Effect of YM-126414 on glucose uptake and redistribution of glucose transporter isotype 4 in muscle cells

Adiponectin is well established to mediate many beneficial metabolic effects, and this has stimulated great interest in development and validation of adiponectin receptor agonists as pharmaceutical tools. This study investigated the effects of ALY688, a peptide-based adiponectin receptor agonist, in rat L6 skeletal muscle cells. ALY688 significantly increased phosphorylation of several adiponectin downstream effectors, including AMPK, ACC and p38MAPK, assessed by immunoblotting and immunofluorescence microscopy. Temporal analysis using cells expressing an Akt biosensor demonstrated that ALY688 enhanced insulin sensitivity. This effect was associated with increased insulin-stimulated Akt and IRS-1 phosphorylation. The functional metabolic significance of these signaling effects was examined by measuring glucose uptake in myoblasts stably overexpressing the glucose transporter GLUT4. ALY688 treatment both increased glucose uptake itself and enhanced insulin-stimulated glucose uptake. In the model of high glucose/high insulin (HGHI)-induced insulin resistant cells, both temporal studies using the Akt biosensor as well as immunoblotting assessing Akt and IRS-1 phosphorylation indicated that ALY688 significantly reduced insulin resistance. Importantly, we observed that ALY688 administration to high-fat high sucrose fed mice also improve glucose handling, validating its efficacy in vivo. In summary, these data indicate that ALY688 activates adiponectin signaling pathways in skeletal muscle, leading to improved insulin sensitivity and beneficial metabolic effects.

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Artemisia princeps Extract Promoted Glucose Uptake in Cultured L6 Muscle Cells via Glucose Transporter 4 Translocation

Bioscience Biotechnology and Biochemistry ◽

10.1271/bbb.100305 ◽

2010 ◽

Vol 74 (10) ◽

pp. 2036-2042 ◽

Cited By ~ 10

Author(s):

Norio YAMAMOTO ◽

Manabu UEDA ◽

Kyuichi KAWABATA ◽

Takuya SATO ◽

Kengo KAWASAKI ◽

...

Keyword(s):

Glucose Uptake ◽

Glucose Transporter ◽

Muscle Cells ◽

Glucose Transporter 4 ◽

Artemisia Princeps ◽

L6 Muscle Cells

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Octaphlorethol A, a novel phenolic compound isolated from a brown alga, Ishige foliacea, increases glucose transporter 4-mediated glucose uptake in skeletal muscle cells

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2012.03.036 ◽

2012 ◽

Vol 420 (3) ◽

pp. 576-581 ◽

Cited By ~ 34

Author(s):

Seung-Hong Lee ◽

Sung-Myung Kang ◽

Seok-Chun Ko ◽

Dae-Ho Lee ◽

You-Jin Jeon

Keyword(s):

Skeletal Muscle ◽

Glucose Uptake ◽

Phenolic Compound ◽

Brown Alga ◽

Glucose Transporter ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Glucose Transporter 4

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The exocyst complex regulates insulin-stimulated glucose uptake of skeletal muscle cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00109.2019 ◽

2019 ◽

Vol 317 (6) ◽

pp. E957-E972

Author(s):

Brent A. Fujimoto ◽

Madison Young ◽

Lamar Carter ◽

Alina P. S. Pang ◽

Michael J. Corley ◽

...

Keyword(s):

Skeletal Muscle ◽

Plasma Membrane ◽

Cell Surface ◽

Glucose Uptake ◽

Glucose Transporter ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Cell Surface Receptor ◽

Exocyst Complex

Skeletal muscle handles ~80–90% of the insulin-induced glucose uptake. In skeletal muscle, insulin binding to its cell surface receptor triggers redistribution of intracellular glucose transporter GLUT4 protein to the cell surface, enabling facilitated glucose uptake. In adipocytes, the eight-protein exocyst complex is an indispensable constituent in insulin-induced glucose uptake, as it is responsible for the targeted trafficking and plasma membrane-delivery of GLUT4. However, the role of the exocyst in skeletal muscle glucose uptake has never been investigated. Here we demonstrate that the exocyst is a necessary factor in insulin-induced glucose uptake in skeletal muscle cells as well. The exocyst complex colocalizes with GLUT4 storage vesicles in L6-GLUT4myc myoblasts at a basal state and associates with these vesicles during their translocation to the plasma membrane after insulin signaling. Moreover, we show that the exocyst inhibitor endosidin-2 and a heterozygous knockout of Exoc5 in skeletal myoblast cells both lead to impaired GLUT4 trafficking to the plasma membrane and hinder glucose uptake in response to an insulin stimulus. Our research is the first to establish that the exocyst complex regulates insulin-induced GLUT4 exocytosis and glucose metabolism in muscle cells. A deeper knowledge of the role of the exocyst complex in skeletal muscle tissue may help our understanding of insulin resistance in type 2 diabetes.

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Unique mechanism of GLUT3 glucose transporter regulation by prolonged energy demand: increased protein half-life

Biochemical Journal ◽

10.1042/bj3330713 ◽

1998 ◽

Vol 333 (3) ◽

pp. 713-718 ◽

Cited By ~ 42

Author(s):

Zayna A. KHAYAT ◽

Anthony L. McCALL ◽

Amira KLIP

Keyword(s):

Glucose Uptake ◽

Protein Content ◽

Glucose Transport ◽

Half Life ◽

Glucose Transporter ◽

Muscle Cells ◽

Mrna Levels ◽

Glut1 Protein ◽

L6 Muscle Cells

L6 muscle cells survive long-term (18 h) disruption of oxidative phosphorylation by the mitochondrial uncoupler 2,4-dinitrophenol (DNP) because, in response to this metabolic stress, they increase their rate of glucose transport. This response is associated with an elevation of the protein content of glucose transporter isoforms GLUT3 and GLUT1, but not GLUT4. Previously we have reported that the rise in GLUT1 expression is likely to be a result of de novo biosynthesis of the transporter, since the uncoupler increases GLUT1 mRNA levels. Unlike GLUT1, very little is known about how interfering with mitochondrial ATP production regulates GLUT3 protein expression. Here we examine the mechanisms employed by DNP to increase GLUT3 protein content and glucose uptake in L6 muscle cells. We report that, in contrast with GLUT1, continuous exposure to DNP had no effect on GLUT3 mRNA levels. DNP-stimulated glucose transport was unaffected by the protein-synthesis inhibitor cycloheximide. The increase in GLUT3 protein mediated by DNP was also insensitive to cycloheximide, paralleling the response of glucose uptake, whereas the rise in GLUT1 protein levels was blocked by the inhibitor. The GLUT3 glucose transporter may therefore provide the majority of the glucose transport stimulation by DNP, despite elevated levels of GLUT1 protein. The half-lives of GLUT3 and GLUT1 proteins in L6 myotubes were determined to be about 15 h and 6 h respectively. DNP prolonged the half-life of both proteins. After 24 h of DNP treatment, 88% of GLUT3 protein and 57% of GLUT1 protein had not turned over, compared with 25% in untreated cells. We conclude that the long-term stimulation of glucose transport by DNP arises from an elevation of GLUT3 protein content associated with an increase in GLUT3 protein half-life. These findings suggest that disruption of the oxidative chain of L6 muscle cells leads to an adaptive response of glucose transport that is distinct from the insulin response, involving specific glucose transporter isoforms that are regulated by different mechanisms.

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Fish Glucose Transporter (GLUT)-4 Differs from Rat GLUT4 in Its Traffic Characteristics but Can Translocate to the Cell Surface in Response to Insulin in Skeletal Muscle Cells

Endocrinology ◽

10.1210/en.2007-0265 ◽

2007 ◽

Vol 148 (11) ◽

pp. 5248-5257 ◽

Cited By ~ 37

Author(s):

Mònica Díaz ◽

Costin N. Antonescu ◽

Encarnación Capilla ◽

Amira Klip ◽

Josep V. Planas

Keyword(s):

Skeletal Muscle ◽

Plasma Membrane ◽

Cell Surface ◽

Glucose Uptake ◽

Brown Trout ◽

Glucose Transporter ◽

Intracellular Localization ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Glut 4

In mammals, glucose transporter (GLUT)-4 plays an important role in glucose homeostasis mediating insulin action to increase glucose uptake in insulin-responsive tissues. In the basal state, GLUT4 is located in intracellular compartments and upon insulin stimulation is recruited to the plasma membrane, allowing glucose entry into the cell. Compared with mammals, fish are less efficient restoring plasma glucose after dietary or exogenous glucose administration. Recently our group cloned a GLUT4-homolog in skeletal muscle from brown trout (btGLUT4) that differs in protein motifs believed to be important for endocytosis and sorting of mammalian GLUT4. To study the traffic of btGLUT4, we generated a stable L6 muscle cell line overexpressing myc-tagged btGLUT4 (btGLUT4myc). Insulin stimulated btGLUT4myc recruitment to the cell surface, although to a lesser extent than rat-GLUT4myc, and enhanced glucose uptake. Interestingly, btGLUT4myc showed a higher steady-state level at the cell surface under basal conditions than rat-GLUT4myc due to a higher rate of recycling of btGLUT4myc and not to a slower endocytic rate, compared with rat-GLUT4myc. Furthermore, unlike rat-GLUT4myc, btGLUT4myc had a diffuse distribution throughout the cytoplasm of L6 myoblasts. In primary brown trout skeletal muscle cells, insulin also promoted the translocation of endogenous btGLUT4 to the plasma membrane and enhanced glucose transport. Moreover, btGLUT4 exhibited a diffuse intracellular localization in unstimulated trout myocytes. Our data suggest that btGLUT4 is subjected to a different intracellular traffic from rat-GLUT4 and may explain the relative glucose intolerance observed in fish.

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High Leptin Levels Acutely Inhibit Insulin-Stimulated Glucose Uptake without Affecting Glucose Transporter 4 Translocation in L6 Rat Skeletal Muscle Cells

Endocrinology ◽

10.1210/endo.142.11.8496 ◽

2001 ◽

Vol 142 (11) ◽

pp. 4806-4812 ◽

Cited By ~ 44

Author(s):

Gary Sweeney ◽

Jessica Keen ◽

Romel Somwar ◽

Daniel Konrad ◽

Rami Garg ◽

...

Keyword(s):

Skeletal Muscle ◽

Glucose Uptake ◽

Glucose Transporter ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Glucose Transporter 4 ◽

Rat Skeletal Muscle

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Ready, set, internalize: mechanisms and regulation of GLUT4 endocytosis

Bioscience Reports ◽

10.1042/bsr20080105 ◽

2008 ◽

Vol 29 (1) ◽

pp. 1-11 ◽

Cited By ~ 20

Author(s):

Costin N. Antonescu ◽

Michelangelo Foti ◽

Nathalie Sauvonnet ◽

Amira Klip

Keyword(s):

Insulin Resistance ◽

Muscle Contraction ◽

Glucose Uptake ◽

Glucose Transporter ◽

Muscle Cells ◽

Fat Cells ◽

Intracellular Membrane ◽

Membrane Compartments ◽

Glucose Transporter Glut4

The facilitative glucose transporter GLUT4, a recycling membrane protein, is required for dietary glucose uptake into muscle and fat cells. GLUT4 is also responsible for the increased glucose uptake by myofibres during muscle contraction. Defects in GLUT4 membrane traffic contribute to loss of insulin-stimulated glucose uptake in insulin resistance and Type 2 diabetes. Numerous studies have analysed the intracellular membrane compartments occupied by GLUT4 and the mechanisms by which insulin regulates GLUT4 exocytosis. However, until recently, GLUT4 internalization was less well understood. In the present paper, we review: (i) evidence supporting the co-existence of clathrin-dependent and independent GLUT4 internalization in adipocytes and muscle cells; (ii) the contrasting regulation of GLUT4 internalization by insulin in these cells; and (iii) evidence suggesting regulation of GLUT4 endocytosis in muscle cells by signals associated with muscle contraction.

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The Proinflammatory Cytokine Tumor Necrosis Factor-α Increases the Amount of Glucose Transporter-4 at the Surface of Muscle Cells Independently of Changes in Interleukin-6

Endocrinology ◽

10.1210/en.2007-1045 ◽

2007 ◽

Vol 149 (4) ◽

pp. 1880-1889 ◽

Cited By ~ 16

Author(s):

Nerea Roher ◽

Victor Samokhvalov ◽

Mònica Díaz ◽

Simon MacKenzie ◽

Amira Klip ◽

...

Keyword(s):

Plasma Membrane ◽

Cell Surface ◽

Glucose Uptake ◽

Proinflammatory Cytokine ◽

Glucose Transporter ◽

De Novo ◽

Muscle Cells ◽

Nuclear Factor Κb ◽

Nuclear Factor ◽

Insulin Resistant

TNFα is a proinflammatory cytokine secreted by macrophages in response to bacterial infection. Recently new evidence has emerged suggesting that stressed or injured myocytes produce TNFα that then acts as an autocrine and/or paracrine mediator. TNFα receptors types 1 and 2 are present in skeletal muscle cells, and muscle cells can secrete, in addition to TNFα, other cytokines such as IL-1β or IL-6. Furthermore, the plasma concentration of TNFα is elevated in insulin-resistant states associated with obesity and type 2 diabetes. Here we show that TNFα increased the amount of glucose transporter (GLUT)-4 at the plasma membrane and also glucose uptake in the L6 muscle cell line stably expressing GLUT4 tagged with the c-myc epitope. Regardless of the state of differentiation of the L6 cells, TNFα did not affect the rate of proliferation or of apoptosis. The stimulatory effects of TNFα on cell surface GLUT4 and glucose uptake were blocked by nuclear factor-κB and p38MAPK pathway specific inhibitors (Bay 11-7082 and SB220025), and these two pathways were stimulated by TNFα. Furthermore, although TNFα increased IL-6 mRNA and protein expression, IL-6 did not mediate the effects of TNFα on cell surface GLUT4 levels, which also did not require de novo protein synthesis. The results indicate that TNFα can stimulate glucose uptake in L6 muscle cells by inducing GLUT4 translocation to the plasma membrane, possibly through activation of the nuclear factor-κB and p38MAPK signaling pathways and independently of the production of IL-6.

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Gundelia tournefortii: Fractionation, Chemical Composition and GLUT4 Translocation Enhancement in Muscle Cell Line

Molecules ◽

10.3390/molecules26133785 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3785

Author(s):

Sleman Kadan ◽

Sarit Melamed ◽

Shoshana Benvalid ◽

Zipora Tietel ◽

Yoel Sasson ◽

...

Keyword(s):

Glucose Transporter ◽

Rapid Development ◽

Muscle Cells ◽

Flash Chromatography ◽

Glucose Disposal ◽

Gas Chromatography Mass Spectrometry ◽

Glut4 Translocation ◽

Toxic Concentrations ◽

L6 Muscle Cells

Type 2 diabetes (T2D) is a chronic metabolic disease, which could affect the daily life of patients and increase their risk of developing other diseases. Synthetic anti-diabetic drugs usually show severe side effects. In the last few decades, plant-derived drugs have been intensively studied, particularly because of a rapid development of the instruments used in analytical chemistry. We tested the efficacy of Gundelia tournefortii L. (GT) in increasing the translocation of glucose transporter-4 (GLUT4) to the myocyte plasma membrane (PM), as a main strategy to manage T2D. In this study, GT methanol extract was sub-fractionated into 10 samples using flash chromatography. The toxicity of the fractions on L6 muscle cells, stably expressing GLUTmyc, was evaluated using the MTT assay. The efficacy with which GLUT4 was attached to the L6 PM was evaluated at non-toxic concentrations. Fraction 6 was the most effective, as it stimulated GLUT4 translocation in the absence and presence of insulin, 3.5 and 5.2 times (at 250 μg/mL), respectively. Fraction 1 and 3 showed no significant effects on GLUT4 translocation, while other fractions increased GLUT4 translocation up to 2.0 times. Gas chromatography–mass spectrometry of silylated fractions revealed 98 distinct compounds. Among those compounds, 25 were considered anti-diabetic and glucose disposal agents. These findings suggest that GT methanol sub-fractions exert an anti-diabetic effect by modulating GLUT4 translocation in L6 muscle cells, and indicate the potential of GT extracts as novel therapeutic agents for T2D.

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