Reversal of Insulin Resistance in Diabetic Rat Adipocytes by Insulin Therapy: Restoration of Pool of Glucose Transporters and Enhancement of Glucose-Transport Activity

Diabetes ◽  
1987 ◽  
Vol 36 (8) ◽  
pp. 925-931 ◽  
Author(s):  
E. Karnieli ◽  
M. Armoni ◽  
P. Cohen ◽  
Y. Kanter ◽  
R. Rafaeloff
Keyword(s):  
Insulin Resistance ◽  
Insulin Therapy ◽  
Glucose Transport ◽  
Glucose Transporters ◽  
Diabetic Rat ◽  
Transport Activity ◽  
Rat Adipocytes

Effect of insulin and glucocorticoids on glucose transporters in rat adipocytes

1987 ◽  
Vol 252 (4) ◽  
pp. E441-E453 ◽  
Author(s):  
C. Carter-Su ◽  
K. Okamoto
Keyword(s):  
Glucose Transport ◽  
Plasma Membranes ◽  
Glucose Transporter ◽  
Cytochalasin B ◽  
Glucose Transporters ◽  
Insulin Binding ◽  
Maximal Response ◽  
Transport Activity ◽  
Rat Adipocytes ◽  
Dose Dependent Fashion

The ability of glucocorticoids to modify the effect of insulin on glucose transport was investigated in both intact isolated rat adipocytes and in membranes isolated from hormone-treated adipocytes. In intact adipocytes, dexamethasone, a potent synthetic glucocorticoid, inhibited insulin-stimulated 3-O-methylglucose transport at all concentrations of insulin tested (0-2,000 microU/ml). Insulin sensitivity, as well as the maximal response to insulin, was decreased by dexamethasone in the absence of a change in insulin binding. The inhibition was observed regardless of which hormone acted first, was blocked by actinomycin D, and resulted from a decrease in Vmax rather than an increase in Kt of transport. In plasma membranes isolated from insulin-treated adipocytes, glucose transport activity and the amount of glucose transporter covalently labeled with [3H]cytochalasin B were increased in parallel in a dose-dependent fashion. The amount of labeled transporter in a low-density microsomal fraction (LDMF) was decreased in a reciprocal fashion. In contrast, addition of dexamethasone to insulin-stimulated cells caused decreases in both transport activity and amount of labeled transporter in the plasma membranes. This was accompanied by a small increase in the amount of [3H]cytochalasin B incorporated into the glucose transporter in the LDMF. These results are consistent with both insulin and glucocorticoids altering the distribution of glucose transporters between the plasma membrane and LDMF, in opposite directions.

scholarly journals Characterization of GTP-binding proteins in Golgi-associated membrane vesicles from rat adipocytes

1992 ◽  
Vol 283 (3) ◽  
pp. 795-801 ◽  
Author(s):  
A Schürmann ◽  
W Rosenthal ◽  
G Schultz ◽  
H G Joost
Keyword(s):  
G Proteins ◽  
Glucose Transport ◽  
Subcellular Distribution ◽  
Sucrose Gradient ◽  
Binding Proteins ◽  
Glucose Transporters ◽  
Beta Subunits ◽  
Transport Activity ◽  
Gtp Binding Proteins ◽  
Gtp Binding

We have previously reported that guanine nucleotides inhibit glucose transport activity reconstituted from adipocyte membrane fractions. In order to further investigate the hypothetical involvement of guanine-nucleotide-binding proteins (GTP-binding proteins) in the regulation of insulin-sensitive glucose transport activity, we studied their subcellular distribution in adipocytes treated or not with insulin. Adipocytes were homogenized and fractionated to yield plasma membranes (PM) and a Golgi-enriched fraction of intracellular membranes (low-density microsomes, LDM). In these membrane fractions, total guanosine 5′-[gamma-[35S]thio]triphosphate ([35S]GTP[S]) binding, alpha- and beta-subunits of heterotrimeric G-proteins, proto-oncogenes Ha-ras and K-ras, and 23-28 kDa GTP-binding proteins were assayed. The levels of alpha s and alpha i (the alpha-subunits of Gs and Gi) were approx. 8-fold lower in LDM than in PM; beta-subunits, Ha-ras and K-ras were not detectable in LDM. Total GTP[S]-binding sites and 23-28 kDa GTP-binding proteins were present in LDM in approximately the same concentrations as in PM. Insulin gave rise to the characteristic translocation of glucose transporters, but failed to alter the subcellular distribution of any of the GTP-binding proteins. Fractionation of the LDM on a discontinuous sucrose gradient revealed that alpha s and alpha i, as detected with antiserum against a common peptide sequence (alpha common), and the bulk of the 23-28 kDa G-proteins sedimented at different sucrose densities. None of the GTP-binding proteins co-sedimented with glucose transporters. Furthermore, the inhibitory effect of GTP[S] on the reconstituted transport activity was lost in the peak fractions of glucose transporters partially purified on the sucrose gradient. These data indicate that LDM from adipocytes contain several GTP-binding proteins in discrete vesicle populations. However, the intracellular GTP-binding proteins are not tightly associated with the vesicles containing the glucose transporter.

Exercise training increases the number of glucose transporters in rat adipose cells

1989 ◽  
Vol 257 (4) ◽  
pp. E520-E530
Author(s):  
M. F. Hirshman ◽  
L. J. Wardzala ◽  
L. J. Goodyear ◽  
S. P. Fuller ◽  
E. D. Horton ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Glucose Transport ◽  
Glucose Transporters ◽  
Membrane Transporters ◽  
Control Group ◽  
Transport Activity ◽  
Insulin Stimulation ◽  
Adipose Cell ◽  
Adipose Cell Size ◽  
Adipose Cells

We studied the mechanism for the increase in glucose transport activity that occurs in adipose cells of exercise-trained rats. Glucose transport activity, glucose metabolism, and the subcellular distribution of glucose transporters were measured in adipose cells from rats raised in wheel cages for 6 wk (mean total exercise 350 km/rat), age-matched sedentary controls, and young sedentary controls matched for adipose cell size. Basal rates of glucose transport and metabolism were greater in cells from exercise-trained rats compared with young controls, and insulin-stimulated rates were greater in the exercise-trained rats compared with both age-matched and young controls. The numbers of plasma membrane glucose transporters were not different among groups in the basal state; however, with insulin stimulation, cells from exercise-trained animals had significantly more plasma membrane transporters than young controls or age-matched controls. Exercise-trained rats also had more low-density microsomal transporters than control rats in the basal state. When the total number of glucose transporters/cell was calculated, the exercise-trained rats had 42% more transporters than did either control group. These studies demonstrate that the increased glucose transport and metabolism observed in insulin-stimulated adipose cells from exercise-trained rats is due, primarily, to an increase in the number of plasma membrane glucose transporters translocated from an enlarged intracellular pool.

scholarly journals Thrombin-induced translocation of GLUT3 glucose transporters in human platelets

1997 ◽  
Vol 328 (2) ◽  
pp. 511-516 ◽  
Author(s):  
R. Lynn SORBARA ◽  
Theresa M. DAVIES-HILL ◽  
Ellen M. KOEHLER-STEC ◽  
J. Susan VANNUCCI ◽  
K. McDonald HORNE ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Glucose Transport ◽  
Glucose Transporter ◽  
Glucose Transporters ◽  
Human Platelets ◽  
Half Time ◽  
Transport Activity ◽  
Kinase C ◽  
Adipose Cells

Platelets derive most of their energy from anaerobic glycolysis; during activation this requirement rises approx. 3-fold. To accommodate the high glucose flux, platelets express extremely high concentrations (155±18 pmol/mg of membrane protein) of the most active glucose transporter isoform, GLUT3. Thrombin, a potent platelet activator, was found to stimulate 2-deoxyglucose transport activity 3-5-fold within 10 min at 25 °C, with a half-time of 1-2 min. To determine the mechanism underlying the increase in glucose transport activity, an impermeant photolabel, [2-3H]2N-4-(1-azi-2,2,2-trifluoethyl)benzoyl-1,3,-bis-(d-mannose-4-ylozy)-2-propylamine, was used to covalently bind glucose transporters accessible to the extracellular milieu. In response to thrombin, the level of transporter labelling increased 2.7-fold with a half-time of 1-2 min. This suggests a translocation of GLUT3 transporters from an intracellular site to the plasma membrane in a manner analogous to that seen for the translocation of GLUT4 in insulin-stimulated rat adipose cells. To investigate whether a similar signalling pathway was involved in both systems, platelets and adipose cells were exposed to staurosporin and wortmannin, two inhibitors of GLUT4 translocation in adipose cells. Thrombin stimulation of glucose transport activity in platelets was more sensitive to staurosporin inhibition than was insulin-stimulated transport activity in adipose cells, but it was totally insensitive to wortmannin. This indicates that the GLUT3 translocation in platelets is mediated by a protein kinase C not by a phosphatidylinositol 3-kinase mechanism. In support of this contention, the phorbol ester PMA, which specifically activates protein kinase C, fully stimulated glucose transport activity in platelets and was equally sensitive to inhibition by staurosporin. This study provides a cellular mechanism by which platelets enhance their capacity to import glucose to fulfil the increased energy demands associated with activation.

Effects of diabetes on myocardial glucose transport system in rats: implications for diabetic cardiomyopathy

1993 ◽  
Vol 264 (3) ◽  
pp. H837-H844 ◽  
Author(s):  
W. T. Garvey ◽  
D. Hardin ◽  
M. Juhaszova ◽  
J. H. Dominguez
Keyword(s):  
Insulin Therapy ◽  
Glucose Transport ◽  
Glucose Utilization ◽  
Myocardial Dysfunction ◽  
Mrna Levels ◽  
Transport Activity ◽  
Glucose Transport System ◽  
Normal Functional ◽  
Biochemical Mechanisms ◽  
Sarcolemmal Vesicles

Biochemical mechanisms underlying impaired myocardial glucose utilization in diabetes mellitus have not been elucidated. We studied sarcolemmal vesicles (SL) in control, streptozotocin-induced diabetic (D), and insulin-treated diabetic (Tx) rats and found that 3-O-methylglucose transport rates were decreased 53% in D rats and were normalized by insulin therapy. Immunoblot analyses of SL revealed that GLUT4 glucose transporters were decreased 56% in D and were normal in Tx rats. Thus diminished transport rates could be fully explained by reduced numbers of SL GLUT4 with normal functional activity. To determine whether SL GLUT4 were decreased due to tissue depletion or abnormal subcellular distribution, we measured GLUT4 in total membranes (SL plus intracellular fractions). Total GLUT4 (per mg membrane protein or per DNA) was decreased 45–51% in D [half time = 3.5 days after streptozotocin], and these values were restored to normal in Tx rats. Also, diabetes decreased GLUT4 mRNA levels by 43%, and this effect was reversed by insulin therapy. We conclude that, in diabetes, 1) impaired myocardial glucose utilization is the result of a decrease in glucose transport activity, and 2) transport rates are reduced due to pretranslational suppression of GLUT4 gene expression and can be corrected by insulin therapy. GLUT4 depletion could limit glucose availability under conditions of increased workload and anoxia and could cause myocardial dysfunction.

Stimulatory effect of lithium on glucose transport in rat adipocytes is not mediated by elevation of IP1

1998 ◽  
Vol 275 (2) ◽  
pp. E272-E277 ◽  
Author(s):  
Xiaoli Chen ◽  
Ellen G. McMahon ◽  
Eric A. Gulve
Keyword(s):  
Glucose Uptake ◽  
Glucose Transport ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Transport Activity ◽  
Concentration Dependent Manner ◽  
Inositol 1 ◽  
Rat Adipocytes ◽  
Increase Glucose Uptake ◽  
Stimulation Of

Lithium has been shown to increase glucose uptake in skeletal muscle and adipose tissues. The therapeutic effect of lithium on bipolar disease is thought to be mediated by its inhibitory effect on myo-inositol-1-monophosphatase (IMPase). We tested the hypothesis that the stimulatory effect of lithium on glucose uptake results from inhibition of IMPase and the resultant accumulation of inositol monophosphates (IP1) by comparing the effects of lithium and a selective IMPase inhibitor, L-690,488, on isolated rat adipocytes. Insulin produced a concentration-dependent stimulation of 2-deoxy-d-[14C]glucose (2-DG) transport (10 μU/ml caused half-maximal activation). Acute exposure to lithium stimulated basal glucose transport activity in a concentration-dependent manner, with a threefold stimulation at 30 mM lithium. Lithium also potentiated insulin-stimulated 2-DG transport. Lithium produced a concomitant increase in IP1 accumulation. In contrast, L-690,488 increased IP1 to levels comparable to those of lithium without stimulatory effects on 2-DG transport. These results demonstrate that stimulatory effects of lithium on glucose transport are not mediated by the inhibition of IMPase and subsequent accumulation of IP1 in rat adipocytes.

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