The enhanced energy metabolism in the tumor margin mediated by RRAD promotes the progression of oral squamous cell carcinoma.

The tumor margin as the invasive front has been proven to be closely related to the progression and metastasis of oral squamous cell carcinoma (OSCC). However, how tumor cells in the marginal region obtain the extra energy needed for tumor progression is still unknown. Here, we used spatial metabolomics and the spatial transcriptome to identify enhanced energy metabolism in the tumor margin of OSCC and identified that the downregulation of Ras-related glycolysis inhibitor and calcium channel regulator (RRAD) in tumor cells mediated this process. The absence of RRAD enhanced the ingestion of glucose and malignant behaviors of tumor cells both in vivo and in vitro. Mechanically, the downregulation of RRAD promoted the internal flow of Ca2+ and elevated its concentration in the nucleus, which resulted in the activation of the CAMKIV-CREB1 axis to induce the transcription of the glucose transporter GLUT3. GLUT inhibitor-1, as an inhibitor of GLUT3, could suppress this vigorous energy metabolism and malignant behaviors caused by the downregulation of RRAD. Taken together, our study revealed that enhanced energy metabolism in the tumor margin mediated by RRAD promotes the progression of OSCC and proved that GLUT3 is a potential target for future treatment of OSCC.

Fetal Hypoglycemia Induced by Placental SLC2A3-RNA Interference Alters Fetal Pancreas Development and Transcriptome at Mid-Gestation.

Glucose, the primary energy substrate for fetal oxidative processes and growth, is transferred from maternal to fetal circulation down a concentration gradient by placental facilitative glucose transporters. In sheep, SLC2A1 and SLC2A3 are the primary transporters available in the placental epithelium, with SLC2A3 located on the maternal-facing apical trophoblast membrane and SLC2A1 located on the fetal-facing basolateral trophoblast membrane. We have previously reported that impaired placental SLC2A3 glucose transport resulted in smaller, hypoglycemic fetuses with reduced umbilical artery insulin and glucagon concentrations, in addition to diminished pancreas weights. These findings led us to subject RNA derived from SLC2A3-RNAi (RNA interference) and NTS-RNAi (non-targeting sequence) fetal pancreases to qPCR followed by transcriptomic analysis. We identified a total of 771 differentially expressed genes (DEGs). Upregulated pathways were associated with fat digestion and absorption, particularly fatty acid transport, lipid metabolism, and cholesterol biosynthesis, suggesting a potential switch in energetic substrates due to hypoglycemia. Pathways related to molecular transport and cell signaling in addition to pathways influencing growth and metabolism of the developing pancreas were also impacted. A few genes directly related to gluconeogenesis were also differentially expressed. Our results suggest that fetal hypoglycemia during the first half of gestation impacts fetal pancreas development and function that is not limited to ß cell activity.

Glucose uptake in trophoblasts of GDM mice is regulated by the AMPK-CLUT3 signaling pathway.

GDM, as a metabolic disease during pregnancy, regulates GLUT3 translocation by AMPK, thereby affecting glucose uptake in trophoblasts. It provides a new research idea and therapeutic target for alleviating intrauterine hyperglycemia in GDM. STZ was used to construct GDM mice, inject AICAR into pregnant mice, and observe fetal and placental weight; flow cytometry was employed for the detection of glucose uptake by primary trophoblast cells; immunofluorescence was applied to detect the localization of GLUT3 and AMPK in placental tissue; Cocofal microscope was used to detect the localization of GLUT3 in trophoblast cells;qRT-PCR and Western blot experiments were carried out to detect the expression levels of GLUT3 and AMPK in placental tissue; CO-IP was utilized to detect the interaction of GLUT3 and AMPK. Compared with the normal pregnancy group, the weight of the fetus and placenta of GDM mice increased (P < 0.001), and the ability of trophoblasts to take up glucose decreased (P < 0.001). In addition, AMPK activity in trophoblasts and membrane localization of GLUT3 in GDM mice were down-regulated compared with normal pregnant mice (P < 0.05). There is an interaction between GLUT3 and AMPK. Activating AMPK in trophoblasts can up-regulate the expression of GLUT3 membrane protein in trophoblasts of mice (P < 0.05) and increase the glucose uptake of trophoblasts (P < 0.05). We speculate that inhibition of AMPK activity in GDM mice results in aberrant localization of GLUT3, which in turn attenuates glucose uptake by placental trophoblast cells. AICAR activates AMPK to increase the membrane localization of GLUT3 and improve the glucose uptake capacity of trophoblasts.

SLC2A3 promotes tumor progression through lactic acid-promoted TGF-ß signaling pathway in oral squamous cell carcinoma.

BACKGROUNDS: Oral squamous cell carcinoma is a malignant tumor of the head and neck, and its molecular mechanism remains to be explored. METHODS: By analyzing the OSCC data from the TCGA database, we found that SLC2A3 is highly expressed in OSCC patients. The expression level of SLC2A3 was verified by RT-PCR and western blotting in OSCC cell lines. The function of SLC2A3 in OSCC cell lines and Lactic acid in SLC2A3-knockdown OSCC cells were detected by colony formation, CCK8, transwell, and wound healing assays. The effect of SLC2A3 on tumor growth and metastasis was tested in vivo. GSEA and Western blot were used to analyze and validate tumor phenotypes and signaling pathway molecules. RESULTS: We analyzed OSCC datasets in the TCGA database and found that SLC2A3 had abnormally high expression and was associated with poor prognosis. We also found that oral squamous cell carcinoma cells had increased proliferation, migration, invasion, EMT phenotype, and glycolysis due to SLC2A3 overexpression. Conversely, SLC2A3 knockdown had the opposite effect. Our in vivo experiments confirmed that SLC2A3 overexpression promoted tumor growth and metastasis while knockdown inhibited it. We also observed that high SLC2A3 expression led to EMT and the activation of the TGF-ß signaling pathway, while knockdown inhibited it. Interestingly, exogenous lactic acid restored the EMT, proliferation, migration, and invasion abilities of oral cancer cells inhibited by knocking down SLC2A3. CONCLUSIONS: Our study reveals that SLC2A3 expression was up-regulated in OSCC. SLC2A3 activates the TGF-ß signaling pathway through lactic acid generated from glycolysis, thus regulating the biological behavior of OSCC.

Effects of down-regulated carbonic anhydrase 8 on cell survival and glucose metabolism in human colorectal cancer cell lines.

Carbonic anhydrase 8 (CA8) is a member of the α-carbonic anhydrase family but does not catalyze the reversible hydration of carbon dioxide. In the present study, we examined the effects of CA8 on two human colon cancer cell lines, SW480 and SW620, by suppressing CA8 expression through shRNA knockdown. Our results showed that knockdown of CA8 decreased cell growth and cell mobility in SW620 cells, but not in SW480 cells. In addition, downregulated CA8 resulted in a significant decrease of glucose uptake in both SW480 and SW620 cells. Interestingly, stable downregulation of CA8 decreased phosphofructokinase-1 expression but increased glucose transporter 3 (GLUT3) levels in SW620 cells. However, transient downregulation of CA8 fails to up-regulate GLUT3 expression, indicating that the increased GLUT3 observed in SW620-shCA8 cells is a compensatory effect. In addition, the interaction between CA8 and GLUT3 was evidenced by pull-down and IP assays. On the other hand, we showed that metformin, a first-line drug for type II diabetes patients, significantly inhibited cell migration of SW620 cells, depending on the expressions of CA8 and focal adhesion kinase. Taken together, our data demonstrate that when compared to primary colon cancer SW480 cells, metastatic colon cancer SW620 cells respond differently to downregulated CA8, indicating that CA8 in more aggressive cancer cells may play a more important role in controlling cell survival and metformin response. CA8 may affect glucose metabolism- and cell invasion-related molecules in colon cancer, suggesting that CA8 may be a potential target in future cancer therapy.

GLUT3 transcriptional activation by ZEB1 fuels the Warburg effect and promotes ovarian cancer progression.

Ovarian cancer (OvCa) is characterized by early metastasis and high mortality rates, underscoring the need for deeper understanding of these aspects. This study explores the role of glucose transporter 3 (GLUT3) driven by zinc finger E-box-binding homeobox 1 (ZEB1) in OvCa progression and metastasis. Specifically, this study explored whether ZEB1 promotes glycolysis and assessed the potential involvement of GLUT3 in this process in OvCa cells. Our findings revealed that ZEB1 and GLUT3 were excessively expressed and closely correlated in OvCa. Mechanistically, ZEB1 activates the transcription of GLUT3 by binding to its promoter region. Increased expression of GLUT3 driven by ZEB1 dramatically enhances glycolysis, and thus fuels Warburg Effect to promote OvCa progression and metastasis. Consistently, elevated ZEB1 and GLUT3 expression in clinical OvCa is correlated with poor prognosis, reinforcing the profound contribution of ZEB1-GLUT3 axis to OvCa. These results suggest that activation of GLUT3 expression by ZEB1 is crucial for the proliferation and metastasis of OvCa via fueling glycolysis, shedding new light on OvCa treatment.

Tumor-associated macrophages drive glycolysis through the IL-8/STAT3/GLUT3 signaling pathway in pancreatic cancer progression.

Glycolytic metabolism is a hallmark of pancreatic ductal adenocarcinoma (PDAC), and tumor-associated stromal cells play important roles in tumor metabolism. We previously reported that tumor-associated macrophages (TAMs) facilitate PDAC progression. However, little is known about whether TAMs are involved in regulating glycolysis in PDAC. Here, we found a positive correlation between CD68+ TAM infiltration and FDG maximal standardized uptake (FDG SUVmax) on PET-CT images of PDAC. We discovered that the glycolytic gene set was prominently enriched in the high TAM infiltration group through Gene Set Enrichment Analysis using The Cancer Genome Atlas database. Mechanistically, TAMs secreted IL-8 to promote GLUT3 expression in PDAC cells, enhancing tumor glycolysis both in vitro and in vivo, whereas this effect could be blocked by the IL-8 receptor inhibitor reparixin. Furthermore, IL-8 promoted the translocation of phosphorylated STAT3 into the nucleus to activate the GLUT3 promoter. Overall, we demonstrated that TAMs boosted PDAC cell glycolysis through the IL-8/STAT3/GLUT3 signaling pathway. Our cumulative findings suggest that the abrogation of TAM-induced tumor glycolysis by reparixin might exhibit an antitumor impact and offer a potential therapeutic target for PDAC.

A high fat diet potentiates neonatal iron overload-induced memory impairments in rats.

PURPOSE: The present study aimed at evaluating possible synergistic effects between two risk factors for cognitive decline and neurodegenerative disorders, i.e. iron overload and exposure to a hypercaloric/hyperlipidic diet, on cognition, insulin resistance, and hippocampal GLUT1, GLUT3, Insr mRNA expression, and AKT phosporylation. METHODS: Male Wistar rats were treated with iron (30 mg/kg carbonyl iron) or vehicle (5% sorbitol in water) from 12 to 14th post-natal days. Iron-treated rats received a standard laboratory diet or a high fat diet from weaning to adulthood (9 months of age). Recognition and emotional memory, peripheral blood glucose and insulin levels were evaluated. Glucose transporters (GLUT 1 and GLUT3) and insulin signaling were analyzed in the hippocampus of rats. RESULTS: Both iron overload and exposure to a high fat diet induced memory deficits. Remarkably, the association of iron with the high fat diet induced more severe cognitive deficits. Iron overload in the neonatal period induced higher insulin levels associated with significantly higher HOMA-IR, an index of insulin resistance. Long-term exposure to a high fat diet resulted in higher fasting glucose levels. Iron treatment induced changes in Insr and GLUT1 expression in the hippocampus. At the level of intracellular signaling, both iron treatment and the high fat diet decreased AKT phosphorylation. CONCLUSION: The combination of iron overload with exposure to a high fat diet only led to synergistic deleterious effect on emotional memory, while the effects induced by iron and by the high fat diet on AKT phosphorylation were comparable. These findings indicate that there is, at least to some extent, an additive effect of iron combined with the diet. Further studies investigating the mechanisms associated to deleterious effects on cognition and susceptibility for the development of age-associated neurodegenerative disorders are warranted.

Glut-3 Gene Knockdown as a Potential Strategy to Overcome Glioblastoma Radioresistance.

The hypoxic pattern of glioblastoma (GBM) is known to be a primary cause of radioresistance. Our study explored the possibility of using gene knockdown of key factors involved in the molecular response to hypoxia, to overcome GBM radioresistance. We used the U87 cell line subjected to chemical hypoxia generated by CoCl2 and exposed to 2 Gy of X-rays, as single or combined treatments, and evaluated gene expression changes of biomarkers involved in the Warburg effect, cell cycle control, and survival to identify the best molecular targets to be knocked-down, among those directly activated by the HIF-1α transcription factor. By this approach, glut-3 and pdk-1 genes were chosen, and the effects of their morpholino-induced gene silencing were evaluated by exploring the proliferative rates and the molecular modifications of the above-mentioned biomarkers. We found that, after combined treatments, glut-3 gene knockdown induced a greater decrease in cell proliferation, compared to pdk-1 gene knockdown and strong upregulation of glut-1 and ldha, as a sign of cell response to restore the anaerobic glycolysis pathway. Overall, glut-3 gene knockdown offered a better chance of controlling the anaerobic use of pyruvate and a better proliferation rate reduction, suggesting it is a suitable silencing target to overcome radioresistance.

Altered Regulation of the Glucose Transporter GLUT3 in PRDX1 Null Cells Caused Hypersensitivity to Arsenite.

Targeting tumour metabolism through glucose transporters is an attractive approach. However, the role these transporters play through interaction with other signalling proteins is not yet defined. The glucose transporter SLC2A3 (GLUT3) is a member of the solute carrier transporter proteins. GLUT3 has a high affinity for D-glucose and regulates glucose uptake in the neurons, as well as other tissues. Herein, we show that GLUT3 is involved in the uptake of arsenite, and its level is regulated by peroxiredoxin 1 (PRDX1). In the absence of PRDX1, GLUT3 mRNA and protein expression levels are low, but they are increased upon arsenite treatment, correlating with an increased uptake of glucose. The downregulation of GLUT3 by siRNA or deletion of the gene by CRISPR cas-9 confers resistance to arsenite. Additionally, the overexpression of GLUT3 sensitises the cells to arsenite. We further show that GLUT3 interacts with PRDX1, and it forms nuclear foci, which are redistributed upon arsenite exposure, as revealed by immunofluorescence analysis. We propose that GLUT3 plays a role in mediating the uptake of arsenite into cells, and its homeostatic and redox states are tightly regulated by PRDX1. As such, GLUT3 and PRDX1 are likely to be novel targets for arsenite-based cancer therapy.

GLUT3 regulates alternative macrophage signaling through a glucose transport-independent role.

Macrophages are key mediators of innate immunity whose functional state can be regulated by glucose transporters. Although abundantly expressed in macrophages, the specific function of GLUT3, an isoform of facilitative glucose transporters, has not been clearly established. In this issue of the JCI, Dong-Min Yu and colleagues identify an alternative role for GLUT3 in promoting M2 macrophage polarization. The authors demonstrated that GLUT3 was upregulated upon M2 stimulation and was required for efficient alternative macrophage polarization and function. They further showed that GLUT3-induced M2 polarization was independent of glucose transport and functioned through Ras-mediated regulation of IL-4R endocytosis and IL-4/STAT6 activation. These findings may guide the development of macrophage-targeted treatments.

Concurrent presence of diabetes affects the GLUT3 programming of glucose metabolism in glioblastoma.

OBJECTIVE: Diabetes mellitus (DM)-mediated impaired glucose metabolism increase in the glioblastoma (GB) risk by inducing hyperglycemia and hyperinsulinemia. An integral membrane transport protein, glucose transporter 3 (GLUT3) facilitates glucose transport into GB tumor cells. We aimed to explore the regulation of GLUT3 in GB tumors of patients who were concurrently diagnosed with DM. PATIENTS AND METHODS: Formalin-fixed paraffin-embedded (FFPE) tumor samples were collected from 93 GB patients and retrospectively analyzed. Of the total, 15 patients were concurrently diagnosed with DM (GB-DM). The role of GLUT3 in tumor aggressiveness was evaluated by analyzing its correlation with Ki67, P53 expression, MALAT1 expression, and peripheral blood hemoglobin A1C (HbA1c) level. T98G cells were treated with empagliflozin and metformin to modulate GLUT3. The RNA expression of GLUT3, SOX2, and MALAT1 was analyzed by real-time qPCR. The lactate levels of T98G cells were measured by Cobas c502 analyzer. A scratch wound assay was performed to investigate the migration rate of T98G cells. RESULTS: GLUT3 expression was lower in GB-DM tumors than in GB-only tumors. In GB-DM, the expression of tumoral GLUT3 and peripheral blood glycated hemoglobin (HbA1c) levels were negatively correlated with P53 and Ki67. A decreased GLUT3 shortened the disease-free survival duration in GB-DM patients. Empagliflozin reduced GLUT3, while metformin-induced GLUT3 in T98G cells. The empagliflozin-mediated GLUT3 suppression induced SOX2 and MALAT1 expressions and influenced the migration capacity of T98G cells. CONCLUSIONS: Our findings suggest that the low GLUT3 expression of the tumors of GB-DM patients may induce the production of adenosine triphosphate (ATP) from cellular energy sources other than glucose metabolism. However, further studies are warranted to confirm these results.

Correlations between class I glucose transporter expression patterns and clinical outcomes in non-small cell lung cancer.

BACKGROUND: Glucose transporters (GLUTs) are highly expressed in various cancers. However, the implications of these variable expression patterns are unclear. This study aimed to clarify the correlation between class I GLUT expression patterns and clinical outcomes in non-small cell lung cancer (NSCLC), including their potential role in inflammatory signaling. METHODS: Biopsy tissues from 132 patients with NSCLC (92 adenocarcinomas [ADC] and 40 squamous cell carcinomas [SQCC]) were analyzed. mRNA expression levels of class I GLUTs (solute carrier 2A [SLC2A]1, SLC2A2, SLC2A3, and SLC2A4) and inflammation-related molecules (toll-like receptors TLR4, RelA/p65, and interleukins IL8 and IL6) were measured. Cellular localization of GLUT3 and GLUT4 was investigated using immunofluorescence. RESULTS: Single, combined, and negative GLUT (SLC2A) expression were observed in 27/92 (29.3%), 27/92 (29.3%), and 38/92 (41.3%, p < 0.001) of ADC and 8/40 (20.0%), 29/40 (72.5%, p < 0.001), and 3/40 (7.5%) of SQCC, respectively. In ADC, the single SLC2A3-expressed group had a significantly poorer prognosis, whereas the single SLC2A4-expressed group had a significantly better prognosis. The combined expression groups showed no significant difference. SLC2A expression was not correlated with SQCC prognosis. SLC2A4 expression correlated with lower IL8 expression. GLUT3 and GLUT4 expressions were localized in the tumor cytoplasm. CONCLUSIONS: In lung ADC, single SLC2A3 expression correlated with poor prognosis, whereas single SLC2A4 expression correlated with better prognosis and lower IL8 expression. GLUT3 expression, which is increased by IL8 overexpression, may be suppressed by increasing the expression of GLUT4 through decreased IL8 expression.

The effect of Apigenin on glycometabolism and cell death in an anaplastic thyroid cancer cell line.

AIMS AND BACKGROUND: A more pronounced characteristic of cancer cells is the energy dependence on glucose, which mitigated by glucose transporters. The comprehension of the regulatory mechanisms behind the Warburg effect holds promise for developing therapeutic interventions for cancers. Studies are lacking which targeted the GLUTs for treatment of malignancy of thyroid tumors. In our current investigation, we have undertaken this study to determine the potential of Apigenin, plant derived flavonoid in modulating tumor apoptosis by targeting GLUTs expression in SW1736 cell line of anaplastic thyroid carcinoma. MATERIAL METHODS: Flow cytometry with propidium iodide staining was used to determine cell apoptosis. For glucose uptake detection, the "GOD-PAP" enzymatic colorimetric test was used to measure the direct glucose levels inside the cells. To determine the expression of GLUT1 and GLUT3 mRNA in the SW1736 cell line qRT-PCR was employed. Protein levels of GLUT1 and GLUT3 in the SW1736 cell line were detected with western blotting. Also, the scratch wound healing assay was conducted for cell migration. RESULTS: According to qRT-PCR analysis, the levels of GLUT1 and GLUT3 mRNA were lower in the group that received Apigenin relative to the control group. The Apigenin treatment of SW1736 cells decreased protein expression of the GLUT1 and GLUT3 levels in conformity to qRT-PCR. The scratch assays revealed that Apigenin treatment of cancer cell lines inhibited cell migration as compared to control. CONCLUSION: These findings demonstrate the possibility of targeting the glucose facilitators' pathway for making thyroid cancer cells more susceptible to programmed cell death.

Establishing mammalian GLUT kinetics and lipid composition influences in a reconstituted-liposome system.

Glucose transporters (GLUTs) are essential for organism-wide glucose homeostasis in mammals, and their dysfunction is associated with numerous diseases, such as diabetes and cancer. Despite structural advances, transport assays using purified GLUTs have proven to be difficult to implement, hampering deeper mechanistic insights. Here, we have optimized a transport assay in liposomes for the fructose-specific isoform GLUT5. By combining lipidomic analysis with native MS and thermal-shift assays, we replicate the GLUT5 transport activities seen in crude lipids using a small number of synthetic lipids. We conclude that GLUT5 is only active under a specific range of membrane fluidity, and that human GLUT1-4 prefers a similar lipid composition to GLUT5. Although GLUT3 is designated as the high-affinity glucose transporter, in vitro D-glucose kinetics demonstrates that GLUT1 and GLUT3 actually have a similar KM, but GLUT3 has a higher turnover. Interestingly, GLUT4 has a high KM for D-glucose and yet a very slow turnover, which may have evolved to ensure uptake regulation by insulin-dependent trafficking. Overall, we outline a much-needed transport assay for measuring GLUT kinetics and our analysis implies that high-levels of free fatty acid in membranes, as found in those suffering from metabolic disorders, could directly impair glucose uptake.

Enforcing GLUT3 expression in CD8+ T cells improves fitness and tumor control by promoting glucose uptake and energy storage.

Despite the tremendous success of adoptive T-cell therapies (ACT) in fighting certain hematologic malignancies, not all patients respond, a proportion experience relapse, and effective ACT of most solid tumors remains elusive. In order to improve responses to ACT suppressive barriers in the solid tumor microenvironment (TME) including insufficient nutrient availability must be overcome. Here we explored how enforced expression of the high-affinity glucose transporter GLUT3 impacted tumor-directed T cells. Overexpression of GLUT3 in primary murine CD8+ T cells enhanced glucose uptake and increased glycogen and fatty acid storage, and was associated with increased mitochondrial fitness, reduced ROS levels, higher abundance of the anti-apoptotic protein Mcl-1, and better resistance to stress. Importantly, GLUT3-OT1 T cells conferred superior control of B16-OVA melanoma tumors and, in this same model, significantly improved survival. Moreover, a proportion of treated mice were cured and protected from re-challenge, indicative of long-term T cell persistence and memory formation. Enforcing expression of GLUT3 is thus a promising strategy to improve metabolic fitness and sustaining CD8+ T cell effector function in the context of ACT.

Comprehensive Analysis of the Role of SLC2A3 on Prognosis and Immune Infiltration in Head and Neck Squamous Cell Carcinoma.

Background: SLC2A3 is upregulated in various cancer types and promotes proliferation, invasion, and metabolism. However, its role in the prognosis and immune regulation of head and neck squamous cell carcinoma (HNSCC) is still obscure. This study is aimed at exploring the prognostic and immunotherapeutic potential of SLC2A3 in HNSCC. Methods: All data were downloaded from TCGA database and integrated via R software. SLC2A3 expression was evaluated using R software, TIMER, CPTAC, and HPA databases. The association between SLC2A3 expression and clinicopathologic characteristics was assessed by R software. The effect of SLC2A3 on survival was analyzed by R software and Kaplan-Meier Plotter. Genomic alterations in SLC2A3 were investigated using the cBioPortal database. Coexpression of SLC2A3 was studied using LinkedOmics and STRING, and enrichment analyses were performed with R software. The relationship between SLC2A3 expression and immune infiltration was determined using TIMER and TISIDB databases. Immune checkpoints and ESTIMATE score were analyzed via the SangerBox database. Results: SLC2A3 expression was upregulated in HNSCC tissues compared to normal tissues. It was significantly related to TNM stage, histological grade, and alcohol history. High SLC2A3 expression was associated with poor prognosis in HNSCC. Coexpression analysis indicated that SLC2A3 mostly participated in the HIF-1 signaling pathway and glycolysis. Furthermore, SLC2A3 expression strongly correlated with tumor-infiltrating lymphocytes in HNSCC. Conclusion: SLC2A3 could serve as a potential prognostic biomarker for tumor immune infiltration in HNSCC.

Impact of Placental SLC2A3 Deficiency during the First-Half of Gestation.

In the ruminant placenta, glucose uptake and transfer are mediated by facilitative glucose transporters SLC2A1 (GLUT1) and SLC2A3 (GLUT3). SLC2A1 is located on the basolateral trophoblast membrane, whereas SLC2A3 is located solely on the maternal-facing, apical trophoblast membrane. While SLC2A3 is less abundant than SLC2A1, SLC2A3 has a five-fold greater affinity and transport capacity. Based on its location, SLC2A3 likely plays a significant role in the uptake of glucose into the trophoblast. Fetal hypoglycemia is a hallmark of fetal growth restriction (FGR), and as such, any deficiency in SLC2A3 could impact trophoblast glucose uptake and transfer to the fetus, thus potentially setting the stage for FGR. By utilizing in vivo placenta-specific lentiviral-mediated RNA interference (RNAi) in sheep, we were able to significantly diminish (p ≤ 0.05) placental SLC2A3 concentration, and determine the impact at mid-gestation (75 dGA). In response to SLC2A3 RNAi (n = 6), the fetuses were hypoglycemic (p ≤ 0.05), exhibited reduced fetal growth, including reduced fetal pancreas weight (p ≤ 0.05), which was associated with reduced umbilical artery insulin and glucagon concentrations, when compared to the non-targeting sequence (NTS) RNAi controls (n = 6). By contrast, fetal liver weights were not impacted, nor were umbilical artery concentrations of IGF1, possibly resulting from a 70% increase (p ≤ 0.05) in umbilical vein chorionic somatomammotropin (CSH) concentrations. Thus, during the first half of gestation, a deficiency in SLC2A3 results in fetal hypoglycemia, reduced fetal development, and altered metabolic hormone concentrations. These results suggest that SLC2A3 may be the rate-limiting placental glucose transporter during the first-half of gestation in sheep.

Transcriptional regulation of glucose transporters in human oral squamous cell carcinoma cells.

The increased glucose uptake observed in cancer cells is mediated by glucose transporters (GLUTs), a class of transmembrane proteins that facilitate the transport of glucose and other substrates across the plasma membrane. Despite the important role of glucose in the pathophysiology of oral squamous cell carcinoma (OSCC), there is very limited data regarding the expression of GLUTs in normal or malignant cells from the oral mucosa. We analysed the messenger RNA (mRNA) expression of all 14 GLUTs in two OSCC (H357/H400) and one non-malignant oral keratinocyte (OKF6) cell line using a quantitative polymerase chain reaction. GLUT expression was evaluated at baseline and after treatment with two specific GLUT inhibitors, namely, BAY876 (GLUT1) and WZB117 (GLUT1, GLUT3 and GLUT4). Here, we show that GLUT1, GLUT3, GLUT4, GLUT5, GLUT6, GLUT8, GLUT12 and GLUT13 transcripts were measurably expressed in all cell lines while GLUT2, GLUT7, GLUT9, GLUT11 and GLUT14 were not expressed. GLUT10 was only found in H357. In the presence of BAY876 and WZB117, OSCC cells exhibited significant alterations in the transcriptional profile of GLUTs. In particular, we observed distinct proliferation-dependent changes of mRNAs to GLUT1, GLUT3, GLUT4, GLUT5 and GLUT6 in response to selective GLUT inhibitors. In summary, we documented for the first time the expression of GLUT5, GLUT6 and GLUT12 in normal and malignant oral keratinocytes. Whilst regulation of GLUT transcripts was cell line and inhibitor specific, GLUT3 was consistently upregulated in actively proliferating OSCC cell lines, but not in OKF6, regardless of the inhibitor used, suggesting that modulation of this transporter may act as one of the primary compensation mechanisms for OSCC cells upon inhibition of glucose uptake.

Differential role of neuronal glucose and PFKFB3 in memory formation during development.

The consumption of glucose in the brain peaks during late childhood; yet, whether and how glucose metabolism is differentially regulated in the brain during childhood compared to adulthood remains to be understood. In particular, it remains to be determined how glucose metabolism is involved in behavioral activations such as learning. Here we show that, compared to adult, the juvenile rat hippocampus has significantly higher mRNA levels of several glucose metabolism enzymes belonging to all glucose metabolism pathways, as well as higher levels of the monocarboxylate transporters MCT1 and MCT4 and the glucose transporters endothelial-GLUT1 and GLUT3 proteins. Furthermore, relative to adults, long-term episodic memory formation in juvenile animals requires significantly higher rates of aerobic glycolysis and astrocytic-neuronal lactate coupling in the hippocampus. Only juvenile but not adult long-term memory formation recruits GLUT3, neuronal 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) and more efficiently engages glucose in the hippocampus. Hence, compared to adult, the juvenile hippocampus distinctively regulates glucose metabolism pathways, and formation of long-term memory in juveniles involves differential neuronal glucose metabolism mechanisms.