Comparison of effects of green tea catechins on apicomplexan hexose transporters and mammalian orthologues

Here we have investigated the inhibitory properties of green tea catechins on the Plasmodium falciparum hexose transporter (PfHT), the Babesia bovis hexose transporter 1 (BboHT1) and the mammalian facilitative glucose transporters, GLUT1 and GLUT5, expressed in Xenopus laevis oocytes. (−)-Epicatechin-gallate (ECG) and (−)-epigallocatechin-gallate (EGCG) inhibited d-glucose transport by GLUT1 and PfHT, and d-fructose transport by GLUT5, with apparent K_i values between 45 and 117 μM. BboHT1 was more potently inhibited by the ungallated catechins (−)-epicatechin (EC) and (−)-epigallocatechin (EGC), with apparent K_i values of 108 and 168 μM, respectively. Site-directed mutagenesis experiments provided little further support for previously reported models of catechin binding to hexose transporters. Furthermore, P. falciparum growth inhibition by catechins was not affected by the external d-glucose concentration. Our results provide new data on the inhibitory action of catechins against sugar transporters but were unable to elucidate the antimalarial mechanism of action of these agents.     

The SLC2 family of facilitated hexose and polyol transporters

The SLC2 family of glucose and polyol transporters comprises 13 members, the glucose transporters (GLUT) 1–12 and the H⁺-myo-inositol cotransporter (HMIT). These proteins all contain 12 transmembrane domains with both the amino and carboxy-terminal ends located on the cytoplasmic side of the plasma membrane and a N-linked oligosaccharide side-chain located either on the first or fifth extracellular loop. Based on sequence comparison, the GLUT isoforms can be grouped into three classes: class I comprises GLUT1–4; class II, GLUT6, 8, 10, and 12 and class III, GLUT5, 7, 9, 11 and HMIT. Despite their sequence similarity and the presence of class-specific signature sequences, these transporters carry various hexoses and HMIT is a H⁺/myo-inositol co-transporter. Furthermore, the substrate transported by some isoforms has not yet been identified. Tissue- and cell-specific expression of the well-characterized GLUT isoforms underlies their specific role in the control of whole-body glucose homeostasis. Numerous studies with transgenic or knockout mice indeed support an important role for these transporters in the control of glucose utilization, glucose storage and glucose sensing. Much remains to be learned about the transport functions of the recently discovered isoforms (GLUT6–13 and HMIT) and their physiological role in the metabolism of glucose, myo-inositol and perhaps other substrates.An erratum to this article can be found at     

Physiological leukocytosis during pregnancy is associated with changes in glucose transporter expression of maternal peripheral blood granulocytes and monocytes

PROBLEM: The scarce data on glucose transporter expression of leukocytes are contradictory and nothing is known about changes accompanying physiological leukocytosis during pregnancy, which imposes acute metabolic demands on the cells. METHOD OF STUDY: Cytospin preparations of intravascular leukocytes were searched immunocytochemically for the high affinity glucose transporters GLUT1, 3 and 4. Pregnancy-associated quantitative changes in transporter expression were assessed by flow cytometry. RESULTS: Granulocytes and monocytes stained for GLUT1, 3 and 4. Major changes in cell surface transporter expression during pregnancy were a 36% (P < 0.05) down-regulation of granulocyte GLUT1 at term, and an increase in monocyte GLUT3 levels to 137% (P < 0.05), paralleled by a 24% (P < 0.05) decrease in GLUT4 content in second trimester. Apart from a minor subpopulation, lymphocytes were negative for these carriers. CONCLUSION: GLUT1, 3 and 4 are abundantly expressed in granulocytes and monocytes. The particular isoforms are differentially regulated during pregnancy, suggesting an individual functional significance.     

葡萄糖对成骨细胞体外发育和葡萄糖载体1表达的影响

目的 探讨葡萄糖对成骨细胞体外发育和葡萄糖载体1表达的影响.方法 组织块培养法培养新生大鼠颅骨成骨细胞,再将成骨细胞分两组培养:正常浓度组(含5.5 mmol/L葡萄糖培养液)和高浓度组(含25.5 mmol/L葡萄糖培养液).四甲基偶氮唑蓝(MTT)法检测细胞增殖,茜素红S钙染色法检测骨结节形成,反转录(RT)PCR和Western免疫印迹检测成骨细胞葡萄糖载体1 mRNA和蛋白表达情况.结果 与正常浓度葡萄糖相比,高浓度葡萄糖在第3、4、5天显著促进成骨细胞的增殖[ (0.390 0±0.002 4)比(0.320 0±0.012 7),( 0.540 0±0.009 4)比(0.440 0±0.004 6),( 0.720 0±0.001 3)比(0.600 0±0.006 1),均P＜0.05],但抑制其矿化和骨结节形成.正常浓度组形成肉眼可见的钙化结节要早于高浓度组(第9天比第14天).实验最后ld(第32天),高浓度组的骨结节数明显少于正常浓度组(P＜0.05).与正常浓度组相比,高浓度葡萄糖使成骨细胞葡萄糖载体l mRNA和蛋白的表达增加.结论 高浓度葡萄糖刺激成骨细胞增殖但抑制细胞矿化可能直接引起成骨细胞骨形成障碍.高浓度葡萄糖引起成骨细胞葡萄糖载体1表达的改变可能在骨质量变化过程中起重要作用.     

3-硝基丙酸预处理对脑缺血耐受模型GLUT1和GLUT3表达的影响

目的: 探讨3-硝基丙酸(3-NPA)预处理对大鼠局灶性脑缺血半暗带区不同再灌注时点GLUT1和GLUT3 mRNA及蛋白水平表达的影响。方法: 雄性SD大鼠40只,随机分为假手术组(sham组,n=4)、预处理对照组(3-NPA组,n=4)、大脑中动脉缺血组(M组,n=16)、3-NPA 预处理组(IPC组,n=16)。M组和IPC组按再灌注时间(4 h、12 h、24 h及48 h)不同又分为4个亚组,每组动物4只。将大鼠在相应时点断头取脑,取缺血侧(左侧)冠状面中间1/3皮质,分别采用RT-PCR和Western blotting方法检测GLUT1、GLUT3 mRNA和蛋白水平表达情况。结果: IPC组GLUT1 mRNA表达在缺血再灌注后4 h开始升高,48 h最大,显著高于sham组和M组相应时点。IPC组GLUT3 mRNA表达在24 h增高,48 h最高,与M组相应时点24 h、48 h及sham组比较显著增高。IPC组比M组的GLUT1蛋白、GLUT3蛋白表达增高,有显著差异(F=5.848,P<0.05;F=6.295,P<0.05),尤以缺血再灌注后48 h两者差异最明显。结论: 3-NPA预处理能诱导脑缺血耐受,其机制可能是上调GLUT1和GLUT3 mRNA及蛋白表达水平,维持脑组织的能量供给。     

GLUT11, but not GLUT8 or GLUT12, is expressed in human skeletal muscle in a fibre type-specific pattern

Nine novel sugar transporter-like proteins have been discovered in the past 5 years. The mRNA for three of these, the glucose transporters (GLUT) GLUT8, GLUT11 and GLUT12, have been detected in human skeletal muscle. In the present study, we examined the pattern of expression and localization of the GLUT isoforms 8, 11 and 12 in human skeletal muscle using an immunohistochemical approach. Biopsies of human skeletal muscle from sedentary or trained healthy adults, from fetal muscle (24 weeks of gestation), from obese type-2 diabetic subjects, and from patients suffering from polymyositis or amyotrophic lateral sclerosis (ALS) were studied. GLUT8 and 12 immunoreactivity was below detection level in both developing and adult muscle fibres. GLUT11 immunoreactivity, however, was present in slow-twitch muscle fibres, but not in fast twitch fibres. Since, in contrast, GLUT4 was expressed in all investigated muscle fibres, the pattern of expression of GLUT11 differs from that of GLUT4, suggesting a specialized function for GLUT11 with a regulation independent from that of GLUT4. Obesity, type-2 diabetes, training, conditions of de- and reinnervation (ALS) and regeneration (polymyositis) failed to induce GLUT8 or -12 expression. Likewise, the fibre type-dependent pattern of GLUT11 immunoreactivity was unaltered. However, some slow muscle fibres lose their GLUT11 immunoreactivity under regeneration. Our results indicate that GLUT11 immunoreactivity, in contrast to that of GLUT4, is expressed exclusively in slow-twitch muscle fibres and is unaffected by physiological and pathophysiological conditions except in primary myopathy. GLUT8 and GLUT12 do not appear to be of importance in human muscle under physiological and pathophysiological conditions.     

Identification of Babesia bovis L-lactate dehydrogenase as a potential chemotherapeutical target against bovine babesiosis

In this study, we characterized a novel Babesia bovis cDNA clone obtained by immunoscreening the cDNA expression phage library with B. bovis-infected bovine serum. The genetic analyses showed that it contained an open reading frame of 993 bp, which was considered to encode B. bovis L-lactate dehydrogenase (BbLDH: E.C. 1.1.1.27) because of the strikingly high amino acid identities of its gene product to the LDHs of Plasmodium falciparum and Toxoplasma gondii. Immunological analyses with the anti-recombinant BbLDH mouse serum showed that 36 kDa of the native BbLDH was expressed not only in the cytoplasm of intra- and extraerythrocytic parasites but also along the membrane of infected erythrocytes. The kinetic properties of recombinant BbLDH proved a certain enzymatic activity of LDH, and the activity was significantly inhibited by the addition of gossypol, a competitive inhibitor of protozoan LDHs. Moreover, 100 microM of the gossypol irretrievably arrested the in vitro growth of B. bovis. The results demonstrated that BbLDH provides a suitable drug target for the design of novel babesial chemotherapeutics.     

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

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

Skeletal muscle fatty acid transporter protein expression in type 2 diabetes patients compared with overweight, sedentary men and age-matched, endurance-trained cyclists

Aim: Membrane fatty acid transporters can modulate the balance between fatty acid uptake and subsequent storage and/or oxidation in muscle tissue. As such, skeletal muscle fatty acid transporter protein expression could play an important role in the etiology of insulin resistance and/or type 2 diabetes. Methods: In the present study, fatty acid translocase (FAT/CD36), plasma membrane‐bound fatty acid‐binding protein (FABPpm) and fatty acid transport protein 1 (FATP1) mRNA and protein expression were assessed in muscle tissue obtained from 10 sedentary, overweight type 2 diabetes patients (60 ± 2 years), 10 sedentary, weight‐matched normoglycemic controls (60 ± 2 years) and 10 age‐matched, endurance trained cyclists (57 ± 1 years). Results: Both FAT/CD36 and FATP1 mRNA and protein expression did not differ between groups. In contrast, FABPpm mRNA and protein expression were approx. 30–40% higher in the trained men compared with the diabetes patients (P < 0.01) and sedentary controls (P < 0.05). Conclusions: Skeletal muscle FAT/CD36, FABPpm and FATP1 mRNA and protein expression are not up‐ or downregulated in a sedentary and/or insulin resistant state. In contrast, FABPpm expression is upregulated in the endurance trained state and likely instrumental to allow greater fatty acid oxidation rates.     

Expression of the GLUT1 glucose transporter, p63 and p53 in thyroid carcinomas

Only few studies have evaluated the usefulness of the GLUT1 and p63 status of thyroid carcinomas in revealing tumorigenesis. We studied GLUT1, p53, and p63 immunoexpression in a total of 86 cases of various thyroid carcinoma types to determine the biological significance of GLUT1 and p63 expression in thyroid carcinomas. GLUT1 was detected in six cases of anaplastic carcinoma and in one case of poorly differentiated carcinoma with membranous staining. p63 was detected in five cases of anaplastic carcinoma, in one case of poorly differentiated carcinoma, and in five cases of papillary carcinoma with nuclear positivity. p53 was detected in six cases of anaplastic carcinoma, in one case of poorly differentiated carcinoma, and in one case of follicular carcinoma with nuclear positivity. Five of seven cases of anaplastic carcinoma expressed all three of these markers. The results suggest that GLUT1, p63, and p53 are not expressed in well-differentiated thyroid carcinomas, and that they are usually expressed late in the course of thyroid tumor progression. These data strongly suggest that in anaplastic carcinomas, impairment of p53-mediated repression results in increased GLUT1 and p63 expression, and that this probably reflects the differential regulation of hypoxia-responsive pathways and basal/stem cell regulatory pathways.     

Genome-wide analysis of peptidase content and expression in a virulent and attenuated Babesia bovis strain pair

Identifying virulence determinants in Apicomplexan parasites remains a major gap in knowledge for members within this phylum. We hypothesized that peptidases would segregate with virulence between a virulent parent Babesia bovis strain and an attenuated daughter strain derived by rapid in vivo passage. Using the complete genome sequence of the virulent T2Bo strain, 66 peptidases were identified and active sites confirmed. The presence, sequence identity and expression levels were tested for each of the 66 peptidases in the virulent parent and attenuated daughter T2Bo strains using whole genome, targeted sequencing approaches and microarrays analyses. Quantitative PCR revealed that there was no significant difference in peptidase expression between the virulent and attenuated strains. We conclude that while peptidases may well play a required role in B. bovis pathogenesis, neither loss of peptidase gene content nor reduced gene expression underlies the loss of virulence associated with in vivo passage and attenuation.     

Expression of the insulin-responsive glucose transporter isoform 4 in blastocysts of C57/BL6 mice

Glucose is the most important energy substrate for mammalian blastocysts. In preimplantation embryos glucose uptake is mainly mediated by facilitative glucose transporter molecules (GLUT). Employing RT-PCR in 3.5-day-old mouse blastocysts of strain C57/BL6 we have investigated the expression of the GLUT isoforms 1–4 and 8. We could not only detect GLUT 1, 3 and 8 but, in contrast to earlier studies, also the insulin-responsive isoform 4. GLUT2 was not expressed. The specificity for GLUT4 amplification was verified by sequence analysis. GLUT4 protein was localized by immunohistochemistry with two GLUT4 antibodies. It was found in ICM and trophoblast cells in the cytoplasmic compartment with a strong perinuclear staining. This is the first report on the expression of the insulin-sensitive GLUT4 isoform in mouse preimplantation embryos.Abbreviations GLUT Glucose transporter - ICM Inner cell mass - TE Trophectoderm     

应激猪睾丸葡萄糖转运蛋白1和葡萄糖转运蛋白2的表达与定位

目的 探讨正常和热应激条件下,葡萄糖转运蛋白1（GLUT1）和葡萄糖转运蛋白2（GLUT2）在成年猪睾丸的表达和定位。 方法 性成熟长白公猪9头,随机分为3组。局部阴囊热刺激组（n=3）,用自制电热毯置阴囊42 ℃加热1 h;环境热应激组（n=3）,每天置于37～40 ℃猪舍环境3 h,连续7 d,每天于热处理结束后,将实验猪驱赶回21～25 ℃猪舍环境;对照组（n=3）,饲养在21～25 ℃猪舍环境。局部热刺激6 h后和环境热应激处理结束24 h后,手术摘除双侧睾丸。用Real-time PCR、Western blotting和免疫组织化学技术检测猪睾丸组织内GLUT1和GLUT2的表达。 结果 Real-time PCR和Western blotting结果显示,与对照组相比,环境热应激组GLUT1蛋白和mRNA的表达差异不显著,局部阴囊热刺激组GLUT1蛋白和mRNA表达显著升高;环境热应激组和局部阴囊热刺激组,GLUT2蛋白和mRNA表达均显著升高。免疫组织化学结果发现,热处理前后,GLUT1蛋白在曲精小管内定位于精母细胞和圆形精子细胞;环境热应激组GLUT1蛋白染色与对照组相比,无明显差异,局部阴囊热刺激后,GLUT1染色变深,表达升高。热处理前后,GLUT2蛋白在曲精小管定位于生精细胞和支持细胞,环境热应激和局部阴囊热刺激导致GLUT2染色变深,表达升高。 结论 葡萄糖转运蛋白GLUT1和GLUT2表达于猪睾丸曲精小管,环境高温和阴囊局部热刺激导致GLUT1和GLUT2在猪睾丸的表达水平改变,提示这两种葡萄糖转运蛋白在猪精子发生过程中发挥重要作用。     

胰岛素促进狗缺血心肌葡萄糖转运子1移位和葡萄糖摄取

观察胰岛素能否刺激缺血心肌葡萄糖转运子 1(GLUT1)移位和葡萄糖摄取。利用自动分析仪测定生理代谢参数 ,应用免疫印迹和免疫荧光法检测GLUT1。胰岛素使缺血心肌细胞质膜GLUT1明显增加 (从 5 2 %± 4%～ 6 7%± 6 % ,P <0 0 5 )。细胞器膜GLUT1则相应减少 ,同时伴随葡萄糖摄取量明显增加 ,是单纯缺血心肌葡萄糖摄取量的 2倍。胰岛素刺激引起GLUT1移位 ,使缺血心肌葡萄糖摄取增加。提示心肌缺血时 ,应用胰岛素有助于增加心肌葡萄糖的摄取和利用     

Large litters rearing changes brain expression of GLUT3 and acetylcholinesterase activity in adult rats

Effects of malnutrition in the brain are more pronounced during the period of growth spurt, corresponding to the suckling in rodents. Neuronal glucose transporter GLUT3 expression and acetylcholinesterase activity were studied in the brain of adult young rats (84 days old) suckled in litters formed by 6 (control group) or 12 pups (malnourished group). In the adult rats, brain weight, blood glucose levels and GLUT3 expression were decreased in malnourished group (5%, 18%, 58%, respectively, P < 0.001, Student's t test) compared to the control. Increased activity of acetylcholinesterase was found in cerebral cortex homogenates and a significant interaction (P = 0.019, ANOVA two-way, Tukey's test) was found between nutritional state and homogenate fraction. In summary, malnutrition during suckling period decreased GLUT3 expression and increased acetylcholinesterase activity in the rat brain that could contribute to possible cognitive deficits and changes of brain metabolic activity.     

Expression of the GLUT1 glucose transporter and p53 in carcinomas of the pancreatobiliary tract

Only few studies have evaluated the usefulness of the GLUT1 and p53 status of pancreatobiliary tract carcinomas in revealing tumorigenesis. We studied GLUT1 and p53 immunoexpression in a total of 355 cases of the pancreatobiliary carcinoma to determine the biological significance of GLUT1 and p53 expression. Positive expression of GLUT1 was identified in 38 out of 67 (57.7%) ampulla of Vater (AV) carcinomas, in 27 out of 52 (51.8%) pancreatic (PA) carcinomas, in 38 out of 121 (31.4%) extrahepatic bile duct (EBD) carcinomas, and in 53 out of 115 (46.5%) gallbladder (GB) carcinomas. GLUT1 expression in pancreatobiliary carcinomas showed some positive correlation with histological grade, T stage, N stage, TNM stage, and lymphatic invasion. However, p53 expression showed no correlation with any prognostic factors. In the Kaplan–Meier test, positive GLUT1 expression was a poor prognostic factor in the pancreatobiliary tract cancers; however, only GB cancers were statistically significant (P=0.002). Our results suggest that GLUT1 expression in the AV, EBD, and GB carcinomas is associated with some prognostic factors, and GLUT1 expression is associated with a worse prognosis in the patients with GB carcinomas.     

High co-infection rates of Babesia bovis,Babesia bigemina,and Anaplasma marginale in water buffalo in Western Cuba

Parasitology Research - Water buffalo is important livestock in several countries in the Latin American and Caribbean regions. This buffalo species can be infected by tick-borne hemoparasites and...