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Glucose Transport Proteins In Diabetes

Payperview: Regulation Of Glucose Transporters In Diabetes - Karger Publishers

Payperview: Regulation Of Glucose Transporters In Diabetes - Karger Publishers

Regulation of Glucose Transporters in Diabetes I have read the Karger Terms and Conditions and agree. It is now widely accepted that insulin stimulates glucose metabolism in its target tissues via recruitment of transporters from a large intracellular pool to the plasma membrane. Recent studies, however, suggest a two-step model for insulin action, of transporter translocation and transporter activation. Data confirming this hypothesis for the first time are presented. It is shown that insulin significantly enhances the intrinsic activity of glucose transporters in human and rat adipose cells, in physiological as well as in diabetic state. The functional activity of transporters is impaired in the diabetic state, but surprisingly, diabetic transporters exhibit normal or even enhanced intrinsic activity. In both noninsulin-dependent diabetes mellitus and streptozotocin-diabetic rats, insulin resistance is associated with 50% transporter depletion in the intracellular pool, thus leading to a decreased number of transporters appearing in the plasma membrane in response to insulin. It is concluded that impaired glucose transport in diabetes is secondary (1) to intracellular transporter depletion, and (2) to the presence of inhibitory factors interfering with the full expression of glucose transporters at the plasma membrane, thus contributing to postreceptor insulin resistance. Continue reading >>

Glucose Transport In The Lens | Iovs | Arvo Journals

Glucose Transport In The Lens | Iovs | Arvo Journals

ARVO Annual Meeting Abstract| December 2002 School Biological Sciences University Auckland Auckland New Zealand Department of Physiology & Biophysics Department of Physiology Department of Physiology & Biophysics Department of Physiology Department of Physiology & Biophysics Department of Physiology Department of Physiology & Biophysics School of Biological Sciences Department of Physiology & Biophysics School of Biological Sciences Commercial Relationships B.R. Smith, None;R. Varadaraj, None;A. Krushinski, None;P. Donaldson, None;R. Mathias, None;J. Kistler, None. Grant Identification: Health Research Council of New Zealand Investigative Ophthalmology & Visual Science December 2002, Vol.43, 4646. doi: You will receive an email whenever this article is corrected, updated, or cited in the literature. You can manage this and all other alerts in My Account BR Smith, R Varadaraj, A Krushinski, P Donaldson, R Mathias, J Kistler; Glucose Transport In the Lens . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4646. ARVO (1962-2015); The Authors (2016-present) Abstract: : Purpose:Transport of glucose in the lens is mediated by members of the facilitative and Na+-dependent glucose transporters. We have investigated which isoforms are expressed in the rat lens, their spatial distribution, their functionality, and their regulation in the diabetic lens. Methods:Glucose uptake was measured using fibre cell membrane vesicles and fluorescently labelled glucose (2-NBDG). Transporter isoforms were identified by RT-PCR, and Northern analysis was used to determine transcript levels. Western blotting and immunocytochemistry, using commercially available antibodies, were employed to verify the presence and spatial distribution of glucose transporter proteins in normal and diabetic lenses. Quanti Continue reading >>

Role Of Glucose Transport Proteins In Diabetes Mellitus Garvey, W Timothy Indiana University-purdue University At Indianapolis, Indianapolis, In, United States

Role Of Glucose Transport Proteins In Diabetes Mellitus Garvey, W Timothy Indiana University-purdue University At Indianapolis, Indianapolis, In, United States

Role of Glucose Transport Proteins in Diabetes Mellitus Insulin resistance is central to the pathogenesis of Type II diabetes (NIDDM), and is largely due to decreased activity of the glucose transport system in target tissue. However, the mechanisms responsible for reduced transport activity are unknown. In pre- liminary studies, we found both cellular depletion and impaired function of glucose transport proteins causing insulin resistance in adipocytes isolated from these patients. Therefore, in the current proposal, we will extensively examine the role of glucose transporters in the cellular insulin resistance of NIDDM, by measuring their number, structure, function, and regulation in target tissue. In adipocytes from control and NIDDM subjects, we will use both cytochalasin B binding and immunologic methods to measure the number and cellular distribution of transporters under basal conditions as well as insulin's ability to recruit intracellular carriers to the cell-surface. Function will be assessed by correlating numbers of cell-surface transporters with glucose transport rates in intact cells, and by correlating glucose transporter number and functional activity of transporters isolated from various subcellular and membrane fractions and then reconstituted into synthetic phospholipid vesicles. The Km and Vmax of substrate uptake will also be measured in whole cells since defects in these functional parameters have mechanistic implications. To test for structural abnormalities, we will combine SDS-PAGE and isoelectric focusing to determine the MW, charge heterogeneity, and extent of post-translational glycosylation of photolabeled transporters, as well as measure the non-enzymatic glycosylation of transporters using an antibody specific for glycosyl-lysine adducts Continue reading >>

Pdb-101: Glucose Transporters

Pdb-101: Glucose Transporters

Glucose transporters deliver glucose molecules one-by-one across cell membranes. GLUT3 is shown on the left in the open outward conformation, and GLUT1 is shown on the right in an open inward conformation. Glucose is the fuel that powers most of the biosphere. Plants build it using energy from the sun, store it in starches and use it to build their infrastructure of cellulose. The glucose we eat is broken down through glycolysis and used to power the many processes of our cells. Thus, it is essential to supply each of our cells with a steady stream of glucose. Glucose is delivered throughout the body by the blood, and each cell gathers what it needs using glucose transporters. Glucose transporters manage the traffic of glucose across the cell's outer membrane. They act by alternating between two states. First, the transporter has an opening facing the outside of the cell, and it picks up a molecule of glucose. Then it shifts shape, and opens towards the inside, releasing glucose into the cell. Glucose transporters generally act passively: since glucose is rapidly phosphorylated by hexokinase , the concentration of free glucose in the cytoplasm is generally very low, and the higher concentration of glucose in the blood drives transport of glucose into the cell. The human genome encodes 14 similar transporters that deliver glucose and other sugars into different types of cells. For instance, GLUT1 (shown here from PDB entry 4pyp ) manages the basal levels of glucose uptake and is very common in red blood cells. GLUT2 helps control the flow of glucose in and out of liver cells, and pancreatic beta cells use it to monitor the level of glucose in the blood, releasing insulin when the level rises. Nerve cells in the brain require a constant supply of glucose, so they use GLU Continue reading >>

A Close-up View Of Glucose Transport

A Close-up View Of Glucose Transport

Association-funded researcher Dr. Tamir Gonen recently published a critical study that provides the information needed to design new diabetes drugs. But it almost didn't happen. In 2009, when Dr. Gonen was applying for an American Diabetes Association Career Development Award, his lab was fairly new, and he had used most of his initial funding. At this point, he was unsure that he could continue his work studying what goes wrong in diabetes. Fortunately, Dr. Gonen was selected for the Career Development Award, which allowed him to continue this important work at a time when federal research funding was decreasing. While the project required many subsequent years of investigation, it did progressand was ultimately successfulbecause of the Association's investment. Dr. Gonen studies proteins that regulate energy balance. Proteins are the molecular machinery that perform most of the cell's functions. They are built based on the DNA code, and they form 3-dimensional structures that allow them to function. A protein's structure can be disrupted because of a mutation - a small change in the genetic code. Depending on the mutation, the protein may no longer be able to perform its function, which can result in disease. A key protein important to regulating blood glucose is called a glucose transporter. It sits in the cell membrane and transports glucose from the blood to the inside of the cell where it is used for energy. With his Association Career Development Award, Dr. Gonen and his teamthen based at the University of Washingtonset out to better understand how the glucose transporter proteins work by looking very closely at their structure. Dr. Gonen explained the value of structural studies with an analogy. If an archeologist far in the future were to find a car with no id Continue reading >>

Type-2 Diabetes Down-regulates Glucose Transporter Proteins And Genes Of The Human Blood Leukocytes

Type-2 Diabetes Down-regulates Glucose Transporter Proteins And Genes Of The Human Blood Leukocytes

Access Details: [subscription number 909981588] Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Scandinavian Journal of Clinical and Laboratory Investigation Publication details, including instructions for authors and subscription information: Type-2 diabetes down-regulates glucose transporter proteins and genes of the D. Kipmen-Korgun a; S. Bilmen-Sarikcioglu b; H. Altunbas c; R. Demir d; E. T. Korgun d a Department of Biochemistry, b Department of Central Laboratory, c Department of Internal Medicine, Division of Endocrinology and Metabolism, d Department of Histology and Embryology, Akdeniz University, Antalya, To cite this Article Kipmen-Korgun, D., Bilmen-Sarikcioglu, S., Altunbas, H., Demir, R. and Korgun, E. T.(2009)'Type-2 diabetes down- regulates glucose transporter proteins and genes of the human blood leukocytes',Scandinavian Journal of Clinical and Laboratory To link to this Article: DOI: 10.1080/00365510802632163 URL: Full terms and conditions of use: This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of th Continue reading >>

Signaling Mechanisms That Regulate Glucose Transport*

Signaling Mechanisms That Regulate Glucose Transport*

Insulin Receptor Signaling Circuits Substrate phosphorylation by the insulin receptor tyrosine kinase appears to involve the binding of phosphorylated receptor tyrosine 960 to phosphotyrosine-binding (PTB)1 domains of substrate proteins (8). Adjacent Pleckstrin homology (PH) domains on some substrate proteins also appear critical for receptor binding and phosphorylation. Tyrosine kinase signaling is often initiated by the recruitment of signaling proteins through their Src homology 2 (SH2) or PTB domains to phosphotyrosine sites. In the case of insulin receptor, tyrosine phosphorylation of four related substrate (IRS) proteins (8) and Gab-1 (9) causes many candidate signaling proteins to be recruited, including: 1) the p110-type phosphatidylinositol 3-kinase (PI 3-kinase) through the SH2 domains of p85 regulatory subunits; 2) Grb2 and the protein tyrosine phosphatase SH-PTP2, which appear to be necessary for p21ras activation (10); 3) the tyrosine kinase Fyn, which in turn may also activate the PI 3-kinase and p21raspathways; and 4) Rho-associated protein serine/threonine kinase ROKα (11), which may modulate processes such as actin assembly and mitogenesis under control of the small GTPase Rho. Insulin receptor signaling can also engage p21ras through tyrosine phosphorylation of Shc and its subsequent binding to complexes of Grb2 and Sos (12). Recently, it has been discovered that proteins can bind directly to the autophosphorylated insulin receptor through their SH2 domains, opening new avenues for investigation (13). As illustrated in Fig. 1, p21rasand the p85/p110-type PI 3-kinases represent two major initial switch elements for insulin receptor signaling. There is also evidence that the p21ras-related GTP-binding proteins Rap (14), Rho (15), and Rac (16) are engage Continue reading >>

Type-2 Diabetes Down-regulates Glucose Transporter Proteins And Genes Of Thehuman Blood Leukocytes.

Type-2 Diabetes Down-regulates Glucose Transporter Proteins And Genes Of Thehuman Blood Leukocytes.

1. Scand J Clin Lab Invest. 2009;69(3):350-8. doi: 10.1080/00365510802632163. Type-2 diabetes down-regulates glucose transporter proteins and genes of thehuman blood leukocytes. Kipmen-Korgun D(1), Bilmen-Sarikcioglu S, Altunbas H, Demir R, Korgun ET. (1)Department of Biochemistry, Akdeniz University, Medical Faculty, Antalya, Turkey. OBJECTIVE: White blood cells are essential in mediating immune and inflammatoryresponses. A prominent feature of these cells during activation of the immunefunction is increased glucose utilization, and this is dependent on thefunctioning of specific glucose transporter (GLUT) isoforms. The few dataavailable on leukocyte glucose transporter expression are limited to type-2diabetes mellitus, and nothing is known about its regulation.MATERIAL AND METHODS: Peripheral blood was drawn from 35 healthy controls and 35 diabetic subjects. Expression of GLUT1, GLUT3 and GLUT4 was determined in theleukocytes of healthy individuals and diabetic patients by flow cytometry,Western blot and semi-quantitative RT-PCR.RESULTS: GLUT 3 was decreased in granulocytes, lymphocytes and monocytes fromdiabetic patients. In monocytes, GLUT3 and GLUT4 were reduced in type-2 diabetic patients. In leukocytes of diabetic patients, GLUT1 and GLUT4, protein and mRNAwere unchanged, but GLUT3 protein and mRNA levels were down-regulated compared tothose of healthy controls.CONCLUSION: Elevated glucose concentration affects leukocyte GLUT expression.Decreased expression of GLUT isoforms in leukocytes may be responsible fordiminished activation of diabetic leukocytes. These situations possiblycontribute to a predisposition to infection and to a decreased immune response indiabetes. Continue reading >>

Regulation Of Glucose Transporters By Insulin And Exercise: Cellular Effects And Implications For Diabetes

Regulation Of Glucose Transporters By Insulin And Exercise: Cellular Effects And Implications For Diabetes

Arch, J. R. S..Subclassification of adrenoceptors: the pharmacology of adrenoceptors in tissues.Pharmacol. Commun.6:223228,1995. Arch, J. R. S.,A. T. Ainsworth,M. A. Cawthorne,V. Piercy,M. V. Sennitt,V. E. Thordy,C. Wilson, andS. Wilson.Atypical adrenoceptor on brown adipocytes as target for antiobesity drugs.Nature309:163165,1984. Arch, J. R. S., andA. J. Kaumann.Beta(3)adrenoceptor and atypical betaAdrenoceptor.Med. Res. Rev.13:663729,1993. Bahr, M.,M. von Holtey,G. Muller, andJ. Eckel.Direct stimulation of myocardial glucose transport and glucose transporter1 (GLUT1) and GLUT4 protein expression by the sulfonylurea glimepiride.Endocrinology136:25472553,1995. Bailey, C. J..Metformin revisited: its actions and indications for use.Diabet. Med.5:315320,1988. Baldwin, S. A.,L. F. Barros, andM. Griffiths.Trafficking of glucose transporterssignals and mechanisms.Biosci. Rep.15:419426,1995. Baldwin, S. A., andG. E. Lienhard.Purification and reconstitution of glucose transporter from human erythrocytes.Methods Enzymol.174:3950,1989. Baltensperger, K.,L. M. Kozma,S. R. Jaspers, andM. P. Czech.Regulation by insulin of phosphatidylinositol 3'kinase bound to alphaand betaisoforms of p85 regulatory subunit.J. Biol. Chem.269:2893728946,1994. Bandyopadhyay, G.,M. L. Standaert,L. Galloway,J. Moscat, andR. V. Farese.Evidence for involvement of protein kinase C (PKC)zeta and noninvolvement of diacylglycerolsensitive PKCs in insulinstimulated glucose transport in L6 myotubes.Endocrinology138:47214731,1997. Bandyopadhyay, G.,M. L. Standaert,L. Zhao,B. Yu,A. Avignon,L. Galloway,P. Karnam,J. Moscat, andR. V. Farese.Activation of protein kinase C , , and ) by insulin in 3T3/L1 cells. Transfection studies suggest a role for PKC in glucose transport.J. Biol. Chem.272:25512558,1997. Baron, A. Continue reading >>

Regulation Of Glucose Transporter Translocation In Health And Diabetes

Regulation Of Glucose Transporter Translocation In Health And Diabetes

Regulation of Glucose Transporter Translocation in Health and Diabetes Vol. 81:507-532 (Volume publication date July 2012) First published online as a Review in Advance on April 5, 2012 Section of Endocrinology and Metabolism, Department of Internal Medicine, and Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8020; email: [emailprotected] To enhance glucose uptake into muscle and fat cells, insulin stimulates the translocation of GLUT4 glucose transporters from intracellular membranes to the cell surface. This response requires the intersection of insulin signaling and vesicle trafficking pathways, and it is compromised in the setting of overnutrition to cause insulin resistance. Insulin signals through AS160/Tbc1D4 and Tbc1D1 to modulate Rab GTPases and through the Rho GTPase TC10 to act on other targets. In unstimulated cells, GLUT4 is incorporated into specialized storage vesicles containing IRAP, LRP1, sortilin, and VAMP2, which are sequestered by TUG, Ubc9, and other proteins. Insulin mobilizes these vesicles directly to the plasma membrane, and it modulates the trafficking itinerary so that cargo recycles from endosomes during ongoing insulin exposure. Knowledge of how signaling and trafficking pathways are coordinated will be essential to understanding the pathogenesis of diabetes and the metabolic syndrome and may also inform a wide range of other physiologies. The Cas9 protein (CRISPR-associated protein 9), derived from type II CRISPR (clustered regularly interspaced short palindromic repeats) bacterial immune systems, is emerging as a powerful tool for engineering the genome in diverse organisms. As an RNA-... Read More Figure 1: CRISPR-associated protein 9 (Cas9)-mediated sequence-specific genomic editing. (a) Co Continue reading >>

Glucose And Lipid Transporters Roles In Type 2 Diabetes

Glucose And Lipid Transporters Roles In Type 2 Diabetes

Glucose and Lipid Transporters Roles in Type 2 Diabetes San Diego Supercomputer Center, UC San Diego, USA These authors contributed equally to this work. These authors contributed equally to this work. San Diego Supercomputer Center, UC San Diego, USA Department of Neurosciences, UC San Diego, USA Type 2 diabetes is a chronic condition encompassing many metabolic processes throughout the body. Glucose and lipid transporters are involved in many of these critical metabolic processes and pathways, and are linked to the development and symptoms of type 2 diabetes. Therapeutic opportunities utilizing these transporters have already begun with the gliflozin drug class of inhibitors of sodium glucose linked co-transporters (SGLT). A range of transporter families: SLC5A (SGLT), SLC2A (GLUT), and ATP binding cassette (ABC) transporters are either connected to glucose or cholesterol homeostasis, significant in a systemic disease like diabetes type 2. Elucidating the roles of these transporters in type 2 diabetes is vital in establishing new and effective options for treatment. Sodium glucose linked co-transporters (SGLT) Sodium glucose linked co-transporters (SGLT) are members of the large solute carrier family of membrane transporter proteins (SLC). The SLC family contains hundreds of members and has three main families involved in glucose transport: SLC2, SLC5, and SLC50. Specifically, the SGLT class of transporters are encoded by the SLC5 gene type. There are twelve different transporter proteins encoded by the SLC5 genes, with six of them going under the alias of SGLT. The SLC5 family (Table 1) are membrane transporters with nearly all being involved in forms of glucose transport and homeostasis, transporting sugars such as glucose, mannose, and myo inositol and located in Continue reading >>

Type2 Diabetes Downregulates Glucose Transporter Proteins And Genes Of The Human Blood Leukocytes

Type2 Diabetes Downregulates Glucose Transporter Proteins And Genes Of The Human Blood Leukocytes

Type2 diabetes downregulates glucose transporter proteins and genes of the human blood leukocytes Get access/doi/full/10.1080/00365510802632163?needAccess=true Objective. White blood cells are essential in mediating immune and inflammatory responses. A prominent feature of these cells during activation of the immune function is increased glucose utilization, and this is dependent on the functioning of specific glucose transporter (GLUT) isoforms. The few data available on leukocyte glucose transporter expression are limited to type2 diabetes mellitus, and nothing is known about its regulation. Material and methods. Peripheral blood was drawn from 35 healthy controls and 35 diabetic subjects. Expression of GLUT1, GLUT3 and GLUT4 was determined in the leukocytes of healthy individuals and diabetic patients by flow cytometry, Western blot and semiquantitative RTPCR. Results. GLUT 3 was decreased in granulocytes, lymphocytes and monocytes from diabetic patients. In monocytes, GLUT3 and GLUT4 were reduced in type2 diabetic patients. In leukocytes of diabetic patients, GLUT1 and GLUT4, protein and mRNA were unchanged, but GLUT3 protein and mRNA levels were downregulated compared to those of healthy controls. Conclusion. Elevated glucose concentration affects leukocyte GLUT expression. Decreased expression of GLUT isoforms in leukocytes may be responsible for diminished activation of diabetic leukocytes. These situations possibly contribute to a predisposition to infection and to a decreased immune response in diabetes. Continue reading >>

Review The Glut4 Glucose Transporter

Review The Glut4 Glucose Transporter

Figure 1. Structural Features of the Insulin-Regulated GLUT4 Glucose Transporter Protein The unique sensitivity of GLUT4 to insulin-mediated translocation appears to derive from sequences shown in the N-terminal (required phenylalanine) and COOH-terminal (required dileucine and acidic residues) regions. These sequences are likely involved in rapid internalization and sorting of GLUT4 in intracellular membranes termed GLUT4 storage vesicles (GSV), as outlined in Figure 3. See text for further details. GLUT4 Is a Key Determinant of Glucose Homeostasis A central role for GLUT4 in whole-body metabolism is strongly supported by a variety of genetically engineered mouse models where expression of the transporter is either enhanced or ablated in muscle or adipose tissue or both. The whole-body GLUT4−/− mouse itself may be less informative due to upregulation of compensatory mechanisms that may promote survival of these animals (Katz et al., 1995; Stenbit et al., 1996). However, heterozygous GLUT4+/− mice that display decreased GLUT4 protein in muscle and adipose tissue show the expected insulin resistance and propensity toward diabetes that is consistent with a major role of GLUT4 in glucose disposal (Rossetti et al., 1997; Stenbit et al., 1997; Li et al., 2000). Interestingly, overexpression of GLUT4 expression in skeletal muscle of such GLUT4+/− animals through crosses with transgenic mice normalizes insulin sensitivity and glucose tolerance (Tsao et al., 1999). Transgenic mice expressing high levels of GLUT4 in adipose tissue (Shepherd et al., 1993; Tozzo et al., 1995) or in skeletal muscle (Tsao et al., 1996, 2001) in turn are both highly insulin sensitive and glucose tolerant. Conversely, conditional depletion of GLUT4 in either adipose tissue or skeletal muscle c Continue reading >>

Glucose Transporter

Glucose Transporter

Glucose Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. Because glucose is a vital source of energy for all life, these transporters are present in all phyla. The GLUT or SLC2A family are a protein family that is found in most mammalian cells. 14 GLUTS are encoded by human genome. GLUT is a type of uniporter transporter protein. Synthesis of free glucose[edit] Most non-autotrophic cells are unable to produce free glucose because they lack expression of glucose-6-phosphatase and, thus, are involved only in glucose uptake and catabolism. Usually produced only in hepatocytes, in fasting conditions other tissues such as the intestines, muscles, brain, and kidneys are able to produce glucose following activation of gluconeogenesis. Glucose transport in yeast[edit] In Saccharomyces cerevisiae glucose transport takes place through facilitated diffusion.[1] The transport proteins are mainly from the Hxt family, but many other transporters have been identified.[2] Name Properties Notes Snf3 low-glucose sensor; repressed by glucose; low expression level; repressor of Hxt6 Rgt2 high-glucose sensor; low expression level Hxt1 Km: 100 mM,[3] 129 - 107 mM[1] low-affinity glucose transporter; induced by high glucose level Hxt2 Km = 1.5[1] - 10 mM[3] high/intermediate-affinityglucose transporter; induced by low glucose level[3] Hxt3 Vm = 18.5, Kd = 0.078, Km = 28.6/34.2[1] - 60 mM[3] low-affinity glucose transporter[3] Hxt4 Vm = 12.0, Kd = 0.049, Km = 6.2[1] intermediate-affinity glucose transporter[3] Hxt5 Km = 10 mM[4] Moderate glucose affinity. Abundant during stationary phase, sporulation and low glucose conditions. Transcription repressed by glucose.[4] Hxt6 Vm = 11.4, Kd = 0.029, Km = 0.9/14,[1] 1.5 mM[3] Continue reading >>

Glucose Transport

Glucose Transport

The oxidation of glucose represents a major source of metabolic energy for mammalian cells. Because the plasma membrane is impermeable to polar molecules such as glucose, the cellular uptake of this important nutrient is accomplished by special carrier proteins called glucose transporters[1][2][3][4][5][6][7]. These are integral membrane proteins located in the plasma membrane that bind glucose and transfer it across the lipid bilayer. The rate of glucose transport is limited by the number of glucose transporters on the cell surface and the affinity of the transporters for glucose. There are two classes of glucose carriers described in mammalian cells: the Na+-glucose cotransporters (SGLTs) and the facilitative glucose transporters (GLUTs)[1-7]. There are two families of glucose transporters The Na+-glucose cotransporter or symporter is expressed by specialized epithelial (brush border) cells of the small intestine and the proximal tubule of the kidney and mediates an active, Na+-linked transport process against an electrochemical gradient[1-3] . It actively transports glucose from the lumen of the intestine or the nephron against its concentration gradient by coupling glucose uptake with that of Na+, which is being transported down its concentration gradient. The Na+ gradient is maintained by the active transport of Na+ across the basolateral (antiluminal) surface of the brush border cells by membrane-bound Na+-K+- ATPase[1-3,7]. The second class of glucose carriers is the facilitative glucose transporters (GLUTs) of which there are 14 genes in the human genome[1,4-7] . These proteins mediate a bidirectional and energy-independent process of glucose transport in most tissues and cells where glucose is transported down its concentration gradient by facilitative diffusio Continue reading >>

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