scholarly journals Impaired Adipogenesis Caused by a Mutated Thyroid Hormone α1 Receptor

2007 ◽  
Vol 27 (6) ◽  
pp. 2359-2371 ◽  
Author(s):  
Hao Ying ◽  
Osamu Araki ◽  
Fumihiko Furuya ◽  
Yasuhito Kato ◽  
Sheue-Yann Cheng
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormone Receptor ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Protein Levels ◽  
Reduced Body ◽  
X Receptors

ABSTRACT Thyroid hormone (T3) is critical for growth, differentiation, and maintenance of metabolic homeostasis. Mice with a knock-in mutation in the thyroid hormone receptor α gene (TRα1PV) were created previously to explore the roles of mutated TRα1 in vivo. TRα1PV is a dominant negative mutant with a frameshift mutation in the carboxyl-terminal 14 amino acids that results in the loss of T3 binding and transcription capacity. Homozygous knock-in TRα1PV/PV mice are embryonic lethal, and heterozygous TRα1PV/+ mice display the striking phenotype of dwarfism. These mutant mice provide a valuable tool for identifying the defects that contribute to dwarfism. Here we show that white adipose tissue (WAT) mass was markedly reduced in TRα1PV/+ mice. The expression of peroxisome proliferator-activated receptor γ (PPARγ), the key regulator of adipogenesis, was repressed at both mRNA and protein levels in WAT of TRα1PV/+ mice. Moreover, TRα1PV acted to inhibit the transcription activity of PPARγ by competition with PPARγ for binding to PPARγ response elements and for heterodimerization with the retinoid X receptors. The expression of TRα1PV blocked the T3-dependent adipogenesis of 3T3-L1 cells and repressed the expression of PPARγ. Thus, mutations of TRα1 severely affect adipogenesis via cross talk with PPARγ signaling. The present study suggests that defects in adipogenesis could contribute to the phenotypic manifestation of reduced body weight in TRα1PV/+ mice.

scholarly journals Adipogenesis is differentially impaired by thyroid hormone receptor mutant isoforms

2010 ◽  
Vol 44 (4) ◽  
pp. 247-255 ◽  
Author(s):  
Alok Mishra ◽  
Xu-guang Zhu ◽  
Kai Ge ◽  
Sheue-Yann Cheng
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptors ◽  
Target Genes ◽  
Thyroid Hormone Receptor ◽  
Fold Increase ◽  
Dominant Negative ◽  
Peroxisome Proliferator ◽  
Loss Of Function ◽  
Peroxisome Proliferator Activated Receptor ◽  
Protein Levels

To understand the roles of thyroid hormone receptors (TRs) in adipogenesis, we adopted a loss-of-function approach. We generated 3T3-L1 cells stably expressing either TRα1 mutant (TRα1PV) or TRβ1 mutant (TRβ1PV). TRα1PV and TRβ1PV are dominant negative mutations with a frameshift in the C-terminal amino acids. In control cells, the thyroid hormone, tri-iodothyronine (T3), induced a 2.5-fold increase in adipogenesis in 3T3-L1 cells, as demonstrated by increased lipid droplets. This increase was mediated by T3-induced expression of the peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα), which are master regulators of adipogenesis at both the mRNA and protein levels. In 3T3-L1 cells stably expressing TRα1PV (L1-α1PV cells) or TRβ1PV (L1-β1PV cells), adipogenesis was reduced 94 or 54% respectively, indicative of differential inhibitory activity of mutant TR isoforms. Concordantly, the expression of PPARγ and C/EBPα at the mRNA and protein levels was more repressed in L1-α1PV cells than in L1-β1PV cells. In addition, the expression of PPARγ downstream target genes involved in fatty acid synthesis – the lipoprotein lipase (Lpl) and aP2 involved in adipogenesis – was more inhibited by TRα1PV than by TRβ1PV. Chromatin immunoprecipitation assays showed that TRα1PV was more avidly recruited than TRβ1PV to the promoter to preferentially block the expression of the C/ebpα gene. Taken together, these data indicate that impaired adipogenesis by mutant TR is isoform dependent. The finding that induction of adipogenesis is differentially regulated by TR isoforms suggests that TR isoform-specific ligands could be designed for therapeutic intervention for lipid abnormalities.

scholarly journals Functional Evidence for Retinoid X Receptor (RXR) as a Nonsilent Partner in the Thyroid Hormone Receptor/RXR Heterodimer

2002 ◽  
Vol 22 (16) ◽  
pp. 5782-5792 ◽  
Author(s):  
Dangsheng Li ◽  
Tong Li ◽  
Fang Wang ◽  
Heather Tian ◽  
Herbert H. Samuels
Keyword(s):  
Thyroid Hormone ◽  
Ligand Binding ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Retinoid X Receptor ◽  
Peroxisome Proliferator ◽  
Type Ii ◽  
Retinoid Receptor ◽  
Peroxisome Proliferator Activated Receptor

ABSTRACT Many members of the thyroid hormone/retinoid receptor subfamily (type II nuclear receptors) function as heterodimers with the retinoid X receptor (RXR). In heterodimers which are referred to as permissive, such as peroxisome proliferator activated receptor/RXR, both partners can bind cognate ligands and elicit ligand-dependent transactivation. In contrast, the thyroid hormone receptor (TR)/RXR heterodimer is believed to be nonpermissive, where RXR is thought to be incapable of ligand binding and is often referred to as a silent partner. In this report, we used a sensitive derepression assay system that we developed previously to reexamine the TR/RXR interrelationship. We provide functional evidence suggesting that in a TR/RXR heterodimer, the RXR component can bind its ligand in vivo. Ligand binding by RXR does not appear to directly activate the TR/RXR heterodimer; instead, it leads to a (at least transient or dynamic) dissociation of a cellular inhibitor(s)/corepressor(s) from its TR partner and thus may serve to modulate unliganded TR-mediated repression and/or liganded TR-mediated activation. Our results argue against the current silent-partner model for RXR in the TR/RXR heterodimer and reveal an unexpected aspect of cross regulation between TR and RXR.

Thyroid hormone (T3) rapidly activates p38 and AMPK in skeletal muscle in vivo

2008 ◽  
Vol 104 (1) ◽  
pp. 178-185 ◽  
Author(s):  
Isabella Irrcher ◽  
Donald R. Walkinshaw ◽  
Treacey E. Sheehan ◽  
David A. Hood
Keyword(s):  
Skeletal Muscle ◽  
Thyroid Hormone ◽  
Dna Binding ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Kinase Phosphorylation ◽  
Fast Twitch

Thyroid hormone (T3) regulates the function of many tissues within the body. The effects of T3 have largely been attributed to the modulation of thyroid hormone receptor-dependent gene transcription. However, nongenomic actions of T3 via the initiation of signaling events are emerging in a number of cell types. This study investigated the ability of short-term T3 treatment to phosphorylate and, therefore, activate signaling proteins in rat tissues in vivo. The kinases investigated included p38, AMP-activated protein kinase (AMPK), and extracellular signal-regulated kinase (ERK) 1/2. Following 2 h of T3 treatment, p38 and AMPK phosphorylation was increased in both the slow-twitch soleus and the fast-twitch plantaris muscles. In contrast, ERK1/2 was not activated in either muscle type. Neither p38 nor AMPK was affected in heart. However, AMPK activation was decreased by T3 in liver. ERK1/2 activation was decreased by T3 in heart, but increased in liver. Possible downstream consequences of T3-induced kinase phosphorylation were investigated by measuring cAMP response element binding protein (CREB) and thyroid hormone receptor DNA binding, as well as peroxisome proliferator-activated receptor-α coactivator-1 mRNA levels. Protein DNA binding to the cAMP or thyroid hormone response elements was unaltered by T3. However, peroxisome proliferator-activated receptor-α coactivator-1 mRNA expression was increased following 12 h of T3 treatment in soleus. These data are the first to characterize the effects of T3 treatment on kinase phosphorylation in vivo. We show that T3 rapidly modifies kinase activity in a tissue-specific fashion. Moreover, the T3-induced phosphorylation of p38 and AMPK in both slow- and fast-twitch skeletal muscles suggests that these events may be important in mediating hormone-induced increases in mitochondrial biogenesis in skeletal muscle.

scholarly journals Liraglutide suppresses obesity and promotes browning of white fat via miR-27b in vivo and in vitro

2021 ◽  
Vol 49 (11) ◽  
pp. 030006052110550
Author(s):  
Xing Wang ◽  
Shuchun Chen ◽  
Dan Lv ◽  
Zelin Li ◽  
Luping Ren ◽  
...  
Keyword(s):  
Uncoupling Protein ◽  
Density Lipoprotein ◽  
Peroxisome Proliferator ◽  
Sprague Dawley ◽  
Peroxisome Proliferator Activated Receptor ◽  
Protein Levels ◽  
White Adipocytes ◽  
White Fat

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.

scholarly journals The Role of PPARγin the Transcriptional Control by Agonists and Antagonists

PPAR Research ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Tamotsu Tsukahara
Keyword(s):  
Transcriptional Repression ◽  
Transcriptional Control ◽  
Thyroid Hormone Receptor ◽  
Therapeutic Potential ◽  
Current Knowledge ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Cyclic Phosphatidic Acid

In recent years, peroxisome proliferator-activated receptor gamma (PPARγ) has been reported to be a target for the treatment of type II diabetes. Furthermore, it has received attention for its therapeutic potential in many other human diseases, including atherosclerosis, obesity, and cancers. Recent studies have provided evidence that the endogenously produced PPARγ antagonist, 2,3-cyclic phosphatidic acid (cPA), which is similar in structure to lysophosphatidic acid (LPA), inhibits cancer cell invasion and metastasisin vitroandin vivo. We recently observed that cPA negatively regulates PPARγ function by stabilizing the binding of the corepressor protein, silencing mediator of retinoic acid and thyroid hormone receptor. We also showed that cPA prevents neointima formation, adipocyte differentiation, lipid accumulation, and upregulation of PPARγ target gene transcription. We then analyzed the molecular mechanism of cPA's action on PPARγ. In this paper, we summarize the current knowledge on the mechanism of PPARγ-mediated transcriptional activity and transcriptional repression in response to novel lipid-derived ligands, such as cPA.

scholarly journals Hepatic gene expression patterns in thyroid hormone-treated hypothyroid rats

2003 ◽  
Vol 31 (2) ◽  
pp. 291-303 ◽  
Author(s):  
JM Weitzel ◽  
S Hamann ◽  
M Jauk ◽  
M Lacey ◽  
A Filbry ◽  
...  
Keyword(s):  
Gene Expression ◽  
Thyroid Hormone ◽  
Expression Patterns ◽  
Regulatory Elements ◽  
Activation Mechanism ◽  
Gene Expression Patterns ◽  
Peroxisome Proliferator ◽  
Gene Promoters ◽  
Protein Levels

Thyroid hormone (T3) is essential for normal development, differentiation and metabolic balance. We have performed DNA microarray experiments using hepatic RNA from hypothyroid and T3-treated hypothyroid rats in order to characterize T3-induced gene expression patterns after various time points (6, 24 and 48 h after the administration of the hormone). Sixty-two of 4608 different genes displayed a reproducible T3-response, and cluster analysis divided these differentially regulated genes into six expression patterns. Thirty-six genes were not significantly regulated within the first 24 h. Transient transfection experiments of eight late-induced gene promoters failed to detect a thyroid hormone response element within their regulatory elements, suggesting an indirect activation mechanism(s). In search for an intermediate factor of T3 action, we examined whether various rather ubiquitous transcription factors, peroxisome proliferator-activated receptors (PPARs) and coactivators of the PPARgamma coactivator 1 family (PGC-1) are regulated by T3. Only PPARgamma and PERC/PGC-1beta exhibit a significant T3-response within the first 6 h after treatment, identifying these factors as candidate components for mediating the late-induced expression pattern. Regulation of early-induced genes within the first 6 h after administration of T3 on transcript levels correlates with altered protein levels after 24 and 48 h in vivo.

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