An intracellular motif of GLUT4 regulates fusion of GLUT4-containing vesicles.

PubMed

Heyward, Catherine A; Pettitt, Trevor R; Leney, Sophie E; Welsh, Gavin I; Tavaré, Jeremy M; Wakelam, Michael J O

2008-05-20

Insulin stimulates glucose uptake by adipocytes through increasing translocation of the glucose transporter GLUT4 from an intracellular compartment to the plasma membrane. Fusion of GLUT4-containing vesicles at the cell surface is thought to involve phospholipase D activity, generating the signalling lipid phosphatidic acid, although the mechanism of action is not yet clear. Here we report the identification of a putative phosphatidic acid-binding motif in a GLUT4 intracellular loop. Mutation of this motif causes a decrease in the insulin-induced exposure of GLUT4 at the cell surface of 3T3-L1 adipocytes via an effect on vesicle fusion. The potential phosphatidic acid-binding motif identified in this study is unique to GLUT4 among the sugar transporters, therefore this motif may provide a unique mechanism for regulating insulin-induced translocation by phospholipase D signalling.

Specialized sorting of GLUT4 and its recruitment to the cell surface are independently regulated by distinct Rabs

PubMed Central

Sadacca, L. Amanda; Bruno, Joanne; Wen, Jennifer; Xiong, Wenyong; McGraw, Timothy E.

2013-01-01

Adipocyte glucose uptake in response to insulin is essential for physiological glucose homeostasis: stimulation of adipocytes with insulin results in insertion of the glucose transporter GLUT4 into the plasma membrane and subsequent glucose uptake. Here we establish that RAB10 and RAB14 are key regulators of GLUT4 trafficking that function at independent, sequential steps of GLUT4 translocation. RAB14 functions upstream of RAB10 in the sorting of GLUT4 to the specialized transport vesicles that ferry GLUT4 to the plasma membrane. RAB10 and its GTPase-activating protein (GAP) AS160 comprise the principal signaling module downstream of insulin receptor activation that regulates the accumulation of GLUT4 transport vesicles at the plasma membrane. Although both RAB10 and RAB14 are regulated by the GAP activity of AS160 in vitro, only RAB10 is under the control of AS160 in vivo. Insulin regulation of the pool of RAB10 required for GLUT4 translocation occurs through regulation of AS160, since activation of RAB10 by DENND4C, its GTP exchange factor, does not require insulin stimulation. PMID:23804653

Triiodothyronine Acutely Stimulates Glucose Transport into L6 Muscle Cells Without Increasing Surface GLUT4, GLUT1, or GLUT3

PubMed Central

Teixeira, Silvania Silva; Tamrakar, Akhilesh K.; Goulart-Silva, Francemilson; Serrano-Nascimento, Caroline; Klip, Amira

2012-01-01

Background Thyroid hormones (THs) act genomically to stimulate glucose transport by elevating glucose transporter (Slc2a) expression and glucose utilization by cells. However, nongenomic effects of THs are now emerging. Here, we assess how triiodothyronine (T3) acutely affects glucose transport and the content of GLUT4, GLUT1, and GLUT3 at the surface of muscle cells, and possible interactions between T3 and insulin action. Methods Differentiated L6 myotubes transfected with myc-tagged Slc2a4 (L6-GLUT4myc) or Slc2a1 (L6-GLUT1myc) and wild-type L6 myotubes were studied in the following conditions: control, hypothyroid (Tx), Tx plus T3, Tx plus insulin, and Tx plus insulin and T3. Results Glucose uptake and GLUT4 content at the cell surface decreased in the Tx group relative to controls. T3 treatment for 30 minutes increased glucose transport into L6-GLUT4myc cells without altering surface GLUT4 content, which increased only thereafter. The total amount of GLUT4 protein remained unchanged among the groups studied. The surface GLUT1 content of L6-GLUT1myc cells also remained unaltered after T3 treatment; however, in these cells glucose transport was not stimulated by T3. In wild-type L6 cells, although T3 treatment increased the total amount of GLUT3, it did not change the surface GLUT3 content. Moreover, within 30 minutes, T3 stimulation of glucose uptake was additive to that of insulin in L6-GLUT4myc cells. As expected, insulin elevated surface GLUT4 content and glucose uptake. However, interestingly, surface GLUT4 content remained unchanged or even dropped with T3 plus insulin. Conclusions These data reveal that T3 rapidly increases glucose uptake in L6-GLUT4myc cells, which, at least for 30 minutes, did not depend on an increment in GLUT4 at the cell surface yet potentiates insulin action. We propose that this rapid T3 effect involves activation of GLUT4 transporters at the cell surface, but cannot discount the involvement of an unknown GLUT. PMID:22663547

Glucose transporters GLUT4 and GLUT8 are upregulated after facial nerve axotomy in adult mice.

PubMed

Gómez, Olga; Ballester-Lurbe, Begoña; Mesonero, José E; Terrado, José

2011-10-01

Peripheral nerve axotomy in adult mice elicits a complex response that includes increased glucose uptake in regenerating nerve cells. This work analyses the expression of the neuronal glucose transporters GLUT3, GLUT4 and GLUT8 in the facial nucleus of adult mice during the first days after facial nerve axotomy. Our results show that whereas GLUT3 levels do not vary, GLUT4 and GLUT8 immunoreactivity increases in the cell body of the injured motoneurons after the lesion. A sharp increase in GLUT4 immunoreactivity was detected 3 days after the nerve injury and levels remained high on Day 8, but to a lesser extent. GLUT8 also increased the levels but later than GLUT4, as they only rose on Day 8 post-lesion. These results indicate that glucose transport is activated in regenerating motoneurons and that GLUT4 plays a main role in this function. These results also suggest that metabolic defects involving impairment of glucose transporters may be principal components of the neurotoxic mechanisms leading to motoneuron death. © 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society of Great Britain and Ireland.

Ethanol stimulates glucose uptake and translocation of GLUT-4 in H9c2 myotubes via a Ca(2+)-dependent mechanism.

PubMed

Yu, B; Schroeder, A; Nagy, L E

2000-12-01

Short-term exposure to ethanol impairs glucose homeostasis, but the effects of ethanol on individual components of the glucose disposal pathway are not known. To understand the mechanisms by which ethanol disrupts glucose homeostasis, we have investigated the direct effects of ethanol on glucose uptake and translocation of GLUT-4 in H9c2 myotubes. Short-term treatment with 12.5-50 mM ethanol increased uptake of 2-deoxyglucose by 1.8-fold in differentiated myotubes. Pretreatment of H9c2 myotubes with 100 nM wortmannin, an inhibitor of phosphatidylinositol 3-kinase, had no effect on ethanol-induced increases in 2-deoxyglucose uptake. In contrast, preincubation with 25 microM dantrolene, an inhibitor of Ca(2+) release from the sarcoplasmic reticulum, blocked the stimulation of 2-deoxyglucose uptake by ethanol. Increased 2-deoxyglucose uptake after ethanol treatment was associated with a decrease in small intracellular GLUT-4 vesicles and an increase in GLUT-4 localized at the cell surface. In contrast, ethanol had no effect on the quantity of GLUT-1 and GLUT-3 at the plasma membrane. These data demonstrate that physiologically relevant concentrations of ethanol disrupt the trafficking of GLUT-4 in H9c2 myotubes resulting in translocation of GLUT-4 to the plasma membrane and increased glucose uptake.

Insulin Stimulates Translocation of Human GLUT4 to the Membrane in Fat Bodies of Transgenic Drosophila melanogaster

PubMed Central

Crivat, Georgeta; Lizunov, Vladimir A.; Li, Caroline R.; Stenkula, Karin G.; Zimmerberg, Joshua; Cushman, Samuel W.; Pick, Leslie

2013-01-01

The fruit fly Drosophila melanogaster is an excellent model system for studies of genes controlling development and disease. However, its applicability to physiological systems is less clear because of metabolic differences between insects and mammals. Insulin signaling has been studied in mammals because of relevance to diabetes and other diseases but there are many parallels between mammalian and insect pathways. For example, deletion of Drosophila Insulin-Like Peptides resulted in ‘diabetic’ flies with elevated circulating sugar levels. Whether this situation reflects failure of sugar uptake into peripheral tissues as seen in mammals is unclear and depends upon whether flies harbor the machinery to mount mammalian-like insulin-dependent sugar uptake responses. Here we asked whether Drosophila fat cells are competent to respond to insulin with mammalian-like regulated trafficking of sugar transporters. Transgenic Drosophila expressing human glucose transporter-4 (GLUT4), the sugar transporter expressed primarily in insulin-responsive tissues, were generated. After expression in fat bodies, GLUT4 intracellular trafficking and localization were monitored by confocal and total internal reflection fluorescence microscopy (TIRFM). We found that fat body cells responded to insulin with increased GLUT4 trafficking and translocation to the plasma membrane. While the amplitude of these responses was relatively weak in animals reared on a standard diet, it was greatly enhanced in animals reared on sugar-restricted diets, suggesting that flies fed standard diets are insulin resistant. Our findings demonstrate that flies are competent to mobilize translocation of sugar transporters to the cell surface in response to insulin. They suggest that Drosophila fat cells are primed for a response to insulin and that these pathways are down-regulated when animals are exposed to constant, high levels of sugar. Finally, these studies are the first to use TIRFM to monitor insulin

IKKβ and NFκB transcription govern lymphoma cell survival through AKT-induced plasma membrane trafficking of GLUT1

PubMed Central

Sommermann, Thomas; O’Neill, Kathleen; Plas, David R.; Cahir-McFarland, Ellen

2011-01-01

All cancer cells require increased nutrient uptake to support proliferation. Here we investigated the signals that govern glucose uptake in B-cell lymphomas and determined that the protein kinase IKKβ induced GLUT1 membrane trafficking in both viral and spontaneous B-cell lymphomas. IKKβ induced AKT activity, while IKKβ-driven NFκB transcription was required for GLUT1 surface localization downstream of AKT. Activated NFκB promoted AKT-mediated phosphorylation of the GLUT1 regulator, AKT Substrate 160kD (AS160), but was not required for AKT phosphorylation of the mammalian target of rapamycin (mTOR) regulator Tuberous Sclerosis 2 (TSC2). In Epstein Barr virus (EBV) transformed B-cells, NFκB inhibition repressed glucose uptake and induced caspase-independent cell death associated with autophagy. After NFκB inhibition, an alternate carbon source ameliorated both autophagy and cell death, whereas autophagy inhibitors specifically accelerated cell death. Taken together, the results suggest that NFκB signaling establishes a metabolic program supporting proliferation and apoptosis resistance by driving glucose import. PMID:21987722

Comparison of GLUT1, GLUT3, and GLUT4 mRNA and the subcellular distribution of their proteins in normal human muscle

NASA Technical Reports Server (NTRS)

Stuart, C. A.; Wen, G.; Gustafson, W. C.; Thompson, E. A.

2000-01-01

Basal, "insulin-independent" glucose uptake into skeletal muscle is provided by glucose transporters positioned at the plasma membrane. The relative amount of the three glucose transporters expressed in muscle has not been previously quantified. Using a combination of qualitative and quantitative ribonuclease protection assay (RPA) methods, we found in normal human muscle that GLUT1, GLUT3, and GLUT4 mRNA were expressed at 90 +/- 10, 46 +/- 4, and 156 +/- 12 copies/ng RNA, respectively. Muscle was fractionated by DNase digestion and differential sedimentation into membrane fractions enriched in plasma membranes (PM) or low-density microsomes (LDM). GLUT1 and GLUT4 proteins were distributed 57% to 67% in LDM, whereas GLUT3 protein was at least 88% in the PM-enriched fractions. These data suggest that basal glucose uptake into resting human muscle could be provided in part by each of these three isoforms.

Impact of pre-gestational and gestational diabetes mellitus on the expression of glucose transporters GLUT-1, GLUT-4 and GLUT-9 in human term placenta.

PubMed

Stanirowski, Paweł Jan; Szukiewicz, Dariusz; Pyzlak, Michał; Abdalla, Nabil; Sawicki, Włodzimierz; Cendrowski, Krzysztof

2017-03-01

Various studies in placental tissue suggest that diabetes mellitus alters the expression of glucose transporter (GLUT) proteins, with insulin therapy being a possible modulatory factor. The aim of the present study was quantitative evaluation of the expression of glucose transporters (GLUT-1, GLUT-4, GLUT-9) in the placenta of women in both, uncomplicated and diabetic pregnancy. Additionally, the effect of insulin therapy on the expression of selected glucose transporter isoforms was analyzed. Term placental samples were obtained from healthy control (n = 25) and diabetic pregnancies, including diet-controlled gestational diabetes mellitus (GDMG1) (n = 16), insulin-controlled gestational diabetes mellitus (GDMG2) (n = 6), and pre-gestational diabetes mellitus (PGDM) (n = 6). Computer-assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected glucose transporter proteins. Morphometric analysis revealed a significant increase in the expression of GLUT-4 and GLUT-9 in insulin-dependent diabetic women (GDMG2 + PGDM) as compared to both, control and GDMG1 groups (p < .05). Significantly increased GLUT-1 expression was observed only in placental specimens from patients with PGDM (p < .05). No statistically significant differences in GLUT expression were found between GDMG1 patients and healthy controls. The results of the study confirmed the presence of GLUT-1, GLUT-4 and GLUT-9 proteins in the trophoblast from both, uncomplicated and diabetic pregnancies. In addition, insulin therapy may increase placental expression of GLUT-4 and GLUT-9, and partially GLUT-1, in women with GDMG2/PGDM.

Immunogold labeling study of the distribution of GLUT-1 and GLUT-4 in cardiac tissue following stimulation by insulin or ischemia.

PubMed

Davey, Katherine A B; Garlick, Pamela B; Warley, Alice; Southworth, Richard

2007-04-01

Whereas glucose transporter 1 (GLUT-1) is thought to be responsible for basal glucose uptake in cardiac myocytes, little is known about its relative distribution between the different plasma membranes and cell types in the heart. GLUT-4 translocates to the myocyte surface to increase glucose uptake in response to a number of stimuli. The mechanisms underlying ischemia- and insulin-mediated GLUT-4 translocation are known to be different, raising the possibility that the intracellular destinations of GLUT-4 following these stimuli also differ. Using immunogold labeling, we describe the cellular localization of these two transporters and investigate whether insulin and ischemia induce differential translocation of GLUT-4 to different cardiac membranes. Immunogold labeling of GLUT-1 and GLUT-4 was performed on left ventricular sections from isolated hearts following 30 min of either insulin, ischemia, or control perfusion. In control tissue, GLUT-1 was predominantly (76%) localized in the capillary endothelial cells, with only 24% of total cardiac GLUT-1 present in myocytes. GLUT-4 was found predominantly in myocytes, distributed between sarcolemmal and T tubule membranes (1.84 +/- 0.49 and 1.54 +/- 0.33 golds/microm, respectively) and intracellular vesicles (127 +/- 18 golds/microm(2)). Insulin increased T tubule membrane GLUT-4 content (2.8 +/- 0.4 golds/microm, P < 0.05) but had less effect on sarcolemmal GLUT-4 (1.72 +/- 0.53 golds/microm). Ischemia induced greater GLUT-4 translocation to both membrane types (4.25 +/- 0.84 and 4.01 +/- 0.27 golds/microm, respectively P < 0.05). The localization of GLUT-1 suggests a significant role in transporting glucose across the capillary wall before myocyte uptake via GLUT-1 and GLUT-4. We demonstrate independent spatial translocation of GLUT-4 under insulin or ischemic stimulation and propose independent roles for T-tubular and sarcolemmal GLUT-4.

Distinct Akt phosphorylation states are required for insulin regulated Glut4 and Glut1-mediated glucose uptake.

PubMed

Beg, Muheeb; Abdullah, Nazish; Thowfeik, Fathima Shazna; Altorki, Nasser K; McGraw, Timothy E

2017-06-07

Insulin, downstream of Akt activation, promotes glucose uptake into fat and muscle cells to lower postprandial blood glucose, an enforced change in cellular metabolism to maintain glucose homeostasis. This effect is mediated by the Glut4 glucose transporter. Growth factors also enhance glucose uptake to fuel an anabolic metabolism required for tissue growth and repair. This activity is predominantly mediated by the Glut1. Akt is activated by phosphorylation of its kinase and hydrophobic motif (HM) domains. We show that insulin-stimulated Glut4-mediated glucose uptake requires PDPK1 phosphorylation of the kinase domain but not mTORC2 phosphorylation of the HM domain. Nonetheless, an intact HM domain is required for Glut4-mediated glucose uptake. Whereas, Glut1-mediated glucose uptake also requires mTORC2 phosphorylation of the HM domain, demonstrating both phosphorylation-dependent and independent roles of the HM domain in regulating glucose uptake. Thus, mTORC2 links Akt to the distinct physiologic programs related to Glut4 and Glut1-mediated glucose uptake.

Prolactin-induced Subcellular Targeting of GLUT1 Glucose Transporter in Living Mammary Epithelial Cells

PubMed Central

Riskin, Arieh; Mond, Yehudit

2015-01-01

Background Studying the biological pathways involved in mammalian milk production during lactation could have many clinical implications. The mammary gland is unique in its requirement for transport of free glucose into the cell for the synthesis of lactose, the primary carbohydrate in milk. Objective To study GLUT1 trafficking and subcellular targeting in living mammary epithelial cells (MEC) in culture. Methods Immunocytochemistry was used to study GLUT1 hormonally regulated subcellular targeting in human MEC (HMEC). To study GLUT1 targeting and recycling in living mouse MEC (MMEC) in culture, we constructed fusion proteins of GLUT1 and green fluorescent protein (GFP) and expressed them in CIT3 MMEC. Cells were maintained in growth medium (GM), or exposed to secretion medium (SM), containing prolactin. Results GLUT1 in HMEC localized primarily to the plasma membrane in GM. After exposure to prolactin for 4 days, GLUT1 was targeted intracellularly and demonstrated a perinuclear distribution, co-localizing with lactose synthetase. The dynamic trafficking of GFP-GLUT1 fusion proteins in CIT3 MMEC suggested a basal constitutive GLUT1 recycling pathway between an intracellular pool and the cell surface that targets most GLUT1 to the plasma membrane in GM. Upon exposure to prolactin in SM, GLUT1 was specifically targeted intracellularly within 90–110 minutes. Conclusions Our studies suggest intracellular targeting of GLUT1 to the central vesicular transport system upon exposure to prolactin. The existence of a dynamic prolactin-induced sorting machinery for GLUT1 could be important for transport of free glucose into the Golgi for lactose synthesis during lactation. PMID:26886772

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.

PubMed

Díaz, Mònica; Antonescu, Costin N; Capilla, Encarnación; Klip, Amira; Planas, Josep V

2007-11-01

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.

Deletion of Rab GAP AS160 modifies glucose uptake and GLUT4 translocation in primary skeletal muscles and adipocytes and impairs glucose homeostasis.

PubMed

Lansey, Melissa N; Walker, Natalie N; Hargett, Stefan R; Stevens, Joseph R; Keller, Susanna R

2012-11-15

Tight control of glucose uptake in skeletal muscles and adipocytes is crucial to glucose homeostasis and is mediated by regulating glucose transporter GLUT4 subcellular distribution. In cultured cells, Rab GAP AS160 controls GLUT4 intracellular retention and release to the cell surface and consequently regulates glucose uptake into cells. To determine AS160 function in GLUT4 trafficking in primary skeletal muscles and adipocytes and investigate its role in glucose homeostasis, we characterized AS160 knockout (AS160(-/-)) mice. We observed increased and normal basal glucose uptake in isolated AS160(-/-) adipocytes and soleus, respectively, while insulin-stimulated glucose uptake was impaired and GLUT4 expression decreased in both. No such abnormalities were found in isolated AS160(-/-) extensor digitorum longus muscles. In plasma membranes isolated from AS160(-/-) adipose tissue and gastrocnemius/quadriceps, relative GLUT4 levels were increased under basal conditions and remained the same after insulin treatment. Concomitantly, relative levels of cell surface-exposed GLUT4, determined with a glucose transporter photoaffinity label, were increased in AS160(-/-) adipocytes and normal in AS160(-/-) soleus under basal conditions. Insulin augmented cell surface-exposed GLUT4 in both. These observations suggest that AS160 is essential for GLUT4 intracellular retention and regulation of glucose uptake in adipocytes and skeletal muscles in which it is normally expressed. In vivo studies revealed impaired insulin tolerance in the presence of normal (male) and impaired (female) glucose tolerance. Concurrently, insulin-elicited increases in glucose disposal were abolished in all AS160(-/-) skeletal muscles and liver but not in AS160(-/-) adipose tissues. This suggests AS160 as a target for differential manipulation of glucose homeostasis.

Invited review: Regulation of skeletal muscle GLUT-4 expression by exercise.

PubMed

Dohm, G Lynis

2002-08-01

The amount of GLUT-4 protein is a primary factor in determining the maximal rate of glucose transport into skeletal muscle. Therefore, it is important that we understand how exercise regulates GLUT-4 expression so that therapeutic strategies can be designed to increase muscle glucose disposal as a treatment for diabetes. Muscle contraction increases the rates of GLUT-4 transcription and translation. Transcriptional control likely requires at least two DNA binding proteins, myocyte enhancer factor-2 and GLUT-4 enhancer factor, which bind to the promoter. Increased GLUT-4 expression may be mediated by the enzyme AMP-activated kinase, which is activated during exercise and has been demonstrated to increase GLUT-4 transcription. Further research needs to be done to investigate whether AMP-activated kinase activates myocyte enhancer factor-2 and GLUT-4 enhancer factor to increase transcription of the GLUT-4 gene.

Insulin Regulates Glut4 Confinement in Plasma Membrane Clusters in Adipose Cells

PubMed Central

Lizunov, Vladimir A.; Stenkula, Karin; Troy, Aaron; Cushman, Samuel W.; Zimmerberg, Joshua

2013-01-01

Insulin-stimulated delivery of glucose transporter-4 (GLUT4) to the plasma membrane (PM) is the hallmark of glucose metabolism. In this study we examined insulin’s effects on GLUT4 organization in PM of adipose cells by direct microscopic observation of single monomers tagged with photoswitchable fluorescent protein. In the basal state, after exocytotic delivery only a fraction of GLUT4 is dispersed into the PM as monomers, while most of the GLUT4 stays at the site of fusion and forms elongated clusters (60–240 nm). GLUT4 monomers outside clusters diffuse freely and do not aggregate with other monomers. In contrast, GLUT4 molecule collision with an existing cluster can lead to immediate confinement and association with that cluster. Insulin has three effects: it shifts the fraction of dispersed GLUT4 upon delivery, it augments the dissociation of GLUT4 monomers from clusters ∼3-fold and it decreases the rate of endocytic uptake. All together these three effects of insulin shift most of the PM GLUT4 from clustered to dispersed states. GLUT4 confinement in clusters represents a novel kinetic mechanism for insulin regulation of glucose homeostasis. PMID:23520472

Insulin regulates Glut4 confinement in plasma membrane clusters in adipose cells.

PubMed

Lizunov, Vladimir A; Stenkula, Karin; Troy, Aaron; Cushman, Samuel W; Zimmerberg, Joshua

2013-01-01

Insulin-stimulated delivery of glucose transporter-4 (GLUT4) to the plasma membrane (PM) is the hallmark of glucose metabolism. In this study we examined insulin's effects on GLUT4 organization in PM of adipose cells by direct microscopic observation of single monomers tagged with photoswitchable fluorescent protein. In the basal state, after exocytotic delivery only a fraction of GLUT4 is dispersed into the PM as monomers, while most of the GLUT4 stays at the site of fusion and forms elongated clusters (60-240 nm). GLUT4 monomers outside clusters diffuse freely and do not aggregate with other monomers. In contrast, GLUT4 molecule collision with an existing cluster can lead to immediate confinement and association with that cluster. Insulin has three effects: it shifts the fraction of dispersed GLUT4 upon delivery, it augments the dissociation of GLUT4 monomers from clusters ∼3-fold and it decreases the rate of endocytic uptake. All together these three effects of insulin shift most of the PM GLUT4 from clustered to dispersed states. GLUT4 confinement in clusters represents a novel kinetic mechanism for insulin regulation of glucose homeostasis.

Transport, metabolism, and endosomal trafficking-dependent regulation of intestinal fructose absorption

PubMed Central

Patel, Chirag; Douard, Veronique; Yu, Shiyan; Gao, Nan; Ferraris, Ronaldo P.

2015-01-01

Dietary fructose that is linked to metabolic abnormalities can up-regulate its own absorption, but the underlying regulatory mechanisms are not known. We hypothesized that glucose transporter (GLUT) protein, member 5 (GLUT5) is the primary fructose transporter and that fructose absorption via GLUT5, metabolism via ketohexokinase (KHK), as well as GLUT5 trafficking to the apical membrane via the Ras-related protein-in-brain 11 (Rab11)a-dependent endosomes are each required for regulation. Introducing fructose but not lysine and glucose solutions into the lumen increased by 2- to 10-fold the heterogeneous nuclear RNA, mRNA, protein, and activity levels of GLUT5 in adult wild-type mice consuming chow. Levels of GLUT5 were >100-fold that of candidate apical fructose transporters GLUTs 7, 8, and 12 whose expression, and that of GLUT 2 and the sodium-dependent glucose transporter protein 1 (SGLT1), was not regulated by luminal fructose. GLUT5-knockout (KO) mice exhibited no facilitative fructose transport and no compensatory increases in activity and expression of SGLT1 and other GLUTs. Fructose could not up-regulate GLUT5 in GLUT5-KO, KHK-KO, and intestinal epithelial cell-specific Rab11a-KO mice. The fructose-specific metabolite glyceraldehyde did not increase GLUT5 expression. GLUT5 is the primary transporter responsible for facilitative absorption of fructose, and its regulation specifically requires fructose uptake and metabolism and normal GLUT5 trafficking to the apical membrane.—Patel, C., Douard, V., Yu, S., Gao, N., Ferraris, R. P. Transport, metabolism, and endosomal trafficking-dependent regulation of intestinal fructose absorption. PMID:26071406

Functional electrical stimulation exercise increases GLUT-1 and GLUT-4 in paralyzed skeletal muscle.

PubMed

Chilibeck, P D; Bell, G; Jeon, J; Weiss, C B; Murdoch, G; MacLean, I; Ryan, E; Burnham, R

1999-11-01

The study purpose was to determine the effect of functional electrical stimulation (FES)-leg cycle ergometer training (30 minutes on 3 d/wk for 8 weeks) on the GLUT-1 and GLUT-4 content of paralyzed skeletal muscle. Biopsy samples of vastus lateralis muscle were obtained pre- and post-training from five individuals with motor-complete spinal cord injury ([SCI] four men and one woman aged 31 to 50 years, 3 to 25 years postinjury involving C5-T8). Western blot analysis indicated that GLUT-1 increased by 52% and GLUT-4 increased by 72% with training (P < .05). This coincided with an increase in the muscle oxidative capacity as indicated by a 56% increase in citrate synthase (CS) activity (P < .05) and an improvement in the insulin sensitivity index as determined from oral glucose tolerance tests (P < .05). It is concluded that FES endurance training is effective to increase glucose transporter protein levels in paralyzed skeletal muscle of individuals with SCI.

Insulin resistance and GLUT-4 glucose transporter in adipocytes from hypertensive rats.

PubMed

Chiappe De Cingolani, Gladys E; Caldiz, Claudia I

2004-03-01

To investigate the mechanisms that cause insulin resistance in hypertension, experiments were performed to study the effect of insulin on glucose transport, GLUT-4 translocation from intracellular to plasma membranes and GLUT-4 phosphorylation in isolated adipocytes from normotensive Wistar (W) and spontaneously hypertensive rats (SHR). Glucose transport was measured in adipocytes incubated with 3-O-d[Methyl-(3)H] glucose with and without insulin (0.1 to 5 nmol/L). GLUT-4 protein was determined by Western blot immunoanalysis with GLUT-4 antibody. Phosphorylation of GLUT-4 was measured by immunoprecipitation with GLUT-4 antibody followed by immunoanalysis with phosphoserine or phosphothreonine antibodies. Compared with adipocytes from W, insulin-stimulated glucose transport was lower in the SHR (P <.05). GLUT-4 protein expression was similar in adipocytes from W and SHR. Insulin increased GLUT-4 translocation from intracellular to plasma membranes in both groups. This effect was lower in the SHR (P <.05). The effect of insulin on GLUT-4 serine phosphorylation showed no changes in plasma membranes from W and decreased in the SHR (P <.05). In intracellular membranes, insulin increased specific GLUT-4 serine phosphorylation in both groups (P <.05), but the increase was lower in the SHR (P <.05). The results suggest that a deficient GLUT-4 translocation to plasma membranes in response to insulin shown in adipocytes from SHR, which was accompanied by a decrease in GLUT-4 phosphorylation at serine site, could be one of the causes of insulin resistance in hypertension.

PKC and Rab13 mediate Ca2+ signal-regulated GLUT4 traffic.

PubMed

Deng, Bangli; Zhu, Xiaocui; Zhao, Yihe; Zhang, Da; Pannu, Alisha; Chen, Liming; Niu, Wenyan

2018-01-08

Exercise/muscle contraction increases cell surface glucose transporter 4 (GLUT4), leading to glucose uptake to regulate blood glucose level. Elevating cytosolic Ca 2+ mediates this effect, but the detailed mechanism is not clear yet. We used calcium ionophore ionomycin to raise intracellular cytosolic Ca 2+ level to explore the underlying mechanism. We showed that in L6 myoblast muscle cells stably expressing GLUT4myc, ionomycin increased cell surface GLUT4myc levels and the phosphorylation of AS160, TBC1D1. siPKCα and siPKCθ but not siPKCδ and siPKCε inhibited the ionomycin-increased cell surface GLUT4myc level. siPKCα, siPKCθ inhibited the phosphorylation of AS160 and TBC1D1 induced by ionomycin. siPKCα and siPKCθ prevented ionomycin-inhibited endocytosis of GLUT4myc. siPKCθ, but not siPKCα inhibited ionomycin-stimulated exocytosis of GLUT4myc. siRab13 but not siRab8a, siRab10 and siRab14 inhibited the exocytosis of GLUT4myc promoted by ionomycin. In summary, ionomycin-promoted exocytosis of GLUT4 is partly reversed by siPKCθ, whereas ionomycin-inhibited endocytosis of GLUT4 requires both siPKCα and siPKCθ. PKCα and PKCθ contribute to ionomycin-induced phosphorylation of AS160 and TBC1D1. Rab13 is required for ionomycin-regulated GLUT4 exocytosis. Copyright © 2017 Elsevier Inc. All rights reserved.

Analysis of correlations between the placental expression of glucose transporters GLUT-1, GLUT-4 and GLUT-9 and selected maternal and fetal parameters in pregnancies complicated by diabetes mellitus.

PubMed

Stanirowski, Paweł Jan; Szukiewicz, Dariusz; Pyzlak, Michał; Abdalla, Nabil; Sawicki, Włodzimierz; Cendrowski, Krzysztof

2017-10-16

The aim of the study was to analyze the correlations between the expression of glucose transporters GLUT-1, GLUT-4, and GLUT-9 in human term placenta and selected maternal and fetal parameters in pregnancies complicated by diabetes mellitus (DM). Placental samples were obtained from healthy control (n = 25) and diabetic pregnancies, including diet-controlled gestational diabetes mellitus (GDMG1) (n = 16), insulin-controlled gestational diabetes mellitus (GDMG2) (n = 6), and pregestational DM (PGDM) (n = 6). Computer-assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected glucose transporter proteins. For the purposes of correlation analysis, the following parameters were selected: type of diabetes, gestational age, maternal prepregnancy body mass index (BMI), gestational weight gain, third trimester glycated hemoglobin concentration, placental weight, fetal birth weight (FBW) as well as ultrasonographic indicators of fetal adiposity, including subscapular (SSFM), abdominal (AFM), and midthigh (MTFM) fat mass measurements. In the PGDM group, the analysis demonstrated positive correlations between the placental expression of GLUT-1, GLUT-4, and GLUT-9 and FBW, AFM, and SSFM measurements (p < .05). Similarly in the GDMG2 patients positive correlations between GLUT-4 expression, FBW and SSFM were observed (p < .05). In the multivariate regression analysis, only the type of diabetes and FBW were significantly associated with GLUTs expression (p < .001). In addition, maternal prepregnancy BMI significantly contributed to GLUT-1 expression (p < .001). The study results revealed that placental expression of GLUT-1, GLUT-4, and GLUT-9 may be involved in the intensification of the fetal growth in pregnancies complicated by GDM/PGDM.

Glucose rapidly decreases plasma membrane GLUT4 content in rat skeletal muscle.

PubMed

Marette, A; Dimitrakoudis, D; Shi, Q; Rodgers, C D; Klip, A; Vranic, M

1999-02-01

We have previously demonstrated that chronic hyperglycemia per se decreases GLUT4 glucose transporter expression and plasma membrane content in mildly streptozotocin- (STZ) diabetic rats (Biochem. J. 284, 341-348, 1992). In the present study, we investigated the effect of an acute rise in glycemia on muscle GLUT4 and GLUT1 protein contents in the plasma membrane, in the absence of insulin elevation. Four experimental groups of rats were analyzed in the postabsorptive state: 1. Control rats. 2. Hyperglycemic STZ-diabetic rats with moderately reduced fasting insulin levels. 3. STZ-diabetic rats made normoglycemic with phlorizin treatment. 4. Phlorizin-treated (normoglycemic) STZ-diabetic rats infused with glucose for 40 min. The uniqueness of the latter model is that glycemia can be rapidly raised without any concomitant increase in plasma insulin levels. Plasma membranes were isolated from hindlimb muscle and GLUT1 and GLUT4 proteins amounts determined by Western blot analysis. As predicted, STZ-diabetes caused a significant decrease in the abundance of GLUT4 in the isolated plasma membranes. Normalization of glycemia for 3 d with phlorizin treatment restored plasma membrane GLUT4 content in muscle of STZ-diabetic rats. A sudden rise in glycemia over a period of 40 min caused the GLUT4 levels in the plasma membrane fraction to decrease to those of nontreated STZ-diabetic rats. In contrast to the GLUT4 transporter, plasma membrane GLUT1 abundance was not changed by the acute glucose challenge. It is concluded that glucose can have regulatory effect by acutely reducing plasma membrane GLUT4 protein contents in rat skeletal muscle. We hypothesize that this glucose-induced downregulation of plasma membrane GLUT4 could represent a protective mechanism against excessive glucose uptake under hyperglycemic conditions accompanied by insulin resistance.

Regulation of muscle GLUT-4 transcription by AMP-activated protein kinase.

PubMed

Zheng, D; MacLean, P S; Pohnert, S C; Knight, J B; Olson, A L; Winder, W W; Dohm, G L

2001-09-01

Skeletal muscle GLUT-4 transcription in response to treatment with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), a known activator of AMP-activated protein kinase (AMPK), was studied in rats and mice. The increase in GLUT-4 mRNA levels in response to a single subcutaneous injection of AICAR, peaked at 13 h in white and red quadriceps muscles but not in the soleus muscle. The mRNA level of chloramphenicol acyltransferase reporter gene which is driven by 1,154 or 895 bp of the human GLUT-4 proximal promoter was increased in AICAR-treated transgenic mice, demonstrating the transcriptional upregulation of the GLUT-4 gene by AICAR. However, this induction of transcription was not apparent with 730 bp of the promoter. In addition, nuclear extracts from AICAR-treated mice bound to the consensus sequence of myocyte enhancer factor-2 (from -473 to -464) to a greater extent than from saline-injected mice. Thus AMP-activated protein kinase activation by AICAR increases GLUT-4 transcription by a mechanism that requires response elements within 895 bp of human GLUT-4 proximal promoter and that may be cooperatively mediated by myocyte enhancer factor-2.

Insulin-mediated translocation of GLUT-4-containing vesicles is preserved in denervated muscles.

PubMed

Zhou, M; Vallega, G; Kandror, K V; Pilch, P F

2000-06-01

Skeletal muscle denervation decreases insulin-sensitive glucose uptake into this tissue as a result of marked GLUT-4 protein downregulation ( approximately 20% of controls). The process of insulin-stimulated glucose transport in muscle requires the movement or translocation of intracellular GLUT-4-rich vesicles to the cell surface, and it is accompanied by the translocation of several additional vesicular cargo proteins. Thus examining GLUT-4 translocation in muscles from denervated animals allows us to determine whether the loss of a major cargo protein, GLUT-4, affects the insulin-dependent behavior of the remaining cargo proteins. We find no difference, control vs. denervated, in the insulin-dependent translocation of the insulin-responsive aminopeptidase (IRAP) and the receptors for transferrin and insulin-like growth factor II/mannose 6-phosphate, proteins that completely (IRAP) or partially co-localize with GLUT-4. We conclude that 1) denervation of skeletal muscle does not block the specific branch of insulin signaling pathway that connects receptor proximal events to intracellular GLUT-4-vesicles, and 2) normal levels of GLUT-4 protein are not necessary for the structural organization and insulin-sensitive translocation of its cognate intracellular compartment. Muscle denervation also causes a twofold increase in GLUT-1. In normal muscle, all GLUT-1 is present at the cell surface, but in denervated muscle a significant fraction (25.1 +/- 6.1%) of this transporter is found in intracellular vesicles that have the same sedimentation coefficient as GLUT-4-containing vesicles but can be separated from the latter by immunoadsorption. These GLUT-1-containing vesicles respond to insulin and translocate to the cell surface. Thus the formation of insulin-sensitive GLUT-1-containing vesicles in denervated muscle may be a compensatory mechanism for the decreased level of GLUT-4.

Effect of carbohydrate supplementation on postexercise GLUT-4 protein expression in skeletal muscle.

PubMed

Kuo, C H; Hunt, D G; Ding, Z; Ivy, J L

1999-12-01

The effect of carbohydrate supplementation on skeletal muscle glucose transporter GLUT-4 protein expression was studied in fast-twitch red and white gastrocnemius muscle of Sprague-Dawley rats before and after glycogen depletion by swimming. Exercise significantly reduced fast-twitch red muscle glycogen by 50%. During a 16-h exercise recovery period, muscle glycogen returned to control levels (25.0 +/- 1.4 micromol/g) in exercise-fasted rats (24.2 +/- 0. 3 micro). However, when carbohydrate supplementation was provided during and immediately postexercise by intubation, muscle glycogen increased 77% above control (44.4 +/- 2.1 micromol/g). Exercise-fasting resulted in an 80% increase in fast-twitch red muscle GLUT-4 mRNA but only a 43% increase in GLUT-4 protein concentration. Conversely, exercise plus carbohydrate supplementation elevated fast-twitch red muscle GLUT-4 protein concentration by 88% above control, whereas GLUT-4 mRNA was increased by only 40%. Neither a 16-h fast nor carbohydrate supplementation had an effect on fast-twitch red muscle GLUT-4 protein concentration or on GLUT-4 mRNA in sedentary rats, although carbohydrate supplementation increased muscle glycogen concentration by 40% (35.0 +/- 0.9 micromol/g). GLUT-4 protein in fast-twitch white muscle followed a pattern similar to fast-twitch red muscle. These results indicate that carbohydrate supplementation, provided with exercise, will enhance GLUT-4 protein expression by increasing translational efficiency. Conversely, postexercise fasting appears to upregulate GLUT-4 mRNA, possibly to amplify GLUT-4 protein expression on an increase in glucose availability. These regulatory mechanisms may help control muscle glucose uptake in accordance with glucose availability and protect against postexercise hypoglycemia.

Transient enhancement of GLUT-4 levels in rat epitrochlearis muscle after exercise training

PubMed Central

Reynolds, Thomas H.; Brozinick, Joseph T.; Larkin, Lisa M.; Cushman, Samuel W.

2009-01-01

The purpose of the present study was to examine the effect of detraining on the glucose transport system after short-term swim training (5 days), long-term swim training (5 wk), and treadmill run training (5 wk). Skeletal muscles were isolated from female Wistar rats at 24 or 48 h posttraining. SST produces a 48% increase in GLUT-4 mRNA, a 30% increase in GLUT-4 protein, and a 60% increase in insulin-stimulated glucose transport activity at 24 h posttraining but not at 48 h posttraining. Similar to SST, long-term swim training produces a 60% increase in GLUT-4 mRNA and a 30% increase in GLUT-4 protein content at 24 h posttraining but not at 48 h posttraining. Finally, treadmill run training produces a transient 35% increase in GLUT-4 protein content that is completely reversed at 48 h after the last bout of exercise. These results demonstrate that the increase in GLUT-4 mRNA and GLUT-4 protein occurs during the first week of exercise training and is rapidly lost after training cessation. We believe that the transient enhancement in GLUT-4 protein after exercise training is due to a short GLUT-4 half-life, a process that is primarily regulated by pretranslational mechanisms. PMID:10846041

Transient enhancement of GLUT-4 levels in rat epitrochlearis muscle after exercise training.

PubMed

Reynolds, T H; Brozinick, J T; Larkin, L M; Cushman, S W

2000-06-01

The purpose of the present study was to examine the effect of detraining on the glucose transport system after short-term swim training (5 days), long-term swim training (5 wk), and treadmill run training (5 wk). Skeletal muscles were isolated from female Wistar rats at 24 or 48 h posttraining. SST produces a 48% increase in GLUT-4 mRNA, a 30% increase in GLUT-4 protein, and a 60% increase in insulin-stimulated glucose transport activity at 24 h posttraining but not at 48 h posttraining. Similar to SST, long-term swim training produces a 60% increase in GLUT-4 mRNA and a 30% increase in GLUT-4 protein content at 24 h posttraining but not at 48 h posttraining. Finally, treadmill run training produces a transient 35% increase in GLUT-4 protein content that is completely reversed at 48 h after the last bout of exercise. These results demonstrate that the increase in GLUT-4 mRNA and GLUT-4 protein occurs during the first week of exercise training and is rapidly lost after training cessation. We believe that the transient enhancement in GLUT-4 protein after exercise training is due to a short GLUT-4 half-life, a process that is primarily regulated by pretranslational mechanisms.

Regulation of GLUT4 activity in myotubes by 3-O-methyl-d-glucose.

PubMed

Shamni, Ofer; Cohen, Guy; Gruzman, Arie; Zaid, Hilal; Klip, Amira; Cerasi, Erol; Sasson, Shlomo

2017-10-01

The rate of glucose influx to skeletal muscles is determined primarily by the number of functional units of glucose transporter-4 (GLUT4) in the myotube plasma membrane. The abundance of GLUT4 in the plasma membrane is tightly regulated by insulin or contractile activity, which employ distinct pathways to translocate GLUT4-rich vesicles from intracellular compartments. Various studies have indicated that GLUT4 intrinsic activity is also regulated by conformational changes and/or interactions with membrane components and intracellular proteins in the vicinity of the plasma membrane. Here we show that the non-metabolizable glucose analog 3-O-methyl-d-glucose (MeGlc) augmented the rate of hexose transport into myotubes by increasing GLUT4 intrinsic activity without altering the content of the transporter in the plasma membrane. This effect was not a consequence of ATP depletion or hyperosmolar stress and did not involve Akt/PKB or AMPK signal transduction pathways. MeGlc reduced the inhibitory potency (increased K i ) of indinavir, a selective inhibitor of GLUT4, in a dose-dependent manner. Kinetic analyses indicate that MeGlc induced changes in GLUT4 or GLUT4 complexes within the plasma membrane, which enhanced the hexose transport activity and reduced the potency of indinavir inhibition. Finally, we present a simple kinetic analysis for screening and discovering low molecular weight compounds that augment GLUT4 activity. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of respiratory muscle training on GLUT-4 in the sheep diaphragm.

PubMed

Bhandari, A; Xia, Y; Cortright, R; Dohm, G L; Bazzy, A R

2000-08-01

Endurance exercise training is associated with enhanced glucose uptake and hence improvement in carbohydrate metabolism. Glucose transport (GLUT) membrane proteins are regulated by a variety of physiological stimuli, including exercise. In limb muscle, both acute exercise and endurance training enhance the expression of the skeletal muscle transporter, GLUT-4. The purpose of this study is to determine whether chronic loading enhances GLUT-4 expression in the diaphragm. The effect of chronic inspiratory flow resistive (IFR) loading on diaphragm GLUT-4 was studied in a model of respiratory muscle endurance training in sheep. IFR loads (resistance 50-100 cm H2O x L(-1) x s(-1)) were maintained for 3 h x d(-1), 5-6 d x wk(-1) for 3 wk. Loading was adjusted so that PaO2 was >60 Torr and PaCO2 <45 Torr in room air. Six untrained sheep were used as controls. GLUT-4 protein and mRNA were analyzed by Western and Northern analysis respectively. GLUT-4 protein levels were two-fold greater in trained animals when compared with controls (P < 0.01). GLUT-4 mRNA levels in the trained muscles was not significantly different from controls. We conclude that in the sheep diaphragm, chronic IFR loading increases GLUT-4 protein levels. This increase may be one of the mechanisms contributing to the improved respiratory muscle endurance previously demonstrated in this animal model of respiratory muscle training.

Expression and localization of GLUT1 and GLUT12 in prostate carcinoma.

PubMed

Chandler, Jenalle D; Williams, Elizabeth D; Slavin, John L; Best, James D; Rogers, Suzanne

2003-04-15

Increased glucose consumption is a characteristic of malignant cells and in prostate carcinoma is associated with the proliferation of both androgen-dependent and independent cells. Transport of polar glucose across the nonpolar membrane relies on glucose transporter proteins, known as GLUTs. Increased expression of GLUT1 is a characteristic of many malignant cells. The authors characterized and cloned the cDNA for a novel glucose transporter, GLUT12, which was identified initially in malignant breast epithelial cells. To the authors' knowledge, there have been no reports on the expression of glucose transporters in the human prostate or human prostate carcinoma cells. The authors evaluated GLUT1 and GLUT12 expression in human prostate carcinoma cells. Reverse transcription-polymerase chain reaction was performed on total RNA extracted from cultured prostate carcinoma cells LNCaP, C4, C4-2, and C4-2B using primers to amplify GLUT1, GLUT12, or the housekeeping gene, 36B4. Total protein extracted from prostate carcinoma cell lines was assessed for GLUT12 protein by Western blot analysis. Cultured cell monolayers were incubated with antibodies to GLUT1 or GLUT12 and a peripheral Golgi protein, Golgi 58K, for detection by immunofluorescent confocal microscopy. Sections of benign prostatic hyperplasia and human prostate carcinoma were stained for immunohistochemical detection of GLUT1 and GLUT12. GLUT1 and GLUT12 mRNA and protein were detected in all cell lines evaluated. Immunofluorescence staining demonstrated both GLUT1 and GLUT12 on the plasma membrane and in the cytoplasm in all cultured prostate carcinoma cell lines, with GLUT1 but not GLUT12 appearing to colocalize with the Golgi. Immunohistochemical staining of benign prostatic hyperplasia indicated expression of GLUT1 but not GLUT12. Malignant tissue stained for GLUT12 but was negative for GLUT1. GLUT1 and GLUT12 are expressed in human prostate carcinoma cells. One possible rationale for the GLUT1 Golgi

Cycle Training Increased GLUT4 and Activation of mTOR in Fast Twitch Muscle Fibers

PubMed Central

Stuart, Charles A.; Howell, Mary E.A.; Baker, Jonathan D.; Dykes, Rhesa J.; Duffourc, Michelle M.; Ramsey, Michael W.; Stone, Michael H.

2009-01-01

Purpose To determine if cycle training of sedentary subjects would increase the expression of the principle muscle glucose transporters, six volunteers completed six weeks of progressively increasing intensity stationary cycle cycling. Methods In vastus lateralis muscle biopsies, changes in expression of GLUT1, GLUT4, GLUT5, and GLUT12 were compared using quantitative immunoblots with specific protein standards. Regulatory pathway components were evaluated by immunoblots of muscle homogenates and immunohistochemistry of microscopic sections. Results GLUT1 was unchanged, GLUT4 increased 66%, GLUT12 increased 104%, and GLUT5 decreased 72%. A mitochondrial marker (cytochrome c) and regulators of mitochondrial biogenesis (PGC-1α and phospho-AMPK) were unchanged, but the muscle hypertrophy pathway component, phospho-mTOR increased 83% after the exercise program. In baseline biopsies, GLUT4 by immunohistochemical techniques was 37% greater in Type I (slow twitch, red) muscle fibers, but the exercise training increased GLUT4 expression in Type II (fast twitch, white) fibers by 50%, achieving parity with the Type I fibers. Baseline phospho-mTOR expression was 50% higher in Type II fibers and increased more in Type II fibers (62%) with training, but also increased in Type I fibers (34%). Conclusion Progressive intensity stationary cycle training of previously sedentary subjects increased muscle insulin-responsive glucose transporters (GLUT4 and GLUT12) and decreased the fructose transporter (GLUT5). The increase in GLUT4 occurred primarily in Type II muscle fibers and this coincided with activation of the mTOR muscle hypertrophy pathway. There was little impact on Type I fiber GLUT4 expression and no evidence of change in mitochondrial biogenesis. PMID:20010125

GLUT4 in the endocrine pancreas--indicating an impact in pancreatic islet cell physiology?

PubMed

Bähr, I; Bazwinsky-Wutschke, I; Wolgast, S; Hofmann, K; Streck, S; Mühlbauer, E; Wedekind, D; Peschke, E

2012-06-01

The glucose transporter GLUT4 is well known to facilitate the transport of blood glucose into insulin-sensitive muscle and adipose tissue. In this study, molecular, immunohistochemical, and Western blot investigations revealed evidence that GLUT4 is also located in the mouse, rat, and human endocrine pancreas. In addition, high glucose decreased and insulin elevated the GLUT4 expression in pancreatic α-cells. In contrast, high glucose increased GLUT4 expression, whereas insulin led to a reduced expression level of the glucose transporter in pancreatic β-cells. In vivo experiments showed that in pancreatic tissue of type 2 diabetic rats as well as type 2 diabetic patients, the GLUT4 expression is significantly increased compared to the nondiabetic control group. Furthermore, type 1 diabetic rats exhibited reduced GLUT4 transcript levels in pancreatic tissue, whereas insulin treatment of type 1 diabetic animals enhanced the GLUT4 expression back to control levels. These data provide evidence for the existence of GLUT4 in the endocrine pancreas and indicate a physiological relevance of this glucose transporter as well as characteristic changes in diabetic disease. © Georg Thieme Verlag KG Stuttgart · New York.

Expression, purification, and functional characterization of the insulin-responsive facilitative glucose transporter GLUT4.

PubMed

Kraft, Thomas E; Hresko, Richard C; Hruz, Paul W

2015-12-01

The insulin-responsive facilitative glucose transporter GLUT4 is of fundamental importance for maintenance of glucose homeostasis. Despite intensive effort, the ability to express and purify sufficient quantities of structurally and functionally intact protein for biophysical analysis has previously been exceedingly difficult. We report here the development of novel methods to express, purify, and functionally reconstitute GLUT4 into detergent micelles and proteoliposomes. Rat GLUT4 containing FLAG and His tags at the amino and carboxy termini, respectively, was engineered and stably transfected into HEK-293 cells. Overexpression in suspension culture yielded over 1.5 mg of protein per liter of culture. Systematic screening of detergent solubilized GLUT4-GFP fusion protein via fluorescent-detection size exclusion chromatography identified lauryl maltose neopentyl glycol (LMNG) as highly effective for isolating monomeric GLUT4 micelles. Preservation of structural integrity and ligand binding was demonstrated via quenching of tryptophan fluorescence and competition of ATB-BMPA photolabeling by cytochalasin B. GLUT4 was reconstituted into lipid nanodiscs and proper folding was confirmed. Reconstitution of purified GLUT4 with amphipol A8-35 stabilized the transporter at elevated temperatures for extended periods of time. Functional activity of purified GLUT4 was confirmed by reconstitution of LMNG-purified GLUT4 into proteoliposomes and measurement of saturable uptake of D-glucose over L-glucose. Taken together, these data validate the development of an efficient means to generate milligram quantities of stable and functionally intact GLUT4 that is suitable for a wide array of biochemical and biophysical analyses. © 2015 The Protein Society.

CELL BIOLOGY SYMPOSIUM: Practical application of the basic aspects of GLUT4 membrane trafficking and insulin signaling on issues related to animal agriculture.

PubMed

Smith, S B

2017-05-01

Because of the relatively short lifespans of beef cattle, membrane trafficking in relation to inflammation is not considered important unless it overtly affects productivity. However, glucose uptake and utilization is important for adipose tissue development in beef cattle, and increasing glucose utilization in intramuscular adipose tissue can increase carcass quality. Research from the 1980s demonstrated a lack of insulin sensitivity in isolated bovine adipocytes and adipose tissue explants incubated in vitro. Insulin did not stimulate glucose or acetate incorporation into fatty acids, nor did it increase concentrations of glycolytic intermediates in bovine adipose tissue incubated with exogenous glucose. Specific binding of [I] iodoinsulin and insulin degradation in bovine isolated adipocytes was low to non-detectable. These early studies indicated that insulin-dependent receptor-mediated signaling was less important in bovine adipose tissue than in adipose tissues of humans, swine, or laboratory species. More recent research demonstrated that glucose transporter protein 4 (GLUT4) expression in muscle and adipose tissue declines markedly after birth in calves, indicating the development of insulin resistance as cattle transition from suckling to functional ruminants. Insulin resistance is important in dairy cattle, causing ketosis and fatty liver. Consistent with this, subcutaneous adipose tissue expression decreases 50% following parturition in dairy cattle, although expression of genes associated with insulin responsiveness (, , and ) is up-regulated by 21 d postpartum. Understanding the underlying mechanisms of insulin resistance in beef and dairy cattle would increase animal health and thereby improve productivity.

Super-resolution microscopy reveals the insulin-resistance-regulated reorganization of GLUT4 on plasma membranes.

PubMed

Gao, Lan; Chen, Junling; Gao, Jing; Wang, Hongda; Xiong, Wenyong

2017-01-15

GLUT4 (also known as SLC2A4) is essential for glucose uptake in skeletal muscles and adipocytes, which play central roles in whole-body glucose metabolism. Here, using direct stochastic optical reconstruction microscopy (dSTORM) to investigate the characteristics of plasma-membrane-fused GLUT4 at the single-molecule level, we have demonstrated that insulin and insulin resistance regulate the spatial organization of GLUT4 in adipocytes. Stimulation with insulin shifted the balance of GLUT4 on the plasma membrane toward a more dispersed configuration. In contrast, insulin resistance induced a more clustered distribution of GLUT4 and increased the mean number of molecules per cluster. Furthermore, our data demonstrate that the F 5 QQI motif and lipid rafts mediate the maintenance of GLUT4 clusters on the plasma membrane. Mutation of F 5 QQI (F 5 QQA-GLUT4) induced a more clustered distribution of GLUT4; moreover, destruction of lipid rafts in adipocytes expressing F 5 QQA-GLUT4 dramatically decreased the percentage of large clusters and the mean number of molecules per cluster. In conclusion, our data clarify the effects of insulin stimulation or insulin resistance on GLUT4 reorganization on the plasma membrane and reveal new pathogenic mechanisms of insulin resistance. © 2017. Published by The Company of Biologists Ltd.

Anorexia and Impaired Glucose Metabolism in Mice With Hypothalamic Ablation of Glut4 Neurons

PubMed Central

Ren, Hongxia; Lu, Taylor Y.; McGraw, Timothy E.

2015-01-01

The central nervous system (CNS) uses glucose independent of insulin. Nonetheless, insulin receptors and insulin-responsive glucose transporters (Glut4) often colocalize in neurons (Glut4 neurons) in anatomically and functionally distinct areas of the CNS. The apparent heterogeneity of Glut4 neurons has thus far thwarted attempts to understand their function. To answer this question, we used Cre-dependent, diphtheria toxin–mediated cell ablation to selectively remove basal hypothalamic Glut4 neurons and investigate the resulting phenotypes. After Glut4 neuron ablation, mice demonstrate altered hormone and nutrient signaling in the CNS. Accordingly, they exhibit negative energy balance phenotype characterized by reduced food intake and increased energy expenditure, without locomotor deficits or gross neuronal abnormalities. Glut4 neuron ablation affects orexigenic melanin-concentrating hormone neurons but has limited effect on neuropeptide Y/agouti-related protein and proopiomelanocortin neurons. The food intake phenotype can be partially normalized by GABA administration, suggesting that it arises from defective GABAergic transmission. Glut4 neuron–ablated mice show peripheral metabolic defects, including fasting hyperglycemia and glucose intolerance, decreased insulin levels, and elevated hepatic gluconeogenic genes. We conclude that Glut4 neurons integrate hormonal and nutritional cues and mediate CNS actions of insulin on energy balance and peripheral metabolism. PMID:25187366

Insulin-induced cortical actin remodeling promotes GLUT4 insertion at muscle cell membrane ruffles

PubMed Central

Tong, Peter; Khayat, Zayna A.; Huang, Carol; Patel, Nish; Ueyama, Atsunori; Klip, Amira

2001-01-01

Insulin stimulates glucose uptake by recruiting glucose transporter 4 (GLUT4) from an intracellular compartment to the cell surface; this phenomenon is defective in type 2 diabetes. Here we examine the involvement of actin filaments in GLUT4 translocation and their possible defects in insulin resistance, using L6 myotubes expressing myc-tagged GLUT4. Insulin caused membrane ruffling, a dynamic distortion of the myotube dorsal surface. Fluorescence microscopy and immunogold staining of surface GLUT4myc coupled to backscatter electron microscopy revealed a high density of this protein in membrane ruffles. The t-SNAREs syntaxin4 and SNAP-23 were also abundant in these regions. Below the membrane, GLUT4 and the vesicular protein VAMP2, but not VAMP3, colocalized with the actin structures supporting the membrane ruffles. GLUT4myc externalization and membrane ruffles were reduced by jasplakinolide and by swinholide-A, drugs that affect actin filament stability and prevent actin branching, respectively. Insulin resistance generated by prolonged (24 hours) exposure of myotubes to high glucose and insulin diminished the acute insulin-dependent remodeling of cortical actin and GLUT4myc translocation, reminiscent of the effect of swinholide-A. We propose that GLUT4 vesicle incorporation into the plasma membrane involves insulin-dependent cortical actin remodeling and that defective actin remodeling contributes to insulin resistance. PMID:11489930

GLUT4 Is Not Necessary for Overload-Induced Glucose Uptake or Hypertrophic Growth in Mouse Skeletal Muscle

PubMed Central

McMillin, Shawna L.; Schmidt, Denise L.; Kahn, Barbara B.

2017-01-01

GLUT4 is necessary for acute insulin- and contraction-induced skeletal muscle glucose uptake, but its role in chronic muscle loading (overload)-induced glucose uptake is unknown. Our goal was to determine whether GLUT4 is required for overload-induced glucose uptake. Overload was induced in mouse plantaris muscle by unilateral synergist ablation. After 5 days, muscle weights and ex vivo [3H]-2-deoxy-d-glucose uptake were assessed. Overload-induced muscle glucose uptake and hypertrophic growth were not impaired in muscle-specific GLUT4 knockout mice, demonstrating that GLUT4 is not necessary for these processes. To assess which transporters mediate overload-induced glucose uptake, chemical inhibitors were used. The facilitative GLUT inhibitor cytochalasin B, but not the sodium-dependent glucose cotransport inhibitor phloridzin, prevented overload-induced uptake demonstrating that GLUTs mediate this effect. To assess which GLUT, hexose competition experiments were performed. Overload-induced [3H]-2-deoxy-d-glucose uptake was not inhibited by d-fructose, demonstrating that the fructose-transporting GLUT2, GLUT5, GLUT8, and GLUT12 do not mediate this effect. To assess additional GLUTs, immunoblots were performed. Overload increased GLUT1, GLUT3, GLUT6, and GLUT10 protein levels twofold to fivefold. Collectively, these results demonstrate that GLUT4 is not necessary for overload-induced muscle glucose uptake or hypertrophic growth and suggest that GLUT1, GLUT3, GLUT6, and/or GLUT10 mediate overload-induced glucose uptake. PMID:28279980

GLUT4 Is Not Necessary for Overload-Induced Glucose Uptake or Hypertrophic Growth in Mouse Skeletal Muscle.

PubMed

McMillin, Shawna L; Schmidt, Denise L; Kahn, Barbara B; Witczak, Carol A

2017-06-01

GLUT4 is necessary for acute insulin- and contraction-induced skeletal muscle glucose uptake, but its role in chronic muscle loading (overload)-induced glucose uptake is unknown. Our goal was to determine whether GLUT4 is required for overload-induced glucose uptake. Overload was induced in mouse plantaris muscle by unilateral synergist ablation. After 5 days, muscle weights and ex vivo [ 3 H]-2-deoxy-d-glucose uptake were assessed. Overload-induced muscle glucose uptake and hypertrophic growth were not impaired in muscle-specific GLUT4 knockout mice, demonstrating that GLUT4 is not necessary for these processes. To assess which transporters mediate overload-induced glucose uptake, chemical inhibitors were used. The facilitative GLUT inhibitor cytochalasin B, but not the sodium-dependent glucose cotransport inhibitor phloridzin, prevented overload-induced uptake demonstrating that GLUTs mediate this effect. To assess which GLUT, hexose competition experiments were performed. Overload-induced [ 3 H]-2-deoxy-d-glucose uptake was not inhibited by d-fructose, demonstrating that the fructose-transporting GLUT2, GLUT5, GLUT8, and GLUT12 do not mediate this effect. To assess additional GLUTs, immunoblots were performed. Overload increased GLUT1, GLUT3, GLUT6, and GLUT10 protein levels twofold to fivefold. Collectively, these results demonstrate that GLUT4 is not necessary for overload-induced muscle glucose uptake or hypertrophic growth and suggest that GLUT1, GLUT3, GLUT6, and/or GLUT10 mediate overload-induced glucose uptake. © 2017 by the American Diabetes Association.

Quantitative Measurement of GLUT4 Translocation to the Plasma Membrane by Flow Cytometry

PubMed Central

Koshy, Shyny; Alizadeh, Parema; Timchenko, Lubov T.; Beeton, Christine

2010-01-01

Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces glucose uptake by insulin-sensitive tissues, most notably the brain, skeletal muscle, and adipocytes. Patients suffering from type-2 diabetes and/or obesity often develop insulin resistance and are unable to control their glucose homeostasis. New insights into the mechanisms of insulin resistance may provide new treatment strategies for type-2 diabetes. The GLUT family of glucose transporters consists of thirteen members distributed on different tissues throughout the body1. Glucose transporter type 4 (GLUT4) is the major transporter that mediates glucose uptake by insulin sensitive tissues, such as the skeletal muscle. Upon binding of insulin to its receptor, vesicles containing GLUT4 translocate from the cytoplasm to the plasma membrane, inducing glucose uptake. Reduced GLUT4 translocation is one of the causes of insulin resistance in type-2 diabetes2,3. The translocation of GLUT4 from the cytoplasm to the plasma membrane can be visualized by immunocytochemistry, using fluorophore-conjugated GLUT4-specific antibodies. Here, we describe a technique to quantify total amounts of GLUT4 translocation to the plasma membrane of cells during a chosen duration, using flow cytometry. This protocol is rapid (less than 4 hours, including incubation with insulin) and allows the analysis of as few as 3,000 cells or as many as 1 million cells per condition in a single experiment. It relies on anti-GLUT4 antibodies directed to an external epitope of the transporter that bind to it as soon as it is exposed to the extracellular medium after translocation to the plasma membrane. PMID:21085106

GLUT4 Mobilization Supports Energetic Demands of Active Synapses.

PubMed

Ashrafi, Ghazaleh; Wu, Zhuhao; Farrell, Ryan J; Ryan, Timothy A

2017-02-08

The brain is highly sensitive to proper fuel availability as evidenced by the rapid decline in neuronal function during ischemic attacks and acute severe hypoglycemia. We previously showed that sustained presynaptic function requires activity-driven glycolysis. Here, we provide strong evidence that during action potential (AP) firing, nerve terminals rely on the glucose transporter GLUT4 as a glycolytic regulatory system to meet the activity-driven increase in energy demands. Activity at synapses triggers insertion of GLUT4 into the axonal plasma membrane driven by activation of the metabolic sensor AMP kinase. Furthermore, we show that genetic ablation of GLUT4 leads to an arrest of synaptic vesicle recycling during sustained AP firing, similar to what is observed during acute glucose deprivation. The reliance on this biochemical regulatory system for "exercising" synapses is reminiscent of that occurring in exercising muscle to sustain cellular function and identifies nerve terminals as critical sites of proper metabolic control. Copyright © 2017 Elsevier Inc. All rights reserved.

Anorexia and impaired glucose metabolism in mice with hypothalamic ablation of Glut4 neurons.

PubMed

Ren, Hongxia; Lu, Taylor Y; McGraw, Timothy E; Accili, Domenico

2015-02-01

The central nervous system (CNS) uses glucose independent of insulin. Nonetheless, insulin receptors and insulin-responsive glucose transporters (Glut4) often colocalize in neurons (Glut4 neurons) in anatomically and functionally distinct areas of the CNS. The apparent heterogeneity of Glut4 neurons has thus far thwarted attempts to understand their function. To answer this question, we used Cre-dependent, diphtheria toxin-mediated cell ablation to selectively remove basal hypothalamic Glut4 neurons and investigate the resulting phenotypes. After Glut4 neuron ablation, mice demonstrate altered hormone and nutrient signaling in the CNS. Accordingly, they exhibit negative energy balance phenotype characterized by reduced food intake and increased energy expenditure, without locomotor deficits or gross neuronal abnormalities. Glut4 neuron ablation affects orexigenic melanin-concentrating hormone neurons but has limited effect on neuropeptide Y/agouti-related protein and proopiomelanocortin neurons. The food intake phenotype can be partially normalized by GABA administration, suggesting that it arises from defective GABAergic transmission. Glut4 neuron-ablated mice show peripheral metabolic defects, including fasting hyperglycemia and glucose intolerance, decreased insulin levels, and elevated hepatic gluconeogenic genes. We conclude that Glut4 neurons integrate hormonal and nutritional cues and mediate CNS actions of insulin on energy balance and peripheral metabolism. © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

GLUT4-containing vesicles are released from membranes by phospholipase D cleavage of a GPI anchor.

PubMed

Kristiansen, Søren; Richter, Erik A

2002-08-01

We have previously developed a cell-free assay from rat skeletal muscle that displayed in vitro glucose transporter 4 (GLUT4) transfer from large to small membrane structures by the addition of a cytosolic protein fraction. By combining protein fractionation and the in vitro GLUT4 transfer assay, we have purified a glycosylphosphatidylinositol (GPI) phospholipase D (PLD) that induces transfer of GLUT4 from small to large membranes. The in vitro GLUT4 transfer was activated and inhibited by suramin and 1,10-phenanthroline (an activator and an inhibitor of GPI-PLD activity, respectively). Furthermore, upon purification of the GLUT4 transporter protein, the protein displayed an elution profile in which the molecular mass was related to the charge, suggesting the presence or absence of phosphate. Second, by photoaffinity labeling of the purified GLUT4 with 3-(trifluoromethyl)-3-(m-[(125)I]iodopenyl)diazirine, both labeled phosphatidylethanolamine and fatty acids (constituents of a GPI link) were recovered. Third, by using phase transition of Triton X-114, the purified GLUT4 was found to be partly detergent resistant, which is a known characteristic of GPI-linked proteins. Fourth, the purified GLUT4 protein was recognized by an antibody raised specifically against GPI links. In conclusion, GLUT4-containing vesicles may be released from a membrane compartment by action of a GPI-PLD.

Molecular and cellular regulation of glucose transporter (GLUT) proteins in cancer.

PubMed

Macheda, Maria L; Rogers, Suzanne; Best, James D

2005-03-01

Malignant cells are known to have accelerated metabolism, high glucose requirements, and increased glucose uptake. Transport of glucose across the plasma membrane of mammalian cells is the first rate-limiting step for glucose metabolism and is mediated by facilitative glucose transporter (GLUT) proteins. Increased glucose transport in malignant cells has been associated with increased and deregulated expression of glucose transporter proteins, with overexpression of GLUT1 and/or GLUT3 a characteristic feature. Oncogenic transformation of cultured mammalian cells causes a rapid increase of glucose transport and GLUT1 expression via interaction with GLUT1 promoter enhancer elements. In human studies, high levels of GLUT1 expression in tumors have been associated with poor survival. Studies indicate that glucose transport in breast cancer is not fully explained by GLUT1 or GLUT3 expression, suggesting involvement of another glucose transporter. Recently, a novel glucose transporter protein, GLUT12, has been found in breast and prostate cancers. In human breast and prostate tumors and cultured cells, GLUT12 is located intracellularly and at the cell surface. Trafficking of GLUT12 to the plasma membrane could therefore contribute to glucose uptake. Several factors have been implicated in the regulation of glucose transporter expression in breast cancer. Hypoxia can increase GLUT1 levels and glucose uptake. Estradiol and epidermal growth factor, both of which can play a role in breast cancer cell growth, increase glucose consumption. Estradiol and epidermal growth factor also increase GLUT12 protein levels in cultured breast cancer cells. Targeting GLUT12 could provide novel methods for detection and treatment of breast and prostate cancer. 2004 Wiley-Liss, Inc.

Changes in photoperiod alter Glut4 expression in skeletal muscle of C57BL/6J mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tashiro, Ayako; Shibata, Satomi; Takai, Yusuke

Seasonal changes in photoperiod influence body weight and metabolism in mice. Here, we examined the effect of changes in photoperiod on the expression of glucose transporter genes in the skeletal muscle and adipose tissue of C57BL/6J mice. Glut4 expression was lower in the gastrocnemius muscle of mice exposed to a short-duration day (SD) than those to a long-duration day (LD), with accompanying changes in GLUT4 protein levels. Although Glut4 expression in the mouse soleus muscle was higher under SD than under LD, GLUT4 protein levels remained unchanged. To confirm the functional significance of photoperiod-induced changes in Glut4 expression, we checkedmore » for variations in insulin sensitivity. Blood glucose levels after insulin injection remained high under SD, suggesting that the mice exposed to SD showed lower sensitivity to insulin than those exposed to LD. We also attempted to clarify the relationship between Glut4 expression and physical activity in the mice following changes in photoperiod. Locomotor activity, as detected via infrared beam sensor, was lower under SD than under LD. However, when we facilitated voluntary activity by using running wheels, the rotation of wheels was similar for both groups of mice. Although physical activity levels were enhanced due to running wheels, Glut4 expression in the gastrocnemius muscle remained unchanged. Thus, variations in photoperiod altered Glut4 expression in the mouse skeletal muscle, with subsequent changes in GLUT4 protein levels and insulin sensitivity; these effects might be independent of physical activity. - Highlights: • Glut4 expression in the gastrocnemius muscle was lowered under short photoperiod. • Insulin sensitivity was lowered under short photoperiod. • Access to running wheels did not alter Glut4 expression in the gastrocnemius muscle. • Photoperiodic changes in Glut4 expression may be independent of physical activity.« less

Brain GLUT4 Knockout Mice Have Impaired Glucose Tolerance, Decreased Insulin Sensitivity, and Impaired Hypoglycemic Counterregulation

PubMed Central

Reno, Candace M.; Puente, Erwin C.; Sheng, Zhenyu; Daphna-Iken, Dorit; Bree, Adam J.; Routh, Vanessa H.; Kahn, Barbara B.

2017-01-01

GLUT4 in muscle and adipose tissue is important in maintaining glucose homeostasis. However, the role of insulin-responsive GLUT4 in the central nervous system has not been well characterized. To assess its importance, a selective knockout of brain GLUT4 (BG4KO) was generated by crossing Nestin-Cre mice with GLUT4-floxed mice. BG4KO mice had a 99% reduction in GLUT4 protein expression throughout the brain. Despite normal feeding and fasting glycemia, BG4KO mice were glucose intolerant, demonstrated hepatic insulin resistance, and had reduced glucose uptake in the brain. In response to hypoglycemia, BG4KO mice had impaired glucose sensing, noted by impaired epinephrine and glucagon responses and impaired c-fos activation in the hypothalamic paraventricular nucleus. Moreover, in vitro glucose sensing of glucose-inhibitory neurons from the ventromedial hypothalamus was impaired in BG4KO mice. In summary, BG4KO mice are glucose intolerant, insulin resistant, and have impaired glucose sensing, indicating a critical role for brain GLUT4 in sensing and responding to changes in blood glucose. PMID:27797912

Eccentric exercise decreases glucose transporter GLUT4 protein in human skeletal muscle.

PubMed Central

Asp, S; Daugaard, J R; Richter, E A

1995-01-01

1. Eccentric exercise causes impaired postexercise glycogen resynthesis. To study whether changes in muscle concentration of the glucose transporter (GLUT4) protein might be involved, seven healthy young men performed one-legged eccentric exercise by resisting knee flexion enforced by a motor-driven device. 2. The GLUT4 protein concentration in the exercised and in the control thigh was unchanged immediately after exercise. On days 1 and 2 after exercise, the GLUT4 protein concentration in the exercised muscle was 68 +/- 10 and 64 +/- 10% (means +/- S.E.M.; P < 0.05), respectively, of the concentration in the control muscle, and had returned to control values on days 4 and 7. 3. The muscle glycogen concentration decreased from 404 +/- 44 to 336 +/- 44 mmol (kg dry wt)-1 (P < 0.05) during exercise. The glycogen concentration remained significantly lower than in the control thigh on days 1 and 2 after exercise but on days 4 and 7 no differences were found. 4. Although no cause-effect relationship was established, these findings may suggest that decreased muscle concentrations of GLUT4 protein, and, hence, a decreased rate of glucose transport into muscle cells, may be involved in the sustained low glycogen concentration seen after eccentric exercise. Images Figure 1 Figure 4 PMID:7738859

Effect of denervation or unweighting on GLUT-4 protein in rat soleus muscle

NASA Technical Reports Server (NTRS)

Henriksen, Erik J.; Rodnick, Kenneth J.; Mondon, Carl E.; James, David E.; Holloszy, John O.

1991-01-01

The study is intended to test the hypothesis that the decreased capacity for glucose transport in the denervated rat soleus and the increased capacity for glucose transport in the unweighted rat soleus are related to changes in the expression of the regulatable glucose transporter protein in skeletal muscle (GLUT-4). Results obtained indicate that altered GLUT-4 expression may be a major contributor to the changes in insulin-stimulated glucose transport that are observed with denervation and unweighting. It is concluded that muscle activity is an important factor in the regulation of the GLUT-4 expression in skeletal muscle.

Brain GLUT4 Knockout Mice Have Impaired Glucose Tolerance, Decreased Insulin Sensitivity, and Impaired Hypoglycemic Counterregulation.

PubMed

Reno, Candace M; Puente, Erwin C; Sheng, Zhenyu; Daphna-Iken, Dorit; Bree, Adam J; Routh, Vanessa H; Kahn, Barbara B; Fisher, Simon J

2017-03-01

GLUT4 in muscle and adipose tissue is important in maintaining glucose homeostasis. However, the role of insulin-responsive GLUT4 in the central nervous system has not been well characterized. To assess its importance, a selective knockout of brain GLUT4 (BG4KO) was generated by crossing Nestin-Cre mice with GLUT4-floxed mice. BG4KO mice had a 99% reduction in GLUT4 protein expression throughout the brain. Despite normal feeding and fasting glycemia, BG4KO mice were glucose intolerant, demonstrated hepatic insulin resistance, and had reduced glucose uptake in the brain. In response to hypoglycemia, BG4KO mice had impaired glucose sensing, noted by impaired epinephrine and glucagon responses and impaired c-fos activation in the hypothalamic paraventricular nucleus. Moreover, in vitro glucose sensing of glucose-inhibitory neurons from the ventromedial hypothalamus was impaired in BG4KO mice. In summary, BG4KO mice are glucose intolerant, insulin resistant, and have impaired glucose sensing, indicating a critical role for brain GLUT4 in sensing and responding to changes in blood glucose. © 2017 by the American Diabetes Association.

Gene expression of glucose transporter (GLUT) 1, 3 and 4 in bovine follicle and corpus luteum.

PubMed

Nishimoto, H; Matsutani, R; Yamamoto, S; Takahashi, T; Hayashi, K-G; Miyamoto, A; Hamano, S; Tetsuka, M

2006-01-01

Glucose is the main energy substrate in the bovine ovary, and a sufficient supply of it is necessary to sustain the ovarian activity. Glucose cannot permeate the plasma membrane, and its uptake is mediated by a number of glucose transporters (GLUT). In the present study, we investigated the gene expression of GLUT1, 3 and 4 in the bovine follicle and corpus luteum (CL). Ovaries were obtained from Holstein x Japanese Black F1 heifers. Granulosa cells and theca interna layers were harvested from follicles classified into five categories by their physiologic status: follicular size (>or= 8.5 mm: dominant; < 8.5 mm: subordinate), ratio of estradiol (E(2)) to progesterone in follicular fluid (>or= 1: E(2) active;<1: E(2) inactive), and stage of estrous cycle (luteal phase, follicular phase). CL were also classified by the stage of estrous cycle. Expression levels of GLUT1, 3 and 4 mRNA were quantified by a real-time PCR. The mRNA for GLUT1 and 3 were detected in the bovine follicle and CL at comparable levels to those in classic GLUT-expressing organs such as brain and heart. Much lower but appreciable levels of GLUT4 were also detected in these tissues. The gene expression of these GLUT showed tissue- and stage-specific patterns. Despite considerable differences in physiologic conditions, similar levels of GLUT1, 3 and 4 mRNA were expressed in subordinate follicles as well as dominant E(2)-active follicles in both luteal and follicular phases, whereas a notable increase in the gene expression of these GLUT was observed in dominant E(2)-inactive follicles undergoing the atretic process. In these follicles, highly significant negative correlations were observed between the concentrations of glucose in follicular fluid and the levels of GLUT1 and 3 mRNA in granulosa cells, implying that the local glucose environment affects glucose uptake of follicles. These results indicate that GLUT1 and 3 act as major transporters of glucose while GLUT4 may play a supporting role in

Creatine supplementation increases glycogen storage but not GLUT-4 expression in human skeletal muscle.

PubMed

van Loon, Luc J C; Murphy, Robyn; Oosterlaar, Audrey M; Cameron-Smith, David; Hargreaves, Mark; Wagenmakers, Anton J M; Snow, Rodney

2004-01-01

It has been speculated that creatine supplementation affects muscle glucose metabolism in humans by increasing muscle glycogen storage and up-regulating GLUT-4 protein expression. In the present study, we assessed the effects of creatine loading and prolonged supplementation on muscle glycogen storage and GLUT-4 mRNA and protein content in humans. A total of 20 subjects participated in a 6-week supplementation period during which creatine or a placebo was ingested. Muscle biopsies were taken before and after 5 days of creatine loading (20 g.day(-1)) and after 6 weeks of continued supplementation (2 g.day(-1)). Fasting plasma insulin concentrations, muscle creatine, glycogen and GLUT-4 protein content as well as GLUT-4, glycogen synthase-1 (GS-1) and glycogenin-1 (Gln-1) mRNA expression were determined. Creatine loading significantly increased total creatine, free creatine and creatine phosphate content with a concomitant 18 +/- 5% increase in muscle glycogen content (P<0.05). The subsequent use of a 2 g.day(-1) maintenance dose for 37 days did not maintain total creatine, creatine phosphate and glycogen content at the elevated levels. The initial increase in muscle glycogen accumulation could not be explained by an increase in fasting plasma insulin concentration, muscle GLUT-4 mRNA and/or protein content. In addition, neither muscle GS-1 nor Gln-1 mRNA expression was affected. We conclude that creatine ingestion itself stimulates muscle glycogen storage, but does not affect muscle GLUT-4 expression.

Insulin stimulated-glucose transporter Glut 4 is expressed in the retina.

PubMed

Sánchez-Chávez, Gustavo; Peña-Rangel, Ma Teresa; Riesgo-Escovar, Juan R; Martínez-Martínez, Alejandro; Salceda, Rocío

2012-01-01

The vertebrate retina is a very metabolically active tissue whose energy demands are normally met through the uptake of glucose and oxygen. Glucose metabolism in this tissue relies upon adequate glucose delivery from the systemic circulation. Therefore, glucose transport depends on the expression of glucose transporters. Here, we show retinal expression of the Glut 4 glucose transporter in frog and rat retinas. Immunohistochemistry and in situ hybridization studies showed Glut 4 expression in the three nuclear layers of the retina: the photoreceptor, inner nuclear and ganglionar cell layers. In the rat retina immunoprecipitation and Western blot analysis revealed a protein with an apparent molecular mass of 45 kDa. ¹⁴C-glucose accumulation by isolated rat retinas was significantly enhanced by physiological concentrations of insulin, an effect blocked by inhibitors of phosphatidyl-inositol 3-kinase (PI3K), a key enzyme in the insulin-signaling pathway in other tissues. Also, we observed an increase in ³H-cytochalasin binding sites in the presence of insulin, suggesting an increase in transporter recruitment at the cell surface. Besides, insulin induced phosphorylation of Akt, an effect also blocked by PI3K inhibition. Expression of Glut 4 was not modified in retinas of a type 1 diabetic rat model. To our knowledge, our results provide the first evidence of Glut4 expression in the retina, suggesting it as an insulin- responsive tissue.

Insulin Stimulated-Glucose Transporter Glut 4 Is Expressed in the Retina

PubMed Central

Sánchez-Chávez, Gustavo; Peña-Rangel, Ma. Teresa; Riesgo-Escovar, Juan R.; Martínez-Martínez, Alejandro; Salceda, Rocío

2012-01-01

The vertebrate retina is a very metabolically active tissue whose energy demands are normally met through the uptake of glucose and oxygen. Glucose metabolism in this tissue relies upon adequate glucose delivery from the systemic circulation. Therefore, glucose transport depends on the expression of glucose transporters. Here, we show retinal expression of the Glut 4 glucose transporter in frog and rat retinas. Immunohistochemistry and in situ hybridization studies showed Glut 4 expression in the three nuclear layers of the retina: the photoreceptor, inner nuclear and ganglionar cell layers. In the rat retina immunoprecipitation and Western blot analysis revealed a protein with an apparent molecular mass of 45 kDa. 14C-glucose accumulation by isolated rat retinas was significantly enhanced by physiological concentrations of insulin, an effect blocked by inhibitors of phosphatidyl-inositol 3-kinase (PI3K), a key enzyme in the insulin-signaling pathway in other tissues. Also, we observed an increase in 3H-cytochalasin binding sites in the presence of insulin, suggesting an increase in transporter recruitment at the cell surface. Besides, insulin induced phosphorylation of Akt, an effect also blocked by PI3K inhibition. Expression of Glut 4 was not modified in retinas of a type 1 diabetic rat model. To our knowledge, our results provide the first evidence of Glut4 expression in the retina, suggesting it as an insulin- responsive tissue. PMID:23285235

Translocation of myocardial GLUT-4 and increased glucose uptake through activation of AMPK by AICAR.

PubMed

Russell, R R; Bergeron, R; Shulman, G I; Young, L H

1999-08-01

Insulin increases glucose uptake through the translocation of GLUT-4 via a pathway mediated by phosphatidylinositol 3-kinase (PI3K). In contrast, myocardial glucose uptake during ischemia and hypoxia is stimulated by the translocation of GLUT-4 to the surface of cardiac myocytes through a PI3K-independent pathway that has not been characterized. AMP-activated protein kinase (AMPK) activity is also increased by myocardial ischemia, and we examined whether AMPK stimulates glucose uptake and GLUT-4 translocation. In isolated rat ventricular papillary muscles, 5-aminoimidazole-4-carboxyamide-1-beta-D-ribofuranoside (AICAR), an activator of AMPK, as well as cyanide-induced chemical hypoxia and insulin, increased 2-[(3)H]deoxyglucose uptake two- to threefold. Wortmannin, a PI3K inhibitor, did not affect either the AICAR- or the cyanide-stimulated increase in deoxyglucose uptake but eliminated the insulin-stimulated increase in deoxyglucose uptake. Immunofluorescence studies demonstrated translocation of GLUT-4 to the myocyte sarcolemma in response to stimulation with AICAR, cyanide, or insulin. Preincubation of papillary muscles with the kinase inhibitor iodotubercidin or adenine 9-beta-D-arabinofuranoside (araA), a precursor of araATP (a competitive inhibitor of AMPK), decreased AICAR- and cyanide-stimulated glucose uptake but did not affect basal or insulin-stimulated glucose uptake. In vivo infusion of AICAR caused myocardial AMPK activation and GLUT-4 translocation in the rat. We conclude that AMPK activation increases cardiac muscle glucose uptake through translocation of GLUT-4 via a pathway that is independent of PI3K. These findings suggest that AMPK activation may be important in ischemia-induced translocation of GLUT-4 in the heart.

Early alterations in soleus GLUT-4, glucose transport, and glycogen in voluntary running rats

NASA Technical Reports Server (NTRS)

Henriksen, Erik J.; Halseth, Amy E.

1994-01-01

Voluntary wheel running (WR) by juvenile female rats was used as a noninterventional model of soleus muscle functional overload to study the regulation of insulin-stimulated glucose transport activity by the glucose transporter (GLUT-4 isoform) protein level and glycogen concentration. Soleus total protein content was significantly greater (+18%;P greater than 0.05) than in age-matched controls after 1 wk of WR, and this hypertrophic response continued in weeks 2-4 (+24-32%). GLUT-4 protein was 39% greater than in controls in 1-wk WR soleus, and this adaptation was accompanied by a similar increase in in vitro insulin-stimulated glucose transport activity(+29%). After 2 and 4 wk of WR, however, insulin-stimulated glucose transport activity had returned to control levels, despite a continued elevation (+25-28%) of GLUT-4 protein. At these two time points, glycogen concentration was significantly enhanced in WR soleus (+21-42%), which coincided with significant reductions in glycogen synthase activity ratios (-23 to-41%). These results indicate that, in this model of soleus muscle functional overload, the GLUT-4 protein level may initially regulate insulin-stimulated glucose transport activity in the absence of changes in other modifying factors. However,this regulation of glucose transport activity by GLUT-4 protein may be subsequently overridden by elevated glycogen concentration.

A novel IRS-1-associated protein, DGKζ regulates GLUT4 translocation in 3T3-L1 adipocytes

PubMed Central

Liu, TingYu; Yu, BuChin; Kakino, Mamoru; Fujimoto, Hitoshi; Ando, Yasutoshi; Hakuno, Fumihiko; Takahashi, Shin-Ichiro

2016-01-01

Insulin receptor substrates (IRSs) are major targets of insulin receptor tyrosine kinases. Here we identified diacylglycerol kinase zeta (DGKζ) as an IRS-1-associated protein, and examined roles of DGKζ in glucose transporter 4 (GLUT4) translocation to the plasma membrane. When DGKζ was knocked-down in 3T3-L1 adipocytes, insulin-induced GLUT4 translocation was inhibited without affecting other mediators of insulin-dependent signaling. Similarly, knockdown of phosphatidylinositol 4-phosphate 5-kinase 1α (PIP5K1α), which had been reported to interact with DGKζ, also inhibited insulin-induced GLUT4 translocation. Moreover, DGKζ interacted with IRS-1 without insulin stimulation, but insulin stimulation decreased this interaction. Over-expression of sDGKζ (short-form DGKζ), which competed out DGKζ from IRS-1, enhanced GLUT4 translocation without insulin stimulation. Taking these results together with the data showing that cellular PIP5K activity was correlated with GLUT4 translocation ability, we concluded that IRS-1-associated DGKζ prevents GLUT4 translocation in the absence of insulin and that the DGKζ dissociated from IRS-1 by insulin stimulation enhances GLUT4 translocation through PIP5K1α activity. PMID:27739494

5'-AMP-activated protein kinase increases glucose uptake independent of GLUT4 translocation in cardiac myocytes.

PubMed

Lee, Christopher T; Ussher, John R; Mohammad, Askar; Lam, Anna; Lopaschuk, Gary D

2014-04-01

Glucose uptake and glycolysis are increased in the heart during ischemia, and this metabolic alteration constitutes an important contributing factor towards ischemic injury. Therefore, it is important to understand glucose uptake regulation in the ischemic heart. There are primarily 2 glucose transporters controlling glucose uptake into cardiac myocytes: GLUT1 and GLUT4. In the non-ischemic heart, insulin stimulates GLUT4 translocation to the sarcolemmal membrane, while both GLUT1 and GLUT4 translocation can occur following AMPK stimulation. Using a newly developed technique involving [(3)H]2-deoxyglucose, we measured glucose uptake in H9c2 ventricular myoblasts, and demonstrated that while insulin has no detectable effect on glucose uptake, phenformin-induced AMPK activation increases glucose uptake 2.5-fold. Furthermore, insulin treatment produced no discernible effect on either Akt serine 473 phosphorylation or AMPKα threonine 172 phosphorylation, while treatment with phenformin results in an increase in AMPKα threonine 172 phosphorylation, and a decrease in Akt serine 473 phosphorylation. Visualization of a dsRed-GLUT4 fusion construct in H9c2 cells by laser confocal microscopy showed that unlike insulin, AMPK activation did not redistribute GLUT4 to the sarcolemmal membrane, suggesting that AMPK may regulate glucose uptake via another glucose transporter. These studies suggest that AMPK is a major regulator of glucose uptake in cardiac myocytes.

Distribution patterns of the glucose transporters GLUT4 and GLUT1 in skeletal muscles of rats (Rattus norvegicus), pigs (Sus scrofa), cows (Bos taurus), adult goats, goat kids (Capra hircus), and camels (Camelus dromedarius).

PubMed

Duehlmeier, R; Sammet, K; Widdel, A; von Engelhardt, W; Wernery, U; Kinne, J; Sallmann, H-P

2007-02-01

Earlier studies demonstrated that forestomach herbivores are less insulin sensitive than monogastric omnivores. The present study was carried out to determine if different distribution patterns of the glucose transporters GLUT1 and GLUT4 may contribute to these different insulin sensitivities. Western blotting was used to measure GLUT1 and GLUT4 protein contents in oxidative (masseter, diaphragm) and glycolytic (longissimus lumborum, semitendinosus) skeletal muscle membranes of monogastric omnivores (rats and pigs), and of forestomach herbivores (cows, adult goats, goat kids, and camels). Muscles were characterized biochemically. Comparing red and white muscles, the isocitrate dehydrogenase (ICDH) activity was 1.5-15-times higher in oxidative muscles of all species, whereas lactate dehydrogenase (LDH) activity was 1.4-4.4-times higher in glycolytic muscles except in adult goats. GLUT4 levels were 1.5-6.3-times higher in oxidative muscles. GLUT1 levels were 2.2-8.3-times higher in glycolytic muscles in forestomach herbivores but not in monogastric animals. We conclude that GLUT1 may be the predominant glucose transporter in glycolytic muscles of ruminating animals. The GLUT1 distribution patterns were identical in adult and pre-ruminant goats, indicating that GLUT1 expression among these muscles is determined genetically. The high blood glucose levels of camels cited in literature may be due to an "NIDDM-like" impaired GLUT4 activity in skeletal muscle.

Dissociation between PGC-1alpha and GLUT-4 expression in skeletal muscle of rats fed a high-fat diet.

PubMed

Higashida, Kazuhiko; Higuchi, Mitsuru; Terada, Shin

2009-12-01

It has recently been reported that a 4-wk high-fat diet gradually increases skeletal muscle peroxisome proliferator activated receptor (PPAR) gamma coactivator-1alpha (PGC-1alpha) protein content, which has been suggested to regulate GLUT-4 gene transcription. However, it has not been reported that a high-fat diet enhances GLUT-4 mRNA expression and protein content in skeletal muscle, suggesting that an increase in PGC-1alpha protein content is not sufficient to induce muscle GLUT-4 biogenesis in a high-fat fed animal. Therefore, we first evaluated the relationship between PGC-1alpha and GLUT-4 expression in skeletal muscle of rats fed a high-fat diet for 4 wk. The PGC-1alpha protein content in rat epitrochlearis muscle significantly increased by twofold after the 4-wk high-fat diet feeding. However, the high-fat diet had no effect on GLUT-4 protein content and induced a 30% decrease in GLUT-4 mRNA expression in rat skeletal muscle (p<0.05). To clarify the mechanism by which a high-fat diet downregulates GLUT-4 mRNA expression, we next examined the effect of PPARdelta activation, which is known to occur in response to a high-fat diet, on GLUT-4 mRNA expression in L6 myotubes. Incubation with 500 nM GW501516 (PPARdelta activator) for 24 h significantly decreased GLUT-4 mRNA in L6 myotubes. Taken together, these findings suggest that a high-fat diet downregulates GLUT-4 mRNA, possibly through the activation of PPARdelta, despite an increase in PGC-1alpha protein content in rat skeletal muscle, and that a posttranscriptional regulatory mechanism maintains GLUT-4 protein content in skeletal muscle of rats fed a high-fat diet.

Dynamic GLUT4 sorting through a syntaxin-6 compartment in muscle cells is derailed by insulin resistance-causing ceramide

PubMed Central

Foley, Kevin P.; Klip, Amira

2014-01-01

ABSTRACT GLUT4 constitutively recycles between the plasma membrane and intracellular depots. Insulin shifts this dynamic equilibrium towards the plasma membrane by recruiting GLUT4 to the plasma membrane from insulin-responsive vesicles. Muscle is the primary site for dietary glucose deposition; however, how GLUT4 sorts into insulin-responsive vesicles, and if and how insulin resistance affects this process, is unknown. In L6 myoblasts stably expressing myc-tagged GLUT4, we analyzed the intracellular itinerary of GLUT4 as it internalizes from the cell surface and examined if such sorting is perturbed by C2-ceramide, a lipid metabolite causing insulin resistance. Surface-labeled GLUT4myc that internalized for 30 min accumulated in a Syntaxin-6 (Stx6)- and Stx16-positive perinuclear sub-compartment devoid of furin or internalized transferrin, and displayed insulin-responsive re-exocytosis. C2-ceramide dispersed the Stx6-positive sub-compartment and prevented insulin-responsive re-exocytosis of internalized GLUT4myc, even under conditions not affecting insulin-stimulated signaling towards Akt. Microtubule disruption with nocodazole prevented pre-internalized GLUT4myc from reaching the Stx6-positive perinuclear sub-compartment and from undergoing insulin-responsive exocytosis. Removing nocodazole allowed both parameters to recover, suggesting that the Stx6-positive perinuclear sub-compartment was required for GLUT4 insulin-responsiveness. Accordingly, Stx6 knockdown inhibited by ∼50% the ability of internalized GLUT4myc to undergo insulin-responsive re-exocytosis without altering its overall perinuclear accumulation. We propose that Stx6 defines the insulin-responsive compartment in muscle cells. Our data are consistent with a model where ceramide could cause insulin resistance by altering intracellular GLUT4 sorting. PMID:24705014

Glycogen supercompensation masks the effect of a traininginduced increase in GLUT-4 on muscle glucose transport.

PubMed

Host, H H; Hansen, P A; Nolte, L A; Chen, M M; Holloszy, J O

1998-07-01

Endurance exercise training induces a rapid increase in the GLUT-4 isoform of the glucose transporter in muscle. In fasted rats, insulin-stimulated muscle glucose transport is increased in proportion to the increase in GLUT-4. There is evidence that high muscle glycogen may decrease insulin-stimulated glucose transport. This study was undertaken to determine whether glycogen supercompensation interferes with the increase in glucose transport associated with an exercise-induced increase in GLUT-4. Rats were trained by means of swimming for 6 h/day for 2 days. Rats fasted overnight after the last exercise bout had an approximately twofold increase in epitrochlearis muscle GLUT-4 and an associated approximately twofold increase in maximally insulin-stimulated glucose transport activity. Epitrochlearis muscles of rats fed rodent chow after exercise were glycogen supercompensated (86.4 +/- 4.8 micromol/g wet wt) and showed no significant increase in maximally insulin-stimulated glucose transport above the sedentary control value despite an approximately twofold increase in GLUT-4. Fasting resulted in higher basal muscle glucose transport rates in both sedentary and trained rats but did not significantly increase maximally insulin-stimulated transport in the sedentary group. We conclude that carbohydrate feeding that results in muscle glycogen supercompensation prevents the increase in maximally insulin-stimulated glucose transport associated with an exercise training-induced increase in muscle GLUT-4.

Effect of short-term training on GLUT-4 mRNA and protein expression in human skeletal muscle.

PubMed

Kraniou, Giorgos N; Cameron-Smith, David; Hargreaves, Mark

2004-09-01

Six untrained, male subjects (23 +/- 1 years old, 84 +/- 5 kg, (O(2)peak)= 3.7 +/- 0.8 l min(-1)) exercised for 60 min at 75 +/- 1%(O(2)peak) on 7 consecutive days. Muscle samples were obtained before the start of cycle exercise training and 24 h after the first and seventh exercise sessions and analysed for citrate synthase activity, glycogen and glucose transporter 4 (GLUT-4) mRNA and protein expression. Exercise training increased (P < 0.05) citrate synthase by approximately 20% and muscle glycogen concentration by approximately 40%. GLUT-4 mRNA levels 24 h after the first and seventh exercise sessions were similar to those measured before the start of exercise training. In contrast, GLUT-4 protein expression was increased after 7 days of exercise training (12.4 +/- 1.5 versus 3.4 +/- 1.0 arbitray units (a.u.), P < 0.05) and although it tended to be higher 24 h after the first exercise session (6.0 +/- 3.0 versus 3.4 +/- 1.0 a.u.), this was not significantly different (P= 0.09). These results support the suggestion that the adaptive increase in skeletal muscle GLUT-4 protein expression with short-term exercise training arises from the repeated, transient increases in GLUT-gene transcription following each exercise bout leading to a gradual accumulation of GLUT-4 protein, despite GLUT-4 mRNA returning to basal levels between exercise stimuli.

Karanjin from Pongamia pinnata induces GLUT4 translocation in skeletal muscle cells in a phosphatidylinositol-3-kinase-independent manner.

PubMed

Jaiswal, Natasha; Yadav, Prem P; Maurya, Rakesh; Srivastava, Arvind K; Tamrakar, Akhilesh K

2011-11-16

Insulin-stimulated glucose uptake in skeletal muscle is decreased in type 2 diabetes due to impaired translocation of insulin-sensitive glucose transporter 4 (GLUT4) from intracellular pool to plasma membrane. Augmenting glucose uptake into this tissue may help in management of type 2 diabetes. Here, the effects of an identified antihyperglycemic molecule, karanjin, isolated from the fruits of Pongamia pinnata were investigated on glucose uptake and GLUT4 translocation in skeletal muscle cells. Treatment of L6-GLUT4myc myotubes with karanjin caused a substantial increase in the glucose uptake and GLUT4 translocation to the cell surface, in a concentration-dependent fashion, without changing the total amount of GLUT4 protein and GLUT4 mRNA. This effect was associated with increased activity of AMP-activated protein kinase (AMPK). Cycloheximide treatment inhibited the effect of karanjin on GLUT4 translocation suggesting the requirement of de novo synthesis of protein. Karanjin-induced GLUT4 translocation was further enhanced with insulin and the effect is completely protected in the presence of wortmannin. Moreover, karanjin did not affect the phosphorylation of AKT (Ser-473) and did not alter the expression of the key molecules of insulin signaling cascade. We conclude that karanjin-induced increase in glucose uptake in L6 myotubes is the result of an increased translocation of GLUT4 to plasma membrane associated with activation of AMPK pathway, in a PI-3-K/AKT-independent manner. Copyright © 2011 Elsevier B.V. All rights reserved.

Estradiol-induced regulation of GLUT4 in 3T3-L1 cells: involvement of ESR1 and AKT activation.

PubMed

Campello, Raquel S; Fátima, Luciana A; Barreto-Andrade, João Nilton; Lucas, Thais F; Mori, Rosana C; Porto, Catarina S; Machado, Ubiratan F

2017-10-01

Impaired insulin-stimulated glucose uptake involves reduced expression of the GLUT4 (solute carrier family 2 facilitated glucose transporter member 4, SLC2A4 gene). 17β-estradiol (E 2 ) modulates SLC2A4 /GLUT4 expression, but the involved mechanisms are unclear. Although E 2 exerts biological effects by binding to estrogen receptors 1/2 (ESR1/2), which are nuclear transcriptional factors; extranuclear effects have also been proposed. We hypothesize that E 2 regulates GLUT4 through an extranuclear ESR1 mechanism. Thus, we investigated the effects of E 2 upon (1) subcellular distribution of ESRs and the proto-oncogene tyrosine-protein kinases (SRC) involvement; (2) serine/threonine-protein kinase (AKT) activation; (3) Slc2a4 /GLUT4 expression and (4) GLUT4 subcellular distribution and glucose uptake in 3T3-L1 adipocytes. Differentiated 3T3-L1 adipocytes were cultivated or not with E 2 for 24 h, and additionally treated or not with ESR1-selective agonist (PPT), ESR1-selective antagonist (MPP) or selective SRC inhibitor (PP2). Subcellular distribution of ESR1, ESR2 and GLUT4 was analyzed by immunocytochemistry; Slc2a4 mRNA and GLUT4 were quantified by qPCR and Western blotting, respectively; plasma membrane GLUT4 translocation and glucose uptake were analyzed under insulin stimulus for 20 min or not. E 2 induced (1) translocation of ESR1, but not of ESR2, from nucleus to plasma membrane and AKT phosphorylation, effects mimicked by PPT and blocked by MPP and PP2; (2) increased Slc2a4 /GLUT4 expression and (3) increased insulin-stimulated GLUT4 translocation and glucose uptake. In conclusion, E 2 treatment promoted a SRC-mediated nucleus-plasma membrane shuttle of ESR1, and increased AKT phosphorylation, Slc2a4 /GLUT4 expression and plasma membrane GLUT4 translocation; consequently, improving insulin-stimulated glucose uptake. These results unravel mechanisms through which estrogen improves insulin sensitivity. © 2017 Society for Endocrinology.

Peripheral insulin resistance in ILK-depleted mice by reduction of GLUT4 expression.

PubMed

Hatem-Vaquero, Marco; Griera, Mercedes; García-Jerez, Andrea; Luengo, Alicia; Álvarez, Julia; Rubio, José A; Calleros, Laura; Rodríguez-Puyol, Diego; Rodríguez-Puyol, Manuel; De Frutos, Sergio

2017-08-01

The development of insulin resistance is characterized by the impairment of glucose uptake mediated by glucose transporter 4 (GLUT4). Extracellular matrix changes are induced when the metabolic dysregulation is sustained. The present work was devoted to analyze the possible link between the extracellular-to-intracellular mediator integrin-linked kinase (ILK) and the peripheral tissue modification that leads to glucose homeostasis impairment. Mice with general depletion of ILK in adulthood (cKD-ILK) maintained in a chow diet exhibited increased glycemia and insulinemia concurrently with a reduction of the expression and membrane presence of GLUT4 in the insulin-sensitive peripheral tissues compared with their wild-type littermates (WT). Tolerance tests and insulin sensitivity indexes confirmed the insulin resistance in cKD-ILK, suggesting a similar stage to prediabetes in humans. Under randomly fed conditions, no differences between cKD-ILK and WT were observed in the expression of insulin receptor (IR-B) and its substrate IRS-1 expressions. The IR-B isoform phosphorylated at tyrosines 1150/1151 was increased, but the AKT phosphorylation in serine 473 was reduced in cKD-ILK tissues. Similarly, ILK-blocked myotubes reduced their GLUT4 promoter activity and GLUT4 expression levels. On the other hand, the glucose uptake capacity in response to exogenous insulin was impaired when ILK was blocked in vivo and in vitro , although IR/IRS/AKT phosphorylation states were increased but not different between groups. We conclude that ILK depletion modifies the transcription of GLUT4, which results in reduced peripheral insulin sensitivity and glucose uptake, suggesting ILK as a molecular target and a prognostic biomarker of insulin resistance. © 2017 Society for Endocrinology.

Differential patterns of inhibition of the sugar transporters GLUT2, GLUT5 and GLUT7 by flavonoids.

PubMed

Gauer, Julia S; Tumova, Sarka; Lippiat, Jonathan D; Kerimi, Asimina; Williamson, Gary

2018-06-01

Only limited data are available on the inhibition of the sugar transporter GLUT5 by flavonoids or other classes of bioactives. Intestinal GLUT7 is poorly characterised and no information exists concerning its inhibition. We aimed to study the expression of GLUT7 in Caco-2/TC7 intestinal cells, and evaluate inhibition of glucose transport by GLUT2 and GLUT7, and of fructose transport by GLUT2, GLUT5 and GLUT7, by flavonoids. Differentiated Caco-2/TC7 cell monolayers were used to investigate GLUT7 expression, as well as biotinylation and immunofluorescence to assess GLUT7 location. For mechanistic sugar transport studies, X. laevis oocytes were injected with individual mRNA, and GLUT protein expression on oocyte membranes was confirmed. Oocytes were incubated with D-[ 14 C(U)]-glucose or D-[ 14 C(U)]-fructose in the presence of flavonoids, and uptake was estimated by liquid scintilation counting. In differentiated Caco-2/TC7 cell monolayers, GLUT7 was mostly expressed apically. When applied apically, or to both compartments, sorbitol, galactose, L-glucose or sucrose did not affect GLUT7 mRNA expression. Fructose applied to both sides increased GLUT7 mRNA (13%, p ≤ 0.001) and total GLUT7 protein (2.7-fold, p ≤ 0.05), while the ratio between apical, basolateral and total GLUT7 protein was unchanged. In the X. laevis oocyte model, GLUT2-mediated glucose and fructose transport were inhibited by quercetin, (-)-epigallocatechin gallate (EGCG) and apigenin, GLUT5-mediated fructose transport was inhibited by apigenin and EGCG, but not by quercetin, and GLUT7-mediated uptake of both glucose and fructose was inhibited by apigenin, but not by quercetin nor EGCG. Expression of GLUT7 was increased by fructose, but only when applied to Caco-2/TC7 cells both apically and basolaterally. Since GLUT2, GLUT5 and GLUT7 show different patterns of inhibition by the tested flavonoids, we suggest that they have the potential to be used as investigational tools to distinguish

Fructose-induced increases in expression of intestinal fructolytic and gluconeogenic genes are regulated by GLUT5 and KHK

PubMed Central

Patel, Chirag; Douard, Veronique; Yu, Shiyan; Tharabenjasin, Phuntila; Gao, Nan

2015-01-01

Marked increases in fructose consumption have been tightly linked to metabolic diseases. One-third of ingested fructose is metabolized in the small intestine, but the underlying mechanisms regulating expression of fructose-metabolizing enzymes are not known. We used genetic mouse models to test the hypothesis that fructose absorption via glucose transporter protein, member 5 (GLUT5), metabolism via ketohexokinase (KHK), as well as GLUT5 trafficking to the apical membrane via the Ras-related protein in brain 11a (Rab11a)-dependent endosomes are required for the regulation of intestinal fructolytic and gluconeogenic enzymes. Fructose feeding increased the intestinal mRNA and protein expression of these enzymes in the small intestine of adult wild-type (WT) mice compared with those gavage fed with lysine or glucose. Fructose did not increase expression of these enzymes in the GLUT5 knockout (KO) mice. Blocking intracellular fructose metabolism by KHK ablation also prevented fructose-induced upregulation. Glycolytic hexokinase I expression was similar between WT and GLUT5- or KHK-KO mice and did not vary with feeding solution. Gavage feeding with the fructose-specific metabolite glyceraldehyde did not increase enzyme expression, suggesting that signaling occurs before the hydrolysis of fructose to three-carbon compounds. Impeding GLUT5 trafficking to the apical membrane using intestinal epithelial cell-specific Rab11a-KO mice impaired fructose-induced upregulation. KHK expression was uniformly distributed along the villus but was localized mainly in the basal region of the cytosol of enterocytes. The feedforward upregulation of fructolytic and gluconeogenic enzymes specifically requires GLUT5 and KHK and may proactively enhance the intestine's ability to process anticipated increases in dietary fructose concentrations. PMID:26084694

Effect of Intermittent Hypoxia and Rimonabant on Glucose Metabolism in Rats: Involvement of Expression of GLUT4 in Skeletal Muscle

PubMed Central

Wang, Xiaoya; Yu, Qin; Yue, Hongmei; Zeng, Shuang; Cui, Fenfen

2015-01-01

Background Obstructive sleep apnea (OSA) and its main feature, chronic intermittent hypoxia (IH) during sleep, is closely associated with insulin resistance (IR) and diabetes. Rimonabant can regulate glucose metabolism and improve IR. The present study aimed to assess the effect of IH and rimonabant on glucose metabolism and insulin sensitivity, and to explore the possible mechanisms. Material/Methods Thirty-two rats were randomly assigned into 4 groups: Control group, subjected to intermittent air only; IH group, subjected to IH only; IH+NS group, subjected to IH and treated with normal saline; and IH+Rim group, subjected to IH and treated with 10 mg/kg/day of rimonabant. All rats were killed after 28 days of exposure. Then, the blood and skeletal muscle were collected. We measured fasting blood glucose levels, fasting blood insulin levels, and the expression of glucose transporter 4 (GLUT4) in both mRNA and protein levels in skeletal muscle. Results IH can slow weight gain, increase serum insulin level, and reduce insulin sensitivity in rats. The expressions of GLUT4 mRNA, total GLUT4, and plasma membrane protein of GLUT4 (PM GLUT4) in skeletal muscle were decreased. Rimonabant treatment was demonstrated to improve weight gain and insulin sensitivity of the rats induced by IH. Rimonabant significantly upregulated the expression of GLUT4 mRNA, PM GLUT4, and total GLUT4 in skeletal muscle. Conclusions The present study demonstrates that IH can cause IR and reduced expression of GLUT4 in both mRNA and protein levels in skeletal muscle of rats. Rimonabant treatment can improve IH – induced IR, and the upregulation of GLUT4 expression may be involved in this process. PMID:26503060

Adaptive responses of GLUT-4 and citrate synthase in fast-twitch muscle of voluntary running rats

NASA Technical Reports Server (NTRS)

Henriksen, E. J.; Halseth, A. E.

1995-01-01

Glucose transporter (GLUT-4) protein, hexokinase, and citrate synthase (proteins involved in oxidative energy production from blood glucose catabolism) increase in response to chronically elevated neuromuscular activity. It is currently unclear whether these proteins increase in a coordinated manner in response to this stimulus. Therefore, voluntary wheel running (WR) was used to chronically overload the fast-twitch rat plantaris muscle and the myocardium, and the early time courses of adaptative responses of GLUT-4 protein and the activities of hexokinase and citrate synthase were characterized and compared. Plantaris hexokinase activity increased 51% after just 1 wk of WR, whereas GLUT-4 and citrate synthase were increased by 51 and 40%, respectively, only after 2 wk of WR. All three variables remained comparably elevated (+50-64%) through 4 wk of WR. Despite the overload of the myocardium with this protocol, no substantial elevations in these variables were observed. These findings are consistent with a coordinated upregulation of GLUT-4 and citrate synthase in the fast-twitch plantaris, but not in the myocardium, in response to this increased neuromuscular activity. Regulation of hexokinase in fast-twitch muscle appears to be uncoupled from regulation of GLUT-4 and citrate synthase, as increases in the former are detectable well before increases in the latter.

Dual role for myosin II in GLUT4-mediated glucose uptake in 3T3-L1 adipocytes.

PubMed

Fulcher, F Kent; Smith, Bethany T; Russ, Misty; Patel, Yashomati M

2008-10-15

Insulin-stimulated glucose uptake requires the activation of several signaling pathways to mediate the translocation and fusion of GLUT4 vesicles to the plasma membrane. Our previous studies demonstrated that GLUT4-mediated glucose uptake is a myosin II-dependent process in adipocytes. The experiments described in this report are the first to show a dual role for the myosin IIA isoform specifically in regulating insulin-stimulated glucose uptake in adipocytes. We demonstrate that inhibition of MLCK but not RhoK results in impaired insulin-stimulated glucose uptake. Furthermore, our studies show that insulin specifically stimulates the phosphorylation of the RLC associated with the myosin IIA isoform via MLCK. In time course experiments, we determined that GLUT4 translocates to the plasma membrane prior to myosin IIA recruitment. We further show that recruitment of myosin IIA to the plasma membrane requires that myosin IIA be activated via phosphorylation of the RLC by MLCK. Our findings also reveal that myosin II is required for proper GLUT4-vesicle fusion at the plasma membrane. We show that once at the plasma membrane, myosin II is involved in regulating the intrinsic activity of GLUT4 after insulin stimulation. Collectively, our results are the first to reveal that myosin IIA plays a critical role in mediating insulin-stimulated glucose uptake in 3T3-LI adipocytes, via both GLUT4 vesicle fusion at the plasma membrane and GLUT4 activity.

Dual role for myosin II in GLUT4-mediated glucose uptake in 3T3-L1 adipocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fulcher, F. Kent; Smith, Bethany T.; Russ, Misty

2008-10-15

Insulin-stimulated glucose uptake requires the activation of several signaling pathways to mediate the translocation and fusion of GLUT4 vesicles to the plasma membrane. Our previous studies demonstrated that GLUT4-mediated glucose uptake is a myosin II-dependent process in adipocytes. The experiments described in this report are the first to show a dual role for the myosin IIA isoform specifically in regulating insulin-stimulated glucose uptake in adipocytes. We demonstrate that inhibition of MLCK but not RhoK results in impaired insulin-stimulated glucose uptake. Furthermore, our studies show that insulin specifically stimulates the phosphorylation of the RLC associated with the myosin IIA isoform viamore » MLCK. In time course experiments, we determined that GLUT4 translocates to the plasma membrane prior to myosin IIA recruitment. We further show that recruitment of myosin IIA to the plasma membrane requires that myosin IIA be activated via phosphorylation of the RLC by MLCK. Our findings also reveal that myosin II is required for proper GLUT4-vesicle fusion at the plasma membrane. We show that once at the plasma membrane, myosin II is involved in regulating the intrinsic activity of GLUT4 after insulin stimulation. Collectively, our results are the first to reveal that myosin IIA plays a critical role in mediating insulin-stimulated glucose uptake in 3T3-LI adipocytes, via both GLUT4 vesicle fusion at the plasma membrane and GLUT4 activity.« less

Role of insulin on exercise-induced GLUT-4 protein expression and glycogen supercompensation in rat skeletal muscle.

PubMed

Kuo, Chia-Hua; Hwang, Hyonson; Lee, Man-Cheong; Castle, Arthur L; Ivy, John L

2004-02-01

The purpose of this study was to investigate the role of insulin on skeletal muscle GLUT-4 protein expression and glycogen storage after postexercise carbohydrate supplementation. Male Sprague-Dawley rats were randomly assigned to one of six treatment groups: sedentary control (Con), Con with streptozocin (Stz/C), immediately postexercise (Ex0), Ex0 with Stz (Stz/Ex0), 5-h postexercise (Ex5), and Ex5 with Stz (Stz/Ex5). Rats were exercised by swimming (2 bouts of 3 h) and carbohydrate supplemented immediately after each exercise session by glucose intubation (1 ml of a 50% wt/vol). Stz was administered 72-h before exercise, which resulted in hyperglycemia and elimination of the insulin response to the carbohydrate supplement. GLUT-4 protein of Ex0 rats was 30% above Con in fast-twitch (FT) red and 21% above Con in FT white muscle. In Ex5, GLUT-4 protein was 52% above Con in FT red and 47% above Con in FT white muscle. Muscle glycogen in FT red and white muscle was also increased above Con in Ex5 rats. Neither GLUT-4 protein nor muscle glycogen was increased above Con in Stz/Ex0 or Stz/Ex5 rats. GLUT-4 mRNA in FT red muscle of Ex0 rats was 61% above Con but only 33% above Con in Ex5 rats. GLUT-4 mRNA in FT red muscle of Stz/C and Stz/Ex0 rats was similar but significantly elevated in Ex5/Stz rats. These results suggest that insulin is essential for the increase in GLUT-4 protein expression following postexercise carbohydrate supplementation.

Effect of baicalin on GLUT4 expression and glucose uptake in myotubes of rats.

PubMed

Fang, Penghua; Yu, Mei; Min, Wen; Wan, Dan; Han, Shiyu; Shan, Yizhi; Wang, Rui; Shi, Mingyi; Zhang, Zhenwen; Bo, Ping

2018-03-01

Although baicalin could attenuate obesity-induced insulin resistance, the detailed mechanism of baicalin on glucose uptake has not been sufficiently explored as yet. The aim of this study was to survey if baicalin might facilitate glucose uptake and to explore its signal mechanisms in L6 myotubes. L6 myotubes were treated with 100, 200, 400 μM baicalin for 6 h, 12 h and 24 h in this study. Then 2-NBDG and insulin signal protein levels in myotubes of L6 cells were examined. We discovered that administration of baicalin enhanced GLUT4, PGC-1α, pP38MAPK, pAKT and pAS160 contents, as well as GLUT4 mRNA and PGC-1α mRNA levels in L6 myotubes. The beneficial metabolic changes elicited by baicalin were abrogated in myotubes of L6 by P38MAPK or AKT inhibitors. These results suggest that baicalin promoted glucose uptake in myotubes by differential regulation on P38MAPK and AKT activity. In conclusion, these data provide insight that baicalin is a powerful and promising agent for the treament of hyperglycemia via AKT/AS160/GLUT4 and P38MAPK/PGC1α/GLUT4 pathway. Copyright © 2018 Elsevier Inc. All rights reserved.

Whey protein hydrolysate increases translocation of GLUT-4 to the plasma membrane independent of insulin in wistar rats.

PubMed

Morato, Priscila Neder; Lollo, Pablo Christiano Barboza; Moura, Carolina Soares; Batista, Thiago Martins; Camargo, Rafael Ludemann; Carneiro, Everardo Magalhães; Amaya-Farfan, Jaime

2013-01-01

Whey protein (WP) and whey protein hydrolysate (WPH) have the recognized capacity to increase glycogen stores. The objective of this study was to verify if consuming WP and WPH could also increase the concentration of the glucose transporters GLUT-1 and GLUT-4 in the plasma membrane (PM) of the muscle cells of sedentary and exercised animals. Forty-eight Wistar rats were divided into 6 groups (n = 8 per group), were treated and fed with experimental diets for 9 days as follows: a) control casein (CAS); b) WP; c) WPH; d) CAS exercised; e) WP exercised; and f) WPH exercised. After the experimental period, the animals were sacrificed, muscle GLUT-1 and GLUT-4, p85, Akt and phosphorylated Akt were analyzed by western blotting, and the glycogen, blood amino acids, insulin levels and biochemical health indicators were analyzed using standard methods. Consumption of WPH significantly increased the concentrations of GLUT-4 in the PM and glycogen, whereas the GLUT-1 and insulin levels and the health indicators showed no alterations. The physical exercise associated with consumption of WPH had favorable effects on glucose transport into muscle. These results should encourage new studies dealing with the potential of both WP and WPH for the treatment or prevention of type II diabetes, a disease in which there is reduced translocation of GLUT-4 to the plasma membrane.

Diverse effects of Glut 4 ablation on glucose uptake and glycogen synthesis in red and white skeletal muscle.

PubMed

Stenbit, A E; Burcelin, R; Katz, E B; Tsao, T S; Gautier, N; Charron, M J; Le Marchand-Brustel, Y

1996-08-01

The ability of muscles from Glut 4-null mice to take up and metabolize glucose has been studied in the isolated white EDL and red soleus muscles. In EDL muscles from male or female Glut 4-null mice, basal deoxyglucose uptake was lower than in control muscles and was not stimulated by insulin. In parallel, glycogen synthesis and content were decreased. Soleus muscles from male Glut 4-null mice took up twice more deoxyglucose in the absence of insulin than control muscles, but did not respond to insulin. In females, soleus deoxyglucose uptake measured in the absence of hormone was similar in Glut 4-null mice and in control mice. This uptake was stimulated twofold in Glut 4-null mice and threefold in control mice. Basal glycogen synthesis was increased by 4- and 2.2-fold in male and female null mice, respectively, compared to controls, and insulin had no or small (20% stimulation over basal) effect. These results indicate that while EDL muscles behaved as expected, soleus muscles were able to take up a large amount of glucose in the absence (males) or the presence of insulin (females). Whether this is due to a change in Glut 1 intrinsic activity or targeting and/or to the appearance of another glucose transporter remains to be determined.

The Inactivation of RabGAP Function of AS160 Promotes Lysosomal Degradation of GLUT4 and Causes Postprandial Hyperglycemia and Hyperinsulinemia.

PubMed

Xie, Bingxian; Chen, Qiaoli; Chen, Liang; Sheng, Yang; Wang, Hong Yu; Chen, Shuai

2016-11-01

The AS160 (Akt substrate of 160 kDa) is a Rab-GTPase activating protein (RabGAP) with several other functional domains, and its deficiency in mice or human patients lowers GLUT4 protein levels and causes severe insulin resistance. How its deficiency causes diminished GLUT4 proteins remains unknown. We found that the deletion of AS160 decreased GLUT4 levels in a cell/tissue-autonomous manner. Consequently, skeletal muscle-specific deletion of AS160 caused postprandial hyperglycemia and hyperinsulinemia. The pathogenic effects of AS160 deletion are mainly, if not exclusively, due to the loss of its RabGAP function since the RabGAP-inactive AS160 R917K mutant mice phenocopied the AS160 knockout mice. The inactivation of RabGAP of AS160 promotes lysosomal degradation of GLUT4, and the inhibition of lysosome function could restore GLUT4 protein levels. Collectively, these findings demonstrate that the RabGAP activity of AS160 maintains GLUT4 protein levels in a cell/tissue-autonomous manner and its inactivation causes lysosomal degradation of GLUT4 and postprandial hyperglycemia and hyperinsulinemia. © 2016 by the American Diabetes Association.

Insulin Recruits GLUT4 from Specialized VAMP2-carrying Vesicles as well as from the Dynamic Endosomal/Trans-Golgi Network in Rat Adipocytes.

PubMed Central

Ramm, Georg; Slot, Jan Willem; James, David E.; Stoorvogel, Willem

2000-01-01

Insulin treatment of fat cells results in the translocation of the insulin-responsive glucose transporter type 4, GLUT4, from intracellular compartments to the plasma membrane. However, the precise nature of these intracellular GLUT4-carrying compartments is debated. To resolve the nature of these compartments, we have performed an extensive morphological analysis of GLUT4-containing compartments, using a novel immunocytochemical technique enabling high labeling efficiency and 3-d resolution of cytoplasmic rims isolated from rat epididymal adipocytes. In basal cells, GLUT4 was localized to three morphologically distinct intracellular structures: small vesicles, tubules, and vacuoles. In response to insulin the increase of GLUT4 at the cell surface was compensated by a decrease in small vesicles, whereas the amount in tubules and vacuoles was unchanged. Under basal conditions, many small GLUT4 positive vesicles also contained IRAP (88%) and the v-SNARE, VAMP2 (57%) but not markers of sorting endosomes (EEA1), late endosomes, or lysosomes (lgp120). A largely distinct population of GLUT4 vesicles (56%) contained the cation-dependent mannose 6-phosphate receptor (CD-MPR), a marker protein that shuttles between endosomes and the trans-Golgi network (TGN). In response to insulin, GLUT4 was recruited both from VAMP2 and CD-MPR positive vesicles. However, while the concentration of GLUT4 in the remaining VAMP2-positive vesicles was unchanged, the concentration of GLUT4 in CD-MPR-positive vesicles decreased. Taken together, we provide morphological evidence indicating that, in response to insulin, GLUT4 is recruited to the plasma membrane by fusion of preexisting VAMP2-carrying vesicles as well as by sorting from the dynamic endosomal-TGN system. PMID:11102509

MicroRNA-133 regulates the expression of GLUT4 by targeting KLF15 and is involved in metabolic control in cardiac myocytes.

PubMed

Horie, Takahiro; Ono, Koh; Nishi, Hitoo; Iwanaga, Yoshitaka; Nagao, Kazuya; Kinoshita, Minako; Kuwabara, Yasuhide; Takanabe, Rieko; Hasegawa, Koji; Kita, Toru; Kimura, Takeshi

2009-11-13

GLUT4 shows decreased levels in failing human adult hearts. We speculated that GLUT4 expression in cardiac muscle may be fine-tuned by microRNAs. Forced expression of miR-133 decreased GLUT4 expression and reduced insulin-mediated glucose uptake in cardiomyocytes. A computational miRNA target prediction algorithm showed that KLF15 is one of the targets of miR-133. It was confirmed that over-expression of miR-133 reduced the protein level of KLF15, which reduced the level of the downstream target GLUT4. Cardiac myocytes infected with lenti-decoy, in which the 3'UTR with tandem sequences complementary to miR-133 was linked to the luciferase reporter gene, had decreased miR-133 levels and increased levels of GLUT4. The expression levels of KLF15 and GLUT4 were decreased at the left ventricular hypertrophy and congestive heart failure stage in a rat model. The present results indicated that miR-133 regulates the expression of GLUT4 by targeting KLF15 and is involved in metabolic control in cardiomyocytes.

Intervention of rosiglitazone on myocardium Glut-4 mRNA expression during ischemia-reperfusion injury in cardio-pulmonary bypass in dogs.

PubMed

Liu, Bin; Liang, Guiyou; Xu, Gang; Liu, Daxin; Cai, Qingyong; Gao, Zhenyu

2013-01-01

During cardiac pulmonary bypass (CPB), myocardial ischemia-reperfusion (I/R) induces heart glucose metabolism impairment. Our previous research showed that the decreased glucose utilization is due to decreased glucose transporter-4 (Glut-4) expression and translocation to myocyte surface membranes. This study further examined whether rosiglitazone, a synthetic agonist of peroxisome proliferator-activated receptor γ, could intervene glucose metabolism by regulating Glut-4 mRNA during I/R in dogs. Cardiac ischemia was induced by cardiopulmonary bypass for 30 or 120 min. Plasma insulin and glucose concentrations were measured at pre-bypass (control), aortic cross-clamp off (I/R) at 15, 45, and 75 min. The left ventricle biopsies were taken for the expression of Glut-4 mRNA by real-time RT-PCR. In dogs receiving 120 min ischemia, coronary arterial, venous glucose concentrations, plasma insulin levels, and insulin resistant index (IRI) were increased, but the expression of Glut-4 mRNA was decreased obviously at 15 min of reperfusion, and recovered gradually. On the other hand, these changes were relatively mild in dogs treated with rosiglitazone in cardioplegic solution and expression of Glut-4 mRNA was increased remarkably. It is concluded that the decrease in total amount of Glut-4 mRNA expression could be one of the important molecular mechanisms, which causes the myocardium insulin resistance. The longer the ischemia period, the decrease in amount of Glut-4 mRNA was more dramatic. Adding rosiglitazone into the cardioplegic solution during I/R can increase the amount of Glut-4 mRNA expression, mitigate the myocardium insulin resistance and improve the myocardium I/R injury during CPB.

Targeted GLUT-4 deficiency in the heart induces cardiomyocyte hypertrophy and impaired contractility linked with Ca(2+) and proton flux dysregulation.

PubMed

Domenighetti, Andrea A; Danes, Vennetia R; Curl, Claire L; Favaloro, Jennifer M; Proietto, Joseph; Delbridge, Lea M D

2010-04-01

There is clinical evidence to suggest that impaired myocardial glucose uptake contributes to the pathogenesis of hypertrophic, insulin-resistant cardiomyopathy. The goal of this study was to determine whether cardiac deficiency of the insulin-sensitive glucose transporter, GLUT4, has deleterious effect on cardiomyocyte excitation-contraction coupling. Cre-Lox mouse models of cardiac GLUT4 knockdown (KD, 85% reduction) and knockout (KO, >95% reduction), which exhibit similar systemic hyperinsulinemic and hyperglycemic states, were investigated. The Ca(2+) current (I(Ca)) and Na(+)-Ca(2+) exchanger (NCX) fluxes, Na(+)-H(+) exchanger (NHE) activity, and contractile performance of GLUT4-deficient myocytes was examined using whole-cell patch-clamp, epifluorescence, and imaging techniques. GLUT4-KO exhibited significant cardiac enlargement characterized by cardiomyocyte hypertrophy (40% increase in cell area) and fibrosis. GLUT4-KO myocyte contractility was significantly diminished, with reduced mean maximum shortening (5.0+/-0.4% vs. 6.2+/-0.6%, 5 Hz). Maximal rates of shortening and relaxation were also reduced (20-25%), and latency was delayed. In GLUT4-KO myocytes, the I(Ca) density was decreased (-2.80+/-0.29 vs. -5.30+/-0.70 pA/pF), and mean I(NCX) was significantly increased in both outward (by 60%) and inward (by 100%) directions. GLUT4-KO expression levels of SERCA2 and RyR2 were reduced by approximately 50%. NHE-mediated H(+) flux in response to NH(4)Cl acid loading was markedly elevated GLUT4-KO myocytes, associated with doubled expression of NHE1. These findings demonstrate that, independent of systemic endocrinological disturbance, cardiac GLUT4 deficiency per se provides a lesion sufficient to induce profound alterations in cardiomyocyte Ca(2+) and pH homeostasis. Our investigation identifies the cardiac GLUT4 as a potential primary molecular therapeutic target in ameliorating the functional deficits associated with insulin-resistant cardiomyopathy

Rapid upregulation of GLUT-4 and MCT-4 expression during 16 h of heavy intermittent cycle exercise.

PubMed

Green, H J; Duhamel, T A; Holloway, G P; Moule, J W; Ranney, D W; Tupling, A R; Ouyang, J

2008-02-01

In this study, we have investigated the hypothesis that an exercise protocol designed to repeatedly induce a large dependence on carbohydrate and large increases in glycolytic flux rate would result in rapid increases in the principal glucose and lactate transporters in working muscle, glucose transporter (GLUT)-4 and monocarboxylate transporter (MCT)4, respectively, and in activity of hexokinase (Hex), the enzyme used to phosphorylate glucose. Transporter abundance and Hex activity were assessed in homogenates by Western blotting and quantitative chemiluminescence and fluorometric techniques, respectively, in samples of tissue obtained from the vastus lateralis in 12 untrained volunteers [peak aerobic power (.VO(2peak)) = 44.3 +/- 2.3 ml.kg(-1).min(-1)] before cycle exercise at repetitions 1 (R1), 2 (R2), 9 (R9), and 16 (R16). The 16 repetitions of the exercise were performed for 6 min at approximately 90% .VO(2peak), once per hour. Compared with R1, GLUT-4 increased (P < 0.05) by 28% at R2 and remained elevated (P < 0.05) at R9 and R16. For MCT-4, increases (P < 0.05) of 24% were first observed at R9 and persisted at R16. No changes were observed in GLUT-1 and MCT-1 or in Hex activity. The approximately 17- to 24-fold increase (P < 0.05) in muscle lactate observed at R1 and R2 was reduced (P < 0.05) to an 11-fold increase at R9 and R16. It is concluded that an exercise protocol designed to strain muscle carbohydrate reserves and to result in large increases in lactic acid results in a rapid upregulation of both GLUT-4 and MCT-4.

In Vitro Evaluations of Cytotoxicity of Eight Antidiabetic Medicinal Plants and Their Effect on GLUT4 Translocation

PubMed Central

Kadan, Sleman; Saad, Bashar; Sasson, Yoel; Zaid, Hilal

2013-01-01

Despite the enormous achievements in conventional medicine, herbal-based medicines are still a common practice for the treatment of diabetes. Trigonella foenum-graecum, Atriplex halimus, Olea europaea, Urtica dioica, Allium sativum, Allium cepa, Nigella sativa, and Cinnamomum cassia are strongly recommended in the Greco-Arab and Islamic medicine for the treatment and prevention of diabetes. Cytotoxicity (MTT and LDH assays) of the plant extracts was assessed using cells from the liver hepatocellular carcinoma cell line (HepG2) and cells from the rat L6 muscle cell line. The effects of the plant extracts (50% ethanol in water) on glucose transporter-4 (GLUT4) translocation to the plasma membrane was tested in an ELISA test on L6-GLUT4myc cells. Results obtained indicate that Cinnamomon cassia is cytotoxic at concentrations higher than 100 μg/mL, whereas all other tested extracts exhibited cytotoxic effects at concentrations higher than 500 μg/mL. Exposing L6-GLUT4myc muscle cell to extracts from Trigonella foenum-graecum, Urtica dioica, Atriplex halimus, and Cinnamomum verum led to a significant gain in GLUT4 on their plasma membranes at noncytotoxic concentrations as measured with MTT assay and the LDH leakage assay. These findings indicate that the observed anti-diabetic properties of these plants are mediated, at least partially, through regulating GLUT4 translocation. PMID:23606883

Metabolically active CD4+ T cells expressing Glut1 and OX40 preferentially harbor HIV during in vitro infection.

PubMed

Palmer, Clovis S; Duette, Gabriel A; Wagner, Marc C E; Henstridge, Darren C; Saleh, Suah; Pereira, Candida; Zhou, Jingling; Simar, David; Lewin, Sharon R; Ostrowski, Matias; McCune, Joseph M; Crowe, Suzanne M

2017-10-01

High glucose transporter 1 (Glut1) surface expression is associated with increased glycolytic activity in activated CD4+ T cells. Phosphatidylinositide 3-kinases (PI3K) activation measured by p-Akt and OX40 is elevated in CD4+Glut1+ T cells from HIV+ subjects. TCR engagement of CD4+Glut1+ T cells from HIV+ subjects demonstrates hyperresponsive PI3K-mammalian target of rapamycin signaling. High basal Glut1 and OX40 on CD4+ T cells from combination antiretroviral therapy (cART)-treated HIV+ patients represent a sufficiently metabolically active state permissive for HIV infection in vitro without external stimuli. The majority of CD4+OX40+ T cells express Glut1, thus OX40 rather than Glut1 itself may facilitate HIV infection. Furthermore, infection of CD4+ T cells is limited by p110γ PI3K inhibition. Modulating glucose metabolism may limit cellular activation and prevent residual HIV replication in 'virologically suppressed' cART-treated HIV+ persons. © 2017 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

Insulin-Responsive Compartments Containing GLUT4 in 3T3-L1 and CHO Cells: Regulation by Amino Acid Concentrations

PubMed Central

Bogan, Jonathan S.; McKee, Adrienne E.; Lodish, Harvey F.

2001-01-01

In fat and muscle, insulin stimulates glucose uptake by rapidly mobilizing the GLUT4 glucose transporter from a specialized intracellular compartment to the plasma membrane. We describe a method to quantify the relative proportion of GLUT4 at the plasma membrane, using flow cytometry to measure a ratio of fluorescence intensities corresponding to the cell surface and total amounts of a tagged GLUT4 reporter in individual living cells. Using this assay, we demonstrate that both 3T3-L1 and CHO cells contain intracellular compartments from which GLUT4 is rapidly mobilized by insulin and that the initial magnitude and kinetics of redistribution to the plasma membrane are similar in these two cell types when they are cultured identically. Targeting of GLUT4 to a highly insulin-responsive compartment in CHO cells is modulated by culture conditions. In particular, we find that amino acids regulate distribution of GLUT4 to this kinetically defined compartment through a rapamycin-sensitive pathway. Amino acids also modulate the magnitude of insulin-stimulated translocation in 3T3-L1 adipocytes. Our results indicate a novel link between glucose and amino acid metabolism. PMID:11416153

Small G proteins in insulin action: Rab and Rho families at the crossroads of signal transduction and GLUT4 vesicle traffic.

PubMed

Ishikura, S; Koshkina, A; Klip, A

2008-01-01

Insulin stimulates glucose uptake into muscle and adipose tissues through glucose transporter 4 (GLUT4). GLUT4 cycles between the intracellular compartments and the plasma membrane. GLUT4 traffic-regulating insulin signals are largely within the insulin receptor-insulin receptor substrate-phosphatidylinositol 3-kinase (IR-IRS-PI3K) axis. In muscle cells, insulin signal bifurcates downstream of the PI3K into one arm leading to the activation of the Ser/Thr kinases Akt and atypical protein kinase C, and another leading to the activation of Rho family protein Rac1 leading to actin remodelling. Activated Akt inactivates AS160, a GTPase-activating protein for Rab family small G proteins. Here we review the roles of Rab and Rho proteins, particularly Rab substrates of AS160 and Rac1, in insulin-stimulated GLUT4 traffic. We discuss: (1) how distinct steps in GLUT4 traffic may be regulated by discrete Rab proteins, and (2) the importance of Rac1 activation in insulin-induced actin remodelling in muscle cells, a key element for the net gain in surface GLUT4.

GLUT-1 Expression in Pancreatic Neoplasia

PubMed Central

Basturk, Olca; Singh, Rajendra; Kaygusuz, Ecmel; Balci, Serdar; Dursun, Nevra; Culhaci, Nil; Adsay, N. Volkan

2011-01-01

Objectives GLUT-1 has been found to have an important role in the upregulation of various cellular pathways and implicated in neoplastic transformation correlating with biological behavior in malignancies. However, literature regarding the significance of GLUT-1 expression in pancreatic neoplasia has been limited and controversial. Methods Immunohistochemical expression of GLUT-1 was tested in a variety of pancreatic neoplasia including ductal adenocarcinomas (DAs), pancreatic intraepithelial neoplasms (PanINs), intraductal papillary mucinous neoplasms (IPMNs), and serous cystadenomas. Results There was a progressive increase in the expression of GLUT-1 from low- to higher-grade dysplastic lesions: All higher-grade PanINs/IPMNs (the ones with moderate/high-grade dysplasia) revealed noticeable GLUT-1 expression. Among the 94 DAs analyzed, there were minimal/moderate expression in 46 and significant expression in 24 DAs. However, all 4 clear-cell variants of DAs revealed significant GLUT-1 immunolabeling, as did areas of clear-cell change seen in other DAs. Moreover, all 12 serous cystadenomas expressed significant GLUT-1. GLUT-1 expression was also directly correlated with DA histological grade (P = 0.016) and tumor size (P = 0.03). Conclusions GLUT-1 may give rise to the distinctive clear-cell appearance of these tumors by inducing the accumulation of glycogen in the cytoplasm. Additionally, because GLUT-1 expression was related to histological grade and tumor size of DA, further studies are warranted to investigate the association of GLUT-1 with prognosis and tumor progression. PMID:21206329

Impaired translocation of GLUT4 results in insulin resistance of atrophic soleus muscle.

PubMed

Xu, Peng-Tao; Song, Zhen; Zhang, Wen-Cheng; Jiao, Bo; Yu, Zhi-Bin

2015-01-01

Whether or not the atrophic skeletal muscle induces insulin resistance and its mechanisms are not resolved now. The antigravity soleus muscle showed a progressive atrophy in 1-week, 2-week, and 4-week tail-suspended rats. Hyperinsulinemic-euglycemic clamp showed that the steady-state glucose infusion rate was lower in 4-week tail-suspended rats than that in the control rats. The glucose uptake rates under insulin- or contraction-stimulation were significantly decreased in 4-week unloaded soleus muscle. The key protein expressions of IRS-1, PI3K, and Akt on the insulin-dependent pathway and of AMPK, ERK, and p38 on the insulin-independent pathway were unchanged in unloaded soleus muscle. The unchanged phosphorylation of Akt and p38 suggested that the activity of two signal pathways was not altered in unloaded soleus muscle. The AS160 and GLUT4 expression on the common downstream pathway also was not changed in unloaded soleus muscle. But the GLUT4 translocation to sarcolemma was inhibited during insulin stimulation in unloaded soleus muscle. The above results suggest that hindlimb unloading in tail-suspended rat induces atrophy in antigravity soleus muscle. The impaired GLUT4 translocation to sarcolemma under insulin stimulation may mediate insulin resistance in unloaded soleus muscle and further affect the insulin sensitivity of whole body in tail-suspended rats.

Impaired Translocation of GLUT4 Results in Insulin Resistance of Atrophic Soleus Muscle

PubMed Central

Xu, Peng-Tao; Song, Zhen; Zhang, Wen-Cheng; Jiao, Bo; Yu, Zhi-Bin

2015-01-01

Whether or not the atrophic skeletal muscle induces insulin resistance and its mechanisms are not resolved now. The antigravity soleus muscle showed a progressive atrophy in 1-week, 2-week, and 4-week tail-suspended rats. Hyperinsulinemic-euglycemic clamp showed that the steady-state glucose infusion rate was lower in 4-week tail-suspended rats than that in the control rats. The glucose uptake rates under insulin- or contraction-stimulation were significantly decreased in 4-week unloaded soleus muscle. The key protein expressions of IRS-1, PI3K, and Akt on the insulin-dependent pathway and of AMPK, ERK, and p38 on the insulin-independent pathway were unchanged in unloaded soleus muscle. The unchanged phosphorylation of Akt and p38 suggested that the activity of two signal pathways was not altered in unloaded soleus muscle. The AS160 and GLUT4 expression on the common downstream pathway also was not changed in unloaded soleus muscle. But the GLUT4 translocation to sarcolemma was inhibited during insulin stimulation in unloaded soleus muscle. The above results suggest that hindlimb unloading in tail-suspended rat induces atrophy in antigravity soleus muscle. The impaired GLUT4 translocation to sarcolemma under insulin stimulation may mediate insulin resistance in unloaded soleus muscle and further affect the insulin sensitivity of whole body in tail-suspended rats. PMID:25713812

IQGAP1 promotes CXCR4 chemokine receptor function and trafficking via EEA-1+ endosomes

PubMed Central

Bamidele, Adebowale O.; Kremer, Kimberly N.; Hirsova, Petra; Clift, Ian C.; Gores, Gregory J.; Billadeau, Daniel D.

2015-01-01

IQ motif–containing GTPase-activating protein 1 (IQGAP1) is a cytoskeleton-interacting scaffold protein. CXCR4 is a chemokine receptor that binds stromal cell–derived factor-1 (SDF-1; also known as CXCL12). Both IQGAP1 and CXCR4 are overexpressed in cancer cell types, yet it was unclear whether these molecules functionally interact. Here, we show that depleting IQGAP1 in Jurkat T leukemic cells reduced CXCR4 expression, disrupted trafficking of endocytosed CXCR4 via EEA-1+ endosomes, and decreased efficiency of CXCR4 recycling. SDF-1–induced cell migration and activation of extracellular signal-regulated kinases 1 and 2 (ERK) MAPK were strongly inhibited, even when forced overexpression restored CXCR4 levels. Similar results were seen in KMBC and HEK293 cells. Exploring the mechanism, we found that SDF-1 treatment induced IQGAP1 binding to α-tubulin and localization to CXCR4-containing endosomes and that CXCR4-containing EEA-1+ endosomes were abnormally located distal from the microtubule (MT)-organizing center (MTOC) in IQGAP1-deficient cells. Thus, IQGAP1 critically mediates CXCR4 cell surface expression and signaling, evidently by regulating EEA-1+ endosome interactions with MTs during CXCR4 trafficking and recycling. IQGAP1 may similarly promote CXCR4 functions in other cancer cell types. PMID:26195666

The impact of N- and O-glycosylation on the functions of Glut-1 transporter in human thyroid anaplastic cells.

PubMed

Samih, Nezha; Hovsepian, Sonia; Notel, Frédéric; Prorok, Maëlle; Zattara-Cannoni, Hélène; Mathieu, Sylvie; Lombardo, Dominique; Fayet, Guy; El-Battari, Assou

2003-04-07

It has been previously shown that glucose transporter Glut-1 expression was detectable by immunostaining in tissue sections from anaplastic carcinoma, but not in normal thyroid tissue. Using human thyroid anaplastic carcinoma cells, we studied the mechanism by which Glut-1 molecules are translocated from the endoplasmic reticulum to the cell surface. The contribution of N- and O-linked glycans for the translocation and activity of Glut-1 transporter is emphasized. The inhibition of N-glycosylation with tunicamycin (TM) led to a 50% decrease in glucose transport while glycosylated and unglycosylated forms of Glut-1 were found at the cell surface. However, the inhibition of N-linked oligosaccharide processing with deoxymannojirimycin (dMJ) and swainsonine (SW) influenced neither the intracellular trafficking nor the activity of the transporter. On the other hand, Glut-1 bound to the O-linked glycan-specific lectin jacalin and the O-glycosylation inhibitor benzyl-N-acetylgalactosamine dramatically inhibited glucose transport. These results show that O- and N-linked oligosaccharides arbored by Glut-1 are essential for glucose transport in anaplastic carcinoma cells. The quantitative and qualitative alterations of Glut-1 glycosylation and the increase in glucose transport are associated with the anaplastic phenotype of human thyroid cells.

GLUT1, MCT1/4 and CD147 overexpression supports the metabolic reprogramming in papillary renal cell carcinoma.

PubMed

Almeida, L M C A; Silva, R; Cavadas, B; Lima, J; Pereira, L; Soares, P; Sobrinho-Simões, M; Lopes, J M; Máximo, V

2017-10-01

Papillary Renal Cell carcinoma (pRCC) is the second most common type of RCC, accounting for about 15% of all RCCs. Surgical excision is the main treatment option. Still, 10 - 15 % of clinically localized tumours will recur and/or develop metastasis early after surgery, and no reliable prognostic biomarkers are available to identify them. It is known that pRCC cells rely on high rates of aerobic glycolysis, characterized by the up-regulation of many proteins and enzymes related with the glycolytic pathway. However, a metabolic signature enabling the identification of advanced pRCC tumours remains to be discovered. The aim of this study was to characterize the metabolic phenotype of pRCCs (subtypes 1-pRCC1 and 2-pRCC2) by evaluating the expression pattern of the glucose transporters (GLUTs) 1 and 4 and the monocarboxylate transporters (MCTs) 1 and 4, as well as their chaperon CD147. We analysed the clinico-pathological data and the protein and mRNA expression of GLUT1, GLUT4 and MCT1, MCT4 and CD147 in tumours from Porto and TCGA series (http://cancergenome.nih.gov/), respectively. With the exception of GLUT4, plasma membrane expression of all proteins was frequently observed in pRCCs. GLUT1 and MCT1 membrane overexpression was significantly higher in pRCC2 and significantly associated with higher pN-stage and higher Fuhrman grade. Overexpression of GLUT1, MCT1/4 and CD147, supports the metabolic reprograming in pRCCs. MCT1 expression was associated with pRCC aggressiveness, regardless of the tumour histotype.

Isolated receptor binding domains of HTLV-1 and HTLV-2 envelopes bind Glut-1 on activated CD4+ and CD8+ T cells

PubMed Central

Kinet, Sandrina; Swainson, Louise; Lavanya, Madakasira; Mongellaz, Cedric; Montel-Hagen, Amélie; Craveiro, Marco; Manel, Nicolas; Battini, Jean-Luc; Sitbon, Marc; Taylor, Naomi

2007-01-01

Background We previously identified the glucose transporter Glut-1, a member of the multimembrane-spanning facilitative nutrient transporter family, as a receptor for both HTLV-1 and HTLV-2. However, a recent report concluded that Glut-1 cannot serve as a receptor for HTLV-1 on CD4 T cells: This was based mainly on their inability to detect Glut-1 on this lymphocyte subset using the commercial antibody mAb1418. It was therefore of significant interest to thoroughly assess Glut-1 expression on CD4 and CD8 T cells, and its association with HTLV-1 and -2 envelope binding. Results As previously reported, ectopic expression of Glut-1 but not Glut-3 resulted in significantly augmented binding of tagged proteins harboring the receptor binding domains of either HTLV-1 or HTLV-2 envelope glycoproteins (H1RBD or H2RBD). Using antibodies raised against the carboxy-terminal peptide of Glut-1, we found that Glut-1 expression was significantly increased in both CD4 and CD8 cells following TCR stimulation. Corresponding increases in the binding of H1RBD as well as H2RBD, not detected on quiescent T cells, were observed following TCR engagement. Furthermore, increased Glut-1 expression was accompanied by a massive augmentation in glucose uptake in TCR-stimulated CD4 and CD8 lymphocytes. Finally, we determined that the apparent contradictory results obtained by Takenouchi et al were due to their monitoring of Glut-1 with a mAb that does not bind cells expressing endogenous Glut-1, including human erythrocytes that harbor 300,000 copies per cell. Conclusion Transfection of Glut-1 directly correlates with the capacities of HTLV-1 and HTLV-2 envelope-derived ligands to bind cells. Moreover, Glut-1 is induced by TCR engagement, resulting in massive increases in glucose uptake and binding of HTLV-1 and -2 envelopes to both CD4 and CD8 T lymphocytes. Therefore, Glut-1 is a primary binding receptor for HTLV-1 and HTLV-2 envelopes on activated CD4 as well as CD8 lymphocytes. PMID:17504522

A potential link between insulin signaling and GLUT4 translocation: Association of Rab10-GTP with the exocyst subunit Exoc6/6b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sano, Hiroyuki; Peck, Grantley R.; Blachon, Stephanie

Insulin increases glucose transport in fat and muscle cells by stimulating the exocytosis of specialized vesicles containing the glucose transporter GLUT4. This process, which is referred to as GLUT4 translocation, increases the amount of GLUT4 at the cell surface. Previous studies have provided evidence that insulin signaling increases the amount of Rab10-GTP in the GLUT4 vesicles and that GLUT4 translocation requires the exocyst, a complex that functions in the tethering of vesicles to the plasma membrane, leading to exocytosis. In the present study we show that Rab10 in its GTP form binds to Exoc6 and Exoc6b, which are the twomore » highly homologous isotypes of an exocyst subunit, that both isotypes are found in 3T3-L1 adipocytes, and that knockdown of Exoc6, Exoc6b, or both inhibits GLUT4 translocation in 3T3-L1 adipocytes. These results suggest that the association of Rab10-GTP with Exoc6/6b is a molecular link between insulin signaling and the exocytic machinery in GLUT4 translocation. - Highlights: • Insulin stimulates the fusion of vesicles containing GLUT4 with the plasma membrane. • This requires vesicular Rab10-GTP and the exocyst plasma membrane tethering complex. • We find that Rab10-GTP associates with the Exoc6 subunit of the exocyst. • We find that knockdown of Exoc6 inhibits fusion of GLUT4 vesicles with the membrane. • The interaction of Rab10-GTP with Exoc6 potentially links signaling to exocytosis.« less

Geniposide promotes autophagy to inhibit insulin resistance in HepG2 cells via P62/NF-κB/GLUT-4

PubMed Central

Jiang, Hongwei; Ma, Yujin; Yan, Junqiang; Liu, Jie; Li, Liping

2017-01-01

Insulin resistance (IR) is known to be an important factor, which can lead to the onset of type 2 diabetes. Autophagy is a cellular process, which sequesters senescent or damaged proteins in autophagosomes for recycling of their products. Insulin and intracellular molecules, including mammalian target of rapamycin (mTOR), are well-known inhibitors of autophagy. In patients with type 2 diabetes, the expression levels of glucose transporter 4 (GLUT-4) in skeletal muscles are significantly decreased, indicating decreased glucose-processing ability. Geniposide is an iridoid compound isolated from Gardenia jasminoides Ellis. Previously, it was reported that geniposide significantly promoted glucose uptake. In the present study, a HepG2 cell model of IR was constructed to determine whether geniposide can promote autophagy to inhibit insulin resistance in HepG2 cells via P62/nuclear factor (NF)-κB/GLUT-4. Cell proliferation was analyzed by performing an MTT assay, and the mRNA expression levels of NF-κB and GLUT-4 were assessed using semi-quantitative polymerase chain reaction and immunohistochemical staining. In addition, the protein levels of GLUT-4, P62 and phosphorylated-P65 were assessed by western blotting. The expression of GLUT-4 was initially increased following geniposide treatment, decreasing in time to its lowest level at 8 h. The expression levels of NF-κB and GLUT-4 in the IR cells treated with and without geniposide were significantly different, compared with those in the control group. Geniposide promoted autophagy in the IR HepG2 cells and significantly improved IR in the HepG2 cells, which may be associated with the dynamic regulation of the P62/NF-κB/GLUT-4 pathway. PMID:28944847

Effects of continuous low-carbohydrate diet after long-term exercise on GLUT-4 protein content in rat skeletal muscle.

PubMed

Kubota, M; Koshinaka, K; Kawata, Y; Koike, T; Oshida, Y

2008-01-01

Stimulation of AMPK and decreased glycogen levels in skeletal muscle have a deep involvement in enhanced insulin action and GLUT-4 protein content after exercise training. The present study examined the chronic effects of a continuous low-carbohydrate diet after long-term exercise on GLUT-4 protein content, glycogen content, AMPK, and insulin signaling in skeletal muscle. Rats were divided randomly into four groups: normal chow diet sedentary (N-Sed), low carbohydrate diet sedentary (L-Sed), normal chow diet exercise (N-Ex), and low carbohydrate diet exercise (L-Ex) groups. Rats in the exercise groups (N-Ex and L-Ex) were exercised by swimming for 6 hours/day in two 3-hour bouts separated by 45 minutes of rest. The 10-day exercise training resulted in a significant increase in the GLUT-4 protein content (p<0.01). Additionally, the GLUT-4 protein content in L-Ex rats was increased by 29% above that in N-Ex rats (p<0.01). Finally, the glycogen content in skeletal muscle of L-Ex rats was decreased compared with that of N-Ex rats. Taken together, we suggest that the maintenance of glycogen depletion after exercise by continuous low carbohydrate diet results in the increment of the GLUT-4 protein content in skeletal muscle.

Insulin and leptin induce Glut4 plasma membrane translocation and glucose uptake in a human neuronal cell line by a phosphatidylinositol 3-kinase- dependent mechanism.

PubMed

Benomar, Yacir; Naour, Nadia; Aubourg, Alain; Bailleux, Virginie; Gertler, Arieh; Djiane, Jean; Guerre-Millo, Michèle; Taouis, Mohammed

2006-05-01

The insulin-sensitive glucose transporter Glut4 is expressed in brain areas that regulate energy homeostasis and body adiposity. In contrast with peripheral tissues, however, the impact of insulin on Glut4 plasma membrane (PM) translocation in neurons is not known. In this study, we examined the role of two anorexic hormones (leptin and insulin) on Glut4 translocation in a human neuronal cell line that express endogenous insulin and leptin receptors. We show that insulin and leptin both induce Glut4 translocation to the PM of neuronal cells and activate glucose uptake. Wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase, totally abolished insulin- and leptin-dependent Glut4 translocation and stimulation of glucose uptake. Thus, Glut4 translocation is a phosphatidylinositol 3-kinase-dependent mechanism in neuronal cells. Next, we investigated the impact of chronic insulin and leptin treatments on Glut4 expression and translocation. Chronic exposure of neuronal cells to insulin or leptin down-regulates Glut4 proteins and mRNA levels and abolishes the acute stimulation of glucose uptake in response to acute insulin or leptin. In addition, chronic treatment with either insulin or leptin impaired Glut4 translocation. A cross-desensitization between insulin and leptin was apparent, where exposure to insulin affects leptin-dependent Glut4 translocation and vice versa. This cross-desensitization could be attributed to the increase in suppressor of cytokine signaling-3 expression, which was demonstrated in response to each hormone. These results provide evidence to suggest that Glut4 translocation to neuronal PM is regulated by both insulin and leptin signaling pathways. These pathways might contribute to an in vivo glucoregulatory reflex involving a neuronal network and to the anorectic effect of insulin and leptin.

Combined creatine and protein supplementation in conjunction with resistance training promotes muscle GLUT-4 content and glucose tolerance in humans.

PubMed

Derave, Wim; Eijnde, Bert O; Verbessem, Patricia; Ramaekers, Monique; Van Leemputte, Mark; Richter, Erik A; Hespel, Peter

2003-05-01

The present study was undertaken to explore the effects of creatine and creatine plus protein supplementation on GLUT-4 and glycogen content of human skeletal muscle. This was investigated in muscles undergoing a decrease (immobilization) and subsequent increase (resistance training) in activity level, compared with muscles with unaltered activity pattern. A double-blind, placebo-controlled trial was performed by 33 young healthy subjects. The subjects' right legs were immobilized with a cast for 2 wk, followed by a 6-wk resistance training program for the right knee extensor muscles. The participants were supplemented throughout the study with either placebo (Pl group) or creatine (Cr group) or with creatine during immobilization and creatine plus protein during retraining (Cr+P group). Needle biopsies were bilaterally taken from the vastus lateralis. GLUT-4 protein expression was reduced by the immobilization in all groups (P < 0.05). During retraining, GLUT-4 content increased (P < 0.05) in both Cr (+24%) and Cr+P (+33%), which resulted in higher posttraining GLUT-4 expression compared with Pl (P < 0.05). Compared with Pl, muscle glycogen content was higher (P < 0.05) in the trained leg in both Cr and Cr+P. Supplements had no effect on GLUT-4 expression or glycogen content in contralateral control legs. Area under the glucose curve during the oral glucose tolerance test was decreased from 232 +/- 23 mmol. l(-1). min(-1) at baseline to 170 +/- 23 mmol. l(-1). min(-1) at the end of the retraining period in Cr+P (P < 0.05), but it did not change in Cr or Pl. We conclude that creatine intake stimulates GLUT-4 and glycogen content in human muscle only when combined with changes in habitual activity level. Furthermore, combined protein and creatine supplementation improved oral glucose tolerance, which is supposedly unrelated to the changes in muscle GLUT-4 expression.

Targeting of GLUT1-GLUT5 chimeric proteins in the polarized cell line Caco-2.

PubMed

Inukai, K; Takata, K; Asano, T; Katagiri, H; Ishihara, H; Nakazaki, M; Fukushima, Y; Yazaki, Y; Kikuchi, M; Oka, Y

1997-04-01

Caco-2, a human differentiated intestinal epithelial cell line, is a promising model for investigating the mechanism of polarized targeting of apical and basolateral membrane proteins. We stably transfected rat GLUT5 cDNA and rabbit GLUT1 cDNA into Caco-2 cells with an expression vector. Immunohistochemical study revealed that the GLUT5 protein expressed was localized at apical membranes and that the GLUT1 expressed was present primarily in the basolateral membranes of cells grown on permeable support. Next, to investigate the domain responsible for determining apical vs. basolateral sorting in glucose transporters, we prepared several GLUT1-GLUT5 chimeric cDNAs and transfected them into Caco-2 cells. A GLUT1 [N terminus approximately sixth transmembrane domain (TM6)]-GLUT5 [intracellular loop (IL) approximately C terminus] chimera was observed exclusively at the apical membrane, while GLUT1 (N terminus approximately IL)-GLUT5 (TM7 approximately C terminus) and GLUT1 (N terminus approximately TM12)-GLUT5 (C-terminal domain) chimeras were observed mainly at the basolateral membrane, a localization similar to that of GLUT1. Moreover, using a recombinant adenovirus expression system, we expressed a GLUT5 (N terminus approximately TM6)-GLUT1(IL)-GLUT5(TM7 approximately C-terminus) chimera, which was observed at the basolateral membrane. Based on these results, the C-terminal domain does not determine isoform-specific targeting of GLUT1 and GLUT5. Rather, it is the intracellular loop in glucose transporters that appears to play a pivotal role in apical-basolateral sorting signals in Caco-2 cells.

Regulation of intracellular trafficking and secretion of adiponectin by myosin II.

PubMed

Bedi, Deepa; Dennis, John C; Morrison, Edward E; Braden, Tim D; Judd, Robert L

2017-08-19

Adiponectin is a protein secreted by white adipocytes that plays an important role in insulin action, energy homeostasis and the development of atherosclerosis. The intracellular localization and trafficking of GLUT4 and leptin in adipocytes has been well studied, but little is known regarding the intracellular trafficking of adiponectin. Recent studies have demonstrated that constitutive adiponectin secretion is dependent on PIP2 levels and the integrity of cortical F-actin. Non-muscle myosin II is an actin-based motor that is associated with membrane vesicles and participates in vesicular trafficking in mammalian cells. Therefore, we investigated the role of myosin II in the trafficking and secretion of adiponectin in 3T3-L1 adipocytes. Confocal microscopy revealed that myosin IIA and IIB were dispersed throughout the cytoplasm of the adipocyte. Both myosin isoforms were localized in the Golgi/TGN region as evidenced by colocalization with the cis-Golgi marker, p115 and the trans-Golgi marker, γ-adaptin. Inhibition of myosin II activity by blebbistatin or actin depolymerization by latrunculin B dispersed myosin IIA and IIB towards the periphery while significantly inhibiting adiponectin secretion. Therefore, the constitutive trafficking and secretion of adiponectin in 3T3-L1 adipocytes occurs by an actin-dependent mechanism that involves the actin-based motors, myosin IIA and IIB. Copyright © 2017 Elsevier Inc. All rights reserved.

Upregulation of GLUT-4 in right ventricle of rats with monocrotaline-induced pulmonary hypertension.

PubMed

Broderick, Tom L; King, Tiffany M

2008-12-01

Pulmonary hypertension is characterized by abnormal vascular remodeling leading to occlusion of pulmonary arteries and increased stress placed on the right ventricle (RV). This causes the RV to hypertrophy and eventually to failure. This study was designed to examine the effects of pulmonary hypertension in rats on right ventricular remodeling and glucose transporter protein (GLUT4) content in right (RV) and left ventricle (LV). Pulmonary hypertension was induced in male Sprague-Dawley rat by a single subcutaneous injection of monocrotaline (MCT) at the concentration of 60 mg/kg. Forty-six days following the injection of MCT, animals were sacrificed. MCT-treated rats displayed significant increases in lung weight and RV weight. Marked RV hypertrophy was evident as the ratio of the RV to LV plus septum weight was nearly 40% higher in MCT-treated rats compared to control rats. Total GLUT4 content from whole homogenates from the RV was increased by approximately 28% in MCT-treated hearts compared to control hearts. No differences, however, in the LV content between groups were observed. Our findings indicate that the structural remodeling of the RV in MCT-induced pulmonary hypertension results in the upregulation of glucose transporters. This increase in RV GLUT4 levels may potentially result in alterations in substrate energy metabolism.

Insulin elicits a ROS-activated and an IP₃-dependent Ca²⁺ release, which both impinge on GLUT4 translocation.

PubMed

Contreras-Ferrat, Ariel; Llanos, Paola; Vásquez, César; Espinosa, Alejandra; Osorio-Fuentealba, César; Arias-Calderon, Manuel; Lavandero, Sergio; Klip, Amira; Hidalgo, Cecilia; Jaimovich, Enrique

2014-05-01

Insulin signaling includes generation of low levels of H2O2; however, its origin and contribution to insulin-stimulated glucose transport are unknown. We tested the impact of H2O2 on insulin-dependent glucose transport and GLUT4 translocation in skeletal muscle cells. H2O2 increased the translocation of GLUT4 with an exofacial Myc-epitope tag between the first and second transmembrane domains (GLUT4myc), an effect additive to that of insulin. The anti-oxidants N-acetyl L-cysteine and Trolox, the p47(phox)-NOX2 NADPH oxidase inhibitory peptide gp91-ds-tat or p47(phox) knockdown each reduced insulin-dependent GLUT4myc translocation. Importantly, gp91-ds-tat suppressed insulin-dependent H2O2 production. A ryanodine receptor (RyR) channel agonist stimulated GLUT4myc translocation and insulin stimulated RyR1-mediated Ca(2+) release by promoting RyR1 S-glutathionylation. This pathway acts in parallel to insulin-mediated stimulation of inositol-1,4,5-trisphosphate (IP3)-activated Ca(2+) channels, in response to activation of phosphatidylinositol 3-kinase and its downstream target phospholipase C, resulting in Ca(2+) transfer to the mitochondria. An inhibitor of IP3 receptors, Xestospongin B, reduced both insulin-dependent IP3 production and GLUT4myc translocation. We propose that, in addition to the canonical α,β phosphatidylinositol 3-kinase to Akt pathway, insulin engages both RyR-mediated Ca(2+) release and IP3-receptor-mediated mitochondrial Ca(2+) uptake, and that these signals jointly stimulate glucose uptake.

Effects of high-intensity swimming training on GLUT-4 and glucose transport activity in rat skeletal muscle.

PubMed

Terada, S; Yokozeki, T; Kawanaka, K; Ogawa, K; Higuchi, M; Ezaki, O; Tabata, I

2001-06-01

This study was performed to assess the effects of short-term, extremely high-intensity intermittent exercise training on the GLUT-4 content of rat skeletal muscle. Three- to four-week-old male Sprague-Dawley rats with an initial body weight ranging from 45 to 55 g were used for this study. These rats were randomly assigned to an 8-day period of high-intensity intermittent exercise training (HIT), relatively high-intensity intermittent prolonged exercise training (RHT), or low-intensity prolonged exercise training (LIT). Age-matched sedentary rats were used as a control. In the HIT group, the rats repeated fourteen 20-s swimming bouts with a weight equivalent to 14, 15, and 16% of body weight for the first 2, the next 4, and the last 2 days, respectively. Between exercise bouts, a 10-s pause was allowed. RHT consisted of five 17-min swimming bouts with a 3-min rest between bouts. During the first bout, the rat swam without weight, whereas during the following four bouts, the rat was attached to a weight equivalent to 4 and 5% of its body weight for the first 5 days and the following 3 days, respectively. Rats in the LIT group swam 6 h/day for 8 days in two 3-h bouts separated by 45 min of rest. In the first experiment, the HIT, LIT, and control rats were compared. GLUT-4 content in the epitrochlearis muscle in the HIT and LIT groups after training was significantly higher than that in the control rats by 83 and 91%, respectively. Furthermore, glucose transport activity, stimulated maximally by both insulin (2 mU/ml) (HIT: 48%, LIT: 75%) and contractions (25 10-s tetani) (HIT: 55%, LIT: 69%), was higher in the training groups than in the control rats. However, no significant differences in GLUT-4 content or in maximal glucose transport activity in response to both insulin and contractions were observed between the two training groups. The second experiment demonstrated that GLUT-4 content after HIT did not differ from that after RHT (66% higher in trained rats than

Intracellular Trafficking Network of Protein Nanocapsules: Endocytosis, Exocytosis and Autophagy.

PubMed

Zhang, Jinxie; Zhang, Xudong; Liu, Gan; Chang, Danfeng; Liang, Xin; Zhu, Xianbing; Tao, Wei; Mei, Lin

2016-01-01

The inner membrane vesicle system is a complex transport system that includes endocytosis, exocytosis and autophagy. However, the details of the intracellular trafficking pathway of nanoparticles in cells have been poorly investigated. Here, we investigate in detail the intracellular trafficking pathway of protein nanocapsules using more than 30 Rab proteins as markers of multiple trafficking vesicles in endocytosis, exocytosis and autophagy. We observed that FITC-labeled protein nanoparticles were internalized by the cells mainly through Arf6-dependent endocytosis and Rab34-mediated micropinocytosis. In addition to this classic pathway: early endosome (EEs)/late endosome (LEs) to lysosome, we identified two novel transport pathways: micropinocytosis (Rab34 positive)-LEs (Rab7 positive)-lysosome pathway and EEs-liposome (Rab18 positive)-lysosome pathway. Moreover, the cells use slow endocytosis recycling pathway (Rab11 and Rab35 positive vesicles) and GLUT4 exocytosis vesicles (Rab8 and Rab10 positive) transport the protein nanocapsules out of the cells. In addition, protein nanoparticles are observed in autophagosomes, which receive protein nanocapsules through multiple endocytosis vesicles. Using autophagy inhibitor to block these transport pathways could prevent the degradation of nanoparticles through lysosomes. Using Rab proteins as vesicle markers to investigation the detail intracellular trafficking of the protein nanocapsules, will provide new targets to interfere the cellular behaver of the nanoparticles, and improve the therapeutic effect of nanomedicine.

Saffron with resistance exercise improves diabetic parameters through the GLUT4/AMPK pathway in-vitro and in-vivo

PubMed Central

Dehghan, Firouzeh; Hajiaghaalipour, Fatemeh; Yusof, Ashril; Muniandy, Sekaran; Hosseini, Seyed Ali; Heydari, Sedigheh; Salim, Landa Zeenelabdin Ali; Azarbayjani, Mohammad Ali

2016-01-01

Saffron is consumed as food and medicine to treat several illnesses. This study elucidates the saffron effectiveness on diabetic parameters in-vitro and combined with resistance exercise in-vivo. The antioxidant properties of saffron was examined. Insulin secretion and glucose uptake were examined by cultured RIN-5F and L6 myotubes cells. The expressions of GLUT2, GLUT4, and AMPKα were determined by Western blot. Diabetic and non-diabetic male rats were divided into: control, training, extract treatment, training + extract treatment and metformin. The exercise and 40 mg/kg/day saffron treatments were carried out for six weeks. The antioxidant capacity of saffron was higher compare to positive control (P < 0.01). High dose of saffron stimulated insulin release in RIN-5F cells and improved glucose uptake in L6 myotubes. GLUT4 and AMPKα expressions increased in both doses of saffron (P < 0.01), whereas GLUT2 not changed (p > 0.05). Serum glucose, cholesterol, triglyceride, low-density lipoprotein, very low-density lipoprotein, insulin resistance, and glycated hemoglobin levels decreased in treated rats compared to untreated (p < 0.01). However, no significant differences were observed in the high-density lipoprotein, insulin, adiponectin, and leptin concentration levels in all groups (p > 0.05). The findings suggest that saffron consuming alongside exercise could improve diabetic parameters through redox-mediated mechanisms and GLUT4/AMPK pathway to entrap glucose uptake. PMID:27122001

Soybean and sunflower oil-induced insulin resistance correlates with impaired GLUT4 protein expression and translocation specifically in white adipose tissue.

PubMed

Poletto, Ana Cláudia; Anhê, Gabriel Forato; Eichler, Paula; Takahashi, Hilton Kenji; Furuya, Daniela Tomie; Okamoto, Maristela Mitiko; Curi, Rui; Machado, Ubiratan Fabres

2010-03-01

Free fatty acids are known for playing a crucial role in the development of insulin resistance. High fat intake is known for impairing insulin sensitivity; however, the effect of vegetable-oil injections have never been investigated. The present study investigated the effects of daily subcutaneous injections (100 microL) of soybean (SB) and sunflower (SF) oils, during 7 days. Both treated groups developed insulin resistance as assessed by insulin tolerance test. The mechanism underlying the SB- and SF-induced insulin resistance was shown to involve GLUT4. In SB- and SF-treated animals, the GLUT4 protein expression was reduced approximately 20% and 10 min after an acute in vivo stimulus with insulin, the plasma membrane GLUT4 content was approximately 60% lower in white adipose tissue (WAT). No effects were observed in skeletal muscle. Additionally, both oil treatments increased mainly the content of palmitic acid ( approximately 150%) in WAT, which can contribute to explain the GLUT4 regulations. Altogether, the present study collects evidence that those oil treatments might generate insulin resistance by targeting GLUT4 expression and translocation specifically in WAT. These alterations are likely to be caused due to the specific local increase in saturated fatty acids that occurred as a consequence of oil daily injections. 2010 John Wiley & Sons, Ltd.

Exercise-induced muscle glucose uptake in mice with graded, muscle-specific GLUT-4 deletion.

PubMed

Howlett, Kirsten F; Andrikopoulos, Sofianos; Proietto, Joseph; Hargreaves, Mark

2013-08-01

To investigate the importance of the glucose transporter GLUT-4 for muscle glucose uptake during exercise, transgenic mice with skeletal muscle GLUT-4 expression approximately 30-60% of normal (CON) and approximately 5-10% of normal (KO) were generated using the Cre/Lox system and compared with wild-type (WT) mice during approximately 40 min of treadmill running (KO: 37.7 ± 1.3 min; WT: 40 min; CON: 40 min, P = 0.18). In WT and CON animals, exercise resulted in an overall increase in muscle glucose uptake. More specifically, glucose uptake was increased in red gastrocnemius of WT mice and in the soleus and red gastrocnemius of CON mice. In contrast, the exercise-induced increase in muscle glucose uptake in all muscles was completely abolished in KO mice. Muscle glucose uptake increased during exercise in both red and white quadriceps of WT mice, while the small increases in CON mice were not statistically significant. In KO mice, there was no change at all in quadriceps muscle glucose uptake. No differences in muscle glycogen use during exercise were observed between any of the groups. However, there was a significant increase in plasma glucose levels after exercise in KO mice. The results of this study demonstrated that a reduction in skeletal muscle GLUT-4 expression to approximately 10% of normal levels completely abolished the exercise-induced increase in muscle glucose uptake.

Methotrexate increases skeletal muscle GLUT4 expression and improves metabolic control in experimental diabetes

USDA-ARS?s Scientific Manuscript database

Long-term administration of 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) mimics the effects of endurance exercise by activating AMP kinase and by increasing skeletal muscle expression of GLUT4 glucose transporter. AICAR is an intermediate in the purine de novo synthesis, and its tissue conc...

Diadenosine tetraphosphate (Ap4A) induces a diabetogenic situation: its impact on blood glucose, plasma insulin, gluconeogenesis, glucose uptake and GLUT-4 transporters.

PubMed

Verspohl, E J; Hohmeier, N; Lempka, M

2003-12-01

Diadenosine polyphosphates such as Ap4A are physiologically released compounds for which both receptors as well as a role as second messengers for influencing insulin release have been shown. So far little is known about their pathophysiological impact on diabetes with respect to blood glucose and plasma insulin, glucose production via gluconeogenesis, glucose uptake and GLUT-4 expression. Rats given an intravenous bolus of Ap4A (0.75 mg/kg) developed a rapid and dramatic increase in blood glucose. Plasma insulin was only transiently increased (for 4 min), but did not follow the normally stimulatory effect of the elevated blood glucose. A bolus of 25 microg Ap4A quickly increased glucose release from perfused rat liver. Glucose uptake was reduced in 3T3 adipocytes. Reduced amounts of translocated GLUT-4 were found in 3T3 cell membranes incubated with 10 microM Ap4A. Thus, Ap4A itself induces a diabetic situation which is likely to be mediated by an increase in gluconeogenesis and/or an insulin resistance caused by a decrease in GLUT-4 and an attenuation of glucose uptake.

Correlation of Glut-1 and Glut-3 expression with F-18 FDG uptake in pulmonary inflammatory lesions

PubMed Central

Wang, Zhen Guang; Yu, Ming Ming; Han, Yu; Wu, Feng Yu; Yang, Guang Jie; Li, Da Cheng; Liu, Si Min

2016-01-01

Abstract The aim of the study was to investigate the correlation of glucose transporter-1 (Glut-1) and glucose transporter-3 (Glut-3) expression with F-18 FDG uptake in pulmonary inflammatory lesions. Twenty-two patients with pulmonary inflammatory lesions underwent positron emission tomography/computed tomography (PET/CT) examination preoperatively, and Glut-1 and Glut-3 expression were detected by immunohistochemistry in these lesions. Correlations of Glut-1 and Glut-3 with 18F-FDG uptake were assessed using Spearman's rank correlation test. The maximum standardized uptake value (SUVmax) of pulmonary inflammatory lesions in 22 patients was 0.50 to 7.50, with a mean value of 3.66 ± 1.62. Immunohistochemical staining scores of Glut-1 and Glut-3 were 2.18 ± 0.96 and 2.82 ± 1.37, respectively. The expression of Glut-1 and Glut-3 was positively correlated with F-18 FDG uptake. Glut-3 expression was evidently higher than Glut-1 expression in 22 patients. Glut-1 and Glut-3 expressions are high in pulmonary inflammatory lesions, and Glut-3 plays a more important role in F-18 FDG uptake in pulmonary inflammatory lesions. PMID:27902598

SLC2A8 (GLUT8) is a mammalian trehalose transporter required for trehalose-induced autophagy.

PubMed

Mayer, Allyson L; Higgins, Cassandra B; Heitmeier, Monique R; Kraft, Thomas E; Qian, Xia; Crowley, Jan R; Hyrc, Krzysztof L; Beatty, Wandy L; Yarasheski, Kevin E; Hruz, Paul W; DeBosch, Brian J

2016-12-06

Trehalose is a disaccharide demonstrated to mitigate disease burden in multiple murine neurodegenerative models. We recently revealed that trehalose rapidly induces hepatic autophagy and abrogates hepatic steatosis by inhibiting hexose transport via the SLC2A family of facilitative transporters. Prior studies, however, postulate that intracellular trehalose is sufficient to induce cellular autophagy. The objective of the current study was to identify the means by which trehalose accesses the hepatocyte cytoplasm, and define the distal signaling mechanisms by which trehalose induces autophagy. We provide gas chromatographic/mass spectrometric, fluorescence microscopic and radiolabeled uptake evidence that trehalose traverses the plasma membrane via SLC2A8 (GLUT8), a homolog of the trehalose transporter-1 (Tret1). Moreover, GLUT8-deficient hepatocytes and GLUT8-deficient mice exposed to trehalose resisted trehalose-induced AMP-activated protein kinase (AMPK) phosphorylation and autophagic induction in vitro and in vivo. Although trehalose profoundly attenuated mTORC1 signaling, trehalose-induced mTORC1 suppression was insufficient to activate autophagy in the absence of AMPK or GLUT8. Strikingly, transient, heterologous Tret1 overexpression reconstituted autophagic flux and AMPK signaling defects in GLUT8-deficient hepatocyte cultures. Together, these data suggest that cytoplasmic trehalose access is carrier-mediated, and that GLUT8 is a mammalian trehalose transporter required for hepatocyte trehalose-induced autophagy and signal transduction.

GLUT2 Accumulation in Enterocyte Apical and Intracellular Membranes

PubMed Central

Ait-Omar, Amal; Monteiro-Sepulveda, Milena; Poitou, Christine; Le Gall, Maude; Cotillard, Aurélie; Gilet, Jules; Garbin, Kevin; Houllier, Anne; Château, Danièle; Lacombe, Amélie; Veyrie, Nicolas; Hugol, Danielle; Tordjman, Joan; Magnan, Christophe; Serradas, Patricia; Clément, Karine; Leturque, Armelle; Brot-Laroche, Edith

2011-01-01

OBJECTIVE In healthy rodents, intestinal sugar absorption in response to sugar-rich meals and insulin is regulated by GLUT2 in enterocyte plasma membranes. Loss of insulin action maintains apical GLUT2 location. In human enterocytes, apical GLUT2 location has not been reported but may be revealed under conditions of insulin resistance. RESEARCH DESIGN AND METHODS Subcellular location of GLUT2 in jejunal enterocytes was analyzed by confocal and electron microscopy imaging and Western blot in 62 well-phenotyped morbidly obese subjects and 7 lean human subjects. GLUT2 locations were assayed in ob/ob and ob/+ mice receiving oral metformin or in high-fat low-carbohydrate diet–fed C57Bl/6 mice. Glucose absorption and secretion were respectively estimated by oral glucose tolerance test and secretion of [U-14C]-3-O-methyl glucose into lumen. RESULTS In human enterocytes, GLUT2 was consistently located in basolateral membranes. Apical GLUT2 location was absent in lean subjects but was observed in 76% of obese subjects and correlated with insulin resistance and glycemia. In addition, intracellular accumulation of GLUT2 with early endosome antigen 1 (EEA1) was associated with reduced MGAT4a activity (glycosylation) in 39% of obese subjects on a low-carbohydrate/high-fat diet. Mice on a low-carbohydrate/high-fat diet for 12 months also exhibited endosomal GLUT2 accumulation and reduced glucose absorption. In ob/ob mice, metformin promoted apical GLUT2 and improved glucose homeostasis. Apical GLUT2 in fasting hyperglycemic ob/ob mice tripled glucose release into intestinal lumen. CONCLUSIONS In morbidly obese insulin-resistant subjects, GLUT2 was accumulated in apical and/or endosomal membranes of enterocytes. Functionally, apical GLUT2 favored and endosomal GLUT2 reduced glucose transepithelial exchanges. Thus, altered GLUT2 locations in enterocytes are a sign of intestinal adaptations to human metabolic pathology. PMID:21852673

CLIC4 regulates cell adhesion and β1 integrin trafficking.

PubMed

Argenzio, Elisabetta; Margadant, Coert; Leyton-Puig, Daniela; Janssen, Hans; Jalink, Kees; Sonnenberg, Arnoud; Moolenaar, Wouter H

2014-12-15

Chloride intracellular channel protein 4 (CLIC4) exists in both soluble and membrane-associated forms, and is implicated in diverse cellular processes, ranging from ion channel formation to intracellular membrane remodeling. CLIC4 is rapidly recruited to the plasma membrane by lysophosphatidic acid (LPA) and serum, suggesting a possible role for CLIC4 in exocytic-endocytic trafficking. However, the function and subcellular target(s) of CLIC4 remain elusive. Here, we show that in HeLa and MDA-MB-231 cells, CLIC4 knockdown decreases cell-matrix adhesion, cell spreading and integrin signaling, whereas it increases cell motility. LPA stimulates the recruitment of CLIC4 to β1 integrin at the plasma membrane and in Rab35-positive endosomes. CLIC4 is required for both the internalization and the serum- or LPA-induced recycling of β1 integrin, but not for EGF receptor trafficking. Furthermore, we show that CLIC4 suppresses Rab35 activity and antagonizes Rab35-dependent regulation of β1 integrin trafficking. Our results define CLIC4 as a regulator of Rab35 activity and serum- and LPA-dependent integrin trafficking. © 2014. Published by The Company of Biologists Ltd.

Effects of space flight on GLUT-4 content in rat plantaris muscle

NASA Astrophysics Data System (ADS)

Tabata, I.; Kawanaka, Kentaro; Sekiguchi, Chiharu; Nagaoka, Shunji; Ohira, Yoshinobu

The effects of 14 days of space flight on the glucose transporter protein (GLUT-4) were studied in the plantaris muscle of growing 9-week-old, male Sprague Dawley rats. The rats were randomly separated into five groups: pre-flight vivarium ground controls (PF-VC) sacrificed approximately 2 h after launch; flight groups sacrificed either approximately 5 h (F-R0) or 9 days (F-R9) after the return from space; and synchronous ground controls (SC-R0 and SC-R9) sacrificed at the same time as the respective flight groups. The flight groups F-R0 and F-R9 were exposed to micro-gravity for 14 days in the Spacelab module located in the cargo bay of the shuttle transport system - 58 of the manned Space Shuttle for the NASA mission named ''Spacelab Life Sciences 2''. Body weight and plantaris weight of SC-R0 and F-R0 were significantly higher than those of PF-VC. Neither body weight nor plantaris muscle weight in either group had changed 9 days after the return from space. As a result, body weight and plantaris muscle weight did not differ between the flight and synchronous control groups at any of the time points investigated. The GLUT-4 content (cpm/µg membrane protein) in the plantaris muscle did not show any significant change in response to 14 days of space flight or 9 days after return. Similarly, citrate synthase activity did not change during the course of the space flight or the recovery period. These results suggest that 14 days of space flight does not affect muscle mass or GLUT-4 content of the fast-twitch plantaris muscle in the rat.

Glucose Transporters in Diabetic Kidney Disease-Friends or Foes?

PubMed

Wasik, Anita A; Lehtonen, Sanna

2018-01-01

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes and a common cause of end-stage renal disease worldwide. DKD manifests as an increased urinary protein excretion (albuminuria). Multiple studies have shown that insulin resistance correlates with the development of albuminuria in non-diabetic and diabetic patients. There is also accumulating evidence that glomerular epithelial cells or podocytes are insulin sensitive and that insulin signaling in podocytes is essential for maintaining normal kidney function. At the cellular level, the mechanisms leading to the development of insulin resistance include mutations in the insulin receptor gene, impairments in the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway, or perturbations in the trafficking of glucose transporters (GLUTs), which mediate the uptake of glucose into cells. Podocytes express several GLUTs, including GLUT1, GLUT2, GLUT3, GLUT4, and GLUT8. Of these, the most studied ones are GLUT1 and GLUT4, both shown to be insulin responsive in podocytes. In the basal state, GLUT4 is preferentially located in perinuclear and cytosolic vesicular structures and to a lesser extent at the plasma membrane. After insulin stimulation, GLUT4 is sorted into GLUT4-containing vesicles (GCVs) that translocate to the plasma membrane. GCV trafficking consists of several steps, including approaching of the GCVs to the plasma membrane, tethering, and docking, after which the lipid bilayers of the GCVs and the plasma membrane fuse, delivering GLUT4 to the cell surface for glucose uptake into the cell. Studies have revealed novel molecular regulators of the GLUT trafficking in podocytes and unraveled unexpected roles for GLUT1 and GLUT4 in the development of DKD, summarized in this review. These findings pave the way for better understanding of the mechanistic pathways associated with the development and progression of DKD and aid in the development of new treatments for this devastating disease.

Exercise-induced muscle glucose uptake in mice with graded, muscle-specific GLUT-4 deletion

PubMed Central

Howlett, Kirsten F; Andrikopoulos, Sofianos; Proietto, Joseph; Hargreaves, Mark

2013-01-01

To investigate the importance of the glucose transporter GLUT-4 for muscle glucose uptake during exercise, transgenic mice with skeletal muscle GLUT-4 expression approximately 30–60% of normal (CON) and approximately 5–10% of normal (KO) were generated using the Cre/Lox system and compared with wild-type (WT) mice during approximately 40 min of treadmill running (KO: 37.7 ± 1.3 min; WT: 40 min; CON: 40 min, P = 0.18). In WT and CON animals, exercise resulted in an overall increase in muscle glucose uptake. More specifically, glucose uptake was increased in red gastrocnemius of WT mice and in the soleus and red gastrocnemius of CON mice. In contrast, the exercise-induced increase in muscle glucose uptake in all muscles was completely abolished in KO mice. Muscle glucose uptake increased during exercise in both red and white quadriceps of WT mice, while the small increases in CON mice were not statistically significant. In KO mice, there was no change at all in quadriceps muscle glucose uptake. No differences in muscle glycogen use during exercise were observed between any of the groups. However, there was a significant increase in plasma glucose levels after exercise in KO mice. The results of this study demonstrated that a reduction in skeletal muscle GLUT-4 expression to approximately 10% of normal levels completely abolished the exercise-induced increase in muscle glucose uptake. PMID:24303141

GLUT3 protein and mRNA in autopsy muscle specimens

NASA Technical Reports Server (NTRS)

Stuart, C. A.; Wen, G.; Jiang, J.

1999-01-01

GLUT3 is expressed in rat muscle, but this glucose transporter protein has not been identified previously in adult human skeletal muscle. We quantified the rapidity of disappearance of mRNA and protein from human skeletal muscle at room temperature and at 4 degrees C. Fifty percent of the immunologically detectable GLUT3 protein disappeared by 1 hour at 20 degrees C and by 2 hours at 4 degrees C. mRNA for GLUT3 was decreased 50% by 2.2 hours at 20 degrees C and by 24 hours at 4 degrees C. Half of the measurable mRNAs for GLUT4, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), alpha-actin, and beta-myosin disappeared by 0.8 to 2.1 hours at 20 degrees C and by 5.0 to 16.6 hours at 4 degrees C. Previous conclusions that GLUT3 is not expressed in human muscle were likely drawn because of artifacts related to degradation of GLUT3 protein in the specimens prior to study. Because of the rapid degradation of protein and mRNA, autopsy specimens of muscle must be obtained within 6 hours of death, and even then, protein and mRNA data will likely dramatically underestimate their expression in fresh muscle. Some previously published conclusions and recommendations regarding autopsy specimens are not stringent enough to consistently yield useful protein and mRNA.

Expressions of IGF-1, ERK, GLUT4, IRS-1 in metabolic syndrome complicated with colorectal cancer and their associations with the clinical characteristics of CRC.

PubMed

Hu, Jianxia; Liu, Xiaoyi; Chi, Jingwei; Che, Kui; Feng, Yan; Zhao, Shihua; Wang, Zhongchao; Wang, Yangang

2018-01-01

Epidemiological data have revealed that colorectal cancer (CRC) risk is increased in patients with Metabolic syndrome. To explore the expressions of IGF-1, ERK, GLUT4, IRS-1 in MS patients with CRC and their associations with the clinical characteristics of CRC. We investigated the expressions of IGF-1, ERK, GLUT4 and IRS-1 in greater omental adipose tissues of 168 MS patients with/without CRC, 85 CRC patients without MS and 98 healthy controls by RT-PCR, and analyzed the relationships between their expressions and clinical characteristics of CRC. The expression levels of IGF-1 and ERK in MS patients with/without CRC were higher while the expression levels of GLUT4 were lower compared with CRC patients without MS and healthy controls (P< 0.01). The expression levels of IGF-1 and ERK in MS patients with CRC were higher while expression levels of GLUT4 were lower compared to MS patients without CRC (P< 0.01). Expression levels of ERK, IGF-1, GLUT4 were associated with clinical characteristics of CRC, including tumor size, distant metastasis and advanced stages (III/IV) (P< 0.05). Expressions of IGF-1, ERK and GLUT4 in greater omental adipose tissues might be useful biomarkers and predictive targets in the diagnosis of CRC.

Expression and phosphorylation of the AS160_v2 splice variant supports GLUT4 activation and the Warburg effect in multiple myeloma

PubMed Central

2013-01-01

Background Multiple myeloma (MM) is a fatal plasma cell malignancy exhibiting enhanced glucose consumption associated with an aerobic glycolytic phenotype (i.e., the Warburg effect). We have previously demonstrated that myeloma cells exhibit constitutive plasma membrane (PM) localization of GLUT4, consistent with the dependence of MM cells on this transporter for maintenance of glucose consumption rates, proliferative capacity, and viability. The purpose of this study was to investigate the molecular basis of constitutive GLUT4 plasma membrane localization in MM cells. Findings We have elucidated a novel mechanism through which myeloma cells achieve constitutive GLUT4 activation involving elevated expression of the Rab-GTPase activating protein AS160_v2 splice variant to promote the Warburg effect. AS160_v2-positive MM cell lines display constitutive Thr642 phosphorylation, known to be required for inactivation of AS160 Rab-GAP activity. Importantly, we show that enforced expression of AS160_v2 is required for GLUT4 PM translocation and activation in these select MM lines. Furthermore, we demonstrate that ectopic expression of a full-length, phospho-deficient AS160 mutant is sufficient to impair constitutive GLUT4 cell surface residence, which is characteristic of MM cells. Conclusions This is the first study to tie AS160 de-regulation to increased glucose consumption rates and the Warburg effect in cancer. Future studies investigating connections between the insulin/IGF-1/AS160_v2/GLUT4 axis and FDG-PET positivity in myeloma patients are warranted and could provide rationale for therapeutically targeting this pathway in MM patients with advanced disease. PMID:24280290

Podocyte-Specific GLUT4-Deficient Mice Have Fewer and Larger Podocytes and Are Protected From Diabetic Nephropathy

PubMed Central

Guzman, Johanna; Jauregui, Alexandra N.; Merscher-Gomez, Sandra; Maiguel, Dony; Muresan, Cristina; Mitrofanova, Alla; Diez-Sampedro, Ana; Szust, Joel; Yoo, Tae-Hyun; Villarreal, Rodrigo; Pedigo, Christopher; Molano, R. Damaris; Johnson, Kevin; Kahn, Barbara; Hartleben, Bjoern; Huber, Tobias B.; Saha, Jharna; Burke, George W.; Abel, E. Dale; Brosius, Frank C.; Fornoni, Alessia

2014-01-01

Podocytes are a major component of the glomerular filtration barrier, and their ability to sense insulin is essential to prevent proteinuria. Here we identify the insulin downstream effector GLUT4 as a key modulator of podocyte function in diabetic nephropathy (DN). Mice with a podocyte-specific deletion of GLUT4 (G4 KO) did not develop albuminuria despite having larger and fewer podocytes than wild-type (WT) mice. Glomeruli from G4 KO mice were protected from diabetes-induced hypertrophy, mesangial expansion, and albuminuria and failed to activate the mammalian target of rapamycin (mTOR) pathway. In order to investigate whether the protection observed in G4 KO mice was due to the failure to activate mTOR, we used three independent in vivo experiments. G4 KO mice did not develop lipopolysaccharide-induced albuminuria, which requires mTOR activation. On the contrary, G4 KO mice as well as WT mice treated with the mTOR inhibitor rapamycin developed worse adriamycin-induced nephropathy than WT mice, consistent with the fact that adriamycin toxicity is augmented by mTOR inhibition. In summary, GLUT4 deficiency in podocytes affects podocyte nutrient sensing, results in fewer and larger cells, and protects mice from the development of DN. This is the first evidence that podocyte hypertrophy concomitant with podocytopenia may be associated with protection from proteinuria. PMID:24101677

MicroRNA-33b-5p is overexpressed and inhibits GLUT4 by targeting HMGA2 in polycystic ovarian syndrome: An in vivo and in vitro study.

PubMed

Yang, Ying; Jiang, Hua; Xiao, Ling; Yang, Xuezhou

2018-06-01

Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disease, but its pathogenesis remains largely unknown. The present study explored the role of microRNA‑33b‑5p (miR‑33b‑5p) in PCOS pathogenesis, with a particular focus on its role in regulating glucose transporter 4 (GLUT4). A rat model of PCOS was developed by injecting female SD rats with insulin and HCG. miR‑33b‑5p, GLUT4, sterol regulatory element‑binding protein 1 (SREBF1), and high mobility group A2 (HMGA2) expression in rat ovarian tissues was examined by qRT‑PCR and immunohistochemistry. The effect of a high dose of either glucose or insulin on miR‑33b‑5p, GLUT4, SREBF1 and HMGA2 expression was also examined in cultured adipocytes by qRT‑PCR and western blotting. Additionally, the luciferase reporter assay and chromatin immunoprecipitation (ChIP) were used to explore the role of miR‑33b‑5p in regulating HMGA2, SREBF‑1 and/or GLUT4. Elevated levels of miR‑33b‑5p expression were detected in the ovarian tissues of insulin resistant PCOS rats, and those levels were negatively correlated with those of GLUT4, HMGA2 and SREBF1 expression (P<0.05). Immunohistochemistry studies revealed that GLUT4, SREBF1, and HMGA2 expression levels in the ovarian tissues of insulin resistant PCOS rats were significantly lower than those in other groups of rats. In cultured adipocytes, excess extracellular glucose or insulin increased miR‑33b‑5p expression but reduced GLUT4, SREBF1 and HMGA2 expression, whereas the levels of GLUT4, SREBF1 and HMGA2 were elevated by inhibition of miR‑33b‑5. HMGA2 could directly bind to the 5'‑promoter region of GLUT4 and promote its expression, and could also promote SREBF1 expression. Moreover, SREBF1 could also directly bind to the 5'‑promoter region of GLUT4 and promote its expression. Our findings revealed that miR‑33b‑5p was overexpressed in the ovarian tissues of insulin resistant PCOS rats, and thus may play an important

Effects of AICAR and exercise on insulin-stimulated glucose uptake, signaling, and GLUT-4 content in rat muscles.

PubMed

Jessen, Niels; Pold, Rasmus; Buhl, Esben S; Jensen, Lasse S; Schmitz, Ole; Lund, Sten

2003-04-01

Physical activity is known to increase insulin action in skeletal muscle, and data have indicated that 5'-AMP-activated protein kinase (AMPK) is involved in the molecular mechanisms behind this beneficial effect. 5-Aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR) can be used as a pharmacological tool to repetitively activate AMPK, and the objective of this study was to explore whether the increase in insulin-stimulated glucose uptake after either long-term exercise or chronic AICAR administration was followed by fiber-type-specific changes in insulin signaling and/or changes in GLUT-4 expression. Wistar rats were allocated into three groups: an exercise group trained on treadmill for 5 days, an AICAR group exposed to daily subcutaneous injections of AICAR, and a sedentary control group. AMPK activity, insulin-stimulated glucose transport, insulin signaling, and GLUT-4 expression were determined in muscles characterized by different fiber type compositions. Both exercised and AICAR-injected animals displayed a fiber-type-specific increase in glucose transport with the most marked increase in muscles with a high content of type IIb fibers. This increase was accompanied by a concomitant increase in GLUT-4 expression. Insulin signaling as assessed by phosphatidylinositol 3-kinase and PKB/Akt activity was enhanced only after AICAR administration and in a non-fiber-type-specific manner. In conclusion, chronic AICAR administration and long-term exercise both improve insulin-stimulated glucose transport in skeletal muscle in a fiber-type-specific way, and this is associated with an increase in GLUT-4 content.

Two chalcones, 4-hydroxyderricin and xanthoangelol, stimulate GLUT4-dependent glucose uptake through the LKB1/AMP-activated protein kinase signaling pathway in 3T3-L1 adipocytes.

PubMed

Ohta, Mitsuhiro; Fujinami, Aya; Kobayashi, Norihiro; Amano, Akiko; Ishigami, Akihito; Tokuda, Harukuni; Suzuki, Nobutaka; Ito, Fumitake; Mori, Taisuke; Sawada, Morio; Iwasa, Koichi; Kitawaki, Jo; Ohnishi, Katsunori; Tsujikawa, Muneo; Obayashi, Hiroshi

2015-07-01

4-Hydroxyderricin (4HD) and xanthoangelol (XAG) are major components of n-hexane/ethyl acetate (5:1) extract of the yellow-colored stem juice of Angelica keiskei. 4-Hydroxyderricin and XAG have been reported to increase glucose transporter 4 (GLUT4)-dependent glucose uptake in 3T3-L1 adipocytes, but the detailed mechanism of this phenomenon remains unknown. This present study was aimed at clarifying the detailed mechanism by which 4HD and XAG increase GLUT4-dependent glucose uptake in 3T3-L1 adipocytes. Both 4HD and XAG increased glucose uptake and GLUT4 translocation to the plasma membrane. 4-Hydroxyderricin and XAG also stimulated the phosphorylation of 5' adenosine monophosphate-activated protein kinase (AMPK) and its downstream target acetyl-CoA carboxylase. In addition, phosphorylation of liver kinase B1 (LKB1), which acts upstream of AMPK, was also increased by 4HD and XAG treatment. Small interfering RNA knockdown of LKB1 attenuated 4HD- and XAG-stimulated AMPK phosphorylation and suppressed glucose uptake. These findings demonstrate that 4HD and XAG can increase GLUT4-dependent glucose uptake through the LKB1/AMPK signaling pathway in 3T3-L1 adipocytes. Copyright © 2015 Elsevier Inc. All rights reserved.

Leptin Reduces the Expression and Increases the Phosphorylation of the Negative Regulators of GLUT4 Traffic TBC1D1 and TBC1D4 in Muscle of ob/ob Mice

PubMed Central

Sáinz, Neira; Rodríguez, Amaia; Catalán, Victoria; Becerril, Sara; Ramírez, Beatriz; Lancha, Andoni; Burgos-Ramos, Emma; Gómez-Ambrosi, Javier; Frühbeck, Gema

2012-01-01

Leptin improves insulin sensitivity in skeletal muscle. Our goal was to determine whether proteins controlling GLUT4 traffic are altered by leptin deficiency and in vivo leptin administration in skeletal muscle of wild type and ob/ob mice. Leptin-deficient ob/ob mice were divided in three groups: control, leptin-treated (1 mg/kg/d) and leptin pair-fed ob/ob mice. Microarray analysis revealed that 1,546 and 1,127 genes were regulated by leptin deficiency and leptin treatment, respectively. Among these, we identified 24 genes involved in intracellular vesicle-mediated transport in ob/ob mice. TBC1 domain family, member 1 (Tbc1d1), a negative regulator of GLUT4 translocation, was up-regulated (P = 0.001) in ob/ob mice as compared to wild types. Importantly, leptin treatment reduced the transcript levels of Tbc1d1 (P<0.001) and Tbc1d4 (P = 0.004) in the leptin-treated ob/ob as compared to pair-fed ob/ob animals. In addition, phosphorylation levels of TBC1D1 and TBC1D4 were enhanced in leptin-treated ob/ob as compared to control ob/ob (P = 0.015 and P = 0.023, respectively) and pair-fed ob/ob (P = 0.036 and P = 0.034, respectively) mice. Despite similar GLUT4 protein expression in wild type and ob/ob groups a different immunolocalization of this protein was evidenced in muscle sections. Leptin treatment increased GLUT4 immunoreactivity in gastrocnemius and extensor digitorum longus sections of leptin-treated ob/ob mice. Moreover, GLUT4 protein detected in immunoprecipitates from TBC1D4 was reduced by leptin replacement compared to control ob/ob (P = 0.013) and pair-fed ob/ob (P = 0.037) mice. Our findings suggest that leptin enhances the intracellular GLUT4 transport in skeletal muscle of ob/ob animals by reducing the expression and activity of the negative regulators of GLUT4 traffic TBC1D1 and TBC1D4. PMID:22253718

Antisense GLUT-1 protects mesangial cells from glucose induction of GLUT-1 and fibronectin expression.

PubMed

Heilig, C W; Kreisberg, J I; Freytag, S; Murakami, T; Ebina, Y; Guo, L; Heilig, K; Loberg, R; Qu, X; Jin, Y; Henry, D; Brosius, F C

2001-04-01

A stable clone of rat mesangial cells expressing antisense GLUT-1 (i.e., MCGT1AS cells) was developed to protect them from high glucose exposure. GLUT-1 protein was reduced 50%, and the 2-deoxy-[(3)H]glucose uptake rate was reduced 33% in MCGT1AS. MCLacZ control cells and MCGT1 GLUT-1-overexpressing cells were used for comparisons. In MCLacZ, 20 mM D-glucose increased GLUT-1 transcription 90% vs. no increase in MCGT1AS. Glucose (8 mM) and 12 mM xylitol [a hexose monophosphate (HMP) shunt substrate] did not stimulate GLUT-1 transcription. An 87% replacement of the standard 8 mM D-glucose with 3-O-methylglucose reduced GLUT-1 transcription 80%. D-Glucose (20 mM) increased fibronectin mRNA and protein by 47 and 100%, respectively, in MCLacZ vs. no increases in MCGT1AS. Fibronectin synthesis was elevated 48% in MCGT1 and reduced 44% in MCGT1AS. We conclude that 1) transcription of GLUT-1 in response to D-glucose depends on glucose metabolism, although not through the HMP shunt, and 2) antisense GLUT-1 treatment of mesangial cells blocks D-glucose-induced GLUT-1 and fibronectin expression, thereby demonstrating a protective effect that could be beneficial in the setting of diabetes.

Adenovirus Protein E4-ORF1 Activation of PI3 Kinase Reveals Differential Regulation of Downstream Effector Pathways in Adipocytes.

PubMed

Chaudhary, Natasha; Gonzalez, Eva; Chang, Sung-Hee; Geng, Fuqiang; Rafii, Shahin; Altorki, Nasser K; McGraw, Timothy E

2016-12-20

Insulin activation of phosphatidylinositol 3-kinase (PI3K) regulates metabolism, including the translocation of the Glut4 glucose transporter to the plasma membrane and inactivation of the FoxO1 transcription factor. Adenoviral protein E4-ORF1 stimulates cellular glucose metabolism by mimicking growth-factor activation of PI3K. We have used E4-ORF1 as a tool to dissect PI3K-mediated signaling in adipocytes. E4-ORF1 activation of PI3K in adipocytes recapitulates insulin regulation of FoxO1 but not regulation of Glut4. This uncoupling of PI3K effects occurs despite E4-ORF1 activating PI3K and downstream signaling to levels achieved by insulin. Although E4-ORF1 does not fully recapitulate insulin's effects on Glut4, it enhances insulin-stimulated insertion of Glut4-containing vesicles to the plasma membrane independent of Rab10, a key regulator of Glut4 trafficking. E4-ORF1 also stimulates plasma membrane translocation of ubiquitously expressed Glut1 glucose transporter, an effect that is likely essential for E4-ORF1 to promote an anabolic metabolism in a broad range of cell types. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

ER/Golgi trafficking is facilitated by unbranched actin filaments containing Tpm4.2.

PubMed

Kee, Anthony J; Bryce, Nicole S; Yang, Lingyan; Polishchuk, Elena; Schevzov, Galina; Weigert, Roberto; Polishchuk, Roman; Gunning, Peter W; Hardeman, Edna C

2017-10-01

We have identified novel actin filaments defined by tropomyosin Tpm4.2 at the ER. EM analysis of mouse embryo fibroblasts (MEFs) isolated from mice expressing a mutant Tpm4.2 (Tpm4 Plt53/Plt53 ), incapable of incorporating into actin filaments, revealed swollen ER structures compared with wild-type (WT) MEFs (Tpm4 +/+ ). ER-to-Golgi, but not Golgi-to-ER trafficking was altered in the Tpm4 Plt53/Plt53 MEFs following the transfection of the temperature sensitive ER-associated ts045-VSVg construct. Exogenous Tpm4.2 was able to rescue the ER-to-Golgi trafficking defect in the Tpm4 Plt53/Plt53 cells. The treatment of WT MEFs with the myosin II inhibitor, blebbistatin, blocked the Tpm4.2-dependent ER-to-Golgi trafficking. The lack of an effect on ER-to-Golgi trafficking following treatment of MEFs with CK666 indicates that branched Arp2/3-containing actin filaments are not involved in anterograde vesicle trafficking. We propose that unbranched, Tpm4.2-containing filaments have an important role in maintaining ER/Golgi structure and that these structures, in conjunction with myosin II motors, mediate ER-to-Golgi trafficking. © 2017 Wiley Periodicals, Inc.

Progressive increase of glucose transporter-3 (GLUT-3) expression in estrogen-induced breast carcinogenesis.

PubMed

Kocdor, M A; Kocdor, H; Pereira, J S; Vanegas, J E; Russo, I H; Russo, J

2013-01-01

Increased glucose uptake and glycolysis are main metabolic characteristics of malignant cells. A family of glucose transporters (GLUTs) facilitates glucose movement across the plasma membranes in a tumor-specific manner. Glucose transporter-1 (GLUT-1), GLUT-3 and recently GLUT-12, have been previously shown in breast cancer cells and are found to be associated with poor prognosis. In addition, it has been shown that estrogen plays critical roles in GLUT regulation, however, the stage-specific GLUT regulation of mammary carcinogenesis is unclear. GLUT expression patterns were investigated in an in vitro-in vivo progressive, estrogen-induced, mammary carcinogenesis model which consisted of four cell lines, with same genetic background. In this model, different stages of tumor initiation and progression are represented, MCF-10F being the normal stage, E2 cells the transformed stage by estrogen, C5 cells, the invasive stage, and T4 cells the tumorigenic stage. In addition, loss of ductulogenesis and solid mass formation in collagen matrix and invasiveness of the cells were counted. Real time PCR showed that GLUT1 expression was downregulated in MCF10F after treatment with 17β-estradiol (E2), and in the invasive cell type (C5), but not in the tumor cells (T4), which had no changes compared to MCF10F. C5 and T4 cells showed the highest rate of GLUT-3 expression. These cells were also found to be associated with loss of ductulogenesis, solid mass formation and higher invasive capacity, whereas, GLUT-12 was downregulated in C5 and T4 cells. Estrogen-induced malignant transformation is associated with remarkable and progressive GLUT-3 expression, GLUT-1 re-expression at further stages, as well as GLUT-12 downregulation.

Methanolic extract of Momordica cymbalaria enhances glucose uptake in L6 myotubes in vitro by up-regulating PPAR-γ and GLUT-4.

PubMed

Kumar, Puttanarasaiah Mahesh; Venkataranganna, Marikunte V; Manjunath, Kirangadur; Viswanatha, Gollapalle L; Ashok, Godavarthi

2014-12-01

The present study was undertaken to evaluate the influence of the methanolic fruit extract of Momordica cymbalaria (MFMC) on PPARγ (Peroxisome Proliferator Activated Receptor gamma) and GLUT-4 (Glucose transporter-4) with respect to glucose transport. Various concentrations of MFMC ranging from 62.5 to 500 μg·mL(-1) were evaluated for glucose uptake activity in vitro using L6 myotubes, rosiglitazone was used as a reference standard. The MFMC showed significant and dose-dependent increase in glucose uptake at the tested concentrations, further, the glucose uptake activity of MFMC (500 μg·mL(-1)) was comparable with rosigilitazone. Furthermore, MFMC has shown up-regulation of GLUT-4 and PPARγ gene expressions in L6 myotubes. In addition, the MFMC when incubated along with cycloheximide (CHX), which is a protein synthesis inhibitor, has shown complete blockade of glucose uptake. This indicates that new protein synthesis is required for increased GLUT-4 translocation. In conclusion, these findings suggest that MFMC is enhancing the glucose uptake significantly and dose dependently through the enhanced expression of PPARγ and GLUT-4 in vitro. Copyright © 2014 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

The Effect of a High-Protein Diet and Exercise on Cardiac AQP7 and GLUT4 Gene Expression.

PubMed

Palabiyik, Orkide; Karaca, Aziz; Taştekin, Ebru; Yamasan, Bilge Eren; Tokuç, Burcu; Sipahi, Tammam; Vardar, Selma Arzu

2016-10-01

High-protein (HP) diets are commonly consumed by athletes despite their potential health hazard, which is postulated to enforce a negative effect on bone and renal health. However, its effects on heart have not been known yet. Aquaporin-7 (AQP7) is an aquaglyceroporin that facilitates glycerol and water transport. Glycerol is an important cardiac energy production substrate, especially during exercise, in conjunction with fatty acids and glucose. Glucose transporter 4 (GLUT4) is an insulin-sensitive glucose transporter in heart. We aimed to investigate the effect of HPD on AQP7 and GLUT4 levels in the rat heart subjected to exercise. Male Sprague-Dawley rats were divided into control (n = 12), exercise (E) training (n = 10), HPD (n = 12), and HPD-E training (n = 9) groups. The HPD groups were fed a 45 % protein-containing diet 5 weeks. The HPD-E and E groups were performed the treadmill exercise during the 5-week study period. Real-time polymerase chain reaction and immunohistochemistry techniques were used to determine the gene expression and localization of AQP7 and GLUT4 in heart tissue. Results of relative gene expression were calculated by the 'Pfaffl' mathematical method using the REST program. Differences in AQP7 and GLUT4 gene expression were expressed as fold change compared to the control group. Heart weight/tibia ratio and ventricular wall thickness were evaluated as markers of cardiac hypertrophy. Further, serum glucose, glycerol, and insulin levels were also measured. AQP7 gene expression was found to be increased in the E (3.47-fold, p < 0.001), HPD (5.59-fold, p < 0.001), and HPD-E (3.87-fold, p < 0.001) groups compared to the control group. AQP7 protein expression was also increased in the HPD and HPD-E groups (p < 0.001). Additionally, cardiac mRNA expression levels of GLUT4 showed a significant increase in the E (2.16-fold, p < 0.003), HPD (7.14-fold, p < 0.001), and HPD-E (3.43-fold, p < 0.001) groups compared to the

Synthesis, in vitro and in silico studies of a PPARγ and GLUT-4 modulator with hypoglycemic effect.

PubMed

Navarrete-Vázquez, Gabriel; Torres-Gómez, Héctor; Hidalgo-Figueroa, Sergio; Ramírez-Espinosa, Juan José; Estrada-Soto, Samuel; Medina-Franco, José L; León-Rivera, Ismael; Alarcón-Aguilar, Francisco Javier; Almanza-Pérez, Julio César

2014-09-15

Compound {4-[({4-[(Z)-(2,4-dioxo-1,3-thiazolidin-5-ylidene)methyl]phenoxy}acetyl)amino]phenoxy}acetic acid (1) was prepared and the in vitro relative expression of PPARγ, GLUT-4 and PPARα, was estimated. Compound 1 showed an increase of 2-fold in the mRNA expression of PPARγ isoform, as well as the GLUT-4 levels. The antidiabetic activity of compound 1 was determined at 50 mg/Kg single dose using a non insulin dependent diabetes mellitus (NIDDM) rat model. The in vivo results indicated a significant decrease of plasma glucose levels, during the 7 h post-administration. Also, we performed a molecular docking of compound 1 into the ligand binding pocket of PPARγ, showing important short contacts with residues Ser289, His323 and His449 in the active site. Copyright © 2014 Elsevier Ltd. All rights reserved.

Decreased expression of GLUT4 in male CG-IUGR rats may play a vital role in their increased susceptibility to diabetes mellitus in adulthood.

PubMed

Duan, Chang; Liu, Min; Xu, Haiyan; Tang, Weiwei; Liu, Jiayun; Hou, Lamei; Li, Lijuan

2016-10-01

Rats with intrauterine growth retardation and catch-up growth (CG-IUGR) after birth show increased susceptibility to diabetes mellitus in adulthood. The expression of glucose transporter type 4 (GLUT4) decreases in female IUGR offspring rats with seminutrient restriction during pregnancy. However, the male CG-IUGR rats also display an increased susceptibility to diabetes mellitus in adulthood. Whether there is another factor, besides GLUT4, in male CG-IUGR rat that mediates their susceptibility to diabetes mellitus? The male IUGR rats with catch-up growth were selected as the research objects. CG-IUGR rats had an increased fasting blood glucose level, and increased serum total cholesterol, triglyceride and free fatty acid levels. Glucose tolerance test and insulin tolerance test showed higher glucose levels and much higher insulin levels after a glucose load in CG-IUGR. The mRNA and protein expressions of IRS-2 in liver tissue, and IRS-1 and GLUT4 in skeletal muscle in CG-IUGR rats were down-regulated, but only the GLUT4 down-regulation displayed strong negative correlations with the decreased glucose tolerance capability by Pearson's analysis. The methylation patterns of CpG islands in the promoter regions of IRS-1, IRS-2 and GLUT4 in CG-IUGR rats varied, which was not significantly correlated with their expressions. The male CG-IUGR rats showed decreased glucose tolerant capability, suggesting increased susceptibility to diabetes mellitus in adulthood. The GLUT4 down-regulation may play a vital role in the development of decreased glucose tolerance in male CG-IUGR rats. The methylation modification of the promoter region of GLUT4 does not appear to be involved in its expression. ©The Author 2016. Published by Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Effects of an acute bout of resistance exercise on fiber-type specific to GLUT4 and IGF-1R expression.

PubMed

Gallagher, Philip M; Touchberry, Chad D; Teson, Kelli; McCabe, Everlee; Tehel, Michelle; Wacker, Michael J

2013-05-01

The effects of resistance exercise on fiber-type-specific expression of insulin-like growth factor I receptor (IGF-1R) and glucose transporter 4 (GLUT4) was determined in 6 healthy males. The expression of both genes increased in Type I fibers (p < 0.05), but only GLUT4 increased (p < 0.05) in Type II fibers. These data demonstrates that an acute bout of resistance exercise can up-regulate mechanisms of glucose uptake in slow and fast-twitch fibers, but the IGF signaling axis may not be as effective in fast-twitch fibers.

GLUT4 translocation is not impaired after acute exercise in skeletal muscle of women with obesity and polycystic ovary syndrome.

PubMed

Dantas, Wagner Silva; Marcondes, José Antonio Miguel; Shinjo, Samuel Katsuyuki; Perandini, Luiz Augusto; Zambelli, Vanessa Olzon; Neves, Willian Das; Barcellos, Cristiano Roberto Grimaldi; Rocha, Michele Patrocínio; Yance, Viviane Dos Reis Vieira; Pereira, Renato Tavares Dos Santos; Murai, Igor Hisashi; Pinto, Ana Lucia De Sá; Roschel, Hamilton; Gualano, Bruno

2015-11-01

The aim of this study was to examine the effects of acute exercise on insulin signaling in skeletal muscle of women with polycystic ovary syndrome (PCOS) and controls (CTRL). Fifteen women with obesity and PCOS and 12 body mass index-matched CTRL participated in this study. Subjects performed a 40-min single bout of exercise. Muscle biopsies were performed before and 60 min after exercise. Selected proteins were assessed by Western blotting. CTRL, but not PCOS, showed a significant increase in PI3-k p85 and AS160 Thr 642 after a single bout of exercise (P = 0.018 and P = 0.018, respectively). Only PCOS showed an increase in Akt Thr 308 and AMPK phosphorylation after exercise (P = 0.018 and P = 0.018, respectively). Total GLUT4 expression was comparable between groups (P > 0.05). GLUT4 translocation tended to be significantly higher in both groups after exercise (PCOS: P = 0.093; CTRL: P = 0.091), with no significant difference between them (P > 0.05). A single bout of exercise elicited similar GLUT4 translocation in skeletal muscle of PCOS and CTRL, despite a slightly differential pattern of protein phosphorylation. The absence of impairment in GLUT4 translocation suggests that PCOS patients with obesity and insulin resistance may benefit from exercise training. © 2015 The Obesity Society.

GLUT-3 expression in human skeletal muscle

NASA Technical Reports Server (NTRS)

Stuart, C. A.; Wen, G.; Peng, B. H.; Popov, V. L.; Hudnall, S. D.; Campbell, G. A.

2000-01-01

Muscle biopsy homogenates contain GLUT-3 mRNA and protein. Before these studies, it was unclear where GLUT-3 was located in muscle tissue. In situ hybridization using a midmolecule probe demonstrated GLUT-3 within all muscle fibers. Fluorescent-tagged antibody reacting with affinity-purified antibody directed at the carboxy-terminus demonstrated GLUT-3 protein in all fibers. Slow-twitch muscle fibers, identified by NADH-tetrazolium reductase staining, possessed more GLUT-3 protein than fast-twitch fibers. Electron microscopy using affinity-purified primary antibody and gold particle-tagged second antibody showed that the majority of GLUT-3 was in association with triads and transverse tubules inside the fiber. Strong GLUT-3 signals were seen in association with the few nerves that traversed muscle sections. Electron microscopic evaluation of human peripheral nerve demonstrated GLUT-3 within the axon, with many of the particles related to mitochondria. GLUT-3 protein was found in myelin but not in Schwann cells. GLUT-1 protein was not present in nerve cells, axons, myelin, or Schwann cells but was seen at the surface of the peripheral nerve in the perineurium. These studies demonstrated that GLUT-3 mRNA and protein are expressed throughout normal human skeletal muscle, but the protein is predominantly found in the triads of slow-twitch muscle fibers.

The inability of phosphatidylinositol 3-kinase activation to stimulate GLUT4 translocation indicates additional signaling pathways are required for insulin-stimulated glucose uptake.

PubMed

Isakoff, S J; Taha, C; Rose, E; Marcusohn, J; Klip, A; Skolnik, E Y

1995-10-24

Recent experimental evidence has focused attention to the role of two molecules, insulin receptor substrate 1 (IRS-1) and phosphatidylinositol 3-kinase (PI3-kinase), in linking the insulin receptor to glucose uptake; IRS-1 knockout mice are insulin resistant, and pharmacological inhibitors of PI3-kinase block insulin-stimulated glucose uptake. To investigate the role of PI3-kinase and IRS-1 in insulin-stimulated glucose uptake we examined whether stimulation of insulin-sensitive cells with platelet-derived growth factor (PDGF) or with interleukin 4 (IL-4) stimulates glucose uptake; the activated PDGF receptor (PDGFR) directly binds and activates PI3-kinase, whereas the IL-4 receptor (IL-4R) activates PI3-kinase via IRS-1 or the IRS-1-related molecule 4PS. We found that stimulation of 3T3-L1 adipocytes with PDGF resulted in tyrosine phosphorylation of the PDGFR and activation of PI3-kinase in these cells. To examine whether IL-4 stimulates glucose uptake, L6 myoblasts were engineered to overexpress GLUT4 as well as both chains of the IL-4R (L6/IL-4R/GLUT4); when these L6/IL-4R/GLUT4 myoblasts were stimulated with IL-4, IRS-1 became tyrosine phosphorylated and associated with PI3-kinase. Although PDGF and IL-4 can activate PI3-kinase in the respective cell lines, they do not possess insulin's ability to stimulate glucose uptake and GLUT4 translocation to the plasma membrane. These findings indicate that activation of PI3-kinase is not sufficient to stimulate GLUT4 translocation to the plasma membrane. We postulate that activation of a second signaling pathway by insulin, distinct from PI3-kinase, is necessary for the stimulation of glucose uptake in insulin-sensitive cells.

A novel fluorescence-based biosynthetic trafficking method provides pharmacologic evidence that PI4-kinase IIIα is important for protein trafficking from the endoplasmic reticulum to the plasma membrane.

PubMed

Bryant, Kirsten L; Baird, Barbara; Holowka, David

2015-02-27

Biosynthetic trafficking of receptors and other membrane-associated proteins from the endoplasmic reticulum (ER) to the plasma membrane (PM) underlies the capacity of these proteins to participate in crucial cellular roles. Phosphoinositides have been shown to mediate distinct biological functions in cells, and phosphatidylinositol 4-phosphate (PI4P), in particular, has emerged as a key regulator of biosynthetic trafficking. To investigate the source of PI4P that orchestrates trafficking events, we developed a novel flow cytometry based method to monitor biosynthetic trafficking of transiently transfected proteins. We demonstrated that our method can be used to assess the trafficking of both type-1 transmembrane and GPI-linked proteins, and that it can accurately monitor the pharmacological disruption of biosynthetic trafficking with brefeldin A, a well-documented inhibitor of early biosynthetic trafficking. Furthermore, utilizing our newly developed method, we applied pharmacological inhibition of different isoforms of PI 4-kinase to reveal a role for a distinct pool of PI4P, synthesized by PI4KIIIα, in ER-to-PM trafficking. Taken together, these findings provide evidence that a specific pool of PI4P plays a role in biosynthetic trafficking of two different classes of proteins from the ER to the Golgi complex. Furthermore, our simple, flow cytometry-based biosynthetic trafficking assay can be widely applied to the study of multiple classes of proteins and varied pharmacological and genetic perturbations.

Acute hypertension provokes acute trafficking of distal tubule Na-Cl cotransporter (NCC) to subapical cytoplasmic vesicles.

PubMed

Lee, Donna H; Riquier, Anne D M; Yang, Li E; Leong, Patrick K K; Maunsbach, Arvid B; McDonough, Alicia A

2009-04-01

When blood pressure (BP) is elevated above baseline, a pressure natriuresis-diuresis response ensues, critical to volume and BP homeostasis. Distal convoluted tubule Na(+)-Cl(-) cotransporter (NCC) is regulated by trafficking between the apical plasma membrane (APM) and subapical cytoplasmic vesicles (SCV). We aimed to determine whether NCC trafficking contributes to pressure diuresis by decreasing APM NCC or compensates for increased volume flow to the DCT by increasing APM NCC. BP was raised 50 mmHg (high BP) in rats by arterial constriction for 5 or 20-30 min, provoking a 10-fold diuresis at both times. Kidneys were excised, and NCC subcellular distribution was analyzed by 1) sorbitol density gradient fractionation and immunoblotting and 2) immunoelectron microscopy (immuno-EM). NCC distribution did not change after 5-min high BP. After 20-30 min of high BP, 20% of NCC redistributed from low-density, APM-enriched fractions to higher density, endosome-enriched fractions, and, by quantitative immuno-EM, pool size of APM NCC decreased 14% and SCV pool size increased. Because of the time lag of the response, we tested the hypothesis that internalization of NCC was secondary to the decrease in ANG II that accompanies high BP. Clamping ANG II at a nonpressor level by coinfusion of captopril (12 microg/min) and ANG II (20 ng.kg(-1).min(-1)) during 30-min high BP reduced diuresis to eightfold and prevented redistribution of NCC from APM- to SCV-enriched fractions. We conclude that DCT NCC may participate in pressure natriuresis-diuresis by retraction out of apical plasma membranes and that the retraction is, at least in part, driven by the fall in ANG II that accompanies acute hypertension.

Polymorphism rs1385129 Within Glut1 Gene SLC2A1 Is Linked to Poor CD4+ T Cell Recovery in Antiretroviral-Treated HIV+ Individuals

PubMed Central

Masson, Jesse J. R.; Cherry, Catherine L.; Murphy, Nicholas M.; Sada-Ovalle, Isabel; Hussain, Tabinda; Palchaudhuri, Riya; Martinson, Jeffrey; Landay, Alan L.; Billah, Baki; Crowe, Suzanne M.; Palmer, Clovis S.

2018-01-01

Untreated HIV infection is associated with progressive CD4+ T cell depletion, which is generally recovered with combination antiretroviral therapy (cART). However, a significant proportion of cART-treated individuals have poor CD4+ T cell reconstitution. We investigated associations between HIV disease progression and CD4+ T cell glucose transporter-1 (Glut1) expression. We also investigated the association between these variables and specific single nucleotide polymorphisms (SNPs) within the Glut1 regulatory gene AKT (rs1130214, rs2494732, rs1130233, and rs3730358) and in the Glut1-expressing gene SLC2A1 (rs1385129 and rs841853) and antisense RNA 1 region SLC2A1-AS1 (rs710218). High CD4+Glut1+ T cell percentage is associated with rapid CD4+ T cell decline in HIV-positive treatment-naïve individuals and poor T cell recovery in HIV-positive individuals on cART. Evidence suggests that poor CD4+ T cell recovery in treated HIV-positive individuals is linked to the homozygous genotype (GG) associated with SLC2A1 SNP rs1385129 when compared to those with a recessive allele (GA/AA) (odds ratio = 4.67; P = 0.04). Furthermore, poor response to therapy is less likely among Australian participants when compared against American participants (odds ratio: 0.12; P = 0.01) despite there being no difference in prevalence of a specific genotype for any of the SNPs analyzed between nationalities. Finally, CD4+Glut1+ T cell percentage is elevated among those with a homozygous dominant genotype for SNPs rs1385129 (GG) and rs710218 (AA) when compared to those with a recessive allele (GA/AA and AT/TT respectively) (P < 0.04). The heterozygous genotype associated with AKT SNP 1130214 (GT) had a higher CD4+Glut1+ T cell percentage when compared to the dominant homozygous genotype (GG) (P = 0.0068). The frequency of circulating CD4+Glut1+ T cells and the rs1385129 SLC2A1 SNP may predict the rate of HIV disease progression and CD4+ T cell recovery in untreated and

Fruit extracts of Momordica charantia potentiate glucose uptake and up-regulate Glut-4, PPAR gamma and PI3K.

PubMed

Kumar, Ramadhar; Balaji, S; Uma, T S; Sehgal, P K

2009-12-10

Momordica charantia fruit is a widely used traditional medicinal herb as, anti-diabetic, anti-HIV, anti-ulcer, anti-inflammatory, anti-leukemic, anti-microbial, and anti-tumor. The present study is undertaken to investigate the possible mode of action of fruit extracts derived from Momordica charantia (MC) and study its pharmacological effects for controlling diabetic mellitus. Effects of aqueous and chloroform extracts of Momordica charantia fruit on glucose uptake and up-regulation of glucose transporter (Glut-4), peroxisome proliferator activator receptor gamma (PPAR gamma) and phosphatidylinositol-3 kinase (PI3K), were investigated to show its efficacy as a hypoglycaemic agent. Dose dependent glucose uptake assay was performed on L6 myotubes using 2-deoxy-D-[1-(3)H] glucose. Up-regulatory effects of the extracts on the mRNA expression level of Glut-4, PPAR gamma and PI3K have been studied. The association of Momordica charantia with the aqueous and chloroform extracts of Momordica charantia fruit at 6 microg/ml has shown significant up-regulatory effect, respectively, by 3.6-, 2.8- and 3.8-fold on the battery of targets Glut-4, PPAR gamma and PI3K involved in glucose transport. The up-regulation of glucose uptake was comparable with insulin and rosiglitazone which was approximately 2-fold over the control. Moreover, the inhibitory effect of the cyclohexamide on Momordica charantia fruit extract mediated glucose uptake suggested the requirement of new protein synthesis for the enhanced glucose uptake. This study demonstrated the significance of Glut-4, PPAR gamma and PI3K up-regulation by Momordica charantia in augmenting the glucose uptake and homeostasis.

PPAR-γ and Akt regulate GLUT1 and GLUT3 surface localization during Mycobacterium tuberculosis infection.

PubMed

Dasgupta, Shyamashree; Rai, Ramesh Chandra

2018-03-01

The success of Mycobacterium tuberculosis (Mtb) as a pathogen stems from its ability to manipulate the host macrophage towards increased lipid biogenesis and lipolysis inhibition. Inhibition of lipolysis requires augmented uptake of glucose into the host cell causing an upregulation of the glucose transporters GLUT1 and GLUT3 on the cell surface. Mechanism behind this upregulation of the GLUT proteins during Mtb infection is hitherto unknown and demands intensive investigation in order to understand the pathways linked with governing them. Our endeavor to investigate some of the key proteins that have been found to be affected during Mtb infection led us to investigate host molecular pathways such as Akt and PPAR-γ that remain closely associated with the survival of the bacilli by modulating the localization of glucose transporters GLUT1 and GLUT3.

Signal transduction meets vesicle traffic: the software and hardware of GLUT4 translocation.

PubMed

Klip, Amira; Sun, Yi; Chiu, Tim Ting; Foley, Kevin P

2014-05-15

Skeletal muscle is the major tissue disposing of dietary glucose, a function regulated by insulin-elicited signals that impart mobilization of GLUT4 glucose transporters to the plasma membrane. This phenomenon, also central to adipocyte biology, has been the subject of intense and productive research for decades. We focus on muscle cell studies scrutinizing insulin signals and vesicle traffic in a spatiotemporal manner. Using the analogy of an integrated circuit to approach the intersection between signal transduction and vesicle mobilization, we identify signaling relays ("software") that engage structural/mechanical elements ("hardware") to enact the rapid mobilization and incorporation of GLUT4 into the cell surface. We emphasize how insulin signal transduction switches from tyrosine through lipid and serine phosphorylation down to activation of small G proteins of the Rab and Rho families, describe key negative regulation step of Rab GTPases through the GTPase-activating protein activity of the Akt substrate of 160 kDa (AS160), and focus on the mechanical effectors engaged by Rabs 8A and 10 (the molecular motor myosin Va), and the Rho GTPase Rac1 (actin filament branching and severing through Arp2/3 and cofilin). Finally, we illustrate how actin filaments interact with myosin 1c and α-Actinin4 to promote vesicle tethering as preamble to fusion with the membrane. Copyright © 2014 the American Physiological Society.

Diabetes Alters the Expression and Translocation of the Insulin-Sensitive Glucose Transporters 4 and 8 in the Atria

PubMed Central

Maria, Zahra; Campolo, Allison R.; Lacombe, Veronique A.

2015-01-01

Although diabetes has been identified as a major risk factor for atrial fibrillation, little is known about glucose metabolism in the healthy and diabetic atria. Glucose transport into the cell, the rate-limiting step of glucose utilization, is regulated by the Glucose Transporters (GLUTs). Although GLUT4 is the major isoform in the heart, GLUT8 has recently emerged as a novel cardiac isoform. We hypothesized that GLUT-4 and -8 translocation to the atrial cell surface will be regulated by insulin and impaired during insulin-dependent diabetes. GLUT protein content was measured by Western blotting in healthy cardiac myocytes and type 1 (streptozotocin-induced, T1Dx) diabetic rodents. Active cell surface GLUT content was measured using a biotinylated photolabeled assay in the perfused heart. In the healthy atria, insulin stimulation increased both GLUT-4 and -8 translocation to the cell surface (by 100% and 240%, respectively, P<0.05). Upon insulin stimulation, we reported an increase in Akt (Th308 and s473 sites) and AS160 phosphorylation, which was positively (P<0.05) correlated with GLUT4 protein content in the healthy atria. During diabetes, active cell surface GLUT-4 and -8 content was downregulated in the atria (by 70% and 90%, respectively, P<0.05). Akt and AS160 phosphorylation was not impaired in the diabetic atria, suggesting the presence of an intact insulin signaling pathway. This was confirmed by the rescued translocation of GLUT-4 and -8 to the atrial cell surface upon insulin stimulation in the atria of type 1 diabetic subjects. In conclusion, our data suggest that: 1) both GLUT-4 and -8 are insulin-sensitive in the healthy atria through an Akt/AS160 dependent pathway; 2) GLUT-4 and -8 trafficking is impaired in the diabetic atria and rescued by insulin treatment. Alterations in atrial glucose transport may induce perturbations in energy production, which may provide a metabolic substrate for atrial fibrillation during diabetes. PMID:26720696

Diabetes Alters the Expression and Translocation of the Insulin-Sensitive Glucose Transporters 4 and 8 in the Atria.

PubMed

Maria, Zahra; Campolo, Allison R; Lacombe, Veronique A

2015-01-01

Although diabetes has been identified as a major risk factor for atrial fibrillation, little is known about glucose metabolism in the healthy and diabetic atria. Glucose transport into the cell, the rate-limiting step of glucose utilization, is regulated by the Glucose Transporters (GLUTs). Although GLUT4 is the major isoform in the heart, GLUT8 has recently emerged as a novel cardiac isoform. We hypothesized that GLUT-4 and -8 translocation to the atrial cell surface will be regulated by insulin and impaired during insulin-dependent diabetes. GLUT protein content was measured by Western blotting in healthy cardiac myocytes and type 1 (streptozotocin-induced, T1Dx) diabetic rodents. Active cell surface GLUT content was measured using a biotinylated photolabeled assay in the perfused heart. In the healthy atria, insulin stimulation increased both GLUT-4 and -8 translocation to the cell surface (by 100% and 240%, respectively, P<0.05). Upon insulin stimulation, we reported an increase in Akt (Th308 and s473 sites) and AS160 phosphorylation, which was positively (P<0.05) correlated with GLUT4 protein content in the healthy atria. During diabetes, active cell surface GLUT-4 and -8 content was downregulated in the atria (by 70% and 90%, respectively, P<0.05). Akt and AS160 phosphorylation was not impaired in the diabetic atria, suggesting the presence of an intact insulin signaling pathway. This was confirmed by the rescued translocation of GLUT-4 and -8 to the atrial cell surface upon insulin stimulation in the atria of type 1 diabetic subjects. In conclusion, our data suggest that: 1) both GLUT-4 and -8 are insulin-sensitive in the healthy atria through an Akt/AS160 dependent pathway; 2) GLUT-4 and -8 trafficking is impaired in the diabetic atria and rescued by insulin treatment. Alterations in atrial glucose transport may induce perturbations in energy production, which may provide a metabolic substrate for atrial fibrillation during diabetes.

GLUT-1 expression in pancreatic neoplasia: implications in pathogenesis, diagnosis, and prognosis.

PubMed

Basturk, Olca; Singh, Rajendra; Kaygusuz, Ecmel; Balci, Serdar; Dursun, Nevra; Culhaci, Nil; Adsay, N Volkan

2011-03-01

GLUT-1 has been found to have an important role in the upregulation of various cellular pathways and implicated in neoplastic transformation correlating with biological behavior in malignancies. However, literature regarding the significance of GLUT-1 expression in pancreatic neoplasia has been limited and controversial. Immunohistochemical expression of GLUT-1 was tested in a variety of pancreatic neoplasia including ductal adenocarcinomas (DAs), pancreatic intraepithelial neoplasms (PanINs), intraductal papillary mucinous neoplasms (IPMNs), and serous cystadenomas. There was a progressive increase in the expression of GLUT-1 from low- to higher-grade dysplastic lesions: All higher-grade PanINs/IPMNs (the ones with moderate/high-grade dysplasia) revealed noticeable GLUT-1 expression. Among the 94 DAs analyzed, there were minimal/moderate expression in 46 and significant expression in 24 DAs. However, all 4 clear-cell variants of DAs revealed significant GLUT-1 immunolabeling, as did areas of clear-cell change seen in other DAs. Moreover, all 12 serous cystadenomas expressed significant GLUT-1. GLUT-1 expression was also directly correlated with DA histological grade (P = 0.016) and tumor size (P = 0.03). GLUT-1 may give rise to the distinctive clear-cell appearance of these tumors by inducing the accumulation of glycogen in the cytoplasm. Additionally, because GLUT-1 expression was related to histological grade and tumor size of DA, further studies are warranted to investigate the association of GLUT-1 with prognosis and tumor progression.

Hypoxia increases expression of selective facilitative glucose transporters (GLUT) and 2-deoxy-d-glucose uptake in human adipocytes

PubMed Central

Stuart Wood, I.; Wang, Bohan; Lorente-Cebrián, Silvia; Trayhurn, Paul

2007-01-01

Hypoxia modulates the production of key inflammation-related adipokines and may underlie adipose tissue dysfunction in obesity. Here we have examined the effects of hypoxia on glucose transport by human adipocytes. Exposure of adipocytes to hypoxia (1% O2) for up to 24 h resulted in increases in GLUT-1 (9.2-fold), GLUT-3 (9.6-fold peak at 8 h), and GLUT-5 (8.9-fold) mRNA level compared to adipocytes in normoxia (21% O2). In contrast, there was no change in GLUT-4, GLUT-10 or GLUT-12 expression. The rise in GLUT-1 mRNA was accompanied by a substantial increase in GLUT-1 protein (10-fold), but there was no change in GLUT-5; GLUT-3 protein was not detected. Functional studies with [3H]2-deoxy-d-glucose showed that hypoxia led to a stimulation of glucose transport (4.4-fold) which was blocked by cytochalasin B. These results indicate that hypoxia increases monosaccharide uptake capacity in human adipocytes; this may contribute to adipose tissue dysregulation in obesity. PMID:17658463

Hypoxia increases expression of selective facilitative glucose transporters (GLUT) and 2-deoxy-D-glucose uptake in human adipocytes.

PubMed

Wood, I Stuart; Wang, Bohan; Lorente-Cebrián, Silvia; Trayhurn, Paul

2007-09-21

Hypoxia modulates the production of key inflammation-related adipokines and may underlie adipose tissue dysfunction in obesity. Here we have examined the effects of hypoxia on glucose transport by human adipocytes. Exposure of adipocytes to hypoxia (1% O(2)) for up to 24 h resulted in increases in GLUT-1 (9.2-fold), GLUT-3 (9.6-fold peak at 8 h), and GLUT-5 (8.9-fold) mRNA level compared to adipocytes in normoxia (21% O(2)). In contrast, there was no change in GLUT-4, GLUT-10 or GLUT-12 expression. The rise in GLUT-1 mRNA was accompanied by a substantial increase in GLUT-1 protein (10-fold), but there was no change in GLUT-5; GLUT-3 protein was not detected. Functional studies with [(3)H]2-deoxy-D-glucose showed that hypoxia led to a stimulation of glucose transport (4.4-fold) which was blocked by cytochalasin B. These results indicate that hypoxia increases monosaccharide uptake capacity in human adipocytes; this may contribute to adipose tissue dysregulation in obesity.

Revisiting the physiological roles of SGLTs and GLUTs using positron emission tomography in mice

PubMed Central

Sala‐Rabanal, Monica; Hirayama, Bruce A.; Ghezzi, Chiara; Liu, Jie; Huang, Sung‐Cheng; Kepe, Vladimir; Koepsell, Hermann; Yu, Amy; Powell, David R.; Thorens, Bernard; Barrio, Jorge R.

2016-01-01

Key points Glucose transporters are central players in glucose homeostasis.There are two major classes of glucose transporters in the body, the passive facilitative glucose transporters (GLUTs) and the secondary active sodium‐coupled glucose transporters (SGLTs).In the present study, we report the use of a non‐invasive imaging technique, positron emission tomography, in mice aiming to evaluate the role of GLUTs and SGLTs in controlling glucose distribution and utilization.We show that GLUTs are most significant for glucose uptake into the brain and liver, whereas SGLTs are important in glucose recovery in the kidney.This work provides further support for the use of SGLT imaging in the investigation of the role of SGLT transporters in human physiology and diseases such as diabetes and cancer. Abstract The importance of sodium‐coupled glucose transporters (SGLTs) and facilitative glucose transporters (GLUTs) in glucose homeostasis was studied in mice using fluorine‐18 labelled glucose molecular imaging probes and non‐invasive positron emission tomography (PET) imaging. The probes were: α‐methyl‐4‐[F‐18]‐fluoro‐4‐deoxy‐d‐glucopyranoside (Me‐4FDG), a substrate for SGLTs; 4‐deoxy‐4‐[F‐18]‐fluoro‐d‐glucose (4‐FDG), a substrate for SGLTs and GLUTs; and 2‐deoxy‐2‐[F‐18]‐fluoro‐d–glucose (2‐FDG), a substrate for GLUTs. These radiolabelled imaging probes were injected i.v. into wild‐type, Sglt1–/–, Sglt2–/– and Glut2–/– mice and their dynamic whole‐body distribution was determined using microPET. The distribution of 2‐FDG was similar to that reported earlier (i.e. it accumulated in the brain, heart, liver and kidney, and was excreted into the urinary bladder). There was little change in the distribution of 2‐FDG in Glut2–/– mice, apart from a reduction in the rate of uptake into liver. The major differences between Me‐4FDG and 2‐FDG were that Me‐4FDG did not enter the brain and was

Kaposi sarcoma associated herpesvirus (KSHV) induces AKT hyperphosphorylation, bortezomib-resistance and GLUT-1 plasma membrane exposure in THP-1 monocytic cell line.

PubMed

Gonnella, Roberta; Santarelli, Roberta; Farina, Antonella; Granato, Marisa; D'Orazi, Gabriella; Faggioni, Alberto; Cirone, Mara

2013-10-23

Phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway regulates multiple cellular processes such as cell proliferation, evasion from apoptosis, migration, glucose metabolism, protein synthesis and proper differentiation in immune cells. Kaposi sarcoma-associated herpesvirus (KSHV), an oncogenic virus associated with several human malignancies, expresses a variety of latent and lytic proteins able to activate PI3K/AKT pathway, promoting the growth of infected cells and a successful viral infection. We found that KSHV latent infection of THP-1 cells, a human monocytic cell line derived from an acute monocytic leukemia patient, resulted in an increase of AKT phoshorylation, not susceptible to bortezomib-induced dephosphorylation, compared to the mock-infected THP-1. Accordingly, THP-1-infected cells displayed increased resistance to the bortezomib cytotoxic effect in comparison to the uninfected cells, which was counteracted by pre-treatment with AKT-specific inhibitors. Finally, AKT hyperactivation by KSHV infection correlated with plasma membrane exposure of glucose transporter GLUT1, particularly evident during bortezomib treatment. GLUT1 membrane trafficking is a characteristic of malignant cells and underlies a change of glucose metabolism that ensures the survival to highly proliferating cells and render these cells highly dependent on glycolysis. GLUT1 membrane trafficking in KSHV-infected THP-1 cells indeed led to increased sensitivity to cell death induced by the glycolysis inhibitor 2-Deoxy-D-glucose (2DG), further potentiated by its combination with bortezomib. KSHV confers to the THP-1 infected cells an oncogenic potential by altering the phosphorylation, expression and localization of key molecules that control cell survival and metabolism such as AKT and GLUT1. Such modifications in one hand lead to resistance to cell death induced by some chemotherapeutic drugs such as bortezomib, but on the other hand, offer an

Protein Kinase WNK1 Promotes Cell Surface Expression of Glucose Transporter GLUT1 by Regulating a Tre-2/USP6-BUB2-Cdc16 Domain Family Member 4 (TBC1D4)-Rab8A Complex*

PubMed Central

Mendes, Ana Isabel; Matos, Paulo; Moniz, Sónia; Jordan, Peter

2010-01-01

One mechanism by which mammalian cells regulate the uptake of glucose is the number of glucose transporter proteins (GLUT) present at the plasma membrane. In insulin-responsive cells types, GLUT4 is released from intracellular stores through inactivation of the Rab GTPase activating protein Tre-2/USP6-BUB2-Cdc16 domain family member 4 (TBC1D4) (also known as AS160). Here we describe that TBC1D4 forms a protein complex with protein kinase WNK1 in human embryonic kidney (HEK293) cells. We show that WNK1 phosphorylates TBC1D4 in vitro and that the expression levels of WNK1 in these cells regulate surface expression of the constitutive glucose transporter GLUT1. WNK1 was found to increase the binding of TBC1D4 to regulatory 14-3-3 proteins while reducing its interaction with the exocytic small GTPase Rab8A. These effects were dependent on the catalytic activity because expression of a kinase-dead WNK1 mutant had no effect on binding of 14-3-3 and Rab8A, or on surface GLUT1 levels. Together, the data describe a pathway regulating constitutive glucose uptake via GLUT1, the expression level of which is related to several human diseases. PMID:20937822

Role of adaptor proteins and clathrin in the trafficking of human kidney anion exchanger 1 (kAE1) to the cell surface.

PubMed

Junking, Mutita; Sawasdee, Nunghathai; Duangtum, Natapol; Cheunsuchon, Boonyarit; Limjindaporn, Thawornchai; Yenchitsomanus, Pa-thai

2014-07-01

Kidney anion exchanger 1 (kAE1) plays an important role in acid-base homeostasis by mediating chloride/bicarbornate (Cl-/HCO3-) exchange at the basolateral membrane of α-intercalated cells in the distal nephron. Impaired intracellular trafficking of kAE1 caused by mutations of SLC4A1 encoding kAE1 results in kidney disease - distal renal tubular acidosis (dRTA). However, it is not known how the intracellular sorting and trafficking of kAE1 from trans-Golgi network (TGN) to the basolateral membrane occurs. Here, we studied the role of basolateral-related sorting proteins, including the mu1 subunit of adaptor protein (AP) complexes, clathrin and protein kinase D, on kAE1 trafficking in polarized and non-polarized kidney cells. By using RNA interference, co-immunoprecipitation, yellow fluorescent protein-based protein fragment complementation assays and immunofluorescence staining, we demonstrated that AP-1 mu1A, AP-3 mu1, AP-4 mu1 and clathrin (but not AP-1 mu1B, PKD1 or PKD2) play crucial roles in intracellular sorting and trafficking of kAE1. We also demonstrated colocalization of kAE1 and basolateral-related sorting proteins in human kidney tissues by double immunofluorescence staining. These findings indicate that AP-1 mu1A, AP-3 mu1, AP-4 mu1 and clathrin are required for kAE1 sorting and trafficking from TGN to the basolateral membrane of acid-secreting α-intercalated cells. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The Rab11 Effector Protein FIP1 Regulates Adiponectin Trafficking and Secretion

PubMed Central

Moreno-Navarrete, Jose Maria; Fernandez-Real, Jose Manuel; Mora, Silvia

2013-01-01

Adiponectin is an adipokine secreted by white adipocytes involved in regulating insulin sensitivity in peripheral tissues. Secretion of adiponectin in adipocytes relies on the endosomal system, however, the intracellular machinery involved in mediating adiponectin release is unknown. We have previously reported that intracellular adiponectin partially compartmentalizes with rab 5 and rab11, markers for the early/sorting and recycling compartments respectively. Here we have examined the role of several rab11 downstream effector proteins (rab11 FIPs) in regulating adiponectin trafficking and secretion. Overexpression of wild type rab11 FIP1, FIP3 and FIP5 decreased the amount of secreted adiponectin expressed in HEK293 cells, whereas overexpression of rab11 FIP2 or FIP4 had no effect. Furthermore shRNA-mediated depletion of FIP1 enhanced adiponectin release whereas knock down of FIP5 decreased adiponectin secretion. Knock down of FIP3 had no effect. In 3T3L1 adipocytes, endogenous FIP1 co-distributed intracellularly with endogenous adiponectin and FIP1 depletion enhanced adiponectin release without altering insulin-mediated trafficking of the glucose transporter Glut4. While adiponectin receptors internalized with transferrin receptors, there were no differences in transferrin receptor recycling between wild type and FIP1 depleted adipocytes. Consistent with its inhibitory role, FIP1 expression was decreased during adipocyte differentiation, by treatment with thiazolidinediones, and with increased BMI in humans. In contrast, FIP1 expression increased upon exposure of adipocytes to TNFα. In all, our findings identify FIP1 as a novel protein involved in the regulation of adiponectin trafficking and release. PMID:24040321

Insulin secretion and GLUT-2 expression in undernourished neonate rats.

PubMed

Lopes Da Costa, Célia; Sampaio De Freitas, Marta; Sanchez Moura, Anibal

2004-04-01

In previous studies, we verified increased insulin sensitivity in adult male offspring of lactating rats readjusting to lack of insulin secretion reduction brought about by protein restriction during lactation. The present study aims to evaluate the effects of maternal protein undernutrition during lactation on glucose-induced insulin secretion and GLUT-2 expression in beta-cells of neonate male and female rats. Lactating Wistar rats were given a protein-free diet during the first 10 days and a normal diet (22% of protein) until weaning. The neonates were separated at birth by sex and diet and studied at 4, 8 and 21 days of lactation. Glucose-induced insulin secretion by pancreatic islets was analyzed by radioimmunoassay and GLUT-2 expression in beta-cells by Western blot. Glucose-induced insulin secretion of the undernourished groups was higher than in the control groups except among females. When comparing the male and female groups and the control and undernourished groups, female neonates showed significantly greater insulin secretion than the male group. Also it was noted that undernutrition induced greater GLUT-2 expression. For instance, comparing the undernourished male and female neonates there was an increase in female GLUT-2 expression on day 4. On the other hand, in undernourished male neonates a GLUT-2 expression increased later in lactation. In conclusion, during a short term, maternal undernutrition induces an increase of the glucose-induced insulin secretion only in male neonates and is associated with an increase in GLUT-2 expression in the beta-cell.

Effect of glucose transport inhibitors on vincristine efflux in multidrug-resistant murine erythroleukaemia cells overexpressing the multidrug resistance-associated protein (MRP) and two glucose transport proteins, GLUT1 and GLUT3.

PubMed Central

Martell, R. L.; Slapak, C. A.; Levy, S. B.

1997-01-01

The relationship between mammalian facilitative glucose transport proteins (GLUT) and multidrug resistance was examined in two vincristine (VCR)-selected murine erythroleukaemia (MEL) PC4 cell lines. GLUT proteins, GLUT1 and GLUT3, were constitutively coexpressed in the parental cell line and also in the VCR-selected cell lines. Increased expression of the GLUT1 isoform was noted both in the PC-V40 (a non-P-glycoprotein, mrp-overexpressing subline) and in the more resistant PC-V160 (overexpressing mrp and mdr3) cell lines. Overexpression of GLUT3 was detected only in the PC-V160 subline. An increased rate of facilitative glucose transport (Vmax) and level of plasma membrane GLUT protein expression paralleled increased VCR resistance, active VCR efflux and decreased VCR steady-state accumulation in these cell lines. Glucose transport inhibitors (GTIs), cytochalasin B (CB) and phloretin blocked the active efflux and decreased steady-state accumulation of VCR in the PC-V40 subline. GTIs did not significantly affect VCR accumulation in the parental or PC-V160 cells. A comparison of protein sequences among GLUT1, GLUT3 and MRP revealed a putative cytochalasin B binding site in MRP, which displayed 44% sequence similarity/12% identity with that previously identified in GLUT1 and GLUT3; these regions also exhibited a similar hydropathy plot pattern. The findings suggested that CB bound to MRP and directly or indirectly lowered VCR efflux and/or CB bound to one or both GLUT proteins, which acted to lower the VCR efflux mediated by MRP. This is the first report of a non-neuronal murine cell line that expressed GLUT3. Images Figure 3 PMID:9010020

Neuromuscular electrical stimulation improves GLUT-4 and morphological characteristics of skeletal muscle in rats with heart failure.

PubMed

de Leon, E B; Bortoluzzi, A; Rucatti, A; Nunes, R B; Saur, L; Rodrigues, M; Oliveira, U; Alves-Wagner, A B; Xavier, L L; Machado, U F; Schaan, B D; Dall'Ago, P

2011-02-01

Changes in skeletal muscle morphology and metabolism are associated with limited functional capacity in heart failure, which can be attenuated by neuromuscular electrical stimulation (ES). The purpose of the present study was to analyse the effects of ES upon GLUT-4 protein content, fibre structure and vessel density of the skeletal muscle in a rat model of HF subsequent to myocardial infarction. Forty-four male Wistar rats were assigned to one of four groups: sham (S), sham submitted to ES (S+ES), heart failure (HF) and heart failure submitted to ES (HF+ES). The rats in the ES groups were submitted to ES of the left leg during 20 days (2.5 kHz, once a day, 30 min, duty cycle 50%- 15 s contraction/15 s rest). After this period, the left tibialis anterior muscle was collected from all the rats for analysis. HF+ES rats showed lower values of lung congestion when compared with HF rats (P = 0.0001). Although muscle weight was lower in HF rats than in the S group, thus indicating hypotrophy, 20 days of ES led to their recovery (P < 0.0001). In both groups submitted to ES, there was an increase in muscle vessel density (P < 0.04). Additionally, heart failure determined a 49% reduction in GLUT-4 protein content (P < 0.03), which was recovered by ES (P < 0.01). In heart failure, ES improves morphological changes and raises GLUT-4 content in skeletal muscle. © 2010 The Authors. Acta Physiologica © 2010 Scandinavian Physiological Society.

Mechanistic Study of Human Glucose Transport Mediated by GLUT1.

PubMed

Fu, Xuegang; Zhang, Gang; Liu, Ran; Wei, Jing; Zhang-Negrerie, Daisy; Jian, Xiaodong; Gao, Qingzhi

2016-03-28

The glucose transporter 1 (GLUT1) belongs to the major facilitator superfamily (MFS) and is responsible for the constant uptake of glucose. However, the molecular mechanism of sugar transport remains obscure. In this study, homology modeling and molecular dynamics (MD) simulations in lipid bilayers were performed to investigate the combination of the alternate and multisite transport mechanism of glucose with GLUT1 in atomic detail. To explore the substrate recognition mechanism, the outward-open state human GLUT1 homology model was generated based on the template of xylose transporter XylE (PDB ID: 4GBZ), which shares up to 29% sequence identity and 49% similarity with GLUT1. Through the MD simulation study of glucose across lipid bilayer with both the outward-open GLUT1 and the GLUT1 inward-open crystal structure, we investigated six different conformational states and identified four key binding sites in both exofacial and endofacial loops that are essential for glucose recognition and transport. The study further revealed that four flexible gates consisting of W65/Y292/Y293-M420/TM10b-W388 might play important roles in the transport cycle. The study showed that some side chains close to the central ligand binding site underwent larger position changes. These conformational interchanges formed gated networks within an S-shaped central channel that permitted staged ligand diffusion across the transporter. This study provides new inroads for the understanding of GLUT1 ligand recognition paradigm and configurational features which are important for molecular, structural, and physiological research of the MFS members, especially for GLUT1-targeted drug design and discovery.

Cell Surface Trafficking of TLR1 Is Differentially Regulated by the Chaperones PRAT4A and PRAT4B*

PubMed Central

Hart, Bryan E.; Tapping, Richard I.

2012-01-01

The subcellular localization of Toll-like receptors (TLRs) is critical to their ability to function as innate immune sensors of microbial infection. We previously reported that an I602S polymorphism of human TLR1 is associated with aberrant trafficking of the receptor to the cell surface, loss of responses to TLR1 agonists, and differential susceptibility to diseases caused by pathogenic mycobacteria. Through an extensive analysis of receptor deletion and point mutants we have discovered that position 602 resides within a short 6 amino acid cytoplasmic region that is required for TLR1 surface expression. This short trafficking motif, in conjunction with the adjacent transmembrane domain, is sufficient to direct TLR1 to the cell surface. A serine at position 602 interrupts this trafficking motif and prevents cell surface expression of TLR1. Additionally, we have found that ER-resident TLR chaperones, PRAT4A and PRAT4B, act as positive and negative regulators of TLR1 surface trafficking, respectively. Importantly, either over-expression of PRAT4A or knock-down of PRAT4B rescues cell surface expression of the TLR1 602S variant. We also report that IFN-γ treatment of primary human monocytes derived from homozygous 602S individuals rescues TLR1 cell surface trafficking and cellular responses to soluble agonists. This event appears to be mediated by PRAT4A whose expression is strongly induced in human monocytes by IFN-γ. Collectively, these results provide a mechanism for the differential trafficking of TLR1 I602S variants, and highlight the distinct roles for PRAT4A and PRAT4B in the regulation of TLR1 surface expression. PMID:22447933

Molecular Tools for Facilitative Carbohydrate Transporters (Gluts).

PubMed

Tanasova, Marina; Fedie, Joseph R

2017-09-19

Facilitative carbohydrate transporters-Gluts-have received wide attention over decades due to their essential role in nutrient uptake and links with various metabolic disorders, including diabetes, obesity, and cancer. Endeavors directed towards understanding the mechanisms of Glut-mediated nutrient uptake have resulted in a multidisciplinary research field spanning protein chemistry, chemical biology, organic synthesis, crystallography, and biomolecular modeling. Gluts became attractive targets for cancer research and medicinal chemistry, leading to the development of new approaches to cancer diagnostics and providing avenues for cancer-targeting therapeutics. In this review, the current state of knowledge of the molecular interactions behind Glut-mediated sugar uptake, Glut-targeting probes, therapeutics, and inhibitors are discussed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Infection of CD4{sup +} T lymphocytes by the human T cell leukemia virus type 1 is mediated by the glucose transporter GLUT-1: Evidence using antibodies specific to the receptor's large extracellular domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Qingwen; Agrawal, Lokesh; VanHorn-Ali, Zainab

2006-05-25

To analyze HTLV-1 cytotropism, we developed a highly sensitive vaccinia virus-based assay measuring activation of a reporter gene upon fusion of two distinct cell populations. We used this system in a functional cDNA screening to isolate and confirm that the glucose transporter protein 1 (GLUT-1) is a receptor for HTLV-1. GLUT-1 is a ubiquitously expressed plasma membrane glycoprotein with 12 transmembrane domains and 6 extracellular loops (ECL). We demonstrate for the first time that peptide antibodies (GLUT-IgY) raised in chicken to the large extracellular loop (ECL1) detect GLUT-1 at the cell surface and inhibit envelope (Env)-mediated fusion and infection. Efficientmore » GLUT-IgY staining was detected with peripheral blood CD4{sup +} lymphocytes purified by positive selection. Further, GLUT-IgY caused efficient inhibition of Env-mediated fusion and infection of CD4{sup +} T and significantly lower inhibition of CD8{sup +} T lymphocytes. The specificity of GLUT-IgY antibodies to GLUT-1 was demonstrated by ECL1 peptide competition studies. Grafting ECL1 of GLUT-1 onto the receptor-negative GLUT-3 conferred significant receptor activity. In contrast, grafting ECL1 of GLUT-3 onto GLUT-1 resulted in a significant loss of the receptor activity. The ECL1-mediated receptor activity was efficiently blocked with four different human monoclonal antibody (HMab) to HTLV-1 Env. The ECL1-derived peptide blocked HTLV-1 Env-mediated fusion with several nonhuman mammalian cell lines. The results demonstrate the utilization of cell surface GLUT-1 in HTLV-1 infection of CD4{sup +} T lymphocytes and implicate a critical role for the ECL1 region in viral tropism.« less

Enhancement of Glucose Uptake by Meso-Dihydroguaiaretic Acid through GLUT4 Up-Regulation in 3T3-L1 Adipocytes.

PubMed

Lee, Anna; Choi, Kyeong-Mi; Jung, Won-Beom; Jeong, Heejin; Kim, Ga-Yeong; Lee, Ju Hyun; Lee, Mi Kyeong; Hong, Jin Tae; Roh, Yoon-Seok; Sung, Sang-Hyun; Yoo, Hwan-Soo

2017-08-28

Type 2 diabetes is characterized by insulin resistance, which leads to increased blood glucose levels. Adipocytes are involved in the development of insulin resistance, resulting from the dysfunction of the insulin signaling pathway. In this study, we investigated whether meso -dihydroguaiaretic acid (MDGA) may modulate glucose uptake in adipocytes, and examined its mechanism of action. MDGA enhanced adipogenesis through up-regulation of peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding protein α in 3T3-L1 adipocytes partially differentiated with sub-optimal concentrations of insulin. MDGA also increased glucose uptake by stimulating expression and translocation of glucose transporter 4 (GLUT4) in adipocytes. These results suggest that MDGA may increase GLUT4 expression and its translocation by promoting insulin sensitivity, leading to enhanced glucose uptake.

A Cause of Permanent Ketosis: GLUT-1 Deficiency.

PubMed

Chenouard, Alexis; Vuillaumier-Barrot, Sandrine; Seta, Nathalie; Kuster, Alice

2015-01-01

GLUT-1-deficiency syndrome (GLUT1-DS; OMIM 606777) is a treatable metabolic disorder caused by a mutation of SLC2A1 gene. The functional deficiency of the GLUT1 protein leads to an impaired glucose transport into the brain, resulting in neurologic disorders.We report on a 6-month-old boy with preprandial malaises who was treated monthly by a sorcerer because of a permanent acetonemic odor. He subsequently developed pharmaco-resistant seizures with microcephaly and motor abnormalities. Metabolic explorations were unremarkable except for a fasting glucose test which revealed an abnormal increase of blood ketone bodies. At the age of 35 months, GLUT1-DS was diagnosed based on hypoglycorrhachia with a decreased CSF to blood glucose ratio, and subsequent direct sequencing of the SLC2A1 gene revealed a de novo heterozygous mutation, c.349A>T (p.Lys117X) on exon 4. It was noteworthy that the patient adapted to the deficient cerebral glucose transport by permanent ketone body production since early life. Excessive ketone body production in this patient provided an alternative energy substrate for his brain. We suggest a cerebral metabolic adaptation with upregulation of monocarboxylic acid transporter proteins (MCT1) at the blood-brain barrier provoked by neuroglycopenia and allowing ketone body utilization by the brain. This case illustrates that GLUT1-DS should be considered in the differential diagnosis of permanent ketosis.

Near-critical GLUT1 and Neurodegeneration.

PubMed

Barros, L Felipe; San Martín, Alejandro; Ruminot, Ivan; Sandoval, Pamela Y; Fernández-Moncada, Ignacio; Baeza-Lehnert, Felipe; Arce-Molina, Robinson; Contreras-Baeza, Yasna; Cortés-Molina, Francisca; Galaz, Alex; Alegría, Karin

2017-11-01

Recent articles have drawn renewed attention to the housekeeping glucose transporter GLUT1 and its possible involvement in neurodegenerative diseases. Here we provide an updated analysis of brain glucose transport and the cellular mechanisms involved in its acute modulation during synaptic activity. We discuss how the architecture of the blood-brain barrier and the low concentration of glucose within neurons combine to make endothelial/glial GLUT1 the master controller of neuronal glucose utilization, while the regulatory role of the neuronal glucose transporter GLUT3 emerges as secondary. The near-critical condition of glucose dynamics in the brain suggests that subtle deficits in GLUT1 function or its activity-dependent control by neurons may contribute to neurodegeneration. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Expression of conventional and novel glucose transporters, GLUT1, -9, -10, and -12, in vascular smooth muscle cells

PubMed Central

Pyla, Rajkumar; Poulose, Ninu; Jun, John Y.

2013-01-01

Intimal hyperplasia is characterized by exaggerated proliferation of vascular smooth muscle cells (VSMCs). Enhanced VSMC growth is dependent on increased glucose uptake and metabolism. Facilitative glucose transporters (GLUTs) are comprised of conventional GLUT isoforms (GLUT1–5) and novel GLUT isoforms (GLUT6–14). Previous studies demonstrate that GLUT1 overexpression or GLUT10 downregulation contribute to phenotypic changes in VSMCs. To date, the expression profile of all 14 GLUT isoforms has not been fully examined in VSMCs. Using the proliferative and differentiated phenotypes of human aortic VSMCs, the present study has determined the relative abundance of GLUT1–14 mRNAs by quantitative real-time PCR analysis. Twelve GLUT mRNAs excluding GLUT7 and GLUT14 were detectable in VSMCs. In the proliferative phenotype, the relative abundance of key GLUT mRNAs was GLUT1 (∼43%) > GLUT10 (∼26%) > GLUT9 (∼13%) > GLUT12 (∼4%), whereas in the differentiated phenotype the relative abundance was GLUT10 (∼28%) > GLUT1 (∼25%) > GLUT12 (∼20%) > GLUT9 (∼14%), together constituting 86–87% of total GLUT transcripts. To confirm the expression of key GLUT proteins, immunoblot and immunocytochemical analyses were performed using GLUT isoform-specific primary antibodies. The protein bands characteristic of GLUT1, -9, -10, and -12 were detected in VSMCs in parallel with respective positive controls. In particular, GLUT1 protein expression showed different molecular forms representative of altered glycosylation. While GLUT1 protein displayed a predominant distribution in the plasma membrane, GLUT9, -10, and -12 proteins were mostly distributed in the intracellular compartments. The present study provides the first direct evidence for GLUT9 and GLUT12 expression in VSMCs in conjunction with the previously identified GLUT1 and GLUT10. PMID:23302780

Green and Chamomile Teas, but not Acarbose, Attenuate Glucose and Fructose Transport via Inhibition of GLUT2 and GLUT5.

PubMed

Villa-Rodriguez, Jose A; Aydin, Ebru; Gauer, Julia S; Pyner, Alison; Williamson, Gary; Kerimi, Asimina

2017-12-01

High glycaemic sugars result in blood-glucose spikes, while large doses of post-prandial fructose inundate the liver, causing an imbalance in energy metabolism, both leading to increased risk of metabolic malfunction and type 2 diabetes. Acarbose, used for diabetes management, reduces post-prandial hyperglycaemia by delaying carbohydrate digestion. Chamomile and green teas both inhibited digestive enzymes (α-amylase and maltase) related to intestinal sugar release, as already established for acarbose. However, acarbose had no effect on uptake of sugars using both differentiated human Caco-2 cell monolayers and Xenopus oocytes expressing human glucose transporter-2 (GLUT2) and GLUT5. Both teas effectively inhibited transport of fructose and glucose through GLUT2 inhibition, while chamomile tea also inhibited GLUT5. Long term incubation of Caco-2/TC7 cells with chamomile tea for 16 h or 4 days did not enhance the observed effects, indicating that inhibition is acute. Sucrase activity was directly inhibited by green tea and acarbose, but not chamomile. These findings show that chamomile and green teas are potential tools to manage absorption and metabolism of sugars with efficacy against high sugar bolus stress inflicted, for example, by high fructose syrups, where the drug acarbose would be ineffective. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal structure of the human glucose transporter GLUT1

NASA Astrophysics Data System (ADS)

Deng, Dong; Xu, Chao; Sun, Pengcheng; Wu, Jianping; Yan, Chuangye; Hu, Mingxu; Yan, Nieng

2014-06-01

The glucose transporter GLUT1 catalyses facilitative diffusion of glucose into erythrocytes and is responsible for glucose supply to the brain and other organs. Dysfunctional mutations may lead to GLUT1 deficiency syndrome, whereas overexpression of GLUT1 is a prognostic indicator for cancer. Despite decades of investigation, the structure of GLUT1 remains unknown. Here we report the crystal structure of human GLUT1 at 3.2 Å resolution. The full-length protein, which has a canonical major facilitator superfamily fold, is captured in an inward-open conformation. This structure allows accurate mapping and potential mechanistic interpretation of disease-associated mutations in GLUT1. Structure-based analysis of these mutations provides an insight into the alternating access mechanism of GLUT1 and other members of the sugar porter subfamily. Structural comparison of the uniporter GLUT1 with its bacterial homologue XylE, a proton-coupled xylose symporter, allows examination of the transport mechanisms of both passive facilitators and active transporters.

A dipeptide and an amino acid present in whey protein hydrolysate increase translocation of GLUT-4 to the plasma membrane in Wistar rats.

PubMed

Morato, P N; Lollo, P C B; Moura, C S; Batista, T M; Carneiro, E M; Amaya-Farfan, J

2013-08-15

Whey protein hydrolysate (WPH) is capable of increasing muscle glycogen reserves and of concentrating the glucose transporter in the plasma membrane (PM). The objective of this study was to determine which WPH components could modulate translocation of the glucose transporter GLUT-4 to the PM of animal skeletal muscle. Forty-nine animals were divided into 7 groups (n=7) and received by oral gavage 30% glucose plus 0.55 g/kg body mass of the following WPH components: (a) control; (b) WPH; (c) L-isoleucine; (d) L-leucine; (e) L-leucine plus L-isoleucine; (f) L-isoleucyl-L-leucine dipeptide; (g) L-leucyl-L-isoleucine dipeptide. After receiving these solutions, the animals were sacrificed and the GLUT-4 analysed by western blot. Additionally, glycogen, glycaemia, insulin and free amino acids were also determined by standard methods. Of the WPH components tested, the amino acid L-isoleucine and the peptide L-leucyl-L-isoleucine showed greater efficiency in translocating GLUT-4 to the PM and of increasing glucose capture by skeletal muscle. Copyright © 2013 Elsevier Ltd. All rights reserved.

Caffeine inhibits glucose transport by binding at the GLUT1 nucleotide-binding site

PubMed Central

Sage, Jay M.; Cura, Anthony J.; Lloyd, Kenneth P.

2015-01-01

Glucose transporter 1 (GLUT1) is the primary glucose transport protein of the cardiovascular system and astroglia. A recent study proposes that caffeine uncompetitive inhibition of GLUT1 results from interactions at an exofacial GLUT1 site. Intracellular ATP is also an uncompetitive GLUT1 inhibitor and shares structural similarities with caffeine, suggesting that caffeine acts at the previously characterized endofacial GLUT1 nucleotide-binding site. We tested this by confirming that caffeine uncompetitively inhibits GLUT1-mediated 3-O-methylglucose uptake in human erythrocytes [Vmax and Km for transport are reduced fourfold; Ki(app) = 3.5 mM caffeine]. ATP and AMP antagonize caffeine inhibition of 3-O-methylglucose uptake in erythrocyte ghosts by increasing Ki(app) for caffeine inhibition of transport from 0.9 ± 0.3 mM in the absence of intracellular nucleotides to 2.6 ± 0.6 and 2.4 ± 0.5 mM in the presence of 5 mM intracellular ATP or AMP, respectively. Extracellular ATP has no effect on sugar uptake or its inhibition by caffeine. Caffeine and ATP displace the fluorescent ATP derivative, trinitrophenyl-ATP, from the GLUT1 nucleotide-binding site, but d-glucose and the transport inhibitor cytochalasin B do not. Caffeine, but not ATP, inhibits cytochalasin B binding to GLUT1. Like ATP, caffeine renders the GLUT1 carboxy-terminus less accessible to peptide-directed antibodies, but cytochalasin B and d-glucose do not. These results suggest that the caffeine-binding site bridges two nonoverlapping GLUT1 endofacial sites—the regulatory, nucleotide-binding site and the cytochalasin B-binding site. Caffeine binding to GLUT1 mimics the action of ATP but not cytochalasin B on sugar transport. Molecular docking studies support this hypothesis. PMID:25715702

Glutamine Enhances the Hypoglycemic Effect of Insulin in L6 Cells via Phosphatidylinositol-3-Kinase (PI3K)/Protein Kinase B (AKT)/Glucose Transporter 4 (GLUT4) Signaling Pathway.

PubMed

Wang, Caijuan; Deng, Yujiao; Yue, Yenan; Chen, Wenting; Zhang, Yu; Shi, Guifang; Wu, Zhongming

2018-03-01

BACKGROUND Diabetes mellitus (DM) is characterized by a decreased blood level of glutamine (Gln), which may contribute to the disturbance in the effect of insulin on skeletal muscle. Therefore, it is crucial to study how to improve the effect of insulin on skeletal muscle by increasing Gln. In the present study, we investigated the effect of Gln on the hypoglycemic action of insulin in skeletal muscle L6 cells at high glucose levels through the insulin signaling pathway and glycogen synthesis pathway. MATERIAL AND METHODS The L6 cells were cultured in and stimulated by Gln and insulin. The glutamine analogue, L-Gamma-Glutamyl-p-nitroanilide (GPNA), was used for verifying the effect of Gln. The expression of insulin signaling molecules, including phosphatidylinositol-3-kinase (PI3K), 3-phosphoinositide-dependent protein kinase-1 (PDK1), protein kinase B (AKT), protein kinase C zeta (PKCz), and glucose transporter 4 (GLUT4), were detected by real-time PCR and Western blot analysis, GLUT4 translocation was observed by immunofluorescence staining, glycogen synthase kinase (GSK) was analyzed by Western blotting, and glucose uptake was measured by glucose oxidase method (GOD). RESULTS The results demonstrated that Gln combined with insulin remarkably up-regulated PI3K and PDK1 and also increased AKT and PKCz phosphorylation. The present study shows that Gln enhanced the impact of insulin on GLUT4 and its translocation. The results of glucose uptake and GSK phosphorylation further confirmed the hypoglycemic effect of Gln accompanied with insulin. The hypoglycemic effect of Gln was reversed by GPNA. CONCLUSIONS These findings suggest that Gln enhances the hypoglycemic role of insulin through the PI3K/AKT/GLUT4 signaling pathway and glycogen synthesis pathway.

Genistein induces estrogen-like effects in ovariectomized rats but fails to increase cardiac GLUT4 and oxidative stress.

PubMed

Al-Nakkash, Layla; Markus, Brandon; Batia, Lyn; Prozialeck, Walter C; Broderick, Tom L

2010-12-01

This study aimed to determine whether a 2-week genistein treatment induced estrogen-like effects in ovariectomized (OVX) Sprague-Dawley rats, after 2 weeks of subcutaneous genistein injections (250 mg/kg of body weight/day). Uterine weight, uterine-to-body weight ratio, femur weight, and femur-to-body weight ratio were all significantly increased with genistein in OVX rats. Body weight was significantly decreased with genistein in OVX rats. Genistein had no effect on the weights of heart, heart-to-body ratio, and fat pad but significantly decreased heart rate and pulse pressure. Genistein had no effect on cardiac GLUT4 protein, oxidative stress, plasma glucose, nonesterified fatty acids, or low-density lipoprotein levels; however, plasma insulin levels were significantly increased. Our results show that a 2-week genistein treatment produced favorable estrogen-like effects on some physical and physiological characteristics in OVX rats. However, based on our experimental conditions, the effects of genistein were not associated with changes in cardiac GLUT4 or oxidative stress.

Palmitate stimulates glucose transport in rat adipocytes by a mechanism involving translocation of the insulin sensitive glucose transporter (GLUT4)

NASA Technical Reports Server (NTRS)

Hardy, R. W.; Ladenson, J. H.; Henriksen, E. J.; Holloszy, J. O.; McDonald, J. M.

1991-01-01

In rat adipocytes, palmitate: a) increases basal 2-deoxyglucose transport 129 +/- 27% (p less than 0.02), b) decreases the insulin sensitive glucose transporter (GLUT4) in low density microsomes and increases GLUT4 in plasma membranes and c) increases the activity of the insulin receptor tyrosine kinase. Palmitate-stimulated glucose transport is not additive with the effect of insulin and is not inhibited by the protein kinase C inhibitors staurosporine and sphingosine. In rat muscle, palmitate: a) does not affect basal glucose transport in either the soleus or epitrochlearis and b) inhibits insulin-stimulated glucose transport by 28% (p less than 0.005) in soleus but not in epitrochlearis muscle. These studies demonstrate a potentially important differential role for fatty acids in the regulation of glucose transport in different insulin target tissues.

GLUT1 deficiency syndrome in clinical practice.

PubMed

Klepper, Joerg

2012-07-01

GLUT1 deficiency syndrome (GLUT1DS) is caused by impaired glucose transport into brain and is effectively treated by means of a ketogenic diet. In clinical practice the diagnosis of GLUT1DS often is challenging due to the increasing complexity of symptoms, diagnostic cut-offs for hypoglycorrhachia and genetic heterogeneity. In terms of treatment alternative ketogenic diets and their long-term side effects as well as novel compounds such as alpha-lipoic acid and triheptanoin have raised a variety of issues. The current diagnostic and therapeutic approach to GLUT1DS is discussed in this review in view of these recent developments. Copyright © 2011. Published by Elsevier B.V.

GLUT-1 Expression in Proliferative Endometrium, Endometrial Hyperplasia, Endometrial Adenocarcinoma and the Relationship Between GLUT-1 Expression and Prognostic Parameters in Endometrial Adenocarcinoma.

PubMed

Canpolat, Tuba; Ersöz, Canan; Uğuz, Aysun; Vardar, Mehmet Ali; Altintaş, Aytekin

2016-01-01

Malignant cells show increased glucose uptake in in vitro and in vivo studies. This uptake is mediated by glucose transporter proteins. GLUT-1 is the most common transporter protein, and its expression is reported to be increase in many human cancers. The aim of this study is to determine the GLUT-1 overexpression in benign, hyperplastic, and malignant endometrial tissues, to evaluate the usefulness of GLUT-1 expression in endometrial hyperplasia, and to determine its role in the neoplastic progression to endometrioid type adenocarcinoma. We also aimed to analyze prognostic clinical parameters, predict prognosis, and survival. We examined immunohistochemical expression of GLUT-1 in 91 cases of endometrial hyperplasia, 100 cases of endometrioid type adenocarcinoma, and 10 proliferative endometrial tissues. The percentage of positive cells and staining intensity were assessed in a semi quantitative fashion and scored (1+ to 3+). GLUT-1 immunoreactivity was not present in proliferative endometrium. Twenty-nine (31.9%) of 91 endometrial hyperplasia cases showed positive immunoreactivity, of which only six were cases of hyperplasia without atypia while 23 of them were cases with atypia. We found GLUT-1 positivity of 95% in endometrioid type adenocarcinoma. GLUT-1 overexpression was not significantly correlated with any of the clinicopathological parameters except histological grade in endometrioid adenocarcinoma; the survival was not found to be correlated with GLUT-1 expression. GLUT-1 immunostaining may be useful in distinguishing hyperplasia without atypia from hyperplasia with atypia; GLUT-1 overexpression is a consistent feature of endometrioid adenocarcinoma. A correlation between GLUT -1 expression and tumor grade has been found, although other prognostic parameters and survival has no meaningful correlation.

Stimulation of GLUT-1 glucose transporter expression in response to hyperosmolarity.

PubMed

Hwang, D Y; Ismail-Beigi, F

2001-10-01

Glucose transporter isoform-1 (GLUT-1) expression is stimulated in response to stressful conditions. Here we examined the mechanisms mediating the enhanced expression of GLUT-1 by hyperosmolarity. GLUT-1 mRNA, GLUT-1 protein, and glucose transport increased after exposure of Clone 9 cells to 600 mosmol/l (produced by addition of mannitol). The stimulation of glucose transport was biphasic: in the early phase (0-6 h) a approximately 2.5-fold stimulation of glucose uptake was associated with no change in the content of GLUT-1 mRNA, GLUT-1 protein, or GLUT-1 in the plasma membrane, whereas the approximately 17-fold stimulation of glucose transport during the late phase (12-24 h) was associated with increases in both GLUT-1 mRNA (approximately 7.5-fold) and GLUT-1 protein content. Cell sorbitol increased after 3 h of exposure to hyperosmolarity. The increase in GLUT-1 mRNA content was associated with an increase in the half-life of the mRNA from 2 to 8 h. A 44-bp region in the proximal GLUT-1 promoter was necessary for basal activity and for the two- to threefold increases in expression by hyperosmolarity. It is concluded that the increase in GLUT-1 mRNA content is mediated by both enhanced transcription and stabilization of GLUT-1 mRNA and is associated with increases in GLUT-1 content and glucose transport activity.

GLUT1 and CAIX expression profiles in breast cancer correlate with adverse prognostic factors and MCT1 overexpression.

PubMed

Pinheiro, C; Sousa, B; Albergaria, A; Paredes, J; Dufloth, R; Vieira, D; Schmitt, F; Baltazar, F

2011-10-01

The goal of the present work was to evaluate the correlation of glucose transporter 1 (GLUT1) and carbonic anhydrase IX (CAIX) with the monocarboxylate transporters 1 (MCT1) and 4 (MCT4) and their chaperone, CD147, in breast cancer. The clinico-pathological value of GLUT1 and CAIX was also evaluated. For that, we analysed the immunohistochemical expression of GLUT1 and CAIX, in a large series of invasive breast carcinoma samples (n=124), previously characterized for MCT1, MCT4 and CD147 expression. GLUT1 expression was found in 46% of the cases (57/124), while CAIX was found in 18% of the cases (22/122). Importantly, both MCT1 and CD147, but not MCT4, were associated with GLUT1 and CAIX expression. Also, GLUT1 and CAIX correlated with each other. Concerning the clinico-pathological values, GLUT1 was associated with high grade tumours, basal-like subtype, absence of progesterone receptor, presence of vimentin and high proliferative index as measured by Ki-67. Additionally, CAIX was associated with large tumour size, high histological grade, basal-like subtype, absence of estrogen and progesterone receptors and presence of basal cytokeratins and vimentin expression. Finally, patients with CAIX positive tumours had a significantly shorter disease-free survival. The association between MCT1 and both GLUT1 and CAIX may result from hypoxia-mediated metabolic adaptations, which confer a glycolytic, acid-resistant and more aggressive phenotype to cancer cells.

Curcumin directly inhibits the transport activity of GLUT1

PubMed Central

Gunnink, Leesha K.; Alabi, Ola D.; Kuiper, Benjamin D.; Gunnink, Stephen M.; Schuiteman, Sam J.; Strohbehn, Lauren E.; Hamilton, Kathryn E.; Wrobel, Kathryn E.; Louters, Larry L.

2016-01-01

Curcumin, a major ingredient in turmeric, has a long history of medicinal applications in a wide array of maladies including treatment for diabetes and cancer. Seemingly counterintuitive to the documented hypoglycemic effects of curcumin, however, a recent report indicates that curcumin directly inhibits glucose uptake in adipocytes. The major glucose transporter in adipocytes is GLUT4. Therefore, this study investigates the effects of curcumin in cell lines where the major transporter is GLUT1. We report that curcumin has an immediate inhibitory effect on basal glucose uptake in L929 fibroblast cells with a maximum inhibition of 80% achieved at 75 μM curcumin. Curcumin also blocks activation of glucose uptake by azide, glucose deprivation, hydroxylamine, or phenylarsine oxide. Inhibition does not increase with exposure time and the inhibitory effects reverse within an hour. Inhibition does not appear to involve a reaction between curcumin and the thiol side chain of a cysteine residue since neither prior treatment of cells with iodoacetamide nor curcumin with cysteine alters curcumin’s inhibitory effects. Curcumin is a mixed inhibitor reducing the Vmax of 2DG transport by about half with little effect on the Km. The inhibitory effects of curcumin are not additive to the effects of cytochalasin B and 75 μM curcumin actually reduces specific cytochalasin B binding by 80%. Taken together, the data suggest that curcumin binds directly to GLUT1 at a site that overlaps with the cytochalasin B binding site and thereby inhibits glucose transport. A direct inhibition of GLUT proteins in intestinal epithelial cells would likely reduce absorption of dietary glucose and contribute to a hypoglycemic effect of curcumin. Also, inhibition of GLUT1 activity might compromise cancer cells that overexpress GLUT1 and be another possible mechanism for the documented anticancer effects of curcumin. PMID:27039889

Insulin stimulates syntaxin4 SNARE complex assembly via a novel regulatory mechanism.

PubMed

Kioumourtzoglou, Dimitrios; Gould, Gwyn W; Bryant, Nia J

2014-04-01

Insulin stimulates glucose transport into fat and muscle cells by increasing the exocytic trafficking rate of the GLUT4 facilitative glucose transporter from intracellular stores to the plasma membrane. Delivery of GLUT4 to the plasma membrane is mediated by formation of functional SNARE complexes containing syntaxin4, SNAP23, and VAMP2. Here we have used an in situ proximity ligation assay to integrate these two observations by demonstrating for the first time that insulin stimulation causes an increase in syntaxin4-containing SNARE complex formation in adipocytes. Furthermore, we demonstrate that insulin brings about this increase in SNARE complex formation by mobilizing a pool of syntaxin4 held in an inactive state under basal conditions. Finally, we have identified phosphorylation of the regulatory protein Munc18c, a direct target of the insulin receptor, as a molecular switch to coordinate this process. Hence, this report provides molecular detail of how the cell alters membrane traffic in response to an external stimulus, in this case, insulin.

Effect of Bisphenol-A (BPA) on insulin signal transduction and GLUT4 translocation in gastrocnemius muscle of adult male albino rat.

PubMed

Mullainadhan, Vigneswari; Viswanathan, Mangala Priya; Karundevi, Balasubramanian

2017-09-01

Environmental estrogens bind to estrogen receptors, mimic estrogenic actions, and have adverse effects on human health like Bisphenol - A (BPA) which is used as a monomer in the production of polycarbonate plastics (PC) and epoxy resins which are used in variety of canned foods. Skeletal muscle plays an essential role in maintaining systemic glucose metabolism. In the present study, we investigated the possible effects of BPA on insulin signalling molecules and GLUT4 translocation in the gastrocnemius muscle of adult male rat. Rats were divided into four groups - Group I: Control (vehicle-corn oil treated), Group II, III and IV were administered with BPA (10, 100 and 400mg/kg b.wt/day, respectively) through oral gavage. Fasting blood glucose level of BPA treated groups showed a significant increase, oral glucose tolerance and insulin tolerance were also impaired in these animals. BPA significantly decreased the protein levels of insulin signalling molecules like IR, IRS-1, Akt, AS160 and its phosphorylated forms and blunts GLUT4 translocation by altering the levels of v- and t- SNARE proteins that assist the translocation process, thereby decreasing glucose uptake and oxidation in the gastrocnemius muscle. These results suggest that BPA has detrimental effects on insulin signalling molecules and GLUT4 translocation in the gastrocnemius muscle and thus impairs glucose homeostasis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Brain Glucose Transporter (Glut3) Haploinsufficiency Does Not Impair Mouse Brain Glucose Uptake

PubMed Central

Stuart, Charles A.; Ross, Ian R.; Howell, Mary E. A.; McCurry, Melanie P.; Wood, Thomas G.; Ceci, Jeffrey D.; Kennel, Stephen J.; Wall, Jonathan

2011-01-01

Mouse brain expresses three principle glucose transporters. Glut1 is an endothelial marker and is the principal glucose transporter of the blood-brain barrier. Glut3 and Glut6 are expressed in glial cells and neural cells. A mouse line with a null allele for Glut3 has been developed. The Glut3−/− genotype is intrauterine lethal by seven days post-coitis, but the heterozygous (Glut3+/−) littermate survives, exhibiting rapid post-natal weight gain, but no seizures or other behavioral aberrations. At twelve weeks of age, brain uptake of tail vein-injected 3H-2-deoxy glucose in Glut3+/− mice was not different from Glut3+/+ littermates, despite 50% less Glut3 protein expression in the brain. The brain uptake of injected 18F-2-fluoro-2-deoxy glucose was similarly not different from Glut3+/− littermates in the total amount, time course, or brain imaging in the Glut3+/− mice. Glut1 and Glut6 protein expressions evaluated by immunoblots were not affected by the diminished Glut3 expression in the Glut3+/− mice. We conclude that a 50% decrease in Glut3 is not limiting for the uptake of glucose into the mouse brain, since Glut3 haploinsufficiency does not impair brain glucose uptake or utilization. PMID:21316350

Expression of Glut-1 is a prognostic marker for oral squamous cell carcinoma patients.

PubMed

Eckert, A W; Lautner, M H W; Taubert, H; Schubert, J; Bilkenroth, U

2008-12-01

Oral squamous cell carcinoma (OSCC) is among the tenth most common human cancers worldwide with evidence of an increase in incidence rate and mortality. Despite advances in treatment modalities, the prognosis of this cancer is still very poor and has not changed over the past two decades. This study is based on samples collected from 42 patients with a primary OSCC. Immunohistochemical staining for Glut-1 was carried out and compared with the clinicopathological data. Thirty-two patients showed in their tumors a weak or undetectable Glut-1 expression, whereas in tumors of 10 patients a moderate to strong Glut-1 expression was detected. In multivariate Cox's regression hazard analysis, patients whose tumors had a moderate to strong Glut-1 expression possessed a 4.9-fold increased risk of tumor-related death compared to the other patients. Our results suggest that Glut-1 expression is an independent prognostic marker for routine assessment of OSCC.

Autophagy-mediated Regulation of BACE1 Protein Trafficking and Degradation*

PubMed Central

Feng, Tuancheng; Tammineni, Prasad; Agrawal, Chanchal; Jeong, Yu Young

2017-01-01

β-Site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is the major neuronal β-secretase for amyloid-β generation and is degraded in lysosomes. The autophagy-lysosomal system plays a key role in the maintenance of cellular homeostasis in neurons. Recent studies established that nascent autophagosomes in distal axons move predominantly in the retrograde direction toward the soma, where mature lysosomes are mainly located. However, it remains unknown whether autophagy plays a critical role in regulation of BACE1 trafficking and degradation. Here, we report that induction of neuronal autophagy enhances BACE1 turnover, which is suppressed by lysosomal inhibition. A significant portion of BACE1 is recruited to the autophagy pathway and co-migrates robustly with autophagic vacuoles along axons. Moreover, we reveal that autophagic vacuole-associated BACE1 is accumulated in the distal axon of Alzheimer's disease-related mutant human APP transgenic neurons and mouse brains. Inducing autophagy in mutant human APP neurons augments autophagic retention of BACE1 in distal axons, leading to enhanced β-cleavage of APP. This phenotype can be reversed by Snapin-enhanced retrograde transport, which facilitates BACE1 trafficking to lysosomes for degradation. Therefore, our study provides new insights into autophagy-mediated regulation of BACE1 turnover and APP processing, thus building a foundation for future development of potential Alzheimer's disease therapeutic strategies. PMID:28028177

Increased intracellular localization of brain GLUT-1 transporter in response to ethanol during chick embryogenesis.

PubMed

Carver, F M; Shibley, I A; Miles, D S; Pennington, J S; Pennington, S N

1999-10-01

Fetal exposure to ethanol is associated with growth retardation of the developing central nervous system. We have previously described a chick model to study the molecular mechanism of ethanol effects on glucose metabolism in ovo. Total membrane fractions were prepared from day 4, day 5, and day 7 chick embryos exposed in ovo to ethanol or to vehicle. By Western blotting analysis, ethanol exposure caused a mean 7- to 10-fold increase in total GLUT-1 and a 2-fold increase in total GLUT-3. However, glucose uptake by ethanol-treated cells increased by only 10%. Analysis of isolated plasma (PM) and intracellular (IM) membranes from day 5 cranial tissue revealed a mean 25% decrease in GLUT-1 in the PM and a 66% increase in the IM in the ethanol group vs. control. The amount of PM GLUT-3 was unchanged but that of IM GLUT-3 was significantly decreased. The data suggest that GLUT-3 cell surface expression may be resistant to the suppressive effects of ethanol in the developing brain of ethanol-treated embryos. The overall increase in GLUT-1 may reflect a deregulation of the transporter induced by ethanol exposure. The increased IM localization and decreased amount of PM GLUT-1 may be a mechanism used by the ethanol-treated cell to maintain normal glucose uptake despite the overall increased level of the transporter.

Placental Glucose and Amino Acid Transport in Calorie-Restricted Wild-Type and Glut3 Null Heterozygous Mice

PubMed Central

Ganguly, Amit; Collis, Laura

2012-01-01

Calorie restriction (CR) decreased placenta and fetal weights in wild-type (wt) and glucose transporter (Glut) 3 heterozygous null (glut3+/−) mice. Because placental nutrient transport is a primary energy determinant of placentofetal growth, we examined key transport systems. Maternal CR reduced intra- and transplacental glucose and leucine transport but enhanced system A amino acid transport in wt mice. These transport perturbations were accompanied by reduced placental Glut3 and leucine amino acid transporter (LAT) family member 2, no change in Glut1 and LAT family member 1, but increased sodium coupled neutral amino acid transporter (SNAT) and SNAT2 expression. We also noted decreased total and active phosphorylated forms of mammalian target of rapamycin, which is the intracellular nutrient sensor, the downstream total P70S6 kinase, and pS6 ribosomal protein with no change in total and phosphorylated 4E-binding protein 1. To determine the role of placental Glut3 in mediating CR-induced placental transport changes, we next investigated the effect of gestational CR in glut3+/− mice. In glut3+/− mice, a key role of placental Glut3 in mediating transplacental and intraplacental glucose transport was established. In addition, reduced Glut3 results in a compensatory increase of leucine and system A transplacental transport. On the other hand, diminished Glut3-mediated intraplacental glucose transport reduced leucine transport and mammalian target of rapamycin and preserved LAT and enhancing SNAT. CR in glut3+/− mice further reduced transplacental glucose transport and enhanced system A amino acid transport, although the increased leucine transport was lost. In addition, increased Glut3 was seen and preserved Glut1, LAT, and SNAT. These placental changes collectively protect survival of wt and glut3+/− fetuses against maternal CR-imposed reduction of macromolecular nutrients. PMID:22700768

Placental glucose and amino acid transport in calorie-restricted wild-type and Glut3 null heterozygous mice.

PubMed

Ganguly, Amit; Collis, Laura; Devaskar, Sherin U

2012-08-01

Calorie restriction (CR) decreased placenta and fetal weights in wild-type (wt) and glucose transporter (Glut) 3 heterozygous null (glut3(+/-)) mice. Because placental nutrient transport is a primary energy determinant of placentofetal growth, we examined key transport systems. Maternal CR reduced intra- and transplacental glucose and leucine transport but enhanced system A amino acid transport in wt mice. These transport perturbations were accompanied by reduced placental Glut3 and leucine amino acid transporter (LAT) family member 2, no change in Glut1 and LAT family member 1, but increased sodium coupled neutral amino acid transporter (SNAT) and SNAT2 expression. We also noted decreased total and active phosphorylated forms of mammalian target of rapamycin, which is the intracellular nutrient sensor, the downstream total P70S6 kinase, and pS6 ribosomal protein with no change in total and phosphorylated 4E-binding protein 1. To determine the role of placental Glut3 in mediating CR-induced placental transport changes, we next investigated the effect of gestational CR in glut3(+/-) mice. In glut3(+/-) mice, a key role of placental Glut3 in mediating transplacental and intraplacental glucose transport was established. In addition, reduced Glut3 results in a compensatory increase of leucine and system A transplacental transport. On the other hand, diminished Glut3-mediated intraplacental glucose transport reduced leucine transport and mammalian target of rapamycin and preserved LAT and enhancing SNAT. CR in glut3(+/-) mice further reduced transplacental glucose transport and enhanced system A amino acid transport, although the increased leucine transport was lost. In addition, increased Glut3 was seen and preserved Glut1, LAT, and SNAT. These placental changes collectively protect survival of wt and glut3(+/-) fetuses against maternal CR-imposed reduction of macromolecular nutrients.

Computer-assisted identification of novel small molecule inhibitors targeting GLUT1

NASA Astrophysics Data System (ADS)

Wan, Zhining; Li, Xin; Sun, Rong; Li, Yuanyuan; Wang, Xiaoyun; Li, Xinru; Rong, Li; Shi, Zheng; Bao, Jinku

2015-12-01

Glucose transporters (GLUTs) are the main carriers of glucose that facilitate the diffusion of glucose in mammalian cells, especially GLUT1. Notably, GLUT1 is a rate-limiting transporter for glucose uptake, and its overexpression is a common characteristic in most cancers. Thus, the inhibition of GLUT1 by novel small compounds to lower glucose levels for cancer cells has become an emerging strategy. Herein, we employed high-throughput screening approaches to identify potential inhibitors against the sugar-binding site of GLUT1. Firstly, molecular docking screening was launched against the specs products, and three molecules (ZINC19909927, ZINC19908826, and ZINC19815451) were selected as candidate GLUT1 inhibitors for further analysis. Then, taking the initial ligand β-NG as a reference, molecular dynamic (MD) simulations and molecular mechanics/generalized born surface area (MM/GBSA) method were applied to evaluate the binding stability and affinity of the three candidates towards GLUT1. Finally, we found that ZINC19909927 might have the highest affinity to occupy the binding site of GLUT1. Meanwhile, energy decomposition analysis identified several residues located in substrate-binding site that might provide clues for future inhibitor discovery towards GLUT1. Taken together, these results in our study may provide valuable information for identifying new inhibitors targeting GLUT1-mediated glucose transport and metabolism for cancer therapeutics.

Enhanced basal activation of mitogen-activated protein kinases in adipocytes from type 2 diabetes: potential role of p38 in the downregulation of GLUT4 expression.

PubMed

Carlson, Christian J; Koterski, Sandra; Sciotti, Richard J; Poccard, German Braillard; Rondinone, Cristina M

2003-03-01

Serine and threonine kinases may contribute to insulin resistance and the development of type 2 diabetes. To test the potential for members of the mitogen-activated protein (MAP) kinase family to contribute to type 2 diabetes, we examined basal and insulin-stimulated Erk 1/2, JNK, and p38 phosphorylation in adipocytes isolated from healthy and type 2 diabetic individuals. Maximal insulin stimulation increased the phosphorylation of Erk 1/2 and JNK in healthy control subjects but not type 2 diabetic patients. Insulin stimulation did not increase p38 phosphorylation in either healthy control subjects or type 2 diabetic patients. In type 2 diabetic adipocytes, the basal phosphorylation status of these MAP kinases was significantly elevated and was associated with decreased IRS-1 and GLUT4 in these fat cells. To determine whether MAP kinases were involved in the downregulation of IRS-1 and GLUT4 protein levels, selective inhibitors were used to inhibit these MAP kinases in 3T3-L1 adipocytes treated chronically with insulin. Inhibition of Erk 1/2, JNK, or p38 had no effect on insulin-stimulated reduction of IRS-1 protein levels. However, inhibition of the p38 pathway prevented the insulin-stimulated decrease in GLUT4 protein levels. In summary, type 2 diabetes is associated with an increased basal activation of the MAP kinase family. Furthermore, upregulation of the p38 pathway might contribute to the loss of GLUT4 expression observed in adipose tissue from type 2 diabetic patients.

Acute exercise increases brain region-specific expression of MCT1, MCT2, MCT4, GLUT1, and COX IV proteins.

PubMed

Takimoto, Masaki; Hamada, Taku

2014-05-01

The brain is capable of oxidizing lactate and ketone bodies through monocarboxylate transporters (MCTs). We examined the protein expression of MCT1, MCT2, MCT4, glucose transporter 1 (GLUT1), and cytochrome-c oxidase subunit IV (COX IV) in the rat brain within 24 h after a single exercise session. Brain samples were obtained from sedentary controls and treadmill-exercised rats (20 m/min, 8% grade). Acute exercise resulted in an increase in lactate in the cortex, hippocampus, and hypothalamus, but not the brainstem, and an increase in β-hydroxybutyrate in the cortex alone. After a 2-h exercise session MCT1 increased in the cortex and hippocampus 5 h postexercise, and the effect lasted in the cortex for 24 h postexercise. MCT2 increased in the cortex and hypothalamus 5-24 h postexercise, whereas MCT2 increased in the hippocampus immediately after exercise, and remained elevated for 10 h postexercise. Regional upregulation of MCT2 after exercise was associated with increases in brain-derived neurotrophic factor and tyrosine-related kinase B proteins, but not insulin-like growth factor 1. MCT4 increased 5-10 h postexercise only in the hypothalamus, and was associated with increased hypoxia-inducible factor-1α expression. However, none of the MCT isoforms in the brainstem was affected by exercise. Whereas GLUT 1 in the cortex increased only at 18 h postexercise, COX IV in the hippocampus increased 10 h after exercise and remained elevated for 24 h postexercise. These results suggest that acute prolonged exercise induces the brain region-specific upregulation of MCT1, MCT2, MCT4, GLUT1, and COX IV proteins.

Severe Hypertriglyceridemia in Glut1D on Ketogenic Diet.

PubMed

Klepper, Joerg; Leiendecker, Baerbel; Heussinger, Nicole; Lausch, Ekkehart; Bosch, Friedrich

2016-04-01

High-fat ketogenic diets are the only treatment available for Glut1 deficiency (Glut1D). Here, we describe an 8-year-old girl with classical Glut1D responsive to a 3:1 ketogenic diet and ethosuximide. After 3 years on the diet a gradual increase of blood lipids was followed by rapid, severe asymptomatic hypertriglyceridemia (1,910 mg/dL). Serum lipid apheresis was required to determine liver, renal, and pancreatic function. A combination of medium chain triglyceride-oil and a reduction of the ketogenic diet to 1:1 ratio normalized triglyceride levels within days but triggered severe myoclonic seizures requiring comedication with sultiam. Severe hypertriglyceridemia in children with Glut1D on ketogenic diets may be underdiagnosed and harmful. In contrast to congenital hypertriglyceridemias, children with Glut1D may be treated effectively by dietary adjustments alone. Georg Thieme Verlag KG Stuttgart · New York.

Distal tubule bicarbonate reabsorption in NH4Cl acidotic rats.

PubMed

Vandorpe, D H; Levine, D Z

1989-08-01

NH4Cl acidosis--a common experimental model of hyperchloremic metabolic acidosis--elicits complex intrarenal responses whereby the fall in plasma bicarbonate concentration can be restored to normal after the initial acid load. Using the technique of in vivo micropuncture of surface distal tubules of the rat kidney, we attempted to further define controlling mechanisms underlying the enhanced bicarbonate reabsorption in this setting. Specifically, we wished to determine the dependence of distal tubule bicarbonate reabsorption (JtCO2) on sodium transport, water reabsorption, and carbonic anhydrase activity. Surface distal tubules of Sprague-Dawley rats made acidotic by ammonium chloride gavage (arterial blood pH: 7.15 +/- 0.01, [HCO3]: 14.8 +/- 0.5 mM) were perfused in vivo at 8 and 24 nL/min with 4 different isoosmotic, 25 mM bicarbonate solutions: Group 1 was perfused with 60 mM Na, Group 2 with 60 mM choline, Group 3 with 60 mM choline + 3 x 10(-4) M amiloride, and Group 4 with 60 mM Na + 10(-3) M acetazolamide. At 8 nL/min, significant bicarbonate reabsorption occurred with all perfusates. JtCO2 was 65 +/- 4, 59 +/- 5, 58 +/- 6, and 40 +/- 4 pmol.min-1.mm-1, in Groups 1, 2, 3, and 4, respectively. However, JtCO2 in Group 4 was significantly less than that in Groups 1 and 2 (p less than 0.01 and p less than 0.05, respectively). Amiloride added to the low sodium perfusate did not reduce bicarbonate reabsorption. We conclude that bicarbonate reabsorption in distal tubules of acidotic rats is acetazolamide-sensitive and is not significantly sustained by sodium or water movements.

Glucose transporter 3 (GLUT3) protein expression in human placenta across gestation

PubMed Central

Brown, Kelecia; Heller, Debra S.; Zamudio, Stacy; Illsley, Nicholas P.

2012-01-01

Conflicting information regarding expression of GLUT3 protein in the human placenta has been reported and the localization and pattern of expression of GLUT3 protein across gestation has not been clearly defined. The objective of this study was characterization of syncytial GLUT3 protein expression across gestation. We hypothesized that GLUT3 protein is present in the syncytial microvillous membrane and that its expression decreases over gestation. GLUT3 protein was measured in samples from a range of gestational ages (first to third trimester), with human brain and human bowel used as a positive and negative control respectively. As an additional measure of specificity, we transfected BeWo choriocarcinoma cells, a trophoblast cell line expressing GLUT3, with siRNA directed against GLUT3 and analyzed expression by Western blotting. GLUT3 was detected in the syncytiotrophoblast at all gestational ages by immunohistochemistry. Using Western blotting GLUT3 was detected as an integral membrane protein at a molecular weight of ~50kDa in microvillous membranes from all trimesters but not in syncytial basal membranes. The identity of the primary antibody target was confirmed by demonstrating that expression of the immunoblotting signal in GLUT3 siRNA-treated BeWo was decreased to 18 ± 6% (mean ± SEM) of that seen in cells transfected with a non-targeting siRNA. GLUT3 expression in microvillous membranes detected by Western blot decreased through the trimesters such that expression in the second trimester (wks 14–26) was 48 ± 7% of that in the first trimester and by the third trimester (wks 31–40) only 34 ± 10% of first trimester expression. In addition, glucose uptake into BeWo cells treated with GLUT3 siRNA was reduced to 60% of that measured in cells treated with the non-targeting siRNA. This suggests that GLUT3-mediated uptake comprises approximately 50% of glucose uptake into BeWo cells. These results confirm the hypothesis that GLUT3 is present in the

Placental glucose transporter (GLUT)-1 is down-regulated in preeclampsia.

PubMed

Lüscher, Benjamin P; Marini, Camilla; Joerger-Messerli, Marianne S; Huang, Xiao; Hediger, Matthias A; Albrecht, Christiane; Baumann, Marc U; Surbek, Daniel V

2017-07-01

Transplacental fetal glucose supply is predominantly regulated by glucose transporter-1 (GLUT1). Altered expression and/or function of GLUT1 may affect the intrauterine environment, which could compromise fetal development and may contribute to fetal programming. To date it is unknown whether placental GLUT1 is affected by preeclampsia, which is often associated with intrauterine growth restriction (IUGR). We addressed the hypothesis that preeclampsia leads to decreased expression and function of placental GLUT1. Placentae were obtained following normal pregnancy and from pregnancies affected by preeclampsia. Washed villous tissue fragments were used to prepare syncytial microvillous (MVM) and basal plasma membranes (BM) microvesicles. GLUT1 protein and mRNA expression was assessed by western blot analysis and qPCR using Fast SYBR Green. A radio-labeled glucose up-take assay using placenta-derived syncytial microvesicles was used to analyze GLUT1 function. GLUT1 protein expression was significantly down-regulated in (apical) MVM of the syncytiotrophoblast in preeclampsia (n = 6) compared to controls (n = 6) (0.40 ± 0.04 versus 1.00 ± 0.06, arbitrary units, P < 0.001, Student's t-test), while GLUT1 mRNA expression did not show a significant difference. In addition, the functional assay in syncytial microvesicles showed a significantly decreased glucose transport activity in preeclampsia (61.78 ± 6.48%, P < 0.05) compared to controls. BM GLUT1 protein expression was unchanged and glucose up-take into BM microvesicles showed no differences between the preeclampsia and control groups. Our study shows for the first time that in preeclampsia placental GLUT1 expression and function are down-regulated at the apical plasma membrane of the syncytiotrophoblast. Further studies are needed to assess whether these changes occur also in vivo and contribute to the development of IUGR in preeclampsia. Copyright © 2017 Elsevier Ltd. All rights reserved.

WZB117 (2-Fluoro-6-(m-hydroxybenzoyloxy) Phenyl m-Hydroxybenzoate) Inhibits GLUT1-mediated Sugar Transport by Binding Reversibly at the Exofacial Sugar Binding Site*

PubMed Central

Ojelabi, Ogooluwa A.; Lloyd, Kenneth P.; Simon, Andrew H.; De Zutter, Julie K.; Carruthers, Anthony

2016-01-01

WZB117 (2-fluoro-6-(m-hydroxybenzoyloxy) phenyl m-hydroxybenzoate) inhibits passive sugar transport in human erythrocytes and cancer cell lines and, by limiting glycolysis, inhibits tumor growth in mice. This study explores how WZB117 inhibits the erythrocyte sugar transporter glucose transport protein 1 (GLUT1) and examines the transporter isoform specificity of inhibition. WZB117 reversibly and competitively inhibits erythrocyte 3-O-methylglucose (3MG) uptake with Ki(app) = 6 μm but is a noncompetitive inhibitor of sugar exit. Cytochalasin B (CB) is a reversible, noncompetitive inhibitor of 3MG uptake with Ki(app) = 0.3 μm but is a competitive inhibitor of sugar exit indicating that WZB117 and CB bind at exofacial and endofacial sugar binding sites, respectively. WZB117 inhibition of GLUTs expressed in HEK293 cells follows the order of potency: insulin-regulated GLUT4 ≫ GLUT1 ≈ neuronal GLUT3. This may explain WZB117-induced murine lipodystrophy. Molecular docking suggests the following. 1) The WZB117 binding envelopes of exofacial GLUT1 and GLUT4 conformers differ significantly. 2) GLUT1 and GLUT4 exofacial conformers present multiple, adjacent glucose binding sites that overlap with WZB117 binding envelopes. 3) The GLUT1 exofacial conformer lacks a CB binding site. 4) The inward GLUT1 conformer presents overlapping endofacial WZB117, d-glucose, and CB binding envelopes. Interrogating the GLUT1 mechanism using WZB117 reveals that subsaturating WZB117 and CB stimulate erythrocyte 3MG uptake. Extracellular WZB117 does not affect CB binding to GLUT1, but intracellular WZB117 inhibits CB binding. These findings are incompatible with the alternating conformer carrier for glucose transport but are consistent with either a multisubunit, allosteric transporter, or a transporter in which each subunit presents multiple, interacting ligand binding sites. PMID:27836974

Glut-1 as a prognostic biomarker in oral squamous cell carcinoma

PubMed Central

Harshani, Jyotsna M; Yeluri, Sivaranjani; Guttikonda, Venkateswara Rao

2014-01-01

Introduction: Glut-1 is a glucose transporter protein, the expression of which is upregulated in malignant cells which show increased glucose uptake. Alterations in expression of Glut-1 have been reported in several pre-malignant and malignant lesions. The objectives of the present study were to compare the expression of Glut-1 in normal persons and in patients with oral squamous cell carcinoma (OSCC), to correlate the expression of Glut-1 with respect to clinical staging of OSCC and to evaluate the expression of Glut-1 with respect to different histopathological grades of OSCC. Materials and Methods: Thirty cases of OSCC were staged clinically and graded histopathologically. Immunohistochemical method was used to detect the expression of Glut-1 in OSCC and the same was compared with the normal subjects. The scores were compared using the chi-square test. Results: Glut-1 expression was detected in all grades of OSCC. A significant correlation with a P value of 0.00004 was found in immunostaining between normal and OSCC. The expression of Glut-1 was significant when compared with different clinical stages with significant P value of 0.0004 and in different histopathological grades of OSCC with a P value of 0.00001. Conclusion: Higher immunohistochemical staining scores were obtained with increased clinical staging and histopathological grades of OSCC. High expression of Glut-1 may be related to poor prognosis in OSCC. PMID:25948991

Calpain I Activation Causes GLUT3 Proteolysis and Downregulation of O-GlcNAcylation in Alzheimer's Disease Brain.

PubMed

Gu, Jianlan; Jin, Nana; Ma, Denglei; Chu, Dandan; Iqbal, Khalid; Gong, Cheng-Xin; Liu, Fei

2018-01-01

Impairment of cerebral glucose uptake/metabolism in individuals with Alzheimer's disease (AD) is believed to lead to downregulation of protein O-GlcNAcylation, which contributes to tau pathogenesis through tau hyperphosphorylation. Level of glucose transporter 3 (GLUT3), a neuronal specific glucose transporter, is decreased in AD brain, which may contribute to impaired brain glucose uptake/metabolism. However, what causes the reduction of GLUT3 in AD brain is not fully understood. Here, we report 1) that decrease of GLUT3 is associated with the reduction of protein O-GlcNAcylation in AD brain, 2) that GLUT3 level is negatively correlated with calpain I activation in human brain, 3) that calpain I proteolyzes GLUT3 at the N-terminus in vitro, and 4) that activation of calpain I is negatively correlated with protein O-GlcNAcylation in AD brain. Furthermore, we found that overexpression of GLUT3 enhances protein O-GlcNAcylation in N2a cells. Overexpression of calpain I suppresses protein O-GlcNAcylation in these cells. These findings suggest a novel mechanism by which calpain I overactivation leads to GLUT3 degradation and the consequent down-regulation of protein O-GlcNAcylation in AD brain.

Semen Cassiae Extract Improves Glucose Metabolism by Promoting GlUT4 Translocation in the Skeletal Muscle of Diabetic Rats

PubMed Central

Zhang, Meiling; Li, Xin; Liang, Hangfei; Cai, Huqiang; Hu, Xueling; Bian, Yu; Dong, Lei; Ding, Lili; Wang, Libo; Yu, Bo; Zhang, Yan; Zhang, Yao

2018-01-01

Diabetes mellitus is a clinical syndrome characterised by hyperglycaemia; its complications lead to disability and even death. Semen Cassiae is a traditional Chinese medicine, which has anti-hypertensive, anti-hyperlipidaemia, anti-oxidation, and anti-ageing properties. Our study was designed to evaluate the action of total anthraquinones of Semen Cassiae extract (SCE) on the improvement of glucose metabolism in diabetic rats and to elucidate the underlying mechanism. First, we evaluated the effect of SCE on normal rats. Next, we observed the effect of SCE using a rat model of diabetes, which was established by feeding rats with high-energy diet for 4 weeks and a single intraperitoneal injection of streptozotocin (STZ; 30 mg/kg) 3 weeks after starting the high-energy diet. Rats in different SCE groups (administered 54, 108, and 324 mg/kg/day of SCE) and metformin group (162 mg/kg/day, positive control drug) were treated with the corresponding drugs 1 week before starting high-energy diet and treatment continued for 5 weeks; meanwhile, rats in the control group were administered the same volume of sodium carboxymethyl cellulose solution (vehicle solution). One week after STZ injection, fasting blood glucose (FBG), oral glucose tolerance (OGT), fasting serum insulin (FSI) and serum lipids were quantified. Finally, the expression of proteins in the phosphatidylinositol-3-kinase (PI3K)–Akt–AS160–glucose transporter isoform 4 (GLUT4) signalling pathway was detected by western blotting. The data indicated that the levels of FBG and serum lipids were significantly lowered, and OGT and FSI were markedly increased in diabetic rats treated with SCE (108 mg/kg/day); however, SCE did not cause hypoglycaemia in normal rats. The molecular mechanisms were explored in the skeletal muscle. SCE markedly restored the decreased translocation of GLUT4 in diabetic rats. Moreover, the protein expressions of phosphorylated-AS160 (Thr642), phosphorylated-Akt (Ser473) and PI3K were

Sodium 4-phenylbutyrate downregulates Hsc70: implications for intracellular trafficking of DeltaF508-CFTR.

PubMed

Rubenstein, R C; Zeitlin, P L

2000-02-01

The most common mutation of the cystic fibrosis transmembrane conductance regulator (CFTR), DeltaF508, is a trafficking mutant that has prolonged associations with molecular chaperones and is rapidly degraded, at least in part by the ubiquitin-proteasome system. Sodium 4-phenylbutyrate (4PBA) improves DeltaF508-CFTR trafficking and function in vitro in cystic fibrosis epithelial cells and in vivo. To further understand the mechanism of action of 4PBA, we tested the hypothesis that 4PBA modulates the targeting of DeltaF508-CFTR for ubiquitination and degradation by reducing the expression of Hsc70 in cystic fibrosis epithelial cells. IB3-1 cells (genotype DeltaF508/W1282X) that were treated with 0.05-5 mM 4PBA for 2 days in culture demonstrated a dose-dependent reduction in Hsc70 protein immunoreactivity and mRNA levels. Immunoprecipitation with Hsc70-specific antiserum demonstrated that Hsc70 and CFTR associated under control conditions and that treatment with 4PBA reduced these complexes. Levels of immunoreactive Hsp40, Hdj2, Hsp70, Hsp90, and calnexin were unaffected by 4PBA treatment. These data suggest that 4PBA may improve DeltaF508-CFTR trafficking by allowing a greater proportion of mutant CFTR to escape association with Hsc70.

WZB117 (2-Fluoro-6-(m-hydroxybenzoyloxy) Phenyl m-Hydroxybenzoate) Inhibits GLUT1-mediated Sugar Transport by Binding Reversibly at the Exofacial Sugar Binding Site.

PubMed

Ojelabi, Ogooluwa A; Lloyd, Kenneth P; Simon, Andrew H; De Zutter, Julie K; Carruthers, Anthony

2016-12-23

WZB117 (2-fluoro-6-(m-hydroxybenzoyloxy) phenyl m-hydroxybenzoate) inhibits passive sugar transport in human erythrocytes and cancer cell lines and, by limiting glycolysis, inhibits tumor growth in mice. This study explores how WZB117 inhibits the erythrocyte sugar transporter glucose transport protein 1 (GLUT1) and examines the transporter isoform specificity of inhibition. WZB117 reversibly and competitively inhibits erythrocyte 3-O-methylglucose (3MG) uptake with K i (app) = 6 μm but is a noncompetitive inhibitor of sugar exit. Cytochalasin B (CB) is a reversible, noncompetitive inhibitor of 3MG uptake with K i (app) = 0.3 μm but is a competitive inhibitor of sugar exit indicating that WZB117 and CB bind at exofacial and endofacial sugar binding sites, respectively. WZB117 inhibition of GLUTs expressed in HEK293 cells follows the order of potency: insulin-regulated GLUT4 ≫ GLUT1 ≈ neuronal GLUT3. This may explain WZB117-induced murine lipodystrophy. Molecular docking suggests the following. 1) The WZB117 binding envelopes of exofacial GLUT1 and GLUT4 conformers differ significantly. 2) GLUT1 and GLUT4 exofacial conformers present multiple, adjacent glucose binding sites that overlap with WZB117 binding envelopes. 3) The GLUT1 exofacial conformer lacks a CB binding site. 4) The inward GLUT1 conformer presents overlapping endofacial WZB117, d-glucose, and CB binding envelopes. Interrogating the GLUT1 mechanism using WZB117 reveals that subsaturating WZB117 and CB stimulate erythrocyte 3MG uptake. Extracellular WZB117 does not affect CB binding to GLUT1, but intracellular WZB117 inhibits CB binding. These findings are incompatible with the alternating conformer carrier for glucose transport but are consistent with either a multisubunit, allosteric transporter, or a transporter in which each subunit presents multiple, interacting ligand binding sites. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

The expression of the class 1 glucose transporter isoforms in human embryonic stem cells, and the potential use of GLUT2 as a marker for pancreatic progenitor enrichment.

PubMed

Segev, Hana; Fishman, Betina; Schulman, Rita; Itskovitz-Eldor, Joseph

2012-07-01

Even before the first appearance of the developing pancreas, glucose is the major substrate in the growing embryo. The transport of glucose across cell membranes is facilitated by a family of membranal glucose transporters (GLUT). We analyzed changes in expression of class 1 glucose transporters (GLUT1-4) during human embryonic stem cell (hESC) and human induced pluripotent stem cell (hiPSC) differentiation, from undifferentiated cells to 28-day-old embryoid bodies (EBs). We also examined the potential use of GLUT2 as a marker for differentiating pancreatic progenitor cells. Using quantitative real time polymerase chain reaction (qPCR), western blot, and immunofluorescence, we observed enhanced expression of GLUT1 and GLUT2 during differentiation, but only minor change in GLUT3 expression. GLUT4 expression was found to be very low both at the RNA and in the protein levels. Expression of the early pancreatic transcription factor, pancreatic duodenal homeobox gene 1 (PDX1), correlated with GLUT2 expression, suggesting the potential use of GLUT2 as a surface marker for tracking pancreatic precursor cells. After sorting EBs according to their membranal GLUT2 expression, GLUT2 and PDX1 expression were found elevated, as was expression of other endodermal markers such as PAX4, NGN3, CXCR4, and SOX17. This simple method may be used to differentiate embryonic stem cells and to isolate from them, using GLUT2 as a surface marker, an enriched pancreatic progenitor cell population in order to achieve insulin-producing cells. The sorted GLUT2 cells may potentially be used in the future as insulin-producing cells for beta cell therapies.

3 CFR - Delegation of Authority Pursuant to Sections 110(d)(4) and 110(f) of the Trafficking Victims...

Code of Federal Regulations, 2014 CFR

2014-01-01

... 3 The President 1 2014-01-01 2014-01-01 false Delegation of Authority Pursuant to Sections 110(d)(4) and 110(f) of the Trafficking Victims Protection Act of 2000, as Amended Presidential Documents Other Presidential Documents Memorandum of July 29, 2013 Delegation of Authority Pursuant to Sections 110(d)(4) and 110(f) of the Trafficking Victims...

3 CFR - Delegation of Authority Pursuant to Sections 110(d)(4) and 110(f) of the Trafficking Victims...

Code of Federal Regulations, 2013 CFR

2013-01-01

... 3 The President 1 2013-01-01 2013-01-01 false Delegation of Authority Pursuant to Sections 110(d)(4) and 110(f) of the Trafficking Victims Protection Act of 2000, as Amended Presidential Documents Other Presidential Documents Memorandum of February 3, 2012 Delegation of Authority Pursuant to Sections 110(d)(4) and 110(f) of the Trafficking...

Human trafficking and health: a cross-sectional survey of NHS professionals’ contact with victims of human trafficking

PubMed Central

Ross, Claire; Dimitrova, Stoyanka; Howard, Louise M; Dewey, Michael; Zimmerman, Cathy; Oram, Siân

2015-01-01

Objectives (1) To estimate the proportion of National Health Service (NHS) professionals who have come into contact with trafficked people and (2) to measure NHS professionals’ knowledge and confidence to respond to human trafficking. Design A cross-sectional survey. Setting Face-to-face mandatory child protection and/or vulnerable adults training sessions at 10 secondary healthcare provider organisations in England, and meetings of the UK College of Emergency Medicine. Participants 782/892 (84.4%) NHS professionals participated, including from emergency medicine, maternity, mental health, paediatrics and other clinical disciplines. Measures Self-completed questionnaire developed by an expert panel. Questionnaire asks about prior training and contact with potential victims of trafficking, perceived and actual human trafficking knowledge, confidence in responding to human trafficking, and interest in future human trafficking training. Results 13% participants reported previous contact with a patient they knew or suspected of having been trafficked; among maternity services professionals this was 20.4%. However, 86.8% (n=679) reported lacking knowledge of what questions to ask to identify potential victims and 78.3% (n=613) reported that they had insufficient training to assist trafficked people. 71% (n=556), 67.5% (n=528) and 53.4% (n=418) lacked confidence in making appropriate referrals for men, women and children, respectively, who had been trafficked. 95.3% (n=746) of respondents were unaware of the scale of human trafficking in the UK, and 76.5% (n=598) were unaware that calling the police could put patients in more danger. Psychometric analysis showed that subscales measuring perceived knowledge, actual knowledge and confidence to respond to human trafficking demonstrated good internal consistency (Cronbach's αs 0.93, 0.63 and 0.64, respectively) and internal correlations. Conclusions NHS professionals working in secondary care are in contact with potential

Murine Glut-1 transporter haploinsufficiency: postnatal deceleration of brain weight and reactive astrocytosis.

PubMed

Ullner, Paivi M; Di Nardo, Alessia; Goldman, James E; Schobel, Scott; Yang, Hong; Engelstad, Kristin; Wang, Dong; Sahin, Mustafa; De Vivo, Darryl C

2009-10-01

Glucose transporter type 1 (Glut-1) facilitates glucose flux across the blood-brain-barrier. In humans, Glut-1 deficiency causes acquired microcephaly, seizures and ataxia, which are recapitulated in our Glut-1 haploinsufficient mouse model. Postnatal brain weight deceleration and development of reactive astrogliosis were significant by P21 in Glut-1(+/-) mice. The brain weight differences remained constant after P21 whereas the reactive astrocytosis continued to increase and peaked at P90. Brain immunoblots showed increased phospho-mTOR and decreased phospho-GSK3-beta by P14. After fasting, the mature Glut-1(+/-) females showed a trend towards elevated phospho-GSK3-beta, a possible neuroprotective response. Lithium chloride treatment of human skin fibroblasts from control and Glut-1 DS patients produced a 45% increase in glucose uptake. Brain imaging of mature Glut-1(+/-) mice revealed a significantly decreased hippocampal volume. These subtle immunochemical changes reflect chronic nutrient deficiency during brain development and represent the experimental correlates to the human neurological phenotype associated with Glut-1 DS.

Co-expression of CD147 and GLUT-1 indicates radiation resistance and poor prognosis in cervical squamous cell carcinoma.

PubMed

Huang, Xin-Qiong; Chen, Xiang; Xie, Xiao-Xue; Zhou, Qin; Li, Kai; Li, Shan; Shen, Liang-Fang; Su, Juan

2014-01-01

The aim of this study was to investigate the association of CD147 and GLUT-1, which play important roles in glycolysis in response to radiotherapy and clinical outcomes in patients with locally advanced cervical squamous cell carcinoma (LACSCC). The records of 132 female patients who received primary radiation therapy to treat LACSCC at FIGO stages IB-IVA were retrospectively reviewed. Forty-seven patients with PFS (progression-free survival) of less than 36 months were regarded as radiation-resistant. Eighty-five patients with PFS longer than 36 months were regarded as radiation-sensitive. Using pretreatment paraffin-embedded tissues, we evaluated CD147 and GLUT-1 expression by immunohistochemistry. Overexpression of CD147, GLUT-1, and CD147 and GLUT-1 combined were 44.7%, 52.9% and 36.5%, respectively, in the radiation-sensitive group, and 91.5%, 89.4% and 83.0%, respectively, in the radiation-resistant group. The 5-year progress free survival (PFS) rates in the CD147-low, CD147-high, GLUT-1-low, GLUT-1-high, CD147- and/or GLUT-1-low and CD147- and GLUT-1- dual high expression groups were 66.79%, 87.10%, 52.78%, 85.82%, 55.94%, 82.90% and 50.82%, respectively. CD147 and GLUT-1 co-expression, FIGO stage and tumor diameter were independent poor prognostic factors for patients with LACSCC in multivariate Cox regression analysis. Patients with high expression of CD147 alone, GLUT-1 alone or co-expression of CD147 and GLUT-1 showed greater resistance to radiotherapy and a shorter PFS than those with low expression. In particular, co-expression of CD147 and GLUT-1 can be considered as a negative independent prognostic factor.

Co-expression of CD147 and GLUT-1 indicates radiation resistance and poor prognosis in cervical squamous cell carcinoma

PubMed Central

Huang, Xin-Qiong; Chen, Xiang; Xie, Xiao-Xue; Zhou, Qin; Li, Kai; Li, Shan; Shen, Liang-Fang; Su, Juan

2014-01-01

The aim of this study was to investigate the association of CD147 and GLUT-1, which play important roles in glycolysis in response to radiotherapy and clinical outcomes in patients with locally advanced cervical squamous cell carcinoma (LACSCC). The records of 132 female patients who received primary radiation therapy to treat LACSCC at FIGO stages IB-IVA were retrospectively reviewed. Forty-seven patients with PFS (progression-free survival) of less than 36 months were regarded as radiation-resistant. Eighty-five patients with PFS longer than 36 months were regarded as radiation-sensitive. Using pretreatment paraffin-embedded tissues, we evaluated CD147 and GLUT-1 expression by immunohistochemistry. Overexpression of CD147, GLUT-1, and CD147 and GLUT-1 combined were 44.7%, 52.9% and 36.5%, respectively, in the radiation-sensitive group, and 91.5%, 89.4% and 83.0%, respectively, in the radiation-resistant group. The 5-year progress free survival (PFS) rates in the CD147-low, CD147-high, GLUT-1-low, GLUT-1-high, CD147- and/or GLUT-1-low and CD147- and GLUT-1- dual high expression groups were 66.79%, 87.10%, 52.78%, 85.82%, 55.94%, 82.90% and 50.82%, respectively. CD147 and GLUT-1 co-expression, FIGO stage and tumor diameter were independent poor prognostic factors for patients with LACSCC in multivariate Cox regression analysis. Patients with high expression of CD147 alone, GLUT-1 alone or co-expression of CD147 and GLUT-1 showed greater resistance to radiotherapy and a shorter PFS than those with low expression. In particular, co-expression of CD147 and GLUT-1 can be considered as a negative independent prognostic factor. PMID:24817962

Hypoxia-Related Marker GLUT-1, CAIX, Proliferative Index and Microvessel Density in Canine Oral Malignant Neoplasia

PubMed Central

Meier, Valeria; Guscetti, Franco; Roos, Malgorzata; Ohlerth, Stefanie; Pruschy, Martin; Rohrer Bley, Carla

2016-01-01

For various types of tumor therapy, it is suggested that co-targeting of tumor microenvironment, mainly tumor vasculature, mediates tumor response mechanisms. Immunohistochemistry for glucose transporter-1 (GLUT-1), carbonic anhydrase-IX (CAIX), Ki-67, and von Willebrand factor VIII for microvessel density (MVD) were performed on formalin-fixed paraffin-embedded samples of canine oral malignant neoplasms. Polarographic oxygen measurements (median pO2) and perfusion data via contrast-enhanced power Doppler ultrasound (median vascularity, median blood volume) provided additional information. Ninety-two samples were analyzed: sarcomas (n = 32), carcinomas (n = 30), and malignant melanomas (n = 30). Polarographic oxygen and perfusion data was available in 22.8% (sarcomas n = 9, carcinomas n = 7, melanomas n = 5), and 27.1% (sarcomas n = 10, carcinomas n = 8, melanomas n = 7) of cases, respectively. GLUT-1 expression was detected in 46.7% of all samples, and was generally weak. CAIX expression was found in 34.8% of all samples. Median Ki-67 score and MVD count was 19% and 17, respectively. The evaluation of the GLUT-1 score and continuous data showed significantly lower GLUT-1 levels in sarcomas (mean 5.1%, SD 6.2) versus carcinomas and melanomas (mean 16.5%/ 19.0%, SD 17.3/ 20.9, p = 0.001). The expression of CAIX correlated mildly positively with GLUT-1 (p = 0.018, rho = 0.250) as well as with Ki-67 (p = 0.014, rho = 0.295). MVD showed a significantly lower level in melanomas (mean 12.6, SD 7.7) versus sarcomas and carcinomas (mean 21.8/ 26.9, SD 13.0/20.4, p = 0.001). Median vascularity and blood volume were significantly lower in sarcomas (mean 10.4%, SD 11.0, and mean 6.3%, SD 6.5, respectively) versus carcinomas (mean 39.2%, SD 16.4 and mean 33.0%, SD 25.6, respectively) and melanomas (mean 36.0%, SD 18.3, and 31.5%, SD 24.5). Between the 3 histological groups, there was neither a significant difference in the GLUT-1 and CAIX score and continuous data, nor the Ki

vGLUT2 heterozygous mice show more susceptibility to clonic seizures induced by pentylenetetrazol.

PubMed

Schallier, Anneleen; Massie, Ann; Loyens, Ellen; Moechars, Diederik; Drinkenburg, Wilhelmus; Michotte, Yvette; Smolders, Ilse

2009-01-01

Glutamate, the most abundant excitatory neurotransmitter in the central nervous system, is well known to be implicated in epileptic seizures. Therefore, impairments in glutamate transport could have an involvement in the mechanism of epileptogenesis. The uptake of glutamate into synaptic vesicles is mediated by vesicular glutamate transporters (vGLUTs). There are three known vGLUT isoforms, vGLUT1-3. In this study, we are particularly interested in the vGLUT2 isoform. We investigated the possible role of vGLUT2 in pentylenetetrazol (PTZ)-induced seizure generation. Seizure threshold of PTZ was compared in vGLUT2 heterozygous knock out (HET) and wild type (WT) mice. In comparison with their WT littermates a lower dose of PTZ was needed in the vGLUT2 HET mice until the onset of the first myoclonic jerk. The threshold for PTZ-induced clonic seizure activity was also lower in the vGLUT2 HET mice. These results indicate, for the first time, that vGLUT2 is likely involved in the epileptogenesis of generalized seizures.

Expression of Ki-67 (MIB-1) and GLUT-1 proteins in non-advanced prostatic cancer.

PubMed

Luczynska, Elzbieta; Gasinska, Anna; Wilk, Waclaw

2012-12-01

The expression of Ki-67 (MIB-1) and glucose transporter-1 (GLUT-1) were evaluated in patients with clinically localized prostate cancer (PC) who had undergone radical prostatectomy with curative intent. 140 low advanced PC specimens were studied. Protein expression was assessed immunohistochemically on tumour sections and expressed as a labelling index, i.e. the percentage of positively stained cells. In the case of Ki-67 nuclear staining and in the case of GLUT-1 membrane and cytoplasmic staining was considered as positive. The patients' mean age was 62.9 ±6.2 years. There were 13 (9.3%) at pTNM stage 1, 78 (55.7%) at stage 2, 40 (28.6%) at stage 3 and 9 (6.4%) at stage 4, respectively. 75 (53.6%) tumours were well differentiated (Gleason score ≤6), 52 (37.1%) moderately differentiated (Gleason score of 7) and 13 (9.3%) poorly differentiated (Gleason score 8-10). The mean pre-operative serum PSA was 9.9 ± SE 0.5 ng/ml, and the mean LI was equal to 8.1 ±0.6% and 29.7 ±2.0%, for MIB-1 and GLUT-1, respectively. Increase of pathological tumor volume and tumor grade was associated with statistically significant growth of PSA (p < 0.011) and MIB-1LI (p < 0.003), however, for GLUT-1 LI the relation was not significant. Ki-67 expression was correlated with PSA levels (p = 0.013) and GLUT-1 scores (p = 0.04). In PC, an increase in the proliferation rate (higher MIB-1LI) in higher pTNM stages and tumour grades may point to Ki-67 as a good marker of biological aggressiveness useful in selecting patients for more aggressive treatment. A correlation between proliferation and GLUT-1 score may be the evidence of active glycolytic metabolism in hypoxic regions.

Glut-1 expression in small cervical biopsies is prognostic in cervical cancers treated with chemoradiation.

PubMed

Kanjanapan, Yada; Deb, Siddhartha; Young, Richard J; Bressel, Mathias; Mileshkin, Linda; Rischin, Danny; Hofman, Michael S; Narayan, Kailash; Siva, Shankar

2017-02-01

Chemoradiation (CRT) is standard therapy for locally advanced cervical cancer (LACC). However, there is a lack of biomarkers to identify patients at high relapse-risk. We examine metabolic (glucose transporter-1 [Glut-1]), hypoxic (hypoxia inducible factor [HIF-1α]; carbonic anhydrase [CA-9]) and proliferative (Ki-67) markers for prognostic utility in LACC. 60 LACC patients treated with CRT had pre-treatment biopsies. Immunohistochemistry was performed for Glut-1, HIF-1a and CA-9, to generate a histoscore from intensity and percentage staining; and Ki-67 scored by percentage of positive cells. For each biomarker, treatment response and survival was compared between low and high-staining groups by logrank testing and multivariate analyses. High Glut-1 expression was associated with inferior progression-free survival (PFS), (hazard ratio [HR] 2.8, p  = 0.049) and overall survival (OS), (HR 5.0, p  = 0.011) on multifactor analysis adjusting for stage, node positivity, tumour volume and uterine corpus invasion. High Glut-1 correlated with increased risk of distant failure (HR 14.6, p  = 0.001) but not local failure. Low Glut-1 was associated with higher complete metabolic response rate on post-therapy positron emission tomography scan (odds ratio 3.4, p  = 0.048). Ki-67 was significantly associated with PFS only (HR 1.19 per 10 units increase, p  = 0.033). Biomarkers for hypoxia were not associated with outcome. High Glut-1 in LACC is associated with poor outcome post CRT. If prospectively validated, Glut-1 may help select patients for more intensive treatment regimens.

Molecular Dynamics Simulations of the Human Glucose Transporter GLUT1

PubMed Central

Park, Min-Sun

2015-01-01

Glucose transporters (GLUTs) provide a pathway for glucose transport across membranes. Human GLUTs are implicated in devastating diseases such as heart disease, hyper- and hypo-glycemia, type 2 diabetes and caner. The human GLUT1 has been recently crystalized in the inward-facing open conformation. However, there is no other structural information for other conformations. The X-ray structures of E. coli Xylose permease (XylE), a glucose transporter homolog, are available in multiple conformations with and without the substrates D-xylose and D-glucose. XylE has high sequence homology to human GLUT1 and key residues in the sugar-binding pocket are conserved. Here we construct a homology model for human GLUT1 based on the available XylE crystal structure in the partially occluded outward-facing conformation. A long unbiased all atom molecular dynamics simulation starting from the model can capture a new fully opened outward-facing conformation. Our investigation of molecular interactions at the interface between the transmembrane (TM) domains and the intracellular helices (ICH) domain in the outward- and inward-facing conformation supports that the ICH domain likely stabilizes the outward-facing conformation in GLUT1. Furthermore, inducing a conformational transition, our simulations manifest a global asymmetric rocker switch motion and detailed molecular interactions between the substrate and residues through the water-filled selective pore along a pathway from the extracellular to the intracellular side. The results presented here are consistent with previously published biochemical, mutagenesis and functional studies. Together, this study shed light on the structure and functional relationships of GLUT1 in multiple conformational states. PMID:25919356

Glucose metabolism transporters and epilepsy: only GLUT1 has an established role.

PubMed

Hildebrand, Michael S; Damiano, John A; Mullen, Saul A; Bellows, Susannah T; Oliver, Karen L; Dahl, Hans-Henrik M; Scheffer, Ingrid E; Berkovic, Samuel F

2014-02-01

The availability of glucose, and its glycolytic product lactate, for cerebral energy metabolism is regulated by specific brain transporters. Inadequate energy delivery leads to neurologic impairment. Haploinsufficiency of the glucose transporter GLUT1 causes a characteristic early onset encephalopathy, and has recently emerged as an important cause of a variety of childhood or later-onset generalized epilepsies and paroxysmal exercise-induced dyskinesia. We explored whether mutations in the genes encoding the other major glucose (GLUT3) or lactate (MCT1/2/3/4) transporters involved in cerebral energy metabolism also cause generalized epilepsies. A cohort of 119 cases with myoclonic astatic epilepsy or early onset absence epilepsy was screened for nucleotide variants in these five candidate genes. No epilepsy-causing mutations were identified, indicating that of the major energetic fuel transporters in the brain, only GLUT1 is clearly associated with generalized epilepsy. Wiley Periodicals, Inc. © 2014 International League Against Epilepsy.

Glucose transporter-1 (GLUT-1) immunoreactivity in benign, premalignant and malignant lesions of the gallbladder.

PubMed

Legan, Mateja; Tevžič, Spela; Tolar, Ana; Luzar, Boštjan; Marolt, Vera Ferlan

2011-03-01

GLUT-1 is a transmembrane glucose transport protein that allows the facilitated transport of glucose into cells, normally expressed in tissues which depend mainly on glucose metabolism. Enhanced expression of GLUT-1 can also be found in a large spectrum of carcinomas. This study aimed to investigate GLUT-1 expression in gallbladder tissue: from normal tissue samples, hyperplasias, low-grade and high-grade dysplasias to gallbladder carcinomas. In all, 115 archived samples of gallbladder tissue from 68 patients, presented after cholecystectomy, were immunohistochemically stained for GLUT-1. According to the intensity of GLUT-1 immunoreactivity, samples were divided into negative (stained 0-10% of cells stained), positive with weak to moderate (10-50%) and positive with strong (>50%) GLUT-1 expression. The GLUT-1 immunoreactivity of the samples showed a characteristic increase from premalignant lesions to carcinomas. Normal gallbladder tissue samples did not express GLUT-1 (100%). Weak expression was shown only focally in hyperplasias, but to a greater extent with low-grade dysplasias (20%), high-grade dysplasias (40%) and carcinomas (51.8%). Normal gallbladder tissue is GLUT-1 negative. GLUT-1 expression in carcinoma tissue is significantly higher than in dysplastic lesions. Strong GLUT-1 expression indicates 100% specificity for detecting gallbladder carcinomas. Therefore, GLUT-1 is a candidate as a diagnostic as well as a tissue prognostic marker in gallbladder carcinoma patients.

Compartmentalization of membrane trafficking, glucose transport, glycolysis, actin, tubulin and the proteasome in the cytoplasmic droplet/Hermes body of epididymal sperm.

PubMed

Au, Catherine E; Hermo, Louis; Byrne, Elliot; Smirle, Jeffrey; Fazel, Ali; Kearney, Robert E; Smith, Charles E; Vali, Hojatollah; Fernandez-Rodriguez, Julia; Simon, Paul H G; Mandato, Craig; Nilsson, Tommy; Bergeron, John J M

2015-08-01

Discovered in 1909 by Retzius and described mainly by morphology, the cytoplasmic droplet of sperm (renamed here the Hermes body) is conserved among all mammalian species but largely undefined at the molecular level. Tandem mass spectrometry of the isolated Hermes body from rat epididymal sperm characterized 1511 proteins, 43 of which were localized to the structure in situ by light microscopy and two by quantitative electron microscopy localization. Glucose transporter 3 (GLUT-3) glycolytic enzymes, selected membrane traffic and cytoskeletal proteins were highly abundant and concentrated in the Hermes body. By electron microscope gold antibody labelling, the Golgi trafficking protein TMED7/p27 localized to unstacked flattened cisternae of the Hermes body, as did GLUT-3, the most abundant protein. Its biogenesis was deduced through the mapping of protein expression for all 43 proteins during male germ cell differentiation in the testis. It is at the terminal step 19 of spermiogenesis that the 43 characteristic proteins accumulated in the nascent Hermes body. © 2015 The Authors.

Human trafficking and health: a cross-sectional survey of NHS professionals' contact with victims of human trafficking.

PubMed

Ross, Claire; Dimitrova, Stoyanka; Howard, Louise M; Dewey, Michael; Zimmerman, Cathy; Oram, Siân

2015-08-20

(1) To estimate the proportion of National Health Service (NHS) professionals who have come into contact with trafficked people and (2) to measure NHS professionals' knowledge and confidence to respond to human trafficking. A cross-sectional survey. Face-to-face mandatory child protection and/or vulnerable adults training sessions at 10 secondary healthcare provider organisations in England, and meetings of the UK College of Emergency Medicine. 782/892 (84.4%) NHS professionals participated, including from emergency medicine, maternity, mental health, paediatrics and other clinical disciplines. Self-completed questionnaire developed by an expert panel. Questionnaire asks about prior training and contact with potential victims of trafficking, perceived and actual human trafficking knowledge, confidence in responding to human trafficking, and interest in future human trafficking training. 13% participants reported previous contact with a patient they knew or suspected of having been trafficked; among maternity services professionals this was 20.4%. However, 86.8% (n=679) reported lacking knowledge of what questions to ask to identify potential victims and 78.3% (n=613) reported that they had insufficient training to assist trafficked people. 71% (n=556), 67.5% (n=528) and 53.4% (n=418) lacked confidence in making appropriate referrals for men, women and children, respectively, who had been trafficked. 95.3% (n=746) of respondents were unaware of the scale of human trafficking in the UK, and 76.5% (n=598) were unaware that calling the police could put patients in more danger. Psychometric analysis showed that subscales measuring perceived knowledge, actual knowledge and confidence to respond to human trafficking demonstrated good internal consistency (Cronbach's αs 0.93, 0.63 and 0.64, respectively) and internal correlations. NHS professionals working in secondary care are in contact with potential victims of human trafficking, but lack knowledge and confidence in

Maintaining HNF6 expression prevents AdHNF3beta-mediated decrease in hepatic levels of Glut-2 and glycogen.

PubMed

Tan, Yongjun; Adami, Guy; Costa, Robert H

2002-04-01

The hepatocyte nuclear factor 3 (HNF-3) proteins are members of the Forkhead Box (Fox) family of transcription factors that play important roles in regulating expression of genes involved in cellular proliferation, differentiation, and metabolic homeostasis. In previous studies we increased liver expression of HNF-3beta by using either transgenic mice (transthyretin HNF-3beta) or recombinant adenovirus infection (AdHNF3beta), and observed diminished hepatic levels of glycogen, and glucose transporter 2 (Glut-2), as well as the HNF-6, HNF-3, HNF-1alpha, HNF-4alpha, and C/EBPalpha transcription factors. We conducted the present study to determine whether maintaining HNF-6 protein expression during AdHNF3beta infection prevents reduction of hepatic levels of glycogen and the earlier-mentioned genes. Here, we show that AdHNF3beta- and AdHNF6-infected mouse liver displayed increased hepatic levels of glycogen, Glut-2, HNF-3gamma, HNF-1alpha, and HNF-4alpha at 2 and 3 days postinfection (PI). Furthermore, restoration of hepatic glycogen levels after AdHNF3beta and AdHNF6 coinfection was associated with increased Glut-2 expression. AdHNF6 infection alone caused a 2-fold increase in hepatic Glut-2 levels, suggesting that HNF 6 stimulates in vivo transcription of the Glut-2 gene. DNA binding assays showed that only recombinant HNF-6 protein, but not the HNF-3 proteins, binds to the mouse -185 to -144 bp Glut-2 promoter sequences. Cotransfection assays in human hepatoma (HepG2) cells with either HNF-3 or HNF-6 expression vectors show that only HNF-6 provided significant transcriptional activation of the Glut-2 promoter. In conclusion, these studies show that the hepatic Glut-2 promoter is a direct target for HNF-6 transcriptional activation.

Expression, Purification, and Structural Insights for the Human Uric Acid Transporter, GLUT9, Using the Xenopus laevis Oocytes System

PubMed Central

Clémençon, Benjamin; Lüscher, Benjamin P.; Fine, Michael; Baumann, Marc U.; Surbek, Daniel V.; Bonny, Olivier; Hediger, Matthias A.

2014-01-01

The urate transporter, GLUT9, is responsible for the basolateral transport of urate in the proximal tubule of human kidneys and in the placenta, playing a central role in uric acid homeostasis. GLUT9 shares the least homology with other members of the glucose transporter family, especially with the glucose transporting members GLUT1-4 and is the only member of the GLUT family to transport urate. The recently published high-resolution structure of XylE, a bacterial D-xylose transporting homologue, yields new insights into the structural foundation of this GLUT family of proteins. While this represents a huge milestone, it is unclear if human GLUT9 can benefit from this advancement through subsequent structural based targeting and mutagenesis. Little progress has been made toward understanding the mechanism of GLUT9 since its discovery in 2000. Before work can begin on resolving the mechanisms of urate transport we must determine methods to express, purify and analyze hGLUT9 using a model system adept in expressing human membrane proteins. Here, we describe the surface expression, purification and isolation of monomeric protein, and functional analysis of recombinant hGLUT9 using the Xenopus laevis oocyte system. In addition, we generated a new homology-based high-resolution model of hGLUT9 from the XylE crystal structure and utilized our purified protein to generate a low-resolution single particle reconstruction. Interestingly, we demonstrate that the functional protein extracted from the Xenopus system fits well with the homology-based model allowing us to generate the predicted urate-binding pocket and pave a path for subsequent mutagenesis and structure-function studies. PMID:25286413

GLUT1 expression in pediatric adrenocortical tumors: a promising candidate to predict clinical behavior.

PubMed

Pinheiro, Céline; Granja, Sara; Longatto-Filho, Adhemar; Faria, André M; Fragoso, Maria C B V; Lovisolo, Silvana M; Bonatelli, Murilo; Costa, Ricardo F A; Lerário, Antonio M; Almeida, Madson Q; Baltazar, Fátima; Zerbini, Maria C N

2017-09-08

Discrimination between benign and malignant tumors is a challenging process in pediatric adrenocortical tumors. New insights in the metabolic profile of pediatric adrenocortical tumors may contribute to this distinction, predict prognosis, as well as identify new molecular targets for therapy. The aim of this work is to characterize the expression of the metabolism-related proteins MCT1, MCT2, MCT4, CD147, CD44, GLUT1 and CAIX in a series of pediatric adrenocortical tumors. A total of 50 pediatric patients presenting adrenocortical tumors, including 41 clinically benign and 9 clinically malignant tumors, were included. Protein expression was evaluated using immunohistochemistry in samples arranged in tissue microarrays. The immunohistochemical analysis showed a significant increase in plasma membrane expression of GLUT1 in malignant lesions, when compared to benign lesions ( p =0.004), being the expression of this protein associated with shorter overall and disease-free survival ( p =0.004 and p =0.001, respectively). Although significant differences were not observed for proteins other than GLUT1, MCT1, MCT4 and CD147 were highly expressed in pediatric adrenocortical neoplasias (around 90%). GLUT1 expression was differentially expressed in pediatric adrenocortical tumors, with higher expression in clinically malignant tumors, and associated with shorter survival, suggesting a metabolic remodeling towards a hyperglycolytic phenotype in this malignancy.

The GLUT-1 XbaI gene polymorphism is associated with vascular calcifications in nondiabetic uremic patients.

PubMed

Rufino, Margarita; Hernández, Domingo; Barrios, Ysamar; Salido, Eduardo

2008-01-01

Glucose transporters mediate the facilitative uptake of glucose into cells, with GLUT-1 being the predominant isoform in vascular smooth muscle cell (VSMC). Clones of human cells overexpressing the GLUT-1 transporter showed a high increase in intracellular glucose concentrations, mimicking the diabetic milieu. It is possible that high intracellular glucose together with uremic factors may play an important role in vascular calcification by transforming VSMC into osteoblast-like cells. The XbaI polymorphism in the GLUT-1 gene has been linked to variations in GLUT-1 expression, with consequent changes in intracellular glucose concentration. To assess the association between the GLUT-1 XbaI gene polymorphism and the presence of VC in nondiabetic uremic patients, a total of 105 nondiabetic patients on hemodialysis were studied. VC were evaluated by conventional simple X-ray. Mean values of serum calcium, phosphorous, cholesterol, triglycerides, HbA1c, PTH and insulin were measured. Height, weight, BMI and waist circumference were also determined. The GLUT-1 XbaI polymorphism in the second intron of the gene was ascertained by means of the polymerase chain reaction and restriction fragment length polymorphism analysis on DNA isolated from peripheral blood DNA. In the absence of an XbaI site, a fragment of 305 bp was seen (so-called x allele), whereas fragments of 232 and 73 bp were generated if the XbaI site was present (X allele). Genotype distribution in all patients was similar to the Caucasian population. However, when the patients were grouped according to the presence or absence of VC, there were marked differences in the frequency of the GLUT1 genotypes: the xx GLUT-1 genotype was more prevalent in the group with VC (30.7 vs. 4.5%, p = 0.001). Stepwise logistic regression demonstrated that the xx GLUT-1 genotype was independently associated with the presence of VC after adjusting for other variables such as age, calcium x phosphrus product, BMI and time on

GLUT2-mediated glucose uptake and availability are required for embryonic brain development in zebrafish.

PubMed

Marín-Juez, Rubén; Rovira, Mireia; Crespo, Diego; van der Vaart, Michiel; Spaink, Herman P; Planas, Josep V

2015-01-01

Glucose transporter 2 (GLUT2; gene name SLC2A2) has a key role in the regulation of glucose dynamics in organs central to metabolism. Although GLUT2 has been studied in the context of its participation in peripheral and central glucose sensing, its role in the brain is not well understood. To decipher the role of GLUT2 in brain development, we knocked down slc2a2 (glut2), the functional ortholog of human GLUT2, in zebrafish. Abrogation of glut2 led to defective brain organogenesis, reduced glucose uptake and increased programmed cell death in the brain. Coinciding with the observed localization of glut2 expression in the zebrafish hindbrain, glut2 deficiency affected the development of neural progenitor cells expressing the proneural genes atoh1b and ptf1a but not those expressing neurod. Specificity of the morphant phenotype was demonstrated by the restoration of brain organogenesis, whole-embryo glucose uptake, brain apoptosis, and expression of proneural markers in rescue experiments. These results indicate that glut2 has an essential role during brain development by facilitating the uptake and availability of glucose and support the involvement of glut2 in brain glucose sensing.

GLUT3 gene expression is critical for embryonic growth, brain development and survival.

PubMed

Carayannopoulos, Mary O; Xiong, Fuxia; Jensen, Penny; Rios-Galdamez, Yesenia; Huang, Haigen; Lin, Shuo; Devaskar, Sherin U

2014-04-01

Glucose is the primary energy source for eukaryotic cells and the predominant substrate for the brain. GLUT3 is essential for trans-placental glucose transport and highly expressed in the mammalian brain. To further elucidate the role of GLUT3 in embryonic development, we utilized the vertebrate whole animal model system of Danio rerio as a tractable system for defining the cellular and molecular mechanisms altered by impaired glucose transport and metabolism related to perturbed expression of GLUT3. The comparable orthologue of human GLUT3 was identified and the expression of this gene abrogated during early embryonic development. In a dose-dependent manner embryonic brain development was disrupted resulting in a phenotype of aberrant brain organogenesis, associated with embryonic growth restriction and increased cellular apoptosis. Rescue of the morphant phenotype was achieved by providing exogenous GLUT3 mRNA. We conclude that GLUT3 is critically important for brain organogenesis and embryonic growth. Disruption of GLUT3 is responsible for the phenotypic spectrum of embryonic growth restriction to demise and neural apoptosis with microcephaly. Copyright © 2014 Elsevier Inc. All rights reserved.

GLUT3 Gene Expression is Critical for Embryonic Growth, Brain Development and Survival

PubMed Central

Carayannopoulos, Mary O.; Xiong, Fuxia; Jensen, Penny; Rios-Galdamez, Yesenia; Huang, Haigen; Lin, Shuo; Devaskar, Sherin U.

2015-01-01

Glucose is the primary energy source for eukaryotic cells and the predominant substrate for the brain. GLUT3 is essential for trans-placental glucose transport and highly expressed in the mammalian brain. To further elucidate the role of GLUT3 in embryonic development, we utilized the vertebrate whole animal model system of Danio rerio as a tractable system for defining the cellular and molecular mechanisms altered by impaired glucose transport and metabolism related to perturbed expression of GLUT3. The comparable orthologue of human GLUT3 was identified and the expression of this gene abrogated during early embryonic development. In a dose-dependent manner embryonic brain development was disrupted resulting in a phenotype of aberrant brain organogenesis, associated with embryonic growth restriction and increased cellular apoptosis. Rescue of the morphant phenotype was achieved by providing exogenous GLUT3 mRNA. We conclude that GLUT3 is critically important for brain organogenesis and embryonic growth. Disruption of GLUT3 is responsible for the phenotypic spectrum of embryonic growth restriction to demise and neural apoptosis with microcephaly. PMID:24529979

Glut-1 as a therapeutic target: increased chemoresistance and HIF-1-independent link with cell turnover is revealed through COMPARE analysis and metabolomic studies.

PubMed

Evans, Andrew; Bates, Victoria; Troy, Helen; Hewitt, Stephen; Holbeck, Susan; Chung, Yuen-Li; Phillips, Roger; Stubbs, Marion; Griffiths, John; Airley, Rachel

2008-03-01

The facilitative glucose transporter Glut-1 is overexpressed and confers poor prognosis in a wide range of solid tumours. The peri-necrotic pattern of expression often seen in human tumour samples is linked with its transcriptional control in hypoxic conditions by hypoxia-inducible factor HIF-1 or through a reduced rate of oxidative phosphorylation. Hypoxia-regulated genes offer promise as novel therapeutic targets as a means of preventing the proliferation and eventual metastatic spread of tissue originating from residual chemically and radio resistant hypoxic cells that have survived treatment. Inhibiting the expression or functionality of Glut-1 may be a way of specifically targeting hypoxic cells within the tumour that depend upon a high rate of glucose uptake for anaerobic glycolysis. We used an array of formalin-fixed, paraffin-embedded samples of the NCI-60 panel of cell lines to carry out immunohistochemical detection of Glut-1 and to select possible candidate lead compounds by COMPARE analysis with agents from the NCI diversity screen, which may work via inhibition of Glut-1 or Glut-1-dependent processes. "Positive" COMPARE hits were mostly conjugated Pseudomonas toxins binding the epidermal growth factor receptor (EGFR). However, correlations with standard anticancer agents were virtually all negative, indicating a link between Glut-1 and chemoresistance. MTT proliferation assays carried out using stable, Glut-1 overexpressing cell lines generated from the bladder EJ138, human fibrosarcoma HT 1080 and the hepatoma wild type Hepa and HIF-1B-deficient c4 tumour cell lines revealed a cell line-dependent increase in chemoresistance to dacarbazine, vincristine and the bioreductive agent EO9 in Glut-1 overexpressing EJ138 relative to WT and empty vector controls. Metabolomic analysis ((31)P-MRS and (1)H MRS) carried out using cell lysates and xenografts generated from Glut-1 overexpressing Hepa and c4 cell lines showed higher glucose levels in Glut-1

Prognostic value of GLUT-1 expression in ovarian surface epithelial tumors: a morphometric study.

PubMed

Ozcan, Ayhan; Deveci, Mehmet Salih; Oztas, Emin; Dede, Murat; Yenen, Mufit Cemal; Korgun, Emin Turkay; Gunhan, Omer

2005-08-01

To investigate the reported increase in the expression of the glucose transporter GLUT-1 in borderline and malignant ovarian epithelial tumors and its relationship to prognosis. In this study, areas in which immunohistochemical membranous staining with GLUT-1 were most evident were selected, and the proportions of GLUT-1 expression in 46 benign, 11 borderline and 42 malignant cases of ovarian epithelial tumors were determined quantitatively with a computer and Zeiss Vision KS 400 3.0 (Göttingen, Germany) for Windows (Microsoft, Redmond, Washington, U.S.A.) image analysis. GLUT-1 expression was determined in all borderline tumors (11 of 11) and in 97.6% of malignant tumors (41 of 42). No GLUT-1 expression was observed in benign tumors. The intensity of GLUT-1 staining was lower in borderline tumors than in malignant cases. This was statistically significant (p = 0.005). As differentiation in malignant tumors increased, proportions of GLUT-1 expression showed a relative increase, but this difference was not statistically significant (p = 0.68). When GLUT-1 expression in borderline and malignant ovarian epithelial tumors was analyzed against prognosis, no statistically significant difference was identified. Assessment of GLUT-1 expression using the image analysis program was more reliable, with higher reproducibility than in previous studies.

Niacin bound chromium treatment induces myocardial Glut-4 translocation and caveolar interaction via Akt, AMPK and eNOS phosphorylation in streptozotocin induced diabetic rats after ischemia-reperfusion injury.

PubMed

Penumathsa, Suresh Varma; Thirunavukkarasu, Mahesh; Samuel, Samson Mathews; Zhan, Lijun; Maulik, Gautam; Bagchi, Manashi; Bagchi, Debasis; Maulik, Nilanjana

2009-01-01

Diabetes, one of the major risk factors of metabolic syndrome culminates in the development of Ischemic Heart Disease (IHD). Refined diets that lack micronutrients, mainly trivalent chromium (Cr(3+)) have been identified as the contributor in the rising incidence of diabetes. We investigated the effect of niacin-bound chromium (NBC) during ischemia/reperfusion (IR) injury in streptozotocin induced diabetic rats. Rats were randomized into: Control (Con); Diabetic (Dia) and Diabetic rats fed with NBC (Dia+NBC). After 30 days of treatment, the isolated hearts were subjected to 30 min of global ischemia followed by 2 h of reperfusion. NBC treatment demonstrated significant increase in left ventricular functions and significant reduction in infarct size and cardiomyocyte apoptosis in Dia+NBC compared with Dia. Increased Glut-4 translocation to the lipid raft fractions was also observed in Dia+NBC compared to Dia. Reduced Cav-1 and increased Cav-3 expression along with phosphorylation of Akt, eNOS and AMPK might have resulted in increased Glut-4 translocation in Dia+NBC. Our results indicate that the cardioprotective effect of NBC is mediated by increased activation of AMPK, Akt and eNOS resulting in increased translocation of Glut-4 to the caveolar raft fractions thereby alleviating the effects of IR injury in the diabetic myocardium.

Cigarette smokers develop altered erythrocyte membrane composition: an investigation unmasking the role of membrane bound integral protein GLUT 1.

PubMed

Sikdar, Jyotirmoy; Seal, Paromita; Roy, Amartya; Haldar, Rajen

2017-04-01

Erythrocytes in cigarette smokers are prone to oxidative damage. Here, we sought to elucidate the facts behind modifications and possible defense system developed in erythrocyte of cigarette smokers. We observed significant increase in stomatocytes and spherocytes, and osmotic fragility of erythrocyte, along with reduced level of protein thiol and increased fluorescence anisotropy in isolated membrane. Denaturing gel electrophoresis indicated alterations in band 3, band 4.2 and band 4.5. Among those, Glut 1 (i.e. band 4.5), which transports glucose (insulin independent) and dehydroascorbate (DHA), was selectively chosen for its long history in reducing reactive oxygen species (ROS). The increased Glut 1 level in smokers was confirmed by immunoblotting and immunocytochemistry. Furthermore, smokers showed significantly higher glucose uptake in whole blood. The intracellular (Ic) ROS (as indicated by 2',7'-dichlorofluorescin) was significantly higher in smokers as evidenced by flow cytometric assay. Glucose and DHA alone or together significantly reduced IcROS at higher rate in smokers. However, in presence of Glut 1 specific blocker, phloretin, neither glucose nor DHA could reduce IcROS in both non-smokers and smokers. This confirms that Glut 1 by transporting glucose or DHA attenuates IcROS. Therefore, we conclude that erythrocytes, although altered morphologically, also develop a defense system by upregulating Glut 1 to combat with enhanced Ic oxidative insult in cigarette smokers.

GLUT2-mediated glucose uptake and availability are required for embryonic brain development in zebrafish

PubMed Central

Marín-Juez, Rubén; Rovira, Mireia; Crespo, Diego; van der Vaart, Michiel; Spaink, Herman P; Planas, Josep V

2015-01-01

Glucose transporter 2 (GLUT2; gene name SLC2A2) has a key role in the regulation of glucose dynamics in organs central to metabolism. Although GLUT2 has been studied in the context of its participation in peripheral and central glucose sensing, its role in the brain is not well understood. To decipher the role of GLUT2 in brain development, we knocked down slc2a2 (glut2), the functional ortholog of human GLUT2, in zebrafish. Abrogation of glut2 led to defective brain organogenesis, reduced glucose uptake and increased programmed cell death in the brain. Coinciding with the observed localization of glut2 expression in the zebrafish hindbrain, glut2 deficiency affected the development of neural progenitor cells expressing the proneural genes atoh1b and ptf1a but not those expressing neurod. Specificity of the morphant phenotype was demonstrated by the restoration of brain organogenesis, whole-embryo glucose uptake, brain apoptosis, and expression of proneural markers in rescue experiments. These results indicate that glut2 has an essential role during brain development by facilitating the uptake and availability of glucose and support the involvement of glut2 in brain glucose sensing. PMID:25294126

The CD20 homologue MS4A4 directs trafficking of KIT toward clathrin-independent endocytosis pathways and thus regulates receptor signaling and recycling

PubMed Central

Cruse, Glenn; Beaven, Michael A.; Music, Stephen C.; Bradding, Peter; Gilfillan, Alasdair M.; Metcalfe, Dean D.

2015-01-01

MS4A family members differentially regulate the cell cycle, and aberrant, or loss of, expression of MS4A family proteins has been observed in colon and lung cancer. However, the precise functions of MS4A family proteins and their mechanistic interactions remain unsolved. Here we report that MS4A4 facilitates trafficking of the receptor tyrosine kinase KIT through endocytic recycling rather than degradation pathways by a mechanism that involves recruitment of KIT to caveolin-1–enriched microdomains. Silencing of MS4A4 in human mast cells altered ligand-induced KIT endocytosis pathways and reduced receptor recycling to the cell surface, thus promoting KIT signaling in the endosomes while reducing that in the plasma membrane, as exemplified by Akt and PLCγ1 phosphorylation, respectively. The altered endocytic trafficking of KIT also resulted in an increase in SCF-induced mast cell proliferation and migration, which may reflect altered signaling in these cells. Our data reveal a novel function for MS4A family proteins in regulating trafficking and signaling, which could have implications in both proliferative and immunological diseases. PMID:25717186

Suppressive effects of a novel CC chemokine receptor 4 antagonist on Th2 cell trafficking in ligand- and antigen-induced mouse models.

PubMed

Komiya, Takaki; Sugiyama, Tetsuya; Takeda, Kazuhiko; Watanabe, Noriki; Imai, Masamichi; Kokubo, Masaya; Tokuda, Natsuko; Ochiai, Hiroshi; Habashita, Hiromu; Shibayama, Shiro

2013-11-15

CC chemokine receptor 4 (CCR4) has been implicated as a preferential marker for T helper type 2 (Th2) cells, and is believed to be involved in the pathology of allergic diseases by controlling Th2 cell trafficking into inflamed tissues. The objective of the study was to characterize the pharmacological properties of E0001-163, a novel CCR4 antagonist. E0001-163 was tested in both in vitro chemotaxis assays as well as in vivo mouse models of CCR4 ligand-induced air pouch and antigen-induced airway inflammation by utilizing in vitro-polarized Th2 cells. In vitro, E0001-163 inhibited migratory response of human Th2-polarized cells to CCL22, a CCR4 ligand, with an IC50 value of 11.9 nM. E0001-163 significantly suppressed CCL22-induced Th2 cell trafficking into mouse air pouch in a dose-dependent manner at doses of 3 and 10mg/kg, suggesting that E0001-163 has an inhibitory effect on CCR4-mediated T cell trafficking in vivo. In addition, E0001-163 partially decreased Th2 cell trafficking and the level of IL-4 in the lungs in Th2-tansferred and ovalbumin (OVA)-challenged mice. T cell trafficking involves multiple chemokine receptors both in acute and chronic phases, and our findings suggest that CCR4, together with other chemokine receptors, may be involved in Th2 cell trafficking under disease conditions. © 2013 Elsevier B.V. All rights reserved.

Inhibitors of GLUT/SLC2A Enhance the Action of BCNU and Temozolomide against High-Grade Gliomas.

PubMed

Azzalin, Alberto; Nato, Giulia; Parmigiani, Elena; Garello, Francesca; Buffo, Annalisa; Magrassi, Lorenzo

2017-04-01

Glucose transport across glioblastoma membranes plays a crucial role in maintaining the enhanced glycolysis typical of high-grade gliomas and glioblastoma. We tested the ability of two inhibitors of the glucose transporters GLUT/SLC2A superfamily, indinavir (IDV) and ritonavir (RTV), and of one inhibitor of the Na/glucose antiporter type 2 (SGLT2/SLC5A2) superfamily, phlorizin (PHZ), in decreasing glucose consumption and cell proliferation of human and murine glioblastoma cells. We found in vitro that RTV, active on at least three different GLUT/SLC2A transporters, was more effective than IDV, a specific inhibitor of GLUT4/SLC2A4, both in decreasing glucose consumption and lactate production and in inhibiting growth of U87MG and Hu197 human glioblastoma cell lines and primary cultures of human glioblastoma. PHZ was inactive on the same cells. Similar results were obtained when cells were grown in adherence or as 3D multicellular tumor spheroids. RTV treatment but not IDV treatment induced AMP-activated protein kinase (AMPKα) phosphorylation that paralleled the decrease in glycolytic activity and cell growth. IDV, but not RTV, induced an increase in GLUT1/SLC2A1 whose activity could compensate for the inhibition of GLUT4/SLC2A4 by IDV. RTV and IDV pass poorly the blood brain barrier and are unlikely to reach sufficient liquoral concentrations in vivo to inhibit glioblastoma growth as single agents. Isobologram analysis of the association of RTV or IDV and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or 4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo[4.3.0]nona-2,7,9-triene-9-carboxamide (TMZ) indicated synergy only with RTV on inhibition of glioblastoma cells. Finally, we tested in vivo the combination of RTV and BCNU on established GL261 tumors. This drug combination increased the overall survival and allowed a five-fold reduction in the dose of BCNU. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

GLUT-1 overexpression: Link between hemodynamic and metabolic factors in glomerular injury?

PubMed

Gnudi, Luigi; Viberti, GianCarlo; Raij, Leopoldo; Rodriguez, Veronica; Burt, Davina; Cortes, Pedro; Hartley, Barry; Thomas, Stephen; Maestrini, Sabrina; Gruden, Gabriella

2003-07-01

Mesangial matrix deposition is the hallmark of hypertensive and diabetic glomerulopathy. At similar levels of systemic hypertension, Dahl salt-sensitive but not spontaneously hypertensive rats (SHR) develop glomerular hypertension, which is accompanied by upregulation of transforming growth factor beta1 (TGF-beta1), mesangial matrix expansion, and sclerosis. GLUT-1 is ubiquitously expressed and is the predominant glucose transporter in mesangial cells. In mesangial cells in vitro, GLUT-1 overexpression increases basal glucose transport, resulting in excess fibronectin and collagen production. TGF-beta1 has been shown to upregulate GLUT-1 expression. We demonstrated that in hypertensive Dahl salt-sensitive (S) rats fed 4% NaCl (systolic blood pressure [SBP]: 236+/-9 mm Hg), but not in similarly hypertensive SHR (SBP: 230+/-10 mm Hg) or their normotensive counterparts (Dahl S fed 0.5% NaCl, SBP: 145+/-5 mm Hg; and Wistar-Kyoto, SBP: 137+/-3 mm Hg), there was an 80% upregulation of glomerular GLUT-1 protein expression (P< or =0.03). This was accompanied by a 2.7-fold upregulation of TGF-beta1 protein expression in glomeruli of DSH compared with DSN rats (P=0.02). TGF-beta1 expression was not upregulated and did not differ in the glomeruli of Wistar-Kyoto and SHR rats. As an in vitro surrogate of the in vivo hemodynamic stress imposed by glomerular hypertension, we used mechanical stretching of human and rat mesangial cells. We found that after 33 hours of stretching, mesangial cells overexpressed GLUT-1 (40%) and showed an increase in basal glucose transport of similar magnitude (both P< or =0.01), which could be blocked with an anti TGF-beta1-neutralizing antibody. These studies suggest a novel link between hemodynamic and metabolic factors that may cooperate in inducing progressive glomerular injury in conditions characterized by glomerular hypertension.

GLUT9 influences uric acid concentration in patients with Lesch-Nyhan disease.

PubMed

Torres, Rosa J; Puig, Juan G

2018-06-01

Patients with deficient hypoxanthine-guanine phosphoribosyltransferase (HPRT) activity present hyperuricemia and/or hyperuricosuria, with a variable degree of neurological manifestations. Hyperuricemia in HPRT deficiency is due to uric acid overproduction and is frequently treated with allopurinol. Renal uric acid excretion is sharply increased in these patients. In recent years, several renal tubular urate transporter single nucleotide polymorphisms (SNPs), including those of the GLUT9, ABCG2 and URAT1 genes, have been described that influence the renal handling of uric acid and modulate serum urate levels. In the present study, we analyzed whether GLUT9, ABCG2 and URAT1 gene SNPs are able to influence uric acid levels and allopurinol response in patients with HPRT deficiency. Three SNPs, URAT1 rs11231825, GLUT9 rs16890979 and ABCG2 rs2231142, previously associated in our population with hyperuricemia and gout, were analyzed in 27 patients with HPRT deficiency treated with allopurinol for at least 5 years. Patients with HPRT deficiency having allele A of rs16890979 in the GLUT9 gene present with a lower serum urate concentration at diagnosis, before allopurinol treatment is instituted, and need lower allopurinol doses to maintain serum urate levels between 268 and 446 μmol/L (4.5 and 7.5 mg/dL). No relationship between rs2231142 in the ABCG2 gene or rs11231825 in the URAT1 gene and serum urate levels or allopurinol response was found in our patients with HPRT deficiency. GLUT9 SNPs influence the renal handling of uric acid and modulate serum urate levels and the response to treatment in patients with uric acid overproduction due to HPRT deficiency. © 2018 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.

Insulin and chromium picolinate induce translocation of CD36 to the plasma membrane through different signaling pathways in 3T3-L1 adipocytes, and with a differential functionality of the CD36.

PubMed

Wang, Yiqun; Van Oort, Masja M; Yao, Minghui; Van der Horst, Dick J; Rodenburg, Kees W

2011-09-01

Chromium picolinate (CrPic) has been indicated to activate glucose transporter 4 (GLUT4) trafficking to the plasma membrane (PM) to enhance glucose uptake in 3T3-L1 adipocytes. In skeletal and heart muscle cells, insulin directs the intracellular trafficking of the fatty acid translocase/CD36 to induce the uptake of cellular long-chain fatty acid (LCFA). The current study describes the effects of CrPic and insulin on the translocation of CD36 from intracellular storage pools to the PM in 3T3-L1 adipocytes in comparison with that of GLUT4. Immunofluorescence microscopy and immunoblotting revealed that both CD36 and GLUT4 were expressed and primarily located intracellularly in 3T3-L1 adipocytes. Upon insulin or CrPic stimulation, PM expression of CD36 increased in a similar manner as that for GLUT4; the CrPic-stimulated PM expression was less strong than that of insulin. The increase in PM localization for these two proteins by insulin paralleled LCFA ([1-(14)C]palmitate) or [(3)H]deoxyglucose uptake in 3T3-L1 adipocytes. The induction of the PM expression of GLUT4, but not CD36, or substrate uptake by insulin and CrPic appears to be additive in adipocytes. Furthermore, wortmannin completely inhibited the insulin-stimulated translocation of GLUT4 or CD36 and prevented the increased uptake of glucose or LCFA in these cells. Taken together, for the first time, these findings suggest that both insulin and CrPic induce CD36 translocation to the PM in 3T3-L1 adipocytes and that their translocation-inducing effects are not additive. The signaling pathway inducing the translocations is different, apparently resulting in a differential activity of CD36.

Wushenziye Formula Improves Skeletal Muscle Insulin Resistance in Type 2 Diabetes Mellitus via PTP1B-IRS1-Akt-GLUT4 Signaling Pathway.

PubMed

Tian, Chunyu; Chang, Hong; La, Xiaojin; Li, Ji-An

2017-01-01

Background. Wushenziye formula (WSZYF) is an effective traditional Chinese medicine in the treatment of type 2 diabetes mellitus (T2DM). Aim. This study aimed to identify the effects and underlying mechanisms of WSZYF on improving skeletal muscle insulin resistance in T2DM. Methods. An animal model of T2DM was induced by Goto-Kakizaki diabetes prone rats fed with high fat and sugar for 4 weeks. Insulin resistance model was induced in skeletal muscle cell. Results. In vivo , WSZYF improved general conditions and decreased significantly fasting blood glucose, glycosylated serum protein, glycosylated hemoglobin, insulin concentration, and insulin resistance index of T2DM rats. In vitro , WSZYF enhanced glucose consumption in insulin resistance model of skeletal muscle cell. Furthermore, WSZYF affected the expressions of molecules in regulating T2DM, including increasing the expressions of p-IRS1, p-Akt, and GLUT4, reducing PTP1B expression. Conclusion . These findings displayed the potential of WSZYF as a new drug candidate in the treatment of T2DM and the antidiabetic mechanism of WSZYF is probably mediated through modulating the PTP1B-IRS1-Akt-GLUT4 signaling pathway.

Wushenziye Formula Improves Skeletal Muscle Insulin Resistance in Type 2 Diabetes Mellitus via PTP1B-IRS1-Akt-GLUT4 Signaling Pathway

PubMed Central

La, Xiaojin; Li, Ji-an

2017-01-01

Background. Wushenziye formula (WSZYF) is an effective traditional Chinese medicine in the treatment of type 2 diabetes mellitus (T2DM). Aim. This study aimed to identify the effects and underlying mechanisms of WSZYF on improving skeletal muscle insulin resistance in T2DM. Methods. An animal model of T2DM was induced by Goto-Kakizaki diabetes prone rats fed with high fat and sugar for 4 weeks. Insulin resistance model was induced in skeletal muscle cell. Results. In vivo, WSZYF improved general conditions and decreased significantly fasting blood glucose, glycosylated serum protein, glycosylated hemoglobin, insulin concentration, and insulin resistance index of T2DM rats. In vitro, WSZYF enhanced glucose consumption in insulin resistance model of skeletal muscle cell. Furthermore, WSZYF affected the expressions of molecules in regulating T2DM, including increasing the expressions of p-IRS1, p-Akt, and GLUT4, reducing PTP1B expression. Conclusion. These findings displayed the potential of WSZYF as a new drug candidate in the treatment of T2DM and the antidiabetic mechanism of WSZYF is probably mediated through modulating the PTP1B-IRS1-Akt-GLUT4 signaling pathway. PMID:29479370

Neonatal hypothyroidism affects testicular glucose homeostasis through increased oxidative stress in prepubertal mice: effects on GLUT3, GLUT8 and Cx43.

PubMed

Sarkar, D; Singh, S K

2017-07-01

Thyroid hormones (THs) play an important role in maintaining the link between metabolism and reproduction and the altered THs status is associated with induction of oxidative stress in various organs like brain, heart, liver and testis. Further, reactive oxygen species play a pivotal role in regulation of glucose homeostasis in several organs, and glucose utilization by Leydig cells is essential for testosterone biosynthesis and thus is largely dependent on glucose transporter 8 (GLUT8). Glucose uptake by Sertoli cells is mediated through glucose transporter 3 (GLUT3) under the influence of THs to meet energy requirement of developing germ cells. THs also modulate level of gap junctional protein such as connexin 43 (Cx43), a potential regulator of cell proliferation and apoptosis in the seminiferous epithelium. Although the role of transient neonatal hypothyroidism in adult testis in terms of testosterone production is well documented, the effect of THs deficiency in early developmental period and its role in testicular glucose homeostasis and oxidative stress with reference to Cx43 in immature mice remain unknown. Therefore, the present study was conducted to evaluate the effect of neonatal hypothyroidism on testicular glucose homeostasis and oxidative stress at postnatal days (PND) 21 and 28 in relation to GLUT3, GLUT8 and Cx43. Hypothyroidism induced by 6-propyl-2-thiouracil (PTU) markedly decreased testicular glucose level with considerable reduction in expression level of GLUT3 and GLUT8. Likewise, lactate dehydrogenase (LDH) activity and intratesticular concentration of lactate were also decreased in hypothyroid mice. There was also a rise in germ cell apoptosis with increased expression of caspase-3 in PTU-treated mice. Further, neonatal hypothyroidism affected germ cell proliferation with decreased expression of proliferating cell nuclear antigen (PCNA) and Cx43. In conclusion, our results suggest that neonatal hypothyroidism alters testicular glucose

Activation of syntaxin 1C, an alternative splice variant of HPC-1/syntaxin 1A, by phorbol 12-myristate 13-acetate (PMA) suppresses glucose transport into astroglioma cells via the glucose transporter-1 (GLUT-1).

PubMed

Nakayama, Takahiro; Mikoshiba, Katsuhiko; Yamamori, Tetsuo; Akagawa, Kimio

2004-05-28

Syntaxin 1C is an alternative splice variant lacking the transmembrane domain of HPC-1/syntaxin 1A. We found previously that syntaxin 1C is expressed as a soluble protein in human astroglioma (T98G) cells, and syntaxin 1C expression is enhanced by stimulation with phorbol 12-myristate 13-acetate (PMA). However, the physiological function of syntaxin 1C is not known. In this study, we examined the relationship between syntaxin 1C and glucose transport. First, we discovered that glucose transporter-1 (GLUT-1) was the primary isoform in T98G cells. Second, we demonstrated that glucose uptake in T98G cells was suppressed following an increase in endogenous syntaxin 1C after stimulation with PMA, which did not alter the expression levels of other plasma membrane syntaxins. We further examined glucose uptake and intracellular localization of GLUT-1 in cells that overexpressed exogenous syntaxin 1C; glucose uptake via GLUT-1 was inhibited without affecting sodium-dependent glucose transport. The value of Vmax for the dose-dependent uptake of glucose was reduced in syntaxin 1C-expressing cells, whereas there was no change in Km. Immunofluorescence studies revealed a reduction in the amount of GLUT-1 in the plasma membrane in cells that expressed syntaxin 1C. Based on these results, we postulate that syntaxin 1C regulates glucose transport in astroglioma cells by changing the intracellular trafficking of GLUT-1. This is the first report to indicate that a syntaxin isoform that lacks a transmembrane domain can regulate the intracellular transport of a plasma membrane protein.

27-Hydroxycholesterol impairs neuronal glucose uptake through an IRAP/GLUT4 system dysregulation

PubMed Central

Mateos, Laura; Maioli, Silvia; Ali, Zeina; Gulyás, Balázs; Winblad, Bengt; Savitcheva, Irina

2017-01-01

Hypercholesterolemia is associated with cognitively deteriorated states. Here, we show that excess 27-hydroxycholesterol (27-OH), a cholesterol metabolite passing from the circulation into the brain, reduced in vivo brain glucose uptake, GLUT4 expression, and spatial memory. Furthermore, patients exhibiting higher 27-OH levels had reduced 18F-fluorodeoxyglucose uptake. This interplay between 27-OH and glucose uptake revealed the engagement of the insulin-regulated aminopeptidase (IRAP). 27-OH increased the levels and activity of IRAP, countered the IRAP antagonist angiotensin IV (AngIV)–mediated glucose uptake, and enhanced the levels of the AngIV-degrading enzyme aminopeptidase N (AP-N). These effects were mediated by liver X receptors. Our results reveal a molecular link between cholesterol, brain glucose, and the brain renin-angiotensin system, all of which are affected in some neurodegenerative diseases. Thus, reducing 27-OH levels or inhibiting AP-N maybe a useful strategy in the prevention of the altered glucose metabolism and memory decline in these disorders. PMID:28213512

Positive Regulatory Control Loop between Gut Leptin and Intestinal GLUT2/GLUT5 Transporters Links to Hepatic Metabolic Functions in Rodents

PubMed Central

Sakar, Yassine; Nazaret, Corinne; Lettéron, Philippe; Ait Omar, Amal; Avenati, Mathilde; Viollet, Benoît; Ducroc, Robert; Bado, André

2009-01-01

Background and Aims The small intestine is the major site of absorption of dietary sugars. The rate at which they enter and exit the intestine has a major effect on blood glucose homeostasis. In this study, we determine the effects of luminal leptin on activity/expression of GLUT2 and GLUT5 transporters in response to sugars intake and analyse their physiological consequences. Methodology Wistar rats, wild type and AMPKα2 −/− mice were used. In vitro and in vivo isolated jejunal loops were used to quantify transport of fructose and galactose in the absence and the presence of leptin. The effects of fructose and galactose on gastric leptin release were determined. The effects of leptin given orally without or with fructose were determined on the expression of GLUT2/5, on some gluconeogenesis and lipogenic enzymes in the intestine and the liver. Principal Findings First, in vitro luminal leptin activating its receptors coupled to PKCβII and AMPKα, increased insertion of GLUT2/5 into the brush-border membrane leading to enhanced galactose and fructose transport. Second in vivo, oral fructose but not galactose induced in mice a rapid and potent release of gastric leptin in gastric juice without significant changes in plasma leptin levels. Moreover, leptin given orally at a dose reproducing comparable levels to those induced by fructose, stimulated GLUT5-fructose transport, and potentiated fructose-induced: i) increase in blood glucose and mRNA levels of key gluconeogenesis enzymes; ii) increase in blood triglycerides and reduction of mRNA levels of intestinal and hepatic Fasting-induced adipocyte factor (Fiaf) and iii) increase in SREBP-1c, ACC-1, FAS mRNA levels and dephosphorylation/activation of ACC-1 in liver. Conclusion/Significance These data identify for the first time a positive regulatory control loop between gut leptin and fructose in which fructose triggers release of gastric leptin which, in turn, up-regulates GLUT5 and concurrently modulates

The expression and significance of HIF-1alpha and GLUT-3 in glioma.

PubMed

Liu, Yang; Li, Yun-ming; Tian, Rui-feng; Liu, Wei-ping; Fei, Zhou; Long, Qian-fa; Wang, Xiao-an; Zhang, Xiang

2009-12-22

HIF-1alpha plays an indispensable role in tumor formation and histogenesis. Target genes involved in glucose transport are acutely transactivated by HIF-1alpha. GLUT-3 protein is the rate-limiting factor related to glucose transport, which is classified as brain-type glucose transporter. This study was the initial one aiming to probe into the co-expression and clinical significance of HIF-1alpha and GLUT-3 in glioma. One hundred and twenty cases of glioma tissues and ten human normal cerebral tissues decompressed in glioma excision were examined using immunohistochemistry and Western blot. The expression of HIF-1alpha and GLUT-3 increased gradually with the increase of pathological grade of glioma, respectively. There was significant difference in the expression of HIF-1alpha and GLUT-3 in every two groups, respectively. There was a positive correlation between HIF-1alpha and GLUT-3. In conclusion, the expression of HIF-1alpha and GLUT-3 in glioma was correlated significantly with tumors' pathological grade, which can be taken as a pair of useful markers for predicting the biological behavior of glioma.

Fanconi-Bickel syndrome: GLUT2 mutations associated with a mild phenotype.

PubMed

Grünert, Sarah Catharina; Schwab, Karl Otfried; Pohl, Martin; Sass, Jörn Oliver; Santer, René

2012-03-01

Fanconi-Bickel syndrome (FBS, OMIM #227810), a congenital disorder of carbohydrate metabolism, is caused by mutations in GLUT2 (SLC2A2), the gene encoding the glucose transporter protein-2. The typical clinical picture is characterized by hepatorenal glycogen accumulation resulting in hepato- and nephromegaly, impaired utilization of glucose and galactose, proximal tubular nephropathy, rickets, and severe short stature. We report on two siblings with FBS and an unusually mild clinical course. A 9.5-year-old boy with failure to thrive was diagnosed at the age of 9 months, his younger sister (4.5 years) was investigated in the first months of life and also diagnosed with FBS. Both patients were found to be compound heterozygous for the novel GLUT2 (SLC2A2) mutations c.457_462delCTTATA (p.153_4delLI) and c.1250C>G (p.P417R). On a diet restricted in free glucose and galactose, both children showed normal growth. Hepatomegaly, nephromegaly and hypophosphatemic rickets have never been observed. Glucosuria and tubular proteinuria were only mild compared to previously reported patients with FBS. This report describes an unusually mild phenotype of FBS expanding the spectrum of this disease. Some clinical signs that have been considered hallmarks of FBS like hepatomegaly and short stature may be absent in this condition. As a consequence, clinicians will have to look for GLUT2 mutations even in patients with isolated glucosuria. Copyright © 2011 Elsevier Inc. All rights reserved.

GLUT-1 immunoexpression in oral epithelial dysplasia, oral squamous cell carcinoma, and verrucous carcinoma.

PubMed

Angadi, Vidya C; Angadi, Punnya V

2015-06-01

Glucose transporters, such as GLUT-1, mediate the important mechanisms involved in cellular glucose influx, allowing cells to proliferate and survive. The significance of GLUT-1 expression in oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC) has been less explored, and no study has investigated it in relation to verrucous carcinoma (VC). We evaluated 30 cases each of OED, OSCC, and VC, graded further on the basis of their differentiation, immunohistochemically for GLUT-1 expression, along with 10 specimens of normal oral mucosa (NOM) as controls. In OSCC, GLUT-1 expression increased with the degree of dysplasia and increasing grade (P < 0.001). The expression in VC was predominantly membranous and intense, resembling well differentiated OSCC. This increase of GLUT-1 expression in OSCC along with the degree of dysplasia and the histologic grade reflects the expanding glycolytic response to hypoxia. This is the first study to have revealed prominent GLUT-1 expression in VC, highlighting its inherent metabolic capacity.

Trafficking of cell surface beta-amyloid precursor protein: retrograde and transcytotic transport in cultured neurons

PubMed Central

1995-01-01

Amyloid beta-protein (A beta), the principal constituent of senile plaques seen in Alzheimer's disease (AD), is derived by proteolysis from the beta-amyloid precursor protein (beta PP). The mechanism of A beta production in neurons, which are hypothesized to be a rich source of A beta in brain, remains to be defined. In this study, we describe a detailed localization of cell surface beta PP and its subsequent trafficking in primary cultured neurons. Full-length cell surface beta PP was present primarily on perikarya and axons, the latter with a characteristic discontinuous pattern. At growth cones, cell surface beta PP was inconsistently detected. By visualizing the distribution of beta PP monoclonal antibodies added to intact cultures, beta PP was shown to be internalized from distal axons or terminals and retrogradely transported back to perikarya in organelles which colocalized with fluid-phase endocytic markers. Retrograde transport of beta PP was shown in both hippocampal and peripheral sympathetic neurons, the latter using a compartment culture system that isolated cell bodies from distal axons and terminals. In addition, we demonstrated that beta PP from distal axons was transcytotically transported to the surface of perikarya from distal axons in sympathetic neurons. Indirect evidence of this transcytotic pathway was obtained in hippocampal neurons using antisense oligonucleotide to the kinesin heavy chain to inhibit anterograde beta PP transport. Taken together, these results demonstrate novel aspects of beta PP trafficking in neurons, including retrograde axonal transport and transcytosis. Moreover, the axonal predominance of cell surface beta PP is unexpected in view of the recent report of polarized sorting of beta PP to the basolateral domain of MDCK cells. PMID:7721945

Economics of human trafficking.

PubMed

Wheaton, Elizabeth M; Schauer, Edward J; Galli, Thomas V

2010-01-01

Because freedom of choice and economic gain are at the heart of productivity, human trafficking impedes national and international economic growth. Within the next 10 years, crime experts expect human trafficking to surpass drug and arms trafficking in its incidence, cost to human well-being, and profitability to criminals (Schauer and Wheaton, 2006: 164-165). The loss of agency from human trafficking as well as from modern slavery is the result of human vulnerability (Bales, 2000: 15). As people become vulnerable to exploitation and businesses continually seek the lowest-cost labour sources, trafficking human beings generates profit and a market for human trafficking is created. This paper presents an economic model of human trafficking that encompasses all known economic factors that affect human trafficking both across and within national borders. We envision human trafficking as a monopolistically competitive industry in which traffickers act as intermediaries between vulnerable individuals and employers by supplying differentiated products to employers. In the human trafficking market, the consumers are employers of trafficked labour and the products are human beings. Using a rational-choice framework of human trafficking we explain the social situations that shape relocation and working decisions of vulnerable populations leading to human trafficking, the impetus for being a trafficker, and the decisions by employers of trafficked individuals. The goal of this paper is to provide a common ground upon which policymakers and researchers can collaborate to decrease the incidence of trafficking in humans.

[Effect of progesterone on the expression of GLUT in the brain following hypoxic-ischemia in newborn rats].

PubMed

Li, Dong-Liang; Han, Hua

2008-08-01

To investigate the expression of GLUT1 and GLUT3 in the hippocampus after cerebral hypoxic-ischemia (HI) in newborn rats and the effect of progesterone (PROG) on them. Forty newborn SD rats were randomly divided into four groups: normal group, sham-operated group, hypoxic-ischemic group and progesterone group. Model of hypoxic-ischemia encephalopathy (HIE) was established in the 7-day-old newborn SD rats. Immunohistochemical method was applied to detect the expression of GLUT1 and GLUT3 in hippocampus. GLUT1 and GLUT3 were slightly seen in normal and sham operation group, there was no obviously difference between the two groups (P > 0.05). The expression of GLUT1 and GLUT3 in hypoxic-ischemia group were all higher than that in sham operated group (P < 0.05). Not only the expression of GLUT in progesterone group were significantly higher than that in sham operated group (P < 0.01), but also than that in hypoxic-ischemia group (P < 0.05). PROG could increase the tolerance of neuron to hypoxic-ischemia with maintaining the energy supply in the brain by up-regulating GLUT expression.

Facilitative glucose transporter gene expression in human lymphocytes, monocytes, and macrophages: a role for GLUT isoforms 1, 3, and 5 in the immune response and foam cell formation.

PubMed

Fu, Yuchang; Maianu, Lidia; Melbert, Barry R; Garvey, W Timothy

2004-01-01

Cellular glucose uptake is mediated by a family of facilitative glucose transporters (GLUT) exhibiting differences in kinetics, substrate specificity, and tissue-specific expression. GLUT isoform expression has not been comprehensively studied in human leukocytes, which participate in immune and inflammatory responses and are critical for host defense. Therefore, we studied the regulated expression of GLUT 1-5 mRNA and protein in isolated human lymphocytes and monocytes and in human THP-1 macrophages and foam cells. Lymphocytes expressed GLUT 1 and GLUT 3 proteins, and cellular levels of both isoforms were augmented 3.5- to 6-fold following activation by phytohemagglutinin (PHA). Monocytes expressed 8.4-fold more GLUT 3 protein and 88% less GLUT 1 than lymphocytes, and activation by lipopolysaccharide (LPS) led to a 1.9-fold increase in GLUT 1. At the level of mRNA expression, GLUT 3 mRNA was the most prevalent GLUT mRNA species in monocytes, while lymphocytes expressed equal numbers of GLUT 1 and GLUT 3 transcripts. Differentiation of THP-1 monocytes into macrophages was associated with marked induction of GLUT 3 and GLUT 5 protein expression, and high levels of GLUT 1, GLUT 3, and GLUT 5 were maintained after transformation to foam cells. GLUT 5 mRNA was expressed in 2-fold greater abundance in macrophages and foam cells than that observed for GLUT 1 mRNA, while the level of GLUT 3 mRNA was intermediate. This facilitative glucose transporters are differentially expressed and regulated in human leukocytes in a pattern that could facilitate cellular functions. Speculatively, high GLUT 1 and GLUT 3 expression could provide cellular fuel for the immune response, and high levels of high-affinity GLUT 3 in macrophages might allow the cell to compete with pathogens for hexoses, even in the presence of low interstitial glucose concentrations. Ample expression of GLUT 1 and GLUT 3 in foam cells could also provide hexose substrates and promote lipid loading. The role for

Fisetin Suppresses Lipid Accumulation in Mouse Adipocytic 3T3-L1 Cells by Repressing GLUT4-Mediated Glucose Uptake through Inhibition of mTOR-C/EBPα Signaling.

PubMed

Watanabe, Marina; Hisatake, Mitsuhiro; Fujimori, Ko

2015-05-27

3,7,3',4'-Tetrahydroxyflavone (fisetin) is a flavonoid found in vegetables and fruits having broad biological activities. Here the effects of fisetin on adipogenesis and its regulatory mechanism in mouse adipocytic 3T3-L1 cells are studied. Fisetin inhibited the accumulation of intracellular lipids and lowered the expression of adipogenic genes such as peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding protein (C/EBP) α and fatty acid-binding protein 4 (aP2) during adipogenesis. Moreover, the mRNA levels of genes such as acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase involved in the fatty acid biosynthesis (lipogenesis) were reduced by the treatment with fisetin. The expression level of the glucose transporter 4 (GLUT4) gene was also decreased by fisetin, resulting in down-regulation of glucose uptake. Furthermore, fisetin inhibited the phosphorylation of the mammalian target of rapamycin (mTOR) and that of p70 ribosomal S6 kinase, a target of the mTOR complex, the inhibition of which was followed by a decreased mRNA level of the C/EBPα gene. The results obtained from a chromatin immunoprecipitation assay demonstrated that the ability of C/EBPα to bind to the GLUT4 gene promoter was reduced by the treatment with fisetin, which agreed well with those obtained when 3T3-L1 cells were allowed to differentiate into adipocytes in medium in the presence of rapamycin, an inhibitor for mTOR. These results indicate that fisetin suppressed the accumulation of intracellular lipids by inhibiting GLUT4-mediated glucose uptake through inhibition of the mTOR-C/EBPα signaling in 3T3-L1 cells.

[Distal hereditary motor neuropathy].

PubMed

Devic, P; Petiot, P

2011-11-01

Distal hereditary motor neuropathy (dHMN), also known as spinal muscular atrophy, represents a group of clinically and genetically heterogeneous diseases caused by degenerations of spinal motor neurons and leading to distal muscle weakness and wasting. Nerve conduction studies reveal a pure motor axonopathy and needle examination shows chronic denervation. dHMN were initially subdivided into seven subtypes according to mode of inheritance, age at onset, and clinical evolution. Recent studies have shown that these subtypes are still heterogeneous at the molecular genetic level and novel clinical and genetic entities have been characterized. To date, mutations in 11 different genes have been identified for autosomal-dominant, autosomal-recessive, and X-linked recessive dHMN. Most of the genes encode protein involved in housekeeping functions, endosomal trafficking, axonal transport, translation synthesis, RNA processing, oxidative stress response and apoptosis. The pathophysiological mechanisms underlying dHMN seem to be related to the "length-dependent" death of motor neurons of the anterior horn of the spinal cord, likely because their large axons have higher metabolic requirements for maintenance. dHMN remain heterogeneous at the clinical and molecular genetic level. The molecular pathomechanisms explaining why mutations in these ubiquitously expressed housekeeping genes result in the selective involvement of spinal motor neurons remain to be unravelled. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Immunoexpression of GLUT-1 and angiogenic index in pleomorphic adenomas, adenoid cystic carcinomas, and mucoepidermoid carcinomas of the salivary glands.

PubMed

de Souza, Lélia Batista; de Oliveira, Lucileide Castro; Nonaka, Cassiano Francisco Weege; Lopes, Maria Luiza Diniz de Sousa; Pinto, Leão Pereira; Queiroz, Lélia Maria Guedes

2017-06-01

This study aimed to evaluate and compare the immunoexpression of glucose transporter-1 (GLUT-1) and angiogenic index between pleomorphic adenomas (PAs), adenoid cystic carcinomas (ACCs), and mucoepidermoid carcinomas (MECs) of the salivary glands, and establish associations with the respective subtype/histological grade. Twenty PAs, 20 ACCs, and 10 MECs were submitted to morphological and immunohistochemical analysis. GLUT-1 expression was semi-quantitatively evaluated and angiogenic index was assessed by microvessel counts using anti-CD34 antibody. Higher GLUT-1 immunoexpression was observed in the MECs compared to PAs and ACCs (p = 0.022). Mean number of microvessels was 66.5 in MECs, 40.4 in PAs, and 21.2 in ACCs (p < 0.001). GLUT-1 expression and angiogenic index showed no significant correlation in the tumors studied. Results suggest that differences in biological behavior of the studied tumors are related to GLUT-1. Benign and malignant salivary gland tumors differ in the angiogenic index; however, angiogenesis may be independent of the tumor cell's metabolic demand.

Illicit Trafficking of Natural Radionuclides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedrich, Steinhaeusler; Lyudmila, Zaitseva

2008-08-07

Natural radionuclides have been subject to trafficking worldwide, involving natural uranium ore (U 238), processed uranium (yellow cake), low enriched uranium (<20% U 235) or highly enriched uranium (>20% U 235), radium (Ra 226), polonium (Po 210), and natural thorium ore (Th 232). An important prerequisite to successful illicit trafficking activities is access to a suitable logistical infrastructure enabling an undercover shipment of radioactive materials and, in case of trafficking natural uranium or thorium ore, capable of transporting large volumes of material. Covert en route diversion of an authorised uranium transport, together with covert diversion of uranium concentrate from anmore » operating or closed uranium mines or mills, are subject of case studies. Such cases, involving Israel, Iran, Pakistan and Libya, have been analyzed in terms of international actors involved and methods deployed. Using international incident data contained in the Database on Nuclear Smuggling, Theft and Orphan Radiation Sources (DSTO) and international experience gained from the fight against drug trafficking, a generic Trafficking Pathway Model (TPM) is developed for trafficking of natural radionuclides. The TPM covers the complete trafficking cycle, ranging from material diversion, covert material transport, material concealment, and all associated operational procedures. The model subdivides the trafficking cycle into five phases: (1) Material diversion by insider(s) or initiation by outsider(s); (2) Covert transport; (3) Material brokerage; (4) Material sale; (5) Material delivery. An Action Plan is recommended, addressing the strengthening of the national infrastructure for material protection and accounting, development of higher standards of good governance, and needs for improving the control system deployed by customs, border guards and security forces.« less

Illicit Trafficking of Natural Radionuclides

NASA Astrophysics Data System (ADS)

Friedrich, Steinhäusler; Lyudmila, Zaitseva

2008-08-01

Natural radionuclides have been subject to trafficking worldwide, involving natural uranium ore (U 238), processed uranium (yellow cake), low enriched uranium (<20% U 235) or highly enriched uranium (>20% U 235), radium (Ra 226), polonium (Po 210), and natural thorium ore (Th 232). An important prerequisite to successful illicit trafficking activities is access to a suitable logistical infrastructure enabling an undercover shipment of radioactive materials and, in case of trafficking natural uranium or thorium ore, capable of transporting large volumes of material. Covert en route diversion of an authorised uranium transport, together with covert diversion of uranium concentrate from an operating or closed uranium mines or mills, are subject of case studies. Such cases, involving Israel, Iran, Pakistan and Libya, have been analyzed in terms of international actors involved and methods deployed. Using international incident data contained in the Database on Nuclear Smuggling, Theft and Orphan Radiation Sources (DSTO) and international experience gained from the fight against drug trafficking, a generic Trafficking Pathway Model (TPM) is developed for trafficking of natural radionuclides. The TPM covers the complete trafficking cycle, ranging from material diversion, covert material transport, material concealment, and all associated operational procedures. The model subdivides the trafficking cycle into five phases: (1) Material diversion by insider(s) or initiation by outsider(s); (2) Covert transport; (3) Material brokerage; (4) Material sale; (5) Material delivery. An Action Plan is recommended, addressing the strengthening of the national infrastructure for material protection and accounting, development of higher standards of good governance, and needs for improving the control system deployed by customs, border guards and security forces.

Dehydroepiandrosterone activates AMP kinase and regulates GLUT4 and PGC-1α expression in C2C12 myotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yokokawa, Takumi; Sato, Koji; Iwanaka, Nobumasa

Exercise and caloric restriction (CR) have been reported to have anti-ageing, anti-obesity, and health-promoting effects. Both interventions increase the level of dehydroepiandrosterone (DHEA) in muscle and blood, suggesting that DHEA might partially mediate these effects. In addition, it is thought that either 5′-adenosine monophosphate-activated protein kinase (AMPK) or peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) mediates the beneficial effects of exercise and CR. However, the effects of DHEA on AMPK activity and PGC-1α expression remain unclear. Therefore, we explored whether DHEA in myotubes acts as an activator of AMPK and increases PGC-1α. DHEA exposure increased glucose uptake but not the phosphorylation levelsmore » of Akt and PKCζ/λ in C2C12 myotubes. In contrast, the phosphorylation levels of AMPK were elevated by DHEA exposure. Finally, we found that DHEA induced the expression of the genes PGC-1α and GLUT4. Our current results might reveal a previously unrecognized physiological role of DHEA; the activation of AMPK and the induction of PGC-1α by DHEA might mediate its anti-obesity and health-promoting effects in living organisms. - Highlights: • We assessed whether dehydroepiandrosterone (DHEA) activates AMPK and PGC-1α. • DHEA exposure increased glucose uptake in C2C12 myotubes. • The phosphorylation levels of AMPK were elevated by DHEA exposure. • DHEA induced the expression of the genes PGC-1α and GLUT4. • AMPK might mediate the anti-obesity and health-promoting effects of DHEA.« less

Resistin modulates glucose uptake and glucose transporter-1 (GLUT-1) expression in trophoblast cells.

PubMed

Di Simone, Nicoletta; Di Nicuolo, Fiorella; Marzioni, Daniela; Castellucci, Mario; Sanguinetti, Maurizio; D'lppolito, Silvia; Caruso, Alessandro

2009-02-01

The adipocytokine resistin impairs glucose tolerance and insulin sensitivity. Here, we examine the effect of resistin on glucose uptake in human trophoblast cells and we demonstrate that transplacental glucose transport is mediated by glucose transporter (GLUT)-1. Furthermore, we evaluate the type of signal transduction induced by resistin in GLUT-1 regulation. BeWo choriocarcinoma cells and primary cytotrophoblast cells were cultured with increasing resistin concentrations for 24 hrs. The main outcome measures include glucose transport assay using [(3)H]-2-deoxy glucose, GLUT-1 protein expression by Western blot analysis and GLUT-1 mRNA detection by quantitative real-time RT-PCR. Quantitative determination of phospho(p)-ERK1/2 in cell lysates was performed by an Enzyme Immunometric Assay and Western blot analysis. Our data demonstrate a direct effect of resistin on normal cytotrophoblastic and on BeWo cells: resistin modulates glucose uptake, GLUT-1 messenger ribonucleic acid (mRNA) and protein expression in placental cells. We suggest that ERK1/2 phosphorylation is involved in the GLUT-1 regulation induced by resistin. In conclusion, resistin causes activation of both the ERK1 and 2 pathway in trophoblast cells. ERK1 and 2 activation stimulated GLUT-1 synthesis and resulted in increase of placental glucose uptake. High resistin levels (50-100 ng/ml) seem able to affect glucose-uptake, presumably by decreasing the cell surface glucose transporter.

In vitro glucose uptake activity of Aegles marmelos and Syzygium cumini by activation of Glut-4, PI3 kinase and PPARgamma in L6 myotubes.

PubMed

Anandharajan, R; Jaiganesh, S; Shankernarayanan, N P; Viswakarma, R A; Balakrishnan, A

2006-06-01

The purpose of the present study is to investigate the effect of methanolic extracts of Aegles marmelos and Syzygium cumini on a battery of targets glucose transporter (Glut-4), peroxisome proliferator activator receptor gamma (PPARgamma) and phosphatidylinositol 3' kinase (PI3 kinase) involved in glucose transport. A. marmelos and S. cumini are anti-diabetic medicinal plants being used in Indian traditional medicine. Different solvent extracts extracted sequentially were analysed for glucose uptake activity at each step and methanol extracts were found to be significantly active at 100ng/ml dose comparable with insulin and rosiglitazone. Elevation of Glut-4, PPARgamma and PI3 kinase by A. marmelos and S. cumini in association with glucose transport supported the up-regulation of glucose uptake. The inhibitory effect of cycloheximide on A. marmelos- and S. cumini-mediated glucose uptake suggested that new protein synthesis is required for the elevated glucose transport. Current observation concludes that methanolic extracts of A. marmelos and S. cumini activate glucose transport in a PI3 kinase-dependent fashion.

GLUT-1 deficiency without epilepsy--an exceptional case.

PubMed

Overweg-Plandsoen, W C G; Groener, J E M; Wang, D; Onkenhout, W; Brouwer, O F; Bakker, H D; De Vivo, D C

2003-01-01

The GLUT-1 deficiency is a metabolic disorder caused by a defect in glucose transport across the blood-brain barrier as a result of a defect in the glucose-transport protein. Patients present with epileptic seizures, delayed development, ataxia and hypotonia, and in many cases acquired microcephaly. In most patients, treatment with a ketogenic diet proved to be successful in controlling the epilepsy. We report a 9-year-old boy with retardation and ataxia, but without epilepsy, caused by GLUT-1 deficiency, proven biochemically and by DNA analysis. Treatment with a medium-chain triglyceride ketogenic diet had a beneficial effect.

Short communication: Protein kinase C regulates glucose uptake and mRNA expression of glucose transporter (GLUT) 1 and GLUT8 in lactating bovine mammary epithelial cells.

PubMed

Zhao, K; Liu, H-Y; Zhao, F-Q; Liu, J-X

2014-07-01

The aim of this study was to determine the role of protein kinase C (PKC) in regulating glucose uptake in lactating bovine mammary epithelial cells (BMEC). The BMEC were cultured and treated with different concentrations of phorbol 12-myristate 13-acetate (PMA;0, 10, 25, 50, 100, and 200 ng/mL), the classic activator of PKC, for 48 h. Compared with the cells with no PMA treatment, 50 and 100 ng of PMA/mL significantly stimulated the glucose uptake of the BMEC, whereas the glucose uptake by the cells treated with the lowest and the highest amounts of PMA (25 and 200 ng/mL, respectively) did not show a significant difference. Consistently, the mRNA expression of glucose transporter (GLUT) 1 and 8 showed a similar pattern of increase under the treatments of PMA. Furthermore, when the cells were pretreated with GF1090203X (0, 0.25, 0.5, 1, and 2 μM), an inhibitor of PKC, for 30 min before exposed to PMA (50 ng/mL), the PMA-induced glucose uptake and GLUT1 and GLUT8 expression were decreased by GF1090203X in a dose-dependent manner. These results demonstrate that PKC is involved in the regulation of glucose uptake by BMEC, and this function may work, at least partly, through upregulating the expression of GLUT1 and GLUT8. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

The Role of SGLT1 and GLUT2 in Intestinal Glucose Transport and Sensing

PubMed Central

Röder, Pia V.; Geillinger, Kerstin E.; Zietek, Tamara S.; Thorens, Bernard; Koepsell, Hermann; Daniel, Hannelore

2014-01-01

Intestinal glucose absorption is mediated by SGLT1 whereas GLUT2 is considered to provide basolateral exit. Recently, it was proposed that GLUT2 can be recruited into the apical membrane after a high luminal glucose bolus allowing bulk absorption of glucose by facilitated diffusion. Moreover, SGLT1 and GLUT2 are suggested to play an important role in intestinal glucose sensing and incretin secretion. In mice that lack either SGLT1 or GLUT2 we re-assessed the role of these transporters in intestinal glucose uptake after radiotracer glucose gavage and performed Western blot analysis for transporter abundance in apical membrane fractions in a comparative approach. Moreover, we examined the contribution of these transporters to glucose-induced changes in plasma GIP, GLP-1 and insulin levels. In mice lacking SGLT1, tissue retention of tracer glucose was drastically reduced throughout the entire small intestine whereas GLUT2-deficient animals exhibited higher tracer contents in tissue samples than wild type animals. Deletion of SGLT1 resulted also in reduced blood glucose elevations and abolished GIP and GLP-1 secretion in response to glucose. In mice lacking GLUT2, glucose-induced insulin but not incretin secretion was impaired. Western blot analysis revealed unchanged protein levels of SGLT1 after glucose gavage. GLUT2 detected in apical membrane fractions mainly resulted from contamination with basolateral membranes but did not change in density after glucose administration. SGLT1 is unequivocally the prime intestinal glucose transporter even at high luminal glucose concentrations. Moreover, SGLT1 mediates glucose-induced incretin secretion. Our studies do not provide evidence for GLUT2 playing any role in either apical glucose influx or incretin secretion. PMID:24587162

Evaluating the Efficacy of GLUT Inhibitors Using a Seahorse Extracellular Flux Analyzer.

PubMed

Wei, Changyong; Heitmeier, Monique; Hruz, Paul W; Shanmugam, Mala

2018-01-01

Glucose is metabolized through anaerobic glycolysis and aerobic oxidative phosphorylation (OXPHOS). Perturbing glucose uptake and its subsequent metabolism can alter both glycolytic and OXPHOS pathways and consequently lactate and/or oxygen consumption. Production and secretion of lactate, as a consequence of glycolysis, leads to acidification of the extracellular medium. Molecular oxygen is the final electron acceptor in the electron transport chain, facilitating oxidative phosphorylation of ADP to ATP. The alterations in extracellular acidification and/or oxygen consumption can thus be used as indirect readouts of glucose metabolism and assessing the impact of inhibiting glucose transport through specific glucose transporters (GLUTs). The Seahorse bioenergetics analyzer can measure both the oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). The proposed methodology affords a robust, high-throughput method to screen for GLUT inhibition in cells engineered to express specific GLUTs, providing live cell read-outs upon GLUT inhibition.

GLUT-1-independent infection of the glioblastoma/astroglioma U87 cells by the human T cell leukemia virus type 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin Qingwen; Agrawal, Lokesh; Walther Cancer Institute, Indianapolis, IN 46208

2006-09-15

The human glucose transporter protein 1 (GLUT-1) functions as a receptor for human T cell leukemia virus (HTLV). GLUT-1 is a twelve-transmembrane cell surface receptor with six extracellular (ECL) and seven intracellular domains. To analyze HTLV-1 cytotropism, we utilized polyclonal antibodies to a synthetic peptide corresponding to the large extracellular domain of GLUT-1. The antibodies caused significant blocking of envelope (Env)-mediated fusion and pseudotyped virus infection of HeLa cells but had no significant effect on infection of U87 cells. This differential effect correlated with the detection of high-level surface expression of GLUT-1 on HeLa cells and very weak staining ofmore » U87 cells. To investigate this in terms of viral cytotropism, we cloned GLUT-1 cDNA from U87 cells and isolated two different versions of cDNA clones: the wild-type sequence (encoding 492 residues) and a mutant cDNA with a 5-base pair deletion (GLUT-1{delta}5) between nucleotides 1329 and 1333. The deletion, also detected in genomic DNA, resulted in a frame-shift and premature termination producing a truncated protein of 463 residues. Transfection of the wild-type GLUT-1 but not GLUT-1{delta}5 cDNA into CHO cells resulted in efficient surface expression of the human GLUT-1. Co-expression of GLUT-1 with GLUT-1{delta}5 produces a trans-inhibition by GLUT-1{delta}5 of GLUT-1-mediated HTLV-1 envelope (Env)-mediated fusion. Co-immunoprecipitation experiments demonstrated physical interaction of the wild-type and mutant proteins. Northern blot and RT-PCR analyses demonstrated lower GLUT-1 RNA expression in U87 cells. We propose two mechanisms to account for the impaired cell surface expression of GLUT-1 on U87 cells: low GLUT-1 RNA expression and the formation of GLUT-1/GLUT-1{delta}5 heterodimers that are retained intracellularly. Significant RNAi-mediated reduction of endogenous GLUT-1 expression impaired HTLV-1 Env-mediated fusion with HeLa cells but not with U87 cells. We

Quercetin inhibits glucose transport by binding to an exofacial site on GLUT1.

PubMed

Hamilton, Kathryn E; Rekman, Janelle F; Gunnink, Leesha K; Busscher, Brianna M; Scott, Jordan L; Tidball, Andrew M; Stehouwer, Nathan R; Johnecheck, Grace N; Looyenga, Brendan D; Louters, Larry L

2018-05-29

Quercetin, a common dietary flavone, is a competitive inhibitor of glucose uptake and is also thought to be transported into cells by GLUT1. In this study, we confirm that quercetin is a competitive inhibitor of GLUT1 and also demonstrate that newly synthesized compounds, WZB-117 and BAY-876 are robust inhibitors of GLUT1 in L929 cells. To measure quercetin interaction with L929 cells, we develop a new fluorescent assay using flow cytometry. The binding of quercetin and its inhibitory effects on 2-deoxyglucose (2DG) uptake showed nearly identical dose dependent effects, with both having maximum effects between 50 and 100 μM and similar half maximum effects at 8.9 and 8.5 μM respectively. The interaction of quercetin was rapid with t 1/2 of 54 s and the onset and loss of its inhibitory effects on 2DG uptake were equally fast. This suggests that either quercetin is simply binding to surface GLUT1 or its transport in and out of the cell reaches equilibrium very quickly. If quercetin is transported, the co-incubation of quercetin with other glucose inhibitors should block quercetin uptake. However, we observed that WZB-117, an exofacial binding inhibitor of GLUT1 reduced quercetin interaction, while cytochalasin B, an endofacial binding inhibitor, enhanced quercetin interaction, and BAY-876 had no effect on quercetin interaction. Taken together, these data are more consistent with quercetin simply binding to GLUT1, but not actually being transported into L929 cells via the glucose channel in GLUT1. Copyright © 2018. Published by Elsevier B.V.

To discuss illicit nuclear trafficking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balatsky, Galya I; Severe, William R; Wallace, Richard K

2010-01-01

The Illicit nuclear trafficking panel was conducted at the 4th Annual INMM workshop on Reducing the Risk from Radioactive and Nuclear Materials on February 2-3, 2010 in Washington DC. While the workshop occurred prior to the Nuclear Security Summit, April 12-13 2010 in Washington DC, some of the summit issues were raised during the workshop. The Communique of the Washington Nuclear Security Summit stated that 'Nuclear terrorism is one of the most challenging threats to international security, and strong nuclear security measures are the most effective means to prevent terrorists, criminals, or other unauthorized actors from acquiring nuclear materials.' Themore » Illicit Trafficking panel is one means to strengthen nuclear security and cooperation at bilateral, regional and multilateral levels. Such a panel promotes nuclear security culture through technology development, human resources development, education and training. It is a tool which stresses the importance of international cooperation and coordination of assistance to improve efforts to prevent and respond to incidents of illicit nuclear trafficking. Illicit trafficking panel included representatives from US government, an international organization (IAEA), private industry and a non-governmental organization to discuss illicit nuclear trafficking issues. The focus of discussions was on best practices and challenges for addressing illicit nuclear trafficking. Terrorism connection. Workshop discussions pointed out the identification of terrorist connections with several trafficking incidents. Several trafficking cases involved real buyers (as opposed to undercover law enforcement agents) and there have been reports identifying individuals associated with terrorist organizations as prospective plutonium buyers. Some specific groups have been identified that consistently search for materials to buy on the black market, but no criminal groups were identified that specialize in nuclear materials or isotope

Sex-Specific Life Course Changes in the Neuro-Metabolic Phenotype of Glut3 Null Heterozygous Mice: Ketogenic Diet Ameliorates Electroencephalographic Seizures and Improves Sociability.

PubMed

Dai, Yun; Zhao, Yuanzi; Tomi, Masatoshi; Shin, Bo-Chul; Thamotharan, Shanthie; Mazarati, Andrey; Sankar, Raman; Wang, Elizabeth A; Cepeda, Carlos; Levine, Michael S; Zhang, Jingjing; Frew, Andrew; Alger, Jeffry R; Clark, Peter M; Sondhi, Monica; Kositamongkol, Sudatip; Leibovitch, Leah; Devaskar, Sherin U

2017-04-01

We tested the hypothesis that exposure of glut3+/- mice to a ketogenic diet ameliorates autism-like features, which include aberrant behavior and electrographic seizures. We first investigated the life course sex-specific changes in basal plasma-cerebrospinal fluid (CSF)-brain metabolic profile, brain glucose transport/uptake, glucose and monocarboxylate transporter proteins, and adenosine triphosphate (ATP) in the presence or absence of systemic insulin administration. Glut3+/- male but not female mice (5 months of age) displayed reduced CSF glucose/lactate concentrations with no change in brain Glut1, Mct2, glucose uptake or ATP. Exogenous insulin-induced hypoglycemia increased brain glucose uptake in glut3+/- males alone. Higher plasma-CSF ketones (β-hydroxybutyrate) and lower brain Glut3 in females vs males proved protective in the former while enhancing vulnerability in the latter. As a consequence, increased synaptic proteins (neuroligin4 and SAPAP1) with spontaneous excitatory postsynaptic activity subsequently reduced hippocampal glucose content and increased brain amyloid β1-40 deposition in an age-dependent manner in glut3+/- males but not females (4 to 24 months of age). We then explored the protective effect of a ketogenic diet on ultrasonic vocalization, sociability, spatial learning and memory, and electroencephalogram seizures in male mice (7 days to 6 to 8 months of age) alone. A ketogenic diet partially restored sociability without affecting perturbed vocalization, spatial learning and memory, and reduced seizure events. We conclude that (1) sex-specific and age-dependent perturbations underlie the phenotype of glut3+/- mice, and (2) a ketogenic diet ameliorates seizures caused by increased cortical excitation and improves sociability, but fails to rescue vocalization and cognitive deficits in glut3+/- male mice. Copyright © 2017 Endocrine Society.

Sex-Specific Life Course Changes in the Neuro-Metabolic Phenotype of Glut3 Null Heterozygous Mice: Ketogenic Diet Ameliorates Electroencephalographic Seizures and Improves Sociability

PubMed Central

Dai, Yun; Zhao, Yuanzi; Tomi, Masatoshi; Shin, Bo-Chul; Thamotharan, Shanthie; Mazarati, Andrey; Sankar, Raman; Wang, Elizabeth A.; Cepeda, Carlos; Levine, Michael S.; Zhang, Jingjing; Frew, Andrew; Alger, Jeffry R.; Clark, Peter M.; Sondhi, Monica; Kositamongkol, Sudatip; Leibovitch, Leah

2017-01-01

We tested the hypothesis that exposure of glut3+/− mice to a ketogenic diet ameliorates autism-like features, which include aberrant behavior and electrographic seizures. We first investigated the life course sex-specific changes in basal plasma–cerebrospinal fluid (CSF)–brain metabolic profile, brain glucose transport/uptake, glucose and monocarboxylate transporter proteins, and adenosine triphosphate (ATP) in the presence or absence of systemic insulin administration. Glut3+/− male but not female mice (5 months of age) displayed reduced CSF glucose/lactate concentrations with no change in brain Glut1, Mct2, glucose uptake or ATP. Exogenous insulin-induced hypoglycemia increased brain glucose uptake in glut3+/− males alone. Higher plasma-CSF ketones (β-hydroxybutyrate) and lower brain Glut3 in females vs males proved protective in the former while enhancing vulnerability in the latter. As a consequence, increased synaptic proteins (neuroligin4 and SAPAP1) with spontaneous excitatory postsynaptic activity subsequently reduced hippocampal glucose content and increased brain amyloid β1-40 deposition in an age-dependent manner in glut3+/− males but not females (4 to 24 months of age). We then explored the protective effect of a ketogenic diet on ultrasonic vocalization, sociability, spatial learning and memory, and electroencephalogram seizures in male mice (7 days to 6 to 8 months of age) alone. A ketogenic diet partially restored sociability without affecting perturbed vocalization, spatial learning and memory, and reduced seizure events. We conclude that (1) sex-specific and age-dependent perturbations underlie the phenotype of glut3+/− mice, and (2) a ketogenic diet ameliorates seizures caused by increased cortical excitation and improves sociability, but fails to rescue vocalization and cognitive deficits in glut3+/− male mice. PMID:28324109

Evaluation of non-coding variation in GLUT1 deficiency.

PubMed

Liu, Yu-Chi; Lee, Jia Wei Audrey; Bellows, Susannah T; Damiano, John A; Mullen, Saul A; Berkovic, Samuel F; Bahlo, Melanie; Scheffer, Ingrid E; Hildebrand, Michael S

2016-12-01

Loss-of-function mutations in SLC2A1, encoding glucose transporter-1 (GLUT-1), lead to dysfunction of glucose transport across the blood-brain barrier. Ten percent of cases with hypoglycorrhachia (fasting cerebrospinal fluid [CSF] glucose <2.2mmol/L) do not have mutations. We hypothesized that GLUT1 deficiency could be due to non-coding SLC2A1 variants. We performed whole exome sequencing of one proband with a GLUT1 phenotype and hypoglycorrhachia negative for SLC2A1 sequencing and copy number variants. We studied a further 55 patients with different epilepsies and low CSF glucose who did not have exonic mutations or copy number variants. We sequenced non-coding promoter and intronic regions. We performed mRNA studies for the recurrent intronic variant. The proband had a de novo splice site mutation five base pairs from the intron-exon boundary. Three of 55 patients had deep intronic SLC2A1 variants, including a recurrent variant in two. The recurrent variant produced less SLC2A1 mRNA transcript. Fasting CSF glucose levels show an age-dependent correlation, which makes the definition of hypoglycorrhachia challenging. Low CSF glucose levels may be associated with pathogenic SLC2A1 mutations including deep intronic SLC2A1 variants. Extending genetic screening to non-coding regions will enable diagnosis of more patients with GLUT1 deficiency, allowing implementation of the ketogenic diet to improve outcomes. © 2016 Mac Keith Press.

Activation of nuclear receptor NR5A2 increases Glut4 expression and glucose metabolism in muscle cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolado-Carrancio, A.; Riancho, J.A.; Sainz, J.

Highlights: • NR5A2 expression in C2C12 is associated with myotube differentiation. • DLPC induces an increase in GLUT4 levels and glucose uptake in C2C12 myotubes. • In high glucose conditions the activation of NR5A2 inhibits fatty acids oxidation. - Abstract: NR5A2 is a nuclear receptor which regulates the expression of genes involved in cholesterol metabolism, pluripotency maintenance and cell differentiation. It has been recently shown that DLPC, a NR5A2 ligand, prevents liver steatosis and improves insulin sensitivity in mouse models of insulin resistance, an effect that has been associated with changes in glucose and fatty acids metabolism in liver. Becausemore » skeletal muscle is a major tissue in clearing glucose from blood, we studied the effect of the activation of NR5A2 on muscle metabolism by using cultures of C2C12, a mouse-derived cell line widely used as a model of skeletal muscle. Treatment of C2C12 with DLPC resulted in increased levels of expression of GLUT4 and also of several genes related to glycolysis and glycogen metabolism. These changes were accompanied by an increased glucose uptake. In addition, the activation of NR5A2 produced a reduction in the oxidation of fatty acids, an effect which disappeared in low-glucose conditions. Our results suggest that NR5A2, mostly by enhancing glucose uptake, switches muscle cells into a state of glucose preference. The increased use of glucose by muscle might constitute another mechanism by which NR5A2 improves blood glucose levels and restores insulin sensitivity.« less

Expression of GLUT-1 in oral squamous cell carcinoma in tobacco and non-tobacco users

PubMed Central

Azad, Neha; Kumari Maurya, Malti; Kar, Meenakshi; Goel, Madhu Mati; Singh, Ajay Kumar; Sagar, Mala; Mehrotra, Divya; Kumar, Vijay

2016-01-01

Background GLUTs are a family of proteins that mediate glucose transport through the membrane, expressed in head and neck squamous cell carcinoma. GLUT-1 positivity in malignant cells indicates increased proliferative activity, energy requirements, aggressive behaviour and poor radiation response. Aim To observe the expression of GLUT-1 protein in oral squamous cell carcinoma in tobacco and non-tobacco users and to correlate the expression with histopathological grading and pathological staging. Methods 50 cases (25 tobacco and 25 non-tobacco) of oral squamous cell carcinoma, selected during period of August 2014 to July 2015. Histopathological grading, TNM and staging were done. Immunohistochemical staining was performed using standard protocol for paraffin embedded sections. Analysis was performed on SPSS software (Windows version 17.0). Results Significant association of GLUT-1 expression was found with history of tobacco (p < 0.001), Bryne's grade (p < 0.001), tumour size (p = 0.001), nodal metastasis (p = 0.022) and stage (p < 0.001). Higher GLUT-1 expression in stage II, stage III and stage IV was found as compared to stage I. GLUT-1 immunoexpression also shows progressive switch from membranous to cytoplasmic to combined location correlating with histopathologic grade and pTNM stage. Conclusion GLUT-1 expression correlates significantly with histological grade and pTNM staging of oral squamous cell carcinoma. It also significantly correlates with tobacco addiction. Thus, GLUT-1 expression may serve as a biomarker for patients of oral squamous cell carcinoma. PMID:26937365

Developmental reprogramming of rat GLUT-5 requires de novo mRNA and protein synthesis.

PubMed

Jiang, L; Ferraris, R P

2001-01-01

Fructose transporter (GLUT-5) expression is low in mid-weaning rat small intestine, increases normally after weaning is completed, and can be precociously induced by premature consumption of a high-fructose (HF) diet. In this study, an in vivo perfusion model was used to determine the mechanisms regulating this substrate-induced reprogramming of GLUT-5 development. HF (100 mM) but not high-glucose (HG) perfusion increased GLUT-5 activity and mRNA abundance. In contrast, HF and HG perfusion had no effect on Na(+)-dependent glucose transporter (SGLT-1) expression but increased c-fos and c-jun expression. Intraperitoneal injection of actinomycin D before intestinal perfusion blocked the HF-induced increase in fructose uptake rate and GLUT-5 mRNA abundance. Actinomycin D also prevented the perfusion-induced increase in c-fos and c-jun mRNA abundance but did not affect glucose uptake rate and SGLT-1 mRNA abundance. Cycloheximide blocked the HF-induced increase in fructose uptake rate but not the increase in GLUT-5 mRNA abundance and had no effect on glucose uptake rate and SGLT-1 mRNA abundance. In neonatal rats, the substrate-induced reprogramming of intestinal fructose transport is likely to involve transcription and translation of the GLUT-5 gene.

Does apical membrane GLUT2 have a role in intestinal glucose uptake?

PubMed

Naftalin, Richard J

2014-01-01

It has been proposed that the non-saturable component of intestinal glucose absorption, apparent following prolonged exposure to high intraluminal glucose concentrations, is mediated via the low affinity glucose and fructose transporter, GLUT2, upregulated within the small intestinal apical border. The evidence that the non-saturable transport component is mediated via an apical membrane sugar transporter is that it is inhibited by phloretin, after exposure to phloridzin. Since the other apical membrane sugar transporter, GLUT5, is insensitive to inhibition by either cytochalasin B, or phloretin, GLUT2 was deduced to be the low affinity sugar transport route. As in its uninhibited state, polarized intestinal glucose absorption depends both on coupled entry of glucose and sodium across the brush border membrane and on the enterocyte cytosolic glucose concentration exceeding that in both luminal and submucosal interstitial fluids, upregulation of GLUT2 within the intestinal brush border will usually stimulate downhill glucose reflux to the intestinal lumen from the enterocytes; thereby reducing, rather than enhancing net glucose absorption across the luminal surface. These states are simulated with a computer model generating solutions to the differential equations for glucose, Na and water flows between luminal, cell, interstitial and capillary compartments. The model demonstrates that uphill glucose transport via SGLT1 into enterocytes, when short-circuited by any passive glucose carrier in the apical membrane, such as GLUT2, will reduce transcellular glucose absorption and thereby lead to increased paracellular flow. The model also illustrates that apical GLUT2 may usefully act as an osmoregulator to prevent excessive enterocyte volume change with altered luminal glucose concentrations.

Does apical membrane GLUT2 have a role in intestinal glucose uptake?

PubMed Central

Naftalin, Richard J

2014-01-01

It has been proposed that the non-saturable component of intestinal glucose absorption, apparent following prolonged exposure to high intraluminal glucose concentrations, is mediated via the low affinity glucose and fructose transporter, GLUT2, upregulated within the small intestinal apical border. The evidence that the non-saturable transport component is mediated via an apical membrane sugar transporter is that it is inhibited by phloretin, after exposure to phloridzin. Since the other apical membrane sugar transporter, GLUT5, is insensitive to inhibition by either cytochalasin B, or phloretin, GLUT2 was deduced to be the low affinity sugar transport route. As in its uninhibited state, polarized intestinal glucose absorption depends both on coupled entry of glucose and sodium across the brush border membrane and on the enterocyte cytosolic glucose concentration exceeding that in both luminal and submucosal interstitial fluids, upregulation of GLUT2 within the intestinal brush border will usually stimulate downhill glucose reflux to the intestinal lumen from the enterocytes; thereby reducing, rather than enhancing net glucose absorption across the luminal surface. These states are simulated with a computer model generating solutions to the differential equations for glucose, Na and water flows between luminal, cell, interstitial and capillary compartments. The model demonstrates that uphill glucose transport via SGLT1 into enterocytes, when short-circuited by any passive glucose carrier in the apical membrane, such as GLUT2, will reduce transcellular glucose absorption and thereby lead to increased paracellular flow. The model also illustrates that apical GLUT2 may usefully act as an osmoregulator to prevent excessive enterocyte volume change with altered luminal glucose concentrations. PMID:25671087

Impaired trafficking of human kidney anion exchanger (kAE1) caused by hetero-oligomer formation with a truncated mutant associated with distal renal tubular acidosis.

PubMed

Quilty, Janne A; Cordat, Emmanuelle; Reithmeier, Reinhart A F

2002-12-15

Autosomal dominant distal renal tubular acidosis (dRTA) has been associated with several mutations in the anion exchanger AE1 gene. The effect of an 11-amino-acid C-terminal dRTA truncation mutation (901 stop) on the expression of kidney AE1 (kAE1) and erythroid AE1 was examined in transiently transfected HEK-293 cells. Unlike the wild-type proteins, kAE1 901 stop and AE1 901 stop mutants exhibited impaired trafficking from the endoplasmic reticulum to the plasma membrane as determined by immunolocalization, cell-surface biotinylation, oligosaccharide processing and pulse-chase experiments. The 901 stop mutants were able to bind to an inhibitor affinity resin, suggesting that these mutant membrane proteins were not grossly misfolded. Co-expression of wild-type and mutant kAE1 or AE1 resulted in intracellular retention of the wild-type proteins in a pre-medial Golgi compartment. This dominant negative effect was due to hetero-oligomer formation of the mutant and wild-type proteins. Intracellular retention of kAE1 in the alpha-intercalated cells of the kidney would account for the impaired acid secretion into the urine characteristic of dRTA.

GLUT-5 expression in neonatal rats: crypt-villus location and age-dependent regulation.

PubMed

Jiang, L; David, E S; Espina, N; Ferraris, R P

2001-09-01

The rat fructose transporter normally appears after completion of weaning but can be precociously induced by early feeding of a high-fructose diet. In this study, the crypt-villus site, the metabolic nature of the signal, and the age dependence of induction were determined. In weaning rats fed high-glucose pellets, GLUT-5 mRNA expression was modest, localized mainly in the upper three-fourths of the villus, and there was little expression in the villus base. When fed high-fructose pellets, GLUT-5 mRNA expression was two to three times greater in all regions except the villus base. Intestinal perfusion in vivo of a nonmetabolizable fructose analog, 3-O-methylfructose, tended to increase fructose uptake rate and moderately increased GLUT-5 mRNA abundance but had no effect on glucose uptake rates and SGLT1 mRNA abundance. Gavage feeding of high-fructose, but not high-glucose, solutions enhanced fructose uptake only in pups > or =14 days, suggesting that GLUT-5 regulation is markedly age dependent. Fructose or its metabolites upregulate GLUT-5 expression in all enterocytes, except those in the crypt and villus base and in pups <14 days old.

Glut-1 translocation in FRTL-5 thyroid cells: role of phosphatidylinositol 3-kinase and N-glycosylation.

PubMed

Samih, N; Hovsepian, S; Aouani, A; Lombardo, D; Fayet, G

2000-11-01

It was previously demonstrated that insulin or TSH treatment of FRTL-5 cells resulted in an elevation of glucose transport and in an increase of cell surface expression of the glucose transporter Glut-1. However, the signaling mechanisms leading to the insulin or TSH-induced increase in the cell surface expression of Glut-1 were not investigated. In the present study, we demonstrated that wortmannin and LY294002, two specific inhibitors of phosphatidylinositol 3-kinase (PI3-kinase), interfere both in the signaling pathways of insulin and TSH leading to glucose consumption enhancement and Glut-1 translocation. Two hours after insulin treatment, TSH or cAMP analog (Bu)2cAMP stimulation, glucose transport was increased and most of the intracellular Glut-1 pool was translocated to plasma membranes. Wortmannin or LY294002 blocked the insulin, (Bu)2cAMP, and the TSH-induced translocation of Glut-1. Wortmannin or LY294002 alone did not alter the basal ratio between intracellular and cell surface Glut-1 molecules. These results suggest that in FRTL-5 cells wortmannin and LY294002 inhibited the insulin, (Bu)2cAMP and TSH events leading to Glut-1 translocation from an intracellular compartment to the plasma membrane. Likewise, (Bu)2cAMP effects on glucose transport and Glut-1 translocation to plasma membrane were repressed by PI3-kinase inhibitors but not by the protein kinase A (PKA) inhibitor H89. We suggest that (Bu)2cAMP stimulates Glut-1 translocation to plasma membrane through PI3-kinase-dependent and PKA-independent signaling pathways. To further elucidate mechanisms that regulate the translocation of Glut-1 to cell membrane, we extended this study to the role played by the N-glycosylation in the translocation and in the biological activity of Glut-1 in FRTL-5 cells. For this purpose we used tunicamycin, an inhibitor of the N-glycosylation. Our experiments with tunicamycin clearly showed that both the glycosylated and unglycosylated forms of the transporter reached

The effect of Glut1 and c-myc on prognosis in esophageal squamous cell carcinoma of Kazakh and Han patients.

PubMed

Zhou, Ya-Xing; Zhou, Ke-Ming; Liu, Qian; Wang, Hui; Wang, Wen; Shi, Yi; Ma, Yu-Qing

2018-04-09

Glucose transporter type 1 (Glut1) plays a crucial role in cancer-specific metabolism. We explored the expression of Glut1 and c-myc, the relationship between them and the effect of Glut1, c-myc on prognosis in esophageal squamous cell carcinoma. Immunohistochemistry was used to examine the expression of Glut1 and c-myc. χ 2 test analyzes the relationship between c-myc, Glut1 and pathological parameters. Spearman correlation analyzes the relationship between c-myc and Glut1. Survival analysis was used to investigate the effect of Glut1 and c-myc on prognosis. Glut1 positivity was associated with tumor size (p < 0.01), depth of invasion (p = 0.021), tumor, node, metastasis (TNM) stage (IA+IB,II+IIB,IIIA+IIIB,IVA+IVB ; p = 0.004), lymph node metastasis (p = 0.002) and nerve invasion (p = 0.050). C-myc positivity was associated with tumor location (p = 0.015), depth of invasion (p = 0.022) and lymph node metastasis (p = 0.035). There was a positive correlation between c-myc and Glut1 (r = 0.321). Patients with Glut1 c-myc co-expression had poorer prognosis. Inhibiting Glut1 c-myc co-expression may improve the prognosis of esophageal squamous cell carcinoma.

Comparative evaluation of molar distalization therapy using pendulum and distal screw appliances

PubMed Central

Cafagna, Alessandra; Fontana, Mattia; Cozzani, Mauro

2015-01-01

Objective To compare dentoalveolar and skeletal changes produced by the pendulum appliance (PA) and the distal screw appliance (DS) in Class II patients. Methods Forty-three patients (19 men, 24 women) with Class II malocclusion were retrospectively selected for the study. Twenty-four patients (mean age, 12.2 ± 1.5 years) were treated with the PA, and 19 patients (mean age, 11.3 ± 1.9 years) were treated with the DS. The mean distalization time was 7 months for the PA group and 9 months for the DS group. Lateral cephalograms were obtained at T1, before treatment, and at T2, the end of distalization. A Mann-Whitney U test was used for statistical comparisons of the two groups between T1 and T2. Results PA and DS were equally effective in distalizing maxillary molars (4.7 mm and 4.2 mm, respectively) between T1 and T2; however, the maxillary first molars showed less distal tipping in the DS group than in the PA group (3.2° vs. 9.0°, respectively). Moreover, significant premolar anchorage loss (2.7 mm) and incisor proclination (5.0°) were noted in the PA group, whereas premolar distal movement (1.9 mm) and no significant changes at the incisor (0.1°) were observed in the DS group. No significant sagittal or vertical skeletal changes were detected between the two groups during the distalization phase. Conclusions PA and DS seem to be equally effective in distalizing maxillary molars; however, greater distal molar tipping and premolar anchorage loss can be expected using PA. PMID:26258063

Paroxysmal eye–head movements in Glut1 deficiency syndrome

PubMed Central

Engelstad, Kristin; Kane, Steven A.; Goldberg, Michael E.; De Vivo, Darryl C.

2017-01-01

Objective: To describe a characteristic paroxysmal eye–head movement disorder that occurs in infants with Glut1 deficiency syndrome (Glut1 DS). Methods: We retrospectively reviewed the medical charts of 101 patients with Glut1 DS to obtain clinical data about episodic abnormal eye movements and analyzed video recordings of 18 eye movement episodes from 10 patients. Results: A documented history of paroxysmal abnormal eye movements was found in 32/101 patients (32%), and a detailed description was available in 18 patients, presented here. Episodes started before age 6 months in 15/18 patients (83%), and preceded the onset of seizures in 10/16 patients (63%) who experienced both types of episodes. Eye movement episodes resolved, with or without treatment, by 6 years of age in 7/8 patients with documented long-term course. Episodes were brief (usually <5 minutes). Video analysis revealed that the eye movements were rapid, multidirectional, and often accompanied by a head movement in the same direction. Eye movements were separated by clear intervals of fixation, usually ranging from 200 to 800 ms. The movements were consistent with eye–head gaze saccades. These movements can be distinguished from opsoclonus by the presence of a clear intermovement fixation interval and the association of a same-direction head movement. Conclusions: Paroxysmal eye–head movements, for which we suggest the term aberrant gaze saccades, are an early symptom of Glut1 DS in infancy. Recognition of the episodes will facilitate prompt diagnosis of this treatable neurodevelopmental disorder. PMID:28341645

GLUT-1 GLUCOSE TRANSPORTERS IN THE BLOOD-BRAIN BARRIER: DIFFERENTIAL PHOSPHORYLATION

PubMed Central

Devraj, Kavi; Klinger, Marianne E.; Myers, Roland L.; Mokashi, Ashwini; Hawkins, Richard A.; Simpson, Ian A.

2013-01-01

Glucose is the primary metabolic fuel for the mammalian brain and a continuous supply is required to maintain normal CNS function. The transport of glucose across the blood-brain barrier (BBB) into the brain is mediated by the facilitative glucose transporter GLUT-1. Prior studies (Simpson et al. 2001) had revealed that the conformations of the GLUT-1 transporter were different in luminal (blood facing) and abluminal (brain facing) membranes of bovine cerebral endothelial cells, based on differential antibody recognition. In this study we have extended these observations and using a combination of 2D-PAGE/Western blotting and immunogold electron microscopy we determined that these different conformations are exhibited in vivo and arise from differential phosphorylation of GLUT-1 and not from alternative splicing or altered O- or N-linked glycosylation. PMID:21910135

Novel role for proteinase-activated receptor 2 (PAR2) in membrane trafficking of proteinase-activated receptor 4 (PAR4).

PubMed

Cunningham, Margaret R; McIntosh, Kathryn A; Pediani, John D; Robben, Joris; Cooke, Alexandra E; Nilsson, Mary; Gould, Gwyn W; Mundell, Stuart; Milligan, Graeme; Plevin, Robin

2012-05-11

Proteinase-activated receptors 4 (PAR(4)) is a class A G protein-coupled receptor (GPCR) recognized through the ability of serine proteases such as thrombin and trypsin to mediate receptor activation. Due to the irreversible nature of activation, a fresh supply of receptor is required to be mobilized to the cell surface for responsiveness to agonist to be sustained. Unlike other PAR subtypes, the mechanisms regulating receptor trafficking of PAR(4) remain unknown. Here, we report novel features of the intracellular trafficking of PAR(4) to the plasma membrane. PAR(4) was poorly expressed at the plasma membrane and largely retained in the endoplasmic reticulum (ER) in a complex with the COPI protein subunit β-COP1. Analysis of the PAR(4) protein sequence identified an arginine-based (RXR) ER retention sequence located within intracellular loop-2 (R(183)AR → A(183)AA), mutation of which allowed efficient membrane delivery of PAR(4). Interestingly, co-expression with PAR(2) facilitated plasma membrane delivery of PAR(4), an effect produced through disruption of β-COP1 binding and facilitation of interaction with the chaperone protein 14-3-3ζ. Intermolecular FRET studies confirmed heterodimerization between PAR(2) and PAR(4). PAR(2) also enhanced glycosylation of PAR(4) and activation of PAR(4) signaling. Our results identify a novel regulatory role for PAR(2) in the anterograde traffic of PAR(4). PAR(2) was shown to both facilitate and abrogate protein interactions with PAR(4), impacting upon receptor localization and cell signal transduction. This work is likely to impact markedly upon the understanding of the receptor pharmacology of PAR(4) in normal physiology and disease.

The two glycolytic markers GLUT1 and MCT1 correlate with tumor grade and survival in clear-cell renal cell carcinoma

PubMed Central

Dadone, Bérengère; Durand, Matthieu; Borchiellini, Delphine; Amiel, Jean; Pouyssegur, Jacques; Rioux-Leclercq, Nathalie; Pages, Gilles; Burel-Vandenbos, Fanny; Mazure, Nathalie M.

2018-01-01

Background Clear-cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer. Although ccRCC is characterized by common recurrent genetic abnormalities, including inactivation of the von Hippel-Lindau (vhl) tumor suppressor gene resulting in stabilization of hypoxia-inducible factors (HIFs), the tumor aggressiveness and outcome of ccRCC is variable. New biomarkers are thus required to improve ccRCC diagnosis, prognosis and therapeutic options. This work aims to investigate the expression of HIF and proteins involved in metabolism and pH regulation. Their correlation to histoprognostic parameters and survival was analyzed. Methods ccRCC of 45 patients were analyzed. HIF-1α, HIF-2α, HAF, GLUT1, MCT1, MCT4, CAIX and CAXII expression was assessed by immunohistochemistry in a semi-quantitative and qualitative manner. The GLUT1, MCT1, MCT4, CAIX and CAXII mRNA levels were analyzed in an independent cohort of 43 patients. Results A significant correlation was observed between increased GLUT1, MCT1, CAXII protein expression and a high Fuhrman grade in ccRCC patients. Moreover, while HIF-1α, HIF-2α and HAF expression was heterogenous within tumors, we observed and confirmed that HIF-2α co-localized with HAF. We confirmed, in an independent cohort, that GLUT1, MCT1 and CAXII mRNA levels correlated with the Fuhrman grade. Moreover, we demonstrated that the high mRNA level of both MCT1 and GLUT1 correlated with poor prognosis. Conclusions This study demonstrates for the first time a link between the aggressiveness of high- Fuhrman grade ccRCC and metabolic reprogramming. It also confirms the role of HIF-2α and HAF in tumor invasiveness. Finally, these results demonstrate that MCT1 and GLUT1 are strong prognostic markers and promising therapeutic targets. PMID:29481555

The two glycolytic markers GLUT1 and MCT1 correlate with tumor grade and survival in clear-cell renal cell carcinoma.

PubMed

Ambrosetti, Damien; Dufies, Maeva; Dadone, Bérengère; Durand, Matthieu; Borchiellini, Delphine; Amiel, Jean; Pouyssegur, Jacques; Rioux-Leclercq, Nathalie; Pages, Gilles; Burel-Vandenbos, Fanny; Mazure, Nathalie M

2018-01-01

Clear-cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer. Although ccRCC is characterized by common recurrent genetic abnormalities, including inactivation of the von Hippel-Lindau (vhl) tumor suppressor gene resulting in stabilization of hypoxia-inducible factors (HIFs), the tumor aggressiveness and outcome of ccRCC is variable. New biomarkers are thus required to improve ccRCC diagnosis, prognosis and therapeutic options. This work aims to investigate the expression of HIF and proteins involved in metabolism and pH regulation. Their correlation to histoprognostic parameters and survival was analyzed. ccRCC of 45 patients were analyzed. HIF-1α, HIF-2α, HAF, GLUT1, MCT1, MCT4, CAIX and CAXII expression was assessed by immunohistochemistry in a semi-quantitative and qualitative manner. The GLUT1, MCT1, MCT4, CAIX and CAXII mRNA levels were analyzed in an independent cohort of 43 patients. A significant correlation was observed between increased GLUT1, MCT1, CAXII protein expression and a high Fuhrman grade in ccRCC patients. Moreover, while HIF-1α, HIF-2α and HAF expression was heterogenous within tumors, we observed and confirmed that HIF-2α co-localized with HAF. We confirmed, in an independent cohort, that GLUT1, MCT1 and CAXII mRNA levels correlated with the Fuhrman grade. Moreover, we demonstrated that the high mRNA level of both MCT1 and GLUT1 correlated with poor prognosis. This study demonstrates for the first time a link between the aggressiveness of high- Fuhrman grade ccRCC and metabolic reprogramming. It also confirms the role of HIF-2α and HAF in tumor invasiveness. Finally, these results demonstrate that MCT1 and GLUT1 are strong prognostic markers and promising therapeutic targets.

Trafficking of cholesterol from cell bodies to distal axons in Niemann Pick C1-deficient neurons.

PubMed

Karten, Barbara; Vance, Dennis E; Campenot, Robert B; Vance, Jean E

2003-02-07

Niemann Pick type C (NPC) disease is a progressive neurodegenerative disorder. In cells lacking functional NPC1 protein, endocytosed cholesterol accumulates in late endosomes/lysosomes. We utilized primary neuronal cultures in which cell bodies and distal axons reside in separate compartments to investigate the requirement of NPC1 protein for transport of cholesterol from cell bodies to distal axons. We have recently observed that in NPC1-deficient neurons compared with wild-type neurons, cholesterol accumulates in cell bodies but is reduced in distal axons (Karten, B., Vance, D. E., Campenot, R. B., and Vance, J. E. (2002) J. Neurochem. 83, 1154-1163). We now show that NPC1 protein is expressed in both cell bodies and distal axons. In NPC1-deficient neurons, cholesterol delivered to cell bodies from low density lipoproteins (LDLs), high density lipoproteins, or cyclodextrin complexes was transported into axons in normal amounts, whereas transport of endogenously synthesized cholesterol was impaired. Inhibition of cholesterol synthesis with pravastatin in wild-type and NPC1-deficient neurons reduced axonal growth. However, LDLs restored a normal rate of growth to wild-type but not NPC1-deficient neurons treated with pravastatin. Thus, although LDL cholesterol is transported into axons of NPC1-deficient neurons, this source of cholesterol does not sustain normal axonal growth. Over the lifespan of NPC1-deficient neurons, these defects in cholesterol transport might be responsible for the observed altered distribution of cholesterol between cell bodies and axons and, consequently, might contribute to the neurological dysfunction in NPC disease.

Domestic Sex Trafficking of Minors: Medical Student and Physician Awareness.

PubMed

Titchen, Kanani E; Loo, Dyani; Berdan, Elizabeth; Rysavy, Mary Becker; Ng, Jessica J; Sharif, Iman

2017-02-01

Our aim was to assess: (1) medical trainee and practicing physician awareness about domestic sex trafficking of minors; and (2) whether respondents believe that awareness of trafficking is important to their practice. We designed an anonymous electronic survey, and a convenience sample was collected from June through October 2013. Voluntary participants were 1648 medical students, residents, and practicing physicians throughout the United States. Data were analyzed for correlations between study cohort characteristics and: (1) agreement with the statement: "knowing about sex trafficking in my state is important to my profession"; (2) knowledge of national statistics regarding the sex trafficking of minors; and (3) knowledge of appropriate responses to encountering a trafficked victim. More practicing physicians than residents or medical students: (1) agreed or strongly agreed that knowledge about human trafficking was important to their practice (80.6%, 71.1%, and 69.2%, respectively; P = .0008); (2) correctly estimated the number of US trafficked youth according to the US Department of State data (16.1%, 11.7%, and 7.9%, respectively; P = .0011); and (3) were more likely to report an appropriate response to a trafficked victim (40.4%, 20.4%, and 8.9%, respectively; P = .0001). Although most medical trainees and physicians place importance on knowing about human trafficking, they lack knowledge about the scope of the problem, and most would not know where to turn if they encountered a trafficking victim. There exists a need for standardized trafficking education for physicians, residents, and medical students. Copyright © 2015 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

A Novel Pulse-Chase Paradigm to Visualize the Trafficking of Transport Vesicles in Neurons

NASA Astrophysics Data System (ADS)

Al-Bassam, Sarmad

In neurons transmembrane proteins are targeted to dendrites in vesicles that traffic solely within the somatodendritic compartment. How these vesicles are retained within the somatodendritic domain is unknown. Here we adapt a novel pulse chase system that allows synchronous release of exogenous transmembrane proteins from the endoplasmic reticulum using FKBP12 and Rapamycin. We demonstrate proof-of-concept and establish protein trafficking controls in incremental steps. We demonstrate the utility of this approach in studying protein trafficking and establish parameters for analysis of time-lapse images. We implement this novel pulse-chase strategy to track the movements of post-Golgi transport vesicles. Surprisingly, we found that post-Golgi vesicles carrying dendritic proteins were equally likely to enter axons and dendrites. However, once such vesicles entered the axon they very rarely moved beyond the axon initial segment, but instead either halted or reversed direction in an actin and Myosin Va-dependent manner. In contrast, vesicles carrying either an axonal or a nonspecifically localized protein only rarely halted or reversed and instead generally proceeded to the distal axon. Thus, our results are consistent with the axon initial segment behaving as a vesicle filter that mediates the differential trafficking of transport vesicles.

Modulation of epithelial sodium channel trafficking and function by sodium 4-phenylbutyrate in human nasal epithelial cells.

PubMed

Prulière-Escabasse, Virginie; Planès, Carole; Escudier, Estelle; Fanen, Pascale; Coste, André; Clerici, Christine

2007-11-23

Sodium 4-phenylbutyrate (4-PBA) has been shown to correct the cellular trafficking of several mutant or nonmutant plasma membrane proteins such as cystic fibrosis transmembrane conductance regulator through the expression of 70-kDa heat shock proteins. The objective of the study was to determine whether 4-PBA may influence the functional expression of epithelial sodium channels (ENaC) in human nasal epithelial cells (HNEC). Using primary cultures of HNEC, we demonstrate that 4-PBA (5 mm for 6 h) markedly stimulated amiloride-sensitive sodium channel activity and that this was related to an increased abundance of alpha-, beta-, and gamma-ENaC subunits in the apical membrane. The increase in ENaC cell surface expression (i) was due to insertion of newly ENaC subunits as determined by brefeldin A experiments and (ii) was not associated with cell surface retention of ENaC subunits because endocytosis of ENaC subunits was unchanged. In addition, we find that ENaC co-immunoprecipitated with the heat shock protein constitutively expressed Hsc70, that has been reported to modulate ENaC trafficking, and that 4-PBA decreased Hsc70 protein level. Finally, we report that in cystic fibrosis HNEC obtained from two cystic fibrosis patients, 4-PBA increased functional expression of ENaC as demonstrated by the increase in amiloride-sensitive sodium transport and in alpha-, beta-, and gamma-ENaC subunit expression in the apical membrane. Our results suggest that in HNEC, 4-PBA increases the functional expression of ENaC through the insertion of new alpha-, beta-, and gamma-ENaC subunits into the apical membrane and also suggest that 4-PBA could modify ENaC trafficking by reducing Hsc70 protein expression.

Experiences of sex trafficking victims in Mumbai, India.

PubMed

Silverman, J G; Decker, M R; Gupta, J; Maheshwari, A; Patel, V; Willis, B M; Raj, A

2007-06-01

To explore mechanisms and contexts related to sex trafficking victimization among South Asian women and girls rescued from brothels in Mumbai, India. Records of residents at a major non-governmental organization providing rescue, shelter and care of minor girls and of women held against their will in brothels in Mumbai were systematically reviewed (n=160). Descriptive statistics were calculated, and demographic differences in trafficking mechanisms and pre-disposing contexts were explored. The majority of victims (51.9%) were trafficked as minors and by individuals previously known to them (59.7%). Traffickers most commonly lured victims via promises of economic opportunity (55.0%) or kidnapped individuals via use of drugs or force (26.3%). Victims were most often trafficked from public settings (e.g., markets, train stations; 50.9%) and via public transportation (94.9%). Almost half (49.4%) reported some type of family disruption as directly leading to their being trafficked; violence involving husbands or other family members (38.0%) and marital separation or abandonment (32.9%) were the most common forms of disruption reported. Differences in experiences of trafficking were identified based on age, nationality, education, and marital status; no differences were found based on religion. The interaction of poverty and gender-based mistreatment of women and girls in families heightens the risk of sex trafficking; further empirical research is needed on this critically understudied issue. Prevention efforts should work to improve economic opportunities and security for impoverished women and girls, educate communities regarding the tactics and identities of traffickers, as well as promote structural interventions to reduce trafficking.

Expression of GLUT-1 glucose transporter in borderline and malignant epithelial tumors of the ovary.

PubMed

Cantuaria, G; Magalhaes, A; Penalver, M; Angioli, R; Braunschweiger, P; Gomez-Marin, O; Kanhoush, R; Gomez-Fernandez, C; Nadji, M

2000-10-01

Cancer cells have increased rates of glucose metabolism when compared to normal cells. One of the mechanisms proposed for the accelerated glucose use in malignant cells is the overexpression of glucose transporters. In this study we evaluated the expression of the GLUT-1 glucose transporter in borderline and malignant epithelial neoplasms of the ovary. Histologic sections of tumor tissues from 21 borderline and 82 malignant epithelial neoplasms of the ovary were stained for GLUT-1 using polyclonal GLUT-1 antibody (Dako, Carpinteria, CA) and the labeled streptavidin biotin procedure. DAB was used as chromagen and tissues were counterstained with hematoxylin. Normal ovarian surface epithelial cells were either negative or weakly positive. Of the 82 carcinomas, 81 (98.8%) were positive for GLUT-1. The staining intensity was significantly associated with the grade of tumor (P = 0.001). Of the 21 borderline neoplasms, 20 (95.2%) were positive for GLUT-1. Carcinomas had a significantly stronger stain than borderline tumors (P = 0.0001). The intensity of the stain was also stronger in serous carcinomas compared to other subtypes (P = 0. 0001). Positive cells demonstrated a cytoplasmic membrane staining that was more intense in tumor cells farther away from blood supply. Overexpression of the GLUT-1 transporter is associated with the histology and grade of the tumors. Our findings show a progressive increase in the expression of the GLUT-1 transporter from the borderline tumor to the high-grade carcinomas. These data suggest that the expression of this transporter may be closely related to the malignant transformation of epithelial ovarian tumors. Copyright 2000 Academic Press.

Molecular cloning and functional characterization of a glucose transporter (CsGLUT) in Clonorchis sinensis.

PubMed

Ahn, Seong Kyu; Cho, Pyo Yun; Na, Byoung-Kuk; Hong, Sung-Jong; Nam, Ho-Woo; Sohn, Woon-Mok; Ardelli, Bernadette F; Park, Yun-Kyu; Kim, Tong-Soo; Cha, Seok Ho

2016-01-01

A complementary DNA (cDNA) encoding a glucose transporter of Clonorchis sinensis (CsGLUT) was isolated from the adult C. sinensis cDNA library. The open reading frame of CsGLUT cDNA consists of 1653 base pairs that encode a 550-amino acid residue protein. Hydropathy analysis suggested that CsGLUT possess 12 putative membrane-spanning domains. The Northern blot analysis result using poly(A)(+)RNA showed a strong band at ~2.1 kb for CsGLUT. When expressed in Xenopus oocytes, CsGLUT mediated the transport of radiolabeled deoxy-D-glucose in a time-dependent but sodium-independent manner. Concentration-dependency results showed saturable kinetics and followed the Michaelis-Menten equation. Nonlinear regression analyses yielded a Km value of 588.5 ± 53.0 μM and a Vmax value of 1500.0 ± 67.5 pmol/oocyte/30 min for [1,2-(3)H]2-deoxy-D-glucose. No trans-uptakes of bile acid (taurocholic acid), amino acids (tryptophan and arginine), or p-aminohippuric acid were observed. CsGLUT-mediated transport of deoxyglucose was significantly and concentration-dependently inhibited by radio-unlabeled deoxyglucose and D-glucose. 3-O-Methylglucose at 10 and 100 μM inhibited deoxyglucose uptake by ~50 % without concentration dependence. No inhibitory effects by galactose, mannose, and fructose were observed. This work may contribute to the molecular biological study of carbohydrate metabolism and new drug development of C. sinensis.

Akt Substrate of 160 kD Regulates Na+,K+-ATPase Trafficking in Response to Energy Depletion and Renal Ischemia

PubMed Central

Alves, Daiane S.; Thulin, Gunilla; Loffing, Johannes; Kashgarian, Michael

2015-01-01

Renal ischemia and reperfusion injury causes loss of renal epithelial cell polarity and perturbations in tubular solute and fluid transport. Na+,K+-ATPase, which is normally found at the basolateral plasma membrane of renal epithelial cells, is internalized and accumulates in intracellular compartments after renal ischemic injury. We previously reported that the subcellular distribution of Na+,K+-ATPase is modulated by direct binding to Akt substrate of 160 kD (AS160), a Rab GTPase-activating protein that regulates the trafficking of glucose transporter 4 in response to insulin and muscle contraction. Here, we investigated the effect of AS160 on Na+,K+-ATPase trafficking in response to energy depletion. We found that AS160 is required for the intracellular accumulation of Na+,K+-ATPase that occurs in response to energy depletion in cultured epithelial cells. Energy depletion led to dephosphorylation of AS160 at S588, which was required for the energy depletion–induced accumulation of Na,K-ATPase in intracellular compartments. In AS160-knockout mice, the effects of renal ischemia on the distribution of Na+,K+-ATPase were substantially reduced in the epithelial cells of distal segments of the renal tubules. These data demonstrate that AS160 has a direct role in linking the trafficking of Na+,K+-ATPase to the energy state of renal epithelial cells. PMID:25788531

Insulin modulates hippocampally-mediated spatial working memory via glucose transporter-4.

PubMed

Pearson-Leary, J; Jahagirdar, V; Sage, J; McNay, E C

2018-02-15

The insulin-regulated glucose transporter, GluT4, is a key molecule in peripheral insulin signaling. Although GluT4 is abundantly expressed in neurons of specific brain regions such as the hippocampus, the functional role of neuronal GluT4 is unclear. Here, we used pharmacological inhibition of GluT4-mediated glucose uptake to determine whether GluT4 mediates insulin-mediated glucose uptake in the hippocampus. Consistent with previous reports, we found that glucose utilization increased in the dorsal hippocampus of male rats during spontaneous alternation (SA), a hippocampally-mediated spatial working memory task. We previously showed that insulin signaling within the hippocampus is required for processing this task, and that administration of exogenous insulin enhances performance. At baseline levels of hippocampal insulin, inhibition of GluT4-mediated glucose uptake did not affect SA performance. However, inhibition of an upstream regulator of GluT4, Akt, did impair SA performance. Conversely, when a memory-enhancing dose of insulin was delivered to the hippocampus prior to SA-testing, inhibition of GluT4-mediated glucose transport prevented cognitive enhancement. These data suggest that baseline hippocampal cognitive processing does not require functional hippocampal GluT4, but that cognitive enhancement by supra-baseline insulin does. Consistent with these findings, we found that in neuronal cell culture, insulin increases glucose utilization in a GluT4-dependent manner. Collectively, these data demonstrate a key role for GluT4 in transducing the procognitive effects of elevated hippocampal insulin. Copyright © 2017 Elsevier B.V. All rights reserved.

Fabrication and Evaluation of a Noncompliant Molar Distalizing Appliance: Bonded Molar Distalizer

PubMed Central

Sodagar, A.; Ahmad Akhoundi, M. S.; Rafighii, A.; Arab, S.

2011-01-01

Objective Attempts to treat class II malocclusions without extraction in non-compliant patients have led to utilization of intraoral molar distalizing appliances. The purpose of this study was to investigate dental and skeletal effects of Bonded Molar Distalizer (BMD) which is a simple molar distalizing appliance. Materials and Methods Sixteen patients (12 girls, four boys) with bilateral half-cusp class II molar relationship, erupted permanent second molars and normal or vertical growth pattern were selected for bilateral distalization of maxillary molars via BMD. The screws were activated every other day, alternately. Lateral cephalograms and study models were obtained before treatment and after 11 weeks activation of the appliance. Results Significant amounts of molar distalization, molar distal tipping and anchorage loss were observed. The mean maxillary first molar distal movement was 1.22±0.936 mm with a distal tipping of 2.97±3.74 degrees in 11 weeks. The rate of distal movement was 0.48 mm per month. Reciprocal mesial movement of the first premolars was 2.26±1.12 mm with a mesial tipping of 4.25±3.12 degrees. Maxillary incisors moved 3.55±1.46 mm and tipped 9.87±5.03 degrees mesially. Lower anterior face height (LAFH) decreased 1.28±1.36 mm. Conclusion BMD is appropriate for distalizing maxillary molars, especially in patients with critical LAFH, although significant amounts of anchorage loss occur using this appliance. PMID:22457837

The relationship between the carrying angle and the distal extent of the 2nd and 4th fingertips.

PubMed

Sönmez, M; Tattemur, Y; Karacan, K; Erdal, M

2012-08-01

The angle towards the lateral side between the arm and forearm when the forearm is in full extension and supination is defined as the carrying angle. It is well known that the 2nd finger is longer in women whereas the 4th finger is longer in men, due to in-utero hormonal effects. In the present study, the relationship between the carrying angle and the distal extent of the 2nd and 4th fingertips is studied. The findings reveal that the carrying angle was greater both in left and right sides in women than in men. In addition, while the distal extent of the 2nd fingertips was longer in women, the 4th fingertip was longer in men. There was a moderately positive correlation between the carrying angle and the distal fingertip lengths. Therefore, it could be suggested that the morphometric factors play role on the distal extent of the fingertips other than the hormonal effects.

Biochemical phenotyping unravels novel metabolic abnormalities and potential biomarkers associated with treatment of GLUT1 deficiency with ketogenic diet.

PubMed

Cappuccio, Gerarda; Pinelli, Michele; Alagia, Marianna; Donti, Taraka; Day-Salvatore, Debra-Lynn; Veggiotti, Pierangelo; De Giorgis, Valentina; Lunghi, Simona; Vari, Maria Stella; Striano, Pasquale; Brunetti-Pierri, Nicola; Kennedy, Adam D; Elsea, Sarah H

2017-01-01

Global metabolomic profiling offers novel opportunities for the discovery of biomarkers and for the elucidation of pathogenic mechanisms that might lead to the development of novel therapies. GLUT1 deficiency syndrome (GLUT1-DS) is an inborn error of metabolism due to reduced function of glucose transporter type 1. Clinical presentation of GLUT1-DS is heterogeneous and the disorder mirrors patients with epilepsy, movement disorders, or any paroxysmal events or unexplained neurological manifestation triggered by exercise or fasting. The diagnostic biochemical hallmark of the disease is a reduced cerebrospinal fluid (CSF)/blood glucose ratio and the only available treatment is ketogenic diet. This study aimed at advancing our understanding of the biochemical perturbations in GLUT1-DS pathogenesis through biochemical phenotyping and the treatment of GLUT1-DS with a ketogenic diet. Metabolomic analysis of three CSF samples from GLUT1-DS patients not on ketogenic diet was feasible inasmuch as CSF sampling was used for diagnosis before to start with ketogenic diet. The analysis of plasma and urine samples obtained from GLUT1-DS patients treated with a ketogenic diet showed alterations in lipid and amino acid profiles. While subtle, these were consistent findings across the patients with GLUT1-DS on ketogenic diet, suggesting impacts on mitochondrial physiology. Moreover, low levels of free carnitine were present suggesting its consumption in GLUT1-DS on ketogenic diet. 3-hydroxybutyrate, 3-hydroxybutyrylcarnitine, 3-methyladipate, and N-acetylglycine were identified as potential biomarkers of GLUT1-DS on ketogenic diet. This is the first study to identify CSF, plasma, and urine metabolites associated with GLUT1-DS, as well as biochemical changes impacted by a ketogenic diet. Potential biomarkers and metabolic insights deserve further investigation.

Biochemical phenotyping unravels novel metabolic abnormalities and potential biomarkers associated with treatment of GLUT1 deficiency with ketogenic diet

PubMed Central

Cappuccio, Gerarda; Pinelli, Michele; Alagia, Marianna; Donti, Taraka; Day-Salvatore, Debra-Lynn; Veggiotti, Pierangelo; De Giorgis, Valentina; Lunghi, Simona; Vari, Maria Stella; Striano, Pasquale; Brunetti-Pierri, Nicola; Kennedy, Adam D.

2017-01-01

Global metabolomic profiling offers novel opportunities for the discovery of biomarkers and for the elucidation of pathogenic mechanisms that might lead to the development of novel therapies. GLUT1 deficiency syndrome (GLUT1-DS) is an inborn error of metabolism due to reduced function of glucose transporter type 1. Clinical presentation of GLUT1-DS is heterogeneous and the disorder mirrors patients with epilepsy, movement disorders, or any paroxysmal events or unexplained neurological manifestation triggered by exercise or fasting. The diagnostic biochemical hallmark of the disease is a reduced cerebrospinal fluid (CSF)/blood glucose ratio and the only available treatment is ketogenic diet. This study aimed at advancing our understanding of the biochemical perturbations in GLUT1-DS pathogenesis through biochemical phenotyping and the treatment of GLUT1-DS with a ketogenic diet. Metabolomic analysis of three CSF samples from GLUT1-DS patients not on ketogenic diet was feasible inasmuch as CSF sampling was used for diagnosis before to start with ketogenic diet. The analysis of plasma and urine samples obtained from GLUT1-DS patients treated with a ketogenic diet showed alterations in lipid and amino acid profiles. While subtle, these were consistent findings across the patients with GLUT1-DS on ketogenic diet, suggesting impacts on mitochondrial physiology. Moreover, low levels of free carnitine were present suggesting its consumption in GLUT1-DS on ketogenic diet. 3-hydroxybutyrate, 3-hydroxybutyrylcarnitine, 3-methyladipate, and N-acetylglycine were identified as potential biomarkers of GLUT1-DS on ketogenic diet. This is the first study to identify CSF, plasma, and urine metabolites associated with GLUT1-DS, as well as biochemical changes impacted by a ketogenic diet. Potential biomarkers and metabolic insights deserve further investigation. PMID:28961260

Sporadic and familial glut1ds Italian patients: A wide clinical variability.

PubMed

De Giorgis, Valentina; Teutonico, Federica; Cereda, Cristina; Balottin, Umberto; Bianchi, Marika; Giordano, Lucio; Olivotto, Sara; Ragona, Francesca; Tagliabue, Anna; Zorzi, Giovanna; Nardocci, Nardo; Veggiotti, Pierangelo

2015-01-01

GLUT1 deficiency syndrome is a treatable neurological disorder characterized by developmental delay, movement disorders and epilepsy. It is caused by mutations in the SLC2A1 gene inherited as an autosomal dominant trait with complete penetrance, even if most detected SCL2A1 mutations are de novo. Our aim is to present a wide series of Italian patients to highlight the differences among subjects with de novo mutations and those with familial transmission. We present clinical and genetic features in a series of 22 GLUT1DS Italian patients. Our patients were classified in two different groups: familial cases including GLUT1DS patients with genetically confirmed affected relatives and sporadic cases with detection of SLC2A1 de novo mutation. We found remarkable differences in the severity of the clinical picture regarding the type of genetic inheritance (sporadic versus familial): sporadic patients were characterized by an earlier epilepsy-onset and higher degree of intellectual disability. No significant differences were found in terms of type of movement disorder, whilst Paroxysmal Exertion-induced Dyskinesia (PED) is confirmed to be the most characteristic movement disorder type in GLUT1DS. In familial cases the clinical manifestation of the disease was particularly variable and heterogeneous, also including asymptomatic patients or those with minimal-symptoms. The finding of a "mild" phenotype in familial GLUT1DS gives rise to several questions: the real incidence of the disease, treatment option with ketogenic diet in adult patients and genetic counseling. Copyright © 2014 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

Getting out of the game: desistance from drug trafficking.

PubMed

Campbell, Howard; Hansen, Tobin

2012-11-01

This ethnographic study was conducted along the U.S.-Mexico border, the centre of the western hemispheric illicit drugs trade. It examines factors that encouraged or discouraged drug traffickers to "get out of the game" (a common slang reference to leaving the drug business). In-depth, life history interviews were conducted of thirty ex-traffickers in the El Paso/Ciudad Juárez area. Participants discussed their experiences exiting drug trafficking and their retrospective, often conflicted, feelings about the trade. Although leaving drug trafficking is a complex and multi-faceted process, the principle factors for study participants were (1) punishment (by authorities or other traffickers), (2) self-image and identity, (3) social ties, (4) life course changes and (5) drug use/abuse. Traffickers often want to quit, but their divided self-identities make it difficult to relinquish the power and exhilaration they derive from the illicit drugs business. Harm reduction policies are needed that address the embeddedness of trafficker identities in dense webs of family, community, street gangs and transnational cartels, and the larger society, as well as the seductive appeal of Hollywood and pro-cartel narco-media. Traffickers need pathways that allow them to exit the illicit drugs business without surrendering their identity. Prison sentences are not enough to encourage traffickers to stop-also needed are culturally sensitive policies that help traffickers get out of the game and stay out. Copyright © 2012 Elsevier B.V. All rights reserved.

Munc13-4 Is a Rab11-binding Protein That Regulates Rab11-positive Vesicle Trafficking and Docking at the Plasma Membrane.

PubMed

Johnson, Jennifer L; He, Jing; Ramadass, Mahalakshmi; Pestonjamasp, Kersi; Kiosses, William B; Zhang, Jinzhong; Catz, Sergio D

2016-02-12

The small GTPase Rab11 and its effectors control trafficking of recycling endosomes, receptor replenishment and the up-regulation of adhesion and adaptor molecules at the plasma membrane. Despite recent advances in the understanding of Rab11-regulated mechanisms, the final steps mediating docking and fusion of Rab11-positive vesicles at the plasma membrane are not fully understood. Munc13-4 is a docking factor proposed to regulate fusion through interactions with SNAREs. In hematopoietic cells, including neutrophils, Munc13-4 regulates exocytosis in a Rab27a-dependent manner, but its possible regulation of other GTPases has not been explored in detail. Here, we show that Munc13-4 binds to Rab11 and regulates the trafficking of Rab11-containing vesicles. Using a novel Time-resolved Fluorescence Resonance Energy Transfer (TR-FRET) assay, we demonstrate that Munc13-4 binds to Rab11a but not to dominant negative Rab11a. Immunoprecipitation analysis confirmed the specificity of the interaction between Munc13-4 and Rab11, and super-resolution microscopy studies support the interaction of endogenous Munc13-4 with Rab11 at the single molecule level in neutrophils. Vesicular dynamic analysis shows the common spatio-temporal distribution of Munc13-4 and Rab11, while expression of a calcium binding-deficient mutant of Munc13-4 significantly affected Rab11 trafficking. Munc13-4-deficient neutrophils showed normal endocytosis, but the trafficking, up-regulation, and retention of Rab11-positive vesicles at the plasma membrane was significantly impaired. This correlated with deficient NADPH oxidase activation at the plasma membrane in response to Rab11 interference. Our data demonstrate that Munc13-4 is a Rab11-binding partner that regulates the final steps of Rab11-positive vesicle docking at the plasma membrane. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Trafficking in persons: a health concern?

PubMed

Zimmerman, Cathy; Kiss, Ligia; Houssain, Mazeda; Watts, Charlotte

2009-01-01

Human trafficking is a phenomenon that has now been documented in most regions in the world. Although trafficking of women and girls for sexual exploitation is the most commonly recognised form of trafficking, it is widely acknowledged that human trafficking also involves men, women and children who are trafficked for various forms of labour exploitation and into other abusive circumstances. Despite the violence and harm inherent in most trafficking situations, there remains extremely little evidence on the individual and public health implications of any form of human trafficking. The Brazilian government has recently launched a national plan to combat human trafficking. However, because the health risks associated with human trafficking have not been well-recognised or documented, there is extremely limited reliable data on the health needs of trafficked persons to inform policy and practices.. Brazilian policy-makers and service providers should be encouraged to learn about the likely range of health impacts of trafficking, and incorporate this into anti-trafficking protection and response strategies. As well as prevention activities, the government, international and local organisations should work together with the public health research community to study the health needs of trafficked persons and explore opportunities to provide safe and appropriate services to victims in need of care.

Flagellin peptide flg22 gains access to long-distance trafficking in Arabidopsis via its receptor, FLS2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jelenska, Joanna; Davern, Sandra M.; Standaert, Robert F.

Diverse pathogen-derived molecules, such as bacterial flagellin and its conserved peptide flg22, are recognized in plants via plasma membrane receptors and induce both local and systemic immune responses. The fate of such ligands was unknown: whether and by what mechanism(s) they enter plant cells and whether they are transported to distal tissues. We used biologically active fluorophore and radiolabeled peptides to establish that flg22 moves to distal organs with the closest vascular connections. Remarkably, entry into the plant cell via endocytosis together with the FLS2 receptor is needed for delivery to vascular tissue and long-distance transport of flg22. This contrastsmore » with known routes of long distance transport of other non-cell-permeant molecules in plants, which require membrane-localized transporters for entry to vascular tissue. Thus, a plasma membrane receptor acts as a transporter to enable access of its ligand to distal trafficking routes.« less

Flagellin peptide flg22 gains access to long-distance trafficking in Arabidopsis via its receptor, FLS2

DOE PAGES

Jelenska, Joanna; Davern, Sandra M.; Standaert, Robert F.; ...

2017-03-01

Diverse pathogen-derived molecules, such as bacterial flagellin and its conserved peptide flg22, are recognized in plants via plasma membrane receptors and induce both local and systemic immune responses. The fate of such ligands was unknown: whether and by what mechanism(s) they enter plant cells and whether they are transported to distal tissues. We used biologically active fluorophore and radiolabeled peptides to establish that flg22 moves to distal organs with the closest vascular connections. Remarkably, entry into the plant cell via endocytosis together with the FLS2 receptor is needed for delivery to vascular tissue and long-distance transport of flg22. This contrastsmore » with known routes of long distance transport of other non-cell-permeant molecules in plants, which require membrane-localized transporters for entry to vascular tissue. Thus, a plasma membrane receptor acts as a transporter to enable access of its ligand to distal trafficking routes.« less

Mass spectrometry for identification of proteins that specifically bind to a distal enhancer of the Oct4 gene

NASA Astrophysics Data System (ADS)

Bakhmet, E. I.; Nazarov, I. B.; Artamonova, T. O.; Khodorkovsky, M. A.; Tomilin, A. N.

2017-11-01

Transcription factor Oct4 is a marker of pluripotent stem cells and has a significant role in their self-renewal. Oct4 gene is controlled by three cis-regulatory elements - proximal promoter, proximal enhancer and distal enhancer. All of these elements are targets for binding of regulatory proteins. Distal enhancer is in our research focus because of its activity in early stages of embryonic development. There are two main sequences called site 2A and site 2B that are presented in distal enhancer. For this moment proteins which bind to a site 2A (CCCCTCCCCCC) remain unknown. Using combination of in vitro method electrophoretic mobility shift assay (EMSA) and mass spectromery we identified several candidates that can regulate Oct4 gene expression through site 2A.

Maternal nutritional manipulation of placental growth and glucose transporter 1 (GLUT-1) abundance in sheep.

PubMed

Dandrea, J; Wilson, V; Gopalakrishnan, G; Heasman, L; Budge, H; Stephenson, T; Symonds, M E

2001-11-01

Glucose transporter 1 (GLUT-1) is the predominant glucose transporter in the placenta but the extent to which its abundance is nutritionally regulated is unknown. This study investigated the effects of restricted maternal nutrition between day 28 and day 80 of gestation followed by re-feeding to either meet or to exceed the total energy requirements on placental size and GLUT-1 abundance at mid-gestation (that is, day 80) and near to term (that is, days 140-145 of gestation; term = 147 days). Singleton bearing ewes either consumed 8.7-9.9 MJ day(-1) of metabolizable energy (that is, well fed) or 3.2-3.8 MJ day(-1) of metabolizable energy (that is, nutrient restricted) from day 28 to day 80 of gestation, after which stage they consumed either 6.5-7.5 MJ day(-1) (that is, adequately fed) or 8.0-10.9 MJ day(-1) (that is, well fed) of metabolizable energy until near to term. In all ewes, at both sampling dates, the abundance of GLUT-1 was higher in the maternal component than in the fetal component of the placenta. Immunohistochemistry confirmed that GLUT-1 was located in the maternal uterine syncytium. At day 80 of gestation, placental mass was lower (P < 0.05) in the nutrient restricted group, but there was no difference in the abundance of GLUT-1 between the nutrient restricted group and the well fed group. At near term, placental mass was greater (P < 0.05) in ewes that were nutrient restricted during early to mid-gestation and then adequately fed up to term compared with ewes that were well fed during early to mid-gestation. This increase was associated with a higher (P < 0.05) abundance of total placental GLUT-1 and a larger fetus. There was no effect of previous nutrient restriction on placental mass, fetal weight or GLUT-1 abundance at term, when ewes were well fed in the second half of gestation. In conclusion, maternal nutrient restriction between early to mid-gestation alters placental growth but has no effect on placental GLUT-1 abundance. Increasing

Phosphatidylinositol-4,5-bisphosphate is required for KCNQ1/KCNE1 channel function but not anterograde trafficking

PubMed Central

Royal, Alice A.

2017-01-01

The slow delayed-rectifier potassium current (IKs) is crucial for human cardiac action potential repolarization. The formation of IKs requires co-assembly of the KCNQ1 α-subunit and KCNE1 β-subunit, and mutations in either of these subunits can lead to hereditary long QT syndrome types 1 and 5, respectively. It is widely recognised that the KCNQ1/KCNE1 (Q1/E1) channel requires phosphatidylinositol-4,5-bisphosphate (PIP2) binding for function. We previously identified a cluster of basic residues in the proximal C-terminus of KCNQ1 that form a PIP2/phosphoinositide binding site. Upon charge neutralisation of these residues we found that the channel became more retained in the endoplasmic reticulum, which raised the possibility that channel–phosphoinositide interactions could play a role in channel trafficking. To explore this further we used a chemically induced dimerization (CID) system to selectively deplete PIP2 and/or phosphatidylinositol-4-phosphate (PI(4)P) at the plasma membrane (PM) or Golgi, and we subsequently monitored the effects on both channel trafficking and function. The depletion of PIP2 and/or PI(4)P at either the PM or Golgi did not alter channel cell-surface expression levels. However, channel function was extremely sensitive to the depletion of PIP2 at the PM, which is in contrast to the response of other cardiac potassium channels tested (Kir2.1 and Kv11.1). Surprisingly, when using the CID system IKs was dramatically reduced even before dimerization was induced, highlighting limitations regarding the utility of this system when studying processes highly sensitive to PIP2 depletion. In conclusion, we identify that the Q1/E1 channel does not require PIP2 or PI(4)P for anterograde trafficking, but is heavily reliant on PIP2 for channel function once at the PM. PMID:29020060

Phosphatidylinositol-4,5-bisphosphate is required for KCNQ1/KCNE1 channel function but not anterograde trafficking.

PubMed

Royal, Alice A; Tinker, Andrew; Harmer, Stephen C

2017-01-01

The slow delayed-rectifier potassium current (IKs) is crucial for human cardiac action potential repolarization. The formation of IKs requires co-assembly of the KCNQ1 α-subunit and KCNE1 β-subunit, and mutations in either of these subunits can lead to hereditary long QT syndrome types 1 and 5, respectively. It is widely recognised that the KCNQ1/KCNE1 (Q1/E1) channel requires phosphatidylinositol-4,5-bisphosphate (PIP2) binding for function. We previously identified a cluster of basic residues in the proximal C-terminus of KCNQ1 that form a PIP2/phosphoinositide binding site. Upon charge neutralisation of these residues we found that the channel became more retained in the endoplasmic reticulum, which raised the possibility that channel-phosphoinositide interactions could play a role in channel trafficking. To explore this further we used a chemically induced dimerization (CID) system to selectively deplete PIP2 and/or phosphatidylinositol-4-phosphate (PI(4)P) at the plasma membrane (PM) or Golgi, and we subsequently monitored the effects on both channel trafficking and function. The depletion of PIP2 and/or PI(4)P at either the PM or Golgi did not alter channel cell-surface expression levels. However, channel function was extremely sensitive to the depletion of PIP2 at the PM, which is in contrast to the response of other cardiac potassium channels tested (Kir2.1 and Kv11.1). Surprisingly, when using the CID system IKs was dramatically reduced even before dimerization was induced, highlighting limitations regarding the utility of this system when studying processes highly sensitive to PIP2 depletion. In conclusion, we identify that the Q1/E1 channel does not require PIP2 or PI(4)P for anterograde trafficking, but is heavily reliant on PIP2 for channel function once at the PM.

The glucose transporter 1 -GLUT1- from the white shrimp Litopenaeus vannamei is up-regulated during hypoxia.