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

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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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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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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ALY688 elicits adiponectin-mimetic signaling and improves insulin action in skeletal muscle cells

AJP Cell Physiology ◽

10.1152/ajpcell.00603.2020 ◽

2021 ◽

Author(s):

Hye Kyoung Sung ◽

Patricia L. Mitchell ◽

Sean Gross ◽

Andre Marette ◽

Gary Sweeney

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Glucose Uptake ◽

Glucose Transporter ◽

Muscle Cells ◽

Temporal Analysis ◽

Skeletal Muscle Cells ◽

Adiponectin Receptor ◽

Metabolic Effects

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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Retinoic acid stimulates glucose transporter expression in L6 muscle cells

Molecular and Cellular Endocrinology ◽

10.1016/0303-7207(95)03473-k ◽

1995 ◽

Vol 108 (1-2) ◽

pp. 161-167 ◽

Cited By ~ 19

Author(s):

Mark W. Sleeman ◽

Hong Zhou ◽

Suzanne Rogers ◽

Kong Wah Ng ◽

James D. Best

Keyword(s):

Retinoic Acid ◽

Glucose Transporter ◽

Muscle Cells ◽

L6 Muscle Cells ◽

Transporter Expression

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Abstract 235: Sarcolemmal Membrane Associated Protein Isoform 1: a Unique Regulator of Glucose Uptake and Metabolism in the Myocardium

Circulation Research ◽

10.1161/res.117.suppl_1.235 ◽

2015 ◽

Vol 117 (suppl_1) ◽

Author(s):

Aaraf Dewan ◽

Maysoon Salih ◽

Christopher Triggle ◽

Hong Ding ◽

Balwant Tuana

Keyword(s):

Glucose Uptake ◽

Glucose Transporter ◽

Glucose Transporter 4 ◽

Specific Expression ◽

Western Blots ◽

Sarcolemmal Membrane ◽

Neonatal Cardiomyocytes ◽

Early Endosomes ◽

Protein Isoform ◽

Uptake And Metabolism

As one of the leading causes of heart disease, diabetes is a problem which needs a solution. Regulation of glucose uptake and metabolism within skeletal and cardiac muscle has proven capable of altering systemic glucose levels and impacting metabolism to potentially improve patient outcomes. Unfortunately, to date, very few muscle specific metabolic regulators are known which can allow us to achieve blood glucose uptake and metabolism. Sarcolemmal Membrane Associated Protein Isoform 1 (SLMAP1) is a novel protein expressed predominantly within muscle tissue. It has been linked to diabetes through animal models, although its role in metabolism remains to be defined. Here we describe a novel role for SLMAP1 in glucose metabolism within the myocardium. We engineered a transgenic (TG) mouse with cardiac specific expression of SLMAP1. Using neonatal cardiomyocytes (NCMs) collected from these mice we performed glucose uptake assays with 2-deoxy-glucose (2DG), measured glycolytic rate using an Extracellular Flux XF24e Bioanalyzer, and analyzed glucose transporter 4 (GLUT4) trafficking using Western Blots, qPCR, and immunofluorescence imaging. NCMs extracted from TG hearts expressing SLMAP1 displayed increased levels of 2DG uptake (93% ± 25%, n=5, P<0.01), basal glycolysis (glycolysis (92 ± 40%, n=5, P<0.05), and maximal glycolysis (75 ± 31%, n=5, P<0.05) compared with wildtype littermates. Confocal microscopy revealed both increased localization of glucose transporter 4 (GLUT4) at the cell surface as well as an expansion of GLUT4 early endosomes in TG NCMs. The data here indicates SLMAP1 as a novel regulator of glucose uptake and metabolism in the myocardium. The targeted expression of SLMAP1 in a muscle specific manner may enhance systemic glycemic control and serve to limit cardiovascular disease in metabolic disorders such as diabetes.

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