The Fast Lane of Hypoxic Adaptation: Glucose Transport Is Modulated via A HIF-Hydroxylase-AMPK-Axis in Jejunum Epithelium

The intestinal epithelium is able to adapt to varying blood flow and, thus, oxygen availability. Still, the adaptation fails under pathologic situations. A better understanding of the mechanisms underlying the epithelial adaptation to hypoxia could help to improve the therapeutic approach. We hypothesized that the short-term adaptation to hypoxia is mediated via AMP-activated protein kinase (AMPK) and that it is coupled to the long-term adaptation by a common regulation mechanism, the HIF-hydroxylase enzymes. Further, we hypothesized the transepithelial transport of glucose to be part of this short-term adaptation. We conducted Ussing chamber studies using isolated lagomorph jejunum epithelium and cell culture experiments with CaCo-2 cells. The epithelia and cells were incubated under 100% and 21% O2, respectively, with the panhydroxylase inhibitor dimethyloxalylglycine (DMOG) or under 1% O2. We showed an activation of AMPK under hypoxia and after incubation with DMOG by Western blot. This could be related to functional effects like an impairment of Na+-coupled glucose transport. Inhibitor studies revealed a recruitment of glucose transporter 1 under hypoxia, but not after incubation with DMOG. Summing up, we showed an influence of hydroxylase enzymes on AMPK activity and similarities between hypoxia and the effects of hydroxylase inhibition on functional changes.

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Regulation of lactate production and glucose transport as well as of glucose transporter 1 and lactate dehydrogenase A mRNA levels by basic fibroblast growth factor in rat Sertoli cells

Journal of Endocrinology ◽

10.1677/joe.0.1730335 ◽

2002 ◽

Vol 173 (2) ◽

pp. 335-343 ◽

Cited By ~ 31

Author(s):

MF Riera ◽

SB Meroni ◽

HF Schteingart ◽

EH Pellizzari ◽

SB Cigorraga

Keyword(s):

Growth Factor ◽

Glucose Transport ◽

Glucose Transporter ◽

Lactate Production ◽

Mrna Levels ◽

Dependent Manner ◽

Short Term ◽

Glucose Transporter 1 ◽

Ldh Activity

By using cultured rat Sertoli cells as a model, both the action of basic fibroblast growth factor (bFGF) on lactate production and the site of this action were studied. bFGF stimulated Sertoli cell lactate production in a dose-dependent manner (basal: 7.3+/-0.5; 0.1 ng/ml bFGF: 7.5+/-0.5; 1 ng/ml bFGF: 7.5+/-0.6; 10 ng/ml bFGF: 10.3+/-1.0; 30 ng/ml bFGF: 15.2+/-1.5; 50 ng/ml bFGF: 15.4+/-1.6 microg/microg DNA). Two major sites for the action of this growth factor were identified. First, bFGF was shown to exert short- and long-term stimulatory effects on glucose transport (basal: 1170+/-102; 30 ng/ml bFGF for 120 min: 1718+/-152 and basal: 718+/-64; 30 ng/ml bFGF for 48 h: 1069+/-69 d.p.m./microg DNA respectively). Short-term bFGF stimulation of glucose transport was not inhibited by the protein synthesis inhibitor cycloheximide. These results indicate that short-term bFGF stimulation of glucose uptake does not involve an increase in the number of glucose transporters. On the other hand, stimulation with bFGF for periods of time longer than 12 h increased glucose transporter 1 (GLUT1) mRNA levels. These increased mRNA levels were probably ultimately responsible for the increments in glucose uptake that are observed in long-term treated cultures. Secondly, bFGF increased lactate dehydrogenase (LDH) activity (basal: 31.0+/-1.4; 30 ng/ml bFGF: 45.7+/- 2.4 mIU/microg DNA). The principal subunit component of those LDH isozymes that favors the transformation of pyruvate to lactate is subunit A. bFGF increased LDH A mRNA levels in a dose- and time-dependent manner. In summary, the results presented herein show that glucose transport, LDH activity and GLUT1 and LDH A mRNA levels are regulated by bFGF to achieve an increase in lactate production. These observed regulatory actions provide unequivocal evidence of the participation of bFGF in Sertoli cell lactate production which may be related to normal germ cell development.

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Impaired intestinal and renal glucose transport in PDK-1 hypomorphic mice

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00024.2006 ◽

2006 ◽

Vol 291 (5) ◽

pp. R1533-R1538 ◽

Cited By ~ 8

Author(s):

Ferruh Artunc ◽

Rexhep Rexhepaj ◽

Harald Völkl ◽

Florian Grahammer ◽

Christine Remy ◽

...

Keyword(s):

Small Intestine ◽

Glucose Transport ◽

Glucose Transporter ◽

Ussing Chamber ◽

Glucose Absorption ◽

Renal Tubules ◽

Glucose Transporter 1 ◽

Glucose Reabsorption ◽

Urinary Glucose ◽

Proximal Tubular

The phosphoinositide-dependent kinase-1 (PDK-1) activates the serum- and glucocorticoid-inducible kinase and protein kinase B isoforms, which, in turn, are known to stimulate the renal and intestinal Na+-dependent glucose transporter 1. The present study has been performed to explore the role of PDK-1 in electrogenic glucose transport in small intestine and proximal renal tubules. To this end, mice expressing ∼20% of PDK-1 ( pdk1 hm) were compared with their wild-type littermates ( pdk1 wt). According to Ussing chamber experiments, electrogenic glucose transport was significantly smaller in the jejunum of pdk1 hm than of pdk1 wt mice. Similarly, proximal tubular electrogenic glucose transport in isolated, perfused renal tubule segments was decreased in pdk1 hm compared with pdk1 wt mice. Intraperitoneal injection of 3 g/kg body wt glucose resulted in a similar increase of plasma glucose concentration in pdk1 hm and in pdk1 wt mice but led to a higher increase of urinary glucose excretion in pdk1 hm mice. In conclusion, reduction of functional PDK-1 leads to impairment of electrogenic intestinal glucose absorption and renal glucose reabsorption. The experiments disclose a novel element of glucose transport regulation in kidney and small intestine.

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The Formation of an Insulin-responsive Vesicular Cargo Compartment Is an Early Event in 3T3-L1 Adipocyte Differentiation

Molecular Biology of the Cell ◽

10.1091/mbc.10.5.1581 ◽

1999 ◽

Vol 10 (5) ◽

pp. 1581-1594 ◽

Cited By ~ 51

Author(s):

Amr K. El-Jack ◽

Konstantin V. Kandror ◽

Paul F. Pilch

Keyword(s):

Glucose Transport ◽

Glucose Transporter ◽

Adipocyte Differentiation ◽

Receptor Trafficking ◽

Early Event ◽

Glucose Transporter 1 ◽

Glut4 Expression ◽

Velocity Gradients ◽

Dependent Inhibition ◽

Intracellular Glucose

Differentiating 3T3-L1 cells exhibit a dramatic increase in the rate of insulin-stimulated glucose transport during their conversion from proliferating fibroblasts to nonproliferating adipocytes. On day 3 of 3T3-L1 cell differentiation, basal glucose transport and cell surface transferrin binding are markedly diminished. This occurs concomitant with the formation of a distinct insulin-responsive vesicular pool of intracellular glucose transporter 1 (GLUT1) and transferrin receptors as assessed by sucrose velocity gradients. The intracellular distribution of the insulin-responsive aminopeptidase is first readily detectable on day 3, and its gradient profile and response to insulin at this time are identical to that of GLUT1. With further time of differentiation, GLUT4 is expressed and targeted to the same insulin-responsive vesicles as the other three proteins. Our data are consistent with the notion that a distinct insulin-sensitive vesicular cargo compartment forms early during fat call differentiation and its formation precedes GLUT4 expression. The development of this compartment may result from the differentiation-dependent inhibition of constitutive GLUT1 and transferrin receptor trafficking such that there is a large increase in, or the new formation of, a population of postendosomal, insulin-responsive vesicles.

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Inhibitors of neuronal and inducible nitric oxide synthase enhance the protective effect of short-term adaptation to hypoxia in Krushinsky-Molodkina rats

Biology Bulletin ◽

10.1134/s1062359015010057 ◽

2015 ◽

Vol 42 (1) ◽

pp. 67-73 ◽

Cited By ~ 2

Author(s):

A. L. Krushinsky ◽

V. S. Kuzenkov ◽

V. E. Dyakonova ◽

V. P. Reutov

Keyword(s):

Nitric Oxide ◽

Nitric Oxide Synthase ◽

Protective Effect ◽

Inducible Nitric Oxide Synthase ◽

Adaptation To Hypoxia ◽

Short Term ◽

Short Term Adaptation ◽

Oxide Synthase ◽

Inducible Nitric Oxide

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Reactive oxygen species downregulate glucose transport system in retinal endothelial cells

AJP Cell Physiology ◽

10.1152/ajpcell.00140.2010 ◽

2011 ◽

Vol 300 (4) ◽

pp. C927-C936 ◽

Cited By ~ 29

Author(s):

Rosa Fernandes ◽

Ken-ichi Hosoya ◽

Paulo Pereira

Keyword(s):

Oxidative Stress ◽

Endothelial Cells ◽

Plasma Membrane ◽

Endothelial Cell ◽

Glucose Transport ◽

Glucose Transporter ◽

Cell Damage ◽

Proteasome Inhibition ◽

Glucose Transporter 1 ◽

Retinal Endothelial Cells

Retinal endothelial cells are believed to play an important role in the pathogenesis of diabetic retinopathy. In previous studies, we and others demonstrated that glucose transporter 1 (GLUT1) is downregulated in response to hyperglycemia. Increased oxidative stress is likely to be the event whereby hyperglycemia is transduced into endothelial cell damage. However, the effects of sustained oxidative stress on GLUT1 regulation are not clearly established. The objective of this study is to evaluate the effect of increased oxidative stress on glucose transport and on GLUT1 subcellular distribution in a retinal endothelial cell line and to elucidate the signaling pathways associated with such regulation. Conditionally immortalized rat retinal endothelial cells (TR-iBRB) were incubated with glucose oxidase, which increases the intracellular hydrogen peroxide levels, and GLUT1 regulation was investigated. The data showed that oxidative stress did not alter the total levels of GLUT1 protein, although the levels of mRNA were decreased, and there was a subcellular redistribution of GLUT1, decreasing its content at the plasma membrane. Consistently, the half-life of the protein at the plasma membrane markedly decreased under oxidative stress. The proteasome appears to be involved in GLUT1 regulation in response to oxidative stress, as revealed by an increase in stabilization of the protein present at the plasma membrane and normalization of glucose transport following proteasome inhibition. Indeed, levels of ubiquitinated GLUT1 increase as revealed by immunoprecipitation assays. Furthermore, data indicate that protein kinase B activation is involved in the stabilization of GLUT1 at the plasma membrane. Thus subcellular redistribution of GLUT1 under conditions of oxidative stress is likely to contribute to the disruption of glucose homeostasis in diabetes.

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Caffeine inhibits glucose transport by binding at the GLUT1 nucleotide-binding site

AJP Cell Physiology ◽

10.1152/ajpcell.00001.2015 ◽

2015 ◽

Vol 308 (10) ◽

pp. C827-C834 ◽

Cited By ~ 14

Author(s):

Jay M. Sage ◽

Anthony J. Cura ◽

Kenneth P. Lloyd ◽

Anthony Carruthers

Keyword(s):

Binding Site ◽

Glucose Transport ◽

Glucose Transporter ◽

Cytochalasin B ◽

Sugar Transport ◽

Nucleotide Binding ◽

Nucleotide Binding Site ◽

Sugar Uptake ◽

Glucose Transporter 1 ◽

Intracellular Atp

Glucose transporter 1 (GLUT1) is the primary glucose transport protein of the cardiovascular system and astroglia. A recent study proposes that caffeine uncompetitive inhibition of GLUT1 results from interactions at an exofacial GLUT1 site. Intracellular ATP is also an uncompetitive GLUT1 inhibitor and shares structural similarities with caffeine, suggesting that caffeine acts at the previously characterized endofacial GLUT1 nucleotide-binding site. We tested this by confirming that caffeine uncompetitively inhibits GLUT1-mediated 3- O-methylglucose uptake in human erythrocytes [ Vmax and Km for transport are reduced fourfold; Ki(app) = 3.5 mM caffeine]. ATP and AMP antagonize caffeine inhibition of 3- O-methylglucose uptake in erythrocyte ghosts by increasing Ki(app) for caffeine inhibition of transport from 0.9 ± 0.3 mM in the absence of intracellular nucleotides to 2.6 ± 0.6 and 2.4 ± 0.5 mM in the presence of 5 mM intracellular ATP or AMP, respectively. Extracellular ATP has no effect on sugar uptake or its inhibition by caffeine. Caffeine and ATP displace the fluorescent ATP derivative, trinitrophenyl-ATP, from the GLUT1 nucleotide-binding site, but d-glucose and the transport inhibitor cytochalasin B do not. Caffeine, but not ATP, inhibits cytochalasin B binding to GLUT1. Like ATP, caffeine renders the GLUT1 carboxy-terminus less accessible to peptide-directed antibodies, but cytochalasin B and d-glucose do not. These results suggest that the caffeine-binding site bridges two nonoverlapping GLUT1 endofacial sites—the regulatory, nucleotide-binding site and the cytochalasin B-binding site. Caffeine binding to GLUT1 mimics the action of ATP but not cytochalasin B on sugar transport. Molecular docking studies support this hypothesis.

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Glucocorticoids Enhance Intestinal Glucose Uptake Via the Dimerized Glucocorticoid Receptor in Enterocytes

Endocrinology ◽

10.1210/en.2011-1747 ◽

2012 ◽

Vol 153 (4) ◽

pp. 1783-1794 ◽

Cited By ~ 25

Author(s):

Sybille D. Reichardt ◽

Michael Föller ◽

Rexhep Rexhepaj ◽

Ganesh Pathare ◽

Kerstin Minnich ◽

...

Keyword(s):

Small Intestine ◽

Glucose Uptake ◽

Molecular Mechanism ◽

Glucose Transport ◽

Transcriptional Control ◽

Glucose Transporter ◽

Gene Activation ◽

Mouse Strains ◽

Glucose Transporter 1

Glucocorticoid (GC) treatment of inflammatory disorders, such as inflammatory bowel disease, causes deranged metabolism, in part by enhanced intestinal resorption of glucose. However, the underlying molecular mechanism is poorly understood. Hence, we investigated transcriptional control of genes reported to be involved in glucose uptake in the small intestine after GC treatment and determined effects of GC on electrogenic glucose transport from transepithelial currents. GRvillinCre mice lacking the GC receptor (GR) in enterocytes served to identify the target cell of GC treatment and the requirement of the GR itself; GRdim mice impaired in dimerization and DNA binding of the GR were used to determine the underlying molecular mechanism. Our findings revealed that oral administration of dexamethasone to wild-type mice for 3 d increased mRNA expression of serum- and GC-inducible kinase 1, sodium-coupled glucose transporter 1, and Na+/H+ exchanger 3, as well as electrogenic glucose transport in the small intestine. In contrast, GRvillinCre mice did not respond to GC treatment, neither with regard to gene activation nor to glucose transport. GRdim mice were also refractory to GC, because dexamethasone treatment failed to increase both, gene expression and electrogenic glucose transport. In addition, the rise in blood glucose levels normally observed after GC administration was attenuated in both mutant mouse strains. We conclude that enhanced glucose transport in vivo primarily depends on gene regulation by the dimerized GR in enterocytes, and that this mechanism contributes to GC-induced hyperglycemia.

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Transepithelial glucose transport in the small intestine

Veterinarska stanica ◽

10.46419/vs.51.6.1 ◽

2020 ◽

Vol 51 (6) ◽

pp. 673-686

Author(s):

Mirela Pavić ◽

Marija Ljubojević ◽

Ivona Žura Žaja ◽

Ivana Prakatur ◽

Manuela Grčević ◽

...

Keyword(s):

Small Intestine ◽

Glucose Transport ◽

Brush Border ◽

Brush Border Membrane ◽

Glucose Transporter ◽

Enzymatic Digestion ◽

Transepithelial Transport ◽

Facilitated Diffusion ◽

Glucose Transporter 2 ◽

Complex Carbohydrates

The duodenum, jejunum and ileum are parts of the small intestine and the sites of the terminal stages of enzymatic digestion, and the majority of nutrient, electrolyte and water absorption. The apical, luminal membrane of the enterocyte is built of numerous microvilli that increase the absorptive surface of the cell. Carbohydrates, in the form of monosaccharides, oligosaccharides and especially polysaccharides, make up the largest quantitative and energetic part of the diet of most animals, including humans. Galactose, fructose and glucose, the final degradation products of polysaccharide and oligosaccharide enzymatic digestion, can be absorbed by enterocytes either by active transport or by facilitated diffusion. In the small intestine, the transepithelial transport of glucose, the most abundant monosaccharide after carbohydrate digestion and the main source of energy, is performed by a specific membrane transporter located in the brush border membrane of the enterocyte, the sodiumglucose cotransporter 1 (SGLT1). While SGLT1 transports glucose across the brush border membrane, a specific basolateral membrane glucose transporter, the sodium-independent glucose transporter 2 (GLUT2), transfers glucose out of the enterocyte down the concentration gradient. The sodium-potassium pump (Na/KATPase), as a sodium and potassium ion transporter, is functionally closely related to the sodium-dependent SGLT1. Na/KATPase is responsible for maintaining the electrochemical gradient of sodium ions, as the driving force for glucose transport via SGLT1. Transepithelial transport of glucose in the small intestine and the differentiation of enterocytes occurs relatively early during the foetal period, allowing glucose to be absorbed from ingested amniotic fluid. Nutrient transport is possible along the whole villus-crypt axis during intrauterine development, while transport shifts toward the villus tip in the mature small intestine. With maturation, glucose transport rates change not only across the villus-crypt axis, but also along the proximodistal axis in the small intestine. The glucose absorption rate shows differences between subunits of the small intestine depending on the age and type of ingested carbohydrates, where complex carbohydrates replace less complex carbohydrates or disaccharides.

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Glucose transport across lagomorph jejunum epithelium is modulated by AMP-activated protein kinase under hypoxia

Journal of Applied Physiology ◽

10.1152/japplphysiol.00436.2017 ◽

2017 ◽

Vol 123 (6) ◽

pp. 1487-1500 ◽

Cited By ~ 5

Author(s):

Franziska Dengler ◽

Reiko Rackwitz ◽

Helga Pfannkuche ◽

Gotthold Gäbel

Keyword(s):

Glucose Transport ◽

Energy Supply ◽

Glucose Transporter ◽

Short Circuit ◽

Short Circuit Current ◽

Transport Mechanisms ◽

Glucose Transporter 1 ◽

Hypoxic Conditions ◽

Adaptation Mechanisms ◽

Amp Activated Protein Kinase

The gastrointestinal epithelium possesses adaptation mechanisms to cope with huge variations in blood flow and subsequently oxygenation. Since sufficient energy supply is crucial under hypoxic conditions, glucose uptake especially must be regulated by these adaptation mechanisms. Therefore, we investigated glucose transport under hypoxic conditions. Jejunal epithelia of rabbits were incubated in Ussing chambers under short-circuit current conditions. Hypoxia was simulated by gassing with 1% O2 instead of 100% O2. The activity of sodium-coupled glucose transporter-1 (SGLT-1) was assessed by measuring the increase of short circuit current ( Isc) after the addition of 2 mM glucose to the mucosal buffer solution. We observed decreased activity of SGLT-1 after hypoxia compared with control conditions. To investigate underlying mechanisms, epithelia were exposed to agonists and antagonists of AMP-activated protein kinase (AMPK) before assessment of SGLT-1-mediated transport and the pAMPK/AMPK protein ratio. Preincubation with the antagonist restored SGLT-1 activity under hypoxic conditions to the level of control conditions, indicating an involvement of AMPK in the downregulation of SGLT-1 activity under hypoxia, which was confirmed in Western blot analysis of pAMPK/AMPK. Transepithelial flux studies using radioactively labeled glucose, ortho-methyl-glucose, fructose, and mannitol revealed no changes after hypoxic incubation. Therefore, we could exclude a decreased transepithelial glucose transport rate and increased paracellular conductance under hypoxia. In conclusion, our study hints at a decreased activity of SGLT-1 under hypoxic conditions in an AMPK-dependent manner. However, transepithelial transport of glucose is maintained. Therefore, we suggest other transport mechanisms, especially glucose transporter 1 and/or 2 to substitute SGLT-1 under hypoxia. NEW & NOTEWORTHY To our knowledge, this is the first approach to simulate hypoxia and study its effects in the jejunal epithelium using the Ussing chamber technique. We were able show that AMPK plays a role in the downregulation of SGLT-1 and that there seems to be an upregulation of other glucose transport mechanisms in the apical membrane of lagomorph jejunum epithelium under hypoxia, securing the epithelial energy supply and thus integrity.

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