Metformin mitigates impaired testicular lactate transport/utilisation and improves sexual behaviour in streptozotocin-induced diabetic rats.

CONTEXT: Lactate is the preferred energy substrate for developing testicular germ cells. Diabetes is associated with impaired testicular lactate transport/utilisation, and poor sexual behaviour. OBJECTIVE: To examine the effects of metformin on parameters involved in testicular lactate production, transport/utilisation, and sexual behaviour in diabetic state. METHODS: Male Sprague-Dawley rats were assigned into normal control (NC), diabetic control (DC), and metformin-treated diabetic group (n = 6/group). Metformin (300 mg/kg b.w./day) was administrated orally for 4 weeks. RESULTS: Intra-testicular glucose and lactate levels, and lactate dehydrogenase (LDH) activity increased, while the mRNA transcript levels of genes responsible for testicular glucose and lactate transport/utilisation (glucose transporter 3, monocarboxylate transporter 4 (MCT4), MCT2, and LDH type C) decreased in DC group. Furthermore, penile nitric oxide increased, while cyclic guanosine monophosphate decreased, with impaired sexual behaviour in DC group. Treatment with metformin improved these parameters. CONCLUSIONS: Metformin increases testicular lactate transport/utilisation and improves sexual behaviour in diabetic state.

Zika virus infection of first trimester trophoblast cells affects cell migration, metabolism and immune homeostasis control.

Zika virus (ZIKV) re-emerged after circulating almost undetected for many years and the last spread in 2015 was the major outbreak reported. ZIKV infection was associated with congenital fetal growth anomalies such as microcephaly, brain calcifications, and low birth weight related to fetal growth restriction. In this study, we investigated the effect of ZIKV infection on first trimester trophoblast cell function and metabolism. We also studied the interaction of trophoblast cells with decidual immune populations. Results presented here demonstrate that ZIKV infection triggered a strong antiviral response in first trimester cytotrophoblast-derived cells, impaired cell migration, increased glucose uptake and GLUT3 expression, and reduced brain derived neurotrophic factor (BDNF) expression. ZIKV infection also conditioned trophoblast cells to favor a tolerogenic response since an increased recruitment of CD14+ monocytes bearing an anti-inflammatory profile, increased CD4+ T cells and NK CD56Dim and NK CD56Bright populations and an increment in the population CD4+ FOXP3+ IL-10+ cells was observed. Interestingly, when ZIKV infection of trophoblast cells occurred in the presence of the vasoactive intestinal peptide (VIP) there was lower detection of viral RNA and reduced toll-like receptor-3 and viperin messenger RNA expression, along with reduced CD56Dim cells trafficking to trophoblast conditioned media. The effects of ZIKV infection on trophoblast cell function and immune-trophoblast interaction shown here could contribute to defective placentation and ZIKV persistence at the fetal-maternal interface. The inhibitory effect of VIP on ZIKV infection of trophoblast cells highlights its potential as a candidate molecule to interfere ZIKV infection during early pregnancy.

HMGA1 Promotes Hepatic Metastasis of Colorectal Cancer by Inducing Expression of Glucose Transporter 3 (GLUT3).

BACKGROUND Colorectal cancer (CRC) is one of the most common cancers worldwide, and more than half of CRC patients have CRC liver metastasis (CRCLM). Mounting evidence indicates that high mobility group protein A1(HMGA1) is overexpressed in many cancer types, but its role in CRCLM has been obscure. MATERIAL AND METHODS Using immunohistochemistry, we assessed the expression of HMGA1 in 73 patients with CRCLM, and compared HMGA1 mRNA in 17 pairs of CRCs, CRCLM tissues, and normal liver tissues. The clinical significance of HMGA1 was evaluated by analyzing its correlation with the clinicopathological factors and overall survival (OS) rates. The function of HMGA1 in CRC invasion was investigated and the underlying mechanism of HMGA1-induced invasion was explored with in vitro experiments. RESULTS In CRCLMs, the high-HMGA1 and low-HMGA1 patients accounted for 53.42% and 46.58% of all patients, respectively. High HMGA1 expression in CRCLM was significantly associated with low OS rates. In vitro experiments demonstrated that HMGA1 promoted glucose transporter 3 (GLUT3) transcription and expression in CRC cells. GLUT3 was required in HMGA1-involved invasion, and GLUT3 expression was associated with poor prognosis of CRCLM. CONCLUSIONS High HMGA1 and GLUT3 expression in CRCLM was significantly correlated with poor prognosis of CRCLM. HMGA1 promoted CRC invasion by elevating GLUT3 transcription and expression.

A Key Role of DNA Damage-Inducible Transcript 4 (DDIT4) Connects Autophagy and GLUT3-Mediated Stemness To Desensitize Temozolomide Efficacy in Glioblastomas.

DNA damage-inducible transcript 4 (DDIT4) is known to participate in various cancers, including glioblastoma multiforme (GBM). However, contradictory roles of DDIT4 exist in inducing cell death and possessing anti-apoptotic functions against cancer progression. Herein, we investigated DDIT4 signaling in GBM and temozolomide (TMZ) drug resistance. We identified that TMZ induced DDIT4 upregulation, leading to desensitization against TMZ cytotoxicity in GBM cells. Higher DDIT4 levels were found in glioma cells and mesenchymal-type GBM patients, and these higher levels were positively correlated with mesenchymal markers. Furthermore, patients with lower DDIT4 levels, especially O-6-methylguanine-DNA methyltransferase (MGMT)-methylated patients, exhibited better TMZ therapeutic efficacy. We determined that higher levels of 5 DDIT4-associated downstream genes, including SLC2A3 (also known as glucose transporter 3 (GLUT3)), can be used to predict a poor prognosis. Among these 5 genes, only GLUT3 was upregulated in both TMZ-treated and DDIT4-overexpressing cells. DDIT4-mediated GLUT3 expression was also identified, and its expression decreased TMZ's cytotoxicity. A significant correlation existed between DDIT4 and GLUT3. DDIT4 signaling was found to be involved in both glycolytic and autophagic pathways. However, GLUT3 only participated in the exhibition of DDIT4-mediated stemness, resulting from glycolytic regulation, but not in DDIT4-mediated autophagic signaling. Finally, we identified TMZ-upregulated activating transcription factor 4 (ATF4) as an upstream regulator of DDIT4-mediated GLUT3/stemness signaling and autophagy. Consequently, ATF4/DDIT4 signaling was connected to both autophagy and GLUT3-regulated stemness, which are involved in TMZ drug resistance and the poor prognoses of GBM patients. Targeting DDIT4/GLUT3 signaling might be a new direction for glioma therapy.

Functional significance of post-myocardial infarction inflammation evaluated by 18F-fluorodeoxyglucose imaging in swine model.

BACKGROUND: The aim of the study was to investigate the relationship between post-myocardial infarction (MI) inflammation and left ventricular (LV) remodeling in a swine model by 18F-fluorodeoxyglucose (FDG) imaging. METHODS: MI was induced in swine by balloon occlusion of the left anterior descending coronary artery. A series of FDG positron emission tomography (PET) images were taken within 2 weeks post-MI, employing a comprehensive strategy to suppress the physiological uptake of cardiomyocytes. Echocardiography was applied to evaluate LV volume, global and regional function. CD68+ macrophage and glucose transporters (GLUT-1, -3 and -4) were investigated by immunostaining. RESULTS: The physiological uptake of myocardium was adequately suppressed in 92.3% of PET scans verified by visual analysis, which was further confirmed by the minimal expression of myocardial GLUT-4. Higher FDG uptake was observed in the infarct than in the remote area and persisted within the observational period of 2 weeks. The FDG uptake of infarcted myocardium on day 1 post-MI was correlated with LV global remodeling, and the FDG uptake of infarcted myocardium on days 1 and 8 post-MI had a trend of correlating with regional remodeling of the infarct area. CONCLUSIONS: We here report a feasible swine model for investigating post-MI inflammation. FDG signal in the infarct area of swine persisted for a longer duration than has been reported in small animals. FDG activity in the infarct area could predict LV remodeling.

Regular Exercise Enhances Cognitive Function and Intracephalic GLUT Expression in Alzheimer's Disease Model Mice.

Brain energy metabolic impairment is one of the main features of Alzheimer's disease (AD) and is considered an underlying factor involved in cognitive impairment. Therefore, brain energy metabolism may represent a new therapeutic target for AD medical interventions. Among nutrients providing energy, glucose, the primary energy source, cannot cross the blood-brain barrier freely without specific glucose transporters (GLUTs), which are essential for the maintenance of cerebral energy metabolism homeostasis. Several converging lines of evidence suggest that GLUT1 deficiency in mice leads to synapse reduction and dysregulation coupled with mitochondrial morphological changes. In this study, the results revealed that regular exercise (RE) decreased the expression of amyloid-ß and phosphorylated tau by western blot, and enhanced the spatial learning and exploration ability of AD model mice as assessed by Morris water maze test. Mitochondrial cristae and edges were clear and intact, ATP production in the brain raised, the number of synapses increased, and GLUT1 and GLUT3 expression levels improved in the central nervous system (CNS) in AD model mice after RE. Changes in GLUT1 and GLUT3 expression at the protein level after RE are an important part of energy metabolic adaptation in AD model mice. Learning and memory improvement are highly associated with mitochondrial integrity and sufficient synapses in the CNS. This research suggests that increased brain energy metabolism attributed to RE exhibits promising therapeutic potential for AD.

LIF, a Novel Myokine, Protects Against Amyloid-Beta-Induced Neurotoxicity via Akt-Mediated Autophagy Signaling in Hippocampal Cells.

BACKGROUND: Leukemia inhibitory factor, a novel myokine, is known to be associated with neural function, but the underlying molecular mechanism remains unclear. METHODS: HT-22 mouse hippocampal cells, primary hippocampal cells, and Drosophila Alzheimer's disease model were used to determine the effect of leukemia inhibitory factor on neurons. Immunoblot analysis and immunofluorescence method were used to analyze biological mechanism. RESULTS: Leukemia inhibitory factor increased Akt phosphorylation in a phosphoinositide-3-kinase-dependent manner in hippocampal cells. Leukemia inhibitory factor also increased the phosphorylation of the mammalian target of rapamycin and the downstream S6K. Leukemia inhibitory factor stimulated the phosphorylation of signal transducer and activator of transcription via extracellular signal-regulated kinases. Leukemia inhibitory factor increased c-fos expression through both Akt and extracellular signal-regulated kinases. Leukemia inhibitory factor blocked amyloid ß-induced neural viability suppression and inhibited amyloid ß-induced glucose uptake impairment through the block of amyloid ß-mediated insulin receptor downregulation. Leukemia inhibitory factor blocked amyloid ß-mediated induction of the autophagy marker, microtubule-associated protein 1A/1B-light chain 3. Additionally, in primary prepared hippocampal cells, leukemia inhibitory factor stimulated Akt and extracellular signal-regulated kinase, demonstrating that leukemia inhibitory factor has physiological relevance in vivo. Suppression of the autophagy marker, light chain 3II, by leukemia inhibitory factor was observed in a Drosophila model of Alzheimer's disease. CONCLUSIONS: These results demonstrate that leukemia inhibitory factor protects against amyloid ß-induced neurotoxicity via Akt/extracellular signal-regulated kinase-mediated c-fos induction, and thus suggest that leukemia inhibitory factor is a potential drug for Alzheimer's disease.

Aging alters glucose uptake in the naïve and injured rodent spinal cord.

Aging results in increased activation of inflammatory glial cells and decreased neuronal viability following spinal cord injury (SCI). Metabolism and transport of glucose is also decreased with age, although the influence of age on glucose transporter (GLUT) expression or glucose uptake in SCI is currently unknown. We therefore performed [18F]Fluorodeoxyglucose (FDG) PET imaging of young (3 month) and middle-aged (12 month) rats. Glucose uptake in middle-aged rats was decreased compared to young rats at baseline, followed by increased uptake 14 days post contusion SCI. qRT-PCR and protein analysis revealed an association between 14 day glucose uptake and 14 day post-injury inflammation. Further, gene expression analysis of neuron-specific GLUT3 and non-specific GLUT4 (present on glial cells) revealed an inverse relationship between GLUT3/4 gene expression and glucose uptake patterns. Protein expression revealed increased GLUT3 in 3 month rats only, consistent with age related decreases in glucose uptake, and increased GLUT4 in 12 month rats only, consistent with age related increases in inflammatory activity and glucose uptake. Inconsistencies between gene and protein suggest an influence of age-related impairment of translation and/or protein degradation. Overall, our findings show that age alters glucose uptake and GLUT3/4 expression profiles before and after SCI, which may be dependent on level of inflammatory response, and may suggest a therapeutic avenue in addressing glucose uptake in the aging population.

Up-regulated miR-29c inhibits cell proliferation and glycolysis by inhibiting SLC2A3 expression in prostate cancer.

Prostate cancer (PCa) is the most commonly cancer in male worldwide. However, the molecular mechanisms underlying the progression of PCa remain unclear. MiR-29c was reported to be down-regulated in several kinds of tumors. Here, we for the first time demonstrated miR-29c was down-regulated in PCa samples. SLC2A3, a regulator of glycolysis, was validated as a direct target of miR-29c. Moreover, functional studies showed miR-29c could inhibit cell growth, induce apoptosis and deceased the rate of glucose metabolism. Accordingly, we identified miR-29c acted as a tumor-suppressor and was down-regulated in PCa. We thought this study will provide useful information to explore the potential candidate biomarkers for diagnosis and prognosis targets of PCa.

Synaptic activity-induced glycolysis facilitates membrane lipid provision and neurite outgrowth.

The formation of neurites is an important process affecting the cognitive abilities of an organism. Neurite growth requires the addition of new membranes, but the metabolic remodeling necessary to supply lipids for membrane expansion is poorly understood. Here, we show that synaptic activity, one of the most important inducers of neurite growth, transcriptionally regulates the expression of neuronal glucose transporter Glut3 and rate-limiting enzymes of glycolysis, resulting in enhanced glucose uptake and metabolism that is partly used for lipid synthesis. Mechanistically, CREB regulates the expression of Glut3 and Siah2, the latter and LDH activity promoting the normoxic stabilization of HIF-1α that regulates the expression of rate-limiting genes of glycolysis. The expression of dominant-negative HIF-1α or Glut3 knockdown blocks activity-dependent neurite growth in vitro while pharmacological inhibition of the glycolysis and specific ablation of HIF-1α in early postnatal mice impairs the neurite architecture. These results suggest that the manipulation of neuronal glucose metabolism could be used to treat some brain developmental disorders.

Insulin-induced enhancement of MCF-7 breast cancer cell response to 5-fluorouracil and cyclophosphamide.

The study was designed to evaluate the potential use of insulin for cancer-specific treatment. Insulin-induced sensitivity of MCF-7 breast cancer cells to chemotherapeutic agents 5-fluorouracil and cyclophosphamide was evaluated. To investigate and establish the possible mechanisms of this phenomenon, we assessed cell proliferation, induction of apoptosis, activation of apoptotic and autophagic pathways, expression of glucose transporters 1 and 3, formation of reactive oxygen species, and wound-healing assay. Additionally, we reviewed the literature regarding theuse of insulin in cancer-specific treatment. We found that insulin increases the cytotoxic effect of 5-fluorouracil and cyclophosphamide in vitro up to two-fold. The effect was linked to enhancement of apoptosis, activation of apoptotic and autophagic pathways, and overexpression of glucose transporters 1 and 3 as well as inhibition of cell proliferation and motility. We propose a model for insulin-induced sensitization process. Insulin acts as a sensitizer of cancer cells to cytotoxic therapy through various mechanisms opening a possibility for metronomic insulin-based treatments.

Epigenetic regulation of placental glucose transporters mediates maternal cadmium-induced fetal growth restriction.

Cadmium (Cd) is one of the most toxic environmental pollutants that cause fetal malformation and growth restriction. However, the molecular mechanisms underlying maternal Cd toxicity on fetal growth remain largely unknown. Specifically, the role of placental nutrient transporters, including glucose transporters (GLUTs), has been poorly characterized in the etiology of Cd-induced fetal growth restriction (FGR). In the present study, we established a murine model of FGR induced by maternal Cd exposure, and examined the toxic effects of Cd on placental GLUTs. Our results showed that GLUT3 is significantly downregulated in Cd-exposed mouse placentas when compared to the normal ones. Data from bisulfite PCR demonstrated the hypermethylation of the promoter region of GLUT3. However, methylation levels remained unchanged in two major repetitive elements (LINE-1 and IAP) in Cd-exposed placentas. Moreover, DNA methyltransferase (DNMT) 3B and DNMT3L were significantly upregulated in Cd-exposed placentas, and there were no expression changes of DNMT1 and DNMT3A. Collectively, our results suggest that changes in DNMT3B and DNMT3L expressions and site-specific DNA methylation may be involved in the etiology of Cd-induced fetal growth restriction through downregulation of GLUT3.

Suppressed glycolytic metabolism in the prostate of transgenic rats overexpressing calcium-binding protein regucalcin underpins reduced cell proliferation.

Regucalcin (RGN) is a calcium-binding protein underexpressed in human prostate cancer cases, and it has been associated with the suppression of cell proliferation and the regulation of several metabolic pathways. On the other hand, it is known that the metabolic reprogramming with augmented glycolytic metabolism and enhanced proliferative capability is a characteristic of prostate cancer cells. The present study investigated the influence of RGN on the glycolytic metabolism of rat prostate by comparing transgenic adult animals overexpressing RGN (Tg-RGN) with their wild-type counterparts. Glucose consumption was significantly decreased in the prostate of Tg-RGN animals relatively to wild-type, and accompanied by the diminished expression of glucose transporter 3 and glycolytic enzyme phosphofructokinase. Also, prostates of Tg-RGN animals displayed lower lactate levels, which resulted from the diminished expression/activity of lactate dehydrogenase. The expression of the monocarboxylate transporter 4 responsible for the export of lactate to the extracellular space was also diminished with RGN overexpression. These results showed the effect of RGN in inhibiting the glycolytic metabolism in rat prostate, which was underpinned by a reduced cell proliferation index. The present findings also suggest that the loss of RGN may predispose to a hyper glycolytic profile and fostered proliferation of prostate cells.

Is the Glut expression related to FDG uptake in PET/CT of non-small cell lung cancer patients?

Though 18F-FDG PET/CT scans are widely used in non-small cell lung cancer (NSCLC), the mechanism of FDG uptake by lung cancer cells has not yet been fully elucidated. This study evaluated the relationship between FDG uptake and the expression of glucose transporters in NSCLC. Sixty-four NSCLC patients who underwent both preoperative 18F-FDG PET/CT scanning and thoracotomy were included. The maximum standardized uptake value (SUVmax) of the primary lung cancer was compared to the immunohistochemistry results for Glut expression and tumor size. In all the NSCLC cases, degree of FDG uptake significantly correlated with both Glut-1 and Glut-3 expression. When stratified by the histology, squamous cell carcinomas showed higher mean SUVmax, Glut-1 expression intensity, and percentage of area positive for Glut-1 expression than adenocarcinomas. Glut-1 and Glut-3 expressions correlated with SUVmax in adenocarcinomas, but there was no significant correlation in squamous cell carcinomas. No significant correlation was observed between tumor size and FDG uptake or Glut expression. These results show that Glut expression was significantly correlated with SUVmax in NSCLC, especially in adenocarcinomas, and that neither FDG uptake nor the expression of Glut was associated with tumor size.

The progression from a lower to a higher invasive stage of bladder cancer is associated with severe alterations in glucose and pyruvate metabolism.

Cancer cells present a particular metabolic behavior. We hypothesized that the progression of bladder cancer could be accompanied by changes in cells glycolytic profile. We studied two human bladder cancer cells, RT4 and TCCSUP, in which the latter represents a more invasive stage. The levels of glucose, pyruvate, alanine and lactate in the extracellular media were measured by Proton Nuclear Magnetic Resonance. The protein expression levels of glucose transporters 1 (GLUT1) and 3 (GLUT3), monocarboxylate transporter 4 (MCT4), phosphofructokinase-1 (PFK1), glutamic-pyruvate transaminase (GPT) and lactate dehydrogenase (LDH) were determined. Our data showed that glucose consumption and GLUT3 levels were similar in both cell lines, but TCCSUP cells displayed lower levels of GLUT1 and PFK expression. An increase in pyruvate consumption, concordant with the higher levels of lactate and alanine production, was also detected in TCCSUP cells. Moreover, TCCSUP cells presented lower protein expression levels of GPT and LDH. These results illustrate that bladder cancer progression is associated with alterations in cells glycolytic profile, namely the switch from glucose to pyruvate consumption in the more aggressive stage. This may be useful to develop new therapies and to identify biomarkers for cancer progression.

Differential microscopic finding and glucose transporter 3 expression in terminal chorionic villi among birth weight-discordant twin placentas.

OBJECTIVE: To evaluate differences in microscopic findings and glucose transporter 3 (GLUT3) expression in terminal chorionic villi (TV) among birth weight-discordant twin (BWDT) placentas compared with the birth weight-concordant twin (BWCT) placentas. METHODS: We retrospectively studied a cohort of 26 BWDT, 10 BWCT, 10 pre-eclampsia singleton and 10 normal singleton pregnancies. Placentas were scored for the percentage of TV, the percentage of TV with syncytial knots, the presence of capillary branching patterns of TV, the capillary to terminal villous ratios, the membranous expression of GLUT3 and the nuclear expression of HIF-1α in trophoblasts and capillary endothelial cells of TV using immunohistochemistry. The clinical characteristics and microscopic findings were analyzed and compared. RESULTS: BWDT placentas exhibited differential percentages of TV, percentages of TV with syncytial knots, capillary to terminal villous ratios, expression of HIF-1α in capillary endothelial cells and expression of GLUT3 in trophoblasts and capillary endothelial cells of TV among each twin pair compared with BWCT placentas (P=0.003, P=0.022, P=0.037, P=0.007, P=0.046 and P=0.002, respectively). Pre-eclampsia singleton placentas exhibited higher GLUT3 expression in trophoblasts, higher HIF-1α expression in capillary endothelial cells of TV and high capillary to terminal villous ratios compared with normal singleton placentas (P=0.001, P<0.001 and P=0.001, respectively). CONCLUSIONS: We observed a strong relationship between characteristics of adaptive change to hypoxia (GLUT3 expression, TV and syncytial knotting and higher capillary to terminal villous ratios) and BWDT pregnancy but not BWCT pregnancy.

AMPK modulates Hippo pathway activity to regulate energy homeostasis.

The Hippo pathway was discovered as a conserved tumour suppressor pathway restricting cell proliferation and apoptosis. However, the upstream signals that regulate the Hippo pathway in the context of organ size control and cancer prevention are largely unknown. Here, we report that glucose, the ubiquitous energy source used for ATP generation, regulates the Hippo pathway downstream effector YAP. We show that both the Hippo pathway and AMP-activated protein kinase (AMPK) were activated during glucose starvation, resulting in phosphorylation of YAP and contributing to its inactivation. We also identified glucose-transporter 3 (GLUT3) as a YAP-regulated gene involved in glucose metabolism. Together, these results demonstrate that glucose-mediated energy homeostasis is an upstream event involved in regulation of the Hippo pathway and, potentially, an oncogenic function of YAP in promoting glycolysis, thereby providing an exciting link between glucose metabolism and the Hippo pathway in tissue maintenance and cancer prevention.

Genome-wide identification of hypoxia-inducible factor-1 and -2 binding sites in hypoxic human macrophages alternatively activated by IL-10.

Macrophages (MΦ) often accumulate in hypoxic areas, where they significantly influence disease progression. Anti-inflammatory cytokines, such as IL-10, generate alternatively activated macrophages that support tumor growth. To understand how alternative activation affects the transcriptional profile of hypoxic macrophages, we globally mapped binding sites of hypoxia-inducible factor (HIF)-1α and HIF-2α in primary human monocyte-derived macrophages prestimulated with IL-10. 713 HIF-1 and 795 HIF-2 binding sites were identified under hypoxia. Pretreatment with IL-10 altered the binding pattern, with 120 new HIF-1 and 188 new HIF-2 binding sites emerging. HIF-1 binding was most prominent in promoters, while HIF-2 binding was more abundant in enhancer regions. Comparison of ChIP-seq data obtained in other cells revealed a highly cell type specific binding of HIF. In MΦ HIF binding occurred preferentially in already active enhancers or promoters. To assess the roles of HIF on gene expression, primary human macrophages were treated with siRNA against HIF-1α or HIF-2α, followed by genome-wide gene expression analysis. Comparing mRNA expression to the HIF binding profile revealed a significant enrichment of hypoxia-inducible genes previously identified by ChIP-seq. Analysis of gene expression under hypoxia alone and hypoxia/IL-10 showed the enhanced induction of a set of genes including PLOD2 and SLC2A3, while another group including KDM3A and ADM remained unaffected or was reduced by IL-10. Taken together IL-10 influences the DNA binding pattern of HIF and the level of gene induction.

Gene and protein expression of glucose transporter 1 and glucose transporter 3 in human laryngeal cancer-the relationship with regulatory hypoxia-inducible factor-1α expression, tumor invasiveness, and patient prognosis.

Increased glucose uptake mediated by glucose transporters and reliance on glycolysis are common features of malignant cells. Hypoxia-inducible factor-1α supports the adaptation of hypoxic cells by inducing genes related to glucose metabolism. The contribution of glucose transporter (GLUT) and hypoxia-inducible factor-1α (HIF-1α) activity to tumor behavior and their prognostic value in head and neck cancers remains unclear. The aim of this study was to examine the predictive value of GLUT1, GLUT3, and HIF-1α messenger RNA (mRNA)/protein expression as markers of tumor aggressiveness and prognosis in laryngeal cancer. The level of hypoxia/metabolic marker genes was determined in 106 squamous cell laryngeal cancer (SCC) and 73 noncancerous matched mucosa (NCM) controls using quantitative real-time PCR. The related protein levels were analyzed by Western blot. Positive expression of SLC2A1, SLC2A3, and HIF-1α genes was noted in 83.9, 82.1, and 71.7% of SCC specimens and in 34.4, 59.4, and 62.5% of laryngeal cancer samples. Higher levels of mRNA/protein for GLUT1 and HIF-1α were noted in SCC compared to NCM (p < 0.05). SLC2A1 was found to have a positive relationship with grade, tumor front grading (TFG) score, and depth and mode of invasion (p < 0.05). SLC2A3 was related to grade and invasion type (p < 0.05). There were also relationships of HIF-1α with pTNM, TFG scale, invasion depth and mode, tumor recurrences, and overall survival (p < 0.05). In addition, more advanced tumors were found to be more likely to demonstrate positive expression of these proteins. In conclusion, the hypoxia/metabolic markers studied could be used as molecular markers of tumor invasiveness in laryngeal cancer.

Significant reduction of the GLUT3 level, but not GLUT1 level, was observed in the brain tissues of several scrapie experimental animals and scrapie-infected cell lines.

Glucose transporters 1 (GLUT1) and 3 (GLUT3) belong to the solute carrier family 2 (SLC2, facilitated glucose transporter) and are the two most important glucose transporters (GLUTs) in brain tissue, and between them, GLUT3 is the primary one for neurons, which is responsible for glucose uptake. To obtain insights into the possible alterations of GLUT1 and GLUT3 in transmissible spongiform encephalopathies (TSEs), the protein levels of GLUT1 and GLUT3 in the brain tissues of agents 263K- and 139A-infected hamsters, as well as agents 139A- and ME7-infected mice, were evaluated. Western blots, immunofluorescent assay (IFA), and immunohistochemical (IHC) assays revealed that at the terminal stages of the infection, GLUT3 level in the brain tissues of scrapie-infected rodents was significantly downregulated, while GLUT1 level remained almost unchanged. The decline of GLUT3 level was closely related with prolonged incubation time. In line with these results in vivo, the GLUT3 level in a prion persistently infected cell line SMB-S15 was also lower than that of its normal cell line SMB-PS. Moreover, the level of hypoxia-inducible factor-1 alpha (HIF-1α), which positively regulated the expressions of GLUTs, was also markedly downregulated in the brains of several scrapie-infected animals. In vitro glucose uptake assays illustrated a markedly decreased 2-[N-(7-nitrobenze-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose uptake activity in SMB-S15 cells. Our data indicate that the reduction of GLUT3 is a common phenomenon in prion diseases, which occurs much earlier than the appearance of clinical symptoms. Defect in glucose uptake and metabolism of neurons, like in other neurodegenerative diseases, for example, Alzheimer's disease (AD), may be one of the essential processes in the pathogenesis of prion diseases.