scholarly journals Absence of down-regulation of the insulin receptor by insulin. A possible mechanism of insulin resistance in the rat

1983 ◽  
Vol 210 (2) ◽  
pp. 373-378 ◽  
Author(s):  
A P Walker ◽  
D J Flint
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Culture Medium ◽  
Insulin Receptors ◽  
Insulin Binding ◽  
Recycling Process ◽  
Down Regulation ◽  
Pregnant Rats ◽  
Pregnancy And Lactation ◽  
Dose Dependent

Insulin resistance occurs in rat adipocytes during pregnancy and lactation despite increased or normal insulin binding respectively; this suggests that a post-receptor defect exists. The possibility has been examined that, although insulin binding occurs normally, internalization of insulin or its receptor may be impaired in these states. Insulin produced a dose-dependent reduction in the number of insulin receptors on adipocytes from virgin rats maintained in culture medium, probably due to internalization of the hormone-receptor complex. In contrast, adipocytes from pregnant and lactating rats did not exhibit this ‘down-regulation’ phenomenon. Down regulation was, however, apparent in all groups when the experiments were performed in Tris buffer (where receptor recycling is inhibited), suggesting that in pregnant and lactating rats insulin receptors are rapidly recycled back to the plasma membrane, whereas in virgin rats this recycling process is less effective. Internalization of insulin was also determined by using 125I-labelled insulin. Adipocytes from pregnant and lactating rats appeared to internalize similar amounts of insulin to virgin rats. In the presence of the lysosomal inhibitor chloroquine, adipocytes from pregnant rats internalized more insulin than virgin or lactating rats. These results suggest that adipocytes from pregnant and lactating rats internalize insulin and its receptor normally, whereas intracellular processing of the insulin receptor may differ from that in virgin rats. In addition the rate of lysosomal degradation of insulin may be altered in adipocytes from pregnant rats.

scholarly journals Tyrosine kinase activity of liver insulin receptor is inhibited in rats at term gestation

1989 ◽  
Vol 263 (1) ◽  
pp. 267-272 ◽  
Author(s):  
C Martínez ◽  
P Ruiz ◽  
A Andrés ◽  
J Satrústegui ◽  
J M Carrascosa
Keyword(s):  
Insulin Receptor ◽  
Kinase Activity ◽  
Insulin Signalling ◽  
Insulin Receptors ◽  
Insulin Binding ◽  
Late Gestation ◽  
Receptor Kinase ◽  
Pregnant Rats ◽  
Insulin Resistant ◽  
32P Incorporation

Late gestation is associated with insulin resistance in rats and humans. It has been reported that rats at term gestation show active hepatic gluconeogenesis and glycogenolysis, and diminished lipogenesis, despite normal or mildly elevated plasma insulin concentrations, indicating a state of resistance to the hormone action. Since autophosphorylation of the insulin receptor has been reported to play a key role in the hormone signal transduction, we have partially purified plasma-membrane liver insulin receptors from virgin and 22-day-pregnant rats and studied their binding and kinase activities. (1) Insulin binding to partially purified receptors does not appear to be influenced by gestation, as indicated by the observed KD and Bmax. values. (2) The rate of autophosphorylation and the maximal 32P incorporation into the receptor beta-subunit from pregnant rats at saturating concentrations of insulin are markedly decreased with respect to the corresponding values for virgin rats. (3) The diminished autophosphorylation rate was due to a decreased responsiveness of the kinase activity to the action of insulin. (4) Phosphorylation of the exogenous substrates casein and poly(Glu80Tyr20) by insulin-receptor kinase was also less when receptors from pregnant rats were used. These results show the existence of an impairment at the receptor kinase level of the insulin signalling mechanism that might be related to the insulin-resistant state characteristic of term gestation in rats.

In vitro regulation of human monocyte insulin receptors by insulin and 1-methyl-3-isobutylxanthine

1983 ◽  
Vol 245 (5) ◽  
pp. E494-E501
Author(s):  
R. H. Whitson ◽  
S. A. Kaplan
Keyword(s):  
Insulin Receptor ◽  
Cultured Cells ◽  
Phosphodiesterase Inhibitor ◽  
Insulin Receptors ◽  
Human Monocyte ◽  
Insulin Binding ◽  
Receptor Downregulation ◽  
Independent Process ◽  
Dose Dependent

Monocytes separated from human blood by Ficoll-Hypaque and adherence to polystyrene flasks were maintained successfully in culture for 7 days. The cultured cells showed normal morphology and good viability. The insulin binding properties of the cultured monocytes were also identical to those of fresh monocytes. In vitro pretreatment of the monocytes with insulin decreased both the number and affinity of insulin receptors, resulting in a 72% reduction in the binding of tracer quantities of 125I-insulin. Insulin-induced receptor down regulation was dose-dependent and specific to the insulin receptor. Monocytes pretreated with insulin in the presence of the cyclic nucleotide phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine (MIX) lost significantly fewer insulin receptors than monocytes treated with insulin alone. Tracer binding to these cells was 62% of control levels. MIX had no effect on basal insulin binding. The cAMP analogues N6,O2'-dibutyryl cAMP and 8-bromo-cAMP did not counteract insulin-induced receptor downregulation by themselves and did not significantly enhance the effects of MIX. These results indicate that MIX may counteract insulin receptor downregulation by a cAMP-independent process.

Suppression of insulin receptor binding by prolonged enteral or parenteral nutrient infusion in the rat: role of gastric inhibitory polypeptide

1989 ◽  
Vol 67 (9) ◽  
pp. 1105-1109 ◽  
Author(s):  
A. R. Baer ◽  
J. Dupré
Keyword(s):  
Insulin Resistance ◽  
Steady State ◽  
Insulin Receptor ◽  
Receptor Binding ◽  
Plasma Insulin ◽  
Gastric Inhibitory Polypeptide ◽  
Insulin Binding ◽  
Down Regulation ◽  
Insulin Receptor Binding ◽  
Nutrient Infusion

In the rat, prolonged enteral or parenteral alimentation with a high-carbohydrate diet results in hyperinsulinemia, which is substantially greater with the parenteral route. Supplementing the parenteral infusate with porcine gastric inhibitory polypeptide (GIP) to approximate plasma immunoreactive GIP levels achieved with enteral feeding further increases steady-state plasma insulin and glucose concentrations, suggesting insulin resistance. We examined the effects of sustained hyperinsulinemia elicited by continuous nutrient infusion on insulin binding to isolated rat adipocytes and the modification of this response by GIP. Compared with a baseline group, both enterally and parenterally alimented groups showed decreased insulin receptor binding affinity. However, despite substantially different steady-state plasma insulin levels, insulin binding was similar with either infusion route. Factors other than plasma insulin concentration alone therefore contribute to insulin receptor down-regulation during prolonged enteral alimentation. Supplementing the parenteral infusate with exogenous GIP resulted in a further reduction in insulin receptor affinity. Thus, adaptation to continuous nutrient infusion is characterized by insulin receptor down-regulation regardless of the route of nutrient delivery. An additional suppression of insulin receptor binding may in part be responsible for the insulin resistance elicited by prolonged exogenous GIP administration.Key words: gastric inhibitory polypeptide, insulin receptor binding, hyperinsulinemia.

Insulin binding and action in adipocytes of pregnant rats: evidence that insulin resistance is caused by post-receptor binding defects

1984 ◽  
Vol 102 (2) ◽  
pp. 209-214 ◽  
Author(s):  
M. Th. Sutter-Dub ◽  
A. Sfaxi ◽  
F. Latrille ◽  
F. Sodoyez-Goffaux ◽  
J. C. Sodoyez
Keyword(s):  
Insulin Resistance ◽  
Biological Effect ◽  
Response Curve ◽  
Glucose Oxidation ◽  
Insulin Receptors ◽  
Insulin Binding ◽  
Receptor Interaction ◽  
Fat Cells ◽  
Pregnant Rats ◽  
Duration Of Pregnancy

ABSTRACT Insulin resistance was investigated in the adipose cell of rats which were at days 16 and 20 of pregnancy. Data are presented to relate insulin binding and biological effect, which was evaluated by the ability of insulin to stimulate [1-14C]glucose oxidation. Adipocytes from pregnant rats bound more insulin than fat cells from control (non-pregnant) animals and the number of insulin receptors per adipocyte increased during pregnancy. Basal glucose oxidation rate was decreased at 16 and 20 days of pregnancy: however, the dose–response curve for insulin-stimulated glucose oxidation was significantly depressed only after 20 days of pregnancy. The concentration at which insulin increased glucose oxidation by 50% increased with the duration of pregnancy. We conclude that during pregnancy in the rat the adipocyte response to insulin was decreased, despite an increase in insulin binding. This result suggests that a major determinant of insulin resistance in rat adipocytes during pregnancy is present after the initial insulin–receptor interaction. Consequently, a post-receptor defect may be largely responsible for the insulin resistance. J. Endocr. (1984) 102, 209–214

scholarly journals Glucocorticoids increase insulin binding and the amount of insulin-receptor mRNA in human cultured lymphocytes

1988 ◽  
Vol 249 (3) ◽  
pp. 715-719 ◽  
Author(s):  
Y Shibasaki ◽  
H Sakura ◽  
M Odawara ◽  
M Shibuya ◽  
Y Kanazawa ◽  
...  
Keyword(s):  
Cell Surface ◽  
Insulin Receptor ◽  
De Novo ◽  
Insulin Receptors ◽  
Fold Increase ◽  
Insulin Binding ◽  
Dependent Manner ◽  
Receptor Mrna ◽  
Dose Dependent ◽  
Receptor Mrnas

The effect of steroid hormones on insulin binding and the amount of insulin-receptor mRNA was examined in IM-9 lymphocytes. Cortisol and cortexolone, but not oestrogen, increased both the binding of insulin and the amount of insulin-receptor mRNA in a time- and dose-dependent manner. Cortisol was most potent, and induced a 2-fold increase in insulin binding and a 4-fold increase in mRNA. The elevation in binding was due to an increased number of insulin receptors at the cell surface. The increase in mRNA involved all four of the insulin-receptor mRNAs and could not be inhibited by cycloheximide. The cortisol-induced increase in mRNA was associated with a 3-4-fold increase in the synthesis of pro-receptor. The relative potency of the three steroids indicated that these effects were mediated by an interaction with the glucocorticoid receptor. The results of this study suggest that cortisol can increase the number of insulin receptors at the cell surface by increasing the amounts of insulin-receptor mRNA and the synthesis de novo of insulin receptors.

Insulin action and resistance in obesity and noninsulin-dependent type II diabetes mellitus

1982 ◽  
Vol 243 (1) ◽  
pp. E15-E30 ◽  
Author(s):  
J. M. Olefsky ◽  
O. G. Kolterman ◽  
J. A. Scarlett
Keyword(s):  
Diabetes Mellitus ◽  
Insulin Resistance ◽  
Insulin Receptor ◽  
Insulin Action ◽  
Insulin Receptors ◽  
Tissue Level ◽  
Dependent Diabetes Mellitus ◽  
Target Tissue ◽  
Severe Insulin Resistance ◽  
Glucose Clamp Technique

Resistance to the action of insulin can result from a variety of causes, including the formation of abnormal insulin or proinsulin molecules, the presence of circulating antagonists to insulin or the insulin receptor, or defects in insulin action at the target tissue level. Defects of the latter type are characteristic of obesity and of noninsulin-dependent diabetes mellitus. Analysis of the nature of the insulin resistance in those disorders has been investigated in intact subjects with the use of the euglycemic glucose clamp technique, and both insulin receptors and insulin-mediated glucose metabolism have been studied in adipocytes and monocytes from affected individuals. In both conditions, the cause of insulin resistance is heterogeneous. In some, insulin resistance appears to be due to a defect in the insulin receptor, whereas others have a defect both in the receptor and at the postreceptor level. In both groups, more severe insulin resistance is due to the postreceptor lesion and is correctable with appropriate therapy.

scholarly journals Impairment of the liver insulin receptor autoactivation cascade at full-term pregnancy in the rat

1995 ◽  
Vol 311 (2) ◽  
pp. 523-529 ◽  
Author(s):  
C Martinez ◽  
J C Molero ◽  
P Ruiz ◽  
A Del Arco ◽  
A Andres ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Structural Changes ◽  
Insulin Receptors ◽  
Kinase Domain ◽  
Full Term ◽  
Beta Subunits ◽  
Pregnant Rats ◽  
Functional Changes ◽  
Domain Truncation ◽  
Alternative Sites

Partially purified liver insulin receptors from full-term pregnant rats show decreased autophosphorylation rates if compared with receptors from virgins. We studied the molecular mechanism of this phenomenon, looking at possible structural and functional changes of several domains. The ATP-binding domain seems to be unaltered in receptors from pregnant rats since Km for ATP was similar to that observed in virgins. In contrast, the Vmax. is decreased some 45%, suggesting changes in the kinase domain. Truncation of a fragment of 10 kDa from the C-terminal tail does not normalize the kinase activity in receptors from pregnant rats, suggesting that this domain is not involved in the inhibitory regulation. Treatment with alkaline phosphatase increases the [32P]Pi incorporation into receptors from pregnant rats; however, the autophosphorylation remains lower than that observed in virgin rats. Tryptic phosphopeptide maps of phosphorylated receptors show that the same phosphopeptides are present in receptors from virgin and pregnant rats. However, the progression through the autoactivation cascade in the kinase domain is impaired in receptors from pregnant rats. Differences in the cleavage by trypsin at the two alternative sites in the kinase domain were observed, indicating possible structural changes in receptors from pregnant rats that could be related to the impairment of the autoactivation cascade. Integrity of the alpha- and beta-subunits, as well as differential expression of the two receptor isotypes, were shown to be unaltered. We conclude that (1) the decreased autophosphorylation rate of the liver insulin receptor from pregnant rats is associated with the impairment of its autoactivation cascade, probably as a consequence of the basal Ser/Thr phosphorylation; and (2) the inhibition of the autoactivation cascade does not account for the overall inhibition of autophosphorylation observed in receptors from pregnant rats.

In-frame exon 2 deletion in insulin receptor RNA in a family with extreme insulin resistance in association with defective insulin binding: a case report

1996 ◽  
Vol 135 (3) ◽  
pp. 357-363 ◽  
Author(s):  
Wolfgang Moritz ◽  
Marianne Böni-Schnetzler ◽  
Wayne Stevens ◽  
E Rudolf Froesch ◽  
James R Levy
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Receptor Binding ◽  
Type A ◽  
Insulin Binding ◽  
Exon 2 ◽  
Receptor Mrna ◽  
Mrna Transcripts ◽  
Extreme Insulin Resistance ◽  
Type A Insulin Resistance

Moritz W, Böni-Schnetzler M, Stevens W, Froesch ER, Levy JR. In-frame exon 2 deletion in insulin receptor RNA in a family with extreme insulin resistance in association with defective insulin binding. Eur J Endocrinol 1996;135:357–63. ISSN 0804–4643 The phenotype and allelic expression of the insulin receptor gene is presented in a family with a patient with type A insulin resistance. Compared to controls, insulin receptor binding in transformed lymphocytes was 100%, 33% and 13% in the father, mother and proband, respectively. Reduced insulin receptor binding co-segregated with altered insulin receptor mRNA expression; the mother and daughter expressed eight insulin receptor mRNA species, including a set of four normal sized and a set of four shorter mRNA transcripts. In the proband the levels of the normal sized mRNA transcripts were suppressed relative to the shorter transcripts. Reverse polymerase chain reaction (PCR) revealed that the shorter transcripts contained an in-frame deletion of exon 2. Sequencing of the entire insulin receptor coding region revealed a paternally inherited A to T substitution in nucleotide 3205, converting isoleucine 996 to phenylalanine. which does not co-segregate with reduced binding. Therefore, we hypothesize that two findings are necessary for the presentation of type A insulin resistance in this patient: an in-frame deletion of the insulin receptor exon 2 that codes for amino acids crucial for insulin binding; and an inhibition of expression of the paternal insulin receptor allele. Marianne Böni-Schnetzler, Division of Endocrinology and Metabolism, Department of Internal Medicine, University Hospital, 8091 Zurich, Switzerland

scholarly journals Insulin receptor desensitization correlates with attenuation of tyrosine kinase activity, but not of receptor endocytosis

1987 ◽  
Vol 245 (2) ◽  
pp. 357-364 ◽  
Author(s):  
A D Blake ◽  
N S Hayes ◽  
E E Slater ◽  
C D Strader
Keyword(s):  
Tyrosine Kinase ◽  
Insulin Receptor ◽  
Receptor Tyrosine Kinase ◽  
Kinase Activity ◽  
Glycogen Synthesis ◽  
Insulin Receptors ◽  
Beta Subunit ◽  
Tyrosine Kinase Activity ◽  
Down Regulation ◽  
Receptor Endocytosis

A model of insulin-receptor down-regulation and desensitization has been developed and described. In this model, both insulin-receptor down-regulation and functional desensitization are induced in the human HepG2 cell line by a 16 h exposure of the cells to 0.1 microM-insulin. Insulin-receptor affinity is unchanged, but receptor number is decreased by 50%, as determined both by 125I-insulin binding and by protein immunoblotting with an antibody to the beta-subunit of the receptor. This down-regulation is accompanied by a disproportionate loss of insulin-stimulated glycogen synthesis, yielding a population of cell-surface insulin receptors which bind insulin normally but which are unable to mediate insulin-stimulated glycogen synthesis within the cell. Upon binding of insulin, the desensitized receptors are internalized rapidly, with characteristics indistinguishable from those of control cells. In contrast, this desensitization is accompanied by a loss of the insulin-sensitive tyrosine kinase activity of insulin receptors isolated from these cells. Receptors isolated from control cells show a 5-25-fold enhancement of autophosphorylation of the beta-subunit by insulin; this insulin-responsive autophosphorylation is severely attenuated after desensitization to a maximum of 0-2-fold stimulation by insulin. Likewise, the receptor-mediated phosphorylation of exogenous angiotensin II, which is stimulated 2-10-fold by insulin in receptors from control cells, is completely unresponsive to insulin in desensitized cells. These data provide evidence that the insulin-receptor tyrosine kinase activity correlates with insulin stimulation of an intracellular metabolic event. The data suggest that receptor endocytosis is not sufficient to mediate insulin's effects, and thereby argue for a role of the receptor tyrosine kinase activity in the mediation of insulin action.

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