TY - JOUR A1 - Arimany-Nardi, Cristina A1 - Minuesa, Gerard A1 - Pastor-Anglada, Marçal A1 - Keller, Thorsten A1 - Erkizia, Itziar A1 - Koepsell, Hermann A1 - Martinez-Picado, Javier T1 - Role of Human Organic Cation Transporter 1 (hOCT1) Polymorphisms in Lamivudine (3TC) Uptake and Drug-Drug Interactions JF - Frontiers in Pharmacology N2 - Lamivudine (3TC), a drug used in the treatment of HIV infection, needs to cross the plasma membrane to exert its therapeutic action. Human Organic cation transporter 1 (hOCT1), encoded by the SLC22A1 gene, is the transporter responsible for its uptake into target cells. As SLC22A1 is a highly polymorphic gene, the aim of this study was to determine how SNPs in the OCT1-encoding gene affected 3TC internalization and its interaction with other co-administered drugs. HEK293 cells stably transfected with either the wild type form or the polymorphic variants of hOCT1 were used to perform kinetic and drug-drug interaction studies. Protein co-immunoprecipitation was used to assess the impact of selected polymorphic cysteines on the oligomerization of the transporter. Results showed that 3TC transport efficiency was reduced in all polymorphic variants tested (R61C, C88R, S189L, M420del, and G465R). This was not caused by lack of oligomerization in case of variants located at the transporter extracellular loop (R61C and C88R). Drug-drug interaction measurements showed that co-administered drugs [abacavir (ABC), zidovudine (AZT), emtricitabine (FTC), tenofovir diproxil fumarate (TDF), efavirenz (EFV) and raltegravir (RAL)], differently inhibited 3TC uptake depending upon the polymorphic variant analyzed. These data highlight the need for accurate analysis of drug transporter polymorphic variants of clinical relevance, because polymorphisms can impact on substrate (3TC) translocation but even more importantly they can differentially affect drug-drug interactions at the transporter level. KW - hOCT1 KW - pharmacogenetics KW - lamivudine KW - HIV infection KW - therapy Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-165236 VL - 7 IS - 175 ER - TY - JOUR A1 - Bhavsar, Shefalee K. A1 - Singh, Yogesh A1 - Sharma, Piyush A1 - Khairnar, Vishal A1 - Hosseinzadeh, Zohreh A1 - Zhang, Shaqiu A1 - Palmada, Monica A1 - Sabolic, Ivan A1 - Koepsell, Hermann A1 - Lang, Karl S. A1 - Lang, Philipp A. A1 - Lang, Florian T1 - Expression of JAK3 Sensitive Na\(^+\) Coupled Glucose Carrier SGLT1 in Activated Cytotoxic T Lymphocytes JF - Cellular Physiology and Biochemistry N2 - Background: Similar to tumor cells, activated T-lymphocytes generate ATP mainly by glycolytic degradation of glucose. Lymphocyte glucose uptake involves non-concentrative glucose carriers of the GLUT family. In contrast to GLUT isoforms, Na+-coupled glucose-carrier SGLT1 accumulates glucose against glucose gradients and is effective at low extracellular glucose concentrations. The present study explored expression and regulation of SGLT1 in activated murine splenic cytotoxic T cells (CTLs) and human Jurkat T cells. Methods: FACS analysis, immunofluorescence, confocal microscopy, chemiluminescence and Western blotting were employed to estimate SGLT1 expression, function and regulation in lymphocytes, as well as dual electrode voltage clamp in SGLT1 ± JAK3 expressing Xenopus oocytes to quantify the effect of janus kinase3 (JAK3) on SGLT1 function. Results: SGLT1 is expressed in murine CTLs and also in human Jurkat T cells. 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose uptake was significantly decreased by SGLT1-blocker phloridzin (0.2 mM) and by pharmacological inhibition of JAK3 with WHI-P131 (156 µM), WHI-P154 (11.2 µM) and JAK3 inhibitor VI (0.5 µM). Electrogenic glucose transport (Iglucose) in Xenopus oocytes expressing human SGLT1 was increased by additional expression of human wild type JAK3, active A568VJAK3 but not inactive K851AJAK3. Coexpression of JAK3 enhanced the maximal transport rate without significantly modifying affinity of the carrier. Iglucose in SGLT1+JAK3 expressing oocytes was significantly decreased by WHI-P154 (11.2 µM). JAK3 increased the SGLT1 protein abundance in the cell membrane. Inhibition of carrier insertion by brefeldin A (5 µM) in SGLT1+JAK3 expressing oocytes resulted in a decline of Iglucose, which was similar in presence and absence of JAK3. Conclusions: SGLT1 is expressed in murine cytotoxic T cells and human Jurkat T cells and significantly contributes to glucose uptake in those cells post activation. JAK3 up-regulates SGLT1 activity by increasing the carrier protein abundance in the cell membrane, an effect enforcing cellular glucose uptake into activated lymphocytes and thus contributing to the immune response. KW - tumor cell KW - Cytotoxic T lymphocytes KW - Glucose uptake KW - Jurkat T cells KW - Energy depletion KW - Janus kinase Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164900 VL - 39 IS - 3 ER - TY - JOUR A1 - Cardani, Diego A1 - Sardi, Claudia A1 - La Ferla, Barbara A1 - D'Orazio, Guiseppe A1 - Sommariva, Michele A1 - Marcucci, Fabrizio A1 - Olivero, Daniela A1 - Tagliabue, Elda A1 - Koepsell, Hermann A1 - Nicotra, Francesco A1 - Balsari, Andrea A1 - Rumio, Christiano T1 - Sodium glucose cotransporter 1 ligand BLF501 as a novel tool for management of gastrointestinal mucositis JF - Molecular Cancer N2 - Background: Recent studies demonstrated that engagement of sodium glucose transporter 1 (SGLT-1) by orally administered D-glucose protects the intestinal mucosa from lipopolysaccharide (LPS)-induced injury. We tested whether SGLT-1 engagement might protect the intestinal mucosa from doxorubicin (DXR)- and 5-fluorouracil (5-FU)-induced injury in animal models mimicking acute or chronic mucositis. Methods: Mice were treated intraperitoneally with DXR, alone or in combination with 5-FU, and orally with BLF501, a glucose-derived synthetic compound with high affinity for SGLT-1. Intestinal mucosal epithelium integrity was assessed by histological analysis, cellular proliferation assays, real-time PCR gene expression assays and Western blot assays. Student's t-test (paired two-tailed) and X-2 analyses were used for comparisons between groups. Differences were considered significant at p < 0.05. Results: BLF501 administration in mice treated with DXR and/or 5-FU decreased the injuries to the mucosa in terms of epithelial integrity and cellular proliferative ability. Co-treatment with BLF501 led to a normal expression and distribution of both zonula occludens-1 (ZO-1) and beta-catenin, which were underexpressed after treatment with either chemotherapeutic agent alone. BLF501 administration also restored normal expression of caspase-3 and ezrin/radixin/moesin (ERM), which were overexpressed after treatment with DXR and 5-FU. In SGLT1-/- mice, BLF501 had no detectable effects. BLF501 administration in wild-type mice with growing A431 tumors did not modify antitumor activity of DXR. Conclusions: BLF501-induced protection of the intestinal mucosa is a promising novel therapeutic approach to reducing the severity of chemotherapy-induced mucositis. KW - apoptosis KW - prevention KW - doxorubicin KW - cancer KW - gastrointestinal mucositis KW - SGLT-1 KW - synthetic D-glucose analogy KW - chemotherapy KW - inflammation KW - clinical practice guidelines KW - intestinal mucositis KW - epithelial cells KW - oral mucositis KW - gene-expression Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117352 SN - 1476-4598 VL - 13 IS - 23 ER - TY - JOUR A1 - Carpaneto, Armando A1 - Koepsell, Hermann A1 - Bamberg, Ernst A1 - Hedrich, Rainer A1 - Geiger, Dietmar T1 - Sucrose- and H+-Dependent Charge Movements Associated with the Gating of Sucrose Transporter ZmSUT1 N2 - Background: In contrast to man the majority of higher plants use sucrose as mobile carbohydrate. Accordingly protondriven sucrose transporters are crucial for cell-to-cell and long-distance distribution within the plant body. Generally very negative plant membrane potentials and the ability to accumulate sucrose quantities of more than 1 M document that plants must have evolved transporters with unique structural and functional features. Methodology/Principal Findings: To unravel the functional properties of one specific high capacity plasma membrane sucrose transporter in detail, we expressed the sucrose/H+ co-transporter from maize ZmSUT1 in Xenopus oocytes. Application of sucrose in an acidic pH environment elicited inward proton currents. Interestingly the sucrose-dependent H+ transport was associated with a decrease in membrane capacitance (Cm). In addition to sucrose Cm was modulated by the membrane potential and external protons. In order to explore the molecular mechanism underlying these Cm changes, presteady-state currents (Ipre) of ZmSUT1 transport were analyzed. Decay of Ipre could be best fitted by double exponentials. When plotted against the voltage the charge Q, associated to Ipre, was dependent on sucrose and protons. The mathematical derivative of the charge Q versus voltage was well in line with the observed Cm changes. Based on these parameters a turnover rate of 500 molecules sucrose/s was calculated. In contrast to gating currents of voltage dependentpotassium channels the analysis of ZmSUT1-derived presteady-state currents in the absence of sucrose (I =Q/t) was sufficient to predict ZmSUT1 transport-associated currents. Conclusions: Taken together our results indicate that in the absence of sucrose, ‘trapped’ protons move back and forth between an outer and an inner site within the transmembrane domains of ZmSUT1. This movement of protons in the electric field of the membrane gives rise to the presteady-state currents and in turn to Cm changes. Upon application of external sucrose, protons can pass the membrane turning presteady-state into transport currents. KW - Sucrose Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-68538 ER - TY - JOUR A1 - Gallo, Linda A. A1 - Ward, Micheal S. A1 - Fotheringham, Amelia K. A1 - Zhuang, Aowen A1 - Borg, Danielle J. A1 - Flemming, Nicole B. A1 - Harvie, Ben M. A1 - Kinneally, Toni L. A1 - Yeh, Shang-Ming A1 - McCarthy, Domenica A. A1 - Koepsell, Hermann A1 - Vallon, Volker A1 - Pollock, Carol A1 - Panchapakesan, Usha A1 - Forbes, Josephine M. T1 - Once daily administration of the SGLT2 inhibitor, empagliflozin, attenuates markers of renal fibrosis without improving albuminuria in diabetic db/db mice JF - Scientific Reports N2 - Blood glucose control is the primary strategy to prevent complications in diabetes. At the onset of kidney disease, therapies that inhibit components of the renin angiotensin system (RAS) are also indicated, but these approaches are not wholly effective. Here, we show that once daily administration of the novel glucose lowering agent, empagliflozin, an SGLT2 inhibitor which targets the kidney to block glucose reabsorption, has the potential to improve kidney disease in type 2 diabetes. In male db/db mice, a 10-week treatment with empagliflozin attenuated the diabetes-induced upregulation of profibrotic gene markers, fibronectin and transforming-growth-factor-beta. Other molecular (collagen IV and connective tissue growth factor) and histological (tubulointerstitial total collagen and glomerular collagen IV accumulation) benefits were seen upon dual therapy with metformin. Albuminuria, urinary markers of tubule damage (kidney injury molecule-1, KIM-1 and neutrophil gelatinase-associated lipocalin, NGAL), kidney growth, and glomerulosclerosis, however, were not improved with empagliflozin or metformin, and plasma and intra-renal renin activity was enhanced with empagliflozin. In this model, blood glucose lowering with empagliflozin attenuated some molecular and histological markers of fibrosis but, as per treatment with metformin, did not provide complete renoprotection. Further research to refine the treatment regimen in type 2 diabetes and nephropathy is warranted. KW - SGLT2 inhibitor KW - empagliflozin KW - glucose lowering agent KW - kidney disease KW - type 2 diabetes Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-167678 VL - 6 IS - 26428 ER - TY - JOUR A1 - Gründemann, Dirk A1 - Gorboulev, Valentin A1 - Gambaryan, Stepan A1 - Veyhl, Maike A1 - Koepsell, Hermann T1 - Drug excretion mediated by a new prototype of polyspecific transporter N2 - CATIO~IC drugs of different types and structures (antihistaminics, antiarrhythmics, sedatives, opiates, cytostatics and antibiotics, for example) are excreted in mammals by epithelial cells of the renal proximal tubules and by hepatocytes in the liver1-4. In the proximal tubules, two functionally disparate transport systems are involved which are localized in the basolateral and luminal plasma membrane and are different from the previously identified neuronal monoamine transporters and A TP-dependent multidrug exporting proteins1-3,5-12. Here we report the isolation of a complementary DNA from rat kidney that encodes a 556-amino-acid membrane protein, OCT1, which has the functional characteristics of organic cation uptake over the basolateral membrane of renal proximal tubules and of organic cation uptake into hepatocytes. OCTl is not homologous to any other known protein and is found in kidney, liver and intestine. As OCTl translocates hydrophobic and hydrophilic organic cations of different structures, it is considered to be a new prolotype of polyspecific transporters that are important for drug elimination. KW - Biologie Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59327 ER - TY - JOUR A1 - Jaschke, Alexander A1 - Chung, Bomee A1 - Hesse, Deike A1 - Kluge, Reinhart A1 - Zahn, Claudia A1 - Moser, Markus A1 - Petzke, Klaus-Jürgen A1 - Brigelius-Flohé, Regina A1 - Puchkov, Dmytro A1 - Koepsell, Hermann A1 - Heeren, Joerg A1 - Joost, Hans-Georg A1 - Schürmann, Annette T1 - The GTPase ARFRP1 controls the lipidation of chylomicrons in the Golgi of the intestinal epithelium JF - Human Molecular Genetics N2 - The uptake and processing of dietary lipids by the small intestine is a multistep process that involves several steps including vesicular and protein transport. The GTPase ADP-ribosylation factor-related protein 1 (ARFRP1) controls the ARF-like 1 (ARL1)-mediated Golgi recruitment of GRIP domain proteins which in turn bind several Rab-GTPases. Here, we describe the essential role of ARFRP1 and its interaction with Rab2 in the assembly and lipidation of chylomicrons in the intestinal epithelium. Mice lacking Arfrp1 specifically in the intestine \((Arfrp1^{vil−/−})\) exhibit an early post-natal growth retardation with reduced plasma triacylglycerol and free fatty acid concentrations. \(Arfrp1^{vil−/−}\) enterocytes as well as Arfrp1 mRNA depleted Caco-2 cells absorbed fatty acids normally but secreted chylomicrons with a markedly reduced triacylglycerol content. In addition, the release of apolipoprotein A-I (ApoA-I) was dramatically decreased, and ApoA-I accumulated in the \(Arfrp1^{vil−/−}\) epithelium, where it predominantly co-localized with Rab2. The release of chylomicrons from Caco-2 was markedly reduced after the suppression of Rab2, ARL1 and Golgin-245. Thus, the GTPase ARFRP1 and its downstream proteins are required for the lipidation of chylo­microns and the assembly of ApoA-I to these particles in the Golgi of intestinal epithelial cells. KW - ARF Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125658 VL - 21 IS - 14 ER - TY - JOUR A1 - Jurowich, Christian Ferdinand A1 - Otto, Christoph A1 - Rikkala, Prashanth Reddy A1 - Wagner, Nicole A1 - Vrhovac, Ivana A1 - Sabolić, Ivan A1 - Germer, Christoph-Thomas A1 - Koepsell, Hermann T1 - Ileal interposition in rats with experimental type 2 like diabetes improves glycemic control independently of glucose absorption JF - Journal of Diabetes Research N2 - Bariatric operations in obese patients with type 2 diabetes often improve diabetes before weight loss is observed. In patients mainly Roux-en-Y-gastric bypass with partial stomach resection is performed. Duodenojejunal bypass (DJB) and ileal interposition (IIP) are employed in animal experiments. Due to increased glucose exposition of L-cells located in distal ileum, all bariatric surgery procedures lead to higher secretion of antidiabetic glucagon like peptide-1 (GLP-1) after glucose gavage. After DJB also downregulation of Na\(^{+}\)-D-glucose cotransporter SGLT1 was observed. This suggested a direct contribution of decreased glucose absorption to the antidiabetic effect of bariatric surgery. To investigate whether glucose absorption is also decreased after IIP, we induced diabetes with decreased glucose tolerance and insulin sensitivity in male rats and investigated effects of IIP on diabetes and SGLT1. After IIP, we observed weight-independent improvement of glucose tolerance, increased insulin sensitivity, and increased plasma GLP-1 after glucose gavage. The interposed ileum was increased in diameter and showed increased length of villi, hyperplasia of the epithelial layer, and increased number of L-cells. The amount of SGLT1-mediated glucose uptake in interposed ileum was increased 2-fold reaching the same level as in jejunum. Thus, improvement of glycemic control by bariatric surgery does not require decreased glucose absorption. KW - glucagon like peptide-1 KW - food intake KW - body weight KW - cotransporter SGLT1 KW - bariatric surgery KW - biliopancreatic diversion KW - intestinal glucose KW - gut hormones KW - duodenal jejunal bypass KW - Y-gastric bypass Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149166 VL - 2015 IS - 490365 ER - TY - JOUR A1 - Koepsell, Hermann T1 - Glucose transporters in the small intestine in health and disease JF - Pflügers Archiv - European Journal of Physiology N2 - Absorption of monosaccharides is mainly mediated by Na\(^+\)-d-glucose cotransporter SGLT1 and the facititative transporters GLUT2 and GLUT5. SGLT1 and GLUT2 are relevant for absorption of d-glucose and d-galactose while GLUT5 is relevant for d-fructose absorption. SGLT1 and GLUT5 are constantly localized in the brush border membrane (BBM) of enterocytes, whereas GLUT2 is localized in the basolateral membrane (BLM) or the BBM plus BLM at low and high luminal d-glucose concentrations, respectively. At high luminal d-glucose, the abundance SGLT1 in the BBM is increased. Hence, d-glucose absorption at low luminal glucose is mediated via SGLT1 in the BBM and GLUT2 in the BLM whereas high-capacity d-glucose absorption at high luminal glucose is mediated by SGLT1 plus GLUT2 in the BBM and GLUT2 in the BLM. The review describes functions and regulations of SGLT1, GLUT2, and GLUT5 in the small intestine including diurnal variations and carbohydrate-dependent regulations. Also, the roles of SGLT1 and GLUT2 for secretion of enterohormones are discussed. Furthermore, diseases are described that are caused by malfunctions of small intestinal monosaccharide transporters, such as glucose-galactose malabsorption, Fanconi syndrome, and fructose intolerance. Moreover, it is reported how diabetes, small intestinal inflammation, parental nutrition, bariatric surgery, and metformin treatment affect expression of monosaccharide transporters in the small intestine. Finally, food components that decrease d-glucose absorption and drugs in development that inhibit or downregulate SGLT1 in the small intestine are compiled. Models for regulations and combined functions of glucose transporters, and for interplay between d-fructose transport and metabolism, are discussed. KW - glucose transporter KW - small intestine KW - regulation KW - SGLT1 KW - GLUT2 KW - GLUT5 KW - glucose-galactose malabsorption KW - fructose intolerance KW - diabetes KW - bariatric surgery Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-232552 SN - 0031-6768 VL - 472 ER - TY - JOUR A1 - Koepsell, Hermann T1 - Glucose transporters in brain in health and disease JF - Pflügers Archiv - European Journal of Physiology N2 - Energy demand of neurons in brain that is covered by glucose supply from the blood is ensured by glucose transporters incapillaries and brain cells. In brain, the facilitative diffusion glucose transporters GLUT1-6 and GLUT8, and the Na+-D-glucosecotransporters SGLT1 are expressed. The glucose transporters mediate uptake of D-glucose across the blood-brain barrier anddelivery of D-glucose to astrocytes and neurons. They are critically involved in regulatory adaptations to varying energy demandsin response to differing neuronal activities and glucose supply. In this review, a comprehensive overview about verified andproposed roles of cerebral glucose transporters during health and diseases is presented. Our current knowledge is mainly based onexperiments performed in rodents. First, the functional properties of human glucose transporters expressed in brain and theircerebral locations are described. Thereafter, proposed physiological functions of GLUT1, GLUT2, GLUT3, GLUT4, andSGLT1 for energy supply to neurons, glucose sensing, central regulation of glucohomeostasis, and feeding behavior are compiled, and their roles in learning and memory formation are discussed. In addition, diseases are described in which functionalchanges of cerebral glucose transporters are relevant. These are GLUT1 deficiency syndrome (GLUT1-SD), diabetes mellitus, Alzheimer’s disease (AD), stroke, and traumatic brain injury (TBI). GLUT1-SD is caused by defect mutations in GLUT1. Diabetes and AD are associated with changed expression of glucose transporters in brain, and transporter-related energy defi-ciency of neurons may contribute to pathogenesis of AD. Stroke and TBI are associated with changes of glucose transporter expression that influence clinical outcome KW - glucosetransporter KW - brain KW - GLUT1 KW - GLUT2 KW - GLUT3 KW - GLUT4 KW - SGLT1 KW - diabetes KW - Parkinson’s disease KW - stroke Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-232746 SN - 0031-6768 VL - 472 ER -