GLUT4 Gene Expression Research Articles

Anti-diabetic potential of Catharanthus roseus Linn. and its effect on the glucose transport gene (GLUT-2 and GLUT-4) in streptozotocin induced diabetic wistar rats.

BackgroundCatharanthus roseus is an important Ayurvedic medication in traditional medicine. It is potentially used in countries like India, South Africa, China and Malaysia for the healing of diabetes mellitus. Although, the molecular mechanisms behind this effect are yet to be exclusively explored. Due to the great antidiabetic and hyperlipidemic potential of c. roseus, we hypothesized that the insulin mimetic effect of ethanolic extract of c. roseus might add to glucose uptake through improvement in the expression of genes of the glucose transporter (GLUT) family messenger RNA (mRNA) in liver.MethodsSTZ-induced diabetic rats treated by ethanolic extract of c. roseus 100 mg/kg and 200 mg/kg; and one group treated with Metformin (100 mg/kg). After final administration of treatment of 4 weeks, blood samples were collected under fasting conditions, and the body weights (BWs) were measured. Total RNA from liver was extracted with the Qiagen RNEasy Micro kit (GERMANY) as described in the manufacturer’s instructions. First-strand complementary DNA (cDNA) was synthesized at 40 °C by priming with oligo-dT12–18 (Invitrogen, USA) and using Super ScriptII reverse transcriptase according to the protocol provided by the manufacturer (Invitrogen, USA). Real-time polymerase chain reaction (PCR) amplifications for GLUT-4 (gene ID: 25139) were conducted using Light-Cycler 480 (Roche, USA) with the SyBr® I nucleic acid stain (Invitrogen, USA) according to the manufacturer's instructions. Polymerase chain reaction products of β-actin primer gene were used as an internal standard.ResultsThe proposed study was framed to look at the antidiabetic efficacy of ethanolic extract of c. roseus and an expression of GLUT-2 and GLUT-4 gene in streptozotocin induced diabetic wistar rats. The doses were administered orally at a rate of 100 and 200 mg/kg and detrain the glucose transport system in liver for 4 weeks. The observed results showed a good positive correlation between intracellular calcium and insulin release levels in isolated islets of Langerhans. The supplementation of ethanolic extract of c. roseus significantly amplified the expression of GLUT gene mRNA by Real Time PCR in liver of diabetic rats.ConclusionsWe conclude that the observed antidiabetic effect of c. roseus on STZ induced diabetes was a result of complex mechanisms of GLUT gene mRNA expression. The findings are very encouraging and greatly advocate its candidature for the design of a novel herbal drug to cure deadly diabetes.

The role of apolipoprotein A-IV in regulating glucagon-like peptide-1 secretion.

Both glucagon-like peptide-1 (GLP-1) and apolipoprotein A-IV (apoA-IV) are produced from the gut and enhance postprandial insulin secretion. This study investigated whether apoA-IV regulates nutrient-induced GLP-1 secretion and whether apoA-IV knockout causes compensatory GLP-1 release. Using lymph-fistula-mice, we first determined lymphatic GLP-1 secretion by administering apoA-IV before an intraduodenal Ensure infusion. apoA-IV changed neither basal nor Ensure-induced GLP-1 secretion relative to saline administration. We then assessed GLP-1 in apoA-IV-/- and wild-type (WT) mice administered intraduodenal Ensure. apoA-IV-/- mice had comparable lymph flow, lymphatic triglyceride, glucose, and protein outputs as WT mice. Intriguingly, apoA-IV-/- mice had higher lymphatic GLP-1 concentration and output than WT mice 30 min after Ensure administration. Increased GLP-1 was also observed in plasma of apoA-IV-/- mice at 30 min. apoA-IV-/- mice had comparable total gut GLP-1 content relative to WT mice under fasting, but a lower GLP-1 content 30 min after Ensure administration, suggesting that more GLP-1 was secreted. Moreover, an injection of apoA-IV protein did not reverse the increased GLP-1 secretion in apoA-IV-/- mice. Finally, we assessed gene expression of GLUT-2 and the lipid receptors, including G protein-coupled receptor (GPR) 40, GPR119, and GPR120 in intestinal segments. GLUT-2, GPR40 and GPR120 mRNAs were unaltered by apoA-IV knockout. However, ileal GPR119 mRNA was significantly increased in apoA-IV-/- mice. GPR119 colocalizes with GLP-1 in ileum and stimulates GLP-1 secretion by sensing OEA, lysophosphatidylcholine, and 2-monoacylglycerols. We suggest that increased ileal GPR119 is a potential mechanism by which GLP-1 secretion is enhanced in apoA-IV-/- mice.

The Effect of Ethanolic Extract of Urtica dioica Leaves on High Levels of Blood Glucose and Gene Expression of Glucose Transporter 2 (Glut2) in Liver of Alloxan-Induced Diabetic Mice

method. Results: The results showed that the nettle extract significantly decreased high levels of blood glucose (P < 0.001). The nettle extract also had a preventive effect on decrease in body weight. In addition, the results showed that the Glut2 gene expression was increased in liver of diabetic mice (P < 0.05) and was significantly prevented by the nettle extract in diabetic + nettle extract group (P < 0.05). Conclusions: It can be concluded that the nettle extract can reduce blood glucose levels in diabetic mice, at least partly, by influencing the Glut2 gene expression in mice liver.

Physiological and molecular responses to an acute bout of reduced-exertion high-intensity interval training (REHIT).

We have previously shown that 6 weeks of reduced-exertion high-intensity interval training (REHIT) improves VO2max in sedentary men and women and insulin sensitivity in men. Here, we present two studies examining the acute physiological and molecular responses to REHIT. In Study 1, five men and six women (age: 26 ± 7 year, BMI: 23 ± 3 kg m(-2), VO2max: 51 ± 11 ml kg(-1) min(-1)) performed a single 10-min REHIT cycling session (60 W and two 20-s 'all-out' sprints), with vastus lateralis biopsies taken before and 0, 30, and 180 min post-exercise for analysis of glycogen content, phosphorylation of AMPK, p38 MAPK and ACC, and gene expression of PGC1α and GLUT4. In Study 2, eight men (21 ± 2 year; 25 ± 4 kg·m(-2); 39 ± 10 ml kg(-1) min(-1)) performed three trials (REHIT, 30-min cycling at 50 % of VO2max, and a resting control condition) in a randomised cross-over design. Expired air, venous blood samples, and subjective measures of appetite and fatigue were collected before and 0, 15, 30, and 90 min post-exercise. Acutely, REHIT was associated with a decrease in muscle glycogen, increased ACC phosphorylation, and activation of PGC1α. When compared to aerobic exercise, changes in VO2, RER, plasma volume, and plasma lactate and ghrelin were significantly more pronounced with REHIT, whereas plasma glucose, NEFAs, PYY, and measures of appetite were unaffected. Collectively, these data demonstrate that REHIT is associated with a pronounced disturbance of physiological homeostasis and associated activation of signalling pathways, which together may help explain previously observed adaptations once considered exclusive to aerobic exercise.

A single-amino-acid mutation in hepatitis C virus NS5A disrupts physical and functional interaction with the transcription factor HNF-1α.

Hepatitis C virus (HCV) infection often causes extrahepatic manifestations, such as type 2 diabetes. We previously reported that HCV infection induces the lysosomal degradation of the transcription factor HNF-1α via an interaction with viral NS5A, thereby suppressing GLUT2 gene expression. However, the molecular mechanism of NS5A-induced degradation of HNF-1α is largely unknown. We aimed to identify the determinants necessary for the degradation of HNF-1α induced by NS5A. Coimmunoprecipitation analysis revealed that the POU specific (POUs) domain spanning from aa 91 to 181 of HNF-1α is responsible for the interaction of NS5A. We also found that the region from aa 121 to 126 of NS5A, which is known as the binding motif of the HCV replication factor FKBP8, is important for the degradation of HNF-1α. A NS5A V121A mutation disrupted the NS5A-HNF-1α interaction as well as the degradation of HNF-1α. Our findings suggest that NS5A Val121 is crucial for viral pathogenesis.

Ferulic acid regulates hepatic GLUT2 gene expression in high fat and fructose-induced type-2 diabetic adult male rat

GLUT2 is a bidirectional glucose transporter present in liver, kidney and pancreas. Studies have shown over-expression of GLUT2 in diabetic conditions. Ferulic acid (FA) is an antidiabetic phenolic phytocompound which is reported to regulate GLUT4 in vitro. The objective of our study is to evaluate the role of FA in the regulation of hepatic GLUT2 expression and the underlying mechanism. Male Wistar rats were divided into 5 groups: control, diabetic (diabetes was induced by giving high fat diet and high fructose water for 60 days), diabetic rats treated with FA (50mg/kg body weight/day, orally for 30 days), diabetic rats treated with metformin (50mg/kg body weight/day, orally for 30 days) and control rats treated with FA (50mg/kg body weight/day orally for 30 days). After 30 days treatment, animals were perfused and liver was dissected out. Glucose uptake and oxidation, expression of GLUT2 and binding of transcription factors - SREBP1c, HNF1α and HNF3β with GLUT2 gene promoter were studied. Over-expression of GLUT2 in hepatic tissue was found in high fat and fructose- induced type-2 diabetic animals. FA treatment reduced the GLUT2 expression in diabetic animals by impairing the interaction between these transcription factors (SREBP1c, HNF1α and HNF3β) and GLUT2 gene promoter.

Placental Transport of Nutrients and Fetal Metabolism in Intrauterine Growth Restricted Rats

Previous studies show that reduced uterine perfusion results in intrauterine growth restriction and impaired fetal nutrition. However, the mechanisms involved are not totally understood. The objective of this study was to investigate whether reduced uterine perfusion alters placental transport of glucose and fatty acids in growth‐restricted fetuses. We used a rat model of growth‐restricted offspring induced by reduced uterine perfusion at 14 days of gestation. At 19 days of gestation fetuses and placentas were excised by cesarean section followed by collection of fetal and maternal blood and tissue. GraphPad software was used for statistical analysis with significance set at P&lt;0.05. Reduced uterine perfusion resulted in male and female growth‐restricted fetuses with lower body weight and placental size compared to controls (P&lt;0.05); and greater placental efficiency in female fetuses. Protein concentration and gene expression of placental glucose transporters GLUT2 and GLUT3 and fatty acids transporter FATP1 were elevated in growth‐restricted fetuses compared to controls (P&lt;0.05). Glucose levels were elevated in female growth‐restricted fetuses compared to male and controls (P&lt;0.05). Analysis of correlation between placental efficiency and fetal glucose level showed negative correlation (Pearson r=‐0.7939) in controls and positive correlation (Pearson r= 0.0747) in growth‐restricted fetuses. These results suggest that reduced uterine perfusion induces compensatory changes in glucose and fatty acids placental transporters to ensure fetal survival and also results in changes on glucose homeostasis in growth‐restricted fetuses

A ‘Humanized’ rat model of pre-diabetes by high fat diet-feeding to weaning wistar rats

This study characterizes the high-fat diet (HFD)-fed rats as a model for ‘pre-diabetes’ or ‘impaired glucose tolerance’ showing clinical presentation and pathophysiology of natural history of pre-diabetes in human. Young Wistar rats (40-50 g) were fed a HFD (45% energy from fat) or a normal diet for 6 month. Body weight gain was faster in 0-2 months, slower body weight gain in 2-4 months and slowest weight gain in 4-6 months. Blood glucose increased after 1 month on HFD feeding and remained elevated at a rate of ~5 mg/dl throughout the 6-monthstudy period. Serum insulin, insulin resistance and insulin-to-glucose ratio were increased progressively in a time-dependent manner. Progressive changes in glucose uptake and GLUT-4gene expression were also observed during 6-months of HFD feeding. The insulin immunohistochemical data showed hypertrophy of pancreatic islets in the pre-diabetic rats. We conclude that the HFD-fed rat model is a ‘humanized’ model for prediabetes, which may be used for studies on pathophysiology and development of new drug.

Cytosolic aconitase activity sustains adipogenic capacity of adipose tissue connecting iron metabolism and adipogenesis.

To gain insight into the regulation of intracellular iron homeostasis in adipose tissue, we investigated the role of iron regulatory protein 1/cytosolic aconitase 1 (ACO1). ACO1 gene expression and activity increased in parallel to expression of adipogenic genes during differentiation of both murine 3T3-L1 cells and human preadipocytes. Lentiviral knockdown (KD) of Aco1 in 3T3-L1 preadipocytes led to diminished cytosolic aconitase activity and isocitrate dehydrogenase 1 (NADP(+)), soluble (Idh1) mRNA levels, decreased intracellular NADPH:NADP ratio, and impaired adipogenesis during adipocyte differentiation. In addition, Aco1 KD in fully differentiated 3T3-L1 adipocytes decreased lipogenic, Idh1, Adipoq, and Glut4 gene expression. A bidirectional cross-talk was found between intracellular iron levels and ACO1 gene expression and protein activity. Although iron in excess, known to increase reactive oxygen species production, and iron depletion both resulted in decreased ACO1 mRNA levels and activity, Aco1 KD led to reduced gene expression of transferrin receptor (Tfrc) and transferrin, disrupting intracellular iron uptake. In agreement with these findings, in 2 human independent cohorts (n = 85 and n = 38), ACO1 gene expression was positively associated with adipogenic markers in subcutaneous and visceral adipose tissue. ACO1 gene expression was also positively associated with the gene expression of TFRC while negatively linked to ferroportin (solute carrier family 40 (iron-regulated transporter), member 1) mRNA levels. Altogether, these results suggest that ACO1 activity is required for the normal adipogenic capacity of adipose tissue by connecting iron, energy metabolism, and adipogenesis.

Enhancement of glucose uptake by Ficus hispida methanolic extract through phosphatidylinositol 3 kinase and inhibiting aldose reductase – An in vitro analysis

IntroductionType 2 diabetes mellitus is a polygenic metabolic syndrome characterized by impaired carbohydrate and lipid metabolism. Diabetes mellitus is commonly associated with secondary disorders such as obesity and genetic predisposition. Prolonged hyperglycemia can also lead to secondary complications such as cataractogenesis, retinopathy and nephropathy through the induction of the polyol pathway. Ficus hispida (FH) is a medium size tree found in India, Sri Lanka and the Andaman Islands in damp localities. Traditionally, different parts of the FH plant have been used in the treatment of various diseases and disorders. MethodologyFH bark was sequentially extracted using different organic solvents ranging from non polar to polar. Glucose uptake assays were performed using 2-deoxy-d-1-[3H] for the FH extracts. Fluorimetric analysis was adopted to assess the aldose reductase inhibitory effect. The gene and protein level expression of the markers were analyzed using RT-PCR and Western blot analysis. ResultsF. hispida methanolic extract (FHME) showed an enhancement in the glucose uptake and upregulated the gene and protein level expression of IRβ, IRS-1, PI3K, GLUT4 and PPARγ. Comparison with wortmannin, a specific PI3K inhibitor confirmed that the active FHME recruits glucose uptake through a PI3K dependent pathway. Subsequently, FHME possesses a significant aldose reductase inhibitory activity. ConclusionThe current study emphasizes the cellular level mechanism of FHME on glucose transport in L6 myotubes and the inhibition of aldose reductase activity.

276 PHOSPHOINOSITIDE 3-KINASE REGULATES EXPRESSION OF KEY ENZYMES AND CELLULAR TRANSPORTERS OF GLUCOSE METABOLISM IN CUMULUS CELLS OF BOVINE COCs CULTURED IN VITRO

The aim was to analyse the function of the PI3K pathway during oocyte maturation in bovine by use of the specific inhibitor, LY294002. Genes studied in cumulus cells (CC) were PDH, G6PDH, GLUT1, and GLUT4. PDH is an important enzyme for oxidative metabolism, G6PDH is related to resumption and progression of oocyte meiosis, and GLUT1 and GLUT4 are glucose transporters. This study was performed in defined medium (MIV B) in absence or presence of 10 ng mL–1 of FSH. Polar body extrusion was analysed after culture and correlated with gene expression. Experimental methods were bovine COC (n = 35–40/well, n = 3 replicates) collected from ovaries obtained from abattoirs (DF, Brazil) and cultivated in either 400 µL of medium MIV B, or MIV B + 100 µM of LY294002, or MIV B + 10 ng mL–1 of FSH; or MIV B + 10 ng mL–1 of FSH + 100 µM of LY294002 during 22 to 24 h. After culture, COC were mechanically denuded and CC from 20 COC/group were isolated. Gene expression of GLUT1, GLUT4, G6PDH, and PDH were measured by real time PCR. The CC of immature COC were also collected and analysed as the calibrator group. Student-Newman-Keuls was performed as a statistical test. The percentage of oocytes that extruded the polar body was determined. Two-way ANOVA, followed by Bonferroni test, and t-test were performed to determine statistical significance. In MIV B, the polar body extrusion rate was 25.48 ± 7.64%, while FSH increased it up to 74.52 ± 10.58% (P &lt; 0.05). The extrusion of polar body was inhibited by LY294002 in the absence or presence of FSH (67.51 ± 6.13 and 31.02 ± 16.97%, respectively, P &lt; 0.05). Gene expression of PDH was not altered by any culture medium in contrast to GLUT1, GLUT4, and G6PDH expression (Table 1). Only G6PDH expression showed the same pattern as the polar body extrusion, in absence or presence of FSH. In conclusion, PI3-K inhibition affects polar body extrusion and expression of genes related to glucose metabolism in CC. Lower G6PDH expression in CC may be related to low rates of polar body extrusion in treated oocytes. Table 1.Gene expression of GLUT1, GLUT4, and G6PDH in CC of COC after culture The authors thank FAP-DF (193.000.577/2009), CNPq, CAPES and Ponte Alta abattoir, Brasilia.

Growth hormone abolishes beneficial effects of calorie restriction in long-lived Ames dwarf mice

Disruption of the growth hormone (GH) axis promotes longevity and delays aging. In contrast, GH over-expression may lead to accelerated aging and shorter life. Calorie restriction (CR) improves insulin sensitivity and may extend lifespan. Long-lived Ames dwarf (df/df) mice have additional extension of longevity when subjected to 30% CR. The aim of the study was to assess effects of CR or GH replacement therapy separately and as a combined (CR+GH) treatment in GH-deficient df/df and normal mice, on selected metabolic parameters (e.g., insulin, glucose, cholesterol), insulin signaling components (e.g., insulin receptor [IR] β-subunit, phosphorylated form of IR [IR pY1158], protein kinase C ζ/λ [p-PKCζ/λ] and mTOR [p-mTOR]), transcription factor p-CREB, and components of the mitogen-activated protein kinase (MAPK) signaling (p-ERK1/2, p-p38), responsible for cell proliferation, differentiation and survival. CR decreased plasma levels of insulin, glucose, cholesterol and leptin, and increased hepatic IR β-subunit and IR pY1158 levels as well as IR, IRS-1 and GLUT-2 gene expression compared to ad libitum feeding, showing a significant beneficial diet intervention effect. Moreover, hepatic protein levels of p-PKCζ/λ, p-mTOR and p-p38 decreased, and p-CREB increased in CR mice. On the contrary, GH increased levels of glucose, cholesterol and leptin in plasma, and p-mTOR or p-p38 in livers, and decreased plasma adiponectin and hepatic IR β-subunit compared to saline treatment. There were no GH effects on adiponectin in N mice. Moreover, GH replacement therapy did not affect IR, IRS-1 and GLUT-2 gene expression. GH treatment abolishes the beneficial effects of CR; it may suggest an important role of GH–IGF1 axis in mediating the CR action. Suppressed somatotrophic signaling seems to predominate over GH replacement therapy in the context of the examined parameters and signaling pathways.

Standardized extract of Ficus deltoidea stimulates insulin secretion and blocks hepatic glucose production by regulating the expression of glucose-metabolic genes in streptozitocin-induced diabetic rats.

BackgroundRecently, there has been increasing interest in Ficus deltoidea Jack. (Moraceae) due to its chemical composition and the potential health benefits. The present study was undertaken to investigate the effect of extracts of F. deltoidea leaves on diabetes.MethodsThe petroleum ether, chloroform and methanol extracts of F. deltoidea were prepared and subjected to standardization using preliminary phytochemical and HPLC analysis. Dose selection was made on the basis of acute oral toxicity study (50–5000 mg/kg b. w.) as per OECD guidelines. Diabetes mellitus was induced with streptozotocin and rats found diabetic were orally administered with the extract (250, 500 and 1000 mg/kg) for 14 days. Levels of blood glucose and insulin were measured in control as well as diabetic rats on 0, 7 and 14th day. In addition, glucose metabolism regulating gene expression was assessed using RT-PCR.ResultsHPLC analysis revealed that the methanol extract is enriched with C-glycosylflavones particularly, vitexin and isovitexin. In oral glucose tolerance test, oral administration of the methanol extract increased the glucose tolerance. The methanol extract showed significant (P < 0.01) antidiabetic activity. The extract treatment caused significant reduction (p < 0.01) in elevated fasting blood glucose level in streptozotocin-induced diabetic rats. The streptozotocin-related weight loss in rats was noticeably reversed by the extract treatment. Finally, RT-PCR analysis revealed a novel mechanisms for the anti-diabetic action of methanol extract of F. deltoidea. The extract exerted its effect via an increase of insulin secretion which impeded the hepatic glucose production, via down-regulation of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase genes expression on one hand, and up-regulation of hepatic GK and PPARγ genes expression on the other hand. The extract caused an increased expression of GLUT-4 gene expression in skeletal muscles which leads to normalize the hyperglycemia. The extract also nullified the toxic effects of streptozitocin by blocking its entry into the islet β-cells through reducing the expression of GLUT-2 gene.ConclusionIt can be concluded that, F. deltoidea could potentially inhibits the streptozitocin-induced hyperglycemia in rats. Further the herb can be utilized as useful remedy for alleviation of diabetes complications.

Subcutaneous adipose tissue zinc-α2-glycoprotein is associated with adipose tissue and whole-body insulin sensitivity.

To examine the regulatory aspects of zinc-α2-glycoprotein (ZAG) association with obesity-related insulin resistance. ZAG mRNA and protein were analyzed in subcutaneous adipose tissue (AT) and circulation of lean, obese, prediabetic, and type 2 diabetic men; both subcutaneous and visceral AT were explored in lean and extremely obese. Clinical and ex vivo findings were corroborated by results of in vitro ZAG silencing experiment. Subcutaneous AT ZAG was reduced in obesity, with a trend to further decrease with prediabetes and type 2 diabetes. ZAG was 3.3-fold higher in subcutaneous than in visceral AT of lean individuals. All differences were lost in extreme obesity. Obesity-associated changes in AT were not paralleled by alterations of circulating ZAG. Subcutaneous AT ZAG correlated with adiposity, adipocyte hypertrophy, whole-body and AT insulin sensitivity, mitochondrial content, expression of GLUT4, PGC1α, and adiponectin. Subcutaneous AT ZAG and adipocyte size were the only predictors of insulin sensitivity, independent on age and BMI. Silencing ZAG resulted in reduced adiponectin, IRS1, GLUT4, and PGC1α gene expression in primary human adipocytes. ZAG in subcutaneous, but not in visceral AT, was markedly reduced in obesity. Clinical, cellular, and molecular evidence indicate that ZAG plays an important role in modulating whole-body and AT insulin sensitivity.

HIF-1α and GLUT1 Gene Expression is Associated with Chemoresistance of Acute Myeloid Leukemia

Much evidence suggests that increased glucose metabolism in tumor cells might contribute to the development of acquired chemoresistance. However, the molecular mechanisms are not fully clear. Therefore, we investigated a possible correlation of mRNA expression of HIF-1α and GLUT1 with chemoresistance in acute myeloid leukemia (AML). Bone marrow samples were obtained from newly diagnosed and relapsed AML (M3 exclusion) cases. RNA interference with short hairpin RNA (shRNA) was used to stably silence GLUT1 or HIF-1α gene expression in an AML cell line and HIF-1α and GLUT1 mRNA expression was measured by real-time quantitative polymerase chain reaction assay (qPCR). High levels of HIF-1α and GLUT1 were associated with poor responsiveness to chemotherapy in AML. Down-regulation of the expression of GLUT1 by RNA interference obviously sensitized drug-resistant HL-60/ADR cells to adriamycin (ADR) in vitro, comparable with RNA interference for the HIF-1α gene. Our data revealed that over-expression of HIF-1α and GLUT1 might play a role in the chemoresistance of AML. GLUT1 might be a potential target to reverse such drug resistance.

CYP2E1 Impairs GLUT4 Gene Expression and Function: NRF2 as a Possible Mediator

Impaired GLUT4 function/expression in insulin target tissues is well-documented in diabetes and obesity. Cytochrome P450 isoform 2E1 (CYP2E1) induces oxidative stress, leading to impaired insulin action. CYP2E1 knockout mice are protected against high fat diet-induced insulin resistance and obesity; however the molecular mechanisms are still unclear. We examined whether CYP2E1 impairs GLUT4 gene expression and function in adipose and muscle cells. CYP2E1 overexpression in skeletal muscle-derived L6 cells inhibited insulin-stimulated Glut4 translocation and 2-deoxyglucose uptake, with the latter inhibition being blocked by vitamin E. CYP2E1 overexpression in L6 and primary rat adipose (PRA) cells suppressed GLUT4 gene expression at promoter and mRNA levels, whereas CYP2E1 silencing had opposite effects. In PRA, CYP2E1-induced suppression of GLUT4 expression was blocked by chlormethiazole (CYP2E1-specific inhibitor) and the antioxidants vitamin E and N-acetyl-l-cysteine. CYP2E1 effect was mediated by the transcription factor NF-E2-related factor 2 (NRF2), as evident from its complete reversal by a coexpressed dominant-negative, but not wild-type NRF2. GLUT4 transcription was suppressed by NRF2 overexpression, and enhanced by NRF2 silencing. Promoter and ChIP analysis showed a direct and specific binding of NRF2 to a 58-326 GLUT4 promoter region that was required to maintain CYP2E1 suppression; this binding was enhanced by CYP2E1 overexpression. We suggest a mechanism for CYP2E1 action that involves: a) suppression of GLUT4 gene expression that is mediated by NRF2; b) impairment of insulin-stimulated Glut4 translocation and function. CYP2E1 and NRF2 are introduced as negative regulators of GLUT4 expression and function in insulin-sensitive cells.

Expression of Glucose Transporter 4 (GLUT4) is Increased by Cinnamaldehyde in C2C12 Mouse Muscle Cells

Background:In diabetes mellitus because of the absence or insufficient sensitivity to insulin, glucose transporter protein in cell membrane, glucose transporter 4, is decreased. GLUT4 is the major glucose transporter in skeletal muscle and adipose tissue, which is under control of insulin. It remains, however, unclear whether cinnamaldehyde plays a regulatory role(s) or not.Objectives:The objective of this study was to investigate the effects of cinnamaldehyde on GLUT4 gene expression.Materials and Methods:This study was an experimental trial. Tests were performed in triplicates. This study examined effects of cinnamaldehyde on Glut4 gene expression in C2C12 skeletal muscle cells by using Real Time PCR. C2C12 myoblasts were cultured in DMEM + 10 % FBS. After differentiation of myoblasts to myotubes, the cells were serum deprived for 5 hours and then treated with 10, 20, or 50 µM of cinnamaldehyde for 1 hour.Results:Our data revealed a significant increase in the expression of Glut4 in cinnamaldehyde treated cells. In addition, GLUT4 mRNA level was increased in a dose dependent manner. Analyses were performed using the SPSS 16 for Windows software. Differences between the groups were determined by one-way ANOVA.Conclusions:These results demonstrate that cinnamaldehyde up regulates the expression of mouse skeletal muscle GLUT4 gene expression.

GLUT3 gene expression is critical for embryonic growth, brain development and survival

Glucose is the primary energy source for eukaryotic cells and the predominant substrate for the brain. GLUT3 is essential for trans-placental glucose transport and highly expressed in the mammalian brain. To further elucidate the role of GLUT3 in embryonic development, we utilized the vertebrate whole animal model system of Danio rerio as a tractable system for defining the cellular and molecular mechanisms altered by impaired glucose transport and metabolism related to perturbed expression of GLUT3. The comparable orthologue of human GLUT3 was identified and the expression of this gene abrogated during early embryonic development. In a dose-dependent manner embryonic brain development was disrupted resulting in a phenotype of aberrant brain organogenesis, associated with embryonic growth restriction and increased cellular apoptosis. Rescue of the morphant phenotype was achieved by providing exogenous GLUT3 mRNA. We conclude that GLUT3 is critically important for brain organogenesis and embryonic growth. Disruption of GLUT3 is responsible for the phenotypic spectrum of embryonic growth restriction to demise and neural apoptosis with microcephaly.

Maternal high-fat diet consumption impairs exercise performance in offspring.

The aim of the present study was to scrutinise the influence of maternal high-fat diet (mHFD) consumption during gestation and lactation on exercise performance and energy metabolism in male mouse offspring. Female C3H/HeJ mice were fed either a semi-synthetic high-fat diet (HFD; 40 % energy from fat) or a low-fat diet (LFD; 10 % energy from fat) throughout gestation and lactation. After weaning, male offspring of both groups received the LFD. At the age of 7·5 weeks half of the maternal LFD (n 20) and the mHFD (n 21) groups were given access to a running wheel for 28 d as a voluntary exercise training opportunity. We show that mHFD consumption led to a significantly reduced exercise performance (P<0·05) and training efficiency (P<0·05) in male offspring. There were no effects of maternal diet on offspring body weight. Lipid and glucose metabolism was disturbed in mHFD offspring, with altered regulation of cluster of differentiation 36 (CD36) (P<0·001), fatty acid synthase (P<0·05) and GLUT1 (P<0·05) gene expression in skeletal muscle. In conclusion, maternal consumption of a HFD is linked to decreased exercise performance and training efficiency in the offspring. We speculate that this may be due to insufficient muscle energy supply during prolonged exercise training. Further, this compromised exercise performance might increase the risk of obesity development in adult life.

Antihyperglycemic Action of Sinapic Acid in Diabetic Rats

Sinapic acid is a hydroxycinnamic acid contained in plants. In an attempt to know the hyperglycemic effect of sinapic acid, this study applied streptozotocin (STZ) to induce type 1-like diabetic rats and fed fructose-rich chow to induce type 2-like diabetic rats. Sinapic acid dose-dependently reduced the hyperglycemia of STZ-diabetic rats (9.8 ± 1.8%, 11.6 ± 0.7%, and 19.4 ± 3.2% at 5 mg/kg, 10 mg/kg, and 25 mg/kg, respectively). Also, sinapic acid attenuated the postprandial plasma glucose without changing plasma insulin in rats. Repeated treatment of sinapic acid increased the gene expression of GLUT4 in soleus muscle of STZ-diabetic rats. Moreover, sinapic acid enhanced glucose uptake into isolated soleus muscle and L6 cells (337.0 ± 29.6%). Inhibition of phospholipase C (PLC) using U73122 (1.00 ± 0.02 μg/mg protein) or protein kinase C (PKC) using chelerythrine (0.97 ± 0.02 μg/mg protein) attenuated the sinapic acid-stimulated glucose uptake (1.63 ± 0.02 μg/mg protein) in L6 cells. Otherwise, the reduced glucose infusion rate (GIR) in fructose-rich chow-fed rats was also raised by sinapic acid. Our results suggest that sinapic acid ameliorates hyperglycemia through PLC-PKC signals to enhance the glucose utilization in diabetic rats.