Genetic impairment of AMPKα2 signaling does not reduce muscle glucose uptake during treadmill exercise in mice

2009 ◽  
Vol 297 (4) ◽  
pp. E924-E934 ◽  
Author(s):  
Stine J. Maarbjerg ◽  
Sebastian B. Jørgensen ◽  
Adam J. Rose ◽  
Jacob Jeppesen ◽  
Thomas E. Jensen ◽  
...  
Keyword(s):  
Glucose Uptake ◽  
Glucose Transporter ◽  
Treadmill Exercise ◽  
Surface Membrane ◽  
Absolute Intensity ◽  
Wild Type ◽  
Running Speed ◽  
Mouse Muscle ◽  
Glucose Clearance

Some studies suggest that the 5′-AMP-activated protein kinase (AMPK) is important in regulating muscle glucose uptake in response to intense electrically stimulated contractions. However, it is unknown whether AMPK regulates muscle glucose uptake during in vivo exercise. We studied this in male and female mice overexpressing kinase-dead AMPKα2 (AMPK-KD) in skeletal and heart muscles. Wild-type and AMPK-KD mice were exercised at the same absolute intensity and the same relative intensity (30 and 70% of individual maximal running speed) to correct for reduced exercise capacity of the AMPK-KD mouse. Muscle glucose clearance was measured using 2-deoxy-[3H]glucose as tracer. In wild-type mice, glucose clearance was increased at 30 and 70% of maximal running speed by 40 and 350% in the quadriceps muscle and by 120 and 380% in gastrocnemius muscle, respectively. Glucose clearance was not lower in AMPK-KD muscles compared with wild-type regardless of whether animals were exercised at the same relative or the same absolute intensity. In agreement, surface membrane content of the glucose transporter GLUT4 was increased similarly in AMPK-KD and wild-type muscle in response to running. We also measured signaling of alternative exercise-sensitive pathways that might be compensatorily increased in AMPK-KD muscles. However, increases in phosphorylation of CaMKII, Trisk95, p38 MAPK, and ERK1/2 were not higher in AMPK-KD than in WT muscle. Collectively, these findings suggest that AMPKα2 signaling is not essential in regulating glucose uptake in mouse skeletal muscle during treadmill exercise and that other mechanisms play a central role.

scholarly journals Essential role of glucose transporter GLUT3 for post-implantation embryonic development

2008 ◽  
Vol 200 (1) ◽  
pp. 23-33 ◽  
Author(s):  
S Schmidt ◽  
A Hommel ◽  
V Gawlik ◽  
R Augustin ◽  
N Junicke ◽  
...  
Keyword(s):  
Essential Role ◽  
Glucose Transporter ◽  
Growth Arrest ◽  
Complete Loss ◽  
Transporter Gene ◽  
Wild Type ◽  
Post Implantation ◽  
Time Point

Deletion of glucose transporter geneSlc2a3(GLUT3) has previously been reported to result in embryonic lethality. Here, we define the exact time point of growth arrest and subsequent death of the embryo.Slc2a3−/−morulae and blastocysts developed normally, implantedin vivo, and formed egg-cylinder-stage embryos that appeared normal until day 6.0. At day 6.5, apoptosis was detected in the ectodermal cells ofSlc2a3−/−embryos resulting in severe disorganization and growth retardation at day 7.5 and complete loss of embryos at day 12.5. GLUT3 was detected in placental cone, in the visceral ectoderm and in the mesoderm of 7.5-day-old wild-type embryos. Our data indicate that GLUT3 is essential for the development of early post-implanted embryos.

scholarly journals Glucose Transporter 8 (GLUT8) Regulates Enterocyte Fructose Transport and Global Mammalian Fructose Utilization

Endocrinology ◽  
2012 ◽  
Vol 153 (9) ◽  
pp. 4181-4191 ◽  
Author(s):  
Brian J. DeBosch ◽  
Maggie Chi ◽  
Kelle H. Moley
Keyword(s):  
Glucose Transporter ◽  
Serum Insulin ◽  
Density Lipoprotein ◽  
Wild Type ◽  
In Vivo Models ◽  
The Metabolic Syndrome ◽  
High Fructose

Enterocyte fructose absorption is a tightly regulated process that precedes the deleterious effects of excess dietary fructose in mammals. Glucose transporter (GLUT)8 is a glucose/fructose transporter previously shown to be expressed in murine intestine. The in vivo function of GLUT8, however, remains unclear. Here, we demonstrate enhanced fructose-induced fructose transport in both in vitro and in vivo models of enterocyte GLUT8 deficiency. Fructose exposure stimulated [14C]-fructose uptake and decreased GLUT8 protein abundance in Caco2 colonocytes, whereas direct short hairpin RNA-mediated GLUT8 knockdown also stimulated fructose uptake. To assess GLUT8 function in vivo, we generated GLUT8-deficient (GLUT8KO) mice. GLUT8KO mice exhibited significantly greater jejunal fructose uptake at baseline and after high-fructose diet (HFrD) feeding vs. wild-type mice. Strikingly, long-term HFrD feeding in GLUT8KO mice exacerbated fructose-induced increases in blood pressure, serum insulin, low-density lipoprotein and total cholesterol vs. wild-type controls. Enhanced fructose uptake paralleled with increased abundance of the fructose and glucose transporter, GLUT12, in HFrD-fed GLUT8KO mouse enterocytes and in Caco2 cultures exposed to high-fructose medium. We conclude that GLUT8 regulates enterocyte fructose transport by regulating GLUT12, and that disrupted GLUT8 function has deleterious long-term metabolic sequelae. GLUT8 may thus represent a modifiable target in the prevention and treatment of malnutrition or the metabolic syndrome.

Insulin promotes glycogen synthesis in the absence of GSK3 phosphorylation in skeletal muscle

2008 ◽  
Vol 294 (1) ◽  
pp. E28-E35 ◽  
Author(s):  
Michale Bouskila ◽  
Michael F. Hirshman ◽  
Jørgen Jensen ◽  
Laurie J. Goodyear ◽  
Kei Sakamoto
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Muscle Glycogen ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Wild Type ◽  
Muscle Glycogen Synthesis ◽  
Mutant Forms

Insulin promotes dephosphorylation and activation of glycogen synthase (GS) by inactivating glycogen synthase kinase (GSK) 3 through phosphorylation. Insulin also promotes glucose uptake and glucose 6-phosphate (G-6- P) production, which allosterically activates GS. The relative importance of these two regulatory mechanisms in the activation of GS in vivo is unknown. The aim of this study was to investigate if dephosphorylation of GS mediated via GSK3 is required for normal glycogen synthesis in skeletal muscle with insulin. We employed GSK3 knockin mice in which wild-type GSK3α and -β genes are replaced with mutant forms (GSK3α/βS21A/S21A/S9A/S9A), which are nonresponsive to insulin. Although insulin failed to promote dephosphorylation and activation of GS in GSK3α/βS21A/S21A/S9A/S9Amice, glycogen content in different muscles from these mice was similar compared with wild-type mice. Basal and epinephrine-stimulated activity of muscle glycogen phosphorylase was comparable between wild-type and GSK3 knockin mice. Incubation of isolated soleus muscle in Krebs buffer containing 5.5 mM glucose in the presence or absence of insulin revealed that the levels of G-6- P, the rate of [14C]glucose incorporation into glycogen, and an increase in total glycogen content were similar between wild-type and GSK3 knockin mice. Injection of glucose containing 2-deoxy-[3H]glucose and [14C]glucose also resulted in similar rates of muscle glucose uptake and glycogen synthesis in vivo between wild-type and GSK3 knockin mice. These results suggest that insulin-mediated inhibition of GSK3 is not a rate-limiting step in muscle glycogen synthesis in mice. This suggests that allosteric regulation of GS by G-6- P may play a key role in insulin-stimulated muscle glycogen synthesis in vivo.

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

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.

scholarly journals RalA controls glucose homeostasis by regulating glucose uptake in brown fat

2018 ◽  
Vol 115 (30) ◽  
pp. 7819-7824 ◽  
Author(s):  
Yuliya Skorobogatko ◽  
Morgan Dragan ◽  
Claudia Cordon ◽  
Shannon M. Reilly ◽  
Chao-Wei Hung ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Brown Fat ◽  
Specific Chemical ◽  
Diet Induced Obesity ◽  
Brown Adipose ◽  
Chemical Inhibitors ◽  
Glucose Transporter Glut4

Insulin increases glucose uptake into adipose tissue and muscle by increasing trafficking of the glucose transporter Glut4. In cultured adipocytes, the exocytosis of Glut4 relies on activation of the small G protein RalA by insulin, via inhibition of its GTPase activating complex RalGAP. Here, we evaluate the role of RalA in glucose uptake in vivo with specific chemical inhibitors and by generation of mice with adipocyte-specific knockout of RalGAPB. RalA was profoundly activated in brown adipose tissue after feeding, and its inhibition prevented Glut4 exocytosis. RalGAPB knockout mice with diet-induced obesity were protected from the development of metabolic disease due to increased glucose uptake into brown fat. Thus, RalA plays a crucial role in glucose transport in adipose tissue in vivo.

Abstract 158: A Tether Containing a UBX Domain (TUG) Mediates Glucose Transporter Translocation in the Ischemic Heart

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Ji Li ◽  
Yina Ma ◽  
Jonathan Bogan
Keyword(s):  
Cell Surface ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Ex Vivo ◽  
Ischemia And Reperfusion ◽  
Ampk Activation ◽  
Glut4 Translocation ◽  
Heart Perfusion ◽  
Intracellular Vesicles

Introduction: The adaptive metabolic regulation of glucose and fatty acid in the heart plays a critical role in limiting cardiac damage caused by ischemia and reperfusion (I/R). TUG (tether containing a UBX domain, for GLUT4) can be cleaved to mobilize glucose transporter GLUT4 from intracellular vesicles to the cell surface in skeletal muscle and adipose in response to insulin stimulation. The energy sensor AMP-activated protein kinase (AMPK) plays an important cardioprotective role in response to ischemic insults by modulating GLUT4 translocation. Hypothesis: TUG is one of the downstream targets of AMPK in the heart. TUG could be phosphorylated by ischemic AMPK and cleaved to dissociate with GLUT4 and increase GLUT4 translocation in the ischemic heart. Methods: In vivo regional ischemia by ligation of left anterior coronary artery and ex vivo isolated mouse heart perfusion Langendorff system were used to test the hypothesis. Results: Antithrombin (AT) is an endogenous AMPK agonist in the heart and used to define the role of TUG in regulating GLUT4 trafficking during ischemia and reperfusion in the heart. AT showed its cardioprotective function through recovering cardiac pumping function and activating AMPK. The results showed that AMPK activation by AT treatment was through LKB1 and Sesn2 complex. Furthermore, the ex vivo heart perfusion data demonstrated that AT administration significantly increase GLUT4 translocation, glucose uptake, glycolysis and glucose oxidation during ischemia and reperfusion (p<0.05 vs . vehicle). Moreover, AT treatment increased abundance of a TUG cleavage product (42 KD) in response to I/R. The TUG protein was clearly phosphorylated by activated AMPK in HL-1 cardiomyocytes. The in vivo myocardial ischemia results demonstrated that ischemic AMPK activation triggers TUG cleavage and significantly increases GLUT4 translocation to the cell surface. Moreover, an augmented interaction between AMPK and TUG was observed during ischemia. Conclusions: Cardiac AMPK activation stimulates TUG cleavage and causes the dissociation between TUG and GLUT4 in the intracellular vesicles. TUG is a critical mediator that modulates cardiac GLUT4 translocation to cell surface and enhances glucose uptake by AMPK signaling pathway.

Muscle glucose uptake during and after exercise is normal in insulin-resistant rats

1993 ◽  
Vol 264 (2) ◽  
pp. E167-E172 ◽  
Author(s):  
M. Kusunoki ◽  
L. H. Storlien ◽  
J. MacDessi ◽  
N. D. Oakes ◽  
C. Kennedy ◽  
...  
Keyword(s):  
Glucose Uptake ◽  
Glucose Transporter ◽  
Treadmill Exercise ◽  
Glycogen Synthesis ◽  
Insulin Stimulation ◽  
Adult Rats ◽  
Insulin Resistant ◽  
Glucose Levels ◽  
Hindlimb Muscles ◽  
Postexercise Recovery

It is not generally known whether impaired stimulation of muscle glucose metabolism in insulin-resistant states is specific to insulin stimulation. Our aim was to examine whether glucose uptake responded normally to exercise and postexercise recovery in insulin-resistant high-fat-fed (HFF) rats. Three-week HFF or Chow-fed [control (Con)] adult rats were studied 5 days after cannulation. Before, during, or immediately after (recovery) 50 min of treadmill exercise, bolus 2-deoxy-[3H]glucose and [14C]glucose were administered to estimate muscle glucose uptake (R'g) and glycogen incorporation rates. Mean exercise and recovery plasma glucose levels were similar in HFF and Con rats. In hindlimb muscles sampled, exercise and recovery R'g were similar in HFF and Con (e.g., red quadriceps exercise 104 +/- 13 vs. 113 +/- 8, recovery 45.3 +/- 3.9 vs. 47.7 +/- 4.5 mumol.100 g-1.min-1, respectively). Moreover, muscle glucose transporter (GLUT-4) content was not reduced in HFF rats. Glycogen resynthesis accounted almost entirely for R'g during recovery and was equivalent between groups. We conclude that impaired muscle glucose uptake and glycogen synthesis in HFF rats are characteristic of insulin but not of exercise or postexercise stimulation.

scholarly journals A Molecular Determinant of West Nile Virus Secretion and Morphology as a Target for Viral Attenuation

2020 ◽  
Vol 94 (12) ◽  
Author(s):  
Justine Basset ◽  
Julien Burlaud-Gaillard ◽  
Maxence Feher ◽  
Philippe Roingeard ◽  
Félix A. Rey ◽  
...  
Keyword(s):  
West Nile Virus ◽  
Rational Design ◽  
Surface Membrane ◽  
Public Health Problem ◽  
M Protein ◽  
Membrane Glycoprotein ◽  
Wild Type ◽  
West Nile ◽  
Viral Attenuation

ABSTRACT West Nile virus (WNV), a member of the Flavivirus genus and currently one of the most common arboviruses worldwide, is associated with severe neurological disease in humans. Its high potential to reemerge and rapidly disseminate makes it a bona fide global public health problem. The surface membrane glycoprotein (M) has been associated with Flavivirus-induced pathogenesis. Here, we identified a key amino acid residue at position 36 of the M protein whose mutation impacts WNV secretion and promotes viral attenuation. We also identified a compensatory site at position M-43 whose mutation stabilizes M-36 substitution both in vitro and in vivo. Moreover, we found that introduction of the two mutations together confers a full attenuation phenotype and protection against wild-type WNV lethal challenge, eliciting potent neutralizing-antibody production in mice. Our study thus establishes the M protein as a new viral target for rational design of attenuated WNV strains. IMPORTANCE West Nile virus (WNV) is a worldwide (re)emerging mosquito-transmitted Flavivirus causing fatal neurological diseases in humans. However, no human vaccine has been yet approved. One of the most effective live-attenuated vaccines was empirically obtained by serial passaging of wild-type yellow fever Flavivirus. However, such an approach is not acceptable nowadays, and the development of a rationally designed vaccine is necessary. Generating molecular infectious clones and mutating specific residues known to be involved in Flavivirus virulence constitute a powerful tool to promote viral attenuation. WNV membrane glycoprotein is thought to carry such essential determinants. Here, we identified two residues of this protein whose substitutions are key to the full and stable attenuation of WNV in vivo, most likely through inhibition of secretion and possible alteration of morphology. Applied to other flaviviruses, this approach should help in designing new vaccines against these viruses, which are an increasing threat to global human health.

scholarly journals Effects of Chronic Undernutrition on Glucose Uptake and Glucose Transporter Proteins in Rat Heart

Endocrinology ◽  
2002 ◽  
Vol 143 (11) ◽  
pp. 4295-4303 ◽  
Author(s):  
M. Lucia Gavete ◽  
Maria Agote ◽  
M. Angeles Martin ◽  
Carmen Alvarez ◽  
Fernando Escriva
Keyword(s):  
Glucose Uptake ◽  
Glucose Transporter ◽  
Surface Membrane ◽  
Subcellular Fractionation ◽  
High Energy ◽  
Regulatory Subunits ◽  
Glut 1 ◽  
Glut 4 ◽  
Energy Demands ◽  
Glucose Transporter Proteins

Abstract The high energy demands of myocardium are met through the metabolism of lipids and glucose. Importantly, enhanced glucose utilization rates are crucial adaptations of the cardiac cell to some pathological conditions, such as hypertrophy and ischemia, but the effects of undernutrition on heart glucose metabolism are unknown. Our previous studies have shown that undernutrition increases insulin-induced glucose uptake by skeletal muscle. Consequently, we considered the possibility of a similar adaptation in the heart. With this aim, undernourished rats both in the basal state and after euglycemic hyperinsulinemic clamps were used to determine the following parameters in myocardium: glucose uptake, glucose transporter (GLUT) content, and some key components of the insulin signaling cascade. Heart membranes were prepared by subcellular fractionation in sucrose gradients. Although GLUT-4, GLUT-1, and GLUT-3 proteins and GLUT-4/1 mRNAs were reduced by undernutrition, basal and insulin-stimulated 2-deoxyglucose uptake were significantly enhanced. Phosphoinositol 3-kinase activity remained greater than control values in both conditions. The abundance of p85α and p85β regulatory subunits of phosphoinositol 3-kinase was increased as was phospho-Akt during hyperinsulinemia. These changes seem to improve the insulin stimulus of GLUT-1 translocation, as its content was increased at the surface membrane. Such adaptations associated with undernutrition must be crucial to improvement of cardiac glucose uptake.

scholarly journals Alterations in Glucose Metabolism During the Transition to Heart Failure: The Contribution of UCP-2

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 552 ◽  
Author(s):  
Hanna Sarah Kutsche ◽  
Rolf Schreckenberg ◽  
Martin Weber ◽  
Christine Hirschhäuser ◽  
Susanne Rohrbach ◽  
...  
Keyword(s):  
Heart Failure ◽  
Glucose Metabolism ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Contractile Function ◽  
Uncoupling Protein ◽  
Left Ventricular ◽  
Mitochondrial Uncoupling ◽  
Glut 4

The cardiac expression of the mitochondrial uncoupling protein (UCP)-2 is increased in patients with heart failure. However, the underlying causes as well as the possible consequences of these alterations during the transition from hypertrophy to heart failure are still unclear. To investigate the role of UCP-2 mechanistically, expression of UCP-2 was silenced by small interfering RNA in adult rat ventricular cardiomyocytes. We demonstrate that a downregulation of UCP-2 by siRNA in cardiomyocytes preserves contractile function in the presence of angiotensin II. Furthermore, silencing of UCP-2 was associated with an upregulation of glucose transporter type (Glut)-4, increased glucose uptake, and reduced intracellular lactate levels, indicating improvement of the oxidative glucose metabolism. To study this adaptation in vivo, spontaneously hypertensive rats served as a model for cardiac hypertrophy due to pressure overload. During compensatory hypertrophy, we found low UCP-2 levels with an upregulation of Glut-4, while the decompensatory state with impaired function was associated with an increase of UCP-2 and reduced Glut-4 expression. By blocking the aldosterone receptor with spironolactone, both cardiac function as well as UCP-2 and Glut-4 expression levels of the compensated phase could be preserved. Furthermore, we were able to confirm this by left ventricular (LV) biopsies of patients with end-stage heart failure. The results of this study show that UCP-2 seems to impact the cardiac glucose metabolism during the transition from hypertrophy to failure by affecting glucose uptake through Glut-4. We suggest that the failing heart could benefit from low UCP-2 levels by improving the efficiency of glucose oxidation. For this reason, UCP-2 inhibition might be a promising therapeutic strategy to prevent the development of heart failure.

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