Expression Of Glucose Transporter Isoforms Research Articles

Upregulated expression of glucose transporter isoform 1 in invasive and metastatic extramammary Paget's disease.

Glucose transporter isoform 1 (GLUT1), which is upregulated in a variety of malignant tumors, facilitates cellular glucose uptake to boost rapid tumor growth and progression. In several types of cancer, inhibition of GLUT1 suppresses tumor proliferation and metastasis, indicating that GLUT1 is a potential target of anticancer therapy. The present study performed immunohistochemistry to analyze GLUT1 expression levels in 51 patients with extramammary Paget's disease (EMPD), including 23 with only intraepidermal lesions and 28 with dermal-invasive lesions. Of the 28 patients with dermal invasion, nine had available samples of lymph node metastasis. GLUT1 staining scores were significantly higher in dermal-invasive (P<0.0001) and metastatic lesions (P=0.0008) compared with in intraepidermal lesions. GLUT1 is upregulated during the transition from preinvasive to invasive or metastatic tumor in EMPD. Moreover, GLUT1 staining scores were statistically higher in intraepidermal tumor cells of dermal-invasive EMPD compared with tumor cells of only in situ EMPD (P=0.0338). GLUT1 is upregulated even during the preinvasive phase in patients with invasive EMPD, suggesting that GLUT1 immunostaining can predict the risk of dermal invasion. The present study provides novel evidence to pursue in vitro and in vivo studies to confirm that upregulated expression of GLUT1 enhances tumor aggressiveness in EMPD.

Lauric acid epigenetically regulates lncRNA HOTAIR by remodeling chromatin H3K4 tri-methylation and modulates glucose transport in SH-SY5Y human neuroblastoma cells: Lipid switch in macrophage activation

Lauric acid (LA) induces apoptosis in cancer and promotes the proliferation of normal cells by maintaining cellular redox homeostasis. Earlier, we postulated LA-mediated regulation of the NF-κB pathway by an epigenetic mechanism. However, the molecular mechanism and possible epigenetic events remained enigmatic. Herein, taking the lead from the alteration in cellular energetics in cancer cells upon LA exposure, we investigated whether LA exposure can epigenetically influence lncRNA HOTAIR, regulate glucose metabolism, and shift the cellular energetic state. Our results demonstrate LA induced modulation of lncRNA HOTAIR in a dose and time dependent manner. In addition, HOTAIR induces the expression of glucose transporter isoform 1 (GLUT1) and is regulated via NF-κB activation. Silencing HOTAIR by siRNA-mediated knockdown suppressed GLUT1 expression suggesting the key role of HOTAIR in LA-mediated metabolic reprogramming. Further, from our ChIP experiments, we observed that silencing HOTAIR subdues the recruitment of NF-κB on the GLUT1 (SLC2A1) promoter region. In addition, by performing western blot and immunocytochemistry studies, we found a dose dependent increase in Histone 3 Lysine 4 tri-methylation (H3K4me3) in the chromatin landscape. Taken together, our study demonstrates the epigenetic regulation in LA-treated SH-SY5Y cancer cells orchestrated by remodeling chromatin H3K4me3 and modulation of lncRNA HOTAIR that apparently governs the GLUT1 expression and regulates glucose uptake by exerting transcriptional control on NF-κB activation. Our work provides insights into the epigenetic regulation and metabolic reprogramming of LA through modulation of lncRNA HOTAIR, remodeling chromatin H3K4 tri-methylation, and shifting the energy metabolism in SH-SY5Y neuroblastoma cells.

Effect of oocyte vitrification on glucose transport in mouse metaphase II oocytes.

Oocyte vitrification has significantly improved the survival rate and become the mainstream method for cryopreserving oocytes. Previous studies have demonstrated that the ultrastructure, mitochondrial function, DNA methylation, and histone modification exhibit an irreversible effect after oocyte vitrification. However, little is known about the effects of oocyte vitrification on glucose transport and metabolism. This study aims to determine whether mouse oocyte vitrification causes abnormal glucose metabolism and identify a strategy to correct abnormal glucose metabolism. Furthermore, this study further investigates the effects of oocyte vitrification on glucose uptake, and glucose metabolism, and energy levels. The results indicated that vitrification significantly reduced the glucose transport activity, NADPH, glutathione, and ATP levels, and increased reactive oxygen species levels in oocytes (P < 0.01). Vitrification also reduced the expression of glucose transporter isoform 1 (GLUT1) (P < 0.01). Adding a GLUT1 inhibitor reduced the glucose uptake capacity of oocytes. Furthermore, the inclusion of vitamin C into thawing and culture solutions restored abnormal glucose transportation and metabolism and improved the survival, two-cell embryo, and blastocyst rates of the vitrified groups via parthenogenesis (P < 0.05). Overall, this method may improve the quality and efficiency of oocyte vitrification.

LncRNA HOTAIR regulates glucose transporter Glut1 expression and glucose uptake in macrophages during inflammation

Inflammation plays central roles in the immune response. Inflammatory response normally requires higher energy and therefore is associated with glucose metabolism. Our recent study demonstrates that lncRNA HOTAIR plays key roles in NF-kB activation, cytokine expression, and inflammation. Here, we investigated if HOTAIR plays any role in the regulation of glucose metabolism in immune cells during inflammation. Our results demonstrate that LPS-induced inflammation induces the expression of glucose transporter isoform 1 (Glut1) which controls the glucose uptake in macrophages. LPS-induced Glut1 expression is regulated via NF-kB activation. Importantly, siRNA-mediated knockdown of HOTAIR suppressed the LPS-induced expression of Glut1 suggesting key roles of HOTAIR in LPS-induced Glut1 expression in macrophage. HOTAIR induces NF-kB activation, which in turn increases Glut1 expression in response to LPS. We also found that HOTAIR regulates glucose uptake in macrophages during LPS-induced inflammation and its knockdown decreases LPS-induced increased glucose uptake. HOTAIR also regulates other upstream regulators of glucose metabolism such as PTEN and HIF1α, suggesting its multimodal functions in glucose metabolism. Overall, our study demonstrated that lncRNA HOTAIR plays key roles in LPS-induced Glut1 expression and glucose uptake by activating NF-kB and hence HOTAIR regulates metabolic programming in immune cells potentially to meet the energy needs during the immune response.

Long non‐coding RNAs regulate NF‐κB activation, inflammation, and glucose metabolism

Inflammation plays a central role in immune response and the inflammatory response is closely linked with metabolism. Our recent study demonstrates that lncRNA HOTAIR plays key roles in NF‐kB activation, cytokine expression, and inflammation. Here, we investigated if HOTAIR plays any role in regulation of glucose metabolism in immune cells during inflammation. Our study demonstrate that lncRNA HOTAIR regulates the expression of glucose transporter isoform 1 (Glut1) which controls the glucose uptake into macrophages. SiRNA‐mediated knockdown of HOTAIR suppressed the LPS‐induced expression of Glut1 and glucose update in macrophages suggesting key roles of HOTAIR in LPS‐induced Glut1 expression and glucose metabolism. HOTAIR induces NF‐kB activation which in turn increases Glut1 expression and glucose metabolism in response to LPS. Beyond HOTAIR, we also discovered several novel lncRNAs (termed as LinfRNA: Long‐noncoding inflammation associated RNA) which are closely associated with inflammation and metabolism. Overall, our study demonstrated that HOTAIR and LinfRNAs play key roles in NF‐kB activation and inflammation and regulate metabolic programming in immune cells potentially to meet the energy needs at the priming of immune response to pathogenic infection or other stressors.Support or Funding InformationNational Institute of Health grant # 1R15 ES019129‐01

18F-Fluorodeoxyglucose uptake on positron emission tomography/computed tomography is associated with metastasis and epithelial-mesenchymal transition in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fifth leading cause of cancer mortality worldwide. Several studies have investigated the relationship between 18F-fluorodeoxyglucose (18F-FDG) uptake on positron emission tomography and the prognosis of patients with HCC, although the relationship between 18F-FDG uptake and expression of EMT-related proteins in these patients remains unclear. We retrospectively enrolled 116 patients with HCC treated by curative surgical resection and who underwent 18F-FDG positron emission tomography/computed tomography (PET/CT) for preoperative staging. The relationship between the tumor-to-liver standardized uptake value ratio (TLR) and the presence of metastasis was determined. By using HCC cell lines with different 18F-FDG uptake, we assessed the effect of 18F-FDG uptake on in vitro cell proliferation and migration on the inhibition of glucose uptake. Ten (29.4%) of 34 patients with high TLRs had extrahepatic metastases, whereas six (7.3%) of 82 patients with low TLRs had extrahepatic metastases (p = 0.002). Hepatocellular carcinomas with high TLRs showed higher expression of glucose transporter isoform 1 and EMT markers than did HCCs with low TLRs. After treatment with a glucose uptake inhibitor, HCC cells with high 18F-FDG uptake showed decreased cell proliferation and migration and a reversal in the expression of EMT markers. High 18F-FDG uptake on PET/CT is associated with frequent extrahepatic metastasis and EMT in patients with HCC. Inhibition of glucose uptake reduced cell proliferation, reversed EMT-related protein expression, and decreased cellular migration. Glycolytic regulation could be a new therapeutic target to reduce tumor growth and metastatic potential in HCCs with a high glycolytic phenotype.

Identification and Optimization of Combinatorial Glucose Metabolism Inhibitors in Hepatocellular Carcinomas

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. The expression of glucose transporter isoform 1, a key factor in transporting glucose into cancer cells, is overexpressed in several human cancers, including HCC. In addition, this has been shown to correlate with a higher proliferation index and more advanced stages in HCC, suggesting that inhibition of glucose metabolism is a promising therapeutic strategy. Our study used high-content screening (HCS) for compounds that target glucose metabolism and effect cell death in HCC cells. Specifically, we showed that a fluorescent 2-deoxyglucose analog, 2-[N-(7-nitrobenz-2- oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose, and CellTrace Calcein Red-Orange AM can be used reliably as readouts for glucose uptake and proliferative index, respectively, to identify drug candidates that simultaneously reduce glucose uptake and induce cell death in HCC cells. Thus, fluorescent glucose uptake bioprobes can be implemented in HCS assays to identify previously unknown regulators of glucose metabolism in HCC. In addition, our study also employs the use of feedback system control (FSC.II), a platform that optimizes the combinations of drugs identified through HCS. The coordinated use of HCS and FSC.II can improve the development of drug combinations and uncover previously unidentified signaling pathways that govern HCC as well as other cancers.

Expression of glucose transporter isoforms and the insulin receptor during hamster preimplantation embryo development

During preimplantation development, embryos of many species are known to express up to five isoforms of the facilitative glucose transporter proteins (GLUT). Development of hamster blastocysts is inhibited by glucose. We therefore investigated GLUT isoform and insulin receptor (IR) expression in hamster preimplantation embryos cultured in glucose-free medium from the 8-cell stage onwards. We show that GLUT1, 3 and 8 mRNA are constitutively expressed from the 8-cell to the blastocyst stage. The IR is expressed from the morula stage onwards. Messenger RNA of the insulin-responsive GLUT4 was not detected at any stage. GLUT1 and 3 were localised by immunocytochemistry. GLUT1 was expressed in both embryoblast and trophoblast, in the latter, mainly in basal and lateral membranes directed towards the blastocoel and embryoblast. GLUT3 was exclusively localised in the apical membrane of trophoblast cells. We show that hamster preimplantation embryos express several GLUT isoforms thus closely resembling embryos of other mammalian species. Despite endogenous IR expression, the insulin-sensitive isoform GLUT4 was not expressed, indicating that the insulin-mediated glucose uptake known from classical insulin target cells may not be relevant for hamster blastocysts.

Type‐2 diabetes down‐regulates glucose transporter proteins and genes of the human blood leukocytes

Objective. White blood cells are essential in mediating immune and inflammatory responses. A prominent feature of these cells during activation of the immune function is increased glucose utilization, and this is dependent on the functioning of specific glucose transporter (GLUT) isoforms. The few data available on leukocyte glucose transporter expression are limited to type‐2 diabetes mellitus, and nothing is known about its regulation. Material and methods. Peripheral blood was drawn from 35 healthy controls and 35 diabetic subjects. Expression of GLUT1, GLUT3 and GLUT4 was determined in the leukocytes of healthy individuals and diabetic patients by flow cytometry, Western blot and semi‐quantitative RT‐PCR. Results. GLUT 3 was decreased in granulocytes, lymphocytes and monocytes from diabetic patients. In monocytes, GLUT3 and GLUT4 were reduced in type‐2 diabetic patients. In leukocytes of diabetic patients, GLUT1 and GLUT4, protein and mRNA were unchanged, but GLUT3 protein and mRNA levels were down‐regulated compared to those of healthy controls. Conclusion. Elevated glucose concentration affects leukocyte GLUT expression. Decreased expression of GLUT isoforms in leukocytes may be responsible for diminished activation of diabetic leukocytes. These situations possibly contribute to a predisposition to infection and to a decreased immune response in diabetes.

Glucose transporter expression on the plasma membrane of resting and activated white blood cells

In white blood cells (WBC), the increase in glucose utilization is a prominent feature during immune response and this depends on the function of specific glucose transporter (GLUT) isoforms. The objective was to examine the effects of activation by Phorbol 12-myristate 13-acetate (PMA) or lipopolysaccharide (LPS) and insulin on the expression of GLUT isoforms in all subpopulations of WBC. Blood was withdrawn from 27 healthy subjects. The expression of GLUT1, GLUT3 and GLUT4 on the plasma membrane of resting and activated monocytes, T- and B-lymphocytes and polymorphonuclear cells (PMNs) was determined in the absence and presence of physiological concentrations of insulin, by flow cytometry. GLUT1 did not respond to insulin in either resting or PMA/LPS activated state. In the resting state, monocytes and B-lymphocytes increased the abundance of GLUT3 and GLUT4 on their plasma membrane in response to insulin; in contrast, T-lymphocytes and PMNs were unresponsive to insulin. In the activated state, monocytes, B- and T- lymphocytes increased the expression of all three GLUT isoforms on their plasma membrane, whilst PMNs increased only GLUT1 and GLUT3; in all WBC, insulin augmented the expression of GLUT4 and GLUT3 isoforms in addition to the stimulation provided by the PMA or LPS treatment alone. Activation of WBC leads to increased expression of GLUT1, GLUT3 and GLUT4 isoforms on their plasma membrane; this process was further augmented by insulin. During infection, these mechanisms may help to redistribute glucose as a potential source of energy away from peripheral tissues and direct it towards cells that mediate the immune response and are therefore crucial to survival.

Differential expression of glucose transporter isoforms during embryonic stem cell differentiation

In mouse blastocysts six facilitative glucose transporter isoforms (GLUT)1–4, 8 and 9 are expressed. We have used the mouse embryonic stem (ES) cell line D3 and spontaneously differentiating embryoid bodies (EB) to investigate GLUT expression and the influence of glucose during differentiation of early embryonic cells. Both ES cells and EBs (2d–20d) expressed GLUT1, 3, and 8, whereas the isoforms 2 and 4 were detectable exclusively in EBs. Differentiation-associated expression of GLUT was analyzed by double staining with stage-specific embryonic antigen (SSEA-1), cytokeratins (CK18, 19), nestin, and desmin. Similar to trophoblast cells in mouse blastocysts the outer cell layer of endoderm-like cells showed a high GLUT3 expression in early EBs. In 20-day-old EBs no GLUT3 protein and only minor GLUT3 mRNA amounts could be detected. A minimal glucose concentration of 5 mM applied during 2 and 8 days of EB culture resulted in up-regulated GLUT4, Oct-4 and SSEA-1 levels and a delay in EB differentiation. We conclude that GLUT expression depends on cellular differentiation and that the expression is modulated by glucose concentration. The developmental and glucose-dependent regulation of GLUT strongly suggests a functional role of glucose and glucose transporters in ES cell differentiation and embryonic development.

Differential expression of glucose transporter isoforms during ES cell differentiation in vitro

The facilitative glucose transporters (GLUT) are a family of structurally related membrane glycoproteins. In mouse blastocysts five different GLUT isoforms are expressed. Whereas the GLUT expression as a cell specific marker is well characterised in adult tissues, the expression during cell differentiation processes is still not clear. We studied mRNA levels and protein abundance of five GLUT isoforms (GLUT1–4, 8) in mouse embryonic stem cell line D3 (ESC) and during spontaneous, neuronal and myogenic differentiation of embryoid bodies (EBs). Both ESC and EBs expressed GLUT1, 3 and 8, whereas GLUT 2 and 4 mRNA were solely detectable in EBs of 15 (GLUT2) or 2 (GLUT4) days. A low glucose concentration of 5mM during EB differentiation regulated GLUT RNA expression and delayed EB growth and differentiation. Using specific cell markers, expression of GLUT3 and 4 was dependent on the differentiating cell type. GLUT3 was localised in the cell membranes of undifferentiated (SSEA-1+) and differentiated (SSEA-1-) cells. In 4 to 15 days EBs the outer cell layer (=SSEA-1-; CK18+ and CK19+) of endoderm-like cells showed a high GLUT3 labelling, similar to trophoblast cells in mouse blastocysts, whereas GLUT3 mRNA was decreased and no GLUT3 labelling was detected at 20d. GLUT4 is expressed in most of the differentiated (SSEA-1-), but not in undifferentiated (SSEA-1+) cells. GLUT4 positiv cells were located in the nucleus of desmin-negative cells, and in cytoplasm and plasma membranes of desmin+/GLUT4+ cells. In differentiated neuronal or myogenic EBs, Nestin and Desmin are co-expressed with GLUT3 and 4, whereas spontaneously differentiating EBs did not express nestin or desmin, indicating that the cell-type specific GLUT3 and 4 expression in spontaneously differentiating EB is not related to a neuronal or myogenic cell type. Our data suggest that during EB differentiation the cell-type specific GLUT expression is similar to the expression pattern in the early embryo.

Glucose transporter isoform 4 is expressed in the syncytiotrophoblast of first trimester human placenta

Placental glucose transport mechanisms in early pregnancy are poorly understood. The aims of this study were to investigate the expression of glucose transporter (GLUT) isoforms 1, 3 and 4 in first trimester villous tissue, to assess the effects of insulin on glucose uptake and compare them with term. The expression of GLUT isoforms was investigated using immunohistochemistry, Western blot and reverse transcription (RT)-PCR in trophoblast tissue from terminations at 6-13 weeks gestation and term. The effects of insulin (300 ng/ml, 1 h) on glucose uptake were studied in villous fragments. In the first trimester, GLUT1 and GLUT3 were present in the microvillous membrane and the cytotrophoblast, and GLUT4 in perinuclear membranes in the cytosol of the syncytiotrophoblast (ST). GLUT4 protein (48 kDa) and mRNA were identified in trophoblast homogenates. Whereas GLUT1 was expressed abundantly in term placenta, the expression of GLUT3 and 4 was markedly lower at term compared with first trimester. Insulin increased glucose uptake by 182% (n=6, P<0.05) in first trimester fragments, but not in term fragments. The insulin-regulatable GLUT4 is expressed in the cytosol of first trimester ST compatible with a role for GLUT4 in placental glucose transport in early pregnancy. The placental expression pattern of GLUT isoforms in early pregnancy is distinct from that later in pregnancy.

Expression of glucose transporter isoform GLUT-2 and glucokinase genes in human brain.

The glucose transporter isoform-2 (GLUT-2) and glucokinase are considered to be components of a glucose sensor system controlling several key processes, and hence may modulate feeding behaviour. We have found GLUT-2 and glucokinase mRNAs in several brain regions, including the ventromedial and arcuate nuclei of the hypothalamus. GLUT-2, glucokinase and glucokinase regulatory protein mRNAs and proteins were present in these areas as determined by biochemical approaches. In addition, glucose-phosphorylating activity with a high apparent Km for glucose that displayed no product inhibition by glucose-6-phosphate was observed. Increased glycaemia after meals may be recognized by specific hypothalamic neurones due to the high Km of GLUT-2 and glucokinase. This enzyme is considered to be the true glucose sensor because it catalyses the rate-limiting step of glucose catabolism its activity being regulated by interaction with glucokinase regulatory protein, that functions as a metabolic sensor.

Effect of murine GM-CSF on the expression of GLUT isoforms during mouse preimplantation embryo development

Objective: Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been known to promote glucose uptake in murine preimplantation embryo. However, the role of the facilitated glucose transporter (GLUT) isoforms on GM-CSF-stimulated glucose uptake during murine preimplantation development has not been examined. The aim of this study was to investigate the role of GLUT isoforms in GM-CSF stimulated mouse preimplantation embryos in vitro. Design: We examined the effect of GM-CSF on the mouse embryo development and determined the expression of the GLUT isoforms in the mouse blastocysts using semiquantitative RT-PCR. Materials/Methods: Mouse 2-cell embryos were collected from the oviducts of 6-week-old ICR mice at 48 hours after hCG injection. Embryos were cultured in P-1 medium supplemented with mouse GM-CSF (0, 1, 5 and 10 ng/ml) for 3 days. Total RNA was isolated from 50 blastocysts and was reverse transcribed into cDNA and amplified by PCR using specific primers for beta-actin, GLUT 1, 2, 3, and 8 target genes between the GM-CSF supplemented groups and control group. Results: The percentage of blastocyst formation correlated with the GM-CSF concentrations (65.5% for control and 68.6%, 73.0%, 76.1% for 1, 5 and 10 ng/ml, respectively). The mean cell number in a blastocyst was significantly higher in the GM-CSF supplemented groups (95.1 ± 20.8, 91.6 ± 12.4, and 92.0 ± 12.4 for 1, 5, and 10 ng/ml, respectively) compared to the control group (67.9. ± 17.1). GLUT 1, 3, and 8 were detected from mouse blastocysts in both the GM-CSF supplemented groups and the control group. Unlike GLUT 1, 3, and 8, GLUT 2 was not expressed in any groups. And there was no significant difference in the expression of GLUT 1, 3, and 8 between in the GM-CSF supplemented groups and the control group. Conclusions: The results of this study suggest that GLUT isoforms may not be responsible for GM-CSF stimulated glucose uptake in mouse preimplantaion embryo. Thus, the further investigation is necessary to identify the mechanism of GM-CSF-stimulated glucose uptake during mouse preimplantation development.

The Molecular Mechanism of the Insulin-mimetic/sensitizing Activity of the Antidiabetic Sulfonylurea Drug Amaryl

The hypoglycemic sulfonylurea drugs cause reduction of blood glucose predominantly via stimulation of insulin release from pancreatic beta cells. In addition, during long-term treatment, an insulin-independent blood glucose-decreasing mechanism is assumed to operate. This may include insulin-sensitizing and insulin-mimetic activity in muscle and adipose tissue. This review summarizes our current knowledge about the putative modes of action of the sulfonylurea compound, Amaryl, in pancreatic beta cells and, in particular, peripheral target cells that form the molecular basis for its characteristic pharmacological and clinical profile. The analysis was performed in comparison with the conventional and the "golden standard" sulfonylurea, glibenclamide. I conclude: (I) The blood glucose decrease provoked by Amaryl can be explained by a combination of stimulation of insulin release from the pancreas and direct enhancement, as well as potentiation of the insulin response of glucose utilization in peripheral tissues only. (II) The underlying molecular mechanisms seemed to rely on beta cells on a sulfonylurea receptor protein, SURX, associated with the ATP-sensitive potassium channel (K(ATP)) and different from SUR1 for glibenclamide, and in muscle and adipose cells on: (a) the increased production of diacylglycerol and activation of protein kinase C; (b) the enhanced expression of glucose transporter isoforms; and (c) the insulin receptor-independent activation of the insulin receptor substrate/phosphatidylinositol-3-kinase pathway. (III) The latter mechanism involved a nonreceptor tyrosine kinase and a number of components, such as caveolin and glycosylphosphatidylinositol structures, which are assembled in caveolae/detergent-insoluble glycolipid-enriched rafts of the target cell plasma membrane. Since hyperinsulinism and permanent K(ATP) closure are supposed to negatively affect the pathogenesis and therapy of non-insulin-dependent diabetes mellitus, the demonstrated higher insulin-independent blood glucose-lowering activity of Amaryl may be therapeutically relevant.

Alteration in immunoexpression of glucose transporter 2 in liver of tumour-bearing rats.

To elucidate interactions between the glucose transport system and hepatic glucose production in the tumour-bearing state, glycogen storage, expression of glucose transporter isoform 2 (Glut 2) and activities of glucose-6-phosphatase (G-6-Pase) and hexokinase were histochemically examined in hepatocytes of tumour-bearing rats. Five male F344 rats, subcutaneously inoculated with methylcholanthrene (MCA)-induced sarcoma cells were compared with five pair-fed animals and four ad libitum fed controls. Glycogen storage was markedly decreased in liver cells of tumour-bearing rats compared to in those of control animals. Glut 2 immunoreactivity was uniformly seen in the cellular membrane of hepatocytes from control animals. In rats bearing sarcoma, the staining intensity was significantly decreased, suggesting that Glut 2 with its bi-directional transport capacity was down-regulated in the tumour-bearing state. Positive staining for hexokinase activity was located in the perivenous area in livers from control animals and was more diffusely located and more intense in livers from tumour-bearing animals. G-6-Pase activity, limited to the peripheral area in livers from controls, extended to the intermediate area and had stronger reactivity in livers from tumour-bearing animals. In the tumour-bearing cachectic condition, glucose may be partially consumed by a futile cycle, hepatic metabolic zonation was disturbed, and the release of glucose from the liver may not be mediated by a facilitative glucose transporter-2.

Expression of glucose transporter isoforms in human oral cancers

Expression of glucose transporter isoforms in human oral cancers

Modulation of Expression of Glucose Transporters GLUT3 and GLUT1 by Potassium and N-Methyl-d-aspartate in Cultured Cerebellar Granule Neurons

Depolarization is known to stimulate neuronal oxidative metabolism. As glucose is the primary fuel for oxidative metabolism in the brain, the entry of glucose into neural cells is a potential control point for any regulatory events in brain metabolism. Therefore, the effects of depolarizing stimuli, high K+ and N-methyl-d-aspartate (NMDA), were examined on the functional expression of glucose transporter isoforms GLUT1 and GLUT3 in primary cultured cerebellar granule neurons. Higher levels of glucose transport activity were observed in neurons cultured in 25 mMKCl (K25) compared to those in 5 and 15 mM KCl (K5 and K15). The elevated glucose transport activity correlated with increased levels of GLUT3 protein and, to a lesser extent, GLUT1. Both GLUT3 and GLUT 1 were regulated at the level of mRNA expression. Addition of NMDA to K5 and K15 cultures increased both glucose uptake and GLUT3 protein levels, with smaller changes in GLUT1. NMDA effects were not additive with K25 effects. All these changes were observed only with chronic exposure of neurons to high K+ or NMDA; no acute effects on glucose uptake or transporter expression were found. Thus, chronic depolarization of primary cerebellar granule neurons acts as a stimulus for the expression of the neuronal GLUT3 glucose transporter isoform.

Expression of glucose transporter isoforms (GLUT1, GLUT2) and activities of hexokinase, pyruvate kinase, and malic enzyme in preneoplastic and neoplastic rat renal basophilic cell lesions.

Sequential changes in the expression of two glucose transporter isoforms (GLUT1, GLUT2), and in the activities of hexokinase, pyruvate kinase and malic enzyme during the development of rat renal basophilic cell tumors were studied using histochemical techniques. Early basophilic cell tubules are similar to proximal convoluted tubules (PCT) in their overall histochemical pattern, particularly in the expression of glucose transporters, suggesting that basophilic cell tubules and tumors derived from them arise from PCT. In comparison with PCT, basophilic cell tubules show slightly increased activities of all the enzymes studied. In basophilic cell tumors, markedly elevated hexokinase and pyruvate kinase activities are accompanied by a considerable reduction in the expression of GLUT2. GLUT1 expression is not found in basophilic cell tubules or PCT. Small basophilic cell tumors also do not express GLUT1, but GLUT1 is regularly expressed in several cell layers surrounding necrotic areas within large basophilic cell tumors. Our results indicate that increased glycolytic activity and reduced GLUT2 expression take place during the development of renal basophilic cell tumors.