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The impact of glycemic variability on brain glucose transport kinetics among individuals with type 1 diabetes mellitus (T1DM) remains unclear. Fourteen individuals with T1DM (age 35 ± 4 years; BMI 26.0 ± 1.4 kg/m2; HbA1c 7.6 ± 0.3) and nine healthy control participants (age 32 ± 4; BMI 23.1 ± 0.8; HbA1c 5.0 ± 0.1) wore a continuous glucose monitor (Dexcom) to measure hypoglycemia, hyperglycemia, and glycemic variability for 5 days followed by 1H MRS scanning in the occipital lobe to measure the change in intracerebral glucose levels during a 2-h glucose clamp (target glucose concentration 220 mg/dL). Hyperglycemic clamps were also performed in a rat model of T1DM to assess regional differences in brain glucose transport and metabolism. Despite a similar change in plasma glucose levels during the hyperglycemic clamp, individuals with T1DM had significantly smaller increments in intracerebral glucose levels (P = 0.0002). Moreover, among individuals with T1DM, the change in brain glucose correlated positively with the lability index (r = 0.67, P = 0.006). Consistent with findings in humans, streptozotocin-treated rats had lower brain glucose levels in the cortex, hippocampus, and striatum compared with control rats. These findings that glycemic variability is associated with brain glucose levels highlight the need for future studies to investigate the impact of glycemic variability on brain glucose kinetics. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Two potential glucose transporter genes were identified from E. multilocularis. • Full-length sequences EmGLUT1 and EmGLUT2 were obtained. • Functional expression analysis demonstrated clear glucose uptake by EmGLUT1. • Both EmGLUTs were stably expressed in each E. multilocularis developmental stage. Abstract Alveolar echinococcosis (AE) is a zoonotic parasitosis caused by larvae of the fox tapeworm, Echinococcus multilocularis. E. multilocularis is distributed widely in the Northern hemisphere, causing serious health problems in various animals and humans. E. multilocularis , like other cestodes, lacks a digestive tract and absorbs essential nutrients, including glucose, across the syncytial tegument on its external surface. Therefore, it is hypothesized that E. multilocularis uses glucose transporters on its surface similar to a closely-related species, Taenia solium. Based on this hypothesis, we cloned and characterized glucose transporter homologues from E. multilocularis. As a result, we obtained full-length sequences of 2 putative glucose transporter genes (EmGLUT1 and EmGLUT2) from E. multilocularis. In silico analysis predicted that these were classified in the solute carrier family 2 group. Functional expression analysis using Xenopus oocytes demonstrated clear uptake of 2-deoxy-D-glucose (2-DG) by EmGLUT1, but not by EmGLUT2 in this experimental system. EmGLUT1 was shown to have relatively high glucose transport activity. Further analyses using the Xenopus oocyte system revealed that 2-DG uptake of EmGLUT1 did not depend on the presence or concentration of Na+ nor H+, respectively. Immunoblot analyses using cultured metacestode, ex vivo protoscolex, and adult worm samples demonstrated that both EmGLUTs were stably expressed during each developmental stage of the parasite. Based on the above-mentioned findings, we conclude that EmGLUT1 is a simple facilitated glucose transporter and possibly plays an important role in glucose uptake by E. multilocularis throughout its life cycle. [ABSTRACT FROM AUTHOR]

Purpose: Demand is increasing for clinical genomic sequencing to provide diagnoses for patients presenting phenotypes indicative of genetic diseases, but for whom routine genetic testing failed to yield a diagnosis. DNA-based testing using high-throughput technologies often identifies variants with insufficient evidence to determine whether they are disease-causal or benign, leading to categorization as variants of uncertain significance (VUS). Methods: We used molecular modeling and simulation to generate specific hypotheses for the molecular effects of variants in the human glucose transporter, GLUT10 (SLC2A10). Similar to many disease-relevant membrane proteins, no experimentally derived 3D structure exists. An atomic model was generated and used to evaluate multiple variants, including pathogenic, benign, and VUS. Results: These analyses yielded detailed mechanistic data, not currently predictable from sequence, including altered protein stability, charge distribution of ligand binding surfaces, and shifts toward or away from transport-competent conformations. Consideration of the two major conformations of GLUT10 was important as variants have conformation-specific effects. We generated detailed molecular hypotheses for the functional impact of variants in GLUT10 and propose means to determine their pathogenicity. Conclusion: The type of workflow we present here is valuable for increasing the throughput and resolution with which VUS effects can be assessed and interpreted. [ABSTRACT FROM AUTHOR]

The present study was undertaken to investigate the hypoglycemic activity and potential mechanisms of action of a flavonoid-rich extract from Sophora davidii (Franch.) Skeels (SD-FRE) through in vitro and in vivo studies. Four main flavonoids of SD-FRE namely apigenin, maackiain, leachianone A and leachianone B were purified and identified. In vitro, SD-FRE significantly promoted the translocation and expression of glucose transporter 4 (GLUT4) in L6 cells, which was significantly inhibited by Compound C (AMPK inhibitor), but not by Wortmannin (PI3K inhibitor) or Gö6983 (PKC inhibitor). These results indicated that SD-FRE enhanced GLUT4 expression and translocation to the plasma membrane via the AMPK pathway and finally resulted in an increase of glucose uptake. In vivo, using a spontaneously type 2 diabetic model, KK-Ay mice received intragastric administration of SD-FRE for 4 weeks. As a consequence, SD-FRE significantly alleviated the hyperglycemia, glucose intolerance, insulin resistance and hyperlipidemia in these mice. Hepatic steatosis, islet hypertrophy and larger adipocyte size were observed in KK-Ay mice. However, these pathological changes were effectively relieved by SD-FRE treatment. SD-FRE promoted GLUT4 expression and activated AMPK phosphorylation in insulin target tissues (muscle, adipose tissue and liver) of KK-Ay mice, thus facilitating glucose utilization to ameliorate insulin resistance. Regulation of ACC phosphorylation and PPARγ were also involved in the antidiabetic effects of SD-FRE. Taken together, these findings indicated that SD-FRE has the potential to alleviate type 2 diabetes. [ABSTRACT FROM AUTHOR]

A growing body of evidence demonstrates that GLUT1-mediated erythrocyte sugar transport is more complex than widely assumed and that contemporary interpretations of emergent GLUT1 structural data are incompatible with the available transport and biochemical data. This study examines the kinetic basis of one such incompatibility-transport allostery-and in doing so suggests how the results of studies examining GLUT1 structure and function may be reconciled. Three types of allostery are observed in GLUT1-mediated, human erythrocyte sugar transport: (1) exofacial cis-allostery in which low concentrations of extracellular inhibitors stimulate sugar uptake while high concentrations inhibit transport; (2) endofacial cis-allostery in which low concentrations of intracellular inhibitors enhance cytochalasin B binding to GLUT1 while high concentrations inhibit binding, and (3) trans-allostery in which low concentrations of ligands acting at one cell surface stimulate ligand binding at or sugar transport from the other surface while high concentrations inhibit these processes. We consider several kinetic models to account for these phenomena. Our results show that an inhibitor can only stimulate then inhibit sugar uptake if (1) the transporter binds two or more molecules of inhibitor; (2) high-affinity binding to the first site stimulates transport, and (3) low-affinity binding to the second site inhibits transport. Reviewing the available structural, transport, and ligand binding data, we propose that exofacial cis-allostery results from cross-talk between multiple, co-existent ligand interaction sites present in the exofacial cavity of each GLUT1 protein, whereas trans-allostery and endofacial cis-allostery require ligand-induced subunit-subunit interactions. [ABSTRACT FROM AUTHOR]

Objective: Caveolin-3 (CAV3) protein is known to be expressed specifically in various myocytes, but its physiological function remains unclear. CAV3, located at the cell membrane, may promote the sensitivity of the Akt signaling pathway, which is closely related to glucose metabolism and to cell growth and proliferation. Methods: The CAV3 gene was stably transfected into C2C12 muscle cells, and the effects were evaluated by biochemical assays, WB and confocal microscopy for the observation of cellular glucose metabolism, growth and proliferation, and the effect of CAV3 on the Akt signaling pathway with no insulin stimulation. Results: After C2C12 cells were transfected with the mouse CAV3 gene, which increased CAV3 expression, the abundance of the CAV3 and GLUT4 proteins on the cell membrane increased, but the total GLUT4 protein content of the cell was unchanged. Glucose uptake was increased, and this did not affect the glycogen synthesis, but the cell surface area and cell proliferation increased. While there were significant increases in p-Akt and p-p70s6K, which is a downstream component of Akt signaling, the level of GSK3β protein, another component of Akt signaling did not change. Conclusions: The muscle, CAV3 protein can activate Akt signaling, increase GLUT4 protein localization in the cell membrane, increase glucose uptake, and promote myocyte growth and proliferation. CAV3 protein has a physiological role in glycometabolism, growth and proliferation, independent of insulin stimulation. [ABSTRACT FROM AUTHOR]

Objectives To evaluate cases diagnosed as “oral hemangiomas” based on the immunohistochemical expression of human glucose transporter protein (GLUT-1) and on histopathological features, and to investigate whether the classification proposed by the ISSVA was used correctly to classify these lesions. Material and methods All cases stored in the archives of an Oral Pathology Service and diagnosed as “oral hemangiomas” were reviewed. Seventy-seven cases were analyzed regarding the expression of GLUT-1. GLUT-1(+) specimens were classified as true infantile hemangioma (IH) and GLUT-1(−) specimens were reclassified based on their histopathological features. The nomenclature of these lesions was evaluated and some cases were reclassified. Results Only 26 (33.8%) of the specimens were indeed IHs. Among the GLUT-1(−) specimens, 20 (26.0%) were reclassified as pyogenic granulomas (PGs) and 31 (40.2%) as vascular malformations. Considering the previously applied nomenclature, only 47.5% of the cases initially diagnosed as “hemangiomas” were IHs. In the group of “capillary hemangiomas”, most cases (56.2%) were PGs. Among the three “cellular hemangiomas”, two were PGs and one was IH. Most (88.8%) “cavernous hemangiomas” were vascular malformations. Conclusion Careful and parameterized review of cases of vascular anomalies is necessary using auxiliary tools such as GLUT-1, since the exclusive use of histopathological findings might be insufficient to differentiate some anomalies. Clinical relevance Accurate clinical examination and the use of biomarkers such as GLUT-1 are essential for the diagnosis. [ABSTRACT FROM AUTHOR]

Some infantile hemangiomas called in literature “minimal or arrested growth hemangiomas” or “abortive hemangiomas” are present at birth and have a proliferative component equaling less than 25% of its total surface area. Often, they are mistaken for vascular malformation. We present five patients (three girls and two boys) with abortive hemangiomas diagnosed between January 2010 and December 2015 localized in acral part of the extremities. They were congenital lesions resembling precursor of hemangiomas but did not show proliferation phase. Immunohistochemical Glut-1 was performed in all of them as a way to confirm the abortive hemangioma diagnosis. The most common appearance was a reticulated erythematous patch with multiple fine telangiectasias on the surface. We remark that one of them presented a segmental patch with two different morphologies and evolutions. The proximal part showed pebbled patches of bright-red hemangioma and presented proliferation and the distal part with a reticulated network-like telangiectasia morphology remained unchanged. We detected lower half of the body preference and dorsal region involvement preference without ventral involvement. The ulceration occurred in three patients with two different degrees of severity. [ABSTRACT FROM AUTHOR]

GLUT1 facilitates the down-gradient translocation of D-glucose across cell membrane in mammals. XylE, an Escherichia coli homolog of GLUT1, utilizes proton gradient as an energy source to drive uphill D-xylose transport. Previous studies of XylE and GLUT1 suggest that the variation between an acidic residue (Asp27 in XylE) and a neutral one (Asn29 in GLUT1) is a key element for their mechanistic divergence. In this work, we combined computational and biochemical approaches to investigate the mechanism of proton coupling by XylE and the functional divergence between GLUT1 and XylE. Using molecular dynamics simulations, we evaluated the free energy profiles of the transition between inward- and outward-facing conformations for the apo proteins. Our results revealed the correlation between the protonation state and conformational preference in XylE, which is supported by the crystal structures. In addition, our simulations suggested a thermodynamic difference between XylE and GLUT1 that cannot be explained by the single residue variation at the protonation site. To understand the molecular basis, we applied Bayesian network models to analyze the alteration in the architecture of the hydrogen bond networks during conformational transition. The models and subsequent experimental validation suggest that multiple residue substitutions are required to produce the thermodynamic and functional distinction between XylE and GLUT1. Despite the lack of simulation studies with substrates, these computational and biochemical characterizations provide unprecedented insight into the mechanistic difference between proton symporters and uniporters. [ABSTRACT FROM AUTHOR]

New Findings What is the topic of this review? This review summarizes the evidence on the localization, electrophysiological properties, agonist specificity and putative physiological role of sodium-glucose transporter 3 (SGLT3)., What advances does it highlight? Published information is reviewed in some detail by comparing human and rodent isoforms, as well as advances in testing hypotheses for the physiological role of SGLT3 as a glucose sensor or incretin release mediator. We provide a critical overview of available published data and discuss a putative functional role for SGLT3 in human and mouse physiology., Sodium-glucose transporter 3 (SGLT3) has attracted interest because of its putative role as a glucose sensor, rather than a sugar transporter, in contrast to its co-family members SGLT1 and SGLT2. Significant progress has been made in characterizing the electrophysiological properties in vitro of the single human SGLT3 isoform and the two mouse isoforms, SGLT3a and SGLT3b. Although early reports indicated SGLT3 expression in the small intestinal myenteric and submucosal neurones, hypothalamic neurones, portal vein and kidney, a lack of reliable antibodies has left unanswered its exact tissue and cellular localization. Several hypotheses for a role of SGLT3 in glucose sensing, gastric emptying, glucagon-like peptide-1 release and post-Roux-en-Y gastric bypass remodelling have been explored, but so far there is only limited and indirect supportive evidence using non-specific agonists/antagonists, with no firm conclusions. There are no published or available data in knockout animals, and translation is difficult because of its different isoforms in human versus rodent, as well as a lack of selective agonists or antagonists, all of which make SGLT3 challenging to study. However, its unique electrophysiological properties, ubiquitous expression at the mRNA level, enrichment in the small intestine and potential, but uncertain, physiological role demand more attention. The purpose of this overview and review of SGLT3 biology is to provide an update, highlight the gaps in our knowledge and try to signpost potential ways forward to define its likely function in vivo. [ABSTRACT FROM AUTHOR]

Background: Altered tumor cell metabolism is an emerging hallmark of cancer; however, the precise role for glucose in tumor initiation is not known. GLUT1 (SLC2A1) is expressed in breast cancer cells and is likely responsible for avid glucose uptake observed in established tumors. We have shown that GLUT1 was necessary for xenograft tumor formation from primary mammary cells transformed with the polyomavirus middle-T antigen but that it was not necessary for growth after tumors had formed in vivo, suggesting a differential requirement for glucose depending on the stage of tumorigenesis.Methods: To determine whether GLUT1 is required early during mammary tumorigenesis, we crossed MMTV-NIC mice, which express activated HER2/NEU/ERBB2 and Cre recombinase, to Slc2a1 Flox/Flox (GLUT1Flox/Flox) mice to generate NIC-GLUT1+/+, NIC-GLUT1Flox/+, and NIC-GLUT1Flox/Flox mice. In addition, we evaluated effects of glucose restriction or GLUT1 inhibition on transformation in MCF10A-ERBB2 breast epithelial cells in three-dimensional culture. Finally, we utilized global gene expression profiling data of primary human breast tumors to determine the relationship between SLC2A1 and stage of tumorigenesis.Results: All of the NIC-GLUT1+/+ mice developed tumors in less than 200 days. In contrast, only 1 NIC-GLUT1Flox/Flox mouse and 1 NIC-GLUT1Flox/+ mouse developed mammary tumors, even after 18 months. Mammary gland development was not disrupted in NIC mice lacking GLUT1; however, epithelial content of mature glands was reduced compared to NIC-GLUT1Flox/+ mice. In MCF10A-ERBB2 cells, glucose restriction or GLUT1 inhibition blocked transformation induced by activated ERBB2 through reduced cell proliferation. In human breast cancers, SLC2A1 was higher in ductal carcinoma in situ compared to the normal breast, but lower in invasive versus in situ lesions, suggesting the requirement for GLUT1 decreases as tumors progress.Conclusions: This study demonstrates a strict requirement for GLUT1 in the early stages of mammary tumorigenesis in vitro and in vivo. While metabolic adaptation has emerged as a hallmark of cancer, our data indicate that early tumor cells rely heavily on glucose and highlight the potential for glucose restriction as a breast cancer preventive strategy. [ABSTRACT FROM AUTHOR]

Orexins are hypothalamic neuropeptides involved in the central regulation of feeding behavior, sleep-wake cycle and other physiological functions. Orexin-A can regulate energy metabolism and increase glucose uptake, suggesting a role in glucose metabolism. In this study, we investigated the effects of orexin-A on GLUT4 mRNA and protein levels and the intracellular signaling mechanisms mediating orexin-A activity in the hepatocytes of grouper. Our results demonstrate that intraperitoneal injection of orexin-A increased the expression of GLUT4 in the liver, and this effect was significantly enhanced by co-injection of glucose. Treatment of primary cultured hepatocytes with either orexin-A or glucose alone had no effect on the expression of GLUT4, while co-treatment with orexin-A and glucose significantly increased the expression of GLUT4. This stimulatory effect was partially blocked by inhibitors to ERK1/2, JNK or p38 MAPK and was further blocked by an orexin receptor antagonist, which indicates that orexin-A could stimulate the expression of GLUT4 in a glucose dependent manner in primary hepatocytes via ERK1/2, JNK and p38 signaling. Our results suggest that orexin-A could play a pivotal role in stimulating glucose utilization in grouper, for a long-term goal, which might be useful in reducing costs in the aquaculture industry. [ABSTRACT FROM AUTHOR]

The gene expression pattern of the glucose transporters (GLUT1, GLUT3, GLUT8, and GLUT12) among pectoralis major and minor, biceps femoris, and sartorius muscles from newly hatched chicks was examined. GLUT1 mRNA level was higher in pectoralis major muscle than in the other muscles. Phosphorylated AKT level was also high in the same muscle, suggesting a relationship between AKT and GLUT1 expression. [ABSTRACT FROM AUTHOR]

It has been reported previously that the expression of glucose transporter member 3 (GLUT3) is increased in malignant glioma cells compared with normal glial cells. However, the regulating mechanism that causes this phenomenon remains unknown. The present study investigated the regulating role of transcription factor specific protein 1 (Sp1) in GLUT3 expression in a human glioma cell line. In the present study, Sp1 was identified to directly bind to the GLUT3 5'-untranslated region in human glioma U251 cells. Small interfering RNA- and the Sp1-inhibitor mithramycin A-mediated Sp1 knockdown experiments revealed that Sp1 depletion decreased glucose uptake and inhibited cell growth and invasion of U251 cells by downregulating GLUT3 expression. Therefore Sp1 is an important positive regulator for the expression of GLUT3 in human glioma cells, and may explain the overexpression of GLUT3 in U251 cells. These results suggest that Sp1 may have a role in glioma treatment. [ABSTRACT FROM AUTHOR]

Congenital anomalies of the kidneys and urinary tract (CAKUT) are genetically highly heterogeneous leaving most cases unclear after mutational analysis of the around 30 causative genes known so far. Assuming that phenotypes frequently showing dominant inheritance, such as CAKUT, can be caused by de novo mutations, de novo analysis of whole-exome sequencing data was done on two patient-parent-trios to identify novel CAKUT genes. In one case, we detected a heterozygous de novo frameshift variant in TBC1D1 encoding a Rab-GTPase-activating protein regulating glucose transporter GLUT4 translocation. Sequence analysis of 100 further CAKUT cases yielded three novel or rare inherited heterozygous TBC1D1 missense variants predicted to be pathogenic. TBC1D1 mutations affected Ser237-phosphorylation or protein stability and thereby act as hypomorphs. Tbc1d1 showed widespread expression in the developing murine urogenital system. A mild CAKUT spectrum phenotype, including anomalies observed in patients carrying TBC1D1 mutations, was found in kidneys of some Tbc1d1 mice. Significantly reduced Glut4 levels were detected in kidneys of Tbc1d1 mice and the dysplastic kidney of a TBC1D1 mutation carrier versus controls. TBC1D1 and SLC2A4 encoding GLUT4 were highly expressed in human fetal kidney. The patient with the truncating TBC1D1 mutation showed evidence for insulin resistance. These data demonstrate heterozygous deactivating TBC1D1 mutations in CAKUT patients with a similar renal and ureteral phenotype, and provide evidence that TBC1D1 mutations may contribute to CAKUT pathogenesis, possibly via a role in glucose homeostasis. [ABSTRACT FROM AUTHOR]

Accumulating evidence shows that activity of the pyruvate kinase M2 (PKM2) isoform is closely related to tumorigenesis. In this study, we investigated the relationship betweenPKM2 expression, tumor invasion, and the prognosis of patients with lung adenocarcinoma. We retrospectively analyzed 65 cases of patients with lung adenocarcinoma who were divided into low and a high expression groups based on PKM2immunohistochemical staining. High PKM2 expression was significantly associated with reduced patient survival. We used small interfering RNA (siRNA) technology to investigate the effect of targeted PKM2-knockout on tumor growth at the cellular level. In vitro, siRNA-mediated PKM2-knockdown significantly inhibited the proliferation, glucose uptake (25%), ATP generation (20%) and fatty acid synthesis of A549 cells, while the mitochondrial respiratory capacity of the cells increased (13%).Western blotting analysis showed that PKM2-knockout significantly inhibited the expression of the glucose transporter GLUT1 and ATP citrate lyase, which is critical for fatty acid synthesis. Further Western blotting analysis showed that PKM2-knockdown inhibited the expression of matrix metalloproteinase 2 (MMP-2) and vascular endothelial growth factor (VEGF), which are important in degradation of the extracellular matrix and angiogenesis, respectively. These observations show that PKM2 activates both glycolysis and lipid synthesis, thereby regulating cell proliferation and invasion. This information is important in elucidating the mechanisms by which PKM2 influences the growth and metastasis of lung adenocarcinoma at the cellular and molecular level, thereby providing the basic data required for the development of PKM2-targeted gene therapy. [ABSTRACT FROM AUTHOR]

The 14-3-3 family of proteins is widely distributed in the CNS where they are major regulators of essential neuronal functions. There are seven known mammalian 14-3-3 isoforms (ζ,,τ,ϵ,η,β, and σ), which generally function as adaptor proteins. Previously, we have demonstrated that 14-3-3ϵ isoform dynamically regulates forward trafficking of GluN2C-containing NMDA receptors (NMDARs) in cerebellar granule neurons, that when expressed on the surface, promotes neuronal survival followingNMDA-induced excitotoxicity. Here,wereport 14-3-3 isoform-specific bindingand functional regulation of GluN2C. In particular, we show that GluN2C C-terminal domain (CTD) binds to all 14-3-3 isoforms except 14-3-3σ, and binding is dependent on GluN2C serine 1096 phosphorylation. Co-expression of 14-3-3 (ζ and ϵ) and GluN1/ GluN2C promotes the forward delivery of receptors to the cell surface. We further identify novel residues serine 145, tyrosine 178, and cysteine 189 onα-helices 6, 7, and 8, respectively, within ζ-isoform as part of the GluN2C binding motif and independent of the canonical peptide binding groove. Mutation of these conserved residues abolishes GluN2C binding and has nofunctional effect on GluN2C trafficking. Reciprocal mutation of alanine 145, histidine 180, and isoleucine 191 on 14-3-3σ isoform promotes GluN2C binding and surface expression. Moreover, inhibiting endogenous 14-3-3 using a high-affinity peptide inhibitor, difopein, greatly diminishes GluN2C surface expression. Together, these findings highlight the isoform-specific structural and functional differences within the 14-3-3 family of proteins, which determine GluN2C binding and its essential role in targeting the receptor to the cell surface tofacilitate glutamatergic neurotransmission. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Stroke is a leading cause of adult morbidity and mortality with very limited treatment options. Evidence from preclinical models of ischemic stroke has demonstrated that the antioxidant N-acetylcysteine (NAC) effectively protects the brain from ischemic injury. Here, we evaluated a new pathway through which NAC exerted its neuroprotection in a transient cerebral ischemia animal model. Our results demonstrated that pretreatment with NAC increased protein levels of hypoxia-inducible factor-1α (HIF-1α), the regulatable subunit of HIF-1, and its target proteins erythropoietin (EPO) and glucose transporter (GLUT)-3, in the ipsilateral hemispheres of rodents subjected to 90min middle cerebral artery occlusion (MCAO) and 24h reperfusion. Interestingly, after NAC pretreatment and stroke, the contralateral hemisphere also demonstrated increased levels of HIF-1α, EPO, and GLUT-3, but to a lesser extent. Suppressing HIF-1 activity with two widely used pharmacological inhibitors, YC-1 and 2ME2, and specific knockout of neuronal HIF-1α abolished NAC’s neuroprotective effects. The results also showed that YC-1 and 2ME2 massively enlarged infarcts, indicating that their toxic effect was larger than just abolishing NAC's neuroprotective effects. Furthermore, we determined the mechanism of NAC-mediated HIF-1α induction. We observed that NAC pretreatment upregulated heat-shock protein 90 (Hsp90) expression and increased the interaction of Hsp90 with HIF-1α in ischemic brains. The enhanced association of Hsp90 with HIF-1α increased HIF-1α stability. Moreover, Hsp90 inhibition attenuated NAC-induced HIF-1α protein accumulation and diminished NAC-induced neuroprotection in the MCAO model. These results strongly indicate that HIF-1 plays an important role in NAC-mediated neuroprotection and provide a new molecular mechanism involved in the antioxidant’s neuroprotection in ischemic stroke. [Copyright &y& Elsevier]

Adipose tissue development and function play a critical role in the regulation of energy balance, lipid metabolism, and the pathophysiology of metabolic syndromes. Although the effect of zinc ascorbate supplementation in diabetes or glycemic control is known in humans, the underlying mechanism is not well described. Here, we investigated the effect of a zinc-chelated vitamin C (ZnC) compound on the adipogenic differentiation of 3T3-L1 preadipocytes. Treatment with ZnC for 8 d significantly promoted adipogenesis, which was characterized by increased glycerol-3-phosphate dehydrogenase activity and intracellular lipid accumulation in 3T3-L1 cells. Meanwhile, ZnC induced a pronounced up-regulation of the expression of glucose transporter type 4 (GLUT4) and the adipocyte-specific gene adipocyte protein 2 (aP2). Analysis of mRNA and protein levels further showed that ZnC increased the sequential expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα), the key transcription factors of adipogenesis. These results indicate that ZnC could promote adipogenesis through PPARγ and C/EBPα, which act synergistically for the expression of aP2 and GLUT4, leading to the generation of insulin-responsive adipocytes and can thereby be useful as a novel therapeutic agent for the management of diabetes and related metabolic disorders. [ABSTRACT FROM AUTHOR]

Abstract: It is well established that ceramide 1-phosphate (C1P) is mitogenic and antiapoptotic, and that it is implicated in the regulation of macrophage migration. These activities require high energy levels to be available in cells. Macrophages obtain most of their energy from glucose. In this work, we demonstrate that C1P enhances glucose uptake in RAW264.7 macrophages. The major glucose transporter involved in this action was found to be GLUT 3, as determined by measuring its translocation from the cytosol to the plasma membrane. C1P-stimulated glucose uptake was blocked by selective inhibitors of phosphatidylinositol 3-kinase (PI3K) or Akt, also known as protein kinase B (PKB), and by specific siRNAs to silence the genes encoding for these kinases. C1P-stimulated glucose uptake was also inhibited by pertussis toxin (PTX) and by the siRNA that inhibited GLUT 3 expression. C1P increased the affinity of the glucose transporter for its substrate, and enhanced glucose metabolism to produce ATP. The latter action was also inhibited by PI3K- and Akt-selective inhibitors, PTX, or by specific siRNAs to inhibit GLUT 3 expression. [Copyright &y& Elsevier]

Abstract: It has been known for 80years that cancer cell growth in an energy-related process supported by an increased glucose metabolism. This phenomenon suggests a need for a corresponding increased uptake of glucose across the plasma membrane through an enhancement in the glucose transporter proteins, SGLT proteins as well as GLUT proteins. The results of many studies have demonstrated that the expression of glucose transporters, especially GLUT1, is increased in a variety of malignancies. GLUT1 overexpression has been found to be associated with tumor progression. It was found that GLUT1 overexpression is associated with poor overall survival in various malignant tumors. [Copyright &y& Elsevier]

The article presents a study carried out for evaluating the correlation between immunohistochemical expression of the protein synuclein-alpha, the membrane protein glucose transporter-1, and survival results in endometrioid endometrial carcinoma. The study employed the technique of tissue microarray and intensity of immunohistochemical reactions were evaluated by the semi-quantitative scoring system.

When exposed to the nonmetabolized glucose derivative alpha methyl glucoside (αMG), both Escherichia coli K-12 (JM109 and MG1655) and E. coli B (BL21) respond by reducing the concentration of the mRNA of the ptsG gene which is responsible for the biosynthesis of the glucose transporter EIICBglu. This occurs through the over-expression of the noncoding small RNA SgrS, which interacts specifically with the mRNA of the ptsG gene and prevents its translation. However, when these bacteria are exposed to a glucose concentration of 40g/L, over-expression of SgrS is observed only in E. coli B (BL21). Unlike E. coli K-12 (JM109 and MG1655), which are affected by high glucose concentration and produce higher levels of acetate, E. coli B (BL21) is not affected. Based on this information, it was assumed that over-expression of SgrS enables E. coli B (BL21) to reduce its acetate excretion by controlling the glucose transport. When SgrS was over-expressed in both E. coli K-12 strains from a multicopy plasmid, it was possible to reduce their acetate excretion levels to those seen in E. coli B. This observation opens a new approach towards controlling bacterial metabolism through the use of noncoding RNA. [ABSTRACT FROM AUTHOR]

Abstract: Renal hypouricemia (RHUC), as an infrequent hereditary disease, is associated with severe complications such as exercise-induced acute renal failure (EIARF). Loss-of-function mutations in urate transporter gene URAT1 (Type 1) and in glucose transporter gene GLUT9 (Type 2) are major causes of this disorder. In this study, URAT1 and GLUT9 were screened in two uncorrelated families from mainland China and a total of five mutations were identified in exons, including two novel heterozygous URAT1 mutations. In four members of the first family, c.151delG (p.A51fsX64) in exon 1 was detected, which resulted in a frameshift and truncated the original 553-residue-protein to 63 amino acid protein. A missense mutation c.C1546A (p.P516T) in exon 9 in GLUT9 was revealed in the second family, which caused a functional protein substitution at codon 516. These two novel mutations were neither identified in the subsequent scanning of 200 ethnically matched healthy control subjects with normal serum UA level nor in a 1000 genome project database. Thus our report identifies two novel loss-of-function mutations (c.151delG in URAT1 and p.P516T in GLUT9) which cause RHUC and renal dysfunction in two independent RHUC pedigrees. [Copyright &y& Elsevier]

Hepatitis C virus (HCV) infection causes not only intrahepatic diseases but also extrahepatic manifestations, including type 2 diabetes. We previously reported that HCV replication suppresses cellular glucose uptake by downregulation of cell surface expression of glucose transporter 2 (GLUT2) (D. Kasai et al., J. Hepatol. 50:883-894, 2009). GLUT2 mRNA levels were decreased in both HCV RNA replicón cells and HCV J6/JFHl-infected cells. To elucidate molecular mechanisms of HCV-induced suppression of GLUT2 gene expression, we analyzed transcriptional regulation of the GLUT2 promoter using a series of GLUT2 promoter-luciferase reporter plasmids. HCV-induced suppression of GLUT2 promoter activity was abrogated when the hepatocyte nuclear factor la (HNF-la)-binding motif was deleted from the GLUT2 promoter. HNF-la mRNA levels were significantly reduced in HCV J6/JFH1-infected cells. Furthermore, HCV infection remarkably decreased HNF-la protein levels. We assessed the effects of proteasome inhibitor or lysosomal protease inhibitors on the HCV-induced reduction of HNF-la protein levels. Treatment of HCV-infected cells with a lysosomal protease inhibitor, but not with a proteasome inhibitor, restored HNF-la protein levels, suggesting that HCV infection promotes lysosomal degradation of HNF-la protein. Overexpression of NS5A protein enhanced lysosomal degradation of HNF-la protein and suppressed GLUT2 promoter activity. Immunoprecipitation analyses revealed that the region from amino acids 1 to 126 of the NS5A domain I physically interacts with HNF-la protein. Taken together, our results suggest that HCV infection suppresses GLUT2 gene expression via downregulation of HNF-la expression at transcriptional and posttranslational levels. HCV-induced downregulation of HNF-la expression may play a crucial role in glucose metabolic disorders caused by HCV. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the effect of a single bout of exercise on GLUT4 gene expression in muscle of patients with type 2 diabetes (T2D) and control subjects, matched for age and body mass index. Nine patients with T2D and nine control subjects performed 60 min of cycling exercise at ∼55% peak power ( Wmax). Skeletal muscle biopsies were obtained at baseline, immediately post and 3-h post exercise. GLUT4 mRNA expression increased (p < 0.05) to a similar extent immediately post exercise in control (∼60%) and T2D (∼66%) subjects, and remained elevated (p < 0.05) 3-h post exercise with no differences between groups. Similarly, p-AMP-activated protein kinase, p38 mitogen-activated kinase and proliferator-activated receptor gamma co-activator-alpha mRNA expression were increased (p < 0.05) post exercise, and were not different between the groups. In conclusion, a single bout of exercise increased skeletal muscle GLUT4 mRNA expression in patients with T2D to a similar extent as in control subjects. [ABSTRACT FROM AUTHOR]

Abstract: Glucose transporter type 1 deficiency syndrome is characterized by infantile onset seizures, development delay, movement disorders, and acquired microcephaly. The phenotype includes allelic variants such as intermittent ataxia, choreoathetosis, dystonia, and alternating hemiplegia of childhood with or without epilepsy. Dystonias involve allelic variants of glucose transporter type 1 deficiency syndrome. Three Chinese patients presented with paroxysmal behavioral disturbance, weakness, ataxia (especially after fasting), and exercise intolerance. Electroencephalogram findings did not correlate with clinical manifestations. Cranial magnetic resonance imaging produced normal results or mild hypomyelination. Hypoglycorrhachia was evident in all cases. Cerebrospinal fluid glucose ranged from 1.63-2.45 mmol/L. Erythrocyte 3-O-methyl-d-glucose uptake was decreased to 58% in patient 1. Three SLC2A1 disease-causing mutations (761delA, P383H, and R400C) were observed. No patient tolerated ketogenic diets. Two patients responded to frequent meals with snacks. Cerebrospinal fluid evaluation constitutes the diagnostic testing permitting early treatment of glucose transporter type 1 deficiency syndrome. Early diagnosis and treatment improve prognoses. [Copyright &y& Elsevier]

Glucose transporter 1 deficiency syndrome (Glut1-DS) is a congenital metabolic disorder characterized by refractory seizures with early infantile onset, developmental delay, movement disorders and acquired microcephaly. Glut1-DS is caused by heterozygous abnormalities of the SLC2A1 (Glut1) gene, whose product acts to transport glucose into the brain across the blood-brain barrier. We analyzed the SLC2A1 gene in 12 Japanese Glut1-DS patients who were diagnosed by characteristic clinical symptoms and hypoglycorrhachia as follows: all patients had infantile-onset seizures and mild to severe developmental delay, and ataxia was detected in 11 patients. For the 12 patients, we identified seven different mutations (three missense, one nonsense, two frameshift and one splice-site) in exons and exon-intron boundaries of the SLC2A1 gene by direct sequencing, of which six were novel mutations. Of the remaining five patients who had no point mutations and underwent investigation by multiplex ligation-dependent probe amplification, a complex abnormality with deletion and duplication was identified in one patient: this is the first case of such recombination of the SLC2A1 gene. Changes in regulatory sequences in the promoter region or genes other than SLC2A1 might be responsible for onset of Glut1-DS in the other four patients (33%) without SLC2A1 mutation. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Insulin resistance (IR) represents an independent risk factor for metabolic, cardiovascular, and neoplastic disorders. Preventing/attenuating IR is a major objective to be reached to preserve population health. Because many insulin-sensitizing drugs have shown unwanted side effects, active harmless compounds are sought after. Dietary anthocyanins have been demonstrated to ameliorate hyperglycemia and insulin sensitivity. This study aimed at investigating whether cyanidin-3-O-β-glucoside (C3G) and its metabolite protocatechuic acid (PCA) might have a role in glucose transport activation in human omental adipocytes and 3T3-L1 cells. RESEARCH DESIGN AND METHODS--In cells treated with 50 µmol/L C3G and 100 µmol/L PCA, [&sup3H]-2-deoxyglucose uptake, GLUT4 transcolation by immunoblotting, adiponectin secretion, and peroxisome proliferator-activated receptor-γ (PPARγ) activation by enzyme-linked immunosorbent assay kits were evaluated. Parallel experiments were carried out in murine adipocyte 3T3-L1. To define the role of PPARγ in modulating polyphenol effects, small interfering RNA technique and PPARγ antagonist were used to inhibit transcription factor activity. RESULTS--C3G and PCA increased adipocyte glucose uptake (P < 0.05) and GLUT4 membrane translocation (P < 0.01). Significant increases (P < 0.05) in nuclear PPARγ activity, as well as in adiponectin and GLUT4 expressions (P < 0.01), were also shown. It is interesting that PPARγ inhibition counteracted the polyphenol-induced adiponectin and GLUT4 upregulations, suggesting a direct involvement of PPARγ in this process. CONCLUSIONS--Our study provides evidence thin C3G and PCA might excel insulin-like activities by PPARγ activation, evidencing a causal relationship between this transcription factor and adiponectin and GLUT4 upregulation. Dietary polyphenols could be included in the preventive/therapeutic armory against pathological conditions associated with IR. [ABSTRACT FROM AUTHOR]

Abstract: Glucose transporter-1 (GLUT1) deficiency syndrome is caused by heterozygous mutations in the SLC2A1 gene, resulting in impaired glucose transport into the brain. It is characterized by a low glucose concentration in the cerebrospinal fluid (hypoglycorrhachia) in the absence of hypoglycemia, in combination with low to normal lactate in the cerebrospinal fluid (CSF). It often results in treatment-resistant infantile epilepsy with progressive developmental disabilities and a complex movement disorder. Recognizing GLUT1 deficiency syndrome is important, since initiation of a ketogenic diet can reduce the frequency of seizures and the severity of the movement disorder. There can be a considerable delay in diagnosing GLUT1 deficiency syndrome, and this point is illustrated by the natural history of this disorder in a 21-year-old woman with severe, progressive neurological disabilities. Her encephalopathy consisted of treatment-resistant seizures, a complex movement disorder, progressive intellectual disability, and deceleration of her head growth after late infancy. Focused evaluation at age 21 revealed GLUT1 deficiency caused by a novel heterozygous missence mutation in exon 7 (c.938C > A; p.Ser313Try) in SLC2A1 as the cause for her disabilities. [Copyright &y& Elsevier]

Glucose is a key fuel and an important metabolic substrate in mammals. Renal proximal tubular cells (PTCs) not only reabsorb filtered glucose but are also believed to play a role in the glucotoxicity associated with renal pathogenesis, such as in diabetes. The proximal tubule environment is where 90% of the filtered glucose is reabsorbed by the low-affinity/high-capacity Na + /glucose cotransporter 2 (SGLT2) and facilitated diffusion glucose transporter 2 (GLUT2). Both active and facilitative glucose transporters have distinct distribution profiles along the proximal tubule related to their particular kinetic characteristics. A number of mechanisms contribute to the changes in the cellular functions, which occur in response to exposure to various endogenous factors. Hyperglycemia was reported to regulate the renal SGLT activities through the reactive oxygen species–nuclear factor- κ B pathways, which suggests that the transcellular glucose uptake within the PTCs contribute to the development of diabetic-like nephropathy. Angiotensin II (ANG II) plays an important role in its development through epidermal growth factor receptor (EGFR) transactivation. Therefore, a combination of high glucose, ANG II, and EGF are involved in diabetic-like nephropathy by regulating the SGLT activity. In addition, endogenously enhanced SGLTs have a cytoprotective function. The renal proximal tubules play a major role in regulating the plasma glucose levels, and there is increasing interest in the renal glucose transporters on account of their potential implications in the treatment of various conditions including diabetes mellitus. [ABSTRACT FROM AUTHOR]