RESUMO
BACKGROUND: The liver fluke Clonorchis sinensis imports large amounts of glucose to generate energy and metabolic intermediates through glycolysis. We hypothesized that C. sinensis absorbs glucose through glucose transporters and identified four subtypes of glucose transporter (CsGTP) and one sodium glucose co-transporter (CsSGLT) in C. sinensis. METHODOLOGY/PRINCIPAL FINDINGS: Expressed sequence tags encoding CsGTPs were retrieved from the C. sinensis transcriptome database, and their full-length cDNA sequences were obtained by rapid amplification of cDNA ends (RACE). The tissue distribution of glucose transporters in C. sinensis adults was determined using immunohistochemical staining. Developmental expression was measured using RT-qPCR. The transport and distribution of glucose into living C. sinensis were monitored using confocal microscopy. Membrane topology and key functional residues of CsGTPs were homologous to their counterparts in animals and humans. CsGTP1, 2, and 4 were transcribed 2.4-5.5 times higher in the adults than metacercariae, while CsGTP3 was transcribed 2.1 times higher in the metacercariae than adults. CsSGLT transcription was 163.6 times higher in adults than in metacercariae. In adults, CsSGLT was most abundant in the tegument; CsGTP3 and CsSGLT were localized in the vitelline gland, uterine wall, eggs, mesenchymal tissue, and testes; CsGTP4 was found in sperm and mesenchymal tissue; and CsGTP1 was mainly in the sperm and testes. In C. sinensis adults, exogenous glucose is imported in a short time and is present mainly in the middle and posterior body, in which the somatic and reproductive organs are located. Of the exogenous glucose, 53.6% was imported through CsSGLT and 46.4% through CsGTPs. Exogenous glucose import was effectively inhibited by cytochalasin B and phlorizin. CONCLUSIONS/SIGNIFICANCE: We propose that CsSGLT cooperates with CsGTPs to import exogenous glucose from the environmental bile, transport glucose across mesenchymal tissue cells, and finally supply energy-demanding organs in C. sinensis adults. Studies on glucose transporters may pave the way for the development of new anthelmintic drugs.
Assuntos
Clonorchis sinensis , Proteínas Facilitadoras de Transporte de Glucose , Glucose , Proteínas de Transporte de Sódio-Glucose , Animais , Clonorchis sinensis/metabolismo , Clonorchis sinensis/genética , Glucose/metabolismo , Proteínas de Transporte de Sódio-Glucose/metabolismo , Proteínas de Transporte de Sódio-Glucose/genética , Proteínas Facilitadoras de Transporte de Glucose/metabolismo , Proteínas Facilitadoras de Transporte de Glucose/genética , Clonorquíase/parasitologia , Transporte BiológicoRESUMO
BACKGROUND: A fructose high-salt (FHS) diet increases systolic blood pressure and Ang II (angiotensin II)-stimulated proximal tubule (PT) superoxide (O2-) production. These increases are prevented by scavenging O2- or an Ang II type 1 receptor antagonist. SGLT4 (sodium glucose-linked cotransporters 4) and SGLT5 are implicated in PT fructose reabsorption, but their roles in fructose-induced hypertension are unclear. We hypothesized that PT fructose reabsorption by SGLT5 initiates a genetic program enhancing Ang II-stimulated oxidative stress in males and females, thereby causing fructose-induced salt-sensitive hypertension. METHODS: We measured systolic blood pressure in male and female Sprague-Dawley (wild type [WT]), SGLT4 knockout (-/-), and SGLT5-/- rats. Then, we measured basal and Ang II-stimulated (37 nmol/L) O2- production by PTs and conducted gene coexpression network analysis. RESULTS: In male WT and female WT rats, FHS increased systolic blood pressure by 15±3 (n=7; P<0.0027) and 17±4 mmâ Hg (n=9; P<0.0037), respectively. Male and female SGLT4-/- had similar increases. Systolic blood pressure was unchanged by FHS in male and female SGLT5-/-. In male WT and female WT fed FHS, Ang II stimulated O2- production by 14±5 (n=6; P<0.0493) and 8±3 relative light units/µg protein/s (n=7; P<0.0218), respectively. The responses of SGTL4-/- were similar. Ang II did not stimulate O2- production in tubules from SGLT5-/-. Five gene coexpression modules were correlated with FHS. These correlations were completely blunted in SGLT5-/- and partially blunted by chronically scavenging O2- with tempol. CONCLUSIONS: SGLT5-mediated PT fructose reabsorption is required for FHS to augment Ang II-stimulated proximal nephron O2- production, and increases in PT oxidative stress likely contribute to FHS-induced hypertension.
Assuntos
Pressão Sanguínea , Frutose , Hipertensão , Túbulos Renais Proximais , Estresse Oxidativo , Proteínas de Transporte de Sódio-Glucose , Animais , Feminino , Masculino , Ratos , Angiotensina II , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Modelos Animais de Doenças , Frutose/efeitos adversos , Frutose/farmacologia , Hipertensão/metabolismo , Hipertensão/genética , Hipertensão/induzido quimicamente , Hipertensão/fisiopatologia , Túbulos Renais Proximais/metabolismo , Túbulos Renais Proximais/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Ratos Sprague-Dawley , Cloreto de Sódio na Dieta/efeitos adversos , Proteínas de Transporte de Sódio-Glucose/genética , Proteínas de Transporte de Sódio-Glucose/metabolismoRESUMO
Genetic mechanisms of blood pressure (BP) regulation remain poorly defined. Using kidney-specific epigenomic annotations and 3D genome information we generated and validated gene expression prediction models for the purpose of transcriptome-wide association studies in 700 human kidneys. We identified 889 kidney genes associated with BP of which 399 were prioritised as contributors to BP regulation. Imputation of kidney proteome and microRNAome uncovered 97 renal proteins and 11 miRNAs associated with BP. Integration with plasma proteomics and metabolomics illuminated circulating levels of myo-inositol, 4-guanidinobutanoate and angiotensinogen as downstream effectors of several kidney BP genes (SLC5A11, AGMAT, AGT, respectively). We showed that genetically determined reduction in renal expression may mimic the effects of rare loss-of-function variants on kidney mRNA/protein and lead to an increase in BP (e.g., ENPEP). We demonstrated a strong correlation (r = 0.81) in expression of protein-coding genes between cells harvested from urine and the kidney highlighting a diagnostic potential of urinary cell transcriptomics. We uncovered adenylyl cyclase activators as a repurposing opportunity for hypertension and illustrated examples of BP-elevating effects of anticancer drugs (e.g. tubulin polymerisation inhibitors). Collectively, our studies provide new biological insights into genetic regulation of BP with potential to drive clinical translation in hypertension.
Assuntos
Hipertensão , Proteoma , Humanos , Pressão Sanguínea/genética , Proteoma/genética , Proteoma/metabolismo , Transcriptoma/genética , Multiômica , Hipertensão/metabolismo , Rim/metabolismo , Proteínas de Transporte de Sódio-Glucose/genética , Proteínas de Transporte de Sódio-Glucose/metabolismoRESUMO
Sodium-dependent glucose transporters (SGLTs) couple a downhill Na+ ion gradient to actively transport sugars. Here, we investigate the impact of the membrane potential on vSGLT structure and function using sugar uptake assays, double electron-electron resonance (DEER), electrostatic calculations, and kinetic modeling. Negative membrane potentials, as present in all cell types, shift the conformational equilibrium of vSGLT towards an outward-facing conformation, leading to increased sugar transport rates. Electrostatic calculations identify gating charge residues responsible for this conformational shift that when mutated reduce galactose transport and eliminate the response of vSGLT to potential. Based on these findings, we propose a comprehensive framework for sugar transport via vSGLT, where the cellular membrane potential facilitates resetting of the transporter after cargo release. This framework holds significance not only for SGLTs but also for other transporters and channels.
Assuntos
Simportadores , Simportadores/metabolismo , Açúcares , Glucose , Potenciais da Membrana , Galactose/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Proteínas de Transporte de Sódio-Glucose/genética , Proteínas de Transporte de Sódio-Glucose/química , Proteínas de Transporte de Sódio-Glucose/metabolismo , Sódio/metabolismo , Conformação ProteicaRESUMO
The targeted use of carbohydrates by feed and food industries to create balanced and cost-effective diets has generated a tremendous amount of research in carbohydrate digestion and absorption in different species. Specifically, this research has led us to a larger observation that identified different organizations of intestinal sodium-dependent glucose absorption across species, which has not been previously collated and reviewed. Thus, this review will compare the kinetic segregation of sodium-dependent glucose transport across the intestine of different species, which we have termed either homogeneous or heterogeneous systems. For instance, the pig follows a heterogeneous system of sodium-dependent glucose transport with a high-affinity, super-low-capacity (Ha/sLc) in the jejunum, and a high-affinity, super-high-capacity (Ha/sHc) in the ileum. This is achieved by multiple sodium-dependent glucose transporters contributing to each segment. In contrast, tilapia have a homogenous system characterized by high-affinity, high-capacity (Ha/Hc) throughout the intestine. Additionally, we are the first to report glucose transporter patterns across species presented from vertebrates to invertebrates. Finally, other kinetic transport systems are briefly covered to illustrate possible contributions/modulations to sodium-dependent glucose transporter organization. Overall, we present a new perspective on the organization of glucose absorption along the intestinal tract.
Assuntos
Absorção Intestinal , Proteínas de Transporte de Sódio-Glucose , Animais , Suínos , Proteínas de Transporte de Sódio-Glucose/metabolismo , Jejuno/metabolismo , Glucose/metabolismo , Proteínas Facilitadoras de Transporte de Glucose/metabolismo , Sódio/metabolismoRESUMO
The human sodium-glucose cotransporter protein (SGLT1) is an important representative of the sodium solute symporters belonging to the secondary active transporters that are critical to the homeostasis of sugar, sodium, and water in the cell. The underlying transport mechanism of SGLT1 is based on switching between inward- and outward-facing conformations, known as the alternating access model, which is crucial for substrate transport, and has also been postulated for water permeation. However, the nature of water transport remains unclear and is disputed along the passive and active transport, with the latter postulating the presence of the pumping effect. To better examine the water transport in SGLT1, we performed a series of equilibrium all-atom molecular dynamics simulations, totaling over 6 µs of sample representative conformational states of SGLT1 and its complexes, with the natural substrates, ions, and inhibitors. In addition to elucidating the basic physical factors influencing water permeation, such as channel openings and energetics, we focus on dynamic flexibility and its relationship with domain motion. Our results clearly demonstrate a dependence of instantaneous water flux on the channel opening and local water diffusion in the channel, strongly supporting the existence of a passive water transport in SGLT1. In addition, a strong correlation found between the local water diffusion and protein domain motion, resembling the "rocking-bundle" motion, reveals its facilitating role in the water transport.
Assuntos
Transportador 1 de Glucose-Sódio , Simportadores , Humanos , Transporte Biológico , Transportador 1 de Glucose-Sódio/metabolismo , Proteínas de Transporte de Sódio-Glucose/metabolismo , Simportadores/metabolismo , Sódio/metabolismo , Água/química , Glucose/metabolismoRESUMO
Sodium-glucose co-transporters (SGLTs) family members are involved in several vital biological functions. Except for SGLT3, they are involved in the mechanisms of active transport of sodium and glucose and several micromolecules. The discovery of functions and mechanisms of SGLT1 inhibition and, in particular, of SGLT2 has radically changed the natural history of some pathologies. SGLT2 inhibitors have revolutionized the therapeutic approach not only of type 2 diabetes mellitus but also of heart failure and chronic kidney failure. Considering the role played by the other SGLTs and the functions still unknown to date, clinical implications of the inhibition of SGLT2 could represent the prelude for a wider modulation of these cotransporters. A better understanding of the role and function of SGLTs could represent a revolution in the therapeutic approach in the hepatological, metabolic, neurological and oncological fields. The purpose of this review is to illustrate the knowledge currently available on SGLTs, its clinical implications and future perspectives.
Assuntos
Diabetes Mellitus Tipo 2 , Humanos , Transportador 2 de Glucose-Sódio/metabolismo , Transportador 2 de Glucose-Sódio/uso terapêutico , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Proteínas de Transporte de Sódio-Glucose/metabolismo , Proteínas de Transporte de Sódio-Glucose/uso terapêutico , Glucose/metabolismo , Sódio/metabolismo , Sódio/uso terapêutico , Hipoglicemiantes/farmacologiaRESUMO
Background: Mediating glucose absorption in the small intestine and renal clearance, sodium glucose cotransporters (SGLTs) have emerged as an attractive therapeutic target in diabetic patients. A substantial fraction of patients, however, only achieve inadequate glycemic control. Thus, we aimed to assess the potential of the SGLT-targeting PET radiotracer alpha-methyl-4-deoxy-4-[18F]fluoro-D-glucopyranoside ([18F]Me4FDG) as a noninvasive intestinal and renal biomarker of SGLT-mediated glucose transport. Methods: We investigated healthy rats using a dedicated small animal PET system. Dynamic imaging was conducted after administration of the reference radiotracer 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), or the SGLT-targeting agent, [18F]Me4FDG either directly into the digestive tract (for assessing intestinal absorption) or via the tail vein (for evaluating kidney excretion). To confirm the specificity of [18F]Me4FDG and responsiveness to treatment, a subset of animals was also pretreated with the SGLT inhibitor phlorizin. In this regard, an intraintestinal route of administration was used to assess tracer absorption in the digestive tract, while for renal assessment, phlorizin was injected intravenously (IV). Results: Serving as reference, intestinal administration of [18F]FDG led to slow absorption with retention of 89.2 ± 3.5% of administered radioactivity at 15 min. [18F]Me4FDG, however, was rapidly absorbed into the blood and cleared from the intestine within 15 min, leading to markedly lower tracer retention of 18.5 ± 1.2% (P < 0.0001). Intraintestinal phlorizin led to marked increase of [18F]Me4FDG uptake (15 min, 99.9 ± 4.7%; P < 0.0001 vs. untreated controls), supporting the notion that this PET agent can measure adequate SGLT inhibition in the digestive tract. In the kidneys, radiotracer was also sensitive to SGLT inhibition. After IV injection, [18F]Me4FDG reabsorption in the renal cortex was significantly suppressed by phlorizin when compared to untreated animals (%ID/g at 60 min, 0.42 ± 0.10 vs. untreated controls, 1.20 ± 0.03; P < 0.0001). Conclusion: As a noninvasive read-out of the concurrent SGLT expression in both the digestive tract and the renal cortex, [18F]Me4FDG PET may serve as a surrogate marker for treatment response to SGLT inhibition. As such, [18F]Me4FDG may enable improvement in glycemic control in diabetes by PET-based monitoring strategies.
Assuntos
Fluordesoxiglucose F18 , Tomografia por Emissão de Pósitrons , Animais , Glucose/metabolismo , Glucosídeos , Florizina , Tomografia por Emissão de Pósitrons/métodos , Ratos , Sódio/metabolismo , Proteínas de Transporte de Sódio-Glucose/metabolismoRESUMO
Neutropenia and neutrophil dysfunction found in deficiencies in G6PC3 and in the glucose-6-phosphate transporter (G6PT/SLC37A4) are due to accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P), an inhibitor of hexokinase made from 1,5-anhydroglucitol (1,5-AG), an abundant polyol present in blood. Lowering blood 1,5-AG with an SGLT2 inhibitor greatly improved neutrophil counts and function in G6PC3-deficient mice and in patients with G6PT-deficiency. We evaluate this treatment in two G6PC3-deficient children. While neutropenia was severe in one child (PT1), which was dependent on granulocyte cololony-stimulating factor (GCSF), it was significantly milder in the other one (PT2), which had low blood 1,5-AG levels and only required GCSF during severe infections. Treatment with the SGLT2-inhibitor empagliflozin decreased 1,5-AG in blood and 1,5-AG6P in neutrophils and improved (PT1) or normalized (PT2) neutrophil counts, allowing to stop GCSF. On empagliflozin, both children remained infection-free (>1 year - PT2; >2 years - PT1) and no side effects were reported. Remarkably, sequencing of SGLT5, the gene encoding the putative renal transporter for 1,5-AG, disclosed a rare heterozygous missense mutation in PT2, replacing the extremely conserved Arg401 by a histidine. The higher urinary clearance of 1,5-AG explains the more benign neutropenia and the outstanding response to empagliflozin treatment found in this child. Our data shows that SGLT2 inhibitors are an excellent alternative to treat the neutropenia present in G6PC3-deficiency.
Assuntos
Doença de Depósito de Glicogênio Tipo I , Neutropenia , Proteínas de Transporte de Sódio-Glucose/metabolismo , Animais , Antiporters/genética , Compostos Benzidrílicos , Glucose-6-Fosfatase/genética , Glucose-6-Fosfatase/metabolismo , Glucosídeos/uso terapêutico , Doença de Depósito de Glicogênio Tipo I/tratamento farmacológico , Doença de Depósito de Glicogênio Tipo I/genética , Humanos , Camundongos , Proteínas de Transporte de Monossacarídeos/genética , Mutação , Neutropenia/tratamento farmacológico , Neutropenia/genética , Monoéster Fosfórico Hidrolases/genéticaRESUMO
We investigated the effect of tofogliflozin, a sodium-dependent glucose cotransporter 2 inhibitor (SGLT2i), on retinal blood flow dysregulation, neural retinal dysfunction, and the impaired neurovascular coupling in type 2 diabetic mice. Tofogliflozin was added to mouse chow to deliver 5 mg/kg/day and 6-week-old mice were fed for 8 weeks. The longitudinal changes in the retinal neuronal function and blood flow responses to systemic hyperoxia and flicker stimulation were evaluated every 2 weeks in diabetic db/db mice that received tofogliflozin (n =6) or placebo (n = 6) from 8 to 14 weeks of age. We also evaluated glial activation and vascular endothelial growth factor (VEGF) expression by immunofluorescence. Tofogliflozin treatment caused a sustained decrease in blood glucose in db/db mice from 8 weeks of the treatment. In tofogliflozin-treated db/db mice, both responses improved from 8 to 14 weeks of age, compared with vehicle-treated diabetic mice. Subsequently, the electroretinography implicit time for the oscillatory potential was significantly improved in SGLT2i-treated db/db mice. The systemic tofogliflozin treatment prevented the activation of glial fibrillary acidic protein and VEGF protein expression, as detected by immunofluorescence. Our results suggest that glycemic control with tofogliflozin significantly improved the impaired retinal neurovascular coupling in type 2 diabetic mice with the inhibition of retinal glial activation.
Assuntos
Compostos Benzidrílicos/farmacologia , Glucosídeos/farmacologia , Acoplamento Neurovascular/fisiologia , Transportador 2 de Glucose-Sódio/metabolismo , Animais , Compostos Benzidrílicos/metabolismo , Glicemia/metabolismo , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Retinopatia Diabética/prevenção & controle , Glucosídeos/metabolismo , Hipoglicemiantes/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Acoplamento Neurovascular/efeitos dos fármacos , Retina/efeitos dos fármacos , Retina/metabolismo , Proteínas de Transporte de Sódio-Glucose/antagonistas & inibidores , Proteínas de Transporte de Sódio-Glucose/metabolismo , Transportador 2 de Glucose-Sódio/efeitos dos fármacos , Inibidores do Transportador 2 de Sódio-Glicose/metabolismo , Inibidores do Transportador 2 de Sódio-Glicose/farmacologia , Fator A de Crescimento do Endotélio Vascular/efeitos dos fármacos , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Hagfish are an excellent model species in which to draw inferences on the evolution of transport systems in early vertebrates owing to their basal position in vertebrate phylogeny. Glucose is a ubiquitous cellular energy source that is transported into cells via two classes of carrier proteins: sodium-glucose-linked transporters (Sglt; Slc5a) and glucose transporters (Glut; Slc2a). Although previous pharmacological evidence has suggested the presence of both sodium-dependent and -independent transport mechanisms in the hagfish, the molecular identities were heretofore unconfirmed. We have identified and phylogenetically characterized both a Slc5a1-like and Slc2a-like gene in the Pacific hagfish (Eptatretus stoutii), the latter sharing common ancestry with other glucose-transporting isoforms of the Slc2a family. To assess the potential postprandial regulation of these glucose transporters, we examined the abundance and localization of these transporters with qPCR and immunohistochemistry alongside functional studies using radiolabeled d-[14C]glucose. The effects of glucose or insulin injection on glucose transport rate and transporter expression were also examined to determine their potential role(s) in the regulation of intestinal glucose carrier proteins. Feeding prompted an increase in glucose uptake across the hindgut at both 0.5 mM (â¼84%) and 1 mM (â¼183%) concentrations. Concomitant increases were observed in hindgut Slc5a1 protein expression. These effects were not observed following either of glucose or insulin injection, indicating these postprandial factors are not the driving force for transporter regulation over this timeframe. We conclude that Pacific hagfish utilize evolutionarily conserved mechanisms of glucose uptake and so represent a useful model to understand early-vertebrate evolution of glucose uptake and regulation.
Assuntos
Feiticeiras (Peixe) , Insulinas , Animais , Glucose/metabolismo , Proteínas Facilitadoras de Transporte de Glucose/genética , Proteínas Facilitadoras de Transporte de Glucose/metabolismo , Feiticeiras (Peixe)/genética , Insulinas/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Sódio/metabolismo , Proteínas de Transporte de Sódio-Glucose/metabolismoRESUMO
Endometrial epithelial cells (EECs) and stromal cells (ESCs) have a close functional association. During the peri-implantation period, EECs with enhanced functional activities secrete a variety of paracrine factors to promote the decidualization of ESCs. However, little is known about the specific process by which EECs secrete paracrine factors to induce the decidualization of ESCs. Some evidence suggests that the activation of sodium-glucose cotransporter 3a (SGLT3a) induces the depolarization of ESCs to affect their function. Therefore, SGLT3a acts as a sensor molecule in certain cell types. In this study, the expression of SGLT3a was investigated in EECs to determine whether its levels increased during the peri-implantation period in female mice. The activation of SGLT3a in mouse EECs induced Na+ -dependent depolarization of the cell membrane and an influx of extracellular Ca2+ , which further promoted the expression and release of the paracrine factors prostaglandin E2 (PGE2) and F2-alpha (PGF2α) by upregulating the expression of cyclooxygenase-2. In turn, PGE2 and PGF2α induced the decidualization of ESCs. Importantly, we identified SGLT3a as a key molecule involved in the cross-talk between EECs and ESCs during the process of uterine decidualization.
Assuntos
Decídua , Dinoprostona , Proteínas de Transporte de Sódio-Glucose/metabolismo , Animais , Células Cultivadas , Dinoprosta/metabolismo , Dinoprostona/metabolismo , Endométrio/metabolismo , Células Epiteliais/metabolismo , Feminino , Camundongos , Células Estromais/metabolismoRESUMO
The kidney plays an important role in glucose homeostasis by releasing glucose into the blood stream to prevent hypoglycemia. It is also responsible for the filtration and subsequent reabsorption or excretion of glucose. As glucose is hydrophilic and soluble in water, it is unable to pass through the lipid bilayer on its own; therefore, transport takes place using carrier proteins localized to the plasma membrane. Both sodium-independent glucose transporters (GLUT proteins) and sodium-dependent glucose transporters (SGLT proteins) are expressed in kidney tissue, and mutations of the genes coding for these glucose transporters lead to renal disorders and diseases, including renal cancers. In addition, several diseases may disturb the expression and/or function of renal glucose transporters. The aim of this review is to describe the role of the kidney in glucose homeostasis and the contribution of glucose transporters in renal physiology and renal diseases.
Assuntos
Glucose/metabolismo , Homeostase/fisiologia , Rim/metabolismo , Proteínas de Transporte de Sódio-Glucose/metabolismo , Animais , Humanos , Nefropatias/metabolismoRESUMO
The taste stimulus glucose comprises approximately half of the commercial sugar sweeteners used today, whether in the form of the di-saccharide sucrose (glucose-fructose) or half of high-fructose corn syrup (HFCS). Therefore, oral glucose has been presumed to contribute to the sweet taste of foods when combined with fructose. In light of recent rodent data on the role of oral metabolic glucose signaling, we examined psychopharmacologically whether oral glucose detection may also involve an additional pathway in humans to the traditional sweet taste transduction via the class 1 taste receptors T1R2/T1R3. In a series of experiments, we first compared oral glucose detection thresholds to sucralose thresholds without and with addition of the T1R receptor inhibitor Na-lactisole. Next, we compared oral detection thresholds of glucose to sucralose and to the non-metabolizable glucose analog, α-methyl-D-glucopyranoside (MDG) without and with the addition of the glucose co-transport component sodium (NaCl). Finally, we compared oral detection thresholds for glucose, MDG, fructose, and sucralose without and with the sodium-glucose co-transporter (SGLT) inhibitor phlorizin. In each experiment, psychopharmacological data were consistent with glucose engaging an additional signaling pathway to the sweet taste receptor T1R2/T1R3 pathway. Na-lactisole addition impaired detection of the non-caloric sweetener sucralose much more than it did glucose, consistent with glucose using an additional signaling pathway. The addition of NaCl had a beneficial impact on the detection of glucose and its analog MDG and impaired sucralose detection, consistent with glucose utilizing a sodium-glucose co-transporter. The addition of the SGLT inhibitor phlorizin impaired detection of glucose and MDG more than it did sucralose, and had no effect on fructose, further evidence consistent with glucose utilizing a sodium-glucose co-transporter. Together, these results support the idea that oral detection of glucose engages two signaling pathways: one that is comprised of the T1R2/T1R3 sweet taste receptor and the other that utilizes an SGLT glucose transporter.
Assuntos
Glucose/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Proteínas de Transporte de Sódio-Glucose/metabolismo , Paladar , Adulto , Feminino , Glucose/análise , Humanos , Masculino , Pessoa de Meia-Idade , Transdução de SinaisRESUMO
Intestinal organoids derived from single cells undergo complex crypt-villus patterning and morphogenesis. However, the nature and coordination of the underlying forces remains poorly characterized. Here, using light-sheet microscopy and large-scale imaging quantification, we demonstrate that crypt formation coincides with a stark reduction in lumen volume. We develop a 3D biophysical model to computationally screen different mechanical scenarios of crypt morphogenesis. Combining this with live-imaging data and multiple mechanical perturbations, we show that actomyosin-driven crypt apical contraction and villus basal tension work synergistically with lumen volume reduction to drive crypt morphogenesis, and demonstrate the existence of a critical point in differential tensions above which crypt morphology becomes robust to volume changes. Finally, we identified a sodium/glucose cotransporter that is specific to differentiated enterocytes that modulates lumen volume reduction through cell swelling in the villus region. Together, our study uncovers the cellular basis of how cell fate modulates osmotic and actomyosin forces to coordinate robust morphogenesis.
Assuntos
Diferenciação Celular , Linhagem da Célula , Mucosa Intestinal/fisiologia , Mecanotransdução Celular , Osmorregulação , Celulas de Paneth/fisiologia , Células-Tronco/fisiologia , Animais , Movimento Celular , Células Cultivadas , Simulação por Computador , Feminino , Mucosa Intestinal/citologia , Mucosa Intestinal/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia Confocal , Microscopia de Vídeo , Modelos Biológicos , Morfogênese , Miosina Tipo II/genética , Miosina Tipo II/metabolismo , Organoides , Pressão Osmótica , Celulas de Paneth/metabolismo , Proteínas de Transporte de Sódio-Glucose/genética , Proteínas de Transporte de Sódio-Glucose/metabolismo , Células-Tronco/metabolismo , Estresse Mecânico , Fatores de TempoRESUMO
Resumen Los receptores del cotransportador de sodio-glucosa han demostrado una gran relevancia en la función miocárdica. Los receptores tipo 1 se encuentran en el miocardio en valores bajos, sin embargo, se elevan en patologías cardiacas por medio de distintos mecanismos moleculares. Por otra parte, los receptores tipo 2 están ausentes en el miocardio. Los fármacos que inhiben este receptor tienen beneficio cardiovascular evidente en estudios clínicos y experimentales, principalmente en pacientes con diabetes mellitus tipo 2 e insuficiencia cardiaca, en los que se ha demostrado una reducción de la mortalidad por causas cardiovasculares y reducción en hospitalización por insuficiencia cardiaca. Existen interrogantes sobre el mecanismo de acción directo de este grupo antihiperglicemiantes sobre el cardiomiocito y se han desarrollado hipótesis y teorías para explicar este efecto. El objetivo de este artículo es revisar y analizar los diferentes mecanismos metabólicos, estructurales, funcionales y mitocondriales en un contexto molecular de los inhibidores del cotransportador sodio-glucosa tipo 2. La acción fisiopatológica del receptor tipo 1 en el miocardio también es importante y se encuentran en desarrollo estudios clínicos para establecer el efecto de su inhibición a nivel cardíaco.
Abstract Sodium-glucose cotransporter receptors have demonstrated relevance in myocardial function. Type 1 receptors are found in the myocardium in low values, however, they are elevated in cardiac pathologies by means of different molecular mechanisms. On the other hand, type 2 receptors are absent in the myocardium. The drugs that inhibit this receptor have been shown to have a cardiovascular benefit demonstrated in clinical and experimental studies, mainly in patients with type 2 diabetes mellitus and heart failure, presenting a reduction in mortality due to cardiovascular causes and a reduction in hospitalization due to heart failure. Due to the above, many questions arise about the mechanism of direct action of this antihyperglycemic group on cardiomyocyte, which is why they have been developed from hypotheses and theories to clarify this action by medicines. The objective of this article is to analyze the different metabolic, structural, functional and mitochondrial mechanisms in a molecular context of the inhibitors of the sodium-glucose cotransporter type 2. On the other hand, to analyze the pathophysiological action of the type 1 receptor in the myocardium, since that future clinical studies will be developed to establish the effect with its inhibition at the cardiac level.
Assuntos
Humanos , Proteínas de Transporte de Sódio-Glucose/metabolismo , Inibidores do Transportador 2 de Sódio-Glicose/farmacocinética , Miocárdio/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Inibidores do Transportador 2 de Sódio-Glicose/metabolismoRESUMO
Active transport of sugars into bacteria occurs through symporters driven by ion gradients. LacY is the most well-studied proton sugar symporter, whereas vSGLT is the most characterized sodium sugar symporter. These are members of the major facilitator (MFS) and the amino acid-Polyamine organocation (APS) transporter superfamilies. While there is no structural homology between these transporters, they operate by a similar mechanism. They are nano-machines driven by their respective ion electrochemical potential gradients across the membrane. LacY has 12 transmembrane helices (TMs) organized in two 6-TM bundles, each containing two 3-helix TM repeats. vSGLT has a core structure of 10 TM helices organized in two inverted repeats (TM 1-5 and TM 6-10). In each case, a single sugar is bound in a central cavity and sugar selectivity is determined by hydrogen- and hydrophobic- bonding with side chains in the binding site. In vSGLT, the sodium-binding site is formed through coordination with carbonyl- and hydroxyl-oxygens from neighboring side chains, whereas in LacY the proton (H3O+) site is thought to be a single glutamate residue (Glu325). The remaining challenge for both transporters is to determine how ion electrochemical potential gradients drive uphill sugar transport.
Assuntos
Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/metabolismo , Proteínas de Transporte de Sódio-Glucose/química , Proteínas de Transporte de Sódio-Glucose/metabolismo , Sítios de Ligação , Transporte Biológico Ativo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Glucose/metabolismo , Lactose/metabolismo , Modelos Moleculares , Proteínas de Transporte de Monossacarídeos/química , Proteínas de Transporte de Monossacarídeos/metabolismo , Conformação Proteica , Açúcares/metabolismo , Simportadores/química , Simportadores/metabolismoRESUMO
AIM: We aimed to determine whether the sodium/glucose cotransporter family member SGLT3, a proposed glucose sensor, is expressed in the intestine and/or kidney, and if its expression is altered in mouse models of obesity and in humans before and after weight-loss surgery. MAIN METHODS: We used in-situ hybridization and quantitative PCR to determine whether the Sglt3 isoforms 3a and 3b were expressed in the intestine and kidney of C57, leptin-deficient ob/ob, and diabetic BTBR ob/ob mice. Western blotting and immunohistochemistry were also used to assess SGLT3 protein levels in jejunal biopsies from obese patients before and after weight-loss Roux-en-Y gastric bypass surgery (RYGB), and in lean healthy controls. KEY FINDINGS: Sglt3a/3b mRNA was detected in the small intestine (duodenum, jejunum and ileum), but not in the large intestine or kidneys of mice. Both isoforms were detected in epithelial cells (confirmed using intestinal organoids). Expression of Sglt3a/3b mRNA in duodenum and jejunum was significantly lower in ob/ob and BTBR ob/ob mice than in normal-weight littermates. Jejunal SGLT3 protein levels in aged obese patients before RYGB were lower than in lean individuals, but substantially upregulated 6 months post-RYGB. SIGNIFICANCE: Our study shows that Sglt3a/3b is expressed primarily in epithelial cells of the small intestine in mice. Furthermore, we observed an association between intestinal mRNA Sglt3a/3b expression and obesity in mice, and between jejunal SGLT3 protein levels and obesity in humans. Further studies are required to determine the possible role of SGLT3 in obesity.
Assuntos
Obesidade/metabolismo , Proteínas de Transporte de Sódio-Glucose/genética , Adulto , Animais , Modelos Animais de Doenças , Regulação para Baixo , Feminino , Derivação Gástrica , Expressão Gênica , Humanos , Insulina/metabolismo , Resistência à Insulina , Mucosa Intestinal/metabolismo , Intestino Delgado/metabolismo , Jejuno/metabolismo , Leptina/deficiência , Leptina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Obesidade/genética , Isoformas de Proteínas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Transporte de Sódio-Glucose/biossíntese , Proteínas de Transporte de Sódio-Glucose/metabolismo , Transcriptoma , Redução de PesoRESUMO
SGLTs are sodium glucose transporters found on the luminal membrane of the proximal tubule, where they reabsorb some 180 g (1 mol) of glucose from the glomerular filtrate each day. The natural glucoside phlorizin completely blocks glucose reabsorption. Oral SGLT2 inhibitors are rapidly absorbed into the blood stream, where theyremain in the circulation for hours. On glomerular filtration, they bind specifically to SGLT2 in the luminal membrane of the early proximal tubule to reduce glucose reabsorption by 50%-60%. Because of glucose excretion, these drugs lower plasma glucose and glycosylated hemoglobin levels in patients with type 2 diabetes mellitus. The drugs also protect against heart and renal failure. The aim of this review is to summarize what is known about the physiology of renal SGLTs and the pharmacology of SGLT drugs.
Assuntos
Diabetes Mellitus Tipo 2 , Inibidores do Transportador 2 de Sódio-Glicose , Diabetes Mellitus Tipo 2/tratamento farmacológico , Glucose/metabolismo , Humanos , Florizina/farmacologia , Proteínas de Transporte de Sódio-Glucose/metabolismo , Inibidores do Transportador 2 de Sódio-Glicose/farmacologiaRESUMO
We describe the dramatic differences in the synthesis and physiological and pharmacokinetical profiling of two sodium-glucose cotransporter (SGLT) drug candidates AVE2268 and AVE8887 with very similar chemical structures. It is a classic example of how a radioactive study was able to spare resources in preclinical development prior to entering a costly clinical program. It also demonstrated that radioactive compounds can be used to study differences between two very similar compounds in vivo.