ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Thyroid Hormone Receptor ◽  
Ectopic Expression ◽  
Cdna Libraries ◽  
Acid Oxidation ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Brown Adipose

PGC1α is a co-activator involved in adaptive thermogenesis, fatty-acid oxidation and gluconeogenesis. We describe the identification of several isoforms of a new human PGC1α homologue, cloned independently and named PGC1β. The human PGC1β gene is localized to chromosome 5, has 13 exons and spans more than 78 kb. Two different 5′ and 3′ ends due to differential splicing were identified by rapid amplification of cDNA ends PCR and screening of human cDNA libraries. We show that PGC1β variants in humans, mice and rats are expressed predominantly in heart, brown adipose tissue, brain and skeletal muscle. PGC1β expression, unlike PGC1α, is not up-regulated in brown adipose tissue in response to cold or obesity. Fasting experiments showed that PGC1α, but not PGC1β, is induced in liver and this suggests that only PGC1α is involved in the hepatic gluconeogenesis. No changes in PGC1β gene expression were observed associated with exercise. Human PGC1β-1a and −2a isoforms localized to the cell nucleus and, specifically, the isoform PGC1β-1a co-activated peroxisome-proliferator-activated receptor-γ, -α and the thyroid hormone receptor β1. Finally, we show that ectopic expression PGC1β leads to increased mitochondrial number and basal oxygen consumption. These results suggest that PGC1β may play a role in constitutive adrenergic-independent mitochondrial biogenesis.

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