scholarly journals The Orphan Nuclear Receptor, NOR-1, Is a Target of β-Adrenergic Signaling in Skeletal Muscle

Endocrinology ◽  
2006 ◽  
Vol 147 (11) ◽  
pp. 5217-5227 ◽  
Author(s):  
Michael A. Pearen ◽  
James G. Ryall ◽  
Megan A. Maxwell ◽  
Naganari Ohkura ◽  
Gordon S. Lynch ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Mrna Expression ◽  
Muscle Mass ◽  
Nuclear Receptor ◽  
Cold Exposure ◽  
Small Interfering Rna ◽  
Muscle Cells ◽  
Orphan Nuclear Receptor ◽  
Expression Of Genes ◽  
Interfering Rna

β-Adrenergic receptor (β-AR) agonists induce Nur77 mRNA expression in the C2C12 skeletal muscle cell culture model and elicit skeletal muscle hypertrophy. We previously demonstrated that Nur77 (NR4A1) is involved in lipolysis and gene expression associated with the regulation of lipid homeostasis. Subsequently it was demonstrated by another group that β-AR agonists and cold exposure-induced Nur77 expression in brown adipocytes and brown adipose tissue, respectively. Moreover, NOR-1 (NR4A3) was hyperinduced by cold exposure in the nur77−/− animal model. These studies underscored the importance of understanding the role of NOR-1 in skeletal muscle. In this context we observed 30–480 min of β-AR agonist treatment significantly and transiently increased expression of the orphan nuclear receptor NOR-1 in both mouse skeletal muscle tissue (plantaris) and C2C12 skeletal muscle cells. Specific β2- and β3-AR agonists had similar effects as the pan-agonist and were blocked by the β-AR antagonist propranolol. Moreover, in agreement with these observations, isoprenaline also significantly increased the activity of the NOR-1 promoter. Stable exogenous expression of a NOR-1 small interfering RNA (but not the negative control small interfering RNA) in skeletal muscle cells significantly repressed endogenous NOR-1 mRNA expression and led to changes in the expression of genes involved in the control of lipid use and muscle mass underscored by a dramatic increase in myostatin mRNA expression. Concordantly the myostatin promoter was repressed by NOR-1 expression. In conclusion, NOR-1 is highly responsive to β-adrenergic signaling and regulates the expression of genes controlling fatty acid use and muscle mass.

scholarly journals The Orphan Nuclear Receptor, NOR-1, a Target of β-Adrenergic Signaling, Regulates Gene Expression that Controls Oxidative Metabolism in Skeletal Muscle

Endocrinology ◽  
2008 ◽  
Vol 149 (6) ◽  
pp. 2853-2865 ◽  
Author(s):  
Michael A. Pearen ◽  
Stephen A. Myers ◽  
Suryaprakash Raichur ◽  
James G. Ryall ◽  
Gordon S. Lynch ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Nuclear Receptor ◽  
Pyruvate Dehydrogenase ◽  
Oxidative Metabolism ◽  
Acid Oxidation ◽  
Orphan Nuclear Receptor ◽  
Adrenergic Signaling ◽  
Interfering Rna

β1–3-Adrenoreceptor (AR)-deficient mice are unable to regulate energy expenditure and develop diet-induced obesity on a high-fat diet. We determined previously that β2-AR agonist treatment activated expression of the mRNA encoding the orphan nuclear receptor, NOR-1, in muscle cells and plantaris muscle. Here we show that β2-AR agonist treatment significantly and transiently activated the expression of NOR-1 (and the other members of the NR4A subgroup) in slow-twitch oxidative soleus muscle and fast-twitch glycolytic tibialis anterior muscle. The activation induced by β-adrenergic signaling is consistent with the involvement of protein kinase A, MAPK, and phosphorylation of cAMP response element-binding protein. Stable cell lines transfected with a silent interfering RNA targeting NOR-1 displayed decreased palmitate oxidation and lactate accumulation. In concordance with these observations, ATP production in the NOR-1 silent interfering RNA (but not control)-transfected cells was resistant to (azide-mediated) inhibition of oxidative metabolism and expressed significantly higher levels of hypoxia inducible factor-1α. In addition, we observed the repression of genes that promote fatty acid oxidation (peroxisomal proliferator-activated receptor-γ coactivator-1α/β and lipin-1α) and trichloroacetic acid cycle-mediated carbohydrate (pyruvate) oxidation [pyruvate dehydrogenase phosphatase 1 regulatory and catalytic subunits (pyruvate dehydrogenase phosphatases-1r and -c)]. Furthermore, we observed that β2-AR agonist administration in mouse skeletal muscle induced the expression of genes that activate fatty acid oxidation and modulate pyruvate use, including PGC-1α, lipin-1α, FOXO1, and PDK4. Finally, we demonstrate that NOR-1 is recruited to the lipin-1α and PDK-4 promoters, and this is consistent with NOR-1-mediated regulation of these genes. In conclusion, NOR-1 is necessary for oxidative metabolism in skeletal muscle.

scholarly journals The Orphan Nuclear Receptor Nur77 Is a Determinant of Myofiber Size and Muscle Mass in Mice

2015 ◽  
Vol 35 (7) ◽  
pp. 1125-1138 ◽  
Author(s):  
Peter Tontonoz ◽  
Omar Cortez-Toledo ◽  
Kevin Wroblewski ◽  
Cynthia Hong ◽  
Laura Lim ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Mass ◽  
Nuclear Receptor ◽  
Muscle Growth ◽  
Muscle Size ◽  
Orphan Nuclear Receptor ◽  
Loss Of Function ◽  
Transgenic Expression ◽  
Primary Myoblasts ◽  
A Cell

We previously showed that the orphan nuclear receptor Nur77 (Nr4a1) plays an important role in the regulation of glucose homeostasis and oxidative metabolism in skeletal muscle. Here, we show using both gain- and loss-of-function models that Nur77 is also a regulator of muscle growth in mice. Transgenic expression of Nur77 in skeletal muscle in mice led to increases in myofiber size. Conversely, mice with global or muscle-specific deficiency in Nur77 exhibited reduced muscle mass and myofiber size. In contrast to Nur77 deficiency, deletion of the highly related nuclear receptor NOR1 (Nr4a3) had minimal effect on muscle mass and myofiber size. We further show that Nur77 mediates its effects on muscle size by orchestrating transcriptional programs that favor muscle growth, including the induction of insulin-like growth factor 1 (IGF1), as well as concomitant downregulation of growth-inhibitory genes, including myostatin, Fbxo32 (MAFbx), and Trim63 (MuRF1). Nur77-mediated increase in IGF1 led to activation of the Akt-mTOR-S6K cascade and the inhibition of FoxO3a activity. The dependence of Nur77 on IGF1 was recapitulated in primary myoblasts, establishing this as a cell-autonomous effect. Collectively, our findings identify Nur77 as a novel regulator of myofiber size and a potential transcriptional link between cellular metabolism and muscle growth.

scholarly journals 6-Mercaptopurine augments glucose transport activity in skeletal muscle cells in part via a mechanism dependent upon orphan nuclear receptor NR4A3

2013 ◽  
Vol 305 (9) ◽  
pp. E1081-E1092 ◽  
Author(s):  
Qinglan Liu ◽  
Xiaolin Zhu ◽  
Lusheng Xu ◽  
Yuchang Fu ◽  
W. Timothy Garvey
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Nuclear Receptor ◽  
Inflammatory Diseases ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Target Cells ◽  
Dependent Manner ◽  
Orphan Nuclear Receptor ◽  
Transport Activity

The purine anti-metabolite 6-mercaptopurine (6-MP) is widely used for the treatment of leukemia and inflammatory diseases. The cellular effects of 6-MP on metabolism remain unknown; however, 6-MP was recently found to activate the orphan nuclear receptor NR4A3 in skeletal muscle cell lines. We have reported previously that NR4A3 (also known as NOR-1, MINOR) is a positive regulator of insulin sensitivity in adipocytes. To further explore the role of NR4A3 activation in insulin action, we explored whether 6-MP activation of NR4A3 could modulate glucose transport system activity in L6 skeletal muscle cells. We found that 6-MP increased both NR4A3 expression and NR4A3 transcriptional activity and enhanced glucose transport activity via increasing GLUT4 translocation in both basal and insulin-stimulated L6 cells in an NR4A3-dependent manner. Furthermore, 6-MP increased levels of phospho-AS160, although this effect was not modulated by NR4A3 overexpression or knockdown. These primary findings provide a novel proof of principle that 6-MP, a small molecule NR4A3 agonist, can augment glucose uptake in insulin target cells, although this occurs via both NR4A3-dependent and -independent actions; the latter is related to an increase in phospho-AS160. These results establish a novel target for development of new treatments for insulin resistance.

scholarly journals Overexpression of PGC-1αIncreases Fatty Acid Oxidative Capacity of Human Skeletal Muscle Cells

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Nataša Nikolić ◽  
Magdalena Rhedin ◽  
Arild C. Rustan ◽  
Len Storlien ◽  
G. Hege Thoresen ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Lipid Metabolism ◽  
Mrna Expression ◽  
Human Skeletal Muscle ◽  
Muscle Cells ◽  
Oxidative Capacity ◽  
Skeletal Muscle Cells ◽  
Expression Of Genes ◽  
Human Myotubes ◽  
Human Skeletal Muscle Cells

We investigated the effects of PGC-1α(peroxisome proliferator-activated receptorγcoactivator-1α) overexpression on the oxidative capacity of human skeletal muscle cellsex vivo. PGC-1αoverexpression increased the oxidation rate of palmitic acid and mRNA expression of genes regulating lipid metabolism, mitochondrial biogenesis, and function in human myotubes. Basal and insulin-stimulated deoxyglucose uptake were decreased, possibly due to upregulation of PDK4 mRNA. Expression of fast fiber-type gene marker (MHCIIa) was decreased. Compared to skeletal musclein vivo, PGC-1αoverexpression increased expression of several genes, which were downregulated during the process of cell isolation and culturing. In conclusion, PGC-1αoverexpression increased oxidative capacity of cultured myotubes by improving lipid metabolism, increasing expression of genes involved in regulation of mitochondrial function and biogenesis, and decreasing expression of MHCIIa. These results suggest that therapies aimed at increasing PGC-1αexpression may have utility in treatment of obesity and obesity-related diseases.

scholarly journals Coculture with Primary Visceral Rat Adipocytes from Control But Not Streptozotocin-Induced Diabetic Animals Increases Glucose Uptake in Rat Skeletal Muscle Cells: Role of Adiponectin

Endocrinology ◽  
2007 ◽  
Vol 148 (9) ◽  
pp. 4411-4419 ◽  
Author(s):  
Vivian Vu ◽  
Wi Kim ◽  
Xiangping Fang ◽  
Yuan-Tao Liu ◽  
Aimin Xu ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Molecular Weight ◽  
Glucose Uptake ◽  
High Molecular Weight ◽  
Small Interfering Rna ◽  
Muscle Cells ◽  
Rat Skeletal Muscle ◽  
Rat Adipocytes ◽  
Adiponectin Receptor 2 ◽  
Interfering Rna

We developed a coculture system comprising primary rat adipocytes and L6 rat skeletal muscle cells to allow investigation of the effects of physiologically relevant mixtures of adipokines. We observed that coculture, or adipocyte-conditioned media, increased glucose uptake in muscle cells. An adipokine that could potentially mediate this effect is adiponectin, and we demonstrated that small interfering RNA-mediated knockdown of adiponectin receptor-2 in muscle cells reduced the uptake of glucose upon coculture with primary rat adipocytes. Analysis of coculture media by ELISA indicated total adiponectin concentration of up to 1 μg/ml, and Western blotting and gel filtration analysis demonstrated that the adipokine profile was hexamer greater than high molecular weight much greater than trimer. We used the streptozotocin-induced rat model of diabetes and found that high-molecular-weight adiponectin levels decreased in comparison with control animals and this correlated with the fact that diabetic rat-derived primary adipocytes in coculture did not stimulate glucose uptake to the same extent as control adipocytes. Coculture induced phosphorylation of AMP-activated protein kinase (T172) and interestingly also insulin receptor substrate-1 (Y612) and Akt (T308 & S473), which could be attenuated after adiponectin receptor-2-small interfering RNA treatment. In summary, we believe that this coculture system represents an excellent model to study the effects of primary adipocyte-derived adipokine mixtures on skeletal muscle metabolism, and here we have established that in the context of physiologically relevant mixtures of adipokines, adiponectin may be an important determinant of positive cross talk between adipocytes and skeletal muscle.

scholarly journals The Orphan Nuclear Receptor 4A1: A Potential New Therapeutic Target for Metabolic Diseases

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Lei Zhang ◽  
Qun Wang ◽  
Wen Liu ◽  
Fangyan Liu ◽  
Ailing Ji ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Lipid Metabolism ◽  
Nuclear Receptor ◽  
Metabolic Diseases ◽  
Early Response ◽  
Orphan Receptor ◽  
Special Focus ◽  
Orphan Nuclear Receptor ◽  
Physiological Functions ◽  
The Impact

Orphan nuclear receptor 4A1 (NR4A1) is a transcriptional factor of the nuclear orphan receptor (NR4A) superfamily that has sparked interest across different research fields in recent years. Several studies have demonstrated that ligand-independent NR4A1 is an immediate-early response gene and the protein product is rapidly induced by a variety of stimuli. Hyperfunction or dysfunction of NR4A1 is implicated in various metabolic processes, including carbohydrate metabolism, lipid metabolism, and energy balance, in major metabolic tissues, such as liver, skeletal muscle, pancreatic tissues, and adipose tissues. No endogenous ligands for NR4A1 have been identified, but numerous compounds that bind and activate or inactivate nuclear NR4A1 or induce cytoplasmic localization of NR4A1 have been identified. This review summarizes recent advances in our understanding of the molecular biology and physiological functions of NR4A1. And we focus on the physiological functions of NR4A1 receptor to the development of the metabolic diseases, with a special focus on the impact on carbohydrate and lipid metabolism in skeletal muscle, liver, adipose tissue, and islet.

Interleukin-6 promotes myogenic differentiation of mouse skeletal muscle cells: role of the STAT3 pathway

2013 ◽  
Vol 304 (2) ◽  
pp. C128-C136 ◽  
Author(s):  
Miriam Hoene ◽  
Heike Runge ◽  
Hans Ulrich Häring ◽  
Erwin D. Schleicher ◽  
Cora Weigert
Keyword(s):  
Skeletal Muscle ◽  
Mrna Expression ◽  
Myogenic Differentiation ◽  
Muscle Cells ◽  
C2c12 Cells ◽  
Skeletal Muscle Cells ◽  
Wild Type ◽  
C2c12 Myoblasts ◽  
Sequence Of Events ◽  
Primary Mouse

Myogenic differentiation of skeletal muscle cells is characterized by a sequence of events that include activation of signal transducer and activator of transcription 3 (STAT3) and enhanced expression of its target gene Socs3. Autocrine effects of IL-6 may contribute to the activation of the STAT3-Socs3 cascade and thus to myogenic differentiation. The importance of IL-6 and STAT3 for the differentiation process was studied in C2C12 cells and in primary mouse wild-type and IL-6−/− skeletal muscle cells. In differentiating C2C12 myoblasts, the upregulation of IL-6 mRNA expression and protein secretion started after increased phosphorylation of STAT3 on tyrosine 705 and increased mRNA expression of Socs3 was observed. Knockdown of STAT3 and IL-6 mRNA in differentiating C2C12 myoblasts impaired the expression of the myogenic markers myogenin and MyHC IIb and subsequently myotube fusion. However, the knockdown of IL-6 did not prevent the induction of STAT3 tyrosine phosphorylation. The IL-6-independent activation of STAT3 was verified in differentiating primary IL-6−/− myoblasts. The phosphorylation of STAT3 and the expression levels of STAT3, Socs3, and myogenin during differentiation were comparable in the primary myoblasts independent of the genotype. However, IL-6−/− cells failed to induce MyHC IIb expression to the same level as in wild-type cells and showed reduced myotube formation. Supplementation of IL-6 could partially restore the fusion of IL-6−/− cells. These data demonstrate that IL-6 depletion during myogenic differentiation does not reduce the activation of the STAT3-Socs3 cascade, while IL-6 and STAT3 are both necessary to promote myotube fusion.

scholarly journals Effects of cholesterol on CCK-1 receptors and caveolin-3 proteins recycling in human gallbladder muscle

2010 ◽  
Vol 299 (3) ◽  
pp. G742-G750 ◽  
Author(s):  
P. Cong ◽  
V. Pricolo ◽  
P. Biancani ◽  
J. Behar
Keyword(s):  
Small Interfering Rna ◽  
Muscle Cells ◽  
High Cholesterol ◽  
Western Blots ◽  
Human Gallbladder ◽  
Recycling Endosomes ◽  
Early Endosomes ◽  
Δ Opioid Receptor ◽  
Interfering Rna ◽  
Bulk Plasma

The contraction of gallbladders (GBs) with cholesterol stones is impaired due to high cholesterol concentrations in caveolae compared with GBs with pigment stones. The reduced contraction is caused by a lower cholecystokinin (CCK)-8 binding to CCK-1 receptors (CCK-1R) due to caveolar sequestration of receptors. We aimed to examine the mechanism of cholesterol-induced sequestration of receptors. Muscle cells from human and guinea pig GBs were studied. Antibodies were used to examine CCK-1R, antigens of early and recycling endosomes, and total (CAV-3) and phosphorylated caveolar-3 protein (pCAV-3) by Western blots. Contraction was measured in muscle cells transfected with CAV3 mRNA or clathrin heavy-chain small-interfering RNA (siRNA). CCK-1R returned back to the bulk plasma membrane (PM) 30 min after CCK-8 recycled by endosomes, peaking at 5 min in early endosomes and at 20 min in recycling endosomes. Pretreatment with cholesterol-rich liposomes inhibited the transfer of CCK-1R and of CAV-3 in the endosomes by blocking CAV-3 phosphorylation. 4-Amino-5-(4-chloro-phenyl)-7-( t-butyl)pyrazolo[3,4- d]pyrimidine (inhibitor of tyrosine kinase) reproduced these effects by blocking pCAV-3 formation, increasing CAV-3 and CCK-1R sequestration in the caveolae and impairing CCK-8-induced contraction. CAV-3 siRNA reduced CAV-3 protein expression, decreased CCK-8-induced contraction, and accumulated CCK-1R in the caveolae. Abnormal concentrations of caveolar cholesterol had no effect on met-enkephalin that stimulates a δ-opioid receptor that internalizes through clathrin. We found that impaired muscle contraction in GBs with cholesterol stones is due to high caveolar levels of cholesterol that inhibits pCAV-3 generation. Caveolar cholesterol increases the caveolar sequestration of CAV-3 and CCK-1R caused by their reduced recycling to the PM.

scholarly journals Effect of differentiation, de novo innervation, and electrical pulse stimulation on mRNA and protein expression of Na+,K+-ATPase, FXYD1, and FXYD5 in cultured human skeletal muscle cells

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0247377
Author(s):  
Vid Jan ◽  
Katarina Miš ◽  
Natasa Nikolic ◽  
Klemen Dolinar ◽  
Metka Petrič ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Mrna Expression ◽  
Human Skeletal Muscle ◽  
De Novo ◽  
Muscle Cells ◽  
Electrical Pulse ◽  
Electrical Pulse Stimulation ◽  
Human Skeletal Muscle Cells ◽  
Pulse Stimulation ◽  
Low Serum

Denervation reduces the abundance of Na+,K+-ATPase (NKA) in skeletal muscle, while reinnervation increases it. Primary human skeletal muscle cells, the most widely used model to study human skeletal muscle in vitro, are usually cultured as myoblasts or myotubes without neurons and typically do not contract spontaneously, which might affect their ability to express and regulate NKA. We determined how differentiation, de novo innervation, and electrical pulse stimulation affect expression of NKA (α and β) subunits and NKA regulators FXYD1 (phospholemman) and FXYD5 (dysadherin). Differentiation of myoblasts into myotubes under low serum conditions increased expression of myogenic markers CD56 (NCAM1), desmin, myosin heavy chains, dihydropyridine receptor subunit α1S, and SERCA2 as well as NKAα2 and FXYD1, while it decreased expression of FXYD5 mRNA. Myotubes, which were innervated de novo by motor neurons in co-culture with the embryonic rat spinal cord explants, started to contract spontaneously within 7–10 days. A short-term co-culture (10–11 days) promoted mRNA expression of myokines, such as IL-6, IL-7, IL-8, and IL-15, but did not affect mRNA expression of NKA, FXYDs, or myokines, such as musclin, cathepsin B, meteorin-like protein, or SPARC. A long-term co-culture (21 days) increased the protein abundance of NKAα1, NKAα2, FXYD1, and phospho-FXYD1Ser68 without attendant changes in mRNA levels. Suppression of neuromuscular transmission with α-bungarotoxin or tubocurarine for 24 h did not alter NKA or FXYD mRNA expression. Electrical pulse stimulation (48 h) of non-innervated myotubes promoted mRNA expression of NKAβ2, NKAβ3, FXYD1, and FXYD5. In conclusion, low serum concentration promotes NKAα2 and FXYD1 expression, while de novo innervation is not essential for upregulation of NKAα2 and FXYD1 mRNA in cultured myotubes. Finally, although innervation and EPS both stimulate contractions of myotubes, they exert distinct effects on the expression of NKA and FXYDs.

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