Value of glucose transport protein 1 expression in detecting lymph node metastasis in patients with colorectal cancer

BACKGROUND There are limited data on the use of glucose transport protein 1(GLUT-1)expre-ssion as a biomarker for predicting lymph node metastasis in patients with colorectal cancer.GLUT-1 and GLUT-3,hexokinase(HK)-II,and hypoxia-induced factor(HIF)-1 expressions may be useful biomarkers for detecting primary tumors and lymph node metastasis when combined with fluorodeoxyglucose(FDG)uptake on positron emission tomography/computed tomography(PET/CT).AIM To evaluate GLUT-1,GLUT-3,HK-II,and HIF-1 expressions as biomarkers for detecting primary tumors and lymph node metastasis with 18F-FDG-PET/CT.METHODS This retrospective study included 169 patients with colorectal cancer who underwent colectomy and preoperative 18F-FDG-PET/CT at Chungbuk National University Hospital between January 2009 and May 2012.Two tissue cores from the central and peripheral areas of the tumors were obtained and were examined by a dedicated pathologist,and the expressions of GLUT-1,GLUT-3,HK-II,and HIF-1 were determined using immunohisto-chemical staining.We analyzed the correlations among their expressions,various clinicopathological factors,and the maximum standardized uptake value(SUVmax)of PET/CT.RESULTS GLUT-1 was found at the center or periphery of the tumors in 109(64.5%)of the 169 patients.GLUT-1 positivity was significantly correlated with the SUVmax of the primary tumor and lymph nodes,regardless of the biopsy site(tumor center,P<0.001 and P=0.012;tumor periphery,P=0.030 and P=0.010,respectively).GLUT-1 positivity and negativity were associated with higher and lower sensitivities of PET/CT,respectively,for the detection of lymph node metastasis,regardless of the biopsy site.GLUT3,HK-II,and HIF-1 expressions were not significantly correlated with the SUVmax of the primary tumor and lymph nodes.CONCLUSION GLUT-1 expression was significantly correlated with the SUVmax of 18F-FDG-PET/CT for primary tumors and lymph nodes.Clinicians should consider GLUT-1 expression in preoperative endoscopic biopsy in interpreting PET/CT findings.

Icariin ameliorates memory deficits through regulating brain insulin signaling and glucose transporters in 3×Tg-AD mice

Icariin,a major prenylated flavonoid found in Epimedium spp.,is a bioactive constituent of Herba Epimedii and has been shown to exert neuroprotective effects in experimental models of Alzheimer’s disease.In this study,we investigated the neuroprotective mechanism of icariin in an APP/PS1/Tau triple-transgenic mouse model of Alzheimer’s disease.We performed behavioral tests,pathological examination,and western blot assay,and found that memory deficits of the model mice were obviously improved,neuronal and synaptic damage in the cerebral cortex was substantially mitigated,and amyloid-βaccumulation and tau hyperphosphorylation were considerably reduced after 5 months of intragastric administration of icariin at a dose of 60 mg/kg body weight per day.Furthermore,deficits of proteins in the insulin signaling pathway and their phosphorylation levels were significantly reversed,including the insulin receptor,insulin receptor substrate 1,phosphatidylinositol-3-kinase,protein kinase B,and glycogen synthase kinase 3β,and the levels of glucose transporter 1 and 3 were markedly increased.These findings suggest that icariin can improve learning and memory impairments in the mouse model of Alzheimer’s disease by regulating brain insulin signaling and glucose transporters,which lays the foundation for potential clinical application of icariin in the prevention and treatment of Alzheimer’s disease.

Relationship Between Serum microRNA-372-3p and Glucose Transporter 4 Levels and Insulin Resistance in Gestational Diabetes Mellitus

Objective:To observe the changes in insulin resistance in patients with gestational diabetes mellitus(GDM)based on the detection of serum microRNA-372-3p and glucose transporter protein 4(GLUT4)levels.Methods:We conducted a retrospective cohort study of 42 patients who were diagnosed with GDM and hospitalized in our hospital during the period from January 2017 to December 2021 and another 42 patients who had normal pregnancy during the same period by collecting their clinical data.We analyzed their serum microRNA expression profiles and miR-372-3p levels to study the relationship between GDM and insulin resistance.Results:The relative expression of miR-372-3p in the serum of patients in the GDM group was significantly higher than that of patients in the control group,but the GLUT 4 level of the GDM group was significantly lower than that of the control group(P<0.05).Compared with the control group,the GDM group had significantly higher levels of fasting blood glucose(FBG),fasting insulin(FINS),2-hour postprandial blood glucose(2h-BG),total cholesterol(TC),triglyceride(TG),and homeostatic model assessment for insulin resistance(HOMA-IR)index but significantly lower homeostasis model assessment ofβ-cell function(HOMA-β)index(P<0.05).The relative expression of miR-372-3p in serum was independently and positively correlated with HOMA-IR,while the level of GLUT4 was independently and negatively correlated with HOMA-IR(P<0.05).Conclusion:Glycosylated hemoglobin test in the early stages of pregnancy(12–13 weeks of gestation)is important to ensure the health of pregnant women and fetuses.The screening and intervention for elevated glucose in pregnant women act as a guideline for the treatment of GDM.Patients with insulin resistance and related complications such as hyperinsulinemia and hypoglycemia should be given priority.

Effects of electroacupuncture on microcirculatory blood flow and glucose transporter function in the hippocampus

Nerve cell metabolism in post brain ischemia depends on increased microcirculation perfusion and transport function of microvascular endothelial cells. In the present study, a rat model of middle cerebral artery occlusion was established to investigate the influence of electroacupuncture （EA） on hippocampal CA1 cerebral blood flow and glucose transporter 1 （GLUT1） expression in the microvascular endothelial cells. Following EA at Neiguan （PC 6）, the cerebral blood flow in the ischemic hippocampal CA1 region was significantly elevated, the number and microvascular integrated absorbance of the GLUTl-positive cells were significantly increased, nerve cell damage was ameliorated, and GLUT1 protein expression in the ischemic hippocampus was significantly increased. Results demonstrate that EA increased the cerebral blood flow of the hippocampal CA1 region and improved the glucose transport function, thereby attenuating neuronal injuries.

Transforming growth factor beta-1 upregulates glucose transporter 1 and glycolysis through canonical and noncanonical pathways in hepatic stellate cells

BACKGROUND Hepatic stellate cells(HSCs)are the key effector cells mediating the occurrence and development of liver fibrosis,while aerobic glycolysis is an important metabolic characteristic of HSC activation.Transforming growth factor-β1(TGF-β1)induces aerobic glycolysis and is a driving factor for metabolic reprogramming.The occurrence of glycolysis depends on a high glucose uptake level.Glucose transporter 1(GLUT1)is the most widely distributed glucose transporter in the body and mainly participates in the regulation of carbohydrate metabolism,thus affecting cell proliferation and growth.However,little is known about the relationship between TGF-β1 and GLUT1 in the process of liver fibrosis and the molecular mechanism underlying the promotion of aerobic glycolysis in HSCs.AIM To investigate the mechanisms of action of GLUT1,TGF-β1 and aerobic glycolysis in the process of HSC activation during liver fibrosis.METHODS Immunohistochemical staining and immunofluorescence assays were used to examine GLUT1 expression in fibrotic liver tissue.A Seahorse extracellular flux(XF)analyzer was used to examine changes in aerobic glycolytic flux,lactate production levels and glucose consumption levels in HSCs upon TGF-β1 stimulation.The mechanism by which TGF-β1 induces GLUT1 protein expression in HSCs was further explored by inhibiting/promoting the TGF-β1/mothersagainst-decapentaplegic-homolog 2/3(Smad2/3)signaling pathway and inhibiting the p38 and phosphoinositide 3-kinase(PI3K)/AKT signaling pathways.In addition,GLUT1 expression was silenced to observe changes in the growth and proliferation of HSCs.Finally,a GLUT1 inhibitor was used to verify the in vivo effects of GLUT1 on a mouse model of liver fibrosis.RESULTS GLUT1 protein expression was increased in both mouse and human fibrotic liver tissues.In addition,immunofluorescence staining revealed colocalization of GLUT1 and alpha-smooth muscle actin proteins,indicating that GLUT1 expression was related to the development of liver fibrosis.TGF-β1 caused an increase in aerobic glycolysis in HSCs and induced GLUT1 expression in HSCs by activating the Smad,p38 MAPK and P13K/AKT signaling pathways.The p38 MAPK and Smad pathways synergistically affected the induction of GLUT1 expression.GLUT1 inhibition eliminated the effect of TGF-β1 on HSC proliferation and migration.A GLUT1 inhibitor was administered in a mouse model of liver fibrosis,and GLUT1 inhibition reduced the degree of liver inflammation and liver fibrosis.CONCLUSION TGF-β1 induces GLUT1 expression in HSCs,a process related to liver fibrosis progression.In vitro experiments revealed that TGF-β1-induced GLUT1 expression might be one of the mechanisms mediating the metabolic reprogramming of HSCs.In addition,in vivo experiments also indicated that the GLUT1 protein promotes the occurrence and development of liver fibrosis.

Transcriptional activation of glucose transporter 1 in orthodontic tooth movement-associated mechanical response

The interplay between mechanoresponses and a broad range of fundamental biological processes, such as cell cycle progression,growth and differentiation, has been extensively investigated. However, metabolic regulation in mechanobiology remains largely unexplored. Here, we identified glucose transporter 1(GLUT1)—the primary glucose transporter in various cells—as a novel mechanosensitive gene in orthodontic tooth movement(OTM). Using an in vivo rat OTM model, we demonstrated the specific induction of Glut1 proteins on the compressive side of a physically strained periodontal ligament. This transcriptional activation could be recapitulated in in vitro cultured human periodontal ligament cells(PDLCs), showing a time-and dose-dependent mechanoresponse. Importantly, application of GLUT1 specific inhibitor WZB117 greatly suppressed the efficiency of orthodontic tooth movement in a mouse OTM model, and this reduction was associated with a decline in osteoclastic activities. A mechanistic study suggested that GLUT1 inhibition affected the receptor activator for nuclear factor-κ B Ligand(RANKL)/osteoprotegerin(OPG)system by impairing compressive force-mediated RANKL upregulation. Consistently, pretreatment of PDLCs with WZB117 severely impeded the osteoclastic differentiation of co-cultured RAW264.7 cells. Further biochemical analysis indicated mutual regulation between GLUT1 and the MEK/ERK cascade to relay potential communication between glucose uptake and mechanical stress response. Together, these cross-species experiments revealed the transcriptional activation of GLUT1 as a novel and conserved linkage between metabolism and bone remodelling.

Current understanding of glucose transporter 4 expression and functional mechanisms

Glucose is used aerobically and anaerobically to generate energy for cells.Glucose transporters(GLUTs)are transmembrane proteins that transport glucose across the cell membrane.Insulin promotes glucose utilization in part through promoting glucose entry into the skeletal and adipose tissues.This has been thought to be achieved through insulin-induced GLUT4 translocation from intracellular compartments to the cell membrane,which increases the overall rate of glucose flux into a cell.The insulin-induced GLUT4 translocation has been investigated extensively.Recently,significant progress has been made in our understanding of GLUT4 expression and translocation.Here,we summarized the methods and reagents used to determine the expression levels of Slc2a4 mRNA and GLUT4 protein,and GLUT4 translocation in the skeletal muscle,adipose tissues,heart and brain.Overall,a variety of methods such real-time polymerase chain reaction,immunohistochemistry,fluorescence microscopy,fusion proteins,stable cell line and transgenic animals have been used to answer particular questions related to GLUT4 system and insulin action.It seems that insulininduced GLUT4 translocation can be observed in the heart and brain in addition to the skeletal muscle and adipocytes.Hormones other than insulin can induce GLUT4 translocation.Clearly,more studies of GLUT4 are warranted in the future to advance of our understanding of glucose homeostasis.

Uses of knockout,knockdown,and transgenic models in the studies of glucose transporter 4

Currently,glucose transporter 4(GLUT4)has been considered as the key player for the insulin-stimulated glucose transport in the muscle and adipose tissues.The development of recombinant DNA techniques allows the creations of genetically knockout,knockdown and transgenic animals and cells for the study of GLUT4’s physiological functions.Here,we have used key words to search the PubMed and summarized the methods used in Slc2a4 gene knockout,GLUT4 knockdown and overexpression in the whole body and tissue specific manner.The whole body GLUT4-null mice have growth retardation,but normal glucose tolerance and basal glucose turnover rates.Compared with whole body Slc2a4 knockout mice,adipose and muscle double knockout mice have impaired insulin tolerance and glucose intolerance.The results of GLUT4 knockdown in 3T3-L1 adipocytes have shown that its expression is needed for lipogenesis after,but not during,differentiation.Transgenic mice with the whole body GLUT4 overexpression have normal body weight and lowered blood glucose level.The adipose tissue specific overexpression of GLUT4 leads to increases in mouse body weight and adipose tissue weight.The insulin-stimulated GLUT4 translocation in the skeletal muscle contributes to the regulation of glucose homeostasis.Data from both transgenic overexpression and tissue specific Slc2a4 knockout indicate that GLUT4 probably plays a role in the glucose uptake in the fasting state.More studies are warranted to use advanced molecular biology tools to decipher the roles of GLUT4 in the control of glucose homeostasis.

An Optimum Dose of Olive Leaf Extract Improves Insulin Receptor Substrate-1,Tyrosine Kinase,and Glucose Transporters,While High Doses Have Genotoxic and Apoptotic Effects

Type 2 diabetes is the most common type of diabetes. Conventionally many drugs are used for the treatment of diabetes such as biguanides, sulfonylureas, meglitinides, etc. But the desired effective treatment is still not to be achieved. So researches are going on for the development of effective alternative therapy against diabetes. Olive leaves are traditionally used in the treatment of the disease. However, studies on its mechanism of action are not yet enough. The aim of this study was to investigate whether olive leaf extract (OLE) improves insulin receptor substrate-1 (IRS-1), tyrosine kinase (TK), GLUT-2, and GLUT-4. Oleuropein levels were analyzed from OLE obtained by using four different solvents, and the highest content of methanol extract was selected for the study. Different concentrations of OLE (2.5 to 320 μg/mL) were incubated with hepatocellular carcinoma (HepG2) cells for 24 hours. After incubation, cell viability was assessed based on luminometric ATP cell viability assay kit. Intracellular reactive oxygen species (ROS) generating level was detected using 2,7dichlorodihydrofluorescein-diacetate (H2DCF-DA) fluorescent probes. Apoptosis was evaluated by acridine orange/ethidium bromide double staining method. Genotoxicity was evaluated by alkaline single cell gel electrophoresis assay (Comet Assay). Protein expression levels of IRS-1, TK, GLUT-2, and GLUT-4 were analyzed by western blotting technique from the obtained cell lysates. Although an optimum doses of OLE (10 μg/mL) maximally increased cell proliferation, decreased ROS generation improved IRS-1, TK, GLUT-2, and GLUT-4 protein expression levels (about fivefold), higher doses (10 to 320 μg/mL) markedly decreased the cell viability, increased DNA damage, apoptosis and ROS generation in a concentration-dependent manner. OLE can be used in the treatment of type 2 diabetes. However, in order to find the most effective and non-toxic concentration, dose optimization is required.

BcSDR1 is involved in regulation of glucose transport and cAMP and MAPK signaling pathways in Botrytis cinerea

Botrytis cinerea is a typical necrotrophic pathogenic fungus that causes severe diseases in a wide range of plant species, leading to significant economic losses. Our previous study showed that BcSDR1 positively regulates growth,development, and pathogenicity of B. cinerea. However, the regulation mechanism of BcSDR1 and the relationship between BcSDR1 and cAMP and MAPK signaling pathways are not well understood. In this study, transcriptome data showed that BcSDR1 is involved in glucose transmembrane transport, signal transduction, secondary metabolism, and other biological processes. BcSDR1 mutant(BCt41) showed remarkably weak sensitivity to cAMP and MAPK signaling pathways specific inhibitors, SQ22536 and U0126, and significantly decreased cAMP content. The key genes of cAMP and MAPK signaling pathways, BcGB1, BcBTP1, BcBOS1, BcRAS1, and BcBMP3 were significantly upregulated,whereas BcPLC1, BcBCG1, BcCDC4, BcSAK1, BcATF1, and BcBAP1 were significantly downregulated(P<0.05).BcSDR1 was obviously upregulated in BcBCG2, BcBCG3, BcPKA1, and BcPKAR RNA interference(RNAi) mutants, but significantly downregulated in BcPKA2, BcBMP1, and BcBMP3 RNAi mutants. Thus, BcBCG2, BcBCG3, BcPKA1, and BcPKAR negatively regulate BcSDR1 expression, whereas BcPKA2, BcBMP1, and BcBMP3 positively regulate BcSDR1expression.

Role of melatonin receptor 1B gene polymorphism and its effect on the regulation of glucose transport in gestational diabetes mellitus

Melatonin receptor 1B(MT2,encoded by the MTNR1B gene),a high-affinity receptor for melatonin,is associated with glucose homeostasis including glucose uptake and transport.The rs10830963 variant in the MTNR1B gene is linked to glucose metabolism disorders including gestational diabetes mellitus(GDM);however,the relationship between MT2-mediated melatonin signaling and a high birth weight of GDM infants from maternal glucose abnormality remains poorly understood.This article aims to investigate the relationship between rs10830963 variants and GDM development,as well as the effects of MT2 receptor on glucose uptake and transport in trophoblasts.TaqMan-MGB(minor groove binder)probe quantitative realtime polymerase chain reaction(qPCR)assays were used for rs10930963 genotyping.MT2 expression in the placenta of GDM and normal pregnant women was detected by immunofluorescence,western blot,and qPCR.The relationship between MT2 and glucose transporters(GLUTs)or peroxisome proliferator-activated receptorγ(PPARγ)was established by western blot,and glucose consumption of trophoblasts was measured by a glucose assay kit.The results showed that the genotype and allele frequencies of rs10830963 were significantly different between GDM and normal pregnant women(P<0.05).The fasting,1-h and 2-h plasma glucose levels of G-allele carriers were significantly higher than those of C-allele carriers(P<0.05).Besides,the protein and messenger RNA(mRNA)expression of MT2 in the placenta of GDM was significantly higher than that of normal pregnant women(P<0.05).Melatonin could stimulate glucose uptake and GLUT4 and PPARγprotein expression in trophoblasts,which could be attenuated by MT2 receptor knockdown.In conclusion,the rs10830963 variant was associated with an increased risk of GDM.The MT2 receptor is essential for melatonin to raise glucose uptake and transport,which may be mediated by PPARγ.

Chronic intermittent hypoxia from pedo-stage decreases glucose transporter 4 expression in adipose tissue and causes insulin resistance

Background The persistence of sleep disordered breathing （SDB） symptoms after tonsil and/or adenoid （T＆A） surgery are common in children with obstructive sleep apnea （OSA）. We tested the hypothesis that disturbances of glucose transporters （GLUTs） in intraabdominal adipose tissue caused by chronic intermittent hypoxia （CIH） from the pedo-period could facilitate the appearance of periphery insulin resistance in Sprague-Dawley （SD） rats. We tested the hypothesis that the changes of GLUTs in adipose tissue may be one of the reasons for persistent SDB among clinical OSA children after T＆A surgery. Methods Thirty 21-day-old SD rats were randomly divided into a CIH group, a chronic continuous hypoxia （CCH） group and a normal oxygen group （control group） and exposed for 40 days. The changes of weight, fasting blood glucose and fasting blood insulin levels were measured. Hyperinsulinemic-euglycemic clamp techniques were used to measure insulin resistance in each animal. Real-time quantitative PCR and Western blotting were used to measure GLUT mRNA and proteins in intraabdominal adipose tissue. Additional intraabdomial white adipose tissue （WAT） was also processed into paraffin sections and directly observed for GLUTs1-4 expression. Results When compared with control group, CIH increased blood fasting insulin levels, （245.07±53.89） pg/ml vs. （168.63±38.70） pg/ml, P=-0.038, and decreased the mean glucose infusion rate （GIR）, （7.25±1.29） mg·kg^-1·min^-1 vs. （13.34±1.54） mg·kg^-1·min^-1, P 〈0.001. GLUT-4 mRNA and protein expression was significantly reduced after CIH compared with CCH or normal oxygen rats, 0.002±0.002 vs. 0.039±0.009, P 〈0.001; 0.642±0.073 vs. 1.000±0.103, P=0.035. Conclusions CIH in young rats could induce insulin resistance via adverse effects on glycometabolism. These findings emphasize the importance of early detection and treatment of insulin insensitivity in obese childhood OSA.

Influence of blood glucose on the expression of glucose transporter proteins 1 and 3 in the brain of diabetic rats

Background The delivery of glucose from the blood to the brain involves its passage across the endothelial cells of the blood-brain barrier （BBB）, which is mediated by the facilitative glucose transporter protein 1 （GLUT1）, end then across the neural cell membranes, which is mediated by GLUT3. This study aimed to evaluate the dynamic influence of hyperglycemia on the expression of these GLUTs by measuring their expression in the brain at different blood glucose levels in e rat model of diabetes. This might help to determine the proper blood glucose threshold level in the treatment of diabetic apoplexy. Methods Diabetes mellitus was induced with streptozotocin （STZ） in 30 rats. The rats were randomly divided into 3 groups： diabetic group without blood glucose control （group DM1）, diabetic rats treated with low dose insulin （group DM2） end diabetic rats treated with high dose insulin （group DM3）. The mRNA end protein levels of GLUT1 end GLUT3 were essayed by reverse trenscriptese-polymerese chain reaction （RT-PCR） end immunohistochemistry, respectively. Results Compared with normal control rats, the G/UT1 mRNA was reduced by 46.08%, 29.80%, 19.22% （P〈0.01） in DM1, DM2, end DM3 group, respectively; end the GLUT3 mRNA was reduced by 75.00%, 46.75%, end 17.89% （P〈0.01） in DM1, DM2, end DM3 group, respectively. The abundance of GLUT1 end GLUT3 proteins had negative correlation with the blood glucose level （P〈0.01）. The density of microvessels in the brain of diabetic rats did not change significantly compared with normal rats. Conclusions Chronic hyperglycemia downreguletes G/UT1 end GLUT3 expression at both mRNA end protein levels in the rat brain, which is not due to the decrease of the density of microvessels. The downreguletion of G/UT1 end GLUT3 expression might be the adaptive reaction of the body to prevent excessive glucose entering the cell that may lead to cell damage.

Compound Tufuling Granules (复方土茯苓颗粒) Regulate Glucose Transporter 9 Expression in Kidney to Influence Serum Uric Acid Level in Hyperuricemia Mice

Objective： To explore the effect of Compound Tufuling Granules （复方土茯苓颗粒, CTG） on regulating glucose transporter 9 （GLUT9） expression in the kidney to influence the uric acid excretion by the kidney and serum uric acid （SUA） level in hyperuricemia mice. Methods： Sixty Kunming male mice were randomly divided into the control group, model group, benzbromarone group, and CTG high-, middle- and low- dose groups. The yeast extract and uricase inhibition method were used to build hyperuricemia model, and the corresponding drugs were administrated on the 7th day. On the 21st day the 24-h urine was collected, on the 22rid day the blood was collected, the SUA level was detected by uricase colorimetry, and the mRNA and protein expressions of GLUT9 were detected by quantitative real-time polymerase chain reaction and Western blot, respectively. Results： Compared with the model group, the levels of SUA and the mRNA and protein expressions of GLUT9 were significantly decreased, and the fraction excretion of uric acid （FEUA） was significantly increased in the CTG groups and benzbromarone group （all P〈0.05）. There was no significant difference in the above indicators between the CTG high-dose group and benzbromarone group （P〉0.05）. SUA is positively related to the GLUT9 mRNA and protein expressions in the kidney （P〈0.05 or P〈0.01）. Conclusions： CTG can significantly reduce the SUA and increase the FEUA. In addition, CTG can effectively inhibit the mRNA and protein expressions of GLUT9 in the kidney of hyperuricemia mice to inhibit the uric acid re-absorption, promote uric acid excretion and reduce SUA.

Dynamic expression of glucose transporters 1 and 3 in the brain of diabetic rats with cerebral ischemia reperfusion

Background Blood glucose control improves the outcome of diabetic patients with stroke, but the target range of blood glucose control remains controversial. The functional recruitment of ischemia penumbra is extremely important to the recovery after stroke. The present study aimed to explore the expression of brain-type glucose transporters （GLUT1 and GLUT3） in cerebral ischemic penumbra at different blood glucose levels and different ischemic-reperfusion time in diabetic hypoxia-ischemia rats. The results might provide an experimental basis for clinical treatment of diabetic patients with stroke. Methods The Wistar rats included in this study were randomly assigned to 4 groups （50 rats each）： normal control group （NC）, uncontrolled diabetic group （DM1）, poorly-controlled diabetic group （DM2）, and well-controlled diabetic group （DM3）. Diabetic rats were induced by single intraperitoneal injection of streptozotocin, and the focal ischemic rat model of middle artery occlusion （MCAO） was made by insertion of fishing thread in 6 weeks after the establishment of the diabetic model. Each group was divided into 5 subgroups （10 rats each）： four focal ischemic subgroups at different ischemic-reperfusion time （at 3,12, 24 and 72 hours after reperfusion, respectively） and one sham-operated subgroup. The mRNA and protein expression of GLUT1 and GLUT3 was assessed by RT-PCR and Western blotting, respectively. Results There was significant difference in the mRNA expression of GLUT1 and GLUT3 between the four focal ischemic subgroups and the sham-operated subgroup at different reperfusion time in each group. The mRNA expression of GLUT1 and GLUT3 in the 4 ischemic groups began to increase at 3 hours, peaked at 24 hours after reperfusion and maintained at a higher level even at 72 hours compared with that of the sham-operated subgroup. The mRNA expression of GLUT1 increased more significantly than that of GLUT3. The mRNA expression of GLUT1 and GLUT3 was significantly different between the diabetic groups and normal control group. The mRNA expression of GLUT1 and GLUT3 was increased more significantty in the diabetic groups than that in the normal control group. There was a significant difference in the mRNA expression in the groups with different blood glucose levels. The mRNA expression tended to decrease with increased blood glucose levels. The expression trend of GLUT1 and GLUT3 protein was similar to that of GLUT1 and GLUT3 mRNA. Conclusions GLUT1 and GLUT3 expression was notably up-regulated in the penumbra region after cerebral ischemia in this study. But the up-regulated amplitude of GLUT1 and GLUT3 in the diabetic rats with cerebral ischemic injury became smaller than that of the normal controls. In the treatment of diabetic patients with cerebral embolism, blood glucose control should not be too strict, otherwise the up-regulation of GLUT1 and GLUT3 induced by cerebral ischemic injury might not be able to meet the needs of energy metabolism in cells. Chin Med J 2009; 122（ 17）： 1996-2001

Effect of Huanglian Jiedu Decoction (黄连解毒汤) on Glucose Transporter 4 Expression in Adipose and Skeletal Muscle Tissues of Insulin Resistant Rats

Objective： To investigate the effects of Huanglian Jiedu Decoction （黄连解毒汤, HLJDD） on glucose transporter 4 （GLUT4） protein expressions in insulin-resistant murine target tissues. Methods： The experimental male Wistar rats were established into insulin resistant models by injecting streptozotocin （STZ 30 mg/kg） via caudal vein and feeding them with high fat high caloric diet, and randomly divided into the model group, the aspirin group and the HLJDD group. Besides, a normal group was set up for control. Changes of body weight （BW）, levels of serum fasting blood glucose （FBG）, serum fasting insulin （FINS） and oral glucose tolerance test （OGTT） were routinely determined. The expression of GLUT4 protein in adipose and skeletal muscle tissues before and after insulin stimulation was determined with Western blot. Results： In the HLJDD group after treatment, BW and FBG got decreased, OGTT improved, and the expression and translocation of GLUT4 protein elevated obviously, either before or after insulin stimulation, as compared with those in the model group, showing significant differences respectively. Conclusion： The mechanism of improving insulin resistance by HLJDD is probably associated with its effect in elevating GLUT4 protein expression and translocation in adipose and skeletal muscle tissues of insulin resistant rats.

Insulin gene enhancer protein 1 mediates glycolysis and tumorigenesis of gastric cancer through regulating glucose transporter 4

Background:Insulin gene enhancer protein 1,(ISL1),a LIM-homeodomain transcription factor,is involved in multiple tumors and is associated with insulin secretion and metabolic phenotypes.However,the role of ISL1 in stimulating glycolysis to promote tumorigenesis in gastric cancer(GC)is unclear.In this study,we aimed to characterize the expression pattern of ISL1 in GC patients and explore its molecular biological mechanism in glycolysis and tumorigenesis.Methods:We analyzed the expression and clinical significance of ISL1 in GC using immunohistochemistry and real-time polymerase chain reaction(PCR).Flow cytometry and IncuCyte assays were used to measure cell proliferation after ISL1 knockdown.RNA-sequencing was performed to identify differentially expressed genes,followed by Kyoto Encyclopedia of Genes and Genomes(KEGG)analysis and Gene Set Enrichment Analysis(GSEA)to reveal key signaling pathways likely regulated by ISL1 in GC.Alteration of the glycolytic ability of GC cells with ISL1 knockdown was validated by measuring the extracellular acidification rate(ECAR)and oxygen consumption rate(OCR)and by detecting glucose consumption and lactate production.The expression of glucose transporter 4(GLUT4)and ISL1 was assessed by Western blotting,immunohistochemistry,and immunofluorescent microscopy.The luciferase reporter activity and chromatin immunoprecipitation assays were performed to determine the transcriptional regulation of ISL1 on GLUT4.Results:High levels of ISL1 and GLUT4 expression was associated with short survival of GC patients.ISL1 knockdown inhibited cell proliferation both in vitro and in vivo.KEGG analysis and GSEA for RNA-sequencing data indicated impairment of the glycolysis pathway in GC cells with ISL1 knockdown,which was validated by reduced glucose uptake and lactate production,decreased ECAR,and increased OCR.Mechanistic investigation indicated that ISL1 transcriptionally regulated GLUT4 through binding to its promoter.Conclusion:ISL1 facilitates glycolysis and tumorigenesis in GC via the transcriptional regulation of GLUT4.

Involvement of glucose transporter 4 in ovarian development and reproductive maturation of Harmonia axyridis(Coleoptera:Coccinellidae)

Glucose is vital to embryogenesis,as are glucose transporters.Glucose transporter 4(Glut4)is one of the glucose transporters,which is involved in rapid uptake of glucose by various cells and promotes glucose homeostasis.Although energy metabolism in insect reproduction is well known,the molecular mechanism of Glut4 in insect reproduction is poorly understood.We suspect that Glut4 is involved in maintaining glucose concentrations in the ovaries and affecting vitellogenesis,which is critical for subsequent oocyte maturation and insect fertility.Harmonia axyridis(Pallas)is a model organism for genetic research and a natural enemy of insect pests.We studied the influence of the Glut4 gene on the reproduction and development of H.axyridis using RNA interference technology.Reverse transcription quantitative polymerase chain reaction analysis revealed that HaGlut4 was most highly expressed in adults.Knockdown of the HaGlut4 gene reduced the transcript levels of HaGlut4,and the weight and number of eggs produced significantly decreased.In addition,the transcript levels of vitellogenin receptor and vitellogenin in the fat bodies and the ovaries of H.axyridis decreased after the interference of Glut4,and decreased the triglyceride,fatty acid,total amino acid and adenosine triphosphate content of H.axyridis.This resulted in severe blockage of ovary development and reduction of yolk formation;there was no development of ovarioles in the developing oocytes.These changes indicate that a lack of HaGlut4 can impair ovarian development and oocyte maturation and result in decreased fecundity.

Targeting fructose metabolism by glucose transporter 5 regulation in human cholangiocarcinoma

Alterations in cellular metabolism may contribute to tumor proliferation and survival.Upregulation of the facilitative glucose transporter(GLUT)plays a key role in promoting cancer.GLUT5 mediates modulation of fructose utilization,and its overexpression has been associated with poor prognosis in several cancers.However,its metabolic regulation remains poorly understood.Here,we demonstrated elevated GLUT5 expression in human cholangiocarcinoma(CCA),using RNA sequencing data from samples of human tissues and cell lines,as compared to normal liver tissues or a cholangiocyte cell line.Cells exhibiting highexpression of GLUT5 showed increased rates of cell proliferation and ATP production,particularly in a fructose-supplemented medium.In contrast,GLUT5 silencing attenuated cell proliferation,ATP production,cell migration/invasion,and improved epithelialemesenchymal transition(EMT)balance.Correspondingly,fructose consumption increased tumor growth in a nude mouse xenograft model,and GLUT5 silencing suppressed growth,supporting the tumor-inhibitory effect of GLUT5 downregulation.Furthermore,in the metabolic pathways of fructolysis-Warburg effect,the expression levels of relative downstream genes,including ketohexokinase(KHK),aldolase B(ALDOB),lactate dehydrogenase A(LDHA),and monocarboxylate transporter 4(MCT4),as well as hypoxia-inducible factor 1 alpha(HIF1A),were altered in a GLUT5 expression-dependent manner.Taken together,these findings indicate that GLUT5 could be a potential target for CCA therapeutic approach via metabolic regulation.

GLUCOSE TRANSPORTER 2: PREVENTION OF STREPTOZOTOCIN-INDUCED REDUCTION OF 5-THIO-D-GLUCOSE

Decreased expression of glucose transporter 2 (GLUT2) has been found to correlate with impaired secreting β-cell function in diabetes. Here, the aim was to study if the GLUT2 of pancreatic islets is a target structure for streptozotocin (STZ) in vitro. GLLT2 expression was determined by Western blot analysis, using lysates prepared from islets of C57BL / 6mice. A dose-dependent decrement of GLUT2 expression was found after incubation of islets with streptozotocin for 30 min. Compared with solvent-incubated islets, a subtoxic dose (4mM) of STZ resulted in a reduction of approximate 58% of GLUT2 expression and a toxic dose