GLUT4 Translocation Activity Research Articles

DNAJB3 attenuates ER stress through direct interaction with AKT.

Metabolic stress involved in several dysregulation disorders such as type 2 diabetes mellitus (T2DM) results in down regulation of several heat shock proteins (HSPs) including DNAJB3. This down regulation of HSPs is associated with insulin resistance (IR) and interventions which induce the heat shock response (HSR) help to increase the insulin sensitivity. Metabolic stress leads to changes in signaling pathways through increased activation of both c-jun N-terminal kinase-1 (JNK1) and the inhibitor of κB inflammatory kinase (IKKβ) which in turn leads to inactivation of insulin receptor substrates 1 and 2 (IRS-1 and IRS-2). DNAJB3 interacts with both JNK1 and IKKβ kinases to mitigate metabolic stress. In addition DNAJB3 also activates the PI3K-PKB/AKT pathway through increased phosphorylation of AKT1 and its substrate AS160, a Rab GTPase-activating protein, which results in mobilization of GLUT4 transporter protein and improved glucose uptake. We show through pull down that AK T1 is an interacting partner of DNAJB3, further confirmed by isothermal titration calorimetry (ITC) which quantified the avidity of AKT1 for DNAJB3. The binding interface was identified by combining protein modelling with docking of the AKT1-DNAJB3 complex. DNAJB3 is localized in the cytoplasm and ER, where it interacts directly with AKT1 and mobilizes AS160 for glucose transport. Inhibition of AKT1 resulted in loss of GLUT4 translocation activity mediated by DNAJB3 and also abolished the protective effect of DNAJB3 on tunicamycin-induced ER stress. Taken together, our findings provide evidence for a direct protein-protein interaction between DNAJB3 and AKT1 upon which DNAJB3 alleviates ER stress and promotes GLUT4 translocation.

Triterpenoid saponins and C21 steroidal glycosides from Gymnema tingens and their glucose uptake activities.

Four new triterpenoid saponins, tigensides A-D (1-4), and one new C21 steroid, tipregnane A(9), together with six known compounds were isolated from the EtOAc fraction of the roots and stems of Gymnema tingens. The chemical structures of the new compounds were determined based on their spectroscopic data, including IR, UV, NMR, and mass spectrometric analysis. All compounds were isolated for the first time. Compounds 1-11 promoted glucose uptake in the range of 1.12 to 2.52 fold, respectively. Compound 2 showed the most potent glucose uptake, with 2.52 fold enhancement. Additionally, compound 2 showed a medium effect on the GLUT4 translocation activity in L6 cells in further study.

Does Orthosiphon stamineus Benth. enhance GLUT4 translocation in the skeletal muscle of induced type II diabetic rats?

Background: GLUT4 acts as the insulin-responsive glucose transporter, thus promoting the uptake of glucose from circulation into muscle and adipose tissue. Aims and Objectives: The present study was conducted to determine the effect Orthosiphon stamineus Benth. extract on GLUT4 translocation in the skeletal muscle of type II diabetic rats using immunofluorescent technique. Materials and Methods: Male Wistar rats aged 10 weeks (180–220 g) were divided into four groups: Normal control group (vehicle receiving group), positive control group (diabetic rats treated with 5 mg/kg metformin), negative control group (diabetic rats not receiving any treatment), and treated group (diabetic rats treated with 1 g/kg O. stamineus Benth. aqueous leaf extract). The rats were treated daily for 14 days where the fasting blood glucose level was measured daily; meanwhile, serum insulin was measured before (after injected with STZ-NAD) and after they get treated (at the end of 14 days). At the end of the treatment, the rats were sacrificed and soleus muscles were dissected, fixed in 10% buffered formalin, and processed for immunofluorescence technique. Results: The findings showed significantly reduced (P < 0.01) mean fasting glucose concentration in positive control and treated groups. Relative pancreas weight and serum plasma concentration were similar in all groups. In the diabetic rats treated with O. stamineus Benth., improvement in the translocation activity of GLUT4 was observed. Conclusion: Our findings suggest that O. stamineus Benth. has the potential in the treatment of Type II diabetes mellitus though the improvement of GLUT4 translocation activity.

Chemical constituents from Sophora tonkinensis and their glucose transporter 4 translocation activities

Bioassay-guided phytochemical investigation of the EtOAc fraction (ST-EtOAc) from the roots of Sophora tonkinensis resulted in the isolation of a new compound 6aR,11aR-1-hydroxy-4-isoprenyl-maackiain (1), along with 12 known compounds (2–13). The structure of the new compound was established by 1D and 2D NMR, MS data and circular dichroism analysis. Polyprenylated flavonoids 6–9 and 11–13 increased GLUT-4 translocation by the range of 1.35–2.75 folds. Sophoranone (8) exerted the strongest activity with 2.75 folds GLUT-4 translocation enhancement at the concentration of 10μM. This is the first report of the GLUT-4 translocation activity of the plant Sophora tonkinensis.

Anti-diabetic activity of stigmasterol from soybean oil by targeting the GLUT4 glucose transporter

ABSTRACTThe present study investigated the anti-diabetic activity and potential mechanism of stigmasterol (SMR), which is a kind of phytosterols derived from the edible soybean oil in vitro and in vivo. SMR displayed a mild GLUT4 translocation activity by 1.44-fold in L6 cells. L6 cells were treated with different concentration of SMR, showing significant effects on the enhancing glucose uptake. SMR administrated orally to the KK-Ay mice significantly alleviated their insulin resistance and oral glucose tolerance with reducing fasting blood-glucose levels and blood lipid indexes such as triglyceride and cholesterol. Moreover, the GLUT4 expression in L6 cells, skeletal muscle and white adipose tissue had been also enhanced. In this paper we conclude that, stigmasterol seems to have potential beneficial effects on the treatment of type 2 diabetes mellitus with the probable mechanism of targeting GLUT4 glucose transporter included increasing GLUT4 translocation and expression.

Synthesis of novel glycosyl-1,2,3-1H-triazolyl methyl quinazolin-4(3H)-ones and their effect on GLUT4 translocation

Cu(OTf)2 catalyzed synthesis of propargylated 2,3-dihydroquinazolin-4(1H)-ones has been accomplished from 2-amino-N-propargyl benzamides and aromatic aldehydes under MW irradiation. Next, a series of novel glycosyl triazolyl methyl quinazolin-4(3H)-ones have been synthesized by CuAAC reaction of propargylated 2,3-dihydroquinazolin-4(1H)-ones with glycosyl azides followed by iodine mediated oxidation. In this series, six compounds showed promising to significant GLUT4 translocation activity comparable to rosiglitazone.

Selective Inhibition of PTP1B by Vitalboside A from Syzygium cumini Enhances Insulin Sensitivity and Attenuates Lipid Accumulation Via Partial Agonism to PPARγ: In Vitro and In Silico Investigation.

Although antidiabetic drugs show good insulin-sensitizing property for T2DM, they also exhibit undesirable side-effects. Partial peroxisome proliferator-activated receptor γ agonism with protein tyrosine phosphatase 1B inhibition is considered as an alternative therapeutic approach toward the development of a safe insulin sensitizer. Bioactivity-based fractionation and purification of Syzygium cumini seeds led to the isolation and identification of bifunctional Vitalboside A, which showed antidiabetic and anti-adipogenic activities, as measured by glucose uptake in L6 and 3T3-L1 adipocytes and Nile red assay. A non-competitive allosteric inhibition of protein tyrosine phosphatase 1B by Vitalboside A was observed, which was confirmed by docking studies. Inhibitor studies with wortmannin and genistein showed an IRTK- and PI3K-dependent glucose uptake. A PI3K/AKT-dependent activation of GLUT4 translocation and an inactivation of GSK3β were observed, confirming its insulin-sensitizing potential. Vitalboside A exhibited partial transactivation of peroxisome proliferator-activated receptor γ with an increase in adiponectin secretion, which was confirmed using docking analysis. Vitalboside A is a bifunctional molecule derived from edible plant showing inhibition of PTP1B and partial agonism to peroxisome proliferator-activated receptor γ which could be a promising therapeutic agent in the management of obesity and diabetes.

Glucose uptake stimulator YM‐138552 activates gene expression and translocation of glucose transporter isotype 4

In this study, we examined the effect of YM-138552 on the glucose uptake, gene expression, and transport activities of the insulin-regulatable glucose transporter isotype 4 (Glut4) in skeletal muscle cells. YM-138552 stimulated medium glucose consumption in a dose-dependent manner (EC50 = 0.07 μM) in myoblast muscle C2C12 cells under differentiation conditions with 2% horse serum supplement. The stimulatory effect of glucose consumption was verified by radiolabeled 2-DG uptake assay. The compound showed dose-dependent stimulation of 2-DG uptake in G8 myoblast muscle cells up to a 1 μM concentration (EC50 = 0.19 μM). To investigate the mechanism of glucose uptake stimulation by YM-138552, the mRNA level of Glut4 was determined using real-time quantitative RT-PCR. The Glut4 mRNA level expressed in C2C12 cells treated with YM-138552 increased up to at least 24 h (227% vs. control), after which it gradually decreased to the initial level at 36 h. In addition, we established that C2C12 cells stably expressed the myc-tagged Glut4 protein (C2C12-Glut4myc) and measured the Glut4 translocation activity. The Glut4 translocation activity was stimulated by treatment of YM-138552 without insulin in a dose-dependent manner (EC50 = 0.62 μM), and no insulin effect (100 nM) was observed. This suggests that YM-138552 has an insulin-like effect. These results suggest that the stimulation of glucose uptake by YM-138552 in muscle cells was partly due to upregulation of the Glut4 gene expression and its translocation activation. Our findings on the in vitro effects of YM-138552 glucose uptake stimulation through the Glut4 transporter may suggest a direction for the development of new drugs for the treatment of NIDDM. Drug Dev. Res. 51:43–48, 2000. © 2000 Wiley-Liss, Inc.

Glucose uptake stimulator YM-138552 activates gene expression and translocation of glucose transporter isotype 4

In this study, we examined the effect of YM-138552 on the glucose uptake, gene expression, and transport activities of the insulin-regulatable glucose transporter isotype 4 (Glut4) in skeletal muscle cells. YM-138552 stimulated medium glucose consumption in a dose-dependent manner (EC50 = 0.07 μM) in myoblast muscle C2C12 cells under differentiation conditions with 2% horse serum supplement. The stimulatory effect of glucose consumption was verified by radiolabeled 2-DG uptake assay. The compound showed dose-dependent stimulation of 2-DG uptake in G8 myoblast muscle cells up to a 1 μM concentration (EC50 = 0.19 μM). To investigate the mechanism of glucose uptake stimulation by YM-138552, the mRNA level of Glut4 was determined using real-time quantitative RT-PCR. The Glut4 mRNA level expressed in C2C12 cells treated with YM-138552 increased up to at least 24 h (227% vs. control), after which it gradually decreased to the initial level at 36 h. In addition, we established that C2C12 cells stably expressed the myc-tagged Glut4 protein (C2C12-Glut4myc) and measured the Glut4 translocation activity. The Glut4 translocation activity was stimulated by treatment of YM-138552 without insulin in a dose-dependent manner (EC50 = 0.62 μM), and no insulin effect (100 nM) was observed. This suggests that YM-138552 has an insulin-like effect. These results suggest that the stimulation of glucose uptake by YM-138552 in muscle cells was partly due to upregulation of the Glut4 gene expression and its translocation activation. Our findings on the in vitro effects of YM-138552 glucose uptake stimulation through the Glut4 transporter may suggest a direction for the development of new drugs for the treatment of NIDDM. Drug Dev. Res. 51:43–48, 2000. © 2000 Wiley-Liss, Inc.

Protein Kinase C-ζ as a Downstream Effector of Phosphatidylinositol 3-Kinase during Insulin Stimulation in Rat Adipocytes: POTENTIAL ROLE IN GLUCOSE TRANSPORT

Insulin provoked rapid increases in enzyme activity of immunoprecipitable protein kinase C-zeta (PKC-zeta) in rat adipocytes. Concomitantly, insulin provoked increases in 32P labeling of PKC-zeta both in intact adipocytes and during in vitro assay of immunoprecipitated PKC-zeta; the latter probably reflected autophosphorylation, as it was inhibited by the PKC-zeta pseudosubstrate. Insulin-induced activation of immunoprecipitable PKC-zeta was inhibited by LY294002 and wortmannin; this suggested dependence upon phosphatidylinositol (PI) 3-kinase. Accordingly, activation of PI 3-kinase by a pYXXM-containing peptide in vitro resulted in a wortmannin-inhibitable increase in immunoprecipitable PKC-zeta enzyme activity. Also, PI-3,4-(PO4)2, PI-3,4,5-(PO4)3, and PI-4,5-(PO4)2 directly stimulated enzyme activity and autophosphoralytion in control PKC-zeta immunoprecipitates to levels observed in insulin-treated PKC-zeta immunoprecipitates. In studies of glucose transport, inhibition of immunoprecipitated PKC-zeta enzyme activity in vitro by both the PKC-zeta pseudosubstrate and RO 31-8220 correlated well with inhibition of insulin-stimulated glucose transport in intact adipocytes. Also, in adipocytes transiently expressing hemagglutinin antigen-tagged GLUT4, co-transfection of wild-type or constitutive PKC-zeta stimulated hemagglutinin antigen-GLUT4 translocation, whereas dominant-negative PKC-zeta partially inhibited it. Our findings suggest that insulin activates PKC-zeta through PI 3-kinase, and PKC-zeta may act as a downstream effector of PI 3-kinase and contribute to the activation of GLUT4 translocation.