Myostatin inhibits proliferation and insulin-stimulated glucose uptake in mouse liver cells

Although myostatin functions primarily as a negative regulator of skeletal muscle growth and development, accumulating biological and epidemiological evidence indicates an important contributing role in liver disease. In this study, we demonstrate that myostatin suppresses the proliferation of mouse Hepa-1c1c7 murine-derived liver cells (50%; p < 0.001) in part by reducing the expression of the cyclins and cyclin-dependent kinases that elicit G1-S phase transition of the cell cycle (p < 0.001). Furthermore, real-time PCR-based quantification of the long noncoding RNA metastasis associated lung adenocarcinoma transcript 1 (Malat1), recently identified as a myostatin-responsive transcript in skeletal muscle, revealed a significant downregulation (25% and 50%, respectively; p < 0.05) in the livers of myostatin-treated mice and liver cells. The importance of Malat1 in liver cell proliferation was confirmed via arrested liver cell proliferation (p < 0.05) in response to partial Malat1 siRNA-mediated knockdown. Myostatin also significantly blunted insulin-stimulated glucose uptake and Akt phosphorylation in liver cells while increasing the phosphorylation of myristoylated alanine-rich C-kinase substrate (MARCKS), a protein that is essential for cancer cell proliferation and insulin-stimulated glucose transport. Together, these findings reveal a plausible mechanism by which circulating myostatin contributes to the diminished regenerative capacity of the liver and diseases characterized by liver insulin resistance.

Download Full-text

Myostatin inhibits IGF-I-induced myotube hypertrophy through Akt

AJP Cell Physiology ◽

10.1152/ajpcell.00043.2009 ◽

2009 ◽

Vol 297 (5) ◽

pp. 1124-1132 ◽

Cited By ~ 117

Author(s):

Michael R. Morissette ◽

Stuart A. Cook ◽

Cattleya Buranasombati ◽

Michael A. Rosenberg ◽

Anthony Rosenzweig

Keyword(s):

Skeletal Muscle ◽

Knockout Mice ◽

Molecular Mechanisms ◽

Muscle Growth ◽

Dominant Negative ◽

Negative Regulator ◽

C2c12 Myotubes ◽

Akt Phosphorylation ◽

Igf I

Myostatin is a highly conserved negative regulator of skeletal muscle growth. Loss of functional myostatin in cattle, mice, sheep, dogs, and humans results in increased muscle mass. The molecular mechanisms responsible for this increase in muscle growth are not fully understood. Previously, we have reported that phenylephrine-induced cardiac muscle growth and Akt activation are enhanced in myostatin knockout mice compared with controls. Here we report that skeletal muscle from myostatin knockout mice show increased Akt protein expression and overall activity at baseline secondary to an increase in Akt mRNA. We examined the functional role of myostatin modulation of Akt in C2C12 myotubes, a well-established in vitro model of skeletal muscle hypertrophy. Adenoviral overexpression of myostatin attenuated the insulin-like growth factor-I (IGF-I)-mediated increase in myotube diameter, as well as IGF-I-stimulated Akt phosphorylation. Inhibition of myostatin by overexpression of the NH2-terminal portion of myostatin was sufficient to increase myotube diameter and Akt phosphorylation. Coexpression of myostatin and constitutively active Akt (myr-Akt) restored the increase in myotube diameter. Conversely, expression of dominant negative Akt (dn-Akt) with the inhibitory myostatin propeptide blocked the increase in myotube diameter. Of note, ribosomal protein S6 phosphorylation and atrogin-1/muscle atrophy F box mRNA were increased in skeletal muscle from myostain knockout mice. Together, these data suggest myostatin regulates muscle growth at least in part through regulation of Akt.

Download Full-text

Myostatin-1 Inhibits Cell Proliferation by Inhibiting the mTOR Signal Pathway and MRFs, and Activating the Ubiquitin-Proteasomal System in Skeletal Muscle Cells of Japanese Flounder Paralichthys olivaceus

Cells ◽

10.3390/cells9112376 ◽

2020 ◽

Vol 9 (11) ◽

pp. 2376

Author(s):

Jiahuan Liu ◽

Mingzhu Pan ◽

Dong Huang ◽

Yanlin Guo ◽

Mengxi Yang ◽

...

Keyword(s):

Skeletal Muscle ◽

Cell Proliferation ◽

Mrna Expression ◽

Biological Effects ◽

Paralichthys Olivaceus ◽

Muscle Growth ◽

Muscle Cells ◽

Signal Pathway ◽

Japanese Flounder ◽

Negative Regulator

Myostatin (MSTN) is a negative regulator of skeletal muscle growth and development. The mechanisms of fish MSTN involved in muscle growth are not fully understood. In the present study, knockdown and overexpression of mstn-1 was performed in cultured Japanese flounder muscle cells to investigate the molecular function and the underlying mechanism of fish MSTN-1. Results showed that mstn-1 knockdown significantly induced cell proliferation and the mRNA expression of myogenic regulatory factors (MRFs), while overexpression of mstn-1 led to a significant decrease of cell proliferation and a suppression of the MRFs mRNA expression. The overexpression of mstn-1 also significantly increased the mRNA expression of ubiquitin–proteasomal pathway of proteolysis genes including muscle RING-finger protein 1 (murf-1) by 204.1% (p = 0.024) and muscle atrophy F-box protein (mafbx) by 165.7% (p = 0.011). However, mystn-1 overexpression inhibited the activation of mTOR signal pathway and the AKT/FoxO1 pathway through decreasing phosphorylation of AKT at Ser 473 by 56.0% (p = 0.001). Meanwhile, mystn-1 overexpression increased the dephosphorylation and nuclear localization of FoxO1 by 394.9% (p = 0.005). These results demonstrate that mstn-1 in Japanese flounder has the effects of inhibiting cell proliferation and growth, and the mTOR and AKT/FoxO1 pathways participated in these biological effects.

Download Full-text

NF-κB-Inducing Kinase (NIK) Mediates Skeletal Muscle Insulin Resistance: Blockade by Adiponectin

Endocrinology ◽

10.1210/en.2011-1343 ◽

2011 ◽

Vol 152 (10) ◽

pp. 3622-3627 ◽

Cited By ~ 26

Author(s):

Sanjeev Choudhary ◽

Sandeep Sinha ◽

Yanhua Zhao ◽

Srijita Banerjee ◽

Padma Sathyanarayana ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Glucose Uptake ◽

Kinase Activity ◽

Pi3 Kinase ◽

Dominant Negative ◽

Muscle Insulin Resistance ◽

Akt Phosphorylation ◽

Skeletal Muscle Insulin Resistance ◽

Obese Subjects

Enhanced levels of nuclear factor (NF)-κB-inducing kinase (NIK), an upstream kinase in the NF-κB pathway, have been implicated in the pathogenesis of chronic inflammation in diabetes. We investigated whether increased levels of NIK could induce skeletal muscle insulin resistance. Six obese subjects with metabolic syndrome underwent skeletal muscle biopsies before and six months after gastric bypass surgery to quantitate NIK protein levels. L6 skeletal myotubes, transfected with NIK wild-type or NIK kinase-dead dominant negative plasmids, were treated with insulin alone or with adiponectin and insulin. Effects of NIK overexpression on insulin-stimulated glucose uptake were estimated using tritiated 2-deoxyglucose uptake. NF-κB activation (EMSA), phosphatidylinositol 3 (PI3) kinase activity, and phosphorylation of inhibitor κB kinase β and serine-threonine kinase (Akt) were measured. After weight loss, skeletal muscle NIK protein was significantly reduced in association with increased plasma adiponectin and enhanced AMP kinase phosphorylation and insulin sensitivity in obese subjects. Enhanced NIK expression in cultured L6 myotubes induced a dose-dependent decrease in insulin-stimulated glucose uptake. The decrease in insulin-stimulated glucose uptake was associated with a significant decrease in PI3 kinase activity and protein kinase B/Akt phosphorylation. Overexpression of NIK kinase-dead dominant negative did not affect insulin-stimulated glucose uptake. Adiponectin treatment inhibited NIK-induced NF-κB activation and restored insulin sensitivity by restoring PI3 kinase activation and subsequent Akt phosphorylation. These results indicate that NIK induces insulin resistance and further indicate that adiponectin exerts its insulin-sensitizing effect by suppressing NIK-induced skeletal muscle inflammation. These observations suggest that NIK could be an important therapeutic target for the treatment of insulin resistance associated with inflammation in obesity and type 2 diabetes.

Download Full-text

Role of TRIB3 in regulation of insulin sensitivity and nutrient metabolism during short-term fasting and nutrient excess

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00663.2011 ◽

2012 ◽

Vol 303 (7) ◽

pp. E908-E916 ◽

Cited By ~ 14

Author(s):

Jiarong Liu ◽

Wei Zhang ◽

Gin C. Chuang ◽

Helliner S. Hill ◽

Ling Tian ◽

...

Keyword(s):

Skeletal Muscle ◽

Oxygen Consumption ◽

Insulin Sensitivity ◽

Glucose Uptake ◽

Glucose Transport ◽

Oxygen Consumption Rate ◽

Glucose Oxidation ◽

Consumption Rate ◽

Negative Regulator ◽

Short Term

We have suggested previously that Tribbles homolog 3 (TRIB3), a negative regulator of Akt activity in insulin-sensitive tissues, could mediate glucose-induced insulin resistance in muscle under conditions of chronic hyperglycemia (Liu J, Wu X, Franklin JL, Messina JL, Hill HS, Moellering DR, Walton RG, Martin M, Garvey WT. Am J Physiol Endocrinol Metab 298: E565–E576, 2010). In the current study, we have assessed short-term physiological regulation of TRIB3 in skeletal muscle and adipose tissues by nutrient excess and fasting as well as TRIB3's ability to modulate glucose transport and mitochondrial oxidation. In Sprague-Dawley rats, we found that short-term fasting enhanced insulin sensitivity concomitantly with decrements in TRIB3 mRNA (66%, P < 0.05) and protein (81%, P < 0.05) in muscle and increments in TRIB3 mRNA (96%, P < 0.05) and protein (∼10-fold, P < 0.05) in adipose tissue compared with nonfasted controls. On the other hand, rats fed a Western diet for 7 days became insulin resistant concomitantly with increments in TRIB3 mRNA (155%, P < 0.05) and protein (69%, P = 0.0567) in muscle and a decrease in the mRNA (76%, P < 0.05) and protein (70%, P < 0.05) in adipose. In glucose transport and mitochondria oxidation studies using skeletal muscle cells, we found that stable TRIB3 overexpression impaired insulin-stimulated glucose uptake without affecting basal glucose transport and increased both basal glucose oxidation and the maximal uncoupled oxygen consumption rate. With stable knockdown of TRIB3, basal and insulin-stimulated glucose transport rates were increased, whereas basal glucose oxidation and the maximal uncoupled oxygen consumption rate were decreased. In conclusion, TRIB3 impacts glucose uptake and oxidation oppositely in muscle and fat according to levels of nutrient availability. The above data for the first time implicate TRIB3 as a potent physiological regulator of insulin sensitivity and mitochondrial glucose oxidation under conditions of nutrient deprivation and excess.

Download Full-text

Myostatin-induced inhibition of the long noncoding RNA Malat1 is associated with decreased myogenesis

AJP Cell Physiology ◽

10.1152/ajpcell.00392.2012 ◽

2013 ◽

Vol 304 (10) ◽

pp. C995-C1001 ◽

Cited By ~ 67

Author(s):

Rani Watts ◽

Virginia L. Johnsen ◽

Jane Shearer ◽

Dustin S. Hittel

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Cell Growth ◽

Noncoding Rna ◽

Transforming Growth Factor ◽

Day Treatment ◽

Global Gene Expression ◽

Transforming Growth Factor Β ◽

Negative Regulator ◽

Human Skeletal Muscle Cells

Myostatin, a member of the transforming growth factor-β (TGF-β) superfamily of secreted proteins, is a potent negative regulator of myogenesis. Free myostatin induces the phosphorylation of the Smad family of transcription factors, which, in turn, regulates gene expression, via the canonical TGF-β signaling pathway. There is, however, emerging evidence that myostatin can regulate gene expression independent of Smad signaling. As such, we acquired global gene expression data from the gastrocnemius muscle of C57BL/6 mice following a 6-day treatment with recombinant myostatin compared with vehicle-treated animals. Of the many differentially expressed genes, the myostatin-associated decrease (−11.20-fold; P < 0.05) in the noncoding metastasis-associated lung adenocarcinoma transcript 1 (Malat1) was the most significant and the most intriguing because of numerous reports describing its novel role in regulating cell growth. We therefore sought to further characterize the role of Malat1 expression in skeletal muscle myogenesis. RT-PCR-based quantification of C2C12 and primary human skeletal muscle cells revealed a significant and persistent upregulation (4- to 7-fold; P < 0.05) of Malat1 mRNA during the differentiation of myoblasts into myotubes. Conversely, targeted knockdown of Malat1 using siRNA suppressed myoblast proliferation by arresting cell growth in the G0/G1phase. These results reveal Malat1 as novel downstream target of myostatin with a considerable ability to regulate myogenesis. The identification of new targets of myostatin will have important repercussions for regenerative biology through inhibition and/or reversal of muscle atrophy and wasting diseases.

Download Full-text

Skeletal Muscle-Selective Knockout of LKB1 Increases Insulin Sensitivity, Improves Glucose Homeostasis, and Decreases TRB3

Molecular and Cellular Biology ◽

10.1128/mcb.00979-06 ◽

2006 ◽

Vol 26 (22) ◽

pp. 8217-8227 ◽

Cited By ~ 155

Author(s):

Ho-Jin Koh ◽

David E. Arnolds ◽

Nobuharu Fujii ◽

Thien T. Tran ◽

Marc J. Rogers ◽

...

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Glucose Homeostasis ◽

Glucose Utilization ◽

Cell Metabolism ◽

Negative Regulator ◽

Akt Inhibitor ◽

Akt Phosphorylation ◽

Energy Sensing

ABSTRACT LKB1 is a tumor suppressor that may also be fundamental to cell metabolism, since LKB1 phosphorylates and activates the energy sensing enzyme AMPK. We generated muscle-specific LKB1 knockout (MLKB1KO) mice, and surprisingly, found that a lack of LKB1 in skeletal muscle enhanced insulin sensitivity, as evidenced by decreased fasting glucose and insulin concentrations, improved glucose tolerance, increased muscle glucose uptake in vivo, and increased glucose utilization during a hyperinsulinemic-euglycemic clamp. MLKB1KO mice had increased insulin-stimulated Akt phosphorylation and a >80% decrease in muscle expression of TRB3, a recently identified Akt inhibitor. Akt/TRB3 binding was present in skeletal muscle, and overexpression of TRB3 in C2C12 myoblasts significantly reduced Akt phosphorylation. These results demonstrate that skeletal muscle LKB1 is a negative regulator of insulin sensitivity and glucose homeostasis. LKB1-mediated TRB3 expression provides a novel link between LKB1 and Akt, critical kinases involved in both tumor genesis and cell metabolism.

Download Full-text

The Possible Role of Complete Loss of Myostatin in Limiting Excessive Proliferation of Muscle Cells (C2C12) via Activation of MicroRNAs

International Journal of Molecular Sciences ◽

10.3390/ijms20030643 ◽

2019 ◽

Vol 20 (3) ◽

pp. 643 ◽

Cited By ~ 2

Author(s):

Peixuan Huang ◽

Daxin Pang ◽

Kankan Wang ◽

Aishi Xu ◽

Chaogang Yao ◽

...

Keyword(s):

Skeletal Muscle ◽

Cell Proliferation ◽

Muscle Growth ◽

Interaction Network ◽

Muscle Cells ◽

Complete Loss ◽

Skeletal Muscle Growth ◽

Excessive Proliferation ◽

Mouse Myoblast

Myostatin (MSTN) is a member of the TGF-β superfamily that negatively regulates skeletal muscle growth and differentiation. However, the mechanism by which complete MSTN deletion limits excessive proliferation of muscle cells remains unclear. In this study, we knocked out MSTN in mouse myoblast lines using a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR/Cas9) system and sequenced the mRNA and miRNA transcriptomes. The results show that complete loss of MSTN upregulates seven miRNAs targeting an interaction network composed of 28 downregulated genes, including TGFB1, FOS and RB1. These genes are closely associated with tumorigenesis and cell proliferation. Our study suggests that complete loss of MSTN may limit excessive cell proliferation via activation of miRNAs. These data will contribute to the treatment of rhabdomyosarcoma (RMS).

Download Full-text