Animals ; Brain ; metabolism ; physiology ; Diet ; Glucose Transporter Type 1 ; genetics ; metabolism ; Glucose Transporter Type 4 ; genetics ; metabolism ; Male ; Mice ; Mice, Inbred ICR ; Physical Conditioning, Animal ; physiology ; RNA, Messenger ; genetics ; metabolism ; Random Allocation

OBJECTIVE: To explore the effect of sodium tungstate on glucose metabolism in adipocytes and its mechanism. METHODS: After 3T3-L1 preadipocytes were differentiated into adipocytes, these adipocytes were incubated with sodium tungstate (0, 150, 300, 500, and 700 micromol/L) for 48 h, and then glucose consumption of the adipocytes was detected by glucose-oxidase assay. Glucose transport was determined by the uptake of 2-deoxy-[3H]-D-glucose, and the expression of glucose transport-4 (GLUT-4) mRNA was identified by semi-quantitative RT-PCR. RESULTS: Sodium tungstate (150 approximately 700 micromol/L) could significantly increase the glucose consumption and glucose transport with a concentration dependent-effect. Sodium tungstate could increase GLUT-4 mRNA expression. CONCLUSION Sodium tungstate can enhance the glucose metabolism of adipocytes by up-regulating the expression of GLUT-4 mRNA.
3T3-L1 Cells ; Adipocytes ; metabolism ; Animals ; Glucose ; metabolism ; Glucose Transporter Type 4 ; biosynthesis ; genetics ; Hypoglycemic Agents ; pharmacology ; Mice ; RNA, Messenger ; biosynthesis ; genetics ; Tungsten Compounds ; pharmacology ; Up-Regulation

BACKGROUNDThe change of glucose transporter 4 (GLUT4) expression could influence glucose uptake in the myocardial cells and then effect myocardial metabolism, which maybe one of the factor for the diabetes cardiovascular disease. This study aimed to explore the influence of glucose and insulin at different concentrations on H9c2 (2-1) cell proliferation and its GLUT4 expression in vitro, and evaluate the correlation between myocardial cells proliferation and GLUT4 expression. This might be helpful for understanding the relationship between glucose metabolism and cardiovascular disease.

METHODSAccording to glucose concentrations in culture medium, cultured H9c2 rat myocardial cells were divided into five groups: control group (NC, glucose concentration 5.0 mmol/L), low glucose group (LG, glucose concentration 0.1 mmol/L), high glucose group 1 (HG1, glucose concentration 10 mmol/L), high glucose group 2 (HG2, glucose concentration 15 mmol/L), high glucose group 3 (HG3, glucose concentration 20 mmol/L). Then according to different insulin concentrations in culture medium, each group was further divided into two subgroups: normal insulin subgroup (INSc, insulin concentration 3.8 mU/L), high insulin subgroup (INSh, insulin concentration 7.6 mU/L). H9c2 (2-1) cells were cultured for 1, 2, 3 days, the proliferation of cells were assayed by cell counting Kit-8 assay, the expressions of GLUT4 mRNA and protein were detected with RT-PCR and Western Blotting technique, and the relation between myocardial cells proliferation and GLUT4 expression was evaluated.

RESULTSCompared with NC group, cell proliferation (OD value) was lower in LG, HG2, HG3 group but higher in HG1 group on the second and the third day (P < 0.05). There was a negative correlation between OD value and the glucose level in HG1, HG2, HG3 groups (P < 0.05). OD value in INSc subgroups was lower than that in INSh subgroups (P < 0.05). GLUT4 mRNA was lower in LG, HG2, HG3 groups than that in NC group (P < 0.05). Compared with NC group, GLUT4 mRNA level in HG1 group was higher on the first day but lower on the second and third day (P < 0.05). In HG1, HG2 and HG3 groups, GLUT4 mRNA level had a negative correlation with the level of glucose (P < 0.05). GLUT4 mRNA in INSc subgroups was lower than that in INSh subgroups (P < 0.05). The expression of GLUT4 protein was similar to that of GLUT4 mRNA. There was a positive correlation between H9c2 cell proliferation and GLUT4 expression (P < 0.02).

CONCLUSIONSGlucose levels could regulate glucose uptake in myocardial cells through influencing GLUT4 expression, and thus affected the cell proliferation and cell function. Insulin levels could affect the myocardial cell function by regulating GLUT4 expression. Effects of glucose and insulin on the myocardial cells proliferation might be mediated through regulating GLUT4 expression. There may be a mechanism of hyperglycemia pre-accommodation (HGPA) in myocardial cells mediated through regulation of GLUT4 expression.

Animals ; Blotting, Western ; Cell Line ; Cell Proliferation ; drug effects ; Glucose ; pharmacology ; Glucose Transporter Type 4 ; genetics ; metabolism ; Insulin ; pharmacology ; Myocardium ; cytology ; Rats ; Reverse Transcriptase Polymerase Chain Reaction

The aim of this project is to establish a fibroblast growth factor-21 (FGF-21) signaling pathway targeted cell model, for screening a class of FGF-21 receptor agonists as anti-diabetic candidates. FGF-21 requires beta klotho transmembrane proteins as co-receptor for the activation of tyrosine kinase FGF receptor (FGFR) signaling, thereby activating a series of intracellular signaling pathways and regulating gene transcription for glucose metabolism. Firstly a recombinant plasmid expressing co-receptor beta klotho and EGFP reporter genes was constructed. After introducing the recombinant plasmid into package cells, the cell culture supernatant was used to infect 3T3-L1 cells, which were then screened for stably expressing beta klotho gene. Administration of FGF-21 increased the expression of GLUT1 and stimulated GLUT1-mediated glucose uptake. This novel cell model can be conveniently used in high-throughput drug screening of FGF-21 or FGF-21 analogues.
3T3-L1 Cells ; Animals ; Drug Evaluation, Preclinical ; Fibroblast Growth Factors ; metabolism ; pharmacology ; Glucose ; metabolism ; Glucose Transporter Type 1 ; genetics ; metabolism ; Glucose Transporter Type 4 ; genetics ; metabolism ; HEK293 Cells ; Humans ; Hypoglycemic Agents ; metabolism ; Membrane Proteins ; genetics ; metabolism ; Mice ; NIH 3T3 Cells ; Plasmids ; RNA, Messenger ; metabolism ; Receptors, Fibroblast Growth Factor ; agonists ; Recombinant Proteins ; genetics ; metabolism ; Retroviridae ; genetics ; Signal Transduction ; Transfection

OBJECTIVETo investigate the effect of resistin overexpression on 3T3-L1 adipocyte lipid and glucose metabolism.

METHODSExpression vector for rat resistin gene was constructed and transfected into 3T3-L1 adipocytes. Cell differentiation and lipid accumulation was determined by Oil Red O staining. Differentiation marker genes (pref-1, C/EBPalpha, FAS) and glucose transporter 4 (GLUT4) gene mRNA expressions were evaluated by reverse transcription-PCR (RT-PCR). Triglyceride (TG) and free fatty acids (FFAs) in adipocytes were measured by colorimetric kit.

RESULTS(1) In resistin-overexpressed adipocytes, the lipid droplets presented at the second day which was earlier than the control cells. (2) The expression of C/EBPalpha and FAS genes in resistin-overexpressed adipocytes were up-regulated and the pref-1 was down-regulated compared with that of the control cells. (3) In resistin-overexpressed adipocytes, cellular TG and FFAs levels were significantly increased (P<0.05). (4) There was no difference in the expression of GLUT4 gene between 3T3-L1 adipocytes and resistin-overexpressed adipocytes (P> 0.05).

CONCLUSIONOverexpression of resistin can affect 3T3-L1 adipocyte lipid metabolism and thereby result in obesity and insulin resistance, but have no effect on GLUT4 gene expression.

3T3-L1 Cells ; Adipocytes ; metabolism ; Animals ; Cell Differentiation ; genetics ; Fatty Acids, Nonesterified ; metabolism ; Gene Expression ; Glucose Transporter Type 4 ; genetics ; Lipid Metabolism ; genetics ; Mice ; Rats ; Resistin ; genetics ; metabolism ; Triglycerides ; metabolism

OBJECTIVETo study the effect of a new obesity-related gene NYGGF4 on the insulin sensitivity and secretory function of adipocytes.

METHODS3T3-L1 preadipocytes transfected with either an empty expression vector (pcDNA3.1; control group) or an NYGGF4 expression vector (NYGGF4-pcDNA3.1) were cultured in vitro and differentiated into the matured adipocytes with the standard insulin plus dexamethasone plus 3-isobutyl-methylxanthine (MDI) induction cocktail. 2-deoxy-D-[3H] glucose uptake was determined by liquid scintillation counting. Western blot was performed to detect the protein content and translocation of glucose transporter 4 (GLUT4). The supernatant concentrations of TNF-alpha, IL-6, adiponectin and resistin were measured using ELISA.

RESULTSNYGGF4 over-expression in 3T3-L1 adipocytes reduced insulin-stimulated glucose uptake. NYGGF4 over-expression impaired insulin-stimulated GLUT4 translocation without affecting the total protein content of GLUT4. The concentrations of TNF-alpha, IL-6, adiponectin and resistin in the culture medium of 3T3-L1 transfected with NYGGF4 were not significantly different from those in the control group.

CONCLUSIONSNYGGF4 over-expression impairs the insulin sensitivity of 3T3-L1 adipocytes through decreasing GLUT4 translocation and had no effects on the secretory function of adipocytes.

3T3-L1 Cells ; Adipocytes ; drug effects ; secretion ; Adiponectin ; secretion ; Animals ; Carrier Proteins ; genetics ; physiology ; Glucose ; metabolism ; Glucose Transporter Type 4 ; analysis ; metabolism ; Insulin ; pharmacology ; Interleukin-6 ; secretion ; Mice ; Resistin ; analysis ; Transfection ; Tumor Necrosis Factor-alpha ; secretion

AMP-activated protein kinase, AMPK, is responsible for regulation of exercise-induced GLUT4 gene expression in skeletal muscle. But the molecular mechanisms for this regulation and key protein in this signaling pathway are obscure. There has been growing recognition that histone acetylation probably represents a central mechanism for regulation of gene transcription, and recent studies showed that numerous gene expressions are regulated by nucleosomal histone acetylation, which is modulated through histone acetyltransferases (HATs) and histone deacetylases (HDACs). So we have a hypothesis that the AMPK regulates GLUT4 gene through recruiting HDACs. Skeletal muscle cells cultured with normal (5 mmol/L) and high (20 mmol/L) glucose concentration were incubated with AICAR, and then total and nuclear AMPKalpha2, HDAC5 protein and GLUT4 mRNA were measured. The results show that the AICAR activated AMPKalpha2, reduced nuclear HDAC5,and increased GLUT4 mRNA in skeletal muscle cells; in contrast, the effect evoked by AICAR was blunted in cultured skeletal muscle cells with high glucose. Therefore, the changes of GLUT4 gene expression under different glucose concentration are closely related to the changes of AMPKalpha2 and HDAC5 protein in skeletal muscle cells. This result demonstrates that HDAC5 plays an important role in regulating GLUT4 gene transcription by AMPK signaling pathway skeletal muscle cells.
AMP-Activated Protein Kinases ; metabolism ; Cells, Cultured ; Glucose Transporter Type 4 ; biosynthesis ; genetics ; Histone Deacetylases ; metabolism ; Humans ; Muscle, Skeletal ; cytology ; enzymology ; metabolism ; RNA, Messenger ; biosynthesis ; genetics ; Signal Transduction ; Transcription, Genetic

Swine is an ideal model for diabetes studies. Insulin and insulin resistance are closely related with diabetes. To investigate the effect of SOCS-3 in insulin resistance, porcine primary adipocyte was treated with insulin (100 nmol/L) and dexamethasone (300 nmol/L) to induce insulin resistance. The simi-quantitative PCR results suggested that insulin increased GLUT4, PPARgamma and SOCS-3 gene expression in primary culture porcine adipocytes and no change of OB gene expression. Under insulin resistance conditions, SOCS-3 and OB gene expression were up-regulated, whereas GLUT4 and PPARgamma gene expression were down-regulated in primary porcine adipocytes. The overexpression of PPARgamma gene resulted in the increase of GLUT4 expression by insulin. Different expression levels of SOCS-3 determined the inhibitory effects of insulin signaling. Induction of insulin resistance by dexamethasone was not only due to inhibition of glucose transportation, but also repression of insulin signaling. SOCS-3 might be a potential gene to block the insulin resistance.
Adipocytes ; cytology ; metabolism ; Animals ; Cells, Cultured ; Dexamethasone ; pharmacology ; Glucose Transporter Type 4 ; biosynthesis ; genetics ; Insulin ; pharmacology ; Insulin Resistance ; Leptin ; biosynthesis ; genetics ; PPAR gamma ; biosynthesis ; genetics ; Suppressor of Cytokine Signaling 3 Protein ; Suppressor of Cytokine Signaling Proteins ; biosynthesis ; genetics ; Swine

OBJECTIVEThe purpose of this study was to assess the feasibility of fluorescent 2-deoxyglucose analog, 2-[N-(7-nitrobenz-2-oxa-1, 3-diaxol-4-yl)amino]-2-deoxyglucose (2-NBDG), that could be taken up by breast cancer cells highly expressing glucose transporter 1 (GLUT-1). The purpose of this study was to clarify if a fluorescent 2-deoxyglucose analog, 2-[N-(7-nitrobenz-2-oxa-1, 3-diaxol-4-yl)amino]-2-deoxyglucose (2-NBDG), can be taken up by breast cancer cells highly expressing glucose transporter 1 (GLUT-1), and to assess whether it can be used as a targeting imaging agent.

METHODSThe expressions of GLUT-1 mRNA and protein in breast cancer MDA-MB-231 cells were detected by RT-PCR and immunohistochemistry, respectively. The difference of GLUT-1 protein expression between breast cancer MDA-MB-231 cells and MCF-7 cells was compared by Western blot. Secondly, MDA-MB-231 cells which were grown in 6-well plates were incubated with 2-NBDG, and the result of 2-NBDG uptake was analyzed by fluorescence microscopy and flow cytometry. The difference of 2-NBDG absorption in MDA-MB-231 and MCF-7 cells was compared by flow cytometry.

RESULTSThe results of RT-PCR and immunohistochemistry confirmed that MDA-MB-231 cells highly expressed GLUT-1. Furthermore, Western blot revealed that GLUT-1 expression of MDA-MB-231 cells (0.946 ± 0.007) was higher than that in the MCF-7 cells (0.833 ± 0.010). Fluorescence microscopic and flow cytometric analysis showed that 2-NBDG was uptaken rapidly by MDA-MB-231 cells. Addition of 50 mmol/L D-glucose to the media with 2-NBDG reduced its uptake by 46.0%. Moreover, flow cytometry indicated that the fluorescence intensity of MDA-MB-231 cells (25.10 ± 0.57) was higher than that of MCF-7 cells (10.12 ± 0.62) when incubated with 2-NBDG for 20 minutes.

CONCLUSIONThe preliminary data clearly demonstrate that 2-NBDG is taken up and accumulated in breast cancer cells that highly express GLUT-1, and may be used as an optical probe for glucose uptake in hypermetabolic malignant cells.

4-Chloro-7-nitrobenzofurazan ; analogs & derivatives ; pharmacokinetics ; Blotting, Western ; Breast Neoplasms ; metabolism ; pathology ; Cell Line, Tumor ; Deoxyglucose ; analogs & derivatives ; pharmacokinetics ; Female ; Flow Cytometry ; Glucose Transporter Type 1 ; genetics ; metabolism ; Humans ; Immunohistochemistry ; RNA, Messenger ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction

OBJECTIVETo investigate the effect of exercise on the expressions of phosphatidylinositol 3 kinase (PI3K) and protein kinase B (PKB) phosphorylation, protein and glucose transport proteins (GLUT4) at both the protein and mRNA levels in the skeletal muscles of type 2 diabetic rats.

METHODSThirty male SD rats were randomly divided into control group with normal diet feeding, diabetic group and diabetic exercise group with high-fat diet feeding. After 8 weeks of the high-fat diet, each rat received an intraperitoneal injection of streptozotocin (STZ, 30 mg/kg). Three weeks after the injection, the rats were rated for the presence of diabetes, and the rats in the exercise groups took swimming training for 4 weeks; all the groups maintained their assigned diets. The gastrocnemius of all the rats were dissected 48 h after the last training session. Western blotting was applied to detect the phosphorylation and protein expression of PI3K and PKB and the protein expression of GLUT4. The expression of GLUT4 mRNA was determined by RT-PCR.

RESULTSCompared with the diabetic group, the diabetic rats in the exercise group showed significantly increased protein expression and phosphorylation of PKB (P<0.05) and elevated GLUT4 protein and mRNA expressions in the skeletal muscles (P<0.01, P<0.05).

CONCLUSIONExercise training can modulates insulin signal transduction through the protein expression and phosphorylation of the protein kinase to promote glucose uptake in the skeletal muscle of type 2 diabetic rats.

Animals ; Diabetes Mellitus, Experimental ; metabolism ; Diabetes Mellitus, Type 2 ; metabolism ; Glucose Transporter Type 4 ; metabolism ; Insulin ; metabolism ; Male ; Muscle, Skeletal ; metabolism ; Phosphatidylinositol 3-Kinases ; genetics ; metabolism ; Phosphorylation ; Physical Conditioning, Animal ; Proto-Oncogene Proteins c-akt ; genetics ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Signal Transduction