Transporter GLUT4 Research Articles

Effect of adrenalectomy and insulin resistance on non‐shivering thermogenesis in the corpulent rat

Glucocorticoid hormones have been reported to impede optimal insulin sensitivity and glucose uptake in peripheral tissues via interactions with GLUT transporters, leading to insulin resistance and impaired glucose uptake via GLUT transporters. The LA/Ntul//‐cp rat expresses obesity in 25% of the offspring by 5 to 6 weeks of age but remains non diabetic throughout much if not all of its lifespan when normally reared. Groups of congenic lean and obese LA/Ntul//‐cp rats were fed low glycemic Purina Chow diets from 6 to 9 weeks of age or overfed with a high energy cafeteria diet (Café) from 9 until 12 weeks of age. Subgroups of obese animals were adrenalectomized (ADX) at 6 weeks of age (WoA) and subjected to the same dietary regimen to determine if the Café overfeeding could enhance the normal thermic response to norepinephrine (NE) in the obese phenotype and to determine if ADX would result in a restoration of glycemic status and NE‐induced thermogenesis in the obese phenotype. Measures of Oral Glucose Tolerance (OGT), Area under the glucose curve (AUC), and NE‐stimulated VO2 were determined (NE, 200 µg, s.c.) at 6, 9 and 12 WoA in all treatment groups and Insulin:Glucose ratios (I:G) at 12 WoA. Obese animal demonstrated hyperphagia at all ages studied, and Obese ADX hyperphagia from 9 to 12 WoA. OGT and AUC indicated modest glucose intolerance in the obese phenotype, and which was restored following ADX at 6 and 9 WoA. NE resulted in a progressive increase in VO2 in lean rats at each age studied, but NE‐stimulated VO2 was lower in the obese phenotype and decreased further after the Café feeding regimen. ADX was associated with a restoration of OGT, I:G and NE stimulated VO2 equivalent to that observed in lean animals at 12 weeks of age. These results are consistent with adrenocorticoid‐mediated insulin resistance likely due to a receptor level defect in insulin sensitivity as a contributory factor in the impairment in OGT and NST in the obese phenotype of this strain.

Slc2a5 (GLUT5) upregulation in hyperuricemia drives risk for fructose induced NAFLD

Epidemiological and observational studies have found a strong correlation between hyperuricemia (clinically elevated serum urate levels) and the onset of metabolic and systemic diseases. To investigate a potential causal role for urate in metabolic disease, we created a humanized mouse model utilizing a loss of function mutation in a critical intestinal urate transport protein, ABCG2. Male animals from this model were hyperuricemic and displayed fat deposition in the liver and significantly elevated serum glucose and insulin levels, hallmarks of metabolic dysfunction, and similar to what is often observed in high fructose diet models of NAFLD (Nonalcoholic fatty liver disease). However, the relationship between hyperuricemia, liver pathogenesis, and altered intestinal fructose uptake is largely unexplored.Using the Q140K+/+ hyperuricemia model we observed higher gene expression of Slc2a5 as well as increased abundance of its protein product, the apical fructose transporter GLUT5, in enterocytes. In addition, ex‐vivo intestinal fructose transport studies revealed a corresponding significant increase of fructose transport across the intestinal tissue of Q140K+/+ mice (16.497 ±5.955 vs. 34.684 ±5.31 µM/cm2). We hypothesized that HNF4a, the critical transcription factor that regulates the expression of many gut transport proteins, and has potential binding sites in the human and mouse Slc2a5 promoter region, might be sensitive to urate levels. Treatment of the human intestinal Caco‐2 cell monolayers with urate increased the protein abundance of both GLUT5 and HNF4a in a dose‐dependent manner, potentially explaining the observed increased mRNA levels of Slc2a5 in our model. We next explored the possibility that the GLUT5 abundance was further altered due to secondary urate effects on the critical transporter scaffold NEDD4 like E3 ubiquitin‐protein ligase (NEDD4L). Nedd4L gene expression was decreased, and its negative regulator, Sgk2, was significantly increased in intestinal tissue from the hyperuricemic model. Follow‐up experiments demonstrated SGK2 protein abundance is increased in Caco‐2 cells by extracellular urate. Further experiments are needed to confirm if hyperuricemia induced up‐regulation of SGK2, and subsequent down‐regulation of NEDD4L would prevent GLUT5 ubiquitination and increase its residence and abundance at the apical membrane.In conclusion, we find that hyperuricemia induced via common variants in the key intestinal urate transporter, ABCG2, can cause NAFLD and metabolic phenotypes indistinguishable from high fructose diet models of NAFLD. Here we demonstrate that urate may significantly upregulate the capacity for fructose reabsorption through the upregulation of Slc2a5 transcription and GLUT5 abundance, a finding that suggests human carriers of ABCG2 variants are not only at higher risk for hyperuricemia and gout but also the development of metabolic syndrome.

RIP140 inhibits glycolysis-dependent proliferation of breast cancer cells by regulating GLUT3 expression through transcriptional crosstalk between hypoxia induced factor and p53

Glycolysis is essential to support cancer cell proliferation, even in the presence of oxygen. The transcriptional co-regulator RIP140 represses the activity of transcription factors that drive cell proliferation and metabolism and plays a role in mammary tumorigenesis. Here we use cell proliferation and metabolic assays to demonstrate that RIP140-deficiency causes a glycolysis-dependent increase in breast tumor growth. We further demonstrate that RIP140 reduces the transcription of the glucose transporter GLUT3 gene, by inhibiting the transcriptional activity of hypoxia inducible factor HIF-2α in cooperation with p53. Interestingly, RIP140 expression was significantly associated with good prognosis only for breast cancer patients with tumors expressing low GLUT3, low HIF-2α and high p53, thus confirming the mechanism of RIP140 anti-tumor activity provided by our experimental data. Overall, our work establishes RIP140 as a critical modulator of the p53/HIF cross-talk to inhibit breast cancer cell glycolysis and proliferation.

Developing a Pipeline for Personalized Diagnoses of Glut1 Deficiency Syndrome

Glut1 deficiency syndrome (Glut1DS) is a brain metabolic disorder, caused by the impairment of glucose transport in the brain. Glut1DS occurs when there is a mutation in the SLC2A1 gene, which encodes for the protein glucose transporter protein type 1. Around 500 people worldwide suffer from this disease, and most deal with symptoms such as seizures, movement disorders, and in more severe cases, microcephaly. A common treatment for Glut1DS is the ketogenic diet, which provides the brain with an alternate energy source. Patients suffering from Glut1DS have been shown to respond more positively to this treatment when they are able to start it early in life.Unfortunately, due to the variety of phenotypes associated with Glut1DS, there is often a large gap between onset of symptoms and diagnosis. This is problematic because a delay in diagnosis means a delay in treatment, leading to more severe disease progression. In order to bridge the gap, our lab applied a suite of bioinformatics techniques to characterize novel mutations and help patients achieve faster diagnoses. Because Glut1DS patients with different mutations experience varying loss of function of the Glut1 transporter, linking mutation type to phenotype could help patients receive a faster diagnosis, allowing them to start treatment earlier.In order to do this, we analyzed and classified different mutations in the SLC2A1 gene based on predicted pathogenicity. By comparing these data to known Glut1DS patient phenotypes, we were able to able to define five mutation classes based on severity. This type of analysis can be used to provide a faster diagnosis and personalized treatment plans for patients based on their mutation class. As personalized medicine for rare genetic diseases progresses, a database of mutations and severity class could help patients start life‐changing treatment much earlier. Additionally, this model for pipeline development could be expanded to assist in the diagnosis of other rare genetic diseases.

An Exercise‐Driven, Insulin‐Independent Glucose Uptake Pathway in Contracting Skeletal Muscle

Glucose uptake by skeletal muscles, which import and store up to 80% of circulating glucose, plays a major role in glucose homeostasis. Prior research has focused largely on the insulin regulated GLUT4 transporter, which mediates glucose uptake in quiescent (non‐contracting) muscles using a canonical insulin‐dependent translocation mechanism. An ongoing paradox in the field is that actively contracting muscles take up glucose at 50‐100x greater rates than quiescent muscles, despite declining insulin levels. For this reason, exercise is a potent treatment for disorders of insulin insufficiency and insulin resistance. However, despite more than 30 years of study, the mechanism by which contracting muscles take up glucose without a requirement for insulin remains incompletely understood. It is proposed that GLUT4‐translocation occurs using signaling pathways that bypass the insulin receptor. However, no GLUT4 models have accounted for all the glucose taken up by contracting muscles or the great discrepancy between measured GLUT4 translocation (2‐fold increase in membrane density) and glucose uptake rate (50‐100‐fold increase), suggesting the existence of additional mechanisms. The goals of this study were to:i) develop a technology based on Inductively Coupled Plasma‐Mass Spectroscopy (ICP‐MS) that allows simultaneous detection of multiple transported species, including 13C‐labeled hexoses; and ii) test the hypothesis that contraction‐stimulated glucose uptake may be linked to Na,K‐ATPase (NKA) transport, which is also dramatically stimulated during muscle contraction. We measured uptake of Rb (a congener for K+), and 13C‐[6C]‐D‐glucose or 13C‐[6C]‐2‐deoxy glucose in isolated mouse EDL muscles stimulated to contract ex vivo. Muscles were obtained from WT mice. Glucose uptake was measured for 5 min at 32 C in a physiological solution containing 200 mM tracer RbCl and 11mM 13C glucose. Following uptake, the Rb and 13C content of the muscle were measured by ICP‐MS. We achieved a Limit of Detection of 54uM for 13C glucose in mouse muscle. This detection power for 13C by ICP‐MS is entirely new and was achieved by combining technical approaches: i) introduction of 13C‐based hexose substrates; ii) modifications to sample preparation that reduce background carbon; iii) ratiometric monitoring of the 13C/12C signal; and iv) 13C‐optimized instrument conditions. Contracting skeletal muscle took up 13C‐[6C]‐labeled‐D‐glucose at a rate of 10.8 mM/g‐min, and Rb at a rate of 1.2 mM/g‐min. The ability to detect glucose and other carbon‐based organic compounds by ICP‐MS is expected to advance studies of coupled transport and other biological processes that require multi‐species detection.

Sustained endocrine and exocrine function in the pancreas of the Pacific spiny dogfish post-feeding.

Secretions of the exocrine pancreas contain digestive enzymes integral to the digestive process. The Pacific spiny dogfish (Squalus suckleyi) has a discrete pancreas, divided into two lobes termed the dorsal and ventral lobes. These lobes drain into the anterior intestine via a common duct to enable digestion. Previous studies have identified that the exocrine pancreas produces (co)lipases, chymotrypsin, carboxypeptidase, and low levels of chitinases; however, investigations into other digestive enzymes are limited. We detect the presence of lipase, trypsin, and carbohydrase and show that activities are equivalent between both lobes of the pancreas. Additionally, we sought to investigate the influence of a single feeding event (2% body weight ration of herring by gavage) on enzyme activities over an extended time course (0, 20, 48, 72, 168h) post-feeding. The results indicate that there are no differences in pancreatic tissue digestive enzyme activities between fed or fasted states. Analysis of acinar cell circumference post-feeding demonstrates a significant increase at 20 and 48h, that returns to fasting levels by 72h. No significant changes were observed regarding whole-tissue insulin or glucagon mRNA abundance or with glucose transporter (glut) 1 or 3. Yet, a significant and transient decrease in glut4 and sodium glucose-linked transporter mRNA abundance was found at 48h post-feeding. We propose that the constant enzyme activity across this relatively large organ, in combination with a relatively slow rate of digestion leads to an evenly distributed, sustained release of digestive enzymes regardless of digestive state.

Towards Selective Binding to the GLUT5 Transporter: Synthesis, Molecular Dynamics and In Vitro Evaluation of Novel C-3-Modified 2,5-Anhydro-D-mannitol Analogs.

Deregulation and changes in energy metabolism are emergent and important biomarkers of cancer cells. The uptake of hexoses in cancer cells is mediated by a family of facilitative hexose membrane-transporter proteins known as Glucose Transporters (GLUTs). In the clinic, numerous breast cancers do not show elevated glucose metabolism (which is mediated mainly through the GLUT1 transporter) and may use fructose as an alternative energy source. The principal fructose transporter in most cancer cells is GLUT5, and its mRNA was shown to be elevated in human breast cancer. This offers an alternative strategy for early detection using fructose analogs. In order to selectively scout GLUT5 binding-pocket requirements, we designed, synthesized and screened a new class of fructose mimics based upon the 2,5-anhydromannitol scaffold. Several of these compounds display low millimolar IC50 values against the known high-affinity 18F-labeled fructose-based probe 6-deoxy-6-fluoro-D-fructose (6-FDF) in murine EMT6 breast cancer cells. In addition, this work used molecular docking and molecular dynamics simulations (MD) with previously reported GLUT5 structures to gain better insight into hexose–GLUT interactions with selected ligands governing their preference for GLUT5 compared to other GLUTs. The improved inhibition of these compounds, and the refined model for their binding, set the stage for the development of high-affinity molecular imaging probes targeting cancers that express the GLUT5 biomarker.

Placental nutrient transporters adapt during persistent maternal hypoglycaemia in rats

Maternal malnutrition is associated with decreased nutrient transfer to the foetus, which may lead to foetal growth restriction, predisposing children to a variety of diseases. However, regulation of placental nutrient transfer during decreased nutrient availability is not fully understood. In the present study, the aim was to investigate changes in levels of placental nutrient transporters accompanying maternal hypoglycaemia following different durations and stages of gestation in rats. Maternal hypoglycaemia was induced by insulin-infusion throughout gestation until gestation day (GD)20 or until end of organogenesis (GD17), with sacrifice on GD17 or GD20. Protein levels of placental glucose transporters GLUT1 (45/55 kDa isotypes) and GLUT3, amino acid transporters SNAT1 and SNAT2, and insulin receptor (InsR) were assessed. On GD17, GLUT1-45, GLUT3, and SNAT1 levels were increased and InsR levels decreased versus controls. On GD20, following hypoglycaemia throughout gestation, GLUT3 levels were increased, GLUT1-55 showed the same trend. After cessation of hypoglycaemia at end of organogenesis, GLUT1-55, GLUT3, and InsR levels were increased versus controls, whereas SNAT1 levels were decreased. The increases in levels of placental nutrient transporters seen during maternal hypoglycaemia and hyperinsulinemia likely reflect an adaptive response to optimise foetal nutrient supply and development during limited availability of glucose.

The glucose transporter GLUT3 controls T helper 17 cell responses through glycolytic-epigenetic reprogramming

Metabolic reprogramming is a hallmark of activated Tcells. The switch from oxidative phosphorylation to aerobic glycolysis provides energy and intermediary metabolites for the biosynthesis of macromolecules to support clonal expansion and effector function. Here, we show that glycolytic reprogramming additionally controls inflammatory gene expression via epigenetic remodeling. We found that the glucose transporter GLUT3 is essential for the effector functions of Th17 cells in models of autoimmune colitis and encephalomyelitis. At the molecular level, we show that GLUT3-dependent glucose uptake controls a metabolic-transcriptional circuit that regulates the pathogenicity of Th17 cells. Metabolomic, epigenetic, and transcriptomic analyses linked GLUT3 to mitochondrial glucose oxidation and ACLY-dependent acetyl-CoA generation as a rate-limiting step in the epigenetic regulation of inflammatory gene expression. Our findings are also important from a translational perspective because inhibiting GLUT3-dependent acetyl-CoA generation is a promising metabolic checkpoint to mitigate Th17-cell-mediated inflammatory diseases.

Interleukin-6 mimics insulin-dependent cellular distribution of some cytoskeletal proteins and Glut4 transporter without effect on glucose uptake in 3T3-L1 adipocytes.

Interleukin (IL)-6, a known proinflammatory cytokine, is released in both visceral adipose tissue and contracting skeletal muscle. In this study, we used microRNA profiling as a screening method to identify miRNA species modified by IL-6 treatment in mouse 3T3-L1 adipocytes. miRNA microarray analysis and qRT-PCR revealed increased expression of miR-146b-3p in adipocytes exposed to IL-6 (1ng/ml) during 8-day differentiation. On the basis of ontological analysis of potential targets, selected proteins associated with cytoskeleton and transport were examined in the context of adipocyte response to insulin, using immunofluorescence and confocal microscopy. We concluded that IL-6: (i) does not affect insulin action on actin cellular distribution; (ii) modulates the effect of insulin on myosin light chain kinase (Mylk) distribution by preventing its shift toward cytoplasm; (iii) mimics the effect of insulin on dynein distribution by increasing its near-nuclear accumulation; (iv) mimics the effect of insulin on glucose transporter Glut4 distribution, especially by increasing its near-nuclear accumulation; (v) supports insulin action on early endosome marker Rab4A near-nuclear accumulation. Moreover, as IL-6 did not disturb insulin-dependent glucose uptake, our results do not confirm the IL-6-induced impairment of insulin action observed in some invitro studies, suggesting that the effect of IL-6 is dose dependent.

Molecular identification and postprandial regulation of glucose carrier proteins in the hindgut of Pacific hagfish, Eptatretus stoutii.

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 (∼84%) and 1 mM (∼183%) 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.

Suprachiasmatic nucleus-mediated glucose entry into the arcuate nucleus determines the daily rhythm in blood glycemia

Glycemia is maintained within very narrow boundaries with less than 5% variation at a given time of the day. However, over the circadian cycle, glycemia changes with almost 50% difference. How the suprachiasmatic nucleus, the biological clock, maintains these day-night variations with such tiny disparities remains obscure. We show that via vasopressin release at the beginning of the sleep phase, the suprachiasmatic nucleus increases the glucose transporter GLUT1 in tanycytes. Hereby GLUT1 promotes glucose entrance into the arcuate nucleus, thereby lowering peripheral glycemia. Conversely, blocking vasopressin activity or the GLUT1 transporter at the daily trough of glycemia increases circulating glucose levels usually seen at thepeak of the rhythm. Thus, biological clock-controlled mechanisms promoting glucose entry into the arcuate nucleus explain why peripheral blood glucose is low before sleep onset.

Computational Modelling of Glucose Uptake in the Enterocyte

We describe an implemented model of glucose absorption in the enterocyte, as previously published by Afshar et al. (2019), The model used mechanistic descriptions of all the responsible transporters and was built in the CellML framework. It was validated against published experimental data and implemented in a modular structure which allows each individual transporter to be edited independently from the other transport protein models. The composite model was then used to study the role of the sodium-glucose cotransporter (SGLT1) and the glucose transporter type 2 (GLUT2), along with the requirement for the existence of the apical Glut2 transporter, especially in the presence of high luminal glucose loads, in order to enhance the absorption. Here we demonstrate the reproduction of the figures in the original paper by using the associated model. EDITOR'S NOTE (v3): Instructions within the manuscript changed, in order to properly execute the model files. Spelling of author's name corrected in filenames. (v4): Abstract fixes.

Computational Modelling of Glucose Uptake in the Enterocyte

We describe an implemented model of glucose absorption in the enterocyte, as previously published by Afshar et al. Afshar et al. (2019), The model used mechanistic descriptions of all the responsible transporters and was built in the CellML framework. It was validated against published experimental data and implemented in a modular structure which allows each individual transporter to be edited independently from the other transport protein models. The composite model was then used to study the role of the sodium-glucose cotransporter (SGLT1) and the glucose transporter type 2 (GLUT2), along with the requirement for the existence of the apical Glut2 transporter, especially in the presence of high luminal glucose loads, in order to enhance the absorption. Here we demonstrate the reproduction of the figures in the original paper by using the associated model. EDITOR'S NOTE (v2): Instructions within the manuscript changed, in order to properly execute the model files. Spelling of author's name corrected in filenames.

Computational Modelling of Glucose Uptake in the Enterocyte

We describe an implemented model of glucose absorption in the enterocyte, as previously published by Afshar et al. (2019), The model used mechanistic descriptions of all the responsible transporters and was built in the CellML framework. It was validated against published experimental data and implemented in a modular structure which allows each individual transporter to be edited independently from the other transport protein models. The composite model was then used to study the role of the sodium-glucose cotransporter (SGLT1) and the glucose transporter type 2 (GLUT2), along with the requirement for the existence of the apical Glut2 transporter, especially in the presence of high luminal glucose loads, in order to enhance the absorption. Here we demonstrate the reproduction of the figures in the original paper by using the associated model. EDITOR'S NOTE (v3): Instructions within the manuscript changed, in order to properly execute the model files. Spelling of author's name corrected in filenames. (v4): Abstract fixes.

Carnosic Acid Attenuates the Free Fatty Acid-Induced Insulin Resistance in Muscle Cells and Adipocytes

Elevated blood free fatty acids (FFAs), as seen in obesity, impair insulin action leading to insulin resistance and Type 2 diabetes mellitus. Several serine/threonine kinases including JNK, mTOR, and p70 S6K cause serine phosphorylation of the insulin receptor substrate (IRS) and have been implicated in insulin resistance. Activation of AMP-activated protein kinase (AMPK) increases glucose uptake, and in recent years, AMPK has been viewed as an important target to counteract insulin resistance. We reported previously that carnosic acid (CA) found in rosemary extract (RE) and RE increased glucose uptake and activated AMPK in muscle cells. In the present study, we examined the effects of CA on palmitate-induced insulin-resistant L6 myotubes and 3T3L1 adipocytes. Exposure of cells to palmitate reduced the insulin-stimulated glucose uptake, GLUT4 transporter levels on the plasma membrane, and Akt activation. Importantly, CA attenuated the deleterious effect of palmitate and restored the insulin-stimulated glucose uptake, the activation of Akt, and GLUT4 levels. Additionally, CA markedly attenuated the palmitate-induced phosphorylation/activation of JNK, mTOR, and p70S6K and activated AMPK. Our data indicate that CA has the potential to counteract the palmitate-induced muscle and fat cell insulin resistance.

NARATIVE REVIEW: POTENSI INULIN UMBI DAHLIA SEBAGAI ANTI DIABETES

Inulin is a type of polysaccharide that is commonly found in nature derived from the dahlia tuber plant, and other plants such as chicory, Jerusalem artichoke, Yaco´n potato and asparagus. Inulin is widely used in industry and pharmaceuticals. In the industrial world, inulin is used as a source of natural sweetener, enhances the taste of food, ferments, and is a low-fiber food source. While in the pharmaceutical world, inulin can be used in several studies, one of which is as an anti-diabetic. This study aims to determine the potential of dahlia tuber inulin as an anti-diabetic. The type of research is a narrative review. Search data using three databases, namely Elsevier (SCOPUS), Pubmed and Google Scholar with a limitation of the last 10 years of articles with the keyword "inulin for diabetes", with the PRISMA method. The results showed that inulin works on glucose absorption in the intestine, lowers blood sugar levels, lowers hemoglobin A1c, increases circulating GLP-1, reduces hyperglycemia, reduces insulin resistance (IR) and hyperlipidemia, reduces oxidative stress, increases insulin and leptin levels, facilitates glucose transport of GLUT4 by activating the PI3K/Akt pathway, is anti-inflammatory, and is involved in the expression of several anti-hyperglycemic genes. The conclusion is that dahlia tuber inulin has an anti-diabetic effect.

Differential Expression of Glucose Transporter Proteins GLUT-1, GLUT-3, GLUT-8 and GLUT-12 in the Placenta of Macrosomic, Small-for-Gestational-Age and Growth-Restricted Foetuses.

Placental transfer of glucose constitutes one of the major determinants of the intrauterine foetal growth. The objective of the present study was to evaluate the expression of glucose transporter proteins GLUT-1, GLUT-3, GLUT-8 and GLUT-12 in the placenta of macrosomic, small-for-gestational-age (SGA) and growth-restricted foetuses (FGR). A total of 70 placental tissue samples were collected from women who delivered macrosomic ≥4000 g (n = 26), SGA (n = 11), growth-restricted (n = 13) and healthy control neonates (n = 20). Computer-assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected GLUT proteins. Immunohistochemical staining identified the presence of all glucose transporters in the placental tissue. Quantitative morphometric analysis performed for the vascular density-matched placental samples revealed a significant decrease in GLUT-1 and increase in GLUT-3 protein expression in pregnancies complicated by FGR as compared to other groups (p < 0.05). In addition, expression of GLUT-8 was significantly decreased among SGA foetuses (p < 0.05). No significant differences in GLUTs expression were observed in women delivering macrosomic neonates. In the SGA group foetal birth weight (FBW) was negatively correlated with GLUT-3 (rho = −0.59, p < 0.05) and positively with GLUT-12 (rho = 0.616, p < 0.05) placental expression. In addition, a positive correlation between FBW and GLUT-12 expression in the control group (rho = 0.536, p < 0.05) was noted. In placentas derived from FGR-complicated pregnancies the expression of two major glucose transporters GLUT-1 and GLUT-3 is altered. On the contrary, idiopathic foetal macrosomia is not associated with changes in the placental expression of GLUT-1, GLUT-3, GLUT-8 and GLUT-12 proteins.

Abstract 13936: Cardiac Beta3-Adrenergic Receptors Increase Pentose Phosphate Pathway Flux And Protect Against Hypertrophic Remodeling By Reducing Oxidative Stress

Introduction: Cardiac beta3-adrenergic receptors (β3AR) mediate effects opposite to those of β1AR and β2AR and are upregulated during the development of hypertrophy or heart failure (HF). We previously showed that upon hemodynamic or neurohormonal stress β3AR confer protection against cardiac fibrosis and hypertrophic remodeling, two key components of the progression towards HF. Hypothesis: We tested the hypothesis that modulations of cardiac metabolism are implicated in the myocardial protection by β3AR Results: In a transgenic mouse model with cardiac-specific expression of the human β3AR (TG; compared to their wild-type littermates (WT)) myocardial glucose uptake is enhanced both in vivo ( 18 Fluoro-deoxy-glucose by PET-CT) and in isolated adult cardiac myocytes exposed to hemodynamic stress by transverse aortic constriction for 9 weeks (TAC). In addition, a decrease in glycaemia during insulin tolerance test as well as an increase in Glut4 transporter in TG post-TAC suggest an insulin-dependency, as well as sensitization underlying the accrued glucose entry. Targeted metabolomics on cardiac tissue from TG (vs. WT) revealed a significant increase of several intermediates of the pentose phosphate pathway (PPP) post-TAC. Transcriptional expression from isolated cardiac myocytes showed an upregulation of several key enzymes of the pathway, that correlate with an elevation of NADPH levels, a major product of the PPP, with no modifications in nucleotides levels, implying a re-entry via the lower glycolysis. Consistent with an upregulated PPP, we found an increase in the ratio of reduced-to-oxidized Glutathione and a decrease in several indicators of oxidative stress (ROS production, MetO) both indicating a reduced oxidative stress. Conclusion: β3AR mediate an increased flux through the PPP, sustained by an enhanced glucose uptake, in cardiac myocytes upon prolonged hemodynamic stress. The associated renewal of the NADPH pool and cellular detoxification of ROS may contribute to the protective role of β3AR against hypertrophic remodeling. As β3AR agonists are currently used in clinical practice for urological indications, these original cardiac protective mechanisms may offer immediate perspectives for the prevention or treatment of HF.

Placental expression of glucose transporters GLUT-1, GLUT-3, GLUT-8 and GLUT-12 in pregnancies complicated by gestational and type 1 diabetes mellitus.

ABSTRACTAims/IntroductionThe aim of the present study was to evaluate the placental expression of glucose transporters GLUT‐1, GLUT‐3, GLUT‐8 and GLUT‐12 in term pregnancies complicated by well‐controlled gestational (GDM) and type 1 pregestational diabetes mellitus (PGDM).Materials and MethodsA total of 103 placental samples were obtained from patients diagnosed with GDM (n = 60), PGDM (n = 20) and a non‐diabetic control group (n = 23). Computer‐assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected GLUT proteins.ResultsImmunohistochemical techniques used for the identification of GLUT‐1, GLUT‐3, GLUT‐8 and GLUT‐12 revealed the presence of all glucose transporters in the placental tissue. Morphometric evaluation performed for the vascular density‐matched placental samples demonstrated a significant increase in the expression of GLUT‐1 protein in patients with PGDM as compared to GDM and control groups (P < 0.05). With regard to the expression of the other GLUT isoforms, no statistically significant differences were observed between patients from the diabetic and control populations. Positive correlations between fetal birthweight and the expression of GLUT‐1 protein in the PGDM group (rho = 0.463, P < 0.05) and GLUT‐12 in the control group (rho = 0.481, P < 0.05) were noted.ConclusionsIn term pregnancies complicated by well‐controlled GDM/PGDM, expression of transporters GLUT‐3, GLUT‐8 and GLUT‐12 in the placenta remains unaffected. Increased expression of GLUT‐1 among women with type 1 PGDM might contribute to a higher rate of macrosomic fetuses in this population.