mRNA Expression Of Glucose Transporter Research Articles

1-Deoxynojirimycin Isolated from a Bacillus subtilis Stimulates Adiponectin and GLUT4 Expressions in 3T3-L1 Adipocytes

We have demonstrated that 1-deoxynojirimycin (DNJ) isolated from Bacillus subtilis MORI could enhance the levels of adiponectin and its receptors in differentiated 3T3-L1 adipocytes, which has been shown to be effective in lowering blood glucose levels and enhancing insulin sensitivity. DNJ was not toxic to differentiated 3T3-L1 adipocytes for up to a concentration of 5 microM. In terms of expression levels of adiponectin and its receptors (AdipoR1 and AdipoR2), DNJ in concentrations as low as 0.5 microM elevated both mRNA and protein levels of adiponectin and transcript levels of AdipoR1 and AdipoR2. In addition, DNJ increased phosphorylation of 5' adenosine monophosphateactivated protein kinase (AMPK) in a statistically significant manner. Finally, treatment with DNJ resulted in increased mRNA expression of glucose transporter 4 (GLUT4), which encodes for a glucose transporter, along with a significant increase in glucose uptake into the adipocytes based on results of a 2-deoxy-D-[3H] glucose uptake assay. Our findings indicate that DNJ may greatly facilitate glucose uptake into adipose tissues by increasing the action of adiponectin via its up-regulated expression as well as its receptor genes. In addition, the glucose-lowering effects of DNJ may be achieved by an increased abundance of GLUT4 protein in the plasma membrane, as a consequence of the increased transcript levels of the GLUT4 gene and the activation of AMPK.

Comparative effects of single-mode vs. duration-matched concurrent exercise training on body composition, low-grade inflammation, and glucose regulation in sedentary, overweight, middle-aged men

The effect of duration-matched concurrent exercise training (CET) (50% resistance (RET) and 50% endurance (EET) training) on physiological training outcomes in untrained middle-aged men remains to be elucidated. Forty-seven men (age, 48.1 ± 6.8 years; body mass index, 30.4 ± 4.1 kg·m(-2)) were randomized into 12-weeks of EET (40-60 min of cycling), RET (10 exercises; 3-4 sets × 8-10 repetitions), CET (50% serial completion of RET and EET), or control condition. The following were determined: intervention-based changes in fitness and strength; abdominal visceral adipose tissue (VAT), total body fat (TB-FM) and fat-free (TB-FFM) mass; plasma cytokines (C-reactive protein (CRP), tumor necrosis factor-α (TNFα) interleukin-6 (IL-6)); muscle protein content of p110α and glucose transporter 4 (GLUT4); mRNA expression of GLUT4, peroxisome proliferator-activated receptor-γ coactivator-1α-β, cytochrome c oxidase, hexokinase II, citrate synthase; oral glucose tolerance; and estimated insulin sensitivity. CET promoted commensurate improvements of aerobic capacity and muscular strength and reduced VAT and TB-FM equivalently to EET and RET (p < 0.05), yet only RET increased TB-FFM (p < 0.05). Although TNFα and IL-6 were reduced after all training interventions (p < 0.05), CRP remained unchanged (p > 0.05). EET reduced area under the curve for glucose, insulin, and C-peptide, whilst CET and RET respectively reduced insulin and C-peptide, and C-peptide only (p < 0.05). Notwithstanding increased insulin sensitivity index after all training interventions (p < 0.05), no change presented for GLUT4 or p110α total protein, or chronic mRNA expression of the studied mitochondrial genes (p > 0.05). In middle-aged men, 12 weeks of duration-matched CET promoted commensurate changes in fitness and strength, abdominal VAT, plasma cytokines and insulin sensitivity, and an equidistant glucose tolerance response to EET and RET; despite no change of measured muscle mechanisms associative to insulin action, glucose transport, and mitochondrial function.

Effect of Antisense Oligodeoxynucleotides Glucose Transporter-1 on Enhancement of Radiosensitivity of Laryngeal Carcinoma

Purpose: Laryngeal carcinomas always resist to radiotherapy. Hypoxia is an important factor in radioresistance of laryngeal carcinoma. Glucose transporter-1 (GLUT-1) is considered to be a possible intrinsic marker of hypoxia in malignant tumors. We speculated that the inhibition of GLUT-1 expression might improve the radiosensitivity of laryngeal carcinoma. Methods: We assessed the effect of GLUT-1 expression on radioresistance of laryngeal carcinoma and the effect of GLUT-1 expressions by antisense oligodeoxynucleotides (AS-ODNs) on the radiosensitivity of laryngeal carcinoma in vitro and in vivo. Results: After transfection of GLUT-1 AS-ODNs: MTS assay showed the survival rates of radiation groups were reduced with the prolongation of culture time (p<0.05); Cell survival rates were significantly reduced along with the increasing of radiation dose (p<0.05). There was significant difference in the expression of GLUT-1mRNA and protein in the same X-ray dose between before and after X-ray radiation (p<0.05). In vivo, the expressions of GLUT-1 mRNA and protein after 8Gy radiation plus transfection of GLUT-1 AS-ODNs were significant decreased compared to 8Gy radiation alone (p<0.001). Conclusion: Radioresistance of laryngeal carcinoma may be associated with increased expression of GLUT-1 mRNA and protein. GLUT-1 AS-ODNs may enhance the radiosensitivity of laryngeal carcinoma mainly by inhibiting the expression of GLUT-1.

High glucose impairs gonadotropin-releasing hormone neurons in the preoptic area of the hypothalamus

Rabbits with high fat diet (HFD)-induced metabolic syndrome (MetS) developed hypogonadotropic hypogonadism (HH) and showed a reduced gonadotropin-releasing hormone (GnRH) immunopositivity in the hypothalamus (Filippi et al., 2009). This study investigated the relationship between MetS and hypothalamic alterations in HFD-rabbits. Gonadotropins levels decreased as a function of MetS severity, glucose intolerance, hypothalamic gene expression of glucose transporter 4 (GLUT4) and interleukin-6 (IL-6). HFD significantly induced mRNA expression and hypothalamic immunopositivity of GLUT4 and IL-6, as well as a low-grade hypothalamic inflammation (microglial activation with unchanged astroglia morphology), while reduced hypothalamic immunopositivity for KiSS-1 receptor (KiSS-1R), whose mRNA expression negatively correlated with glucose intolerance. Moreover, high glucose exposure down-regulated KiSS-1/KiSS-1R system and GnRH expression in human GnRH-secreting neuroblasts. A subset of HFD rabbits was treated with the farnesoid-X receptor agonist obeticholic acid, able to ameliorate glucose metabolism (Morelli et al., 2012). This treatment significantly increased GnRH mRNA and reduced GLUT4 and IL-6 immunopositivity. Our results suggest that HFD-induced glucose dysregulation negatively affects GnRH neuron function through an inflammatory injury at the hypothalamic level.

Toward the Beginning of Time: Circadian Rhythms in Metabolism Precede Rhythms in Clock Gene Expression in Mouse Embryonic Stem Cells

The appearance, progression, and potential role for circadian rhythms during early development have previously focused mainly on the suprachiasmatic nucleus (SCN) and peri- and postnatal expression of canonical clock genes. More recently, gene expression studies in embryonic stem cells have shown that some clock genes are expressed in undifferentiated cells; however rhythmicity was only established when cells are directed toward a neural fate. These studies also concluded that a functional clock is not present in ESCs, based solely on their gene expression. The null hypothesis underlying the present study is that embryonic stem cells become rhythmic in both clock gene expression and glucose utilization only when allowed to spontaneously differentiate. Undifferentiated stem cells (ESCs, n = 6 cultures/timepoint for all experiments) were either maintained in their pluripotent state or released into differentiation (dESCs, n = 6 cultures/timepoint for all experiments). Glucose utilization was assayed through 2-deoxyglucose uptake measurement, and clock gene and glucose transporter expression was assayed every 4 hours for 2 days in ESCs and dESCs by quantitative PCR (qPCR) in the same cell lysates. Undifferentiated stem cells expressed a self-sustained rhythm in glucose uptake that was not coincident with rhythmic expression of clock genes. This physiological rhythm was paralleled by glucose transporter mRNA expression. Upon differentiation, circadian patterns of some but not all clock genes were expressed, and the amplitude of the glucose utilization rhythm was enhanced in dESCs. These data provide the earliest evidence of a functional circadian clock, in addition to further challenging the idea that rhythmic transcription of clock genes are necessary for rhythmic physiological output and suggest a role for a clock-controlled physiology in the earliest stages of development.

Modulation of intestinal glucose transport in response to reduced nitrogen supply in young goats1

The reduction of dietary protein is a common approach in ruminants to decrease the excretion of N because ruminants are able to recycle N efficiently by the rumino-hepatic circulation. In nonruminant species an impact on other metabolic pathways such as glucose metabolism was observed when dietary protein intake was reduced. However, an impact of dietary N reduction in goats on glucose metabolism especially on intestinal glucose absorption is questionable because ruminants have very efficient endogenous recycling mechanisms. Therefore, the aim of the present study was to characterize the intestinal absorption of glucose in growing goats kept on different N supply under isoenergetic conditions. The different CP concentrations (20, 16, 10, 9, and 7% CP) of the experimental diets were adjusted by adding urea to the rations. Intestinal flux rates of glucose were determined by Ussing chamber experiments. For a more mechanistic approach, the Na(+)-dependent uptake of glucose into intestinal brush-border membrane vesicles (BBMV) and the expression patterns of the Na(+)-dependent glucose transporter SGLT1 and the glucose transporter 2 (GLUT2) were determined. Reduced N intake resulted in a decrease of plasma glucose (P < 0.001) and insulin (P = 0.004) concentrations whereas the intestinal flux rates of glucose were elevated (P < 0.001), which were inhibited by phlorizin. However, the uptake of glucose into intestinal BBMV was not changed whereas the expression of SGLT1 on mRNA (P < 0.05) and protein abundance (P = 0.03) was decreased in response to a reduced N intake. The mRNA expression of GLUT2 was not affected. From these data, it can be concluded that the intestinal absorption of glucose was modulated by changes in dietary N intake. It is suggested that intracellular metabolism or basolateral transport systems or both might be activated during this feeding regimen because the apical located SGLT1 might not be involved. Therefore, an impact of dietary N reduction on glucose metabolism in growing goats occurred as in monogastric animals.

4-Hydroxyisoleucine stimulates glucose uptake by increasing surface GLUT4 level in skeletal muscle cells via phosphatidylinositol-3-kinase-dependent pathway

To determine the effect of 4-Hydroxyisoleucine (4-HIL), an unusual amino acid isolated from the seeds of Trigonella foenum-graecum, on glucose uptake and the translocation of glucose transporter 4 (GLUT4) to plasma membrane in skeletal muscle cells and to investigate the underlying mechanisms of action. Rat skeletal muscle cells (L6-GLUT4myc) were treated with 4-HIL, and the effect on glucose uptake was determined by measuring the incorporation of radio-labeled 2-deoxy-[(3)H]-D-glucose (2-DG) into the cell. Translocation of GLUT4myc to plasma membrane was measured by an antibody-coupled colorimetric assay. The prolonged exposure (16h) of L6-GLUT4myc myotubes to 4-HIL caused a substantial increase in the 2-DG uptake and GLUT4 translocation to the cell surface, without changing the total amount of GLUT4 and GLUT1. Cycloheximide treatment reversed the effect of 4-HIL on GLUT4 translocation to the basal level suggesting the requirement of new protein synthesis. The 4-HIL-induced increase in GLUT4 translocation was completely abolished by wortmannin, and 4-HIL significantly increased the basal phosphorylation of AKT (Ser-473), but did not change the mRNA expression of AKT, IRS-1, GLUT4, and GSK3β. Results suggest that 4-HIL stimulates glucose uptake in L6-GLUT4myc myotubes by enhancing translocation of GLUT4 to the cell surface in a PI-3-kinase/AKT-dependent mechanism.

Phosphodiesterase Inhibitor Improves Renal Tubulointerstitial Hypoxia of the Diabetic Rat Kidney

Background/AimsRenal hypoxia is involved in the pathogenesis of diabetic nephropathy. Pentoxifyllin (PTX), a nonselective phosphodiesterase inhibitor, is used to attenuate peripheral vascular diseases. To determine whether PTX can improve renal hypoxia, we investigated its effect in the streptozocin (STZ)-induced diabetic kidney.MethodsPTX (40 mg/kg, PO) was administered to STZ-induced diabetic rats for 8 weeks. To determine tissue hypoxia, we examined hypoxic inducible factor-1α (HIF-1α), heme oxygenase-1 (HO-1), vascular endothelial growth factor (VEGF), and glucose transporter-1 (GLUT-1) levels. We also tested the effect of PTX on HIF-1α in renal tubule cells.ResultsPTX reduced the increased protein creatinine ratio in diabetic rats at 8 weeks. HIF-1α, VEGF, and GLUT-1 mRNA expression increased significantly, and the expression of HO-1 also tended to increase in diabetic rats. PTX significantly decreased mRNA expression of HIF-1α and VEGF at 4 and 8 weeks, and decreased HO-1 and GLUT-1 at 4 weeks. The expression of HIF-1α protein was significantly increased at 4 and 8 weeks in tubules in the diabetic rat kidney. PTX tended to decrease HIF-1α protein expression at 8 weeks. To examine whether PTX had a direct effect on renal tubules, normal rat kidney cells were stimulated with CoCl2 (100 µM), which enhanced HIF-1α mRNA and protein levels under low glucose conditions (5.5 mM). Their expressions were similar even after high glucose (30 mM) treatment. PTX had no effect on HIF-1α expression.ConclusionsPTX attenuates tubular hypoxia in the diabetic kidney.

T3Rapidly IncreasesSLC2A4Gene Expression and GLUT4 Trafficking to the Plasma Membrane in Skeletal Muscle of Rat and Improves Glucose Homeostasis

Glucose transporter 4 (GLUT4) is highly expressed in muscle and fat tissue, where triiodothyronine (T(3)) induces solute carrier family 2 facilitated glucose transporter member 4 (SLC2A4) gene transcription. T(3) was also shown to rapidly increase glucose uptake in myocytes exposed to cycloheximide, indicating that it might act nongenomically to regulate GLUT4 availability. We tested this hypothesis by evaluating, in thyroidectomized rats (Tx rats), the acute and/or chronic T(3) effects on GLUT4 mRNA expression and polyadenylation, protein content, and trafficking to the plasma membrane (PM) in skeletal muscle, as well as on blood glucose disappearance rate (kITT) after insulin administration. Rats were surgically thyroidectomized and treated with T(3) (0.3 to 100 μg/100 g body weight) from 10 minutes to 5 days, and killed thereafter. Sham-operated (SO) rats were used as controls. Total RNA was extracted from the skeletal muscles (soleus [SOL] and extensorum digitalis longus [EDL]) and subjected to Northern blotting analysis using rat GLUT4 cDNA probe. Total protein was extracted and subjected to specific centrifugations for subcellular fractionation, and PM as well as microsomal (M) fractions were subjected to Western blotting analysis, using anti-GLUT4 antiserum as a probe. GLUT4 mRNA polyadenylation was examined by a rapid amplification of cDNA ends-poly(A) test (RACE-PAT). Thyroidectomy reduced skeletal muscle GLUT4 mRNA, mRNA poly(A) tail length, protein content, and trafficking to the PM, as well as the kITT. The acute T(3) treatment rapidly (30 minutes) increased all these parameters compared with Tx rats. The 5-day T(3) treatment increased GLUT4 mRNA and protein expression, and restored GLUT4 trafficking to the PM and kITT to SO values. The results presented here show for the first time that, in parallel to its transcriptional action on the SLC2A4 gene, T(3) exerts a rapid post-transcriptional effect on GLUT4 mRNA polyadenylation, which might increase transcript stability and translation efficiency, leading to the increased GLUT4 content and availability to skeletal muscle, as well as on GLUT4 translocation to the PM, improving the insulin sensitivity, as shown by the kITT.

Positive and Negative Feedback Regulation in the Production and Secretion of Insulin from INS-1 Cells by Testosterone

Type 2 diabetes is often developed in genetically predisposed subjects combined with sedentary life style or environmental factors. In women with polycystic ovary syndrome, hyperandrogenism is often accompanied with hyperinsulinemia and insulin resistance. Further, some studies have found associations of hyperandrogenemia with β-cell dysfunction and type 2 diabetes. We therefore tested the impairment effect of testosterone on glucose-stimulated insulin secretion in INS-1 cells. INS-1 cells were treated with different concentrations of testosterone and examined at different time points. In contrast to control, excess testosterone treatment for 48 h could promote glucose-stimulated insulin secretion and enhance pancreatic/duodenal homeobox-1 and glucose transporter-2 mRNA expression up to 2-fold. Alternatively, long-time and high-concentration testosterone treatment significantly impaired glucose-stimulated insulin secretion and insulin mRNA levels and promoted malondialdehyde content. Androgen receptor antagonist flutamide could partly attenuate glucose-stimulated insulin secretion. These results indicate that direct in vitro exposure of INS-1 cells to testosterone had both concentration- and time-dependent effects on glucose-stimulated insulin secretion, gene expression, and oxidative stress. These findings showed to some extent that excess circulation of testosterone might impair β-cell function, and further contribute to the etiology of insulin resistance in polycystic ovary syndrome.

Protein restriction during gestation alters histone modifications at the glucose transporter 4 (GLUT4) promoter region and induces GLUT4 expression in skeletal muscle of female rat offspring

Maternal nutrition during pregnancy is an intrauterine factor that results in alteration of the offspring genome and associates with disease risk in the offspring. We investigated the impact of a maternal low-protein (LP) diet on the expression of glucose transporter 4 (GLUT4) in offspring skeletal muscle. GLUT4 is an insulin-regulated glucose transporter involved in insulin sensitivity and carbohydrate metabolism in muscle cells. We observed sex-dependent GLUT4 mRNA expression and increased GLUT4 protein content in female pup skeletal muscle with maternal LP. Analysis of transcriptional and epigenetic regulation of increased skeletal muscle GLUT4 expression in offspring rats revealed the regulatory mechanisms involved. The protein level of myocyte enhancer factor 2A (MEF2A), which has been known as an activator of GLUT4 transcription via the ability to carry out specific binding to the GLUT4 MEF2 binding sequence, increased in female pups whose mothers were fed a LP diet. Modifications of chromatin structure, including acetylated histone H3, acetylated histone H4 and di-methylated histone H3 at lysine 4, were detected at a significantly increased level at the GLUT4 promoter region in female pup muscle following a maternal LP diet. Glycogen content was also detected as up-regulated, accompanied by increased glycogen synthase in LP female offspring muscle. These results document that maternal protein restriction during pregnancy induces GLUT4 expression in female offspring skeletal muscle but not in males, which may indicate sex-dependent adaptation of glucose metabolism to a maternal LP diet.

Exercise-induced galanin release facilitated GLUT4 translocation in adipocytes of type 2 diabetic rats

Although galanin has been shown to increase insulin sensitivity in skeletal muscle of rats, there is no literature available about the effect of galanin on Glucose Transporter 4 (GLUT4) translocation from intracellular membrane pools to plasma membranes in adipocytes of type 2 diabetic rats. In the present study M35, a galanin antagonist was used to elucidate whether exercise-induced galanin release increased GLUT4 translocation in adipocytes of streptozotocin-induced diabetic rats. The present findings showed that plasma galanin levels after swimming training in all four trained groups were higher compared with each sedentary control. M35 treatment had an inhibitory effect on glucose infusion rates in the euglycemic–hyperinsulinemic clamp test and GLUT4 mRNA expression levels in adipocytes. Moreover, M35 treatment reduced GLUT4 concentration in both plasma membranes and total cell membranes. The ratios of GLUT4 contents in plasma membranes to total cell membranes in four drug groups were lower compared with each control. These data demonstrate a beneficial role of endogenous galanin to transfer GLUT4 from internal stores to plasma membranes in adipocytes of type 2 diabetic rats. Galanin plays a significant role in regulation of glucose metabolic homeostasis and is an important hormone relative to diabetes.

Insulin Sensitizing Effects of Oligomannuronate-Chromium (III) Complexes in C2C12 Skeletal Muscle Cells

BackgroundIt was known that the insulin resistance in skeletal muscle is a major pathogenic factor in diabetes mellitus. Therefore prevention of metabolic disorder caused by insulin resistance and improvement of insulin sensitivity are very important for the therapy of type 2 diabetes. In the present study, we investigated the ability of marine oligosaccharides oligomannuronate and its chromium (III) complexes from brown alga to enhance insulin sensitivity in C2C12 skeletal muscle cells.Methodology/Principal FindingsWe demonstrated that oligomannuronate, especially its chromium (III) complexes, enhanced insulin-stimulated glucose uptake and increased the mRNA expression of glucose transporter 4 (GLUT4) and insulin receptor (IR) after their internalization into C2C12 skeletal muscle cells. Additionally, oligosaccharides treatment also significantly enhanced the phosphorylation of proteins involved in both AMP activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) and phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathways in C2C12 cells, indicating that the oligosaccharides activated both the insulin signal pathway and AMPK pathways as their mode of action. Moreover, oligosaccharides distributed to the mitochondria after internalization into C2C12 cells and increased the expression of transcriptional regulator peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), carnitine palmitoyl transferase-1 (CPT-1), and phosphorylated acetyl-CoA carboxylase (p-ACC), which suggested that the actions of these oligosaccharides might be associated with mitochondria through increasing energy expenditure. All of these effects of marine oligosaccharides were comparable to that of the established anti-diabetic drug, metformin. In addition, the treatment with oligosaccharides showed less toxicity than that of metformin.Conclusions/SignificanceOur findings indicate that oligomannuonate and its chromium (III) complexes improved insulin sensitivity in C2C12 skeletal muscle cells, and acted as a novel glucose uptake stimulator with low toxicity, and could be used as dietary supplementary or potential drug for type 2 diabetes mellitus.

Maternal Gestational Dietary Fat has Minimal Effects on Serum Lipid Profiles and Hepatic Glucose Transporter 2 and No Effect on Glucokinase Expression in Neonatal Wistar Rat Offspring

The study investigated the effects of maternal diets, varying in fat content, on lipid profiles and the expression of hepatic glucose transporter 2 (GLUT2) and glucokinase (GK) in neonatal Wistar rat offspring. Dams were maintained on diets of 10% (control), 20% (20F), 30% (30F) and 40% (40F) fat as energy throughout gestation; daily food intakes and weekly body weights were measured. Circulating fasting glucose, insulin and glucagon concentrations were determined in dams and their neonatal offspring. In neonates, total serum triglyceride, total and individual serum fatty acid concentrations, hepatic GLUT2 and GK mRNA and protein expression were determined. In dams, overall food intake of 20F (645.50 ± 25.26 g) and 40F (716.30 ± 14.15 g) dams was reduced compared to control (1007.00 ± 44.83 g) and 30F (924.50 ± 21.16 g) dams. The 20F neonates displayed elevated blood glucose concentrations (4.63 ± 0.153 mmol/l) compared to control neonates (4.14 ± 0.112 mmol/l). In 30F neonates, serum palmitoleic acid was reduced (1.63 ± 0.21% vs. 3.56 ± 0.38%) whereas stearic acid was elevated (10.05 ± 0.40% vs. 7.40 ± 0.72%) compared to control neonates. Further, the palmitoleic acid/palmitic acid ratio was reduced in 30F neonates (0.085 ± 0.009% vs. 0.165 ± 0.020% in control neonates). The 40F neonates displayed elevated GLUT2 immunoreactivity (22.86 ± 0.760%) compared to 20F (11.46 ± 2.701%) and 30F (6.45 ± 1.759%) neonates. Gestational programming with different dietary fat proportions minimally affects lipid profiles and hepatic GLUT2 immunoreactivity in neonatal offspring.

Anti-Inflammatory and Antioxidant Properties of a New Arylidene-Thiazolidinedione in Macrophages

Thiazolidinediones (TZDs) are a class of drugs used for treatment of type 2 diabetes. However, the therapy with currently available TDZs (e.g. rosiglitazone) is associated with important side effects, such as edema and weight gain, suggesting that the investigation of alternative TZDs with better pharmacological properties is warranted. In this study, we investigated both anti-inflammatory and antioxidant properties of a new chemically modified TZD, the arylidene-thiazolidinedione 5-(4-methanesulfonyl-benzylidene)-3-(4-nitrobenzyl)-thiazolidine-2,4-dione (SF23), and compared the results to those obtained with rosiglitazone. We found that our SF23 displays a weaker affinity for PPARγ, up-regulating in a lower magnitude the expression of both PPARγ and CD36 compared to rosiglitazone. In lipopolysaccharide (LPS)-stimulated macrophages, SF23 decreased nitrite production and attenuated the mRNA expression of both iNOS and COX-2. These anti-inflammatory effects were comparable to those obtained with rosiglitazone. Interestingly, SF23, but not rosiglitazone, prevented LPS-induced mitochondrial membrane hyperpolarization, apoptosis, reactive oxygen species (ROS) generation, and the expression of NADPH oxidase subunits, Nox1 and Nox2. In addition, in macrophages from Nrf2⁻/⁻ mice, SF23 protected against LPSinduced cellular death and ROS production, whereas rosiglitazone was only able to protect normal Nrf2⁺/⁺ cells against oxidative injury, suggesting that, unlike rosiglitazone, the antioxidant activity of SF23 might be Nrf2-independent. Finally, in macrophages exposed to high concentrations of glucose, SF23 induced significant increases in the mRNA expression of glucose transporters, insulin receptor substrate and mitoNEET. Altogether, our data indicate that our new chemically modified TDZ displays similar anti-inflammatory properties, but superior antioxidant effects on the LPS-stimulated macrophages compared to rosiglitazone.

Effect of Tinospora crispa on glucose uptake in skeletal muscle: role of glucose transporter 1 expression and extracellular signal-regulated kinase1/2 activation

Background: Tinospora crispa (TC) has been used for years as diabetic remedy in Thai-traditional medicine. It has recently been reported that the aqueous extract from TC’s dried stem enhances glucose transport of L6 myotubes. Objective: Investigate the effects of the water-ethanol extract of T. crispa (WETC) on glucose transport in a rat muscle cell-line L6 myotubes, and explore the mechanism of action of T. crispa in muscle cells. Materials and methods: Glucose uptake rate was determined with the [3H] 2-deoxyglucose uptake method and the cell viability was assessed by sulforhodamine B (SRB) assay. Expressions of glucose transporter 1 (GLUT1), GLUT4, extracellular signal regulated kinase 1/2 (ERK1/2), and AMP-activated protein kinase (AMPK) were measured by quantitative Reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis. Results: At 400 μg/mL, WETC significantly stimulated glucose uptake into L6 myotubes after 24 hours incubation (246.10.1% above basal; p <0.05). The enhancement of glucose transport by WETC was blocked by cycloheximide, a protein synthesis inhibitor. The up-regulation of GLUT1 protein was accompanied by a significant increased in GLUT1 mRNA expression. ERK1/2 was significantly activated in WETC-treated L6 myotubes. In addition, WETC treatment increased AMPK activity in L6 myotubes. Conclusion: T. crispa increased glucose transport activity of L6 myotubes by enhancing GLUT1 expression, a result of AMPK stimulation. Keywords: AMPK, ERK1/2, Glucose uptake, GLUT1, GLUT4, Tinospora crispa

Retinol-binding protein 4 in adipose and placental tissue of women with gestational diabetes

In the present study, we evaluated serum levels of retinol-binding protein 4 (RBP4) and the expression of RBP4, glucose transporter-4 (GLUT4) and peroxisome proliferator activated receptor gamma (PPARγ) mRNA (using quantitative real time-PCR) in subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT) and placental tissue obtained from patients with gestational diabetes (GDM) and healthy pregnant women. Serum RBP4 concentrations and its expression in SAT were higher in the women with GDM than in the controls (p = 0.03). No association between serum or tissue RBP4 and the indices of insulin resistance was noted. In the GDM group serum RBP4 correlated with its mRNA expression in SAT (r = 0.67, p = 0.007). Stepwise regression analysis revealed that RBP4 mRNA expression in SAT was independently predicted by GLUT4 mRNA expression (β = 0.59, p = 0.003) and the presence of GDM (β = 0.46, p = 0.01), whereas RBP4 mRNA expression in VAT was related to PPARγ mRNA expression (β = 0.64, p = 0.0003) and the patient's age (β = −0.38, p = 0.03). In conclusion, our results suggest that the elevated expression of RBP4 in SAT may contribute to the increase in circulating RBP4 in GDM subjects.

Capsaicin‐Sensitive Primary Afferent (CSPA) Fibers are Involved in the Regulation of Glucose Transport and the Expression of its Transporters in the Small Intestine in Rats

Previous studies have shown that CSPA fibers are involved in the regulation of alanine absorption in the small intestine. However, their effect on glucose absorption has not been yet fully characterized. This study examines the effect of CSPA fibers on glucose absorption and determines their effect on mRNA expression of glucose transporters (GLUT). Glucose absorption was measured in a jejunal segment perfused with 20mM glucose using the single-pass perfusion technique. CSPA ablation was achieved by subcutaneous injections of 1% capsaicin under light anesthesia at different time intervals. Sham rats received vehicle injections. Two weeks post-treatment, verification of desensitization was done by standard method. Glucose absorption in the jejunum showed a 68% increase in capsaicin-treated rats compared to sham. mRNA expressions of sodium-glucose cotransporter (SGLT1), GLUT2 and Na+-K+-ATPase were determined in jejunal samples by real-time PCR with actin as the housekeeping gene. A 14-fold increase in SGLT1 and a 7-fold increase in Na+-K+-ATPase mRNA expression were detected in capsaicin-treated rats as compared to sham. No significant increase in GLUT2 mRNA expression was noted in capsaicin-treated rats. Our results show that ablation of CSPA fibers increased glucose absorption by increasing the expression of its transporter. This indicates that CSPA fibers exercise an inhibitory tone in the small intestine that regulates epithelial absorption of glucose. This work is partially supported by the Lebanese National Council for Scientific Research.

Expression and clinical significance of glucose transporter 1 mRNA in bronchial brushing liquid‐based cytology specimens from patients with and without lung cancer

The aim of this study was to evaluate the diagnostic utility of glucose transporter 1 (GLUT1) mRNA expression in bronchial brushing specimens from patients with lung cancer. GLUT1 mRNA levels were detected by reverse transcription-polymerase chain reaction (RT-PCR) in SurePath(TM) liquid-based cytology bronchial brushing specimens from patients with lung cancer (n=76) and benign lung disease (n=154). Compared with patients with benign disease and compared with cytology, GLUT1 mRNA was found significantly more frequently in patients with all carcinomas, squamous cell carcinomas, adenocarcinomas and small cell carcinomas, as well as central, peripheral and diffuse carcinomas (P<0.01). Minor differences were noted in GLUT1 mRNA and cytology results between histological types and tumour location but were not statistically significant. The diagnostic performance of RT-PCR analysis of GLUT1 mRNA was significantly higher than cytology in terms of sensitivity (97.4 ± 3.6% versus 65.8 ± 10.7) and negative predictive value (98.6 ± 1.9%, versus 85.6 ± 5.1%) but specificity (90.9 ± 4.5%) and positive predictive value (84.1 ± 7.6%) were lower than cytology (100%). Using liquid-based cytology, RT-PCR can be performed on bronchial brushing specimens to detect GLUT1 mRNA expression, and may be a useful adjunct to cytology diagnosis. It was more sensitive than cytology but its lower specificity should be taken into account.

Effect of mild hypothermia on the expression of hypoxia-inducible factor-1a and glucose transporter-1 in a rat model of chronic cerebral ischemia-reperfusion

Objective To investigate the effect of mild hypothermia on the expression of hypoxia-inducible factor-1α (HIF-1α) and glucose transporter-1 (GLUT-1) in a rat model of chronic cerebral ischemia-reperfusion.Methods Thirty-six female SD rats weighing 170-210 g were randomly divided into 3 groups (n = 12 each):sham operation group (group S), normal body temperature group (group NT ) and mild hypothermia group (group MH). Arterio-venous fistula was established by end-to-end anastomosis between the right common carotid artery and right external jugular vein for 6 weeks followed by reperfusion. In group MH, mild hypothermia was induced at the initiation of reperfusion and the rectal temperature was reduced to 31.5-32.5 ℃. In group S and NT, the rectal temperature was maintained at 37-38 ℃. Six rats in each group were sacrificed at 3 and 48 h of reperfusion. The brains were immediately removed for determination of the expression of HIF-1α, GLUT-1, HIF-1α mRNA and GLUT-1 mRNA and microscopic examination. Results Compared with group S, the expression of HIF-1α and HIF-1α mRNA at 3 and 48 h of reperfusion and GLUT-1 mRNA at 3 h of reperfusion was up-regulated, while the expression of GLUT-1 and GLUT-1 mRNA at 48 h of reperfusion was down-regulated in group NT (P ＜ 0.05).Compared with group NT, the expression of HIF-1α and HIF-1α mRNA at 48 h of reperfusion and HIF-1α mRNA and GLUT-1 mRNA at 3 h of reperfusion was down-regulated, while the expression of GLUT-1 and GLUT-1 mRNA at 48 h of reperfusion was up-regulated in group MH (P ＜ 0.05).Microscopic examination showed that the injury to the ultrastructure of blood-brain barrier was significantly attenuated in group MH compared with group NT. Conclusion Mild hypothermia can attenuate chronic ischemia-reperfusion injury by down-regulating the expression of HIF-1α and up-regulating the expression of GLUT-1. Key words: Hypothermia, induced; Reperfusion injury; Brain; Hypoxia-inducible factor 1, alpha subunit; Glucose transporter type 1